**In Press**
**2002**
Asher, W., J. Edson, W.R. McGillis, R.H. Wanninkhof, D.T. Ho, and T.
Litchendorf. Fractional area whitecap coverage and air-sea gas transfer
velocities measured during GasEx-98. In Gas Transfer at Water
Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H.
Wanninkhof (eds.). AGU Geophysical Series, Volume 127 (ISBN
0875909868), 199-203 (2002).
GasEx-98 was an air-sea exchange process cruise conducted aboard the NOAA
ship Ronald H. Brown in the North Atlantic during May and June of
1998. During the cruise, air-sea gas transfer velocities for carbon dioxide
were measured using the direct-covariance method. Because the sampling
times for the covariance method are on the same order as the time scales of
changes in meteorological forcing, the GasEx-98 results provide a unique data
set for investigating whether changes in different forcing mechanisms
correlate with changes in gas transfer. In particular, fractional area
whitecap coverage, WC, was measured during daylight hours
using a dual-camera video system mounted on a bow tower. Several high wind
speed events occurred during the cruise, and the resulting correlation between
wind speed and WC is consistent with previous oceanic
measurements. The whitecap coverage data were combined with the wind speed
records and these data were used in a parameterization of whitecap-mediated
gas transfer to predict transfer velocities. These predicted transfer
velocities are in good agreement with the transfer velocities derived from
the direct-covariance data.
Atlas, D., C.W. Ulbrich, and F.D. Marks. Reply. Journal of Geophysical
Research, 107(D1):10.1029/2001JD000658 (2002).
No abstract.
Baringer, M.O. Historical record of Florida Current observations. AGU
2001 Fall Meeting, San Francisco, CA, December 10-14, 2001. Supplement
to EOS, Transactions, American Geophysical Union, 82(47):F681-F682,
OS52C-09 (2002).
Daily transports of the Florida Current have been inferred since 1982 through
the use of submerged submarine telephone cables that measure the voltage
differences across the Straits of Florida. Using all 16 years of data, the
annual cycle ranges from a minimum of 30 Sv in January to a maximum of 33.5
Sv in July. The annual cycle is not stable throughout the entire period;
however, the first eight years show a slightly larger peak-to-peak annual
range of 5 Sv, while the second eight years have a semi-annual cycle with a
distinct minimum in July and peak-to-peak range of 4 Sv. Filtered Florida
Current transports contain a two to three year variation between 2 and 3 Sv
in amplitude and a decadal variation of about ±2 Sv. The decadal changes
in the Florida Current transport are significantly correlated (R =
0.75 at 95% significance) to the North Atlantic Oscillation Index. This
presentation will discuss this recent extended time series in the context of
historical observations of the Florida Current.
Bentamy, A., K.B. Katsaros, W.M. Drennan, and E.B. Forde. Daily surface
wind fields produced by merged satellite data. In Gas Transfer at Water
Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof
(eds.). AGU Geophysical Monograph Series, Volume 127 (ISBN
0875909868), 343-349 (2002).
Surface wind speed is the dominant variable over most of the ocean for the
magnitude of air-sea exchange of trace gases, as well as wind stress, heat,
and water vapor. Satellite data of surface winds are now produced routinely
by scatterometers and radiometers on several satellites. Employing surface
wind data from these various sensors and the Kriging technique with its
associated variograms, which consider both space and time wind vector
structures, we have produced 1° latitude by 1° longitude gridded
wind fields over the global ocean on a daily basis. The present data set
covers the period of the NASA scatterometer (NSCAT), September 1996 through
June 1997. NSCAT data is merged with scatterometer data from the European
Remote Sensing (ERS) satellite 2, and the wind speeds from two of the Special
Sensor Microwave/Imagers (SSM/I) operating during that period. The accuracy
of the resulting daily wind fields is determined by comparisons with
moored-buoy wind speed and direction measurements, which are deployed and
maintained by four different institutions in the Atlantic and Pacific Oceans.
The root-mean-square (rms) difference values are less than 1.5 m/s. No
significant difference was found between statistical parameters estimated
over the equatorial zone and middle latitudes. To investigate the global
patterns of these new satellite wind fields, comparisons with the National
Environmental Prediction Center's (NCEP) re-analysis products have been
carried out. The satellite data and the NCEP products have similar
statistical error structure, but the merged wind fields provide complete
coverage at much higher spatial resolution.
Carsey, T.P., and H.E. Willoughby. Ozone measurements from Atlantic tropical
cyclones. AGU 2001 Fall Meeting, San Francisco, CA, December 10-14,
2001. Supplement to EOS, Transactions, American Geophysical Union,
82(47):F123, A51F-0112 (2002).
Tropical cyclones (TCs, hurricanes) are episodic mesoscale features of the
tropical and subtropical oceans that are likely to have a large impact on the
distributions and fluxes of trace gases. The troposphere boundary layer,
possibly enriched by enhanced exchange of dissolved gases from the sea
surface, is transported upward as high as 15 km and redistributed over a
large horizontal area. Measurements of selected trace gases should,
therefore, be useful in understanding hurricane dynamics and structure; for
example, to resolve an ongoing controversy about the lifetime of air within
the eye and mixing areas of the eyewall boundary (Willoughby, Mon. Wea.
Rev., 126, 3053, 1998). However, few systematic measurements of
significant trace gases in TCs have been obtained. NOAA-AOML has measured
ozone (O3) in eyewall crossings for a number of Atlantic TCs
during the 1998 and 1999 seasons on board NOAA P-3 hurricane research
flights. Ozone concentrations showed considerable variation across the
eyewall and within the eye; significant changes were also observed as the
hurricane aged. These results, related measurements, and their implications
for TC structure and marine tropospheric chemistry, will be presented.
Donelan, M.A., and R.H. Wanninkhof. Gas transfer at water surfaces:
Concepts and issues. In Gas Transfer at Water Surfaces, M.A. Donelan,
W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical
Monograph Series, Volume 127 (ISBN 0875909868), 1-10 (2002).
This introductory paper puts the technical articles to follow in the context
of the need to understand gas transfer at water surfaces and to apply
improved methods to the estimation of the exchange of gases between air and
water. We summarize the physical and chemical background to processes of
interfacial gas transfer, discuss field and laboratory approaches to
measuring the gas exchange rate, and to elucidating its causes. Finally, we
illustrate the application of acquired understanding in gas transfer to the
global flux of carbon dioxide. This issue is of societal relevance in
predicting and possibly reducing anthropogenic causes of climate change.
Dugdale, R.C., A.G. Wischmeyer, F.P. Wilkerson, F. Chai, R.T. Barber, M.
Jiang, and T.-H. Peng. The impact of diatoms on climate variability:
Comparison of model output and core data for opal and CO2.
AGU 2001 Fall Meeting, San Francisco, CA, December 10-14, 2001.
Supplement to EOS, Transactions, American Geophysical Union,
82(47):F799, PP52B-02 (2002).
The modern equatorial Pacific upwelling system has been shown by modeling
and field studies to be Si(OH)4 limited for diatoms. The origin of
low Si(OH)4 water flowing into the Equatorial Undercurrent (EU) at
its western origin is found in the Southern Ocean where unusually high ratios
of Si(OH)4:NO3 uptake by diatoms during the productivity
season results in a region from which water with a low
Si(OH)4:NO3 ratio is advected northward as Sub Antarctic
Mode Water, and eventually providing about half of the water but only about
30% of the Si(OH)4 for the EU. Modeling results suggest a
bell-shaped curve for the relationship between Si(OH)4
concentration in the source water for the present equatorial upwelling and
surface TCO2 concentration. Similar variables were then compared
on paleoceanographic time scales. Opal concentrations measured in a central
equatorial core (W8402A-14GC) and Vostoc ice-core CO2
concentrations placed on the same time scale show a clear cycle of the two
variables during the last 128 kyr. Glacial terminations (Term II, 132-129
kyr and Term I, 14 kyr) are characterized by high concentrations of both opal
and CO2. During maximum ice volume (33-18 kyr), opal and
CO2 are at minimum, low values. Beginning at Termination II
(132-129 kyr), the cycle is described by an increase in opal and a rapid
decrease in CO2 during the initial post-termination phase,
followed by a slow decrease in both opal and CO2 to maximum ice
volume. A very rapid rise in both opal and CO2 then occurs,
essentially the transition from the last glacial maximum (LGM) to Term I.
Shorter (10 kyr) minor loops also appear in the plot of this data. The model
prediction of a maximum in surface TCO2 at intermediate
Si(OH)4 concentrations appears in the core data with opal
concentration about 0.08 gm cm-3 and CO2 about 280 ppmv.
The potential for various sources of Si(OH)4 to the equatorial
Pacific, including the Southern Ocean, rivers and dust, to contribute to the
apparent opal-CO2 cycle are discussed. The implications of this
link between silica and CO2 in both modern and paleo data are that
the equatorial upwelling system diatoms may be key contributors to variations
in global carbon partitioning and, hence, climate variability.
Eastin, M.D., P.G. Black, and W.M. Gray. Flight-level thermodynamic
instrument wetting errors in hurricanes. Part I: Observations. Monthly
Weather Review, 130(4):825-841 (2002).
Flight-level thermodynamic errors caused by the wetting of temperature and
moisture sensors immersed within the airstream are studied using data from
666 radial legs collected in 31 hurricanes at pressure levels ranging from
850 to 500 mb. Concurrent measurements from a modified Barnes radiometer and
a Rosemount 102 immersion thermometer are compared to identify regions,
called instrument wetting events (IWE), in which Rosemount temperatures are
significantly cooler than radiometer-derived temperatures by a specified
amount. A total of 420 IWE are identified in the data set. Roughly 50% of
the radial legs contain at least one instrument wetting event. More than 90%
of IWE are associated with updrafts containing cloud water and are confined
to scales less than 10 km. IWE are also found to be more frequent in eyewalls
and intense hurricanes. Thermodynamic errors within IWE and convective
updrafts and downdrafts are summarized as distributions of average
temperature, specific humidity, virtual potential temperature, and equivalent
potential temperature error. Distributions are skewed toward larger error
values at all levels. Median average errors within IWE indicate that the
thermodynamic quantities are typically too low by ~1°C, 1 g
kg-1, ~1.5 K, and ~5 K, respectively. The largest errors
(>90% of the distribution) are nearly twice the median values. Error
magnitudes tend to increase with height, but rarely achieve theoretical
predictions. In addition, more than 65% of updrafts and 35% of downdrafts
are found to contain significant thermodynamic errors. A correction method
used in earlier studies was found to be inadequate at removing the majority
of errors, but reduced the errors by 30%V50% on average.
Eastin, M.D., P.G. Black, and W.M. Gray. Flight-level thermodynamic
instrument wetting errors in hurricanes. Part II: Implications.
Monthly Weather Review, 130(4):842-851 (2002).
The implications of flight-level instrument wetting error removal upon the
mean thermodynamic structure across the eyewall, buoyancy of rainband
vertical motions, and vertical energy fluxes near the top of the inflow
layer, are studied. Thermodynamic quantities across the mean eyewall are
found to increase at all levels. As a result, maximum radial gradients of
each quantity are shifted from the center of the eyewall cloud toward the
outer edge. The increase in equivalent potential temperature lifts eyewall
values to comparable magnitudes observed in the eye. The mean virtual
potential temperature deviation of rainband updrafts increases from slightly
negative to slightly positive. This increase and shift in sign are more
pronounced in stronger updrafts. The mean deviation in rainband downdrafts
decreases slightly toward neutral conditions. Vertical sensible heat fluxes
near the top of the inflow layer are found to shift from downward to upward.
Upward latent heat fluxes increase. Implications of these results upon
hurricane structure and evolution are discussed.
Feely, R.A., R.H. Wanninkhof, D.A. Hansell, M.F. Lamb, D. Greeley, and K.
Lee. Water column CO2 measurements during the GasEx-98
Expedition. In Gas Transfer at Water Surfaces, M.A. Donelan, W.M.
Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical
Monograph Series, Volume 127 (ISBN 0875909868), 173-180 (2002).
During the recent GasEx-98 cruise in the North Atlantic aboard the NOAA
ship Ronald H. Brown, carbon measurements were performed in the
areas of 46°N, 20.5°W. This process study followed a warm core
ring tagged with the deliberately introduced tracer, SF6.
Continuous surface water measurements were combined with vertical profiles
sampled daily to depths up to 1000 m for carbon mass balance studies.
Dissolved inorganic carbon (DIC) and fCO2 measurements were
conducted onboard in both underway and discrete analysis modes. During the
25-day experiment in the tagged patch surface water, fCO2 values
averaged 275 ± 9 µatm, providing a constant condition of
undersaturation and flux of CO2 into the ocean. Using the
Wanninkhof (1992) exchange coefficient, the estimated CO2 flux
ranged from approximately 1-27 mol m-2 yr-1. The
largest CO2 flux occurred during a large wind event beginning on
June 6. After the event, DIC and fCO2 values decreased for a
few days, as a result of increased productivity associated with the strong
mixing event. The DIC results were combined with the TOC, TON, and nutrient
data to provide a mass balance for carbon within the patch. The results for
the 25-day period indicate DIC increases in the mixed layer ranging from
0.2-1.8 µmol kg-1 d-1 due to gas exchange.
Foster, R.C., S. Chen, J. Tenerelli, W.T. Liu, P. Chang, and M.D.
Powell. Intercomparisons of remotely sensed scatterometer winds with
aircraft hurricane wind observations using a mesoscale model as a baseline.
AGU 2001 Fall Meeting, San Francisco, CA, December 10-14, 2001.
Supplement to EOS, Transactions, American Geophysical Union,
82(47):F625, OS31A-0386 (2002).
Observations from NOAA/AOML/HRD hurricane research flights and satellite
scatterometers both provide valuable data on the surface wind field within a
hurricane. The aircraft flight level data and GPS dropsondes are the primary
in-situ hurricane wind observations. Winds from the HRD flight data must be
combined over the duration of the flight and reconciled into a composite
field for a given time. These constraints limit the spatial coverage. The
polar-orbiting SeaWinds on the QuikSCAT scatterometer provides 1800-km wide
swaths of essentially instantaneous wind vector fields over the sea surface.
These wind vectors are derived from measurements of radar backscatter at
multiple look directions over 25 km2 footprints. Heavy rainfall,
such as in hurricane rainbands, can contaminate the scatterometer winds.
However, different backscatter processing techniques are affected differently.
The primary difficulty in using the aircraft observations to validate the
scatterometer winds in hurricanes is that it is rare to have simultaneous
scatterometer and aircraft fields. We use a high-resolution mesoscale model
(MM5) simulation of Hurricane Floyd as a benchmark against which SeaWinds and
NOAA-HRD surface winds can be separately compared. The benchmark MM5
simulation uses quadruple nested grids of 45, 15, 5 and 1.76 km and produced
a very good simulation of Floyd in both track and intensity. MM5 forecasts
of surface winds are available every hour which allows us to match closely
in time with HRD surface wind analyses and with QuikSCAT swaths. We use
these comparisons to assess the performance of SeaWinds in the near- and
far-field regions of the hurricane and for the standard and near-real-time
wind processing.
Goni, G.J., P.G. Black, J.J. Cione, M. Mainelli, and J.A.
Trinanes. Near-real time altimeter-derived estimates of hurricane heat
potential. AGU 2001 Fall Meeting, San Francisco, CA, December 10-14,
2001. Supplement to EOS, Transactions, American Geophysical Union,
82(47):F253, G11A-07 (2002).
The intensification of hurricanes involves a combination of different
favorable atmospheric and ocean conditions. After a series of events where
the sudden intensification of hurricanes occurred when their path passed
over oceanic warm features, it is now speculated that the ocean may have a
more important role on storm intensification than previously thought. While
the investigation of the importance of warm rings and eddies on hurricane
sudden intensification is a topic of research at a very early stage,
preliminary results have shown their importance on the intensification of
Hurricanes Opal (1995) and Bret (1999) in the Gulf of Mexico. Since then,
monitoring of the upper ocean thermal structure has become a key element in
the study of hurricane-ocean interaction with respect to the prediction
of sudden hurricane intensification. Although AVHRR-derived sea surface
temperature observations can be obtained several times a day, they only
provide information of the temperature of the skin surface layer which
could very well not be related to the ocean thermal conditons in the upper
tens of meters. Alternatively, sea height anomaly data, as derived from
altimetry, may provide information of the upper ocean thermal structure
and its dynamics when combined with historical hydrographic data. The
hurricane heat potential is a parameter proportional to the integrated
vertical temperature between the sea surface and the 26°C isotherm,
which is the approximate sea surface temperature needed for a storm to
maintain hurricane strength. Specific research objectives are now focused to
determine the hurricane heat potential in the Caribbean Sea, Gulf of Mexico,
and tropical Atlantic, and with special emphasis on warm core rings, the Loop
and Florida Currents, and the Gulf Stream. The close relationship that exists
between the dynamic height and the ocean mass field allows these two
parameters to be used within a two-layer reduced gravity ocean scheme to
monitor the upper layer thickness, which is defined to go from the surface
to the depth of the 20°C isotherm. Although there are many factors
controlling the sea height anomaly, it is assumed here that most of its
variability is due to changes in the thickness of the upper layer and to
steric and barotropic effects. The thermal profiles are then constructed
using near-real time altimeter-derived upper layer thickness from three
altimeters by NOAA/NESDIS along with the sea surface temperature fields.
Estimates of this parameter are posted daily during hurricane season to help
forecasters and scientists identify regions of high hurricane heat potential
and possible hurricane intensification.
Johns, W.E., T.L. Townsend, D.M. Fratantoni, and W.D. Wilson. On the
Atlantic inflow to the Caribbean Sea. Deep-Sea Research, 49(2):211-243
(2002).
New observations are summarized that lead to the first comprehensive
description of the mean inflow distribution in the passages connecting the
Atlantic Ocean with the Caribbean Sea. The total Caribbean inflow of 28 Sv
is shown to be partitioned approximately equally between the Windward Islands
Passages (~10 Sv), Leeward Islands Passages (~8 Sv), and the Greater
Antilles Passages (~10 Sv). These results are compared to a numerical
model study using a six-layer, 1/4° resolution Atlantic Basin version of
the NRL Layered Ocean Model. Results from two simulations are described,
including a purely wind-forced model driven by Hellerman and Rosenstein
(J. Phys. Oceanogr., 13:1093-1104, 1983) monthly winds, and a model
with an additional 14 Sv meridional overturning cell driven by inflow/outflow
ports at the northern (65°N) and southern (20°S) model boundaries.
The purely wind-driven version of the model exhibits a total Caribbean inflow
of 17 Sv, consistent with expectations from steady, non-topographic Sverdrup
theory. Nearly all of the wind-driven inflow occurs north of Martinique at
latitude ~15°N. The net transport through the Lesser Antilles
passages south of 15°N (Grenada, St. Vincent, and St. Lucia passages)
is nearly zero when the model is forced by winds alone. The addition of a
14 Sv meridional cell in the model increases the net Caribbean inflow to
28 Sv, with nearly all of the additional 11 Sv of inflow entering through the
southern Lesser Antilles passages. The modeled inflow distribution resulting
from the combined wind and overturning forced experiment is found to compare
favorably with the observations. The seasonal cycle of the total inflow in
the combined forcing experiment has a mixed annual/semiannual character with
maximum in spring and summer and minimum in fall, with a total range of about
4 Sv. The seasonal cycle of the Florida Current resulting from this inflow
variation is in good qualitative agreement with observations. Most of the
seasonal inflow variation occurs through the Windward Islands passages in
the far southern Caribbean, whose annual cycle slightly leads that of the
Florida and Yucatan Currents. Variability of the modeled inflow on shorter
time scales shows a dramatic change in character moving northward along the
Antilles arc. The southern passages exhibit large fluctuations on 30-80 day
time scales, which decay to very small amplitudes north of Dominica. Much of
this variability is caused by North Brazil Current Rings that propagate
northwestward from the equatorial Atlantic and interact with the abrupt
island arc topography. The total range of transport variability in individual
passages predicted by the model is consistent with observations. However,
observations are presently too limited to confirm the seasonal cycles or
variability spectra in the Caribbean passages.
Katsaros, K.B., P.W. Vachon, W.T. Liu, and P.G. Black. Microwave remote
sensing of tropical cyclones from space. Journal of Oceanography,
58:137-151 (2002).
This article reviews several microwave instruments employed in research and
analysis of tropical cyclones (TCs), typhoons, and hurricanes. The
instruments discussed include scatterometers, microwave radiometers,
synthetic aperture radars (SAR), and rain radar from space. Examples of
the particular contribution by one or more of these instruments in analysis
of several storms illustrate the comprehensive new views provided by the
SeaWinds scatterometers, the detailed high-resolution wind field provided
by RADARSAT SAR, particularly inside and in the vicinity of hurricane
"eyes," and the presence of secondary flows in the region between rainbands
in TCs. The high spatial resolution of precipitation data from the Tropical
Rainfall Measuring Mission's rain radar, combined with scatterometer or SAR
data, give a significant improvement in the details that can be seen from
space, at the surface, and in the precipitating areas of TCs. The microwave
instruments provide the penetrating view below the upper level cirrus
clouds.
Lamb, M.F., C.L. Sabine, R.A. Feely, R.H. Wanninkhof, R.M. Key, G.C. Johnson,
F.J. Millero, K. LEE, T.-H. PENG, A. Kozyr, J.L. Bullister, D. Greeley, R.H.
Byrne, D.W. Chipman, A.G. Dickson, C. Goyet, P.R. Guenther, M. Ishii, K.M.
Johnson, C.D. Keeling, T. Ono, K. Shitashima, T. Tilbrook, T. Takahashi,
D.W.R. Wallace, Y.W. Watanabe, C. Winn, and C.S. Wong. Consistency and
synthesis of Pacific Ocean CO2 survey data. Deep-Sea
Research, Part II, 49(1-3):21-58 (2002).
Between 1991 and 1999, carbon measurements were made on 25 WOCE/JGOFS/OACES
cruises in the Pacific Ocean. Investigators from 15 different laboratories
and four countries analyzed at least two of the four measurable ocean carbon
parameters (DIC, TAlk, fCO2, and pH) on almost all cruises. The
goal of this work is to assess the quality of the Pacific carbon survey data
and to make recommendations for generating a unified data set that is
consistent between cruises. Several different lines of evidence were used to
examine the consistency, including comparison of calibration techniques,
results from certified reference material analyses, precision of at-sea
replicate analyses, agreement between shipboard analyses and replicate
shore-based analyses, comparison of deep water values at locations where
two or more cruises overlapped or crossed, consistency with other hydrographic
parameters, and internal consistency with multiple carbon parameter
measurements. With the adjustments proposed here, the data can be combined to
generate a Pacific Ocean data set, with over 36,000 unique sample locations
analyzed for at least two carbon parameters in most cases. The best data
coverage was for DIC, which has an estimated overall accuracy of
~3 µmol kg-1. TAlk, the second most common carbon
parameter analyzed, had an estimated overall accuracy of
~5 µmol kg-1. To obtain additional details on this
study, including detailed crossover plots and information on the availability
of the compiled, adjusted data set, visit the Global Data Analysis Project
web site at http://cdiac.esd.ornl.gov/oceans/glodap.
Landsea, C.W. Atlantic hurricane activity: 1851-1900. AGU 2001 Fall
Meeting, San Francisco, CA, December 10-14, 2001. Supplement to EOS,
Transactions, American Geophysical Union, 82(47):F299, GC21A-05 (2002).
This presentation reports on the second year's work of a three-year project
to re-analyze the North Atlantic hurricane database (or HURDAT). The original
database of six-hour positions and intensities were put together in the 1960s
in support of the Apollo space program to help provide statistical track
forecast guidance. In the intervening years, this database, which is now
freely and easily accessible on the Internet from the National Hurricane
Center's (NHC) webpage, has been utilized for a wide variety of uses:
climatic change studies, seasonal forecasting, risk assessment for county
emergency managers, analysis of potential losses for insurance and business
interests, intensity forecasting techniques, and verification of official
and various model predictions of track and intensity. Unfortunately, HURDAT
was not designed with all of these uses in mind when it was first put together
and not all of them may be appropriate given its original motivation. One
problem with HURDAT is that there are numerous systematic as well as some
random errors in the database which need correction. Additionally, analysis
techniques have changed over the years at NHC as our understanding of
tropical cyclones has developed, leading to biases in the historical database
that have not been addressed. Another difficulty in applying the hurricane
database to studies concerned with landfalling events is the lack of exact
location, time, and intensity at hurricane landfall. Finally, recent efforts
into uncovering undocumented historical hurricanes in the late 1800s and
early 1900s led by Jose Fernandez-Partagas have greatly increased our
knowledge of these past events, which are not yet incorporated into the
HURDAT database. Because of all of these issues, a re-analysis of the
Atlantic hurricane database is being attempted that will be completed in
three years. As part of the re-analyses, three files will be made available:
(1) the revised Atlantic HURDAT (with six hour intensities and positions);
(2) a HURDAT meta text file with detailed information about each suggested
change proposed in the revised HURDAT; and (3) a "center fix" file composed
of actual observations of tropical cyclone positions and intensity estimates
from aircraft, satellite, radar, and synoptic platforms. All changes made to
HURDAT will be approved by a NHC committee, as this database is one that
is officially maintained by them. Results will be presented at the conference,
including a revised climatology of U.S. hurricane strikes back to 1851.
Landsea, C.W., S.B. Goldenberg, A.M. Mestas-Nunez, and W. Gray. The
recent increase in Atlantic hurricane activity: Causes and implications.
AGU 2001 Fall Meeting, San Francisco, CA, December 10-14, 2001.
Supplement to EOS, Transactions, American Geophysical Union,
82(47):F680, OS52B-10 (2002).
The years 1995 to 2000 experienced the highest level of North Atlantic
hurricane activity in the reliable record. Compared with the generally low
activity of the previous 24 years (1971-1994), the past six years have seen
a doubling of overall activity for the whole basin, a 2.5 fold increase in
major hurricanes (>49 m/s), and a fivefold increase in hurricanes affecting
the Caribbean. The greater activity results from simultaneous increases in
North Atlantic sea surface temperatures and decreases in vertical wind shear.
Because these changes exhibit a multidecadal time scale, the present high
level of hurricane activity is likely to persist for an additional
~10 to 40 years. The shift in climate calls for a reevaluation of
preparedness and mitigation strategies.
Lawrence, J.R., S.D. Gedzelman, J.F. Gamache, and M.L. Black. Stable
isotope ratios: Hurricane Olivia. Journal of Atmospheric
Chemistry, 41(1):67-82 (2002).
The oxygen and hydrogen isotopic compositions of rains from Hurricane Olivia
(1994) in the eastern Pacific were measured. The rains were collected on 24
and 25 September during airplane flights conducted at an elevation of 3 km.
Hurricane Olivia peaked in intensity to a category-4 storm between the two
dates. Isotope ratios of rains from Hurricane Olivia were markedly lower
(delta18O = -13.9 parts per thousand to -28.8 parts per thousand)
than that of rain collected from a thunderstorm at an elevation of 2.3 km
outside the influence of Olivia (delta18O = -3.8 parts per
thousand). A distinct decrease in isotope ratios from the first day to the
next (delta18O = -18.4 parts per thousand to V21.9 parts per
thousand) in Hurricane Olivia was attributed to decreased updraft velocities
and outflow aloft. This shifted the isotopic water mass balance so that fewer
hydrometeors were lifted and more ice descended to flight level. A decrease
in the average deuterium excess from the first day to the next (delta =
15.5 to 7.1 parts per thousand) was attributed to an increase in the relative
humidity of the water vapor "source" area. We hypothesize that the "source"
region for the rain was in the boundary layer near the storm center and that
because the hurricane was at peak intensity prior to the second day the
relative humidity was higher.
Macdonald, A.M., M.O. Baringer, K. Lee, D.W. Wallace, and R.H.
Wanninkhof. Subtropical Atlantic carbon transport. International WOCE
Newsletter, 42:14-19 (2002).
No abstract.
Macdonald, A.M., R.H. Wanninkhof, M.O. Baringer, P.E. Robbins, and D.W.
Wallace. Oceanic biogeochemical fluxes: A summary of the JGOFS portion
of the WOCE/JGOFS Transport Workshop, Southampton, June 25-29, 2001.
International WOCE Newsletter, 42:20-21 (2002).
No abstract.
Rogers, R.F., S.D. Aberson, J. Kaplan, and S.B. Goldenberg. A pronounced
upper-tropospheric warm anomaly encountered by the NOAA Gulfstream-IV
aircraft in the vicinity of deep convection. Monthly Weather Review,
130(1):180-187 (2002).
Recent flights near deep convection by the National Oceanic and Atmospheric
Administration's Gulfstream-IV surveillance aircraft have occasionally
experienced significant positive temperature anomalies that sometimes impact
the aircraft performance. One such event occurred over the Bahamas on 23
August 1999. During a 20-s time period, when the plane was cruising at an
altitude of 175 hPa, the flight-level ambient temperature rose 15°C and
returned to ambient values, concurrent with significant fluctuations in the
horizontal and vertical winds. Large temperature anomalies such as that
reported here can cause the avionics on the aircraft to compensate with a
sudden decrease in air speed and a loss of altitude. Possible explanations
for this anomaly include instrument error and convectively forced gravity
waves or upper-level subsidence.
Rona, P.A., K.G. Bemis, D.R. Jackson, C.D. Jones, K. Mitsuzawa, D.R.
Palmer, and D. Silver. Acoustic imaging time series of plume behavior at
Grotto Vent, Endeavor Observatory, Juan de Fuca Ridge. AGU 2001 Fall
Meeting, San Francisco, CA, December 10-14, 2001. Supplement to
EOS, Transactions, American Geophysical Union, 82(47):F613-F614,
OS21B-0445 (2002).
A time series (24 hours) of acoustic images record the behavior of the
principal buoyant plume (height interval 0-40 m above seafloor) discharging
from black smoker chimneys on the north tower of the Grotto Vent sulfide
edifice in the Main Endeavour Vent Field. The plume imaging was performed
using the Simrad SM2000 sonar system (frequency 200 kHz) mounted on ROV
Jason from a fixed position on the seafloor with a nearly horizontal
slant range to the vent of about 20 m at a water depth of about 2190 m. The
acoustic imaging is based on Rayleigh backscattering from mineral particles
suspended in the plume that are small (microns) relative to the wavelength of
the acoustic pulse (centimeter) such that intensity of backscatter is
proportional to particle load. The acoustic time series data were acquired
on 26-27 July 2000 as part of the VIP (Vent Imaging Pacific) 2000 cruise. We
applied our computer visualization and quantification methods to reconstruct
the plume three-dimensional volume object and to measure dimensions and o
rientation. Plume expansion with height corresponds to model prediction
(diameter 2 to 20 m). Particle load decreases with height following model
predications. The plume centerline constructed by joining the local center of
mass of successive horizontal slices with height through the buoyant plume
alternately bends between 0 and 30 degrees to the northeast and southwest
in a complex cycle. The plume bending appears to correspond to the regional
mixed semidiurnal tidal cycle (H. Mofjeld, personal communication), with a
component related to a prevailing northeasterly current (R. Thomson, personal
communication). The effectiveness of tracking plume behavior for this short
time series shows the potential of the acoustic method for long-term
monitoring of the activity and interactions of plumes in seafloor
hydrothermal fields.
Sabine, C.L., R.A. Feely, R.H. Wanninkhof, R.M. Key, F.J. Millero, K. Lee,
T.-H. Peng, A. Kozyr, J.L. Bullister, M.F. Lamb, and D. Greeley. Carbon
tracers for ocean circulation. 2001 Report of the WOCE JGOFS Ocean Transport
Workshop, WOCE Rept. No. 174/2001, 42-43 (2001).
No abstract.
Schecter, D.A., M.T. Montgomery, and P.D. Reasor. A theory for the vertical
alignment of a quasigeostrophic vortex. Journal of the Atmospheric
Sciences, 59(2):150-168 (2002).
This article presents a new theory for the rate at which a quasigeostrophic
vortex realigns, under conservative dynamics, after being tilted by an
episode of external vertical shear. The initial tilt is viewed as the
excitation of a three-dimensional "vortex Rossby mode." This mode, that is,
the tilt, decays exponentially with time during its early evolution. The
decay rate, gamma, is proportional to the potential vorticity gradient at a
critical radius, where the fluid rotation is resonant with the mode. The
decay rate gamma also depends on the internal Rossby deformation radius
lR, which is proportional to the stratification strength of
the atmospheric or oceanic layer containing the vortex. The change of gamma
with lR is sensitive to the form of the vortex. For the
case of a "Rankine-with-skirt" vortex, the magnitude of gamma increases
(initially) with increasing lR. On the other hand, for the
case of a "Gaussian" vortex, the magnitude of gamma decreases with increasing
lR. The relevance of this theory to tropical cyclogenesis
is discussed.
Schecter, D.A., M.T. Montgomery, and P.D. Reasor. On the vertical alignment
of an atmospheric vortex. AGU 2001 Fall Meeting, San Francisco, CA,
December 10-14, 2001. Supplement to EOS, Transactions, American
Geophysical Union, 82(47):F76, A32B-0045 (2002).
During its early stages of development, anatmospheric vortex can be destroyed
by episodes of external verticalshear. However, some vortices survive because
they have a dominanttendency to stand upright. We will review a recent theory
for the vertical alignment of a quasi-geostrophic (QG) vortex. In this theory,
vertical alignment occurs by the damping of a discrete vortex Rossby mode.
The damping rate gamma (i.e., the alignment rate) is proportional to
the potential vorticity gradient at a critical radius, where the rotation
frequency of the vortex is resonant with the mode. Furthermore, gamma
varies with the vortex height and the level of atmospheric stratification.
We find that gamma can either increase or decrease with these parameters,
depending on the radial structure of the vortex. We will also present a
more general theory that covers the vertical alignment of rapidly rotating
vortices, such as tropical cyclones. This new theory is based on the
asymmetric balance equations of Shapiro and Montgomery. As in QG theory,
vertical alignment is viewed as the damping of a discrete mode. However,
the damping rate gamma varies with an additional parameter: the Rossby
number Ro of the vortex. The value of gamma can vary
non-monotonically with Ro, but always converges to QG
theory as Ro approaches zero.
Soloviev, A., J. Edson, W.R. McGillis, P. Schluessel, and R.H.
Wanninkhof. Fine thermohaline structure and gas exchange in the near-surface
layer of the ocean during GasEx-98. In Gas Transfer at Water
Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H.
Wanninkhof (eds.). AGU Geophysical Monograph Series, Volume 127
(ISBN 0875909868), 181-185 (2002).
During the GasEx-98 field campaign, observations of the upper ocean structure
were performed to identify relationships between the fine thermohaline
structure, turbulence, and gas exchange in the near-surface layer of the
ocean. The upper ocean dynamics were then simulated using a one-dimensional
mixed layer model with the mixing parameterization developed during the TOGA
Coupled Ocean-Atmosphere Response Experiment (COARE). The model was
initialized with the temperature, salinity, and velocity profiles in the
upper 50 m thick layer of the ocean obtained from the
conductivity-temperature-depth (CTD) and acoustic Doppler current profiler
(ADCP) measurements and was forced with the air-sea heat and momentum fluxes
measured by Edson et al. (1999). The model produced a set of parameters,
including the time and depth dependent mixing coefficient and the depth of
the mixed layer. The simulated mixed layer depth is consistent with the
depth of the actively mixed layer determined from the turbulence profiles
taken occasionally during GasEx-98 Leg 2 with a free-rising profiler.
Moderate wind speed conditions prevailed during GasEx-98 Leg 2 with several
storms and a few periods of calm weather. Both the modeling and experimental
results demonstrate that under conditions of low wind speed, the
surface-generated turbulence is constrained within a relatively thin surface
layer of the ocean. In the near-surface layer, appreciable temperature,
salinity, and gas concentration differences are formed because of diurnal
warming or precipitation effects. These results are applied to the
estimation of the effect of mixed layer processes on the bulk-flux
formulation for the air-sea exchange of gases.
Taylor, M.A., D.B. Enfield, and A.A. Chen. The influence of the tropical
Atlantic versus the tropical Pacific on Caribbean rainfall. AGU 2001 Fall
Meeting, San Francisco, CA, December 10-14, 2001. Supplement to
EOS, Transactions, American Geophysical Union, 82(47):F680,
OS52B-12 (2002).
The Caribbean rainfall season runs from May through November and is
distinctly bimodal in nature. The bimodality allows for a convenient division
into an early season (May-June-July) and a late season
(August-September-October). Evidence suggests that interannual variability
in the early season is influenced strongly by anomalies in the sea surface
temperatures of the tropical North Atlantic, with positive anomalies over a
narrow latitudinal band (0-20°N) being associated with enhanced
Caribbean rainfall. The coincidence of this band with the main development
region for tropical waves suggests a modification of the development of the
waves by the warmer tropical Atlantic. The strong influence of the tropical
North Atlantic wanes in the late season, with the equatorial Pacific and
equatorial Atlantic becoming more significant modulators of interannual
variability. The spatial pattern of significant correlation suggests strongly
the influence of the El Niņo/La Niņa phenomenon, with a warm Pacific
associated with a depressed late season and vice versa. There additionally
seems to be a robust relationship between late season Caribbean rainfall and
an east-west gradient of SST between the two equatorial oceanic basins.
Oppositely signed SST anomalies in the NINO3 region and the central
equatorial Atlantic (0-15°W, 5°S-5°N) are well correlated
with Caribbean rainfall for this period.
Trinanes, J.A., G.J. Goni, and R.L. Molinari. An altimeter/GTS web-interface
at NOAA/AOML. AGU 2001 Fall Meeting, San Francisco, CA, December 10-14,
2001. Supplement to EOS, Transactions, American Geophysical Union,
82(47):F257, G22A-0206 (2002).
Altimeter data are of great interest for studying ocean dynamics. Sea surface
height measurements aid scientists in many ways, such as improving model
results, tracking eddies, and estimating upper layer depths. In an operative
environment, altimeter-derived sea surface height anomalies (SHA) are
available through NOAA/NESDIS in a near-real-time basis, with a two-day
average delay. A Web-interface has been developed to graphically display
these data. Coverage is worldwide and the region of interest can be
interactively selected. As an additional product, geostrophic currents are
also estimated using the SHA values, and a 1 × 1 degree climatological
mean dynamic-height field relative to the 1000-m depth level. These currents
can be displayed as vectors overlayed on the dynamic height field, or as a
scalar field showing the most active areas. Processing is done on the fly
using the parameters sent by the client (time, geographic area, overlaying
points and/or contours, mask depths). Besides the altimeter products, data
from the Global Telecommunications System (GTS) can also be visualized and
retrieved. These data are ingested into the database four times per day and
comprise data from a large number of floating platforms (drifters, VOS)
around the world. GTS and altimeter-derived products can be displayed together
(e.g., geostrophic altimeter-derived currents can be compared with
drifter trajectories using the same interface).
Wang, C. Atlantic climate variability and its associated atmospheric
circulation cells. Journal of Climate, 15(13):1516-1536 (2002).
Phenomena important for Atlantic climate variability include the Atlantic
zonal equatorial mode, the tropical Atlantic meridional gradient mode, and
the North Atlantic Oscillation (NAO). These climate phenomena and their
associated atmospheric circulation cells are described and discussed using
the NCEPVNCAR reanalysis field and the NCEP sea surface temperature (SST)
from January 1950 to December 1999. Atmospheric divergent wind and vertical
motion are used for the identification of atmospheric circulation cells.
During the peak phase of the Atlantic equatorial mode, the Atlantic Walker
circulation weakens and extends eastward, which results in surface westerly
wind anomalies in the equatorial western Atlantic. These westerly wind
anomalies are partly responsible for warming in the equatorial eastern
Atlantic that occurs in the second half of the year. The Atlantic equatorial
mode involves a positive ocean-atmosphere feedback associated with the
Atlantic Walker circulation, similar to the Pacific El Niņo. The tropical
Atlantic meridional gradient mode is characterized by a strong SST gradient
between the tropical North Atlantic (TNA) and the tropical South Atlantic.
Corresponding to the meridional gradient mode is an atmospheric meridional
circulation cell in which the air rises over the warm SST anomaly region,
flows toward the cold SST anomaly region aloft, sinks in the cold SST anomaly
region, then crosses the equator toward the warm SST region in the lower
troposphere. The analysis presented here suggests that the Pacific El Niņo
can affect the TNA through the Walker and Hadley circulations, favoring the
TNA warming in the subsequent spring of the Pacific El Niņo year. The NAO,
characterized by strong westerly airflow between the Icelandic low and the
Azores high, is also related to an atmospheric meridional circulation. During
the high NAO index, the atmospheric Ferrel and Hadley cells are strengthened,
consistent with surface westerly and easterly wind anomalies in the North
Atlantic and in the mid-to-tropical Atlantic, respectively.
Wang, C. Atmospheric circulation cells associated with the El
Niņo-Southern Oscillation. Journal of Climate, 15(4):399-419 (2002).
Atmospheric circulation cells associated with the El Niņo-Southern
Oscillation (ENSO) are described and examined using the NCEP-NCAR reanalysis
field and the NCEP sea surface temperatures (SST) from January 1950 to
December 1999. The divergent wind and pressure vertical velocity are employed
for the identification of atmospheric circulation cells. The warm phase of
ENSO shows positive SST anomalies in the equatorial eastern Pacific and along
the east coast of Asia and the west coast of North America, and negative SST
anomalies in the off-equatorial western Pacific and in the central North
Pacific. Associated with this SST anomaly distribution are variations of
atmospheric zonal and meridional circulation cells over the Pacific. The
equatorial zonal Walker circulation cell is weakened, consistent with previous
schematic diagrams. The anomalous meridional Hadley circulation cell in the
eastern Pacific shows the air rising in the tropics, flowing poleward in the
upper troposphere, sinking in the subtropics, and returning back to the
tropics in the lower troposphere. The anomalous Hadley cell in the western
Pacific is opposite to that in the eastern Pacific. The divergent wind and
vertical velocity also show a midlatitude zonal cell (MZC) over the North
Pacific. The mean MZC is characterized by the air rising in the central North
Pacific, flowing westward and eastward in the upper troposphere, descending
in the east coast of Asia and the west coast of North America, then returning
back to the central North Pacific in the lower troposphere. The anomalous MZC
during the mature phase of El Niņo shows an opposite rotation to the mean MZC,
indicating a weakening of the MZC.
Wang, C. ENSO and atmospheric circulation cells. CLIVAR Exchanges,
7:9-11 (2002).
No abstract.
Wanninkhof, R.H., S.C. Doney, T. Takahashi, and W.R. McGillis. The effect of
using time-averaged winds on regional air-sea CO2 fluxes. In
Gas Transfer at Water Surfaces, M.A. Donelan, W.M. Drennan, E.S.
Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical Monograph
Series, Volume 127 (ISBN 0875909868), 351-356 (2002).
Gas transfer velocities are frequently related to wind speeds in order to
estimate air-sea gas fluxes on regional and global scales. Since the gas
exchange-wind speed relationships are non-linear, the wind speed distribution
will have an effect on the fluxes if time-averaged winds are used. Commonly,
a Weibull distribution is assumed for monthly or yearly averaged wind speeds.
Although this is a reasonable assumption for global winds, significant
regional deviations from this distribution exist. For areas with steady
winds such as the trade wind regions and Westerlies in the Southern Ocean,
the Weibull assumption will overestimate the long-term gas transfer
velocities. Using regional wind speed distribution patterns based on 6-hour
NCEP re-analysis winds instead of a Weibull distribution, the global oceanic
CO2 uptake estimate decreases by 5% if a quadratic dependence with
wind speed is assumed and by 26% if a cubic dependence of gas exchange with
wind speed is used.
Ward, B., and P.J. Minnett. An autonomous profiler for near surface
temperature measurements. In Gas Transfer at Water Surfaces,
M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.).
AGU Geophysical Monograph Series, Volume 127 (ISBN 0875909868),
167-172 (2002).
This paper describes the profiling instrument SkinDeEP (Skin Depth
Experimental Profiler), which measures the temperature of the water column
from a depth of about 6 m to the surface with high resolution thermometers.
The instrument operates in an autonomous mode as it has the capability to
change buoyancy by inflating a neoprene bladder attached to the body of the
profiler. Measurements are recorded only during the ascending phase of the
profile so as to minimize disturbances at the surface. Results from
deployment of the profiler show strong temperature gradients within the bulk
waters under conditions of high insolation. These data were compared to the
skin temperatures as measured by the M-AERI (Marine-Atmospheric Emitted
Radiance Interferometer), a high accuracy infrared spectroradiometer. The
corresponding bulk-skin temperature differences, DELTA-T, were shown to
have strong dependence on the depth of the bulk measurement during the daytime
with low wind speeds, but at higher wind speeds, the depth dependence
vanishes. One set of profiles under nighttime conditions is also presented,
showing the presence of overturning and thus a heterogeneous temperature
structure within the bulk.
Wilson, W.D., and W.E. Johns. Physical oceanography of the Caribbean
Sea: Some recent observations. AGU 2001 Fall Meeting, San Francisco,
CA, December 10-14, 2001. Supplement to EOS, Transactions, American
Geophysical Union, 82(47):F678, OS52B-01 (2002).
Recent oceanographic observations in the Caribbean Sea and Gulf of Mexico
(the Intra-Americas Sea, IAS) have contributed to our understanding of IAS
circulation, the dynamics forcing the circulation, and the role of the IAS
in hemispheric ocean processes. Specifically, recent results from several
programs will be presented and discussed: The Windward Islands Passages
Program, designed to measure upper ocean transport and water mass properties
of the exchange between the Atlantic Ocean and the Caribbean Sea, is entering
its tenth year of observations. Mean transport estimates based on 10 to 20
sections now exist for the major passages between Trinidad and the Virgin
Islands. Approximately 19 of the estimated 32 Sv in the Florida Straits enter
through these passages, of which approximately 12 enter south of Dominica,
and six in the Grenada Passage. The Caribbean Inflow Variability Experiment is
designed to continuously monitor the transport through the Grenada Passage.
Plans are in place to monitor a submarine telephone cable between Grenada and
Trinidad to estimate transport; at present, several shipboard velocity
sections and year-long pressure gauge records are available as part of the
program. Dominant low-frequency signals in the cross-passage pressure
difference are 30-60 days. The NOPP Year of the Ocean Drifting Buoy Program
placed over 150 WOCE-style surface drifting buoys in the IAS during 1998-2000.
Analysis of drifter tracks shows the best picture to date of IAS surface
currents, including well-resolved gyres in the southwest Caribbean
(Panama-Colombia) region. Monitoring of Florida Straits transport via
submarine cable is once again active, complemented by quarterly CD and
transport cruises. Analyses of historical transport data (Baringer and
Larsen, 2001) have shown correlations between low frequency transport
variability and climate indices (e.g., NAO). Additionally, full-depth
velocity profiles across the Straits are available weekly from the 38 kHz
ADCP mounted on the Explorer of the Seas cruise ship. Availability of
these and other observational resources, its semi-enclosed and well-bounded
geography, and its significance to downstream North American oceanic and
atmospheric conditions make the IAS an excellent region for model development
and validation.
Zhang, J.-Z., and J. Chi. Automated analysis of nanomolar concentrations
of phosphate in natural waters with liquid waveguide. Environmental
Science and Technology, 36(5):1048-1053 (2002).
Concentrations of phosphate in natural waters are often below the detection
limits of conventional nutrient auto-analyzers by either gas-segmented
continuous flow analysis or flow injection analysis. A liquid waveguide
capillary flow cell has been used to extend the sensitivity of a conventional
auto-analyzer for automated analysis of nanomolar concentrations of phosphate
in natural waters. Total reflection of light can be achieved within the
liquid core of the flow cell, as the refractive index of cell wall coated
with Teflon 1600 is lower than water. This property allows the manufacturers
to construct long liquid waveguide capillary flow cells in a helical, rather
than linear shape, with compact dimensions. A small sample volume is required
because the internal volume of a 2-m long capillary flow cell is only
approximately 0.5 cm3. Adaptation of this long flow cell to
auto-analyzers significantly enhances the sensitivity of automated
colorimetric analysis of phosphate with molybdenum blue method, allowing for
accurate and precise determination of nanomolar concentrations of phosphate
in natural waters. The advantages of this technique are a low detection limit
(0.5 nM), small sample volume (2 mL), high precision (2% at 10 nM levels), and
automation for rapid analysis of a large number of samples.
Zhang, J.-Z., and F.J. Millero. Comment on "A kinetic study of the
oxidation of S(IV) in seawater." Environmental Science and
Technology, 36(4):817 (2002).
No abstract.
**2001**
Aberson, S.D. The ensemble of tropical cyclone track forecasting models
in the North Atlantic Basin (1976-2000). Bulletin of the American
Meteorological Society, 82(9):1895-1904 (2001).
The suite of tropical cyclone track forecast models in the Atlantic basin
from the 1976 to 2000 hurricane seasons are treated as a forecast ensemble.
The 12-h ensemble mean forecast, adjusted for forecast difficulty, has
improved at a rate of just under 1% per year, and the improvement rate
increases to almost 2.4% per year for the 72-h forecasts. The average size
of the 72-h (48-h) error in 1976 is less than the average size of the 48-h
(36-h) error in 2000. The average 36-h forecast error in 2000 is comparable
to the 24-h forecast error in 1976. The ensemble currently spans the true
path of the tropical cyclone in the cross-track direction more than 90% of
the time and in the alongtrack direction between 60% and 90% of the time
depending on the forecast lead time. The ensemble spread is unable to
provide estimates of individual forecast reliability, likely making
probabilistic landfall forecasts from this ensemble unreliable. The
reliability of the spread in the cross-track direction suggests the
possibility of limiting hurricane watch and warning regions depending upon
the ensemble spread at landfall.
Aberson, S.D., S.J. Majumdar, and C.H. Bishop. A real-time ensemble for
the prediction of hurricane tracks in the Atlantic basin. Preprints,
18th Conference on Weather Analysis and Forecasting and 14th Conference
on Numerical Weather Prediction, Fort Lauderdale, FL, July 30-August 2,
2001. American Meteorological Society, Boston, 456-457 (2001).
No abstract.
Alvarez-Zarikian, C.A., P.L. Blackwelder, T. Hood, H.R. Wanless, T.A.
Nelsen, and C. Featherstone. Impact on the sedimentary record derived from
micropaleontological data. Proceedings, 2001 Florida Bay and Adjacent
Marine Systems Science Conference, Key Largo, FL, April 23-26, 2001.
University of Florida, 58-59 (2001).
Hurricanes are the strongest force causing immediate and long-term
environmental changes to coastal areas in the lower Everglades and Florida
Bay, and their sedimentary record. Hurricane-induced sediment erosion and
deposition, and bi-directional sediment transport, can disrupt the sediment
record, blending the signature of other ecological factors (i.e.,
salinity fluctuations) and leaving behind a complex overprint of natural and
anthropogenic influences. Their frequency is also a potential mechanism for
carbon storage and removal. Paleohurricane impact in the stratigraphic
record is marked by abrupt changes in microfaunal abundance and community
structure, as well as in quantitative and qualitative organic carbon content
and sediment texture. Hurricane signatures, verifiable by offsets in
210Pb-geochronology data, are found in sediment cores recovered
from Florida and Oyster Bays. Sediment core location controls the magnitude
of variations in the sediment record. Semi-protected areas such as Oyster
Bay exhibit the least amount of sediment disruption during and following the
Labor Day Hurricane of 1935 and Hurricane Donna in 1960, whereas unprotected
or less protected areas such as the First National Bank and Jimmy Key in
western and central Florida Bay, respectively, experience the greatest
effects.
Alvarez-Zarikian, C.A., P.K. Swart, T. Hood, P.L. Blackwelder, T.A. Nelsen,
and C. Featherstone. A century of environmental variability in Oyster Bay
using ostracode ecological and isotopic data as paleoenvironmental tools.
Bulletin of American Paleontology, 361:133-143 (2001).
Stable isotopic analysis (delta18O and delta13C) and
characterization of the ostracode community structure were carried out from
a high-resolution sediment core recovered from Oyster Bay in the west of the
Everglades National Park. Because of its location between Shark River Slough
(SRS) and the Gulf of Mexico, the Oyster Bay core locality experiences extreme
salinity fluctuations due to the interaction of freshwater run-off,
precipitation, and marine water inputs. Ostracode population dynamics
and isotopic variability over the 20th century are linked to natural and
anthropogenic forces that affect the south Florida coastal ecosystem on
interannual to decadal time scales. Three ostracode assemblages can be
recognized within the 100 year sediment-core record: the first extending
from the turn of the century to about 1950; the second, from the early
1950s to the late 1970s; and the third to core recovery in 1995. An
abrupt decrease in ostracode abundance, species diversity, and shifts in
species dominance occurred in the mid-1980s and reflects episodes of
environmental stress. Markedly enriched delta18O values from
the ostracode Peratocytheridea setipunctata and the benthic
foraminifer Ammonia parkinsoniana typica at this time are concurrent
with a major regional drought in south Florida, as well as with documented
algal blooms and major die-off of sea grasses in Florida Bay. In addition,
the timing of these events is contemporaneous to the onset of the South
Florida Water Management District "Rainfall Plan" and the closing of the
Buttonwood Canal. Higher ostracode abundance and species richness occurs
between the late 1950s and late 1970s. Stable isotopic data and ostracode
assemblage characteristics suggest a period of relative environmental
stability and possibly improved water circulation in Whitewater Bay and
Oyster Bay. Fluctuations in community structure during this time are most
systematic and appear to be temporally correlated to rainfall variability
patterns. Water management policies at this time are also discernable from
the microfaunal and isotopic record, particularly the Congressionally
mandated Monthly Minimum Allocation Plan of water supply to SRS. Before
1950, hurricane events and their effects are the major cause for immediate
modifications within the ostracode community, although our data show that
ostracode populations are capable of rapid recovery. Over the complete
record of the last century, the effects of water management practices can be
assessed from information embedded in the ostracode record. Nevertheless,
the effects of natural climatic variability in Oyster Bay appear to outweigh
the impact of anthropogenic forces.
Baringer, M.O., and J.C. Larsen. Sixteen years of Florida Current
transport at 27°N. Geophysical Research Letters,
28(16):3179-3182 (2001).
Daily transports of the Florida Current have been inferred since 1982 through
the use of submerged submarine telephone cables that measure the voltage
difference across the Straits of Florida. Using all 16 years of data, the
annual cycle ranges from a minimum of 30 Sv in January to a maximum of 33.5
Sv in July. The annual cycle is not stable throughout the entire period,
however; the first eight years show a slightly larger peak-to-peak annual
range of 5 Sv, while the second eight years have a semi-annual cycle with a
distinct minimum in July and peak-to-peak range of 4 Sv. Filtered Florida
Current transports contain a two to three year variation between 2 and 3 Sv
in amplitude and a decadal variation of about ą2 Sv. The decadal changes in
the Florida Current transport are significantly correlated (R =
0.75 at 95% significance) to the North Atlantic Oscillation Index.
Bentamy, A., K.B. Katsaros, A.M. Mestas-Nunez, E.B. Forde, W.M. Drennan,
and H. Roquet. Latent heat fluxes over the ocean from merged satellite
data. Intercomparison and Validation of Ocean-Atmosphere Flux Fields
Workshop, Potomac, MD, May 21-24, 2001. WCRP-115-WMO/TD-No. 1083,
205-208 (2001).
The specific objectives of this paper emphasize estimation of global latent
heat flux over the oceans with high spatial and temporal resolution using
satellite radar and radiometer measurements. Consistency of the same surface
parameters retrieved from several satellites is assured. The flux fields
are compared to in-situ observations and atmospheric analysis fields globally
and in different regions of the ocean with particular focus on the tropical
oceans.
Brenner, R.J., M.J. Dagg, and P.B. Ortner. Growth, grazing, distribution,
and carbon demand in the plankton of Florida Bay. Proceedings, 2001
Florida Bay and Adjacent Marine Systems Science Conference, Key Largo,
FL, April 23-26, 2001. University of Florida, 103-104 (2001).
The zooplankton community of Florida Bay was examined over four years from
September 1994 through November 1998 to determine zooplankton distribution
and abundance and to allow calculation of community metabolic demands. Net
zooplankton were collected at 10 sites within the Bay on a bimonthly basis
using a 64 µm net, and copepod nauplii were collected from the surface
at each site using a 10L bucket and 20 µm mesh. The net zooplankton
were split into four functional groups: copepods, copepods nauplii,
meroplanktonic larvae, and "others." The microplankton community was also
investigated using the dilution technique of Landry and Hassett (1982).
Microphytoplankton growth and microzooplankton grazing rates were determined
fluorometrically at four sites, one in each region, from May 1997 through
September 1998. Community structure within the microphytoplankton was
determined using HPLC analysis. All data were used to determine if the four
regions of Phlips et al. (1995), which were established based on
primarily physical characteristics of the waters within each region, were
applicable to the zooplankton community of Florida Bay. The copepod
community was typically dominated by three genera--Acartia, Oithona,
and Paracalanus--though other genera occasionally constituted >20% of
the copepod stock. The "others" category was typically composed of
chaetognaths, larvaceans, medusae, isopods, flatworms, and polychaetes,
with distributions and abundances varying with no obvious seasonality.
Copepods and their nauplii dominated the net zooplankton numerically and
in terms of biomass and metabolic demands. Seasonal trends were apparent
for most parameters within each group, with maxima occurring most
frequently during the summer or fall and minima in the winter.
Broecker, W.S., C. Langdon, T. Takahasi, and T.-H. Peng. Factors
controlling the rate of CaCO3 precipitation on Great Bahama
Bank. Global Biogeochemical Cycles, 15(3):589-596 (2001).
Measurements by Langdon et al. (2000) in the man-made mesocosm coral
reef at Biosphere 2's ocean reveal a strong dependence of calcification rate
on the degree of supersaturation of CaCO3 in seawater. A similar
trend was previously encountered on the Bahama Banks, where Halimeda
and other calcifiers are likely responsible for aragonite precipitation
(Broecker and Takahashi, 1966). In this paper, we compare these two sets of
results and conclude that the dependence on saturation state is significant
but less strong in the Bahamas. However, it must be kept in mind that to
some extent, the reduction of CaCO3 precipitation on the Bahama
Banks may be due to impact of higher salinity on the growth of the calcifying
algae. However, if, as many sedimentologists are convinced, the precipitation
of CaCO3 on the Bahama Banks is inorganic (Macintyre and Reid, 1992;
Milliman et al., 1993), then the comparison of the Bahamas and
Biosphere 2 results for dependence of calcification rate on saturation state
is telling us something quite different.
Campos, E., A. Busalacchi, S.L. Garzoli, J. Lutjeharms, R. Matano, P.
Nobre, D. Olson, A. Piola, C. Tanajura, and I. Wainer. Important aspects
of the South Atlantic to the understanding of the global climate. In
Observing the Oceans in the 21st Century: A Strategy for Global Ocean
Observations, C.J. Koblinsky and N.R. Smith (eds.). GODAE Project
Office, 19 pp. (2001).
Important aspects of the South Atlantic physical oceanography are discussed,
and an attempt is made to identify key processes and areas which need to be
monitored in order to understand the role of that part of the ocean in the
global climate variability. Given the importance of the South Atlantic, it
becomes crucial that variables such as sea surface temperature, currents, and
surface fluxes be monitored on a continuous basis if one wishes to determine
and predict the relationship between oceanic variability in the South Atlantic
and global or regional climate. Thus, we understand that efforts should be
concentrated in the study of the air-sea-land interactions leading to sea
surface temperature variability, and the processes associated with the
inter-hemispheric exchange of mass and heat by the Atlantic Meridional
Overturning Cell. The knowledge of long-term variations of the Atlantic
thermohaline circulation and how these variations lead to changes in SST
and oceanic heat transports are key issues to be addressed. With regard to
the thermohaline circulation, we identify some key locations where very
important processes occur, and need to be monitored. These are the
Brazil-Malvinas Confluence, the Agulhas Retroflection, the Benguela Current,
and the bifurcation of the South Equatorial Current (SEC). Based on the
topics discussed in this article, a sustainable observational program in
the South Atlantic is proposed, based on a combination of ship-based
hydrographic samplings, moored arrays of current meters and other profiling
instruments, satellite-tracked drifters and ARGO floats, repeat cruises and
SOOP XBT lines, acoustic measurements, surface flux measurements, and remote
sensing. Contribution of the South American oceanographic community would be
of great interest in the monitoring of the Brazil-Malvinas Confluence and
South Equatorial Current Bifurcation regions. Cooperation with the African
community would be desirable for the surveys in the Agulhas Retroflection and
the Benguela Current.
Daly, K.L., W.O. Smith, G.C. Johnson, G.R. DiTullio, D.R. Jones, C.W. Mordy,
R.A. Feely, D.A. Hansell, and J.-Z. Zhang. Hydrography, nutrients, and
carbon pools in the Pacific sector of the Southern Ocean: Implications for
carbon flux. Journal of Geophysical Research, 106(C4):7107-7124 (2001).
We investigated the hydrography, nutrients, and dissolved and particulate
carbon pools in the western Pacific sector of the Antarctic Circumpolar
Current (ACC) during austral summer 1996 to assess the region's role in the
carbon cycle. Low fCO2 values along two transects
indicated that much of the study area was a sink for atmospheric
CO2. The fCO2 values were lowest near the Polar
Front (PF) and the Subtropical Front (STF), concomitant with maxima of
chlorophyll a and particulate and dissolved organic carbon. The
largest biomass accumulations did not occur at fronts, which had high surface
geostrophic velocities (20-51 cm s-1), but in relatively low
velocity regions near fronts or in an eddy. Thus, vertical motion and
horizontal advection associated with fronts may have replenished nutrients
in surface waters but also dispersed phytoplankton. Although surface waters
north of the PF have been characterized as a "high nutrient-low chlorophyll"
region, low silicic acid (Si) concentrations (2-4 µM) may limit
production of large diatoms and, therefore, the potential carbon flux. Low
concentrations (4-10 µM Si) at depths of winter mixing constrain the
level of Si replenishment to surface waters. It has been suggested that an
increase in aeolian iron north of the PF may increase primary productivity
and carbon export. Our results, however, indicate that while diatom growth
and carbon export may be enhanced, the extent ultimately would be limited by
the vertical supply of Si. South of the PF, the primary mechanism by which
carbon is exported to deep water appears to be through diatom flux. We
suggest that north of the PF, particulate and dissolved carbon may be exported
primarily to intermediate depths through subduction and diapycnal mixing
associated with Subantarctic Mode Water and Antarctic Intermediate Water
formation. These physical-biological interactions and Si dynamics should
be included in future biogeochemical models to provide a more accurate
prediction of carbon flux.
Enfield, D.B. Evolution and historical perspective of the 1997-1998 El
Niņo-Southern Oscillation event. Bulletin of Marine Science,
69(1):7-25 (2001).
The ocean thermal history of the 1997-98 El Niņo episode is described in
detail, with emphasis on developments along the equator and eastern
Pacific coastlines. The temporal evolution of the warming and its causes
are traced from the western Pacific, past the Galapagos Islands, and on
to the subpolar gyres off North and South America. Along the equator, the
event was characterized by a subsurface warm anomaly that slowly made its
way from west to east across the Pacific from mid-1996 until early 1997,
whence it triggered the onset of surface anomalies at the eastern
terminus of the equatorial waveguide. The thermocline depression off
Ecuador intensified from mid-1997 through the end of the year,
culminating in a mature phase with maximum sea surface temperature
anomalies (SSTA) around November-December 1997. The event gradually
abated thereafter until the beginning of the subsequent cool phase (La
Niņa) was detected in July 1998. Following their arrivals at the eastern
boundary, equatorial Kelvin waves proceeded poleward into both
hemispheres as coastal trapped waves, carrying the thermocline depression
signal with them along with associated nutrient deficiencies and
ecosystem impacts. The poleward propagation of SSTA was more uniform and
faster south of the equator, reaching south-central Chile with amplitudes
of 2°C or greater. North of the equator the propagation was
discontinuous, with decreased anomalies south of 20°N and a revival
of SSTA in excess of 2°C, north of there, but with considerably
larger time lags than observed off Chile. The possible reasons for these
interhemispheric differences are discussed. The magnitude of the event
is also discussed in an historical context, with emphasis on comparisons
to the El Niņo of 1982-83. Each of the two events, in its own way,
set records. However, the two events are generally comparable in their
magnitudes and the extent of their impacts, while both are top-ranked
events for the period after 1950. In the centennial context, however,
these events are not unprecedented, considering that they were probably
enhanced by strong decadal warming during the 1980s and 1990s. An
attempt is made to assess the accuracy of model forecasts of the
1997-1998 event. Two recent studies are discussed which generally agree
that statistical and dynamical models under-predicted the equatorial
warming prior to its onset and failed to capture the strong, early onset
at all. Predictions of the late-1997 climax, with shorter lead times,
improved once the data showing large mid-1997 anomalies were ingested
into the models. However, the revised predictions were not in time to
guide the successful atmospheric climate outlook for North America,
which was issued in June 1997 on the basis of observed strong anomalies
on the equator.
Enfield, D.B., and A.M. Mestas-Nunez. Interannual to multidecadal
climate variability and its relationship to global sea surface
temperatures. In Interhemispheric Climate Linkages, V. Markgraf
(ed.). Academic Press (ISBN 0124726704), 17-29 (2001).
As a benchmark to help profile paleoclimates across the Americas we
develop an overview of what is known of modern climate variability on a
planetary scale, with emphasis on climate manifestations in the Western
Hemisphere. From instrumental observations taken as early as the mid-19th
century, we look at both atmospheric and oceanic variables and consider
their relationships on timescales ranging from interannual to
multidecadal. We focus on three of the most important climate modes: the
interannual El Niño-Southern Oscillation (ENSO), the interdecadal
Pacific Decadal Oscillation (PDO), and the multidecadal North Atlantic
Oscillation (NAO). The variable of greatest interest is sea surface
temperature (SST) because it is arguably the least understood of the
atmospheric boundary conditions for prehistoric climates and yet one of
the most critical for effecting atmospheric model simulations of those
climates. The analysis begins by computing a global distribution of the
trend in SST, which turns out to be highly non-uniform, with
characteristics that may reflect low-frequency changes in shallow water
mass formation. We then compute a global, canonical mode for ENSO that
preserves the amplitude and phase structures of interannual ENSO
variability worldwide. The ranking of the modal amplitudes of ENSO events
differs from the absolute amplitudes obtained by indexing SST data
directly. This reflects the importance of the (non-ENSO)
decadal-multidecadal climate modes in modifying the intensity of
ENSO-related ocean warmings. Comparing the global mode between the ends
of the 19th and 20th centuries, we see essentially no difference in
amplitudes and frequency of ENSO on the global warming timescale,
although such changes have occurred on shorter, multidecadal timescales.
Upon removal of the global ENSO mode from the data, the residual
variability is subjected to two different analyses that extract very
similar spatio-temporal patterns of SST for the PDO- and NAO-like climate
modes. The climate variations with longer timescales (PDO, NAO) together
account for about the same amount of variance as ENSO, globally, and in
some regions, e.g., the northeastern North Pacific, may rival ENSO
in their climate and marine impacts. The NAO, in particular, involves an
Atlantic-Pacific connection that may arise through fluctuations in the
polar vortex, an aspect which may also characterize previous climates. In
our discussion, we speculate on what might be learned from the
instrumental record regarding possible characteristics of ancient
climates, especially regarding the possibility that ENSO may have been
considerably different or even absent in the mid-Holocene.
Enfield, D.B., and A.M. Mestas-Nunez. The Atlantic multidecadal
oscillation and its relationship to rainfall and river flows in the
continental U.S. Greater Everglades Ecosystem Restoration Science
Conference, Naples, FL, December 11-15, 2000. South Florida Ecosystem
Restoration Task Force and Working Group, 325 (2001).
An Atlantic Multidecadal Oscillation (AMO) has recently been identified that
may have had a large impact on European and American climates in the 19th and
20th centuries and may be driven by the Atlantic thermohaline circulation
(Schlesinger and Ramankutty, 1994; Enfield and Mestas-Nunez, 1999; Kerr,
2000; Delworth and Mann, 2000). As an index of the oceanic expression of
the AMO, we have computed the 10-year running means of North Atlantic SST
anomaly (SSTA) from the Kaplan et al. (1998) SSTA analysis
(1856-1999). In agreement with other studies, we find AMO maxima (positive
SSTA) during 1860-1880 and 1940-1960, and minima during 1905-1925 and
1970-1990, with periods ranging from 65 to 80 years. We find a significant
(95%) correlation of the AMO with monthly precipitation for many of the
climate divisions of the continental U.S. (1895-1992). We use a Monte Carlo
approach with frequency-domain phase randomization of the serially correlated
data to judge the significance. Over much of the Mississippi River Basin the
significant correlations are negative, as is the integrated rainfall over the
basin. Strong negative correlations are also found in the northern Rocky
Mountains. Positive correlations are limited to two small regions:
south-central Florida and in the Pacific Northwest east of the Cascades. At
hydrological checks, we also find a significant negative correlation with
the directly measured Mississippi River outflow, and a significant positive
correlation with the inflow into Lake Okeechobee (south-central Florida). To
diagnose the relationships, we construct composite averages (for recent
contrasting phases of the AMO) of tropospheric NCEP/NCAR reanalysis variables
(1950-present). We also examine the strength of ENSO-rainfall correlations
for both phases of the AMO.
Enfield, D.B., A.M. Mestas-Nunez, and P.J. Trimble. The Atlantic
multidecadal oscillation and its relation to rainfall and river flows in
the continental U.S. Geophysical Research Letters, 28(10):2077-2080
(2001).
North Atlantic sea surface temperatures for 1856-1999 contain a 65-80 year
cycle with a 0.4°C range, referred to as the Atlantic Multidecadal
Oscillation (AMO) by Kerr (2000). AMO warm phases occurred during 1860-1880
and 1940-1960, and cool phases during 1905-1925 and 1970-1990. The signal is
global in scope, with a positively correlated co-oscillation in parts of the
North Pacific, but it is most intense in the North Atlantic and covers the
entire basin there. During AMO warmings, most of the United States sees less
than normal rainfall, including Midwest droughts in the 1930s and 1950s.
Between AMO warm and cool phases, Mississippi River outflow varies by 10%
while the inflow to Lake Okeechobee, Florida varies by 40%. The geographical
pattern of variability is influenced mainly by changes in summer rainfall.
The winter patterns of interannual rainfall variability associated with El
Niņo-Southern Oscillation are also significantly changed between AMO phases.
Feely, R.A., C.L. Sabine, T. Takahashi, and R. Wanninkhof. Uptake and
storage of carbon dioxide in the ocean: The global CO2 survey.
Oceanography, 14(4):18-32 (2001).
No abstract.
Fine, R.A., K.A. Maillet, K.F. Sullivan, and D. Willey. Circulation and
ventilation flux of the Pacific Ocean. Journal of Geophysical
Research, 106(C10):22,159-22,178 (2001).
The flux of water from the mixed layer into the thermocline/intermediate
layers of the Pacific Ocean is quantified using chlorofluorocarbon (CFC)
and hydrographic data. The total ventilation flux of at least 123 Sv for
the South Pacific (SP) only slightly exceeds that of at least 111 Sv for
the North Pacific (NP). Although the overall ventilation flux (to 27.3
sigmatheta) is similar in the NP and SP, the partitioning
amongst the water masses is markedly different. In the NP, the
partitioning is equal between the wind-driven (< 26.5
sigmatheta) and thermohaline (>26.5-27.3
sigmatheta) layers. While in the SP, the ventilation flux of
the thermohaline layers exceeds by nearly 2:1 the wind-driven layers.
The wind-driven subtropical gyre thermocline ventilation flux for the NP
(41 Sv) exceeds the SP (25 Sv), and both agree well with literature
estimates of Sverdrup transports. The ventilated volumes and ages are
related to the wind stress curl and surface buoyancy fluxes. In the
thermocline, ventilation of Shallow Salinity Minimum Water (22 m
yr-1 in the NP, 15 m yr-1 in the SP) and
Subtropical Mode Water is more effective in the NP than in the SP. In
contrast, in the thermohaline layers direct air-sea exchange during
convective formation of Subantarctic Mode and Antarctic Intermediate
Water is more effective in ventilating the SP than processes in the NP.
These same differences are also used to explain the larger volume of the
shadow zone in the NP. In the subpolar regions, the ventilation fluxes
can be used to infer formation rates of 8 Sv for the NP Intermediate
Water and 9 Sv for the Subantarctic Mode Water. Into the tropical
Pacific there is a substantial flux of 35 Sv of extratropical water for
the wind-driven layers and 36 Sv for the thermohaline layers. The
relatively young CFC-derived ages (5-20 years increasing with increasing
density) show that a climate anomaly introduced into the subtropical
thermocline could be transported into the tropics relatively quickly.
Garzoli, S.L. CLIVAR workshop on tropical Atlantic variability.
CLIVAR Exchanges, 6(4):33-35 (2001).
No abstract.
Garzoli, S.L., and R.L. Molinari. Ageostrophic transport in the upper layers
of the tropical Atlantic Ocean. Geophysical Research Letters,
28(24):4619-4622 (2001).
A test of the theoretical Ekman relation in the tropical Atlantic Ocean is
performed by comparing estimated Ekman transport with observations collected
along two transects symmetric about the equator (6°N and 6°S).
Ekman transport is calculated theoretically using ship winds and
climatological data. Total ageostrophic transport is obtained by subtracting
the observed geostrophic transports from the measured total transports using
the data collected along the two transects. Along 6°S, both the zonal
mean ageostrophic transport and its variability with longitude can be
accounted for by the theoretical Ekman transport. Along 6°N, the total
ageostrophic and Ekman transports agree, but significant differences are
found in the cumulative transport curves between the African coast and about
40°W. These departures from theory may be related to the effect of
advective terms in the Ekman relation and/or other ageostrophic motion at the
reference depth for the comparisons.
Goldenberg, S.B., C.W. Landsea, A.M. Mestas-Nunez, and W.M. Gray. The
recent increase in Atlantic hurricane activity: Causes and implications.
Science, 293:474-479 (2001).
The years 1995 to 2000 experienced the highest level of North Atlantic
hurricane activity in the reliable record. Compared with the generally low
activity of the previous 24 years (1971 to 1994), the last six years have
seen a doubling of overall activity for the whole basin, a 2.5-fold increase
in major hurricanes (>50 m/s), and a fivefold increase in hurricanes affecting
the Caribbean. The greater activity is caused by simultaneous increases in
North Atlantic sea-surface temperatures and decreases in vertical wind shear,
both of which are known to favor hurricane formation. Because these changes
exhibit a multidecadal time scale, the present high level of hurricane
activity is likely to persist for an additional 10 to 40 years. The shift
in climate calls for a reevaluation of preparedness and mitigation strategies.
Goni, G.J., and W.E. Johns. A census of North Brazil Current rings
observed from TOPEX/POSEIDON altimetry: 1992-1998. Geophysical Research
Letters, 28(1):1-4 (2001).
Six years of TOPEX/POSEIDON altimeter data are used to investigate the
formation of rings and eddies shed by the North Brazil Current. Upper layer
thickness maps were used to identify 34 of these features formed in the North
Brazil Current retroflection region, an average of more than five rings and
eddies per year. The ensemble of ring trajectories closely parallels the
500 m isobath, and one out of six rings penetrate into the Caribbean Sea
through the southern Lesser Antilles. The rest of the rings and eddies
follow a northern trajectory past Barbados once they reach 58°W. Their
estimated mean translation speed is 14 km/day and their mean length scale is
approximately 100 km. Our results suggest that the formation rate of NBC
rings and eddies is nearly twice that previously thought, and that they may
account for more than one-third of the interhemispheric transport within the
Atlantic meridional overturning cell.
Goni, G.J., and I. Wainer. Brazil Current front dynamics from altimeter
data. Journal of Geophysical Research, 106(C12):31,117-31,128 (2001).
The southwestern Atlantic is characterized by the confluence of the Brazil
and Malvinas Currents forming very strong surface and subsurface fronts which
can be detected from hydrographic and remote sensing procedures. Three data
sets, consisting of TOPEX/Poseidon-derived sea height anomalies and the
climatologically-derived depth of the 10°C isotherm and reduced
gravity, are used within a two-layer dynamical ocean model context to monitor
the Brazil Current front and to investigate its variability during a six-year
period (1993 through 1998). Results reveal that the fronts exhibit motions
that are larger zonally than meridionally, showing strong interannual
variability with annual mean amplitudes that range from 1 to 6 degrees. The
annual and semiannual components account for more than 75% of the variability
of the frontal oscillations. In the annual cycle, the frontal motions appear
to be closely related to fluctuations in the baroclinic transport of the Brazil
Current and are only influenced by the Malvinas Current when the Brazil
Current transport is very small.
Goodwin, K.D., R.K. Varner, P.M. Crill, and R.S. Oremland. Consumption
of tropospheric levels of methyl bromide by C1 bacteria and comparison to
saturation kinetics. Applied and Environmental Microbiology,
67(12):5437-5443 (2001).
Pure cultures of methylotrophs and methanotrophs are known to oxidize methyl
bromide (MeBr); however, their ability to oxidize tropospheric concentrations
(parts per trillion by volume [pptv]) has not been tested. Methylotrophs and
methanotrophs were able to consume MeBr provided at levels that mimicked the
tropospheric mixing ratio of MeBr (12 pptv) at equilibrium with surface waters
(~2 pM). Kinetic investigations using picomolar concentrations of MeBr
in a continuously stirred tank reactor (CSTR) were performed using strain
IMB-1 and Leisingeria methylohalidivorans strain MB2T,
terrestrial and marine methylotrophs capable of halorespiration. First-order
uptake of MeBr with no indication of threshold was observed for both strains.
Strain MB2T displayed saturation kinetics in batch experiments
using micromolar MeBr concentrations, with an apparent
Ks of 2.4 µM MeBr and a Vmax of 1.6
nmol h-1 (106 cells)-1. Apparent
first-order degradation rate constants measured with the CSTR were consistent
with kinetic parameters determined in batch experiments, which used 35- to
1 x 107-fold higher MeBr concentrations. Ruegeria algicola
(a phylogenetic relative of strain MB2T), the common heterotrophs
Escherichia coli and Bacillus pumilus, and a toluene-oxidizer,
Pseudomonas mendocina KR1, were also tested. These bacteria showed no
significant consumption of 12 pptv MeBr; thus, the ability to consume ambient
mixing ratios of MeBr was limited to C1-oxidizing bacteria in
this study. Aerobic C1 bacteria may provide model organisms for
the biological oxidation of tropospheric MeBr in soils and waters.
Hare, J.A., D.E. Hoss, A.B. Powell, M. Konieczna, D.S. Peters, S.R. Cummings,
and R. Robbins. Larval distribution and abundance of the family
Scombridae and Scombrolabracidae in the vicinity of Puerto
Rico and the Virgin Islands. Bulletin of the Sea Fisheries Institute,
2(153):13-29 (2001).
Fishes of the family Scombridae are important recreational and commercial
species throughout the western Central Atlantic Ocean. There remain, however,
many questions regarding the biology of these fishes that are crucial for the
protection of sustainable fisheries. To provide some basic information, this
study examines larval distribution and abundance in the vicinity of Puerto
Rico and the Virgin Islands, an area of sparse information compared to the
Gulf of Mexico and the southeastern United States coast. Seasonal, horizontal,
and vertical distributions were examined and species-specifics patterns were
described. Thunnus atlanticus and Katsuwonus pelamis were
abundant during a November/December cruise, while Thunnus atlanticus,
Katsuwonus pelamis and Euthynnus alletteratus were abundant
during a May cruise. Regional differences were found in the distribution of
some species and species specific vertical distributions were identified.
Thunnus atlanticus was more surface oriented than Euthynnus
alletteratus and Katsuwonus pelamis. These results are discussed
relative to prior work in the region.
Hendee, J.C., E. Mueller, C. Humphrey, and T. Moore. A data-driven expert
system for producing coral bleaching alerts at Sombrero Reef in the Florida
Keys. Bulletin of Marine Science, 69(2):673-684 (2001).
A computer expert system shell was employed to provide interpretations of
near real-time acquired combinations of meteorological and oceanographic
parameters from a SEAKEYS (Sustained Ecological Research Related to Management
of the Florida Keys Seascape) station at Sombrero Reef. When environmental
conditions were conducive to coral bleaching, according to different models,
alerts were automatically posted to the World-Wide Web and emailed to
researchers so they could verify and study bleaching events as they might
happen. The models were refined using feedback from field data on bleaching
recorded after alerts from the expert system. The expert system was
programmed to produce alerts when sea temperatures over 30°C occurred,
or when temperatures of 30°C occurred concomitant with low winds.
Alerts were produced in June 1998 when these conditions were met, but
bleaching did not occur. Reconfiguration of the system, which included a
point system for three models (high sea temperature only, high sea temperature
plus low winds, high sea temperature plus low winds plus low tide), resulted
in the transmittal of alerts which coincided with bleaching during early
August 1998. Bleaching occurred after sea temperature reached an average of
31.5°C over a period of three days, with excursions over 31.8°C
occurring over 15 times during those three days. High sea temperatures, low
wind speeds, and a very low tide occurred coincident to the time of
bleaching, but it was not possible to tell if these were factors acting
synergistically.
Hood, E.M., R.H. Wanninkhof, and L. Merlivat. Short time scale variations of
fCO2 in a North Atlantic warm-core eddy: Results from the
GASEX-98 carbon interface ocean atmosphere (CARIOCA) buoy data. Journal
of Geophysical Research, 106(C2):2561-2572 (2001).
During a Lagrangian deliberate tracer study in the North Atlantic, the
1998 Gas Exchange Experiment (GASEX-98), hourly measurements of wind speed,
sea surface temperature, fCO2, and fluorescence were made from two
carbon interface ocean atmosphere (CARIOCA) drifting buoys in a warm-core
eddy near 46°N and 21.5°W over a period of approximately 20 days.
Shipboard measurements of fCO2 near the buoys were used to verify
the buoy operation, calibrate the buoy measurements, and assess the
performance of the fCO2 sensor. The strong air-sea
fCO2 gradient in the eddy and intense atmospheric forcing
during the experiment provided ideal conditions for demonstrating the
potential of autonomous drift buoy measurements for studies of surface
ocean biogeochemistry, where changes of fCO2 were rapid and
large. During the experiment, a storm occurred with wind speeds reaching
as high as 16-17 m s-1, leading to a sharp decrease in sea
surface temperature and an increase in fCO2 of ~30 µatm.
The magnitude of this sudden change in fCO2 is equal to
approximately half of the annual range of fCO2 in this area.
The air-sea flux estimate for the ~20 day experiment using the Wanninkhof
(1992) gas transfer velocity formulation was -0.012 mol m-2
d-1 and using the Liss and Merlivat (1986) formulation was
-0.007 mol m-2 d-1. The storm event, lasting three
to four days, accounted for ~38% of the flux over this period.
Approximately 16 hours after the onset of the storm, there was an
increase in surface fluorescence coincident with the initial increase in
fCO2. Nitrate measurements made from the ship in the eddy
show a sharp peak in surface concentrations ~24 hours after the increase
in winds and ~6-8 hours after the increase in surface fluorescence.
After the upwelling of the NO3 the fluorescence increases more
sharply while the fCO2 decreases, consistent with biological
productivity. The surface fluorescence measurements remain higher than
prestorm conditions for ~5 days after the NO3 has disappeared.
Humphrey, J.C., J. Absten, S.L. Vargo, J.C. Ogden, J.C. Hendee, T.A. Nelsen,
D. Danaher, C.L. Jeffris, and D. Burwell. SEAKEYS: Florida Keys monitoring
initiative. Proceedings, 2001 Florida Bay and Adjacent Marine Systems
Science Conference, Key Largo, FL, April 23-26, 2001. University of
Florida, 87-88 (2001).
The Sustained Ecological Research Related to the Management of the Florida
Keys Seascape (SEAKEYS) program was organized in 1991 by the Florida
Institute of Oceanography with initial funding from the John D. and Catherine
T. MacArthur Foundation, and has been maintained through continuing support
provided by the South Florida Ecosystem Restoration, Prediction and
Monitoring program, administered by the National Oceanic and Atmospheric
Administration (NOAA). The SEAKEYS environmental monitoring program was
designed to provide data for a long-term database of meteorological and
oceanographic data from the Florida Straits and Florida Bay. The SEAKEYS
network provides wind speed, wind gust, air temperature, barometric pressure,
sea temperature, and salinity for all stations; and tide level,
precipitation, photosynthetically active radiation, fluorometry, and
transmissometry for selected stations. These data are transmitted hourly to
a GOES satellite, and from there are downloaded for data and information
management purposes. SEAKEYS data have been used to characterize the
dynamics of several hurricanes since 1992, and have been of great benefit to
hurricane forecasters at the National Weather Service and at AOML's Hurricane
Research Division in Miami, Florida. Daily data are posted to NOAA's Coral
Health and Monitoring Program Web site (http://www.coral.noaa.gov), while
historical data are available at http://www.neptune.noaa.gov. These data
have also allowed researchers to correlate meteorological and hydrographic
dynamics, e.g., El Niņo/La Niņa conditions, with environmental
changes in Florida Bay and the Florida Keys National Marine Sanctuary.
Johns, E., R.H. Smith, W.D. Wilson, T.N. Lee, and E. Williams. Influence
of hurricanes, tropical storms, and cold fronts on south Florida coastal
waters. Proceedings, 2001 Florida Bay and Adjacent Marine Systems Science
Conference, Key Largo, FL, April 23-26, 2001. University of Florida,
14-15 (2001).
The south Florida climate is characterized by a tropical dry season/wet
season pattern, with a wet season typically beginning in June with the onset
of summer rainy conditions, and much drier conditions from November to April.
The regional climate is also affected in late summer by the passage of
tropical cyclones, and in the winter by the passage of cold fronts. These
extreme weather events are evident not only in the standard meteorological
measurements such as barometric pressure, wind speed and direction, air
temperature, and precipitation, but are also manifested in such oceanographic
variables as sea surface temperature, sea surface height, current speed and
direction, sea surface salinity, and water column turbidity. As part of a
joint University of Miami/NOAA project entitled Circulation and exchange of
Florida Bay and connecting waters of the Gulf of Mexico and the Florida Keys,
a variety of observations have been collected beginning in December 1995.
These measurements, which were expanded in scope beginning in September 1997,
now include bimonthly interdisciplinary shipboard surveys of salinity,
temperature, fluorescence, and nutrients, as well as satellite-tracked
surface drifters and moored arrays of currents, temperature, and
conductivity. The study area extends from Florida Bay north to Naples,
Florida, southwest to the Dry Tortugas, east to Key West and then northeast
to Miami, Florida. In addition to the bimonthly surveys, observations are
obtained monthly within Florida Bay using a shallow draft catamaran equipped
with a continuous flow-through thermosalinograph system. Since 1995, a number
of tropical cyclones have come close enough to affect south Florida
environmental conditions by means of extreme wind, rain, or both. Although
none of these recent tropical cyclones have come close to matching the
historically most severe events of the region (e.g., the well-known
Labor Day hurricane in 1935, Hurricane Donna in 1960, and Hurricane Andrew in
1992), they still influenced the regional meteorological and oceanographic
climate.
Johns, E., P.B. Ortner, R.H. Smith, W.D. Wilson, T.N. Lee, and E.
Williams. Salinity variability in Florida Bay from monthly high resolution
surveys. Proceedings, 2001 Florida Bay and Adjacent Marine Systems Science
Conference, Key Largo, FL, April 23-26, 2001. University of Florida,
16-17 (2001).
As part of NOAA's South Florida Ecosystem Restoration, Prediction and Modeling
(SFERPM) program, a time series of high resolution salinity maps of Florida
Bay has been obtained using a shallow draft catamaran equipped with a
continuous flow-through thermosalinograph system. Each survey is completed
within two consecutive days. These maps, produced at an approximately monthly
interval from March 1997 to the present, cover the three major subdivisions of
Florida Bay, i.e., the northeast Bay, the central Bay, and the western
Bay. The three Bay regions respond differently to meteorological and other
forcing mechanisms due to their differing degrees of isolation from other
coastal waters. For example, the northeast Bay is relatively isolated by the
geometry of its coastlines and the shallow mud banks which separate it from
the central Bay. The northeast Bay is subject to time-varying inputs of fresh
water from the rivers and canals of the Taylor Slough and, as a result, has an
extremely large salinity variability related to seasonal and interannual
precipitation patterns, as well as to water management practices. On the
other hand, the central region of Florida Bay, although also fairly isolated
in terms of its topography (except at its southern border where exchange of
water with the Atlantic occurs through a few narrow tidal channels between
the Florida Keys), has few direct sources of fresh water. Thus, the salinity
of the central Bay exhibits a different pattern of variability, responding to
the changing balance between local evaporation and precipitation which
regularly produces periods of hypersalinity interspersed with much lower
salinity periods on a timescale of several months or longer. The persistence
of these high or low salinity periods is indicative of long residence times
for these basins. Western Florida Bay, on the other hand, has an open western
boundary and thus is subject to open exchange of water with the eastern Gulf
of Mexico and the southwest Florida shelf. The numerous rivers of the
southwest Florida coast, such as the Shark, Broad, and Lostmans Rivers,
contribute a time-varying source of fresh water from the Shark River Slough
area of the Everglades which at times can flow around Cape Sable and interact
with western Florida Bay, providing another source of salinity variability
there. Due to the more open exchange with the surrounding Gulf of Mexico and
southwest Florida shelf waters, the salinity of the western part of the Bay
does not exhibit the long residence times of the northeast and central Bay,
but instead can change rather rapidly when influenced by tropical storms, the
passage of cold fronts, and other extreme forcing events. Determination of
the rates and pathways of exchange between the interior basins of Florida Bay
and with the southwest Florida shelf is a critical need for predicting the
effects of modifying the fresh water supply to the Everglades as part of the
Everglades restoration effort. At present, it is not understood how the
proposed changes in water delivery, with increased fresh water flows to the
Shark River and Taylor Slough, will affect salinity variability within Florida
Bay. However, it is generally agreed that the large seasonal and longer
period variations of salinity within the Bay have significant impacts on the
sea grass and plankton communities within the Bay, and possibly also with
adjacent marine ecosystems of the southwest Florida shelf and the Florida
Keys National Marine Sanctuary due to transport processes linking the
regions.
Kaplan, J., and M. DeMaria. On the decay of tropical winds after landfall in
the New England area. Journal of Applied Meteorology,
40(2):280-286 (2001).
A version of the Kaplan and DeMaria empirical model for predicting the decay
of tropical cyclone 1-min maximum sustained surface winds after landfall is
developed for the New England region. The original model was developed from
the National Hurricane Center (NHC) best-track wind estimates for storms that
made landfall in the United States south of 37°N from 1967 to 1993. In
this note, a similar model is developed for U.S. storms north of 37°N,
which primarily made landfall in New York or Rhode Island and then moved
across New England. Because of the less frequent occurrence of New England
tropical cyclones, it was necessary to include cases back to 1938 to obtain
a reasonable sample size. In addition, because of the faster translational
speed and the fairly rapid extratropical transition of the higher-latitude
cases, it was necessary to estimate the wind speeds at 2-h intervals after
landfall, rather than every 6 h, as in the NHC best track. For the model
development, the estimates of the maximum sustained surface winds of nine
landfalling storms (seven hurricanes and two tropical storms) at 2-h
intervals were determined by an analysis of all available surface data.
The wind observations were adjusted to account for variations in anemometer
heights, averaging times, and exposures. Results show that the winds in the
northern model decayed more (less) rapidly than those of the southern model,
when the winds just after landfall are greater (less) than 33 knots. It is
hypothesized that this faster rate of decay is due to the higher terrain near
the coast for the northern sample and to the more hostile environmental
conditions (e.g., higher vertical wind shear). The slower decay rate
when the winds fall below 33 knots in the northern model might be due to the
availability of a baroclinic energy source as the storms undergo extratropical
transition.
Katsaros, K.B. Basin boundaries. In Wind Stress Over the Ocean,
I.S.F. Jones and Y. Toba (eds.). Cambridge University Press, 270-275 (2001).
No abstract.
Katsaros, K.B. Evaporation and humidity. In Encyclopedia of Ocean
Sciences, J.H. Steele, S.A. Thorpe, and K.K. Turekian (eds.). Academic
Press, London, 870-877 (2001).
No abstract.
Katsaros, K.B. Sensors for mean meteorology. In Encyclopedia of Ocean
Sciences, J.H. Steele, S.A. Thorpe, and K.K. Turekian (eds.). Academic
Press, London, 2744-2751 (2001).
No abstract.
Katsaros, K.B., E.B. Forde, P. Chang, W.T. Liu. QuikSCAT facilitates
early identification of tropical depressions in 1999 hurricane season.
Geophysical Research Letters, 28(6):1043-1046 (2001).
Far from land and surface ship observations, most tropical depressions are
identified by examining images from geostationary satellites for the presence
of rotation of the convective cloud masses. During the 1999 hurricane season,
surface wind maps obtained by the SeaWinds scatterometer for the tropical
Atlantic and Caribbean Sea were examined to test the hypotheses that tropical
depressions (TDs) could be observed with this satellite sensor, before
identification by the traditional means. SeaWinds was able to detect the
presence of tropical depressions by early observations of a closed circulation
in the surface winds. The satellite's unprecedented large swath width of
1800 km allows twice a day observation of most of the tropical oceans.
Katzberg, S.J., R.A. Walker, J.H. Roles, T. Lynch, and P.G. Black. First
GPS signals reflected from the interior of a tropical storm: Preliminary
reults from Hurricane Michael. Geophysical Research Letters,
28(10):1981-1984 (2001).
Using GPS signals reflected from the ocean surface is developing into a
simple technique for measuring sea-state and inferring surface wind speeds.
Theoretical models have been developed which are considered valid to
approximately 24 m/s. The GPS reflection technique has an obvious extension
to extremely high sea states, cyclones, and extra-tropical storms. In October
2000, a GPS system mounted in a NOAA hurricane hunter research aircraft was
flown into Hurricane Michael off the South Carolina coast. The first
acquisition of GPS signals reflected from the sea surface inside tropical
cyclones was accomplished. This paper presents some examples of the data
sets, as well as early wind speed retrieval results using direct extensions
of current models. Data from the GPS wind speed retrievals, as well as from
direct aircraft measurements, are compared and discussed.
Knaff, J.A., and C.W. Landsea. Application of the El Niņo-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 10(2):31-34 (2001).
No abstract.
Knaff, J.A., and C.W. Landsea. Application of the El Niņo-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 10(3):40-42 (2001).
No abstract.
Kollias, P., B.A. Albrecht, and F.D. Marks. Raindrop sorting induced by
vertical drafts in convective clouds. Geophysical Research Letters,
28(14):2787-2790 (2001).
Evidence of raindrop sorting by a convective updraft is presented. Using a
vertically pointing 94-GHz Doppler radar (lambda = 3.2 mm) and capitalizing
on the resonant nature of the backscattering cross-section as a function of
the raindrop size (Mie scattering), the vertical air motions to an accuracy
of 0.1 m s-1, and the shape of the raindrop size distribution are
retrieved from the Doppler spectra. The interaction of vertical drafts and
raindrops is documented for the first time by high resolution radar data. The
updraft structure clearly causes horizontal and vertical sorting of the
raindrops. In the updraft core, small raindrops (D < 1.7 mm) that have
terminal velocities less than the updraft velocities (6-7 m s-1)
and a clear absence of drops > 3 mm are observed. Towards the updraft
periphery, a gradual increase in the raindrop sizes is documented where large
raindrops (D > 3 mm) are observed. The observations demonstrate the
importance of updrafts in distributing the raindrops in space.
Landsea, C.W. Comment on "Changes in the rates of North Atlantic major
hurricane activity during the 20th century." Geophysical Research
Letters, 28(14):2871-2872 (2001).
No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niņo-Southern
Oscillation CLImatology PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 10(1):31-33 (2001).
No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niņo-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 10(4):41-43 (2001).
No abstract.
Lee, T.N., E. Williams, E. Johns, W.D. Wilson, and N.P. Smith. Transport
processes linking south Florida coastal ecosystems. In The Everglades,
Florida Bay, and Coral Reefs of the Florida Keys: An Ecosystem
Sourcebook, K.G. Porter and J.W. Porter (eds.). CRC Press (ISBN
0849320267), 309-342 (2001).
No abstract.
Liu, W.T., and K.B. Katsaros. Air-sea fluxes from satellite data. In
Ocean Circulation and Climate: Observing and Modeling the Global
Ocean, G. Siedler, J. Church, and J. Gould (eds.). Academic Press,
173-180 (2001).
No abstract.
Macdonald, A.M., M.O. Baringer, and A. Ganachaud. Heat transport and
climate. In Encyclopedia of Ocean Sciences, J.H. Steele, S.A. Thorpe,
and K.K. Turekian (eds), London, Academic Press, Vol. 2, 1195-1206 (2001).
No abstract.
Marks, F.D. Quantitative precipitation forecasting in hurricanes: Issues and
opportunities. Preprints, Symposium on Precipitation Extremes: Prediction,
Impacts, and Responses, Albuquerque, NM, January 14-19, 2001. American
Meteorological Society, Boston, 293-296 (2001).
No abstract.
Mayer, D.A., R.L. Molinari, M.O. Baringer, and G.J. Goni. Transition regions
and their role in the relationship between sea surface height and subsurface
temperature structure in the Atlantic Ocean. Geophysical Research
Letters, 28(20):3943-3946 (2001).
Expendable bathythermograph (XBT) profiles and TOPEX/Poseidon altimeter data
(T/P) are compared for the years 1993 through 1997 to determine how much can
be understood about water column variability from XBTs given only sea height
anomalies (SHA) from T/P. Our focus is on the annual cycle along two well
sampled XBT sections in the Atlantic Ocean from 10°S to 40°N.
Regions of transition are identified that separate the mid-latitudes where
surface buoyancy fluxes dominate the forcing of sea level, from those in the
equatorial region where thermocline effects dominate. Zones of transition
occur in the vicinity of troughs where small fluctuations in SHA belie the
true nature of water column variability. Here, surface and thermocline
variability tend to cancel each other. Thus, the character of SHA in
transition regions emphasizes how important direct observations can be in
interpreting satellite altimetric observations correctly when both surface
and thermocline variability are important but are compensating in nature.
McGillis, W.R., J.B. Edson, J.D. Ware, J.W.H. Dacey, J.E. Hare, C.W.
Fairall, and R.H. Wanninkhof. Carbon dioxide flux techniques performed
during GasEx-98. Marine Chemistry, 75(4):267-280 (2001).
A comprehensive study of air-sea interactions focused on improving the
quantification of CO2 fluxes and gas transfer velocities was
performed within a large open ocean CO2 sink region in the North
Atlantic. This study, GasEx-98, included shipboard measurements of direct
covariance CO2 fluxes, atmospheric CO2 profiles,
atmospheric DMS profiles, water column mass balances of CO2, and
measurements of deliberate SF6-3He tracers, along with
air-sea momentum, heat, and water vapor fluxes. The large air-sea differences
in partial pressure of CO2 caused by a springtime algal bloom
provided high signals for accurate CO2 flux measurements.
Measurements were performed over a wind speed range of 1-16 m
s-1 during the three-week process study. This first comparison
between the novel air-side and more conventional water column measurements of
air-sea gas transfer show a general agreement between independent air-sea gas
flux techniques. These new advances in open ocean air-sea gas flux
measurements demonstrate the progress in the ability to quantify air-sea
CO2 fluxes on short time scales. This capability will help improve
the understanding of processes controlling the air-sea fluxes which, in turn,
will improve our ability to make regional and global
CO2 flux estimates.
Mestas-Nunez, A.M., and D.B. Enfield. Eastern equatorial Pacific SST
variability: ENSO and non-ENSO components and their climatic associations.
Journal of Climate, 14(3):391-402 (2001).
Using an updated Kaplan et al. global SST anomaly (SSTA) dataset
(1870-1999), we construct a canonical representation of El Niņo-Southern
Oscillation (ENSO). When this canonical ENSO is subtracted from the data,
we are left with a residual (non-ENSO) dataset for SSTA that includes
inter-seasonal to multi-decadal variability. Over the eastern equatorial
Pacific (NINO3), the canonical ENSO accounts for about 79% of the total
SSTA variability, while the residual, dominated by decadal time scales,
accounts for the rest. In particular, about 40-50% of the amplitudes of
the strong 1982-1983 and 1997-1998 El Niņo events were accounted for by the
residual variability. The non-ENSO variability is characterized by the
known shift from cold to warm in the eastern tropical Pacific in the mid
to late 1970s, as well as by a non-stationary interannual variance
increase during the 1980s and 1990s. Composite maps of surface (SST, sea
level pressure, and winds) and tropospheric (divergent winds, velocity
potential, and vertical velocity) variables are used to compare the spatial
patterns characterizing the canonical ENSO and the residual components of the
NINO3 variability. We find that the residual composites only share large
amplitude fluctuations of SST anomalies in the equatorial Pacific east of
the dateline. When these composites are separated into decadal and
interannual components, the decadal part resembles closely the structure
of the Pacific Decadal Oscillation (PDO). The major patterns of
tropospheric variability associated with the ENSO and decadal non-ENSO
components are quite different. At low latitudes, they imply nearly
opposite impacts on far-field regional climates, based on their
respective warming (or cooling) phases within the NINO3 region. This
unexpected result for low latitude climate associations runs contrary to
the naive expectation (recently shown to be true for North America) that
a decadally warm tropical east Pacific will reinforce the climate effects
associated with ENSO alone. This indicates that in the tropics climate
outlooks may be more accurate if based on separately analyzed
relationships between these SSTA components and their associated climate
fluctuations.
Mestas-Nunez, A.M., D.B. Chelton, and D.B. Enfield. North Pacific
circulation variability from TOPEX/POSEIDON sea level observations.
Proceedings, 5th Pacific Ocean Remote Sensing Conference (PORSEC),
Goa, India, December 5-8, 2000. National Institute of Oceanography,
1:263-267 (2001).
We analyze seven years (October 1992-October 1999) of sea level observations
from the TOPEX/POSEIDON (T/P) satellite altimeter data to investigate the
large-scale ocean circulation variability of the North Pacific from seasonal
to interannual time scales. We focus in the mid-latitude western regions and
use the T/P observations to estimate the barotropic volume transport
variability of the Kuroshio, Oyashio, and Kuroshio Extension currents. We
base our transport variability estimates on altimetric sea level differences,
and our results agree well with simple wind-driven Sverdrup theory and with
a global numerical ocean model simulation.
Michaels, M., M. Shepard, S.D. Aberson, H.A. Friedman, and K. Murphy.
Survey results of Society membership: The face of our profession at the
threshold of the new millennium. Bulletin of the American Meteorological
Society, 82(7):1331-1352 (2001).
In the spring of 1999, the American Meteorological Society surveyed its
membership in order to update demographic information on the Society and to
gain a more detailed perspective on the workplace. The survey was sent out
with the dues statement and was solicited on a separate form returned
independently to protect privacy and maintain anonymity. The responses were
captured in a newly employed, machine-readable format to provide an ease of
statistical analysis and data compilation not available in prior survey
analysis. This data collection and subsequent demographic analysis represents
the first attempt to update information regarding the membership since the
1993 survey results were published by Zevin and Seitter. The format of the
1999 survey was designed to logically follow and expand upon the historical
data of the membership collected at varying intervals since 1975. The 1999
survey was broken into six parts. The sections on demographics, education,
and current employment closely followed the previous surveys from 1993 and
1990 to facilitate direct comparisons between historical datasets whenever
possible. The last three sections were reworked to elicit more declarative
responses regarding personal circumstances, workplace circumstances, and
additional issues concerning career choice and AMS membership, respectively.
An additional space was provided for narrative comments regarding
opportunities for women and minorities in the AMS-related sciences. Some
10,000 members were sent the 1999 dues statement and enclosed survey
questionnaire. A total of 4,669 members responded. The following is a
detailed analysis of the data collected from the 1999 membership survey.
Millero, F.J., W.T. Hiscock, F. Huang, M. Roche, and J.-Z. Zhang. Seasonal
variation of the carbonate system in Florida Bay. Bulletin of Marine
Science, 68(1):101-123 (2001).
The carbonate system has been studied in the Florida Bay from 1997 to 2000.
Measurements of pH, total alkalinity (TA), and total inorganic carbon dioxide
(TCO2) were made from 20 stations in the Bay and used to calculate
the partial pressure of carbon dioxide (pCO2) and the saturation
states of aragonite (OMEGAArg) and calcite (OMEGACal).
The results were found to correlate with the salinity. The pH was low and
the pCO2 was high for the freshwater input from the mangrove
fringe due to the photochemical and biological oxidation of organic material.
The TA and TCO2 for the freshwater input are higher than seawater
due to the low values of pH and OMEGA. The pH was high and the
pCO2 was low in November in regions where the chlorophyll is high
due to biological production. During the summer when the salinity is the
highest, the normalized values of TA and TCO2 were lower than
average seawater, due to the inorganic precipitation of CaCO3
caused by the resuspension of sediments or the biological loss by macroalgae.
A transect across the mangrove fringe near the outflow of Taylor Slough shows
that PO4 and TA increases as the freshwater enters the Bay. This
is thought to be due to the dissolution of CaCO3 in the low pH
waters from the bacterial and photo oxidation of plant material.
Millero, F.J., F. Huang, X. Zhu, X. Liu, and J.-Z. Zhang. Adsorption and
desorption of phosphate on the calcite and aragonite in seawater.
Aquatic Geochemistry, 7(1):33-56 (2001).
The adsorption and desorption of phosphate on calcite and aragonite were
investigated as a function of temperature (5-45°C) and salinity
(0-40) in seawater pre-equilibrated with CaCO3. An increase in
temperature increased the equilibrium adsorption; whereas an increase in
salinity decreased the adsorption. Adsorption measurements made in NaCl
were lower than the results in seawater. The higher values in seawater
were due to the presence of Mg2+ and Ca2+ ions. The
increase was five times greater for Ca2+ than
Mg2+. The effects of Ca2+ and Mg2+ are
diminished with the addition of SO42-, apparently
due to the formation of MgSO4 and CaSO4 complexes
in solution and/or SO42- adsorption on the surface
of CaCO3. The adsorbed Ca2+ and Mg2+ on
CaCO3 (at carbonate sites) may act as bridges to
PO43- ions. The bridging effect of Ca2+
is greater than Mg2+, apparently due to the stronger
interactions of Ca2+ with PO43-. The
apparent effect of salinity on the adsorption of PO4 was
largely due to changes in the concentration of
HCO3- in the solutions. An increase in the
concentration of HCO3- caused the adsorption of
phosphate to decrease, especially at low salinities. The adsorption at
the same level of HCO3- (2 mM) was nearly
independent of salinity. All of the adsorption measurements were modeled
empirically using a Langmuir-type adsorption isotherm
[[PO4]ad = Km Cm
[PO4]T /(1 + Km
[PO4]T)], where [PO4]ad and
[PO4]T are the adsorbed and total dissolved
phosphate concentrations, respectively. The values of Cm (the
maximum monolayer adsorption capacity, mol/g) and Km (the
adsorption equilibrium constant, g/(mol)) over the entire temperature (t,
°C) and salinity (S) range were fitted to [Cm = 17.067 +
0.1707t - 0.4693S + 0.0082S2 (sigma = 0.7)] [ln Km
= -2.412 + 0.0165t - 0.0004St - 0.0008S2 (sigma = 0.1)].
These empirical equations reproduce all of our measurements of
[PO4]ad up to 14 µmol/g and within ą0.7
µmol/g. The kinetic data showed that the phosphate uptake on
carbonate minerals appears to be a multi-step process. Both the
adsorption and desorption were quite fast in the first stage (less than
30 min) followed by a much slower process (lasting more than one week).
Our results indicate that within 24 hours aragonite has a higher sorption
capacity than calcite. The differences between calcite and aragonite
become smaller with time. Consequently, the mineral composition of the
sediments may affect the short-term phosphate adsorption and desorption
on calcium carbonate. Up to 80% of the adsorbed phosphate is released
from calcium carbonate over one day. The amount of PO4 left on
the CaCO3 is close to the equilibrium adsorption. The release
of PO4 from calcite is faster than from aragonite.
Measurements with Florida Bay sediments produced results between those
for calcite and aragonite. Our results indicate that the calcium
carbonate can be both a sink and source of phosphate in natural waters.
Morisseau-Leroy, N., M.K. Solomon, and G.P. Momplaisir. Oracle 9i
SQLI Programming. McGraw-Hill (ISBN 0072190930), 687 pp. (2001).
No abstract.
Nelsen, T.A., G. Garte, C. Featherstone, H.R. Wanless, J.H. Trefry, W.-J.
Kang, S. Metz, C. Alvarez-Zarikian, T. Hood, P. Swart, G. Ellis, P.
Blackwelder, L. Tedesco, C. Slouch, J.F. Pachut, and M. O'Neal. Linkages
between the south Florida peninsula and coastal zone: A sediment-based
history of natural and anthropogenic influences. In The Everglades,
Florida Bay, and Coral Reefs of the Florida Keys: An Ecosystem
Sourcebook, K.G. Porter and J.W. Porter (eds.). CRC Press (ISBN
0849320267), 415-449 (2001).
No abstract.
Ochoa, J., J. Sheinbaum, A. Badan, J. Candela, and W.D. Wilson. Geostrophy
via potential vorticity inversion in the Yucatan Channel. Journal of
Marine Research, 59(5):725-747 (2001).
It has become common practice to measure ocean current velocities together
with the hydrography by lowering an ADCP on typical CTD casts. The velocities
and densities thus observed are considered to consist mostly of a background
contribution in geostrophic balance, plus internal waves and tides. A method
to infer the geostrophic component by inverting the linearized potential
vorticity (PV) provides plausible geostrophic density and
velocity distributions. The method extracts the geostrophic balance closest
to the measurements by minimizing the energy involved in the difference,
supposed to consist of PV-free anomalies. The boundary
conditions and the retention of PV by the geostrophic
estimates follow directly from the optimization, which is based on simple
linear dynamics and avoids both the use of the thermal wind equation on the
measured density, and the classical problem of a reference velocity. By
construction, the transport in geostrophic balance equals the measured
one. Tides are the largest source of error in the calculation. The method
is applied to six ADCP/CTD surveys made across the Yucatan Channel in the
springs of 1997 and 1998 and in the winter of 1998-1999. Although the time
interval between sections is sometimes close to one inertial period, large
variations on the order of 10% are found from one section to the next.
Transports range from 20 to 31 Sv with a net average close to 25 Sv,
consisting of 33 Sv of inflow into the Gulf of Mexico and 8 Sv of outflow
into the Caribbean Sea. The highest velocities are 2.0 m sec-1
into the Gulf of Mexico near the surface on the western side of the channel,
decreasing to 0.1 m sec-1 by 400 to 500 m depth. Beneath the
core of the Yucatan Current a countercurrent, with speeds close to 0.2 m
sec-1 and an average transport of 2 Sv, hugs the slopes of the
channel from 500 to 1500 m depth. Our data show an additional 6 Sv of return
flow within the same depth range over the abrupt slope near Cuba, which
is likely to be the recirculating fraction of the Yucatan Current deep
extension, unable to outflow through the Florida Straits. The most
significant southerly flows do not occur in the deepest portion of the
channel, but at depths around 1000 m.
Ooyama, K.V. A dynamic and thermodynamic foundation for modeling the
moist atmosphere with parameterized microphyics. Journal of the
Atmospheric Sciences, 58(15):2073-2102 (2001).
Moist convection is an exquisite yet powerful participant in the creation of
weather on our planet. To facilitate numerical modeling of weather systems in
a moist atmosphere, a direct and consistent application of dynamic and
thermodynamic principles, in conjunction with parameterized microphysics, is
proposed. An earlier formulation of reversible thermodynamics, in terms of the
mass of air and water substance and the total entropy, is now extended to
include the irreversible process of precipitation through parameterized
microphysics. The dynamic equations are also formulated to account
consistently for the mass and momentum of precipitation. The theoretical
proposal is tested with a two-dimensional model that utilizes a versatile and
accurate spectral method based on a cubic-spline representation of the spatial
fields. In order to allow a wide range of scale interactions, the model
is configured on multiply-nested domains of outwardly decreasing resolution,
with noise-free, two-way interfaces. The semi-implicit method provides
efficient time integration for the nested spectral model. The tests performed
are the simulation of the growth of single-cell clouds and also the generation
of self-sustaining multicell squall lines, and the effects of various
resolutions on the simulations are examined. The results favorably compare
with similar results found in the literature, but also offer new insights
into the interplay between dynamics and precipitation.
Ortner, P.B., L.C. Hill, M.J. Dagg, J. Rabelais, and G.
Thayer. Mesozooplankton abundance variability within Florida Bay
(1994-2000). Proceedings, 2001 Florida Bay and Adjacent Marine Systems
Science Conference, Key Largo, FL, April 23-26, 2001. University of
Florida, 195-196 (2001).
Since 1994, NOAA's South Florida Ecosystem Restoration Prediction and
Modeling (SFERPM) program has supported regular monitoring of plankton
populations in Florida Bay and adjacent coastal waters along the west
Florida shelf and seaward of the Florida Keys. One reason is that the
zooplankton of Florida Bay had received comparatively little attention prior
to this work with not a single published report quantitatively characterizing
the resident population. Another impetus for doing so was the relationship
between zooplankton grazing and phytoplankton blooms. However, bloom
incidence might be but one aspect of a more general phenomenon, ecosystem
shift, and habitat change. A change of state in the Bay ecosystem could have
enormous consequence to the commercially and recreationally significant
living resources to which the Bay represents a nursery ground and was,
therefore, a particularly important issue to NOAA. Initial results supported
this notion. However, as additional data have accumulated, we now have
little doubt that these initial hypotheses were over simplified. The
ecosystem in Florida Bay does not appear to be undergoing a monotonic change
to a more pelagic state. In this respect, the results appear consistent with
the SERC surveys indicating that over the same time period plankton blooms
have, in general, not systematically increased throughout Florida Bay.
By coincidence, we may have initiated our study close to the apex of
phytoplankton bloom intensity. Based on enumerations from 64 µm net
tows, the abundance of copepods and other holoplanktonic macroplankton
was moderate in the fall of 1994 through mid-winter 1995 but declined
markedly thereafter to exceedingly low levels until ca. spring 1996 when
it returned to similar levels. Thereafter to the present, it has increased
markedly. Taxa vary but values more than five times higher than those
present in 1994 have become common. The increase has occurred without any
apparent increase in their apparent food source, the phytoplankton. This is
not surprising, however. In shallow subtropical estuaries such as Florida
Bay, a substantial fraction of the trophic base supporting zooplankton
populations may be derived from primary production by seagrass and benthic
algae rather than phytoplankton, vitiating any direct positive relationship
between the abundances of zooplankton and phytoplankton. Interestingly, a
similar trend was observed in the western, central, and eastern regions of
the Bay despite their systematic differences in salinity, water column
chlorophyll, bloom incidence, etc. In contrast, the abundance of a
dominant water column planktivore, Anchovia mitchelli, the bay
anchovy, varied almost inversely with the abundance of its prey. Bay anchovy
abundance in the same regions was high until 1996, when it dominated the
forage fish community, but has declined precipitously thereafter to levels
observed during the mid-1980s. However, sampling has been insufficient to
provide rigorous estimates of bay anchovy abundance. Concentrations
sufficient to appreciably reduce zooplankton numbers were observed with some
regularity. In short, the recent history of phytoplankton, zooplankton,
and planktivorous fish abundance provides little or no support for the
concept of a fundamental persistent Bay shift from a demersal benthic
production-based ecosystem to a pelagic water column production-based
ecosystem.
Peltola, E., K. Lee, R. Wanninkhof, R. Feely, M. Roberts, D. Greeley,
M.O. Baringer, G. Johnson, J. Bullister, C. Mordy, J.-Z. Zhang, P. Quay,
F. Millero, D. Hansell, and P. Minnett. Chemical and hydrographic
measurements on a Climate and Global Change Cruise along 24°N in the
Atlantic Ocean WOCE Section A5R (repeat) during January-February 1998.
NOAA Data Report, OAR AOML-41, 199 pp. (2001).
This document contains data and metadata from a zonal cruise along nominally
24.5°N in the Atlantic Ocean from Las Palmas, Canary Islands in Spain to
Miami, Florida. The cruise took place from January 23 to February 24, 1998
aboard the NOAA Ship Ronald H. Brown under auspices of the National
Oceanic and Atmospheric Administration (NOAA). This report presents the
analytical and quality control procedures performed during the cruise and
bottle data from the cruise. The research was sponsored by the NOAA Climate
and Global Change Program under: (i) The Ocean-Atmosphere Carbon Exchange
Study (OACES); and (ii) the World Ocean Circulation Experiment (WOCE) repeat
hydrography program. Samples were taken from up to 36 depths at 130 stations.
The data presented in this report includes the analyses of water samples for:
salinity, nutrients, total dissolved inorganic carbon dioxide (DIC), fugacity
of carbon dioxide (fCO2), total alkalinity (TA), pH, total
organic carbon (TOC), total nitrogen (TN), total phosphorus (TP),
chlorofluorocarbons, and stable carbon isotopic ratio of DIC
(13C/12C). Basic hydrographic parameters, pressure,
CTD salinity, temperature and the calculated potential temperature, and
potential density are included as well.
Phoebus, P.A., D.R. Smith, P.J. Croft, H.A. Friedman, M.C. Hayes, K.A.
Murphy, M.K. Ramamurthy, B. Watkins, and J.W. Zeitler. Meeting summary:
Ninth AMS symposium of education. Bulletin of the American Meteorological
Society, 82(2):295-303 (2001).
The American Meteorological Society held its Ninth Symposium on Education in
conjunction with the 80th Annual Meeting in Long Beach, California. The theme
of this year's symposium was "Atmospheric and Oceanographic
Education-Expanding our Vision for the New Millennium." Thirty-five oral
presentations and 53 poster presentations summarized a variety of educational
programs or examined educational issues for both the precollege and university
levels. There was a special session reporting on a recent survey conducted
by the Board on Women and Minorities, as well as a special session on the
educational applications of satellite meteorology and oceanography. Over
200 people representing a wide spectrum of the Society attended one or more
of the sessions in this two-day conference. The program for the Ninth
Symposium on Education can be viewed in the October 1999 issue of the
Bulletin.
Pinker, R.T., K.B. Katsaros, and B. Zhang. Prospects for satellite
estimates of net air-sea flux. Intercomparison and Validation of
Ocean-Atmosphere Flux Fields Workshop, Potomac, MD, May 21-24, 2001.
WCRP-115-WMO/TD-No. 1083, 223-227 (2001).
No abstract.
Powell, M.D., and S.D. Aberson. Accuracy of United States tropical cyclone
landfall forecasts in the Atlantic Basin (1976-2000). Bulletin of the
American Meteorological Society, 82(12):2749-2768 (2001).
About 13% of all Atlantic basin tropical cyclone forecasts issued from 1976
to 2000 are for landfalls along the United States coastline, and 2% more are
for storms forecast to make landfall in the United States but that remain at
sea. Landfall position and time forecasts are skillful at all forecast time
periods and are more skillful than Atlantic basin track forecasts as a whole,
but within 30 h of predicted landfall, timing errors demonstrate an early bias
of 1.5-2.5 h. Landfall forecasts are most accurate for storms moving at
oblique or normal angles to the coastline and slow-moving storms. During the
last quarter century, after adjustment for forecast difficulty, no
statistically significant improvement or degradation is noted for landfall
position forecasts. Time of landfall forecasts indicate no degradation at any
period and significant improvement for the 19-30 h period. The early bias and
lack of improvement are consistent with a conservative or "least regret"
forecast and warning strategy to account for possible storm accelerations.
Landfall timing uncertainty is ~11 h at 24 and 36 h, which suggests that
hurricane warnings could be disseminated about 12 h earlier (at 36 h, rather
than 24 h, before predicted landfall) without substantial loss of lead time
accuracy (although warning areas necessarily would be larger). Reconsideration
of the National Weather Service Strategic Plan and United States Weather
Research Program track forecast goals is recommended in light of these
results.
Reasor, P.D., and M.T. Montgomery. Three-dimensional alignment and
corotation of weak, TC-like vortices via linear vortex Rossby waves.
Journal of the Atmospheric Sciences, 58(16):2306-2330 (2001).
The vertical alignment of an initially tilted geostrophic vortex is shown
here to be captured by linear vortex Rossby wave dynamics when the vortex
cores at upper and lower levels overlap. The vortex beta Rossby number,
defined as the ratio of nonlinear advection in the potential vorticity
equation to linear radial advection, is less than unity in this case. A
useful means of characterizing a tilted vortex flow in this parameter regime
is through a wave-mean flow decomposition. From this perspective, the
alignment mechanism is elucidated using a quasigeostrophic model in both its
complete and linear equivalent barotropic forms. Attention is focused on
basic-state vortices with continuous and monotonically decreasing potential
vorticity profiles. For internal Rossby deformation radii larger than the
horizontal scale of the tilted vortex, an azimuthal wavenumber 1 quasi mode
exists. The quasi mode is characterized by its steady cyclonic propagation,
long lifetime, and resistance to differential rotation, behaving much like a
discrete vortex Rossby wave. The quasi mode traps disturbance energy, causing
the vortex to precess, or corotate, and thus prevents alignment. For
internal deformation radii smaller than the horizontal vortex scale, the
quasi mode disappears into the continuous spectrum of vortex Rossby waves.
Alignment then proceeds through the irreversible redistribution of potential
vorticity by the sheared vortex Rossby waves. Further decreases in the
internal deformation radius result in a decreased dependence of vortex
evolution on initial tilt magnitude, consistent with a reduction of the
vortex beta Rossby number. These results are believed to have relevance to
the problem of tropical cyclone (TC) genesis. Cyclogenesis initiated through
the merger and alignment of low-level convectively generated positive
potential vorticity within a weak incipient vortex is captured by
quasi-linear dynamics. A potential dynamical barrier to TC development in
which the quasi mode frustrates vertical alignment can be identified using
the linear alignment theory in this case.
Rizzoli, P., A. Busalacchi, R. Fine, J. McCreary, R.L. Molinari, and F.
Schott. Meeting summary: CLIVAR workshop on shallow tropical-subtropical
overturning cells (STCs) and their interaction with the atmosphere: Venice,
Italy, 9-13 October 2000. Bulletin of the American Meteorological
Society, 82(12):2815-2816 (2001).
No abstract.
Rogers, R.F., and J.M. Fritsch. Surface cyclogenesis from
convectively-driven amplification of mid-level mesoscale convective
vortices. Monthly Weather Review, 129(4):605-637 (2001).
Mesoscale convective vortices (MCVs) are mid-tropospheric warm-core cyclonic
circulations that often develop in the stratiform region of mesoscale
convective systems. Typically, divergent, anticyclonically-circulating,
mesoscale cold anomalies appear both above and below the MCV. The upper
level cold anomaly is usually found near the tropopause while the low-level
anomaly is surface-based and exhibits locally higher pressure. One aspect
of MCVs that has received much attention recently is the role that they may
play in tropical cyclogenesis. Of special interest is how an MCV amplifies
when deep convection redevelops within the borders of its mid-level cyclonic
circulation and how the amplified MCV transforms the divergent surface-based
cold pool with anomalously high surface pressure into a convergent cyclonic
circulation with anomalously low pressure. The Pennsylvania State
University/National Center for Atmospheric Research mesoscale model MM5 is
used to simulate an MCV that was instrumental in initiating, within the
borders of the mid-level vortex's circulation, several successive cycles of
convective development and decay over a two-day period. After each cycle of
convection, both the horizontal size of the cyclonic circulation and the
magnitude of the potential vorticity associated with the vortex were observed
to increase. The simulation reproduces the development and evolution of the
MCV and associated convective cycles. Mesoscale features responsible for the
initiation of convection within the circulation of the vortex and the
impact of this convection on the structure and evolution of the vortex
are investigated. A conceptual model is presented to explain how
convective redevelopment within the MCV causes low-level heights to fall
and cyclonic vorticity to grow downward to the surface. Applying this
conceptual model to a tropical marine environment is also considered.
Sainz-Trapaga, S.M., G.J. Goni, and T. Sugimoto. Identification of the
Kuroshio Extension, its bifurcation and northern branch from altimetry
and hydrographic data during October 1992-August 1999: Spatial and
temporal variability. Geophysical Research Letters, 28(9):1759-1762
(2001).
A methodology is proposed using altimeter-derived upper layer thickness and
baroclinic transport to identify the Kuroshio Extension, the Bifurcation
Point, and the Northern Branch, by combining TOPEX/POSEIDON altimeter and
climatological data within a two-layer reduced gravity model. Results
obtained from the Japanese coast to 175°W show that the location of the
Bifurcation Point presents interannual variability that is related with
upstream conditions. The longitude of the Bifurcation Point ranged from
147 to 160°E. Estimates of baroclinic transport at the Kuroshio
Extension and its Northern Branch decrease steadily to the east trough, the
region of study from 35 to 11 and from 10 to 3 Sv, respectively.
Schecter, D.A., M.T. Montgomery, and P.D. Reasor. The alignment of a
geophysical vortex by the resonant damping of a vortex Rossby mode. AGU
2001 Spring Meeting, Boston, MA, May 29-June 2, 2001. Supplement to
EOS, Transactions, American Geophysical Union, 82(20):S47, A41C-10
(2001).
During its early stages of development, a geophysical vortex such as a
tropical cyclone or an ocean eddy can be destroyed by episodes of external
vertical shear. However, some vortices can survive because they have a
dominant tendency to stand upright. We will demonstrate that the process of
vertical alignment can often be viewed as the damping of a 3-D vortex Rossby
mode. This mode decays exponentially with time, by a resonant "wave-fluid"
interaction. In general, the exponential decay rate gamma of the vortex
Rossby mode increases with the vorticity gradient at a critical radius, where
the fluid rotation is resonant with the mode. The decay rate, gamma, is also
affected by the level of atmospheric/oceanic stratification, measured by the
internal Rossby deformation radius lR. However, the
rate of change of gamma with lR is sensitive to the
form of the vortex. For the case of a "Rankine-with-skirt" vortex, the
magnitude of gamma increases (initially) with lR. On the
other hand, for the case of a "Gaussian" vortex, the magnitude of gamma
decreases as lR increases. It has been shown that a similar
resonant wave-fluid interaction can cause 2-D vortex axisymmetrization. The
analogy between axisymmetrization and vertical alignment will be addressed.
Schmid, C., R.L. Molinari, and S.L. Garzoli. New observations of the
intermediate depth circulation in the tropical Atlantic. Journal of
Marine Research, 59(2):281-312 (2001).
The intermediate depth (around 1000 m) circulation in the interior tropical
Atlantic has been described as several narrow flow bands. Due to a lack of
data, these currents have previously only been poorly resolved in space and
time. Recent observations, obtained during the mid-1997 Seward
Johnson cruise and from PALACE floats which cover the period summer 1997
to spring 2000, allow a more detailed description of the intermediate depth
circulation in the tropical Atlantic. The PALACE trajectories display several
well defined currents between the equator and 4°N at 800 to 1100 m. Two
regimes separated by the eastern edge of the Mid-Atlantic Ridge seem to exist
at these latitudes. Velocities in the eastern regime are lower than in the
western regime and, at some latitudes, the zonal flow in the two regimes is
going in opposite directions. Farther south, between 4°S and
2°S, westward velocities of the central South Equatorial Current
dominate the circulation. The flow north of 4°N and south of 4°S
is governed by up to several month-long periods of eastward or westward flow,
with only weak preferences for either direction. The southern region is
characterized by the (meandering) transition between the central South
Equatorial Current and the South Equatorial Countercurrent. It has been
proposed earlier that these two currents do not extend eastward beyond about
10°W, and that the intermediate water follows a cyclonic path east of
10°W between about 5°S and 25°S. This could be interpreted
as an intermediate expression of the Angola Gyre. Such a circulation is not
found in the present data set. It is also noted that no significant
cross-equatorial flow is found in the PALACE data.
Schubert, W.H., S.A. Hausman, M. Garcia, K.V. Ooyama and H.-C. Kuo. Potential
vorticity in a moist atmosphere. Journal of the Atmospheric Sciences,
58(21):3148-3157 (2001).
The potential vorticity principle for a nonhydrostatic, moist,
precipitating atmosphere is derived. An appropriate generalization of the
well-known (dry) Ertel potential vorticity is found to be P =
rho-1 (2OMEGA + gradient x u) gradient
thetarho, where rho is the total density, consisting of the
sum of the densities of dry air, airborne moisture (vapor and cloud
condensate), and precipitation; u is the velocity of the dry air
and airborne moisture; and thetarho = Trho
(p0/p)Ra/CPa is the virtual
potential temperature, with Trho = p/(rho
Ra) the virtual temperature, p the total pressure
(the sum of the partial pressures of dry air and water vapor),
p0 the constant reference pressure, Ra
the gas constant for dry air, and CPa the specific heat at
constant pressure for dry air. Since thetarho is a function of
total density and total pressure only, its use as the thermodynamic variable
in P leads to the annihilation of the solenoidal term, that is,
gradient thetarho (gradientrho ×
gradientp) = 0. In the special case of an absolutely
dry atmosphere, P reduces to the usual (dry) Ertel potential
vorticity. For balanced flows, there exists an invertibility principle
that determines the balanced mass and wind fields from the spatial
distribution of P. It is the existence of this invertibility
principle that makes P such a fundamentally important dynamical
variable. In other words, P (in conjunction with the boundary
conditions associated with the invertibility principle) carries all the
essential dynamical information about the slowly evolving balanced part
of the flow.
Smith, D.R., M.C. Hayes, M.K. Ramamurthy, J.W. Zeitler, K.A. Murphy, P.J.
Croft, J.M. Nese, H.A. Friedman, H.W. Robinson, C.D. Thormeyer, P.A. Ruscher,
and R.E. Pandya. Meeting summary: 10th AMS symposium on education.
Bulletin of the American Meteorological Society, 82(12):2817-2824
(2001).
The American Meteorological Society held its 10th Symposium on Education in
conjunction with the 82nd Annual Meeting in Albuquerque, New Mexico. The
theme of 2001's symposium was "enhancing public awareness of the atmospheric
and oceanic environments." Thirty-six oral presentations and 38 poster
presentations summarized a variety of educational programs or examined
educational issues at both the precollege and university levels. There was a
special session on increasing awareness of meteorology and oceanography
through popular and informal educational activities, as well as a joint
session with the 17th International Conference on Interactive Information
and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology
on using the World Wide Web to deliver information pertaining to the
atmosphere, oceans, and coastal zone. Over 200 people representing a wide
spectrum of the Society attended one or more of the sessions in this
two-day conference. The program for the 10th Symposium on Education can be
viewed in the November 2000 issue of the Bulletin.
Smith, R.H., E. Johns, W.D. Wilson, T.N. Lee, and E. Williams. Moored
observations of salinity variability in Florida Bay and south Florida
coastal waters on daily to interannual time scales. Proceedings, 2001
Florida Bay and Adjacent Marine Systems Science Conference, Key Largo,
FL, April 23-26, 2001. University of Florida, 42-43 (2001).
In support of the South Florida Ecosystem Restoration, Prediction, and
Modeling Program (SFERPM), a three year, physical oceanographic study of the
connectivity between Florida Bay and the surrounding waters of the Gulf of
Mexico, the southwest Florida shelf, and the Atlantic Ocean was conducted.
The field survey included a moored array equipped with current meters, bottom
pressure sensors, and conductivity/temperature sensors, satellite-tracked
surface drifters, and bimonthly interdisciplinary shipboard surveys with
continuous underway thermosalinograph observations of surface salinity,
temperature, and fluorescence. The moored conductivity/temperature array
consists of 21 sensors positioned from the Florida Keys reef tract, through
western Florida Bay and around Cape Sable, extending northward off the mouths
of the Shark, Broad, and Lostmans Rivers, to Indian Key just south of Marco
Island, Florida. Salinity time series collected from this array are affected
by the local precipitation/evaporation balance, riverine discharge from the
Everglades which is, in turn, influenced by precipitation as well as
anthropogenic factors, fluctuations in the Gulf of Mexico Loop Current,
meteorological forcing events such as hurricanes and tropical storms in the
summer and cold fronts in the winter, and interannual meteorological events
such as El Niņo. Though the bulk of the array was deployed in late 1997, the
effects of the 1997/1998 El Niņo on the climate patterns of south Florida can
be seen throughout the salinity time series. A wet season/dry season
reversal is evident in 1998 with salinity minima occurring at our moorings
in April (traditionally the most saline period of the year due to dryer,
winter weather) and maxima prevalent in late summer (contradictory to typical
wet season conditions).
Testud, J., S. Oury, R.A. Black, P. Amayenc, and X. Dou. The concept of
"normalized" distribution to describe raindrop spectra: A tool for cloud
physics and cloud remote sensing. Journal of Applied Meteorology,
40(6):1118-1140 (2001).
The shape of the drop size distribution (DSD) reflects the physics of rain.
The DSD is the result of the microphysical processes that transform the
condensed water into rain. The question of the DSD is also central in radar
meteorology, because it rules the relationships between the radar reflectivity
and the rainfall rate R. Normalizing raindrop spectra is the only way
to identify the shape of the distribution. The concept of normalization of DSD
developed in this paper is founded upon two reference variables, the liquid
water content LWC and the mean volume diameter Dm. It is
shown mathematically that it is appropriate to normalize by
N0* proportional to LWC/Dm4
with respect to particle concentration and by Dm with
respect to drop diameter. Also, N0* may be defined as the
intercept parameter that would have an exponential DSD with the same LWC and
Dm as the real one. The major point of the authors' approach
is that it is totally free of any assumption about the shape of the DSD. This
new normalization has been applied to the airborne microphysical data of the
Tropical Ocean and Global Atmosphere-Coupled Ocean Atmosphere Response
Experiment (TOGA-COARE) collected by the National Center for Atmospheric
Research Electra aircraft. The classification of the TOGA-COARE raindrop
spectra into four categories (one stratiform, and three convective [0-10,
10-30, and 30-100 mm h-1]) allowed the following features to be
identified. (1) There is a distinct behavior of N0*
between stratiform and convective rains; typical values are 2.2 ×
106 m4 for stratiform and 2 × 107
m4 for convective. (2) In convective rain, there is a clear trend
for Dm to increase with R, but there is no
correlation between N0* and R. (3) The "average"
normalized shape of the DSD is remarkably stable among the four rain
categories. This normalized shape departs from the exponential, but also from
all the analytical shapes considered up to now (e.g., gamma,
lognormal, modified gamma). The stability of the normalized DSD shape and
the physical variability of N0* and Dm
are discussed in respect to the equilibrium theory of List et al. The
stability of the shape implies that two parameters (and only two) are needed
to describe the DSD. This stability supports the robustness of rain relations
parameterized by N0*. The same TOGA-COARE dataset is used
to check that the rain relations parameterized by N0* are
much less dispersed than the classical ones, even after rain-type
classification.
Tokarczyk, R., K.D. Goodwin, and E.S. Saltzman. Methyl bromide loss rate
constants in the North Pacific Ocean. Geophysical Research Letters,
28(23):4429-4432 (2001).
The degradation rate constant of CH3Br in the North Pacific Ocean
was measured in surface seawater between September and October 1999, using the
stable isotope (13CH3Br) incubation technique. Total
degradation rate constants ranged from 0.02-0.43 d-1, decreasing
in colder waters as a result of the temperature-dependence of chemical losses.
Biological rate constants ranged from 0.01-0.20 d-1. In
subtropical waters (13-20°N), biological loss rate constants were small
compared to chemical loss rate constants. North of Hawaii, biological
processes played an increasingly significant role in CH3Br
degradation. In subpolar waters (40-58°N), biological losses dominated
the removal of methyl bromide. Comparison of the measured loss rate constants
with surface water CH3Br concentrations suggest that the
CH3Br production rate is higher in warm, low latitude waters than
in cold subpolar waters at this time of year. Diel studies revealed a midday
maximum in biological degradation of methyl bromide.
Wang, C. A unified oscillator model for the El Niņo-Southern Oscillation.
Journal of Climate, 14(1):98-115 (2001).
The delayed oscillator, the western Pacific oscillator, the
recharge-discharge oscillator, and the advective-reflective oscillator
have been proposed to interpret the oscillatory nature of the El
Niņo-Southern Oscillation (ENSO). All of these oscillator models assume a
positive ocean-atmosphere feedback in the equatorial eastern and central
Pacific. The delayed oscillator assumes that the western Pacific is an
inactive region and wave reflection at the western boundary provides a
negative feedback for the coupled system to oscillate. The western
Pacific oscillator emphasizes an active role of the western Pacific in
ENSO. The recharge-discharge oscillator argues that discharge and
recharge of equatorial heat content cause the coupled system to
oscillate. The advective-reflective oscillator emphasizes the importance
of zonal advection associated with wave reflection at both the western
and eastern boundaries. Motivated by the existence of these different
oscillator models, a unified oscillator model is formulated and derived
from the dynamics and thermodynamics of the coupled ocean-atmosphere
system. Consistent with ENSO anomaly patterns observed in the tropical
Pacific, this oscillator model considers sea surface temperature
anomalies in the equatorial eastern Pacific, zonal wind stress anomalies
in both the equatorial central Pacific and the equatorial western
Pacific, and thermocline depth anomalies in the off-equatorial western
Pacific. If the western Pacific wind-forced response is neglected,
thermocline and zonal wind stress anomalies in the western Pacific are
decoupled from the coupled system, and the unified oscillator reduces to
the delayed oscillator. If wave reflection at the western boundary is
neglected, the unified oscillator reduces to the western Pacific
oscillator. The mathematical form of the recharge-discharge oscillator
can also be derived from this unified oscillator. Most of the physics of
the advective-reflective oscillator are implicitly included in the
unified oscillator, and the negative feedback of wave reflection at the
eastern boundary is added to the unified oscillator. With appropriate
model parameters chosen to be consistent with those of previous
oscillator models, the unified oscillator model oscillates on interannual
time scales.
Wang, C. On the ENSO mechanisms. Advances in Atmospheric Sciences,
18:674-691 (2001).
The El Niņo-Southern Oscillation (ENSO) is an interannual phenomenon involved
in the tropical Pacific Ocean-atmosphere interactions. The oscillatory nature
of ENSO requires both positive and negative ocean-atmosphere feedbacks. The
positive feedback is dated back to Bjerknes' hypothesis in the 1960s, and
different negative feedbacks have been proposed since the 1980s associated
with the delayed oscillator, the western Pacific oscillator, the
recharge-discharge oscillator, and the advective-reflective oscillator. The
delayed oscillator assumes that wave reflection at the western boundary
provides a negative feedback for the coupled system to oscillate. The
western Pacific oscillator emphasizes equatorial wind in the western Pacific
that provides a negative feedback for the coupled system. The
recharge-discharge oscillator argues that discharge and recharge of
equatorial heat content causes the coupled system to oscillate. The
advective-reflective oscillator emphasizes the importance of zonal
advection associated with wave reflection at both the western and eastern
boundaries. All of these physics are summarized in a unified ENSO
oscillator. The delayed oscillator, the western Pacific oscillator, the
recharge-discharge oscillator, and the advective-reflective oscillator
can be extracted as special cases of the unified oscillator. As suggested
by this unified oscillator, all of the previous ENSO oscillator
mechanisms may be operating in nature.
Wang, C., and D.B. Enfield. The tropical Western Hemisphere warm pool.
Geophysical Research Letters, 28(8):1635-1638 (2001).
The Western Hemisphere warm pool (WHWP) of water warmer than 28.5°C
extends from the eastern North Pacific to the Gulf of Mexico and the
Caribbean, and at its peak, overlaps with the tropical North Atlantic.
It has a large seasonal cycle and its interannual fluctuations of area
and intensity are significant. Surface heat fluxes warm the WHWP through
the boreal spring to an annual maximum of SST and areal extent in the
later summer/early fall, associated with eastern North Pacific and Atlantic
hurricane activities and rainfall from northern South America to the southern
tier of the United States. SST and area anomalies occur at high temperatures
where small changes can have a large impact on tropical convection.
Observations suggest that a positive ocean-atmosphere feedback operating
through longwave radiation and associated cloudiness is responsible for the
WHWP SST anomalies. Associated with an increase in SST anomalies is a
decrease in atmospheric sea level pressure anomalies and an anomalous
increase in atmospheric convection and cloudiness. The increase in
convective activity and cloudiness results in less longwave radiation loss
from the surface, which then reinforces SST anomalies.
Wang, C., and R.H. Weisberg. Ocean circulation influences on sea surface
temperature in the equatorial central Pacific. Journal of Geophysical
Research, 106(C9):19,515-19,526 (2001).
Velocity data from an array of acoustic Doppler current profilers moored
about 0, 140°W from May 1990 through June 1991 during the Tropical
Instability Wave Experiment are used in conjunction with Tropical
Atmosphere Ocean array data and a blended sea surface temperature (SST)
product to study the processes that control SST variations. The horizontal
velocity data allow us to calculate the vertical velocity component by
vertically integrating the continuity equation. Given the three-dimensional
temperature flux divergence, we examine the role of the ocean circulation on
SST. Upwelling and downwelling are found to be associated with cooling and
warming, respectively, suggesting that a vertical velocity component of
either sign affects SST. Both the temperature flux divergence and advective
formulations for the ocean circulations influence in the temperature budget
show times when the ocean circulation appears to provide the primary control
on SST and times when this is not the case, with the flux divergence
formulation performing better than the advective formulation. Statistically,
within a bandwidth encompassing the tropical instability waves and the
intraseasonal variations, roughly half of the SST variation is accounted
for by the ocean circulation. These results are encouraging, given that
data sets with different spatial and temporal scales have been used. They
suggest that future field experimentation which utilizes a flux divergence
array with velocity and temperature data sampled at the same spatial and
temporal scales will yield quantitatively improved results. The analyses also
show that the ocean circulation on average provides a cooling effect requiring
the net surface heat flux to be positive on average to maintain the mean
background state. The cooling effect is mainly controlled by mean ocean
circulation and temperature fields.
Waworuntu, J.M., S.L. Garzoli, and D.B. Olson. Dynamics of the Makassar
Strait. Journal of Marine Research, 59(2):313-325 (2001).
Data collected as part of the Arlindo Project ("Arlindo" is an acronym for
Arus Lintas Indonen, meaning "throughflow" in Bahasa Indonesia) from October
1996 through March 1998 are analyzed to study the characteristics of the flow
through the the Makassar Strait. Analysis of inverted echo sounders (IES)
and bottom pressure data (PIES), combined with TOPEX/POSEIDON
satellite-derived sea height anomaly, suggest that a minimum of three-layer
approximation is necessary to explain the dynamics of the flow in the Makassar
Strait. The simple two-layer model used in several studies of the throughflow
is rejected based on total incompatibility with the data sets. A three-layer
model with significant contributions by the middle layer provides a consistent
interpretataion of PIES and satellite data. Results are interpreted in the
framework of the large-scale circulation.
Willoughby, H.E., and R.W. Jones. Nonlinear motion of a barotropic vortex in
still air and in an environmental zonal flow. Journal of the Atmospheric
Sciences, 58(14):1907-1923 (2001).
This study employs a Vortex Tracking Semispectral (VTSS) model cast in
cylindrical coordinates that move with the vortex. Variables are represented
spectrally in azimuth only, so that the model becomes a set of linear
equations for each azimuthal wavenumber component, forced by the environmental
flow and coupled by wave-wave interactions that account for all of the
nonlinearity. The vortex is advected by the surrounding wind and propagates
when potential vorticity (PV) gradients due to the surrounding flow or the
beta effect force wavenumber one (WN1) asymmetries. Nonlinearity generally
plays a dissipative role. Although propagation is faster in stronger PV
gradients, nonlinear interactions cause the motions due to superposed PV
gradients to be slower than the sum of their individual motions. In still air
or uniform wind on a beta plane, the wave energy spectrum falls off rapidly
with wavenumber. For most situations, the calculations converge for truncation
at WN6 on a 4000-km domain. In an anticyclonically sheared environmental zonal
flow, the spectrum of asymmetric energy narrows because the WN2 asymmetry is
forced directly by the environmental deformation. The deformation-induced
asymmetry interferes destructively with WN2 due to internal wave-wave
interaction. In a cyclonically sheared zonal flow, the deformation-induced
and nonlinearly-induced asymmetries interfere constructively, resulting in a
broader spectrum. Energy cascades from WN2 to wavenumbers >2. A reverse
cascade also carries energy to WN1, changing the beta gyres and the motion.
Consequent perturbation of WN1 leads to slow convergence of the predicted
vortex position after 10 simulated days with increasing spectral resolution.
When imposed mass sources and sinks are used to supply energy directly to the
asymmetries in the middle of the spectrum, similar wave-wave interactions
force WN1, leading to a trochoidal vortex track.
Wright, C.W., E.J. Walsh, D. Vandemark, W.B. Krabill, A.W. Garcia, S.H.
Houston, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane directional wave
spectrum spatial variation in the open ocean. Journal of Physical
Oceanography, 31(8):2472-2488 (2001).
The sea surface directional wave spectrum was measured for the first time in
all quadrants of a hurricane's inner core over open water. The NASA airborne
Scanning Radar Altimeter (SRA) carried aboard one of the NOAA WP-3D hurricane
research aircraft at 1.5-km height acquired the open-ocean data on 24 August
1998 when Bonnie, a large hurricane with 1-min sustained surface winds of
nearly 50 m s-1, was about 400 km east of Abaco Island, Bahamas.
The NOAA aircraft spent more than five hours within 180 km of the eye and
made five eye penetrations. Grayscale coded images of Hurricane Bonnie wave
topography include individual waves as high as 19 m peak to trough. The
dominant waves generally propagated at significant angles to the downwind
direction. At some positions, three different wave fields of comparable energy
crossed each other. Partitioning the SRA directional wave spectra enabled
determination of the characteristics of the various components of the
hurricane wave field and mapping of their spatial variation. A simple model
was developed to predict the dominant wave propagation direction.
Yao, Q., S.L. Garzoli, R. Zantopp, and W.E. Johns. North Brazil Current
Rings Experiment: Time series data report. NOAA Data Report (PB2001-106244),
OAR-AOML-40, 104 pp. (2000).
This data report presents the data collected through moored instrumentation
during the North Brazil Current Rings Experiment, a joint effort between the
University of Miami's Rosenstiel School of Marine and Atmospheric Science,
NOAA's Atlantic Oceanographic and Meteorological Laboratory, the Woods Hole
Oceanographic Institution, and Columbia University's Lamont Doherty Earth
Observatory. The program is funded by the National Science Foundation (NSF)
and the National Oceanic and Atmospheric Administration (NOAA). The main goal
of this program is to study the contribution of the North Brazil Current
(NBC) rings to inter-hemispheric exchange of heat and salt and to determine
their role in climate.
Zhang, J.-Z. Oxidation of hydrogen sulfide by various oxidants in
natural waters. Trends in Geochemistry, 1(2000):53-68 (2001).
This article reviews the literature on the oxidation of H2S by
various oxidants, including oxygen, hydrogen peroxide, iodate, chromate,
ferrate, Fe(III) hydroxides, and Mn(IV) oxides, in natural waters. The
rates of H2S oxidation increased with oxidants in an order of
chromate, oxygen, hydrogen peroxide, iodate, Fe(III) hydroxides, Mn(IV)
oxides, and ferrate. Effect of pH on the rates of oxidation by various
oxidants indicated that HS- is a reactive species while
H2S is less reactive or, in some cases, non-reactive. The
oxidation by oxygen has been a subject of extensive studies and its rates
have been measured over a wide range of environmental conditions such as pH,
temperature, and salinity. Dissolved and particulate metals have a
significant effect on the rates of oxidation and the product formation. The
reaction conditions and resulting product formation (S,
Sn2-, SO32-,
S2O32- and SO42-)
were examined to unravel the reaction pathway.
Zhang, J.-Z., and C.J. Fischer. The role of sediment resuspension in the
phosphorus cycle in Florida Bay. Proceedings, 2001 Florida Bay and
Adjacent Marine Systems Science Conference, Key Largo, FL, April 23-26,
2001. University of Florida, 98-99 (2001).
The mass mortality of sea grass and frequent algal blooms in Florida Bay are
a result of eutrophication. Existing data indicate that phosphorus is the
limiting nutrient, while nitrogen is abundant. Therefore, the supply of
phosphorus is critical to the onset and persistence of phytoplankton blooms
in Florida Bay. Biogenic calcium carbonates are major components of the
sediments (>90%) in the Florida Bay. Our studies have shown that phosphorus
is strongly adsorbed on the surface of calcium carbonate sediment. Sediments
in Florida Bay can easily be suspended by storms and tidal mixing due to
shallow water depth (~3 m). Phosphorus cycling processes such as release
from adsorption to and coprecipitation with suspended sediment may play an
important role in the supply phosphorus to phytoplankton bloom. Our project
has been focused on the following three aspects: (1) The time scales of
phosphate availability through sediment resuspension in Florida Bay water and
kinetic of interaction of sedimentary phosphorus with seawater; (2) the
distribution coefficients for phosphorus partitioning between
sediment/seawater in Florida Bay; and (3) the reactivity and partitioning
of various pools of sedimentary phosphorus in Florida Bay surface sediments.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Continuous flow analysis of
phosphate in natural waters using hydrazine as a reductant.
International Journal of Environmental Analytical Chemistry,
80(1):61-73 (2001).
The use of hydrazine to reduce 12-molybdophosphoric acid to
phosphomolybdenum blue in continuous flow analysis of phosphate in
natural water samples is characterized. Using hydrazine in gas-segmented
continuous flow phosphate analysis minimizes coating and silicate
interference in comparison with using ascorbic acid. The addition of Sb
to the molybdate reagent increases sensitivity at temperatures greater
than 50°C but causes severe additional coating. The degree of coating
was found to be a function of pH. Minimal coatings were achieved at a
final solution pH of 0.5. Silicate interference was found to increase
dramatically with color development temperature. At room temperature no
detectable silicate interference was found. We recommend hydrazine in
preference to ascorbic acid for gas-segmented continuous flow phosphate
analysis with optimal reaction conditions of room temperature color
development and a final solution pH of 0.5.
Zhang, J.-Z., C.R. Kelble, and F.J. Millero. Gas-segmented continuous
flow analysis of iron in water with a long liquid waveguide capillary
flow cell. Analytica Chimica Acta, 438:49-57 (2001).
A long liquid waveguide capillary flow cell has been successfully adapted to
a gas-segmented continuous flow auto-analyzer for trace analysis of iron in
water. The flow cell was made of new material, Teflon AF-2400, which has a
refractive index (1.29) lower than water (1.33). Total reflection of light
can be achieved provided that the incident angle at each reflection on the
water/Teflon interface is greater than the critical angle. Teflon AF-2400 is
superior to currently used materials in both refractivity and mechanical
stability. This allows for construction of a long liquid waveguide capillary
flow cell in a helical, rather than linear shape, with compact dimensions.
Since the internal volume of a 2 m-long, 550 µm ID liquid waveguide
capillary flow cell is only approximately 0.5 cm3, a small sample
volume is required. Utilization of this long flow cell significantly enhances
the sensitivity of automated colorimetric analysis of iron by the ferrozine
method, allowing for accurate determination of nanomolar concentrations of
iron in natural waters. The advantages of this technique are low detection
limit (0.1 nM), small sample volume (2 ml), high precision (1%), and
automation for rapid analysis of a large number of samples. This technique
is applicable to any gas-segmented continuous flow analysis or flow injection
analysis with spectrophotometric detection.
Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. Enhanced new production observed
from the diurnal cycle of nitrate in an oligotrophic anticyclonic eddy.
Geophysical Research Letters, 28(8):1579-1582 (2001).
A diurnal study in an anticyclonic eddy provides the first evidence of
nutrient dynamics consistent with the observed trends in solar radiation,
oxygen concentration changes, and estimates of the eddy diffusive flux of
nitrate from nitracline. A new production rate of 24 mmol C m-2
d-1 was determined from nitrate inventory changes at nM levels
in the mixed layer using a liquid waveguide technique combined with eddy
diffusion estimates across the base of the mixed layer from temporal
changes in the vertical penetration of SF6. The new production
supported by nitrate from deepening of the mixed layer after storm events is
two times larger than that from the daily diffusive flux. Our results
demonstrate that new production in the oligotrophic ocean can be enhanced
by a supply of nitrate through the eddy turbulence-induced diffusive flux
and entrainment during storms.
**2000**
Aberson, S.D. A tropical cyclone ensemble forecasting system for the
North Atlantic Basin. AGU 2000 Fall Meeting, San Francisco, CA,
December 15-19, 2000. Supplement to EOS, Transactions, American
Geophysical Union, 81(48):F585, NG12A-05 (2000).
A real-time, 41-member VICBAR orthonormalized bred-mode ensemble forecasting
system has been run once per day during the 1998 and 1999 hurricane seasons,
and twice per day during the 2000 hurricane season, in the North Atlantic
basin. VICBAR is a movable, nested-mesh shallow-water model using the National
Centers for Environmental Prediction Aviation and Medium-Range Forecast Models
as both initial and time-dependent boundary conditions. The numerics are based
on cubic b-splines so as to eliminate discontinuities on the mesh boundaries.
The deterministic run has provided skillful forecasts competitive with other
track forecast models since 1989. The 850-200 hPa mass-weighted flow is
combined with a vortex representative of the tropical cyclone including an
asymmetry for the initial motion. Within 1500 km of the storm center, the
forecast is wholly barotropic; more than 2500 km away from the storm center,
the forecast is entirely that of the global model, with a transition region
between the two circles. Forecasts extend to 120 h. This is the first ensemble
forecasting system available for tropical cyclone track prediction in the
Atlantic. Global models are either unable to skillfully forecast tracks, or,
in some ensemble forecasting systems, the tropical regions are not perturbed.
The three-year sample will be evaluated to show the value of the ensemble
forecasting system, whether the ensemble spans the reality of the track,
whether the ensemble mean provides an improved forecast over individual
ensemble members and the control forecast, and whether the system can provide
probabilistic forecasts of events such as landfall. Further uses of the
ensemble, such as providing information for operational hurricane targeting
missions with the National Oceanic and Atmospheric Administration's
Gulfstream-IV jet aircraft, and for ensemble-based data assimilation schemes,
add to the potential value of the ensemble.
Aberson, S.D. Improvements to the ensemble of tropical cyclone track
forecasting models in the North Atlantic basin. Minutes, 54th
Interdepartmental Hurricane Conference, Houston, TX, February 14-18,
2000. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A140-A146 (2000).
No abstract.
Aberson, S.D. The first three years of operational targeting with the NOAA
Gulfstream-IV. Preprints, 4th Symposium on Integrated Observing
Systems, Long Beach, CA, January 9-14, 2000. American Meteorological
Society, Boston, 198-199 (2000).
No abstract.
Aberson, S.D. Three years of tropical cyclone synoptic surveillance in the
Atlantic basin. Preprints, 24th Conference on Hurricanes and Tropical
Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, 108-109 (2000).
Since 1997, NOAA has performed more than 50 synoptic surveillance missions in
the core and environments of tropical cyclones threatening the United States
mainland, Puerto Rico, and the Virgin Islands with their G-IV and P3 aircraft.
GPS dropwindsonde observations are taken approximately every 250 km along the
flight tracks and sent to the National Centers for Environmental Prediction
and the National Hurricane Center for incorporation in numerical guidance and
for subjective evaluation. The impact of these data on both track and
intensity forecasts will be presented. Since small differences in initial
conditions are known to grow in the numerical models at different rates,
targeting the fastest growing modes has been studied. Results of such
targeting, including methods to find target locations and sampling strategies,
will be presented.
Aberson, S.D. Woman and minorities in meteorology since 1950. Program
of the 80th Annual Meeting and Exhibition, Long Beach, CA, January 9-14,
2000. American Meteorological Society, Boston, 70-71 (2000).
No abstract.
Aberson, S.D. Women's trends: The changing status of women in the
profession/society. Preprints, 9th Symposium on Education, Long Beach,
CA, January 9-14, 2000. American Meteorological Society, Boston, 70-71
(2000).
No abstract.
Aberson, S.D., and K. Bedka. The operational ensemble of tropical cyclone
track guidance at the National Hurricane Center (1976-1998). Preprints,
24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston, 177-178
(2000).
A suite of operational track forecast models has been run at NHC in support
of NHC s task to provide tropical cyclone track forecasts. Official NHC
forecasts have improved at a rate faster than 1% during the 1990s, suggesting
substantial improvements to the numerical guidance. This operational ensemble
since 1976 has been analyzed as a set to mark the improvements of the guidance
with time. The improvements in the ability of the guidance to span the actual
track of tropical cyclones, the performance of the ensemble mean with time,
and changes in individual model performance are to be presented.
Atlas, D., C.W. Ulbrich, F.D. Marks, R.A. Black, E. Amitai, P.T. Willis,
and C.E. Samsury. Partitioning tropical oceanic convective and stratiform
rains by draft strength. Journal of Geophysical Research,
105(D2):2259-2267 (2000).
The discrimination of convective from stratiform tropical oceanic
rains by conventional radar-based textural methods is problematic because
of the small size and modest horizontal reflectivity gradients of the
oceanic convective cells. In this work, the vertical air motion measured
by an aircraft gust probe is used as a discriminator which is independent
of the textural methods. A threshold draft magnitude approximately equal
to 1 m s-1 separates the two rain types. Simultaneous airborne
in-situ observations of drop size distributions (DSD) made during the
Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment
(TOGA COARE) were used to compute Z, R, and other integral parameters.
The data were quality controlled to minimize misclassifications. The
convective and stratiform rains, observed just below the melting level but
adjusted to surface air density, are characterized by power law Z-R
relations (Z = 129R1.38 [convective]) and
224R1.28 [stratiform]). However, at R < 10 mm
h-1, the convective population is essentially coincident with the
small-drop size, small-Z portion of the stratiform population. Tokay
and Short (1996) found a similar result when their algorithm did not separate
the rain types unambiguously at R < 10 mm h-1. The
physical reasons for the wide variability of the drop size spectra and
Z-R points in stratiform rain and their overlap with that of
convective rain are proposed. The subtle distinctions in the microphysical
properties and the Z-R relations by rain type could not be found by
Yuter and Houze using the same airborne DSD data set as that in this work
and a radar-based textural classification algorithm.
Bauer, S., and M.S. Swenson. Eddy-mean flow decomposition and
eddy-diffusivity estimates in the tropical Pacific Ocean. AGU 2000 Fall
Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 81(48):F739, OS21D-08 (2000).
Eddy diffusivity is a statistic that provides a quantitative measure of the
diffusive transport caused by mesoscale motions. The principal objective of
this work is to estimate eddy diffusivities of the surface velocity field in
the tropical Pacific Ocean. The data are satellite-tracked drifting buoys
from 1979 through mid-1996. The tropical Pacific surface current system is
characterized by: (1) nonstationarity due to rapid response time of equatorial
and near-equatorial dynamics; (2) strong meridional shear in the large-scale
mean; and (3) an energetic mesoscale velocity component. Taylor (1921) defined
eddy diffusivity as the integral of the autocovariance of Lagrangian eddy
velocities, requiring both stationary and homogeneous statistics of the eddy
field. Eddy velocities were obtained in this study by removing the splined
mean field to eliminate mean shear as described in Part 1 (Bauer et
al., 1998) and binned spatially to group data that have similar dispersion
characteristics. Temporal partitions were made to create stationary eddy
statistics. Zonal diffusivity estimates (ku) vary with
latitude from about 5 ×107 to 76 × 107
cm2/s. Largest estimates are in regions of strong meridional shear
and large eddy variance between 4°S and 10°N. However, meridional
diffusivity estimates (kv) are nearly constant throughout
the tropics, varying from 2 × 107 to 9 × 107
cm2/s. Simple autoregressive models provide the analysis with
estimates of Lagrangian integral time scale (a measure of the turbulence
decorrelation time scale). First order (AR(1)) and second order (AR(2))
autoregressive processes adequately describe the eddy transport statistics.
All zonal eddy transport statistics and meridional statistics from low
variance regions (generally poleward of 4°S and 10°N) can be
modeled by AR(1) statistics modified by inertial wave oscillations. Meridional
statistics of the near-equatorial regions (between 4°S and 10°N)
are characterized by large meridional eddy variance associated in part with
tropical instability waves (TIWs), and by low meridional diffusivity: Wave
motion increases eddy variance but does not diffuse water parcels with
periodic trajectory motion. Therefore, meridional eddy diffusivities are low
in these regions and are modeled by AR(2) statistics. Further, an independent
confirmation of the diffusivity estimates in the central and eastern Pacific
was obtained by comparing tracer flux divergence computed from a
parameterization using diffusivity estimates of our analysis and that from
direct eddy Reynolds stress flux divergence. Thus, our results show that
diffusivity can be estimated for regions that have not been considered before,
either because of lack of data or because of the complexities of the velocity
field.
Beal, L.M., R.L. Molinari, T.K. Chereskin, and P.E. Robbins. Reversing
bottom circulation in the Somali Basin. Geophysical Research Letters,
27(16):2565-2568 (2000).
Two sets of direct velocity measurements were taken, concurrent with
hydrographic data, in the bottom waters of the northern Somali Basin
in June and September 1995. The velocities indicate a temporal flow
reversal in the bottom circulation, which is consistent with the changing
density structure between the sections. In June, there is evidence of a
southward Deep Western Boundary Current with a transport of 5 Sv. By
September, flow close to the boundary is northward, with a transport of
2.6 Sv. Furthermore, the deep density gradient across the interior of
the Somali Basin also changes between occupations, implying a cyclonic
circulation in June and anticyclonic flow in September. Rossby wave
activity is high in this region during the southwest monsoon, yet there
is also evidence of a strong barotropic component to the Great Whirl in
September, which may cause the reversal in the abyssal circulation.
Bentamy, A., P. Flament, Y. Quilfen, K.B. Katsaros, and H. Roquet. Analysis
of ocean surface winds derived from ERS-1, ERS-2, and NSCAT measurements.
CERSAT News, Issue No. 11, 2 pp. (2000).
No abstract.
Black, M.L., and J.L. Franklin. GPS dropsonde observations of the wind
structure in convective and non-convective regions of the hurricane eyewall.
Preprints, 24th Conference on Hurricanes and Tropical Meteorology,
Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society,
Boston, 448-449 (2000).
GPS dropsonde observations in the inner core regions of tropical cyclones
have shown remarkable vertical variation in the wind structure. Vertical
profiles from sondes released in the convective portions of the hurricane
eyewall frequently exhibit multiple low to mid-level wind maxima. These
maxima may contain peak winds significantly higher than those measured at
typical reconnaissance altitudes (3 km). Convective mixing is thought to
be a mechanism that may bring this high momentum air to altitudes at or
near the sea-surface. In non-convective regions, both outside and within
the eyewall, however, the wind profiles typically do not have the large
low-level wind maxima and the wind speed frequently decreases rapidly
toward the surface in the boundary layer. Preliminary analyses of
dropsonde wind profiles have suggested systematic differences in the
shape of these soundings. An important result from these analyses is that
the surface wind speed is a substantially higher fraction of the wind at
altitude in convective regions than in non-convective or stratiform
regions. We plan on classifying several hundred dropsonde observations
according to the convective environment they fall through. The
classifications will be based upon simultaneous radar observations from
NOAA P-3 research flights into tropical cyclones in various stages of
development. Individual profiles from convective and non-convective
regions of the storms will be presented to highlight some of the observed
differences in wind structure. A brief statistical analyses is planned to
describe the variance in the mean structure derived from these
classifications. A discussion of some of the possible physical mechanisms
for the difference in the observed wind profiles will be discussed.
Black, M.L., A.B. Damiano, and S.R. White. Meteorological aspects of the
first eye penetration by the NOAA G-IV aircraft. Minutes, 54th
Interdepartmental Hurricane Conference, Houston, TX, February 14-18,
2000. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A97 (2000).
No abstract.
Black, M.L., A.B. Damiano, and S.R. White. The first eyewall penetration
by the NOAA G-IV aircraft. Preprints, 24th Conference on Hurricanes and
Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, 175-176 (2000).
On August 9, 1999, NOAA's Aircraft Operations Center (AOC) was tasked by the
Tropical Prediction Center/National Hurricane Center and the Central Pacific
Hurricane Center (CPHC) to deploy the NOAA Gulfstream G-IV jet aircraft and
crew to Honolulu, Hawaii for synoptic surveillance missions around Hurricanes
Eugene and Dora. Both of these storms had tracked westward across the eastern
Pacific basin into the area of responsibility of CPHC (west of 140°W)
and posed potential threats to Hawaii. After a successful G-IV mission around
Hurricane Eugene on 12 August, a similar flight-track was designed to collect
synoptic data from GPS dropsondes around Hurricane Dora on 14 August. At the
time, Dora was steadily weakening from a peak intensity of 120 kts on 13
August with maximum sustained surface winds forecast to be 70 kts during the
mission. Dora was a compact hurricane with a circular, well-defined eye and
had only a couple of weak rainbands outside of the central dense overcast. A
deviation from the proposed flight track was planned to fly the G-IV on a
heading towards the eye during the closest approach to Hurricane Dora. The
maneuver's purpose was to observe the structure of a hurricane at altitudes
>40,000 feet with the aircraft's nose radar system. During the flight, the
G-IV crew observed that Hurricane Dora was closer to the flight track than
was forecast, so that when the aircraft turned toward the south side of the
storm, the eyewall was approximately 80 nmi away. After a brief discussion of
the structure of Dora and safety considerations, the flight director and
aircraft commander decided to fly into the eye before heading back to the
original track. This represented the first time that the G-IV would penetrate
the eyewall of a hurricane, and would do so at an altitude of 45,000 feet
(~145 mb). The aircraft flew through a thick cirrus cloud cover in the eyewall
and that thinned while in the eye. Two GPS dropsondes were released while in
(above) the eye of Hurricane Dora, and a third sonde was dropped just outside
of the southwest eyewall while the G-IV was exiting the storm. Both of the
eye drops drifted near or into the eyewall as they descended and one of them
showed winds in excess of 80 kts at altitudes below 3000 ft. During the
penetration, wind speeds at a flight level of 45,000 feet were approximately
5 kts and the wind direction showed anticyclonic flow.
Black, P.G., E.W. Uhlhorn, M.D. Powell, and J. Carswell. A new era in
hurricane reconnaissance: Real-time measurement of surface wind structure
and intensity via microwave remote sensing. Minutes, 54th
Interdepartmental Hurricane Conference, Houston, TX, February 14-18,
2000. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A122-A126 (2000).
No abstract.
Black, P.G., E.W. Uhlhorn, M.D. Powell, and J. Carswell. A new era in
hurricane reconnaissance: Real-time measurement of surface wind structure
and intensity via microwave remote sensing. Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, 199-200 (2000).
No abstract.
Black, P.G., E.W. Uhlhorn, J.J. Cione, G.J. Goni, L.K. Shay, S.D. Jacob,
E.J. Walsh, and E.A. D'Asaro. Hurricane intensity change modulated by
air-sea interaction effects based on unique airborne measurements during
the 1998-1999 hurricane seasons. Proceedings, 10th Conference on
Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL,
May 29-June 2, 2000. American Meteorological Society, Boston, J7-J8 (2000).
No abstract.
Boebel, O., S. Anderson-Fontana, C. Schmid, I. Ansorge, P. Lazarevich,
J.R.E. Lutjeharms, M. Prater, T. Rossby, and W. Zenk. KAPEX RAFOS float
data report, 1997-1999. Part A: The Agulhas and South Atlantic Current
components. GSO Technical Report 2000-2/UCT Oceanography Report 2000-1,
194 pp. (2000).
No abstract.
Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black.
Environmental influences on the rapid intensification of Hurricane Opal
(1995) over the Gulf of Mexico. Monthly Weather Review,
128(2):322-352 (2000).
Hurricane Opal intensified rapidly and unexpectedly over the Gulf
of Mexico between 1800 UTC 3 October 1995 and 1000 UTC 4 October 1995.
During this period, the storm central pressure decreased from 963 to 916
hPa and sustained winds reached 68 m s-1. Analyses that include
high-resolution GOES-8 water vapor winds and European Centre for
Medium-Range Weather Forecasts (ECMWF) and National Centers for
Environmental Prediction (NCEP) gridded datasets are employed to examine
the rapid intensification phase of Opal. Opal first reached tropical
storm strength on 29V30 September 1995 as it interacted with a trough
while situated over the Yucatan Peninsula. Opal deepened moderately (20
hPa) in the 24 h ending 1200 UTC 2 October as it achieved minimal
hurricane strength and as it turned northeastward. The deepening occurred
in conjunction with an environmental flow interaction as determined by an
Eliassen balanced vortex outflow calculation. As Opal accelerated toward
the Gulf coast by 1200 UTC 3 October, it approached the equatorward
jet-entrance region of a progressive synoptic-scale trough. The trough
tail extended southwestward toward the lower Texas coast. As the
poleward portion of the trough moved eastward, the equatorward end of
the trough lagged behind, stretched meridionally, and partially fractured
as it encountered a deformation region over the northwest Gulf. Enhanced
outflow and increased divergence in the upper troposphere poleward of
Opal was associated with the deformation zone and the partially fractured
trough tail. An analysis of the 300-200-hPa layer-averaged divergence
and 6-h divergence change based on an analysis of the water vapor winds
shows a significant increase in the magnitude and equatorward extension
of the divergence core toward Opal that begins at 1200 UTC 3 October and
is most apparent by 1800 UTC 3 October and 0000 UTC 4 October. This
divergence increase is shown to precede convective growth in the eyewall
and the onset of rapid intensification and is attributed to a
jet-trough-hurricane interaction in a low-shear environment. Calculations
of balanced vortex outflow based on the ECMWF and NCEP gridded datasets
confirms this interpretation. A crucial finding of this work is that the
jet-trough-hurricane interaction and explosive intensification of Opal
begins near 0000 UTC 4 October when the storm is far from its maximum
potential intensity (MPI), and the 850-200-hPa shear within 500 km of the
center is weak (2-3 m s-1). In this first stage of rapid
intensification, the winds increase by almost 15 m s-1 to
52 m s-1 prior to the storm reaching an oceanic warm-core eddy.
The second stage of rapid intensification occurs between 0600 and 1000 UTC
4 October when Opal is over the warm-core eddy and sustained winds increase
to 68 m s-1. During this second stage, conditions are still
favorable for a jet-trough-hurricane interaction as demonstrated by the
balanced vortex outflow calculation. Opal weakens rapidly after 1200 UTC
4 October when the storm is near its MPI, the shear is increasing, and the
eye is leaving the warm-core eddy. This weakening occurs as Opal moves
closer to the trough. It is suggested that an important factor in determining
whether a storm-trough interaction is favorable or unfavorable for
intensification is how far a storm is from its MPI. The results suggest
that a favorable storm-trough interaction ("good trough") can occur when
a storm is far from its MPI. It is suggested that although the ECMWF
(and to lesser extent NCEP) analyses reveal the trough-jet-hurricane
interaction through the balanced vortex outflow calculation, that the
failure of the same models to predict the rapid intensification of Opal
can be attributed to the inability of the model to resolve the eye and
internal storm structure and the associated influence of the
trough-jet-hurricane interaction on the diabatically driven storm
secondary circulation. The analyses also indicate that the high spatial
and temporal resolution of the GOES-8 water vapor winds reveal important
mesoscale details of the trough-jet-hurricane interaction that would
otherwise be hidden.
Chai, F., R. Dugdale, R.T. Baraber, M. Jiang, and T.-H. Peng. Ecosystem
modeling in the equatorial Pacific upwelling region. AGU 2000 Ocean
Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 80(49):OS29,
OS11P-06 (2000).
The equatorial Pacific Ocean is the dominant oceanic source of carbon
dioxide to the atmosphere, an annual net flux of 1.0 Pg carbon. This net
sea-to-air flux of carbon is the result of a complex interplay between
physical and biological processes in the region. A physical-biogeochemical
model has been developed and used to investigate physical variations,
ecosystem responses, and biogeochemical consequences. The ecosystem model,
embedded into a three-dimensional circulation model, is capable of
reproducing the low silicate, high nitrate, low chlorophyll (LSHNLC)
conditions in the equatorial Pacific upwelling region. Linkage of the
ecosystem components to the carbon system provides a model estimated
sea-to-air flux of carbon which is comparable with the observations. The
ecosystem responses to the tropical instability waves have been documented
to exam the transition from a "balanced" to "bloom" state of phytoplankton
production. The physical-biogeochemical model results show a consistent
decrease of the sea-to-air CO2 flux during El Niņo events.
Cione, J.J., P.G. Black, and S.H. Houston. Surface observations in the
hurricane environment. Monthly Weather Review, 128(5):1550-1561
(2000).
Composite analyses of marine surface observations from 37 hurricanes
between 1975 and 1998 show that the difference between the sea surface
temperature and the surface air temperature significantly increases just
outside the hurricane inner core. This increase in the sea-air contrast
is primarily due to a reduction in surface air temperature and is more
likely to occur when sea temperatures are at least 27°C. Results show
that 90% of the observed cooling occurs 3.25°-1.25° latitude from
the hurricane center, well outside the region of strongest surface winds.
Since surface pressure only decreases 3 mb over this interval, the 2°C
drop in air temperature is not a result of adiabatic expansion. For the
subset of observations that contained moisture measurements, surface
specific humidity decreased 1.2 g kg-1 4.5°-1.75°
latitude from the storm center. This finding suggests that the observed
reduction in surface air temperature is not simply a result of
near-surface evaporation from sea spray or precipitation. An alternate
explanation may be that outside the hurricane inner core, unsaturated
convective downdrafts act to dry and evaporatively cool the near-surface
environment. Between 3.25° and 1.25° radius, composite analyses
show that low-level inflow is not isothermal, surface moisture is not
constant, and the near-surface environment is not in thermodynamic
equilibrium with the sea. Calculations based on these observations show
that thetae decreases between 4.0° and 1.25° radius
and then quickly rises near the inner core as surface pressures fall and
specific humidity increases. Surface fluxes of heat and moisture are also
observed to significantly increase near the inner core. The largest increase
in surface sensible heat flux occurs radially inward of 1.5°, where
surface winds are strong and sea-air temperature contrasts are greatest. As
a result, the average Bowen ratio is 0.20°-0.5° radius from the
composite storm center. This increase in sensible heat flux (in conjunction
with near-saturated conditions at low to midlevels) may help explain why
average surface air temperatures inside 1.25° radius remain relatively
constant, despite the potential for additional cooling from evaporation
and adiabatic expansion within the high wind inner core.
Cione, J.J., E.W. Uhlhorn, and P.G. Black. Atmospheric boundary layer and
upper ocean structure observed in Hurricane Erika (1997). Proceedings,
10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston, J70-J71
(2000).
No abstract.
Cione, J.J., P. Molina, J. Kaplan, and P.G. Black. SST time series directly
under tropical cyclones: Observations and implications. Preprints, 24th
Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL,
May 29-June 2, 2000. American Meteorological Society, Boston, 1-2 (2000).
No abstract.
Cook, T.M., L.K. Shay, P.G. Black, G.J. Goni, M.M. Huber, S.D. Jacob, and J.J.
Cione. Coupled air-sea interactions during Hurricane Bonnie. Proceedings,
10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston, J68-J69
(2000).
No abstract.
Cosca, C.E., R.A. Feely, R.H. Wanninkhof, J. Boutin, J. Etcheto, and M.J.
McPhaden. Seasonal and interannual variations of the fCO2-SST
relationships in the equatorial Pacific. AGU 2000 Ocean Sciences
Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 80(49):OS28, OS11O-11 (2000).
In order to utilize satellite temperature data for determining high-resolution
variations of CO2 distributions in the equatorial Pacific, we have
developed seasonal and interannual fCO2-SST relationships from
shipboard data. The data were gathered onboard the NOAA ships Baldridge,
Discoverer, and Ka'imimoana from 1992 through 1998 as a companion
project to the biannual deployment of the TAO moorings. The cruises during
the 6-year period included 55 10°S to 10°N crossings of the
equatorial Pacific between 95°W and 165°E, and spanned two major
ENSO events (1992-1994 and 1997-1998). Data were collected during the
warm boreal spring season (February through June) and during the cooler
boreal fall season (July through December) of each year, making it
possible to examine the interannual and seasonal variability of the
fCO2-SST relationship. A linear fit through all 55 data sets
yields an inverse correlation between SST and fCO2, with an
R2 of 0.583 and an RMS of 28.4 µatm. When separated,
there is a significant difference between the regression lines for El Niņo
versus non-El Niņo data sets. During non-El Niņo periods, we observed
seasonal differences in the fCO2-SST relationship. The regression
lines through the spring and fall data sets have higher R2 and
lower RMS values than the composite non-El Niņo regression line, and the
slopes are significantly different at the 95% confidence level. The slope
for the fall season is less negative than during spring, suggesting higher
biological productivity occurred during the fall non-El Niņo seasons. The
regression line for the composite El Niņo data, which shows no significant
seasonal variability, has a slope very similar to the non-El Niņo spring
slope, indicating less influence by biological processes. These
relationships have been combined with satellite-based temperature data to
provide a composite time-space map of DELTA-fCO2 in the
equatorial Pacific.
D'Asaro, E.A., and P.G. Black. Turbulence in the ocean boundary layer below
Hurricane Dennis. Proceedings, 10th Conference on Interaction of the Sea
and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, J62-J63 (2000).
No abstract.
Dodge, P.P., S.M. Spratt, F.D. Marks, D.W. Sharp, and J.F. Gamache. Dual-Doppler
analyses of mesovortices in a hurricane rainband. Preprints,
24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston, 302-303
(2000).
The U.S. Weather Research Program identified landfalling tropical cyclones as
a major focus for research in the coming years. In 1998, the Hurricane
Research Division (HRD) of NOAA's Atlantic Oceanographic and Meteorological
Laboratory coordinated experiments with other agencies and university groups
in Hurricanes Bonnie, Earl, and Georges. On these flights, airborne Doppler
radar data were collected to combine with WSR-88D radar data in
three-dimensional analyses to document evolution of tropical cyclones as they
make landfall, and to provide data for testing WSR-88D tropical cyclone
algorithms. Hurricane Bonnie made landfall in near Wilmington, North Carolina
as a Category 2 hurricane on 26 August. There were two HRD missions near the
time of landfall. The first flight concentrated on examining the structure of
the spiral rainbands and the second flight surveyed the hurricane as it
interacted with the coast. During the flights, there was a vigourous rainband
~180 km northeast of the center with several mesocyclones (as identified on
the Morehead City WSR-88D) that later produced confirmed tornadoes on land.
Both NOAA aircraft had to deviate around strong cells in this band, between
1540 and 1830 UTC, and those deviations resulted in small Doppler analysis
boxes enclosing some of the mesocyclones. A companion paper (Spratt et
al.) uses dropsondes and adjacent radiosondes to describe the local
environment in which the Bonnie mesocylones were embedded, and in this paper
we will present windfield analyses, from combining WSR-88D and airborne
Doppler radar data, that provide the three dimensional structure of the
mesocyclones. The Doppler data are too coarse to resolve actual tornadoes,
but the parent mesoscale circulations are clearly resolved.
Dunion, J.P., S.H. Houston, M.D. Powell, C.S. Velden, and P.G. Black. Using
surface adjusted GOES low-level cloud-drift winds to improve the estimation
of tropical cyclone outer wind radii. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 488-489 (2000).
No abstract.
Dye, J.E., E. Defer, A. Grainger, M. Poellot, H. Christian, M. Bateman,
D. Mach, M. Stewart, P.T. Willis, and F. Merceret. Electric field and
associated microphysical measurements in the anvil of a decaying Florida
thunderstorm. AGU 2000 Fall Meeting, San Francisco, CA, December
15-19, 2000. Supplement to EOS, Transactions, American Geophysical
Union, 81(48):F91, A62D-09 (2000).
The Airborne Field Mill Mission 2000 (ABFM 2000) was conducted during June
2000 to investigate the decay time and spatial distribution of electric
fields and microphysical and radar structure in anvils of dissipating storms
near Kennedy Space Center (KSC). The University of North Dakota Citation jet
aircraft was flown with six electric field meters to determine the
three-dimensional electric field, an array of particle probes to characterize
particle concentrations, sizes and types, and standard instruments for
measuring state parameters. Ground-based instruments included the KSC
Lightning Detection and Ranging (LDAR) system, KSC field mill network,
KSC cloud-to-ground lightning network, radar, and rawinsondes. In this paper
we present measurements from the June 13 case in which the Citation
investigated the temporal and spatial distribution of electric fields and
microphysics of the anvil from before last lightning to 2 hours after the
last flash. Numerous penetrations were made across the anvil early in the
flight and later along the anvil axis. Although electric fields were in
excess of 50 kV/m near the core, the fields decreased with distance from the
core and became less than a few kV/m at distances of about 50-60 km from the
storm core even while lightning was occurring. The stronger fields tended to
be associated with reflectivities greater than 20 dBz and concentrations of
particles larger than 1 mm size.
Enfield, D.B., and A.M. Mestas-Nunez. Global modes of ENSO and non-ENSO SST
variability and their associations with climate. In: El Niño and
the Southern Oscillation: Multiscale Variability and Global and Regional
Impacts, H.F. Diaz and V. Markgraf (eds.). Cambridge University Press
(ISBN 0521621380), 89-112 (2000).
In this chapter we review much of the recent work by others regarding the
nature of the global modes of sea surface temperature (SST) variability
and the SST involvement in interannual to multidecadal climate variability.
We also perform our own analysis of global SST so as to describe and
separate the SST variability associated with El Niño-Southern
Oscillation (ENSO) from the low-frequency modes not associated with ENSO
(non-ENSO). ENSO is a global phenomenon with significant phase propagation
between basins, which we preserve and describe using complex empirical
orthogonal function (CEOF) analysis, and subsequently remove from the global
SST data. A second CEOF analysis of the residuals reveals three non-ENSO
modes of low-frequency variability that are identified with and related
to signals described in the reviewed literature: (1) a secular trend
representing the global warming signal with associated superimposed decadal
variability; (2) an interdecadal mode with maximal realization in the
extratropical North Pacific; and (3) a multidecadal mode with maximal
realization in the extratropical North Atlantic. Regression- and SVD-based
analyses of the relationships between the SST data and a high-quality
precipitation data set demonstrate for the interannual-to-decadal time scales
of the western hemisphere tropics that (a) tropical Atlantic SSTA is
comparable to the Pacific ENSO in its relevance to regional rainfall and is
not redundant with respect to ENSO; and (b) non-ENSO variability explains a
significant fraction of the total covariance between the two variables. We
are led to conclude that present operational climate predictions can be
significantly improved by extending numerical SST predictions from the
Pacific to the world ocean and by enabling these models to emulate the
observed non-ENSO modes of global variability.
Enfield, D.B., and A.M. Mestas-Nunez. Tropospheric direct circulations
associated with the climatic components of SST variability in the equatorial
Pacific. Proceedings, 10th Conference on Interaction of the Sea and
Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, J49-J50 (2000).
Using an updated version of the Kaplan et al. SST dataset
(1870-1998), we have constructed a global complex EOF mode of SST
anomalies that reproduces the known canonical aspects of El
Niņo-Southern Oscillation (ENSO), including phase propagation of SST
within and between ocean basins. When the global ENSO mode is subtracted
from the data, we are left with a non-ENSO residual dataset for SST
anomalies that includes fluctuations from inter-seasonal to multidecadal
time scales. Reconstructed for the NINO3 index region, the global ENSO
mode accounts for about three-fourths of the total SST anomaly
variability, while the residual, dominated by decadal time scales,
accounts for the rest. Interestingly, about 40-50% of the amplitudes of
the record-setting 1982-83 and 1997-98 El Niņo events is accounted for
by the residual variability. Related to this, the ranking of the
canonical ENSO events changes significantly with respect to the NINO3
index based on data (e.g., 1972-73 is equal to or stronger than
1982-83 and 1997-98). Based on indices of the canonical ENSO and
residual (non-ENSO) variabilities in the NINO3 region, we construct the
associated boreal winter (DJF) global composite maps of the tropospheric
direct circulation (NCAR/NCEP reanalysis, 1950-1999): velocity potential
and and irrotational flow at 850 and 200 hPa, and vertical velocity at
500 hPa. Questions we address include: (1) Does the tropospheric
circulation anomaly associated with decadal-scale warming in the NINO3
region reinforce the corresponding anomaly associated with superimposed
ENSO warmings? (2) If the warm/cold associations for the two time scales
are significantly different, how so and where, and what are the
implications for climate predictions?
Feely, R.A., C.E. Cosca, R.H. Wanninkhof, M.J. McPhaden, C.S. Meinen, J.
Boutin, and J. Etcheto. The role of ENSO on the phasing of the
CO2 signal in the equatorial Pacific. AGU 2000 Ocean Sciences
Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 80(49):OS279, OS42J-02 (2000).
Recent modeling studies, based upon inversions of atmospheric
CO2, delta13C, and O2/N2 records
from Cape Grim, Tasmania by Rayner et al. (1999), have suggested a
decrease in the equatorial Pacific Ocean source of CO2 to the
atmosphere which precedes the SOI by about seven to ten months. In order to
test this model result, we have utilized satellite temperature data to
obtain high-resolution variations of fCO2 distributions in the
eastern equatorial Pacific based on shipboard fCO2-SST
relationships. The data were gathered onboard the NOAA ships Baldridge,
Discoverer, and Ka'imimoana from 1992 through 1998 as a
companion project to the biannual deployment of the TAO moorings. The
results indicate rapid drops in surface water fCO2 at
110°W, 125°W and 140°W several months ahead of the peak SST
anomalies associated with the 1986-1887, 1991-1992, and 1997-1998 warm ENSO
events. These rapid changes in fCO2 are inversely correlated with
the integrated volume of the warm water above the 20°C isotherm in the
eastern equatorial Pacific. During the onset phase of warm ENSO events, the
propagation of Kelvin waves from west to east along the equatorial waveguide
results in a deepening of the thermocline and a rapid decrease in surface
water fCO2. The phasing of the beginning of the decrease in
fCO2 is approximately six to eight months ahead of the minimum in
the SOI index. During strong El Niņo events, such as the 1997-2998 ENSO event,
seawater fCO2 values decrease by as much as 125 µatm over
the course of a few weeks, indicating a rapid decrease in the outgassing of
CO2 near the equator. These results help to explain the dramatic
decrease in the growth rate of CO2 in the atmosphere that occurs
at the beginning of each ENSO event.
Feely, R.A., C.L. Sabine, R.H. Wanninkhof, R.M. Key, G.C. Johnson, F.J.
Millero, K. Lee, T.-H. Peng, J.L. Bullister, A. Kozyr, and M.F. Lamb.
Synthesis of global ocean CO2 survey data. AGU 2000 Fall
Meeting, San Francisco, CA, December 15-19, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 81(48):F691,
OS72E-01 (2000).
The synthesis of the global ocean CO2 survey data is proceeding
by ocean basin. Between 1991 and 1998, investigators analyzed dissolved
inorganic carbon (DIC) and one or more other carbon system parameters
(TAlk, pCO2, or pH) on WOCE/JGOFS/OACES cruises in the Indian,
Pacific, and Atlantic Oceans. The analysis of the Indian Ocean data is
published in Sabine et al., GBC, 13, 179-198, 1999) and can be
obtained at: http://cdiac.esd.ornl.gov/oceans/glodap/index.html. DIC and
TAlk were measured on all cruises, with an estimated overall accuracy of
2-4 µmol kg-1, respectively. For the Pacific Ocean,
investigators from 15 different laboratories and four countries analyzed at
least two of the four measurable ocean carbon parameters. Several different
lines of evidence were used to examine the consistency among data sets and
recommend adjustments. The analysis included comparison of calibration
techniques, results from certified reference material analyses, precision
of at-sea replicate analyses, agreement between shipboard analyses and
replicate shore-based analyses, comparison of deep water values at locations
where two or more cruises overlapped or crossed, consistency with other
hydrographic parameters, and internal consistency with multiple carbon
parameter measurements. With the adjustments recommended here, the data can
be combined to generate a Pacific Ocean data set with over 36,000 unique
sample locations. The best data coverage was for DIC, which has an estimated
overall accuracy of ~3 µmol kg-1 after the recommended
adjustments. TAlk, the second most common carbon parameter, has an estimated
overall accuracy of ~5 µmol kg-1. The data have been
integrated into a unified, internally-consistent data set and the physical
and chemical controls of the basinwide distributions of DIC and TAlk will be
discussed. The synthesis of the Atlantic data is just getting underway and
will be conducted in association with the European Carbon Dioxide in the
North Atlantic Ocean (CARINA) Project, with a projected completion date of
mid-2002.
Feuer, S.E., M.L. Black, and J.L. Franklin. The asymmetric wind structure of
tropical cyclones in various shear environments. Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 450-451 (2000).
The Hurricane Research Division (HRD) of NOAA's Atlantic Oceanographic
and Meteorological Laboratory conducts an annual field program involving
research flights into tropical cyclones with NOAA WP-3D aircraft. As part of
this program, dropwindsondes are launched from the aircraft during a variety
of airborne experiments. Since 1996, dropsondes based on satellite navigation
from built-in Global Positioning System (GPS) modules have been deployed in
and around the tropical cyclones. These GPS sondes demonstrate a remarkable
ability to accurately measure kinematic and thermodynamic quantities,
including winds to an accuracy of 0.5-2.0 m s-1 at approximately
5 m resolution, as they descend from flight level to the surface. This study
focuses on documenting the vortex-scale wind structure in the middle and
lower troposphere of three hurricanes: Bonnie (1998), Guillermo (1997), and
Bret (1999), which had experienced high, moderate, and low 200-850 mb
environmental shear, respectively. These hurricanes are all well sampled by
GPS sondes released within 300 km of the center during HRD's Vortex Motion and
Evolution (VME) and modified Air-Sea Interaction experiments. Objective
analyses of the dropsonde data are performed to resolve significant wind
features approximately 50-300 km from the center and filter out smaller
scales. Using the analyzed field, the distribution of kinematic asymmetries
is contrasted among the storms and is related to the shear and reflectivity
fields simultaneously collected from airborne radar systems. Variations in
the height of analyzed wind features are also described.
Ffield, A., K. Vranes, A.L. Gordon, R.D. Susanto, and S.L. Garzoli.
Temperature variability within Makassar Strait. AGU 2000 Ocean Sciences
Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 80(49):OS17, OS11I-05 (2000).
The Indonesian throughflow impacts the global climate system by carrying
warm Pacific water from about 5°N, through the Indonesian Seas, into
the Indian Ocean at 12°S. As part of the U.S./Indonesian Arlindo
program, recent mooring observations of ocean temperature provide the
first high-resolution, long-term record of temperature variability in the
Makassar Strait of the Indonesian Seas. The mooring observations span the
entire cycle of the strong 1997/1998 El Niņo, and they reveal the
complexity of the Makassar Strait thermocline with significant short and
long period temperature variations as a function of both depth and time.
A high correspondence (r = 0.67) is found between variability in the
average thermocline temperature, to variability in the southward Makassar
volume transport: during high (low) volume transport, the average
temperature of the thermocline is also high (low). In addition, during
the measurement period, the Makassar thermocline temperature corresponds
strongly (r = -0.87) to NINO3. This implies that the Makassar
temperature field, when coupled with the throughflow, transmitted the
equatorial Pacific El Niņo and La Niņa temperature fluctuations into the
Indian Ocean with potential consequences to the climate system. The Makassar
mooring temperature observations are related to 15 years of regional XBT
data to better estimate the semi-annual, annual (monsoonal), and
interannual (ENSO) characteristics of the mooring temperature observations,
and of the Makassar Strait thermocline in general. The potential of Makassar
XBT measurements to efficiently monitor the Makassar throughflow as part of
the developing global monitoring system is assessed.
Ffield, A., K. Vranes, A.L. Gordon, R.D. Susanto, and S.L. Garzoli.
Temperature variability within the Makassar Strait. Geophysical
Research Letters, 27(2):237-240 (2000).
Recent mooring observations of ocean temperature provide the first
high-resolution, long-term record of temperature variability in the
Makassar Strait of the Indonesian Seas. The mooring observation span the
entire cycle of the strong 1997/1998 El Niņo. A high correlation
(r = 0.67) is found between variability in the average thermocline
temperature, to variability in the southward Makassar volume transport:
during high (low) volume transport, the average temperature of the
thermocline is also high (low). In addition, from nearly 15 years of XBT
data, the Makassar thermocline temperature is shown to be highly
correlated (r = 0.77) to SOI. This reveals that the Makassar
temperature field, when coupled with the throughflow, transmits the equatorial
Pacific El Niņo and La Niņa temperature fluctuations into the Indian
Ocean. The ENSO variability in the internal energy transport is
calculated: 0.63 PW during the La Niņa months of December 1996 through
February 1997, and 0.39 PW during the El Niņo months of December 1997
through February 1998.
Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D.
Fratantoni, P. Richardson, and G.J. Goni. CTD/O2, LADCP,
and XBT measurements collected aboard the R/V Seward Johnson,
February-March 1999: North Brazil Current Rings Experiment, cruise 2
(NBC-2). NOAA Data Report, OAR-AOML-37, 291 pp. (2000).
Summaries of conductivity-temperature-depth (CTD/O2), lowered
acoustic Doppler current profiler (LADCP), and expendable bathythermograph
(XBT) measurements and hydrographic data acquired on an oceanographic
research cruise during the winter of 1999 aboard the Harbor Branch
Oceanographic Institution ship R/V Seward Johnson are presented.
Data acquisition and processing systems are described, and calibration
procedures are documented. Station location, CTD/O2, LADCP, XBT
summary data listings, and profiles are included for each station.
Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D.
Fratantoni, P. Richardson, and G.J. Goni. CTD/O2, LADCP, and
XBT measurements collected aboard the R/V Seward Johnson,
February-March 2000: North Brazil Current Rings Experiment, cruise 3
(NBC-3). NOAA Data Report, OAR-AOML-38 (PB2001-100486), 258 pp. (2000).
Summaries of conductivity-temperature-depth (CTD)/O2, lowered
acoustic Doppler current profiler (LADCP) measurements, and hydrographic
data acquired on an oceanographic research cruise during the winter of 2000
aboard the Harbor Branch Oceanographic Institution ship R/V Seward
Johnson are presented. Data acquisition and processing systems are
described, and calibration procedures are documented. Station location,
CTD/O2, LADCP summary data listings, and profiles are
included for each station.
Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D.
Fratantoni, P. Richardson, and G.J. Goni. CTD/O2, LADCP,
and XBT measurements collected aboard the R/V Seward Johnson,
November-December 1998: North Brazil Current Rings Experiment, cruise 1
(NBC-1). NOAA Data Report, OAR-AOML 39 (PB2001-101653), 276 pp. (2000).
Summaries of conductivity-temperature-depth (CTD/O2), lowered
acoustic Doppler current profiler (LADCP), expendable bathythermograph
(XBT) measurements, and hydrographic data acquired on an oceanographic
research cruise during the fall of 1998 aboard the Harbor Branch
Oceanographic Institution ship R/V Seaward Johnson are presented.
Data acquisition and processing systems are described, and calibration
procedures are documented. Station location, CTD/O2, LADCP,
XBT summary data listings, and profiles are included for each station.
Franklin, J.L., M.L. Black, and K. Valde. Eyewall wind profiles in
hurricanes determined by GPS dropwindsondes. Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, 446-447 (2000).
No abstract.
Friedman, H.A., F. Horsfall, and E. Van Coverden. Pipeline: What does the
future hold for the society and the profession as we access those in the
educational pipeline. Preprints, 9th Symposium on Education, Long
Beach, CA, January 9-14, 2000. American Meteorological Society, Boston,
75 (2000).
The composition of students in the educational pipeline is examined with
respect to the number of women and minorities enrolled in colleges and
universities that offer degree programs in atmospheric, oceanographic,
and hydrologic sciences. Data from recent AMS surveys of its members
and from information supplied by colleges and universities are examined
to ascertain if some change has taken place, especially with respect to
women and minorities in science fields. Barriers to a more diverse
composition in the profession are discussed.
Gamache, J.F., M.L. Black, and H.E. Willoughby. Radial variation of
azimuthally averaged flow across the hurricane core as observed with
airborne Doppler radar. Preprints, 24th Conference on Hurricanes and
Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000.
American Meteorological Society, Boston, 416-417 (2000).
Examination of the variation of azimuthally averaged zonal and meridional
winds in the cores of Hurricanes Olivia and Jimena indicate that the vertical
shear increased with increasing radius. Divergent wind fields computed for
the hurricane core have azimuthally averaged flow that tends to oppose the
overall wind shear, which is in agreement with one of the model results shown
by Jones. Additionally, in the core, winds at smaller radii imply a more
vertically aligned storm center than do winds at larger radii. These results
will be documented in several hurricanes, including Olivia and Jimena.
Garraffo, Z.D., W.E. Johns, E.P. Chassignet, and G.J. Goni. Impact of
North Brazil Current rings on the eastern Caribbean. AGU 2000 Ocean
Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 80(49):OS69,
OS12P-04 (2000).
The influence of North Brazil Current (NBC) rings on the eastern Caribbean
is investigated using new results from a high-resolution North Atlantic
model simulation, ship surveys, drifters, and Topex/Poseidon (T/P) altimetry.
North Brazil Current rings are large (~400-km diameter) anticyclonic
eddies that periodically pinch off from the North Brazil Current
Retroflection and propagate northwestward toward the Lesser Antilles,
carrying with them water masses and biogenic materials from the equator
and Amazon regions. Results from the high-resolution MICOM North Atlantic
model and from five years of T/P altimetry now suggest that approximately
five NBC rings are formed each year, nearly twice what had been previously
documented. New shipboard surveys obtained as part of an intensive
1998-2000 in-situ study of NBC rings have shown that these rings
can have highly varying vertical structures, ranging from shallow (<200 m)
to deep (>1000 m) features, and even subsurface intensified rings with
maximum swirl velocities in the thermocline. A similar range of features is
produced in the MICOM-simulated rings. The model results and altimetry
suggest that the strongest and deepest reaching NBC rings are the ones most
likely to travel well northward along the Lesser Antilles arc before
breaking up and dispersing their waters. The passage of the rings along
the island arc and their interaction with the island topography strongly
influences flow and transport variations through the Lesser Antilles passages.
Garzoli, S.L., and G.J. Goni. Combining altimeter observations and
oceanographic data for ocean circulation and climate studies. In
Satellites, Oceanography, and Society, D. Halpern (ed.). Elsevier
Oceanographic Series (ISBN 0444505016), 63, 79-95 (2000).
Calibrating Topography Experiment (TOPEX)/Poseidon (T/P) altimeter data to
inverted echo sounder measurements is one of the methodologies developed to
advance the study of the South Atlantic Ocean. The mass transport of the main
boundary currents can be monitored using dynamic height time series obtained
from altimeter-derived sea surface height anomalies. A two-layer model yields
upper-layer thickness and surface dynamic height of the ocean in areas of
strong vertical stratification to identify and track anticyclonic rings, such
as those shed from the Agulhas retroflection, which play an important role in
the interocean exchange of heat and mass. Interannual variability of boundary
currents, derived from analysis of the first five years of T/P data, is
discussed. A combination of T/P data and in-situ observations provides
significant contributions to the study of ocean dynamics for climate
applications.
Goldenberg, S.B. Intraseasonal predictability of Atlantic basin hurricane
activity. Preprints, 24th Conference on Hurricanes and Tropical
Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, 59-60 (2000).
The Atlantic basin hurricane season officially lasts from 1 June through
30 November. The vast majority of the activity (>95% of the major hurricane
activity) occurs during the peak months August, September, and October.
Previous analyses have demonstrated that early season (June-July) overall
tropical cyclone activity has no relationship to the activity during the
remainder of the season. Results will be presented that demonstrate that if
the June-July activity is stratified properly, it can yield a strong
predictive signal for the activity during the rest of the season. The
occurrence of a certain type of activity in June or July is, in fact, a
sufficient (but not necessary) condition for a year with above-average
activity. Results will also be discussed showing how just as the June-July
activity contains a signal to help predict the activity for the coming
months, June-September (or simply August-September) activity can give a
clear indication of what is to come during the final peak month of October.
Goldenberg, S.B., C.W. Landsea, and G.D. Bell. Summary of the 1999 Atlantic
hurricane season: A climatic perspective. Minutes, 54th Interdepartmental
Hurricane Conference, Houston, TX, February 14-18, 2000. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A251-A256 (2000).
The tropical cyclone activity from the 1999 Atlantic hurricane season will be
related to observed fluctuations in various climatic factors such as ENSO,
Atlantic SSTs, and vertical shear. The character of the season's activity
will also be discussed with respect to different time scales: multi-decadal,
interannual, and intraseasonal. Implications for Atlantic activity in the
coming season (2000) and decade will also be addressed. For the last two
seasons, NOAA has issued forecasts of the Atlantic basin hurricane activity
as a collaboration between scientists at NOAA's Climate Prediction Center,
Hurricane Research Division, and National Hurricane Center. Verifications of
the forecasts for the 1998 and 1999 seasons will be discussed.
Goldenberg, S.B., C.W. Landsea, and G.D. Bell. Summary of the 1999 Atlantic
hurricane season: A climatic perspective. Proceedings, 24th Annual Climate
Diagnostics and Prediction Workshop, Tucson, AZ, November 1-5, 1999.
National Weather Service, 1-4 (2000).
No abstract.
Goni, G.J., S.M. Sainz-Trapaga, and T. Sugimoto. Transport estimates
and variability of the Kuroshio Extension Current from satellite altimetry
data. AGU 2000 Western Pacific Geophysics Meeting, Tokyo, Japan, June
27-30, 2000. Supplement to EOS, Transactions, American Geophysical
Union, 81(22):WP77-WP78, OS32B-06 (2000).
Satellite altimetry observations of sea level in combination with
historical vertical profiles of ocean density and dynamical modeling
provide an excellent tool to understand the global meso- and large-scale
ocean circulation. A two-layer dynamical model is used in conjunction
with six years of TOPEX/POSEIDON (T/P) altimeter-derived sea height
anomaly to monitor the upper ocean transport in a region east of Japan
from 1993 to 1998. The key objective of this work is to estimate the
upper layer thickness and investigate the baroclinic transport variability
along a selected T/P groundtrack, in which a two-year time series of the
14°C isotherm derived from inverted echo sounders is available. The
upper layer thickness field is used to monitor the Kuroshio Extension front,
which is found to fluctuate between 33.7°N and 36.5°N. The
across-track upper layer velocity and baroclinic transports are used to
monitor the Kuroshio Extension axis. Estimates in this work reveal that the
axis fluctuates between 32.1°N and 35.9°N. Two events are
identified, one in 1996 and another in 1997, with unusual southern paths
of the Kuroshio Extension axis, and related to large variations in
baroclinic transport values. It is speculated that these extreme southern
excursions of the axis may be compensating for large changes in relative
vorticity and upper layer thickness.
Goni, G.J., L.K. Shay, P.G. Black, S.D. Jacob, T.M. Cook, J.J. Cione, and
E.W. Uhlhorn. Role of the upper ocean structure on the intensification
of Hurricane Bret from satellite altimetry. Proceedings, 10th Conference
on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, J5-J6 (2000).
No abstract.
Gonzalez, N.M., F.E. Muller-Karger, S.C. Estrada, R. Perez de los Reyes,
I.V. del Rio, P.C. Perez, and I.M. Arenal. Near-surface phytoplankton
distribution in the western Intra-Americas Sea: The influence of El
Niño and weather events. Journal of Geophysical Research,
105(C6):14,029-14,043 (2000).
The space-time variation of phytoplankton pigments in the vicinity of the
island of Cuba is examined using digital images obtained with the Coastal
Zone Color Scanner (CZCS) sensor, flown aboard the Nimbus-7 satellite
from 1978 to 1986. The results are compared to historical in-situ
hydrographic observations. A marked seasonality in pigment concentration
is observed in waters around Cuba, with an average of 0.07 mg
m-3 in summer (April-September) and 0.13 mg m-3
during winter (October-March). The range of variation in pigment concentration
is larger in the Gulf of Mexico relative to that in the western Caribbean
Sea. Four biogeographical areas are identified based on groups of pixels with
similar patterns of time variability. Area I: southwest of Cuba, Yucatan
Channel, and Florida Strait; Area II: central Gulf of Mexico; Area III:
east of Cuba; and Area IV: central Caribbean Sea, south of Jamaica and
Hispaniola. Two major factors led to anomalies in the seasonal cycle of
pigment concentrations. During the 1982-1983 El Niņo-Southern Oscillation
(ENSO) event, positive anomalies are observed in pigment concentration in
the northwestern Caribbean and in the Gulf of Mexico. This is due to
intense mixing of the water column driven by the higher frequency of cold
fronts during winter and associated strong winds. The 1982-1983 El Niņo
therefore had a fertilizing effect on this region. Another positive anomaly
was observed during non-ENSO years, specifically during 1980-1981. This
anomaly is associated with a higher frequency of hurricanes and extra-tropical
low-pressure systems.
Hendee, J.C. A data-driven soft real-time expert system for producing
coral bleaching alerts. Ph.D. Thesis, Nova Southeastern University, 131
pp. (2000).
In the Florida Keys there are many physical, chemical, and biological
events of interest and concern to personnel of the Florida Keys National
Marine Sanctuary, marine biologists, oceanographers, fishermen, and divers.
Large volumes of continuously-generated meteorological and oceanographic
data from instruments in the SEAKEYS (Sustained Ecological Research
Related to Management of the Florida Keys Seascape) network help to
understand these events. However, since no one has the time to look at
every printout of data from every station, every day, seven days a week,
it is highly desirable to have an automated system that can monitor
parameters of interest and produce specialized alerts of specific events,
as indicated by prescribed or abnormal ranges, or combinations of
parameters. A soft real-time expert system was developed to produce such
alerts based on data input from the SEAKEYS network. The prototype system
collected data from the Sombrero Reef station in the network and produced
automated e-mail and World-Wide Web alerts when conditions were thought
to be conducive to, or predictive of, coral bleaching, which occurs under
environmental conditions stressful to corals. Configuration of the system
included a point system for three coral bleaching models (high sea
temperature only, high sea temperature plus low winds, high sea temperature
plus low winds plus low tide). The approach is an important development in
the use of knowledge-based systems to solve environmental problems, as it
provides for knowledge synthesis (in the form of data summaries) from any
environmental ASCII data stream or table, be it real-time or not.
Hendee, J.C. An environmental information synthesizer for expert
systems: A framework for use in near real-time detection of harmful algal
blooms. Proceedings, 17th International Conference of The Coastal
Society: Coasts at the Millennium, Portland, OR, July 9-12, 2000. The
Coastal Society, 233-241 (2000).
As an enhancement to the SEAKEYS environmental monitoring network in the
Florida Keys National Marine Sanctuary, software called the Environmental
Information Synthesizer for Expert Systems (EISES) has been utilized
together with a specially developed expert system to model and report the
near real-time sensing of environmental conditions conducive to the onset
of a harmful algal bloom (HAB, e.g., "red tide"). Actual near
real-time in-situ fluorometry data was matched with wind speeds and
photosynthetically active radiation at the Long Key SEAKEYS station in
Florida Bay to simulate the onset of an HAB. These incidences were
e-mailed to the knowledge engineer as they occurred, and could in the
future be e-mailed to regulatory agencies, or posted to a Web site, as is
done with a similarly developed expert system for coral bleaching. This
approach shows promise with the future remote detection of HAB pigment
data via in-situ or satellite sensors.
Houston, S.H., P.P. Dodge, M.D. Powell, M.L. Black, G.M. Barnes, and P.S.
Chu. Surface winds in hurricanes from GPS-sondes: Comparisons with
observations. Preprints, 24th Conference on Hurricanes and Tropical
Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, 339 (2000).
The Hurricane Research Division (HRD) of NOAA began dropping NCAR Global
Positioning System (GPS) sondes in the vicinity of tropical cyclones (TC) on
an experimental basis in 1996. High-resolution vertical profiles of wind speed
and direction, temperature, dew point, and pressure were collected from
flight-level to the surface. The boundary layer and near surface winds
measured by sondes are considered particularly important, since few surface
wind instruments operate in sustained wind speeds greater than 50 m/s. There
have been some uncertainties about whether the profiles of boundary layer
(especially near the surface) winds and thermodynamic measurements made by
sondes in TC convective eyewalls were representative of conditions observed
at the surface. In addition, the averaging times of sonde winds relative to
fixed earth measurements from standard anemometers have been uncertain.
Based on the preliminary results from data in relatively high winds from
three hurricanes in 1998, the sondes appeared to be recording very accurate
and representative wind speeds when compared to in-situ measurements from
marine platforms. There appeared to be a slight negative bias in the sondes'
reported surface wind speeds, while there was hardly any bias in the wind
speeds adjusted to 10 m using the mean boundary layer winds averaged over
the lowest 500 m layer. The pressure and temperature observations also showed
good agreement between the sondes and surface platforms. Although these
results are very preliminary, it appeared that the sondes provided accurate
measurements in the boundary layer and near surface observations which are
extremely beneficial for operational and research purposes. The sample size
has been increased during the 1999 hurricane season. Therefore, more
definitive statistics for sondes and surface platform comparisons that
were available during the 1996-1999 hurricane seasons will be presented
at the conference.
Jacob, S.D., L.K. Shay, P.G. Black, and S.H. Houston. Upper ocean response
to hurricane wind asymmetries. Proceedings, 10th Conference on Interaction
of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000.
American Meteorological Society, Boston, J66-J67 (2000).
No abstract.
Jacobs, S.D., L.K. Shay, A.J. Mariano, and P.G. Black. The 3D oceanic
mixed layer response to Hurricane Gilbert. Journal of Physical
Oceanography, 30(6):1407-1429 (2000).
Upper-ocean heat and mass budgets are examined from three snapshots of data
acquired during and after the passage of Hurricane Gilbert in the western
Gulf of Mexico. Measurements prior to storm passage indicated a warm core
eddy in the region with velocities of O(1) m s-1. Based
upon conservation of heat and mass, the three-dimensional mixed layer
processes are quantified from the data. During and subsequent to hurricane
passage, horizontal advection due to geostrophic velocities is significant
in the eddy regime, suggesting that prestorm oceanic variability is important
when background flows have the same magnitude as the mixed layer current
response. Storm-induced near-inertial currents lead to large vertical
advection magnitudes as they diverge from and converge toward the storm
track. Surface fluxes, estimated by reducing flight-level winds to 10 m,
indicate a maximum wind stress of 4.2 N m-2 and a heat flux of
1200 W m-2 in the directly forced region. The upward heat flux
after the passage of the storm has a maximum of 200 W m-2
corresponding to a less than 7 m s-1 wind speed. Entrainment
mixing across the mixed layer base is estimated using three bulk entrainment
closure schemes that differ in their physical basis of parameterization.
Entrainment remains the dominant mechanism in controlling the heat and
mass budgets irrespective of the scheme. Depending on the magnitudes of
friction velocity, surface fluxes and/or shear across the mixed layer
base, the pattern and location of maximum entrainment rates differ in the
directly forced region. While the general area of maximum entrainment is
in the right-rear quadrant of the storm, the shear-induced entrainment
scheme predicts a narrow region of cooling compared to the stress-induced
mixing scheme and observed SST decreases. After storm passage, the
maximum contribution to the mixed layer dynamics is associated with
shear-induced entrainment mixing forced by near-inertial motions up to
the third day as indicated by bulk Richardson numbers that remained below
criticality. Thus, entrainment based on a combination of surface fluxes,
friction velocity, and shear across the entrainment zone may be more
relevant for three-dimensional ocean response studies.
Jiang, M., F. Chai, R.C. Dugdale, R.T. Barber, T.-H. Peng, Y. Chao, and
F.P. Wilkerson. Physical-biogeochemical modeling: Modulation of decadal
variability on ENSO events in the equatorial Pacific. AGU 2000 Fall
Meeting, San Francisco, CA, December 15-19, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 81(48):F702, OS11B-18
(2000).
Although decadal scale physical changes have been observed at several
locations in the Pacific Ocean, how these subtle but pervasive variations
have altered ecosystem processes and biogeochemical fluxes remains largely
unclear. To improve our understanding of physical variability and the
ecosystem response in the Pacific Ocean, a coupled physical-biogeochemical
model has been developed. A 10-component biogeochemical model has been
embedded in a Modular Ocean Model (MOM) with modifications and configurations
for the Pacific Ocean by Chao et al. at the JPL. The model is used
to simulate both physical and biogeochemical conditions between 1955-1993.
Based on this long-term model simulation, we present the results focused on
the role of decadal variations on the ENSO events occurring before/after the
climatic regime shift in 1976/1977. It is generally agreed that the signals
of Pacific Decadal Oscillation (PDO) primarily originate from the northwest
Pacific and affect the equatorial Pacific through intergyre exchanges or
atmospheric teleconnections. The detailed nature of ENSO events may be
modulated by these persistent processes. As a consequence, the ecosystem
behaviors in the equatorial Pacific should be affected by the modulated
ENSO, primarily through the depth of nutricline and upwelling variability.
With preliminary modeled results, we examine the possible decadal trends of
macro-nutrients (nitrate and silicate), which are regulating the primary
production, and the evolution of nutrient concentrations during ENSO before
and after climatic shifts. The phytoplankton responses to different levels of
available macro-nutrients are studied as well.
Jones, R.W., and H.E. Willoughby. Linear motion of a two-layer baroclinic
hurricane in shear. Preprints, 24th Conference on Hurricanes and Tropical
Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, 83-84 (2000).
No abstract.
Kang, W.-J., J.H. Trefy, T.A. Nelsen, H.R. Wanless. Direct atmospheric
inputs versus runoff fluxes of mercury to the lower Everglades and
Florida Bay. Environmental Science and Technology,
34(19):4058-4063 (2000).
Age-dated sediments from the lower Everglades and Florida Bay provide a
record of inputs of excess Hg from direct atmospheric input versus
runoff. Direct atmospheric fluxes of excess Hg to sediments in the lower
Everglades and Florida Bay, calculated using a mass balance model for
excess 210Pb, currently average 24 ± 9 µg
m-2 yr-1 and are comparable with recent results
from bulk atmospheric deposition. In contrast, present-day runoff fluxes
of excess Hg to area sediments are variable, ranging from about 4-160
µg m-2 yr-1. The runoff flux now carries
60-80% of the total flux of excess Hg to the sediments in areas near
river sloughs but less than 20% of the total flux of excess Hg in more
remote areas of Florida Bay. These results show the greater importance
of runoff relative to direct atmospheric deposition for Hg inputs to many
areas of the lower Everglades and immediately adjacent Florida Bay.
Thus, the choice of future water management strategies can play an
important role in controlling Hg inputs to the lower Everglades and
portions of Florida Bay.
Kaplan, J., and M. DeMaria. Large-scale characteristics of rapidly
intensifying tropical cyclones in the North Atlantic basin. Preprints,
24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston,
232-233 (2000).
An analysis of recent operational Atlantic basin tropical cyclone forecasts
issued by the National Hurricane Center indicates that tropical cyclone
intensity forecasting has proven to be less skillful than has tropical
cyclone track prediction. Moreover, the forecasting of rapid intensity
change has proven to be especially difficult, as was underscored by the
failure of operational models to adequately predict the rapid intensification
of Hurricanes Opal (1995) and Bret (1999). In this study, data obtained from
the SHIPS database for the period from 1989-1999 will be utilized to identify
the large-scale conditions that appear to be conducive to rapid
intensification. This will be accomplished by evaluating the magnitude of
various synoptic variables (e.g., vertical shear, relative-eddy
angular momentum fluxes) that were present at the start of each period of
rapid intensification to determine if these conditions were significantly
different from those associated with storms whose rates of intensification
were much less rapid. In addition, data collected by the Hurricane Research
Division during the 1999 hurricane season may also be employed to determine
if the statistical results obtained by analyzing the SHIPS database can be
confirmed by more detailed case studies.
Katsaros, K.B. Millennium perspectives. Bulletin of the American
Meteorological Society, 81(4):837-838 (2000).
No abstract.
Katsaros, K.B., and R.T. Pinker. Algorithm improvement for novel
applications in earth science research. Proceedings, First Meteosat
Second Generation Research Announcement of Opportunity Workshop,
Bologna, Italy, May 17-19, 2000. European Space Agency, ESA SP-452,
103-106 (2000).
No abstract.
Katsaros, K.B., P. Vachon, P.G. Black, P.P. Dodge, and E.W. Uhlhorn.
Wind fields from SAR: Could they improve our understanding of storm
dynamics? John Hopkins APL Technical Digest, 21(1):86-93 (2000).
Four hurricane images obtained by RADARSAT are examined for what
they reveal about the storms. Features seen include strong variations in
backscatter from the surface in and around convective cells associated
with rain cells and rainbands, coupled with increased backscatter in
regions of high wind outflow. Long linear features of scale 3-6 km are
observed in three of the four hurricanes, probably from secondary
circulations in the atmospheric boundary layer (roll vortices). They
occur between convective rainbands, where the descending motion could
produce a well-defined boundary layer. Although the origins of and the
mechanisms producing the features are still not clear, the high
resolution, wide-swath coverage modes of synthetic aperture radar provide
new observations and present important questions for further research.
Kelly, P.S., K.M.M. Lwiza, R.K. Cowen, and G.J. Goni. Low-salinity
pools at Barbados, West Indies: Their origin, frequency, and variability.
Journal of Geophysical Research, 105(C8):19,699-19,708 (2000).
A vertical array of conductivity-temperature sensors moored off the west
coast of Barbados, West Indies, from May 1996 to November 1997 revealed
a heterogeneous and variable salinity pattern punctuated by six intrusions
of low-salinity water (<34.5 psu) into the region. A typical intrusion
extended to 30 m depth and lasted ~25 days, although one intrusion
extended to 47 m and lasted 94 days. Water samples taken during an
intrusion in May 1997 have Radium 228/226 activity ratios of approximately
1, consistent with previous measurements in Barbados of water that
originated in the Amazon River mixing zone. The Amazon water likely was
translated to Barbados in rings spawned from the North Brazil Current.
Analysis of sea height anomaly derived from the TOPEX/Poseidon satellite
supports this conclusion and reveals that, contrary to previous studies,
rings are shed throughout the year, mostly during spring. The intrusions of
low-salinity water and their associated velocities dramatically changed
the already variable flow in our study area. We believe the complex salinity
and flow we observed represented the disorganized remnants of rings that
were at or near the ends of their lives. The changes we observed in the
velocity and water structure are interesting in their own right as evidence
of the Barbados region as a mixing zone and for their influence on
recruitment of larval fishes to the reef along the island's west coast.
Kiesling, T.L., J. Fell, and P.B. Ortner. Rapid molecular identification
of copepods froma plankton tow. AGU 2000 Ocean Sciences Meeting, San
Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions,
American Geophysical Union, 80(49):OS234, OS41F-04 (2000).
Florida Bay is a 1000 square mile subtropical lagoon located between the
Florida Keys and the Florida mainland. Like other estuarine systems, Florida
Bay serves as a nursery ground for commercially and recreationally important
species of fish. Despite the fact that the primary source of food for many
first-feeding larval fish is copepod nauplii, the trophodynamic role of the
zooplankton community in Florida Bay has historically been ignored. There is
currently a multi-agency effort underway to describe the Florida Bay
zooplankton community. Along with traditional sorting methods, molecular
methods are being designed to identify and quantify juvenile stages of
copepods so that their trophodynamic role can be more accurately defined.
We have developed a microtiter plate based hybridization assay to identify
copepod species in a mixed sample. With this method, species-specific probes
based on DNA sequence are used to identify the copepod species. This method
is superior to other PCR-based identification procedures, which require
several PCR reactions using several species-specific primers to determine
the identity of the DNA. Our technique requires one PCR reaction, which
creates an amplicon using universal primers that target a region containing
the probe sequences. This amplicon can be tested with a macroarray of
several different probes on a single plate. This is especially important
when dealing with the limited amounts of DNA that are extracted from these
small metazoans. We isolated eight of the most common species of copepods
found in Florida Bay, extracted their DNA and sequenced the large subunit of
ribosomal DNA for each species. The rDNA sequences were compared and
species-specific probes were designed based on base pair differences. Each
probe was immobilized to the wells of a microtiter plate. The plates were
hybridized with amplified and labeled target DNA from a mixed sample of
copepods. If the DNA from the species in question was present in the DNA
mix, it would bind to the species-specific probe. The labeled target DNA,
once bound to the probe, can be detected via a colorimetric assay. With
this method, We were able to identify each of six species of copepods from
mixed samples. Testing is now proceeding with the juvenile forms of the
copepods. Efforts are also underway to make the method quantitative.
King, D.B., J.H. Butler, S.A. Montzka, S.A. Yvon-Lewis, and J.W. Elkins.
Implications of methyl bromide supersaturations in the temperate North
Atlantic Ocean. Journal of Geophysical Research,
105(D15):19,763-19,769 (2000).
Methyl bromide saturation anomalies measured in the springtime North
Atlantic and summertime North Pacific Oceans during 1998 revealed persistent
supersaturations in the temperate waters of the northeastern Atlantic but
undersaturtions in tropical waters of both oceans. A comparison of data
from this study with those from a previous cruise to the northeastern
Atlantic suggests that methyl bromide is cycled seasonally in these waters
and perhaps in all temperate open-ocean waters. This means that the
calculated net flux of methyl bromide into the oceans is slightly less
negative than previously reported. With these new insights we estimate that
the global air-sea flux of methyl bromide ranges from -11 to -20 Gg
yr-1. Data combined from this and three previous cruises support
a flux dependence upon sea surface temperature, as reported recently by
Groszko and Moore (1998). Whereas sea surface temperature can account for
40-70% of the observed variability in methyl bromide globally, it is able
to reproduce only a small fraction of the observed seasonal cycle in the
temperate northeastern Atlantic. The development of reliable predictions of
air-sea fluxes of methyl bromide will require information on additional
variables as well.
King, D.B., J.H. Butler, S.A. Montzka, S.A. Yvon-Lewis, and J.W. Elkins.
Correction to "Implications of methyl bromide supersaturations in the
temperate North Atlantic Ocean." Journal of Geophysical Research,
105(D20):24,713-24,714 (2000).
No abstract.
King, D.B., J.H. Butler, S.A. Yvon-Lewis, S.A. Montzka, and J.W. Elkins.
Measurements of climatically important halocarbons in the North Pacific
Ocean. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19,
2000. Supplement to EOS, Transactions, American Geophysical Union,
81(48):F277, B22A-01 (2000).
Atmospheric halocarbons are significant contributors to stratospheric ozone
depletion and radiative heating of the atmosphere. Although we have a
reasonable understanding of the budgets of those species that are solely
anthropogenic, the calculated budgets of many naturally produced halocarbons
are not in balance. The oceanic contribution to these budgets can be complex,
is often large, and currently is not that well understood. Future changes
in global climate likely will alter the concentrations of natural halocarbons
in the air and seawater and, consequently, their air-sea fluxes. Field
measurements identify gross sensitivities that models can then use to
assess the potential effects of such changes in global climate. NOAA/CMDL
has measured the saturations of about 20 halocarbons during five separate
research cruises, dating back to 1994. These field missions have encompassed
a number of oceanic regions over different seasons. The results provide clues
as to the overall behavior of these gases in the surface ocean and lower
atmosphere. Here we present data from our most recent field project to the
North Pacific Ocean (10°N-58°N) during September and October of
1999. CH3Br was generally undersaturated, with supersaturations
observed in some coastal waters. CH3Cl was supersaturated south of
48°N, yet undersaturated in the Gulf of Alaska. CH3I was
supersaturated everywhere. Other brominated compounds, such as
CH2Br2 and CHBr3, were generally
supersaturated with higher values occurring in the subtropics. A correlation
between CH2Br2 and CHBr3 seawater partial
pressures suggests that these compounds have similar oceanic sources and/or
sinks. Nucleophilic substitution can account for only some of the production
of these compounds, implying that production from unidentified processes,
such as photolysis or biology, is important. Relationships between the methyl
halides and sea surface temperature can be useful in developing predictive
models of organic halide concentrations and fluxes to the atmosphere.
Correlations with other physical properties, such as chlorophyll, wind speed,
and solar irradiance, are also investigated.
Knaff, J.A., and Landsea, C.W. Application of the El Niņo-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 9(3):48-50 (2000).
No abstract.
Lamb, M.F., C.L. Sabine, R.M. Key, J.L. Bullister, F.J. Millero, R.H.
Wanninkhof, T.-H. Peng, A. Kozyr, and R.A. Feely. Dissolved inorganic
carbon crossover points in the Pacific Ocean. AGU 2000 Ocean Sciences
Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 80(49):OS122, OS22F-03 (2000).
Between 1991 and 1996, carbon measurements were made on 25 U.S. WOCE, U.S.
JGOFS, and NOAA OACES cruises in the Pacific Ocean. These cruises were
co-sponsored by the National Science Foundation, the U.S. Department of
Energy, and NOAA's Climate and Global Change Program. Although at least two
carbon parameters were measured on all of the cruises, dissolved inorganic
carbon (DIC) was the only parameter common to all of the cruises. The
measurements were collected over six years by ten different laboratories.
Together, these data comprise the most comprehensive high-precision survey
of carbon distributions in the Pacific Ocean with a greater than ten-fold
increase in the number of samples analyzed than for the GEOSECS expedition
of the early 1970s. As a part of the JGOFS Synthesis and Modeling Project,
we have been working to combine these data into an internally consistent,
unified data set. Additional DIC data collected by international
investigators have also been included, where possible, to fill in holes in
the U.S. survey program. In an effort to ensure the accuracy and internal
consistency of these data, we have compared the deep water (>2000 m) DIC
values measured on different cruises in areas where two or more cruises
overlapped or crossed (within ~100 km). Data from each of the
comparison stations were plotted against the density anomaly referenced to
3000 dbar (sigma 3). Polynomial fits of the data from each cruise were
evaluated at evenly-spaced intervals over the density range common to both
sets of stations. These results, together with information on the
calibration procedures, analyses of Certified Reference Materials (CRMs),
the quality of duplicate analyses, internal consistency with other carbon
parameters, and with large-scale correlations with hydrographic parameters,
were used to suggest minor adjustments to some of the cruises to optimize the
internal consistency of the data. Our results show that a unified Pacific
data set of over 30,000 samples can be achieved with an estimated
precision and accuracy of ą2 µmol/kg.
Lamb, M.F., C.L. Sabine, R.A. Feely, F.J. Millero, R.H. Wanninkhof, R.M.
Key, G.C. Johnson, K. Lee, T.-H. Peng, A. Kozyr, J.L. Bullister, and D.
Greeley. Consistency and proposed adjustments of Pacific Ocean
CO2 survey data. AGU 2000 Fall Meeting, San Francisco,
CA, December 15-19, 2000. Supplement to EOS, Transactions, American
Geophysical Union, 81(48):F700, OS11B-10 (2000).
Between 1991 and 1996, carbon measurements were made on 24 WOCE/JGOFS/OACES
survey cruises in the Pacific Ocean. This combined database will be used to
determine the distribution and inventory of carbon parameters in the Pacific
Ocean, and will enhance our understanding of the ocean carbon cycle,
including estimates of the anthropogenic CO2 uptake by the
oceans. Of the four measurable carbon parameters, (dissolved inorganic
carbon (DIC), total alkalinity (TAlk), fugacity of CO2
(fCO2), and pH), DIC was measured on all the cruises, and
TAlk was the second most measured. We examined the data where cruises
overlapped using several independent techniques, and have proposed
adjustments that will result in a consistent, unified data set. Based on
our results, we recommend DIC adjustments for P16N, P17N, and P2, and
TAlk adjustments for P8S, P17C, P17N, P2 and P31. Details of our
proposed adjustments are posted at
http://cdiac.esd.ornl.gov/oceans/glodap/index.html. This CO2
data set represents the most comprehensive high-precision survey of carbon
distributions in the Pacific Ocean since the GEOSECS expedition, and
provides an order of magnitude improvement in the quality and quantity of
Pacific DIC and Talk data. With the proposed adjustments, DIC and TAlk
have an estimated overall accuracy of ~3 and 5 µmol
kg-1 respectively.
Landsea, C.W. Climate variability of tropical cyclones: Past, present,
and future. In Storms (Volume 1), R.A. Peilke, Sr. and R.A. Peikle,
Jr. (eds.). Routledge, New York (ISBN 041517239X), 220-241 (2000).
No abstract.
Landsea, C.W. El Niņo-Southern Oscillation and the seasonal predictability
of tropical cyclones. In El Niņo and the Southern Oscillation: Multiscale
Variability and Global and Regional Impacts, H.F. Diaz and V. Markgraf
(eds). Cambridge University Press (ISBN 0521621380), 149-181 (2000).
Perhaps the most dramatic effect that El Niņo has upon the climate system is
in changing tropical cyclone characteristics around the world. This chapter
reviews how tropical cyclone frequency, intensity, and areas of occurrence
are altered in all of the cyclone basins by the phases of El Niņo-Southern
Oscillation (ENSO). In addition to ENSO, other global (such as the
stratospheric Quasi-Biennial Oscillation) and local factors (such as sea
surface temperature, monsoon intensity and rainfall, sea level pressures, and
tropospheric vertical shear) can also help modulate tropical cyclone
ariability. Understanding how these various factors relate to tropical
cyclone activity can be challenging due to the fairly short (on the scale of
only tens of years) record of reliable data. Despite this limitation, many of
the factors that have been linked to tropical cyclones, the foremost of which
being ENSO, have substantial lead relationships and can be utilized to provide
seasonal forecasts of tropical cyclones. Details of methodologies that have
been developed for the North Atlantic, northwest Pacific, south Pacific and
Australian basin tropical cyclones are presented, as well as the real-time
forecasting performance of Atlantic hurricanes as issued by Professor William
Gray.
Landsea, C.W., and J.A. Knaff. Application of the El Niño-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 9(1):32-34 (2000).
No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niño-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 9(2):31-33 (2000).
No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niņo-Southern
Oscillation CLImatology PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 9(4):48-50 (2000).
No abstract.
Landsea, C.W., and J.A. Knaff. How much "skill" is there in forecasting
El Ni Niņo? Weatherzine, 23:2-4 (2000).
No abstract.
Landsea C.W., and J.A. Knaff. How much skill was there in forecasting
the very strong 1997-1998 El Niņo? Bulletin of the American
Meteorological Society, 81(9):2107-2120 (2000).
The very strong 1997-1998 El Niņo was the first major event in which
numerous forecasting groups participated in its real-time prediction. A
previously developed simple statistical tool, the El Niņo-Southern
Oscillation Climatology and Persistence (ENSO-CLIPER) model, is utilized
as a baseline for determination of skill in forecasting this event. Twelve
statistical and dynamical models were available in real time for evaluation.
Some of the models were able to outperform ENSO-CLIPER in predicting either
the onset or the decay of the 1997-1998 El Niņo, but none were successful
at both for a medium-range two season (6-8 months) lead time. There were no
models, including ENSO-CLIPER, able to anticipate even one-half of the actual
amplitude of the El Niņo's peak at medium-range (6-11 months) lead. In
addition, none of the models showed skill (i.e., lower
root-mean-square error than ENSO-CLIPER) at the zero season (0-2 months)
through the two season (6-8 months) lead times. No dynamical model and only
two of the statistical models (the canonical correlation analysis [CCA] and
the constructed analog [ANALOG]) outperformed ENSO-CLIPER by more than 5% of
the root-mean-square error at the three season (9-11 months) and four season
(12-14 months) lead time. El Niņo impacts were correctly anticipated by
national meteorological centers one-half year in advance, because of the
tendency for El Niņo events to persist into and peak during the boreal
winter. Despite this, the zero to two season (0-8 month) forecasts of the
El Niņo event itself were no better than ENSO-CLIPER and were in that
sense, not skillful, a conclusion that remains unclear to the general
meteorological and oceanographic communities.
Landsea, C.W., and J.A. Knaff. How much skill was there in forecasting
the very strong 1997-1998 El Niño? Proceedings, 10th Conference
on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May
29-June 2, 2000. American Meteorological Society, Boston, J46 (2000).
No abstract.
Landsea, C.W., C.A. Anderson, G. Clark, P. Hungerford, C. Neumann, M. Zimmer,
and J. Fernandez-Partagas. The Atlantic hurricane database re-analysis
project: Results for 1851-1885. Minutes, 54th Interdepartmental Hurricane
Conference, Houston, TX, February 14-18, 2000. Office of the Federal
Coordinator for Meteorological Services and Supporting Research, Washington,
D.C., A230-A231 (2000).
No abstract.
Landsea, C.W., C. Anderson, N. Charles, G. Clark, J. Fernandez-Partagas,
P. Hungerford, C. Neumann, and M. Zimmer. The Atlantic hurricane database
re-analysis project: Results for 1851-1885. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 542-543 (2000).
No abstract.
Lawrence, J.R., S.D. Gedzelman, and J.F. Gamache. Tropical cyclogenesis
and stable isotope ratios of water. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 260-261 (2000).
No abstract.
Leaman, K.D., W.D. Wilson, and Z.D. Garraffo. Physical variability of
surface currents in the the Panama-Colombia Gyre: Nature, causes, and
comparisons with a high-resolution numerical model. AGU 2000 Ocean
Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 80(49):OS33,
OS11R-09 (2000).
As part of the National Oceanographic Partnership Program Year of the Ocean
(YOTO) contribution, a total of 32 WOCE surface drifters have to date been
launched in the southwestern Caribbean Sea using vessels of the Colombian
Navy. These deployments consist of groups of eight surface drifters launched
nominally every three to four months on a line between Cartagena and San
Andres Island. All drifters have been drogued at a depth of 15 m and are
designed to report surface positions and temperatures. This launch program
is planned to continue through at least the next year with launches of six
floats roughly every three months. These drifter tracks can be found at Web
pages for the NOPP drifters (www.drifters.doe.gov), the IAS oceanography
page (IASlinks.org), or the Intra-Americas Sea Initiative page
(www.rsmas.miami.edu/groups/IASI/IASIhome.htm). The purpose of these
deployments is to explore the structure and variability of a prominent
circulation feature in the southwestern Caribbean known as the
Panama-Colombia Gyre (PCG). This cyclonic gyre has been revealed by the
drifter tracks obtained so far to be a permanent feature of the
circulation but one that shows considerable seasonal and shorter-term
variability as well. Retention times for drifters launched in the PCG
are order several months. Very few drifters from the open Caribbean find
their way into the PCG; however, a large number of PCG drifters exit the
PCG at various locations and times, and a significant number of these
become trapped in shelf waters south of Cuba. This latter fact has
implications for biological problems of larval transport and
interconnectivity of coastal habitats. Observed drifter tracks are
compared to numerical surface drifters "deployed" in a high-resolution
isopycnic-coordinate numerical model. Similar seasonal variability is
observed in both real and numerical drifter trajectories; in particular,
a deformation of the flow field in late summer has been observed in the
model, as well as in two sequential years of drifter observations. Over
longer periods, numerical drifter concentrations in the PCG decrease
until a balance is achieved between northward Ekman advection and
diffusion of drifters from the interior.
Lee, K., J.-Z. Zhang, and R. Wanninkhof. Carbon export in nitrate-depleted
tropical and subtropical oceans: Implication of nitrogen fixation. AGU
2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement
to EOS, Transactions, American Geophysical Union, 81(48):F693,
OS72E-12 (2000).
The export of carbon from surface waters to the interior of the ocean is a
central mechanism controlling the net uptake of carbon dioxide from the
atmosphere. Existing estimates of the vertical carbon export vary greatly
in regional and global comparisons. We estimate the biologically-mediated
vertical carbon export, referred to as "new production," from the mean
annual cycle of total inorganic carbon concentration normalized to salinity
(NDIC = DIC × 35/S) in the mixed layer. It is assumed that the
decrease in NCT from early spring to fall is solely caused by biological
uptake and subsequent transport out of the upper oceans. Seasonal drawdown
of NDIC in the mixed layer is quantified from regional algorithms relating
NDIC to sea surface temperature (SST) and nitrate (NO3-)
combined with seasonal changes in climatological SST and
NO3- fields, and separately from the surface partial
pressure of CO2 and alkalinity fields using thermodynamic models.
The two independent methods show similar regional trends and yield global
new production values of 7.5 GtC/yr and 8.6 GtC/yr, respectively. A
significant fraction of the global total, 0.8-1.1 GtC/yr, is exported in
the absence of measurable nitrate levels in the oligotrophic tropical and
subtropical oceans. This estimate is a direct indication of carbon export
supported by nitrogen fixation. The value constitutes a significant fraction
(30-50%) of the total new production in the oligotrophic oceans.
Lee, K., F.J. Millero, R.H. Byrne, R.A. Feely, and R. Wanninkhof. The
recommended dissociation constants for carbonic acid seawater.
Geophysical Research Letters, 27(2):229-232 (2000).
A coherent representation of carbonate dissociation constants and
measured inorganic carbon species is essential for a wide range of
environmentally important issues such as oceanic uptake of anthropogenic
CO2 and carbon cycle depictions in ocean circulation models.
Previous studies have shown varying degrees of discordance between
calculated and measured CO2-system parameters. It is unclear
if this is due to errors in thermodynamic models or in measurements. In
this work, we address this issue using a large field data set (15,300
water samples) covering all ocean basins. Our field data, obtained using
laboratory-calibrated measurement protocols, are most consistent with
calculated parameters using the dissociation constants of Mehrbach et
al. (1973) as refit by Dickson and Millero (1987). Thus, these
constants are recommended for use in the synthesis of the inorganic
carbon data collected during the global CO2 survey during
the 1990s and for characterization of the carbonate system in seawater.
Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng.
Global relationships of total inorganic carbon with temperature and
nitrate in surface seawater. Global Biogeochemical Cycles,
14(3):979-994 (2000).
High quality total inorganic carbon (CT) measurements
made in the major ocean basins as part of the Joint Global Ocean Flux
Study (JGOFS), the National Oceanic and Atmospheric Administration/Ocean
Atmosphere Carbon Exchange Study (NOAA/OACES), and the Department of
Energy/World Ocean Circulation Experiment (DOE/WOCE) programs are related
to sea surface temperature (SST) and nitrate (NO3-).
A simple two-parameter function with SST and NO3-
of the form NCT = a +
b SST + c SST2 + d NO3
- fits salinity (S)-normalized surface CT
(NCT = CT × 35/S) data
for different parts of the oceans within an area-weighted error of
±7 µmol kg-1 (1 sigma). Estimated values of
NCT using the derived algorithms with
NO3- and SST are compared with values calculated
from the surface partial pressure of CO2
(pCO2SW) (Takahashi et al., 1997) and total
alkalinity (AT) (Millero et al., 1998) fields
using thermodynamic models. Comparisons of the estimated values of
NCT with measurements not used to derive the same
algorithms, and comparisons with the values calculated from global
AT and pCO2SW fields, give a
realistic uncertainty of ±15 µmol kg-1 in estimated
CT. The derived correlations of NCT
with SST and NO3- presented here make it possible
to estimate surface CT over the ocean from
climatological SST, S, and NO3- fields.
Lee, W.-C., and F.D. Marks. An objective method to determine tropical
cyclone center near landfall from WSR-88D data: The GBVTD-simplex algorithm.
Preprints, 24th Conference on Hurricanes and Tropical Meteorology,
Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society,
Boston, 310-311 (2000).
No abstract.
Lee, W.-C., and F.D. Marks. Tropical cyclone kinematic structure
retrieved from single Doppler radar observations, Part II: The
GBVTD-simplex center finding algorithm. Monthly Weather Review,
128(6):1925-1936 (2000).
This paper is the second of a series and focuses on developing an
algorithm to objectively identify tropical cyclone (TC) vorticity centers
using single-Doppler radar data. The first paper dealt with the
formulation of a single-Doppler radar TC wind retrieval technique, the
ground-based velocity-track-display (GBVTD), and the results are verified
using analytical TCs. It has been acknowledged that the quality of the
GBVTD-retrieved TC circulation strongly depends on accurately knowing its
center position. However, existing single-Doppler radar center finding
algorithms are limited to estimate centers for axisymmetric TCs. The
proposed algorithm uses a simplex method to objectively estimate the TC
vorticity center by maximizing GBVTD-retrieved mean tangential wind.
When tested with a number of axisymmetric and asymmetric analytical TCs,
the accuracy of the TC centers estimated by the GBVTD-simplex algorithm
is approximately equal to 340 m from the true center. When adding 5 m
s-1 random noise to the Doppler velocities, the accuracy of the
TC centers is nearly unchanged at 350 m. When applying the GBVTD-simplex
algorithm to Typhoon Alex (1987), the estimated uncertainty varies between
0.1 and 2 km. When the overall velocity gradient is weak, the uncertainties
in the retrieved TC centers are usually large. The GBVTD-simplex algorithm
sometimes has problems finding a solution when a large sector of Doppler
radar data is missing in conjunction with weak velocity gradients. The
GBVTD-simplex algorithm significantly reduces the uncertainties in
estimating TC center position compared with existing methods and improves
the quality of the GBVTD-retrieved TC circulation. The GBVTD-simplex
algorithm is computationally efficient and can be easily adapted for
real-time applications.
Lee, W.-C., B. J.-D. Jou, P.-L. Chang, and F.D. Marks. Tropical cyclone
kinematic structure retrieved from single-Doppler radar observations. Part
III: Evolution and structures of Typhoon Alex (1987). Monthly Weather
Review, 128(12):3982-4001 (2000).
This paper is the third of a series that focuses on the applications of the
ground-based velocity track display (GBVTD) technique and the GBVTD-simplex
center finding algorithm developed in the previous two papers to a real
tropical cyclone (TC). The evolution and structure of Typhoon Alex (1987),
including full tangential winds, mean radial winds, one component of the mean
flow, and their derived axisymmetric angular momentum and perturbation
pressure fields are reconstructed from 16 volume scans (6.5 h of data with
a 2-h gap) from the Civil Aeronautic Administration (CAA) Doppler radar
while Typhoon Alex moved across the mountainous area in northern Taiwan.
This analysis retrieves a plausible and physically consistent
three-dimensional primary circulation of a landfalling TC using a single
ground-based Doppler radar. Highly asymmetric wind structures were resolved
by the GBVTD technique where the maximum relative tangential wind at
z = 2 km evolved from 52 m s-1 (before landfall), to
less than 40 m s-1 (after landfall), to less than 35 m
s-1 (entering the East China Sea). Alex's eye began to fill with
precipitation while its intensity decreased rapidly after landfall, a
characteristic of circulations disrupted by terrain. The mean radial wind
field revealed a layer of low-level inflow in agreement with past TC
observations. The outward slope of the eyewall reflectivity maximum was
consistent with the constant angular momentum contours within the
eyewall. After Alex entered the East China Sea, its circulation became
more axisymmetric. The axisymmetric perturbation pressure field was
retrieved using the gradient wind approximation which, when used in
conjunction with one or more surface pressure measurements within the
analysis domain, can estimate the central pressure. The retrieved
perturbation pressure fields at two time periods were compared with
surface pressures reported in northern Taiwan. Considering the
assumptions involved and the influence of terrain, good agreement (only
1V2-mb deviation) was found between them. This agreement indicates the
relative quality of the GBVTD-retrieved axisymmetric circulation and
suggests GBVTD-retrieved quantities can be useful in operational and
research applications.
Lonfat, M., F.D. Marks, and S. Chen. A study of the rain distribution in
tropical cyclones using TRMM/TMI. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 480-481 (2000).
No abstract.
Lonfat, M., F.D. Marks, and S. Chen. Characterization of the rain
distribution in tropical cyclones using TRMM/TMI-PR. AGU 2000 Spring
Meeting, Washington, D.C., May 30-June 3, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 81(19):S237-S238,
H42B-16 (2000).
The goals of this study are (1) to improve our understanding of tropical
cyclone (TC) precipitation fields by developing a climatology of rainfall
distribution and vertical profiles of hydrometeors and heating in TCs around
the globe, and (2) to develop methodologies to validate operational and
research model forecasts of TC rainfall distribution and structure. Surface
rain estimates from the NASA Tropical Rainfall Measuring Mission (TRMM)
Microwave Imager (TMI) and Precipitation Radar (PR) were used to study
the global TC rainfall distribution. From November 1997 to December 1998,
87 storms were observed, providing approximately 1200 events, ranging from
tropical storm intensity to category 4 hurricanes. At the time of the
satellite measurement, approximately 70% of the events were tropical storms,
25% were category 1-2 hurricanes, and 5% were category 3 or higher. Although
the sample size for major hurricanes is smaller than other categories, we
have more than 50 observations, which is an order of magnitude larger than
previous studies. TMI was used to develop the climatology, as the instrument
swath allows a more extended coverage of the storms than PR. For each
event, we derive mean rain rates in 10-km rings around the TC center.
Averaging these distributions produces rates up to 5 mm h-1
close to the center. Rain rates decrease rapidly below 1 mm
h-1 by 200 km radius. We examine the rain rate distribution as
a function of the storm intensity and geographical location. Close to the
storm center, the mean rates are greater than 15 mm h-1 for
category 3 and higher hurricanes, and about 3 mm h-1 for tropical
storms. Rain distributions show strong asymmetries in the rain patterns
between the different basins. PR data were used on several individual 1999
storm cases (Floyd and Bret) and compared to TMI distributions. This
comparison pointed out a problem in version 4 of the TMI surface rain
algorithm. We are also in the process of comparing our TC rain rate
distributions with a high-resolution model simulation. Our study provides
a broad description of hurricane precipitation distributions, which is of
fundamental use as a climatological basis, notably for simulation purpose,
and gives a feedback for TRMM/TMI algorithm improvement as well.
Lonfat, M., F.D. Marks, and S.S. Chen. Comparison of TRMM/TMI-PR and
airborne radar rainfall distributions in severe Atlantic hurricanes.
AGU 2000 Fall Meeting, San Francisco, CA, December 15-19, 2000.
Supplement to EOS, Transactions, American Geophysical Union,
81(48):F158, A21G-08 (2000).
The goals of this study are to improve our understanding of tropical cyclone
(TC) precipitation fields by constructing rainfall distributions in severe
hurricanes, and to validate Tropical Rainfall Measuring Mission (TRMM) results
by comparing distributions with aircraft radar observations. Surface rain
estimates from the NASA TRMM Microwave Imager (TMI) and Precipitation Radar
(PR) are used to determine rainfall distributions for five major 1998-1999
Atlantic hurricanes (category 3 or higher). Only TRMM orbits which fully
observe TC cores are considered in order to improve comparisons with
aircraft data. Airborne radar data aboard the NOAA WP-3D aircrafts are
examined for individual cases such as Floyd. For each event, we derive mean
rain rates in 10 km rings around the TC center. Averaging distributions for
TRMM/TMI produces rates up to 8 mm h-1 close to the center,
within about 70 km. Rates are below 1 mm h-1 by 250 km. Rain
rates from TRMM/PR are similar in magnitude close to the center, but decrease
more sharply with radial distance than TMI rates. Probability density
functions (PDF) are constructed as well. Both TMI and PR PDF resemble normal
distributions. The TMI distribution is narrower and shifted to larger rain
rates than the PR curve. Peaks are located at about 8 and 5 mm
h-1 respectively. TRMM/PR results seem to match better with
airborne radar distributions than TMI does.
Luo, J., P.B. Ortner, D. Forcucci, and S.R. Cummings. Diel vertical
migration of zooplankton and mesopelagic fish in the Arabian Sea.
Deep-Sea Research, II, 47(7-8):1451-1473 (2000).
Acoustic (153 kHz ADCP and 12 kHz hull-mounted transducers) data and
MOCNESS (MOC01 and MOC10) net tow samples collected in the Arabian Sea
during the Spring Intermonsoon (April/May) and Southwest Monsoon (August)
in 1995 documented substantial diel migrations of fish and zooplankton
despite the year-round presence of an oxygen minimum (<0.2 ml
l-1 at 125-150 m). Fish and zooplankton layers were
distinguished by comparing 12 kHz sonar and 153 kHz ADCP backscatter
data, which indicated that the strongly migrating layers were
predominantly composed of fishes. Fish vertical migration speeds were
independently estimated from the slopes of the volume scattering layers
and from the vertical velocity components of the ADCP, yielding average
speeds of 4 and 3 cm s-1 and maximum speeds of 13 and 10 cm
s-1, respectively. A few migrating zooplankton layers were
identified with an average speed of about 2 cm s-1 and maximum
speeds as high as 8 cm s-1. Migration depths for both
zooplankton and fish differed somewhat amongst stations and appeared to
be related to local hydrographic conditions (principally the vertical
gradients in DO and water temperature). Zooplankton displacement volumes
at individual sites suggested that zooplankton biomass during the
Southwest Monsoon could be as much as fivefold greater than during the
Spring Intermonsoon. This observation was confirmed for the region in
general by first deriving a relationship between ADCP backscatter
intensity and daytime zooplankton biomass and then comparing the latter
between cruises using daytime ADCP data taken along a 1500 km transect
that extended from the coast of Somalia to the center of the northern
basin.
Marks, F.D., M.L. Black, and H.A. Friedman. 2000 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, FL (published for limited distribution),
97 pp. (2000).
No abstract.
Marks, F.D., L. Selevan, and J.F. Gamache. WSR-88D derived rainfall
distributions in Hurricane Danny (1997). Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 298-299 (2000).
A tropical cyclone (TC) poses a significant quantitative precipitation
forecast (QPF) problem as evidenced by the recent tragic loss of life and
property from rainfall during Hurricanes Mitch (1998) and Floyd (1999).
Improved QPF is one of the primary objectives of the U. S. Weather Research
Program (USWRP), and a specific goal of the Hurricane at Landfall effort
under USWRP. Estimates of rainfall based on radar and other remote sensors
offer promising avenues for improvement. The current level of QPF skill for
TCs in the United States is to predict the peak storm rainfall amount using
the "rule of thumb" first proposed by Kraft in the late 1950s, which states
that the maximum storm rainfall amount will be 100 inches divided by the
storm forward motion in knots. While this "rule of thumb" provides a
reasonable estimate of the peak storm total rain, it provides no information
about the distribution of rain in space or time. There is also no adjustment
in the rule for storm intensity, topography, or other dynamical or
microphysical parameters. A major stumbling block to improving over this
simple "rule of thumb" is a lack of a comprehensive climatology of TC
precipitation, i.e., a description of the distribution of rain in space and
time. This study focuses on the distribution of WSR-88D radar derived rain in
space and time during Hurricane Danny from 17-21 September 1997. The WSR 88D
radars provides 1-h mean rain estimates (R) over a domain extending
to 230 km range from the radar with a 4 × 4 km resolution (Digital
Precipitation Array, DPA). Over the four days, Danny, a category 1 hurricane,
was visible from four different WSR-88D radars as it tracked slowly
east-northeastward along the Gulf coast. The rain estimates from the four
radars provide an excellent opportunity to estimate the TC precipitation
distribution in space and time as the storm passed along the Louisiana,
Mississippi, and Alabama coasts. The radial distribution of the mean R
is calculated in 10 km radial bands out to 300 km from the storm center
for each hour and for the total four-day period. The probability distribution
of R is also computed for each 10 km radial band in 1 dBR
(10log10R) steps from 0.3-300 mm h-1 (-5 to 25
dBR) for each hour and the total four-day period. These distributions in
range and intensity are compared to results from earlier studies done using
rain gage estimates.
Mayer, D.A., M.O. Baringer, R.L. Molinari, and G.J. Goni. Comparison
of hydrographic and altimetric estimates of sea level height variability
in the Atlantic Ocean. AGU 2000 Fall Meeting, San Francisco, CA,
December 15-19, 2000. Supplement to EOS, Transactions, American
Geophysical Union, 81(48):F740, OS21D-13 (2000).
Using an ensemble of expendable bathythermograph (XBT) profiles and
TOPEX/Poseidon (T/P) altimeter data, we have considered how much can be
inferred about the internal field of mass from sea level changes for the
period 1993 through 1997. Sea height anomalies (SHA) derived from T/P data
are compared to temperature anomalies (TA) and to dynamic height anomalies
(DHA) from 10°S to 40°N along two well sampled XBT sections on the
western and eastern sides of the Atlantic Ocean. XBT profiles were matched
(time/location) to SHA, converted into DHA using TS relationships and then
binned monthly into 2° of latitude by 4° of longitude boxes. The
vertical mass distribution cannot always be inferred from SHA alone.
Specifically, the relationships between SHA and both TA and DHA can be
problematic if SHA are small. This occurs in the transition regions
between the tropics (where temperature variability is largest in the
thermocline due to wind-driven ocean dynamics), and in the subtropics
(where variability is largest near the surface due to surface fluxes).
Transition regions are characterized by competing influences between
surface and thermocline variability that act in opposition; hence, SHA
are not particularly well suited in drawing inferences about the
temperature of the upper ocean. Generally, the relationships between SHA
and DHA for residual signals (obtained by removing the annual cycle) are
poor. The exceptions are in two areas of large sea height variability in
the western basin where there is significant interannual variability. The
first is in the tropics in the vicinity of the tropical gyre trough, and
the second is in the Gulf Stream near 70°W, 38°N. An analysis of
Panulirus data at (32.2°N, 64.5°W) suggests that in-situ
data may be needed down to at least 1000 m where interannual variability
accounts for about 40% of the SHA variance.
McAdie, C.J., and P.P. Dodge. Maximum sustained winds in Hurricane Irene
as measured by the Miami WSR-88D. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 212-213 (2000).
No abstract.
McArthur, C., R. Ferry, and J.R. Proni. Amenities monitoring for dredged
material disposal management. Proceedings, 17th Conference of the
Coastal Society: Coasts at the Millennium, Portland OR, July 9-12,
2000. The Coastal Society, 6 pp. (2000).
Valuable amenities are present throughout U.S. coastal waters, from coral
reefs, to oyster beds, to coastal fisheries. In essentially every case in
which navigation and/or maintenance dredging is contemplated, the issues of
potential impact of dredging activities on nearby amenities arise. In order
to evaluate that potential impact, long-term monitoring of amenities is
required. Key management issues related to amenities include: (1) reduction
or elimination of dredging impacts; (2) scheduling ("windows") for dredging
and dredged material disposals; (3) monitoring of transport to, and effects
upon amenities; and (4) compliance with defined procedures for dredging
activities. While the data needed for management decisions may vary from
location to location, certain basic measurement needs appear almost
universally: (1) characterization and quantification of dredged sediments
arriving at amenities sites; (2) determination of "natural" sediment ranges at
amenities sites; (3) photosynthetic light reductions; (4) sediment
resuspension and transport; and (5) other sources of materials of potential
impact to amenities sites. Dredging and disposal must also be considered in
the context of temporal "windows." In the Miami Offshore Disposal Site
project, data for management of dredging activities is coordinated between
the disposal and amenities (coral reef) sites where dumping windows are
determined by realtime current meter data, indicating potential transport to
the reef site. In the Pacific Northwest, "curtains" of dredge-related
sediment may inhibit upstream spawning activities of valued fisheries
resources and thus they are subject to similar temporal windows.
Mestas-Nunez, A.M. Orthogonality properties of rotated empirical
modes. International Journal of Climatology, 20(12):1509-1516
(2000).
The properties (spatial orthogonality and temporal uncorrelatedness) of
orthogonally-rotated empirical modes depend on the normalization of the
modes prior to rotation. It is shown here that these properties also depend
on how the empirical modes are formulated. The preferred convention is one
that allows us to reconstruct the data from the unrotated or rotated modes.
When the empirical modes are normalized so that the spatial eigenvectors
are unit length (i.e., EOFs), the rotated modes preserve spatial
orthogonality but are no longer temporally uncorrelated. Relaxing the
temporal orthogonality in this way does not prejudice conclusions that can
be inferred regarding the temporal couplings of the rotated modes.
Mestas-Nunez, A.M., and D.B. Enfield. El Niņo-Southern Oscillation:
Canonical and non-canonical aspects. Proceedings, 24th Annual Climate
Diagnostics and Prediction Workshop, Tucson, AZ, November 1-5, 1999.
National Weather Service, 111-114 (2000).
The main goal of this paper is to investigate and compare the atmospheric
signatures associated with the canonical ENSO and residual components of
the SST anomaly variability in the eastern tropical Pacific. An expanded
version of this paper will appear in the Journal of Climate
(Mestas-Nuņez and Enfield, 2001).
Molinari, R.L., and J.F. Festa. Effect of subjective choices on the
objective analysis of sea surface temperature data in the tropical Atlantic
and Pacific Oceans. Oceanologica Acta, 23(1):3-14 (2000).
Many subjective choices are required to perform an objective interpolation
(OI) analysis of environmental variables. Herein, we consider the effects
on the statistical analysis of sea surface temperature (SST) using (1) a
structure function or covariance analysis, (2) different analytical
expressions to represent the statistics of the raw data, and (3) different
historical SST data sets. The historical data sets are the well-sampled
Comprehensive OceanAtmospheric Data Set (COADS) and the poorly sampled
historical expendable bathythermograph (XBT) data set. Results from these
analyses are used to generate error maps for a poorly-sampled, two month
XBT array and a proposed well-sampled profiling float array. For the
relatively data-rich COADS analysis, decorrelation scales are the same
using either the structure function or covariance analyses. Results differ
for the data-poor XBT analysis. Representative decorrelation scales in the
Pacific (Atlantic) are about 11-14 (6-10) degrees in the zonal direction
and 4-7 (3-6) degrees in the meridional direction. As COADS SST data are
less precise than XBT SST data, error and signal variances are greater for
the former. The choice of analytical fit to the raw data (needed to generate
error maps) has a dramatic effect on the resulting uncertainty fields.
Gaussian fits, because of their parabolic shape near the origin, result
in smaller errors than exponential fits for the same observing array.
Finally, the proposed float array can achieve the accuracies needed to
resolve satisfactory upper layer heat content changes over larger areas
than the present XBT network.
Morisseau-Leroy, N., M.K. Solomon, and J. Basu. Oracle 8i: Java
Component Programming. Osborne McGraw-Hill (ISBN 0072127376),
697 pp. (2000).
No abstract.
Murillo, S.T., W.-C. Lee, and F.D. Marks. Evaluating the GBVTD-tropical
center finding simplex algorithm. Preprints, 24th Conference on Hurricanes
and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000.
American Meteorological Society, Boston, 312-313 (2000).
The GBVTD simplex algorithm has been tested using axisymmetric and asymmetric
analytic tropical cyclones by Lee et al. (1999). The algorithm
objectively identifies the tropical cyclone center by maximizing the
GBVTD-derived mean tangential wind field. Lee and Marks (1999) applied the
GBVTD simplex algorithm to Typhoon Alex (1987). However, a true center was
not available to verify the accuracy of the algorithm. This study applies
the GBVTD simplex algorithm to Hurricane Danny (1997). The estimated storm
track derived by the algorithm is compared to radar and aircraft storm fixes.
The derived track is in good agreement with the true storm track within 2 km.
Results will be presented that show how the GBVTD simplex algorithm improves
the quality of the GBVTD retrieved wind analysis.
Nelsen, T.A., S.J. Stamates, B.J. Elkind, W.P. Dammann, and J.R. Proni.
Field evaluation of the temporal and spatial variations in total suspended
matter and current fields at Chesapeake Bay Site 104 and contiguous areas.
Final Report, U.S. Army Corps of Engineers, MIPR No. W81W3@00604995, 47 pp.
(2000).
No abstract.
Nolan, D.S., M.T. Montgomery, and P.D. Reasor. Studies of the wavenumber
one instability in hurricane-like vortices. Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, 29-30 (2000).
No abstract.
Ooyama, K.V. A dynamic and thermodynamic foundation for modeling the moist
atmosphere with classical thermodynamics and parameterized microphysics.
Preprints, 24th Conference on Hurricanes and Tropical Meteorology,
Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society,
Boston, 561-562 (2000).
No abstract.
Otero, S., N. Morisseau-Leroy, N. Carrasco, and M.D. Powell. A distributed
real-time hurricane wind analysis system. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 197-198 (2000).
No abstract.
Parrish, J.R., M.L. Black, S.H. Houston, P.P. Dodge, and J.J. Cione. The
structure of Hurricane Irene over South Florida. Preprints, 24th
Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL,
May 29-June 2, 2000. American Meteorological Society, Boston, 456-457
(2000).
On October 15, 1999, Hurricane Irene made landfall on the southwest coast of
Florida and tracked to the northeast across the peninsula before emerging
into the Atlantic Ocean north of Palm Beach. Irene was a Category 1 hurricane
at landfall with maximum sustained surface winds estimated at 65 kts and a
central pressure of ~982 mb. A NOAA WP-3D aircraft conducted a landfall
research mission during the time Irene was crossing Florida. The aircraft,
operated by the Aircraft Operations Center (AOC) and staffed by scientists
from HRD, flew at an altitude of 8,000 feet and completed a flight track that
provided coverage over the South Florida Peninsula and adjacent coastal
waters in the Gulf of Mexico, Florida Bay, and Atlantic Ocean. In addition to
the in-situ wind and thermodynamic measurements at flight-level, observations
from the airborne Doppler tail radar, lower-fuselage radar, GPS dropsondes,
and step-frequency microwave radiometer (SFMR, surface wind speeds) were
collected by the AOC and HRD crew. A detailed description of the wind and
thermodynamic structure of Irene while over South Florida will be presented.
Of particular interest is comparisons of flight-level wind measurements with
surface observations from regular observing sites over land and from C-MAN
and buoy measurements, and those from the GPS dropwindsondes and the SFMR.
Satellite imagery showed that intense, deep convection was occurring over
the center of Irene, obscuring the eye and eyewall that was visible on radar
displays beneath the high clouds. An unusual aspect of Irene was the
extremely dry air that was entraining into the west side of the storm and
that may have contributed to some of the observed asymmetries and to the
clear-air turbulence encountered by the P-3 aircraft.
Peng, T.-H., and F. Chai. Modeling the carbon cycle in the equatorial
Pacific Ocean. Proceedings, Marine Environment: The Past, Present, and
Future, Kaohsiung, Taiwan, January 26-28, 1999. Sueichan Press, 240-255
(2000).
An ocean ecosystem model of the equatorial Pacific Ocean has been developed
with new and export productivity regulated by Si and Fe to synthesize and
analyze data collected during the JGOFS process-study-oriented survey cruises
in 1992. The data also include those obtained by NOAA/OACES cruises in concert
with the JGOFS EqPac process study. The circulation model is based on the
Modular Ocean Model of the NOAA/GFDL ocean general circulation model. The
ecosystem model is originally formulated by Chai et al. (1996),
and is now expanded to consist of nine components describing two sizes of
phytoplankton, two sizes of zooplankton, two detritus pools, and three
dissolved nutrients: silicate, nitrate, and ammonium. The carbonate chemistry
is parameterized in the model to evaluate the variations of pCO2
and, hence, the CO2 flux across the air-sea interface. At this
initial stage, a test case by using a 1D model is performed to simulate
low-silicate, high-nitrate, and low-chlorophyll conditions in the equatorial
Pacific, and to investigate how the carbon system behaves in this ecosystem
structure. The model includes the vertical upwelling and diffusion processes.
The modeled upwelling rate and vertical diffusivity, from a 3D circulation
model, were initially averaged for the region with latitudes 5°S to
5°N, and longitude 180° to 90°W, the "cold tongue" of the
equatorial Pacific. Temperature is used to calibrate model upwelling and
vertical diffusion rates. Comparison of model results with the observations
made during the NOAA/OACES EqPac 1992 expeditions indicates that the vertical
profiles of DIC, NO3, and Si(OH)4 are consistent with
the measurements made in the fall season when the ocean was in a normal
non-El Niņo condition. A tight fit of profiles between model and observation
is not possible because of spatial variations of the observed values. A 3D
simulation is required, which is in progress. The 1D model CO2
evasion rate is estimated to be 2.9 mol/m2/yr, which is
consistent with the range of estimates from measurements made during non-El
Niņo conditions.
Peng, T.-H., and R.H. Wanninkhof. Re-evaluation of GEOSECS carbon data in
the Pacific Ocean based on recent high quality measurements. AGU 2000
Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 81(48):F701,
OS11B-11 (2000).
Inorganic carbon data collected during the GEOSECS program in the early 1970s
represent results of the first systematic geochemical survey on a global
scale. These data sets have become an essential baseline for studies of
temporal variations of geochemical properties since this time. This is
especially true for estimating the oceanic uptake of anthropogenic
CO2 by determining the increase in concentration of total
dissolved inorganic carbon (DIC) since GEOSECS. It is essential that the
accuracy of this historic data set is consistent with recent high quality
carbon data resulting from improvements in measurement techniques and the
use of reference material. Here we report the results of the re-evaluation of
GEOSECS inorganic carbon data in the Pacific Ocean by examining deep water
properties at crossover stations between GEOSECS and WOCE cruises. We find
that DIC and total alkalinity (TA) measurements made during the GEOSECS
program are systematically higher than those made during the recent global
CO2 survey. We suggest that the originally reported GEOSECS DIC
should be revised downward by 30.3 µmol/kg and TA by 18.1
µmol/kg. Comparison of temperature, salinity, and oxygen concentrations
show that these properties are consistent with each other, although they were
measured two decades apart. The corrected GEOSECS carbon data will be made
available to the research community through NOAA/AOML's public web site.
Powell, M.D. Performance of the HRD real-time Hurricane Wind Analysis
System in 1999. Minutes, 54th Interdepartmental Hurricane Conference,
Houston, TX, February 14-18, 2000. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A232-A237 (2000).
No abstract.
Powell, M.D. Tropical cyclones during and after landfall. In Storms
(Volume 1), R. Peilke, Sr. and R. Peikle, Jr. (eds.). Routledge, New York
(ISBN 041517239X), 196-219 (2000).
No abstract.
Powell, M.D., and S.D. Aberson. Accuracy of U.S. hurricane landfall
forecasts in the Atlantic basin (1976-1998). Minutes, 54th
Interdepartmental Hurricane Conference, Houston, TX, February 14-18,
2000. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A138-A139 (2000).
No abstract.
Powell, M.D., and S.D. Aberson. Accuracy of U.S. hurricane landfall
forecasts in the Atlantic basin (1976-1998). Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, 326 (2000).
No abstract.
Powell, M.D., A. Lazar-Viront, and D. Bowman. Documentation of automatic
weather station wind exposure in tropical cyclone areas. Minutes, 54th
Interdepartmental Hurricane Conference, Houston, TX, February 14-18,
2000. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A260-A264 (2000).
No abstract.
Powell, M.D., T.A. Reinhold, and R.D. Marshall. Tropical cyclone boundary
layer wind variability. Proceedings, 10th Conference on Interaction of
the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, J57 (2000).
No abstract.
Proni, J.R. Using acoustical methods to study and monitor the discharge
of sewage and dredged-material in the coastal ocean. Proceedings,
Fifth European Conference on Underwater Acoustics (ECUA 2000), Lyon,
France, July 10-13, 2000. European Acoustics Association, Volume 1,
755-760 (2000).
Acoustical backscatter has been shown to be very effective in the study and
monitoring of sewage efffluent and dredged material released into the coastal
waters. Acoustical detection of a detrainment phenomenon in discharge
plumes shows the extreme sensitivity of effluent distributions to small water
column density changes. Acoustic measurements, as part of an ensemble of
sensor systems, reveal turbidity changes occurring at environmentally valuable
biological communities such as coral reefs and oyster beds. Examples of
acoustic observations are presented.
Quilfen Y., A. Bentamy, P. Delecluse, K.B. Katsaros, and N. Grima.
Prediction of sea level anomalies using ocean circulation model forced by
scatterometer wind and validation using TOPEX/Poseidon data. IEEE
Transactions on Geoscience and Remote Sensing, 38(4):1871-1884 (2000).
Uncertainties in the surface wind field have long been recognized as a major
limitation in the interpretation of results obtained by oceanic circulation
models. It is especially true in the tropical oceans, where the response to
wind forcing is very strong on short time scales. The purpose of this paper
is to show that these uncertainties can be greatly reduced by using
spaceborne wind sensors that provide accurate measurements on a global basis.
Surface winds over the global oceans have been measured by scatterometry
since the launch of the European Remote Sensing Satellite (ERS-1) in August
1991 by the European Space Agency, Noordwijk, The Netherlands, and is
currently provided by ERS-2, launched in April 1995. The ground-track wind
vectors are processed to compute mean weekly surface winds onto a 1°
square grid at the Institut Francais de Recherche pour l'Exploitation de la
Mer (IFREMER), Plouzane, France. These winds are validated by comparison
with the buoy array in the tropical Pacific Ocean, showing good agreement.
In order to further evaluate this wind field, the three-dimensional ocean
model OPA7 developed at Laboratoire d'Océanographie Dynamique et de
Climatologie, Paris, France, is forced over the tropical oceans by the
ERS-derived wind stress fields and by fields from the atmospheric model
"Arpege/Climat." Selected ocean parameters are defined in order to validate
the ocean model results with measurements of the tropical ocean and global
atmosphere (TOGA) buoys in the Pacific Ocean. The ability of the model to
describe the short scale (a few weeks to a few years) oceanic variability is
greatly enhanced when the satellite-derived surface forcing is used. In
this paper, we present further comparison of the ocean model results with
the TOPEX-Poseidon altimeter measurements. Simulated and measured sea
level variability are described over the three tropical oceans. The annual
and semi-annual signals, as well as the interannual variability, partly
linked to the El Niņo-Southern Oscillation (ENSO) phenomenon, are well
simulated by the OPA7 model when the satellite winds are used. Furthermore,
it shows that the objective method, kriging technique, used to interpolate
the mean ERS wind fields, dramatically reduces the effects of the satellite
bandlike sampling. In the last part of this paper, we focus on the
relationship between the wind stress anomalies and the sea level anomalies
in the case of the 1997-1998 El Niņo event. It clearly shows that sea level
anomalies in the eastern and western parts of the Pacific are strongly
linked to wind stress anomalies in the central Pacific. The forthcoming
scatterometers aboard the METOP and ADEOS satellites will provide a much
better coverage. It will enable the wind variability spatial and
temporal scales to be resolved better, in order that wind uncertainties
no longer blur the interpretation of ocean circulation numerical model
results.
Reasor, P.D., and M.T. Montgomery. 3D alignment and co-rotation of weak,
TC-like vortices via linear vortex Rossby waves. Preprints, 24th
Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL,
May 29-June 2, 2000. American Meteorological Society, Boston, 268-269
(2000).
No abstract.
Reasor, P.D., M.T. Montgomery, F.D. Marks, and J.F. Gamache.
Low-wavenumber structure and evolution of the hurricane inner core
observed by airborne dual-Doppler radar. Monthly Weather Review,
128(6):1653-1680 (2000).
The asymmetric dynamics of the hurricane inner-core region is examined
through a novel analysis of high temporal resolution, three-dimensional
wind fields derived from airborne dual-Doppler radar. Seven consecutive
composites of Hurricane Olivia's (1994) wind field with 30-min time
resolution depict a weakening storm undergoing substantial structural
changes. The symmetric and asymmetric mechanisms involved in this
transformation are considered separately. To zeroth order the weakening
of the primary circulation is consistent with the axisymmetric vortex
spindown theory of Eliassen and Lystad for a neutrally-stratified
atmosphere. Vertical shear, however, increased dramatically during the
observation period, leading to a strong projection of the convection onto
an azimuthal wavenumber 1 pattern oriented along the maximum vertical
shear vector. Recent theoretical ideas elucidating the dynamics of
vortices in vertical shear are used to help explain this asymmetry. The
role of asymmetric vorticity dynamics in explaining some of the physics
of hurricane intensity change motivates a special focus on Olivia's
vorticity structure. It is found that an azimuthal wavenumber 2 feature
dominates the asymmetry in relative vorticity below 3-km height. The
characteristics of this asymmetry deduced from reflectivity and wind
composites during a portion of the observation period show some
consistency with a wavenumber 2 discrete vortex Rossby edge wave.
Barotropic instability is suggested as a source for the wavenumber 2
asymmetry through a series of barotropic numerical simulations. Trailing
bands of vorticity with radial wavelengths of 5-10 km are observed in the
inner core approximately 20 km from the storm center, and may be
symmetrizing vortex Rossby waves. Elevated reflectivity bands with radial
scales comparable to those of the vorticity bands, also near 20-25-km
radius, may be associated with these vorticity features.
Richardson, P.L., S.L. Garzoli, C.M. Duncombe Rae, D.M. Fratantoni, and G.J.
Goni. Float trajectories at 750 m in the Benguela Current (KAPEX). AGU
2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement
to EOS, Transactions, American Geophysical Union, 81(48):F716,
OS11F-09 (2000).
Thirty RAFOS floats were launched at Intermediate Water depths (approximately
750 m) in the Benguela Current along 30°S and its extension along
7°W. The floats have surfaced after 18-24 month missions and are being
tracked. Preliminary results from the overall subsurface displacements show
that the floats drifted westward at typical speeds of 2-5 cm/sec. Six floats
looped in three Agulhas rings for long times as they also translated westward.
Eleven floats crossed over the mid-Atlantic Ridge into the western Atlantic in
the latitude band 23°S-33°S. Three floats reached 25°W and
one reached 30°W. Two of these farthest westward-drifting floats were
in Agulhas rings, suggesting that they translate faster than the background
water at 750 m. A summary of the new trajectories will be represented along
with some hydrography, altimetry, and surface-drifter tracks. Intermediate
Water is an important part of the northward-flowing limb of the thermohaline
circulation in the Atlantic. The floats show the path of Intermediate Water
as it flows westward along the northern side of the subtropical gyre, across
the mid-Atlantic Ridge and into the western Atlantic.
Rogers, R.F. Surface-based modification of convectively-generated
mesovortices and its implications for tropical cyclogenesis. Preprints,
24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston,
151-152 (2000).
Numerical simulations have been performed on a long-lived midlevel
mesovortex over the continental United States that was instrumental in
initiating and organizing multiple cycles of deep convection. These
simulations showed how the cycles of convective redevelopment amplify the
mid- to upper-level warm core of the vortex, causing the cyclonic vorticity
to strengthen in the midlevels and penetrate down into the lower troposphere,
briefly reaching the surface. However, low-level cooling caused by
convective and mesoscale downdrafts and adiabatic ascent offsets the impact
of the mid- to upper-level warming, limiting the extent to which the
cyclonic vorticity penetrates to the surface. In this study the impact of
weakening the surface-based cold pool on the structure of the simulated
mesovortex is investigated. Methods for weakening the cold pool in the
simulations include: eliminating the convective (subgrid-scale) and
mesoscale (resolvable-scale) downdrafts and replacing the lower land
boundary with a water surface of varying temperatures. The resultant
structures of the mesovortex for these different conditions are compared
to explain how a mesovortex, with cyclonic vorticity initially confined to
the midlevels, can grow downward to the surface, marking a key step in the
tropical cyclogenesis process.
Rogers, R.F., J.M. Fritsch, and W.C. Lambert. A simple technique for
using radar data in the dynamic initialization of a mesoscale model.
Monthly Weather Review, 128(7):2560-2574 (2000).
A simple technique for using radar reflectivity to improve model
initialization is presented. Unlike previous techniques, the scheme
described here does not infer rain rates and heating profiles from
assumed relationships between remotely-sensed variables and precipitation
rates. Rather, the radar data are only used to tell the model when and
where deep moist convection is occurring. This information is then used
to activate the model's convective parameterization scheme in the grid
elements where convection is observed. This approach has the advantage
that the convective precipitation rates and heating profiles generated by
the convective parameterization are compatible with the local (grid
element) environment. The premise is that if convection is forced to
develop when and where it is observed during a data assimilation period,
convectively-forced modifications to the environment will be in the
correct locations at the model initial forecast time and the resulting
forecast will be more accurate. Three experiments illustrating how the
technique is applied in the simulation of deep convection in a
warm-season environment are presented: a control run in which no radar
data are assimilated, and two additional runs where radar data are
assimilated for 12 h in one run and 24 h in the other. The results
indicate that assimilating radar data can improve a model's description
of the mesoscale environment during the pre-forecast time period, thereby
resulting in an improved forecast of precipitation and the mesoscale
environment.
Rogers, R.F., S.S. Chen, J.E. Tenerelli, and M. Lonfat. A numerical study of
the distribution of precipitation in Hurricane Bonnie (1998). Preprints,
24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston,
408-409 (2000).
As the damage that accompanied the floods from Hurricanes Georges and Mitch
of 1998 and Floyd and Irene of 1999 dramatically highlighted, rainfall is
one of the most significant impacts that accompanies a landfalling tropical
cyclone. However, quantitative precipitation forecasting (QPF) is one of
the most difficult problems in tropical cyclone forecasting. Rainfall
measured at a particular location during the landfall of a tropical cyclone
depends on many factors, such as the location with respect to the storm's
track, the intensity and distribution of rainfall around the storm, the
translational speed of the storm, and local effects such as topography and
orientation of the coast. Understanding how these and other factors
influence the precipitation distribution of landfalling hurricanes is an
important step in improving hurricane QPFs. In this study, the distribution
of precipitation from Hurricane Bonnie (1998) is explored by performing a
numerical simulation using the primitive-equation, nonhydrostatic
mesoscale model MM5. A six-day simulation is performed, and precipitation
fields from the innermost domain (5-km grid length) are compared against
observations. The wealth of observational information that accompanied
the third phase of the NASA Convection and Moisture Experiment (CAMEX-3)
field program, including the NASA TRMM satellite and various airborne
observations from the NOAA P-3's and G-IV and the NASA DC-8 and ER-2, are
used to validate the simulation. Statistics related to precipitation
distribution, such as radial profiles of rainfall, radial-height profiles
of hydrometeors, and probability distributions of various rainfall
thresholds, are presented for the simulation and the observations from
the TRMM satellite. Validation of these parameters will lend confidence
in the skill of the model in capturing the precipitation distribution and
enable an investigation of the physical processes governing the distribution
to be performed in a later study.
Rogers, R.F., S.D. Aberson, J. Kaplan, S.B. Goldenberg, B. Damiano, R.
McNamara, and J. Parrish. Pronounced upper-tropospheric temperature
anomalies encountered by the Gulfstream-IV in the vicinity of deep
convection. Minutes, 54th Interdepartmental Hurricane Conference,
Houston, TX, February 15-18, 2000. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
275-279 (2000).
In several instances during the 1999 hurricane season, temperature sensors
aboard the NOAA Gulfstream-IV (G-IV) aircraft measured significant
temperature increases (some as large as 40°C) while flying between
41,000 and 45,000 feet in the vicinity of deep convection. Similar
temperature anomalies have been encountered by commercial aircraft flying
at similar altitudes and balloon measurements taken at high temporal
frequency in the proximity of deep convection. In this presentation, the
observations gathered from the G-IV are summarized and compared to
observations taken previously. While it is still not certain whether or
not the anomalies measured by the sensors aboard the G-IV last year owed
their existence to real meteorological phenomena or to instrument
deficiencies, it is important to document this occurrence, since the
response of the aircraft's autopilot is to change altitude and airspeed.
Suggestions for how to avoid this from happening again are also offered.
Rona, P.A., D.R. Jackson, K.G. Bemis, C.D. Jones, K. Mitsuzawa, and D.R.
Palmer. Acoustic imaging of seafloor hydrothermal flow regimes at the
RIDGE Endeavour Observatory, Juan de Fuca Ridge. AGU 2000 Fall
Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 81(48):F629, OS52I-06 (2000).
We report preliminary results of acoustic imaging of black smoker plumes and
diffuse flow in the Main Endeavour Field of the Endeavour segment of the Juan
de Fuca Ridge on the VIP (Vents Imaging Pacific) 2000 cruise of the R/V
Thompson (21-31 July 2000) using innovative methods developed by our
group. We modified a state-of-the-art sonar system (Simrad SM 2000; 200 kHz)
to perform the imaging while mounted on ROV Jason and developed specialized
processing methods for acoustic remote sensing and visualization/quantification
of hydrothermal flow. We carried out four types of acoustic experiments
coordinated with selected in-situ measurements of hydrothermal discharge
temperatures and flow rates, as follows: (1) Panoramic imaging (range 10 m to
150 m) of four vent clusters each tens of meters wide and high
(Peanut-Puffer-Bastille group; Salut, S&M, and Grotto sites), which shows
seafloor features, plumes (based on acoustic backscatter from suspended
particulate matter), and diffuse flow (based on acoustic scintillation
thermometry). The images reveal differences between the four vent clusters in
intensity of venting and partitioning between black smoker discharge and
diffuse flow. (2) A time series of panoramic images (hourly during 24-hour
period), which shows the effect of a mixed semi-diurnal tide on
intensely-venting plumes and diffuse flow (Grotto site). (3) Flow rates in
black smoker plumes, which were measured using the coherent Doppler method.
(4) Acoustic mapping of diffuse flow, which was conducted to test stationary
and moving modes (multiple sites). The preliminary results are evaluated in
terms of the applicability of our acoustic and processing methods for
synoptic imaging and long-term monitoring of these hydrothermal flow regimes.
Sabine, C.L., R.H. Wanninkhof, R.M. Key, C. Goyet, and F.J. Millero.
Seasonal CO2 fluxes in the tropical and subtropical Indian
Ocean. Marine Chemistry, 72(1):33-53 (2000).
Improved estimates of the variability in air-sea CO2 fluxes on
seasonal and interannual time scales are necessary to help constrain the net
partitioning of CO2 between the atmosphere, oceans, and terrestrial
biosphere. Few direct measurements of the carbon system have been made in
the main Indian Ocean basin. In the mid 1990s, several global carbon
measurement programs focused on the Indian Ocean, greatly increasing the
existing carbon database for this basin. This study examines the combined
surface CO2 measurements from three major U.S. programs in the
Indian Ocean: the global carbon survey cruises, conducted in conjunction with
the World Ocean Circulation Experiment (WOCE); the NOAA Ocean-Atmosphere
Carbon Exchange Study (OACES) Indian Ocean survey; and the Joint Global
Ocean Flux Study (JGOFS) Arabian Sea Process Study. These data are fit
with multiparameter linear regressions as a function of commonly-measured
hydrographic parameters. These fits are then used with NCEP/NCAR
reanalysis and Levitus 94 gridded values to evaluate the seasonal
variability of surface seawater CO2 in the tropical and
subtropical Indian Ocean and to estimate the magnitude of the Indian Ocean
as a net sink for atmospheric CO2. The net annual flux for the
Indian Ocean (north of 36°S) was -12.4 ą 0.5 × 1012
mol of carbon (equivalent to -0.15 Pg C) in 1995. The relatively small net
flux results from the very different surface water pCO2
distributions and seasonal variations in the northern and southern Indian
Ocean. The equatorial and northern hemisphere regions have values that are
generally above atmospheric values. During the southwest monsoon,
pCO2 values in the Arabian Sea coastal upwelling region are among
the highest observed in the oceans. The upwelling is seasonal in nature,
however, and only affects a relatively small area. The Indian Ocean
equatorial region generally has values slightly above atmospheric. Unlike
the Pacific and Atlantic Oceans, however, no clear equatorial upwelling
signature was observed in 1995. The Southern Hemisphere Indian Ocean, which
represents the largest region by area, generally has values below
atmospheric. The strongest undersaturations are observed in the austral
winter, with summer values reaching near or slightly above atmospheric.
Sabine, C.L., R.A. Feely, R.M. Key, F.J. Millero, R.H. Wanninkhof, T.-H.
Peng, A. Kozyr, J.L. Bullister, K. Lee, and M.F. Lamb. Anthropogenic
CO2 distributions in the Pacific. AGU 2000 Fall Meeting,
San Francisco, CA, December 15-19, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 81(48):F692, OS72E-02 (2000).
As a part of the JGOFS synthesis and modeling project, researchers have
been working to synthesize the WOCE/JGOFS/NOAA global carbon survey data to
better understand carbon cycling in the oceans. Working with international
investigators, we have compiled a Pacific Ocean data set with over 36,000
unique sample locations analyzed for at least two carbon parameters. These
data are being used to estimate the distribution of anthropogenic
CO2 in the Pacific using the delta-C technique. The physical and
geochemical makeup of the Pacific waters, however, poses a particular
challenge for the anthropogenic calculations. This measurement-based
approach requires a number of assumptions that will be examined with
respect to the Pacific. Preliminary estimates of the anthropogenic
CO2 distribution indicate that the largest inventories are
in the subtropical South and North Pacific. These distributions will be
discussed and compared with three-dimensional global carbon model estimates.
Sabine, C.L., M.F. Lamb, J.L. Bullister, R.A. Feely, G.L. Johnson, R.M. Key,
A. Kozyr, K. Lee, F.J. Millero, T.-H. Peng, and R.H. Wanninkhof. U.S. JGOFS
team examines Pacific Ocean CO2 data quality. International
WOCE Newsletter, 38:10-14 (2000).
No abstract.
Sainz-Trapaga, S.M., G.J. Goni, and T. Sugimoto. Identification and
variability of the Kuroshio Extension and its northern branch from
altimeter and hydrographic data during October 1992-August 1999. AGU
2000 Western Pacific Geophysics Meeting, Tokyo, Japan, June 27-30,
2000. Supplement to EOS, Transactions, American Geophysical Union,
81(22):WP80, OS41A-08 (2000).
The Kuroshio Extension to the east of Japan is an eastward-flowing,
meandering jet with current velocities at its core over 100 cm
s-1. This jet presents two quasi-stationary meanders with crests
at 144°E and 150°E, and becomes wider and weaker to the east.
These and other hydrodynamic modifications along its course can be related
to the Shatsky Rise and the Emperor Sea Mounts, the main bathymetric features
encountered by the Kuroshio Extension while flowing to the east. The
Kuroshio Extension usually bifurcates between 150°E and 165°E,
where its northern branch deviates northeastward along the Shatsky Rise
approaching the subarctic front. Due to the lack of a long-term and continuous
monitoring system, several aspects of the variability at the different
regions of the Kuroshio Extension remains unclear. In this work,
altimeter-derived sea height anomaly data from November 1992 to August
1999 is combined with climatological hydrographic data within a two-layer
reduced gravity ocean model to identify the Kuroshio Extension and its
northern branch, to estimate their baroclinic transports, and to study
their variabilities, from the Japanese coast to 175°W. Results reveal
different patterns of variability to the east and west of 155°E.
East of 155°E, the Kuroshio Extension and its northern branch show a
clear seasonal cycle. The location of the Kuroshio Extension and its northern
branch have both maximum standard deviations from the mean between
150°E and 170°E. This area is characterized by the separation of
the northern branch from the Kuroshio Extension. Moreover, the northern branch
deviates to the northeast while the main path to the southeast, showing
here its lower mean axis position. The location of the Bifurcation Point,
partly determined by the bottom topography, correlates also with the
Kuroshio Extension axis location and its transport.
Sandrik, A., C.W. Landsea, and B. Jarvinen. The North Florida hurricane
of 29 September 1896: A historical case of extreme inland high winds.
Preprints, 24th Conference on Hurricanes and Tropical Meteorology,
Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society,
Boston, 547-548 (2000).
No abstract.
Schaefer, J.K., K.D. Goodwin, I. McDonald, J.C. Murrell, and R.S. Oremland.
Methyl halide oxidation by a novel marine methylotroph, Ruegeria sp.
strain MB2. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19,
2000. Supplement to EOS, Transactions, American Geophysical Union,
81(48):F278, B22A-05 (2000).
Strain MB2 was isolated from coastal seawater with the capacity to utilize
methyl bromide as a sole carbon and energy source. Additional carbon sources
included the methylotrophic substrates: methyl chloride, methionine, and
glycine betaine, as well as the complex substrates casein and yeast extract.
This bacterium, however, was unusual for a methylotroph in that it was unable
to grow on methylated amines, dimethyl sulfide, formate, methane, acetate, or
glucose. Cells were capable of complete oxidation of methyl bromide and methyl
iodide with stoichiometric release of bromide and iodide, respectively.
Specific growth rates were 0.07 h-1, 0.05 h-1, and
0.04 h-1 for methyl bromide, methyl chloride, and methyl iodide,
respectively. Methyl bromide oxidation was readily inducible in casein-grown
cells. Strain MB2 exhibited a requirement for NaCl and Mg2+
similar to that found in seawater. Analysis of the 16S rDNA gene placed this
strain in the a-subgroup of the Proteobacteria with significant
homology to the genus Ruegeria. We propose the identity of strain
MB2 as a novel species, designated Ruegeria methylhalovorans sp. nov.
Characterization of strains such as MB2 should enhance understanding of the
mechanisms involved in the oxidation of methyl halides in the oceans.
Schmid, C., S.L. Garzoli, and R.L. Molinari. The intermediate depth
circulation in the tropical Atlantic. AGU 2000 Ocean Sciences
Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS,
Transactions, American Geophysical Union,80(49):OS44, OS12D-18 (2000).
The intermediate circulation in the interior tropical Atlantic consists,
according to the current knowledge, of several narrow zonal currents.
Especially south of the equator, many changes of direction have been
reported. Due to a lack of data, this flow pattern is only poorly resolved
in space and time. Recent observations, both during the mid-1997
Seward Johnson cruise and from PALACE trajectories which extend from
mid-1997 to today, allow a more detailed description of the intermediate
depth circulation in the tropical Atlantic. The PALACE floats indicate
that the intermediate layer flow between the equator and about 4°N
consists of two different regimes which are separated by the eastern edge
of the Mid-Atlantic Ridge. Velocities in the eastern regime are lower.
The zonal flow in the two regimes is going in opposite directions at
certain latitudes. We will discuss how the different regimes are related
to the water masses and the interbasin exchange. Further south, between
4° and 2°S, westward velocities are clearly dominating the
circulation. This latitude range is often occupied by the central South
Equatorial Current. The flow between 8° and 4°S is governed by
short periods (up to several months) of flow towards the east or west with
only weak preferences of either one of the directions. This region is
characterized by the (meandering) transition between the central South
Equatorial Current and the South Equatorial Countercurrent. It has been
proposed earlier that these two currents do not extend beyond about 8°W
and that the intermediate water follows a cyclonic path east of 10°W
between about 5° and 25°S. This could be seen as an intermediate
expression of the Angola Gyre. Such a circulation is not visible in the
PALACE trajectories to date.
Schmid, C., G. Siedler, and W. Zenk. Dynamics of intermediate water
circulation in the subtropical South Atlantic. Journal of Physical
Oceanography, 30(12):3191-3211 (2000).
The circulation of the low-salinity Antarctic Intermediate Water
in the South Atlantic and the associated dynamical processes are studied,
using recent and historical hydrographic profiles, Lagrangian and
Eulerian current measurements as well as wind stress observations. The
circulation pattern inferred for the Antarctic Intermediate Water
supports the hypothesis of an anticyclonic basin-wide recirculation of
the intermediate water in the subtropics. The eastward current of the
intermediate anticyclone is fed mainly by water recirculated in the
Brazil Current and by the Malvinas Current. An additional source region
is the Polar Frontal Zone of the South Atlantic. The transport in the
meandering eastward current ranges from 6 Sv to 26 Sv (1 Sv =
106 m3 s-1). The transport of the
comparably uniform westward flow of the gyre varies between 10 Sv and
30 Sv. Both transports vary with longitude. At the western boundary
near 28°S, in the Santos Bifurcation, the westward current splits
into two branches. About three quarters of the 19 Sv at 40°W go
south as an intermediate western boundary current. The remaining
quarter flows northward along the western boundary. Simulations with a
simple model of the ventilated thermocline reveal that the wind-driven
subtropical gyre has a vertical extent of over 1200 m. The transports
derived from the simulations suggest that about 90% of the transport in
the westward branch of the intermediate gyre and about 50% of the
transport in the eastward branch can be attributed to the wind-driven
circulation. The structure of the simulated gyre deviates from
observations to some extent. The discrepancies between the simulations
and the observations are most likely caused by the interoceanic exchange
south of Africa, the dynamics of the boundary currents, the nonlinearity,
and the seasonal variability of the wind field. A simulation with an
inflow/outflow condition for the eastern boundary reduces the transport
deviations in the eastward current to about 20%. The results support the
hypothesis that the wind field is of major importance for the subtropical
circulation of Antarctic Intermediate Water followed by the interoceanic
exchange. The simulations suggest that the westward transport in the
subtropical gyre undergoes seasonal variations. The transports and the
structure of the intermediate subtropical gyre from the Parallel Ocean
Climate Model (Semtner/Chervin model) agree better with observations.
Schott, F., C. Boning, H. Bryden, R.L. Molinari, P. Schlosser, C. Wunsch,
and L. Stramma. 2000 Report of the WOCE North Atlantic Workshop. WOCE
Report No. 169/2000, 110 pp. (2000).
No abstract.
Schubert, W.H., S.A. Hausman, M. Garcia, K.V. Ooyama, and H.-C. Kuo. Potential
vorticity in a moist atmosphere. Preprints, 24th Conference on
Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2,
2000. American Meteorological Society, Boston, 563-564 (2000).
No abstract.
Shay, L., G.J. Goni, and P.G. Black. Effects of a warm oceanic
feature on Hurricane Opal. Monthly Weather Review,
128(5):1366-1383 (2000).
On 4 October 1995, Hurricane Opal deepened from 965 to 916 hPa in the Gulf
of Mexico over a 14-h period upon encountering a warm core ring (WCR) in
the ocean shed by the Loop Current during an upper-level atmospheric trough
interaction. Based on historical hydrographic measurements placed within
the context of a two-layer model and surface height anomalies (SHA) from
the radar altimeter on the TOPEX mission, upper-layer thickness fields
indicated the presence of two warm core rings during September and October
1995. As Hurricane Opal passed directly over one of these WCRs, the 1-min
surface winds increased from 35 to more than 60 m s-1, and the
radius of maximum wind decreased from 40 to 25 km. Pre-Opal SHAs in the
WCR exceeded 30 cm where the estimated depth of the 20°C isotherm was
located between 175 and 200 m. Subsequent to Opal's passage, this depth
decreased approximately 50 m, which suggests upwelling underneath the storm
track due to Ekman divergence. The maximum heat loss of approximately 24
Kcal cm-2 relative to depth of the 26°C isotherm was a
factor of 6 times the threshold value required to sustain a hurricane.
Since most of this loss occurred over a period of 14 h, the heat content
loss of 24 Kcal cm-2 equates to approximately 20 kW
m-2. Previous observational findings suggest that about
10%-15% of upper-ocean cooling is due to surface heat fluxes. Estimated
surface heat fluxes based upon heat content changes range from 2000 to
3000 W m-2 in accord with numerically simulated surface heat
fluxes during Opal's encounter with the WCR. Composited AVHRR-derived
SSTs indicated a 2°-3°C cooling associated with vertical mixing
in the along-track direction of Opal except over the WCR where
AVHRR-derived and buoy-derived SSTs decreased only by about
0.5°-1°C. Thus, the WCR's effect was to provide a regime of
positive feedback to the hurricane rather than negative feedback induced
by cooler waters due to upwelling and vertical mixing as observed over the
Bay of Campeche and north of the WCR.
Shay, L.K., G.J. Goni, P.G. Black, S.D. Jacob, J.J. Cione, and E.W.
Uhlhorn. Global analogues of deep warm upper ocean layers: Hurricane
heat potential estimates. Proceedings, 10th Conference on Interaction
of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000.
American Meteorological Society, Boston, J3-J4 (2000).
No abstract.
Spratt, S.M., F.D. Marks, P.P. Dodge, and D.W. Sharp. Examining the
pre-landfall environment of mesovortices within a Hurricane Bonnie (1998)
outer rainband. Preprints, 24th Conference on Hurricanes and Tropical
Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American
Meteorological Society, Boston, 300-301 (2000).
No abstract.
Tenerelli, J.E., S.S. Chen, M. Lonfat, R. Foster, and R.F. Rogers. Surface
winds in Hurricane Floyd: A comparison between numerical simulations,
aircraft data, and QuikScat satellite data. Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, 418-419 (2000).
A principal benefit of numerical simulations of hurricanes is that they
provide detailed, high-resolution information on the structure and evolution
of the atmosphere that cannot be obtained through current observational
techniques. However, simulations can be strongly dependent on the initial
and boundary data, as well as on the physical parameterizations in the
numerical model, and so it is necessary to compare simulation results with
observational data when available. The objectives of this study are to:
(1) validate model simulations of Hurricane Floyd with all available
observations, including in-situ and remote sensing data sets; and (2)
explore the impact of the observations on high-resolution model simulations.
One important aspect of the model simulations is the surface wind field.
The surface wind has a substantial impact on the fluxes of heat and moisture
at the surface, which in turn have a large influence on the storm intensity
and structure. Yet, near the surface, the model results are influenced
greatly by the parameterization of boundary layer and surface processes.
Hurricane Floyd presents an excellent opportunity for model-observation
intercomparison of winds near the surface. Several swaths of data from
NASA's QuikScat satellite were obtained while Floyd was over water.
Additionally, surface winds derived from NOAA/HRD aircraft observations
were obtained at several times during the life of the storm. In this
study, we conduct a four-day long simulation of Floyd using the PSU/NCAR
nonhydrostatic mesoscale model (MM5) with one fixed mesh and two levels
of moving nested grid. We compare surface winds derived from QuikScat
and aircraft data to the surface winds in our numerical simulation of
Floyd. Additionally, we compare vertical profiles of reflectivity and
hydrometeors from the simulations with those derived from the TMI and PR
instruments on NASA's TRMM satellite. Although the TRMM swaths, the
QuikScat swaths, and HRD data are not coincident in time, the MM5
simulations' continuity in time allows a comparison with all observational
data sources. The MM5 can be used as a cross-validation platform. This
model-observation comparison is the first step towards the goal of
assimilating observed surface winds into the MM5.
Tokarczyk, R., E.S. Saltzman, and K.D. Goodwin. Degradation of methyl
bromide in surface waters of Atlantic and Pacific Ocean. AGU 2000 Fall
Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 81(48):F277, B22A-03 (2000).
The ocean plays a complex role in the global biogeochemical cycle of methyl
bromide as both a source and sink for atmospheric CH3Br. The
loss of methyl bromide in seawater occurs by both chemical and biological
mechanisms. This study is an effort to measure the oceanic loss rate of
methyl bromide using a shipboard stable isotope
(13CH3Br) incubation technique. Data are presented from
two expeditions: the GASEX-98 cruise across the Atlantic and western coastal
North Pacific (May-July 1998) and the KWAJEX cruise in the North Pacific
ocean (11°N to 57°N, September-October 1999). The methyl bromide
lifetimes measured in this study ranged from approximately 2.5 to 50 days.
Chemical loss rate constants were obtained by following the first-order loss
of 13CH3Br in 0.2 µm filtered seawater, and
biological loss rate constants were inferred from the difference between the
loss rate in unfiltered waters and the chemical loss rate. Chemical loss rate
constants varied strongly with water temperature, in accordance with previous
measurements of the rates of hydrolysis and chloride substitution in seawater.
Biological degradation was observed in most water samples, at rates that can
be significant to the lifetime of seawater CH3Br. These losses are attributed
to bacterial activity on the basis of earlier filtration experiments carried
out in coastal seawater. In contrast to the chemical loss rate constants,
biological losses do not show a consistent correlation with water temperature
but do exhibit variability between various water masses. In general, chemical
losses control the lifetime of oceanic methyl bromide in warmer waters and
biological losses are significant in colder waters.
Uhlhorn, E.W., K.B. Katsaros, and M.D. Powell. Assimilation of
scatterometer-derived winds into real-time tropical cyclone surface wind
analyses. Preprints, 10th Conference on Satellite Meteorology and
Oceanography, Long Beach, CA, January 9-14, 2000. American
Meteorological Society, Boston, 214-215 (2000).
No abstract.
Uhlhorn, E.W., P.G. Black, L.K. Shay, J.J. Cione, S.D. Jacob, and G.J.
Goni. Warm core ocean features in the central and eastern Gulf of Mexico.
Preprints, 24th Conference on Hurricanes and Tropical Meteorology,
Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society,
Boston, 147-148 (2000).
No abstract.
Wainer, I., P. Gent, and G.J. Goni. Annual cycle of the
Brazil-Malvinas confluence region in the National Center for Atmospheric
Research climate system model. Journal of Geophysical Research,
105(C11):26,167-26,177 (2000).
The objective of this study is to compare the mean and seasonal variability
of the circulation in the southwest Atlantic with observations. The results
used in the comparison are from the last 200 years of a 300-year control
integration of the Climate System Model (CSM). The area of study includes
the confluence region between the subtropical and subpolar waters represented
by the Brazil and Malvinas Currents. The seasonal variation of transport and
its relationship to changes in the wind stress forcing and in the sea surface
temperature are examined and compared to available oceanographic observations.
This study shows that a coarse resolution climate model, such as the CSM, can
successfully reproduce major characteristics of the Brazil-Malvinas
confluence seasonality, although the mesoscale features involving
recirculation and meander dynamics are not resolved. The CSM transport
values in the region of 38°S are consistent with
hydrographically-derived values. The transport of the CSM Brazil Current
is higher during austral summer and smaller during austral winter.
Conversely, the Malvinas Current transport is weaker during austral summer
and stronger during austral winter. This is also consistent with
observations. The CSM seasonal cycle in transport associated with both
the Brazil and Malvinas Currents and its meridional displacement is closely
linked to the seasonal variations in the local wind stress curl. However,
the displacement is much smaller in the model than in observations. The CSM
results show that the latitudinal displacement of the 24°C and
17°C at the South American coast between austral summer and winter
is 20° and 12°, respectively. This is very similar to the
displacement seen in observations.
Walsh, E.J., C.W. Wright, D.C. Vandemark, W.B. Krabill, A.W. Garcia, S.H.
Houston, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane directional
wave spectrum spatial variation in the open ocean and at landfall. Minutes,
54th Interdepartmental Hurricane Conference, Houston, TX, February 14-18,
2000. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A116-A121 (2000).
The sea surface directional wave spectrum was measured for the first time in
all quadrants of a hurricane in open water using the NASA/GSFC airborne
scanning radar altimeter (SRA) carried aboard one of the NOAA WP-3D hurricane
research aircraft at 1.5 km height. The data were acquired on 24 August 1998
when Hurricane Bonnie was east of the Bahamas and moving slowly to the north.
Two days later, the SRA documented the directional wave spectrum spatial
variation again as Bonnie made landfall near Wilmington, North Carolina.
Walsh, E.J., C.W. Wright, D.C. Vandemark, W.B. Krabill, A.W. Garcia, S.H.
Houston, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane directional
wave spectrum spatial variation at landfall. Preprints, 24th Conference
on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June
2, 2000. American Meteorological Society, Boston, 327-328 (2000).
No abstract.
Wang, C. A unified theory for the El Niņo-Southern Oscillation.
Proceedings, 10th Conference on Interaction of the Sea and
Atmosphere, Ft. Lauderdale, Florida, May 29-June 2, 2000. American
Meteorological Society, Boston, J42-J43 (2000).
No abstract.
Wang, C. On the atmospheric responses to tropical Pacific heating during
the mature phase of El Niņo. Journal of Atmospheric Sciences,
57(22):3767-3781 (2000).
The atmospheric heating and sea surface temperature (SST) anomalies
during the mature phase of El Niņo are observed to show both eastern and
western Pacific anomaly patterns, with positive anomalies in the
equatorial eastern/central Pacific and negative anomalies in the
off-equatorial western Pacific. The detailed spatial patterns of the
heating anomalies differ from the SST anomalies. The heating anomalies
are more equatorially confined than the SST anomalies, and maxima of
positive and negative heating anomalies are located farther to the west
than the SST anomalies. The Gill/Zebiak atmospheric model assumes that
the atmospheric initial heating has the same spatial patterns as the SST
anomalies. This assumption results in some unrealistic model simulations
for El Niņo. When the model heating anomaly forcing is modified to
resemble the observed heating anomalies during the mature phase of El
Niņo, the model simulations have been improved to: (1) successfully
simulate equatorial easterly wind anomalies in the western Pacific; (2)
correctly simulate the position of maximum westerly wind anomalies; and
(3) reduce unrealistic easterly wind anomalies in the off-equatorial
eastern Pacific. This paper shows that off-equatorial western Pacific
negative atmospheric heating (or cold SST) anomalies are important in
producing equatorial easterly wind anomalies in the western Pacific.
These off-equatorial cold SST anomalies in the western Pacific also
contribute to equatorial westerly wind anomalies observed in the central
Pacific during the mature phase of El Niņo. Although off-equatorial cold
SST anomalies in the western Pacific are smaller than equatorial positive
SST anomalies in the eastern Pacific, they are enough to produce
atmospheric responses of comparable magnitude to the equatorial eastern
Pacific. This is because the atmospheric mean state is convergent in the
western Pacific and divergent in the equatorial eastern Pacific. By
either removing the atmospheric mean convergence or removing
off-equatorial cold SST anomalies in the western Pacific, the atmospheric
responses show no equatorial easterly wind anomalies in the western
Pacific. In the Gill/Zebiak model, the mean wind divergence field is an
important background state, whereas the mean SST is secondary.
Wang, C. The El Niņo-Southern Oscillation. Proceedings, International
Conference on Climate and Environment Variability and Predictability,
Shanghai, China, August 7-11, 2000. International Commission on Dynamic
Meteorology/International Association of Meteorology and Atmospheric
Sciences, 126 (2000).
No abstract.
Wang, C., and R.H. Weisberg. The 1997-1998 El Niņo evolution relative to
previous Niņo events. Journal of Climate, 13(2):488-501 (2000).
The evolution of the 1997-1998 El Niņo is described using NCEP sea
surface temperature (SST) and outgoing longwave radiation (OLR) data,
NCEP-NCAR reanalysis sea level pressure (SLP) fields, and FSU surface
wind data. From November 1996 to January 1997, the eastern Pacific is
characterized by equatorial cold SST and high SLP anomalies, while the
western Pacific is marked by off-equatorial warm SST anomalies and
off-equatorial anomalous cyclones. Corresponding to this distribution are
high OLR anomalies in the equatorial central Pacific and low OLR
anomalies in the off-equatorial far western Pacific. The off-equatorial
anomalous cyclones in the western Pacific are associated with a switch in
the equatorial wind anomalies over the western Pacific from easterly to
westerly. These equatorial westerly anomalies then appear to initiate
early SST warmings around the date line in January/February 1997 and
around the far eastern Pacific in March 1997. Subsequently, both the
westerly wind and warm SST anomalies, along with the low OLR anomalies,
grow and progress eastward. The eastward propagating warm SST anomalies
merge with the slower westward spreading warm SST anomalies from the far
eastern Pacific to form large-scale warming in the equatorial eastern and
central Pacific. The anomaly patterns in the eastern and central Pacific
continue to develop, reaching their peak values around December 1997. In
the western Pacific, the off-equatorial SST anomalies reverse sign from
warm to cold. Correspondingly, the off-equatorial SLP anomalies in the
western Pacific also switch sign from low to high. These off-equatorial
high SLP anomalies initiate equatorial easterly wind anomalies over the
far western Pacific. Like the equatorial westerly wind anomalies that
initiate the early warming, the equatorial easterly wind anomalies over
the far western Pacific appear to have a cooling effect in the east and,
hence, help facilitate the 1997-1998 El Niņo decay. The paper also
compares the 1997-1998 El Niņo with previous warm events, and discusses
different ENSO mechanisms relevant to the 1997-1998 El Niņo.
Wilkerson, J.C., and J.R. Proni. Monitoring tropical and subtropical
rainfall over the ocean using underwater acoustic techniques. Proceedings,
Fifth European Conference on Underwater Acoustics (ECUA 2000), Lyon,
France, July 10-13, 2000. European Acoustics Association, Volume 1,
741-746 (2000).
Measurements of underwater sound produced by rain were made at three U.S.
coastal sites to determine feasibility and limitations of acoustic detection
and classification of rainfall over water. In the study, concurrent radar
observations were used to identify convective and stratiform regions of the
precipitating clouds overhead. Acoustic-derived classifications of rain type,
based on information in the 4-30 kHz frequency band, were in general agreement
with radar-derived classifications. A correlation of 0.9 was found to exist
between sound spectrum levels (in decibels) in the 4-10 kHz frequency band
and rain rate, suggesting the use of acoustical methods for rainfall
estimation. Testing of the acoustic technique in deep water is currently
underway at the U.S. Navy Atlantic Undersea Test and Evaluation Center,
Bahamas. Examples of acoustic spectra are presented.
Willoughby, H.E. Costs and benefits of hurricane forecasting. Preprints,
24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston, 557
(2000).
No abstract.
Willoughby, H.E. Observations through models to forecasts. AGU 2000 Fall
Meeting, San Francisco, CA, December 15-19, 2000. Supplement to
EOS, Transactions, American Geophysical Union, 81(48):F115, A72E-04
(2000).
Isaac Cline forecast the Galveston Hurricane of 1900 based upon incomplete
climatology, misleading instructions from Washington, and what he could see
and feel. Since then, hurricane meteorologists have learned to use radio ship
reports (1900s), upper air observations (1930s), aircraft reconnaissance and
radar (1940s), statistical models (1950s), polar-orbiting satellites and
barotropic models (1960s), geostationary satellites and baroclinic models
(1970s), Doppler radar (1980s), and targeted observations and coupled models
(1990s). These developments produced a ~1% annual decline in mean
track forecast errors between 1970 and 2000. Over the same period, average
hurricane mortality was 25 souls annually, compared with estimates of >200
annually if forecasting had not improved. The successful strategy has been
evacuation of the storm-surge inundation zone on a length of coastline wide
enough to allow for forecast error. Accelerating coastal development increases
demands on the forecast system. Essential improvement of track forecasts will
stem from better specification of the "steering" flow that accounts for
80% of motion. The improvement will continue as a result of assimilation of
remotely-sensed data and targeted in-situ observations from piloted
and autonomous aircraft. By 2050, the limit of deterministic track forecasting
will be reached with 24 h error of ~100 km. Even before then,
ensemble-based, probabilistic forecasting will be the key for rational
decisions. The great hurricane catastrophe of the 21st century will happen
through the poorly understood process of "rapid deepening," in which the sea
and atmosphere combine to intensify a category 2 hurricane to category 4 in
~24 h. In the worst case, deepening begins late in the day as the storm
accelerates overnight toward a poorly-prepared city. A substantial basic and
applied science investment is essential to produce adequate forecasts of this
potentially devastating phenomenon.
Willoughby, H.E. The proposed upgrade of NOAA's Gulfstream-IV for tropical
cyclone reconnaissance. Minutes, 54th Interdepartmental Hurricane
Conference, Houston, TX, February 14-18, 2000. Office of the Federal
Coordinator for Meteorological Services and Supporting Research, Washington,
D.C., A239-A241 (2000).
No abstract.
Willoughby, H.E. and R.W. Jones. Are the beta gyres really normal modes?
Preprints, 24th Conference on Hurricanes and Tropical Meteorology,
Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society,
Boston, 187-188 (2000).
No abstract.
Wilson, W.D., and K.D. Leaman. The NOPP Year of the Ocean drifter program:
A new Lagrangian perspective on IAS circulation. AGU 2000 Ocean Sciences
Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS,
Transactions, American Geophysical Union, 80(49):OS234, OS41E-24
(2000).
Since March of 1998, 130 "WOCE-type" drifting buoys, drogued at 15 m, have
been launched in the Gulf of Mexico and the Caribbean Sea and its approaches,
providing in excess of 15,000 "drifter days" of data to date. Buoys were
provided by the U.S. National Ocean Partnership Program (NOPP); launch
coordination was provided by scientists at NOAA/AOML and UM/RSMAS; and
logistical and data processing support was provided by the NOAA/AOML Global
Drifter and Data Assembly Centers. Buoys were launched with the cooperation
of commercial ships, the Colombian Navy, the U.S. Coast Guard, and research
vessels working in the region. Drifter track figures and data have been made
available in real time via the World-Wide Web at www.IASlinks.org and
www.drifters.doe.gov. Repeated launches were concentrated in three areas:
The Panama-Colombia gyre in the southwest Caribbean; the island passages in
the eastern Caribbean; and in the North Brazil Current rings, a primary
source of mesoscale variability upstream of the Caribbean. This strategy was
designed to maintain maximum coverage within the IAS, as well as study
propagation of variability through the region, the formation and
intensification of the Caribbean Current, and the structure and permanence
of the circulation within the Panama-Colombia gyre. Individual drifter
tracks are shown which illustrate pathways and time scales of connectivity
within the region. There is also sufficient data coverage to estimate fields
of mean velocity, velocity variability, and several different indicators of
dispersal. Drifter-derived fields are compared to existing estimates of
mean velocity (ship drift, climatological, geostrophic, and Ekman estimates)
and variability (ship drift, altimetry). Discussion will focus on the
usefulness of Lagrangian measurements for larval and other transport
studies, and diagnostics of the large-scale IAS circulation field. A
companion presentation by Leaman and Wilson will focus on drifters in the
Panama-Colombia Gyre and comparison with the high-resolution MICOM
model. The merits of a cooperative plan for maintaining long-term
drifter coverage of the IAS will be considered.
Wilson, W.D., and K.D. Leaman. Transport pathways through the Caribbean:
The tropical origins of the Gulf Stream. Current, 16(1):14-18
(2000).
No abstract.
Wright, C.W., E.J. Walsh, D.C. Vandemark, W.B. Krabill, A.W. Garcia, S.H.
Houston, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane directional
wave spectrum spatial variation in the open ocean. Proceedings, 10th
Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale,
FL, May 29-June 2, 2000. American Meteorological Society, Boston, J1-J2
(2000).
No abstract.
Yvon-Lewis, S.A. Methyl bromide in the atmosphere and ocean. IGACtivities
Newsletter, 19:9-12 (2000).
No abstract.
Yvon-Lewis, S.A., J.H. Butler, P.A. Matrai, and E.S. Saltzman. The cycling
of methyl bromide in the North Atlantic and eastern Pacific Oceans. AGU
2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement
to EOS, Transactions, American Geophysical Union, 81(48):F277,
B22A-02 (2000).
Methyl bromide (CH3Br) saturation anomalies, degradation rates,
and net production rates were measured during the 1998 Gas Exchange cruise
(GasEx98) and the subsequent transit to Newport, Oregon. This cruise was
conducted aboard the NOAA ship Ronald H. Brown between May 8 and July
27, 1998. Persistent CH3Br supersaturations were observed (King
et al., 2000; JGR, 105 [D15], 19,763-19,769), which suggested
seasonal cycling of CH3Br in temperate regions when compared to
previous observations (Lobert et al., 1996; NOAA Technical
Memorandum, ERL CMDL-10, Boulder, CO). King et al. (2000)
demonstrated that 40-70% of the global variability in the
CH3Br saturation anomaly could be explained by variations in
sea-surface temperature (SST). However, in temperate North Atlantic waters,
variations in SST could explain only 15% of the apparent seasonal variability
in the CH3Br saturation anomaly. During this cruise, results from
the first open ocean measurements of the chemical and biological degradation
rate constants for CH3Br agreed with laboratory estimates of the chemical
degradation rate constant and showed biological degradation was ubiquitous
(Tokarczyk and Saltzman, 2000; JGR, submitted). Biological
degradation accounted for up to 40% of the total degradation of
CH3Br in individual water samples. Additionally, the first
open ocean incubation experiments to examine the net production of
CH3Br in seawater suggest that a substantial fraction of
CH3Br is produced in the dissolved portion of the sample (0.2 mm
filtered seawater) and that up to 50% of the variability in net
CH3Br production can be explained statistically by variations in
SST in the waters sampled. Here, we incorporate the data discussed above into
an air-sea exchange model to examine the cycling of CH3Br and to
assess the impact of the biologically-mediated processes on its uptake from
and emission to the atmosphere. This well-constrained system allows us to
examine the uptake fluxes, a function of the observed chemical and biological
degradation rate constants, the net fluxes, determined from the observed
saturation anomalies, and the observed net production rates independently.
Zhang, J.-Z. Shipboard automated determination of trace concentrations
of nitrite and nitrate in oligotrophic water by gas-segmented continuous
flow analysis with a liquid waveguide capillary flow cell. Deep-Sea
Research, Part I, 47(6):1157-1171 (2000).
Incorporation of a liquid waveguide capillary flow cell to a
gas-segmented continuous flow auto-analyzer significantly enhances the
sensitivity of automated colorimetric analysis. Nanomolar concentrations
of nitrite and nitrate in oligotrophic surface seawater can be accurately
determined. The advantages of this technique are low detection limit,
high precision, and automation for rapid analysis of a large number of
samples. This technique has been successfully used on shipboard
measurements of about 1000 seawater samples during a one-month cruise in
North Atlantic.
Zhang, J.-Z. The use of pH and buffer intensity to quantify the carbon
cycle in the ocean. Marine Chemistry, 70(1-3):121-131 (2000).
The pH of seawater is governed by the content of total carbon dioxide and
ionic equilibra between hydrogen ions and various inorganic carbon species
in seawater. Buffer intensity is defined as a measure of the ability of
seawater to accommodate the addition of acid or base without appreciable pH
change. It can be calculated from pH and total carbon dioxide of seawater.
pH data in conjunction with buffer intensity can be used to quantify the
carbon cycle in the ocean. The total amount of acid that has been released
or consumed by any biogeochemical processes can be calculated from the
change in pH multiplied by buffer intensity of seawater, dCH
= d(beta-pH). This approach has been used to quantify the remineralization
process in the Antarctic Intermediate Water in the South Pacific. Based on
the observational data (pH, total carbon dioxide, O2, and
nutrient measurements on P18 cruise), calculated elemental remineralization
ratios are 173, 107, and 14.3 for O/P, C/P and N/P, respectively. The
dissolution of calcium carbonate accounts for 21.5% of carbon increased from
the remineralization in the Antarctic Intermediate Water.
Zhang, J.-Z., and C.R. Kelble. Gas-segmented continuous flow analysis of
iron in water with a long liquid waveguide capillary flow cell.
Proceedings, 8th International Conference on Flow Analysis,
Warsaw, Poland, June 25-29, 2000. International Union of Pure and
Applied Chemistry, 107 (2000).
A long liquid waveguide capillary flow cell has been successfully adapted
into a gas-segmented continuous flow auto-analyzer for trace analysis of
iron. The flow cell was made of a new material, Teflon AF-2400, that has a
refractive index (1.29) lower than water (1.33). Total reflection of light
can be achieved when the light beams intersect the water/AF-2400 Teflon
tubing interfaces at greater than critical angle. Teflon AF-2400 is superior
to currently used materials in both refractivity and mechanical stability.
This allows the construction of a long liquid waveguide capillary flow cell
in helical, rather than linear shape, with compact dimension. Small sample
volumes are required since the internal volume of a 2 m-long liquid
waveguide capillary flow cell with 550 µm ID is only approximately
0.5 cm3. According to the Lambert-Beer law, the absorbance of a
sample in spectrophotometry is proportional to the light path length in the
flow cell. Utilization of this long flow cell significantly enhances the
sensitivity of automated colorimetric analysis of iron by the ferrozine
method. Nanomolar concentrations of iron in natural water can be accurately
determined. The advantages of this technique are low detection limit, small
sample volume, high precision, and automation for rapid analysis of a large
number of samples. This technique has potential application in many
spectrophotometric detections to augment the capability of gas-segmented
continuous flow analysis and flow injection analysis.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Comparison of open tubular
cadmium reactors and packed cadmium columns in automated gas-segmented
continuous flow nitrate analysis. International Journal of
Environmental Analytical Chemistry, 76(2):99-113 (2000).
Detailed procedures are provided for preparing packed cadmium columns to
reduce nitrate to nitrite. Experiments demonstrated the importance of
conditioning both open tubular cadmium reactor (OTCR) and packed
copper-coated cadmium columns to achieve 100% reduction efficiency. The
effects of segmentation bubbles in the OTCR upon reduction efficiency and
baseline noise in nitrate analysis are investigated using an auto-analyzer.
Metal particles derived from segmentation bubbles in OTCR result in i
nterference with continuous flow analyses. Therefore, packed columns are
recommended for determination of low level nitrate in natural waters.
Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. New production in
oligotrophic waters: Estimation based on diel cycle of nitrate.
Proceedings, Joint Global Ocean Flux Study (JGOFS) Open Science
Conference, Bergen, Norway, April 13-17, 2000. JGOFS International
Project Office, 76-77 (2000).
New production can be estimated from accurate measurements of inventory
change in nitrate at nM levels in the photic zone. A strong diel cycle was
observed in nitrate concentrations in response to photosynthesis in the
eastern North Atlantic during the GASEX-98 cruise. During a diel study,
nitrate concentration was 92 nM in the morning and decreased to 12 nM by
6 p.m. It increased after dark, presumably due to the diffusive flux from
the nitracline. Oxygen showed a similar diel cycle with a change in
concentration of about 2 µM. The vertical eddy diffusivity was derived
from temporal changes in concentrations of a deliberate tracer, SF6, below
the mixed layer. Together with vertical nitrate distributions, the nitrate
flux from nitracline throughout the nighttime can account for a nitrate
concentration of 102 nM by morning, which is in good agreement with measured
nitrate of 92 nM at 6 a.m. The new production estimated from changes of
nitrate inventory in the photic zone during the day was 28 mmole
C/m2 d. Increases in the mixed layer nitrate were observed
during storm events that deepened the mixed layer and brought the nitrate
to the surface. The storm-induced nitrate disappeared within two days,
indicating a rapid uptake by phytoplankton. The relative importance of
sporadic storm events versus daily diffusive flux in supply nitrate to new
production can be estimated based on nitrate inventory changes in the
photic zone.
Zhang, J.-Z., C.W. Mordy, L.I. Gordon, A. Ross, and H.E. Garcia.
Temporal trends in deep ocean Redfield ratios. Science, 289:1839
(2000).
No abstract.
**1999**
Aberson, S.D. Ensemble-based products to improve tropical cyclone
forecasting. Preprints, 23rd Conference on Hurricanes and Tropical
Meteorology, Dallas, TX, January 10-15, 1999. American
Meteorological Society, Boston, 843-844 (1999).
No abstract.
Aberson, S.D. Targeting and sampling strategies to improve hurricane
forecasts. Preprints, 23rd Conference on Hurricanes and Tropical
Meteorology, Dallas, TX, January 10-15, 1999. American
Meteorological Society, Boston, 105-107 (1999).
No abstract.
Aberson, S.D., and J.L. Franklin. Impact on hurricane track and
intensity forecasts of GPS dropwindsonde observations from the
first-season flights of the NOAA Gulfstream-IV jet aircraft. Bulletin
of the American Meteorological Society, 80(3):421-428 (1999).
In 1997, the Tropical Prediction Center (TPC) began operational
Gulfstream-IV jet aircraft missions to improve the numerical guidance for
hurricanes threatening the continental United States, Puerto Rico, and
the Virgin Islands. During these missions, the new generation of Global
Positioning System dropwindsondes were released from the aircraft at
150-200-km intervals along the flight track in the environment of the
tropical cyclone to obtain profiles of wind, temperature, and humidity
from flight level to the surface. The observations were ingested into the
global model at the National Centers for Environmental Prediction, which
subsequently served as initial and boundary conditions to other numerical
tropical cyclone models. Because of a lack of tropical cyclone activity
in the Atlantic basin, only five such missions were conducted during the
inaugural 1997 hurricane season. Due to logistical constraints, sampling
in all quadrants of the storm environment was accomplished in only one of
the five cases during 1997. Nonetheless, the dropwindsonde observations
improved mean track forecasts from the Geophysical Fluid Dynamics
Laboratory hurricane model by as much as 32%, and the intensity forecasts
by as much as 20% during the hurricane watch period (within 48 h of
projected landfall). Forecasts from another dynamical tropical cyclone
model (VICBAR) also showed modest improvements with the dropwindsonde
observations. These improvements, if confirmed by a larger sample,
represent a large step toward the forecast accuracy goals of TPC. The
forecast track improvements are as large as those accumulated over the
past 20-25 years, and those for forecast intensity provide further
evidence that better synoptic-scale data can lead to more skillful
dynamical tropical cyclone intensity forecasts.
Albrecht, B., T. Faber, A. Savtchenko, D. Churchill, F.D. Marks, and P.G.
Black. Surface-based remote sensing of a landfalling tropical storm.
Preprints, 23rd Conference on Hurricanes and Tropical Meteorology,
Dallas, TX, January 10-15, 1999. American Meteorological Society,
Boston, 489-492 (1999).
No abstract.
Atlas, D., C.W. Ulbrich, F.D. Marks, E. Amitai, and C.R. Williams. Systematic
variation of drop size and radar-rainfall relations. Journal of Geophysical
Research, 104(D6):6155-6169 (1999).
Time histories of the characteristics of the drop size distribution of
surface disdrometer measurements collected at Kapingamarangi Atoll were
partitioned for several storms using rain rate, R, reflectivity
factor Z, and median diameter of the distribution of water content
D0. This partitioning produced physically based
systematic variations of the drop size distribution (DSD) and Z-R
relations in accord with the precipitation types viewed simultaneously by
a collocated radar wind profiler. These variations encompass the
complete range of scatter around the mean Z-R relations previously
reported by Tokay and Short (1996) for convective and stratiform rain and
demonstrate that the scatter is not random. The systematic time or space
variations are also consistent with the structure of mesoscale convective
complexes with a sequence of convective, transition, and stratiform rain
described by various authors. There is a distinct inverse relation
between the coefficient A and the exponent of the Z-R
relations which has been obscured in prior work because of the lack of
proper discrimination of the rain types. Contrary to previous practice,
it is evident that there is also a distinct difference in the DSD and the
Z-R relations between the initial convective and the trailing
transition zones. The previously reported Z-R relation for
convective rain is primarily representative of the transition rain that
was included in the convective class. The failure of present algorithms
to distinguish between the initial convective and the trailing transition
rains causes an erroneous apportionment of the diabatic heating and
cooling and defeats the primary intent of discriminating stratiform from
convective rains.
Alvarez-Zarikian, C., P.L. Blackwelder, T. Hood, T.A. Nelsen, and C.M.
Featherstone. A century of hydrological variability in the lower Everglades
National Park as interpreted from stable isotopes on ostracods and
foraminifers. 1999 Florida Bay and Adjacent Marine Systems Science
Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999.
University of Florida Sea Grant Program, 198 (1999).
Stable isotopic analysis of selected ostracods and foraminifers were carried
out from high-resolution sediment cores collected from Oyster and Florida
Bays. The core localities provide distinctive environmental conditions in
which the effects of freshwater runoff, rainfall, and, consequently, salinity,
can be assessed. Oyster Bay lies at the end of the Shark River Slough and is
an area that experiences extreme salinity fluctuations due to the interaction
between freshwater runoff and marine water input from the Gulf of Mexico due
to tidal flow. A second core, collected near Jimmy Key, in the center of
Florida Bay, provides a contrasting salinity history in which salinity has
remained close to marine during this century. Stable isotope
(13C, 18O) trends of ostracods and foraminifers at
Oyster Bay and Jimmy Key suggest a general transition to more saline
conditions over this time period. Relative abundance of salinity-sensitive
species confirmed this observations. Moreover, stable isotopes indicate an
increase in salinity variability over time, which is represented in the
microfaunal assemblage by survivor-mode dominance by highly-tolerant species,
both in foraminifers and ostracods, that occurred during a period of drought
or highly evaporative conditions during the mid to late 1980s that also lead
to reduced flow from Shark River Slough. Fluctuations on stable isotope
values appeared to be more a direct response to regional rainfall than
freshwater runoff; however, distinct patterns can be temporally correlated
to freshwater management strategies by the South Florida Water Management
District.
Alvarez-Zarikian, C., T. Hood, P. Blackwelder, T.A. Nelsen, P. Swart, H.
Wanless, J. Trefry, and W.-J. Kang. Paleoecological significance of
temporal fluctuations in assemblages and isotopic composition of
ostracoda and foraminifera from Florida Bay. AGU 1999 Spring
Meeting, Boston, MA, June 1-4, 1999. EOS, Transactions,
American Geophysical Union, 80(17):S178, OS31A-17 (1999).
Microfaunal populations and stable isotopic analysis of selected
ostracods and benthic foraminifers were examined from high-resolution
sediment cores in the lower Everglades/Florida Bay ecosystem.
Microfaunal characteristics and population fluctuations can be
temporarily related to forces of natural (hurricanes, precipitation) and
anthropogenic (historic practices from the South Florida Water Management
District [SFWMD]) origin since the turn of the century. Dramatic shifts
in community structure are observed in both microfaunal groups and are
represented by major swings in species diversity and dominance, and total
loss of numerous species. Before the 1960s, significant crashes in the
community structure of both groups were temporally correlated with major
hurricanes, but fairly rapid recoveries indicate a relatively resilient
community. Community changes during the 1970s were most systematic, and
temporally correlate with changes in SFWMD policy. In Oyster Bay, the
1970s Monthly Water Allocation Plan corresponds to a boom period for
ostracods and benthic foraminfers possibly due to a more efficient water
flow and exchange. This is followed by a dramatic crash in both groups
corresponding to the start of the SFWMD's Rainfall Plan and the closing
of the Buttonwood Canal in the early 1980s, from which neither community
has recovered. Sediment cores from Oyster Bay and near Jimmy Key in
Florida Bay show a reduction in the number of species and a pronounced
dominance of survivor-type species since that time. delta-180 data from
ostracods and foraminifers shift to heavier values during this period,
indicating drought conditions. Microfaunal and isotopic data from this
study complemented with an analysis of historical rainfall, gauged
freshwater flow, and limited near-shore salinity data show a significant
increase in the magnitude and range of seasonal salinity variability due
to fluctuations in regional rainfall and the current water management
plan, resulting in significantly drier conditions in the lower portion of
Shark River Slough.
Amat, L.R., M.D. Powell, and S.H. Houston. A real-time, Internet-based
application for the archival, quality control, and analysis of hurricane
surface wind observations. Preprints, 15 International Conference on
Interactive Information and Processing Systems for Meteorology,
Oceanography, and Hydrology, Dallas, TX, January 10-15, 1999.
American Meteorological Society, Boston, 573-576 (1999).
No abstract.
Atakturk, S.S., and K.B. Katsaros. Wind stress and surface waves
observed on Lake Washington. Journal of Physical Oceanography,
29(4):633-650 (1999).
New results from turbulent flux measurements made over Lake Washington
include the following:
(1) The only direct measure of the vertical transport of the horizontal
momentum, heat, and matter in the surface boundary layer is the so-called
eddy correlation method. However, even if the measurement errors are
negligible, the results obtained from point observations may show large
scatter due to lack of stationarity and horizontal homogeneity in the
turbulent field and to the sampling variability. Scatter may be greatly
reduced by spatial averaging. In this study, such an effect is achieved
by determining the surface roughness length; hence, the neutral drag
coefficient from the measured wave height spectrum, which reflects the
atmospheric input integrated over the fetch. Applicability and usefulness
of the approach for general field measurements and remote sensing is
discussed.
(2) The evolution of the wave field observed on Lake Washington agrees in
peak frequency and the slope of the equilibrium range parameter as a
function of "wind forcing" with other observations, while the magnitude
is significantly smaller (by a factor of 2.1) than the values
obtained from larger bodies of water. Based on the results obtained from
a wave model, we attribute this observed difference to the narrower width
of the water body on Lake Washington. These findings indicate that the
state-of-the-art spectral parameterization of surface waves has
limitations in describing the observations from a natural but small body
of water.
Baringer, M.O., and R.L. Molinari. Atlantic Ocean baroclinic heat flux
at 24-26°N. Geophysical Research Letters, 26(3):353-356 (1999).
The spatially varying, interior geostrophic baroclinic heat flux
component of the total meridional oceanic heat flux near 24°N in the
Atlantic Ocean is examined using four transatlantic hydrographic sections
including the October 1957 Discovery II IGY section, the September
1981 Atlantis section, the August 1992 Hesperides section, t
he February 1998 Ronald H. Brown section and the 1982 Levitus and
the Lozier, Owens, Curry climatologies. The 1992 section is complemented
by shorter western boundary sections obtained concurrently during the
Trident cruise. We find an average southward baroclinic heat flux of 0.9
0.3 PW with an annual cycle amplitude of 0.3 PW. More than 90% of the
annual cycle is captured within 30° of the western boundary.
Baringer, M.O., and J.F. Price. A review of the physical oceanography of
the Mediterranean Outflow. Marine Geology, 155(1-2):63-82 (1999).
The physical oceanography of the Mediterranean Sea is reviewed with
particular emphasis on the Mediterranean outflow in the Gulf of Cadiz.
In this region the dense Mediterranean water forms a high velocity bottom
current that interacts strongly with the sea floor. The major energy
source for the plume comes from the release of potential energy as the
plume descends the continental slope, and the major energy sink is work
against bottom stress, which is as large as 4 Pa where the plume begins
to descend the continental slope. In this region the current makes a
nearly inertial turn that would otherwise appear to be steered by the
underlying topography. The Mediterranean plume entrains the overlying
North Atlantic Central Water and thereby loses much of its density
anomaly. The mixed Mediterranean water becomes neutrally buoyant in the
lower portion of the North Atlantic thermocline near Cape St. Vincent.
There are then two preferred transport modes having somewhat different
temperature and salinity whose distinct characteristics can be found far
into the open North Atlantic. The temperature, salinity and volume of
the Mediterranean water in the Strait of Gibraltar and in the Gulf of
Cadiz appear to be roughly constant since modern measurements have been
made. The estimated westward transport of Mediterranean water has gone
down considerably as direct measurement techniques have been applied. A
recent estimate is that the westward transport of pure Mediterranean water
is only about a half a Sv (1 Sv = 106 m3/s); the
transport of mixed Mediterranean water in the western Gulf of Cadiz is
larger by about a factor of three or four because of the entrainment of
North Atlantic water.
Bentamy, A.P., P. Queffeulou, Y. Quilfen, and K.B. Katsaros. Ocean
surface wind fields estimated from satellite active and passive microwave
instruments. IEEE Transactions on Geoscience and Remote Sensing,
37(5):2469-2486 (1999).
This study examines the consistency of surface wind speeds estimated from
the European Remote Sensing Satellite (ERS-1) scatterometer, ERS-1 altimeter,
and the special sensor microwave/imager (SSM/I). The goal is to combine
these wind estimates to produce surface wind fields. With this in mind,
a comparison with buoy wind measurements and comparison among the three
sensors is performed. According to the in-situ data, the rms errors of
the three wind estimates are all within 2 m/s. The differences between
the remotely-sensed and buoy wind speeds are studied according to
atmospheric and oceanic variables, and their impact is shown. A large
data base is obtained from the comparisons among the three sensor winds.
The rms values of the differences between the scatterometer and the
altimeter and between the scatterometer and the SSM/I are 1.67 and 1.45
m/s, respectively. There is no global bias between the scatterometer and
the SSM/I, but between the scatterometer and the altimeter wind speeds,
the bias is about 0.3 m/s. Furthermore, it is shown that the difference
between the scatterometer and the altimeter wind estimates is dependent
on the significant wave height, while the difference between the
scatterometer and the SSM/I winds is dependent on the integrated water
vapor content. The comparison enables some corrections to be made for
consistency and combining products. The use of combining scatterometer,
altimeter, and SSM/I wind estimates is illustrated by two examples.
Berberian, G.A., and A.Y. Cantillo. Oceanographic conditions in the
Gulf of Mexico and Straits of Florida: Fall 1976. NOAA Data Report, OAR
AOML-36 (PB2000-106209), 64 pp. (1999).
NOAA conducted an investigation in the Gulf of Mexico and the Straits of
Florida of oceanographic conditions and nutrients and trace metal levels in
seawater during September and October 1976 aboard the NOAA Ship
Researcher. This report lists the chemical data obtained from
118 stations. Collection and analyses methodologies, as well as results,
are described.
Bishop, C.H., S. Majumdar, I. Szunyogh, Z. Toth, and S.D. Aberson. Using
ensembles to simulate the impact of targeted observations. Preprints,
23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX,
January 10-15, 1999. American Meteorological Society, Boston, 117-118
(1999).
No abstract.
Black, M.L. Recent observations of the hurricane eyewall: Unusual and
complex structure. Preprints, 23rd Conference on Hurricanes and Tropical
Meteorology, Dallas, TX, January 10-15, 1999. American
Meteorological Society, Boston, 313-316 (1999).
No abstract.
Black, M.L., and J.L. Franklin. Recent observations of the convective
structure associated with low-level wind maxima in the hurricane
eyewall. Preprints, 29th International Conference on Radar
Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American
Meteorological Society, Boston, 370-373 (1999).
No abstract.
Black, R.A., and J. Hallett. Electrification of the hurricane.
Journal of the Atmospheric Sciences, 56(12):2004-2028 (1999).
A survey of reports of electrical activity in hurricanes and typhoons
from flight notes and personal experience (18 years, >230 eyewall
penetrations for R. A. Black; ~20 years for J. Hallett, plus that of
others at the Hurricane Research Division), and perusal of flight notes
dating from 1980, show that lightning in and within 100 km or so of the
eyewall is usually sparse. However, occasionally, significant electrical
activity (>one flash per minute) occurs in or near the eyewall. National
Oceanic and Atmospheric Administration WP-3D aircraft penetrations
through a number of storms relate the lightning occurrence to strong
vertical velocity (>10 m s-1) and the presence of supercooled
liquid cloud droplets extending to temperatures below 20°C. Specific
measurements of cloud properties during eyewall penetrations show that
the supercooled cloud water content increases with upward velocities >
~5.0 m s-1, as does the presence of large (>2 mm)
supercooled drops. Measurements at temperatures >-13°C show that the
transition of supercooled cloud water to ice along an outward radial in
all systems is associated with local electric fields (occasionally >20 kV
m-1) and negative charge above positive charge. In systems
with stronger vertical velocity there is a larger region of supercooled
cloud extending to lower temperatures where charge separation may occur,
as judged by the presence of regions containing graupel, small ice, and
cloud droplets. The ratio of ice to supercooled water increases radially
outward from the eyewall and depends upon altitude (temperature). The
spatial distribution of charge is further influenced by the relation of
vertical velocity to the radial flow, with the upper charge regions
tending to be advected outward. In symmetrical, mature hurricanes,
supercooled water usually occurs only in regions at temperatures above
about -5°C. The upward transport of supercooled cloud water is
limited by a balance between water condensed in the eyewall updraft and
its erosion by ice in downdrafts descending in the outward regions of the
eyewall. This ice originates from both primary and secondary ice
nucleation in the updraft. This is consistent with an exponential
increase in ice concentration, as the rate at which the ice particle
concentrations increase depends on the production of secondary particles
by preexisting graupel, some of which ultimately grow into new graupel,
and its outward transport in the anvil flow aloft. Penetrations at
temperatures as low as -15°C show the presence of electric fields
consistent with specific laboratory-derived criteria for charge separated
during ice-graupel collisions, given that a liquid water-dependent sign
reversal temperature may occur. Such a reversal may result from either a
changing temperature in the vertical, a changing cloud liquid water
content in the horizontal, or a combination of the two. Since
cloud-to-ground (CG) lightning can be observed with remote detection
networks that provide the polarity and frequency of CG lightning, there
is potential that hurricane evolution may be detected remotely and that
lightning may be usable as an indicator of a change in the storm
intensity and/or track.
Blackwelder, P.L., T. Hood, C. Alvarez-Zarikian, P. Swart, C.M.
Featherstone, and T.A. Nelsen. Historical salinity effects on microfauna
in the lower Everglades and Florida Bay. 1999 Florida Bay and Adjacent
Marine Systems Science Conference, Programs and Abstracts, Key Largo,
FL, November 1-5, 1999. University of Florida Sea Grant Program, 181 (1999).
A multi-faceted approach examines the relationship between microfauna
(ostracods and foraminifers) and salinity in Florida Bay and its environs.
Several "levels" of microfaunal population variability were examined, which
range from overall population characteristics to species- and
individual-specific isotopic composition and morphological differences.
These levels include documentation of changes in population abundance and
diversity over time with variability in salinity and individual
species-specific responses, which produce decipherable salinity-related
records. Isotopic composition of stained individuals living in the surface
sediment in each environment, as well as documentation of salinity related
ostracod valve morphological change are studied. Attention is focused on
those species capable of withstanding the greatest salinity fluctuations.
Core and surface microfaunal populations at Oyster Bay, Jimmy Key, and First
National Bank are compared and contrasted. These three sites comprise
distinct environmental regimes with well-documented salinity records. Oyster
Bay has experienced the greatest salinity variability of the three sites, as
well as freshest overall conditions over the last 100 years. The Jimmy
Key site, in the center of the Bay, has experienced higher average
salinity with less variability over this period. Taphonomic microfaunal
studies routinely utilize population characteristics as a tool for
paleoenvironmental reconstruction. This study extends population work to
include species and individual-specific characteristics, which may record
salinity variability. In addition to the field and core collections, we
are culturing ostracods to examine isotopic and morphological relationships
under controlled conditions. This multi-faceted approach extends our
population characterization work to include documentation of physiological
response of individuals within the microfaunal populations to documented
changes in salinity. This data will extend the use of microfauna as
indicators of modern and paleo-salinity change.
Boebel, O., C. Schmid, and W. Zenk. Kinematic elements of Antarctic
Intermediate Water in the western South Atlantic. Deep Sea Research,
Part II, 46(1-2):355-392 (1999).
The northward flowing Antarctic Intermediate Water (AAIW) is a
major contributor to the large-scale meridional circulation of water
masses in the Atlantic. Together with bottom and thermocline water, AAIW
replaces North Atlantic Deep Water that penetrates into the South
Atlantic from the north. On the northbound propagation of AAIW from its
formation area in the southwestern region of the Argentine Basin, the
AAIW progresses through a complex spreading pattern at the base of the
main thermocline. This paper presents trajectories of 75 subsurface
floats, seeded at AAIW depth. The floats were acoustically tracked,
covering a period from December 1992 to October 1996. Discussions of
selected trajectories focus on mesoscale kinematic elements that
contribute to the spreading of AAIW. In the equatorial region,
intermittent westward and eastward currents were observed, suggesting a
seasonal cycle of the AAIW flow direction. At tropical latitudes, just
offshore the intermediate western boundary current, the southward
advection of an anticyclonic eddy was observed between 5°S and
11°S. Farther offshore, the flow lacks an advective pattern and is
governed by eddy diffusion. The westward subtropical gyre return current
at about 28°S shows considerable stability with the mean kinetic
energy to eddy kinetic energy ratio being around one. Farther south, the
eastward deeper South Atlantic Current is dominated by large-scale meanders
with particle velocities in excess of 60 cm s-1. At the
Brazil-Falkland Current Confluence Zone, a cyclonic eddy near 40°S,
50°W seems to act as injector of freshly mixed AAIW into the
subtropical gyre. In general, much of the mixing of the various blends of
AAIW is due to the activity of mesoscale eddies, which frequently reoccupy
similar positions.
Boebel O., C. Schmid, G. Podesta, and W. Zenk. Intermediate water in the
Brazil-Malvinas Confluence Zone: A Lagrangian view. Journal of
Geophysical Research, 104(C9):21,063-21,082 (1999).
The subsurface flow within the subantarctic and subtropical regions around
the Brazil-Malvinas Confluence Zone is studied, using daily hydrographic
and kinematic data from four subsurface floats and a hydrographic section
parallel to the South American shelf. The trajectories are mapped against
sea-surface flow patterns as visible in concurrent satellite sea-surface
temperature images, with focus on the November 1994 and October/November
periods. The unprecedented employment of Lagrangian-S diagrams enables us
to trace the advection of patches of fresh Antarctic Intermediate Water
(AAIW) from the Confluence Zone into the subtropical region. The fresh
AAIW consists of a mixture of subtropical AAIW and Malvinas Current core
water. Within the subtropical gyre, these patches are discernible for
extended periods and drift over long distances, reaching north to
34.26°S and east to 40.26°W. The cross-frontal migration of
quasi-isobaric floats across the Confluence Zone from the subtropical to
the subantarctic environment is observed on three occasions. The reverse
process, float migration from a subpolar to a subtropical environment was
observed once. These events were located near 40.26°S, 50.26°W,
the site of a reoccurring cold core feature. Subsurface float and SST data
comparison reveals similarities with analogous observations made in the
Gulf Stream (Rossby, 1996) where cross-frontal processes were observed
close to meander crests. The limited number of floats of this study and
the complex structure of the Brazil-Malvinas Confluence Zone, however,
restricts the analysis to a description of two events.
Boebel, O., R.E. Davis, M. Ollitrault, R.G. Peterson, P.L. Richardson, C.
Schmid, and W. Zenk. Direct observations of the western South Atlantic
intermediate depth circulation. Geophysical Research Letters,
26(21):3329-3332 (1999).
The subsurface oceanic circulation is an important part of the Earth
climate system. Subsurface currents traditionally are inferred
indirectly from distributions of temperature and dissolved substances,
occasionally supplemented by current meter measurements.
Neutrally-buoyant floats, however, now enable us to obtain for the first
time directly measured intermediate depth velocity fields over large
areas such as the western South Atlantic. Here, our combined data set
provides unprecedented observations and quantification of key flow
patterns, such as the Subtropical Gyre return flow (12 Sv; 1 Sverdrup =
106 m3 s-1), its bifurcation near the
Santos Plateau and the resulting continuous narrow and swift northward
intermediate western boundary current (4 Sv). This northward flowing
water passes through complex equatorial flows and finally enters into
the North Atlantic.
Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black.
Environmental influences on the rapid intensification of Hurricane Opal
(1995) over the Gulf of Mexico. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 983-984 (1999).
No abstract.
Bourles, B., R.L. Molinari, E. Johns, W.D. Wilson, and K.D. Leaman.
Upper layer currents in the western tropical North Atlantic (1989-1991).
Journal of Geophysical Research, 104(C1):1361-1376 (1999).
Shipboard Acoustic Doppler Current Profiler (ADCP) measurements and
hydrographic observations of temperature, salinity, and dissolved oxygen
are used to examine the upper water column flow field in the North Brazil
Current (NBC) retroflection region of the western tropical Atlantic
Ocean. Observations are presented from six cruises, one conducted in
August 1989 and the other five conducted during the Western Tropical
Atlantic Experiment (WESTRAX) between January 1990 and September 1991.
The upper water column is divided into two layers, an upper thermocline
layer located between the surface and the 24.5 sigma theta isopycnal
surface, and a lower subthermocline layer located between the 24.5 and
26.75 isopycnals. In the upper layer the NBC retroflects north of the
equator to form the eastward flowing North Equatorial Counter Current
(NECC). During the six cruises the retroflection appeared complete.
However, data coverage did not extend shoreward of the 200 m isobath, so
the possibility of a continuous flow over the shelf still remains. There
were also indications of several NBC rings which had apparently separated
from the NBC retroflection and drifted to the northwest towards the
eastern Caribbean Sea. North of the NBC retroflection and the NECC, the
North Equatorial Current (NEC) flows west as the southern limb of the
subtropical gyre. Part of the NEC is observed to retroflect cyclonically
to join the eastward NECC flow. In the lower layer, beneath the NBC, the
North Brazil Undercurrent (NBUC) retroflects to feed the eastward North
Equatorial Undercurrent (NEUC). To the north, a deeper component of the
NEC recurves to also contribute to the NEUC.
Boutin, J., J. Etcheto, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, H.Y.
Inoue, M. Ishii, R.D. Ling, P.D. Nightingale, N. Metzl, and R.H.
Wanninkhof. Satellite sea surface temperature: A powerful tool for
interpreting in-situ pCO2 measurements in the equatorial
Pacific Ocean. Tellus B, 51(2):490-508 (1999).
In order to determine the seasonal and interannual variability of the
CO2 released to the atmosphere from the equatorial Pacific, we
have developed pCO2-temperature relationships based
upon shipboard oceanic CO2 partial pressure measurements,
pCO2, and satellite sea surface temperature, SST,
measurements. We interpret the spatial variability in
pCO2 with the help of the SST imagery. In the eastern
equatorial Pacific, at 5°S, pCO2 variations of up
to 100 µatm are caused by undulations in the southern boundary of
the equatorial upwelled waters. These undulations appear to be periodic
with a phase and a wavelength comparable to tropical instability waves,
TIW, observed at the northern boundary of the equatorial upwelling. Once
the pCO2 signature of the TIW is removed from the Alize
II cruise measurements in January 1991, the equatorial
pCO2 data exhibit a diel cycle of about 10 µatm
with maximum values occurring at night. In the western equatorial
Pacific, the variability in pCO2 is primarily governed
by the displacement of the boundary between warm pool waters, where
air-sea CO2 fluxes are weak, and equatorial upwelled waters
which release high CO2 fluxes to the atmosphere. We detect
this boundary using satellite SST maps. East of the warm pool,
DELTA-P is related to SST and SST anomalies. The 1985-1997
CO2 flux is computed in a 5° wide latitudinal band as a
combination of DELTA-P and CO2 exchange coefficient,
K, deduced from satellite wind speed, U. It exhibits up to
a factor 2 seasonal variation caused by K-seasonal variation and a
large interannual variability, a factor 5 variation between 1987 and
1988. The interannual variability is primarily driven by displacements
of the warm pool that makes the surface area of the outgassing region
variable. The contribution of DELTA-P to the flux variability is
about half of the contribution of K. The mean CO2 flux
computed using either the Liss and Merlivat (1986) or the Wanninkhof
(1992) K-U parameterization amounts to 0.11 GtC yr-1 or
to 0.18 GtC yr-1, respectively. The error in the integrated
flux, without taking into account the uncertainly on the K-U
parameterization, is less than 31%.
Bove, M.C., J.B. Elsner, C.W. Landsea, X. Niu, and J.J. O'Brien. Effect
of El Niņo on U.S. landfalling hurricanes, revisited. Preprints, 23rd
Conference on Hurricanes and Tropical Meteorology, Dallas, TX,
January 10-15, 1999. American Meteorological Society, Boston, 278-281
(1999).
No abstract.
Broecker, W.S., S. Sutherland, and T.-H. Peng. A possible 20th-century
slowdown of Southern Ocean deep water formation. Science,
286(5442):1132-1135 (1999).
Chlorofluorocarbon-11 inventories for the deep Southern Ocean appear to
confirm physical oceanographic and geochemical studies in the Southern
Ocean, which suggests that no more than 5 × 106 cubic meters
per second of ventilated deep water is currently being produced. This result
conflicts with conclusions based on the distributions of the
carbon-14/carbon ratio and a quasi-conservative property, PO4,
in the deep sea, which seem to require an average of about 15 ×
106 cubic meters per second of Southern Ocean deep ventilation
over about the past 800 years. A major reduction in Southern Ocean deep
water production during the 20th century (from high rates during the Little
Ice Age) may explain this apparent discordance. If this is true, a seesawing
of deep water production between the northern Atlantic and Southern Oceans
may lie at the heart of the 1500-year ice-rafting cycle.
Broecker, W.S., E. Clark, D.C. McCorkle, T.-H. Peng, I. Hajdas, and G.
Bonani. Evidence for a reduction in the carbonate ion content of the
deep sea during the course of the Holocene. Paleoceanography,
14(6):744-752 (1999).
The paleo carbonate ion proxy proposed by Broecker et al. (1999)
is applied in a search for trends in the Holocene acidity of waters in
the transition zone between North Atlantic Deep Water (NADW) and
Antarctic Bottom Water (AABW). A clear signal emerges that the carbonate
ion content of waters in this zone declined during the last 8000 years.
In order to determine whether this decline represents a strengthening of
the northward penetrating tongue of low CO3 content AABW or a
global reduction of CO3 ion, measurements were made on a core
from the Ontong Java Plateau in the western equatorial Pacific. Evidence
for a similar decline in CO3 ion over the course of the Holocene
was obtained, lending support of the latter explanation. Such a drop is
consistent with the recent finding by Indermuhle et al. (1999) that
the CO2 content of the atmosphere (as recorded in the Taylor
Dome Antarctica ice core) rose by 20 to 25 ppm during the last 8000 years.
Butler, J.H., D.B. King, and S.A. Yvon-Lewis. Computation of the air-sea
exchange coefficient from halocarbon disequilibria. AGU 1999 Spring
Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions,
American Geophysical Union, 80(17):S46, A31C-10 (1999).
Studies conducted by NOAA during the past decade show that it is possible to
use measurements of halocarbon saturation anomalies to calculate air-sea gas
transfer velocities. These methods provide independent, averaged measures of
air-sea transfer in the open ocean and are based upon the exchange of
halocarbon across the air-sea interface on a broad scale; the source and
sink are both ubiquitous. Computations can be made for conservative
halocarbons, such as CFC-11 or CFC-12, for a hydrolyzable halocarbon such as
CH3CCl3, or even for a chemically and biologically
reactive compound such as CH3Br, if accompanied by measures of
production and degradation. During GasEx-98, we acquired data on a number of
trace halocarbons from which we can estimate air-sea exchange. The method that
appears to be most useful with respect to this data set involves computations
from disequilibria of conservative gases (e.g., CFCs) during heating
of a water mass. Unfortunately, the waters during much of the cruise were
not sufficiently warm for hydrolysis of CH3CCl3 to be
the dominant loss mechanism. Nevertheless, disequilibrium computations for
this gas did require consideration of hydrolysis. We also attempted to
obtain air profiles of halocarbons, but most gases were not sufficiently
supersaturated for this to be reliable. Exceptions were CH3I and
isoprene (a hydrocarbon), both of which were highly supersaturated and
which, under limited sampling conditions, yielded reasonable profiles in
the air.
Butler, J.H., D.B. King, S.A. Yvon-Lewis, J.M. Lobert, S.A.
Montzka, and J.W. Elkins. Seasonal and temporal variability in the
distribution of methyl bromide in the surface ocean. International Union
of Geodesy and Geophysics, XXII General Assembly, Birmingham, England,
July 18-30, July 1999. IUGG99 Abstracts, A110 (1999).
The ocean is both the largest source and the second largest sink
for methyl bromide (CH3Br) in the atmosphere, yet we still
don't fully understand how the ocean regulates the atmospheric burden of
this gas, nor can we predict accurately how the oceanic fluxes of methyl
bromide will respond to global change. From first-order calculations, it
is clear that the steady-state, net flux of this gas from the ocean will
act in opposition to changes in the atmospheric burden. However, the
distribution of the oceanic sources and sinks of CH3Br appears
to be patchy on both small and large scales. The open oceans are
typically undersaturated in CH3Br, with coastal waters
typically supersaturated. Warm waters tend to be undersaturated; cooler
waters can be super- or undersaturated. However, there are significant
exceptions to any generalities. Although the chemical degradation of
dissolved CH3Br is predominantly a function of sea-surface
temperature, production appears to be mainly biological and there is
strong evidence for biological degradation as well. Here, we examine the
distribution of methyl bromide from recent studies of its saturation in
the Pacific, Atlantic, and Southern Oceans to examine spatial and
temporal dependencies upon its net flux and, consequently, its production
and degradation.
Campos, E., A. Busalacchi, S.L. Garzoli, J. Lutjeharms, R. Matano, P. Nobre,
D.B. Olson, A. Piola, C. Tanajura, and I. Wainer. The South Atlantic and
the climate. OCEANOBS99: International Conference on the Ocean Observing
System for Climate, Saint Raphael, France, October 18-22, 1999. Centre
National d'Etudes Spatiales, Vol. 1, 16 pp. (1999).
As a contribution to the OCEANOBS99 objectives, we give a brief description
of the present knowledge of the South Atlantic and identify some key
processes and areas which need to be monitored in order to understand the
role of that part of the ocean in the global climate. Included are
suggestions of strategies for a first approximation towards an ocean
climate monitoring system in the South Atlantic.
Cantillo, A.Y., L. Pikula, and K. Hale. Preliminary data and document
rescue of material relevant to the south Florida ecosystem. 1999 Florida
Bay and Adjacent Marine Systems Science Conference, Programs and
Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea
Grant Program, 246 (1999).
There are significant amounts of unpublished documents and data on the
marine and estuarine environment of Florida that are so far unavailable
to the scientific community, academia, and the general public. These
data and documents are important because they represent the Florida
coastal ecosystems in times past, and are the basis for comparing past
with current conditions. Currently, an innovative prototype data and
document rescue effort is underway that combines the expertise of a
senior scientist with that of librarians. Its main purpose is to
inventory unpublished documents and data, perform a quality-assurance
review of the scientific content, convert the material to electronic and
printed form, and make it available through printed and online
resources. If the data and documents are not rescued, they will be lost
as printed material physically deteriorates, personnel retire, and
corporate memory disappears. Examples of rescued documents relevant to
the south Florida ecosystem are presented and the data and document
rescue approach discussed.
Cantillo, A.Y., K. Hale, R. Caballero, E. Collins, and L. Pikula.
Environmental history of Biscayne Bay. 1999 Florida Bay and Adjacent
Marine Systems Science Conference, Programs and Abstracts, Key Largo,
FL, November 1-5, 1999. University of Florida Sea Grant Program, 218 (1999).
Biscayne Bay is surrounded on the north by the growing urban areas of
Dade County, which includes Miami and Miami Beach, and on the south by the
sparsely inhabited Homestead area and the northern Florida Keys. Its
environmental history is closely related to the development of the
Greater Miami area. Urban development of the northern part of the Bay
during the 1920s began the decline that remained largely unchecked until
the early 1970s. Recently, environmental degradation of the Bay has
reversed. This work describes the major events impacting the Bay's
ecosystem and how it has changed over time.
Carsey, T.P. Shipboard measurements of active nitrogen gases during
INDOEX. AGU 1999 Fall Meeting, San Francisco, CA, December 13-17,
1999. Supplement to EOS, Transactions, American Geophysical Union,
80(46):F162, A22A-01 (1999).
A suite of active nitrogen gases (NO, NO2, and NOy)
were measured on board the NOAA ship Ronald H. Brown during the
INDOEX experiment during February-March 1999. The cruise track included
crossing of the Indian Ocean ITCZ, as well as several air mass types in
that region including clean marine and heavily anthropogenically influenced
air masses. The results will be presented and discussed in the context of
related meteorological and chemical data.
Checkley, D.M., P.B. Ortner, F.E. Werner, L.R. Settle, and S.R. Cummings.
Spawning habitat of the Atlantic menhaden in Onslow Bay, North Carolina.
Fisheries Oceanography, 8:22-36 (1999).
The Continuous, Underway Fish Egg Sampler (CUFES) was used to sample
pelagic eggs of the Atlantic menhaden (Brevoortia tyrannus) from a
3-m depth off North Carolina in winter 1993-1994 and 1994-1995.
Simultaneous measurements were made of temperature, salinity, and the
concentration of chlorophyll a. The maximal concentration of eggs was 346
eggs m-3. Eggs were highly aggregated in patches which
occurred between the Gulf Stream and mid-shelf fronts (17-23°C,
36.0-36.4 ppm). Unexpectedly, eggs were found almost exclusively in
water of 20-60 m (mode 20 m) bottom depth. Thus, spawning appears
related to bathymetry as well as hydrography. Variograms for egg
concentration indicated a mean (± SE) patch scale of 3.6 ± 1.7
km and a high degree of spatial variance explained by CUFES sampling.
Lagrangian modeling of particles moving in response to tides, winds, and
a prescribed flow from the north indicated that the region of observed,
maximal occurrence of eggs is favorable for the retention of eggs and
larvae on the shelf adjacent to inlets used to enter nursery areas.
Cione, J.J., P.G. Black, and S.H. Houston. Cooling and drying within the
hurricane near-surface environment? Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 1027-1030 (1999).
No abstract.
Cook, S.K. Vertical thermal structure of midshelf waters: Water
temperatures and climatological conditions south of New England,
1974-1983. NOAA Technical Report, NMFS-134, 43 pp. (1999).
No abstract.
DeMaria, M., and J. Kaplan. An updated Statistical Hurricane Intensity
Prediction Scheme (SHIPS) for the Atlantic and eastern North Pacific
basins. Weather and Forecasting, 14(3):326-337 (1999).
Updates to the Statistical Hurricane Intensity Prediction Scheme (SHIPS)
for the Atlantic basin are described. SHIPS combines climatological,
persistence, and synoptic predictors to forecast intensity changes using
a multiple regression technique. The original version of the model was
developed for the Atlantic basin and was run in near-real time at the
Hurricane Research Division beginning in 1993. In 1996, the model was
incorporated into the National Hurricane Center operational forecast
cycle, and a version was developed for the eastern North Pacific basin.
Analysis of the forecast errors for the period 1993-1996 shows that SHIPS
had little skill relative to forecasts based upon climatology and
persistence. However, SHIPS had significant skill in both the Atlantic
and east Pacific basins during the 1997 hurricane season. The regression
coefficients for SHIPS were rederived after each hurricane season since
1993 so that the previous season's forecast cases were included in the
sample. Modifications to the model itself were also made after each
season. Prior to the 1997 season, the synoptic predictors were determined
only from an analysis at the beginning of the forecast period. Thus,
SHIPS could be considered a "statistical-synoptic" model. For the 1997
season, methods were developed to remove the tropical cyclone circulation
from the global model analyses and to include synoptic predictors from
forecast fields, so the current version of SHIPS is a
"statistical-dynamical" model. It was only after the modifications for
1997 that the model showed significant intensity forecast skill.
Dickerson, R.R., K.P. Rhoads, T.P. Carsey, S.J. Oltmans, J.P. Burrows,
and P.J. Crutzen. Ozone in the remote marine boundary layer: A possible
role for halogens. Journal of Geophysical Research,
104(D17):21,385-21,395 (1999).
On the spring 1995 cruise of the National Oceanic and Atmospheric
Administration research vessel Malcolm Baldrige, we measured very
large diurnal variations in ozone concentrations in the marine boundary
layer. Average diurnal variations of about 32% of the mean were observed
over the tropical Indian Ocean. We simulated these observations with the
Model of Chemistry in Clouds and Aerosols, a photochemical box model with
detailed aerosol chemistry. The model was constrained with photolysis
rates, humidity, aerosol concentrations, NO, CO, and O3
specified by shipboard observations and ozonesondes. Conventional
homogeneous chemistry, where ozone photolysis to O(1D)
and HOx chemistry dominate ozone destruction, can account for
a diurnal variation of only about 12%. On wet sea-salt aerosols (at
humidities above the deliquesence point), absorption of HOBr leads to
release of BrCl and Br2, which photolyze to produce Br atoms
that may provide an additional photochemical ozone sink. After eight
days of simulation, these Br atoms reach a peak concentration of 1.2
× 107 cm-3 at noon and destroy ozone through a
catalytic cycle involving BrO and HOBr. Reactive Br lost to HBr can be
absorbed into the aerosol phase and reactivated. The model predicts a
diurnal variation in O3 of 22% with aerosol-derived Br
reaction explaining much, but not all, of the observed photochemical
loss. The lifetime of ozone under these conditions is short, about two
days. These results indicate that halogens play an important role in
oxidation processes and the ozone budget in parts of the remote marine
boundary layer.
Digby, S., T. Antczak, R. Leben, G. Born, S. Barth, R. Cheney, D. Foley,
G.J. Goni, G. Jacobs, and L. Shay. Altimeter data for operational use in
the marine environment. Proceedings, Oceans '99 MTS/IEEE Conference,
Seattle, WA, September 13-16, 1999. Marine Technology Society, 605-613 (1999).
TOPEX/Poseidon has been collecting altimeter data continuously since October
1992. Altimeter data have been used to produce maps of sea surface height,
geostrophic velocity, significant wave height, and wind speed. This
information is of proven use to mariners as well as to the scientific
community. Uses of the data include commercial and recreational vessel
routing, ocean acoustics, input to geographic information systems developed
for the fishing industry, identification of marine mammal habitats, fisheries
management, and monitoring ocean debris. As with sea surface temperature data
from the Advanced Very High Resolution Radiometer (AVHRR) in the late 1980s
and early 1990s, altimeter data from TOPEX/Poseidon and ERS-1 and -2 are in
the process of being introduced to the marine world for operational maritime
use. It is anticipated that over the next few years companies that specialize
in producing custom products for shipping agencies, fisheries, and yacht
race competitors will be incorporating altimeter data into their products.
The data are also being incorporated into weather and climate forecasts by
operational agencies both in the United States and Europe. This paper will
discuss these products, their uses, operational demonstrations, and means of
accessing the data.
Doddridge, B.G., W.T. Luke, C.A. Piety, R.R. Dickerson, A.M. Thompson,
J.C. Witte, J.E. Johnson, T.S. Bates, P.K. Quinn, and T.P. Carsey. Trace
gas and aerosols over the Atlantic Ocean during the ACE-Aerorsols cruise.
AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999.
Supplement to EOS, Transactions, American Geophysical Union,
80(46):F163, A22A-09 (1999).
The ACE-Aerosols cruise was conducted on board the NOAA R/V Ronald H.
Brown (R-104) on January 14-February 20, 1999. This paper focuses on
measurements conducted during a North-South Atlantic Ocean transect from
Norfolk, Virginia to Cape Town, South Africa, January 14-February 8, 1999.
Hourly-averaged marine boundary layer (MBL) carbon monoxide data ranged
from 105 to 200 ppbv and 45 to 75 ppbv in the northern and southern
hemisphere (SH), respectively. Aerosol optical depth showed significant
variability along the same transect, with elevated values dominated by upper
level transport from Africa. Hourly MBL ozone data ranged from 6 to 40 ppbv,
showing a diurnal cycle superimposed upon a strong hemispheric gradient,
and were strongly influenced by several pollution episodes, corroborated
by bulk aerosol chemistry data. Using these tracers, along with computed
air parcel trajectories, cruise data indicate substantial influence of
Saharan, equatorial, and SH subtropical regions of Africa on the remote
Atlantic Ocean MBL.
Dodge, P.P., R.W. Burpee, and F.D. Marks. The kinematic structure of a
hurricane with sea-level pressure less than 900 mb. Monthly Weather
Review, 127(6):987-1004 (1999).
A National Oceanic and Atmospheric Administration aircraft recorded the
first Doppler radar data in a tropical cyclone with a minimum sea level
pressure (MSLP) <900 mb during a reconnaissance mission in Hurricane
Gilbert on 14 September 1988, when its MSLP was ~895 mb. A previous
mission had found an MSLP of 888 mb, making Gilbert the most intense
tropical cyclone yet observed in the Atlantic basin. Radar reflectivity
identified the hurricane eye, inner and outer eyewalls, a stratiform
region between the eyewalls, and an area outside the outer eyewall that
contained a few rainbands but that had mostly stratiform rain.
Pseudo-dual Doppler analyses depict the three-dimensional kinematic
structure of the inner eyewall and a portion of the outer eyewall. The
vertical profiles of tangential wind and reflectivity maxima in the inner
eyewall are more erect than in weaker storms, and winds >50 m
s-1 extended to 12 km, higher than has been reported in
previous hurricanes. The inner eyewall contained weak inflow throughout
most of its depth. In contrast, the portion of the outer eyewall
described here had shallow inflow and a broad region of outflow. The
stratiform region between the two eyewalls had lower reflectivities and
was the only region where the vertically incident Doppler radar data
seemed to show downward motion below the freezing level. Gilbert's
structure is compared with other intense Atlantic and eastern North
Pacific hurricanes with MSLP >900 mb. Storms with lower MSLP have higher
wind speeds in both inner and outer eyewalls, and wind speeds >50 m
s-1 extend higher in storms with lower MSLP. Hurricanes
Gilbert and Gloria (1985), the strongest Atlantic hurricanes yet analyzed
by the Hurricane Research Division, had different outer eyewall
structures. Gloria's outer eyewall had a deep region of inflow, while
Gilbert's inflow layer was shallow. This may explain differences in the
subsequent evolution of the two storms.
Dodge, P.P., S.H. Houston, W.-C. Lee, J.F. Gamache, and F.D. Marks.
Windfields in Hurricane Danny (1997) at landfall from combined WSR-88D
and airborne Doppler radar data. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 61-62 (1999).
No abstract.
Donnelly, W.J., J.R. Carswell, R.E. McIntosh, P.S. Chang, J.C. Wilkerson,
F.D. Marks, and P.G. Black. Revised ocean backscatter models at C and
Ku-bands under high wind conditions. Journal of Geophysical Research,
104(C5):11,485-11,498 (1999).
A series of airborne scatterometer experiments designed to collect C and
Ku-band ocean backscatter data in regions of high ocean surface winds has
recently been completed. Over 100 hours of data were collected using the
University of Massachusetts C and Ku-band scatterometers, CSCAT and
KUSCAT. These instruments measure the full azimuthal normalized radar
cross section (NRCS) of a common surface area of the ocean simultaneously
at four incidence angles. Our results demonstrate limitations of the
current empirical models, CMOD4, SASSII and NSCAT1, that relate ocean
backscatter to the near surface wind at high wind speeds. The discussion
focuses on winds in excess of 15 m/sec in clear atmospheric conditions.
The scatterometer data is collocated with measurements from ocean data
buoys and GPS dropsondes, and a Fourier analysis is performed as a
function of wind regime. A three-term Fourier series is fit to the
backscatter data, and a revised set of coefficients is tabulated. These
revised models, CMOD4HW and KUSCAT1, are the basis for a discussion of
the NRCS at high wind speeds. Our scatterometer data show a clear over
prediction of the derived NRCS response to high winds based on the CMOD4,
SASSII and NSCAT1 models. Furthermore, saturation of the NRCS response
begins to occur above 15 m/sec. Sensitivity of the upwind and crosswind
response is discussed with implications towards high wind speed
retrieval. wind speed retrieval.
Ellsberry, R.L., and F.D. Marks. The Hurricane Landfall Workshop
summary. Bulletin of the American Meteorological Society,
80(4):683-685 (1999).
No abstract.
Enfield, D.B., and E.J. Alfaro. The dependence of Caribbean rainfall on
the interaction of tropical Atlantic and Pacific Oceans. Journal of
Climate, 12(7):2093-2103 (1999).
Seasonally-stratified analyses of rainfall anomalies over the
Intra-Americas Sea and surrounding land areas and of onset and end dates
of the Central American rainy season show that the variability of the
tropical Atlantic sea surface temperature anomaly (SSTA) is more strongly
associated with rainfall over the Caribbean and Central America than is
tropical eastern Pacific SSTA. Seasonal differences include the
importance of antisymmetric configurations of tropical Atlantic SSTA in
the dry season but not in the rainy season. Both oceans are related to
rainfall, but the strength of the rainfall response appears to depend on
how SSTA in the tropical Atlantic and eastern Pacific combine. The
strongest response occurs when the tropical Atlantic is in the
configuration of a meridional dipole (antisymmetric across the ITCZ) and
configuration of a meridional dipole (antisymmetric across the ITCZ) and
the eastern tropical Pacific is of opposite sign to the tropical North
Atlantic. When the tropical North Atlantic and tropical Pacific are of
the same sign, the rainfall response is weaker. The rainy season in lower
Central America tends to start early and end late in years that begin
with warm SSTs in the tropical North Atlantic, and the end dates are also
delayed when the eastern equatorial Pacific is cool. This
enhancement of date departures for zonally antisymmetric configurations
of SSTA between the North Atlantic and Pacific is qualitatively
consistent with the results for rainfall anomalies.
Enfield, D.B., and A.M. Mestas-Nunez. Contrary tropospheric direct
circulations associated with Pacific decadal variability and canonical
ENSO oscillations. AGU 1999 Fall Meeting, San Francisco, CA, December
13-17, 1999. Supplement to EOS, Transactions, American Geophysical
Union, 80(46):F180, A31D-07 (1999).
Our analysis shows that the intensity of the 1982-1983 and 1997-1998 El
Niņo events, occurring only 15 years apart, are among the three or four
warmest in 130 years of trans-Pacific sampling. However, when the 130 year
record of global sea surface temperatures (SST) is subjected to a complex
empirical orthogonal function (CEOF) analysis, the leading mode has all the
known characteristics (amplitude and phase) of the El Niņo-Southern
Oscillation (ENSO), yet the associated canonical variation of SST in the
equatorial Pacific does not include the spectacular amplitudes of the 1980s
and 1990s, seen in the unanalyzed SST data. When the equatorial
reconstruction of the global ENSO mode is subtracted from the SST data, the
residual equatorial variability (NINO3 region) is seen to have a pronounced
decadal variability, with many of the characteristics that others have
identified with the Pacific Decadal Oscillation (PDO). As much as 50% of
the total amplitudes of the NINO3 SST anomalies in 1982-1983 and 1997-1998
are explained by this residual, which was unusually high after 1978. In this
paper, we describe and compare the surface oceanic (SST) and atmospheric
(pressure, winds) characteristics associated with these two components of
the NINO3 variability (ENSO and residual). We also examine the anomalous
direct circulation (Walker and Hadley circulations) of the global troposphere
associated with each component. The tropospheric analysis, of greatest
interest to this session, yields a startling result: the anomalous direct
circulation associated with the canonical ENSO warmings in the NINO3
series is in most ways opposite to that associated with the residual
(decadal) warmings. The contrary behavior of the two components extends
to convection near the dateline, over the Amazon basin and over the
Indian Ocean, while the Hadley circulations in the Pacific and Atlantic
sectors are also affected in opposite ways. A unique feature of the
decadal component is the occurrence of a stronger winter monsoon over
India and northeast Africa, in association with warm background SSTs in
the eastern equatorial Pacific.
Enfield, D.B., and A.M. Mestas-Nunez. Multiscale variabilities in
global sea surface temperatures and their relationships with tropospheric
climate patterns. Journal of Climate, 12(9):2719-2733 (1999).
El Niño-Southern Oscillation (ENSO) is a global phenomenon with
significant phase propagation within and between basins. We capture and
describe this in the first mode of a complex empirical orthogonal
function (CEOF) analysis of sea surface temperature anomaly (SSTA) from
the mid-19th century through 1991. We subsequently remove the global ENSO
from the SSTA data, plus a linear trend everywhere, in order to consider
other global modes of variability uncontaminated by the intra- and
inter-basin effects of ENSO. An ordinary EOF analysis of the SSTA
residuals reveals three non-ENSO modes of low-frequency variability that
are related to slow oceanic and climate signals described in the
literature. The first two modes have decadal-to-multidecadal time scales
with high loadings in the Pacific. They bear some spatial similarities to
the ENSO pattern but are broader, more intense at high latitudes, and
differ in the time domain. A CEOF analysis confirms that they are not
merely the phase-related components of a single mode and that all three
modes are without significant phase propagation. The third mode is a
multidecadal signal with maximal realization in the extratropical North
Atlantic southeast of Greenland. It is consistent with studies that have
documented connections between North Atlantic SSTA and the tropospheric
North Atlantic Oscillation (NAO). All three SSTA modes have
mid-tropospheric associations related to previously classified Northern
Hemisphere teleconnection patterns. The relationships between SSTA modes
and tropospheric patterns are consistent with the ocean-atmosphere
interactions discussed in previous studies to explain low-frequency
climate oscillations in the North Pacific and North Atlantic sectors. The
first three leading modes of non-ENSO SSTA are most related,
respectively, to the tropospheric patterns of the Pacific North American
(PNA), the North Pacific (NP) and the Arctic Oscillations (AO),
respectively. The 500 hPa pattern associated with the third SSTA mode
also bears similarities to the NAO in its Atlantic sector. This North
Atlantic mode has a region of high, positive SSTA loadings in the Gulf of
Alaska, which appear to be connected to the North Atlantic SSTA by a
tropospheric bridge effect in the AO.
Enfield, D.B., A.M. Mestas-Nunez, D.A. Mayer, and L. Cid-Serrano. How
ubiquitous is the dipole relationship in tropical Atlantic sea surface
temperatures? Journal of Geophysical Research, 104(C4):7841-7848
(1999).
Several kinds of analysis are applied to the departures of sea surface
temperatures from climatology (SSTA, 1856-1991) to determine the degree
to which SSTA of opposite sign in the tropical North and South Atlantic
occur. Antisymmetric ("dipole") configurations of SSTA on basin scales
are not ubiquitous in the tropical Atlantic. Unless the data are
stratified by both season and frequency, inherent dipole behavior cannot
be demonstrated. Upon removing the global ENSO signal in SSTA (which is
symmetric between the North and South Atlantic) from the data, the
regions north or south of the intertropical convergence zone have
qualitatively different temporal variabilities and are poorly
correlated. Dipole configurations do occur infrequently (12-15% of the
time), but no more so than expected by chance for
stochastically-independent variables. Non-dipole configurations that
imply significant meridional SSTA gradients occur much more frequently,
nearly half of the time. Cross-spectral analysis of seasonally averaged
SSTA indices for the North and South Atlantic show marginally significant
coherence with antisymmetric phase in two period bands: 8-12 years for
the boreal winter-spring, and 2.3 years for the boreal summer-fall.
Antisymmetric coherence is optimal for a small sub-region west of Angola
in the South Atlantic, with respect to SSTA of basin scale in the
tropical North Atlantic. Dipole variability, even where optimal,
explains only a small fraction of the total variance in tropical Atlantic
SSTA (<7%).
Enfield, D.B., A.M. Mestas-Nunez, D.A. Mayer, and L. Cid-Serrano.
The dipole in tropical Atlantic SST: Common? Random? Intrinsic?
Proceedings, 23rd Annual Climate Diagnostics and Prediction
Workshop, Miami, Florida, October 26-30, 1998. National Weather
Service, 223-226 (1999).
In this paper we clarify the confusing and apparently contradictory views
regarding tropical Atlantic dipole variability. The issue is revisited
by using a recently reconstructed 136-year SST anomaly (SSTA) analysis
for the globe (Kaplan et al., 1998; henceforth, K98). An expanded
analysis will appear in the Journal of Geophysical Research-Oceans
(Enfield et al., 1999).
Etcheto, J., J. Boutin, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, R.D.
Ling, P.D. Nightingale, and R.H. Wanninkhof. Air-sea CO2 flux
variability in the equatorial Pacific Ocean near 100°W. Tellus
B, 51(3):734-747 (1999).
The interannual variability of the CO2 partial pressure
(pCO2) in the surface layer of the east equatorial
Pacific Ocean near 100°W is studied and compared with the sea
surface temperature (SST) monitored from satellites. This variability is
shown to be correlated with the SST anomaly rather than with the
temperature itself. The pCO2OC variability is related
to the variability of the upwelling systems (the equatorial upwelling and
the upwelling along the American coast), the main influence being from
the coastal upwelling via the surface water advected from the east. A
method is derived to interpolate the pCO2OC
measurements using the SST satellite measurements. By combining the
result with the exchange coefficient (K) deduced from the wind
speed provided by satellite-borne instruments, we deduce the air-sea
CO2 flux and, for the first time, we continuously monitor its
temporal variation. The variability of this flux is mainly due to the
variability of K, with a clear seasonal variation. The flux
obtained using the Liss and Merlivat (1986) relationship averaged from
April 1985 to June 1997 in the region 97.5°-107.5°W, 0-5°S
is 1.67 mole m-2 yr-1 of CO2, leaving the
ocean with an estimated accuracy of 30%.
Etcheto, J., J. Boutin, D.C.E. Bakker, Y. Dandonneau, R.A. Feely, H.Y.
Inoue, M. Ishii, R.D. Ling, L. Merlivat, P.D. Nightingale, N.Metzl, and
R.H. Wanninkhof. pCO2 in the equatorial Pacific and Atlantic
Oceans: Determination of air-sea CO2 flux using satellite-borne
instruments. Proceedings, Second International Symposium on
CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999.
Center for Global Environmental Research (CGER-I037-99), 119-125 (1999).
No abstract.
Feely, R.A., M.F. Lamb, D.J. Greeley, and R.H. Wanninkhof. Comparison of
the carbon system parameters at the global CO2 survey crossover
locations in the North and South Pacific Ocean between 1990-1996. Technical
Report, ORNL/CDIAC-115, Oak Ridge National Laboratory/Carbon Dioxide
Information Analysis Center, 73 pp. (1999).
As a collaborative program to measure global ocean carbon inventories
and provide estimates of the anthropogenic carbon dioxide (CO2)
uptake by the oceans, the National Oceanic and Atmospheric Administration
and the U.S. Department of Energy have sponsored the collection of ocean
carbon measurements as part of the World Ocean Circulation Experiment and
Ocean-Atmosphere Carbon Exchange Study cruises. The cruises discussed
here occurred in the North and South Pacific from 1990 through 1996. The
carbon parameters from these 30 crossover locations have been compared to
ensure a consistent global data set emerges from the survey cruises. The
results indicate that for dissolved inorganic carbon, fugacity of
CO2, and pH, the agreement at most crossover locations are well
within the design specifications for the global CO2 survey,
whereas in the case of total alkalinity, the agreement between crossover
locations is not as close.
Feely, R.A., C.L. Sabine, R.M. Key, and T.-H. Peng. CO2 survey
synthesis results: Estimating the anthropogenic carbon dioxide sink in
the Pacific Ocean. U.S. JGOFS News, 9(4):1-4 (1999).
Our results to date suggest that the cumulative amount of anthropogenic
CO2 in the global ocean is somewhere between 105 and 118 PgC
through the year 1996. These results can be utilized as a constraint on
other global carbon model simulations, similar to Princeton/Geophysical
Fluid Dynamics Laboratory Ocean Biogeochemical Model and National Center
for Atmospheric Research model simulations. As we refined and complete
the estimates of the oceanic uptake of anthropogenic CO2, the
results will be compared to CO2 uptake estimates for the
atmosphere and terrestrial biosphere.
Feely, R.A., R.H. Wanninkhof, T. Takahashi, and P. Tans. Influence of
El Niņo on the equatorial Pacific contribution to atmospheric
CO2 accumulation. Nature, 398:597-601 (1999).
The equatorial ocean is an important CO2 source to the
atmosphere, contributing annually 0.7-1.5 Pg of carbon as CO2,
as much as 80% of which is attributed to the equatorial Pacific. This
source is known to change significantly by ENSO events. To better
understand the regional and interannual variability of CO2
fluxes from the equatorial Pacific, field measurements of the partial
pressure of CO2 (pCO2) have been made in the
equatorial Pacific region since 1992. Here, we report that during the
1991-1994 ENSO period the net annual sea-to-air flux of CO2
was 0.3 PgC from the fall of 1991 to the fall of 1992, 0.6 PgC in 1993,
and 0.7 PgC in 1994. These fluxes are 30%-80% of the 0.9 PgC observed
during the non-El Niņo year of 1996. The total reduction of the
sea-to-air CO2 flux during the 1991-1994 El Niņo is estimated
to be 0.8-1.2 PgC, which accounts for 16-36% of the atmospheric anomaly
(the difference between the annual atmospheric CO2 increase in
PgC yr-1 and the long-term average increase of 3.18 PgC
yr-1) observed over the same period.
Feely, R.A., C.L. Sabine, R.M. Key, T.-H. Peng, and R.H. Wanninkhof. The
U.S. global CO2 survey in the North and South Pacific Ocean.
Preliminary synthesis results. Proceedings, Second International
Symposium on CO2 in the Oceans, Tsukuba, Japan, January
18-22, 1999. Center for Global Environmental Research (CGER-I037-99),
193-198 (1999).
As a collaborative program to measure global ocean carbon inventories and
provide estimates of the anthropogenic CO2 uptake in the oceans,
the National Oceanic and Atmospheric Administration, the U.S. Department of
Energy, and the National Science Foundation have co-sponsored the collection
of ocean carbon measurements as part of the World Ocean Circulation
Experiment (WOCE) and Ocean-Atmospheric Carbon Exchange Study (OACES). The
cruises discussed here occurred in the North and South Pacific from 1990
through 1996. The new estimates for anthropogenic CO2,
employing the DELTA-C* method of Gruber et al. (1996), indicate that
the largest buildup of anthropogenic CO2 occurs in subtropical
waters. Along 155°W, anthropogenic CO2 penetrates to a
maximum depth of 900 m at about 37°N in the North Pacific and 1300 m
at about 48°S in the South Pacific. Strong shoaling of anthropogenic
CO2 occurs southward of 50°S and northward of 48°N.
The anthropogenic CO2 inventories from the observations are
smaller than the Princeton Ocean Biogeochemical Model (POBM) model
estimates, primarily because the Princeton model produces too much deep
convective mixing of anthropogenic CO2 in the Southern Ocean.
The NCAR Climate System Ocean model, which has very different physics and
biological parameterizations, appears to do a better job of reproducing the
general patterns in the data-based section.
Feely, R.A., R.H. Wanninkhof, D. Hansell, M.F. Lamb, K. Lee, and R.D.
Castle. Water column CO2 measurements during the GasEx 98
cruise. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999.
Supplement to EOS, Transactions, American Geophysical Union,
80(17):S46, A31C-11 (1999).
During the recent GasEx 98 cruise in the North Atlantic aboard the NOAA
Ship Ronald H. Brown, carbon measurements were performed in the
area of 46°N, 20.5°W. This process study followed a warm core
ring tagged with the deliberately-introduced tracer, SF6. Continuous surface
water measurements were combined with vertical profiles sampled twice
daily to depths up to 1000 m for carbon mass balance studies. Dissolved
inorganic carbon (DIC) and fCO2 measurements were conducted
onboard in both underway and discrete analysis modes. During the 25-day
experiment in the tagged patch, surface water fCO2 values averaged
275 ą 9 µatm, providing a constant condition of undersaturation and
flux of CO2 into the ocean. Using the Wanninkhof (1992) exchange
coefficient, the estimated CO2 flux ranged from 2-10 moles
m-2 yr-1. The largest CO2 flux occurred
during a large storm beginning on June 6. After the storm, DIC and
fCO2 values decreased for a few days as a result of increased
productivity associated with the strong mixing event. The DIC were
combined with the DOC, oxygen, and nutrient data to provide a mass
balance for carbon within the patch. The mass balance of CO2
can be reconciled with the gas transfer velocities determined during the
cruise.
Fine, R.A., L. Merlivat, W. Roether, W.M. Smethie, and R.H. Wanninkhof.
Observing tracers and the carbon cycle. OCEANOBS99: International
Conference on the Ocean Observing System for Climate, Saint Raphael,
France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1,
14 pp. (1999).
A program for repeated sampling of tracers and variables essential for
quantitative understanding of the carbon cycle is recommended within
CLIVAR/GOOS. The program is critical to our monitoring and understanding
of climate change, both natural and anthropogenic. The objectives are:
quantification of changes in the rates and spatial patterns of oceanic
carbon uptake, fluxes, and storage of anthropogenic CO2;
detection and possible quantification of changes in water mass renewal and
mixing rates; and provision of a stringent test of the time integration of
models' natural and anthropogenic climate variability. The strategy is to
put in place a global observing network for tracers and CO2 to
document the continuing large-scale evolution of these fields. Hydrographic
lines are advocated, although it is realized that there has to be a limit
on these observations due to logistical and resource constraints. Thus,
there is the need to supplement these observations with time series and
autonomous measurements to provide detail in the temporal evolution of
the fields.
Franklin, J.F., M.L. Black, and S.E. Feuer. Wind profiles in hurricanes
determined by GPS dropwindsondes. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 167-168 (1999).
No abstract.
Fratantoni, D.M., P.L. Richardson, W.E. Johns, C.I. Fleurant, R.H. Smith,
S.L. Garzoli, W.D. Wilson, and G.J. Goņi. The North Brazil Current Rings
Experiment. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999.
Supplement to EOS, Transactions, American Geophysical Union,
80(17):S179, OS31B-10 (1999).
North Brazil Current rings are large (400 km diameter) anticyclonic
vortices shed from the retroflecting North Brazil Current (NBC) in the
low-latitude western Atlantic Ocean. NBC rings carry a large volume of
South Atlantic water northwestward along the coast of South America
towards the islands of the southeastern Caribbean. These rings are
thought to be one of several processes responsible for the northward
transport of upper-ocean water across the equatorial-tropical gyre
boundary and into the North Atlantic subtropical gyre. Such transport is
required to close the Atlantic meridional overturning cell (MOC) forced
by the high-latitude production and southward export of North Atlantic
Deep Water. The objective of this multi-institutional study is to
obtain, for the first time, comprehensive observations of the NBC
retroflection, the NBC ring formation process, and the physical structure
and evolution of NBC rings as they translate along the low-latitude
western boundary. We seek to understand the process of NBC ring
generation and to quantify the role of NBC rings as a component of the
Atlantic MOC. To accomplish our objectives we used several complementary
measurement techniques including detailed shipboard CTD/ADCP/XBT surveys,
surface drifter and subsurface RAFOS float observations, moored velocity
and temperature-salinity measurements, and a moored array of inverted
echo sounders. We will present results obtained during the first two NBC
rings cruises in November-December 1998 and February-March 1999. A total
of three rings were surveyed in detail, each differing substantially from
the others in intensity and vertical structure. Maximum azimuthal
surface velocities were typically of order 150 cm/s at a radius of
120-150 km from the ring center. In one ring, coherent swirl velocities
of 20 cm/s were observed to extend as deep as 2000 m. Two of the three
rings exhibited subsurface velocity maxima near 100 m depth. We will
present a summary of our shipboard and surface drifter observations and
share some initial conclusions regarding the physical structure and
watermass composition of NBC rings.
Gamache, J.F. Airborne Doppler observations of intensity change in
eastern Pacific Hurricane Guillermo. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 325-328 (1999).
No abstract.
Garzoli, S.L., and R.L. Molinari. Ageostrophic currents in the tropical
Atlantic. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999.
Supplement to EOS, Transactions, American Geophysical Union,
80(17):S179, OS31B-09 (1999).
Between 23 June 1997 and 12 August 1997, the R/V Seward Johnson
completed two basin-wide transects in the Atlantic along 6°N and
6°S and a partial transect along the equator. During this time, the
vessel occupied 81 oceanographic stations at which hydrographic, CTD, and
lowered acoustic Doppler current profiler (LADCP) measurements were acquired.
Hull-mounted ADCP data were collected continuously along the transects. In
this paper, the data collected along 6°N and 6°S are analyzed and
discussed. Direct measurement of the ageostrophic transport are obtained and
compared with estimates of the Ekman transports derived from wind
measurements. Estimates of divergence are compared with other results in
terms of upwelling. From the present analysis it may be concluded that in
the tropical Atlantic, the Ekman drift plays an important role in the upper
layer (<300 m) transports but does not account totally for the ageostrophic
ones. At 6°N, instability waves and inertial currents are dominant. At
6°S, most of the ageostrophic transport can be attributed to Ekman with
the difference explained by inertial waves.
Garzoli, S.L., P.L. Richardson, C.M. Dumcombe Rae, D.M. Fratantoni, G.J.
Goni, and A.J. Roubicek. Three Agulhas rings observed during the
Benguela Current Experiment. Journal of Geophysical Research,
104(C9):20,971-20,986 (1999).
A field program to study the circulation of the Benguela Current and its
extension into the southeastern Atlantic Ocean has completed the survey
and instrument deployment phase. We report here new observations of
three Agulhas rings north and west of Cape Town, South Africa. Three
mesoscale anticyclonic rings initially identified by means of
TOPEX/POSEIDON altimetry were surveyed with expendable bathythermographs
(XBTs), conductivity-temperature-depth-oxygen (CTDO) profiles, direct
current measurements from a lowered acoustic Doppler current profiler
(LADCP), a hull-mounted acoustic Doppler current profiler (ADCP), and
satellite-tracked surface drifters. Characteristics of the rings are
presented and their origins are discussed. Two are typical Agulhas rings
surveyed at different times after their generation; the third Agulhas
ring has an anomalous watermass structure whose most likely origin is the
Subtropical Front.
Garzoli, S.L., D.B. Enfield, G. Reverdin, G. Mitchum, R.H. Weisberg, P.
Chang, and J. Carton. COSTA: A Climate Observing System for the Tropical
Atlantic. OCEANOBS99: International Conference on the Ocean Observing
System for Climate, Saint Raphael, France, October 18-22, 1999. Centre
National d'Etudes Spatiales, Vol. 1, 19 pp. (1999).
This paper summarizes the discussions that took place during the COSTA
(Climate Observing System for the Tropical Atlantic) workshop held in Miami,
Florida during May 1999. The main objective of the workshop was to
coordinate the present efforts in the region and to set the scientific
basis for an extended and more permanent observing system. The intent of
the COSTA workshop, based in the CLIVAR (global) and ACVE (basin)
experience, was to formulate the basis for an extended and more permanent
(regional) tropical Atlantic observing system, building on the present
existing monitoring programs and process studies, and the current scientific
underlayment. The first part of this paper establishes the importance and
the role of the tropical Atlantic in climate fluctuations and their impact
in society. This is followed by a description of the climate variability in
the Atlantic sector, its relationship to tropical Atlantic variability,
especially sea surface temperature (SST), and to the North Atlantic
Oscillation and meridional overturning circulation. The possible mechanisms
behind tropical Atlantic SST fluctuations and their relation to climate is
also discussed, highlighting, in particular, the role of surface fluxes in
the off-equatorial regions, the equatorial ocean-atmosphere interactions,
and their relationships to movements of the Inter-Tropical Convergence Zone.
The second part of this paper summarizes the scientific discussions and
recommendations from the working groups who centered their discussions in
the following themes: (1) SST and surface fluxes; (2) sea level and
subsurface structure; (3) circulation; and (4) modeling and data
assimilation. Finally, the present status of the observing system and a
summary of recommendations is presented.
Godin, O.A., D. Yu. Mikhin, and D.R. Palmer. Ocean current monitoring in
the coastal zone. Oceanologia, 13:174 (1999).
A new technique has recently been put forward for real-time monitoring of
ocean currents in the coastal zone. The acoustic technique, called
matched non-reciprocity tomography (MNT), is being developed to extend
traditional ocean acoustic tomography to the coastal zone. It should
provide maps of the current field extending out tens of kilometers in
range and throughout the water column. These maps will have applications
to several important scientific problems such as measuring ocean
circulation and upwelling and monitoring global climate change.
Alternative approaches for monitoring currents in the coastal zone are
surveyed and their limitations when compared with the MNT approach are
discussed. Non-reciprocity tomography is based on recent progress in the
theory of acoustic propagation in moving media and in the use of
matched-field processing to solve tomographic inverse problems. The MNT
technique can be viewed as an application of matched-field processing to
a judiciously selected acoustic observable that is sensitive to flow
velocity, but insensitive to sound speed and bathymetric variations, and
leads to robust inversions for the depth-dependence of the velocity. The
development of non-reciprocity tomography is reviewed in this article in
the context of extended opportunities the technique offers in monitoring
ocean dynamics in the coastal zone by acoustic means. Applications of the
MNT technique to problems not directly related to coastal current
monitoring are also noted.
Goldenberg, S.B., and C.W. Landsea. Relationships between decadal-scale
fluctuations in vertical shear from NCEP/NCAR reanalysis data and
Atlantic basin tropical cyclone activity. Preprints, 23rd Conference
on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 1089-1091 (1999).
No abstract.
Goni, G.J. Transport estimates of the Kuroshio Current from
satellite altimeter data. In Ecosystem Dynamics of the Kuroshio
Oyashio Transition Region, M. Terazaki, K. Ohtani, T. Sugimoto,
and Y. Watanabe (eds.). Japan Marine Science Foundation,
Tokyo, 1-8 (1999).
The Kuroshio, together with the Gulf Stream, its counterpart in the North
Atlantic, are the two major western boundary currents in the northern
hemisphere. These currents have been viewed as the principal channel of
water exchange between the equatorial regions, where heat is added to the
oceans to be later removed in the polar regions. The transport of the
Kursohio current remains one of the largest uncertainties in the
meridional heat flux estimate across the North Pacific subtropical gyre.
Estimates of the Kuroshio mean transports vary from 21 Sv to 33 Sv (1
S v =106 m3 s-1). Some characteristics of
the dynamics of this current and its variability will be also briefly
addressed in this work. One very important issue in ocean dynamics is
to constantly monitor the subsurface thermal structure and transport of
a western boundary current. This work presents a methodology that uses
a combination of satellite altimetry-derived sea height anomaly and
inverted echosounder-derived hydrographic data to estimate the thickness
of the ocean upper layer and baroclinic transport. The estimates reveal
that during the end of 1996 and beginning of 1997 the Kuroshio Current
presents an anomalous behavior.
Goni, G.J., and W.E. Johns. Synoptic study of North Brazil Current
rings from altimeter data. AGU 1999 Spring Meeting, Boston, MA, June
1-4, 1999. Supplement to EOS, Transactions, American Geophysical
Union, 80(17):S179, OS31B-12 (1999).
TOPEX/POSEIDON-derived sea height anomaly fields from 1993 to 1998 are used
to study the mesoscale variability off northeastern South America between 0
to 15°N and 40 to 65°W. The North Brazil Current (NBC) and the
anticyclonic rings generated at this current's retroflection are the major
sources of mesoscale variability in the region. Space-time diagrams show a
very pronounced annual cycle of the sea height anomaly field. Once this
annual cycle is removed, the sea height residuals clearly show the northwest
translation of the North Brazil Current rings generated at the retroflection.
Using a two-layer model, the sea height anomaly field is converted into an
upper layer thickness field using parameters derived from historical
hydrographic data, where the base of the upper layer is defined by the
20° isotherm. The maps of the upper layer thickness are used to find
the trajectory of each ring, their velocities, length scales, and mass
transport. These maps also show that 5 to 8 rings are formed every year,
with the greatest frequency of formation being in boreal spring. The rings
translation velocities range between 7 and 18 km/day. These rings seem to
have preferred trajectories which are closely related to changes in
bathymetry. Estimates of the baroclinic transport of the North Brazil
Current from a T/P groundtrack across the upstream part of the retroflection
show that peaks in the transport are usually followed by the formation of
rings.
Goni, G.J., M.M. Huber, and L.K. Shay. TOPEX/POSEIDON-derived Atlantic
Ocean hurricane heat content estimates. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, American Meteorological Society 79th
Annual Meeting, Dallas, TX, January 10-15, 1999. American
Meteorological Society, Boston, 1037-1042 (1999).
No abstract.
Goodwin, K.D., R.A. Varner, P.M. Crill, and R.S. Oremland. Uptake of
near-ambient levels of methyl bromide by strain IMB-1, a facultative
methylotrophic bacterium. AGU 1999 Spring Meeting, Boston, MA, June
1-4, 1999. Supplement to EOS, Transactions, American Geophysical
Union, 80(17):S64, A42C-06 (1999).
A bacterium isolated from agricultural soils, Strain IMB-1, is a facultative
methylotroph able to grow on high levels (500 µM) of the agricultural
fumigant, methyl bromide (CH3Br). Agricultural and structural
fumigation can release 20 to 80% of the gas that is applied, creating a
potential source of stratospheric-ozone-destroying Br radicals. Investigation
of Strain IMB-1 has focused on harnessing its ability to consume high levels
of CH3Br (ppmv) in order to decrease the amounts of
CH3Br released during the soil fumigation process. However,
agricultural soils have also been determined to irreversibly break down
ambient levels of CH3Br (pptv). Strain IMB-1 was thus tested for
its ability to consume near-ambient levels of CH3Br with the use of a
permeation tube/dynamic dilution system during dynamic flow-through
incubations. Strain IMB-1 grown in the presence of 0.3% CH3Br
was able to consume CH3Br supplied at 12 parts per trillion by
volume (pptv). The presence of glucose or methylamine did not inhibit
CH3Br consumption. Glucose-grown cells were induced to uptake
12 pptv CH3Br by exposure to 0.3% CH3Br during either
exponential or stationary phases of growth. Glucose-grown cells were induced
to uptake 12 pptv by exposure to 100 pptv CH3Br only during
exponential growth. The uptake rate of CH3Br by IMB-1 grown on
glucose was linearly related to concentration in the range from 12 to
19,430 pptv.
Graber, H.C., M.A. Donelan, S. Atakturk, W.M. Drennan, and K.B.
Katsaros. Marine flux-profile relations from an air-sea interaction spar
buoy. Proceedings, Symposium on the Wind-Driven, Air-Sea Interface,
Sydney, Australia, January 10-15, 1999, M. Banner (ed.). The University
of New South Wales, 317-324 (1999).
The Air-Sea Interaction Spar (ASIS) is a new autonomous spar buoy
designed to permit long-term measurements of processes at the air-sea
interface. During a two-month deployment in the Gulf of Mexico in
April/May 1997, the buoy recorded waves as high as 3.5 m and wind speeds
up to 20 m/s. The ASIS buoy was instrumented to measure high resolution
wave directional properties, wind stress, and four level profiles of wind
speed, temperature, and humidity. These data are used to examine marine
flux-profile relations and to explore the effect of a thick wave boundary
layer on the validity of Monin-Obukhov similarity theory.
Gray, J. National Oceanic and Atmospheric Administration research and
operation priorities. In Proceedings, South Florida Measurement Center
Workshop: Establishment of a Center for Innovative Oceanography in the
21st Century, Dania, FL, February 24-26, 1999. National Science
Foundation, 207-213 (1999).
No abstract.
Grima, N., A. Bentamy, K.B. Katsaros, Y. Quilfen, P. Delecluse, and C.
Levy. Sensitivity of an oceanic general circulation model forced by
satellite wind stress fields. Journal of Geophysical Research,
104(C4):7967-7989 (1999).
Satellite wind and wind stress fields at the sea surface, derived from
the scatterometers on European Remote Sensing satellites 1 and 2 (ERS-1
and ERS-2) are used to drive the ocean general circulation model (OGCM)
"OPA" in the tropical oceans. The results of the impact of ERS winds are
discussed in terms of the resulting thermocline, current structures, and
sea level anomalies. Their adequacy is evaluated on the one hand by
comparison with simulations forced by the Arpege-Climat model and on the
other hand by comparison with measurements of the Tropical
Atmosphere-Ocean (TAO) buoy network and of the TOPEX/Poseidon altimeter.
Regarding annual mean values, the thermal and current responses of the
OGCM forced by ERS winds are in good agreement with the TAO buoy
observations, especially in the central and eastern Pacific Ocean. In
these regions the South Equatorial Current, the Equatorial Undercurrent,
and the thermocline features simulated by the OGCM forced by
scatterometer wind fields are described. The impact of the ERS-1 winds is
particularly significant to the description of the main oceanic
variability. Compared to the TAO buoy observations, the high-frequency (a
few weeks) and the low-frequency of the thermocline and zonal current
variations are described. The correlation coefficients between the time
series of the thermocline simulated by ERS winds and that observed by the
TAO buoy network are highly significant; their mean value is 0.73, over
the whole basin width, while it is 0.58 between Arpege model simulation
and buoy observations. At the equator the time series of the zonal
current simulated by the ERS winds, at three locations (110°W,
140°W, and 165°E) and at two depths, are compared to the TAO
current meter and acoustic Doppler current profiler (ADCP) measurements.
The mean value of the significant correlation coefficients computed with
the in-situ measurements in 0.72 for ERS, while it is 0.51 for the
Arpege-Climat model. Thus, ERS wind fields through the OGCM generate more
realistic current variations than those obtained with Arpege climate winds,
and they are particularly efficient in capturing abrupt changes ("wind
bursts") which may be important regarding ocean dynamics.
Hansen, D.V., and W.C. Thacker. Estimation of salinity profiles in the
upper ocean. Journal of Geophysical Research, 104(C4):7921-7934
(1999).
A new algorithm is presented for estimating salinity profiles in the
upper ocean from measurements of temperature profiles and surface
salinity. In application to the eastern tropical Pacific the method
replicates a large fraction of the variability of salinity in the upper
few tens of meters and provides modest to substantial improvement at
nearly all levels. Estimated salinity profiles are able to characterize
barrier layers, regions formed by a halocline within the thermal mixed
layer. The rms error of geopotential-height calculations based on
estimated salinity profiles is reduced more than 50 percent by this
method relative to methods not using surface salinity. Even without the
surface salinity measurement some reduction of error in geopotential
heights can be obtained relative to previous methods.
Hellin, J., M. Haig, and F.D. Marks. Rainfall characteristics of Hurricane
Mitch. Nature, 399:316 (1999).
No abstract.
Hendee, J.C. An environmental information synthesizer for expert
systems. 1999 Florida Bay and Adjacent Marine Systems Science
Conference, Programs and Abstracts, Key Largo, FL, November 1-5,
1999. University of Florida Sea Grant Program, 217 (1999).
As an enhancement to the SEAKEYS environmental monitoring network,
software called the Environmental Information Synthesizer for Expert
Systems (EISES) has been constructed which synthesizes knowledge from
near real-time acquired meteorological and oceanographic data. This
knowledge is acquired in the form of facts which can be used by expert
systems designed to monitor and match environmental parameters as they
meet criteria generally thought to be conducive to certain biological
events. The initial expert system constructed to use the facts from
EISES, which we have dubbed the Coral Reef Early Warning System (CREWS),
represents a first step in the construction of a larger coral reef
specific expert system. When environmental conditions are conducive to
coral bleaching, according to different bleaching theories or models,
CREWS produces alerts which are automatically posted to the Web and
emailed to researchers so they can verify and study bleaching events as
they might happen. The models are refined using feedback from field data
on bleaching recorded after alerts from the expert system. CREWS has now
been implemented not only for the Florida Keys National Marine Sanctuary,
but also for the Great Barrier Reef Marine Park Authority, and will
hopefully be developed in the future for other coral reef sanctuaries or
parks throughout the world. In addition to CREWS, expert systems for
Florida Bay are being developed with collaborators to model juvenile
pink shrimp and fish spawning migrations (with UM/RSMAS and NOAA/NMFS)
and conditions conducive to harmful algal blooms (with NOAA/NESDIS).
Some other example events that might be monitored or predicted from
EISES expert systems include good diving and/or fishing conditions
(e.g., clear water, low winds), at remote locations, phytoplankton
blooms, hypo- or hypersaline influxes from Florida Bay, and excessive
dissolved nutrient encroachment (inferred from high fluorometry values).
Hood, M., R.H. Wanninkhof, and L. Merlivat. The effects of wind-induced
mixing on short timescale surface variability of fCO2 and
fluorescence: Results from the GasEx-98 CARIOCA buoy data. AGU 1999
Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS,
Transactions, American Geophysical Union, 80(17):S47, A31C-12 (1999).
During the Lagrangian deliberate tracer study in the North Atlantic, GasEx-98,
hourly measurements of wind speed, sea surface temperature, fCO2,
and fluorescence were made from two CARIOCA drifting buoys near 46°N
and 21.5°W over a period of approximately 20 days. Shipboard
measurements of fCO2 were used to calibrate the buoy data, and
the hourly time series of the two buoys and the ship were in good agreement.
Using these data, we investigated the air-sea flux of CO2,
the importance of short-term wind-induced mixing events for longer-term
estimates of flux, and the physical versus biological processes controlling
surface variability of fluorescence. The air-sea flux estimate for the
~20 day experiment using the Wanninkhof (1992) gas transfer velocity
formulation was -0.012 mol m-2 d-1, and using the Liss
and Merlivat (1986) formulation was -0.007 mol m-2
d-1. A storm with wind speeds reaching as high as 16-17 m
s-1 led to a sharp decrease in sea surface temperature and an
increase in fCO2 of approximately 30 µatm. The magnitude of
this sudden change in fCO2 is equal to approximately half of the
annual range of fCO2 in this area and accounted for approximately
38% of the flux over the 20-day period. Approximately 16 hours after the
onset of the storm, there was an increase in surface fluorescence coincident
with the initial increase in fCO2. Nitrate measurements made from
the ship show a sharp peak in surface concentrations about 24 hours after
the increase in winds and approximately 6-8 hours after the increase in
surface fluorescence. This increase in surface fluorescence that occurs in
tandem with the increase in fCO2 and decrease in SST and before
the arrival of nutrients to the surface suggests an upwelling of a relatively
shallow chlorophyll maximum in this area. Phaeopigment to chlorophyll ratios
are consistent with this mechanism. After the upwelling of the
NO3, the fluorescence increases more sharply while the
fCO2 decreases, consistent with biological productivity.
Houston, S.H., and M.D. Powell. Hurricanes and tropical storms in
Florida Bay. Florida Sea Grant College Program, FLSGP-G-99-016, 2 pp.
(1999).
No abstract.
Houston, S.H., W.A. Shaffer, M.D. Powell, and J. Chen. Comparisons of
HRD and SLOSH surface wind fields in hurricanes: Implications for storm
surge modeling. Weather and Forecasting, 14(5):671-686 (1999).
Surface wind observations analyzed by the Hurricane Research Division
(HRD) were compared to those computed by the parametric wind model used
in the National Weather Service Sea, Lake, and Overland Surges from
Hurricanes (SLOSH) model's storm surge computations for seven cases in
five recent hurricanes. In six cases, the differences between the SLOSH
and HRD surface peak wind speeds were 6% or less, but in one case
(Hurricane Emily of 1993) the SLOSH computed peak wind speeds were 15%
less than the HRD. In all seven cases, statistics for the modeled and
analyzed wind fields showed that for the region of strongest winds, the
mean SLOSH wind speed was 14% greater than that of the HRD and the mean
inflow angle for SLOSH was 19° less than that of the HRD. The radii
beyond the region of strongest winds in the seven cases had mean wind
speed and inflow angle differences that were very small. The SLOSH
computed peak storm surges usually compared closely to the observed
values of storm surge in the region of the maximum wind speeds, except
Hurricane Emily where SLOSH underestimated the peak surge. HRD's
observation-based wind fields were input to SLOSH for storm surge
hindcasts of Hurricanes Emily and Opal (1995). In Opal, the HRD input
produced nearly the same computed storm surges as those computed from the
SLOSH parametric wind model, and the calculated surge was insensitive to
perturbations in the HRD wind field. For Emily, observation-based winds
produced a computed storm surge that was closer to the peak observed
surge, confirming that the computed surge in Pamlico Sound was sensitive
to atmospheric forcing. Using real-time, observation-based winds in SLOSH
would likely improve storm surge computations in landfalling hurricanes
affected by synoptic and mesoscale factors that are not accounted for in
parametric models (e.g., a strongly sheared environment, convective
asymmetries, and stably stratified boundary layers). An accurate
diagnosis of storm surge flooding, based on the actual track and wind
fields, could be supplied to emergency management agencies, government
officials, and utilities to help with damage assessment and recovery
efforts.
Houston, S.H., G. Forbes, A. Chiu, W.-C. Lee, and P.P. Dodge. Super
Typhoon Paka's (1997) surface winds. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 1032-1033 (1999).
No abstract.
Huang, H., R.E. Fergen, J.J. Tsai, and J.R. Proni. Evaluation of mixing
zone models: CORMIX, PLUMES, and OMZA with field data from two Florida
ocean outfalls. Proceedings, Second International Symposium on
Environmental Hydraulics, Hong Kong, China, December 16-18, 1998.
Environmental Hydraulics, pp. 249-254 (1999).
This paper presents an evaluation of three mixing zone models: CORMIX,
PLUMES, and OMZA using field data from two Florida ocean outfalls:
Hollywood and Miami-Central outfalls. The hollywood outfall has a single
port outlet and the Miami-Central outfall has a multiport diffuser. Both
outfalls discharge secondary effluent. For the nearfield, all of the
three models predict realistic initial dilutions for the tests at the
outfall except three cases in CORMIX predictions and two cases in PLUMES
predictions (out of 20 cases). For the nearfield and farfield combined,
CORMIX significantly overestimates dye concentrations for the tests at
the Hollywood outfall but underestimates dye concentrations within the
300 m to 400 m range for the tests at the Miami-Central outfall. PLUMES
predictions agree reasonably well with the filed data for the range from
300 m to 800 m but do not agree well within the 300 m range for the tests
at both outfalls. OMZA predictions agree well with the field data within
the 800 m range for the test at both outfalls.
Huber, M.M., L.K. Shay, and G.J. Goni. The Atlantic Ocean's role on
intensity change. Preprints, 23rd Conference on Hurricanes and Tropical
Meteorology, American Meteorological Society 79th Annual Meeting,
Dallas, TX, January 10-15, 1999. American Meteorological Society,
Boston, 36-39 (1999).
No abstract.
Humphrey, J.C., S.L. Vargo, J.C. Ogden, and J.C. Hendee. SEAKEYS 1999:
Florida Keys monitoring initiative. 1999 Florida Bay and Adjacent
Marine Systems Science Conference, Program and Abstracts, Key Largo,
FL, November 1-5, 1999. University of Florida Sea Grant Program,
240-241 (1999).
The Sustained Ecological Research Related to the Management of
the Florida Keys Seascape (SEAKEYS) program was organized in 1991 by the
Florida Institute of Oceanography (FIO) with initial funding from the
John D. and Catherine T. MacArthur Foundation, and continuing funding
from the South Florida Ecosystem Restoration, Prediction and Monitoring
(SFERPM) program, administered by the National Oceanic and Atmospheric
Administration (NOAA). The SEAKEYS environmental monitoring program,
which is basically an oceanographic extension to the
meteorologically-oriented Coastal-Marine Automated Network of NOAA, has
accumulated an unparalleled long-term database of meteorological and
oceanographic data from the Florida Straits and Florida Bay. During 1998,
the SEAKEYS network was upgraded with more precise oceanographic sensors,
and selected stations were augmented with fluorometers, transmissometers,
and water-level sensing equipment. A seventh monitoring station, a
cooperative effort between FIO and the University of South Florida's
Department of Marine Science (USF/DMS), was completed in Northwest
Florida Bay at 25°05'00"N, 81°05'30"W during summer, 1998. This
station also contains a full suite of meteorological and oceanographic
instrumentation and also transmits its data hourly via a NOAA GOES
satellite. The Northwest Florida Bay station is the northwestern most
station in the SEAKEYS network, as well as the southernmost link in the
West Florida Coastal Ocean Monitoring and Prediction System of USF/DMS.
Turbulent weather was prominent during 1998 in the Florida Keys. Severe
conditions reported by the SEAKEYS stations included the Ground Hog Day
Storm, Hurricane Georges, and Tropical Storm Mitch. In most cases the
SEAKEYS stations contained the only instruments to measure the
meteorological and oceanographic measurements accompanying these events
in the Florida Keys. The Long Key station measured the highest winds (119
mph) in South Florida during the Ground Hog Day Storm of February 2,
1998. On September 25, 1998 the eye of Hurricane Georges passed over Key
West at 1150 EDT as wind speeds dropped from 85.2 mph to 9.6 mph. The eye
moved across the Dry Tortugas station at 1610 EDT with barometric
pressures dropping to 974.4 mb. Winds gusted to hurricane force only
after the eye passed at 2100 EDT. Georges' most severe winds in the
Florida Keys gusted to 113 mph at Sombrero Reef, with a sustained wind
speed of 94 mph. Long Key, Molasses Reef, and Fowey Rocks received gusts
of tropical storm force. The tide station at Sombrero Reef reported a
storm water level of 2.87 feet above mean lower low water. This
contrasted with below normal levels reported at a station on Florida Bay.
Hurricane Mitch passed northwest of the Florida Keys on the evening of
November 4, 1998, bringing peak winds of 62.4 mph at Molasses Reef and
sustained gale force winds until the following afternoon. Numerous
localized tornadoes spawned by this storm caused extensive damage in the
Upper Keys. Daily near real-time SEAKEYS data are available to
researchers via NOAA's Coral Health and Monitoring Program (CHAMP) Web
site at http://www.coral.noaa.gov, while historical data are available at
http://www.neptune.noaa.gov. The Coral Reef Early Warning System (CREWS),
which utilizes the near real-time data from six SEAKEYS stations, is an
online expert system which monitors environmental conditions on the reef
that are theoretically conducive to coral bleaching. If these conditions
occur, alerts are sent via email to researchers and posted to the Web at
http://www.coral.noaa.gov/sferpm/seakeys/es.
Johns, E., W.D. Wilson, and T.N. Lee. Surface salinity variability of
Florida Bay and southwest Florida coastal waters. 1999 Florida Bay and
Adjacent Marine Systems Science Conference, Programs and Abstracts,
Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program,
169-171 (1999).
No abstract.
Johns, E., W.D. Wilson, and R.L. Molinari. Direct observations of
velocity and transport in the passages between the Intra-Americas Sea and
the Atlantic Ocean, 1984-1996. Journal of Geophysical Research,
104(C11):25,805-25,820 (1999).
Shipboard acoustic Doppler current profiler observations of the velocity
in the upper 200 m of the water column collected during 1984-1996 using
the National Oceanic and Atmospheric Administration R/V Malcolm
Baldrige are used to examine the velocity structure and transport in
the passages between the Atlantic Ocean and the Intra-Americas Sea
(IAS). Data were colected during 23 cruises along the following
sections: across the Straits of Florida, in the Northwest Providence
Channel (NWPC), across the northern passages into the Caribbean Sea
(Windward, Mona, and Anegada), across the eastern Caribbean along
63°30'W, thereby forming a closed quadrangle, and in the Grenada
Passage. The Florida Current, the eastern Caribbean, and the Grenada
Passage share a similar mean velocity structure characterized by
high-velocity, surface intensified flows with strong vertical and
horizontal shears. The northern Caribbean passages (NWPC, Windward,
Mona, and Anegada) share a different common mean velocity structure, with
subsurface velocity maxima directed into the IAS, and surface-intensified
counterflows along one side of each paassage. On average, there is a
transport balance in the upper 200 m between waters entering and exiting
the IAS, with the 16.5 ± 2.4 Sv (1 Sv = 106 m3
s-1) transport of the Florida Current at 27°N comprised
of 0.4 ± 0.8 Sv from the NWPC, 2.2 ± 1.5 Sv from the Windward
Passage, 2.8 ± 2.1 and 2.4 ± 2.8 Sv from the Mona and Anegada
passages, respectively, and 9.5 ± 4.7 Sv across the eastern
Caribbean, for a total of 17.3 Sv. The four passages north of 17°N
(from NWPC to Anegada Passage) have a combined transport of 7.8 Sv,
nearly half of the transport of the Florida Current in the upper 200 m.
Of the 9.5 Sv flowing through the eastern Caribbean between 11°N and
17°N, 4.9 ± 2.6 Sv, or more than half, come from the Grenada
Passage. This is significant to the subject of cross-equatorial exchange
of mass, heat, and salt, as the Grenada Passage is where the highest
transport of waters originating in the southern hemisphere is thought to
enter the Caribbean.
Jones, R.W., and M. DeMaria. Further studies of the optimization of a
hurricane track prediction model using the adjoint equations. Monthly
Weather Review, 127(7):1586-1598 (1999).
The method of model fitting, or adjoint method, is applied to a
barotropic hurricane track forecast model described by DeMaria and Jones
using a large sample of forecast cases. The sample includes all Atlantic
tropical cyclones that reached hurricane intensity during the 1989-1993
hurricane seasons (141 72-h forecasts of 17 storms). The cases considered
by DeMaria and Jones are a subset of the present sample. Model-fitting
calculations using strong, weak, strong followed by weak, or weak
followed by strong model constraints are discussed for data assimilation
periods varying from 6 to 72 h. Generally, the best track forecasts occur
for shorter assimilation periods and for weak constraints, although only
the 12-h assimilation with the weak constraint has less track error than
the control forecast without assimilation, and only for the 12-h
forecast. The principle reason for this lack of improvement is that the
fit of the model to the observed track is good at the middle of the
assimilation period, but not very good at the end where the forecast
begins. When a future track position at 6 h is included in the
assimilation, in order to improve the track fit at the synoptic data
time, the resulting track errors average about 10% smaller than the
control forecast. The control forecast may also be improved in the same
way. In that case, the best assimilation forecasts have 2.5% smaller
track errors than the modified control forecasts.
Jones, R.W., and H.E. Willoughby. Results of generalizing a semispectral
shallow-water barotropic hurricane tracking model into a two-layer
baroclinic model. Preprints, 23rd Conference on Hurricanes and
Tropical Meteorology, Dallas, TX, January 10-15, 1999. American
Meteorological Society, Boston, 747-750 (1999).
No abstract.
Kaplan, J., and M. DeMaria. Climatological and synoptic characteristics
of rapidly intensifying tropical cyclones in the North Atlantic basin.
Preprints, 23rd Conference on Hurricanes and Tropical Meteorology,
Dallas, TX, January 10-15, 1999. American Meteorological Society,
Boston, 592-595 (1999).
No abstract.
Kelly, P.S., K.M. Lwiza, R.K. Cowen, and G.J. Goni. Low-salinity
lenses at Barbados, West Indies: Their origin, frequency, and variability.
AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to
EOS, Transactions, American Geophysical Union, 80(17):S185, OS42C-01
(1999).
A vertical array of conductivity-temperature sensors moored west of Barbados,
West Indies, from May 1996 to November 1997 revealed a heterogeneous and
variable salinity pattern punctuated by six intrusions of low-salinity water
(less than 34.5 psu). A typical intrusion extended to 30 m depth and lasted
~25 days, although one intrusion extended to 47 m and lasted 94 days.
Water samples taken during an intrusion in May 1997 have Radium 228/226
activity ratios of approximately 1, consistent with previous measurements in
Barbados of water that originated in the Amazon River mixing zone. The
Amazon water likely was translated to Barbados in rings spawned from the
North Brazil Current (NBC). Analysis of sea height anomaly derived from the
TOPEX/Poseidon satellite altimeter supports this conclusion and reveals
that, contrary to previous studies, rings are shed throughout the year,
mostly during spring. The intrusions of low-salinity water and their
associated velocities dramatically changed the already variable flow in our
study area. The complex salinity and flow we observed represented the effects
of NBC rings passing the island, perhaps disrupted by the relatively shallow
Tobago-Barbados ridge. The complex velocity and water structure are
interesting in their own right as evidence of the Barbados region as a
mixing zone and for their influence on recruitment of larval fishes to the
reef along the island's west coast.
Landsea, C.W., and J.A. Knaff. Application of the El Niņo-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 8(4):34-36 (1999).
No abstract.
Landsea, C.W., and J.F. Knaff. How much "skill" did the various
forecasting methods available have for the 1997-1998 El Niņo event?
Preprints, Second Hayes Symposium on Seasonal to Interannual Climate
Variability--The 1997/1998 ENSO Cycle, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 73 (1999).
No abstract.
Landsea, C.W., R.A. Pielke, A.M. Mestas-Nunez, and J.A. Knaff.
Atlantic basin hurricanes: Indices of climatic changes. Climatic
Change, 42:89-129 (1999).
Accurate records of basin-wide Atlantic and U.S. landfalling hurricanes
extend back to the mid 1940s and the turn of the century, respectively,
as a result of aircraft reconnaissance and instrumented weather stations
along the U.S. coasts. Such long-term records are not exceeded elsewhere
in the tropics. The Atlantic hurricanes, U.S. landfalling hurricanes, and
U.S. normalized damage time series are examined for interannual trends
and multidecadal variability. It is found that only weak linear trends
can be ascribed to the hurricane activity and that multidecadal
variability is more characteristic of the region. Various environmental
factors including Caribbean sea level pressures and 200 mb zonal winds,
the stratospheric Quasi-Biennial Oscillation, the El Niño-Southern
Oscillation, African West Sahel rainfall, and Atlantic sea surface
temperatures, are analyzed for interannual links to the Atlantic
hurricane activity. All show significant, concurrent relationships to the
frequency, intensity, and duration of Atlantic hurricanes. Additionally,
variations in the El Niño-Southern Oscillation are significantly
linked to changes in U.S. tropical cyclone-caused damages. Finally, much
of the multidecadal hurricane activity can be linked to the Atlantic
Multidecadal Mode, an empirical orthogonal function pattern derived from
a global sea surface temperature record. Such linkages may allow for
prediction of Atlantic hurricane activity on a multidecadal basis. These
results are placed into the context of climate change and natural hazards
policy.
Landsea, C.W., C.A. Anderson, G. Clark, J. Fernandez-Partagas, P.
Hungerford, C. Neumann, and M. Zimmer. The Atlantic hurricane database
re-analysis project. Preprints, 23rd Conference on Hurricanes and
Tropical Meteorology, Dallas, TX, January 10-15, 1999. American
Meteorological Society, Boston, 394-397 (1999).
No abstract.
Lapitan, R.L., R.H. Wanninkhof, and A.R. Mosier. Methods for stable gas
flux determination in aquatic and terrestrial systems. In Approaches to
Scaling of Trace Gas Fluxes in Ecosystems, A.F. Bouwman (ed.), Elsevier,
Amsterdam, 27-66 (1999).
A general description of the current approaches for measuring
trace gas fluxes in aquatic and terrestrial systems is presented in this
paper. Our aim is to provide an overview of the current methodologies
employed in trace gas flux measurements and the most recent advancements
made; with emphasis on the uncertainties observed and potential areas for
future developments required to further minimize these uncertainties
brought about by spatial and temporal variabilities of fluxes in the
field. The increase in sensitivity and improved response time of
analytical devices for measuring trace gases within the last five years,
such as advancements in laser spectroscopy, have significantly improved
the effectiveness of the current methods of measuring these gases in
aquatic and terrestrial systems. Systematic errors in trace gas flux
estimates have also been reduced with the refinements in estimates of the
gas transfer velocity,k, through the use of tracers in the two
systems. Footprint corrections of micrometeorological flux measurements in
terrestrial systems have provided a better means of identifying the
spatial sources of trace gases, and thus, have increased the scope of
inference from trace gas flux measurements. Despite these improvements,
however, flux measurement errors still remain high. Experimental and
sampling designs that can efficiently and effectively deal with the
spatial and temporal variabilities in trace gas flux measurements to the
minimum are of utmost priority. The same can be said of the modeling
procedures; that is, there is a need for an effective method that can
reduce instead of propagate potential errors in scaling from field plot
to regional or global scales.
Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global
distribution of total inorganic carbon in surface water. Proceedings,
Second International Symposium on CO2 in the Oceans,
Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental
Research (CGER-I037-99), 493-496 (1999).
No abstract.
Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely.
Interannual variations in oceanic uptake of anthropogenic carbon dioxide
for the period of 1982-1995. Proceedings, Second International Symposium
on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999.
Center for Global Environmental Research (CGER-I037-99), 31-34 (1999).
No abstract.
Lee, T.N., E. Williams, E. Johns, and W.D. Wilson. First year results
from enhanced observations of circulation and exchange processes in
western Florida Bay and connecting coastal waters, including effects of
El Niņo and Hurricane Georges. 1999 Florida Bay and Adjacent Marine
System Science Conference, Programs and Abstracts, Key Largo, FL,
November 1-5, 1999. University of Florida Sea Grant Program, 145-147
(1999).
No abstract.
Majumdar, S.J., S.D. Aberson, C.H. Bishop, and Z. Toth. Real time
hurricane track targeting using a VICBAR ensemble. Preprints, 23rd
Conference on Hurricanes and Tropical Meteorology, Dallas, TX,
January 10-15, 1999. American Meteorological Society, Boston,
755-756 (1999).
No abstract.
Marks, F.D., and H.A. Friedman. 1999 Hurricane Field Program Plan.
U.S. Department of Commerce, NOAA/Atlantic Oceanographic and Meteorological
Laboratory, Miami Florida (published for limited distribution), 142 pp.
(1999).
No abstract.
Marks, F.D., P.P. Dodge, and C. Sandin. WSR-88D observations of
hurricane atmospheric boundary layer structure at landfall. Preprints,
23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX,
January 10-15, 1999. American Meteorological Society, Boston, 1051-1054
(1999).
No abstract.
McGillis, W., J. Edson, and R.H. Wanninkhof. Direct air-sea flux
measurements of carbon dioxide over the North Atlantic Ocean and the
comparison to indirect methods. Proceedings, Second International
Symposium on CO2 in the Oceans, Tsukuba, Japan, January
18-22,1999. Center for Global Environmental Research (CGER-I037-99),
367-377 (1999).
To date, large uncertainties in the extent of the CO2 flux
between the atmosphere and ocean have prevented us from accurately
quantifying how the increasing atmospheric CO2 burden partitions
between the ocean and the terrestrial biosphere. This limits our ability to
accurately predict future atmospheric CO2 levels. We have
recently designed a direct CO2 flux measurement system that
considerably improves our estimates of air-sea gas exchange. The system
measures the direct air-sea flux of CO2 in the atmospheric
boundary layer using eddy correlation (direct covariance). It was
successfully deployed during the large scale experiment to study air-sea
gas fixes, GASES98, which was conducted in the CO2 sink region
of the North Atlantic during May/June of 1998. The seasonal algal bloom
caused air-sea pCO2 differences of between -80 to ~100
µatm. This large concentration gradient generated large signals for
accurate measurement of the CO2 flux using a close path
CO2 sensor. In addition to the CO2 gas flux, the
comprehensive atmospheric flux measurement suite included momentum, heat,
and moisture fluxes. Atmospheric flux and air-sea gas concentration
measurements were performed for over 500 hours, providing more than 1000
observations. Wind speeds between 1 and 16 m/s were experienced over the
range of these observations. Preliminary flux estimates from our system
compare extremely well with previous estimates of the gas transfer velocity
for wind speeds below 7 m/s. At higher wind speeds, the transfer velocities
obtained from our system are as much as 20-50% higher than those estimated
by empirical relationships. Based on accurate air-sea CO2
coefficients obtained by our investigation and atmospheric and surface
ocean pCO2 data obtained to date, estimates of the global ocean
CO2 sink are now feasible. Our findings will also provide better
predictions of the seasonal and interannual variability of sea-air
CO2 flux observed in various global regions.
McTaggart, K.E., G.C. Johnson, C.I. Fleurant, and M.O. Baringer.
CTD/O2 measurements collected on a Climate and Global Change
cruise along 24°N in the Atlantic Ocean (WOCE section A6) during
January-February 1998. NOAA Data Report, ERL PMEL-68 (PB99-155194),
368 pp. (1999).
Summaries of CTD/O2 measurements and hydrographic data acquired
on a Climate and Global Change cruise during the winter of 1998 aboard the
NOAA ship Ronald H. Brown are presented. The majority of these data were
collected along 24.5°N from 23.5°W to 69°W. Completing
the transatlantic section are data collected along a northeast-southwest
dogleg off the coast of Africa, and along a second, short, zonal section
along 26.5°N off the coast of Abaco Island from 69°W to
77°W, jogging north along 27°N in the Straits of Florida to
80°W. Data acquisition and processing systems are described and
calibration procedures are documented. Station location, meteorological
conditions, CTD/O2 summary data listings, profiles, and
potential temperature-salinity diagrams are included for each cast.
Section plots of oceanographic variables and hydrographic data listings
are also given.
Mestas-Nunez, A.M., and D.B. Enfield. Rotated global modes of
non-ENSO sea surface temperature variability. Journal of
Climate, 12(9):2734-2746 (1999).
A varimax rotation was applied to the EOF modes of global SST derived by
Enfield and Mestas-Nuñez (1999). The SST anomaly record is more
than a century long, with a global complex EOF representation of ENSO and
a linear trend removed at every grid point. The rotated EOF modes capture
localized centers of variability that contribute to the larger scale
spatial patterns of the unrotated modes. The first rotated EOF represents
a multidecadal signal with larger response in the North Atlantic. The
second rotated EOF represents an interdecadal uctuation with larger
response in the eastern North Pacific and out of phase fluctuations of
smaller amplitude in the central North Pacific. The third rotated EOF
captures interdecadal fluctuations in the eastern tropical Pacific with a
dominant peak that coincides with the 1982-83 ENSO. The fourth rotated
EOF has an interdecadal to multidecadal nature with larger response in
the central equatorial Pacific and quasi-symmetric out of phase response
in the western North and South Pacific. The fifth mode represents
multidecadal fluctuations with large response at about 40°N in the
North Pacific. The sixth mode has interannual to interdecadal time scales
with largest response confined to the South Atlantic. Our rotated modes
are dominated by intra- rather than interocean uctuations supporting the
hypothesis that the non-ENSO variability is more regional than global in
nature. Analyses of sea level pressure and surface wind stress show that
in general the non-ENSO rotated EOFs are consistent with an ocean response
to local atmospheric forcing. An exception is the eastern tropical Pacific
mode which is more consistent with an atmospheric response to changes in the
ocean SST.
Mestas-Nunez, A.M., and D.B. Enfield. Rotated global modes of non-ENSO
sea surface temperature. Proceedings, 23rd Annual Climate Diagnostics
and Prediction Workshop, Miami, Florida, October 26-30, 1998. National
Weather Service, 162-165 (1999).
No abstract.
Molinari, R.L. Lessons learned from operating global ocean observing
networks. Bulletin of the American Meteorological Society,
80(7):1413-1420 (1999).
The Global Ocean Observing System Center (GOOSC) at the National Oceanic
and Atmospheric Administration's (NOAA) Atlantic Oceanographic and
Meteorological Laboratory operates two global observing networks, a
drifting buoy array, and a Voluntary Observing Ship network. The arrays
provide in real time surface atmospheric and subsurface oceanographic
data needed by NOAA weather and climate forecasters. The data are used in
delayed mode to verify model simulations of the ocean and atmosphere, to
provide in situ calibration/validation data for remote sensing
observations, and to increase understanding of the dynamics of the ocean
and atmosphere. The operational and research lessons learned in the
operation of the GOOSC are reviewed. Operationally, it was learned that,
because of costs, international participation is required to maintain
global networks; data management methodology is a critical component of
operations; and integrated observing systems using multiple platforms
provide more accurate products. Scientifically, it was learned, for
example, that accurate characterizations of the salinity field must be
available in model simulations. As more data become available it is found
that scales of important phenomena such as equatorial upwelling are
smaller, and high-frequency signals can impact on the mean structure of
the upper ocean. These findings must be considered when designing
effective sampling strategies.
Molinari, R.L., S.L. Garzoli, and R.W. Schmitt. Equatorial currents at
1000 m in the Atlantic Ocean. Geophysical Research Letters,
26(3):361-364 (1999).
Twenty-seven Profiling ALACE (PALACE) floats were deployed in the
equatorial Atlantic during July-August 1997. The floats were ballasted
to drift at 1000 m for 10 to 14 days, return to the surface while
obtaining a temperature profile, transmit data via satellite, and then
after one day return to 1000 m. One-year float paths are now available.
Floats deployed on the equator were launched into a deep westward jet.
The jet extends some 1-2° north of the equator, with eastward motion
observed in floats to the north of 2°N. The equatorial current
reverses in the central basin to the east in mid-October and then back to
the west in mid-February. Flow to the north also reverses. The short
space and time scales contrast with earlier work based on fewer floats that
inferred space scales of some 5 -10 in latitude and time scales greater
than one year. The new results are consistent with models that indicate
that equatorial Rossby waves are the cause of the reversing currents.
Morisseau-Leroy, N., M.K. Solomon, G.P. Momplaisir, T. Kurian, and E.
Griffin. Oracle 8I SQLJ Programming. Osborne McGraw-Hill
(ISBN 0072121602), 557 pp. (1999).
No abstract.
Murillo, S.T., and J.J. O'Brien. The influence of ENSO on eastern
Pacific tropical cyclones. Preprints, 23rd Conference on Hurricanes
and Tropical Meteorology, Dallas, TX, January 10-15, 1999.
American Meteorological Society, Boston, 437-438 (1999).
No abstract.
Murillo, S.T., W.-C. Lee, K. Hondl, P.P. Dodge, C. McAdie, and F.D.
Marks. Implementation of the GBVTD technique in nowcasting hurricane
wind fields using the WSR-88D. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 311-312 (1999).
No abstract.
Nelsen, T.A., and J.R. Proni. Detecting, mapping, sampling, and
analyzing oceanic suspended particulate matter: Methods complementary to
acoustic detection of environmentally sensitive ocean outfall and dumped
materials. Joint Meeting, 137th Regular Meeting of the Acoustical
Society of America and 2nd Convention of the European Acoustics
Association: Forum Acousticum 99, Berlin, Germany, March 15-19, 1999.
Journal of the Acoustical Society of America, 105(2):1322 (1999).
Natural systems such as lakes, rivers, and oceans can be described by
dissolved and particulate components. Particulate sources in coastal
oceanic environments include natural materials from seaward riverine and
estuarine flows and anthropogenic sources such as ocean dumping and
outfalls. Plumes of suspended particulate matter (SPM) can be natural
(lithogenic and biogenic), anthropogenic, and any mixture of these.
Because SPM can range from environmentally neutral (i.e.,lithogenic
and biogenic) to hazardous (heavy metals, bacteria), detecting, tracking,
sampling, and sourcing SPM plumes can be beneficial for the environment
and human health. Acoustic methods have proven successful in detecting
and mapping oceanic SPM over large spatial areas but are limited in
resolving internal fine structure, estimating relative contributions of
merged plumes from various sources (e.g., river outflow vs. dumping),
and differentiating between introduced and in-situ SPM. To complement
acoustics, CTD/optical/water survey tools have been employed for guided
sampling of plumes. Water samples for total suspended matter (TSM) and
particle size distributions have proven useful to both calibrate acoustic
measurements and provide insight into signatures provided by particle
size distributions. Signatures, determined by factor and component
analyses, allows mapping of SPM components, as well as estimating their
dilution and long-termed budgets.
Nelsen, T.A., and J.R. Proni. Distribution and movement of discharged
dredged material at the San Juan Ocean Disposal site. Final Report to
the U.S. Army Corps of Engineers, MIPR No. W32CS580843181, 57 pp. (1999).
No abstract.
Nelsen, T.A., and J.R. Proni. Signatures contained in suspended
particulate matter with application to coastal-ocean environmental
studies. In Coastal Engineering and Marine Developments, C.
Brebbia and P Anagnostopoulos (eds.). WIT Press, Southampton,
328-346 (1999).
Suspended particulate matter (SPM) samples from the New York Bight Apex
collected during a sewage-dump experiment were analyzed for chemical as
well as physical parameters such as particle-size distributions. The
latter provided a signature of the SPMs' sewage component that allowed
differentiation from other components. These results were applied to a
series of eight Water Column Characterization (WCC) cruises in this area.
Co-analysis of WCC and sewage dump particle-size distributions by factor
analysis and Distribution Component Analysis revealed patterns that
allowed differentiation of sewage-derived components for all WCC samples.
From this, a long-termed budget of SPM components, including
sewage-derived materials, was constructed. Given this, we conclude that
useful tools are available for developing signatures of anthropogenic
components of SPM plumes which are independent of study sites or subject
materials. These signatures can be applied to understand the sources,
pathways, and sinks of such materials in the coastal ocean, as well as
constructing long-termed budgets thereof. Ultimately such estimates can
be critical to waste management strategies and decisions in an ever more
anthropogenically-impacted coastal ocean.
Nelsen, T.A., G. Garte, C.M. Featherstone, P.L. Blackwelder, T. Hood, C.
Alvarez-Zarikian, P. Swart, H.R. Wanless, L. Tedesco, C. Souch, J. Pachut,
and J. Arthur. Understanding long-term rainfall, freshwater flow, and
salinity patterns with concomitant responses of benthic microfauna, stable
isotopes, and pollen in Oyster and Florida Bays. 1999 Florida Bay and
Adjacent Marine Systems Science Conference, Programs and Abstracts,
Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program,
189-190 (1999).
Salinity records exhibited variability from the decadal scale to the monthly
scale that can be accounted for by changing patterns in regional rainfall.
Changes in salinity, both near the outflow of the Shart River Slough at Oyster
Bay, and in central Florida Bay near Jimmy Key, show a direct response to
regional rainfall on these time scales. Moreover, regional rainfall,
represented by the 80+ year record at Homestead, Florida, proved
representative of the study area and indicated high correlation with flow
into Shark River Slough prior to major watershed construction instigated in
the early 1960s. During subsequent periods of water management strategies,
enacted from the mid-1960s to present, results indicate essentially no
correlation between regional ranfall and flow during the Monthly Allocation
Plan. In contrast, correlations most closely paralleled pre-construction,
apparently more natural condtions, during the Rainfall Plan. Investigated
characteristics for the benthic microfaunal community (foraminifers and
ostracods) such as stable isotopes, abundance, and community diversity,
exhibited changes and trends that apparently more closely paralleled
natural rather than anthropogenic influences over the whole period of
record. At both Jimmy Key and Oyster Bay, foraminifer and ostracod data
indicate direct correlation to rainfall patterns for temporal scales
ranging from decadal down to the limit-of-resolution of our geochronology.
An exception to this natural influence was observed from the late-1940s to
mid-1950s during which time a dual transition occurred in the sediments
adjacent to the Shark River Slough in Oyster Bay. Organic carbon content
permanently declined from above- to below-average with concurrent onset of
major increases in foraminifer and ostracod abundances. These events
temporally conicided with the construction of the Everglades Agricultural
Area, which impounded 700,000 acres of organic-rich swampland. These effects
were not observed for sediments representing the same time period at Jimmy
Key. Stable isotope (delta 18O, delta 13O) trends alone
for ostracods and foraminifers at Oyster Bay and Jimmy Key showed mixed
signals, with most data suggesting upcore trends to less fresh, more marine
conditions. However, when long-term trends for relative abundance of
salinity-sensitive species were examined, for the same time periods and
locations, they confirmed a statistically valid upcore trend toward less
fresh, more marine conditions at both Oyster and Florida Bay study sites.
This trend was coincident with a weak decline in regional rainfall over the
same time span. Changes in the stable isotopic values of these microfauna
indicated, to the limits of our geochronology, direct responses to regional
rainfall. Such responses more closely paralleled rainfall than freshwater
runoff, even adjacent to the outflow of the Shark River Slough. At Oyster
Bay, istracod stable isotope (delta18O) trends correlated better
with variabions in regional rainfall than with freshwater outflow from the
adjacent Shark River Slough. Crashes in microfaunal abundances at Oyster
Bay and more gradual declines at Jimmy Key were salinity related. This
abundance drop was concurrent with an equally dramatic drop in community
diversity. The latter was characterized by survivor-mode dominance by two
microfaunal species and occurred over a period of drought at both sites and
the related reduced flow from Shart River Slough. A non-traditional use of
pollen allowed evaluation of the degree of paleo-flushing from Shark River
Slough that not only correlated well with existing flow and rainfall records
but suggests validity as a flushing proxy for pre-record eras. Analysis of
regional pollen indicated taxa associations that allowed discrimination of
pollen zonations from coastal mangrove to upland slough environments. This,
in turn, allowed reconstruction in the sediment record of historical periods
of major to minor flushing from Shark River Slough.
Ooyama, K.V. Boundary-layer parameterization in a cloud-resolving model
using the radical thermodynamic formulation. Preprints, 23rd Conference
on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 150-152 (1999).
No abstract.
Ortner, P.B., L.B. Crowder, and D.E. Hoss. The South Atlantic Bight
Recruitment Experiment: Introduction and overview. Fisheries
Oceanography, 8:1-6 (1999).
The South Atlantic Bight Recruitment Experiment (SABRE) brought together
an interdisciplinary team of scientists to conduct research to enhance our
understanding of the relationship between variation in environmental factors
and the variable recruitment of "estuarine dependent" fishes within the
South Atlantic Bight. The project sought to develop a new fusion of
government and academic scientists, each possessing unique skills, to
address the difficult problem of recruitment variability in fishes. This
fusion required the development of appropriate and, at that time, novel
management and administrative strategies. SABRE initially focused on
recruitment dynamics of Atlantic menhaden, Brevoortia tyrannus, in
the South Atlantic Bight, but expanded over time to include several
estuarine-dependent species and much of the Middle Atlantic Bight as well.
The project was conducted from 1991 to 1997 and resulted in a substantial
improvement in our understanding of the life history and ecology of Atlantic
menhaden and the potential constraints upon its recruitment. SABRE also
contributed to our understanding of the physical oceanography of the
western North Atlantic shelf and adjacent coastal inlets and the
implications of physical dynamics upon the potential pathways for larval
transport.
Ortner, P.B., M.J. Dagg, G.S. Kleppel, and C.R. Tomas. Grazing by
zooplankton in Florida Bay waters. Florida Sea Grant College Program,
FLSGP-G-99-012, 2 pp. (1999).
No abstract.
Palmer, D.R. Parabolic approximations for global acoustic propagation
modeling. NOAA Technical Memorandum, ERL AOML-94 (PB99-171571), 54 pp.
(1999).
Motivated by the difficulty in using the splitting matrix method
to obtain parabolic approximations to complicated wave equations, we have
developed an alternative method. It is three-dimensional, does not a
priori assume a preferred direction or path of propagation in the
horizontal, determines spreading factors, and results in equations that
are energy conserving. It is an extension of previous work by several
authors relating parabolic equations to the horizontal ray acoustics
approximation. Unlike previous work, it applies the horizontal ray
acoustics approximation to the propagator rather than to the Green's
function or the homogenous field. The propagator is related to the
Green's function by an integral over the famous "fifth parameter" of Fock
and Feynman. Methods for evaluating this integral are equivalent to
narrow-angle approximations and their wide-angle improvements. When this
new method is applied to simple problems, it gives the standard results.
In this paper, it is described by applying it to a problem of current
interest: the development of a parabolic approximation for modeling
global underwater and atmospheric acoustic propagation. The oceanic or
atmospheric waveguide is on an Earth (or other heavenly body) that is
modeled as an arbitrary convex solid of revolution. The method results in
a parabolic equation that is energy conserving and has a spreading factor
that describes field intensification for antipodal propagation.
Significantly, it does not have the singularities in its range-sliced
version possessed by many parabolic equations developed for global
propagation. The work is generalized to allow for refracted geodetics and
the possibility that the depth dependence of the pressure field can be
described by adiabatic normal modes.
Peng, T.-H., and F. Chai. Modeling the carbon cycle in the equatorial
Pacific Ocean. Proceedings, Second International Symposium on
CO2 in the Ocean, Tsukuba, Japan, January 18-22, 1999.
Center for Global Environmental Research (CGER-I037-99), 183-189 (1999).
As part of the U.S. JGOFS SMP program, we have developed an ocean ecosystem
model of the equatorial Pacific Ocean with new and export productivity
regulated by Si and Fe to synthesize and to analyze data collected during
the process-study-oriented survey cruises in 1992. The circulation model is
based on the Modular Ocean Model of the NOAA/GFDL ocean general circulation
model. The ecosystem model consists of nine components describing two size
phytoplankton, two size zooplankton, two detritus pool, and three dissolved
nutrients: silicate, nitrate, and ammonium. The carbonate chemistry is
parameterized in the model to evaluate the variations of pCO2,
and hence the CO2 flux across the air-sea interface. At this
initial stage, a test case by using a 1D model is performed to simulate
low-silicate, high-nitrate, and low-chlorophyll conditions in the equatorial
Pacific, and to investigate how the carbon system behaves in this
ecosystem structure. The model includes the vertical upwelling and
diffusion processes. The upwelling rate and vertical diffusivity were
initially averaged for the region 5°S to 5°N, 180°W to
90°W, the "cold tongue" of the equatorial Pacific from the parameter
values of 3D model simulations. Temperature is used to calibrate model
upwelling and vertical diffusion rates. Comparison of model results with
the observations made during the NOAA/OACES EqPac 1992 expeditions indicates
that the vertical profiles of DIC, NO3 and Si(OH)4
are consistent with the measurements made in the fall season when the
ocean was in a normal non-El Niño condition. A tight fit of profiles
between model and observation is not possible because of spatial variations
of the observed values. A 3D simulation is required, which is in progress.
The 1D model CO2 evasion rate is estimated to be 2.9
mol/m2/yr, which is within the range of estimates from
measurements made during non-El Niño conditions.
Peng, T.-H., and R.H. Wanninkhof. Re-evaluation of historical carbon
data based on recent high-quality measurements. AGU 1999 Fall
Meeting, San Francisco, CA, December 13-17, 1999. Supplement to EOS,
Transactions, American Geophysical Union, 80(46):F579, OS51E-15 (1999).
In the Indian Ocean, crossover stations between GEOSECS and recent NOAA/DOE
CO2 survey sampling cruises are selected. Measurements of
temperature, salinity, oxygen, TCO2, and alkalinity for samples
taken below 2000 m depth at these crossover stations are compared. Because
water masses below this depth are relatively stable with respect to
anthropogenic disturbances, the carbon chemistry and hydrographic properties
should remain unchanged in the last three decades. Hence, comparison of deep
water properties between new and old data will provide information regarding
the need for correction or adjustment in the older data sets. Systematic
differences between the two data sets reflect the need for such correction.
We apply "Linear Least-Squares Multiple Regression" of TCO2
against salinity, potential temperature, oxygen, and alkalinity of deep
waters in new data sets. Using this relationship, TCO2 is
predicted from these parameters measured during GEOSECS at the crossover
station. The difference between the predicted TCO2 and the GEOSECS observed
TCO2 is the adjustment needed for this historical data. The
overall average is 21.6 ą 4.1 mol/kg, which is the mean adjustment needs
to be made to all GEOSECS TCO2 measurements in the Indian Ocean.
Peng, T.-H., J.-J. Hung, R.H. Wanninkhof, and F.J. Millero. Carbon budget
in the East China Sea in spring. Tellus B, 51(2):531-540 (1999).
Results of total dissolved inorganic carbon (DIC) and total alkalinity
(TA) measurements made in the East China Sea (ECS) during a geochemical
expedition of KEEP (Kuroshio Edge Exchange Processes) program in May of
1996 show that ECS is a CO2 sink during the spring season.
The mean difference of fCO2 (fugacity of CO2)
between the atmosphere and surface water is calculated to be 28 µatm,
and the resulting net CO2 invasion flux is 2.1
mol/m2/yr, which gives about 0.03 GtC/yr of
CO2 uptake in this continental shelf in spring. This study
supports the notion that shelf regions can be a significant
CO2 sink. The riverine alkalinity, which discharges into ECS,
is estimated to be 1,743 µmol/kg on the basis of a linear relationship
between TA and salinity. The observed salinity-normalized alkalinity in
ECS is higher than that in the open sea, and this excess alkalinity is
estimated to be 42 µmol/kg. With the known rate of the Changjiang
discharge, this excess TA gives a mean residence time of 1.2 years for
the continental shelf water in the ECS. The DIC in the ECS is also found
to be higher than that in the open sea. This excess DIC is estimated to be
about 76 ± 70 µmol/kg, which is equal to a net carbon input to
ECS of 3.9 ± 3.6 mol/m2/yr. Based on the riverine
alkalinity input, the equivalent riverine carbon flux from Changjiang
discharge is estimated to be about 1.8 mol/m2/yr. With
net CO2 invasion flux of 2.1 ± 2.8
mol/m2/yr, the remaining 0 ± 4.6 mol/m2/yr
could come from remineralization of organic matter derived from biological
pump in the shelf or terrestrial sources. Although this preliminary
carbon budget implies that gas exchange and riverine input are the main
sources of excess carbon in ECS, the contribution of biological carbon
flux can not be ruled out because of the large uncertainty associated
with these estimates.
Pielke, R.A., and C.W. Landsea. La Niņa, El Niņo, and Atlantic hurricane
damages in the United States. Bulletin of the American Meteorological
Society, 80(10):2027-2034 (1999).
Hurricanes result in considerable damage in the United States. Previous
work has shown that Atlantic hurricane landfalls in the United States
have a strong relationship with the El Niņo-Southern Oscillation phenomena.
This paper compares the historical record of La Niņa and El Niņo events
defined by eastern Pacific sea surface temperature with a data set of
hurricane losses normalized to 1997 values. A significant relationship
is found between the ENSO cycle and U.S. hurricane losses, with La Niņa
years exhibiting much more damage. Used appropriately, this relationship
is of potential value to decision makers who are able to manage risk based
on probabilistic information.
Pielke, R.A., C.W. Landsea, R.T. Musulin, and M. Downton. Evaluation of
catastrophe models using a normalized historical record: Why it is needed
and how to do it. Journal of Risk and Insurance, 18:177-194 (1999).
No abstract.
Powell, M.D. Hurricanes at landfall. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 107-108 (1999).
No abstract.
Powell, M.D., and S.H. Houston. Comments on "A multiscale numerical study
of Hurricane Andrew (1992). Part I: Explicit simulation and
verification." Monthly Weather Review, 127(7):1706-1710 (1999).
No abstract.
Powell, M.D., T.A. Reinhold, and R.D. Marshall. GPS sonde insights on
boundary layer wind structure in hurricanes. Proceedings, 10th
Conference on Wind Engineering, Copenhagen, Denmark, June 21-24,
1999. ICWE, 307-314 (1999).
No abstract.
Powell, M.D., P.G. Black, S.H. Houston, and T.A. Reinhold. GPS sonde
insights on boundary layer structure in hurricanes. Preprints, 23rd
Conference on Hurricanes and Tropical Meteorology, Dallas, TX,
January 10-15, 1999. American Meteorological Society, Boston,
881-884 (1999).
No abstract.
Proni, J.R., and T.A. Nelsen. Integrated measurements of sewage
effluent and dredged material discharges. In Coastal Engineering
and Marine Developments, C. Brebbia and P Anagnostopoulos (eds.).
WIT Press, Southampton, 368-379 (1999).
A series of measurements to characterize sewage effluent discharge plumes
and dredged material discharge plumes were carried out in coastal ocean
waters off the coast of Puerto Rico in April 1998. A multiple sensor suite
including an acoustic backscatter profiler, a towed optical backscatter
containing CTD device, a vertical cast CTD having an optical
transmissometer and oxygen sensors, and an acoustic Doppler current
profiler (ADCP) was utilized to determine the subsurface plume spatial
distribution and dilution. The sewage effluent plumes resulted from
discharges at several diffusers located approximately one or more miles
from the coastline. Using the multiple sensor systems listed above, it
was possible to relate measurements made at water locations distant from
the diffuser to plumes emanating from various parts of the diffuser under
study. That is, a "connectivity" was established so that quantities
inherent in the effluent discharge could be used for dilution calculations.
Typical "initial" dilutions observed were on the order of 60:1. Using
inherent tracers, such as plume salinity, effluent plume distributions
were determined out to several hundred meters from the diffuser.
"Macro" scale comparisons of multiple sensor outputs were carried out
with good general agreement on plume distributions. Comparisons between
in-situ "contact" sensors, e.g., temperature and salinity probes,
and in-situ remote sensor probes, e.g., optical and acoustic
backscatter, optical transmissivity (transmissometry), were made with
good agreement resulting.
Proni, J.R., and T.A. Nelsen. Puerto Rico outfall/dredged material
disposal studies: April 13-26, 1998. Contract EPA/IAG DW13937869-01-04
(Final report). U.S. Environmental Protection Agency, 74 pp. (1999).
No abstract.
Proni, J.R., and T.A. Nelsen. Recent advances in coastal ocean pollution
research and monitoring. Joint Meeting, 137th Regular Meeting of the
Acoustical Society of America and 2nd Convention of the European
Acoustics Association: Forum Acousticum 99, Berlin, Germany, March
15-19, 1999. Journal of the Acoustic Society of America,
105(2):1323 (1999).
Design of both real-time studies of oceanic discharges of potential
pollutants such as sewage effluent, and long-term monitoring of same,
are complicated by a number of factors. These factors include lack of
knowledge of the space and time distribution of the discharge plume,
proper placement sites for sample gathering, and lack of knowledge of the
space-time distribution of "interfering" plumes (plumes from sources
other than the discharge plume under study). Progress has been made in
the development of "integrated sensor suites" which produce data with
substantial synergistic benefits. Ocean acoustics plays a key role in
integrated sensor suite data unification. In a recent study in the
coastal waters off San Juan, Puerto Rico, the ability of acoustics systems
to view essentially the complete oceanic water enabled a connection to be
made between salinity, temperature, and turbidity measurements gathered
in the upper 5 m in the water column to a specific port of a sewage
effluent diffuser. Having established the "connectivity" of the distal
field measurement to a specific port, a dilution value at the distal
point could confidently be calculated. This example is but one of many
of the synergies available from utilization of multiple sensor suites
unified through acoustics.
Quilfen, Y., A. Bentamy, K.B. Katsaros, and G. Lorand. Estimation of
ocean-atmosphere turbulent fluxes from satellite measurements.
Proceedings, 1999 International Geoscience and Remote Sensing Symposium
(IGARSS '99), Hamburg, Germany, June 28-July 2, 1999. Institute of
Electrical and Electronic Engineers, 2 pp. (1999).
No abstract.
Reasor, P.D., M.T. Montgomery, and F.D. Marks. The asymmetric structure
of Hurricane Olivia's inner core. Preprints, 23rd Conference on
Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15,
1999. American Meteorological Society, Boston, 301-304 (1999).
No abstract.
Rodbell, D.T., G.O. Seltzer, D.M. Anderson, M.B. Abbott, D.B. Enfield,
and J.H. Newman. A high-resolution ~15,000 year record of El Niño
driven alluviation in southwestern Ecuador. Science, 283:516-520
(1999).
Debris flows have deposited inorganic laminae in an alpine lake 75
kilometers east of the Pacific Ocean, in Ecuador. These storm-induced
events are dated by radiocarbon, and the age of laminae that are less
than 200 years old matches the historic record of El Niño events.
From about 15,000 to about 7,000 calendar years before the present, the
periodicity of clastic deposition is greater than or equal to 15 years;
thereafter, there is a progressive increase in frequency to periodicities
of 2-8.5 years. This is the modern El Niño periodicity, which was
established about 5,000 calendar years before present. This may reflect
the onset of a steeper zonal sea surface temperature gradient, which was
driven by enhanced trade winds.
Roemmich, D., O. Boebel, Y. Desaubies, H. Freeland, B. King, P.-Y.
Letraon, R.L. Molinari, W.B. Owens, S. Riser, U. Send, K. Takeuchi, and
S. Wijffels. Argo: The global array of profiling floats. OCEANOBS99:
International Conference on the Ocean Observing System for Climate,
Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes
Spatiales, Vol. 1, 12 pp. (1999).
A broad-scale global array of temperature/salinity (T/S) profiling floats,
known as Argo, is planned as a major component of the ocean observing system,
with deployment scheduled to begin in 2000. Conceptually, Argo builds on
the existing upper-ocean thermal networks, extending their spatial and
temporal coverage, depth range and accuracy, and enhancing them through
addition of salinity and velocity measurements. The name Argo is chosen to
emphasize the strong complementary relationship of the global float array
with the Jason altimeter mission. For the first time, the physical state
of the upper ocean will be systematically measured and assimilated in near
real time. Objectives of Argo fall into several categories. Argo will
provide a quantitative description of the evolving state of the upper ocean
and the patterns of ocean climate variability, including heat and freshwater
storage and transport. The data will enhance the value of the Jason
altimeter through measurement of subsurface vertical structure (T(z),
S(z)) and reference velocity, with sufficient coverage and resolution for
interpretation of altimetric sea surface height variability. Argo data
will be used for initialization of ocean and coupled forecast models,
data assimilation, and dynamical model testing. A primary focus of Argo
is seasonal to decadal climate variability and predictability, but a wide
range of applications for high-quality global ocean analyses is anticipated.
The initial design of the ARGO network is based on experience from the
present observing system, on newly gained knowledge of variability from the
TOPEX/Poseidon altimeter, and on estimated requirements for climate and
high-resolution ocean models. Argo will provide 100,000 T/S profiles and
reference velocity measurements per year from about 3000 floats distributed
over the global oceans at 3-degree spacing. Floats will cycle to 2000 m
depth every 10 days, with a 4-5 year lifetime for individual instruments.
All Argo data will be publicly available in near real-time via the GTS, and
in scientifically quality-controlled form with a few months delay. Global
coverage should be achieved during the Global Ocean Data Assimilation
Experiment, which together with CLIVAR and GCOS/GOOS, provide the major
scientific and operational impetus for Argo. The design emphasizes the need
to integrate Argo within the overall framework of the global ocean observing
system. International planning for Argo, including sampling and technical
issues, is coordinated by the Argo Science Team. Nations presently having
Argo plans that include float procurement or production include Australia,
Canada, France, Germany, Japan, the U.K., and the U.S.A., plus a European
Union proposal. Combined deployments from these nations may exceed 700
floats per year as early as 2001. Broad participation in Argo by many
nations is anticipated and encouraged either through float procurement,
logistical support for float deployment, or through analysis and
assimilation of Argo data.
Rogers, R.F. Amplification of warm-core vortices by convective
redevelopment: A key component of tropical cyclogenesis. Preprints,
23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX,
January 10-15, 1999. American Meteorological Society, Boston, 929-932
(1999).
No abstract.
Rogers, R.F., and J.M. Fritsch. Amplification of warm-core vortices by
convective redevelopment: A key component of tropical cyclogenesis.
Preprints, Eighth Conference on Mesoscale Processes, Boulder,
CO, June 28-July 1, 1999. American Meteorological Society, Boston,
55-60 (1999).
Theories explaining the transition of a relatively disorganized area of
convection into a coherent, self-sustaining system (i.e., tropical
cyclogenesis) have traditionally relied upon the presence of a vortex
before genesis can occur. Observations have confirmed the need for these
vortices, often detecting them in radar and satellite imagery several days
prior to the formation of a tropical depression. However, observational,
theoretical, and numerical studies of similar systems over land have found
that the initial vortices are often confined to the mid-troposphere.
Therefore, an important question to address is how these vortices grow
down to the surface in maritime tropical environments, for it is not until
the vortex is reflected at the surface that intensification can begin,
provided the large-scale environment is not unfavorable. This study
investigates how midlevel vorticity within mesoscale convective vortices
(MCVs) can amplify and grow downward to the surface by the redevelopment
of deep convection. It is shown that the diabatic heating within the
convection can increase the magnitude of the balanced warm core of the
vortex, further lowering heights beneath the warm core and causing a
cyclonic circulation closer to the surface. This cyclonic vorticity can
develop in the lower troposphere even in the presence of the anomalously
cold air of the low-level cold pool, given a sufficiently strong warm core
aloft. The factors that play a key role in governing the downward
penetration of vorticity to the surface are 1) onset of deep moist
convection; 2) local reduction of the Rossby radius of deformation; and
3) weakening of the surface-based cold pool. These concepts are explored
by performing a 48-hour numerical simulation of an observed MCV that
underwent multiple cycles of convective redevelopment, amplifying after
each cycle. The model was successful in reproducing the creation and
evolution of the MCV. The amplitude of the midlevel vortex increased
considerably after each convective cycle, as cyclonic vorticity reached
the surface during the third cycle. Conditions prior to the third cycle
showed a strong southwesterly low-level jet that was transporting warm,
moist air over an outflow boundary left from the previous convective cycle
and underneath the existing MCV. Deep convection developed within the
existing cyclonic circulation and intense latent heat release amplified
the warm core. As a result of this warming, lower-tropospheric
geopotential heights lowered, creating low-level convergence which
increased cyclonic vorticity under the amplifying vortex. This
convergence led to an intense vortex in the lower troposphere during the
strongest periods of the convective cycle, despite the fact that the
lower troposphere was anomalously cold during the entire period. A
conceptual model incorporating these ideas is presented.
Schmid, C. On the circulation in the tropical Atlantic. AGU 1999 Spring
Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS,
Transactions, American Geophysical Union, 80(17):S179, OS31B-08 (1999).
The circulation in the tropical Atlantic is studied using recent and
historical Lagrangian observations. The measurements of the Lagrangian
velocities were performed at two levels: near the surface and at intermediate
depth. The surface measurements were collected with surface drifters whose
drogues were centered at 15 m depth. The intermediate layer measurements
derive from an array of 17 PALACE floats deployed in the tropical Atlantic
during the summer of 1997. They cycle between about 1000 m and the surface
to take a temperature profile every 11 days. Between the two profiles, the
PALACE floats drift at depth for 10 days. The presentation will focus on the
description of the velocity field and the analysis of the seasonal
variability. The available surface drifter data allow the estimation of the
mean monthly circulation patterns over large parts of the tropical Atlantic.
The resulting fields show the seasonal reversal of the North Equatorial
Countercurrent with predominantly westward velocities in the first half of
the year and eastward velocities during the second half of the year. The
PALACE floats also indicate the existence of a seasonal variability at about
1000 m.
Smith, N.R., D.E. Harrison, R. Bailey, O. Alves, T. Delcroix, K. Hanawa,
B. Keeley, G. Meyers, R.L. Molinari, and D. Roemmich. The role of XBT
sampling in the ocean thermal network. OCEANOBS99: International
Conference on the Ocean Observing System for Climate, Saint Raphael,
France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1,
26 pp. (1999).
This paper evaluates the present role of the XBT program and proposes a
strategy for the future under the assumption that there are other direct
and indirect contributions to sampling the temperature and salinity of the
ocean. Since the focus is on XBT sampling, the paper restricts its scope
to the upper ocean, mostly above 1000 m. The conclusions of the paper are
based on a study and workshop that were convened specifically to look at
the design of the ship-of-opportunity network and to look at options for
its implementation in the future under the assumption that Argo happens.
The paper also addresses issues related to data distribution and management.
The primary conclusion is that the network of the future should place
greatest emphasis on line sampling, at intermediate to high densities, and
assume that a proposed profiling float array, Argo, will largely take over
the role formerly occupied by area (broadcast) sampling. It is argued that
line sampling exclusively addresses several needs of the ocean observing
system that cannot easily be addressed by other forms of sampling. Further,
it is argued that such a mode complements other in-situ components such as
moorings and floats, as well as remotely-sensed surface topography. A
new network is outlined with a strategy for implementation that ensures
continuity between existing and planned networks. We conclude the data
management system that was established around the SOOP program requires
substantial renovation if it is to adequately address the needs of the
data gatherers and suppliers, and the data users (modelers, scientists,
operational applications).
Smith, R.H. IASlinks.org: Online management and distribution of
oceanographic and meteorological data for the Gulf of Mexico and
Caribbean Sea. Proceedings, First Biennial Intra-Americas Sea
Initiative (IASI) Science Meeting, Panama City, Panama, November
9-11, 1999. University of Miami (1999).
There is a growing recognition of the connectivity among oceanic processes
within the Gulf of Mexico and Caribbean Sea region (Intra-Americas Sea).
Recent technological breakthroughs in communication, specifically the
Internet, provide a common denominator for scientific collaboration and
data exchange among the region's institutions and government agencies that
collect data and utilize data products. The growing need for regional scale
models requires that interaction between research endeavors take place,
enabling the creation of larger, regional data sets and a more unified
approach to understanding the oceanography, climate, and ecology of the
Intra-Americas Sea. The Internet web site, http://IASlinks.org, hosted
by NOAA/AOML in Miami, Florida, has been developed to facilitate the
sharing of resources, results, and data sets relevant to research conducted
throughout the Intra-Americas Sea region. The site is presently designed
with indices describing the different types of research and the different
institutions, agencies, and personnel involved, with regular highlights of
specific regional research topics; it is our hope that the site will continue
to expand, becoming a more complete representation of observational programs
presently underway in and around the Gulf of Mexico and Caribbean Sea. The
usefulness of a venue such as IASlinks.org will continue to be realized as
scientists and operational observing systems throughout the Intra-Americas
Sea make more of their data available over the Internet. In particular, the
Internet as a medium for data exchange will play a pivotal role in the
forthcoming IOCARIBE-GOOS regional observing system. IASlinks will complement
the IASI web site, which will emphasize research programs, education, and
training. This collaborative atmosphere, where scientific information and
resources are shared with one another, will provide investigators working in
the region the ability to tackle larger questions regarding climate,
circulation, the propagation of species, and the connectivity of regional
marine environments.
Swenson, M.S., and D.V. Hansen. Tropical Pacific Ocean mixed-layer budget:
The Pacific cold tongue. Journal of Physical Oceanography,
29(1):69-82 (1999).
Data from satellite-tracked drifting buoys and VOS/XBT profiles for the
years 1979-1995 were used to evaluate the seasonal cycle of how major
oceanic processes redistribute heat in the cold tongue region of the
tropical Pacific. The most active processes for the annual cycle are
local heat storage and heat export by entrainment of upwelling and by
mean meridional advection. Heat export by zonal advection, however, is
not negligible, and meridional eddy heat fluxes associated with tropical
instability waves effect a negative feedback that offsets a considerable
fraction of that produced by the mean meridional advection. All of these
processes mimic the essentially one cycle per year of the surface wind
stress, as do those of the depths of both the bottom of the surface mixed
layer and the thermocline. Because it is associated with poleward Ekman
transports, upwelling, and baroclinic adjustment near the equator, the
zonal wind stress component appears to be the more important. The
meridional wind stress, while weaker in the annual mean, has a larger
annual variation and, therefore, has equal influence on the annual
variation of the scalar stress and perhaps the mixed layer thickness.
The Monin-Obukov length is found to underestimate the mixed layer
thickness very considerably. Finally, we produce the first estimates of
the seasonal cycle of eddy heat flux convergence, which plays a
significant role in the evolution of the cold tongue, and show that the
eddy heat flux convergence can be quantitatively modeled as eddy
diffusion with a diffusivity derived from single-particle buoy statistics.
Takahashi, T., R.H. Wanninkhof, R.A. Feely, R.F. Weiss, D.W. Chipman, N.
Bates, J. Olafsson, C.Sabine, and S.C. Sutherland. Net sea-air
CO2 flux over the global oceans: An improved estimate based on
the sea-air pCO2 difference. Proceedings, Second International
Symposium on CO2 in the Oceans, Tsukuba, Japan, January
18-22, 1999. Center for Global Environmental Research (CGER-I037-99),
9-15 (1999).
No abstract.
Tedesco, L.P., C. Souch, J. Pachut, J.A. Arthur, H.R. Wanless, P.L.
Blackwelder, T. Hood, C. Alvarez-Zarikian, J. Trefry, W.J. Kang, S. Metz,
and T.A. Nelsen. The signature of hurricane sedimentation in the lower
Everglades/Florida Bay ecosystem: Recognition of sedimentologic,
geochemical, and microfaunal indicators. 1999 Florida Bay and Adjacent
Marine Systems Science Conference, Programs and Abstracts, Key Largo,
FL, November 1-5, 1999. University of Florida Sea Grant Program, 194-195
(1999).
Winter storm and hurricane resuspension and transport processes are
responsible for building the bulk of the sediment sequence in the accreting
bank flanks in both northwest Oyster Bay (Whitewater Bay) and Florida Bay.
Repetitive resuspension by winter storms provides fine silt-sized carbonate,
siliceous and organic laminae as thin event laminae, mostly a millimeter or
less in thickness. As these repetitive winter storms produce similar wind
and transport sequences in an area, the constituent composition and mineralogy
of the laminae are similar. Vertical profiles of excess 210Pb
activity in sediments from northwest Oyster Bay, Jimmy Key, and First National
Bank showed that sedimentation at these sites has been in steady state during
the last 40 years. However, two to three discontinuities of short duration
(<2 years) in the decay profiles of excess 210Pb activities were
observed in the sedimentary records from northwest Oyster Bay, Jimmy Key, and
First National Bank. Based on excess 210Pb-based ages, the discontinuities
occurred at about 1960, 1948, and 1935, dates coincident with major
hurricanes passing through Florida Bay: Donna in September 1960 (category
4); an unnamed hurricane in September 1948 (category 3); and the Great Labor
Day Hurricane in September 1935 (category 5). Hurricane layers from 1935,
1948, 1960 (Donna), and 1992 (Andrew) in Oyster Bay are identified by a sharp
surface on which sand-sized shell, carbonate peloids, and organic detritus are
concentrated and overlain by a white, fine sand to silt layer, 0.5-2 cm in
thickness. Sedimentologic and geochemical data on discontinuity surfaces show
that the base of each hurricane layer is an erosional surface from which
several centimeters of sediment was eroded. This is expected as the upper
3-10 cm of the sediment in these accreting flanks is a very soft zone with as
much as 80% water content that could easily be removed. Discontinuities of
210Pb profiles and, therefore, erosion were more pronounced in
open water sites such as Jimmy Key and First National Bank (3-20 cm thick)
relative to the more protected, mangrove coastline surrounded environment of
northwest Oyster Bay (~2 cm thick). Major hurricanes (categories 4 and 5)
are devastating to the red and black mangrove communities, causing destruction
to 50-100% of the forest in the eye wall of the storm. This loss is reflected
in the organic detritus content of sediments in cores from northwest Oyster
Bay and other areas surrounded by extensive mangrove coastlines. Prior to a
major hurricane, the macro-organic detritus is mainly partly decayed fragments
of mangrove leaves released from the adjacent forests. Defoliation,
uprooting, and death of the forest during and following the storm result in a
change in the amount and composition of organic detritus in sediments.
Organic detritus is composed of fine root hairs for a period of 5-10 years
following the event. This reflects an extended period of erosion and release
of root-hair detritus from the disrupted and decaying mangrove peat
substrate. Organic detritus gradually decreases and becomes dominated by
leaf detritus as the forest recovers. Hurricane-related signals in the
microfaunal assemblage data (benthic ostracods and foraminifers) are both
site- and event-specific. The two hurricanes that significantly modified
the microfaunal assemblages from Jimmy Key and northwest Oyster Bay are
the Labor Day Hurricane of 1935 and Hurricane Donna (1960). Hurricane Donna
resulted in peaks in relative abundance of atypical benthic foraminifer
species at both sites. At Jimmy Key, the species comprising this peak were
derived from elsewhere within Florida Bay. In contrast, in northwest Oyster
Bay, species were comprised of continental shelf species transported from the
Gulf of Mexico by Donna's last winds. An example of hurricane-specific
effects can be seen in the differing signals recorded by the 1935 and 1960
hurricanes at Jimmy Key. The 1960 hurricane left a distinct lag-type deposit,
whereas the 1935 hurricane sediments were essentially barren of microfauna.
High organic carbon influx and subsequent oxygen depletion associated with
these hurricane events appear to be recorded in the microfaunal assemblages
as well.
Thacker, W.C. Principal predictors. International Journal of
Climatology, 19:821-834 (1999).
Principal predictors are linear combinations of variables from
one set that efficiently describe the collective variability of those
from a second set. Their defining eigenproblem is similar to that of
canonical-correlation analysis, and when the two sets are taken to be the
same, principal predictors reduce to principal components. Within the
context of a forecast model for the circulation in the Gulf of St.
Lawrence, they are shown to be capable of providing a low-dimensional
characterization of high-resolution model dynamics.
Uhlhorn, E.W., P.G. Black, and A.F. Hasler. Evolution of mesoscale flow
in a mature tropical cyclone as determined from satellite imagery.
Preprints, 23rd Conference on Hurricanes and Tropical Meteorology,
Dallas, TX, January 10-15, 1999. American Meteorological Society,
Boston, 200-203 (1999).
No abstract.
Vachon, P.W., and K.B. Katsaros. Atmospheric cyclones from spaceborne
SAR. Backscatter, 10(4):14-19 (1999).
No abstract.
Vachon, P.W., K.B. Katsaros, P.G. Black, and P.P. Dodge. RADARSAT
synthetic aperture radar measurements of some 1998 hurricanes.
Proceedings, 1999 International Geoscience and Remote Sensing Symposium
(IGARSS '99), Hamburg, Germany, June 28-July 2, 1999. Institute of
Electrical and Electronic Engineers, 1631-1633 (1999).
The RADARSAT synthetic aperture radar (SAR) acquired C-band and
HH polarization images over four 1998 hurricanes: Bonnie, Danielle,
Georges, and Mitch. We present the SAR images and discuss their
quantitative use in understanding hurricane morphology. The SAR provides
a complementary "view from below" that is most beneficial when considered
in the context of more conventional hurricane observations.
Wang, C., R.H. Weisberg, and J.I. Virmani. Western Pacific interannual
variability associated with the El Niņo-Southern Oscillation. Journal
of Geophysical Research, 104(C3):5131-5149 (1999).
Observations of sea surface temperature (SST), sea level pressure
(SLP), surface wind, and outgoing longwave radiation (OLR) show that the
El Niņo-Southern Oscillation (ENSO) displays western Pacific anomaly
patterns in addition to eastern Pacific anomaly patterns. During the
warm phase of ENSO, warm SST and low SLP anomalies in the equatorial
eastern Pacific and low OLR anomalies in the equatorial central Pacific
are accompanied by cold SST and high SLP anomalies in the off-equatorial
western Pacific and high OLR anomalies in the off-equatorial far western
Pacific. Also, while the zonal wind anomalies over the equatorial
central Pacific are westerly, those over the equatorial far western
Pacific are easterly. The nearly out-of-phase behavior between the
eastern and western tropical Pacific is also observed during the cold
phase of ENSO, but with anomalies of opposite sign. These western
Pacific interannual anomaly patterns are robust features of ENSO,
independent of data sets. It is argued that equatorial easterly
(westerly) wind anomalies over the far western Pacific during the warm
(cold) phase of ENSO are initiated by off-equatorial western Pacific cold
(warm) SST anomalies, and that these winds are important for the
evolution of ENSO. An atmosphere model is employed to demonstrate that
small off-equatorial western Pacific cold (warm) SST anomalies (compared
to those in the east) are sufficient to produce equatorial easterly
(westerly) wind anomalies as observed over the far western Pacific. The
coupled ocean-atmosphere model of Zebiak and Cane is then modified to
investigate the evolution of the western Pacific interannual anomaly
patterns in a coupled ocean-atmosphere system, by including a meridional
structure to the subsurface temperature parameterization in the western
Pacific. The modified model produces both western and eastern Pacific
interannual anomaly patterns.
Wang, C., R.H. Weisberg, and H. Yang. Effects of the wind
speed-evaporation-SST feedback on the El Niņo-Southern Oscillation.
Journal of the Atmospheric Sciences, 56(10):1391-1403 (1999).
The thermodynamical process of latent heat flux is added to an
analogical delayed oscillator model of the El Niņo-Southern Oscillation
(ENSO) that mainly considers equatorial ocean dynamics and produces
regular, non-phase-locked oscillations. Latent heat flux affects the
model sea surface temperature (SST) variations by a positive feedback
between the surface wind speed and SST operating through evaporation
which is called the wind speed-evaporation-SST feedback. The wind
speed-evaporation-SST feedback in which the atmosphere interacts
thermodynamically with the ocean through surface heat flux differs from
the conventional zonal wind stress-SST feedback in which the atmosphere
interacts dynamically with the ocean through momentum flux. The
combination of equatorial ocean dynamics and thermodynamics produces
relatively more realistic model oscillations. When the annual cycle
amplitude of the zonal wind in the wind speed-evaporation-SST feedback is
gradually increased, the model solution undergoes a transition from
periodic to chaotic and then to periodic oscillations for some ranges of
the parameters, whereas for other ranges of the parameters the transition
goes from periodic to quasi-periodic and then to periodic oscillations.
The route to chaos is the intermittency route. Along with such
irregularity, the nonlinear interactions between the annual and
interannual cycles operating through the wind speed-evaporation-SST
feedback also produce a phase-locking of ENSO to the seasonal cycle. The
model ENSO onset and peak occur in the boreal winter and spring,
respectively, consistent with the observed phase-locking of ENSO in the
far eastern Pacific. It is shown that ENSO decadal or interdecadal
variability may result from the nonlinear interactions between the annual
and interannual cycles in the tropics.
Wanninkhof, R.H. An overview of GAS EX-98. AGU 1999 Spring Meeting,
Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American
Geophysical Union, 80(17):S49, A32A-01 (1999).
The gas experiment in the North Atlantic (GAS EX-98) had as its main
objective to improve our knowledge of air-sea CO2 fluxes.
Understanding of the physics controlling the gas transfer in the field
necessitates measuring gas transfer on the time scales of the
environmental forcing (sub-hour). Conventional waterside mass balance
methods have a response time of at least a day such that we must rely on
micrometeorological measurements, or proxies of CO2 such as heat,
along with assumption of similarities. Since micrometeorological measurements
have yielded too high fluxes compared to mass balance approaches in the
past, the first step was to reconcile the measurements.
Micrometeorological CO2 flux estimates were obtained from
gradients of CO2 and dimethyl sulfide in the (air) marine
boundary layer, and by CO2 co-variance measurements. Gas
transfer velocities were measured using the dual-deliberate tracer technique
with 3He and SF6 in the water column. Changes of CO2 in the
water column were used as overall constraints for the gas fluxes after
accounting for changes of CO2 concentrations due to biology.
The selection of study location was based on the site being a constrained
watermass in an eddy in a large CO2 sink region. The anticyclonic
(warm core) eddy inhibited dispersion of the deliberate tracers, thereby
extending the duration of the experiment, and SF6 concentrations were
measurable for the duration of the 24-day process study. The large
CO2 sink, averaging -85 µatm during the study, improved
the signal to noise for the direct flux measurements. The post-bloom
environment was thought to minimize the biological signal compared to the
change due to CO2 invasion in the water column mass balance.
However, despite the near absence of major nutrients, several lines of
evidence suggest rapid biological cycling. The independent estimates of gas
transfer velocities agreed well with each other. This is the first time
that such concordance is observed between the micrometeorological-based
measurements and the water column mass balance based observations. The
results from the co-variance data of McGillis and Edson (see abstract in
this session) can be fit with a cubic dependence with wind speed. Such a
relationship can be reconciled with global flux constraints based on bomb
14C. If such a relationship holds universally over the ocean,
the net global CO2 uptake would increase by a half based on the
monthly pCO2 climatology of Takahashi (1997).
Wanninkhof, R.H. Recent advances in determining air-sea CO2
fluxes. Proceedings, Second International Symposium on CO2
in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global
Environmental Research (CGER-I037-99), 101-104 (1999).
Uncertainties in inverse calculations to determine regional carbon fluxes
between the atmospheric, oceanic, and terrestrial reservoirs (Fan et
al., 1998) have clearly indicated the need to improve our oceanic carbon
flux estimate. There have been significant advances in several aspects of
air-sea flux determinations to address this question, including direct
estimates of fluxes by co-variance and gradient measurements in the
air-boundary layer, extrapolation routines using remote sensing products,
and a rapidly increasing observational database of air-sea partial pressure
differences. The gas fluxes are commonly expressed as F =
k s DELTA-pCO2 where F is the air-sea flux
CO2 (mol m-2 day-1), k is the gas
transfer velocity (m day-1), s is the solubility (mol
m3 µatm-1) and DELTA-pCO2 is the
air-water partial pressure difference (µatm). This overview discusses
recent research aimed at improving estimates of F, k, and
DELTA-pCO2.
Wanninkhof, R.H., and W.M. McGillis. A cubic relationship between
air-sea CO2 and wind speed. Geophysical Research
Letters, 26(13):1889-1892 (1999).
Using recent laboratory and field results we explore the possibility of a
cubic relationship between gas exchange and instantaneous (or short-term)
wind speed, and its impact on global air-sea fluxes. The theoretical
foundation for such a dependency is based on retardation of gas transfer
at low to intermediate winds by surfactants, which are ubiquitous in the
world's oceans, and bubble-enhanced transfer at higher winds. The
proposed cubic relationship shows a weaker dependence of gas transfer at
low wind speed and a significantly stronger dependence at high wind speed
than previous relationships. A long-term relationship derived from such a
dependence, combined with the monthly CO2 climatology of
Takahashi (1997), leads to an increase in the global annual oceanic
CO2 uptake from 1.4 Gigaton C yr-1 to 2.2 Gigaton C
yr-1. Although a cubic relationship fits within global
bomb-14C oceanic uptake constraints, additional checks are
warranted, particularly at high wind speeds where the enhancement is most
pronounced.
Wanninkhof, R.H., E. Lewis, R.A. Feely, and F.J. Millero. The optimal
carbonate dissociation constants for determining pCO2
from alkalinity and total inorganic carbon. Marine Chemistry,
65(3-4):291-301 (1999).
In many numerical ocean chemistry models total dissolved inorganic carbon
(DIC) and total alkalinity (TA) are transported between subsurface boxes,
and partial pressure pCO2 is calculated from TA and DIC
in the surface box in order to account for air-sea exchange of carbon
dioxide. The conversion is commonly performed by solving the thermodynamic
relationships for equilibria between carbonate, bicarbonate, and aqueous
CO2 using apparent carbonate dissociation constants. Four
independent determinations of the constants have been performed for
seawater in the past 50 years. These results have been corrected, refit,
and combined by others, creating a virtual cottage industry of laboratory
and field verification and cross checks. Here we show that, based on
extensive field observations in three major ocean basins, the calculated
surface pCO2 from TA and DIC corresponds best with the
measured pCO2 of the constants proposed by Mehrbach
et al.
Wanninkhof, R.H., S. Doney, T.-H. Peng, J.L. Bullister, K. Lee, and
R.A. Feely. Comparison of methods to determine the anthropogenic
CO2 invasion into the Atlantic Ocean. Tellus B,
51(2):511-530 (1999).
A comparison of different methods of estimating anthropogenic
CO2 into the Atlantic Ocean through the center of the basin
between 62°N and 42°S is performed using referenced high
quality total dissolved inorganic carbon (DIC) data. The specific
anthropogenic input is determined utilizing analytical procedures as
described in Gruber et al. (1996), and Chen and Millero (1979) to
correct for remineralization and to estimate preanthropogenic
endmembers. These estimates are compared with results of the Princeton
ocean biogeochemical model (OBM). The results show the specific
inventories of anthropogenic carbon agreeing to within 20% but with
different uptake patterns. The differences are largely caused by
differing assumptions about mixing and winter outcrop endmembers. The
same photosynthetic quotients (Redfield ratios) were used each methods.
Varying these constants within the range of literature values causes
changes in specific inventories of similar magnitude as the different
methodologies. Comparison of anthropogenic CO2 uptake and
chlorofluorocarbon ages, and preanthropogenic photosynthetic quotients
utilizing the analytical methods suggest that anthropogenic
CO2 penetration is too shallow following the procedure
according to Gruber et al. (1996), and too deep using those of
Chen and Millero (1979) in the North Atlantic. The results support
previous observations that the uptake of CO2 in the North
Atlantic is disproportionate to its surface area. This is caused by a
combination of deep water formation and deep winter mixed layers.
Whung, P.-Y., C.J. Fischer, and T. Meyers. Atmospheric deposition of
nitrogen and phosphorous to the South Florida Bay ecosystems. 1999
Florida Bay and Adjacent Marine Systems Science Conference, Programs and
Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea
Grant Program, 87 (1999).
The monitoring nutrient deposition to South Florida Bay is now underway. A
10-m meteorological tower was installed at the Keys Marine Laboratory at
Long Key in April 1998. Air samples, both dry and wet deposition such as
gaseous ammonia (NH3), particulate ammonium
(NH4+), particulate nitrate
(NO3-), organic phosphorous (org-PO4), and
total phosphorous (PO4), are measured. Meteorological parameters
such as wind speed, wind direction, air temperature, relative humidity, and
solar radiation are also collected at the sampling site. Atmosphere nitrogen,
which includes NH3, NH4+, and
NO3-, was sampled using treated filter packs. The
preliminary results for the gaseous nitrogen species during the period of
April 1998 and March 1999 showed that the NH3 concentrations varied
greatly (between 0.034 and 0.76 ug/m3), with relatively higher
concentrations in the summer season. The averaged particulate
NH4+ and NO3- concentrations
were 1.20 ug/m3 and 2.17 ug/m3, respectively. The
observed atmospheric NH3 concentrations in South Florida Bay were
similar to the averaged NH3 concentrations in other coastal regions
(such as Tampa Bay and Chesapeake Bay). Since late October 1998, aerosol
monitoring of phosphorous and wet deposition of nitrogen has been underway.
The sampling protocol, sample analysis, and shipping logistics have been
worked out in collaboration with the laboratory at the Illinois State Water
Survey who conducted the analysis for the National Atmospheric Deposition
Program (NADP). Samples collected through mid-February have been analyzed.
For this period, the average dry deposition rate of ammonium aerosol was
estimated to be about 0.18 mg/m2/wk, compared to an average wet
deposition rate of 0.1 mg/m2/wk. The averaged weekly wet
deposition rate of nitrate was on the order of 0.7 mg/m2/wk. For
phosphorous, there has only been one week in which the wet deposition data
were above the detectable limit. However, measurable air concentrations have
been obtained each week in order to obtain a dry deposition rate. At this
time, the averaged weekly PO4- deposition rate was
estimated to be about 0.1 mg/m2/wk. The analysis for organic
contributions (that do not show up as PO4) (which includes the
organic fraction) have been 30% higher than the inorganic fractions. Further
analyses of elemental ratios will be used to determine the possible origin of
this organic fraction.
Wilkerson, J.C., J.R. McCollum, and J.R. Proni. A methodology for
validating satellite estimates of rainfall over the ocean using
underwater acoustic techniques. AGU 1999 Spring Meeting, Boston, MA,
June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical
Union, 80(17):S99, H21A-05 (1999).
Current methods for validating satellite estimates of precipitation over
the open ocean use rain gauge or radar data. The rain gauge data come from
low-lying islands and atolls or from moored buoys. The intercomparison of
satellite and rain gauge estimates leads to uncertainties in the satellite
error estimates due largely to the differences in spatial coverage.
Satellite rainfall estimates cover tens to hundreds of km2 while
the representative area measured by a rain gauge is only several
cm2. In addition to sampling uncertainties, most of these
gauges are in the tropical Pacific, while satellite estimation errors
depend upon location on the globe. Radar rainfall estimates have sufficient
spatial resolution for comparisons with satellite estimates, but the amount
of radar data from coastal sites or ships is scarce. In addition, satellite
rainfall estimation techniques based on passive microwave emission cannot be
applied to grid boxes containing coast, which further limits the amount of
comparison data. Due to the current difficulties in validation of oceanic
rainfall estimates, we have examined the possibility of utilizing underwater
acoustics for oceanic rainfall estimation. It has subsequently been shown
that underwater sound can, in fact, be used to detect and classify rainfall
in coastal ocean regions and that rainfall estimation to useful accuracy
appears feasible. The acoustic technique is now being tested in the deep ocean
at the U.S. Navy Atlantic Undersea Test and Evaluation Center located in
the Tongue of the Ocean, Bahamas. A 12-hydrophone array tethered to the
ocean floor at a depth of 1.5 km has been made available to NOAA for
investigation. Acoustic data from the array, covering a 500 km2
area of the ocean surface, is sampled continuously once every 12 seconds giving
temporal and spatial data coverage comparable to that of satellite
rainfall estimates. This paper presents results of an initial comparison
of four satellite rainfall products for the acoustic site with concurrent
estimates of rainfall from the underwater array made at comparable time
and space scales. These data are supported by independent measurements
of rainfall over the array from a WR 74C weather radar located at Nassau,
60 km distant. Products from the Geostationary Operational Environmental
Satellite (GOES) include estimates from the Global Precipitation Index
(GPI), the GOES Multi-Spectral Rainfall Algorithm (GMSRA), and the Auto
Estimator. Rainfall observations from the Special Sensor Microwave
Imager (SSM/I) on the Defense Meteorological Satellite Program (DMSP)
polar orbiting satellites are also examined.
Willis, P.T. An evaluation of NEXRAD (WSR88D) data as a measure of fresh
water flux into the Florida Bay/Everglades system. 1999 Florida Bay and
Adjacent Marine Systems Science Conference, Programs and Abstracts, Key
Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program,
153 (1999).
The radar measurement of rain provides excellent spatial and temporal
resolution over a large area. This is true even over water areas, where a
dense gauge network may be impossible or prohibitively expensive. But, since
the radar does not measure rainfall rate directly, but measures the sixth
moment of the raindrop size distribution (dsd), the measurement requires a
definitive relation between rainfall rate and the shape of the drop size
distribution. The shape of the dsd is not uniquely related to the rainfall
rate. This is a source of error, and scatter, in the radar rainfall rate
measurements. A major thrust of the project has been to characterize the
shape of raindrop size distributions in south Florida. The project described
herein involves the measurement of dsd's at a site at the ENP Research Center,
and a comparison of the radar rain measurements to the gauge measurements from
the extensive gauge network associated with the Florida Bay/Everglades
Restoration project. The raw radar data has a spatial scale of approximately
1 x 1 km and a time resolution of 5-6 min. The NEXRAD hydrologic product
(dpa) has been smoothed to a spatial scale of 4 x 4 km and a time resolution
of 1 hr. This can be easily averaged to larger scales, and longer times to
provide desired products. The radar data are empirically related to the
gauge data using a probability matching methodology (PMM) which forces the
overall match of the radar mean rainfall rate and the mean gauge rainfall and
also forces an empirical match in data bin intervals. From extensive data
comparisons between the dpa and 1-hr gauge data it is found that the radar
significantly underestimates the higher rainfall rates, and overestimates the
lower rainfall rates. This is true even from a smaller sample of the full
resolution radar data, and high-resolution gauge and disdrometer data. The
match provided by the PMM is virtually the same as that from the 4 km/1 hr
data. The stability of this relation is being checked with an additional
year of radar and gauge data, and the result will be reported. A single
gauge/radar rainfall product that retains the best features of each data
type is being developed using a cokriging methodology. Sample one-month mean
radar data, and combined products using the empirical calibrations, are
presented. Planned improvements and future work are also presented.
Willis, P.T. The WSR-88D tropical Z-R relationship in south Florida.
Preprints, 23rd Conference on Hurricanes and Tropical Meteorology,
Dallas, TX, January 10-15, 1999. American Meteorological Society,
Boston, 237-240 (1999).
No abstract.
Willoughby, H.E. Hurricane heat engines. Nature, 401:649-650
(1999).
No abstract.
Willoughby, H.E. Vortex tracking semispectral hurricane models.
Preprints, 23rd Conference on Hurricanes and Tropical Meteorology,
Dallas, TX, January 10-15, 1999. American Meteorological Society,
Boston, 662-665 (1999).
No abstract.
Wilson, W.D. Atlantic western boundary currents. Proceedings, South
Florida Measurement Center Workshop: Establishment of a Center for Innovative
Oceanography in the 21st Century, Dania, FL, February 24-26, 1999.
National Science Foundation, 131-140 (1999).
No abstract.
Wilson, W.D., E. Johns, R.H. Smith, T.N. Lee, and E. Williams. Interaction
of freshwater riverine discharges from the Everglades with the Gulf of
Mexico and Florida Bay: Preliminary results from a moored array and
shipboard surveys. 1999 Florida Bay and Adjacent Marine Systems
Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5,
1999. University of Florida Sea Grant Program, 175-177 (1999).
No abstract.
Wilson, W.D., S.L. Garzoli, G.J. Goni, W.E. Johns, R.H. Smith, C.I.
Fleurant, P.L. Richardson, and D.M. Fratantoni. The North Brazil Current
Retroflection: Two recent surveys. AGU 1999 Spring Meeting, Boston,
MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical
Union,80(17):S179, OS31B-11 (1999).
The North Brazil Current is the low-latitude western boundary current
that flows northward across the equator in the western Atlantic along the
coast of Brazil. The NBC is the main source of inter-hemispheric warm
water transport in the Atlantic. Its retroflection supplies water to
equatorial zonal currents at various latitudes and depths, and rings
separate from the retroflection at irregular intervals and propagate into
the western tropical Atlantic. Because of its broad spatial extent, and
non-linear and rapidly changing nature, synoptic surveys that adequately
describe the NBC are difficult to perform. Two such surveys, by far the
most complete to date, were conducted as part of the North Brazil Current
Rings Experiment in November/December 1998 and February/March 1999.
Surveys contain data from XBT, CTD, and shipboard and lowered ADCP data
sources, providing water properties and current velocities to 2000 m.
Continuity between cruises is provided by satellite altimetry. In
November/December, 1998, the near-surface currents of the retroflection
reached to nearly 9°N, 52°W, and a closed recirculation center
was evident, which separated shortly thereafter to form an NBC ring. At
sub-thermocline level, only the closed circulation of the ring was seen,
with the subsurface retroflection completely turning eastward near
4° to 5°N, east of 48°W. During the February/March 1999
survey, the retroflection was found further to the south, its
northernmost tip extending to only 7°N, 51°W, with a newly
formed NBC ring found just northwest of the retroflection.
Yvon-Lewis, S.A., J.H. Butler, D.B. King, S.A. Montzka, J. Rodriguez,
J.M. Lobert, and M. Ko. The oceanic contribution to organic bromine in
the atmosphere. International Union of Geodesy and Geophysics, XXII
General Assembly, Birmingham, England, July 18-30, July 1999. IUGG99
Abstracts, A110 (1999).
The ocean delivers considerable organic bromine into the troposphere.
Although many of the oceanic, bromine-containing compounds are
short-lived in the troposphere, they can be convected periodically into
the stratosphere, where they contribute to the destruction of
stratospheric ozone. Methyl bromide (CH3Br) and the halons are
recognized as being the primary carriers of bromine into the
stratosphere, but contributions from other compounds may be significant.
Some of these other trace gases include CH2Br2,
CHBr3, CH2BrCl, CHBr2Cl, and
CHBrCl2. All of these gases are produced to some extent in the
ocean and their collective sea-air flux is of the same order as the total
flux of CH3Br from all sources. We have been measuring
CH3Br, CH2Br2, CHBr3, and
other bromine-containing compounds in air and surface seawater samples on
research cruises in the Pacific, Atlantic, and Southern Oceans since
1994. Results show CH3Br undersaturations throughout much of
the ocean, suggesting that the ocean is a net sink for this brominated
trace gas. However, results for CH2Br2,
CHBr3, and the other bromine-containing compounds show these
trace gases to be supersaturated throughout much of the ocean, often with
higher degrees of saturation in the tropics and subtropics. These data
are presented here and will be used in conjunction with a two-dimensional
model to examine the role that the oceans play in the cycling of
atmospheric organic bromine.
Zhang, J.-Z. Ship determination of nM nitrite and nitrate by gas-segmented
continuous flow analysis with a liquid waveguide capillary flow cell.
AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999.
Supplement to EOS, Transactions, American Geophysical Union,
80(46):F46, B12B-09 (1999).
Incorporation of a 2-m long liquid waveguide capillary flow cell to a
gas-segmented continuous flow auto-analyzer significantly enhances the
sensitivity of automated colorimetric analysis. Nanomolar concentrations of
nitrite and nitrate in oligotrophic surface seawater can be accurately
determined. Using this technique the diel cycle of nitrate at nM level in
oligotrophic water was observed. The advantages of this technique are low
detection limit, high precision, and automation for rapid analysis of a
large numbers of samples. This technique has been successfully used on
shipboard measurements of about 1000 seawater samples during a one-month
cruise in North Atlantic.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Laboratory glassware as a
contaminant in silicate analysis of natural water samples. Water
Research, 33(12):2879-2883 (1999).
When glassware is used for the storage of water samples, reagents, and
standard solutions, dissolution of silicate from the glass containers can
contaminate the samples. Experimental results demonstrate that dissolution
from glassware can introduce micromolar silicate within a few hours. The
extent of dissolution depends upon contact time, salinity, and pH of the
solution, and the size and shape of the containers.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Optimization of performance
and minimization of silicate interference in continuous flow phosphate
analysis. Talanta, 49(2):293-304 (1999).
Specific reaction conditions for automated continuous flow analysis of
phosphate are optimized in regard to minimizing coating and silicate
interference, while maintaining high sensitivity. Use of Sb in the reagent
increases sensitivity and yields absorbances with little temperature
dependence. Coating can be minimized by using a final solution at a pH
>0.5. At final pH of 0.78, there is maximum interference from silicate in
the sample. We recommend, therefore, as an optimal reaction condition with
minimal silicate interference, the use of Sb, a final solution pH of 1.00,
room temperature for the reaction, and a [H+]/Mo ratio of 70. An equation
is provided to correct silicate interference in high precision phosphate
determination.
Zhang, J-Z., R.H. Wanninkhof, and K. Lee. New production estimated from
diel cycle of nutrient and oxygen in the mixed layer. AGU 1999 Spring
Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS,
Transactions, American Geophysical Union, 80(17):S50, A32A-03 (1999).
New production can be estimated from accurate measurement of inventory
change in nutrient at nM level in the mixed layer. A strong diel cycle was
observed in nutrient concentration in response to photosynthesis in an
anticyclonic eddy in North Atlantic during the GASEX-98 cruise. During a
diel study, nitrate concentration was about 92 nM in the morning and
decreased to 12 nM at 6 p.m. Nitrate concentration increased after dark,
presumably due to the diffusive flux from the nitracline. Oxygen data in
the mixed layer also showed a similar diel cycle. The oxygen production
during the day caused concentrations to increase by about 2 uM. Under
steady state conditions, eddy diffusion is a dominant process for
transportation of nutrient to the euphotic zone to sustain the new
production. The vertical eddy diffusion coefficients were derived from
temporal changes in concentrations of a deliberate tracer, SF6, in the upper
thermocline. Together with vertical nitrate distributions, the nitrate
flux from nitracline could be estimated. Such a diffusive flux throughout
the night can account for a nitrate concentration of 102 nM by morning,
which is in good agreement with measured nitrate of 92 nM at 6 a.m. The
new production estimated from changes of nitrate inventory in the mixed
layer during the day was 28 mmole C/m2, which is in good
agreement with 31 mmole C/m2 estimated from the oxygen inventory
change. Increases in mixed layer nutrients were observed during a storm
event that deepened the mixed layer and brought the nutrient to the surface
(1.2 uM nitrate). A good correlation between wind speed and the
concentrations of nitrate and nitrite is observed. Addition of nitrate to
the mixed layer by the storm disappeared within two days, indicating a
rapid nutrient cycle by marine organisms. The relative importance of
sporadic storm events versus daily diffusive flux in supply nutrient to new
production can be estimated from accurate measurement of inventory change
of nutrient and oxygen in the mixed layer.
Zhang, J.-Z., C.J. Fischer, C.R. Kelble, and F.J. Millero. Phosphate
distribution coefficients for suspended sediments in Florida Bay.
1999 Florida Bay and Adjacent Marine System Science Conference,
Programs and Abstracts Key Largo, FL, November 1-5, 1999. University
of Florida Sea Grant Program, 77 (1999).
The distribution coefficient Kd (Kd = Cs/Cw,
where Cs is concentration of phosphorus on particle surface and
Cw in seawater) is a key parameter that governs phosphorus
partitioning between seawater and particle surface. To estimate the
distribution coefficient for phosphorus partitioning between suspended
sediments and seawater, surface sediments were collected from Florida Bay
at various locations with different environmental conditions. The sediments
were equilibrated with low nutrient seawater for 24 hours at constant
temperature. The particles were then separated from seawater by filtration.
The phosphate concentrations in equilibrated seawater were determined by
spectrophotometric method using an autoanalyzer. The sediments were then
equilibrated with a 1 M MgCl2 solution at pH of 8 for 4 hours.
The sorbed and desorbable phosphorus was then extracted into the solution by
a complexing reaction with MgCl2. The extracted phosphate was
determined after separation from the suspended sediments. The results showed
a linear correlation between phosphate concentrations in seawater and
exchangeable phosphate on the sediments surface. Preliminary estimated
Kd is of 100 L/kg. Further experiments are underway to study the
effect of salinity and temperature on the Kd. A fitted equation of
Kd as a function of salinity and temperature can be used in a water
quality model to predict the fate of input phosphorus in Florida Bay.
**1998**
Aberson, S.D. Five-day tropical cyclone track forecasts in the North
Atlantic basin. Weather and Forecasting, 13(4):1005-1015 (1998).
Statistical analyses of the most recent 40 years of hurricane tracks
(1956-1995) are presented, leading to a version of the North Atlantic
climatology and persistence (CLIPER) model that exhibits much smaller
forecast biases but similar forecast errors compared to the previously
used version. Changes to the model involve the inclusion of more accurate
historical tropical cyclone track data and a simpler derivation of the
regression equations. Nonlinear systems analysis shows that the
predictability timescale in which the average errors increase by a factor
e is approximately 2.5 days in the Atlantic basin, which is larger
than that found by similar methods near Australia. This suggests that
five-day tropical cyclone track forecasts may have some benefit, and,
therefore, a version of CLIPER extended to five days to be used as a
baseline to measure this skill is needed.
Aberson, S.D. Impact of the Gulfstream-IV jet aircraft on hurricane
forecasts. Minutes, 52nd Interdepartmental Hurricane Conference,
Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator
for Meteorological Services and Supporting Research, Washington, D.C.
(paper was mistakenly omitted from the Minutes) (1998).
No abstract.
Aberson, S.D. Targeted observations to improve tropical cyclone
forecasts. Scientific Programme, XXIII General Assembly, European
Geophysical Society, Nice, France, April 20-24, 1998. European
Geophysical Society, 256 (1998).
No abstract.
Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone intensity. Preprints, Symposium on Tropical Cyclone
Intensity Change, American Meteorological Society 78th Annual Meeting,
Phoenix, AZ, January 11-16, 1998. American Meteorological Society,
Boston, 150-153 (1998).
No abstract.
Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone tracks. Preprints, 12th Conference on Numerical Weather
Prediction, American Meteorological Society 78th Annual Meeting,
Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston,
290-292 (1998).
No abstract.
Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone tracks and intensity. Scientific Programme, XXIII
General Assembly, European Geophysical Society, Nice, France, April
20-24, 1998. European Geophysical Society, 255 (1998).
No abstract.
Aberson, S.D., R.E. Tuleya, and M.A. Bender. Ensemble forecasting of
hurricane track and intensity using the GFDL model during 1997. Minutes,
52nd Interdepartmental Hurricane Conference, Clearwater, FL, January
26-30, 1998. Office of the Federal Coordinator for Meteorological
Services and Supporting Research, Washington, D.C.,143-145 (1998).
Tropical cyclone track predictions have shown considerable skill past
three days, and intensity predictions are beginning to show some skill.
While most forecasts are good, great variability in the utility of
individual forecasts occurs. Ensemble forecasting provides a mechanism
by which the inherent uncertainty in model forecasts can be assessed.
During the 1996 and 1997 hurricane seasons, more than 100 sets of
ensemble forecasts using a two-mesh version of the Geophysical Fluid
Dynamics Laboratory (GFDL) hurricane model have been run, based upon the
bred growing modes produced operationally at the National Centers for
Environmental Prediction (NCEP). Results of these track and intensity
forecasts will be presented, including information as to how well the
models conform to the "perfect model" scenario, whether the forecasts
envelope the evolution of the atmosphere, and whether information on the
utility of individual model forecasts can be obtained from the
ensembles. Plans to continue ensemble forecasting runs during the 1998
hurricane season will be presented.
Aberson, S.D., R.E. Tuleya, and J. Heming. Five-day forecasts of tropical
cyclone tracks in the Atlantic basin. Minutes, 52nd Interdepartmental
Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of
the Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C. (paper was mistakenly omitted from the Minutes)
(1998).
Tropical cyclone track predictions have improved so that skill, as
assessed by the improvement of forecasts over a forecast provided by a
simple statistical model based upon climatology and persistence, averages
more than 30% at 72 h, the current standard length of forecasts. Because
of the possibility of such skill levels at longer forecast times during
the 1997 Atlantic hurricane season, four tropical cyclone track models
produced quasi-operational 120 h forecasts. The models were a new
version of CLIPER, with which to assess skill, and extensions of the
currently run VICBAR, GFDL, and UKMO models. Individual track forecasts
and skill assessments for the various models will be shown, and
recommendations for future work in this area, both operationally and for
research, will be made.
Alfaro, E., L. Cid, and D.B. Enfield. Relationships between the start
and end date of the rainy season in Central America and the tropical
Atlantic and Pacific Oceans. Investigaciones Marinas, 26:59-69
(1998).
In recent years, several studies have shown that anomalies in the sea
surface temperature of the tropical Atlantic and Pacific Oceans are
related to variations in the intensity and timing of the rainy season in
Central America. In order to study anomalous behavior of the rainy season
over Central America, tropical Atlantic and Pacific Oceans indices are
used to produce correlation series with the starting and ending date
(IELL and TELL) of the rainy season. The North Atlantic (ATN) and
SOI-Niño3 indices show the main correlations with the IELL and the TELL
respectively.
Amat, L.R., M.D. Powell, and S.H. Houston. WANDA: HRD's real-time
tropical cyclone "Wind Analysis Distributed Application." Preprints,
16th Conference on Weather Analysis and Forecasting, Symposium on the
Research Foci of the U.S. Weather Research Program, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January
11-16, 1998. American Meteorological Society, Boston, J29-J31 (1998).
No abstract.
Asher, W.E., and R.H. Wanninkhof. The effect of bubble-mediated gas
transfer on purposeful dual gaseous-tracer experiments. Journal of
Geophysical Research, 103(C5):10,555-10,560 (1998).
For air-water gas exchange across unbroken surfaces, the only
gas-dependent parameter affecting the transfer velocity is the molecular
diffusivity of the transferring species. In contrast, bubble-mediated
transfer processes can cause the transfer velocity to depend on both
molecular diffusivity and aqueous-phase solubility. This can complicate
the analysis of data from dual-gaseous tracer gas transfer experiments.
Bubble effects also complicate the estimation of transfer velocities for
other gases from the transfer velocity calculated using the dual-tracer
data. Herein, a method for incorporating the effects of bubble-mediated
gas transfer processes on the transfer velocity is presented. This new
procedure is used to analyze the data from two recent dual-tracer gas
transfer experiments. Transfer velocities that include the effect of
bubbles are calculated using the data from two previous oceanic
dual-gaseous tracer experiments. Comparing these transfer velocities with
transfer velocities calculated by neglecting the effect of bubbles shows
that bubble-mediated transfer increased the transfer velocity of helium 3
by 5% at a wind speed of 10.6 m s-1. However, when using the
transfer velocities form helium 3 to calculate transfer velocities for
carbon dioxide under the same conditions, including the effect of bubbles,
decreases the transfer velocity of carbon dioxide by 18%. This shows that
bubble-mediated transfer does not have a large effect on the analysis of
dual-tracer data, but it is important in relating transfer velocities
determined using helium 3 and sulfur hexafluoride to transfer velocities
of more soluble gases at wind speeds above 10 m s-1.
Asher, W.E., and R.H. Wanninkhof. Transient tracers and air-sea gas
transfer. Journal of Geophysical Research, 103(C8):15,9393-15,958
(1998).
This paper provides a review of the physics and chemistry associated with
air-sea gas transfer of transient atmospheric trace gases and the
available laboratory and field measurement techniques used to study
air-water gas transfer. The mechanistic principals and their relation to
the measurement techniques are used to show that the error associated
with estimating air-sea transfer velocities of transient tracers from
transfer velocities measured using proxy tracers can be significant if an
incorrect dependence of the transfer velocity on molecular diffusivity is
assumed. Bubble-mediated transfer processes are also demonstrated to have
a significant effect on the parameterization of the transfer velocity.
Atakturk, S.S., and K.B. Katsaros. Estimates of surface humidity and
wind speed obtained from satellite data in the stratocumulus regime in
the Azores region. In Remote Sensing of the Pacific Ocean by
Satellites, R.A. Brown (ed.). Southwood Press, Marrickville,
Australia, 16-22 (1998).
No abstract.
Bauer, S., M.S. Swenson, A. Griffa, A.J. Mariano, and K. Owens.
Eddy-mean flow decomposition and eddy-diffusivity estimates in the
equatorial Pacific. Journal of Geophysical Research,
103(C13):30,855-30,872 (1998).
The ocean-atmospheric dynamics of the tropical Pacific Ocean create
longitudinally coherent zonal flow () with strong meridional shear () in
the large-scale mean and energetic mesoscale (O(100 km)) component.
Parameterization of the effects of the mesoscale field depends on the
separation of the large-scale mean and mesoscale eddy components in order
to compute meaningful eddy diffusivity estimates in flow regimes that
demonstrate strong currents and strong shear. Large gradients in the
large-scale mean have precluded diffusivity estimation by traditional
binning techniques. In this first of two publications, a method is
developed for using Lagrangian data to estimate the diffusivity
addressing the inhomogeneity of the mean flow. The spatially dependent
estimate of the mean field is computed with a least squares bicubic
smoothing spline interpolation scheme with an optimized roughness
parameter which guarantees minimum energy in the fluctuation field at low
frequencies. Numerical simulations based on a stochastic model of a
turbulent shear flow are used to validate our approach in a conceptually
simple but realistic scenario. The technique is applied to near-surface
drifter observations obtained from 1979-1996 from two dynamically
distinct time-space regions of the tropical Pacific Ocean. The first
region, in the SEC, is characterized by a linear zonal shear mean flow
and an approximately exponential autocovariance structure in the
residuals. The residual velocity variance is s2 ~ 130
cm2 s-2 for both components and horizontal
diffusivities are 7 × 107 cm2 s-1,
and 3 × 10 cm2 s-1. The second region, in
the NECC and the NEC, has a mean flow with a strong zonal shear and a
weak northward velocity. The autocovariance is approximately exponential
for the zonal component while the meridional component has a negative lobe
at about 10 days probably due to the presence of instability waves. The
variance is approximately tripled compared to the SEC region estimate
while the meridional diffusivity estmate is nearly the same magnitude.
The zonal diffusivity is estimated to be 15 × 107
cm2 s-1.
Black, M.L., S.H. Houston, and G. Carter. AFRES-NOAA flight-level data
comparisons. Minutes, 52nd Interdepartmental Hurricane Conference,
Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator
for Meteorological Services and Supporting Research, Washington, D.C.
(paper was mistakenly omitted from the Minutes) (1998).
A coordinated flight between an Air Force Reserve (AFRES) C-130 aircraft
and both National Oceanic and Atmospheric Administration (NOAA) WP-3D
aircraft was conducted on 12 July 1997. This mission was the third in
recent years and resulted from a recommendation made at the 49th
Interdepartmental Hurricane Conference. The AFRES and NOAA aircraft each
recorded, at 1-sec intervals, the standard suite of flight-level
meteorological data (winds, temperature, dew point, pressure) and
navigational information (e.g., position, true air speed, heading,
etc.). The data were collected during clear and moderate-wind
conditions along the Florida west coast, about 100 miles north of Tampa.
The NOAA and AFRES aircraft conducted "fly-bys" adjacent to an Air Force
Aerostat balloon which was carrying a NOAA calibrated instrument package.
The balloon approaches were at altitudes ranging from 1,000 to 10,000 feet
and provide the basis for the intercomparisons. A GPS dropwindsonde was
released along the coast to supply another set of independent
measurements. Comparisons between the flight-level data collected from
the balloon, the dropsonde, and the NOAA and AFRES aircraft will be
presented. Recommendations, if any, will be made to improve the data
collection, processing, and strategies for future intercomparison
flights. Additionally, the calibration information gained from this
flight will be used to investigate the data quality from concurrent
flights into tropical cyclones by both the NOAA and AFRES aircraft this
past hurricane season.
Black, P.G., and L.K. Shay. Observations of tropical cyclone intensity
change due to air-sea interaction processes. Preprints, Symposium on
Tropical Cyclone Intensity Change, American Meteorological Society 78th
Annual Meeting, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 161-168 (1998).
No abstract.
Black, P.G., F.D. Marks, P. Dodge, I. Popstefanija and R. Pauwl. First
observations from the vertically scanning Doppler radar (VSDR): A key to
G-IV reconnaissance operations. Minutes, 52nd Interdepartmental Hurricane
Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A236-A256 (1998).
No abstract.
Boebel, O., C. Duncombe Rae, S.L. Garzoli, J. Lutjeharms, P. Richardson,
T. Rossby, C. Schmid, and W. Zenk. Float experiment studies interocean
exchanges at the tip of Africa. EOS, Transactions, American Geophysical
Union, 79(1):7-8 (1998).
No abstract.
Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black.
Environmental influences on the rapid intensification stage of Hurricane
Opal (1995) over the Gulf of Mexico. Preprints, Symposium on Tropical
Cyclone Intensity Change, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 105-112 (1998).
No abstract.
Bove, M.C., J.J. O'Brien, J.B. Eisner, C.W. Landsea, and X. Niu. Effect
of El Niño on U.S. landfalling hurricanes, revisited. Bulletin
of the American Meteorological Society, 79(11):2477-2482 (1998).
Changes in the frequency of U.S. landfalling hurricanes with respect to
the El Niño-Southern Oscillation (ENSO) cycle are assessed.
Ninety-eight years (1900-1997) of U.S. landfalling hurricanes are
classified, using sea surface temperature anomaly data from the equatorial
Pacific Ocean, as occurring during an El Niño (anomalously warm
tropical Pacific waters), La Niña (anomalously cold tropical Pacific
waters), or neither (neutral). The mean and variance of U.S. landfalling
hurricanes are determined for each ENSO phase. Each grouping is then
tested for Poisson distribution using a chi-squared test. Resampling using
a "bootstrap" technique is then used to determine the 5% and 95% confidence
limits of the results. Last, the frequency of major U.S. landfalling
hurricanes (sustained winds of 96 kt or more) with respect to ENSO phase
is assessed empirically. The results indicated that El Niño events
show a reduction in the probability of a U.S. landfalling hurricane, while
La Niņa shows an increase in the chance of a U.S. hurricane strike.
Quantitatively, the probability of two or more landfalling U.S. hurricanes
during an El Niño is 28%, of two or more landfalls during neutral
conditions is 48%, and of two or more landfalls during La Niņa is 66%. The
frequencies of landfalling major hurricanes show similar results. The
probability of one or more major hurricane landfall during El Niño
is 23% but is 58% during neutral conditions and 63% during La Niña.
Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles, Part I, Keeling's
World: Is CO2 Greening the Earth? Eldigio Press,
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New
York, 111 pp. (1998).
This section's hero is Charles David Keeling. In the late 1950s, he had
the wisdom to establish two stations for the continuous precise
measurement of atmospheric carbon dioxide, one high on Hawaii's extinct
volcano Mauna Loa and the other at the South Pole. The records from these
stations provide the foundation upon which all studies of man's
perturbation of the Earth's carbon cycle rest. Not only did Keeling have
the foresight to establish these stations but also the tenacity to make
sure that year in and year out they produced accurate results. Keeling
took on this task as part of a career-long effort to understand the flux
of CO2 gas through the atmosphere, into the ocean and into and
out of the terrestrial biosphere. He was the first to realize the wealth
of information contained in the spatial and seasonal texture of the
atmosphere's CO2 content. In addition to his direct scientific
contribution, he fostered a secondary one. Son, Ralph, is doing for
atmospheric O2 all the kinds of things papa did for
atmospheric CO2.
Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles, Part II, Martin's
World: CO2's Glacial Hideout? Eldigio Press,
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New
York, 73 pp. (1998).
The selection of the hero of this section has proven difficult. Under
consideration were those who first measured the low CO2
contents of air trapped in glacial age ice, those who used carbon isotope
ratios and cadmium contents in foraminifera to set constraints on
scenarios designed to explain this drop, and those who demonstrated that
the high latitude outcrops of the deep sea dictated the CO2
content of the entire surface ocean and, in turn, that of the
atmosphere. But in the end, we initially selected a dark horse, David
Archer, who at the time this book was being written, put his finger on
what appeared to be the mechanism responsible for the atmosphere's
glacial to interglacial CO2 cycle. He obtained microelectrode
O2 and pH data from the upper few centimeters of deep sea
sediments which clearly demonstrated the importance of bacterial
respiration as a driver of calcite dissolution. Encouraged by preliminary
boron-isotope-based paleo pH measurements which suggested large deep sea
CO=3 concentrations during glacial time, Archer
showed that an increase in the rain rate of organic matter could generate
the required CO=3 ion change with little or no
change in lysocline depth. But alas, now five years later, Archer's
hypothesis has like its predecessors fallen on hard times. Danny Sigman,
while a graduate student at Woods Hole, demonstrated that the requisite
large separation between the saturation horizon and the lysocline could
not be sustained. So in this second edition, we replace David Archer with
the late John Martin who pioneered the concept that the availability of
iron limits plant productivity in many parts of the oceans. He also
pointed out that the large excess of iron carried to the sea during
glacial time by the several-fold higher dust rain may have been
responsible for the CO2 drawdown.
Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles, Part III, Walker's
World: CO2 , Chemical Traffic Controller? Eldigio Press,
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New
York, 93 pp. (1998).
This section's hero is James C.G. Walker, a space physicist at the
University of Michigan. In 1981, together with his colleagues P.B. Hays
and J.F. Kasting, he published a paper which lays out in beautiful
simplicity the role of atmospheric CO2 as the chemical
policeman controlling the flow of continental weathering products to the
sea, and thereby maintaining a balance between the rate of outgassing of
CO2 gas from our planet's interior and the rate of
CO2 removal to sea floor sediments as calcite. The important
consequence of this police action is its influence on Earth climate.
Walker and his colleagues pointed out that early in the Earth's history
the tendency toward cooler temperatures related to the faintness of the
young Sun was mostly likely compensated by higher atmospheric
CO2 contents. In an attempt to explain the cooling of the
Earth over the last 100 million years, the role of Walker's mechanism was
subsequently expanded by Berner, Lasaga and Garrels, who postulated that
the cooling was driven by a decrease in the planetary outgassing rate
related to a progressive slowing of plate motions. This suggestion was
met with wide interest and became known as the BLAG hypothesis in honor
of its creators. In the enthusiasm to explore all the aspects of BLAG,
the earlier contribution of Walker tended to be forgotten. Hopefully, in
naming this section, we will help to return the credit for the
CO2 policing concept to its originator, James C.G. Walker.
Broecker, W.S., S.L. Peacock, S. Walker. R. Weiss, E. Fahrbach, M.
Schroeder, U. Mikolajewicz, C. Heinze, R. Key, T.-H. Peng, and
S. Rubin. How much deep water is formed in the Southern Ocean?
Journal of Geophysical Research, 103(C8):15,833-15,843 (1998).
Three tracers are used to place constraints on the production rate of
ventilated deep water in the Southern Ocean. The distribution of the
water mass tracer PO4* ("phosphate star") in the deep sea
suggests that the amount of ventilated deep water produced in the
Southern Ocean is equal to or greater than the outflow of North Atlantic
Deep Water from the Atlantic. Radiocarbon distributions yield an export
flux of water from the North Atlantic which has averaged about 15 Sv over
the last several hundred years. CFC inventories are used as a direct
indicator of the current production rate of ventilated deep water in the
Southern Ocean. Although coverage is as yet sparse, it appears that
the CFC inventory is not inconsistent with the deep water production rate
required by the distributions of PO4* and radiocarbon. It has
been widely accepted that the major part of the deep water production in
the Southern Ocean takes place in the Weddell Sea. However, our estimate
of the Southern Ocean ventilated deep water flux is in conflict with
previous estimates of the flux of ventilated deep water from the Weddell
Sea, which lie in the range 1-5 Sv. Possible reasons for this difference
are discussed.
Bryan, G.H., R.F. Rogers, and J.M. Fritsch. Cloud-scale resolution
simulations in moist absolutely unstable layers. Preprints, Eighth
Pennsylvania State University/National Center for Atmospheric Research's
Mesoscale Model Users Workshop, Boulder, CO. National Center for
Atmospheric Research, 59-62 (1998).
No abstract.
Butler, J.H., J.W. Elkins, S.A. Montzka, T.M. Thompson, T.H. Swanson,
A.D. Clarke, F.L. Moore, D.F. Hurst, P.A. Romashkin, S.A. Yvon-Lewis,
J.M. Lobert, M. Dicorleto, G.S. Dutton, L.T. Lock, D.B. King, R.E. Dunn,
E.A Ray, M. Pender, P.R. Wamsley, and C. M. Volk. Nitrous oxide and
halocompounds. In Climate Monitoring and Diagnostics Laboratory
Summary Report No. 24, D.J. Hofmann, J.T. Peterson, and R.M. Rosson
(eds.). National Technical Information Services, Springfield, VA,
91-121 (1998).
No abstract.
Castle, R.D., R.H. Wanninkhof, J.L. Bullister, S.C. Doney, R.A. Feely,
B.E. Huss, E. Johns, F.J. Millero, K. Lee, D. Frazel, D. Wisegarver, D.
Greeley, F. Menzia, M. Lamb, G. Berberian, and L.D. Moore. Chemical and
hydrographic profiles and underway measurements from the eastern North
Atlantic during July and August of 1993. NOAA Data Report, ERL
AOML-32 (PB98-131865), 82 pp. (1998).
From July 4-August 30, 1993, the National Oceanic and Atmospheric
Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES)
and Radiatively Important Trace Species (RITS) programs participated in
an oceanographic research cruise aboard the NOAA ship Malcolm
Baldrige. The objectives of the OACES component were to determine
the source and sink regions of CO2 in the equatorial and
North Atlantic during the summer and to establish a baseline of total
carbon inventory in the region. Data were collected from 5°S to
Iceland along a nominal longitude of 20°W. This report presents only
the OACES-related data from legs 1, 2A, and 2B, including hydrography,
nutrients, carbon species, dissolved oxygen, total inorganic carbon,
chlorofluorocarbons, total alkalinity, pH, and salinity. Included are
contour plots of the various parameters and descriptions of the sampling
techniques and analytical methods used in data collection.
Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark. A
new look at the diurnal variation of global oceanic precipitation from
the ocean TOPography EXperiment (TOPEX) and the TOPEX Microwave
Radiometer (TMR). International Journal of Remote Sensing,
19(1):171-180 (1998).
New results on the diurnal variation of global oceanic precipitation are
obtained by using one year's TOPEX (ocean TOPography EXperiment) and TMR
(TOPEX Microwave Radiometer) data, derived from the dual-frequency (Ku
and C band) capacity of the altimeter and the non-Sun-synchronous orbit
of the satellite. The diurnal variation is characterized by a
three-maximum structure which peaks at 00:00, 08:00, and 16:00 local
time. The midnight-morning-afternoon maxima and dawn-noon-evening minima
pattern seems to correlate with the results of most previous studies and
to offer a unified picture of the diurnal variation of oceanic rainfall.
A slight daytime (06:00-18:00) preference of oceanic precipitation
appears to be significant in all seasons with the day/night ratio varying
from 1.032 to 1.141 and the annual mean being 1.082. Examination of the
geographical distribution of the timing of diurnal variation shows that
the majority of the world oceans favor an afternoon maximum and an
evening minimum. Moreover, the northern hemisphere is more coherent in
reaching its maximum, while the southern hemisphere in reaching its
minimum. In addition, the mechanisms responsible for the diurnal
variations are discussed.
Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark.
Identification of possible wave damping by rain using TOPEX and TMR data.
Remote Sensing of Environment, 63(1):40-48 (1998).
A global picture of wave damping by rain (WDBR), a phenomenon familiar to
seafarers for centuries, has been so far unavailable owing to the fact
that neither rules nor tools exist for its systematic measurement. The
situation has changed following the launch of the first dual-frequency
(5.3 GHz and 13.6 GHz) radar altimeter TOPEX, along with the
three-frequency (18 GHz, 21 GHz, and 37 GHz) radiometer TMR (TOPEX
Microwave Radiometer). In this study, a scheme for detecting possible
WDBR using TOPEX/TMR data is proposed. The geographical distribution of
identified WDBR is consistent with the simultaneous presence of high sea
state and intensive rainfall. Frequent occurrences of WDBR are observed
in the midlatitude of the two hemispheres, particularly in the Pacific
Ocean. In contrast, WDBR rarely occurs in the majority of the tropical
and subtropical oceans. The global seasonality of WDBR is found to be
weak as a result of the hemispheric phase opposition of sea state and
rainfall in their annual variations. Knowledge of spatial distribution
and temporal variation of WDBR is useful in dealing with potential
systematic biases in satellite wind and wave measurements due to rain/sea
interaction. It would have been interesting to compare the WDBR with
coincident estimates of global rainfall from the SSM/I (Special Sensor
Microwave/Imager).
Cione, J.J., and P.G. Black. Surface thermodynamic observations within
the tropical cyclone inner core. Preprints, Symposium on Tropical
Cyclone Intensity Change, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 141-145 (1998).
No abstract.
Cione, J.J., S. Raman, L.J. Pietrafesa, R.A. Neuherz, K. Keeter, and X.
Li. The use of pre-storm low-level baroclinicity in determining and
implementing the Atlantic surface cyclone intensification index.
Boundary Layer Meteorology, 89:211-224 (1998).
The lateral motion of the Gulf Stream off the eastern seaboard of the
United States during the winter season can act to dramatically enhance
the low level baroclinicity within the coastal zone during periods of
offshore cold advection. The relative close proximity of the Gulf Stream
current off the mid-Atlantic coast can result in the rapid and intense
destabilization of the marine atmospheric boundary layer directly above
and shoreward of the Gulf Stream within this region. This airmass
modification period oftentimes precedes either wintertime coastal
cyclogenesis or the cyclonic re-development of existing mid-latitude
cyclones. A climatological study investigating the relationship between
the severity of the pre-storm, cold advective period, and subsequent
cyclogenic intensification was undertaken by Cione et al. in 1993.
Findings from this study illustrate that the thermal structure of the
continental airmass, as well as the position of the Gulf Stream front
relative to land during the pre-storm period (i.e., 24-48 h prior
to the initial cyclonic intensification), are linked to the observed rate
of surface cyclonic deepening for storms that either advected into or
initially developed within the Carolina-southeast Virginia offshore
coastal zone. It is a major objective of this research to test the
potential operational utility of this pre-storm low level baroclinic
linkage to subsequent cyclogenesis in an actual National Weather Service
(NWS) coastal winter storm forecast setting. The ability to produce
coastal surface cyclone intensity forecasts recently became available to
North Carolina State University researchers and NWS forecasters. This
statistical forecast guidance utilizes regression relationships derived
from a nine-season (January 1982- April 1990), 116-storm study conducted
by Cione et al. (1993). During the period between February 1994 and
February 1996, the Atlantic Surface Cyclone Intensification Index (ASCII)
was successfully implemented in an operational setting by the NWS at the
Raleigh-Durham forecast office for 10 winter storms. Analysis of these
ASCII forecasts will be presented.
Crane, M.L. Project ACCESS: Community coastal monitoring for year 2007.
Earth System Monitor, 8(4):12-16 (1998).
No abstract.
Donelan, M.A., H.C. Graber, S. Ataktürk, W.M. Drennan,, E.A. Terray, and
K.B. Katsaros. Marine flux-profile relations from an air-sea interaction
spar buoy. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February
9-13, 1998. Supplement to EOS, Transactions, American Geophysical
Union, 79(1):OS99, OS31J-09 (1998).
During the Spring of 1997, the Air Sea Interaction Spar (ASIS) buoy was
deployed in the northeastern Gulf of Mexico. Continuous data on profiles of
wind speed, temperature, and humidity were obtained with concurrent wind
stress, heat flux, and wave directional properties. This paper examines
the flux-profile relations and the effect of non-local or non-equilibrium
wave fields on them.
Doney, S.C., J.L. Bullister, and R.H. Wanninkhof. Climatic variability
in upper ocean ventilation rates diagnosed using chlorofluorocarbons.
Geophysical Research Letters, 25(9):1399-1402 (1998).
The chlorofluorocarbon CFC-12 (CCl2-F2) distributions
from two occupations of a meridional hydrographic section in the eastern
North Atlantic are used to describe the oceanic penetration of CFCs and
change in the integrated ventilation patterns over the five years from 1988
to 1993. The CFC-12 water-column inventories increased by 30-40%, despite
a slowing atmospheric growth rate (14%), because of continuing uptake by
undersaturated subsurface water masses whose response is lagged by the
ventilation time-scales. After removing the long-term CFC temporal trend
using a tracer age based normalization technique, we observe a distinct
dipole pattern in upper ocean ventilation, with reduced convection in the
subpolar gyre and enhanced production of saline subtropical underwater in
1993. These differences are discussed in relation to interannual
variability in atmospheric surface forcing, upper ocean anomalies, and
convection patterns associated with the North Atlantic Oscillation.
Duncombe Rae, C., S.L. Garzoli, P. Richardson, and D. Fratantoni. Hydrography
of some rings in the southeast Atlantic. AGU 1998 Ocean Sciences
Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS,
Transactions, American Geophysical Union, 79(1):OS131, OS41D-02 (1998).
Mesoscale rings and eddies in the southeast Atlantic Ocean have three
potential sources: the Brazil-Malvinas Current Confluence, the Agulhas
Current Retroflection, and the South Atlantic Subtropical Front. Previous
hydrographic surveys have identified Agulhas rings and Brazil eddies in the
region of the Cape Basin. During a component cruise of KAPEX (Cape of Good
Hope Experiment), an experiment to track the flow of intermediate water
around the southern tip of Africa and through the Benguela Current, three
large eddies were encountered in the Cape Basin and east of the Mid-Atlantic
Ridge during September 1997. The eddies were detected in satellite altimetry
before the cruise and surveyed with XBT, CTD and LADCP profiles. One of the
rings, closest to the Agulhas retroflection, appeared a typical Agulhas ring
in its first year after shedding, with a single surface isothermal stad of
16.1°C down to 280 m. The ring furthest from the supposed shedding
point exhibited two lenses, 130-210 m and 320-420 m depth, at 15.27°C
and 14.45°C, respectively, in addition to the surface mixed layer,
17.6°C, suggesting an Agulhas ring which had experienced two winter
mixing periods since leaving the retroflection. The middle ring had a stad
of 12.22°C between 440 and 600 m and showed little evidence of
convective overturning events above that level, apart from a surface mixed
layer (160 m, 16.7-16.8°C) which was evident also in the background
water column. The origin, structure, and temperature-salinity characteristics
of these three eddies are examined. It is surmised that these eddies were
shed from the Agulhas retroflection and subsequently modified by atmospheric
cooling, convective overturning during winter, and possibly interaction with
the Subtropical Front.
Dunion, J., S.H. Houston, C. Velden, M.D. Powell, and P.G. Black. Use of
GOES high-density low-level VIS winds to improve the estimation of
tropical cyclone outer wind radii. Minutes, 52nd Interdepartmental
Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of
the Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A72-A87 (1998).
UW-CIMSS recently began providing real-time GOES low-level VIS winds in
the vicinity of tropical cyclones on a demonstrational basis to NOAA's
Hurricane Research Division (HRD). These data were included in many of
HRD's real-time tropical cyclone surface wind analyses which were sent
to NHC forecasters on an experimental basis during 1997. These wind
analyses are used as guidance in their tropical cyclone advisories and
warnings. The satellite observations provide essential coverage in the
periphery of hurricanes where conventional in-situ observations
(e.g., ships, buoys, etc.) are often widely spaced or
non-existent and reconnaissance aircraft do not normally fly. The GOES
VIS winds were adjusted to the surface using a PBL model. These adjusted
data were used in real-time surface wind analyses for Hurricanes Danny
and Erika of 1997 and were available for post-storm analyses in 1996
Hurricanes Edouard, Fran, Hortense, and Lili. The satellite observations
improved the estimation of the 34 kt wind radii in many cases and also
helped place the 50 kt wind radii for some cases. Examples of the impact
of these data on hurricane surface wind analyses will be shown.
Statistics on comparisons (>100 cases) of the adjusted and unadjusted
GOES VIS winds with in-situ surface measurements will be presented.
Also, in some cases GPS-sonde profiles were available in the vicinity of
the GOES VIS winds. Comparisons of these highly detailed soundings with
the satellite winds and their height assignments will be shown. The
potential for further improvement of outer wind radii estimation through
joint use of GOES VIS winds and satellite-based scatterometer surface
winds will be discussed.
Durand, P., H. Dupuis, D. Lambert, B. Bénech, A. Druilhet, K.B.
Katsaros, P.K. Taylor, and A. Weill. Comparison of sea surface flux
measured by instrumented aircraft and ship during SOFIA and SEMAPHORE
experiments. Journal of Geophysical Research,
103(C11):25,125-25,136 (1998).
Two major campaigns (Surface of the Oceans, Fluxes and Interactions with
the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphére,
Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale
(SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were
conducted in 1992 and 1993, respectively, in the Azores region. Among the
various platforms deployed, instrumented aircraft and ship allowed the
measurement of the turbulent flux of sensible heat, latent heat, and
momentum. From coordinated missions we can evaluate the sea surface
fluxes from (1) bulk relations and mean measurements performed aboard the
ship in the atmosphere surface layer and (2) turbulence measurements
aboard aircraft, which allowed the flux profiles to be estimated through
the whole atmospheric boundary layer and therefore to be extrapolated
toward the sea surface level. Continuous ship fluxes were calculated
with bulk coefficients deduced from inertial-dissipation measurements in
the same experiments, whereas aircraft fluxes were calculated with
eddy-correlation technique. We present a comparison between these two
estimations. Although momentum flux agrees quite well, aircraft
estimations of sensible and latent heat flux are lower than those of the
ship. This result is surprising, since aircraft momentum flux estimates
are often considered as much less accurate than scalar flux estimates.
The various sources of errors on the aircraft and ship flux estimates are
discussed. For sensible and latent heat flux, random errors on aircraft
estimates, as well as variability of ship flux estimates, are lower than
the discrepancy between the two platforms, whereas the momentum flux
estimates cannot be considered as significantly different. Furthermore,
the consequence of the high-pass filtering of the aircraft signals on the
flux values is analyzed; it is weak at the lowest altitudes flown and
cannot therefore explain the discrepancies between the two platforms but
becomes considerable at upper levels in the boundary layer. From
arguments linked to the imbalance of the surface energy budget,
established during previous campaigns performed over land surfaces with
aircraft, we conclude that aircraft heat fluxes are probably also
underestimated over the sea.
Eads, L.J., H.A. Friedman, and D.J. Garcia. From humble beginnings as
the Inner City Marine Project to selection as a National School of
Excellence. Preprints, Seventh Symposium on Education, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January
11-16, 1998. American Meteorological Society, Boston, 162-165 (1998).
The evolution of the MAST Academy (Maritime and Science Technology High
School), a Dade County Magnet School of Choice, from its predecessor, the
Inner City Marine Project (ICMP), is described. ICMP originated after
Dade County experienced civil unrest in the Black community in 1984. At
that time, Dr. Linda J. Eads, currently MAST Academy's principal, was
assigned to design a program in maritime education which emphasized
career exploration for minorities. The ICMP operated from the District
Office of the Dade County Public Schools and targeted elementary and
middle schools in the inner city with high minority populations. When
the MAST Academy opened its doors in 1991, the ICMP became the MAST
Academy Outreach Department which continued to provide programs for the
targeted schools. The MAST Academy presently carries on the tradition of
the ICMP by providing high school students with specialized marine-theme
science and technology courses. In 1996, the MAST Academy was selected
as a U.S. Department of Education National Blue Ribbon School of Excellence.
Ellis, G., P. Swart, M. Lutz, C. Alvarez-Zarikian, P. Blackwelder, T.A.
Nelsen, H. Wanless, and J. Trefry. The stable isotope composition of
foraminifera, ostracods, and organic material in a dated core from
Whitewater Bay. Proceedings, 1998 Florida Bay Science Conference,
Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 2
pp. (1998).
No abstract.
Ellsberry, R.L., and F.D. Marks. U.S. Weather Research Program Hurricane
Landfall Workshop Report. Technical Note, NCAR/TN-442, 40 pp. (1998).
No abstract.
Feely, R.A., R.H. Wanninkhof, C.D. Cosca, and K. Lee. The impact of the
1997-1998 El Niņo on the air-sea exchange flux of CO2 in the
oceans. AGU 1998 Fall Meeting, San Francisco, CA, December 6-10,
1998. Supplement to EOS, Transactions, American Geophysical Union,
79(45):F507, OS41H-08 (1998).
As part of the NOAA Ocean Atmosphere Carbon Exchange Study (OACES),
measurements of CO2 partial pressure were made in the atmosphere
and in the surface waters of the central and eastern equatorial Pacific
from 1992 to 1998. Surface water pCO2 data indicate significant
diurnal, seasonal, and interannual variations. The largest variations were
associated with the 1997-98 ENSO event, which reached maximum intensity
in the winter of 1997-1998. The lower surface pCO2 values
during the 1997-98 ENSO period were the result of the combined effects of
both remotely and locally forced physical processes: (1) development of a
low-salinity surface cap as part of the formation of the warm pool in the
western and central equatorial Pacific; and (2) deepening of the
thermocline by propagating Kelvin waves in the eastern Pacific. Both
these processes serve to reduce pCO2 values towards near
equilibrium values at the height of the warm phase of ENSO. These changes
resulted in a lower-than-normal CO2 flux to the atmosphere. The
annual average fluxes indicate that strong ENSOs exchange about 0.3-0.4
GtC/yr to the atmosphere; whereas, during non-El Niņo years the equatorial
Pacific exchanges about 0.9-1.0 GtC/yr to the atmosphere. This difference is
enough to account for approximately one-third of the atmospheric anomaly
during an El Niņo. Our models suggest that this effect occurs in
temperate and polar regions as well. Thus, the ENSO process is the major
controlling factor of the interannual variability of the air-sea exchange
of CO2 in the oceans. During decades dominated by strong ENSO
events, such as this one, as much as 2-3 Gt more C are retained by the oceans
compared with normal decades. Clearly, the equatorial Pacific is a very
important region for studying climate feedbacks of greenhouse warming.
Feely, R.A., R.H. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and
P.P. Murphy. A new automated underway system for making high precision
pCO2 measurements onboard ships of opportunity. Analytica
Chimica Acta, 377:185-191 (1998).
We have developed a new temperature-controlled, automated underway system
for making atmospheric and surface ocean pCO2 measurements
onboard research vessels equipped with an uncontaminated seawater intake
system. Uncontaminated seawater is supplied to a showerhead plexiglass
equilibrator at the rate of approximately 50 liters/minute. After about
3 minutes, the air trapped in the equilibrator is equilibrated with
seawater. This air is sampled six times per hour. In addition,
atmospheric air is sampled three times per hour from the intake on the
bow flagstaff through 3/8" DekabonTM tubing to the underway
system. The CO2 measurements are made with a differential,
non-dispersive, infrared analyzer LiCorTM (model 6252). The
underway system operates on an hourly cycle with the first quarter of each
hour devoted to calibration with three CO2 standards, each
measured for 5 minutes. A second order polynomial calibration curve is
calculated from the voltage values of the standards. The remaining time
in each hour is used to measure equilibrator air (15 min), bow air (15
min), and equilibrator air once again (15 min). To date, we have
successfully used the underway pCO2 system on 12 cruises of
the NOAA Ship Ka'imimoana in the equatorial Pacific. The
analytical precision of the system is approximately 0.3-0.4 ppm for
seawater and for air.
Ffield, A., C.I. Fleurant, R.L. Molinari, and W.D. Wilson. NOAA Ship
Malcolm Baldrige 1995 cruises: MB95-02, MB95-04, and MB95-07
hydrographic data. LDEO-98-1, Technical Report, 310 pp. (1998).
No abstract.
Fleurant, C.I., and R.L. Molinari. Comparison of bottle salinity and
bottle oxygen values from WHP repeat lines I7N, I1W, I8N, and I8S.
International WOCE Newsletter, 33:27-29 (1998).
No abstract.
Franklin, J.L., and M.L. Black. GPS dropwindsonde data in hurricanes.
Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater,
FL, January 26-30, 1998. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A111-A142 (1998).
The 1997 hurricane season was the first with both NOAA WP-3D aircraft
equipped with the new NCAR GPS dropwindsonde system. The GPS sonde
replaces the old Omega-based ODW, in use since the early 80's on the
P-3s. During the season, the first successful dropwindsonde releases (of
any kind) were made in a hurricane eyewall (Guillermo). These were
followed by additional eyewall releases in Hurricane Erika. The wind
profiles show that surface winds in the eyewall may be much higher than
what is typically inferred from flight-level reconnaissance data. Very
strong jets resolved by the GPS dropsondes in and just above the boundary
layer may be indicative of peak surface gusts.
Fratantoni, D.M., P.L. Richardson, C.M. Duncombe Rae, and S.L. Garzoli.
Three warm-core rings in the eastern south Atlantic. AGU 1998 Ocean
Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to
EOS, Transactions, American Geophysical Union, 79(1):OS131, OS41D-04
(1998).
During the September 1997 Benguela Current Experiment, three large (300 km)
anticyclonic rings were identified and surveyed near 30°S in the eastern
South Atlantic. Preliminary analysis suggests that these rings were formed
from the retroflecting Agulhas Current south of Africa. Two of the rings were
observed west of the Walvis Ridge and appear to have been freely translating
for nearly two years. The transport of intermediate water (approximate depth
range 400-1000 m) within Agulhas rings is thought to be an important
interbasin transport pathway associated with the global-scale thermohaline
circulation. Employing an array of Lagrangian floats and drifters, this
experiment and others associated with the U.S., German, and South African
KAPEX (Cape of Good Hope Experiment) program constitute the first direct
examination of this pathway. In-situ hydrographic and direct velocity
measurements were performed aboard the R/V Seward Johnson. Nominal
ring positions were estimated prior to departure using satellite altimetry.
During the cruise intensive shipboard XBT and ADCP surveys revealed the
three-dimensional structure of temperature and velocity associated with each
ring and facilitated a determination of the ring center. Multiple
acoustically-tracked subsurface RAFOS floats (at 700 m depth) and
satellite-tracked surface drifters were then launched near the center of
each ring to measure ring translation and the evolution of core
properties over a two-year period. Additional floats and drifters were
deployed along 30°S and 7°W to characterize the background flow of
surface and intermediate water in the Benguela Current and the eastern
South Atlantic subtropical gyre. In this poster we describe the horizontal
structure of these large (300 km diameter) and energetic (40 cm/s) warm-core
rings using both in-situ and Lagrangian measurements. We present synoptic
plan-view depictions of thermocline depth, upper-ocean velocity, and
integrated heat content for each ring. The scale and intensity of each ring
is discussed in the context of a translation history compiled from archived
TOPEX/Poseidon altimetry. Finally, surface drifter trajectories are used to
assess ring translation and to describe the temporal evolution of azimuthal
velocity structure and intensity.
Friedman, H.A., and D.J. Garcia. Tropical cyclone public awareness
programmes: Preparing for the twenty-first century. Preprints, Seventh
Symposium on Education, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 166-168 (1998).
During the period from 1969 to 1993, a total of 1551 tropical cyclones,
typhoons, and hurricanes occurred worldwide. Literally millions of lives
are affected each year, and billions of dollars are lost as a result of
these storms. At present, we can do little, if anything, to lessen the
occurrence, frequency, or intensity of tropical cyclones, or to influence
their paths. But over the past three decades, significant advances have
been made in mankind's capability to prepare for and mitigate their
damaging effects. Concerted international scientific efforts have resulted
in better understanding the phenomenon of tropical cyclones, their
formation, characteristics, path of movement, and effects. Technical
advances in weather monitoring equipment satellites, computers, improved
radar systems, and other space age meteorological tools enable scientists
today to vigilantly monitor cyclones as they form, track them as they move,
and predict with some accuracy where they are likely to impact on land and
people. Correspondingly, meteorological services in many countries have been
substantially improved in recent years. Cyclone monitoring equipment has
been installed in most cyclone-prone regions of the world. National systems
have been linked to regional and international networks through which
meteorological data is shared and warnings of approaching cyclones conveyed.
In many localities, local communication systems and administrative procedures
have been strengthened to ensure that information about approaching cyclones
is passed to communities most at risk. While great strides have been made in
our ability to understand and live with cyclones, still more must be
done. We must strive to further expand our basic knowledge about tropical
cyclones, upgrade tools needed for weather monitoring and prediction,
improve the warning and communications network, and strengthen meteorological
services. It is a useful reminder that the primary objectives of these varied
activities is to prevent the loss of lives and prevent or minimize property
damage from cyclones. The need for continued effort is reconfirmed by the
deaths and destruction left in the wake of each tropical cyclone that affects
populated areas today; a problem that is likely to continue and increase in
seriousness as coastal populations enlarge. The goal of preventing loss of
life and reducing property damage from tropical cyclones, however, can not
be achieved simply through improved technical and meteorological services.
Accurate prediction and timely notice are critically important, but loss of
life and property can only be minimized if officials and the general public
are knowledgeable of the hazards faced, understand the warnings provided,
and take the proper actions to protect life and property before, during,
and after a cyclone. The process required to achieve a public state of
readiness is commonly referred to as an awareness program. A resource
guide, designed to provide a framework for the development and
implementation of local tropical cyclone awareness programs, will be
discussed. The Internet was used extensively to obtain up-to-date
information on worldwide issues concerning tropical cyclones. The guide's
design encourages interactive use by disaster preparedness officials and
educators at the local level. Questionnaires and community-specific
checklists are provided to elicit local participation in the process of
creating tropical cyclone awareness.
Garcia, D.J., H.A. Friedman, and L.J. Eads. MAST Academy outreach:
Serving the community with marine theme programs. Preprints, Seventh
Symposium on Education, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 169-171 (1998).
The MAST Academy's Outreach Department provides marine theme enrichment
programs which emphasize career opportunities for targeted schools with
high minority enrollments. Enrichment programs include the Land SHARC
(Science Hands-on and Related Careers) and WOW (Weather On Wheels) mobile
laboratories, environmental field trips, internships, and the MAST
Mariners Program, a middle school summer course focused on, but not
exclusively for, minority students. The role of NOAA's Atlantic
Oceanographic and Meteorological Laboratory (AOML) and other outside
agencies in providing school year and summer internships for MAST Academy
students is discussed. Meteorologists from AOML's Hurricane Research
Division serve as advisory board members for the WOW; their contributions
to the program are presented.
Garzoli, S.L., C. Duncombe Rae, D. Fratantoni, G.J. Goni, J. Mantel,
A. Roubicek, P. Fratantoni, and C. Whittle. Benguela Current Experiment.
AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998.
Supplement to EOS, Transactions, American Geophysical Union,
79(1):OS131, OS41D-01 (1998).
Although intermediate water is an important component of the northward-flowing
meridional circulation cell in the Atlantic, the pathways, velocity, and
variability of this water are poorly known. In order to study the northward
flow of intermediate water in the Benguela Current and its extension, a
program was initiated by scientists of WHOI, NOAA/AOML, and Sea Fisheries
(South Africa). The main objective was to obtain the first subsurface
Lagrangian float measurements of the northward flow of intermediate water in t
he eastern South Atlantic and to measure the characteristics of this water.
This program is a component of KAPEX (Cape of Good Hope Experiment), a joint
U.S., Germany, and South Africa effort. During September 1997, we participated
in a cruise aboard the RV Seward Johnson from Cape Town to Recife.
The main objectives of this cruise were: to launch an array of RAFOS floats
and surface drifters; to perform an intensive survey to determine the
characteristics of the flow; and to search for and study Agulhas rings in
the area. Agulhas rings are considered to be one of the main carriers of
Indian Ocean waters into the Atlantic. Hydrographic casts
(CTD-O2) and direct measurements of currents (ADCP/LADCP) were
performed along 30°S (between 14°E and 7°W) and along
7°W (between 33°S and 18°S) to study the characteristics and
paths of the intermediate water flow at the time of deployments. Three
anticyclonic rings were identified through intensive XBT surveys guided by
satellite images of sea surface height. CTD/LADCP stations were performed
and RAFOS floats and drifters launched in a radial from the center of the
rings. The eddies are tentatively identified as being Agulhas rings,
although a deep (600 m), cold (12.2°C), mixed layer in one ring raises
questions about its origin. Thirty-two RAFOS floats and 11 surface drifters
were launched along the sections and in the rings. This poster will provide
an overview of the Benguela Current Experiment and the preliminary results
from the September 1997 cruise.
Goni, G.J., and S.L. Garzoli. Origin and evolution of the Benguela
Current Experiment rings by altimetry. AGU 1998 Ocean Sciences
Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS,
Transactions, American Geophysical Union, 79(1):OS131, OS41D-03 (1998).
Historical hydrographic data is used to compute the mean upper layer
thickness and reduced gravity in the southeastern Atlantic. These parameters,
along with the altimeter-derived sea surface height anomaly, are used to
derive the upper layer thickness of the ocean. This product proved to be an
efficient means to identify and track anticyclonic rings. In September 1997,
as part of the Benguela Current Experiment, a cruise on the R/V Seward
Johnson guided by the TOPEX/POSEIDON product identified and surveyed
three rings. The water mass characteristics of these rings indicate that at
least two of them could have their origin in the Agulhas retroflection. The
third ring has hydrographic characteristics that raise questions about its
origin. This poster shows the results of a study of these rings based on
altimetry. Synoptic maps of the upper layer thickness are analyzed to
determine the trajectories of the rings in the region for a period of two
years previous to the Benguela Current Experiment. The origins and evolution
of the three rings observed during the September 1997 cruise are established
and discussed. The translation velocity, available potential energy, and heat
content are calculated from the altimeter data. A comparison between the
shipboard and altimeter-derived values of the upper layer thickness is also
presented.
Goodwin, K.D., J.K. Schaefer, and R.S. Oremland. Bacterial oxidation of
dibromomethane and methyl bromide in natural waters and enrichment
cultures. Applied and Environmental Microbiology, 64(12):4629-4636
(1998).
Bacterial oxidation of 14CH2Br2 and
14CH3Br was measured in freshwater, estuarine,
seawater, and hypersaline-alkaline samples. In general, bacteria from the
various sites oxidized similar amounts of
14CH2Br2 and comparatively less
14CH3Br. Bacterial oxidation of
14CH3Br was rapid in freshwater samples compared to
bacterial oxidation of 14CH3Br in more saline
waters. Freshwater was also the only site in which methyl
fluoride-sensitive bacteria (e.g., methanotrophs or nitrifiers)
governed brominated methane oxidation. Half-life calculations indicated
that bacterial oxidation of CH2Br2 was potentially
significant in all of the waters tested. In contrast, only in freshwater
was bacterial oxidation of CH3Br as fast as chemical removal.
The values calculated for more saline sites suggested that bacterial
oxidation of CH3Br was relatively slow compared to chemical
and physical loss mechanisms. However, enrichment cultures demonstrated
that bacteria in seawater can rapidly oxidize brominated methanes. Two
distinct cultures of nonmethanotrophic methylotrophs were recovered; one
of these cultures was able to utilize CH2Br2 as a
sole carbon source, and the other was able to utilize CH3Br
as a sole carbon source.
Graber, H.C., M.A. Donelan, S. Atakturk, W.M. Drennan, and K.B. Katsaros.
Evaluation of NSCAT scatterometer winds with wind stress measurements in
the Gulf of Mexico. AGU 1998 Fall Meeting, San Francisco, CA,
December 6-10, 1998. Supplement to EOS, Transactions, American
Geophysical Union, 79(45):F417, OS72G-03 (1998).
Wind vectors and radar backscatter observed by the NASA scatterometer (NSCAT)
are compared with wind and wind stress measurements from an air-sea
interaction spar (ASIS) buoy and wind measurements from a nearby NDBC discus
buoy. ASIS is a new autonomous spar buoy designed to permit long-term
measurements of interfacial processes. During a two-month deployment in the
Gulf of Mexico in April 1997, the buoy experienced several fronts associated
with rapid changes in wind speed and direction. The ASIS buoy was equipped
for motion-corrected measurements of the wind stress vector, as well as high
resolution wave directional properties. These are used to explore wind and
backscatter measurements of scatterometers. Time difference and spatial
separation between NSCAT and buoy observations were limited to less than 30
minutes and 25 km, respectively.
Gray, W.M., C.W. Landsea, J.A. Knaff, P.W. Mielke, and K.J. Berry.
Verification of the 1997 seasonal hurricane forecasts and a prediction
for 1998. Minutes, 52nd Interdepartmental Hurricane Conference,
Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator
for Meteorological Services and Supporting Research, Washington, D.C.,
A331-A338 (1998).
No abstract.
Hacker, E., E. Firing, W.D. Wilson, and J.C. Kindle. Evidence for a North
Equatorial Countercurrent in the eastern Indian Ocean during the northeast
monsoon. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February
9-13, 1998. Supplement to EOS, Transactions, American Geophysical
Union, 79(1):OS75, OS21J-02 (1998).
Data collected during February and March 1995 as part of the WOCE
Hydrographic Program Expedition in the Indian Ocean provide evidence for
an eastward-flowing countercurrent, a possible North Equatorial
Countercurrent (NECC), extending from 80°E south of Sri Lanka to
about 92°E. The current is associated with a local surface salinity
maximum (34.5 psu) representing its probable northwest Indian Ocean source.
At 80°E, the combination of shipboard and lowered acoustic Doppler
current profiler (ADCP) data shows weak flow to the east between 2°N
and 2.8°N near the surface, with flow to the east extending from
1.5°N to 4°N at a depth of 100 m. The eastward flow is imbedded
in a westward flow of lower salinity water extending from 3°S to
6°N. The westward flow represents a combination of the outflow of
fresher, surface Bay of Bengal water and westward return flow of the
eastward-flowing South Equatorial Countercurrent water. At 92°E, the
NECC is part of an intense circulation feature with eastward flow extending
from 3°N to 6°N and peak speed of 0.8 m/s. NOAA data from the
repeat hydrographic line along 80°E during late October 1995, during
the monsoon transition period, show evidence of a weak eastward flow in the
upper 100 m between 4°N to 5°N imbedded in a broader westward flow
between 1°N and 6°N. The observations are compared to model
circulation features from the NRL high-resolution, three-layer, non-linear,
model forced by ECMWF winds. Although the NRL model does not show an NECC
south of Sri Lanka, it does show a weak countercurrent trough further to the
east between 4°N and 7°N. The temporal and spatial smoothing of
historical data products may be the reason that the NECC has not been
reported previously.
Hansen, D.V., and M.S. Swenson. Application of oceanic heat budgets to
evaluation of surface heat flux climatologies. Proceedings, First
International Conference on Reanalyses, Washington, D.C., October
27-31, 1997. World Climate Research Programme, 40 (1998).
We are using the extensive WOCE/TOGA data sets from drifting buoys and
VOS/XBT measurements for quantification of climatological heat budget
processes in the equatorial cold tongue and NECC regions of the eastern
tropical Pacific Ocean. One interesting application of the results is in
their implication for the net surface heat flux. Early results suggest
that the heat flux climatology generated from the NCEP/NCAR Reanalysis
Project is superior to other popular climatologies. A major factor in the
improvement appears to be the annual cycle of downward shortwave radiation.
Hasler, A.F., K. Palaniappan, C. Kambhammetu, P.G. Black, E.W. Uhlhorn,
and D. Chesters. High-resolution wind fields within the inner core and
eye of a mature tropical cyclone from GOES 1-min images. Bulletin of
the American Meteorological Society, 79(11):2483-2496 (1998).
Mesoscale wind fields have been determined for a mature hurricane with
high spatial and temporal resolution, continuity, and coherency. These
wind fields, near the tropopause in the inner core and at low levels
inside the eye, allow the evolution of mesoscale storm features to be
observed. Previously, satellite-derived winds near hurricanes have been
determined only at some distance from the eye over a typical time period
of 1V2 h. Hurricane reconnaissance aircraft take 30 min to 1 h to
complete an inner-core pattern. With the long observation periods of
these previous methods, steady-state conditions must be assumed to give a
complete description of the observed region. With the advent of 1-min
interval imagery, and fourfold improvement of image dynamic range from
NOAA's current generation of GOES satellites, there is a new capability
to measure inner-core tropical cyclone wind fields near the tropopause
and within the eye, enabling mesoscale dynamical processes to be
inferred. These measurements give insights into the general magnitude and
structure of the hurricane vortex, along with very detailed measurements
of the cloud-top wind's variations in response to convective outbursts.
This paper describes the new techniques used to take advantage of the
GOES satellite improvements that, in turn, allowed the above innovations
to occur. The source of data for this study is a nearly continuous 12-h
sequence of 1-min visible images from NOAA GOES-9 on 6 September 1995.
These images are centered on Hurricane Luis with maximum winds of 120 kt
(CAT4) when it was 250 km northeast of Puerto Rico. A uniform
distribution of long-lived cirrus debris with detailed structure is
observed in the central dense overcast (CDO), which has been tracked
using the 1-min images. The derived wind field near the tropopause at
approximately 15 km in the CDO region has a strong closed circulation
with speeds up to 25 m s-1, which pulses in response to the
convective outbursts in the eyewall. Cloud displacements are computed at
every pixel in every image, resulting in a quarter-million uVv winds in
each of 488 hurricane images observed at 1- to 4-min intervals over 12 h.
For analysis and presentation, these ultradense wind fields are reduced to
8- or 16-km grids using a 7-min time base by smoothing displacement vectors
in space and time. Cloud structures were tracked automatically on a
massively parallel processing computer, but with manual spot-checking.
Manual tracking has been used to follow CDO structure over long time
periods, up to 90 min for a small test sample. Cloud tracking for the
wind fields presented here is accomplished using a Massively Parallel
Semi-Fluid Motion Analysis (MPSMA) automatic technique. This robust
deformable surface-matching algorithm has been implemented on the
massively parallel Maspar supercomputer. MPSMA automatic tracking
typically follows a feature for 7 min. For this time base the error of
these winds is estimated to be 1.5 m s-1. However, systematic
navigation and height assignment errors in the moderately sheared hurricane
environment must still be considered. Spatial and temporal smoothing of
the wind field have been performed to reduce systematic navigation errors
and small-scale turbulent noise. The synthesis used here to compute the
wind fields gives an order of magnitude reduction in the amount of data
presented compared to the amount of data processed. Longer tracking could
give higher accuracy but would smooth out the smaller-scale spatial and
temporal features that appear dynamically significant. The authors
believe that the techniques described in this paper have great potential
for further research on tropical cyclones and severe weather as well as
in operational use for nowcasting and forecasting. United States and
foreign policymakers are urged to augment the GOES, GMS, FY2, and
Meteosat geostationary satellite systems with dual imaging systems such
that 1-min observations are routinely taken.
Hendee, J.C. An expert system for marine environmental monitoring in the
Florida Keys National Marine Sanctuary and Florida Bay. Proceedings,
2nd International Conference on the Coastal Environment, Cancun,
Mexico, September 8-10, 1998. Computational Mechanics Publications/WIT
Press, Southampton, 57-66 (1998).
The National Oceanic and Atmospheric Administration's (NOAA, U.S.
Department of Commerce) Atlantic Oceanographic and Meteorological
Laboratory (AOML) works cooperatively with the Florida Institute of
Oceanography (FIO) in the implementation of the SEAKEYS (Sustained
Ecological Research Related to Management of the Florida Keys Seascape)
network, which is situated along 220 miles of coral reef tract within the
Florida Keys National Marine Sanctuary (FKNMS). This network is itself
actually an enhanced framework of seven Coastal-Marine Automated Network
(C-MAN) stations for long-term monitoring of meteorological parameters
(wind speed, wind gusts, air temperature, barometric pressure, relative
humidity). To the C-MAN network, SEAKEYS adds oceanographic parameters
(sea temperature, photosynthetically active radiation, salinity,
fluorometry, optical density) to the stations. As a recent enhancement
to the SEAKEYS network, an expert system shell is being employed to
provide daily interpretations of near real-time acquired data for the
benefit of scientists, fishermen, and skin divers. These interpretations
are designed to be automatically emailed to Sanctuary managers and to the
FIO maintainers of the network. The first set of interpretations include
those dealing with environmental conditions conducive to coral bleaching.
Other marine environmental interpretations are slated to follow.
Hendee, J.C., C. Humphrey, and T. Moore. A data-driven expert system for
producing coral bleaching alerts. Proceedings, 7th International
Conference on the Development and Application of Computer Techniques to
Environmental Studies, Las Vegas, Nevada, November 10-12, 1998.
Computational Mechanics Publications/WIT Press, Southampton, 139-147
(1998).
As a recent enhancement to the SEAKEYS (Sustained Ecological Research
Related to Management of the Florida Keys Seascape) environmental
monitoring network, an expert system shell was employed to provide daily
interpretations of near real-time acquired combinations of meteorological
and oceanographic parameters as they meet criteria generally thought to
be conducive to coral bleaching. These interpretations were
automatically posted to the World-Wide Web and emailed to Florida Keys
National Marine Sanctuary managers and scientists so they could witness
and study bleaching events as they might happen, and so that a model
could be developed with greater precision in identifying physical factors
conducive to coral bleaching. The expert system, as a model, was
successful in showing that certain assumptions by experts regarding
coral bleaching apparently do not hold at Sombrero Reef.
Henderson-Sellers, A., H. Zhang, G. Berz, K. Emanuel, W. Gray, C.W.
Landsea, G. Holland, J. Lighthill, S.-L. Shieh, P. Webster, and K.
McGuffie. Tropical cyclones and global climate change: A post-IPCC
assessment. Bulletin of the American Meteorological Society,
79(1):19-38 (1998).
The very limited instrumental record makes extensive analyses of the
natural variability of global tropical cyclone activities difficult in
most of the tropical cyclone basins. However, in the two regions where
reasonably reliable records exist (the North Atlantic and the western
North Pacific), substantial multidecadal variability (particularly for
intense Atlantic hurricanes) is found, but there is no clear evidence of
long-term trends. Efforts have been initiated to use geological and
geomorphological records and analysis of oxygen isotope ratios in
rainfall recorded in cave stalactites to establish a paleoclimate of
tropical cyclones, but these have not yet produced definitive results.
Recent thermodynamical estimation of the maximum potential intensities
(MPI) of tropical cyclones shows good agreement with observations.
Although there are some uncertainties in these MPI approaches, such as
their sensitivity to variations in parameters and failure to include some
potentially important interactions such as ocean spray feedbacks, the
response of upper-oceanic thermal structure and eye and eyewall
dynamics do appear to be an objective tool with which to predict
present and future maxima of tropical cyclone intensity. Recent studies
indicate the MPI of cyclones will remain the same or undergo a modest
increase of up to 10%-20%. These predicted changes are small compared
with the observed natural variations and fall within the uncertainty
range in current studies. Furthermore, the known omissions (ocean spray,
momentum restriction, and possibly also surface to 300-hPa lapse rate
changes) could all operate to mitigate the predicted intensification. A
strong caveat must be placed on analysis of results from current GCM
simulations of the "tropical-cyclone-like" vortices. Their realism, and
hence prediction skills (and also that of "embedded" mesoscale models),
is greatly limited by the coarse resolution of current GCMs and the
failure to capture environmental factors that govern cyclone intensity.
Little, therefore, can be said about the potential changes of the
distribution of intensities as opposed to maximum achievable intensity.
Current knowledge and available techniques are too rudimentary for
quantitative indications of potential changes in tropical cyclone
frequency. The broad geographic regions of cyclogenesis and, therefore,
also the regions affected by tropical cyclones are not expected to change
significantly. It is emphasized that the popular belief that the region
of cyclogenesis will expand with the 26 C SST isotherm is a fallacy. The
very modest available evidence points to an expectation of little or no
change in global frequency. Regional and local frequencies could change
substantially in either direction, because of the dependence of cyclone
genesis and track on other phenomena (e.g., ENSO) that are not yet
predictable. Greatly improved skills from coupled global ocean-atmosphere
models are required before improved predictions are possible.
Hitchcock, G.L., C. Wiebinga, and P.B. Ortner. CTD hydrographic data
from the Global Ocean Ecosystem Dynamics (GLOBEC) Indian Ocean cruises.
University of Miami Technical Report, 97-006, 69 pp. (1998).
No abstract.
Hitchcock, G., G.A. Vargo, T. Lee, E. Johns, E. Williams, and J. Jurado.
The influence of circulation on nutrient distributions in western Florida
Bay. Proceedings, 1998 Florida Bay Science Conference, Miami,
Florida, May 12-14, 1998. Florida Sea Grant College Program, 98-99 (1998).
No abstract.
Hood, T., C. Alvarez-Zarikian, P. Blackwelder, P. Swart, T.A. Nelsen,
H.R. Wanless, J.H. Trefry, and L. Tedesco. The sediment record as a
monitor of natural and anthropogenic changes in the lower
Everglades/Florida Bay ecosystem. Proceedings, 1998 Florida Bay
Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea
Grant College Program, 33-34 (1998).
No abstract.
Houston, S.H., and M.D. Powell. Reconstruction of surface wind fields
for hurricanes affecting Florida Bay. Preprints, Second Conference on
Coastal Atmospheric and Oceanic Prediction and Processes, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 241-244 (1998).
Hurricanes constitute episodic events which affect the physical and
oceanographic processes within Florida Bay. These effects are manifested
by significant changes in water-levels, waves, currents, and sediment
transport processes. In addition, these storms impact plant and animal
life in the Bay and the surrounding areas. Hurricane wind fields are now
being made available to researchers, such as oceanographers and
biologists, on a Hurricane Research Division World Wide Web site
(http://www.aoml.noaa.gov/hrd). Researchers can use the wind fields to
estimate the potential impacts of future tropical cyclones on the south
Florida ecosystem and especially on Florida Bay. The hurricanes used in
this study were the Labor Day Hurricane of 1935, Donna of 1960, Betsy of
1965, Felix of 1987, and Andrew of 1992. These tropical cyclones
represented vastly different scenarios for the type of event that might
be expected over extreme south Florida. The 1935 hurricane was a category
5 storm and is the most intense hurricane known to have struck the USA.
This hurricane had a relatively small, concentrated wind field when it
crossed the Florida Keys and Florida Bay. Hurricane Donna (1960) was a
category 4 hurricane with a much broader wind field that crossed the Keys
and Bay on a similar track to the 1935 Hurricane. Hurricane Andrew was
a fast moving category 4 hurricane when it struck south Florida recently.
However, its strongest winds covered only a very small area, especially to
the south of the storm track. The direct impact of Andrew on Florida Bay
appears to have been minimal, but decomposing organic storm debris in the
Everglades likely contributed to water quality problems in the Bay.
Houston, S.H., and M.D. Powell. Surface wind field in Florida Bay
hurricanes. Proceedings, 1998 Florida Bay Science Conference,
Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program,
35 (1998).
No abstract.
Houston, S.H., and M.D. Powell. Surface wind fields in hurricanes.
Proceedings, Third International Symposium, Waves '97,
Virginia Beach, VA, November 3-7, 1997. American Society of Civil
Engineers (ASCE), 1391-1399 (1998).
No abstract.
Houston, S.H., and M. D. Powell. The potential impact of GPS sondes in
real-time surface wind analyses for hurricanes. Minutes, 52nd
Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30,
1998. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A-110 (1998).
During the 1996 and 1997 hurricane seasons, GPS sondes were dropped
within the inner core of some tropical cyclones (i.e., Josephine of
1996; Danny, Erika, Guillermo, and Linda of 1997). The data from these
sondes provided some highly detailed boundary layer profiles and surface
measurements of each tropical cyclone's wind and thermodynamic properties
after the fact. During the upcoming 1998 hurricane season, two potential
developments may make the GPS sonde data useful for defining the
hurricane's surface wind structure in real-time: (1) The GPS sonde "temp
drop message" sent from AFRES and NOAA missions in and near hurricanes
(including drops from the NOAA G-IV) may include additional essential
information that will likely enhance the real-time use of these sondes.
For example, the splash location and time are two additional parameters
that may be available in the drop messages. (2) When it is deemed
necessary by NHC for the issuance of warnings and (or) other critical
factors, GPS sondes may be dropped along the flight-track of tasked
reconnaissance flights. These drops have the potential to provide
estimates of the peak surface winds and may help define some of the wind
radii (i.e., 34, 50, and/or 64 kt wind radii) in those quadrants
where the drops are made. This study examines the potential impacts additional
wind and thermodynamic observations from sondes might have on surface
wind analyses in hurricanes, which are currently provided to NHC's
forecasters in real-time by HRD on an experimental basis. Some examples
of post-storm analyses in 1997 hurricanes utilizing these new data in
addition to conventional data sources will be presented and the potential
impacts will be assessed. In addition, some preliminary comparisons of
the boundary layer measurements from GPS sondes with reliable in-situ
surface observations (e.g., buoys, C-MAN's, etc.) of wind,
temperature, and pressure in the vicinity of tropical cyclones will be
shown.
Houston, S.H., M. Lawrence, S. Spisak, and S.T. Murillo. A verification
of National Hurricane Center forecasts of surface wind speed radii in
hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change,
American Meteorological Society 78th Annual Meeting, Phoenix, AZ,
January 11-16, 1998. American Meteorological Society, Boston, 139-140
(1998).
The National Hurricane Center (NHC) issues a position and intensity
forecast every six hours on all tropical cyclones in the Atlantic and
eastern Pacific basins. This forecast is contained in the
forecast/advisory product and includes a forecast of the horizontal
distribution of the surface wind field. This distribution is given as
radii in four quadrants from the center of the tropical cyclone to three
wind speed values: 17.5, 25.7, and 32.9 m s-1 (i.e., 34,
50, and 64 kt, respectively). A set of opportunistic marine observations w
ere collected to determine the wind speed radii from the center of each
tropical cyclone to the observation site. This can be done when a tropical
cyclone's wind field affects a measurement platform with the required
wind speeds. The wind speed radii based on the marine platform data were
used to verify the official NHC radii forecasts described above. The
preliminary results are for 17.5 m s-1 wind speeds and are
based on only 25 cases. Statistics will be presented showing that the
mean absolute error of the 25 cases of verification is about 83 km (45 nm)
at the initial (i.e., 0 h) forecast period and decreases about 25%
by the 36 h forecast. There is a positive bias (the forecasts were larger
than observed) of about 37 km (20 nm) for these cases, which also appears
to decrease with longer forecast periods. The small number of cases limits
our analysis to simple averages. This is the first time that such a data
set has been prepared and that forecasts of tropical cyclone intensity in
terms of wind speed radii have been verified. Details on the method of
verification will be given along with the final statistics of the study,
including 17.5 and 25.7 m s-1 radii verification.
Huang, H., R.E. Fergen, J.R. Proni, and J.J. Tsai. Initial dilution
equations for buoyancy-dominated jets in currents. Journal of Hydraulic
Engineering, 124:105-108 (1998).
Initial dilution of submerged, single, round, buoyancy-dominated jets in
a current is considered. Two simple semi-empirical equations, one for
centerline dilution and the other for minimum surface dilution, are
presented. These equations are derived based on the continuity equation
for the buoyant jet flow with a hypothesis that shear entrainment and
forced entrainment can be added. Available laboratory and field data are
used to determine the constants in the equations. Unlike asymptotic
equations which apply for the limiting flow regimes, the proposed
equations span all flow regimes, from the buoyancy-dominated near field
(BDNF), to the transition, and to the buoyancy-dominated far field
(BDFF), providing continuous predictions for dilutions.
Jameson, A.R., A.B. Kostinski, and R.A. Black. The texture of clouds.
Journal of Geophysical Research-Atmospheres, 103(D6):6211-6220
(1998).
Using a precise definition of clustering, it is shown that in two
tropical cumulus clouds, droplets appear to be bunched over distances
ranging from at least a kilometer or more down to several centimeters. A
statistical framework is proposed for quantifying clustering in terms of
a Poisson probability mixture. While these observations require further
substantiation in many different clouds, droplet clustering may play a
role in diverse phenomena from the coalescence growth of raindrops to the
scattering of radiation by clouds.
Johns, E., and W.D. Wilson. Direct observations of velocity structure in
the passages between the Intra-Americas Sea and the Atlantic Ocean,
1984-1996. Proceedings, Conference on the Transports and Linkages of
the Intra-Americas Sea (IAS), Cozumel, Mexico, November 1-5, 1997.
IOC/IOCARIBE/MMS, 36 (1998).
Shipboard acoustic Doppler current profiler (ADCP) velocity data
collected between 1984 and 1996 in connection with several NOAA research
programs have been used to examine the mean and variability of the
velocity structure within the Straits of Florida, the Northwest
Providence Channel, a northern approach to the Windward Passage, the Mona
and Anegada Passages, and across the eastern Caribbean Sea. Historically,
direct velocity data collection in these important passages between the
Gulf of Mexico, the Caribbean Sea, and the Atlantic Ocean has been very
sparse. Herein, we examine the transport and velocity structure in the
passages using a more complete data set than previously available. This
newer data set allows computation of statistically significant mean and
standard deviations of the transport and velocity fields, and examination
of the temporal (seasonal to interannual) variability of these fields.
Comparison will be made of the mean and varying flow fields with the
results of previous studies and with available time series of regional
forcing functions such as the COADS wind stress data set. Most
importantly, the mean transports should prove useful to numerical
modelers of the Intra-Americas Sea for calibration and refinement of
model boundary conditions.
Johns, E., W.D. Wilson, and T.N. Lee. Interaction of Florida Bay waters
with the Gulf of Mexico and the Atlantic Ocean. Proceedings, 1998
Meeting of the Oceanography Society and the Intergovernmental
Oceanographic Commission on Coastal and Marginal Seas, Paris, France,
June 1-4, 1998. Oceanography, 11, No. 2 supplement, 38 (1998).
As part of the South Florida Ecosystem Restoration program, an
observational study of the circulation of Florida Bay and its connection
with the surrounding waters of the Gulf of Mexico, the southwest Florida
shelf, and the Atlantic Ocean is presently underway. Measurement systems
include moored arrays equipped with current meters, bottom pressure
sensors and conductivity-temperature sensors, satellite-tracked surface
drifters, and shipboard ADCP. Bimonthly interdisciplinary surveys include
continuous thermosalinograph observations of surface salinity,
temperature, and fluorescence. Early results show that there is a net
southeastward flow of 1 to 4 cm/s which transports waters from the Gulf
of Mexico and the Everglades across western Florida Bay and through the
channels of the Florida Keys, on a time scale of 1 to 3 months depending
on local wind forcing. This net flow, with a volume transport of 1000 to
2000 m3/s, has the potential to deliver harmful algal blooms
and excess nutrients out to the environmentally sensitive coral reefs of
the Florida Keys National Marine Sanctuary. The ongoing study now focuses
on refining and quantifying the flow between the Gulf of Mexico, Florida
Bay, and the Atlantic and its response to seasonal and episodic meteorological
forcing. In addition, new emphasis is placed on examining the fate of the
freshwater river discharges from the Everglades into the Gulf of Mexico,
and the relation of the river plume dispersion to regional wind and
rainfall distributions.
Kaplan, J., and M. DeMaria. Climatological and synoptic characteristics
of rapidly intensifying tropical cyclones in the North Atlantic basin.
Preprints, Symposiuim on Tropical Cyclone Intensity Change, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January
11-16, 1998. American Meteorological Society, Boston, 119-123 (1998).
No abstract.
Katsaros, K.B. Microwave remote sensing with radiometers. In Remote
Sensing of the Pacific Ocean by Satellites, R.A. Brown (ed.).
Southwood Press, Marrickville, Australia, 13-15 (1998).
No abstract.
Katsaros, K.B. Turbulent flux of water vapor in relation to the wave
field and atmospheric stratification. In Physical Processes in Lakes
and Oceans, J. Imberger (ed.). Coastal and Estuarine Studies, Volume
54, American Geophysical Union, 37-46 (1998).
Field measurements of evaporation rate, momentum, and heat flux together
with mean meteorological quantities allow inferences to be drawn
concerning the sheltering of air in the troughs of large waves and the
possible differences between moisture and heat fluxes in very stable
regimes over water. Interpretation of the measurements in terms of the
processes near the surface are based on the Monin-Obukhov similarity
theory. The results presented indicate that in the presence of water
waves and under strong atmospheric stable stratification further
detailed measurements are needed to fully explain the processes at work
and that Monin-Obukhov theory may need modification.
King, D.B., S.A. Yvon-Lewis, S.A. Montzka, and J.H. Butler. Dependence
of trace halocarbon saturation anomalies on sea-surface properties.
AGU 1998 Fall Meeting, San Francisco, CA, December 6-10, 1998.
Supplement to EOS, Transactions, American Geophysical Union,
79(45):F429, OS11F-02 (1998).
If global warming results in an increase in sea surface temperature, the
saturations and air-sea fluxes of trace gases in the surface ocean are also
likely to change. Since many of these gases are involved in tropospheric
chemistry, global warming, and even the destruction of stratospheric ozone,
it would be useful to predict how their fluxes into and out of the oceans
might be altered as a result of climate change. Although such an effort
requires an intricate examination of biological and chemical activity, a
first step in understanding the nature of this behavior is mapping their
degree of saturation in waters of different temperature, location, and
chemical properties. As part of a joint expedition to the Atlantic and
Pacific Oceans, we have measured the saturation anomalies of a number of
trace gases in surface waters in an effort to evaluate the dependence of
their air-sea fluxes upon sea-surface properties. Data collected on this
cruise demonstrate that the fates of some compounds may be easier to
predict than others. Some gases are conservative in seawater, and their
integrated fluxes over a year are small. Other gases are consumed by
chemical reaction. For example, methyl chloroform, an anthropogenic
trace gas that is no longer emitted in significant amounts to the
atmosphere, was undersaturated in warm surface waters, but not in cooler
waters, which is consistent with enhanced hydrolysis in warmer water.
Other compounds, such as the methyl halides, are produced and consumed by
a variety of processes. Methyl bromide was generally undersaturated at
sea surface temperatures above 25°C, becoming supersaturated at colder
temperatures. Yet, there were several regions where it was
supersaturated in the warmer waters, indicating that the concentration of
this gas in the surface ocean is controlled by more than just chemical
removal. Methyl chloride and methyl iodide were supersaturated for the
duration of the cruise, with the degree of saturation decreasing with
surface water temperature. If the saturation of these compounds were
controlled solely by chemical removal, the trend would have been the
opposite of what was observed. We relate the measured saturation
anomalies to pertinent sea-surface properties, including those measurable
by satellite (e.g., SeaWiFS), to see if any useful correlations
can be derived.
Landsea, C.W., and R.A. Pielke. Trends in U.S. hurricane losses, 1925
1995. Preprints, Ninth Symposium on Global Change Studies, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 210-212 (1998).
No abstract.
Landsea, C.W., J. Kaplan, and M. DeMaria. The differing roles of the
large-scale environment in the intensity changes of recent Atlantic
hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change,
American Meteorological Society 78th Annual Meeting, Phoenix, AZ,
January 11-16, 1998. American Meteorological Society, Boston, 113-114
(1998).
No abstract.
Landsea, C.W., N. Nicholls, and J. Gill. Australian region tropical
cyclones: Recent trend and interannual predictions. Preprints, Ninth
Conference on Interaction of the Sea and Atmosphere, American
Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 1-4 (1998).
No abstract.
Landsea, C.W., G.D. Bell, W.M. Gray, and S.B. Goldenberg. The extremely
active 1995 Atlantic hurricane season: Environmental conditions and
verification of seasonal forecasts. Monthly Weather Review,
126(5):1174-1193 (1998).
The 1995 Atlantic hurricane season was a year of near-record hurricane
activity with a total of 19 named storms (average is 9.3 for the base
period 1950-1990) and 11 hurricanes (average is 5.8), which persisted for
a total of 121 named storm days (average is 46.6) and 60 hurricane days
(average is 23.9), respectively. There were five intense (or major)
Saffir-Simpson category 3, 4, or 5 hurricanes (average is 2.3 intense
hurricanes) with 11.75 intense hurricane days (average is 4.7). The net
tropical cyclone activity, based upon the combined values of named
storms, hurricanes, intense hurricanes and their days present, was 229%
of the average. Additionally, 1995 saw the return of hurricane activity
to the deep tropical latitudes: seven hurricanes developed south of
25°N (excluding all of the Gulf of Mexico) compared with just one
during all of 1991-1994. Interestingly, all seven storms that formed
south of 20°N in August and September recurved to the northeast
without making landfall in the United States. The sharply increased
hurricane activity during 1995 is attributed to the juxtaposition of
virtually all of the large-scale features over the tropical North Atlantic
that favor tropical cyclogenesis and development. These include extremely
low vertical wind shear, below-normal sea level pressure, abnormally warm
ocean waters, higher than average amounts of total precipitable water, and
a strong west phase of the stratospheric quasi-biennial oscillation. These
various environmental factors were in strong contrast to those of the
very unfavorable conditions that accompanied the extremely quiet 1994
hurricane season. The favorable conditions for the 1995 hurricane season
began to develop as far back as the previous winter. Their onset well
ahead of the start of the hurricane season indicates that they are a
cause of the increased hurricane activity, and not an effect. The extreme
duration of the atmospheric circulation anomalies over the tropical North
Atlantic is partly attributed to a transition in the equatorial Pacific
from warm episode conditions (El Niņo) to cold episode conditions (La
Niņa) prior to the onset of the hurricane season. Though the season as a
whole was extremely active, 1995's Atlantic tropical cyclogenesis showed
a strong intraseasonal variability with above-normal storm frequency
during August and October and below normal for September. This
variability is likely attributed to changes in the upper-tropospheric
circulation across the tropical North Atlantic, which resulted in a
return to near-normal vertical shear during September. Another
contributing factor to the reduction in tropical cyclogenesis during
September may have been a temporary return to the near-normal SSTs across
the tropical and subtropical North Atlantic, caused by the enhanced
tropical cyclone activity during August. Seasonal hurricane forecasts for
1995 issued at Colorado State University on 30 November 1994, 5 June
1995, and 4 August 1995 correctly anticipated an above-average season,
but underforecast the extent of the extreme hurricane activity.
Landsea, C.W., W.M. Gray, J.A. Knaff, P.W. Mielke, and K.J. Berry.
Verification of the 1997 seasonal hurricane forecast and a prediction for
1998. Minutes, 52nd Interdepartmental Hurricane Conference,
Clearwater, FL, January 27, 1998. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A-331-A-338 (1998).
The forecast for the 1998 Atlantic hurricane season issued by Dr. Bill
Gray and collaborators (including myself) will be discussed. This
prediction, to be issued in early December 1997, will be updated in early
April, early June, and early August. Uncertainties in the predictors,
especially in El Niņo, Atlantic sea surface temperatures, and Sahel
rainfall, will be discussed in how they may impact the number and
intensity of tropical cyclones this year. I will also analyze and
discuss the performance of the 1997 forecasts.
Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely. Low
interannual variability in recent oceanic uptake of atmospheric carbon
dioxide. Nature, 396(12):155-158 (1998).
An improved understanding of the partitioning of carbon between the
atmosphere, terrestrial biosphere, and ocean allows for more accurate
predictions of future atmospheric CO2 concentrations under
various fossil-fuel CO2 emission scenarios. One of the more
poorly quantified relevant processes is the interannual variability in
the uptake of fossil-fuel CO2 from the atmosphere by the
terrestrial biosphere and ocean. Existing estimates, based on atmospheric
measurements, indicate that the oceanic variability is large. Here we
estimate the interannual variability in global net air-sea CO2
flux using changes in the observed wind speeds and the partial pressure of
CO2 (pCO2) in surface seawater and the overlying air.
Changes in seawater pCO2 are deduced from interannual anomalies
in sea surface temperature and the regionally and seasonally varying
temperature-dependence of seawater pCO2, assuming that variations
in sea surface temperature reflect seawater pCO2 changes caused
by thermodynamics, biological processes, and water mixing. The calculated
interannual variability in oceanic CO2 uptake of 0.4 Gt C
yr-1(2 sigma) is much less than that inferred from the analysis
of atmospheric measurements. Our results suggest that variable sequestration
of carbon by the terrestrial biosphere is the main cause of observed
year-to-year variations in the rate of atmospheric CO2
accumulation.
Lee, T.N., E. Johns, W.D. Wilson, and E. Williams. Florida Bay
circulation and exchange study. Proceedings, 1998 Florida Bay Science
Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College
Program, 43-44 (1998).
No abstract.
Marks, F.D., and H.A. Friedman. 1998 Hurricane Field Program Plan.
U.S. Department of Commerce, NOAA/Atlantic Oceanographic and Meteorological
Laboratory, Miami, Florida (published for limited distribution), 144 pp.
(1998).
The objective of the National Oceanic and Atmospheric Administration
(NOAA) hurricane research field program is the collection of descriptive
data that are required to support analytical and theoretical hurricane
studies. These studies are designed to improve the understanding of the
structure and behavior of hurricanes. The ultimate purpose is to develop
improved methods of hurricane prediction. Ten major experiments have
been planned, by principal investigators at the Hurricane Research
Division (HRD)/Atlantic Oceanographic and Meteorological Laboratory
(AOML) of NOAA and the Mission Planning Committee for the National
Aeronautics and Space Administration (NASA) Third Convection and Moisture
Experiment (CAMEX-3), for the 1998 Hurricane Field Program. These
experiments will be conducted with the NOAA/Aircraft Operations Center
(AOC) WP-3D and Gulfstream IV-SP aircraft and the NASA DC-8 and ER-2
aircraft.
Marks, F.D., and L.K. Shay. Landfalling tropical cyclones: Forecast
problems and associated research opportunities. Preprints, 16th
Conference on Weather Analysis and Forecasting, Symposium on the Research
Foci of the U.S. Weather Research Program, American Meteorological
Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 520-523 (1998).
No abstract.
Marks, F.D., L.K. Shay, and PDT-5 (Fifth Prospectus Development Team).
Landfalling tropical cyclones: Forecast problems and associated research
opportunities. Report of the Fifth Prospectus Development Team to the
U.S. Weather Research Program. Bulletin of the American Meteorological
Society, 79(8):305-323 (1998).
The Fifth Prospectus Development Team of the U.S. Weather Research
Program was charged to identify and delineate emerging research
opportunities relevant to the prediction of local weather, flooding, and
coastal ocean currents associated with landfalling U.S. hurricanes
specifically, and tropical cyclones in general. Central to this theme
are basic and applied research topics, including rapid intensity change,
initialization of and parameterization in dynamical models, coupling of
atmospheric and oceanic models, quantitative use of satellite
information, and mobile observing strategies to acquire observations to
evaluate and validate predictive models. To improve the necessary
understanding of physical processes and provide the initial conditions
for realistic predictions, a focused, comprehensive mobile observing
system in a translating storm-coordinate system is required. Given the
development of proven instrumentation and improvement of existing
systems, three-dimensional atmospheric and oceanic data sets need to be
acquired whenever major hurricanes threaten the United States. The
spatial context of these focused three-dimensional data sets over the
storm scales is provided by satellites, aircraft, expendable probes
released from aircraft, and coastal (both fixed and mobile), moored, and
drifting surface platforms. To take full advantage of these new
observations, techniques need to be developed to objectively analyze
these observations, and initialize models aimed at improving prediction
of hurricane track and intensity from global-scale to mesoscale dynamical
models. Multinested models allow prediction of all scales from the
global, which determine long-term hurricane motion to the convective
scale, which affect intensity. Development of an integrated analysis and
model forecast system optimizing the use of three-dimensional
observations and providing the necessary forecast skill on all relevant
spatial scales is required. Detailed diagnostic analyses of these data
sets will lead to improved understanding of the physical processes of
hurricane motion, intensity change, the atmospheric and oceanic boundary
layers, and the air-sea coupling mechanisms. The ultimate aim of this
effort is the construction of real-time analyses of storm surge, winds,
and rain, prior to and during landfall, to improve warnings and provide
local officials with the comprehensive information required for recovery
efforts in the hardest hit areas as quickly as possible.
Masters, J.C., and R.H. Wanninkhof. Continuous pCO2 measurements
as a method to characterize upwelling along the northwestern Arabian Sea
boundary. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February
9-13, 1998. Supplement to EOS, Transactions, American Geophysical
Union, 79(1):OS52, OS21G-11 (1998).
Upwelling zones are identified using surface water pCO2 and other
biogeochemical parameters in the northwestern Arabian Sea based on
observations from May through August 1995. This time frame encompasses
the beginning of the southwest monsoon through the first monsoonal break.
The Ekman dynamics associated with the wind stress create an upwelling
structure along the northwestern boundary of the Arabian Sea. The
characteristics of upwelled water are low temperature, high nutrients,
high dissolved inorganic carbon (DIC), and high pCO2 relative
to the surrounding waters. Each parameter has a unique response time and
can be used to characterize the upwelling zone. An underway monitoring
system collected pCO2 data from the surface water and the marine
boundary air. The pCO2 measurements, taken at 4-minute intervals,
were plotted against the ship track and produced a high-resolution
representation of the upwelling structure, boundaries, and water mass
movement though time. Temperature, salinity, fluorescence, and nitrate
values were used to further define the water mass and upwelling zones.
Satellite sea surface temperature images were used to produce a more
complete two-dimensional picture of the water mass movement on the surface.
When upwelled water reaches the surface, the physical and chemical
characteristics of the water are affected by incident radiation, wind stress,
and photosynthesis. As the primary production consumes nutrients, the
concentration of chlorophyll a increases and pCO2
decreases. The parameters change as a function of the time the water mass
spends on the surface. By the time the upwelled water warms to adjacent
conditions, the pCO2 has decreased but remains elevated
compared to the surrounding waters. The nutrients are depleted and there
are high chlorophyll a concentrations. Thus, in conjunction with
concentrations of chlorophyll a and nutrients, pCO2 can
be used as a non-conservative tracer of an upwelled water mass. The results
show that coastal upwelling took place during the entire five-month period
at approximately 10°N, 51°E, 19°N, 58°E, and 22°N,
59.5°E. During the southwest monsoon, the upwelling in these areas
strengthened, as manifested by lower sea surface temperatures (29°C
in May to 20°C in August) and higher pCO2 (430 ppm to 720
ppm). The mass transport of upwelled water moves offshore in "squirts" or
"jets" as shown by large changes in pCO2 over approximately 20 km
scales. These narrow jets diffuse offshore into a larger surface area and
their pCO2 decreases as a function of time, slower than the time
it takes for the water temperature to equilibrate with its surroundings.
Mayer, D.A., and R.H. Weisberg. El Niño-Southern Oscillation-related
ocean-atmosphere coupling in the western equatorial Pacific. Journal of
Geophysical Research, 103(C9):18,635-18,648 (1998).
Using 43 years of Comprehensive Ocean-Atmosphere Data Set (COADS) and
related data for the period 1950-1992, an examination is made into the
regional dependence of ocean-atmosphere coupling in relation to the El
Niño-Southern Oscillation (ENSO). The cross correlation between sea
surface temperature (SST) and sea level pressure (SLP) anomalies over
the global tropics shows two patterns of significant negative
correlation consistent with a local hydrostatic response of SLP to SST:
(1) the eastern Pacific, where the correlation is symmetric about and
largest on the equator; and (2) the western Pacific, where symmetric
regions of negative correlation are found off the equator, separated by
a region of positive correlation on the equator. Anomalies within these
two patterns vary out of phase with each other. While the SLP anomalies
on both sides of the basin are of similar magnitude, the SST anomalies
in the east are much larger than those in the west. Despite this
disparity in the SST anomaly magnitudes between the eastern and western
Pacific, we argue that the ocean-atmosphere couplings in the western and
west-central Pacific are important for ENSO. The off-equator SST
anomalies in the west enhance the SLP anomalies there and they appear to
initiate easterly wind anomalies over the far western Pacific during the
peak El Niño phase of ENSO. As these easterlies evolve, their
effect upon the ocean tends to oppose that of the westerly wind
anomalies found over the west-central Pacific. These competing effects
suggest a mechanism that may contribute to coupled ocean-atmosphere
system oscillations. The west-central equatorial Pacific (the region
separating the eastern and western patterns), while exhibiting large
momentum and heat flux exchanges, shows minimum correlation between SST
and SLP. Thus, neither the SST and SLP anomaly magnitudes nor the
correlation between them are alone indicative of ocean-atmosphere
coupling, and the regional dependence for such coupling in relation to
ENSO appears more complicated than mechanistic interpretations of ENSO
would suggest.
Mayer, D.A., G.J. Goni, and R.L. Molinari. Comparison of hydrographic
and altimetric estimates of sea level height variability in the Atlantic
Ocean. AGU 1998 Fall Meeting, San Francisco, CA, December 6-10,1998.
Supplement to EOS, Transactions, American Geophysical Union,
79(45):F432, OS12A-06 (1998).
Hydrographic estimates of dynamic height (DH) derived from expendable
bathythermograph (XBT) data and average temperature salinity (TS)
relationships are compared to sea height anomalies (SHA) derived from
TOPEX/Poseidon (T/P) altimeter data along two sections of the Atlantic
Ocean. Our inquiry examines the relationship between the variability of
dynamic effects in the upper 500 m of the water column and SHA over
seasonal to interannual time scales for the period 1993 through 1997. Our
spatial domain extends from 30°S to 50°N. Emphasis is on two
well sampled sections representative of the western and eastern regions
of the Atlantic. Both the XBT and T/P data are matched by time and location
within 2° of latitude by 4° of longitude quadrangles and then
binned by month. The SHA signal is compared to DH derived with respect
to reference depths ranging from 50 m to 500 m. DH is estimated from T/P
data by computing their linear correlations along both sections. The
subtropics show correlations that remain relatively constant throughout
most of the water column. This reveals the dominant effects of seasonal
heating on SHA due to surface fluxes. In contrast, correlations in the
tropics can be sharply depth dependent, suggesting the effects of ocean
dynamics (thermocline depth) on SHA due to the seasonal cycle of the zonal
currents and their system of ridges and troughs. Correlations are
generally significant at the 90% significance level (SL). With a few
exceptions, most of the relationship between SHA and DH is a consequence
of the annual cycle. Correlations degrade well below the 90% SL if the
annual cycle is removed before the correlations are computed. In both
the tropics and subtropics, most of the dynamic height signal can be
accounted for by using reference depths of 500 m. However, the DH does
not fully account for the SHA by a factor of 2 or more in some instances.
This discrepancy can be attributed to factors such as the use of average
historical TS relationships, the spatial averaging within each 2°
by 4° quadrangle, reference depths to only 500 m, and barotropic
effects.
Mayer, D.A., R.L. Molinari, and J.F. Festa. The mean and annual cycle of
upper layer temperature fields in relation to Sverdrup dynamics within
the gyres of the Atlantic Ocean. Journal of Geophysical Research,
103(C9):18,545-18,566 (1998).
Using 28 years of expendable bathythermograph data (1967-1994), we
describe the mean and annual cycle of the upper ocean temperature fields
in the Atlantic from 30°S to 50°N in the context of the
basin-scale wind-driven gyres (Sverdrup stream function field) which
provide a framework for describing the oceanographic measurements. We
examine the circulation field implied by the temperature distributions
which are used as a proxy for the field of mass. Similarities between
the temperature and stream function fields increase with depth. In the
lower to subthermocline depths of the tropical and equatorial gyres, the
zonal currents form a closed circulation. A Southeastward Boundary Current
is suggested near and below 150 m that provides closure for the tropical
gyre, and the equatorial gyre axis is southward of that suggested by the
stream function field. Higher in the water column, the North Equatorial
Countercurrent (NECC) may be a surface manifestation of the North
Equatorial Undercurrent (NEUC) where the latter can be interpreted as the
southern limb of the tropical gyre. Because there are large vertical
shears in the tropics, the equatorial gyre is not clearly indicated in
the vertically integrated temperature field but appears below about 200
m. Here, the South Equatorial Undercurrent (SEUC) can be interpreted as
the eastward flowing northern limb of the equatorial gyre and is opposite
in direction to the westward flowing South Equatorial Current above. Both
the NEUC and SEUC are analagous to currents in the Pacific that are
governed by non-Sverdrup dynamics. Despite the shortcomings of the data,
the mean annual cycle appears to be relatively stable, and we have
discounted the possibility that in regions where it represents a
significant percentage of the total variance, it is changing slowly over
the 28 years of record. The wind-forcing fields, which undergo large
meridional movements (5-6 of latitude) during their annual cycle, with
some exceptions, have essentially no counterpart in gyre movements
between their seasonal extremes. Most of the variability associated with
the annual cycle is confined to the upper 300 m. Greatest variability,
where ranges exceed 6°C, occurs in the northwestern Atlantic in late
winter and early spring. During this time of year south of the Gulf
Stream and below about 100 m, water temperatures exhibit a systematic
phase lag with depth. The next largest area of variability, where ranges
can also exceed 6°C, resides in the tropical western basin between the
equator and 10°N just below 100 m. In the eastern basin, ranges
decrease and shoal. Additionally, the phase fields are consistent with the
intensification and relaxation of the tropical ridge-trough system where
the NECC disappears in March in the west but the NECC/NEUC complex is
strongest in September.
McElligott, S., R.H. Byrne, K. Lee, R.H. Wanninkhof, F.J. Millero, and
R.A. Feely. Discrete water column measurements of CO2
fugacity and pHT in seawater: A comparison of direct measurements and
thermodynamic calculations. Marine Chemistry, 60(1-2):63-73
(1998).
The NOAA Equatorial Pacific CO2 system data set (~2500
water samples) has been evaluated to assess the internal consistency of
measurements and calculations involving CO2 fugacity and
pHT. This assessment represents the first large scale field
comparison of pHT and fCO2 data. Comparisons
of direct discrete CO2 fugacity (fCO2)
measurements with CO2 fugacity calculated from total inorganic
carbon (CT), total alkalinity (AT), and
spectrophotometric pH (pHT = -log[H+]T)
indicate that a variety of improvements are needed in the parameter
measurements and thermodynamic relationships used to relate
fCO2, CT, AT, and
pHT in seawater. CO2 fugacity calculated from
CT and pHT or AT and pHT agree
with direct measurements to no better than 1%. Comparisons of measured
fugacity, fCO2 (measured), and CO2 fugacity
calculated from CT and pHT, fCO2
(CT, pHT), indicate that the precision of
fCO2 calculations is good relative to direct
measurements. In contrast, due to the extreme sensitivity of
fCO2 and [H+]T calculations to
relatively small errors in both CT and AT,
CO2 fugacity, as well as [H+]T,
calculated from CT and AT are very imprecise and
render comparisons with direct measurements of little use. Consequently,
precise calculations of fCO2 require the use of direct
pHT measurements.
Mestas-Nunez, A.M., and D.B. Enfield. Rotated global modes of
multiyear sea surface temperature variability. AGU 1998 Ocean Sciences
Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS,
Transactions, American Geophysical Union, 79(1):OS75, OS22H-04 (1998).
El Niņo-Southern Oscillation (ENSO) is a global phenomenon with significant
phase propagation which we capture in the first mode of a complex empirical
orthogonal function (EOF) analysis of sea surface temperature anomaly (SSTA)
from the mid-19th century through 1991. We subsequently remove the global
ENSO from the SSTA data, plus a linear trend everywhere, in order to
consider other global modes of variability uncontaminated by the effects of
ENSO. An ordinary EOF analysis of the SSTA residuals reveals three non-ENSO
modes that are related to slow oceanic and climate signals described in the
literature. The first two modes both have an interdecadal time scale with
high loadings in the Pacific. The third mode is a multidecadal signal with
maximal realization in the extratropical North Atlantic southeast of
Greenland. It also has high loadings in the tropical Atlantic, anticorrelated
across the intertropical convergence zone, and strong variability of opposite
sign in the eastern tropical Pacific. Unlike ENSO and the secular global
warming, it is not known if the variability at intermediate (decadal to
multidecadal) time scales is global or regional in nature. To investigate
the presence of localized centers of variability, we perform a varimax
rotation of the ordinary non-ENSO EOFs. The first rotated mode has
multidecadal scales with maximal realization in the North Atlantic. The
second rotated mode has interdecadal scales with maximal realization in
the western tropical Pacific and captures the interdecadal warm anomaly
that contributed to the strong ENSO of 1983. These first two rotated
modes capture the Atlantic and western tropical Pacific counterparts of
the third Atlantic multidecadal unrotated mode. The third rotated mode is
a multidecadal signal with maximal realization in the mid-latitude
eastern North Pacific. The relation of these and higher order rotated
modes to the unrotated modes and to published climatic signals are discussed.
Millero, F.J., and J.-Z. Zhang. Adsorption of phosphate on calcium
carbonate. Proceedings, 1998 Florida Bay Science Conference,
Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program,
115 (1998).
No abstract.
Millero, F.J., W. Yao, K. Lee, J.-Z. Zhang, and D.M. Campbell. Carbonate
system in the waters near the Galapagos Islands. Deep-Sea Research
II, 45(6):1115-1134 (1998).
During the IRONEX cruise in the equatorial Pacific Ocean, the carbonate
parameters TA (total alkalinity), TCO2 (total inorganic carbon),
pH, and fCO2 (fugacity of CO2), were
determined both in a small (8 × 8 km) patch of water fertilized with
Fe and in the waters around the Galapagos Islands. The CO2
parameters, along with hydrographic properties, were found to be uniform
in the surface waters of the study area before the addition of iron. A
significant decrease of the surface TCO2 (7 ĩmol kg-1)
and fCO2 (11 ĩatm) in the patch was detected within 48
h of the iron release. This decrease, however, did not continue and was
lower than expected from the complete utilization of
NO3- due to the addition of iron. The shipboard iron a
ddition experiments (3 nM fe) resulted in a continual decrease of
TCO2 (up to 48 ĩmol kg-1) and complete consumption
of the nutrients. A good correlation was found between TCO2, pH,
and fCO2 with temperature in the surface waters around
the Galapagos Islands. The salinity (S = 35) normalized alkalinities
were quite uniform (NTA = 2310 ą 9 mol kg-1) throughout the
region. The effect of high primary production on the CO2
system in the downstream plume is overshadowed by the upwelling waters
with high CO2.
Millero, F.J., D.G. Purkerson, P. Steinberg, E. Peltola, K. Lee C.
Edwards, J. Goen, and M.P. Roche. The carbon dioxide system in the Ross
Sea during the JGOFS Southern Ocean Process Study. University of Miami
Technical Report, RSMAS-98-001, 159 pp. (1998).
In the austral summer of 1996 and austral fall of 1997, we participated
in the Joint Global Ocean Flux Study (JGOFS) supported by the National
Science Foundation (NSF) in the Southern Ocean aboard the R/V
Nathaniel B. Palmer. The first cruise was a survey across the
Antarctic Convergence Zone from Port Lyttelton, New Zealand to the Ross
Sea and back. The Process 1 and 3 cruises were in the Ross Sea. The
first process cruise originated in Port Lyttelton, New Zealand and ended
in McMurdo Station, Antarctica. The third process cruise originated and
ended in Port Lyttelton, New Zealand. This report gives the results of
our pH, total alkalinity (TA), and total inorganic carbon dioxide
(TCO2) measurements made during these cruises. The pH,
TCO2, and TA results were obtained by potentiometric titration
of seawater samples with hydrochloric acid (HCl), while the
TCO2 was determined by coulometry. Spectroscopic pH
measurements were also made. Measurements of pH, TA, and TCO2
were made on certified reference material (CRM) throughout the cruises to
assess the quality of the measurements. The reproducibility of these CRM
measurements by potentiometric titration were ±1.6 µmol
kg-1 in TA, ±2.2 µmol kg-1 in
TCO2, and ±0.005 in pH. The reproducibility in
TCO2 by coulometry were ±1 µmol kg-1 and
±0.001 in the spectroscopic values of pH. The at sea measurements
agreed with the assigned values of ±2 µmol kg-1 in
TA, ±5 µmol kg-1 in TCO2, and ±0.002
in pH. All the measurements done at sea were adjusted for these
differences. The values of pH, TA, and TCO2 for the
measurements in the Ross Sea are examined for the process studies along
with surface nutrients and pCO2.
Molinari, J., S. Skubis, D. Vollaro, F. Alsheimer, and H.E. Willoughby.
Potential vorticity analysis of tropical cyclone intensification.
Journal of the Atmospheric Sciences, 55(6):2632-2644 (1998).
The interaction of marginal Tropical Storm Danny (1985) with an
upper-tropospheric positive potential vorticity anomaly was examined. The
intensification mechanism proposed earlier for mature Hurricane Elena
appears to be valid for Danny as well, despite significant differences in
the synoptic-scale environment and in the stage of the tropical cyclone
prior to the interaction. Both storms experienced rapid pressure falls as
a relatively small-scale positive upper potential vorticity anomaly began
to superpose with the low-level tropical cyclone center. The interaction
is described in terms of a complex interplay between vertical wind shear,
diabatic heating, and mutual advection among vortices at and below the
level of the outflow anticyclone. Despite this complexity, the
superposition principle appears to be conceptually useful to describe the
intensification of tropical cyclones during such interactions.
Molinari, R.L., H.F. Bezdek, M. Latif, and A. Groetzner. A comparison of
modeled and observed mean and decadal time-scale Atlantic air-sea
structure. Proceedings, Atlantic Climate Variability Meeting,
Palisades, New York, September 24-26, 1997. University Corporation for
Atmospheric Research, 78-79 (1998).
No abstract.
Molinari, R.L., R.A. Fine, W.D. Wilson, J. Abell, M. McCartney, and R.
Curry. A fast-track for recently formed Labrador Sea Water: The Deep
Western Boundary Current of the North Atlantic. Proceedings, Atlantic
Climate Variability Meeting, Palisades, New York, September 24-26,
1997. University Corporation for Atmospheric Research, 80 (1998).
No abstract.
Molinari, R.L., R.A. Fine, W.D. Wilson, R.G. Curry, J. Abell, and M.S.
McCartney. The arrival of recently formed Labrador Sea Water in the Deep
Western Boundary Current at 26.5°N. Geophysical Research
Letters, 25(13):2249-2252 (1998).
The Deep Western Boundary Current (DWBC) of the North Atlantic is a
principal conduit between the formation region for Labrador Sea Water
(LSW) and the oceanic interior to the south. Time series (1985-1997) of
hydrographic properties obtained in the DWBC at 26.5°N show that
prior to 1994, temperature, salinity, and transient tracer properties
within the LSW density range showed little indication of recently formed
parcels. Properties characteristic of a newer version of LSW (cooler,
fresher, and higher tracer concentrations) were observed beginning in
1994 and continuing through 1997. Longer time series of temperature and
salinity, developed from a regional data base, show both the 1994 and
a 1980-1981 event in the Abaco region. Both events are consistent with
anomalies in the Labrador Sea that occurred some 10 years earlier. The
10-year transit time from the Labrador Sea to 26.5°N is less than the
18-year transit time inferred from earlier studies.
Murphy, P.P., R.A. Feely, and R.H. Wanninkhof. On obtaining
high-precision measurements of oceanic pCO2 using
infrared analyzers. Marine Chemistry, 62(1-2):103-115 (1998).
Assessments of ocean carbon uptake using the air-sea disequilibrium of
CO2 require very high quality measurements of
pCO2 in the atmosphere and in surface seawater. These
measurements are often collected and analyzed using infrared detectors.
Laboratory data are presented here which suggest that errors of the order
of several parts per million in xCO2 can result if the
analyzer temperature and pressure are not carefully matched during
calibration and sampling. Field data were examined to address questions
about the importance of measuring analysis temperature and pressure under
more extreme conditions, sample averaging, and calibration frequency. The
results indicate that calibration frequency can be minimized without
significant compromises in data quality if the analyzer temperatures and
pressures are suitably monitored and/or controlled. Daily calibrations gave
results to within 0.4 ppm of the results obtained by hourly calibration
when the temperature of the analyzer was controlled to ą0.2°C and the
voltages were corrected for pressure differences between calibration and
sampling.
Nelsen, T.A., H. Wanless, P. Blackwelder, T. Hood, C. Alvarez-Zarikian,
P. Swart, J. Trefry, W.-J. Kang, L. Tedesco, and M. O'Neil. The sediment
record as a monitor of anthropogenic changes in the lower
Everglades/Florida Bay ecosystem. Proceedings, 1998 Florida Bay
Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea
Grant College Program (1998).
Florida Bay is a shallow subtropical estuary (~2200 km2,
mean depth ~2 m) that lies at the southern end of peninsular Florida
and is subject to both natural and anthropogenically-induced changes.
Nearshore areas receive not only atmospheric input but also freshwater
input from natural sheetflow, major and minor creeks (Shark River and
Taylor Sloughs respectively), an unquantified input from groundwater and
direct precipitation, as well as anthropogenic sources (c-111 canal). A
paleoecological evaluation of this region was instigated using
high-resolution retrospective analysis of regional sediments. It
integrated sedimentology, geochronology (PB210,
Cs137), biology (foraminifera and ostracods), chemistry
(organic carbon, heavy metals, stable isotopes), and palynology to
allow a broad scope of characterization. These data were complemented
with an analysis of historical rainfall, freshwater flow, and limited
nearshore salinity data. Placed within a temporal context by
geochronology, sediment accumulation rates of ~1 cm per year in
recovered sequences permitted evaluation back to about the turn of the
century, thus allowing high-resolution evaluation of other co-sampled
parameters over a time period that encompasses both natural and
anthropogenic changes. Results from geochronology that were supported
by other co-sampled parameters indicated disburbed horizons that
temporarily correlate with major hurricanes. Moreover, foraminifera
and ostracod community structures showed changes that temporally
correlated with both natural rainfall patterns and anthropogenic
effects such as water management practices. Sediment burdens of
heavy metals also showed time-based changes that temporally correlated
with documented anthropogenic usage patterns.
Nelsen, T.A., H.R. Wanless, P. Blackwelder, T. Hood, C. Alvarez-Zarikian,
P. Swart, J.H. Trefry, W.-J. Kang, L. Tedesco, and M. O'Neal. The
sediment record as a monitor of natural and anthropogenic changes in the
lower Everglades/Florida Bay ecosystem. Proceedings, ASLO/ESA Land-Water
Interface: Science for a Sustainable Biosphere, St. Louis, Missouri,
June 8-13, 1998. American Society of Limnology and Oceanography, A-64
(1998).
Florida Bay is a shallow subtropical estuary (~2200 km2,
mean depth ~2 m) that lies at the southern end of peninsular Florida
and is subject to both natural and anthropogenically-induced changes.
Nearshore areas receive not only atmospheric input but also freshwater
input from natural sheetflow, major and minor creeks (Shark River and
Taylor Sloughs respectively), an unquantified input from groundwater and
direct precipitation, as well as anthropogenic sources (c-111 canal). A
paleoecological evaluation of this region was instigated using
high-resolution retrospective analysis of regional sediments. It
integrated sedimentology, geochronology (Pb210,
Cs137), biology (foraminifera and ostracods), chemistry
(organic carbon, heavy metals, stable isotopes) and palynology to allow a
broad scope of characterization. These data were complemented with an
analysis of historical rainfall, freshwater flow, and limited near-shore
salinity data. Placed within a temporal context by geochronology,
sediment accumulation rates of ~1 cm per year in recovered sequences
permitted evaluation back to about the turn of the century, thus allowing
high-resolution evaluation of other co-sampled parameters over a time
period that encompasses both natural and anthropogenic changes. Results
from geochronology, that were supported by other co-sampled parameters,
indicated disturbed horizons that temporally correlate with major
hurricanes. Moreover, foraminifera and ostracod community structures
showed changes that temporally correlated with both natural rainfall
patterns and anthropogenic effects such as water management practices.
Sediment burdens of heavy metals also showed time-based changes that
temporally correlated with documented anthropogenic usage patterns.
Nicholls, N., C.W. Landsea, and J. Gill. Recent trends in Australian
region tropical cyclone activity. Meteorology and Atmospheric
Physics, 65:197-205 (1998).
No abstract.
Niyogi, D.S., J.J. Cione, and S. Raman. Gulf Stream influence on the
North Carolina mesoclimate. Preprints, 2nd Conference on Coastal
Atmospheric and Oceanic Prediction, American Meteorological Society 78th
Meeting, Phoenix, AZ, January 12-16, 1998. American Meteorological
Society, Boston, 421-424 (1998).
No abstract.
Ogden, J.C., S.L. Vargo, J.C. Hendee, R. Timko, J.C. Humphrey, and T.C.
Moore. SEAKEYS 1998: An enhanced Florida Bay monitoring initiative.
Proceedings, 1998 Florida Bay Science Conference, Miami, Florida,
May 12-14, 1998. Florida Sea Grant College Program, 118 (1998).
No abstract.
Ortner, P.B., M.J. Dagg, G.S. Kleppel, R. Brenner, and C. Tomas. Trophic
pathways in the pelagic environment of Florida Bay. Proceedings, 1998
Florida Bay Science Conference, Miami, Florida, May 12-14, 1998.
Florida Sea Grant College Program, 143-145 (1998).
No abstract.
Peltola, E., R. Wanninkhof, R. Molinari, B.E. Huss, R. Feely, J.
Bullister, J.-Z. Zhang, F. Chavez, A. Dickson, A. Ffield, D. Hansell, F.
Millero, P. Quay, R. Castle, G. Thomas, R. Roddy, T. Landry, M. Roberts,
H. Chen, D. Greeley, K. Lee, M. Roche, J.A. Goen, F. Millero, K. Buck, M.
Kelly, F. Menzia, A. Huston, T. Waterhouse, S. Becker, and C. Mordy.
Chemical and hydrographic measurements during the Indian Ocean I8 repeat
cruise (IR8N) in September and October 1995. NOAA Data Report, ERL
AOML-34 (PB99-126948), 176 pp. (1998).
This document contains data and metadata from the I8 repeat cruise in
the Indian Ocean cruise in 1995 from Fremantle, Australia to Male in the
Maldives. From September 22 to October 25, 1995, the National Oceanic
and Atmospheric Administration (NOAA) sponsored an oceanographic research
cruise conducted aboard the NOAA Ship Malcolm Baldrige. This report
presents the analytical and quality control procedures and data from the
cruise that was conducted for the Ocean-Atmosphere Carbon Exchange Study
(OACES). Samples were taken at 101 stations. The data presented in this
report includes hydrography, nutrients, total dissolved inorganic carbon
dioxide (DIC), fugacity of carbon dioxide (fCO2), total
alkalinity (TA), pH, total organic carbon and nitrogen data (TOC/TON),
chlorofluorocarbons, 13C, and biological parameters.
Peng, T.-H., and F. Chai. Modeling of the carbon cycle in the equatorial
Pacific Ocean. AGU 1998 Western Pacific Geophysics Meeting, Taipei,
Taiwan, July 21-24, 1998. Supplement to EOS, Transactions, American
Geophysical Union, 79(24):W41, OS41A-10 (1998).
As a part of the U.S. JGOFS program, field data relating to hydrographic,
chemical, and biological properties in the equatorial Pacific have been
collected during the process-study-oriented survey cruises in 1992. To
synthesize and analyze these data for a better understanding of the carbon
cycle dynamics, an ocean ecosystem model of the equatorial Pacific Ocean has
been developed. The circulation model is based on the Modular Ocean Model
of the NOAA/GFDL ocean general circulation model. It consists of five
components describing phytoplankton, zooplankton, detritus, and two forms
of dissolved inorganic nitrogen: nitrate and ammonium. The carbonate
chemistry is parameterized in the model to evaluate the variations of
pCO2, and hence the CO2 flux across the air-sea
interface. At this initial stage, a test case by using a one-dimensional
model is performed to investigate how the carbon system behaves in the
ecosystem structure. The model includes the vertical upwelling and diffusion
processes. The upwelling rate and the diffusivity were averaged for the
region 5°S to 5°N, 180° to 90°W, the "cold tongue" of
the equatorial Pacific. Results of this one-dimensional testing model and
comparison with the observed data collected in 1992 will be presented.
Peng, T.-H., R. Key, and H.G. Ostlund. Temporal variations of bomb
radiocarbon in the Pacific Ocean. Marine Chemistry, 60:3-14
(1998).
The natural and anthropogenic components of the radiocarbon measurements
from seawater samples can be successfully separated by an improved
method, which is based on a very well-defined relationship between
natural radiocarbon and dissolved silica observed mainly during the
GEOSECS survey for waters beneath 1000 m depth. This relationship is
further reconfirmed by the 14C measurements from large volume
samples taken in the deep waters in the Pacific Ocean during the recent
WOCE survey program. Analysis of upper ocean 14C
measurements made along 152°W, and north of 20°'N, in the
northeastern Pacific Ocean during the NOAA's CGC91 cruise, which is a
part of the WOCE survey program, indicates that the bomb 14C
inventory in this part of the ocean has increased by 22% since the
GEOSECS measurements made in 1974. This increase is consistent with the
model prediction of 25% for the northern hemisphere ocean. Change of
the surface water bomb 14C values during this period is
insignificant. This feature is also consistent with the model
simulation. Results of this new analysis will provide useful
information of the temporal variations of bomb 14C inventory
in the ocean, in addition to the spatial distribution, which can be used
as powerful constraints in calibrating the global ocean carbon cycle
models, especially those based on three dimensional ocean general
circulation models, for estimating the uptake of CO2 by the
ocean.
Peng, T.-H., R.H. Wanninkhof, J.L. Bullister, R.A. Feely, and T.
Takahashi. Quantification of decadal anthropogenic CO2 uptake
in the Indian Ocean based on dissolved inorganic carbon measurements.
Nature, 396(10):560-563 (1998).
The increase of total dissolved inorganic carbon (DIC) in the ocean
caused by the uptake of fossil fuel CO2 is estimated mostly by
ocean models. These model estimates need to be verified using field
measurements. However, the direct detection of the anthropogenic
CO2 signal in the ocean has been hampered by the relatively
small annual increase in DIC in seawater (~1 ĩmol/kg/yr, as compared with
background DIC of ~2000 ĩmol/kg) and by lack of high-precision measurements
in the past. With the recent improvement in DIC analyses techniques, it
has now become possible to detect the anthropogenic CO2 signal
on decadal time scales. Here we report a significant increase in DIC
between the GEOSECS survey in 1978 and the recent NOAA-OACES survey in
1995 in the Indian Ocean. The anthropogenic CO2 signal is 12 ą
4.5 ĩmol/kg at ~300 m (potential density, sigmatheta = 26.6)
and the signal decreases on denser isopycnal horizons down to undetectable
near ~1000 m (sigmatheta = 27.2). The data are used to illustrate
the isopycnal analysis and corrections necessary to determine the
anthropogenic CO2 increase over time. The work can be used as
a guide for future observational strategies to assess uptake of
anthropogenic CO2.
Pielke, R.A., and C.W. Landsea. Normalized hurricane damages in the
United States: 1925-1995. Weather and Forecasting, 13(3):621-631
(1998).
Hurricanes are the costliest natural disasters in the United States.
Understanding how both hurricane frequencies and intensities vary from
year to year, as well as how this is manifested in changes in damages that
occur, is a topic of great interest to meteorologists, public and private
decision makers, and the general public alike. Previous research into
long-term trends in hurricane-caused damage along the U.S. coast has
suggested that damage has been quickly increasing within the last two
decades, even after considering inflation. However, to best capture the
year-to-year variability in tropical cyclone damage, consideration must
also be given toward two additional factors: coastal population changes
and changes in wealth. Both population and wealth have increased
dramatically over the last several decades and act to enhance the recent
hurricane damages preferentially over those occurring previously. More
appropriate trends in the United States hurricane damages can be
calculated when a normalization of the damages are done to take into
account inflation and changes in coastal population and wealth. With
this normalization, the trend of increasing damage amounts in recent
decades disappears. Instead, substantial multidecadal variations in
normalized damages are observed: the 1970s and 1980s actually incurred
less damages than in the preceding few decades. Only during the early
1990s does damage approach the high level of impact seen back in the
1940s through the 1960s, showing that what has been observed recently is
not unprecedented. Over the long term, the average annual impact of
damages in the continental United States is about $4.8 billion (1995 $),
substantially more than previous estimates. Of these damages, over 83%
are accounted for by the intense hurricanes (Saffir-Simpson categories 3,
4, and 5), yet these make up only 21% of the U.S.-landfalling tropical
cyclones.
Powell, M.D., and S.D. Aberson. How well do we forecast the position and
time of hurricane landfall? Preprints, 16th Conference on Weather
Analysis and Forecasting, Symposium on the Research Foci of the U.S.
Weather Research Program, American Meteorological Society 78th Annual
Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 9-12 (1998).
No abstract.
Powell, M.D., and S.H. Houston. Surface wind fields of 1995 Hurricanes
Erin, Opal, Luis, Marilyn, and Roxanne at landfall. Monthly Weather
Review, 126(5):1259-1273 (1998).
Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne were the most
destructive hurricanes of 1995. At landfall, Luis and Marilyn contained
maximum sustained winds (marine exposure) estimated at near 60 and 46 m
s-1, respectively. The strongest landfalling storm of the 1995
season, Luis, decreased in intensity from a category 4 to 3 on the
Saffir-Simpson scale shortly before the eyewall crossed the Islands of
Antigua, Barbuda, St. Kitts-Nevis, St. Barthelemy, St. Martin, and
Anguilla. Hurricane Marilyn strengthened as it approached the U.S. Virgin
Islands, with St. Thomas bearing the brunt of the north and south eyewall
winds of 46 m s-1 (marine exposure) and St. Croix being
affected by the relatively weak western eyewall peak winds of 35-40 m
s-1 (marine exposure). For Luis and Marilyn, only surface winds
with marine exposures were analyzed because of unknown small-scale
interactions associated with complex island terrain with 500-1000-m
elevations. Wind engineering studies suggest that wind acceleration over
blunt ridges can increase or "speed up" winds by 20%-80%. Topographic
effects were evident in damage debris analyses and suggest that an
operational method of assessing terrain-induced wind gusts (such as a
scaled down mesoscale model) is needed. After landfall as a marginal
hurricane over central Florida, Hurricane Erin regained strength over
the Gulf of Mexico with a well-defined radar reflectivity structure. Erin
struck the Florida panhandle near Navarre Beach with maximum sustained
surface winds of 35-40 m s-1 affecting the Destin-Ft. Walton
area. Hurricane Opal made landfall in nearly the identical area as Erin,
with maximum sustained surface winds of 40-45 m s-1, having weakened from
an intensity of nearly 60 m s-1 only 10 h earlier. Opal was characterized
by an asymmetric structure that was likely related to cold front
interaction and an associated midlevel southwesterly jet. Roxanne struck
Cozumel, Mexico, with sustained surface winds (marine exposure) of 46
s-1, crossed the Yucatan, and meandered in the southwest Gulf
of Mexico for several days. While in the Bay of Campeche, Roxanne's large
area of hurricane-force winds disabled a vessel, which led to the drowning
deaths of five oil industry workers. High-resolution wind records are
critical to preserving an accurate extreme wind climatology required for
assessment of realistic building code risks. Unfortunately, power
interruptions to Automated Surface Observing Stations (ASOS) on the U.S.
Virgin Islands (St. Croix, St. Thomas) and Destin, Florida, prevented
complete wind records of the eyewall passages of Marilyn and Opal,
respectively.
Powell, M.D., and S.K. Rinard. Marine forecasting at the 1996 centennial
olympic games. Weather and Forecasting, 13(3):764-782 (1998).
A team of meteorologists from the United States, Canada, and Australia
provided marine weather support to the sailing events of the 1996
Centennial Olympic Games, held in Wassaw Sound near Savannah, Georgia.
The team conducted research on the weather and climate and developed a
set of forecast products designed to inform athletes, volunteers, and
race managers of the wind, tidal current, wave, and weather behavior
expected each day during the pre-Olympic and Olympic periods. The Olympic
period proved to be a challenge with thunderstorms delaying, abandoning,
or postponing races on half of the days. Thunderstorm development and
movement was linked to the timing and strength of the sea breeze as well
as the direction and speed of the gradient wind. Numerous thunderstorm
warnings were issued with the assistance of the WSR-88D radar and the
Warning Decision Support System. Frequent lightning was a legitimate
safety concern due to the long distances between race courses and lack of
suitable shelter; fortunately no one was injured during the lightning
episodes. Forecasters benefited from access to a variety of monitoring
tools and models including real-time Olympic buoy wind and current time
series displays; satellite and radar imagery animation; 2-, 8-, and 10-km
resolution mesoscale models; a live video feed of race coverage; and
communications with forecasters aboard patrol craft offshore. Official
wind forecasts, mesoscale models, and a simple vector addition model
performed better than climatology and persistence as defined by mean
vector error and rms wind direction error. Climatology was difficult to
beat on the basis of wind speed error.
Powell, M.D., S.H. Houston, L.R. Amat, and N. Morisseau-Leroy. The HRD
real-time hurricane wind analysis system. Journal of Wind Engineering
and Industrial Aerodynamics, 77&78:53-64 (1998).
The HRD real-time wind analysis system is currently undergoing evaluation
in the operational forecasting environment of the National Hurricane
Center. The system is an object-oriented, distributed, three-tiered
client-server application that assimilates disparate observations and
processes the data into a common framework for exposure, height, and
averaging time. The data are then examined collectively or by type,
quality controlled, and passed on to a scale-controlled objective
analysis algorithm. Several products are derived from the analysis wind
field and storm track, yielding effective tools for disaster assessment,
emergency management, and recovery.
Proni, J.R., and J.C. Wilkerson. Underwater acoustic monitoring for
satellite rainfall estimation validation. Proceedings, 6th International
Conference for Precipitation, Mauna Lani Bay, Hawaii, June 29-July 1,
1998. NASA/NOAA, 2-10 (1998).
Application of underwater acoustic techniques to the monitoring of
rainfall over water is demonstrated at four acoustically distinct ocean
sites based on information in the 4-30 kHz frequency band. Rainfall
detection and classification as to type (convective or stratiform) are
possible because underwater sound spectral characteristics of rain are
different from the normally prevailing underwater background noise in the
ocean, and because there are distinct differences in the sound levels and
spectral shapes of the acoustic signature of the two rain types. Rain
type classification is determined by an acoustic discriminant,
DR, which is defined as the difference in the average
spectral levels between the 10-30 and 4-10 kHz bands. Rainfall estimation
potential is based on the high correlation between sound spectral levels
in decibels (in the 4-10 kHz frequency band) and radar reflectivity dBz.
Data obtained from a spatially distributed 12-hydrophone array on the ocean
floor, at a depth of 1.5 km, demonstrates the potential of monitoring
rainfall at the sea surface on spatial (420 km2) and temporal
(five samples/minute) scales suitable for validating precipitation estimates
from remote sensors carried on geostationary and polar orbiting satellites.
Proni, J.R., and J.C. Wilkerson. Wind-generated acoustic spectral
effects in the surf zone in the presence and absence of rainfall at Duck,
North Carolina. Proceedings, 16th International Congress on Acoustics
and 135th Meeting of the Acoustical Society of America, Seattle,
Washington, June 20-26, 1998. Journal of the Acoustical Society of
America, 103(5):2865-2866 (1998).
Concurrent underwater sound, wind, radar, and rainfall measurements were
made on November 5, 1992, off Duck, North Carolina. A wind speed
increment from 5 m/s to 13 m/s in 90 seconds resulted in a reduction in
the rainfall sound spectrum level beginning at about 50 kHz and extending
downward in frequency with time to about 10 kHz. The reduction in
rainfall-generated sound spectrum level with time is thought to be due to
sound absorption by the evolving wind-generated bubble field.
Proni, J.R., C. McArthur, and G. Schuster. Adaptive dredged material
discharge for the Port of Miami. Proceedings, Ports '98, Long
Beach, California, March 8-11, 1998. American Society of Civil Engineers,
1249-1257 (1998).
In a joint effort of the U.S. Army Corps of Engineers, the U.S.
Environmental Protection Agency, the National Oceanic and Atmospheric
Administration, the State of Florida, the Port of Miami, and the
University of Miami, a novel, environmentally adaptively controlled
procedure was developed, wherein a vital port expansion and maintenance
dredging operation was carried out while affording maximum protection to
sensitive coral reefs. After establishing the existence and spatial
disposition of a residual water column discharge plume, via acoustic
backscattering methods, a real-time current measurement system was
established at the offshore dredged material disposal site to be
utilized. Dredged material discharges then proceeded on a schedule in
conformity with the ambient currents, so that material transport to the
coral reefs of concern was minimized.
Quilfen, Y., B. Chapron, T. Elfouhaily, K.B. Katsaros, and J. Tournadre.
Observations of tropical cyclones by high-resolution scatterometry.
Journal of Geophysical Research, 103(C4):7767-7786 (1998).
Unprecedented views of surface wind fields in tropical cyclones
(hereafter TCs) are provided by the European Remote Sensing Satellite
(ERS) C-band scatterometer. Scatterometer measurements at C band are
able to penetrate convective storms clouds, observing the surface wind
fields with good accuracy. However, the resolution of the measurements
(50 × 50 km2) limits the interpretation of the scatterometer
signals in such mesoscale events. The strong gradients of the surface
wind existing at scales of a few kilometers are smoothed in the measured
features such as the intensity and location of the wind maxima and the
position of the center. Beyond the ERS systems, the scatterometers
on-board the ADEOS and METOP satellites, designed by the Jet Propulsion
Laboratory and by the European Space Agency, respectively, will be able
to produce measurements of the backscattering coefficient at about
25 × 25 km2 resolution. A few sets of ERS-1 orbits sampling
TC events were produced with an experimental 25 × 25 km2
resolution. Enhancing the resolution by a factor of 2 allows location of
the wind maxima and minima in a TC with a much better accuracy than at
50 km resolution. In addition, a better resolution reduces the geophysical
noise (variability of wind speed within the cell and effect of rain) that
dominates the radiometric noise and, hence, improves the definition of
the backscattering measurements. A comprehensive analysis of the
backscattering measurements in the case of high winds and high sea states
obtained within TCs is proposed in order to refine the interpretation of
the wind vector derived from a backscattering model that is currently
only calibrated up to moderate winds (<20 m/s) in neutral conditions.
Observations of the TOPEX-POSEIDON dual-frequency altimeter are also used
for that purpose. Patterns of the surface winds in TCs are described and
characteristic features concerning asymmetries in the maximum winds and
in the divergence field are discussed.
Roubicek, A.J., S.L. Garzoli, P.L. Richardson, C.M. Dumcombe Rae, and
D.M. Fratantoni. Benguela Current Experiment, R/V Seward Johnson
Cruise SJ9705, Cape Town, September 4, 1997-Recife, September 30, 1997.
NOAA Data Report, ERL AOML-33 (PB98-164775), 215 pp. (1998).
The main objective of this program is to study the pathways, velocity,
transport, and variability of the Benguela Current and its extension with
emphasis on tracking floats in the intermediate water. It is expected
that the results of this program will make a significant contribution
towards the understanding of inter-ocean (Indian to Atlantic) and
inter-basin (South and North Atlantic) exchange of intermediate water
and its role in heat and mass exchanges. This program is a component of
KAPEX (Cape of Good Hope Experiment), a joint U.S., German, and South
African experiment. In March 1997, a German cruise on the Polarstern
led by W. Zenk and O. Boebel launched 35 RAFOS floats and five sound sources
(including one of the U.S. sources near 20°S, 4°E) in the general
area west and southwest of Cape Town. During August 1997, a U.S. cruise on
the R/V Seward Johnson led by T. Rossby launched three sound sources
east and southeast of Cape Town; 50 RAFOS floats will be launched in the
Agulhas Current starting in November 1997. During the Benguela Current
Experiment cruise on the RV Seward Johnson in September 1997, 32
RAFOS floats and two sound sources were launched in the general area west
and northwest of Cape Town. During KAPEX, over 100 RAFOS floats and nine
sound sources will measure ocean trajectories for the first time in the
Agulhas Current, in its rings which enter the South Atlantic, and in the
Benguela Current and its extension, which is the source of water moving
northward through the Atlantic in the meridional overturning circulation
cell. In addition, temperature, salinity, and velocity profiles will
document the water mass and velocity structure of the Benguela Current,
its extension, and several Agulhas rings.
Shapiro, L.J., and S.B. Goldenberg. Atlantic sea surface temperatures and
tropical cyclone formation. Journal of Climate, 11(4):578-590 (1998).
It has long been accepted that interannual fluctuations in sea surface
temperature (SST) in the Atlantic are associated with fluctuations in
seasonal Atlantic basin tropical cyclone frequency. To isolate the
physical mechanism responsible for this relationship, a singular value
decomposition (SVD) is used to establish the dominant covarying modes of
tropospheric wind shear and SST, as well as horizontal SST gradients. The
dominant SVD mode of covarying vertical shear and SST gradients, which
comprises equatorially confined near-zonal vertical wind shear
fluctuations across the Atlantic basin, is highly correlated with both
equatorial eastern Pacific SST anomalies (associated with El Niņo) and
west African Sahel rainfall. While this mode is strongly related to
tropical storms, hurricanes, and major hurricane frequency in the
Atlantic, it is not associated with any appreciable Atlantic SST signal.
By contrast, the second SVD mode of covarying vertical shear and
horizontal SST gradient variability, which is effectively uncorrelated
with the dominant mode, is associated with SST fluctuations concentrated
in the main tropical cyclone development region between 10°N and
20°N. This mode is significantly correlated with tropical storm and
hurricane frequency but not with major hurricane frequency. Statistical
tests confirm the robustness of the mode, and lag correlations and physical
reasoning demonstrate that the SST anomalies are not due to the
developing tropical cyclones themselves. Anomalies of SST and vertical
shear during years where the mode has substantial amplitude confirm the
resemblance of the individual fields to the modal structure, as well as
the association of hurricane development with the warmer SSTs. Although
SSTs are of secondary importance to vertical shear in modulating
hurricane formation, explaining only 10% of the interannual variability
in hurricane frequency over the 50% explained by vertical shear, the
results support the conclusion that warmer SSTs directly enhance
development. The lack of correlation with major hurricanes implies that
the underlying SSTs are not a significant factor in the development of
these stronger systems.
Shay, L., G.J. Goni, F.D. Marks, J.J. Cione, and P.G. Black. Role of
warm ocean features on intensity change: Hurricane Opal. Preprints,
Symposium on Tropical Intensity Change, American Meteorological Society
78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 131-138 (1998).
No abstract.
Sheinbaum, J., J. Candela, W.D. WILSON, J. Ochoa, and A. Badan.
Shipboard ADCP and lower ADCP observations in the Yucatan Channel. AGU
1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998.
Supplement to EOS, Transactions, American Geophysical Union,
79(1):OS125, OS32P-01 (1998).
Observations obtained during two cruises in December 1996 and in May/June
1997 within the CANEK Project are discussed. The cruises were onboard the
R/V Justo Sierra, equipped with a ship-mounted RDI 75 kHz ADCP,
usually measuring up to 400 m depth, and covered the area around the Yucatan
Channel within 20° to 22.5°N. Both cruises show a persistent
and swift Yucatan Current flowing towards the Gulf of Mexico, on the
western side of the Channel, with surface magnitudes as large as 2 m/s.
Transport estimates in the upper 300 m indicate that this current was
transporting around 8 Sv into the Gulf during both cruises, for an
equivalent cross-shelf section about 50 km in length at around 22°N
and oriented nearly in west-east direction. A complete cross-Channel section
between Isla Contoy, Yucatan and Cabo San Antonio, Cuba, during the May
cruise, gives a total transport of 19 Sv into the Gulf in the upper 300
m. Ship-mounted ADCP velocities from the top 300 m are used to reference
velocity measurements from a Lower-ADCP (LADCP), an RDI 300 kHz acoustic
Doppler current profiler attached to a CTD-rosette frame which samples
the whole water column. Total and deep transport estimates, together
with methods to filter out tidal transports, are also discussed.
Sheinbaum, J., J. Candela, J. Ochoa, A. Badan, I. Gonzalez, W.D. Wilson,
and R.H. Smith. Velocity and transport measurements with a
lower-acoustic Doppler current profile in the Yucatan Channel: Some
preliminary results. Proceedings, Conference on the Transports and
Linkages of the Intra-Americas Sea (IAS), Cozumel, Mexico, November
1-5, 1997. IOC/IOCARIBE/MMS, 57 (1998).
We present preliminary results from the extensive surveys carried out
onboard UNAM'S R/V Justo Sierra using a shipboard ADCP and a
CTD/LADCP during December 1996 and May 1997 in the Yucatan Channel.
These cruises were part of the CANEK Project, a collaborative effort
between CICESE, ICMyL-UNAM, UAM (Mexico), NOAA (USA), and IOC (Cuba),
to measure the exchange between the Carribean Sea and the Gulf of Mexico.
Velocity measurements and transport estimates from both instruments are
analyzed and compared. The May 1997 cruise had a standard GPS instrument
to fix ship positions, which were recorded almost continuously (every
second) during the whole cruise. These data were filtered before velocity
and transport calculations were carried out. Details of the data processing
and sensitivity of absolute velocity estimates from the LADCP instrument
to the ship's position are discussed.
Swart, P., K.S. White, D.B. Enfield, P. Milne, and R.E. Dodge. Stable oxygen
isotopic composition of corals from the Gulf of Guinea as indicators of
periods of extreme precipitation conditions in the sub-Sahara. Journal
of Geophysical Research, 103(C12):27,885-27,891 (1998).
Analyses of scleractinian coral skeletons from the Gulf of Guinea in
the eastern Atlantic reveal that the corals from this region can be
used to identify periods of severe drought and above average precipitation
in the Subsahara. Data presented in this paper show a positive correlation
between the magnitude of the Sahel drought and the d18O values of the
Principe coral skeleton. The explanation for this positive correlation is
that the salinity of the Gulf of Guinea is strongly influenced by the
outflow of the Niger and Zaire Rivers. The outflow of these rivers is also
correlated with the fluorescence of the Principe coral. These periods of
high freshwater input correlate with periods of higher rainfall in the
Subsahara and have affected the d18O values of the coral skeleton. The
correlations between Principe coral d18O values and Atlantic NATL (r =
-0.34), the dipole (r = -0.45), and the latitudinal position of the ITCZ
(r = -0.37) illustrate that the d18O values in the Principe coral reflect
climate dynamics of the region that affect the precipitation patterns in
the Subsahara.
Swenson, M.S., and D.V. Hansen. Drifter-based estimates of the seasonal
cycle of heat advection in the NECC of the eastern tropical Pacific.
AGU 1998 Fall Meeting, San Francisco, CA, December 6-10, 1998.
Supplement to EOS, Transactions, American Geophysical Union,
79(45):F431, OS12A-05 (1998).
Drifter-based estimates of the seasonal cycle of heat advection in the
NECC of the eastern tropical Pacific is based on over 2500 estimates of
weekly averaged velocity and DT/Dt from drifting buoys and over 2100 XBT
casts in the region 4°N-11°N, 145°W-115°W from the
historical data base in the Pacific for 1979-1996. This is the region of
the North Equatorial Countercurrent (NECC) over which the Intertropical
Convergence Zone is usually found. The NECC exhibits a strong seasonal
cycle in zonal velocity and mixed-layer depth structure. We estimate the
contribution to the mixed layer heat budget in this region arising from
horizontal advection and diffusion during the march of the seasonal
cycle. These contributions are compared with estimates of the remaining
terms in an attempt to close the budget and identify the mechanisms which
dominate during different seasons. The estimates will include eddy heat
flux estimates. Finally, we will attempt to evaluate existent surface
flux climatologies based on the balances we find.
Swenson, M.S., and H.F. Bezdek. On ocean-atmosphere coupling in the North
Atlantic. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February
9-13, 1998. Supplement to EOS, Transactions, American Geophysical
Union, 79(1):OS77, OS22I-08 (1998).
We explore the geographical variability of the structure of the cross
correlation function between sea surface temperature anomalies (SSTA) and
anomalies of the sum of the latent and sensible heat fluxes (LSHFA) in
the North Atlantic based on summaries from the Comprehensive Ocean
Atmosphere Data Set (COADS) summaries from 1947-1990. Two distinct cross
correlation structures emerge, one of which dominates in the open ocean
at midlatitudes and the other of which dominates in the western boundary
current and in the tropics. The former is characterized by a strong
antisymmetry, while the latter is one-sided with a peak at zero-lag. A
simple stochastic model (vector first-order auto-regressive model) is
proposed to account for the observed structure. This is the simplest
auto-regressive model that can produce the antisymmetric aspect in the
cross correlation found in the open ocean midlatitude region. The model
reproduces the results with great fidelity, but requires essential mutual
coupling between SSTA and LSHFA to reproduce the open ocean midlatitudes
result. The residuals from the fit contain low-frequency behavior with
decadal time scales.
Thomas, G.G., R. Benway, S. Cook, Y.-H. Daneshzadeh, and W.S. Krug. Surface
salinity and temperature from ships of opportunity. Proceedings, Ocean
Community Conference '98, Baltimore, MD, November 16-19, 1998.
Marine Technology Society, 160-165 (1998).
Thermosalinograph (TSG) data collected aboard both NOAA research vessels
and ships participating in the National Oceanic and Atmospheric
Administration's (NOAA) Volunteer Observing Ship (VOS) program plays an
important role in the study of meridional circulation in the world's
oceans. Sea surface temperature (SST) and sea surface salinity (SSS) are
valuable measurements in our attempt to understand the interaction
between the world's oceans and global climate. The ability to collect
and calibrate these data sets to insure a high standard of data quality
is necessary to validate their use in NOAA's Global Ocean Observing
System (GOOS) Center data base at the Atlantic Oceanographic and
Meteorological Laboratory (AOML) located in Miami, Florida.
Wang, C., and R.H. Weisberg. Climate variability of the coupled
tropical-extratropical ocean atmosphere system. Geophysical Research
Letters, 25(21):3979-3982 (1998).
Observations show that tropical and extratropical Pacific SST
anomalies vary out-of-phase, and that the atmospheric meridional Hadley
and zonal Walker Circulations are related to these variations. A
tropical-extratropical model is constructed to show oscillations
consistent with observations. The positive feedback introduced by the
Walker Circulation causes tropical warming so that the air rises and
flows toward the subtropics where it sinks. When the sinking air
approaches the sea surface, it flows both equatorward and poleward
enhancing tropical easterly and extratropical westerly winds,
respectively. Enhanced extratropical westerlies increases wind speed and
hence evaporation, resulting in extratropical cooling. The Walker and
Hadley Circulations thus result in tropical warming and extratropical
cooling, respectively. The tropical warming and extratropical cooling
increase the meridional SST difference and hence the meridional heat
transport which erodes the tropical warming and extratropical cooling.
Enhanced tropical easterlies due to the Hadley Circulation cools the
tropical ocean through ocean dynamics. These negative feedbacks help the
system to switch from warm to cold phases, and vice versa.
Wang, C., and R. H. Weisberg. Observations of meridional scale frequency
dependence in the coupled tropical ocean-atmosphere system. Journal of
Geophysical Research, 103(C2):2811-2816 (1998).
It is generally observed in models of the coupled tropical
ocean-atmosphere system that the meridional scales for oscillations at
interannual periods are larger than an oceanic equatorial Rossby
radius of deformation. Using nine years of the high-resolution Optimum
Interpolation sea surface temperature (SST) product of the NOAA/NCEP,
analyses are made on the frequency dependence of the observed meridional
scales, with emphasis on the latitudinal structures in the central
Pacific at 140°W. On the relatively short intraseasonal and seasonal
time scales the SST variations are found to occur over a meridional scale
of the oceanic equatorial Rossby radius of deformation suggested by
conventional equatorially trapped wave theory. In contrast to this, on
the longer annual and interannual time scales the meridional scales are
found to increase beyond the oceanic equatorial Rossby radius of
deformation. A physical explanation for this meridional scale increase
with decreasing frequency in the coupled tropical ocean-atmosphere system
is discussed.
Wanninkhof, R.H., and R.A. Feely. fCO2 dynamics in the
Atlantic, Pacific, and South Indian Oceans. Marine Chemistry,
60(1-2):15-31 (1998).
Subsurface fugacities of CO2 (fCO2(20)) can be
used in combination with total dissolved inorganic carbon (DIC) to precisely
calculate total alkalinity. Thus, it can be used to determine dissolution
of calcium carbonate (hard tissue) and remineralization of organic material
(soft tissue), to quantify saturation constants of calcite and aragonite in
seawater, and to characterize water masses. fCO2(20) is
a good tracer of biological transformation since it is thermodynamically
related to the other inorganic carbon system parameters and it has a
dynamic range from 200 to 2000 ĩatm in the world's ocean. Precision of
fCO2 measurements is better than 0.3% and the values are
well calibrated using compressed gas reference standards. Increases of
fCO2(20) are observed as the water masses age during
movement from the Atlantic to the Indian and South Pacific Oceans. As an
example of the determination of the ratio of soft tissue remineralization
to hard tissue dissolution from fCO2(20) and DIC, the
trends along the 27.2 isopyncal for the subtropical gyres of the three
basins are investigated. Little CaCO3 dissolves along this
isopycnal in the Atlantic and the South Pacific while the soft tissue
remineralization to hard tissue dissolution ratio in the Indian Ocean is
4.5:1. The difference in this ratio along the 27.2 isopycnal appears to
be a combination of the calcite and aragonite saturation levels and the
supply of aragonite tests.
Weisberg, R.H., and D.A. Mayer. Interhemisphere and intergyre exchange
processes. AGU 1998 Fall Meeting, San Francisco, CA, December 6-10,
1998. Supplement to EOS, Transactions, American Geophysical Union,
79(45):F484, OS31F-10 (1998).
Given that tropical ocean and atmosphere property fields have large
annual cycles, intergyre and interhemisphere exchanges are likely to be
seasonally dependent. Using COADS, we describe the annual variability of
the tropical Atlantic Ocean wind-driven circulation and its implications
for property exchanges. Focus is on three gyres: the anticyclonic
northern hemisphere subtropical gyre, the cyclonic tropical gyre north of
the equator, and the clockwise equatorial gyre. In the tropical gyre,
the Sverdrup circulation argues against a continuous western boundary
current for transporting water between the equatorial region and the
Caribbean in boreal winter. Instead, the Sverdrup circulation implies a
southeastward flowing boundary current, bringing to question the
mechanisms for the interhemisphere and intergyre exchanges of heat and
mass. A conceptual model is proposed involving two stages. First, the
western boundary current closing the clockwise equatorial gyre is
instrumental in transporting heat across the equator and storing warm
water mass between the North Equatorial Countercurrent ridge and the
North Equatorial Current trough in boreal summer. Transport farther
north into the subtropical gyre in boreal winter is then accomplished by
Ekman transport, as the seasonal change in wind stress deepens the
thermocline, allowing for northward Sverdrup transport over the region of
warmest waters. Once in the subtropical gyre, the Ekman transport
continues to be northward despite the Sverdrup transport reversing to be
southward. These stages constitute a rectification of the annual cycle
wherein different regions play additive roles during different times of
year. With Ekman and geostrophic transports being important, we also
look at how they combine to form divergence on the equator. We use
vertical velocity estimates from an equatorial central Pacific array of
moorings deployed during TIWE. Upwelling (downwelling) is observed above
(below) the EUC core, and while the divergence is centered on the
equator, poleward surface and equatorward subsurface flows are larger at
1°S than at 1°N. The results are consistent with interior fluid
pathways to the equator in the central Pacific. These gyre and vertical
velocity analyses demonstrate that three-dimensional and time dependent
processes are at work in transporting properties across hemispheres and
gyres.
White, S.R., J.D. McFadden, and J.L. Franklin. Atmospheric observations
with the NOAA Gulfstream IV-SP. Preprints, 10th Symposium on
Meteorological Observations and Instrumentation, Phoenix, AZ,
January 11-16, 1998. American Meteorological Society, Boston,
38-41 (1998).
No abstract.
Whung, P.-Y., and C.J. Fischer. Input of atmospheric nitrogen species in
the Florida Bay area: Its role in the nitrogen budget of Florida Bay.
Proceedings, 1998 Florida Bay Science Conference, Miami, Florida,
May 12-14, 1998. Florida Sea Grant College Program, 71 (1998).
No abstract.
Willoughby, H.E. Tropical cyclone eye thermodynamics. Monthly Weather
Review, 126(12):3053-3067 (1998).
In intense tropical cyclones, sea level pressures at the center are
50-100 hPa lower than outside the vortex, but only 10-30 hPa of the total
pressure fall occurs inside the eye between the eyewall and the center.
Warming by dry subsidence accounts for this fraction of the total
hydrostatic pressure fall. Convection in the eyewall causes the warming
by doing work on the eye to force the thermally indirect subsidence.
Soundings inside hurricane eyes show warm and dry air aloft, separated by
an inversion from cloudy air below. Dewpoint depressions at the inversion
level, typically 850-500 hPa, are 10-30 K rather than the 100 K that
would occur if the air descended from tropopause level without dilution
by the surrounding cloud. The observed temperature and dewpoint
distribution above the inversion can, however, be derived by 100 hPa of
undilute dry subsidence from an initial sounding that is somewhat more
stable than a moist adiabat. It is hypothesized that the air above the
inversion has remained in the eye since it was enclosed when the eyewall
formed and that it has subsided at most a few kilometers. The cause of
the subsidence is the enclosed air's being drawn downward toward the
inversion level as the air below it flows outward into the eyewall.
Shrinkage of the eye's volume is more than adequate to supply the volume
lost as dry air is incorporated into the eyewall or converted to moist
air by turbulent mixing across the eye boundary. The moist air below the
inversion is in thermodynamic contact with the sea surface. Its moisture
derives from evaporation of seawater inside the eye, frictional inflow of
moist air under the eyewall, and from moist downdrafts induced as
condensate mixes into the eye. The moist air's residence time in the eye
is much shorter than that of the dry air above the inversion. The height
of the inversion is determined by the balance between evaporation,
inflow, and inward mixing on one hand and loss to the eyewall updrafts on
the other.
Wilson, W.D. Constructing an IAS regional Global Ocean Observing
System. Proceedings, Conference on the Transports and Linkages of the
Intra-Americas Sea (IAS), Cozumel, Mexico, November 1-5, 1997.
IOC/IOCARIBE/ MMS, 66 (1998).
The Global Ocean Observing System (GOOS) was established as an
international program in 1993 by the IOC, WMO, UNEP, and ICSU. The main
elements are the collection and timely distribution of oceanic data and
products, including assessments, assimilation of data into numerical
prediction models, the development and transfer of technology, and
capacity building within participating member states to develop analysis
and application capability. To date, national GOOS operational
activities worldwide are primarily split between global programs
(supported almost entirely by a small number of highly developed
countries) and regional networks of linked coastal and nearshore
programs, such as EURO-GOOS in the EU and NEAR-GOOS in northeastern
Asia. The IOC suggests that "...In regions having existing IOC
Sub-Commissions (e.g., IOCARIBE), countries organizing regional GOOS
activities will do so in consultation with the Sub-Commission."
Subsequently, both IOC and IOCARIBE have expressed support for the
development of an IAS regional GOOS. Because of the nature of the
IOCARIBE member states, which contain far fewer autonomous national
oceanographic programs than eastern Asia or western Europe, the IAS GOOS
paradigm will have a somewhat different structure than NEAR-GOOS or
EURO-GOOS. It is hoped that this talk will promote a dialogue about
planning for the implementation of an IAS regional GOOS. For discussion
purposes, some important issues to be addressed in planning an IAS GOOS
include: (1) identification of customer concerns, e.g., fisheries,
climate studies, pollution management, etc., in keeping with the
primary GOOS goal of providing practical benefits to society; (2) Design
of a scientifically sound, expandable pilot observing system for continual
monitoring; (3) model development to provide a framework for data
synthesis and program expansion; (4) utilization of existing and planned
regional programs and regional parts of global programs as components for
cost-efficiency; and (5) regional dispersal of technology and capacity
building for synoptic data acquisition, management, and utilization.
Wilson, W.D., and W.E. Johns. Measurements of transport and water mass
exchange in the passages to the Caribbean Sea. AGU 1998 Ocean Sciences
Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS,
Transactions, American Geophysical Union, 79(1):OS125, OS32P-03 (1998).
Physical oceanographic measurements from 14 cruises during 1991-1997 in the
Antilles island passages have been analyzed to study water exchange between
the Atlantic Ocean and the Caribbean Sea. This region is generally thought
to be an important site for the entrainment of upper ocean waters of South
Atlantic origin into the North Atlantic circulation system, a process
necessary to balance southward North Atlantic outflow in deeper layers. The
magnitude of this exchange, comprising the North Atlantic thermohaline
Meridional Overturning Circulation (MOC), is thought to be around 15 Sv.
While earlier cruises were concentrated on passages south of 15°N
(Wilson and Johns, 1997, DSR, 44[3]), recent results also include
five occupations of the more northern passages of the Lesser Antilles,
allowing estimation of significant mean transports through all the passages.
Net transport above 800 m in the passages south of Dominica (15°N) is
estimated to be 12.2 Sv, partitioned among Grenada (6.1), St. Vincent (2.8),
St. Lucia (2.0), and Dominica (1.3). The northern passages, Guadeloupe (1.0),
Antigua (2.9), and Anegada (2.8), account for an additional 6.7 Sv. Allowing
a maximum of 1 Sv of unresolved inflow, approximately 20 Sv of the 32 Sv that
leaves the Straits of Florida at 27°N enters through the passages of
the Lesser Antilles. This is quite consistent in total and in spatial
distribution with geostrophic transports relative to 800 m calculated from
high-resolution historical T-S data at 60°W. Too few sections in the
Mona and Windward passages are available to estimate mean transports there.
Consideration of these data, historical data, Sverdrup theory, and numerical
model results suggests that very little of the mean inflow through the
southern passages can be attributed to wind-driven circulation, and that
most of that transport is derived from South Atlantic waters crossing the
equator in the upper limb of the Atlantic thermohaline cell. The remainder
of the upper ocean thermohaline likely follows a different route into the
subtropical gyre, possibly flowing northward in the interior and entering
the Caribbean through the northern passages.
Wilson, W.D., W. Johns, and E. Johns. Atlantic-Caribbean water exchange:
A quantitative summary of observations. Proceedings, Conference on the
Transports and Linkages of the Intra-Americas Sea (IAS), Cozumel,
Mexico, November 1-5, 1997. IOC/IOCARIBE/MMS, 65 (1998).
The need for good models of IAS circulation is growing as regional
researchers seek input for studies of air-ocean-land interaction, climate
variability, fisheries management, and pollution control. Proper
boundary conditions will be essential to the operation and validation of
these models. The water masses that enter, transit, and exit the IAS are
determined by interaction between the Atlantic thermohaline and
wind-driven circulations as well as regional modifications within the IAS
itself. Existing data on transports into, within, and out of the IAS are
quantitatively summarized to aid understanding of the IAS general
circulation, provide initial conditions, and serve as benchmarks for
model evaluation. Passages are categorized as inflows (passages of the
Antilles and Bahamas), internal (Pedro Banks, Yucatan Channel, western
Straits of Florida), or outflows (northern Straits of Florida). Inflow
passages are further subdivided by geographic location
(southern/northern); transport and water mass characteristics vary
markedly between northern and southern due to their location relative to
the western Atlantic gyre and wind field structure. Range of variability
as well as mean flow values are estimated when possible, as this is
important to evaluation of model dynamics. A significant result of this
summary is a "best estimate" of mean transport distribution and
variability by region, passage, and depth levels. These values are
compared to transports derived from mean hydrographic and wind fields.
Wilson, W.D., D. Wallace, R. Olivacce, R.A. Watlington, and W.E. Johns.
Monitoring the pulse of the DWBC in the Anegada Passage. Proceedings,
Conference on the Transports and Linkages of the Intra-Americas Sea
(IAS), Cozumel, Mexico, November 1-5, 1997. IOC/IOCARIBE/MMS, 63
(1998).
A serial station in the Anegada Passage, site of significant surface
transport and of the deepest exchange between the Atlantic Ocean and the
Caribbean Sea, is contributing to earlier observations at this location
to provide a useful background against which variability of the Deep
Western Boundary Current (DWBC) can be contrasted. Profiles of dissolved
inorganic carbon, dissolved oxygen, chlorofluorocarbons, and standard
hydrographic variables have successfully portrayed the several water
masses transiting this location at depths down to 1900 m. Significantly,
the southward advance of the prodigious flow Labrador Sea Water observed
at Abaco is expected to manifest itself at this station within the coming
year. ACTS is a project of the University of the Virgin Islands
conducted in partnership with Brookhaven National Laboratory and the NOAA
Atlantic Oceanographic and Meteorological Laboratory. The study, in
itself, represents a successful collaborative model whereby long-term
oceanic observations are conducted at minimal expense.
Yvon-Lewis, S.A., J.H. Butler, P.A. Matrai, E.S. Saltzman, D.B. King, R.
Tokarczyk, K. Sullivan, B. Yocis, W. Grosko, and H. Wright. An
investigation into the use of SeaWiFS data to study the biogeochemical
cycling of methyl bromide. AGU 1998 Fall Meeting, San Francisco,
CA, December 6-10, 1998. Supplement to EOS, Transactions, American
Geophysical Union, 79(45):F429, OS11F-01 (1998).
The objectives of this study are to evaluate the effects of oceanic
biological degradation and production of methyl bromide
(CH3Br) on its uptake by and emission from the ocean, to
relate the derived parameters to satellite measurements of oceanic and
atmospheric properties, and to evaluate the use of satellite data in
modeling oceanic fluxes of this gas. Results of this study will have a
direct, and likely significant, impact upon our understanding of the
lifetime and budget of atmospheric methyl bromide and may be useful in
future assessments of the budget of atmospheric CH3Br as
anthropogenic emissions decrease. The first step in this investigation
was completed during a cruise in the North Atlantic in May and June 1998,
where in-situ measurements of CH3Br saturation anomalies and
measurements of biological degradation and production rates for
CH3Br were made. Results from these measurements will be
included in a global model if the production rates, degradation rates,
and/or saturation anomalies can be linked to a property or properties
that are recorded by satellite, particularly ocean color from the
Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Here, we will present
the preliminary results from the field measurements described above and
results from our initial efforts to correlate these measurements with a
SeaWiFS data product.
Zegowitz, V., and S.K. Cook. World Meteorological Organization-Volunteer
Observing Ship Program. Proceedings, Ocean Community Conference
'98, Baltimore, MD, November 16-19, 1998. Marine Technology Society,
6 pp. (1998).
As one of our astute, well-informed political figures said recently, "What
do we need the Weather Service for, we have the Weather Channel!" Just where
DOES the data come from to make a good marine forecast? Even those of you
who have wandered here by mistake are about to be exposed to a little bit
of information about a big contributor to this process, the World
Meteorological Organization (WMO) Voluntary Observing Ship (VOS) program.
Zhang, J.-Z., and P.B. Ortner. Effect of thawing conditions on the
recovery of reactive silicic acid from frozen natural water samples.
Water Research, 32(8):2553-2555 (1998).
A method for thawing frozen samples for silicic acid analysis is
recommended. The maximum recovery of silicic acid is achieved by thawing
the frozen samples in a refrigerator (at 4°C) in the dark for at least
four days. This method significantly improves the recovery of silicic
acid from frozen fresh water samples. It also permits close to 100%
recovery of reactive silicic acid from frozen seawater samples even after
three months storage.
**1997**
Aberson, S.D. Adaptive observations in a hurricane environment.
Preprints, 22nd Conference on Hurricanes and Tropical Meteorology,
Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston,
308-309 (1997).
No abstract.
Aberson, S.D. Five-day statistical hurricane track forecasts.
Minutes, 51st Interdepartmental Hurricane Conference, Miami,
FL, March 24-28, 1997. Office of the Federal Coordinator for
Meteorological Services and Support Research, Washington, D.C., A-3 (1997).
A dimensional analysis of five-day hurricane tracks is presented to
calculate the number of predictors necessary to accurately predict
tracks. While the dimensions of the hurricane tracks are large,
statistical analyses can still be used as a benchmark by which other
methods can be assessed. A new version of CLIPER is developed which
eliminates problems with the original dependent data sets and extends
the forecasts to five days. The new version updates the original CLIPER,
which used data from 1930 through 1970, a time during which many tracks
are conjecture and many are missed completely. The new version eliminates
the Gulf of Mexico tropical cyclones from the Atlantic basin, and
corrects for problems in the original Gulf of Mexico data. The new
version also eliminates non-physical cross-terms in the multiple linear
regression. Independent forecasts are made for the 1996 hurricane season
and compared to the older version of the model. Model biases of the two
versions are compared.
Aberson, S.D. The prediction of the performance of a nested barotropic
hurricane track forecast model. Weather and Forecasting,
12(1):24-30 (1997).
Linear multiple regression and discriminant analyses provide estimates of
the errors of track forecasts from a nested barotropic hurricane track
forecast model (VICBAR), which was run in the North Atlantic Basin during
the 1989-94 hurricane seasons. Predictors are determined from the
synoptic situation, the magnitude of atmospheric changes in the
environment of the tropical cyclone, the consistency between current and
past predictions, and the past performance of the model for each
particular storm. This technique distinguishes cases in which VICBAR
performs well from those for which it performs poorly and can provide
skillful operational predictions of model performance to forecasts.
Acero-Schertzer, C.E., D.V. Hansen, and M.S. Swenson. Evaluation and
diagnosis of surface currents in the NCEP ocean analyses. Journal of
Geophysical Research, 102(C9):21,037- 21,048 (1997).
Ensemble average currents from the 15 m depth level of the NCEP analyses
of the tropical Pacific Ocean are evaluated against surface mixed layer
current observations obtained from an extensive set of satellite-tracked
drifting buoys. These averages display many climatological
characteristics of the region, but are not intended to serve as a
climatology because the data from the analyses are trimmed to match the
time-space distribution of the observations. Substantial discrepancies
between the analyses and the observations are revealed. First, the
near-equatorial meridional currents and divergence have approximately
twice the magnitude in the analyses as in the observations. This
discrepancy is largely independent of whether temperature profile data
are assimilated or not, and is attributed to the parameterization of
vertical viscosity. Second, the zonal flow in both the NECC and the SEC
is much stronger in the analyses than in the observations, especially in
the western Pacific. This discrepancy is associated with assimilation of
temperature profile data. It arises because salinity is an active
variable in the underlying analysis model, but is not controlled by
boundary fluxes or other observations. Under the uncontrolled influence
of advection and strong horizontal diffusion, the salinity distribution
becomes nearly homogeneous. Consequently, the analyses do not account
for observed temperature-salinity correlations when density is computed
following assimilation of temperature profile data. This leads to
erroneous pressure gradients that drive excessively strong geostrophic
currents and force large accelerations near the western boundary. Our
results indicate that it is important to consider the consequences on the
density structure of neglecting salinity during the assimilation of
temperature data. We recommend that surface salinity observations from
drifting buoys and volunteer observing ships be initiated to improve the
ocean analyses.
Baringer, M.O., and J.F. Price. Mixing and spreading of the Mediterranean
Outflow. Journal of Physical Oceanography, 27(8):1654-1677 (1997).
Hydrographic and expendable current profiler (XCP) data taken during the
Gulf of Cadiz Expedition on September 21-27, 1988 were analyzed to
diagnose the mixing, spreading, and descent of the Mediterranean Outflow.
The theta/S properties and the thickness and width of the outflow were
very similar to that seen in earlier surveys (for example, by Heezen and
Johnson, 1969). The transport of pure Mediterranean water (S=38.4) was
estimated to be about half a Sv, which is considerably lower than
historical estimates, most of which were indirect, but comparable to
other recent estimates made from direct velocity observations. The total
outflow transport was about 0.7 Sv at the west end of the Strait of
Gibraltar, and increased to about 1.9 Sv within the western Gulf of
Cadiz. This increase in transport occurred by entrainment of fresher
North Atlantic Central Water (NACW), and the salinity anomaly of the
outflow was rapidly eroded. The velocity-weighted salinity decreased to
36.7 within 60 km of the Strait, during the initial descent of the
continental slope, and decreased by about another 0.1 before the deeper
portion of the outflow began to float off of the bottom near Cape St.
Vincent. Entrainment appears to have been correlated with the occurrence
of bulk Froude numbers slightly greater than 1. In the western Gulf of
Cadiz, where entrainment was much weaker, Froude numbers were well below
1. The outflow began in the eastern Strait of Gibraltar as a narrow (10
km wide) current having a very narrow range of theta/S properties (theta
varies by < 0.5°C). The outflow broadened as it descended the
continental slope of the northern Gulf of Cadiz, and reached a maximum
width of 90 km in the western Gulf of Cadiz. The descent of the outflow
was very asymmetric: the offshore and downslope edge of the flow descends
rapidly, while the onshore and shallower edge of the outflow descends
slowly. The northern, nearshore side remained considerably higher in
the water column and thus entrained relatively warm and salty NACW. This
caused the outflow to develop horizontal theta/S variability and, by
about 100 km downstream, the across-stream variation in temperature on an
isopycnal was more than 2°C. Much of the volume transport in the
western Gulf of Cadiz was contained in two preferred modes, often called
cores, apparently because of topographic steering effects. The deeper,
offshore core had a central sigmatheta = 27.8, and the
shallower nearshore core, which was still in contact with the bottom in
the Gulf of Cadiz, had a central sigmatheta = 27.5.
Baringer, M.O., and J.F. Price. Momentum and energy balance of the
Mediterranean Outflow. Journal of Physical Oceanography,
27(8):1678-1692 (1997).
Hydrographic and expendable current profiler (XCP) data taken during
the Gulf of Cadiz Expedition in September 1988 were analyzed to describe
some aspects of the dynamics of the Mediterranean Outflow. During the
initial descent of the continental slope, the outflow current executes a
90 degrees right turn that appears to be approximately inertial. The
estimated geostrophic velocity greatly underestimated the actual current,
and the estimated curvature Rossby number is about 0.5. A form of the
Bernoulli function was evaluated to infer the total stress (entrainment
stress and bottom drag) acting on the outflow. Total stress was as large
as 5 Pa where the outflow begins to descend the continental slope and
where currents were in excess of 1 m/s. The entrainment stress, estimated
independently from property fluxes, reached a maximum of only about 1 Pa,
which was less than the inferred bottom stress. By about 100 km downstream,
the current was aligned approximately along the topography. The current
amplitude and the estimated stress were much less, about 0.3 m/s and less
than 0.5 Pa. The entrainment stress was very small in the region well
downstream of the Strait. Bottom stress thus appears to be the crucial
element in the dynamics of the Mediterranean Outflow, allowing or causing
the outflow to descend some 1000 m into the North Atlantic. In the regions
of strongest bottom stress the inferred drag coefficient was about 3 ×
10- 3. Entrainment stress was much smaller by comparison, but
the entrainment effect upon the density anomaly was crucial in eroding the
density anomaly of the outflow.
Black, M.L., and J.R. Parrish. The structure of the hurricane eyewall
at altitudes reached by the NOAA Gulfstream-IV aircraft. Minutes, 51st
Interdepartmental Hurricane Conference, Miami, FL, March 24-28, 1997.
Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A-16 (1997).
Starting with the 1997 Atlantic hurricane season, the recently acquired and
specially instrumented NOAA Gulfstream-IV (G-IV) jet aircraft will conduct
synoptic reconnaissance missions in the periphery of tropical cyclones.
The missions are designed to sample, via dropsondes, vertical profiles of
the environmental air from flight altitudes of 40,000-45,000 ft. The flights
are intended to avoid the convectively active eyewall and rainband regions
of the storms. In future seasons, however, research and reconnaissance needs
may warrant high altitude penetrations of the hurricane core. Before
conducting flights directly into tropical cyclones, the structure of the
deep convection, especially in the eyewall, needs to be assessed to determine
the types of flight conditions the G-IV might experience. The purpose of
this report is to use the remote-sensing capabilities of the NOAA WP-3D
aircraft to document and describe the structure of the hurricane eyewall at
high altitudes. Vertcally-pointing Doppler radials from the tail radars on
the NOAA P-3 aircraft yield estimates of the two-dimensional (radius-height
plane) reflectivity and vertical velocity structure. Observations from more
than 200 radial legs through the eyewalls of tropical cyclones have shown
that vertical velocity extrema with magnitudes >10 m/s can occur at heights
up to 15 km, well above the maximum attainable altitude of the G-IV. These
extrema occur infrequently (<10% chance) but can contain steep vertical
velocity gradients that may produce moderate to severe turbulence, similar
to that experienced by the P-3 aircraft at lower altitudes. Examples of the
various types of vertical velocity structures that the G-IV may encounter
in eyewall penetrations will be presented.
Black, M.L., R.W. Burpee, and F.D. Marks. The asymmetric distribution
of vertical motions and precipitation in the hurricane eyewall.
Preprints, 22nd Conference on Hurricanes and Tropical Meteorology,
Ft. Collins, CO, May 19-23, 1997. American Meteorological Society,
Boston, 100-101 (1997).
No abstract.
Black, M.L., J.F. Gamache, H.E. Willoughby, C.E. Samsury, F.D. Marks,
and R.W. Burpee. Airborne radar observations of shear-induced asymmetries
in the convective structure of Hurricane Olivia (1994). Proceedings,
28th Conference on Radar Meteorology, September 9-12, 1997, Austin,
TX. American Meteorological Society, Boston, 577-578 (1997).
The Hurricane Research Division of NOAA conducted dual aircraft
experiments on successive days in eastern Pacific Hurricane Olivia. The
flights occurred on 24 September 1994 while Olivia was intensifying and
25 September when the hurricane was initially at maximum intensity
followed by a period of rapid filling. The data collected from the
flights into Hurricane Olivia provide a unique opportunity to investigate
and describe the interplay between environmental wind shear, eye-wall
convection, and intensity changes. Radar systems on the WP-3D research
aircraft recorded radar reflectivity from the horizontally-scanning,
lower-fuselage (LF) radar (5-cm), and reflectivity and Doppler radials
from the tail radar (3-cm) which scans in a plane perpendicular to the
aircraft track. On September 24th, the hurricane was embedded in weak
easterly shear and observations from the LF radar showed that the
convection in Olivia's eyewall was highly asymmetric. The deepest
convection and highest reflectivities were concentrated in the south and
southeast portions of the eyewall, while the northern portions contained a
stratiform-like precipitation structure. Vertical profiles of
reflectivity and vertical velocity derived from vertically-pointing
radials from the tail Doppler radar further describe the nature of these
asymmetries. Large and strong updrafts were located just upwind of the
heaviest precipitation while downward motion dominated in the eyewall
region slightly downwind of the precipitation maximum. Much weaker and
smaller up- and downdrafts existed in the low-reflectivity region of the
northern eyewall. Olivia intensified during the 24-hour period between
flights while the environmental shear was weak, ahead of a
mid-tropospheric trough. On the 25th, when the aircraft first arrived
near the center, Olivia's eyewall appeared on LF radar images as a highly
symmetric, nearly continuous ring of high reflectivities (>40 dBZ).
Doppler radar observations of the vertical velocity structure,
however, still showed an asymmetric structure, albeit not as pronounced
as the previous day. During the flight, westerly shear increased
dramatically, Olivia's central pressure rose, and large asymmetries in
the eyewall reflectivity field developed in an apparent response to the
changing vertical wind shear. Olivia's weakening may also have been
partially due to the storm moving over a region of cooler sea-surface
temperatures. Convective cells with strong updrafts formed in the
eastern eyewall (downshear), and advected around to the high-reflectivity
region of the northern eyewall. Strong downdrafts appeared to form at
high altitudes, adjacent to and slightly downwind of the large and strong
updrafts, and rotated around the eyewall to the weak-reflectivity region
of the western eyewall (upshear). Near the end of the flight, the
magnitude of the updrafts decreased and the convective tops were lower in
altitude, conditions that are consistent with a weakening hurricane.
Black, R.A. Giant raindrops observed from large aircraft. Preprints,
22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins,
CO, May 19-23, 1997. American Meteorological Society, Boston, 494-495 (1997).
No abstract.
Boebel, O., C. Schmid, and W. Zenk. Flow and recirculation of Antarctic
Intermediate Water across the Rio Grande Rise. Journal of Geophysical
Research, 102(C9):20,967-20,986 (1997).
The flow of the low-salinity Antarctic Intermediate Water (AAIW) at
700-1150 m depth across the Rio Grande Rise and the lower Santos Plateau
is studied under the auspices of the World Ocean Circulation Experiment
(WOCE) in the context of the Deep Basin Experiment. Our data set consists
of several hydrographic sections, a collection of 15 RAFOS float
trajectories, and records from 14 moored current meters. The data were
gathered during different intervals between 1990 and 1994. The inferred
flow field strongly supports a basinwide anticyclonic recirculation cell
in the subtropical South Atlantic underneath the wind-driven gyre. Its
center, which appears to be southeast of the Rio Grande Rise, separates
the eastward advection of AAIW below the South Atlantic Current from the
westward flowing, recirculating AAIW. The two near-shelf limbs closing
the circumference of AAIW flow are formed in the east by the deep
Benguela Current, potentially modulated by salty inflow of Indian Ocean
Intermediate Water, and in the west by the Brazil Current system.
Further important circulation elements are the Brazil-Falkland (Malvinas)
Confluence Zone at 40°S and an unnamed divergence at 28°S close
to the 1000 m isobath. The resulting broad southward flow of AAIW
augments the share of modified, i.e., saltier, intermediate water
in the source region of the South Atlantic Current, while the smaller
northward flow marks the source of a narrow equatorward Western Intermediate
Boundary Current, ultimately leaving the South Atlantic. This
shelf-trapped jet is clearly documented in hydrographic data from
19°S and in nearby current meter records. The jet contrasts a
sluggish flow across this latitude east of 35°W. A continuous flow
of AAIW from its subpolar region in the southwestern Argentine Basin all
along the western slope toward the equator appears unlikely between
35°S and 25°S.
Bringi, V.N., K.Knupp, A. Detwiler, L. Liu, I.J. Caylor, and R.A.
Black. Evolution of a Florida thunderstorm during the Convection and
Precipitation Experiment: The case of August 9, 1991. Monthly
Weather Review, 125(9):2131-2160 (1997).
The relationships among kinematic, microphysical, and electric field
properties within a multicell Florida thunderstorm are investigated using
observations from three Doppler radar (one with multiple wavelength and
polarization diversity capabilities), four instrumented penetrating
aircraft, a surface-based electric field mill network, and other
observation facilities. The storm was convectively active for about 1 h
and at least five primary cells developed within the storm during this
time, one of which went through three consecutive development cycles. The
updrafts in this storm were 2-4 km wide, exhibited bubble-like evolution,
and had lifetimes of 10-20 min. The maximum updraft determined by the
multiple Doppler analysis was about
20 m s-1. A differential
reflectivity (ZDR) "column," indicating regions containing
millimeter-size raindrops, extending above the freezing level, was
associated with each cell during its developing stages. This column
reached altitudes exceeding 6 km (-8°C) in the stronger updrafts. As
the ZDR columns reached maximum altitude, a "cap" of
enhanced linear depolarization ratio (LDR) and enhanced 3-cm wavelength
attenuation (A3) formed, overlapping the upper regions of the
ZDR column. These parameters indicate rapid development
of mixed-phase conditions initiated by freezing of supercooled raindrops.
Lightning was observed only in the central and strongest convective cell.
Electric fields exceeding 10 k V m-1 were noted during aircraft
penetrations in this as well as several other cells that did not produce
lightning. Fields exceeding 1 k V m-1 were noted by the
instrumented aircraft at midcloud levels within a few minutes of development
of mixed-phase conditions at these levels or aloft. The first intracloud
lightning was detected by the surface field mill network within 5 min of
development of mixed-phase conditions aloft in the first cycle of development
in the central cell, and the first cloud-to-ground event was noted within
9 min of this development. Lightning continued through two additional
cycles of updraft growth in this central region and diminished as the
convection subsided after about 30 min. Aircraft-measured electric fields
and lightning retrievals from the surface field meter network are consistent
with a tendency for negative charge to accumulate above the 6.5 km
(-12°C) level within regions of radar reflectivity maxima and for
positive charge to accumulate in the anvil region well above 9 km
(-30°C).
Butler, J.H., and S.A. Yvon-Lewis. Estimating lifetimes of atmospheric
trace gases with respect to oceanic loss: Two approaches. AGU 1997
Spring Meeting, Baltimore, MD, May 27-30, 1997. Supplement to
EOS,Transactions, American Geophysical Union, 78(17):S90, A42E-12
(1997).
The flux of a gas across the air-sea interface typically is estimated as
the product of the air-sea, gas-transfer coefficient and the difference
in the partial pressure of the gas between the water and the air.
Although there is some uncertainty in the value and mechanism selected
for the transfer coefficient, this approach is generally considered a
reasonable way to evaluate the rate at which a gas passes between the
ocean and the atmosphere. Problems can arise, however, when one tries to
compute the partial lifetime of this gas in the atmosphere with respect
to its loss in the ocean. So long as the gas is not produced in the
ocean, this calculated flux can be used to derive a partial lifetime.
However, if the gas is simultaneously produced and consumed in the ocean,
the lifetime estimate calculated in this way will be too long. This can
be accounted for if one considers that the calculated flux from the
atmosphere to the ocean is a net flux and that it will change in
opposition to changes in the atmospheric burden of the gas. In this
sense, the ocean acts as a "buffer" for the gas in the atmosphere, yet
the effect is calculable. An alternative approach, involving the
separation of inward and outward fluxes, gets past the lifetime and
emission problem and allows for an accurate calculation of the partial
atmospheric lifetime. This approach also provides for the computation of
emissions from undersaturated waters or uptake by supersaturated waters.
Each approach is internally consistent and both can be used, along with
information on other non-oceanic fluxes, to describe the budgets of
atmospheric trace gases. However, each carries with it certain caveats
and limitations that must be considered in constructing these budgets.
This talk will address these issues, with specific emphasis on methyl
bromide and other trace gases of interest in ozone depletion and
global warming.
Carsey, T.P., D.D. Churchill, M.L. Farmer, C.J. Fischer, A.A. Pszenny,
V.B. Ross, E.S. Saltzman, M. Springer-Young, and B. Bonsang. Nitrogen
oxides and ozone production in the North Atlantic marine boundary
layer. Journal of Geophysical Research, 102(D9):10,653-10,665
(1997).
Measurements of reactive nitrogen gases (NO, NO2, NOy), as
well as related chemical (O3, CO, aerosol black carbon, radon,
selected nonmethane hydrocarbons) and meteorological parameters, were made
on board the R/V Malcolm Baldrige prior to and subsequent to the
1992 ASTEX (Atlantic Stratocumulus Transition Experiment) in the North
Atlantic Ocean during June and July 1992. Results showed indications of
well-defined plumes from North America and Europe from both chemistry and
back trajectory data. Elevated ozone concentrations were also observed
in air masses from uninhabited continental regions. Chemical and
meteorological data were incorporated into a simple photochemical model
in which ozone destruction predominated over generation. The principal
reaction leading to ozone destruction was O(1D) +
H2O - 2OH.
Checkley, D.M., P.B. Ortner, L.R. Settle, and S.R. Cummings. A continuous,
underway fish egg sampler (CUFES). Fisheries Oceanography,
6(2):58-73 (1997).
We describe a method to sample the highly contagious distribution of
pelagic fish eggs. CUFES, the continuous, underway fish egg sampler,
consists of a submersible pump, concentrator, electronics, and sample
collector. This system operates continuously and under nearly all sea
conditions, providing a real-time estimate of the volumetric abundance of
pelagic fish eggs at pump depth, usually 3 m. CUFES-derived estimates of
volumetric abundance agree well with those from nets towed at pump depth
and with a real abundance estimated from vertically-integrated plankton
tows. CUFES has been used successfully to sample the eggs of menhaden,
pinfish, sardine, and anchovy off the coasts of the eastern and western
United States and South Africa. Two large patches of eggs of the
Atlantic menhaden were sampled off North Carolina in winter 1993-1994,
had a linear scale of 5-10 km, and were found in waters between the Gulf
Stream and mid-shelf front. Spawning location may be related to
bathymetry. CUFES is now being used to estimate spawner biomass by the
Daily Egg Production Method. An optical plankton counter provided
accurate estimates of the number of Atlantic menhaden eggs sampled by
CUFES. Automation of egg counting in CUFES is under development.
Chelton, D.B., and A.M. Mestas-Nunez. The large-scale, wind-driven
response of the North Pacific. International WOCE Newsletter,
25:3-6 (1997).
In this note, we present the results of an investigation of the validity
of the time-varying Sverdrup balance in the North Pacific based on
analysis of three years of: (1) a simple flat bottom Sverdrup model; (2)
the primitive equation global ocean circulation model developed by the
Parallel Ocean Program (POP) at the Los Alamos National Laboratory; and
(3) observations of sea surface height (SSH) by the TOPEX/POSEIDON (T/P)
altimeter. The three-year period considered here is October 1992
through November 1995. We conclude that much of the large-scale,
low-frequency variability in the North Pacific can be accounted for by
simple Sverdrup dynamics.
Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark.
Global oceanic precipitation: A joint view by TOPEX and the TOPEX
microwave radiometer. Journal of Geophysical Research,
102(C5):10,457-10,471 (1997).
The TOPEX/POSEIDEN mission offers the first opportunity to observe rain
cells over the ocean by a dual-frequency radar altimeter (TOPEX) and
simultaneously observe their natural radiative properties by a
three-frequency radiometer (TOPEX microwave radiometer (TMR)). This
work is a feasibility study aimed at understanding the capability and
potential of the active/passive TOPEX/TMR system for oceanic rainfall
detection. On the basis of past experiences in rain flagging, a joint
TOPEX/TMR rain probability index is proposed. This index integrates
several advantages of the two sensors and provides a more reliable rain
estimate than the radiometer alone. One year's TOPEX/TMR data are used
to test the performance of the index. The resulting rain frequency
statistics show quantitative agreement with those obtained from the
Comprehensive Ocean-Atmosphere Data Set (COADS) in the Intertropical
Convergence Zone (ITCZ), while qualitative agreement is found for other
regions of the world ocean. A recent finding that the latitudinal
frequency of precipitation over the Southern Ocean increases steadily
towards the Antarctic continent is confirmed by our result. Annual and
seasonal precipitation maps are derived from the index. Notable features
revealed include an overall similarity in rainfall pattern from the
Pacific, the Atlantic, and the Indian Oceans and a general phase
reversal between the two hemispheres, as well as a number of regional
anomalies in terms of rain intensity. Comparisons with simultaneous
Global Precipitation Climatology Project (GPCP) multisatellite
precipitation rates and COADS rain climatology suggest that systematic
differences also exist. One example is that the maximum rainfall in the
ITCZ of the Indian Ocean appears to be more intensive and concentrated
in our result compared to that of the GPCP. Another example is that the
annual precipitation produced by TOPEX/TMR is constantly higher than
those from GPCP and COADS in the extratropical regions of the northern
hemisphere, especially in the northwest Pacific Ocean. Analyses of the
seasonal variations of prominent rainy and dry zones in the tropics and
subtropics show various behaviors such as systematic migration,
expansion, and contraction, merging and breakup, and pure intensity
variations. The seasonality of regional features is largely influenced
by local atmospheric events such as monsoon, storm, or snow activities.
The results of this study suggest that TOPEX and its follow-on may serve
as a complementary sensor to the special sensor microwave/imager in
observing global oceanic precipitation.
Chereskin, T.K., W.D. Wilson, H.L. Bryden, A. Ffield, and J. Morrison.
Observations of the Ekman balance at 8°30'N in the Arabian Sea
during the 1995 southwest monsoon. Geophysical Research Letters,
24(21):2541-2544 (1997).
The Ekman transport is estimated from two sets of hydrographic and
shipboard acoustic Doppler current profiler (ADCP) velocity observations
made during June and September 1995, during the southwest monsoon in the
Arabian Sea. Both sets of measurements were made along latitude
8°30'N, designated as World Ocean Circulation Experiment (WOCE)
line I1W, from Somalia to Sri Lanka. The Ekman transport estimates
calculated from ageostrophic velocity were southward: 17.6 ± 2.4
106 m3 s-1 in June and 7.9 ± 2.7
106 m3 s-1 in September. These direct
estimates were in good agreement with those predicted by the Ekman
balance using both shipboard and climatological winds. The vertical
structure of the ageostrophic velocity and the stratification were quite
different between the two occupations of the transect. The wind-driven
momentum was confined to a very shallow layer in June (about 50 m) and
the surface layer was strongly stratified, with a maximum salinity layer
at depths between 50 and 70 m. The ageostrophic velocity penetrated much
deeper in September (to about 160 m) and the pycnocline was
correspondingly deeper. In both cases, the Ekman transport penetrated
beneath the mixed layer, to the top of the pycnocline.
Cione, J.J., and S. Raman. The impact of SST gradients on propagating
low-level mesovortices near the Gulf Stream. Preprints, Conference on
Coastal Oceanic and Atmospheric Prediction, Atlanta, GA, January 28-
February 2, 1996. American Meteorological Society, Boston, 204-211 (1997).
No abstract.
DeMaria, M., and J. Kaplan. An operational evaluation of a statistical
intensity prediction scheme (SHIPS). Preprints, 22nd Conference on
Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997.
American Meteorological Society, Boston, 280-281 (1997).
No abstract.
Dietrich, D.E., C.A. Lin, A.M. Mestas-Nunez, and D.-S. Ko. A high
resolution numerical study of Gulf of Mexico fronts and eddies.
Meteorology and Atmospheric Physics, 64:187-201 (1997).
The Gulf of Mexico (GOM) circulation is simulated using the DieCAST ocean
model, with a horizontal resolution of 1/12 degree and 20 vertical
layers. The results compare well with observations of both large and
small scale features, including Loop Current frontal occlusions
associated with frontal eddies. The simulation is carried out without
any data assimilation. The frontal eddies tend to be spaced at about 90
degree intervals around the Loop Current, leading to a Loop Current head
shaped like a square with rounded corners. The pattern rotates as eddies
circle the Loop, and frontal eddies elongate as they squeeze through the
Florida Strait. Major warm core eddies separate regularly from the Loop
Current and propagate to the western GOM. Old warm core eddies in the
western Gulf dissipate through bottom drag effects, which also generate
cyclonic parasitic eddies. Newly arrived warm core eddies merge with old
ones in the western GOM. Recently separated elongated Loop Current
eddies can rotate and reattach temporarily to the Loop Current. The
barotropic flow component develops eddies between the main separated warm
core eddy and the Loop Current due to eastward dispersion, as the main
eddy itself propagates westward into the Gulf.
Dodge, P.P., S.H. Houston, and J.F. Gamache. Three-dimensional windfields
in Hurricane Fran (1996) at landfall. Preprints, 22nd Conference on
Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997.
American Meteorological Society, Boston, 115-116 (1997).
No abstract.
Dodge, P.P., S.H. Houston, and J.F. Gamache. Windfields in Hurricane
Fran (1996) at landfall from combined WSR-88D and airborne Doppler radar
data. Proceedings, 28th Conference on Radar Meteorology, Austin,
TX, September 9-12, 1997. American Meteorological Society, Boston,
575-576 (1997).
The Hurricane Research Division's (HRD) Tropical Cyclone Windfields at
Landfall Experiment collects data in landfalling tropical cyclones from
NOAA aircraft to improve real-time and post- storm surface wind analyses
that are prepared by HRD. The real-time analyses are provided to
forecasters at the Tropical Prediction Center. Airborne Doppler radar
data are combined with National Weather Service WSR-88D radar data in
three-dimensional analyses to document the evolution of tropical
cyclones at landfall, and to provide corroborating data for testing
WSR-88D tropical cyclone algorithms. From 2056 UTC, 5 September 1996, to
0348, 6 September 1996, the NOAA research aircraft RF42 flew in
Hurricane Fran as it moved ashore in North Carolina. A "figure 4" pattern
at 5,000 ft, overflights of marine and coastal surface platforms, and
several passes along radials from the Wilmington and Morehead City
WSR-88D radars in North Carolina provided flight-level wind data that
were included in HRD's surface wind analyses. The research flight
concluded with an overland "figure 4" pattern at 14,000 ft that passed
near the Raleigh WSR-88D, and then through Fran's center when it was 70
km north-northwest of the Wilmington WSR-88D. The portable Doppler radar
on wheels from the University of Oklahoma also recorded data at the
Wilmington airport during the landfall, so there is a rich data set to
describe convective and mesoscale features in Hurricane Fran. At the
conference, we will present windfields synthesized from the airborne and
WSR-88D radars that describe the kinematic structure as Fran moved over
the coast. The comparison of vertical structure of the wind fields near
the coast and 200 km inland should be particularly interesting. We will
also discuss the problems of combining airborne and ground-based Doppler
radar data.
Donelan, M.A., W.M. Drennan, and K.B. Katsaros. The air-sea momentum
flux conditions of wind sea and swell. Journal of Physical
Oceanography, 27(10):2087-2099 (1997).
During the Surface Wave Dynamics Experiment, direct measurements of
momentum, heat, and water vapor fluxes were obtained from a mast on the
foredeck of a SWATH (small water-plane area, twin hull) ship in deep
water off the state of Virginia. Directional wave spectra were obtained
simultaneously from a six or three-wire wave-staff array mounted at the
bow of the ship. One hundred and twenty-six 17-minute runs of flux and
wave data obtained with the ship steaming slowly into the wind are
examined for the effects of the relative direction of the wind sea and
background swell on the momentum transfer. The adequacy of the inertial
dissipation method, which depends on the high-frequency turbulent
fluctuations for evaluating the wind stress, is also examined for any
effects of swell. The results show that the presence of counter- and
cross-swells can result in drag coefficients that are much larger than
the value for a pure wind sea. The eddy correlation and inertial
dissipation methods for measuring wind stress are found to diverge during
the complex sea conditions. The authors interpret the latter observations
as an indication that the traditional inertial dissipation method, in
which the pressure and transport terms in the kinetic energy balance
equation are assumed to be in balance, may be unsuitable for use in a
marine boundary layer disturbed by swell.
Drennan, W.M., M.A. Donelan, E.A. Terray, and K.B. Katsaros. On waves,
oceanic turbulence, and their interaction. Geophysica, 33:17-28
(1997).
No abstract.
Dupuis, H., P.K. Taylor, A. Weill, and K.B. Katsaros. Inertial
dissipation method applied to derive turbulent fluxes over the ocean
during the Surface of the Fluxes and Interactions with the
Atmosphere/Atlantic Stratocumulus Transition Experiment (SOFIA/ASTEX)
and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites
Oceaniques: Recherche Experimentale (SEMAPHORE) experiments with low
to moderate wind speeds. Journal of Geophysical Research,
102(C9):21,115-21,129 (1997).
The transfer coefficients for momentum and heat have been determined for
10 m neutral wind speeds (U10n) between 0 and 12
m/s using data from the Surface of the Ocean, Fluxes and Interactions
with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphere,
Proprietes des Heterogeneites Oceaniques: Recherche Experimentale
(SEMAPHORE) experiments. The inertial dissipation method was applied to
wind and pseudo virtual temperature spectra from a sonic anemometer,
mounted on a platform (ship) which was moving through the turbulence
field. Under unstable conditions the assumptions concerning the turbulent
kinetic energy (TKE) budget appeared incorrect. Using a bulk estimate for
the stability parameter, Z/L (where Z is the height and
L is the Obukhov length), this resulted in anomalously low drag
coefficients compared to neutral conditions. Determining Z/L
iteratively, a low rate of convergence was achieved. It was concluded
that the divergence of the turbulent transport of TKE was not negligible
under unstable conditions. By minimizing the dependence of the calculated
neutral drag coefficient on stability, this term was estimated at about
-0.65 Z/L. The resulting turbulent fluxes were then in close
agreement with other studies at moderate wind speed. The drag and
exchange coefficients for low wind speeds were found to be
Cen × 103 = 2.79
U10n-1 + 0.66
(U10n < 5.2 m/s), Cen ×
103 = Chn × 103 = 1.2
(U10n > 5.2 m/s), and Cdn ×
103 = 11.7 U10n-2 + 0.668
(U10n < 5.5 m/s), which imply a rapid increase of
the coefficient values as the wind decreased within the smooth flow
regime. The frozen turbulence hypothesis and the assumptions of isotropy
and an inertial subrange were found to remain valid at these low wind
speeds for these shipboard measurements. Incorporation of a free
convection parameterization had little effect.
Elfouhaily, T., B. Chapron, K.B. Katsaros, and D. Vandemark. A unified
directional spectrum for long and short wind-driven waves. Journal of
Geophysical Research, 102(C7):15,781-15,796 (1997).
Review of several recent ocean surface wave models finds that while
comprehensive in many regards, these spectral models do not satisfy
certain additional, but fundamental, criteria. We propose that these
criteria include the ability to properly describe diverse fetch
conditions and to provide agreement with in-situ observations of Cox and
Munk (1954), Jahne and Riemer (1990), and Hara et al. (1994) data
in the high-wavenumber regime. Moreover, we find numerous analytically
undesirable aspects such as discontinuities across wavenumber limits,
nonphysical tuning or adjustment parameters, and noncentrosymmetric
directional spreading functions. This paper describes a two-dimensional
wavenumber spectrum valid over all wavenumbers and analytically amenable
to usage in electromagnetic models. The two regime model is formulated
based on the Joint North Sea Wave Project (JONSWAP) in the long-wave
regime and on the work of Phillips (1985) and Kitaigorodskii (1973) at
the high wavenumbers. The omnidirectional and wind-dependent spectrum is
constructed to agree with past and recent observations including the
criteria mentioned above. The key feature of this model is the similarity
of description for the high- and low-wavenumber regimes; both forms are
posed to stress that the air-sea interaction process of friction between
wind and waves (i.e., generalized wave age, u/c) is
occurring at all wavelengths simultaneously. This wave age
parameterization is the unifying feature of the spectrum. The spectrum's
directional spreading function is symmetric about the wind direction and
has both wavenumber and wind speed dependence. A ratio method is
described that enables comparison of this spreading function with
previous noncentrosymmetric forms. Radar data are purposefully excluded
from this spectral development. Finally, a test of the spectrum is made
by deriving roughness length using the boundary layer model of
Kitaigorodskii. Our inference of drag coefficient versus wind speed and
wave age shows encouraging agreement with Humidity Exchange Over the Sea
(HEXOS) campaign results.
Enfield, D.B., and D.A. Mayer. Tropical Atlantic sea surface temperature
variability and its relation to El Niño-Southern Oscillation.
Journal of Geophysical Research, 102(C1):929-945 (1997).
Past analyses of tropical Atlantic sea surface temperature variability
have suggested a dipole behavior between the northern and southern
tropics, across the Intertropical Convergence Zone (ITCZ). By analyzing
an improved 43-year (1950-1992) record of SST (Smith et al., 1996)
and other data derived from the Comprehensive Ocean-Atmosphere Data Set
(COADS), it is shown that the regions north and south of the ITCZ are
statistically independent of each other at the seasonal to interannual
time scales dominating the data, confirming the conclusions of Houghton
and Tourre (1992). Some dipole behavior does develop weakly during the
boreal spring season, when there is a tendency for SST anomaly west of
Angola to be opposite of that in the tropical North Atlantic. It is
further shown that tropical Atlantic SST variability is correlated with
Pacific El Niño-Southern Oscillation (ENSO) variability in several
regions. The major region affected is the North Atlantic area of
northeast trades west of 40°W along 10°N-20°N and extending
into the Caribbean. There, about 50-80% of the anomalous SST variability is
associated with the Pacific ENSO, with Atlantic warmings occurring 4-5
months after the mature phases of Pacific warm events. An analysis of
local surface flux fields derived from COADS data show that the
ENSO-related Atlantic warmings occur as a result of reductions in the
surface northeast trade wind speeds, which in turn reduce latent and
sensible heat losses over the region in question, as well as cooling due
to entrainment. This ENSO connection is best developed during the boreal
spring following the most frequent season of maximum ENSO anomalies in
the Pacific. A region of secondary covariability with ENSO occurs along
the northern edge of the mean ITCZ position and appears to be associated
with northward migrations of the ITCZ when the North Atlantic warmings
occur. Although easterly winds are intensified in the western equatorial
Atlantic in response to Pacific warm events, they do not produce strong
local changes in SST. Contrary to expectations from studies based on
equatorial dynamics, these teleconnected wind anomalies do not give rise
to significant correlations of SST in the Gulf of Guinea with the Pacific
ENSO. As the teleconnection sequence matures, strong southeast trades at
low southern latitudes follow the development of the North Atlantic SST
anomaly and precede by several months the appearance of weak negative SST
anomalies off Angola and stronger positive anomalies extending eastward
from southern Brazil along 15°-30°S.
Enfield, D.B., and A.M. Mestas-Nunez. Global modes of ENSO and
non-ENSO sea surface temperature variability. AGU 1997 Fall Meeting,
San Francisco, CA, December 8-12, 1997. Supplement to EOS,
Transactions, American Geophysical Union, 78(46):F349, OS21D-05 (1997).
El Niņo-Southern Oscillation (ENSO) is a global phenomenon with significant
phase propagation within and between basins, which we capture and describe
in the first mode of a complex empirical orthogonal function (CEOF) analysis
of sea surface temperature anomaly (SSTA) from the mid-19th century through
1992. We subsequently remove the global ENSO from the SSTA data, plus a
linear trend everywhere, in order to consider other global modes of
variability uncontaminated by the intra- and inter-basin effects of ENSO.
An ordinary EOF analysis of the SSTA residuals reveals three non-ENSO modes
of low-frequency variability that are related to slow oceanic and climate
signals described in the literature. The first two modes both have an
interdecadal time scale with high loadings in the Pacific; they bear some
spatial similarities to the ENSO pattern but are broader and differ in the
time domain. A CEOF analysis confirms that they are not merely the
phase-related components of a single mode and that all three modes are
without significant phase propagation. The third mode is a multidecadal
signal with maximal realization in the extratropical North Atlantic
southeast of Greenland. It also has high loadings in the tropical Atlantic,
anticorrelated across the intertropical convergence zone (ITCZ), and strong
variability of opposite sign in the eastern tropical Pacific. All three
modes have significant loadings over the central and/or eastern equatorial
Pacific. Temporal extrema in the first and third modes during 1982-1983
explain the large magnitude of that ENSO event, which in the global ENSO
mode is large but equalled or exceeded by four other events.
Faber, T., L.K. Shay, S.D. Jacob, S.H. Houston, and P.G. Black. Observed
air-sea interactions during Hurricane Emily. Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 433-434 (1997).
No abstract.
Feely, R.A., R.H. Wanninkhof, C. Goyet, D.E. Archer, and T. Takahashi.
Variability of CO2 distributions and sea- air fluxes in the
central and eastern equatorial Pacific during the 1991-1994 El Niño.
Deep-Sea Research II, 44(9-10):1851-1867 (1997).
As part of the U.S. JGOFS Program and the NOAA Ocean-Atmosphere Carbon
Exchange Study (OACES), measurements of CO2 partial pressure
were made in the atmosphere and in the surface waters of the central and
eastern equatorial Pacific during the boreal spring and autumn of 1992, the
spring of 1993, and the spring and autumn of 1994. Surface-water
pCO2 data indicate significant diurnal, seasonal, and
interannual variations. The largest variations were associated with the
1991-1994 ENSO event, which reached maximum intensity in the spring of 1992.
The lower values of surface-water DELTApCO2 observed during the
1991-1994 ENSO period were the result of the combined effects of both
remotely and locally forced physical processes. The warm pool, which
reached a maximum eastward extent in January-February of 1992, began in
September of 1991 as a series of westerly wind events lasting about 30
days. Each wind event initiated an eastward-propagating Kelvin wave which
caused a deepening of the thermocline. By the end of January 1992 the
thermocline was at its maximum depth, so that the upwelled water was warm
and CO2-depleted. In April of the same year, the local winds
were weaker than normal, and the upwelling was from shallow depths. These
changes resulted in a lower-than-normal CO2 flux to the
atmosphere. The results show that for the one-year period from the fall of
1991 until the fall of 1992, approximately 0.3 GtC were released to the
atmosphere; 0.6 GtC were released in 1993, and 0.7 GtC in 1994, in good
agreement with the model results of Ciais et al. (Science,
269, 1098-1102; J. Geophys. Res., 100, 5051-5070). The net reduction
of the ocean-atmosphere CO2 flux during the 1991-1994 El Niņo
was on the order of 0.8-1.2 GtC. Thus, the total amount of CO2
sequestered in the equatorial oceans during the prolonged 1991-1994 El
Niņo period was about 25% higher than the severe El Niņo of 1982-1983.
Festa, J.F., and R.L. Molinari. Comparison of thermal statistics derived
from observational data sets in the tropical Atlantic and Pacific Oceans.
NOAA Technical Memorandum, ERL AOML-91 (PB97-208177), 78 pp. (1997).
Statistical analysis of surface and subsurface temperature data in the
tropical Atlantic and Pacific Oceans is presented. The statistics were
estimated from the Comprehensive Ocean-Atmospheric Data Set (COADS) and
the historical expendable bathythermograph (XBT) observations. Spatial
structure functions (semivariograms) for the anomaly fields of sea
surface temperature and the temperature at 200 m and 400 m were estimated
for a 2 degree by 2 degree grid in the tropical oceans. Dominant scales
of spatial variability are identified and compared with other investigations.
Ffield, A., J. Toole, and W.D. Wilson. Seasonal circulation in the South
Indian Ocean. Geophysical Research Letters, 24(22):2773-2776 (1997).
Two World Ocean Circulation Experiment hydrographic cruises in March and
June 1995, along with Topex-Poseidon altimeter data and National
Meteorological Center wind data, are used to estimate seasonal changes
in the South Indian Ocean subtropical gyre. Mean annual curves derived
from the altimeter and wind data reveal strengthening of the
anticyclonic gyre in March and September, and weakening in June and
December. The seasonal changes correspond to variations in the wind
field south of 30 S at the equinoxes and solstices. In addition, the
wind-driven gyre is further north in July, and further south in March.
These variations in strength and location of the South Indian Ocean gyre
may influence inter-ocean transports south of Africa. Despite the
inferred mean annual seasonal variations in the South Indian Ocean gyre,
volume transports estimated in 1995 from the hydrographic data are close
to mean values. Apparently, a mesoscale eddy in March disrupts the
stronger fall gyre, whereas in June the weaker winter gyre is delayed by
1 month.
Gamache, J.F. Evaluation of a fully three-dimensional variational
Doppler analysis technique. Proceedings, 28th Conference on Radar
Meteorology, Austin, TX, September 9-12, 1997. American
Meteorological Society, Boston, 422-423 (1997).
A method is described that deduces the three-dimensional wind field from
two or more independent Doppler observations and from the continuity
equation, using a simultaneous three-dimensional variational solution of
the Doppler projection equations and the continuity equation. The
solution minimizes a cost function that includes (1) the difference
between observed Doppler radial velocities (corrected for precipitation
fall speed) and the projection of the analysis velocities upon the
observed Doppler pointing angles, (2) the error in the discretized
continuity equation, and (3) and the difference between a velocity component
and the surrounding six grid points. The third part of the cost function
is included to quiet noise in the solution. A much higher weight is given
to the second term since it represents the solution to the continuity
equation at only one grid cell. Otherwise, when all grid cells are
combined there would be substantial "leakage" in the continuity equation.
Errors in the discretized continuity equation are less than 10-6
s-1 at individual grid points. Analytical wind fields will be
resampled and the ability of the variational analysis to repeat the
analytical field will be discussed at the conference. The technique has
already been applied to the core of several hurricanes, convection within
a developing tropical storm, and several cases in TOGA COARE. By the time
of the conference it may also have been applied to a VORTEX case.
Bubble-like features have been seen in several of these cases, and the
bubble locations are very consistent with the radar reflectivity
presentation. Several of these examples will be shown at the conference.
Gamache, J.F. Wind shear and sea surface temperature in hurricanes
observed by airborne Doppler radar. Minutes, 51st Interdepartmental
Hurricane Conference, Miami, FL, March 24-28, 1997. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-17-A-18 (1997).
The relationships between sea surface temperature (SST), vertical wind
shear, and hurricane structure and intensity change are described
for two eastern Pacific hurricanes. Two NOAA WP-3D Doppler-equipped
aircraft observed Hurricane Jimena on 23 September 1991 and Hurricane
Olivia on 24 and 25 September 1994. Aircraft flight tracks were
coordinated for optimum Doppler wind analysis of inner core (radius <30
km) winds. Hurricane Jimena maintained virtually steady intensity for
24 hours, while Hurricane Olivia deepened 1-2 mb/hr during the mission
on the 24th and filled at 3 mb/hr during the mission on the 25th. The
missions yielded four wind analyses in Hurricane Jimena and seven for
each of the two days in Olivia. The average interval between analyses is
about 35 minutes. At the time of the mission, Jimena was located at
13.3°N, 109.6°W over warm tropical waters. The shear between
1 and 10 km was southeast at 15 m/s, and the hurricane remained at a
nearly constant intensity. Hurricane Olivia intensified into a
hurricane early on 24 September 1994. As the aircraft first reached
Olivia, it was located near 15.2°N,118.0°W. During three
hours on station the central pressure decreased by about 6 mb. The
hurricane had a mean shear during the mission of east at 7 m/s between
1 and 9 km, and the asymmetric distribution of greater precipitation to
the south was sustained throughout the mission. During the 24th the
hurricane traveled west-northwestward and was over warm tropical water
(28.2°C). As the aircraft began their penetrations on 25 September,
Olivia was near its maximum intensity. The radar presentation was highly
symmetric, and the shear between 1 and 9 km was 3 m/s from the west. In
three hours the shear had increased to 15 m/s from west-northwest, and
are highly asymmetric precipitation pattern had developed with dBZ greater
than 50 seen to the north of center and nothing above 40 dBZ to the south
of center. Mean winds at the 9-km level decreased by 15 m/s. The role
of shear in producing this change may be confused by Olivia passing the
SST front as it travelled nearly northward at 5 m/s, so the SST by the end
of the mission was 27°C. Another interesting feature that may be
described at the Interdepartmental Conference is a highly convective
feature in the northeast eyewall late on 25 September in Olivia that had
an elevated echo maximum and apparently a low-reflectivity vault where the
strongest updrafts were. Analysis has just begun of this feature.
Hopefully, it will be described at the next conference.
Gamache, J.F., H.E. Willoughby, M.L. Black, and C.E. Samsury. Wind shear,
sea surface temperature, and convection in hurricanes observed by airborne
Doppler radar. Preprints, 22nd Conference on Hurricanes and Tropical
Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological
Society, Boston, 121-122 (1997).
No abstract.
Garzoli, S.L., G.J. Goni, A.J. Mariano, and D.B. Olson. Monitoring
the upper southeastern Atlantic transports using altimeter data.
Journal of Marine Research, 55(3):453-481 (1997).
A large in-situ data set, collected in the southeastern Atlantic Ocean,
is merged with the TOPEX/POSEIDON altimeter observations in order to
verify the use of altimeter data in monitoring the transports of the
Agulhas/Benguela system. Comparisons between altimeter observations and
either moored current meters or inverted echo sounder measurements shows
that the sea surface elevation anomaly is significantly correlated with
the thermocline depth and the surface dynamic height, respectively.
Knowing the least-squares regression parameters, it is possible to
calculate the transports by using geostrophy and either a two-layer or a
continuously-stratified model. The transports obtained from fits of
dynamic height to altimeter sea surface height are similar to the ones
calculated with the moored instruments. In the southern part of the
area under analysis, around 35°S, close to the Agulhas
retroflection, the transports obtained from the two-layer model are
overestimated. Across the Benguela Current, at 30°S, transports are
still overestimated but of the same order as the measured ones. In
this part of the region, the two-layer model can be successfully used to
calculate the total and barotropic transports of the Benguela Current.
Analysis of the three years of geostrophic transport obtained from the
altimeter data indicate that the mean Benguela Current transport does
not change interannually more than 20%. However, the primary
interannual variability derives from the source water that forms the
Benguela Current.
German, C.R., D.L. Bourles, E.T. Brown, J. Hergt, S. Colley, N.C. Higgs,
E.M. Ludford, T.A. Nelsen, R.A. Feely, G. Raisbeck, and F. Yiou.
Hydrothermal scavenging on the Juan de Fuca Ridge:
230Thxs, 10Be, and REE in ridge-flank
sediments. Geochimica et Cosmochimica Acta, 61(19):4067-4078 (1997).
We have investigated the geochemistry of a hydrothermally-enriched
sediment core recovered from the western flank of the N.Cleft Segment,
Juan de Fuca Ridge, 8 km west of the "MegaPlume" area previously
identified near 45°N. The core contains varying biogenic, lithogenic,
and hydrothermal components, as reflected in CaCO3, Al, and Fe
contents, respectively. Horizons of pronounced hydrothermal input, in
core-top sediments and at depth, exhibit increased concentrations of Fe,
Cu, Zn, Pb, and shifts in Pb isotopic compositions toward nonradiogenic
(MORB/hydrothermal) values. REE concentrations co-vary with hydrothermal
Fe down-core, and shale-normalized REE distributions patterns exhibit
both negative Ce-anomalies and positive Eu-anomalies, indicative of input
from plume-particle fall-out. Unsupported 230Thxs
activities down-core are consistent with continuous slow sediment
accumulation rates of 0.54 cm/ky for 200 ky since the deposition of the
deeper Fe-rich horizon. 10Be(0) and 9Be
isotope concentrations also co-vary with hydrothermal Fe down-core and
exhibit 10Be(0) 9Be ratios which
approach that of Pacific Ocean deep water, indicative of a
seawater-scavenging source. 10Be(0)
230Thxs(0) ratios throughout most of Core GC88-6
are greater than mean Pacific Ocean values, indicating that hydrothermal
scavenging can lead to significant net removal of dissolved 10Be
into ridge-flank sediments.
Goldenberg, S.B., C.W. Landsea, and L.J. Shapiro. Are we seeing the
beginning of a long-term upturn in Atlantic basin major hurricane
activity? Proceedings, Tropical Cyclone Symposium, Melbourne,
Australia, December 9-13 1996. U.S. Office of Naval Research, 10 pp.
(1997).
No abstract.
Goldenberg, S.B., L.J. Shapiro, and C.W. Landsea. Are we seeing a
long-term upturn in Atlantic basin major hurricane activity related
to decadal-scale SST fluctuations? Preprints, 7th Conference on
Climate Variations, Long Beach, CA, February 2-6, 1997. American
Meteorological Society, Boston, 305-310 (1997).
No abstract.
Goldenberg, S.B., L.J. Shapiro, and C.W. Landsea. Mounting evidence for
a decadal-scale upturn in Atlantic basin tropical cyclone activity.
Preprints, 22nd Conference on Hurricanes and Tropical
Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological
Society, Boston, 507-508 (1997).
No abstract.
Goldenberg, S.B., L.J. Shapiro, and C.W. Landsea. The hyperactive
1995 Atlantic hurricane season: Just a spike or a harbinger of things
to come? Proceedings, 21st Climate Diagnostics and Prediction
Workshop, Hunstville, AL, October 28-November 1, 1996. American
Meteorological Society, Boston, 9-12 (1997).
For over 25 years the North Atlantic hurricane basin has experienced a
relative lull in tropical cyclone activity, in particular, in major
hurricane (maximum sustained surface winds of at least 50 m/s) activity
and in overall activity in the deep tropics. After the experience of
renewed "normal" activity in 1988 and 1989, it was suggested that the
Atlantic basin was returning to a long-term period of higher activity
such as what was experienced back in the decades of the 1950s and 1960s
and some earlier periods. The renewed activity in 1988 and 1989 was
followed, however, by a marked downturn in activity from 1991 to 1994. In
fact, the inhabitants of the regions surrounding the Caribbean
experienced no hurricanes from 1990-1994. As a result of the resumption
of the below-normal activity, primarily attributed to the highly
anomalous, long-lasting warm event (El Niño) in the tropical
Pacific, the notion that the Atlantic basin had entered a high-activity
decade was pretty much discarded. The warm event in the Pacific finally
ended in early 1995 and was followed by one of the most active hurricane
seasons in the Atlantic on record, including renewed activity in the
Caribbean, and with almost every measure of activity over twice the
long-term mean. Of particular note was that the season produced five
major hurricanes for the first time since 1964. Most of the major
hurricanes in the North Atlantic basin form from easterly (African) wave
disturbances and are especially sensitive to fluctuations in the tropical
climate on the interannual and interdecadal time scales. The chief issue
that will be addressed in the current study is whether or not the activity
of the 1995 season was simply an anomalous "spike" or a harbinger of
longer-term climate shifts signaling the probability of greater activity
over the next decade or so.
Goldenberg, S.B., L.J. Shapiro, and C.W. Landsea. The hyperactive 1995
Atlantic hurricane season: A spike or a harbinger of things to come?
Workshop Proceedings, Climate Change and Climate Variability in
the Atlantic, Halifax, Nova Scotia, December 3-6, 1996. American
Meteorological Society, Boston, 113-119 (1997).
No abstract.
Goni, G.J., S.L. Garzoli, A.J. Roubicek, D.B. Olson, and O.B. Brown.
Agulhas ring dynamics from TOPEX/POSEIDON satellite altimeter data.
Journal of Marine Research, 55(5):861-883 (1997).
The transfer of warm water from the Indian Ocean into the South Atlantic
subtropical gyre takes place in the form of rings and filaments formed
when the Agulhas Current retroflects south of Africa between 15°E
and 25°E. A survey of the rings formed from September 1992 until
December 1995 in the retroflection region was carried out using
TOPEX/POSEIDON altimeter data. A two-layer model was used to estimate
the upper layer thickness from the altimeter-derived sea surface height
anomaly data. An objective analysis scheme was used to construct a map
of upper layer thickness every 10 days. Seventeen rings and their
trajectories were identified using these maps. The shedding of rings
from the Agulhas Current was neither continuous nor periodic, and for
long periods there is no formation of rings. Several rings remained in
the region for more than a year and, at any given time, two to six rings
coexisted in the region east of the Walvis Ridge. The results showed
that the number of rings translating simultaneously in this region is
larger during the first half of each year. The upper layer transport of
the Agulhas Current in the retroflection region was computed and a close
association between high variations in transport and ring shedding was
found. Rings translated west-northwest at translation speeds ranging
from 5-16 km day-1 following formation. The values of
available potential energy computed for the rings place them among the
most energetic rings observed in the world oceans, with values of up to
70 × 1015 J. Transport computations indicate that each
ring contributes in the average approximately 1 Sv of Agulhas Current
waters to the Benguela Current.
Gordon, A.L., S. Ma, D.B. Olson, P. Hacker, A. Ffield, L.D. Talley,
W.D. Wilson, and M.O. Baringer. Advection and diffusion of Indonesian
throughflow within the Indian Ocean South Equatorial Current.
Geophysical Research Letters, 24(21):2573-2576 (1997).
Warm, low salinity Pacific water weaves through the Indonesian Seas into
the eastern boundary of the Indian Ocean. The Indonesian Throughflow
Water (ITW) adds freshwater into the Indian Ocean as it spreads by the
advection and diffusion within the Indian Ocean's South Equatorial
Current (SEC). The low salinity throughflow trace, centered along
12°S, stretches across the Indian Ocean, separating the monsoon
dominated regime of the northern Indian Ocean from the more typical
subtropical stratification to the south. ITW is well represented within
the SEC thermocline, extending with concentrations above 80% of initial
characteristics from the sea surface to 300-m within the eastern half of
the Indian Ocean, with 60% concentration reaching well into the western
Indian Ocean. The ITW transport within the SEC varies from 4 to 12
× 106 m3 sec-1, partly in response
to variations of the injection rate at the eastern boundary and to the
likelihood of a zonally elongated recirculation cell between the
Equatorial Counter Current and the SEC within the Indian Ocean. Lateral
mixing disperses the ITW plume meridionally with an effective isopycnal
mixing coefficient of 1.1 to 1.6 × 104 m2
sec-1.
Gray, W.M., J.D. Sheaffer, and C.W. Landsea. Climate trends associated
with multi-decadal variability of Atlantic hurricane activity. In
Hurricanes, Climate, and Socioeconomic Impacts, H.F. Diaz and
R.S. Pulwarty (eds.). Springer, Berlin, 15-53 (1997).
No abstract.
Haddad, Z.S., D.A. Short, S.L. Durden, E. Im, S. Hensley, M.B. Grable,
and R.A. Black. A new parameterization of the rain drop size distribution.
IEEE, Transactions of Geoscience and Remote Sensing, 35(3):532-539
(1997).
This paper revisits the problem of finding a parametric form for rain
drop size distribution (DSD) which (1) is an appropriate model for
tropical rainfall, and (2) involves statistically-independent parameters.
Using TOGA/COARE data, we derive a parameterization which meets these
criteria. This new parameterization is an improvement on the one that
was derived in [3], using TRMM ground truth data from Darwin, Australia.
The new COARE data allows us to verify that the spatial variability of
the two "shape" parameters is relatively small, thus confirming that this
parameterization should be particularly useful for remote sensing
applications. We also derive new DSD-based radar-reflectivity-rain-rate
power laws, whose coefficients are directly related to the shape parameters
of the DSD. Perhaps most important, since the coefficients are independent
of the rain-rate itself, and very little spatially, the relations are
ideally suited for rain retrieval algorithms. It should also prove
straightforward to extend this method to the problems of extimating cloud
hydrometeors from remote-sensing measurements.
Hasler, A.F., P.G. Black, V.M. Karyampudy, M. Jentoft-Nilsen, K.
Palaniappan, and D. Chesters. Preprints, 22nd Conference on
Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997.
American Meteorological Society, Boston, 201-202 (1997).
No abstract
Hendee, J.C. Object-oriented analysis and design of a near real-time
marine environmental data acquisition and reporting system. Proceedings,
8th International Coral Reef Symposium, Panama City, Panama, June 24-28,
1996. Smithsonian Tropical Research Institute, 2:1569-1574 (1997).
The National Oceanic and Atmospheric Administration's Coral Health and
Monitoring Program has cooperated with the Florida Institute of
Oceanography in developing a near real-time marine environmental
monitoring and reporting system. Using an object-oriented analysis
technique, this report describes how data are retrieved from satellite
data and archiving facilities, then reformatted for presentation via a
Remote Bulletin Board system and facsimile. Using an object-oriented
design technique, a new system is designed using a requirements analysis
of the original system.
Hitchcock, G.L., W.J. Wiseman, W.C. Boicourt, A.J. Mariano, N. Walker,
T.A. Nelsen, and E. Ryan. Property fields in an effluent plume of the
Mississippi River. Journal of Marine Systems, 12:109-126 (1997).
Surface property distributions were mapped in the Mississippi River plume
during May and August 1993 while following surface drifters. Prevailing
winds were the primary factor controlling the orientation of the plume.
In May, under typical southeasterly winds, the plume turned
anticyclonically towards the coast, while in August, under anomalous
westerly winds, the plume turned east. Remote imagery of sea surface
temperature and suspended sediments confirmed the direction of the
plume. Optimally interpolated maps of surface salinity, temperature,
chlorophyll a fluorescence, and transmissivity from underway
sampling, and periodic nutrient samples, reveal the plume structure. In
May, concentrations of nitrate, silicate, and phosphate decreased linearly
with increasing salinity. Chlorophyll a increased to peak
concentrations of 10 µg 1-1 in the plume, although higher
pigment biomass was observed near the coast. In August, nitrate and silicate
concentrations decreased conservatively near the mouth of Southwest Pass,
except where pigment biomass was enhanced in a convergent surface front.
Surface nutrient concentrations in the plume also decreased with
increasing salinity. The observations provide the first Lagrangian view
of surface property distributions in the Mississippi River plume, and
indicate that significant temporal variability exists in physical and
biological properties within a day after waters are discharged from the
river delta.
Ho, D.T., L.F. Bliven, R.H. Wanninkhof, and P. Schlosser. The effect of
rain on air-water gas exchange. Tellus, 49B:149-158 (1997).
The relationship between gas transfer velocity and rain rate was
investigated at NASA's Rain- Sea Interaction Facility (RSIF) using
several SF6 evasion experiments. During each experiment, a
water tank below the rain simulator was supersaturated with
SF6, a synthetic gas, and the gas transfer velocities were
calculated from the measured decrease in SF6 concentration
with time. The results from experiments with 18 different rain rates (7
to 110 mm h-1) and 1 of 2 dropsizes (2.8 or 4.2 mm diameter)
confirm a significant and systematic enhancement of air-water gas
exchange by rainfall. The gas transfer velocities derived from our
experiment were related to the kinetic energy flux calculated from the
rain rate and dropsize. The relationship obtained for mono-dropsize rain
at the RSIF was extrapolated to natural rain using the kinetic energy
flux of natural rain calculated from the Marshall-Palmer raindrop size
distribution. Results of laboratory experiments at RSIF were compared to
field observations made during a tropical rainstorm in Miami, Florida and
show good agreement between laboratory and field data.
Ho, D.T., R.H. Wanninkhof, J.C. Masters, R.A. Feely, and C.E. Cosca.
Measurement of underway fCO2 in the eastern equatorial
Pacific on NOAA ships Malcolm Baldrige and Discoverer
from February to September 1994. NOAA Data Report, ERL AOML-30
(PB97-169056), 58 pp. (1997).
From February through September 1994, underway measurements of the
fugacity (partial pressure) of carbon dioxide (fCO2) were
performed in the eastern equatorial Pacific as part of the Ocean
Atmosphere Carbon Exchange Study (OACES) of the National Oceanic and
Atmospheric Administration (NOAA). The measurements were performed with
semi-autonomous instruments which measured the fugacity in the air and in
the headspace of an equilibrator drawing water from the bow of the ship,
from which the fCO2 of the surface water is calculated. From
the difference in fugacity in air and water, the CO2 flux from
the equatorial Pacific can be estimated. On the NOAA ship Malcolm
Baldrige the system measured three reference standards, three air
values, and eight water values per hour. The system on the
Discoverer measured three standards, one 19-minute average air
sample, and one 20-minute average water sample per hour. This report
contains a description of the methodology and reduction of the
fCO2 and ancillary measurements. The results from the cruises
of the Malcolm Baldrige in the equatorial Pacific in the (boreal)
spring and fall of 1994 and from the Discoverer along nominally
110°W in the spring of 1994 are shown in a series of graphs with
fCO2 air and water versus latitude as top panel and
temperature and salinity versus latitude as bottom panel.
Hopkins, M., M. DeMaria, and J. Kaplan. Evaluation of an empirical inland
wind model for the landfall of Hurricane Fran (1996). Minutes, 51st
Interdepartmental Hurricane Conference, Miami, FL March 24-28, 1997.
Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A-22 (1997).
A simple empirical model for predicting the winds from landfalling
hurricanes has been developed for the Gulf and east coasts of the U.S.
This model was originally developed to estimate the maximum sustained
surface winds near the center of landfalling storms, but was generalized
to predict the two-dimensional field of maximum winds (wind swath). The
performance of the model during the landfall of Hurricane Fran will be
evaluated by comparing the predicted winds with all available surface
observations. Plans for improving the swath part of the model using a
combined wind data set from several recent landfalling storms will also
be described.
Houston, S.H., M.D. Powell, and P.P. Dodge. Surface wind fields for
Hurricanes Bertha and Fran (1996). Minutes, 51st Interdepartmental
Hurricane Conference, Miami, FL, March 24-28, 1997. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-23 (1997).
Hurricanes Bertha and Fran made landfall near Wilmington, North Carolina
within two months of each other in 1996. These tropical cyclones
contained maximum sustained surface winds (marine exposure at 10 m)
estimated to be 46 m s-1 and
50 m s-1,
respectively, at the time of landfall. Fran caused more loss of life
and greater estimated U.S. property damage (34 deaths and $3.2 billion)
than Bertha (8 deaths and $250 million). In both storms, the property
losses were primarily due to storm surge and waves along the coast rather
than directly from the wind. Fran also caused considerable damage due to
inland flooding resulting from heavy rainfall across a large swath of the
eastern U.S. as it moved northward after landfall. The Hurricane Research
Division (HRD) has been providing real-time tropical cyclone surface wind
fields to forecasters at the National Hurricane Center (NHC) since 1993;
there were 134 of these analyses made in 1996. The analysis system contains
adjustment techniques for exposure and interactive data quality control
that produce a field of input observations conforming to a common
framework for exposure, height, and averaging period. In Hurricane Bertha,
HRD transmitted 14 real-time surface wind fields to NHC. The real-time and
post-storm surface wind analyses indicate that the peak sustained surface
winds in Bertha were primarily over the Atlantic Ocean at the time of
landfall. The storm rapidly weakened after landfall and, based on the HRD
wind fields, it is very unlikely that the peak sustained surface winds
were observed at any point along the coastline of North Carolina. During
Hurricane Fran, HRD produced 28 real-time surface wind fields for NHC.
These, together with post-storm analyses, indicated that Fran's surface
winds at landfall were stronger and spread over a larger area north and
east of the center than Bertha. Unlike Bertha, the coastal areas were
affected by Fran's strongest winds, especially in advance of landfall.
Real-time and post-storm surface wind analyses in Hurricanes Bertha and
Fran will be discussed, along with their utility for NHC's marine
forecasts, emergency management, and storm surge forecasting.
Houston, S.H., M.D. Powell, and P.P. Dodge. Surface wind fields in 1996
Hurricanes Bertha and Fran at landfall. Preprints, 22nd Conference on
Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997.
American Meteorological Society, Boston, 92-93 (1997).
No abstract.
Humphrey, J.C., T.C. Moore, J.C. Hendee, and J.C. Ogden. SEAKEYS:
Real-time monitoring of the Florida Keys reef tract and Florida Bay.
28th Meeting Association of Marine Laboratories of the Caribbean
(ALMC-97), San Pedro, Costa Rica, July 21-25, 1997. University of
Costa Rica, 51 (1997).
No abstract.
Johns, E., R.A. Fine, and R.L. Molinari. Deep flow along the western
boundary south of the Blake Bahama Outer Ridge. Journal of Physical
Oceanography, 27(10):2187-2208 (1997).
In June-July 1990, hydrographic, chloroflourocarbon (CFC), and direct
velocity observations were taken in the western North Atlantic between
the Blake Bahama Outer Ridge (BBOR) at 30°N and San Salvador Island
at 24°N. The deep flow in the region, dominated by the Deep Western
Boundary Current (DWBC), forms a pattern of strong, narrow currents and
cyclonic gyres close to the continental slope, with broad, weaker
southward flow offshore. The CFCs reveal that in general the most
recently ventilated water (i.e., having the highest CFC
concentrations) is found along the western boundary as two distinct cores
within the DWBC between potential temperatures 4-6°C and
1.9-2.4°C. Geostrophic transport streamlines are constructed for
the DWBC layers, referenced using direct velocity observations at
26.5°N and assuming mass conservation between closed areas bounded
by the hydrographic sections. The tracers and transports are used to
define the spatial scales and strengths of the recirculation gyres and
to examine their relationship to bottom topography and their role in
ventilating the interior. Geostrophic transports for the DWBC layers
which transit the region and continue equatorward along the western
boundary are approximately 5 Sv for the 4-6°C layer; 14 Sv for
the 2.4-4.0°C layer; 9 Sv for the 1.9-2.4°C layer; and 3 Sv
below 1.9°C, for a total equatorward DWBC transport of 31 Sv below
6°C. A cyclonic gyre with one or more embedded gyres extends out
to about 74°W, transporting 12 Sv of water intermediate CFC
concentrations. Farther offshore, a broad band of southward flow
contributes an additional 16 Sv of water with lower CFC concentration to
the total equatorward transport. This flow may be connected to a much
larger elongated cyclonic recirculation gyre which reaches equatorward to
the Guiana Basin off northeastern Brazil. The close correspondence of
the tracer distributions with the regional topography indicates that
the major topographic features in this region strongly influence the
circulation, particularly in the deep and bottom layers. It appears that
the most recently ventilated water, between 4-6°C and 1.9-2.4°C,
does not reach the southern top of the BBOR, but rather it bypasses the
BBOR to the north of the study region and turns back westward following
the isobaths toward the western boundary north of 30°N. Only in the
coldest layer (<1.9°C) are the relatively highest CFCs observed
south of 30°N on the BBOR. The layer containing the shallow CFC
core (4-6°C) is apparently less constrained by the bottom topography;
3 Sv are carried westward across the axis of the BBOR forming an extended
zonal high CFC and salinity distribution related to the Gulf Stream
recirculation. South of the BBOR, due to the steep topography west of
the Blake Basin, the DWBC is channeled into a narrow equatorward boundary
flow. At the San Salvador Spur, some of the more recently ventilated
water appears to be deflected northward following the isobaths in a
cyclonic gyre around the extension of the Bahama Ridge. The cyclonic
gyres between the BBOR and the San Salvador Spur appear to be localized
features close to the western boundary that may have little impact on
the larger scale deep North Atlantic circulation. Nevertheless, the
gyres serve to ventilate the interior by diluting the tracer concentration
carried equatorward by the DWBC.
Jones, R.W., and H.E. Willoughby. Sensitivity of a spectral shallow-water
barotropic vortex to variations of domain size and spectral truncation.
Preprints, 22nd Conference on Hurricanes and Tropical Meteorology,
Ft. Collins, CO, May 19-23, 1997. American Meteorological Society,
Boston, 577-578 (1997).
Recent studies by Willoughby (1992, 1994, 1995) discuss the motion of a
vortex on a beta plane for various environmental flows with a linear and
non-linear version of the model. The domain size was 3000 km. Experiments
for a 6000 km domain show small 50-km track differences by 10 days for an
all cyclonic vortex with no environmental flow. Experiments with
environmental flows will also be reported. The spectral truncation is
wave number 3 for the non-linear model. Spectral truncations at wave
numbers 2 and 4 will be reported. The purpose of these calculations is to
show that highly truncated models are good enough to describe the
dynamics of vortex motion on a beta plane with environmental flows. In
the future, a baroclinic model will be developed for theoretical studies
and for application to real-time hurricane tracking.
Kaplan, J., C.W. Landsea, M. DeMaria, and J.J. Cione. The differing
roles of the large-scale environment in the intensity changes of three
1996 Atlantic hurricanes. Preprints, 22nd Conference on Hurricanes
and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American
Meteorological Society, Boston, 358-359 (1997).
No abstract.
Knaff, J.A., and C.W. Landsea. An El Niño-Southern Oscillation
CLImatology and PERsistence (CLIPER) forecasting scheme. Weather and
Forecasting, 12(3):633-652 (1997).
A statistical prediction method is developed for the El
Niño-Southern Oscillation (ENSO) phenomena which is based entirely
on the optimal combination of persistence, month-to-month trend of initial
conditions and climatology. The selection of predictors is by design
intended to avoid any pretense of predictive ability based on "model
physics" and the like, but rather is to specify the optimal "no-skill"
forecast as a baseline comparison for more sophisticated forecast methods.
Multiple least squares regression using the method of leaps and bounds is
employed to test a total of fourteen possible predictors for the selection
of the best predictors, based upon 1950-1994 developmental data. A range of
zero to four predictors were chosen in developing twelve separate regression
models, developed separately for each initial calendar month. The
predictands to be forecast include the Southern Oscillation (pressure)
Index (SOI) and the Niño 1+2, Niño 3, Niño 4 and Niño
3.4 SST indices for the equatorial eastern and central Pacific at lead
times ranging from zero seasons (0-2 months) through seven seasons (18-20
months). Though hindcast ability is strongly seasonally dependent,
substantial improvement is achieved over simple persistence wherein largest
gains occur for two to seven season (6 to 21 months) lead times. For example,
expected maximum forecast ability for the Niño 3.4 SST region,
depending on the initial date, reaches 92, 85, 64, 41, 36, 24, 24 and 28
percent of variance for leads of zero to seven seasons. Comparable maxima of
persistence only forecasts explain 92, 77, 50, 17, 6, 14, 21 and 17
percent, respectively. More sophisticated statistical and dynamical
forecasting models are encouraged to utilize this ENSO-CLIPER model in
place of persistence when assessing whether they have achieved
forecasting skill; to this end, real-time results for this model are made
available via a Web site.
Lamb, M.F., J.L. Bullister, R.A. Feely, G.C. Johnson, D.P. Wisegarver,
B. Taft, R.H. Wanninkhof, K.E. McTaggart, K.A. Krogslund, C.W. Mordy,
K. Hargreaves, D. Greeley, T. Lantry, H. Chen, B.E. Huss, F.J. Millero,
R.H. Byrne, D.A. Hansell, F.P. Chavez, P.D. Quay, P.R. Guenther, J.-Z.
Zhang, W. Gardner, M.J. Richardson, and T.-H. Peng. Chemical and
hydrograph measurements in the eastern Pacific during the CGC94
expedition (WOCE section P18). NOAA Data Report, ERL PMEL-61 (PB97-158075),
235 pp. (1997).
No abstract.
Landsea, C.W. Comments on "Will greenhouse gas-induced warming over the
next 50 years lead to higher frequency and greater intensity of
hurricanes?" Tellus, 49A:622-623 (1997).
No abstract.
Landsea, C.W. Indices of global tropical cyclone activity. CLIVAR/GCOS/WMO
Workshop on Indices and Indicators for Climate Extremes, Asheville,
North Carolina, 10 pp. (1997).
No abstract.
Landsea, C.W., G.D. Bell, W.M. Gray, and S.B. Goldenberg. The hyperactive
1995 Atlantic hurricane season: A juxtaposition of favorable conditions.
Preprints, 22nd Conference on Hurricanes and Tropical Meteorology,
Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston,
505-506
(1997).
No abstract.
Landsea, C.W., N. Nicholls, W.M. Gray, and L.A. Avilia. Reply to comment
by R.W. Wilson on "Downward trend in the frequency of intense Atlantic
hurricanes during the past five decades. Geophysical Research
Letters, 24(17):2205-2206 (1997).
No abstract.
Landsea, C.W., W.M. Gray, P.W. Mielke, K.J. Berry, and J.A. Knaff. A
seasonal hurricane forecast for 1997. Minutes, 51st Interdepartmental
Hurricane Conference, Miami, FL, March 24-28, 1997. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., B-183 (1997).
The forecast for the 1997 Atlantic hurricane season issued by Dr. Bill
Gray and collaborators (including myself) will be discussed. This
prediction was issued in early December 1996 and will be updated in early
April, early June, and early August. Uncertainties in the predictors,
especially in El Niño and Sahel rainfall, will be discussed in how
they may impact the number and intensity of tropical cyclones this year. I
will also briefly discuss the performance of the 1996 forecasts.
Lee, K., F.J. Millero, and R.H. Wanninkhof. The carbon dioxide system
in the Atlantic Ocean. Journal of Geophysical Research,
102(C7):15,693-15,708 (1997).
During the National Oceanic and Atmospheric Administration's Ocean
Atmosphere Carbon Exchange Study expedition in the eastern North Atlantic
in summer 1993, measurements of four CO2 parameters, along
with hydrographic properties, were made: fugacity of CO2,
fCO2 (measured at 20°C and in situ); pH (measured at
20°C); total inorganic carbon, TCO2; and total
alkalinity, TA. The major objective of this cruise was to establish a
benchmark against which future measurements of the transient invasion of
CO2 can be made. The large-scale distributions of surface
water CO2 parameters were related to temperature and salinity
in this region. The subsurface TA and TCO2 measurements were
fitted to multiple linear functions of salinity, in situ temperature,
apparent oxygen utilization, and silicate. The measurements of the
inorganic carbon system were also used to examine the internal
consistency of the carbonate system in this area. The measurements were
internally consistent to ±1.3% in fCO2, ±0.006 in
pH, ±3 µmol kg- 1 in TCO2, and ±3
µmol kg-1 in TA if proper carbonic acid dissociation
constants are used for different input combinations. The thermodynamic
constants of Goyet and Poisson (1989), Roy et al. (1993), Millero
(1995), and Lee and Millero (1995) were most consistent with the
measurements of pH (at 20°C), TCO2, and TA. However, if
fCO2 (at 20°C) is used in thermodynamic calculations, the
constants of Mehrbach et al. (1973) gave the best representation
of measurements. The constants of Lee and Millero (1995) were also in
reasonable agreement with these measurements.
Lobert, J.M., S.A. Yvon-Lewis, J.H. Butler, S.A. Montzka, and R.C. Myers.
Undersaturations of CH3Br in the Southern Ocean.
Geophysical Research Letters, 24(2):171-172 (1997).
Dry mole fractions of methyl bromide (CH3Br) in marine
boundary layer air and air equilibrated with surface seawater were
measured in the Southern Ocean. Saturation anomalies were consistently
negative at -36 ± 7%. The observed undersaturations do not support
recently published predictions of highly supersaturated Antarctic waters,
but instead suggest a net uptake of atmospheric CH3Br by cold,
productive oceans. The observations do not appear to be supported by
known chemical degradation rates and present strong evidence for an
unidentified, oceanic sink mechanism such as biological breakdown. Our
estimate for the global, net, oceanic sink for atmospheric methyl bromide
remains negative at -21 (-11 to -32) Gg y-1.
Marks, F.D., and P.P. Dodge. Hurricane concentric eyewall
characteristics as revealed by airborne Doppler radar analyses.
Preprints, 22nd Conference on Hurricanes and Tropical Meteorology,
Ft. Collins, CO, May 19-23, 1997. American Meteorological Society,
Boston, 102-103 (1997).
No abstract.
Marks, F.D., and H.A. Friedman. 1997 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 132 pp. (1997).
The objectives of the National Oceanic and Atmospheric Administration
(NOAA) hurricane research field program is the collection of descriptive
data that are required to support analytical and theoretical hurricane
studies. These studies are designed to improve the understanding of the
structure and behavior of hurricanes. The ultimate purpose is to develop
improved methods for hurricane prediction. Ten major experiments have
been planned, primarily by principal investigators at the Hurricane
Research Division (HRD)/Atlantic Oceanographic and Meteorological
Laboratory (AOML) of NOAA, for the 1997 hurricane field program. These
experiments will be conducted with the NOAA/Aircraft Operations Center
(AOC) WP-3D and Gulfstream IV-SP aircraft.
Marks, F.D., and L.N. Shay. Landfalling tropical cyclones: Forecast
problems and associated research opportunities: Report of the Fifth
Prospectus Development Team of the U.S. Weather Research Program.
Minutes, 51st Interdepartmental Hurricane Conference, Miami, FL,
March 24-28, 1997. Office of the Federal Coordinator for Meteorological
Services and Supporting Research, Washington, D.C., A-26 (1997).
The Fifth Prospectus Development Team (PDT-5) of the U.S. Weather
Research Program was charged to identify and delineate emerging research
opportunities relevant to the prediction of local weather, flooding, and
coastal ocean currents associated with landfalling U.S. hurricanes,
specifically, and tropical cyclones, in general. Central to this theme
are fundamental and applied issues including: rapid intensity change;
initialization of and parameterization in dynamical models; coupling of
atmospheric and oceanic models; quantitative use of satellite
information; and optimal adaptive observing strategies to validate
predictive models. To acquire the necessary understanding and provide
the initial conditions for improved prediction, a focused, comprehensive
observing system in a translating storm-coordinate system is required.
With the development of proven instrumentation and improvement of
existing systems, three-dimensional wind and thermodynamic data sets can
be obtained whenever major hurricanes threaten the United States.
Satellites, aircraft, expendable probes released from aircraft, and
coastal, moored, and drifting surface platforms are needed to estimate
the upper-ocean temperatures and currents, air-sea interactions, the
distribution of storm surge, boundary layer winds, rainfall, and
potential damage. In the hurricane core, airborne Doppler radar,
supplemented by a suite of other instruments, would measure tropospheric
winds including critical areas of the boundary layer and outflow region.
Microwave systems would determine surface winds, ocean waves, and storm
surge. On the hurricane periphery, dropsondes would be released from
turboprop and jet aircraft to map the atmospheric temperature, humidity,
and wind structure. Satellites would acquire both storm-scale and
surrounding environmental data. To take full advantage of these new
observations, techniques need to be developed to objectively analyze
these observations, and initialize models aimed at improving prediction
of hurricane track and intensity from global-scale and mesoscale
dynamical models. Multi-nested models allow prediction of all scales from
the global, which determine long-term hurricane motion, to the
convective-scale, which affect intensity. Development of an integrated
analysis and model forecast system optimizing the use of observations and
providing the necessary forecast skill on all relevant spatial scales is
required. Detailed diagnostic analyses of these data sets will lead to
improved understanding of the physical processes of hurricane motion,
intensity change, the atmospheric boundary layer, and air-sea coupling.
Ultimately, the aim is on development of real-time analyses of storm
surge, winds, and rain, before and during landfall, to improve warnings
and provide local officials with the information needed to focus recovery
efforts in the hardest hit areas as quickly as possible.
Martin, D., M. Tsivou, B. Bonsang, C. Abonnel, T.P. Carsey, M.
Springer-Young, and A.A. Pszenny. Hydrogen peroxide
(H2O2) in the marine atmospheric boundary layer
during the ASTEX/MAGE experiment in the eastern subtropical North
Atlantic. Journal of Geophysical Research, 102:6003-6015 (1997).
No abstract.
Masters, J.C., R.H. Wanninkhof, D.T. Ho, M. Steckley, R.A. Feely, and C.
Cosca. Continuous air and surface seawater measurements of
fCO2 on board the NOAA ship Malcolm Baldrige
around-the-world cruise in 1995. NOAA Data Report, ERL AOML-31
(PB98-105950), 65 pp. (1997).
From February 1995 through January 1996 the NOAA ship Malcolm
Baldrige conducted scientific operations on an around-the-world
tour. The majority of work occurred in the Indian Ocean. The
CO2 groups of the National Oceanic and Atmospheric
Administration's (NOAA) Atlantic Oceanographic and Meteorological
Laboratory (AOML) and Pacific Marine Environmental Laboratory (PMEL)
operated a continuously flowing partial pressure carbon dioxide analyzer.
Samples were taken from both the surface water and the overlying
atmosphere to determine carbon dioxide flux across the gas/water
interface. Other parameters such as salinity, barometric pressure, and
temperature were used to reduce the data and calculate the fugacity of
CO2*. Total dissolved inorganic carbon (DIC) samples of
surface water were also collected. Data were collected on each leg of
the cruise. Leg 1 was a transit from Miami to Durban, South Africa. Leg
2 operated from Durban to Colombo, Sri Lanka. Leg 3 operated from Colombo
to Muscat, Oman. Leg 4 operated from Muscat to Victoria, Seychelles.
Leg 5 operated from Victoria to Muscat, Oman. Leg 6 operated from Muscat
to Diego Garcia. Leg 7 consisted of a transit from Diego Garcia to
Fremantle, Australia followed by the major scientific operations between
Fremantle and Male, Maldive Islands. Leg 8 included another transit from
Male to Darwin, Australia. Operations began after leaving Darwin and
headed into the western equatorial Pacific. The ship inported in American
Samoa and continued to Panama, Miami, Florida and finished in Charleston,
South Carolina. Descriptions of sampling methods and graphical data
summaries are given in this report.
McCarthy, M.C., L.D. Talley, and M.O. Baringer. Deep upwelling and
diffusivity in the southern Central Indian Basin. Geophysical
Research Letters, 24(22):2801-2804 (1997).
Transport of the deepest water westward through a gap at 28°S in the
NinetyEast Ridge between the Central Indian Basin and the West Australia
Basin is calculated from hydrographic data collected as part of the WOCE
Hydrographic Program section I8N. Zero reference velocity levels at
mid-depth were chosen through consideration of water masses. The small
transport of 1.0 Sv westward through the gap of water denser than
sigma4 = 45.92 kg/m3 must all upwell in the
southern Central Indian Basin. Of this, 0.7 Sv upwells between the
central and western sill sections, that is, close to the sill itself.
Using the areas covered by the isopycnal, we calculate an average
vertical velocity of 3.3 × 10-3 cm/s close to the sill
and of 4.2 × 10-4 cm/s west of the sill. Associated
average vertical diffusivities are 105 cm2/s close
to the sill and 13 cm2/s west of the sill, in this very near
bottom layer.
McCartney, M.S., R.G. Curry, and H.F. Bezdek. The interdecadal warming
and cooling of Labrador Sea Water. ACCP Notes, 1-10 (1997).
No abstract.
McLeish, W., D.V. Hansen, and J.R. Proni. Coastal currents induced by
Hurricane Andrew. Florida Scientist, 60(4):254-264 (1997).
Ocean current meters in 18 and 24 m depth water along the southeast
Florida coast recorded water motions as Hurricane Andrew crossed the
narrow continental shelf with the storm center 32 km from the
southernmost current meter. Wind speeds up to 48 m s-1 at the
meter closest to the storm path were associated with recorded mean current
speeds up to 94 cm s-1. The greatest water speeds, however,
were transient motions from the wind waves. These motions caused major
changes to the bottom and to objects lying on it. Direct and remotely
sensed observations showed an increasing degree of turbulence in the
water as the hurricane approached, stirring both air bubbles and bottom
sediment throughout the water and mixing the water so that vertical shear
in the current was suppressed. Thus, beneath the strong wind stress
there was not a mean water flow in the direction of the wind at the
surface and a flow in the opposite direction near the bottom, as had been
indicated in previous studies. Some of the water that had been forced
toward shore by the strong west moving wind in the hurricane eyewall
moved northward along the coast. In a region where the wind speed was
less but still of hurricane force, water was displaced offshore contrary
to the direction of the wind stress. At the same time that the offshore
current developed, wave motions became much more severe: it appears that
the new countercurrent may have induced major hurricane waves to break in
this farther offshore location.
Mielke, P.W., K.J. Berry, C.W. Landsea, and W.M. Gray. A single-sample
estimate of shrinkage in meteorological forecasting. Weather and
Forecasting, 12(4):847-858 (1997).
An estimator of shrinkage based on information contained in a single
sample is presented and the results of a simulation study are reported.
The effects of sample size, amount, and severity of nonrepresentative
data in the population, inclusion of noninformative predictors, and least
(sum of) absolute deviations and least (sum of) squared deviations
regression models are examined on the estimator. A single-sample
estimator of shrinkage based on drop-one cross-validation is shown to be
highly accurate under a wide variety of research conditions.
Molinari, R.L., D.A. Mayer, J.F. Festa, and H.F. Bezdek. Multi-year
variability in the near surface temperature structure of the midlatitude
western North Atlantic Ocean. Journal of Geophysical Research,
102(C2):3267-3278 (1997).
Between 1966 and 1995, subsurface temperature data have been collected
in the western North Atlantic Ocean using expendable bathythermographs.
Data coverage is sparse in both time and space, but evidence for decadal
variability in the upper 400 m of the water column is found. The data
were averaged by month onto a 2 degree of latitude by 4 degree of
longitude grid. Thirty-one quadrangles in the region bounded by
17°N and 43°N and 78°W and 66°W have sufficient data
to provide consistent results. Anomaly time series at 0, 100, 200, 300,
and 400 m were estimated by subtracting a mean monthly climatology. The
individual records were detrended and filtered to highlight the longer
period signals. The analysis resulted in 25-year records (1969-1993) for
study. Within the thermocline of the subtropical gyre and the Gulf
Stream at 100 and 200 m, periods of predominately positive temperature
anomaly end in 1971, 1982, and 1990, while periods of negative anomaly
end in 1976 and 1985. Only the events ending in 1971, 1976, and 1990 are
in the majority of the records at 300 and 400 m. Most of the events also
appear in the sea surface temperature (SST) records, but are somewhat
masked by significant noise at the surface. Meridional-vertical
temperature sections through the subtropical gyre show that transitions
from negative to positive anomaly events are characterized by a deepening
of the isotherms throughout the section and transitions from positive to
negative events by a rising of the isotherms. Significant lateral
migration of the axis of the Gulf Stream, although possibly masked by the
2 degree averaging, is not necessary to explain either type of event.
The transitions in the SST and 100 m temperature time series occur at
essentially the same time as the transitions in an index of the North
Atlantic Oscillation (NAO) that has also been detrended (i.e.,
1971, 1976, 1980, 1984, 1988). The 1971, 1976, and 1988 NAO events are
also observed at 300 and 400 m as described earlier. Periods of positive
(negative) subsurface temperature anomaly are coincidental with periods
of positive (negative) NAO index. Thus, earlier results showing
connections between the NAO and western Atlantic SST at decadal time
scales are now extended to at least 400 m in the water column. Trends
were computed from the individual 25-year records. The trends at all
depths are predominately negative (positive) north (south) of 38°N.
Inferences from the horizontal distribution of the trends and results
from earlier studies suggest that the 1969-1993 period may be a phase of
a 30- to 50-year signal observed in the northern Atlantic since the
beginning of the century.
Murillo, S.T., S.H. Houston, and M.D. Powell. Composites of surface marine
observations for hurricanes during 1975-1996. Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 78-79 (1997).
No abstract.
Ooyama, K.V. Footnotes to "conceptual evolution." Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 13-18 (1997).
No abstract.
Ooyama, K.V. The semi-implicit integration of a nested spectral model
and the result of tests in squall-line simulation. Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 531-532 (1997).
No abstract.
O'Sullivan, D.W., F.J. Millero, C. Goyet, E. Peltola, E.A. Degler, B.
Adams, R.G.J. Bellerby, G. Eischeid, and S.J. McCue. Carbon dioxide
system measurements on Arabian Sea waters. University of Miami Technical
Report, RSMAS 97-005, 283 pp. (1997).
In 1995, we participated on a number of research cruises in the Arabian
Sea as part of the Joint Global Ocean Flux Study (JGOFS) sponsored by the
National Science Foundation (NSF). This report gives the results of our
total inorganic carbon dioxide (TCO2), total alkalinity (TA),
and potentiometric pH measurements made on Arabian Sea waster samples
during these cruises. The MIAMI titration system was used to determine
pH, TA and TCO2 for the waters studied. More reliable
TCO2 results were obtained using the WHOI coulometric system
and these results are reported in the JGOFS data base. Measurements made
on Certified Reference Material (CRM) for two different batches of CRM
were used to monitor the performance of the potentiometric and
coulometric CO2 measurements. The reproducibility of the
coulometry measurements of TCO2 was to ą 1.2 µmol
kg-1 (N = 115). The potentiometric measurements on CRM gave a
reproducibility of ą 2.7 µmol kg-1 in TCO2, ą
3.2 µmol kg-1 in TA, and ą 0.007 in pH (N = 177). The
surface measurements of pH and normalized TA were quite uniform
throughout the year (pH = 8.084 ą 0.016, NTA = 2288 ą 5 µmol
kg-1); normalized TCO2 was more variable
(NTCO2 = 1949 ą 20 µmol kg-1). The depth
profiles of pH, TA, and TCO2 were similar to those in the
Indian Ocean.
Parrish, J.R., and M.L. Black. The NOAA G-IV and the tropical cyclone
environment. Preprints, 22nd Conference on Hurricanes and Tropical
Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological
Society, Boston, 123-124 (1997).
No abstract.
Powell, M.D., and S.H. Houston. Surface wind fields of 1995 Hurricanes
Erin, Opal, Luis, Marilyn, and Roxanne at landfall. Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 90-91 (1997).
No abstract.
Proni, J.R., and T.A. Nelsen. Final Report: Deep Ocean Relocation
Project, Phase II: Application of acoustical and tracer methodologies
to the deep ocean relocation of dredge material. Contract Report
ARPAC 558.AOO, Naval Research Laboratory, Washington, D.C., 37 pp.
(1997).
One of the major challenges facing the United States today is disposal of
contaminated dredged material. Inexorable economic and population
pressures assure that this challenge will exist for the foreseeable
future. One concept for dealing with this material is deep ocean
disposal or deep ocean relocation (DOR). A key component of DOR concepts
is monitoring of the geosynthetic fabric containers (GFCs), which will be
used to contain the dredged material, during descent through the oceanic
water column to the ocean bottom. The present report deals with the use
of acoustical and tracer methodologies for monitoring DOR-associated
plumes. Discussed herein is the feasibility of utilizing active
acoustical systems to monitor both GFCs and any escaping plumes. A
discussion of nepheloid layer characteristics of relevance to GFC
detection is presented.
Proni, J.R., and R.G. Williams. Acoustic measurements of currents and
effluent plume dilutions in the western edge of the Florida Current.
In Acoustic Remote Sensing Applications, S.P. Singal (ed.).
Narosa Publishing House, New Delhi, India, 537-550 (1997).
The Southeast Florida Outfall Experiment (SEFLOE), carried out in the
western boundary of the Florida Current off southeast Florida, USA,
between 1988 and 1993, was the most extensive application of acoustics to
wastewater effluent studies performed in the United States. The
objective was to provide a scientific basis for managerial regulations
for effluent discharges. This article describes the acoustical
measurements to map effluent plume distributions, and the
three-dimensional current regime. Current meters were installed near
each outfall near the top and bottom of the water column. An acoustic
Doppler current profiler (ADCP) was deployed on the bottom in the
vicinity of the outfalls. Research ships towed active acoustical systems
over the diffusers. Examples are given of the outfall plume distribution
and the principal current regimes. A conceptual three-dimensional model
is developed to compare with observed data. The acoustical measurements
are shown to serve as a surrogate for the effluent constituent distributions.
Rhoads, K.P., P. Kelley, R.R. Dickerson, T.P. Carsey, and M.L. Farmer.
Composition of the troposphere over the Indian Ocean during the monsoonal
transition. Journal of Geophysical Research,
102(D15):18,981-18,996 (1997).
The atmosphere over the equatorial Indian Ocean is a unique environment
in which to study the chemical and radiative effects of an intense
source of anthropogenic emissions from the northern hemisphere directly
coupled to the relatively pristine background conditions present in the
southern hemisphere. As an initial investigation into the role of the
intertropical convergence zone (ITCZ) on interhemispheric transport of
pollutants, a number of trace atmospheric species were measured aboard
the National Oceanic and Atmospheric Administration (NOAA) R/V
Malcolm Baldrige between Durban, South Africa, and Colombo, Sri
Lanka, from March 12 to April 22, 1995. Sharp increases in the
concentrations of carbon monoxide (CO), carbon dioxide (CO2),
and aerosols were associated with four distinct meteorological regimes
transected by the cruise track from 33°S to 9°N. Across the
ITCZ, aerosol concentrations, including non-sea-salt sulfate, nitrate,
and ammonium, increased by a factor of 4. Surface zone measurements
showed a latitudinal gradient with a minimum near the equator and a
strong diurnal variation in the equatorial regions. The latitudinal
profile of gas-phase reactive nitrogen paralleled ozone and was higher
in the remote southern hemisphere than in the remote northern
hemisphere. Evidence of direct anthropogenic impact on the region was
observed more than 1500 km from the southern tip of India. Back
trajectories, calculated with NOAA's medium range forecast data using
the Hybrid Single Particle Lagrangian Integrated Trajectory (HY- SPLIT)
program, identified the origin of the air mass regimes characterized by
the trace gas and aerosol data. Continental emissions in the northern
hemisphere were shown to have a major impact on the radiative properties
and oxidizing capacity of the marine atmosphere.
Rogers, R.F. A component of tropical cyclogenesis: Convective
redevelopment within a warm-core mesovortex. Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Fort Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 555-556 (1997).
Theories explaining the transition of a relatively disorganized area of
convection into a coherent self-sustaining system (i.e., tropical
cyclogenesis) have traditionally relied upon the presence of a vortex
before genesis can occur. Observations have confirmed the need for these
vortices, often detecting them in radar and satellite imagery several
days prior to the formation of a tropical depression. However,
observational, theoretical, and numerical studies of similar systems over
land have found that the initial vortices are confined to the
mid-troposphere. Therefore, an important question to address is how
these vortices grow down to the surface in maritime tropical
environments, for it is not until the vortex is reflected at the surface
that intensification can begin, provided the large-scale environment is
not unfavorable. Viewing these vortices in the framework of potential
vorticity (PV) allows a consideration of their penetration depth, which
describes the vertical extent of the effects of the anomaly. This depth
is a function of the magnitude of the PV anomaly itself--strengthening
the PV anomaly will increase the penetration depth. One mechanism to
explain how a vortex can grow downward is to increase the strength of the
PV anomaly by initiating convection within the existing anomaly.
Observations indicating successive cycles of convection before a named
storm exists support this hypothesis. Understanding the mechanisms
responsible for these repeated "internal" convective cycles is therefore
critical to understanding whether a vortex will penetrate to the
surface. Theories have been advanced in the literature as to how
vortices are instrumental in initiating new convective outbreaks.
However, the scale of the systems have prevented detailed observational
studies which could verify or refute these hypotheses, necessitating the
use of a high-resolution numerical model. In this study, a case of
multiple convective regeneration by a mesoscale convective system
(MCS)-generated mesovortex was investigated using the Penn State/NCAR
mesoscale model MM5. The case involved a vortex that developed in an MCS
in Colorado and tracked across the country over a three-day period,
initiating five distinct convective cycles during its lifetime.
Preliminary results of the simulation of one of the convective
redevelopments will be reported, with the goal of examining and comparing
to theory the processes whereby the vortex induces this redevelopment.
The effect of the convective redevelopment on the vortex size and
strength will also be examined.
Samsury, C.E., M.L. Black, P.P. Dodge, and R.E. Orville. Utilization of
airborne and NEXRAD data in the analysis of cloud-to-ground lightning in
1995 and 1996 tropical cyclones. Preprints, 22nd Conference on
Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23,
1997. American Meteorological Society, Boston, 125-126 (1997).
No abstract.
Slansky, C.M., R.A. Feely, and R.H. Wanninkhof. The stepwise linear
regression method for calculating anthropogenic CO2 invasion
into the North Pacific Ocean. In Biogeochemical Processes in the
North Pacific, S.Tsunogai (ed.). Japan Marine Science Foundation,
70-79 (1997).
No abstract.
Takahashi, T., R.A. Feely, R.F. Weiss, R.H. Wanninkhof, D.W. Chipman,
S.C. Sutherland, and T.T. Takahashi. Global air-sea flux of
CO2: An estimate based on measurements of sea-air
pCO2 difference. Proceedings, National Academy of
Science, USA 94:8292-8299 (1997).
Approximately 250,000 measurements made for the pCO2
difference between surface water and the marine atmosphere,
DELTApCO2, have been assembled for the global oceans.
Observations made in the equatorial Pacific during El Niño events
have been excluded from the data set. These observations are mapped on
the global 4° × 5° grid for a single virtual calendar year
(chosen arbitrarily to be 1990) representing a non-El Niño year.
Monthly global distributions of DELTApCO2 have been
constructed using an interpolation method based on a lateral
advection-diffusion transport equation. The net flux of CO2
across the sea surface has been computed using DELTApCO2
distributions and CO2 gas transfer coefficients across sea
surface. The annual net uptake flux of CO2 by the global
oceans thus estimated ranges from 0.60 to 1.34 Gt-C yr-1
depending on different formulations used for wind speed dependence on the
gas transfer coefficient. These estimates are subject to an error of up
to 75% resulting from the numerical interpolation method used to estimate
the distribution of DELTApCO2 over the global oceans.
Temperate and polar oceans of both hemispheres are the major sinks
for atmospheric CO2, whereas the equatorial oceans are the
major sources for CO2. The Atlantic Ocean is the most
important CO2 sink, providing about 60% of the global ocean
uptake, while the Pacific Ocean is neutral because of its equatorial
source flux being balanced by the sink flux of the temperate oceans. The
Indian and Southern Oceans take up about 20% each.
Talley, L.D., and M.O. Baringer. Preliminary results from WHP sections
I8N/I5E in the central Indian Ocean. Geophysical Research Letters,
24(22):2789-2792 (1997).
The R/V Knorr departed Colombo, Sri Lanka on March 10, 1995 and
arrived in Fremantle, Australia on April 15, 1995 to carry out its third
WOCE hydrographic leg in the Indian Ocean. Basic technical support was
provided by Scripps Institution of Oceanography's Oceanographic Data
Facility. Acoustic Doppler current profiler (ADCP) operations were carried
out by the University of Hawaii (Firing). The basic sampling program was
accomplished very smoothly. The full cruise report can be obtained from the
author. The cruise track is shown in the overview figure for this
newsletter, labeled I8N and I5E. The latter portion was a nominal repeat
of the 1987 section (Toole and Warren, 1993). The goals of the sampling
were to obtain a section through the center of the Central Indian Basin,
and to repeat the crossing of the northward flow of deep water just to the
west of Australia. Particular attention was paid to a potential source of
deep water for the Central Indian Basin, through a sill in the NinetyEast
Ridge, located at about 28°S. It was also possible to deviate from
the 32°S section, and sample in the deep water south of Broken Ridge
instead of along the top of the ridge. Between Broken Ridge and
Australia we chose to move the section slightly north of the original
position of I5E in order to resolve whether the deep flow splits around
Dirck Hartog Ridge. All stations were to within 10 m of the bottom and
included a 36-bottle rosette/CTD cast with lowered ADCP. A ship-mounted
ADCP was operated throughout. Basic station spacing was 30 nmi, and was
reduced at the equator, Sri Lankan, and Australian coasts and crossings
of the NinetyEast and Broken Ridges. The CTD data stream consisted of
elapsed time, pressure, two temperature channels, conductivity, oxygen,
altimeter, and transmissometer signals. Water samples were collected for
analyses of salt, oxygen, silica, phosphate, nitrate, and nitrite on all
stations and of CFC-11, CFC-12, carbon tetrachloride, helium-3, helium-4,
tritium, AMS C14, pCO2, total dissolved inorganic carbon,
alkalinity, and barium on selected stations. Water sample results were
compared with preliminary data acquired on prior WOCE legs and with
earlier data. The comparisons are available in the cruise report and show
that the WOCE data collected on legs 1 through 3 are a uniform data set;
they also show significant differences from Geosecs salinity and
phosphate which are attributable to measurement precision.
Thacker, W.C., and R. Lewandowicz. A comparison of low-dimensional
representations of sea-surface temperature anomalies in the North
Atlantic. International Journal of Climatology, 17:953-967
(1997).
Correlation-matrix principal components of North Atlantic sea-surface
temperature anomalies for the interval 1950-1970 account for the
anomalous variability observed during the interval 1972-1992 better than
do similar numbers of covariance-matrix principal components, regional
averages, or carefully selected local anomalies. When drift in the
seasonal cycle is taken into account, local anomalies for the 127 6°
× 4° longitude-by-latitude North Atlantic cells could be
recovered with an average skill as high as 0.79. Surprisingly, skill
increased monotonically with increasing numbers of principal components,
and the maximum value was not obtained until 62 were used to characterize
the field. Clearly, far more principal components carry useful
information about local details than has been previously suspected.
Thacker, W.C., and R. Lewandowicz. Partitioning the North Atlantic into
regions of similar seasonal sea-surface temperature anomalies.
International Journal of Climatology, 17:3-23 (1997).
Mean sea-surface temperatures were computed within 127 6° ×
4° longitude-by-latitude cells comprising most of the North Atlantic
for 171 three-month seasons from 1950 through 1992, the mean seasonal
cycle was removed, and cells with correlated seasonal anomalies were
clustered into regions of coherent thermal behavior. Clustering
algorithms consistently produced smaller thermal regions in the vicinity
of the Gulf Stream, and while the regions were generally contiguous, a
disjoint region was consistently found near the Grand Banks. Examining
within-region variability as a function of the number of regions revealed
no obvious "best" number of regions. For 26 regions, correlations
between pairs of cells within a common region were typically 0.7; for 13
regions, a sizeable fraction were less than 0.5; and for only seven regions,
within-region correlations were distributed fairly uniformly between 0.2
and 0.8.
Vaughan, S.L., and R.L. Molinari. Temperature and salinity variability
in the Deep Western Boundary Current. Journal of Physical
Oceanography, 27(5):749-761 (1997).
A ten-year time series (1984-1993) of repeat hydrographic sections from
offshore Abaco Island, the Bahamas (26.5°N), is used to define the
mean and time dependent characteristics of the Deep Western Boundary
Current (DWBC). The DWBC flow is divided into four vertical layers based
on chlorofluorocarbon (CFC) concentration and formations regions (upper
layer, CFC core, theta ~ 3.9-5.0°C; second layer, classical
Labrador Sea Water, theta ~ 3.2-3.9°C; third layer, CFC
minimum, theta ~ 2.4-3.2°C; deepest layer, CFC core, theta
~ 1.85-2.4°C). Time series analysis of mean layer properties
and their anomalies showed that the temperature and salinity of each
layer did not increase or decrease monotonically with time. Variations
in temperature and salinity were characterized by two to three-year
period oscillations. Variability between years is illustrated by
subtracting repeat sections of temperature and salinity along levels of
both constant pressure and constant potential density. To determine an
original water mass modification that could be responsible for the
observed variability in the section differences, an analytical method,
which uses both types of differencing schemes, was applied to the DWBC
data. Variability in the upper layer between 1987 and 1993 was shown to
originate primarily from an increased salinity of the source waters for
this layer. Variability in the second layer was shown to arise from a
combination of cooling and salinification. Variability in the two
deepest layers seemed to be almost entirely due to vertical movement of
the isopycnals. Increases in potential temperature and salinity observed
in a sublayer of the second layer defined by sigma1.5 ~
34.68-34.74 (classical Labrador Sea Water) from 1991 to 1993 was shown to
be mainly the result of cooling. It is suggested that this cooling may
have originally occurred in the central Labrador Sea during the period of
active deep water renewal in the early 1970s.
Wanninkhof, R.H., and W.E. Asher. Use of the deliberate dual-gaseous
tracer method to measure gas transfer velocities. 1997 AGU Spring
Meeting, Baltimore, MD, May 27-30, 1997. Supplement to EOS,
Transactions, American Geophysical Union, 78(17):S89, A42E-06 (1997).
Use of the deliberate dual-gaseous tracer method to measure gas transfer
velocities, the deliberately injected gases, helium-3 (3He) and
sulfur hexafluoride (SF6), have been used in the past decade to
measure air-sea gas transfer velocities in coastal oceans. The method relies
on knowledge of the relative exchange rates of the gases. It is successful
because the exchange rates of the two gases differ by about a factor of
three and because both gases can be measured at extremely low levels. Our
results from two different field experiments and laboratory studies indicate
that the measurements are robust and quantitative at low to intermediate wind
speeds. The field results are in accordance with independently-determined gas
exchange-wind speed relationships by the authors. Interpretation of the dual
tracer results at higher wind speeds is problematic because of the influence
of bubbles. In particular, the conversion of the 3He gas transfer results to
gas transfer velocities of climate-relevant gases is uncertain. We will give
an overview of the methodology, present results of two coastal gas transfer
experiments, and discuss the power and shortcomings of the technique.
Wanninkhof, R.H., G. Hitchcock, W.J. Wiseman, G. Vargo, P.B. Ortner,
W.E. Asher, D.T. Ho, P.Schlosser, M.-L. Dickson, R. Masserini, K. Fanning,
and J.-Z. Zhang. Gas exchange, dispersion, and biological productivity
on the west Florida shelf: Results from a Lagrangian tracer study.
Geophysical Research Letters, 24(14):1767-1770 (1997).
A Lagrangian tracer study was performed on the west Florida shelf in
April 1996 using deliberately injected trace gases. Although such
studies have been performed previously, this work is the first where the
deliberate tracers, in conjunction with carbon system parameters, are
used to quantify changes in water column carbon inventories due to
air-sea exchange and net community metabolism. The horizontal dispersion
and the gas transfer velocity were determined over a period of 2 weeks
from the change in both the concentrations and the concentration ratio of
the two injected trace gases, sulfur hexafluoride (SF6) and
helium-3 (3He). Horizontal diffusion estimates were about an
order of magnitude greater than calculated from empirical equations, and
the difference is attributed to vertical shear. The second moment of the
patch grew to 1.6 × 103 km2 over a period of
11 days. The gas transfer velocity, normalized to CO2
exchange at 20°C, was 8.4 cm hr-1 at an average wind
speed, U10, of 4.4 m s-1 for the duration of the
experiment, which is in good agreement with empirical estimates.
Remineralization rates exceeded productivity, causing an increase in
dissolved inorganic carbon of about 1 µmol kg-1
day-1 in the water column. During this period of senescence,
80% of the increase in inorganic carbon is attributed to community
remineralization and 20% due to invasion of atmospheric CO2.
This net remineralization is in accordance with in situ and
on-deck incubation experiments.
Weisberg, R.H., and C. Wang. A western Pacific oscillator paradigm for
the El Niņo-Southern Oscillation. Geophysical Research Letters,
24:779-782 (1997).
A data-based hypothesis is presented on the mechanism of the El
Niņo-Southern Oscillation (ENSO), a major determinant of interannual
global climate variability. The hypothesis emphasizes
the importance of off-equator sea surface temperature and sea level
pressure variations west of the dateline for initiating equatorial
easterly winds over the far western Pacific. These winds compete with
westerly winds over the equatorial central Pacific enabling the coupled
ocean-atmosphere system to oscillate. Consistent with this hypothesis, an
analogical oscillator model is constructed that
produces ENSO-like oscillations. The proposed mechanism differs from the
delayed oscillator paradigm in that wave reflection at the western
boundary is not a necessary condition for the coupled ocean-atmosphere
system to oscillate.
Weisberg, R.H., and C. Wang. Slow variability in the equatorial
west-central Pacific in relation to ENSO. Journal of Climate,
10(8):1998-2017 (1997).
Six years of upper ocean velocity, temperature and surface wind data
collected in the west-central Pacific at 0°, 170°W reveal a
slow ocean dynamical mode associated with the El Niņo-Southern
Oscillation (ENSO). Latent and sensible heat flux calculations using the
basin-wide Tropical Atmosphere Ocean (TAO) array data show a coincident,
slow ocean-atmosphere thermodynamical mode. Beginning with the La Niņa
conditions in 1988 through the peak El Niņo conditions in 1992, the
Equatorial Undercurrent (EUC) speed decreased along with the surface
zonal wind stress and the zonal pressure gradient. Simultaneous with
these were increasing trends in the Richardson number above the EUC core
and in sea surface temperature (SST). After peak warming was achieved the
variations in all of these quantities reversed in a movement toward their
previous La Niņa conditions. As this evolved within the ocean the
sensible and latent heat fluxes increased with large values emanating
eastward from the western Pacific. The largest interannual perturbations,
then, for both the surface momentum and heat flux quantities during this
recent ENSO cycle were within the west-central Pacific, the transition
region between the warmest waters found in the western Pacific warm pool
and the coldest waters found in the eastern Pacific cold tongue. The
observed ocean and atmosphere variability represents a positive feedback.
This raises a question about the origin of negative feedback that is
necessary for the coupled system to oscillate. Arguing from the
standpoint of a Gill atmosphere and observed SST/sea level pressure
correlation patterns, the paper draws a connection between condensation
heating in the equatorial west-central Pacific and easterly winds over
the equatorial western Pacific during the mature phase of El Niņo. The
formation of such easterlies by ocean-atmosphere coupling over the
western Pacific is hypothesized as providing a negative feedback for
reversing the sign of anomalous SST in the equatorial central Pacific.
This mechanism may complement, but it is different from, the delayed
oscillator mechanism for ENSO.
Willis, P.T., P.P.Dodge, F.D. Marks, D. Smith, and D. Churchill.
Evaluation of the accuracy of the NEXRAD radar rainfall estimates in
tropical summer convective rainfall over the Everglades/Florida Bay.
Preprints, 22nd Conference on Hurricanes and Tropical
Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological
Society, Boston, 679-680 (1997).
No abstract.
Willoughby, H.E. More about hurricane eye thermodynamics. Preprints,
22nd Conference on Hurricanes and Tropical Meteorology, May 19-23,
1997, Ft. Collins, Colorado. American Meteorological Society, Boston,
96-97 (1997).
No abstract.
Wilson, W.D., and W.E. Johns. Velocity structure and transport in the
Windward Islands Passages. Deep Sea Research, 44(3):487-520
(1997).
During 1991-1994, repeated measurements of current structure and water
mass properties were made in the major southern passages to the Caribbean
Sea between Trinidad and Dominica. A total of 10 cruises were performed
in different seasons, consisting primarily of serial station occupations
in the Grenada, St. Vincent, St. Lucia, and Dominica Passages. This data
set is by far the most comprehensive available in these passages and
better determines the mean flow and range of variability than do previous
studies. The flow structure in these passages is characterized by a
strong and relatively stable inflow above the thermocline (approximately
the upper 100 m), and a more highly variable flow regime within and below
the thermocline. Typical near-surface inflow velocities in Grenada and St.
Vincent passages were 40-60 cm/s, with maximum observed currents of 90
cm/s. Frequently, counterflows were observed below this surface layer
flowing out of the Caribbean, trapped to the southern side of the
passages. This subsurface counterflow appeared to be strongest and most
prevalent in Grenada Passage, where outflow speeds as large as 30 cm
s-1 were observed.
Yvon-Lewis, S.A., and J.H. Butler. The oceanic lifetime and budget of
atmospheric methyl bromide. 1997 AGU Spring Meeting, Baltimore,
MD, May 27-30, 1997. Supplement to EOS, Transactions, American
Geophysical Union, 78(17):S90, A42E-12 (1997).
Methyl bromide (CH3Br) has become of interest recently because
of its involvement in the depletion of stratospheric ozone. However,
unlike the chlorofluorocarbons, which are entirely anthropogenic, methyl
bromide has both natural and anthropogenic sources. At ~10 parts
per trillion in the troposphere, methyl bromide is believed to be the
single largest contributor of stratospheric Br. Once in the
stratosphere, Br is estimated to be 40 to 100 times more effective in
depleting stratospheric ozone than chlorine. Known sinks for atmospheric
methyl bromide include photolysis at high altitudes and reaction with OH,
uptake by the oceans and loss to soils. In the ocean, dissolved methyl
bromide is degraded via hydrolysis and chloride substitution. Recently,
it has been shown that methyl bromide also undergoes biological
degradation, which may be due to bacterial uptake. Results from field
studies, showing large undersaturations in polar and sub-polar waters,
also suggest an additional, perhaps biological, sink mechanism. Previous
calculations of the partial atmospheric lifetime of methyl bromide with
respect to oceanic degradation have only considered the chemical
degradation mechanisms. We use a global, coupled ocean-atmosphere box
model to examine the potential effect that biological degradation and its
distribution can have on the lifetime of atmospheric methyl bromide. The
results of this study show that both the value of the oceanic degradation
rate constant and its global distribution are important in determining
the calculated atmospheric lifetime. The "best" estimate of the partial
lifetime of atmospheric methyl bromide with respect to oceanic loss now
comes to 1.7-1.8 y with a full possible range of 0.85-3.7 y, which,
together with other, non-oceanic losses, yields a total atmospheric
lifetime of 0.7 y with a range of 0.5-0.9 y due only to uncertainty in
the oceanic lifetime. A subsequent revision of the budget for
atmospheric methyl bromide indicates that a source or sources of methyl
bromide totaling 90 to Gg/y (1/2 of the total sink strength) has not yet
been identified.
Yvon-Lewis, S.A., and J.H. Butler. The potential effect of oceanic
biological degradation on the lifetime of atmospheric CH3Br.
Geophysical Research Letters, 24(10):1227-1230 (1997).
We use a global, coupled ocean-atmosphere box model to examine the
potential effect that biological degradation and its distribution can
have on the lifetime of atmospheric CH3Br. The results of
this study show that both the value of the oceanic degradation rate
constant and its global distribution are important in determining the
calculated atmospheric lifetime. The "best" estimate of the partial
lifetime of atmospheric CH3Br with respect to oceanic loss now
comes to 1.7-1.8 y with a full possible range of 0.85-3.7 y, which,
together with other, non-oceanic losses, yields a total atmospheric
lifetime of 0.7 y (0.5-0.9 y). A subsequent revision of the budget for
atmospheric CH3Br indicates that estimated sinks of
CH3Br today exceed estimated sources by about 90 Gg
y-1.
Yvon-Lewis, S.A., and J. H. Butler. The uptake of atmospheric trace gases
by the ocean. AGU 1997 Fall Meeting, San Francisco, CA, December
8-12, 1997. Supplement to EOS, Transactions, American Geophysical
Union, 78(46):F93, OS21D-05 (1997).
A global ocean-atmosphere model was developed to study the uptake of
CH3Br by the oceans. With this model we significantly reduced
the uncertainties in the partial atmospheric lifetime of CH3Br
with respect to its oceanic uptake (to, CH3Br) (Yvon and
Butler, Geophys. Res. Lett., 23(1), 53-56, 1996). Results from
this model have also demonstrated that the distribution of the oceanic
degradation term is important in caculating the partial atmospheric
lifetime of a trace gas with respect to oceanic loss processes and,
consequently, its total atmospheric lifetime (Yvon-Lewis and Butler,
Geophys. Res. Lett., 24(10):1227-1230, 1997). It is now possible
to determine the partial atmospheric lifetime with respect to oceanic
degradation of any trace gas for which the oceanic degradation rate
constant can be calculated. The results from model runs for several
trace gases including, CH3Br, CH3Cl, and
CH3I, suggested that the total atmospheric lifetimes of these
trace gases should be reduced by 38%, ~3%, and ~2%. These reductions are
due solely to the inclusion of the oceanic chemical degradation loss
process. When adapted for CH3CCl3, the model results
reduced an earlier estimate for the partial atmospheric lifetime of this
trace gas with respect to oceanic uptake by 31%. For some gases, these
reductions are even greater when biological removal is included. The
results from the study of these and other gases, including some HCFCs,
will be presented.
Zhang, J.-Z. Distinction and quantification of carry-over and sample
interaction in gas segmented continuous flow analysis. Journal of
Automatic Chemistry, 19(6):205-212 (1997).
The formulae for calculation of carry-over and sample interaction are
derived for the first time in this study. A scheme proposed by Thiers et
al. (two samples of low concentration followed by a high concentration
sample and low concentration sample) is verified and recommended for the
determination of the carry-over coefficient. The derivation demonstrates
that both widely used schemes of a high concentration sample followed by
two low concentration samples, and a low concentration sampled followed
by two high concentration samples, actually measure the sum of the carry-
over coefficient and sample interaction coefficient. A scheme of three
low concentration samples followed by a high concentration sample is
proposed and verified for determination of the sample interaction
coefficient. Experimental results indicate that carry-over is a strong
function of cycle time and a weak function of ratio of sample time to
wash time. Sample dispersion is found to be a function of sample time.
Fitted equations can be used to predict the carry-over, absorbance, and
dispersion given sample times, and wash times for an analytical system.
Results clearly show the important role of intersample air segmentation
in reducing carry-over, sample interaction, and dispersion.
Zhang, J.-Z., and G.A. Berberian. Determination of dissolved silicate
in estuarine and coastal waters by gas segmented continuous flow
colorimetric analysis. In Methods for the Determination of Chemical
Substances in Marine and Estuarine Environmental Matrices, Supplement
1. Environmental Protection Agency, EPA 600/R-97072,
366.0-1-366.0-2 (1997).
No abstract.
Zhang, J.-Z., P.B. Ortner, and C.J. Fischer. Determination of nitrite
in estuarine and coastal waters by gas segmented continuous flow
colorimetric analysis. In Methods for the Determination of Chemical
Substances in Marine and Estuarine Environmental Matrices, Supplement
1. Environmental Protection Agency, EPA 600/R-97072,
353.4-1-353.4-2 (1997).
No abstract.
Zhang, J.-Z., P.B. Ortner, C.J. Fischer, and L.D. Moore. Determination of
ammonia in estuarine and coastal waters by gas segmented continuous flow
colorimetric analysis. In Methods for the Determination of Chemical
Substances in Marine and Estuarine Environmental Matrices, Supplement
1. Environmental Protection Agency, EPA 600/R-97072,
349.0-1-349.0-2 (1997).
No abstract.
**1996**
Asher, W.E., and R.H. Wanninkhof. The effect of breaking waves on the
analysis of dual-tracer gas exchange measurements. Proceedings, Third
International Symposium on Air-Water-Gas Transfer, Heidelberg, Germany,
July 24-27, 1995. Aeon Verlag and Studio, 517-528 (1996).
The dual-gaseous tracer technique is a new and reliable method for
directly measuring air-sea gas transfer velocities. However, analysis of
data from these experiments requires the assumption that the dependence
of the transfer velocity on molecular diffusivity is constant. Modeling
and laboratory studies indicate that this could be an invalid assumption
when gas transfer through bubbles generated by breaking waves is a
significant portion of the sea-to-air gas flux. Here, a parameterization
of the transfer velocity in terms of wind speed and fractional area
whitecap coverage is developed that includes the effects of
bubble-mediated exchange processes. It is shown that transfer velocities
estimated using this parameterization are consistent with available
oceanic gas exchange measurements. The parameterization is then used to
investigate the consequences of including whitecap-related transfer
processes in the analyses of data derived from dual-tracer experiments.
In the case of the tracer pair, sulfur hexafluoride and helium-3, it is
shown that assuming a constant diffusivity dependence underestimates
transfer velocities of helium-3 by up to 20% at high wind speeds. It is
also shown that using the parameterization to normalize the transfer
velocity for helium-3 to carbon dioxide results in a 6% decrease in the
estimated transfer velocity compared to constant-diffusivity dependence
estimates.
Asher, W.E., B.J. Higgins, L.M. Karle, P.J. Farley, C.R. Sherwood, W.W.
Gardiner, R.H. Wanninkhof, H. Chen, T.P. Lantry, M. Steckley, E.C.
Monahan, Q. Wang, and P.M. Smith. Measurements of gas transfer, whitecap
coverage, and brightness temperature in a surf pool: An overview of
WABEX-93. Proceedings, Third International Symposium on Air-Water-Gas
Transfer, Heidelberg, Germany, July 24-27, 1995. Aeon Verlag and Studio,
205-216 (1996).
Toward a method for estimating air-sea gas transfer velocities,
kL, from remote measurements of fractional area whitecap
coverage, WC, a gas exchange experiment was conducted in an
outdoor surf pool during the October 1993 Wave Basin Experiment
(WABEX-93). For both spilling and plunging breaking waves, measurements
were made of WC; air-water fluxes of carbon dioxide, helium,
nitrous oxide, oxygen, and sulfur hexafluoride; microwave brightness
temperature of the water surface, sigma; aqueous-phase turbulence
velocities; and bubble size spectra. The data show that kL,
scales as a common, linear relation with WC for both spilling
and plungin breaking waves. The gas transfer data have been used to
develop an empirical parameterization for predicting kL from
WC, Schmidt number, and solubility.
Bishop, J.R., and W.P. Dammann. Cabling and mooring a remotely operated
ADCP for real-time data acquisition. Proceedings, Ocean 96 MTS/IEEE,
Ft. Lauderdale, Florida, September 23-26, 1996. Marine Technological
Society, Vol. 1, 116-119 (1996).
As part of a joint U.S. Army Corps of Engineers, Port of Miami, State
of Florida, U.S. EPA, University of Miami (Rosenstiel School), National
Oceanic and Atmospheric Administration (NOAA) offshore dredged material
disposal program, a real time current monitoring system (RTCMS) was
designed by the Ocean Acoustics Division (OAD) of the Atlantic
Oceanographic and Meteorological Laboratory (AOML) for deployment
offshore of Miami. This system consists of an acoustic Doppler
current profiler (ADCP) moored on the ocean floor at a point southwest
of the Offshore Dredge Material Disposal Site (ODMDS) and cabled to a
nearshore site. The nearshore site chosen was a range marker at the
Miami Harbor entrance. From the range marker the data is transmitted
via radio modem to the NOAA/AOML/OAD offices on Virginia Key. The
high current regime and the requirement for periodic maintenance of
the ADCP added unique challenges to the design of the cable and
mooring system. Cable selection and routing was performed so as to
minimize risk of damage due to recreational activities. For purposes
of deployment and serviceability, the cabling and mooring system was
divided into three sections. The first section extends from the range
marker to a common point in 60 feet of water. The cable was laid and
anchored in sandy areas where possible in order to avoid reef impact.
The second section connects the common point to the first mooring
point at a depth of 400 feet. The final section couples the first
mooring point to the ADCP mooring point. The ADCP mooring section
consists of a two-point moor with a subsurface center float to suspend
the cable above the bottom. The deployment of the system was
accomplished in two days on board a 95-foot research vessel equipped
with a stern mounted A-frame and deck winches. Divers were utilized
to attach the cable to anchors in the shallow water sections, and to
inspect the cable after installation.
Black, M.L., R.W. Burpee, and F.D. Marks. Vertical motion
characteristics of tropical cyclones determined with airborne Doppler
radial velocities. Journal of the Atmospheric Sciences,
53(13):1887-1909 (1996).
Vertical motions in seven Atlantic hurricanes are determined from data
recorded by Doppler radar on research aircraft. The database consists of
Doppler velocities and reflectivities from vertically pointing radar rays
collected along radial flight legs through hurricane centers. The
vertical motions are estimated throughout the depth of the troposphere
from the Doppler velocities and bulk estimates of particle fallspeeds.
Portions of the flight tracks are subjectively divided into eyewall,
rainband, stratiform, and "other" regions. Characteristics of the
vertical velocity and radar structure are described as a function of
altitude for the entire data set and each of the four regions. In all of
the regions, more than 70% of the vertical velocities range from -2 to 2
m s-1. The broadest distribution of vertical motion is in the
eyewall region where ~5% of the vertical motions are >5 m
s-1. Averaged over the entire data set, the mean vertical
velocity is upward at all altitudes. Mean downward motion occurs only in
the lower troposphere of the stratiform region. Significant vertical
variations in the mean profiles of vertical velocity and reflectivity are
discussed and related to microphysical processes. In the lower and
middle troposphere, the characteristics of the Doppler-derived vertical
motions are similar to those described in an earlier study using
flight-level vertical velocities, even though the horizontal resolution
of the Doppler data is ~750 m compared to ~125 m from the
in-situ flight-level measurements. The Doppler data are available
at higher altitudes than those reached by turboprop aircraft and provide
information on vertical as well as horizontal variations. In a vertical
plane along the radial flight tracks, Doppler up- and downdrafts are
defined at each 300-m altitude interval as vertical velocities whose
absolute values continuously exceed 1.5 m s-1, with at least
one speed having an absolute value greater than 3.0 m s-1.
The properties of the Doppler drafts are lognormally distributed. In
each of the regions, updrafts outnumber downdrafts by at least a factor
of 2 and updrafts are wider and stronger than downdrafts. Updrafts in
the eyewall slope radially outward with height and are significantly
correlated over larger radial and vertical extents than in the other
three regions. If the downwind (tangential) slope with height of
updrafts varies little among the regions, updrafts capable of
transporting air with relatively large moist static energy from the
boundary layer to the upper troposphere are primarily in the eyewall
region. Downdrafts affect a smaller vertical and horizontal area than
updrafts and have no apparent radial slope. The total upward or downward
mass flux is defined as the flux produced by all of the upward or
downward Doppler vertical velocities. The maximum upward mass flux in
all but the "other" region is near 1-km altitude, an indication that
boundary-layer convergence is efficient in producing upward motion.
Above the sea surface, the downward mass flux decreases with altitude.
At every altitude, the total net mass flux is upward, except for the
lower troposphere in the stratiform region where it is downward.
Doppler-derived up- and downdrafts are a subset of the vertical velocity
field that occupy small fractions of the total area, yet they contribute
a substantial fraction to the total mass flux. In the eyewall and
rainband regions, for example, the Doppler updrafts cover less than 30%
of the area but are responsible for >75% and >50% to the total upward
mass flux, respectively. The Doppler downdrafts typically encompass less
than 10% of the area yet provide ~50% of the total downward mass
flux in the eyewall and ~20% of the total downward flux in the
rainband, stratiform, and "other" regions.
Black, M.L., S.H. Houston, R.G. Carter, A.B. Damiano, and R. McNamara.
AFRES-NOAA flight-level data comparisons. Minutes, 50th
Interdepartmental Hurricane Conference, Miami, FL, March 26-29, 1996.
Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A.8 (1996).
A coordinated flight between an Air Force Reserve (AFRES) aircraft and
both National Oceanic and Atmospheric Administration (NOAA) WP-3D
aircraft was conducted on 24 October 1995. This mission resulted from a
recommendation made at the 49th Interdepartmental Hurricane Conference.
The AFRES and NOAA aircraft each recorded, at 1-sec intervals, the
standard suite of flight-level meteorological data (winds, temperature,
dew point, pressure) and navigational information (e.g., position,
true air speed, heading, etc.). The data were collected during clear
and light-wind conditions along the Florida west coast, north of Tampa.
During portions of the flight, the WP-3D aircraft flew in close formation
and executed calibration maneuvers. The NOAA and AFRES aircraft conducted
"fly-bys" adjacent to an Air Force Aerostat balloon which was carrying a
NOAA calibrated instrument package. The balloon approaches were at
altitudes ranging from 1,000 to 15,000 feet and provide the basis for the
intercomparisons. Comparisons between the flight-level data collected
from the balloon, NOAA, and AFRES aircraft will be presented.
Recommendations, if any, will be made to improve the data collection,
processing, and strategies for future intercomparison flights.
Additionally, the calibration information gained from this flight will be
used to investigate the data quality from concurrent flights into
tropical cyclones by both the NOAA and AFRES aircraft this past hurricane
season. One or more examples of flight-level data collected in hurricane
flights will be presented.
Black, P.G., J.R. Proni, J.C. Wilkerson, and C.E. Samsury. Oceanic
rainfall detection and classification in tropical and subtropical
mesoscale convective systems using underwater acoustic methods.
Monthly Weather Review, 125(9):2014-2042 (1996).
Measurements of the underwater sound produced by rain were made at three
U.S. coastal sites in a study to determine the feasibility and
limitations of the acoustic detection and classification of rainfall over
water. In the analysis of the rain sound spectra, concurrent radar
reflectivity observations were used to identify convective and stratiform
regions of the precipitating clouds overhead. It was found that acoustic
classifications of rainfall as to type, based on information in the 4-30
kHz frequency band, were in general agreement with radar-derived
classifications. The classification technique is based on use of an
acoustic discriminant, DR, defined as the difference in
average spectral levels between the 10-30 kHz and 4-10 kHz bands. A high
correlation was found between sound spectrum levels (in dB) in the 4-10
kHz frequency band and radar reflectivity, dBZ, suggesting the possible
use of the 4-10 kHz band sound spectral level as a classification tool in
the same way that radar reflectivity is used in classifying
precipitation. Our results demonstrate the feasibility of the acoustic
method for detecting and classifying rainfall at sea.
Black, P.G., M.D. Powell, S.H. Houston, M.L. Black, and M. Hopkins. An
air-deployable drifting buoy observing system for monitoring hurricane
surface structure in critical air-sea interaction and landfall
situations. Minutes, 50th Interdepartmental Hurricane Conference,
Miami, FL, March 26-29, 1996. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C., A.5
(1996).
The 1995 hurricane season illustrated the need for accurate
in-situ measurement of air-sea interaction processes and the
importance they play in governing intensity estimation, as well as the
need for in-situ surface wind observations near the point of
hurricane landfall. A long-lasting cold pool in the North Atlantic SSTs,
generated by a stationary Hurricane Felix, may have contributed to the
weakening of Hurricane Luis, as Luis' cold wake may, in turn, have
contributed to the weakening of Hurricane Marilyn. Hurricane Opal's
rapid intensification occurred over a warm Loop Current eddy and its
rapid weakening was accompanied by SST decreases along the coast ahead of
the storm. A nearly-stationary Hurricane Roxanne gradually weakened in
the Bay of Campeche in response to strong self-induced SST cooling.
Strong air-sea stability offshore from Opal's landfall, together with a
single strong eyewall convective cell, produced surface winds that were
difficult to estimate from 700 mb reconnaissance data. To address this
need, the first operational test of an air-deployed drifting buoy array
was carried out during the 1995 season in Hurricanes Luis and Marilyn for
the purpose of (1) testing the logistical feasibility of deploying buoy
surface sensors in the path of a hurricane, (2) relaying data via
satellite in real time to National Hurricane Center (NHC) forecasters and
the National Meteorological Center (NMC) data base, and (3) testing their
survivability. On 8 September 1995 from 20-21 UTC, three wind
speed/direction (WSD) buoys and seven mini-drifting buoys (CLODS) were
deployed 300 nmi ahead of Hurricane Luis. The deployment was conducted by
the Air Force Reserve 53rd Weather Reconnaissance Squadron from a WC-130
aircraft. One WSD wind sensor failed and three CLODS failed on
deployment. Seven buoys measured pressure, air, and sea temperature at
hourly intervals, surviving 50 ft seas. The eye crossed the line near 12
UTC, 9 September, passing over one WSD and one CLOD, which reported
minimum pressures within 1 mb of that reported by AFRES dropsonde
observations. The highest 10-m, sustained wind estimated from the 1-m
buoy data was 80 kt with a peak gust of 110 kt. Hurricane forecasters
used the data to estimate the radius of gale force and 50 kt winds, which
impacted warnings for Bermuda. Information on the extent of surface winds
was also passed on to Canadian forecasters concerned about the subsequent
landfall in Newfoundland. The data were coded and processed by NMC,
appearing on most surface charts. Some coding errors occurred, which are
now being remedied. The buoys also observed a 3.5°C drop in SSTs to
the right of the storm. The experiment was repeated in Hurricane Marilyn
on 18 September 1995 from 1430 to 1530 UTC, with AFRES aircraft deploying
three additional WSD buoys and eight CLODs approximately 250 nmi ahead of
the storm in a region just south of the Luis buoy locations. A WSD wind
vane was damaged on deployment and five of the eight CLODs failed. This
still provided NHC forecasters with an unprecedented array of six WSD
buoys (four with working anemometers) and seven CLODs for a total of 13
platforms. Of these, three WSD and three CLODs passed through the eye.
The lowest measured pressure was about 5 mb higher than reported by NOAA
and AFRES aircraft. These data allowed forecasters to discern the surface
hurricane, storm, and gale force wind distribution with great precision.
It also showed that the cold wake left by Luis a week earlier was strong
and covering the eastern semi-circle of Marilyn as it traveled parallel
to Luis' track, a factor which may have been responsible for the storm
weakening on 19 September. A NOAA WP-3D flight was flown on 19 September
to correspond with the time that the storm was over the buoy array. Three
additional CLODs equipped with acoustic sensors for wind speed and rain
rate detection were deployed along with 35 AXBTs to sample SST and mixed
layer depth at fine spatial resolution. These two experiments showed that
drifting buoys can be successfully deployed ahead of a hurricane with
sufficient accuracy to provide detailed surface wind fields, estimate the
surface pressure distribution, and monitor the SST field for possible
effects on storm intensity in a real time mode that can enhance
forecaster confidence in estimating wind distribution radii. As such, it
appears to be a useful tool in critical landfall or strong air-sea
interaction situations.
Blackwelder, P., T. Hood, C. Alvarez-Zarikian, T.A. Nelsen, and
B. McKee. Benthic foraminifera from the NECOP study area impacted
by the Mississippi River plume and seasonal hypoxia. Quaternary
International, 31:19-36 (1996).
Benthic foraminifera influenced by the Mississippi River plume and
seasonal hypoxia were assessed from Louisiana inner-continental
shelf sediment samples. Surface foraminifera assemblages were
representative of in-situ populations as established by
staining techniques. Community diversity and richness/evenness
analyses indicate three regimes: high stress (sediment dominated),
intermediate stress (hypoxia dominated), and low stress (low sediment
accumulation/high oxygen). Epistominella vitrea and
Buliminella morgani are useful tracers of rapid sediment
accumulation rate and hypoxia. A bottom-water productivity signal
west of the Mississippi River plume is indicated by benthic and
planktic foraminifera abundance peaks. Surface benthic foraminifera
trends are utilized to interpret changes in historical community
structure from hypoxic-area sediments deposited since the turn of
the century. The hypoxia-tolerant species Buliminella morgani
increases markedly upcore, while hypoxia-intolerant species decrease
or disappear. Diversity and dominance trends temporally correspond
to a dramatic increase in U.S. fertilizer application. The results
of this study have application to paleoenvironmental research spanning
longer geologic timescales. The documented relationships between
population structure and stressors in river-dominated marine systems
may provide a useful analog for recognition of these conditions in
the fossil record.
Bufkin, J.M., and U. Rivero. Real-time digital data communication
system for a remotely operated ADCP. Proceedings, Ocean 96 MTS/IEEE,
Ft. Lauderdale, Florida, September 23-26, 1996. Marine Technological
Society, Vol. 1, 72-75 (1996).
An acoustic Doppler current profiler (ADCP) is moored adjacent to the
Miami Offshore Dredged Material Disposal Site to monitor in real-time
ocean currents during dredge disposal operations. The mooring site is
an active shipping channel which would present a low survivability rate
for surface radio communications buoys. There are also environmentally
sensitive areas which prevent the direct cabling of the ADCP into
shore. By combining hardwired cable and radio transmission techniques,
a remote telemetry system was designed and installed at a fixed
navigational marker that provides system reliability and a stable
platform to work from. Most ADCP systems that provide real-time data
are cabled back to a recording site which also supplies power to the
ADCP down the cable. A self-powered ADCP was utilized since cabling
to shore was not a viable option. This presented problems in powering
the interface to the data cable and had to be overcome. Powering down
the cable was limited since the telemetry unit at the other end of the
cable also had to be battery powered. From the ADCP a cable was laid to
the closest fixed workable point, which happened to be a navigation marker
at the entrance to the Port of Miami. This cable extends approximately
three miles, and proper cable drivers had to be located that would deal
with this distance. At the navigation marker, a telemetry unit was
designed that buffers the received data from the ADCP cable by using
a micro controller, and then transmits this data by a UHF radio modem.
The data is received and stored by computer at our laboratory
approximately five miles away. Power consumption proved to be a major
concern, since there are no available power sources at the navigation
marker. The ADCP operates from its own internal battery pack, and the
telemetry unit was designed to operate from batteries with solar panels
to supplement the power. It is able to operate for months unattended.
The system was installed in June of 1995, and has since proved to be
an extremely reliable system. The design of the telemetry system has
proven to be robust, and lends itself to future experiments where
data must be transmitted from a remote site.
Burpee, R.W., J.L. Franklin, S.J. Lord, R.E. Tuleya, and S.D. Aberson.
The impact of Omega dropwindsondes on operational hurricane track forecast
models. Bulletin of the American Meteorological Society,
77(5):925-933 (1996).
Since 1982, the Hurricane Research Division (HRD) has conducted a series
of experiments with research aircraft to enhance the number of observations
in the environment and the core of hurricanes threatening the United States.
During these experiments, the National Oceanic and Atmospheric
Administration WP-3D aircraft crews release Omega dropwindsondes (ODWs)
at 15-20 min intervals along the flight track to obtain profiles of wind,
temperature, and humidity between flight level and the sea surface. Data
from the ODWs are transmitted back to the aircraft and then sent via
satellite to the Tropical Prediction Center and the National Centers for
Environmental Prediction (NCEP), where the observations become part of the
operational database. This paper tests the hypothesis that additional
observations improve the objective track forecast models that provide
operational guidance to the hurricane forecasters. The testing evaluates
differences in forecast tracks from models run with and without the ODW
data in a research mode at HRD, NCEP, and the Geophysical Fluid Dynamics
Laboratory. The middle- and lower-tropospheric ODW data produce
statistically significant reductions in 12-60 h mean forecast errors. The
error reductions, which range from 16% to 30%, are at least as large as
the accumulated improvement in operational forecasts achieved over the last
20-25 years. This breakthrough provides strong experimental evidence that
more comprehensive observations in the hurricane environment and core will
lead to immediate improvements in operational forecast guidance.
Carsey, T.P., and M.L. Farmer. Nitrogen oxides in the Pacific MBL During
ACE-1. 1996 AGU Fall Meeting, San Francisco, CA, December 15-19,
1996. Supplement to EOS, Transactions, American Geophysical Union,
77(46):F76, A12A-16 (1996).
Nitric oxide, nitrogen dioxide, NOy, and PAN (peroxyacetyl nitrate) were
measured in the Pacific Ocean boundary layer aboard the R/V
Discoverer during the Pacific transit cruise, October 11-November 10,
1995, Seattle to Hobart, Tasmania, and during the ACE-1 cruise, November
15-December 13, 1995, south and east of Tasmania. NO, NO2,
and NOy measurements employed a chemiluminescent NO detector with
appropriate conversion; calibration employed standard gases (NO) or calibrated
permeation devices (NO2, NOy). PAN measurements were made
with an automated gas chromatograph utilizing a packed column and electron
capture detection; calibration was performed using PAN generated by
photolytic reaction of acetone with O2 and NO2,
molybdenum catalyst conversion and chemiluminescent analysis. Mixing ratios
of measured nitrogen species will be discussed in relation to meteorological
conditions and concentrations of other relevant chemical species.
Carsey, T.P., M.L. Farmer, C.J. Fischer, A. Mendez, V.B. Ross, M.
Springer-Young, and M.P. Zetwo. Atmospheric chemistry measurements
during Leg 4, 1993 North Atlantic cruise, R/V Malcolm Baldrige.
NOAA Data Report, ERL AOML-28(PB96-162581), 137 pp. (1996).
During September 1993, AOML conducted a multi-leg cruise aboard the
Malcolm Baldrige in the North Atlantic from Iceland to Miami,
Florida. The objective was to evaluate the distribution and transport of
tropospheric ozone and ozone precursors in the North Atlantic. The
investigation was associated with the North Atlantic Regional Experiment
(NARE), a component of the International Global Atmospheric Chemistry
(IGAC) project. The cruise track traversed three diverse wind and
chemical regimes: pristine polar westerlies, polluted westerlies, and
marine southeasterlies. Along this cruise track a large suite of
chemical and meteorological data were measured. These included ozone,
carbon monoxide in air and surface water, NO, NO2, Noy,
peroxyacetyl nitrate, SO2, non-methane hydrocarbons (NMHC),
and aerosols. The measurements and instrumentation are described in this
data report.
Cione, J.J., and S. Raman. Surface cyclone intensity forecasting within the
mid-Atlantic Gulf Stream locale using pre-storm low level baroclinic
indices. Preprints, AMS Conference on Coastal Oceanic and Atmospheric
Prediction, Atlanta, Georgia, January 28-February 2, 1996. American
Meteorological Society, Boston (1996).
No abstract.
Cione, J.J., and S. Raman. The impact of storm track on low level
mesocyclonic intensification and storm structure within the Gulf Stream
locale. Preprints, AMS Conference on Coastal Oceanic and Atmospheric
Prediction, Atlanta, Georgia, January 28-February 2, 1996. American
Meteorological Society, Boston (1996).
No abstract.
Clark, J.F., P. Schlosser, H.J. Simpson, M. Stute, R.H. Wanninkhof, and
D.T. Ho. Relationship between gas transfer velocities and wind speeds
in the tidal Hudson River determined by the dual tracer technique.
Proceedings, Third International Symposium on Air-Water-Gas Transfer,
Heidelberg, Germany, July 24-27, 1995. Aeon Verlag and Studio, 785-799
(1996).
Gas transfer velocities were determined using the dual tracer technique
(3He and SF6) for two 40-60 km reaches of the tidal
Hudson River. The experiments were performed near Poughkeepsie, New York
in 1993 and near Catskill, New York in 1994. During both experiments
wind speeds were measured above the river. The shape of daily axial
SF6 distributions and the evolution of peak concentrations
followed patterns predicted by the one-dimensional advection-diffusion
equation. Mean gas transfer velocities calculated from the 1994 data
using the temporal change in SF6 inventory (4.6 ± 0.4 cm
hr-1) and the tracer ration (5.3 ± 0.2 cm
hr-1) are in good agreement, suggesting that the dual tracer
technique yields reasonable results. The relationships between gas
transfer velocity and wind speeds found during these experiments are very
similar to those observed previously for lakes, suggesting that wind is
the primary source of surface turbulence in these reaches of the tidal
Hudson River. The results of the 1993 and 1994 experiments agree very
well, indicating that the local geometry of the river is of secondary
importance.
Claud, C., K.B. Katsaros, N.M. Mognard, and N.A. Scott. Comparative
satellite study of mesoscale disturbances in polar regions. Global
Atmosphere and Ocean System, 4(2-4):233-273 (1996).
Mesoscale disturbances in cold air outbreaks (polar lows) occur quite
often in high latitude areas of both hemispheres. The lack of
conventional meteorological observations over these areas implies heavy
reliance on satellite remotely-sensed information. Six lows which formed
at different places around the world have been examined in order to
derive their dominant features and environments. For this purpose, the
combination of a vertical atmospheric sounder (TOVS), a microwave imager
(SSM/I) and an altimeter (Geosat) has been used. While most retrieved
atmospheric parameters are quite variable from case to case, a number of
general statements about polar lows can be made: they all occur in areas
of cold and dry air outbreaks; in agreement with the low integrated water
vapor content values, the amount of liquid precipitation is very light,
and the cloud liquid water content moderate; both SSM/I and Geosat
indicate that surface wind speeds in the cloud bands forming the
developed systems are of strong to gale force, while the cloud-free
center is characterized by low values. Strongest winds and largest wave
heights occur on the southwestern flank of the lows in the northern
hemisphere and on the north flank in the southern hemisphere.
Dagg, M.J., E.P. Green, B.A. McKee, and P.B. Ortner. Biological removal
of fine grain lithogenic particles from a large river plume. Journal
of Marine Research, 54:149-160 (1996).
The pelagic tunicate, Oikopleura dioica, feeds by non-selectively
filtering particles in the size range of 0.1-10 µm. On the
continental shelf of the northern Gulf of Mexico, dominated by the
Mississippi River, particulate matter in this size range contains not
only microplankton but also numerous lithogenic particles. When O.
dioica is abundant it dominates total zooplankton grazing. By
ingesting small (<2 µm) lithogenics that effectively do not sink as
separate particles, and repackaging them into larger, more rapidly
sinking particles, it also significantly alters the fates of these
materials and the properties of the surface waters in and around the
discharge plume of the Mississippi River.
Dammann, W.P., J.M. Bufkin, U. Rivero, S.J. Stamates, and J.R. Proni.
Near real-time observations of offshore current profiles and their
application to dredge material disposal activities. Proceedings,
Eco-Informa '96: Global Networks for Environmental Information, Lake
Buena Vista, FL, November 4-7, 1996. Environmental Research Institute
of Michigan, Vol. 11, 563-568 (1996).
An acoustic Doppler current profiler (ADCP) is presently located
approximately 7 km east of the Miami Harbor entrance at approximately 130
m depth. This device measures profiles of the current speed and direction
in the upper 50 m of the water column directly above the instrument and
transmits its data to a computer on shore. These data, sent at 20-minute
intervals, are utilized to determine suitability of conditions for
disposal of dredge materials. The computer performs a running one-hour
average of the current vectors over the 50 m interval and transmits the
east- west component to a watchstander hourly via telephone pager. If the
westerly component of the current vector exceeds 12 cm per second,
disposal operations are suspended. As of the date of this presentation,
processed profiles of the data will be available via connection to the
world wide web.
Daneshzadeh, Y.-H., J.F. Festa, and R.L. Molinari. Quality control of XBT
data collected in the Atlantic Ocean: 1990-1991. NOAA Data Report, ERL
AOML-29, 77 pp. (1996).
Delayed mode and real-time XBT data collected in the Atlantic Ocean
during 1990 and 1991 were scientifically quality controlled at NOAA's
Atlantic Oceanographic and Meteorological Laboratory (AOML) and the
results of the quality control are presented in detail as tables and
figures.
DeCosmo, J., K.B. Katsaros, S.D. Smith, R.J. Anderson, W.A. Cost, K.
Bumke, and H. Chadwick. Air-sea exchange of water vapor and sensible
heat: The Humidity Exchange Over the Sea (HEXOS) results. Journal of
Geophysical Research, 101(C5):12,001-12,016 (1996).
Surface layer fluxes of sensible heat and water vapor were measured from
a fixed platform in the North Sea during the Humidity Exchange Over the
Sea (HEXOS) Main Experiment (HEXMAX). Eddy wind stress and other
relevant atmospheric and oceanic parameters were measured simultaneously
and are used to interpret the heat and water vapor flux results. One of
the main goals of the HEXOS program was to find accurate empirical heat
and water vapor flux parameterization formulas for high wind conditions
over the sea. It had been postulated that breaking waves and sea spray,
which dominate the air-sea interface at high wind speeds, would
significantly affect the air-sea heat and water vapor exchange for wind
speeds above 15 m/s. Water vapor flux has been measured at wind speeds
up to 18 m/s, sufficient to test these predictions, and sensible heat
flux was measured at wind speeds up to 23 m/s. Within experimental
error, the HEXMAX data do not show significant variation of the flux
exchange coefficients with wind speed, indicating that modification of
the models is needed.
DeMaria, M., and J. Kaplan. Performance of the SHIPS intensity forecast
model during the 1995 Atlantic hurricane season. Minutes, 50th
Interdepartmental Hurricane Conference, Miami, FL, March 26-29, 1996.
Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A.25 (1996).
After the 1994 hurricane season, the statistical hurricane intensity
prediction scheme (SHIPS) was modified to include 200 mb temperature as a
predictor. This predictor increased the skill of the developmental sample
(1989-1994) by 5%-10%. Results from independent cases during the 1995
season showed that this additional variable degrades the SHIPS
forecasts. This increase in error appears to be related to modifications
in the global model physics that were implemented in early 1995. The
revised version of the global model has a temperature bias relative to
the earlier version. A method was devised to correct for the temperature
bias in the SHIPS forecasts. Results from forecasts with and without the
bias correction will be compared.
Dickerson, R.R., P. Kelley, K.P. Rhodes, T.P. Carsey, M.L. Farmer, and
P. Crutzen. Measurement of reactive nitrogen compounds over the Indian
Ocean. Chemical Engineering News, 74:84 (1996).
No abstract.
Dietrich, D.E., M.J. Bowman, C.A. Lin, and A.M. Mestas-Nunez.
Numerical studies of small island wakes in the ocean. Geophysical
and Astrophysical Fluid Dynamics, 83:195-231 (1996).
Two and three-dimensional oceanic flows around small islands patterned
after Barbados, West Indies (13 deg10 min N latitude: 59 deg 30 min W
longitude) were modeled numerically to investigate island wake effects.
The two-dimensional simulations closely agreed with laboratory flows, for
both attached and shedding wake regimes. As expected, results for a flat
bottom confirmed that the Coriolis terms strongly affect pressure but not
the flow. For idealized, yet typical incident flow speeds, water column
stratification, island topography, and appropriate Coriolis terms,
three-dimensional simulations readily produced elongated wake patterns,
dominated by surface intensified von Karman-like vortices. Effects of
grid resolution, viscosity, bathymetry, and Coriolis forces on wake
characteristics were studied. For islands with typical bottom slopes,
realistically small horizontal eddy diffusivity has a minor effect
compared to bottom drag in generating vorticity. Near-shore bathymetry
(viz., the absence or presence of a continental shelf surrounding
the island) plays a major role in determining the scale, intensity, and
shedding period of vortices. The addition of a 15 km wide continental
shelf around the island increased the shedding period by 67%, while
reducing the Coriolis force by 50% reduced the shedding period by only
14%. Although observational data is sparse, inferred flow patterns do
show von Karman-like structures near Barbados, even if eddies are not
located exactly as expected. The numerical computations demonstrate that
shedding eddy wakes are easily generated, and lend encouragement to the
further search for organized wakes downstream of the island.
Dodge, P.P., S.H. Houston, and C. McAdie. Combined airborne and NEXRAD
Doppler radar analyses of the inner core of Hurricane Erin. Minutes, 50th
Interdepartmental Hurricane Conference, Miami, FL, March 26-29, 1996.
Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A.10-A.11 (1996).
An accurate real-time description of the tropical cyclone surface wind
field near landfall is important for warning, preparedness, and recovery
efforts. Research has helped reduce uncertainties in track and landfall
forecasts, but now there is an opportunity to improve the accuracy of the
surface wind fields in tropical cyclones, especially near landfall.
Scientists at the Hurricane Research Division (HRD) designed the Tropical
Cyclone Windfields Near Landfall experiment, part of the Hurricane Field
Program, to gather flight-level wind data and make surface wind estimates
to improve real-time and post-storm surface wind analyses in tropical
storms and hurricanes. One of the objectives of this experiment is to
collect airborne Doppler radar to combine with WSR-88D radar data in
post-storm three-dimensional wind analyses. In the experiment, a time
series of dual-Doppler data sets is collected by flying a single NOAA
WP-3D toward or away from a WSR-88D Doppler radar. The aircraft Doppler
radar rays are approximately orthogonal to the ground-based Doppler radar
rays in that pattern, yielding true dual-Doppler coverage. By 1997, the
Atlantic and Gulf coasts will be covered by the network of WSR-88D
Doppler radars deployed by the National Weather Service (NWS), Department
of Defense, and Federal Aviation Administration. The NWS will equip each
radar with a digital recorder to store the base data. The WSR-88D will
collect volume scans every 5-6 min. The flight pattern for this
experiment is designed to obtain dual-Doppler analyses at intervals of
10-20 min in the inner core. On 1 August 1995, an Aircraft Operations
Center WP-3D flew an HRD research mission to record airborne Doppler
radar data in Hurricane Erin near the time of landfall on the east coast
of Florida. From 2235 UTC to 0204 UTC on 2 August, the aircraft made
several penetrations through the eye when the storm was within Doppler
range of the Melbourne WSR-88D. The aircraft track was aligned along a
radial from the WSR-88D. At the conference we will present preliminary
analyses of Erin's wind field derived from airborne and WSR-88D Doppler
data collected at 0150 UTC, when the center of circulation was ~170
km from the Melbourne radar.
Drennan, W.M., M.A. Donelan, E.A. Terray, and K.B. Katsaros. Oceanic
turbulence dissipation measurements in SWADE. Journal of Physical
Oceanography, 26(5):808-815 (1996).
Recent experiments measuring turbulence dissipation rates in the upper
ocean can be divided into two types: those supporting an analogy between
the upper ocean and lower atmosphere, with dissipation rates following
wall layer behavior, and those finding oceanic dissipation rates to be
much higher than wall layer predictions. In an attempt to reconcile these
two diverse sets of observations, Terray et al. proposed a
wave-dependent scaling of the dissipation rate based on the significant
wave height and the rate of energy input from the wind to the waves.
Their parameterization was derived from observations of strongly forced,
fetch-limited waves, although they conjectured that it would apply in
typical oceanic conditions as well. This paper reports new measurements
of turbulent kinetic energy dissipation made in the North Atlantic Ocean
from a SWATH ship during the recent Surface Waves Dynamics Experiment
(SWADE). These data support the scaling of Terray et al.,
verifying its validity when applied to the more fully developed waves
typical of the ocean.
Duncombe Rae, C.M., S.L. Garzoli, and A.L. Gordon. The eddy field of the
southeast Atlantic Ocean: A statistical census from the Benguela Sources
and Transports (BEST) project. Journal of Geophysical
Research-Oceans, 101(C5):11,949-11,964 (1996).
Data collected during the Benguela Sources and Transports project were
examined to determine some statistical properties of the eddy field
observed in the Cape Basin. Seven anticyclonic eddies were encountered
during the hydrographic surveys. Two of these were shown to be of Brazil
Current origin (this paper and Smythe-Wright et al., 1996).
Inverted echo sounder (IES) records of acoustic travel time were scaled
to the depth of the thermocline, represented in the Cape Basin by the
10°C isotherm. These records indicate that a minimum of four to six
eddies, assumed to be of Agulhas origin, entered the Cape Basin per year
during the sampling period. They were associated with depressions in the
10°C isotherm records ranging from 100 to 400 m and of a duration
between 30 and 100 days. The thermocline appears to shallow appreciably
after the passage of an eddy before relaxing to the local mean.
Estimates of the heat and salt contents of the hydrographically surveyed
eddies indicated that the mean available heat and salt anomalies of the
eddies were 0.55 × 1020 J and 3.5 × 1012
kg, respectively. Extrapolating the hydrographic data to the eddies
detected in the IES record shows the eddy field responsible for the
transfer of 2.2 to 3.3 × 1020 J y-1
(0.007 PW), 14 to 21 × 1012 kg salt yr-1, and 2
.6 to 3.8 × 106 m3 s-1.
Enfield, D.B. Relationships of inter-American rainfall to tropical
Atlantic and Pacific SST variability. Geophysical Research
Letters, 23(23):3305-3308 (1996).
Area-averaged anomalies of sea surface temperature (SSTA) and rainfall,
developed from large-scale data sets, have been used to explore the
relative importance of Pacific versus Atlantic SST variability for
inter-American (50°S-50°N) climate variability at interannual time
scales. SSTA in the tropical Pacific and tropical North Atlantic are
comparably related to rainfall north of 15°S, with clear associations
distributed between the southeastern United States (US) in the north and
northern South America in the south. Although NINO3 explains 25% of the
variance of the North Atlantic SSTA index, the rainfall correlations with
North Atlantic SSTA are for the most part opposite in sign to those with
NINO3. Hence, a significant part of the Atlantic SSTA probably has a direct
association with rainfall, rather than being merely an indirect proxy for
Pacific ENSO linkages. In contrast to the North Atlantic, South Atlantic
SSTA appear to be only related to rainfall in northeast (NE) Brazil. The
entire region between Venezuela and NE Brazil appears to be sensitive to
both the ITCZ and to antisymmetric configurations of SSTA across the ITCZ,
in a manner consistent with the relationships between SST, surface wind
and surface wind divergence fields, and with previous studies.
Ffield, A., W.D. Wilson, J.M. Toole, and H.L. Bryden. The impact of eddies
on the southwestern Indian Ocean. 1996 AGU Fall Meeting, San
Francisco, CA, December 15-19, 1996. Supplement to EOS, Transactions,
American Geophysical Union, 77(46):F406, OS21C-09 (1996).
In the Indian Ocean, the Agulhas Current advects warm water southward,
balancing slower northward interior flow and input of Indonesian throughflow
water. The net transfer of properties through the southwestern Indian Ocean
provides the primary link of Indian Ocean water masses to the global ocean.
Mesoscale eddies in this region complicate determination of volume transports
and associated fluxes of heat and freshwater. While an eddy may contribute
nearly zero mass flux across a section when viewed synoptically, over time
it can transfer significant heat and freshwater. As part of NOAA/AOML's
contribution to the international Indian Ocean WOCE effort, temperature,
salinity, and oxygen measurements, along with hull-mounted and lowered ADCP
measurements, were obtained along 33°S near the east African coast
during March 1995. The characteristics of several energetic eddies revealed
in the March 1995 data are presented and compared to other hydrographic
observations obtained along the same section. Drifter and altimetry data from
the NASA Ocean Altimeter Pathfinder Data Project are used to monitor the
spatial and temporal variability of eddies in the southwestern Indian Ocean
as well. Together, these data are used to assess the importance of eddy
fluxes to the net mass, heat, and freshwater budgets of the Indian Ocean.
Franklin, J.L., S.E. Feuer, J. Kaplan, and S.D. Aberson. Tropical cyclone
motion and surrounding flow relationships: Searching for beta gyres in
Omega dropwindsonde datasets. Monthly Weather Review,
124(1):64-84 (1996).
In 1982, the National Oceanic and Atmospheric Admininstration's Hurricane
Research Division began a series of experiments to collect Omega
dropwindsonde (ODW) observations within about 1000 km of the center of
tropical cyclones. By 1992, 16 ODW datasets had been collected in ten
Atlantic basin hurricanes and tropical storms. Objective wind analyses for
each dataset, at ten levels from 100 mb to the surface, have been produced
using a consistent set of analysis parameters. The objective analyses,
which resolve synoptic-scale features in the storm environment with an
accuracy and confidence unattainable from routine operational analyses,
have been used to examine relationships between a tropical cyclone's motion
and its surrounding synoptic-scale flow. Tropical cyclone motion is found
to be consistent with barotropic steering of the vortex by the surrounding
flow within 3° latitude (333 km) of the cyclone center. At this
radius, the surrounding deep-layer mean flow explains over 90% of the
variance in vortex motion. The analyses show vorticity asymmetries that
strongly resemble the beta gyres common to barotropic models, although
other synoptic features in the environment make isolation of these gyres
from the wind fields difficult. A reasonably strong relationship is found
between the motion of the vortex (relative to its large scale surrounding
flow) and the absolute vorticity gradient of the vortex environment.
Gamache, J.F., and F.D. Marks. Analysis of airborne Doppler
observations of the weakening of eastern Pacific Hurricane Olivia on 25
September 1994. Minutes, 50th Interdepartmental Hurricane Conference,
Miami, FL, March 26-29, 1996. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C., A.9
(1996).
The two NOAA WP-3D aircraft observed Hurricane Olivia on 25 September
1994 as its minimum pressure increased by approximately 10 mb in 2.5
hours, and its mean upper-level eyewall winds decreased by more than
10 m s-1. Winds at all levels became much more
asymmetrical. Both aircraft carried vertically scanning Doppler radars in
their tails, and a coordinated pattern was flown that provided full
coverage of the inner core every 30 minutes. Our analysis extends out to
30 km from storm center. As the aircraft arrived around 2000 UTC, the
radar presentation was highly symmetrical, and the first Doppler analysis
shows that the tangential wind structure was also highly symmetrical.
Three hours later, the reflectivity to the south of the center had
weakened, and a highly convective region with reflectivities over 55 dBZ
had developed to the north. During the same period, the mean wind shear
(difference between 1 km and 9 km levels) in the eyewall increased from
approximately 10 m s-1 to over 20 m s-1. The storm
had already recurved at the beginning of the on-station time, so the rapid
changes over the next 3 hours in minimum pressure, upper-level winds, and
symmetry may have resulted from a destructive interaction with the
larger-scale flow. The three-dimensional structures of reflectivity,
tangential wind, and radar reflectivity will be shown at the conference.
Garzoli, S.L. SACC: South Atlantic Climate Change. U.S. Department
of Commerce, NOAA/Atlantic Oceanographic and Meteorological Laboratory,
Miami, Florida, 27 pp. (1996).
No abstract.
Garzoli, S.L., and A.L. Gordon. Origins and variability of the Benguela
Current. Journal of Geophysical Research-Oceans, 101(C1):879-906
(1996).
A subset of the Benguela Sources and Transports (BEST) 1992-1993 data is
analyzed to study the magnitude and variability of the large-scale
transports in the area. The data consist of inverted echo sounder series
and CTD stations. The mean 16-month transport values for the upper 1000
m indicate that of the 13 Sv northward transport within the Benguela
Current, 50% is derived from the central Atlantic (which from geometry
may be chiefly South Atlantic water), 25% comes from the Indian Ocean
(which may be chiefly Agulhas water), and the remaining 25% may be a
blend of Agulhas and tropical Atlantic water. A simple schematic of the
transport pattern in which a somewhat restricted corridor for Agulhas
eddies translation is envisioned. To the west of the eddy corridor flows
the South Atlantic source for the Benguela Current; to the east is the
Agulhas (Indian Ocean) source. The corridor is breached by South
Atlantic and Indian Ocean water as the transient eddy field stirs these
water masses.
Garzoli, S.L., A.L. Gordon, V.M. Kamenkovich, D. Pillsbury, and C.M.
Duncombe Rae. Variability and sources of the southeastern Atlantic
circulation. Journal of Marine Research, 54(6):1039-1071 (1996).
The 1992-1993 Benguela Sources and Transport (BEST) time series provides
a quantitative view of Benguela Current transport and the eddy field
across 30°S, as well as an estimate of the relation between its
barotropic and baroclinic components. This is done by a simultaneous
analysis of all the different data sets: inverted echo sounders, pressure
sensors, CTD, current meter moorings, and ADCP. The analysis of the
time series indicate that the annual mean baroclinic transport of the
Benguela Current is approximately 13 Sv. The total transport is 16 Sv.
The stationary flow associated with the Benguela Current is mostly confined
along the African Continent while a transient flow, composed by large
eddies shed from the Agulhas retroflection, composes the western portion
of the flow. In the stationary part of the Benguela Current, both
barotropic and baroclinic components are equally important while in the
transient part, the barotropic is more substantial. Several eddies were
observed during the experiment that translates to the west. They start
with a speed of 12 km/day and close to the Walvis Ridge it has already
diminished to 6-7 km/day. It can be assumed that after crossing the
Walvis Ridge, due to their strong barotropic component (they feel the
bottom), the speed decreases to that estimate previously obtained in the
middle of the basin. The sources of the Benguela Current may include
Indian and South Atlantic subtropical thermocline water; the relatively
saline, low oxygen tropical Atlantic water and the cooler, fresher
subantarctic water. The South Atlantic thermocline and subantarctic
inflow is derived from the eastward flowing South Atlantic Current. The
Indian Ocean water is injected into the Benguela Current through the
Agulhas retroflection eddy and filament processes. A complex stirring
effect of contrasting water types is envisioned. The changes in
thermocline salinity correlate with transport: in general, when the
northward transport is increasing the thermocline salinity also
increases. This indicates that the Benguela Current increases in strength
by bringing in more subtropical water. As the Agulhas input is most
effective in boosting the salinity of the upper thermocline (the South
Atlantic Current water being deficient in salinity relative to the Indian
Ocean source), we suggest that the spatial variations in transport are
tied to Agulhas water influx, presumably within and associated with the
eddy field.
Goldenberg, S.B., and L.J. Shapiro. Physical mechanisms for the
association of El Niño and west African rainfall with Atlantic major
hurricane activity. Journal of Climate, 9(6):1169-1187 (1996).
Physical mechanisms responsible for the contemporaneous association,
shown in earlier studies, of North Atlantic basin major hurricane (MH)
activity with western Sahelian monsoon rainfall and an equatorial eastern
Pacific sea surface temperature index of El Niño are examined, using
correlations with 200- and 700-mb level wind data for the period
1968-1992. The use of partial correlations isolates some of the
relationships associated with the various parameters. The results
support previous suggestions that the upper- and lower-level winds over
the region in the basin between ~10°N and 20°N where most
MHs begin developing and critical determinants of the MH activity in each
hurricane season. In particular, interannual fluctuations in the winds
that produce changes in the magnitude of vertical shear are one of the
most important factors, with reduced shear being associated with
increased activity and stronger shear with decreased activity. The
results show that most of these critical wind fluctuations are explained
by their relationship to the SST and rainfall fluctuations. Results
confirm previous findings that positive (warm) eastern Pacific SST and
negative (drought) Sahelian rainfall anomalies are associated with
suppressed Atlantic basin tropical cyclone activity through an
equatorially confined near-zonal circulation with upper-level westerlies
and lower-level easterlies that act to increase the climatological
westerly vertical shear in the main development region. SST and rainfall
anomalies of the opposite sense are related to MH activity through a
zonal circulation with upper-level easterly and lower-level westerly wind
anomalies that act to cancel out some of the climatological westerly
vertical shear. The results also show that changes in vertical shear to
the north of the main development region are unrelated to, or possibly
even out of phase with, changes in the development region, providing a
possible physical explanation for the observations from recent studies of
the out-of-phase relationship of interannual fluctuations in MH activity
in the region poleward of ~25°N with fluctuations in activity
to the south. The interannual variability of MH activity explained by
Sahel rainfall is almost three times that explained by the eastern
Pacific SSTs. It is demonstrated that a likely reason for this result is
that SST-associated vertical shears are more equatorially confined, so
that the changes in shear in the main development region have a stronger
association with the rainfall than with the SSTs.
Goldenberg, S.B., L.J. Shapiro, and C.W. Landsea. The hyperactive 1995
Atlantic hurricane season, Part II: Just a "spike" or a harbinger of
things to come? Minutes, 50th Interdepartmental Hurricane
Conference, Miami, FL, March 26-29, 1996. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A.35 (1996).
After a relative lull in overall activity during the preceding four
years, in 1995 the Atlantic hurricane basin experienced one of the most
active seasons on record, with almost every measure of activity over
twice the long-term mean. Of particular note was that the season
produced five major hurricanes (maximum sustained surface winds >50 m/s)
for the first time since 1964. Most of the major hurricanes in the North
Atlantic basin form from easterly (African) wave disturbances and are
especially sensitive to fluctuations in the tropical climate on the
interannual and interdecadal time scales. The fluctuations on these
scales that resulted in the "hyperactive" 1995 season and the
implications of these fluctuations for the years ahead will be
discussed. The chief issue that will be addressed is whether or not the
activity of the 1995 season was simply an anomalous "spike" or a
harbinger of long-term climate shifts signaling the probability of
greater activity in the years to come.
Goni, G.J., S. Kamholz, S.L. Garzoli, and D.B. Olson. Dynamics of
the Brazil/Malvinas Confluence based on inverted echo sounders and
altimetry. Journal of Geophysical Research-Oceans,
101(C7):16,273-16,289 (1996).
We use data from the GEOSAT altimeter and from ten inverted echo sounder
(IES) moorings deployed in the southwest Atlantic Ocean off the Argentine
continental shelf to investigate several aspects of the dynamics of the
upper layer in the Brazil/Malvinas Confluence region. We use the
altimeter data to estimate the sea-height anomalies at each IES location,
and the IES data to compute the upper-layer thickness, taken in this work
to go to the depth of the 8°C isotherm. We first discuss the sea
height and upper-layer thickness variations caused by the passage of the
Brazil Current, Malvinas Current, and warm anticyclonic and cold cyclonic
eddies. We introduce a two-layer model in which we decompose the sea
height into its baroclinic and barotropic contributions. We then propose
a method to monitor the thickness of the upper layer and the barotropic
and baroclinic transports as a function of the sea-height anomalies and
the statistics of the upper-layer thickness and reduced gravity for the
region. We compute the reduced gravity values from the slope of a linear
fit between the sea-height anomalies and the upper-layer thicknesses. We
estimate the reduced gravity values for this region to range from 0.005
to 0.011 m s-2. We also estimate the mean barotropic
sea-height difference using two methods: conservation of mass and
conservation of potential vorticity. Finally, we compute the time series
for the baroclinic and barotropic transports during the GEOSAT Exact
Repeat Mission (ERM) time period. Our results suggest that the mean
baroclinic transport in the upper layer decreases from 12 Sv at around
35°S to 7 Sv at 37°S. Our results also indicate that there is
a significant barotropic contribution to the upper-layer transport in the
Confluence region.
Goni, G.J., S.L. Garzoli, A.J. Mariano, D.B. Olson, and O.B. Brown.
Monitoring the upper layer southeastern Atlantic transports and eddy field
using altimeter data. 1996 AGU Fall Meeting, San Francisco, CA,
December 15-19, 1996. Supplement to EOS, Transactions, American
Geophysical Union, 77(46):F16, U11C-08 (1996).
Sea height anomaly data derived from TOPEX/POSEIDON and thermocline depth and
dynamic height derived from a set of five inverted echosounders and four
moored current meters are used in conjunction in the southeastern Atlantic
Ocean to monitor the thermocline depth and transports of the Agulhas/Benguela
system. Comparisons between TOPEX/POSEIDON altimeter observations and data
from the moored instruments show that the sea surface height anomaly is
significantly correlated to the thermocline depth and the sea surface dynamic
height. A two-layer approximation with thermocline deviations and a reduced
gravity is used to describe the vertical structure of the ocean. The reduced
gravity is estimated from the slope of the linear fit of the thermocline
depth and sea height anomaly data. The thermocline depth and baroclinic
and geostrophic transports are then computed using simple expressions
derived from the two-layer model. Analysis of three years of geostrophic
transport estimates obtained from TOPEX/POSEIDON data indicate that the
Benguela Current may undergo interannual variability up to 20%. However,
the primary variability derives from the source waters that form the
Benguela Current, i.e., waters from the South Atlantic, Indian Ocean,
and tropical Atlantic. The analysis of the depth of the altimeter-derived
thermocline field is used to study the formation of rings in the Agulhas
retroflection region, to monitor their trajectories, and to estimate
their kinetic and available potential energy.
Hacker, P., E. Firing, W.D. Wilson, and R.L. Molinari. Direct
observations of the current structure east of the Bahamas. Geophysical
Research Letters, 23(10):1127-1130 (1996).
Quasisynoptic absolute velocity sections were obtained in the western
North Atlantic to the east of the Bahamas on five cruises from 1992 to
1994, showing complex spatial and temporal variability of the currents
throughout the water column. Lowered acoustic Doppler current profilers
were used on all cruises; for comparison, an acoustically-tracked
free-fall profiler was used on the August 1992 and June 1993 cruises.
Where simultaneous profiles from both methods are available,
depth-averaged differences are less than 0.01 m s-1 in the
ensemble mean and standard deviation. Though small, the mean difference
appears to be statistically non-zero for one of the two Doppler profilers
used; no cause has been found. The individual velocity sections show a
banded structure of currents in the offshore direction with strong
baroclinic and depth-averaged components extending over the full sampling
domain. Two sections show a picture of the southward-flowing Deep
Western Boundary Current (DWBC) differing from previous observations.
During August 1992 and June 1993 the mean DWBC core was located more than
100 km offshore; in observations prior to 1990 it was usually near 50 km
offshore. Net southward transport below 800 m integrated from the coast
to 400 km offshore varied from 15 to 50 Sv with a mean of about 40 Sv (1
Sv = 1 × 106 m3 s-1). Our mean is
consistent with previous estimates; our sections add new evidence that
the transport is highly variable to at least 400 km offshore.
Halliwell, G.R., and D.A. Mayer. Frequency response properties of
forced climatic SST anomaly variability in the North Atlantic. Journal
of Climate, 9(12):3575-3587 (1996).
Frequency response properties of North Atlantic (5-57°N) sea surface
temperature anomaly (Tsa) variability over periods of several
months to 20 years are characterized using the Cooperative Ocean Atmosphere
Data Set (COADS). Significant direct forcing of Tsa
variability by the anomalous wind field (primarily through the resulting
anomalous surface turbulent heat flux) is observed in the Western Wind and
Trade Wind belts, but not between these belts within the interior of the
oceanic subtropical gyre. To analyze the response to this forcing, it is
necessary to separate the total anomalous surface turbulent heat flux
into a component representing the wind forcing and a component
predominantly representing the negative linear feedback (Newtonian
relaxation) that is the dominant damping mechanism of large-scale
climatic Tsa variability. At frequencies where wind forcing is
important, good agreement exists between frequency response properties
estimated from data and properties theoretically predicted by a simple
linearized slab mixed layer temperature balance. In particular, this
balance quantifies the influence of negative feedback damping on the
amplitude and phase lag of the response. In the Westerlies, wind forcing
is effective over periods from several months to 8 yr, primarily 2-4 yr,
and is ineffective at periods of 8-20 yr where forcing by variable
oceanic flow has been demonstrated to be important. In the Trades, wind
forcing is effective over periods from 8 mo to 13.3 yr, primarily 2-3 yr
and 7-13.3 yr. Wind forcing in the Trades is less effective at periods
of 3-6 yr where ENSO variability is significant. At frequencies where
wind forcing in the Westerlies is significant, forcing and feedback have
an equally large influence on Tsa, indicating that the
wind-forced response is damped primarily by the negative feedback contained
in the anomalous surface turbulent heat flux. In the Trades, feedback by
anomalous surface turbulent heat flux is not large enough to balance the
wind forcing; other processes must contribute significantly to the
damping there. At frequencies where wind forcing is important,
Tsa in the Westerlies is not coherent with Tsa in
the Trades. The anomalous wind fluctuations driving Tsa in the
Westerlies (Trades) are associated with anomalous surface pressure
variability in the Icelandic low (subtropical high). Response to a
coherent North Atlantic Oscillation (Icelandic Low varying out-of-phase
with the subtropical high) is, therefore, not observed. The large
Tsa fluctuations observed in the western basin within the
Westerly Wind belt propagate to the east and northeast across the Atlantic
at a characteristic speed of 6 km day-1.
Hansen, D.V., and H.F. Bezdek. On the nature of decadal anomalies in North
Atlantic sea surface temperature. Journal of Geophysical Research,
101(C4):8749-8758 (1996).
North Atlantic sea surface temperature data from the Comprehensive
Ocean-Atmosphere Data Set (COADS) were used to investigate the behavior
of temperature anomalies on multiple-year time scales during the period
1948-1992. Monthly anomaly time series for each 2° square from the
equator to 70°N were low-pass filtered at four years and normalized
by the local standard deviation. Attention is focused on the extreme
events, the upper and lower deciles, of the anomaly time series. A 45-year
sequence of January maps shows the already familiar phenomena of generally
cold conditions prior to 1951, a long warm interval from 1951 through 1967,
and again a cold period from 1968 through 1977. The years 1978 through 1982
were largely devoid of persistent strong anomalies, but moderate cold
conditions returned during 1983-1986. Warm cnoditions dominated the North
Atlantic from 1987 onward. Within these thermal epochs, however, a total
of five cold anomaly features and nine warm anomaly features have been
identified. These features have individual lifetimes of three to ten years.
A typical size is 20° of latitude or longitude, but they range from
barely detectable to spanning the width of the basin, the latter especially
in lower latitudes. Most of the anomalies move long distances along certain
preferred paths. These paths generally follow the routes of the subarctic
and subtropical gyres. Anomalies originating off North America along the
boundary between the gyres move northeastward toward the Norwegian Sea along
the approximate route of the North Atlantic Current. Midlatitude anomalies
originating at the eastern boundary tend to spread both northward and
southward along the coast. The speed of these movements (1-3 km
d-1) is generally less than the expected speed of the
near-surfce ocean circulation. Simple ideas about the effects of beta
dynamics and air-sea heat exchanges are briefly considered but do not
provide a satisfactory explanation for the movements of the anomalies.
The long time scale of these extreme events and the continuity of their
movements suggest a useful degree of predictability of sea surface
temperature based on persistence and propagation of features.
Hansen, D.V., and P.M. Poulain. Quality control and interpolations
of WOCE/TOGA drifter data. Journal of Atmospheric and Oceanic
Technology, 13(4):900-909 (1996).
Satellite-tracked drifting buoy data are being collected by numerous
investigators and agencies in several countries for the WOCE/TOGA
Surface Velocity Program. By the end of the century and thereafter
this global data set will provide the definitive climatology and
chronology of the surface currents of the world ocean. To expedite
completion of research quality data sets for archival and
dissemination, a data acquisition activity is being conducted at
NOAA/AOML, Miami, Florida. At AOML data from drifting buoys of
cooperating operators are quality controlled and optimally
interpolated to uniform six-hour interval trajectories for archival
at the Marine Environmental Data Service (Canada). This report
describes in detail the procedures used in preparing these data
for the benefit of second or third party users, or future buoy
operators who may wish to process data in a consistent way.
Particular attention is given to provide quantitative estimates
for uncertainty of interpolation.
Hansen, D.V., and M.S. Swenson. Mixed layer circulation during EqPac
and some thermochemical implications for the equatorial cold tongue.
Deep Sea Research II, 43(4-6):707-724 (1996).
Surface currents inferred from satellite-tracked drifting buoys were used
to develop a chronology of surface currents in the central Pacific for
the year encompassing the EqPac field program. Salient features of the
chronology are the early months of the program witnessed anomalous
eastward current surges near the equator within the moderate El Niño
event, followed by a period of anomalously strong westward flow near the
equator and eastward flow in the North Equatorial Countercurrent that
led, in mid-summer, to an eruption of tropical instability waves that
continued until the end of the field program. None of these events was
particularly unusual, but they were departures from climatology that
influence the interpretation of the biochemical measurements made for
EqPac. Results from a semi-quantitative conceptual model indicate that
tropical instability waves have more important long-term, as well as
short-term, consequences for thermochemical properties of the cold tongue
than previously recognized.
Hendee, J.C. Object-oriented analysis of a near real-time marine
environmental data acquisition and reporting system. NOAA Technical
Memorandum, ERL AOML-90 (PB97-114573), 64 pp. (1996).
The National Oceanic and Atmospheric Administration's Coral Health and
Monitoring Program has cooperated with the Florida Institute of
Oceanography in developing a near real-time marine environmental
monitoring and reporting system. Using the latest in object-oriented
analysis techniques, this report describes how data are retrieved from
satellite data and archiving facilities, then reformatted for
presentation via a remote bulletin board system and facsimile.
Hendee, J.C. Object-oriented design of a near real-time marine
environmental data acquisition and reporting system. NOAA Technical
Memorandum, ERL AOML-89 (PB97-114581), 29 pp. (1996).
The National Oceanic and Atmospheric Administration's Coral Health and
Monitoring Program in Miami, Florida has for the last several years worked
cooperatively with the Florida Institute of Oceanography in monitoring
meteorological and oceanographic events at selected Coastal-Marine
Automated Network sites in the Florida Straits. In a previous report,
an object-oriented analysis (OOA) was conducted of the existing system
with an eye toward redesigning the system. This report builds on the OOA
results from the previous study and utilizes the latest in object-oriented
design techniques to design a new system.
Houston, S.H., and M.D. Powell. Real-time surface wind analyses during
the 1995 hurricane season. Minutes, 50th Interdepartmental Hurricane
Conference, Miami, FL, March 26-29, 1996. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A.29 (1996).
During the 1995 hurricane season, HRD personnel conducted experimental
analyses of surface wind distribution in real time and made the analyses
available to duty hurricane forecasters and storm surge forecast
specialists. More than 80 analyses were conducted. The analyses are
based on compositing all available observations from Air Force
reconnaissance aircraft, ships, buoys, C-MAN platforms, and surface
aviation reports. All data are quality controlled and then processed to
conform to a common framework for height (10 m), exposure (marine or open
terrain over land), and averaging period (maximum sustained 1 min wind
speed). Several hours of observations are usually required to provide
sufficient data density and coverage for an analysis, and an analysis
domain consists of three or more nested meshes within which the scale of
resolvable features can be controlled. The resulting objective analysis
is representative of the mean state of the storm during the chosen time
period, and a typical 10 hour reconnaissance mission will yield two to
three analyses. The analysis product is a streamline and isotach contour
plot for a given mesh and is designed to convey the location and strength
of the maximum wind, as well as the extent of hurricane force, 50 kt,
and/or tropical storm force winds. Analyses conducted in Hurricanes
Erin, Felix, Luis, Marilyn, and Opal will be compared to dependent and
independent surface wind observations. In some situations there is
wide-spread agreement (e.g., Felix, Marilyn, Erin). In other
cases (e.g., Luis, Opal), where there is incomplete or
questionable surface information or where single level aircraft
observations do not adequately convey the level that most influences the
surface, there is mixed agreement.
Houston, S.H., W.A. Schaffer, M.D. Powell, and J. Chen. Incorporating
HRD surface wind fields into the SLOSH model. Preprints, Conference on
Coastal Oceanic and Atmospheric Prediction, Atlanta, GA, January
28-February 2, 1996. American Meteorological Society, Boston, 265-267
(1996).
NOAA's Hurricane Research Division (HRD) has developed new methods to
analyze surface winds in tropical cyclones based on all available surface
wind observations, including aircraft flight-level observations adjusted
to the surface. As part of NOAA's Coastal Ocean Program research on
coastal hazards, HRD and the Techniques Development Laboratory (TDL) have
evaluated the parametric wind model used as input to the National Weather
Service's (NWS) Sea, Lake, and Overland Surges from Hurricanes (SLOSH)
model through comparisons with HRD's surface wind analyses in recent
hurricanes (Hugo of 1989, Bob of 1991, Andrew of 1992, and Emily of
1993). These comparisons indicated that the SLOSH parametric wind model
adequately represented the wind fields in most cases. However, in the
case of Emily's closest approach to North Carolina, there were
significant underestimates in portions of the SLOSH model wind profile.
These reduced winds input to the SLOSH model resulted in an underestimate
of storm surge along some sections of the North Carolina coastline. The
HRD surface wind fields would likely improve the storm surge calculations
for this tropical cyclone if they could be input to the SLOSH model.
Techniques are presented here which allow the use of the HRD surface wind
fields as input for hindcasting the storm surge in the SLOSH model.
Examples are shown for applying these techniques to some recent
hurricanes which affected the United States coastline.
Huang, H., R.E. Fergen, J.R. Proni, and J.J. Tsai. Probabilistic
analysis of ocean outfall mixing zones. Journal of Environmental
Engineering, 122:359-367 (1996).
A methodology for ocean outfall mixing zone analysis is presented. It is
based on a combination of four deterministic models for predicting
hydrodynamic mixing behaviors of the discharged effluent, a continuous
time domain simulation method, and an exceedance probability field
concept. The approach provides a framework for evaluating mixing zones
in compliance with receiving water criteria that are set in statistical
terms. The approach was applied to the Hollywood outfall located off the
east coast of south Florida. An exceedance probability field for
effluent at a specified relative concentration of 0.021 was created.
This field was applicable for determining the exceedance
probability-based concentrations of any conservative pollutant at the
regulatory mixing zone edge. A comparison of the probabilistic approach
with the worst-case approach was made. The use of the worst-case
approach was found to be too conservative for the subject outfall.
Huber, M., M. DeMaria, and J. Kaplan. Evaluation of an empirical inland
wind decay model for the landfall of Hurricane Opal. Minutes, 50th
Interdepartmental Hurricane Conference, Miami, FL, March 26-29, 1996.
Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A.28-A.29 (1996).
Surface wind observations in the southeast U.S. during the landfall of
Hurricane Opal are used to evaluate an empirical inland wind decay model.
The model applies a simple two-parameter decay equation to the hurricane
wind field at landfall to estimate the maximum sustained surface wind as
a storm moves inland. The hurricane wind field at landfall is modeled as
a symmetric vortex plus a wave number one asymmetry that is proportional
to the storm motion. The model was run using operational information to
estimate the landfall storm structure. The model was also run where a
post-storm wind analysis prepared by Mark Powell and Sam Houston of the
Hurricane Research Division was used to estimate the landfall storm
structure. Results from these two runs will be compared with the observed
wind field.
Johns, E., W.D. Wilson, and R.L. Molinari. Transport balance of the
Intra-Americas Sea: Results from NOAA's Subtropical Atlantic Climate
Study. EOS, Transactions, American Geophysical Union, 76(3),
OS117 (1996).
No abstract.
Kaplan, J., M. DeMaria, and M. Huber. A preliminary evaluation of
forecasts from an empirical inland wind decay model for Hurricane Erin
(1995). Minutes, 50th Interdepartmental Hurricane Conference, Miami,
FL, March 26-29, 1996. Office of the Federal Coordinator for Meteorological
Services and Supporting Research, Washington, D.C., A.28 (1996).
In early August of 1995, Hurricane Erin made landfall along both the east
coast and panhandle of Florida before eventually becoming extratropical
and dissipating near the Virginia/Maryland border. Erin's track across
the data-rich Florida peninsula make it a good candidate for evaluating
an Empirical Inland Wind Decay Model (IWDM) developed recently at the
Hurricane Research Division (HRD) and employed by the National Hurricane
Center (NHC) during the 1995 hurricane season for the first time. The
IWDM is a simple, two-parameter model developed based upon the assumption
that tropical cyclone wind speeds decay exponentially with time after
landfall. The decay model has several potential applications including
the capability of providing an estimate of the swath of inland wind
speeds produced by a landfalling tropical cyclone. This particular model
application will be evaluated for landfalling Hurricane Erin by comparing
the IWDM predicted wind speeds to the winds at all available inland
surface observing stations. Erin's structure and intensity at landfall
required to produce the forecast wind swath were determined from
information contained in operational NHC hurricane advisories, as well as
from detailed near real-time wind analyses produced by Sam Houston and
Mark Powell of HRD. The accuracy of the forecast wind swaths produced
using both techniques will be discussed.
Landsea, C.W., S.B. Goldenberg, W.M. Gray, and G.D. Bell. The
hyperactive 1995 Atlantic hurricane season, Part I: A juxtaposition of
favorable conditions. Minutes, 50th Interdepartmental Hurricane
Conference, Miami, FL, March 26-29, 1996. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A.34-A.35 (1996).
The 1995 Atlantic hurricane season was a year of near-record hurricane
activity: a total of 19 named storms (average is 9.3 for the base period
1950-1990) and 11 hurricanes (average is 5.8) which persisted for a total
of 121 named storm days (average is 46.6) and 62 hurricane days (average
is 23.9), respectively. There were five intense (or major) hurricanes of
Saffir/Simpson category 3, 4, or 5 (average is 2.3 intense hurricanes)
with 11.5 intense hurricane days (average is 4.7). The net tropical
cyclone activity, based upon the combined values of named storms,
hurricanes, intense hurricanes, and their days present, was 229% of the
average. This unusually active hurricane season was the result of the
juxtaposition of nearly all the physical factors known to enhance
seasonal hurricane activity. This convergence of favorable factors has
occurred about ten times during the last century. These environmental
factors included extremely low vertical wind shear, below-normal sea
level pressure and above-normal SST throughout the Caribbean and tropical
North Atlantic, as well as a strong west phase of the stratospheric
quasi-biennial oscillation. The low vertical wind shear partially
resulted from cool phase conditions of the El Niño-Southern
Oscillation. Significantly, these anomalies were present in the pre-season
environmental fields, as far back as February, and thus preceded the
development of any hurricanes. Seasonal hurricane forecasts for 1995
issued at Colorado State University on 30 November 1994, 5 June 1995, and
4 August 1995 were able to anticipate an above-average season, but
underforecast the extent of the extreme hurricane activity. The 1996
seasonal forecast will be briefly discussed.
Landsea, C.W., N. Nicholls, W.M. Gray, and L.A. Avila. Downward trends
in the frequency of intense Atlantic hurricanes during the past five
decades. Geophysical Research Letters, 23:1697-1700 (1996).
There is concern that the enhanced greenhouse effect may be affecting
extreme weather events such as tropical cyclones. The North Atlantic
basin offers a reliable, long-term record of tropical cyclone activity,
though it may not be representative of tropical cyclones throughout the
rest of the tropics. The most recent years of 1991 through 1994 have
experienced the quietest cyclone activity on record in terms of frequency
of tropical storms, hurricanes, and intense hurricanes. This was
followed by the 1995 hurricane season, one of the busiest in the past 50
years. Despite 1995's activity, a long-term (five decade) downward trend
continues to be evident primarily in the frequency of intense hurricanes.
In addition, the mean maximum intensity (i.e., averaged over all
cyclones in a season) has decreased, while the maximum intensity attained
by the strongest hurricane each year has not shown a significant change.
Lobert, J.M., J.H. Butler, L.S. Geller, S.A. Yvon, S.A. Montzka, R.C.
Myers, A.D. Clarke, and J.W. Elkins. BLAST94: Bromine latitudinal air/sea
transect 1994 - Report on oceanic measurements of methyl bromide and
other compounds. NOAA Technical Memorandum, ERL CMDL-10 (PB96-154471),
45 pp. (1996).
No abstract.
Marks, F.D., and H.A. Friedman. 1996 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 138 pp. (1996).
The basic objective of NOAA's hurricane research field program is the
collection of descriptive data that are required to support analytical
and theoretical hurricane studies. These studies are designed to improve
the understanding of the structure and behavior of hurricanes. The
ultimate purpose is to develop improved methods for hurricane
prediction. Nine major experiments have been planned, primarily by
principal investigators at the Hurricane Research Division (HRD)/Atlantic
Oceanographic and Meteorological Laboratory (AOML) of NOAA, for the 1996
Hurricane Field Program. These experiments will be conducted with the
NOAA/Aircraft Operations Center (AOC) WP-3D and Gulfstream IV-SP aircraft.
Maul, G.A., M.H. Bushnell, N.J. Bravo, and D.V. Hansen. Observed sea
surface height and modeled dynamic height anomaly departures in the
tropical Pacific Ocean: 1986-1989. Oceanologica Acta,
20(4):569-584 (1996).
No abstract.
McCartney, M.S., R.G. Curry, and H.F. Bezdek. North Atlantic's
transformation pipeline. Oceanus, 39(2):19-23 (1996).
No abstract.
Mielke, P.W., K.J. Berry, C.W. Landsea, and W.M. Gray. Artificial skill
and validation in weather forecasting. Weather and Forecasting,
11(2):153-169 (1996).
The results of a simulation study of multiple regression prediction
models for meteorological forecasting are reported. The effects of
sample size, amount, and severity of nonrepresentative data in the
population, inclusion of noninformative predictors, and least (sum of)
absolute deviations (LAD) and least (sum of) squared deviations (LSD)
regression models are examined on five populations constructed from
meteorological data. Artificial skill is shown to be a product of small
sample size, LSD regression, and nonrepresentative data. Validation of
sample results is examined, and LAD regression is found to be superior
to LSD regression when sample size is small and nonrepresentative data
are present.
Millero, F.J., and E. Peltola. Total alkalinity measurements in the
Southern Ocean: World Ocean Circulation Experiment, Leg S4(I). University
of Miami Technical Report, RSMAS 96-005, 98 pp. (1996).
In the spring and summer of 1996, we participated in a research cruise in
the Southern Ocean (S4(I)) as a part of the Joint Global Ocean Flux Study
(JGOFS)/World Ocean Circulation Experiment (WOCE) sponsored by the
Department of Energy (DOE). This report gives the results of our pH,
total alkalinity (TA), and total inorganic carbon dioxide
(TCO2) determined from potentiometric measurements during the
cruise. At sea measurements made on Certified Reference Material (CRM
Batch 31) using the two cells indicate that the systems have a
reproducibility of ą 2.7 µmol kg-1 in TA, ą 2.9 µmol
kg-1 in TCO2 and ą 0.005 in pH. The TA measurements made on
CRM at sea (2131 ą 3 µmol kg-1) were in good agreement
with the laboratory measurements (2130 ą 1.4 µmol kg-1).
The normalized values of TA (NTA = 2375 ą 5 µmol kg-1)
and normalized TCO2 (NTCO2 = 2230 ą 10 µmol
kg-1) were quite uniform for the surface waters. The deep
waters had similar carbonate properties (pH = 7.60 ą 0.02, TA = 2355 ą 10
µmol kg-1, TCO2 = 2240 ą 10 µmol
kg-1). Our titration results will be combined with the partial
pressure of carbon dioxide (pCO2) and total carbon dioxide
(TCO2) measurements, made by Dr. Taro Takahashi's research
group from Lamont-Doherty Earth Observatory at Columbia University, to
fully characterize the CO2 system in these waters.
Napp, J.M., L.S. Inzce, P.B. Ortner, D. Siefert, and S. Britt. The
plankton of Shelikof Strait as predators, prey, and competitors of larval
pollock. Fisheries Oceanography, 5:19-38 (1996).
The vertical distribution of walleye pollock eggs and larvae in Shelikof
Strait, Gulf of Alaska, was investigated using data from 36 Multiple
Opening-Closing Net and Environmental Sensing System (MOCNESS) tows taken
in April and May 1986-1988. Most eggs were found from below 150 m to
near bottom, ~300 m, but were progressively shallower later in the
season. Eggs in middle stages of development were shallower than younger
or older eggs. The vertical distribution of eggs was positively related
to observed differences in seawater temperature but showed no
relationship to density. Larvae hatch at incubation depth and quickly
rise to the upper 50 m of the water column where they remain during
larval development. Larger larvae(~7-10 mm standard length) undergo
limited diel vertical migration within the upper 50 m. They are deepest
during the day, shallowest at dusk, slightly deeper at night, and even
deeper at dawn. Their mean depths of occurrence were between 21 and 37 m
at all times. At these depths, prey (copepod nauplii) generally
were at densities sufficient for larval pollock growth in laboratory
studies. Pronounced thermoclines and pycnoclines were present in the
part of the water column inhabited by the larvae in late May. Larvae
appear to remain below the upper mixed layer during periods of increased
turbulence, but at depths during daytime where light was sufficient for
feeding, and where prey densities were adequate.
Nelsen, T.A. Chapter 14: Coastal ocean water resources: Linkages
with terrestrial freshwater resources, anthropogenic influences, and
climate change. In Diachronic Climatic Impacts on Water
Resources, A.N. Angelakis and A.S. Issar (eds.). NATO ASI Series,
Vol. I36, Springer-Verlag, Berlin Heidelberg, 319-347 (1996).
No abstract.
Nelsen, T.A., M.P. Zetwo, H. Wanless, P. Blackwelder, P. Swart, T. Hood,
C. Alvarez-Zarikian, J. Trefry, S. Metz, W.-J. Kang, R. Trocine, L.
Tedesco, M. Capps, and M. O'Neal. The sediment record as a monitor of
natural and anthropogenic changes in the lower Everglades/Florida Bay
ecosystem: A high resolution study. 1996 Florida Bay Science Conference,
Miami, Florida, June 1996. Florida Sea Grant/University of Florida
Publication, 62-65 (1996).
No abstract.
Nystuen, J.A., J.R. Proni, P.G. Black, and J.C. Wilkerson. A comparison
of automatic rain gauges. Journal of Atmospheric and Oceanic
Technology, 13(1):62-73 (1996).
Automatic rain gauge systems are required to collect rainfall data at
remote locations, especially oceanic sites where logistics prevent
regular visits. Rainfall data from six different types of automatic rain
gauge systems have been collected for a set of summertime subtropical
rain events and for a set of wintertime rain events at Miami, Florida.
The rain gauge systems include three types of collection gauges:
weighing, capacitance, and tipping bucket; two gauges that inherently
measure rainfall rate: optical scintillation and underwater acoustical
inversion; and one gauge that detects individual raindrops: the
disdrometer. All of these measurement techniques perform well; that is,
they produce rainfall estimates that are highly correlated to one
another. However, each method has limitations. The collection gauges
are affected by flow irregularities between the catchment basin and the
measurement chambers. This affects the accuracy of rainfall-rate
measurements from these instruments, especially at low rainfall rates.
In the case of the capacitance gauge, errors in 1-min rainfall rates can
exceed +10 mm h-1. The rainfall rate gauges showed more
scatter than the collection gauges for rainfall rates over 5 mm
h-1, and the scatter was relatively independent of rainfall
rate. Changes in drop size distribution within an event could not be
used to explain the scatter observed in the optical rain gauge data. The
acoustical inversion method can be used to measure the drop size
distribution, allowing rainfall classification and estimation of other
rain parameters, for example, reflectivity or liquid water content, in
addition to rainfall rate. The acoustical inversion method has the
advantage of an extremely large catchment area, resulting in very high
time resolution. The disdrometer showed a large scatter relative to the
other rain gauge systems for low rainfall rates. This is consistent with
the small catchment area for the disdrometer system.
Palmer, D.R. Rayleigh scattering from nonspherical particles.
Journal of the Acoustical Society of America, 99(4):1901-1912
(1996).
A comprehensive framework is developed for calculating the intensity
received by a monostatic sonar system due to backscattering from a
cloud of nonspherical particles suspended in the ocean. The cloud
can consist of different types of particles having arbitrary shapes,
volume distributions, and orientations, as well as an overall mass
density that varies spatially within the cloud. In the Rayleigh
region it is possible to average over particle orientation exactly.
The averaged backscattered intensity depends on particle shape
through the eigenvalues of a tensor that can, in principle, be
determined by solving a boundary value problem for a harmonic
function. Since the solution to this boundary value problem is out
of reach practically, bounds are obtained on the backscattered
intensity that are independent of particle shape. These bounds
form the basis for obtaining estimates of the error that is made
by assuming the particles in the cloud scatter sound as if they
were spherical. A number of examples and applications are
considered, the most important of which is the feasibility of a
sonar to image black smoker hydrothermal plumes. The reassuring
result that the spherical particle assumption is likely to lead to
feasibility criteria that underestimate the performance of a sonar
is obtained. The isoperimetric bounds are combined with the
principle of maximum entropy, applied to the distribution of particle
shapes, to obtain a new expression for the square of the amplitude
for backscattering at wave number k0 from a
particle of volume V, specific bulk modulus e and a specific
density h: PHI2 = (k02
V/4 pi)2 [(e - 1)/e +
(h2 - 1)/2h]2. This amplitude
is obtained by averaging over particle orientation and particle
shape and is to be compared to the corresponding quantity for a
shere PHIsp2 = (k02
V/4 pi)2 [(e - 1)/e + (3
(h - 1))/(2h + 1)]2. The use of the new
expression is preferred in situations where it is known the particle
shapes are quite variable and irregular and where 1.0 < h
< 2.5. In all the examples considered it is found the error
that results from assuming the particles scatter sound as if they
were spherical is small. This is comforting and consistent with
one's intuition that in the Rayleigh region the scattered sound
should be somewhat insensitive to the shape of the scatterer.
Peng, T.-H., R.H. Wanninkhof, and R. Feely. An evaluation of anthropogenic
CO2. 1996 AGU Fall Meeting, San Francisco, CA, December
15-19, 1996. Supplement to EOS, Transactions, American Geophysical
Union, 77(46):F407, OS21D-02 (1996).
The annual increase in total dissolved inorganic carbon (DIC) in seawater
caused by the increase in atmospheric CO2 partial pressure is very small
(~1 umol/kg/yr). This is a result of the large initial DIC concentration
(~2000 umol/kg) in the ocean. However, advancements in DIC measurements
in recent years have made it possible to detect the anthropogenic
CO2 signal on decadal time scales. There have been many
geochemical survey cruises in the world oceans on which
CO2 system parameters have been measured since the historical
GEOSECS survey in 1972-1978. The anthropogenic CO2 signal in the
ocean has been determined by analyzing CO2 survey data obtained
from the NOAA-OACES NATL93 cruise in the North Atlantic, the NOAA-OACES CGC91
cruise in the Northeastern Pacific, and the NOAA-OACES IO95 cruise in the
Indian Ocean. After elimination of contribution from respiration of organic
matter by using AOU and Redfield ratios, the salinity normalized total DIC
concentrations along isopycnal surfaces representing the upper thermocline
waters are compared between the new measurements and those observed during
GEOSECS. The anthropogenic increase in DIC in the North Atlantic between
current cruises and GEOSECS-TTO are apparent, but are not conclusive. In the
northeastern Pacific, we can see an increase of 18 umol/kg at
sigmatheta = 26.4 between 1974 and 1991. In the Indian Ocean, an
increase of 17 umol/kg at sigmatheta = 26.6 between 1978 and
1995 is observed. These increases in DIC become smaller with denser
isopycnal surfaces as expected.
Powell, M.D., S.H. Houston, and T.A. Reinhold. Hurricane Andrew's landfall
in south Florida. Part I: Standardizing measurements for documentation
of surface wind fields. Weather and Forecasting, 11(3):304-328 (1996).
Hurricane Andrew's landfall in south Florida left a swath of destruction,
including many failed anemometer recording systems. Extreme destruction
led to exaggerated claims of the range of wind speeds that caused such
damage. The authors accumulated all available data from surface
platforms at heights ranging from 2 to 60 m and reconnaissance aircraft
at altitudes near 3 km. Several procedures were used to represent the
various types of wind measurements in a common framework for exposure,
measurement height, and averaging period. This set of procedures allowed
documentation of Andrew's winds in a manner understandable to both
meteorologists and wind engineers. The procedures are accurate to ±10%
for marine and land observing platforms, and boundary layer model
adjustments of flight-level winds to the surface compare within 20% of
the nearest surface measurements. Failure to implement the adjustment
procedures may lead to errors of 15%-40%. Quality control of the data is
discussed, including treatment of peak wind observations and
determination of the radius of maximum winds at the surface.
Powell, M.D., and S.H. Houston. Hurricane Andrew's wind field at landfall
in south Florida. Part II: Surface wind fields and potential real-time
applications. Weather and Forecasting,11(3):329-349 (1996).
All available wind data associated with Hurricane Andrew's passage were
analyzed for periods corresponding to landfall south of Miami and
emergence from southwest Florida. At landfall in southeast Florida,
maximum sustained (1 min) surface wind speeds (VM1) reached
62 m s-1 in the northern eyewall over land; by the time Andrew
exited the Florida peninsula, the peak value of VM1 over land
decreased to 44 m s-1. Radar reflectivity observations from
Tampa and Melbourne could not support an obvious correlation of convective
cell development with coastal convergence during landfall on the southeast
coast. On the southwest coast, however, convective cell development in
the southern eyewall was supported by a coastal convergence maximum.
Comparison of the wind swath with two independent Fujita-scale damage
maps indicated that peak swath speeds compared well with speed
equivalents in the worst damaged areas but were higher than equivalents
in moderately damaged areas. Comparison of the analysis maximum wind
swath with an engineering survey of damaged homes suggests that homes
exposed to a wide range of wind directions while subjected to high
wind speeds suffered the most damage. Potential real-time applications
of wind field products include warning dissemination, emergency
management, storm surge and wave forecasting, and wind engineering.
Development of damage assessment models for disaster mitigation is
addressed from the viewpoint of an electrical utility.
Powell, M.D., S.H. Houston, P.P. Dodge, and M.L. Black. Wind fields of
Hurricanes Marilyn and Opal at landfall. Minutes, 50th Interdepartmental
Hurricane Conference, Miami, FL, March 26-29, 1996. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A.29-A.30 (1996).
Hurricane Marilyn strengthened rapidly while approaching St. Thomas in
the U.S. Virgin Islands. A great deal of wind and storm surge-related
damage occurred throughout the island. Thanks to the hard work of the
San Juan Weather Service Forecast Office, a record of the peak winds in
the northern eyewall was recovered from an ASOS station at the airport.
These data will be compared to real time analyses of Air Force
reconnaissance winds adjusted to the surface. Hurricane Opal underwent
rapid changes in intensity as it approached the northwest Florida Gulf
coast. After strengthening to a minimum central sea level pressure of
916 mb with a small, well-organized eyewall and outer rainband in the
central Gulf of Mexico, Opal interacted with a cold front and mid-lower
tropospheric jet and weakened considerably by landfall. The pressure
increased to 942 mb, the intense circular inner eyewall maintained
convective reflectivity features only in the northern half of the eye,
and the eyewall wind maximum was poorly defined and weaker than the outer
wind maximum located in an outer rainband well to the east of the
center. Opal caused significant storm surge damage, but widespread wind
damage was not observed. Preliminary analyses of airborne Doppler radar
measurements collected by NOAA research aircraft 4 h before landfall
suggest that the interaction with the jet produced a flow through the
storm from southwest to northeast. This flow increased with height and
caused asymmetries in the surface wind field. The jet had the affect of
causing the level of maximum winds to rotate as a function of azimuth.
Peak winds were found at the 3 km level on the southeast side of the
storm where the jet helped to reinforce the flow. At landfall, 1 km level
winds on the east side of the storm may have been less affected by the
jet and, therefore, weaker than those at 3 km. In the absence of
convective reflectivity features that could transport momentum from 3 km,
weaker surface winds would prevail, consistent with relatively minor
wind damage. On the west side of the storm at 3 km, the jet had the
effect of canceling a portion of the flow leading to a distinct wind
minimum. The level of maximum winds on the west side was at 1 km, because
the jet was weakest near the surface. Hence, surface wind measurements
from C-MAN platforms on the west side of the storm were stronger than Air
Force aircraft reconnaissance observations at 3 km. The NOAA WP-3D
aircraft data will be combined with WSR-88D data from Eglin Air Force
Base to further define the wind field from 1 km and above. If these data
support the preliminary analyses, we may need to be more aware of the
possible affects that changing synoptic situations may have on the wind
field. Data collected from a given level may not provide enough
information to gauge what is occurring at the surface; we may need to
hasten the transfer of improved surface wind remote sensing systems from
research to operations.
Proni, J.R., S.J. Stamates,and J.F. Craynock. Massachusetts Bay water
column particulate horizons study. Contract Report DW13940107-01-0, U.S.
Environmental Protection Agency, 33 pp. (1996).
No abstract.
Proni, J.R., W.P. Dammann, J.F. Craynock, S.J. Stamates, D. Commons, R.
Fergen, H. Huang, R. Ferry, B. Goldenberg, J. Mandrup-Poulson, J. Monson,
and R. Williams. Worst case effluent discharge conditions and adaptive
processing of effluents for southeast Florida outfalls. Proceedings,
68th Annual Conference, WEFTEC '95, Miami Beach, FL, October 21-25,
1995. Water Environment Federation, 147-158 (1996).
Of substantial interest to entities regulating coastal ocean effluent
discharges are so-called "worst case" conditions. In general, "worst
case" conditions refer to conditions of poorest dilution as determined by
criteria involving ambient current speed distributions. A unique feature
of the coastal waters off southeast Florida is the proximity of the
Florida Current or Gulf Stream, one of the most powerful oceanic currents
on earth with an average daily transport through the Straits of Florida
of approximately 32 × 106 m3/sec. An extensive
study called the Southeast Florida Outfall Experiment (SEFLOE) was carried
out between 1988 and 1994 on the effluent discharges from four major
southeast Florida coastal ocean outfalls. All four of these outfalls are
located within the western boundary regime of the Florida Current and,
therefore, pose unique challenges in determining "worst case" conditions.
All four outfall sites are located in water of 30 m depth and are alternately
"within" and "external to" the Florida Current. As a consequence of
their locations, each of the outfalls is subject to three different
ambient current and, hence, dilution regimes. These regimes are (i) site
occupied by the Florida Current, (ii) site external to the Florida
Current but occupied by a relatively large scale, e.g., kilometers,
current eddy, or (iii) site external to the Florida Current but occupied
by short-period, e.g., 3-12 hour current variations, possibly being
linear and non-linear tides. "Worst case" dilution conditions in the
sense of poorest initial and/or subsequent dilution are observed during
the occurrence of regime (iii) above. During this regime very small mean
currents are observed.
Rogers, R.F., and J.M. Fritsch. A general framework for convective
trigger functions. Monthly Weather Review, 124(11):2438-2452 (1996).
A general framework for the trigger function used in convective
parameterization routines in mesoscale models is proposed. The framework
is based on the diagnosis of the accessibility of potential buoyant
energy. Specifically, the trigger function (1) estimates the magnitude
of the largest vertical velocity perturbation from a source layer, and
(2) calculates the total amount of inhibition between the source layer
and the level of free convection. The calculation of perturbation
magnitude accounts for such factors as subgrid-scale inhomogeneities, a
convective boundary layer, and convergence within the source layer.
Specific formulations to quantify these factors are proposed. The
trigger is tested in a simulation using the PSU-NCAR mesoscale model
MM5. The event chose for simulation is a summertime case exhibiting a
variety of environments. The results of the simulation are compared with
a simulation using the Fritsch-Chappell (FC) trigger function. It is
found that decisions made by the new trigger function are more physically
consistent with the local environment than decisions made by the FC trigger.
Rogers, R.F., and J.M. Fritsch. Mesoscale modeling of weakly-forced
convection: Sensitivity to surface property specification. Preprints,
11th Conference on Numerical Weather Prediction, Norfolk, VA, August
19-23, 1996. American Meteorological Society, Boston, 386-388 (1996).
It has long been known that properly accounting for the fluxes of heat,
moisture, and momentum from the surface is vital in obtaining reliable
forecasts at all scales of motion. The importance of accurately
representing these processes becomes most readily evident in simulations
of convective activity in weakly-forced environments. Traditionally
without access to air-surface interaction models, mesoscale models have
relied upon specifications of surface parameters (e.g., albedo,
moisture availability, roughness length, etc.) at each grid point
in order to calculate the surface fluxes and boundary layer evolution.
These specifications are based upon categorical decisions in which each
grid element is assigned fixed values for each particular surface
parameter. The values are considered to be representative of the
dominant condition within that grid element. Values vary in discrete
steps from one category of surface condition to another. Thus, a given
grid element may be, for example, 55% forest and 45% grassland and
therefore be assigned a category of "forest." An adjacent element may
have the reverse distribution (i.e., 45% forest and 55% grassland)
and be assigned a category of "grassland." These specifications are
usually time-invariant and, due to the necessity of making categorical
assignments, can result in sharp (i.e., step function) artificial
gradients of surface parameters across grid points where the actual land
surface type transitions vary much more gently. The effects of these
time-invariant step functions are investigated in a simulation of
convective activity in a weakly-forced environment using the Penn
State/NCAR mesoscale model MM5. It is found that significant vertical
circulations develop as a result of the artificially sharp gradients in
surface parameters and that these circulations are then instrumental in
spuriously initiating parameterized convection. The ability of the model
to simulate realistic boundary layer evolution and convective initiation
is therefore severely compromised in locations where these step-functions
occur. A test wherein the step functions are relaxed by smoothing the
surface parameter fields is then conducted to determine how removal of
the artificially sharp gradients affect the model solution. Results
reveal that the boundary layer assumes a more realistic structure and
spurious convection is reduced or eliminated over the areas where the
step functions were located in the unsmoothed run. The impact of
altering these fields on the subsequent simulation is discussed.
Roux, F., and F.D. Marks. Extended velocity track display (EVTD):
An improved processing method for Doppler radar observations of tropical
cyclones. Journal of Atmospheric and Oceanographic Technology,
13:875-899 (1996).
We present an improved version of the Velocity Track Display (VTD)
method, proposed by Lee et al. (1994) to deduce the primary vortex
circulation in hurricanes from airborne Doppler radar data obtained
during straight-line legs through the storm center. VTD allows the
derivation of one projection of the mean horizontal wind, the wave number
0, 1, and 2 components of the tangential wind and one projection of the
radial wind, in a series of concentric rings centered on the storm
circulation center. The extended VTD (EVTD) algorithm determines
additional information through a combination of data collected during
successive legs: the Cartesian components of the mean horizontal wind,
the wave number 0, 1, and 2 components of the tangential wind, and the
wave number 0 and 1 components of the radial wind. Application of EVTD
to airborne Doppler data collected on 17 September 1989 in Hurricane Hugo
is discussed. Comparisons between the EVTD-derived winds, the
flight-level measurements, and winds deduced from "pseudo-dual Doppler"
analyses show qualitatively good agreement. These results reveal the
asymmetric structure of the storm and show that it was in a deepening
stage, with increasing tangential wind, inflow, and upward velocity.
Further applications are finally discussed.
Schott, F.A., and R.L. Molinari. The western boundary circulation of the
subtropical warmwater sphere. In The Warmwater Sphere of the North
Atlantic Ocean, W. Krauss (ed.). Gebrüder Borntraeger, Berlin,
Stuttgart, 229-252 (1996).
Herein, we review observational, empirical, and modeling studies of the
western boundary region of the North Atlantic's subtropical gyre.
Emphasis is placed on recent observational studies that consider both
interaction between wind-driven and thermohaline driven currents and
characterize the annual and interannual time scales of the regional
circulation.
Severinghaus, J.P., W.S. Broecker, T.-H. Peng, and G. Bonani. Transect
along 24°N latitude of 14C in dissolved inorganic carbon
in the subtropical North Atlantic Ocean. Radiocarbon,
38(3):407-414 (1996).
The distribution of bomb-produced 14C in the ocean provides a
powerful constraint for circulation models of upper ocean mixing. We
report 14C measurements from an east-west section of the main
thermocline at 24°N latitude in the subtropical North Atlantic Ocean
in summer 1992, and one profile from the Gulf of Mexico in 1993. Observed
gradients reflect the transient invasion of bomb 14C into the
thermocline via mixing along isopycnals from the poleward outcrop, with
progressively more sluggish mixing at greater depths. A slight deepening
of the profile is observed over the 20-year period since the GEOSECS
survey at one location where the comparison is possible.
Sirkes, Z., E. Tziperman, and W.C. Thacker. Combining data and a global
primitive equation ocean general circulation model using the adjoint
method. In Modern Approaches to Data Assimilation in Ocean
Modeling, P. Malanotte-Rizzoli (ed.), Elsevier, Amsterdam, 119-145
(1996).
A primitive equation ocean general circulation model (PE OGCM) in a global
configuration similar to that used in coupled ocean-atmosphere models is
fitted to climatological data using the adjoint method. The ultimate
objective is the use of data assimilation for the improvement of the ocean
component of coupled models, and for the calculation of initial conditions
for initializing coupled model integrations. We argue that oceanic models
that are used for coupled climate studies are an especially appropriate
target for data assimilation using the adjoint method. It is demonstrated
that a successful assimilating of data into a fully complex PE OGCM
critically depends on a very careful choice of the surface boundary
condition formulation, on the optimization problem formulation, and on the
initial guess for the optimization solution. The use of restoring rather
than fixed surface-flux boundary conditions for the temperature seems to
result in improved model results. The convergence of the optimization
seems very sensitive to the cost formulation in a PE model, and a successful
cost formulation is discussed and demonstrated. Finally, the use of simple,
sub-optimal assimilation schemes for obtaining an initial guess for the
adjoint optimization is advocated and demonstrated.
Springer-Young, M., D.J. Erickson, III, and T.P. Carsey. Carbon monoxide
gradients in the marine boundary layer of the North Atlantic Ocean.
Journal of Geophysical Research-Atmospheres, 101(D2):4479-4484
(1996).
We present an observational data set that suggests that the ocean source
of carbon monoxide (CO) may influence the atmospheric CO concentration in
the marine boundary layer (MBL). Atmospheric CO concentration gradient
data obtained during the 1992 Atlantic Stratocumulus Transition
Experiment (ASTEX) show significantly (range of 2-47 ppbv, average of 15
ppbv) more CO at an altitude of 0.05 to 0.5 m above sea level as compared
to 10 m above sea level. The seawater CO concentrations needed to
support the fluxes obtained from an atmospheric gradient calculation are
much higher than generally reported in the literature. However, studies
of CO production by Jones and Amador (1993) and data from Seiler (1978)
suggest the possibility that CO production and the resultant flux to the
MBL could be 1-2 orders of magnitude higher than currently documented
using seawater pumped from depths of 4-10 m below the air-sea interface.
We infer that the surface ocean production and sea-air exchange of
photochemically produced trace gases such as CO may participate in
physical, chemical, and biological processes on vastly different spatial
and temporal scales than those inherent to more stable species such as
CO2.
Stamates, S.J., J.F. Craynock, J.R. Proni, V. Fox-Norse, and D.A.
Tomey. Acoustic reflector of opportunity distribution as a surrogate
for inferring effluent distribution in a survey of Massachusetts Bay.
Proceedings, Ocean 96 MTS/IEEE, Ft. Lauderdale, Florida, September
23-26, 1996. Marine Technological Society, Vol. 1, 313-320 (1996).
In 1998, the Massachusetts Water Resources Authority (MWRA) expects to
complete the construction of a new oceanic wastewater outfall system
which will have the capacity to release as much as 1.2 ×
109 (gal) of treated wastewater per day. The design of the
system is such that during summer months the effluent plume should be
trapped beneath the seasonal thermocline. It is proposed that the
spatio-temporal distribution of acoustic reflectors (probably
biological) present in the seasonal thermocline is a reasonable
surrogate for inferring the spatio-temporal distribution of acoustic
reflectors that will result from the release of wastewater effluent.
In September 1995, a joint U.S. EPA, MWRA, NOAA survey of
Massachusetts Bay was conducted. The primary data sets gathered were
acoustic backscatter profiles at 20 kHz and 200 kHz made every 0.5
(sec) with 0.5 (m) vertical resolution. Also, CTD casts and water bottle
samples were taken at selected locations. Oceanographic phenomena, such
as internal waves and tidal surges in conjunction with topographic
features, cause the surrogate scattering layers to be vertically
modulated with possible mixing of materials normally trapped within
layer boundaries. Analysis of acoustic backscatter measurements
provide visualizations of such events and allow for the estimation
of the surrogate scattering layer distributions in the vertical and
horizontal planes. Quantitative comparison of acoustic backscatter
strength with CTD derived density and transmissometry measurements give
an indication of the relationship of the surrogate scattering layers
to the water density structure at selected sites in the study (and an
indication of the reliability of the surrogate). In addition to its
role as a surrogate for wastewater, the relationship of the surrogate
scattering material layers with respect to the isopycnal surfaces is
also considered for the purpose of evaluating the exposure of biota
to future wastewater discharge.
Thacker, W.C. Climatic fingerprints, patterns, and indices. Journal
of Climate, 9(9):2259-2261 (1996).
The purpose of this note is to point out that Hasselmann's (1993) optimal
fingerprints for detecting climatic change follow from the geometrical
interpretation of covariance as an inner product.
Thacker, W.C. Metric-based principal components: Data uncertainties.
Tellus, 48A:584-592 (1996).
Seeking an index characterizing the best-determined mode of variability
leads to a natural generalization of principal-component analysis with an
explicit metric characterizing the uncertainties of the data. This
formalism, which distinguishes between state-space patterns and patterns
of coefficients defining principal components, allows the more accurate
data to exert a greater influence on the definition of the indices than
they do in conventional principal-component analysis; in all other
aspects, the new formalism is the same as the old. Within the context of
the simple example of Breterton et al. (1992), metric-based
principal-component analysis is shown to be capable of finding correlated
patterns of variability in two different data sets.
Thacker, W.C., and R. Lewandowicz. Climatic indices, principal components,
and the Gauss-Markov theorem. Journal of Climate, 9(8):1942-1958
(1996).
If indices are to be used as the variables predicted by linear
statistical models, it is important to be able to recover as much local
information as possible from the values forecast for the indices. Here
it is shown that the indices that encapsulate the most information about
the local climatic state are determined by a generalized (two-matrix)
eigenvalue problem that is equivalent to the usual (one-matrix)
eigenvalue problem involving the sample correlation matrix. Thus, the
best indices in the sense of providing the most location-specific
information are the familiar principal-component indices. Regarding the
indices as predictors in linear statistical models similar to those
routinely used for estimating meteorological fields from observations
reveals the role of the Gauss-Markov theorem in EOF analyses. From this
perspective each index can be characterized by two EOF-like maps: the
first illustrating the linear combinations of the data used to define the
index, and the second displaying the Gauss-Markov weights for the index
to predict local variables, both of which are related to the eigenvectors
of the sample correlation matrix. Other maps can be used to display
information about sampling errors: one to characterize the uncertainty of
the weights; another to display the skill with which the index accounts
for the training data; and a third to show how well it explains independent
data. Such maps are illustrated within the context of 43 years of North
Atlantic seasonal sea-surface temperature anomalies. The analysis
presented here underlies two additional points. First, any linear
combination of the indices would result in an equivalent model yielding
exactly the same forecast. Consequently, it may be desirable to use indices
that are easier to interpret physically. Second, when indices are regarded
as being variables of a linear statistical model, the analysis of sampling
error can be formulated in terms of the uncertainty of the Gauss-Markov
weights inferred from a limited training set rather than in terms of the
sample-to-sample variability of eigenvalues and eigenvectors.
Tsai, J.J., J.R. Proni, H. Huang, and J.F. Craynock. Initial and
near-field subsequent dilution at the Key West Outfall. Proceedings,
68th Annual Conference, WEFTEC '95, Miami Beach, FL, October 21-25,
1995. Water Environment Federation, 139-146 (1996).
A one-year field study of discharge from the Key West Outfall was
conducted from June 1993 to July 1994. A towed CTD was used to measure
salinity about every other month with a fixed current mooring next to the
outfall. Salinity deficit was used as a tracer to estimate the minimum
surface dilution at the boil and near field subsequent dilution. The
measured dilution was rapid within 200 m and reached 100:1 at about 500 m
from the boil.
Wang, C., and R.H. Weisberg. Stability of equatorial modes in a
simplified coupled ocean-atmosphere model. Journal of Climate,
9(12):3132-3148 (1996).
The stability, periodicity, and horizontal structure of equatorial modes
in a coupled ocean-atmosphere model, simplified by the assumption that
zonal wind stress anomalies are proportional to sea surface temperature
(SST) anomalies lagged by a zonal phase difference, are examined
analytically. The gravest coupled Rossby and Kelvin modes coexist with
westward and eastward slow modes. Two of these four modes, one
propagating westward and the other eastward, are destabilized in each
case depending upon the model parameters. For some particular parameter
choices, coupled Rossby and Kelvin modes merge with westward and eastward
slow modes, respectively. For other parameters, however, they separate
and remain distinct from the slow modes. For all of these modes the
primary modifications by coupling relative to uncoupled oceanic
equatorial waves are a decrease in phase speed and an increase in
meridional scale. Among the model parameter effects, those of the zonal
phase lag between the wind stress and SST anomalies and the coefficients
of thermal and mechanical damping are the most interesting. The frequency
of all modes is symmetric about zero phase lag, whereas the growth rate
is antisymmetric relative to the uncoupled damping rate. Wind anomalies
to the west of SST anomalies favor slow (coupled Rossby and Kelvin) mode
growth (decay). Slow (coupled Rossby and Kelvin) mode damping is mainly
thermal (mechanical). It may be concluded that coupling affects the
structure, propagation, and stability properties of equatorial modes at
low frequency. Determining where within the equatorial waveguide and with
what efficiency coupling occurs would, therefore, seem to be critical for
improved understanding of the ENSO phenomenon.
Wanninkhof, R.H., and M. Knox. Chemical enhancement of CO2
exchange in natural waters. Limnology and Oceanography,
41(4):689-697 (1996).
Exchange of carbon dioxide (CO2) under low turbulence conditions
and high pH can be enhanced by hydration reactions of CO2 with
hydroxide ions and water molecules in the boundary layer. A series of field
experiments was performed on several lakes, including alkaline closed-basin
lakes, using enclosures (helmets) to study the enhancement process in nature.
In addition, the enhancement of CO2 exchange was studied in
laboratory experiments using freshwater and seawater. The results of the
experiments are compared with published theoretical calculations. Within the
experimental uncertainties and shortcomings of the chemical enhancement
models, reasonable agreement was observed between experimental and
theoretical results for seawater. The experiments indicate, in accordance
with theory, that chemical enhancement has a minor effect on air-sea gas
exchange of CO2 under average oceanic turbulence conditions.
However, for the equatorial CO2 source regions, with high
temperatures and low winds, the calculated CO enhancement amounts
to 4% to 8% of the total exchange. The observations on lakes show poorer
agreement with models which is attributed to experimental uncertainty and
poor characterization of the chemistry of the lake waters. The experiments
show that chemical enhancement of CO2 is ubiquitous for the
alkaline close basin lakes with enhancements of up to a factor of three.
Wanninkhof, R.H. W.E. Asher, and E.C. Monahan. The influence of bubbles
on air-water-gas exchange: Results from gas transfer experiments during
WABEX-93. Proceedings, Third International Symposium on Air-Water-Gas
Transfer, Heidelburg, Germany, July 24-27, 1995. Aeon Verlag and Studio,
239-254 (1996).
Bubble-mediated gas transfer velocities were determined in a freshwater
surf pool during WABEX-93. Gas transfer of N2O, He, and
SF6 were measured under eight different mechanically-generated,
breaking-wave conditions. Contrary to gas transfer across an air-water
interface, where the transfer is solely a function of surface turbulence
and the molecular diffusion coefficient of the gas, exchange through
bubbles is also a function of the solubility of the gas, bubble size, and
bubble penetration depths. The relative rates of gas transfer through
bubbles of N2O, CO2, He, and SF6 for
the experiment are compared with models developed by Woolf (1995) and
Keeling (1992). The model of Woolf shows reasonable agreement with the
observed results while that of Keeling overpredicts the exchange of
N2O. The trend suggests that in the surf pool experiments the
solubility dependence of the model of Keeling is too strong while that of
Woolf is slightly too weak compared to the observations.
Wanninkhof, R.H., S. Doney, T.-H. Peng, R. Feely, and J.L. Bullister.
Penetration of anthropogenic CO2 into the North Atlantic Ocean.
EOS, Transactions, American Geophysical Union, 76:128 (1996).
Transient tracers such as 14C and chlorofluorocarbons offer a
powerful constraint on the penetration depth and inventory of anthropogenic
CO2 in the North Atlantic. A qualitative comparison is
performed between the transient tracers and anomalies in preformed carbon
from a cruise in the North Atlantic along 20/25°W from 5°S to
62°N in 1993 as part of NOAA's Ocean-Atmosphere Carbon Exchange Study
(OACES). The analysis is performed in an isopycnal reference frame to
distinguish between different water masses. From the apparent oxygen
utilization and change in total alkalinity (calculated from pCO2
and DIC) in CFC-free water, the pre-anthropogenic preformed carbon at each
isopycnal is determined. Based on the CFC ages of the water along the
isopycnal and fossil fuel CO2 release histories, the fraction
of atmospheric fossil fuel burden taken up with time is determined. These
estimates are compared with air-sea fluxes of CO2 into the
ocean at the outcrop regions.
Wanninkhof, R.H., R.A. Feely, H. Chen, C. Cosca, and P.P. Murphy.
Surface water fCO2 in the eastern equatorial Pacific during
the 1992-1993 El Niño. Journal of Geophysical Research,
101(C7):16,333-16,343 (1996).
The fugacity of CO2 in surface water (fCO2W) was
measured in the eastern equatorial Pacific (EEP) during the boreal spring
and fall of 1992 and in the spring of 1993. A prolonged El Niño
occurred during this period with anomalously warm sea surface temperatures
(SST) during the spring of 1992 and 1993. Correspondingly, the
fCO2W values were lower than historical non-El Niño
values at the equator. However, the fCO2W in the spring of
1993 was up to 50 µatm higher than in the spring of 1992, despite
similar SSTs. The trend is attributed to the slower response times of
factors causing fCO2W decrease compared to rapid increase of
fCO2W by upwelling cold water with high carbon content and
subsequent heating. During the fall of 1992, SSTs south of the equator
were 5°C cooler than in the spring, which is indicative of vigorous
upwelling of water with high CO2 content from below the
thermocline. Decreases in fCO2W due to net biological
productivity and gas exchange take of the order of months, causing the
fCO2W levels during the spring of 1993 to be elevated compared
to the spring of the previous year. Our data and data obtained in 1986
and 1989 along 110°W suggest that fCO2W maxima in the
equatorial Pacific can be either associated with temperature minima or
temperature maxima. Despite the multitude of factors which influence
fCO2W, most of the variance can be accounted for with changes
in nitrate and SST. A multilinear regression of fCO2W with
SST and nitrate for the 1992 data has a standard error in predicted
fCO2W of 10 µatm. Air-sea fluxes of CO2 in
the EEP were estimated to be 30% higher in the spring of 1993 and 10%
higher in the fall of 1992 than in the spring of 1992.
Weisberg, R.H., C. Wang, and D.A. Mayer. An oscillator paradigm for
El Niño-Southern Oscillation. 1996 AGU Fall Meeting, San
Francisco, CA, December 15-19, 1996. Supplement to EOS, Transactions,
American Geophysical Union, 77(46):F40, U32A-03 (1996).
A data-based hypothesis is developed on the mechanism of the El
Niņo-Southern Oscillation (ENSO). This hypothesis emphasizes the
importance of off-equator sea surface temperature (SST) and sea level
pressure (SLP) variations in the western Pacific for providing a
negative feedback that is necessary for the coupled ocean-atmosphere
system to oscillate. The negative feedback derives from equatorial
easterly winds over the far western Pacific, driven by off-equator high
SLP during the mature phase of El Niņo. The off-equator high SLP
follows from off-equator low SST that is related to upwelling favorable
wind stress curl set up by equatorial west-central Pacific convection.
The resulting easterlies over the western equatorial Pacific compete
with westerlies over the west-central equatorial Pacific to reverse the
sign of the central equatorial Pacific SST anomalies. An analog model
embodying these conceptual ideas produces ENSO-like oscillations on
interannual time scales. While this oscillator paradigm involves forced
oceanic equatorial wave dynamics, it does not require wave reflection at
the western boundary.
Willoughby, H.E. Hurricane research from forty thousand feet. Minutes,
50th Interdepartmental Hurricane Conference, Miami, FL, March 26-29,
1996. Office of the Federal Coordinator for Meteorological Services and
Supporting Research, Washington, D.C., A.9 (1996).
NOAA's commissioning of its new Gulfstream IV (G-IV) mid-level jet
represents an unprecedented opportunity to answer questions about
hurricane motion and intensification. In its initial configuration, the
airplane will be able to fly 4,000 nautical miles, attain pressure
altitudes near 14 km, and dispense GPS dropsondes. It will carry a
C-band nose radar and a workstation to process dropsonde messages for
transmission. The G-IV will represent the hurricane research community's
first routine access (apart from a few flights by jet aircraft borrowed
from NASA) to the upper troposphere since the 1960s. The primary mission
of the G-IV will be "synoptic surveillance," dispensing dropwindsondes in
the hurricane's surroundings to improve track forecasts. We expect
~20% smaller error based upon experience with turboprop WP-3Ds flying
similar missions. With additional instrumentation, primarily
microwave/surface wind sensors, the G-IV will ultimately be able to obtain
center fixes. These operational missions justify the G-IV's existence, but
what can the jet do to improve physical understanding? Because the sounding
data will represent nearly the whole tropospheric column, the G-IV can
provide a nearly complete picture of the storm's interaction with its
surroundings. A simple circumnavigation at 300 to 600 km will support
determination of eddy and mean-flow boundary fluxes. The operational
synoptic missions will capture the structure of the environmental flow
and storm-induced eddies, but radial penetrations at 200 hPa, after the
G-IV is certified to fly into hurricanes, may prove to be the best way to
evaluate these interactions. From decades of experience with turboprops
operating in the lower and mid troposphere, we know a great deal about
the convective and vortex-scale structure and dynamics of hurricanes.
These observations, combined with conventional synoptic analyses, have
led to a consensus that understanding of forcing by upper tropospheric
eddies and of advection by vertically-averaged winds are the keys to
prediction of intensity and track. The G-IV and the existing WP-3Ds,
with their powerful radars and other sensors, are the tools needed to
forge this understanding.
Willoughby, H.E., and P.G. Black. Hurricane Andrew in Florida: Dynamics
of a disaster. Bulletin of the American Meteorological Society,
77(3):543-549 (1996).
Four meteorological factors aggravated the devastation when Hurricane
Andrew struck south Florida: completed replacement of the original
eyewall by an outer, concentric eyewall while Andrew was still at sea;
storm translation so fast that the eye crossed the populated coastline
before the influence of land could weaken it appreciably; extreme wind
speed, 82 m s-1 winds measured by aircraft flying at 2.5 km;
and formation of an intense, but nontornadic, convective vortex in the
eyewall at the time of landfall. Although Andrew weakened for 12 h
during the eyewall replacement, it contained vigorous convection and was
reintensifying rapidly as it passed onshore. The Gulf Stream just
offshore was warm enough to support a sea level pressure 20-30 hPa lower
than the 922 hPa attained, but Andrew hit land before it could reach this
potential. The difficult-to-predict mesoscale and vortex-scale phenomena
determined the course of events on that windy morning, not a long-term
trend toward worse hurricanes.
Willoughby, H.E., and P.G. Black. Correction to Hurricane Andrew
in Florida: Dynamics of a disaster (letters to the editor). Bulletin
of the American Meteorological Society, 77(5):962 (1996).
No abstract.
Wilson, W.D., E. Firing, J. Kindle, F. Schott, D. Quadfasel, and C. Flagg.
Equatorial currents in the western Indian Ocean during 1995. 1996 AGU
Fall Meeting, San Francisco, CA, December 15-19, 1996. Supplement to
EOS, Transactions, American Geophysical Union, 77(46):F392,
OS12A-03 (1996).
Because of the strong, seasonally-varying surface forcing fields, the
tropical Indian Ocean has long been recognized by physical oceanographers
as an important natural laboratory for studying upper ocean dynamical
processes. In 1995, the intensive Indian Ocean WOCE and other coincident
field programs (e.g., JGOFS) led to a remarkable concentration of
shipboard data collection resources in the region, including the research
vessels Knorr, Thomas G. Thompson, Malcolm Baldrige, and
Meteor. All were equipped with hull-mounted acoustic Doppler current
profilers (ADCPs) and high quality navigation equipment, and nine underway
velocity sections were collected in the vicinity of 55°E between
5°N and 5°S during April through December 1995. Additionally,
full-depth lowered ADCP (LADCP) velocity measurements are available for
many of the sections. This region is especially important to understanding
monsoon current dynamics, as it is the link between the equatorial wave guide
and the western boundary current (Somali Current) regime. Considerable
modeling and observational effort has been spent on this region, trying to
determine the relative importance of local and remote wind forcing to the
rapid changes observed in the Somali Current. The sections are presented,
especially noting their relationship to changes in the equatorial wind field
as shown by the FNMOC NOGAPS analysis and their similarities to theoretical
and modeled equatorial wave dynamical processes. The April 1995 section,
during the monsoon transition period, is dominated by an equatorial
undercurrent centered near 100 m, with westward flow below and weak
symmetric off-equatorial eastward jets. By late June 1995, some two months
after the southwest monsoon onset, there is a westward core at 100 m, with
enhanced off-equatorial eastward flows; the changes are consistent with the
arrival of equatorial Rossby waves from the interior. Mid-July and early
August sections show the effects of the Somali Current low-latitude
turnoff jet, which crosses the equator southward near 55°E and returns
eastward near 3°S. Sections in late August and early September show
the development of the low-latitude effects of the Somali Current, and a
final section in January 1996 shows the current field associated with the
northeast monsoon.
Yvon, S.A., and J.H. Butler. An improved estimate of the oceanic lifetime
of atmospheric CH3Br. Geophysical Research Letters,
23(1):53-56 (1996.)
Previous estimates of the partial atmospheric lifetime of
CH3Br with respect to degradation in the ocean have not fully
accounted for co-variation of sea-surface and boundary layer properties.
Here we substantially reduce uncertainty in this calculation by using a
coupled, ocean-atmosphere box model and a tightly gridded data set of
oceanic and atmospheric properties. The best estimate of the partial
atmospheric lifetime of CH3Br with respect to the ocean is 2.7
y with a possible range, due mainly to the choice of computational
procedures for critical terms, of 2.4 to 6.5 y. This range is about
one-third of that estimated previously. The total atmospheric lifetime,
based upon oceanic, atmospheric, and proposed soil losses with all of
their uncertainties, is 0.8 (0.6 to 1.4) y. Only 28% of this total
uncertainty is attributable to the uncertainty in oceanic loss.
Yvon, S.A., and E.S. Saltzman. Atmospheric sulfur cycling in the
tropical Pacific marine boundary layer (12°S, 135°W): A
comparison of field data and model results 2. Sulfur dioxide. Journal
of Geophysical Research, 101:6899-6910 (1996).
The atmospheric chemistry of sulfur dioxide over the tropical South
Pacific Ocean is investigated using results from field measurements and
numerical models. Simultaneous real time measurements of sulfur dioxide
and its biogenic precursor dimethylsulfide were made at 12°S,
135°W for a six-day period from March 3-9, 1992. The mean
SO2 and DMS concentrations were 71 ± 56 pptv (1 sigma)
and 453 ± 93 pptv (1 sigma) respectively. These measurements are
compared to those predicted by a time-dependent photochemical box model
of the marine boundary layer. Model estimates of the yield of
SO2 from DMS oxidation range from 27-54%. Even with low
yields, DMS is the dominant source of SO2 in this region.
Estimates of vertical entrainment velocities based on the tropospheric
ozone budget suggest that vertical entrainment is a minor source of
SO2. The relative rates of various loss mechanisms for
SO2 are: dry deposition to the sea surface (58%), in-cloud
oxidation (9%), OH oxidation (5%), an uptake by sea-salt aerosols (28%).
Yvon, S.A., E.S. Saltzman, T.S. Bates, and D.J. Cooper. Atmospheric
sulfur cycling in the tropical Pacific marine boundary layer (12°S,
135°W): A comparison of field data and model results 1.
Dimethylsulfide. Journal of Geophysical Research, 101:6911-6918
(1996).
Shipboard measurements of atmospheric and seawater DMS were made at
12°S, 135°W for six days during March 1992. The mean seawater
DMS concentration during this period was 4.1 ± 0.45 nM (1 sigma,
n = 260), and the mean atmospheric DMS mole fraction was 453
± 93 pmol mol-1 (1 sigma, n = 843). Consistent
atmospheric diel cycles were observed, with a nighttime maximum and a
daytime minimum and an amplitude of approximately 85 pmol mol-1
. Photochemical box model calculations were made to test
the sensitivity of modeled atmospheric DMS concentrations to the
following parameters: (1) sea-to-air flux; (2) boundary layer height; (3)
oxidation rate; and (4) vertical entrainment velocities. The observed
relationship between mean oceanic and atmospheric DMS levels require the
use of and air-sea exchange coefficient which is at the upper limit end
of the range of commonly used parameterizations. The amplitude of the
diel cycle in atmospheric DMS is significantly larger than that predicted
by a photochemical model. This suggests the sea-to-air flux is higher
than was previously thought, and the rate of daytime oxidation of DMS is
substantially underestimated by current photochemical models of DMS
oxidation.
Yvon, S.A., J.M.C. Plane, C.-F. Nien, D.J. Cooper, and E. S. Saltzman.
The interaction between the nitrogen and sulfur cycles in the polluted
marine boundary layer. Journal of Geophysical Research,
101:1379-1386 (1996.)
Simultaneous measurements are reported of the nitrate radical
(NO3), nitrogen dioxide (NO2), ozone
(O3), and dimethylsulfide (DMS) in the nighttime marine
boundary layer over Biscayne Bay in South Florida. These field
observations are analyzed and used to initialize a boundary layer box
model which examines the relative importance of the various sinks for
NOx in the marine boundary layer. The results show that the
observed lifetime of NO3 (< 6 min.) is probably
controlled both by the loss of nitrogen pentoxide
(N2O5) to reaction with water vapor and aerosols
and by the reaction between NO3 and DMS. The model is then
extended to investigate the loss of nitrogen oxides from an air parcel
that remains in the boundary layer with a constant sea-to-air DMS flux
for several days. The principal conclusions are (1) that DMS is an
important sink for NO3 at lower NO2 levels and
(2) that the reaction between NO3 and DMS is an important
sink for DMS in the marine boundary layer and could exceed that of the
daytime removal by OH.
Yvon, S.A., J.H. Butler, S.A. Montzka, J.M. Lobert, A.D. Clarke, and
J.W. Elkins. A comparison of GC/ECD and GC/MS techniques for measuring
CH3. EOS, Transactions, American Geophysical Union,
77(46):F110 (1996).
No abstract.
**1995**
Aberson, S.D., S.J. Lord, M. DeMaria, and M.S. Tracton.
Short-range ensemble forecasting of hurricane tracks. Preprints,
21st Conference on Hurricanes and Tropical Meteorology, Miami, FL,
April 24-28, 1995. American Meteorological Society, Boston,
494-496 (1995).
The National Meteorological Center has produced ensemble forecasts
once each day using the Medium-Range Forecast (MRF) model since
December of 1992. Small perturbations representing the fastest
growing modes are added to and subtracted from the initial conditions
in order to estimate possible error growth in the model. The mean of
each ensemble provides a more reliable forecast than any of the
individual forecasts on average, and the ensembles themselves may
provide reliable estimates of the range and likelihood of alternative
meteorological scenarios. In addition to using the large sample of
runs to assess the impact on forecasting, the sample can be used as
boundary conditions for other models with more specific goals. The
VICBAR hurricane track forecast model will be run for all tropical
cyclones in the North Atlantic and North Pacific Oceans for cases
between 1 September and 15 September 1994, using the MRF ensembles
as boundary conditions. Because the VICBAR model is concerned only
with forecasting the location of a tropical cyclone at a particular
time, analysis of results is much simpler than for a global model
such as the MRF. Results of this study can be used to answer some
of the important questions concerning ensemble forecasting, and
these can be extended to more general forecast models. These issues
include assessing the impact of ensembles on forecast skill,
different methods of displaying results of the ensemble, measuring
the probability of certain members of the ensemble occurring, and
studying whether the atmospheric reality can truly be represented
by any of the members of the ensemble.
Atlas, D., P.T. Willis, and F.D. Marks. The effect of convective
updrafts and downdrafts on reflectivity-rain rate relations and water
budgets. Preprints, 27th Conference on Radar Meteorology, Vail,
CO, October 9-13, 1995. American Meteorological Society, Boston, 19-22
(1995).
No abstract.
Bianchi, A., and S.L. Garzoli. Variability and motion of the
Brazil-Malvinas Front. Geochimica Acta, 22 (1995).
No abstract.
Bitterman, D.S. Automated XBT launcher for use on ships-of-opportunity.
Proceedings, IEEE Oceans '95 Conference, San Diego, CA, October
9-12, 1995. Institute of Electrical and Electronic Engineers (1995).
Currently, the NOAA Volunteer Observing Ship network employs a larger number
of merchant vessels to make routine expendable bathythermograph (XBT) and
meteorological measurements throughout the world's oceans. While these data
have proven to be very useful, there is a need to improve the quality and
increase the density of the observations. The XBT profiles are frequently
compromised due to the need to launch the probe from less than optimal
locations on the ship. Also, the ship's officers can only commit a limited
amount of time to this work which severely limits the number of XBT
deployments. To improve the XBT measurements, an automated XBT launcher
was designed and is currently being tested. It consists of a lightweight,
compact launcher mechanism which is linked to a personal computer that
performs all control functions and logs data from the deployments. The
launcher can be loaded with six probes and can be placed at any location
on the ship. The deployments can then be made automatically at
predetermined times or geographical positions as determined from a GPS
navigation receiver. The system is currently being used for high density
XBT surveys on a Mexican registered freighter running between Spain and
Mexico.
Bitterman, D.S., and R.C. Millard. Shipboard thermosalinograph
intercomparison test results from the NOAA research vessel
Malcolm Baldrige. NOAA Technical Memorandum, ERL
AOML-82 (PB95-147898), 47 pp. (1995).
An intercomparison test of three commercially available
thermosalinographs (TSGs) considered for installation on
volunteer observing ships of opportunity was conducted
onboard the NOAA Ship Malcolm Baldrige during the period
June 2 to September 22, 1993. A Seabird Electronics Company
(SBE) Model SBE-21 TSG, a Falmouth Scientific Instruments, Inc.
(FSI) TSG, and an Ocean Sensors Instrument, Inc. (OSI) Model
OS-200 TSG were evaluated in the test. The three systems were
plumbed in series and run continuously for all four months of
the cruise. Temperature and conductivity measurements from each
TSG were logged to a personal computer (PC). Water samples were
drawn every six hours and analyzed for salinity. After removing
anomalous sections of data, a drift rate for each instrument was
then determined by comparing the thermosalinograph computed
salinities to those from the water samples. The OSI
thermosalinograph exhibited a salinity drift rate of +0.00738
practical salinity units (psu) per day, the FSI drift rate was
+0.001 psu per day, and the SBE drift rate was +0.00063 psu per
day. The salinity drift is composed of both conductivity and
temperature drifts. The OSI and FSI temperature measurements
exhibited systematic temperature errors under various conditions
encountered during the test. The SBE TSG needs to improve the
flushing of their conductivity cell.
Black, M.L., R.W. Burpee, and F.D. Marks. Two-dimensional
spatial structure of hurricane updrafts and downdrafts. Preprints,
21st Conference on Hurricanes and Tropical Meteorology, Miami, FL,
April 24-28, 1995. American Meteorological Society, Boston,
605-607 (1995).
Vertical motions in seven Atlantic hurricanes are determined from
data recorded by Doppler radars on research aircraft. The data
base consists of Doppler velocities and reflectivities from
vertically pointing radar rays collected along 185 radial flight
legs through the hurricane centers. The vertical motions are
estimated throughout the depth of the troposphere from the Doppler
velocities and bulk estimates of particle fallspeeds. Portions of
the flight tracks are subjectively divided into eyewall, rainband,
stratiform, and "other" regions. At each altitude, Doppler updrafts
and downdrafts are defined to contain vertical motions continuously
greater than 1.5 m s-1 with at least one speed greater
than 3.0 m s-1. Two-dimensional correlation maps
centered on the updraft and downdraft maxima at 2.5 and 7.5 km
altitude identify the preferred spatial structure of the drafts.
The eyewall updrafts correlate significantly over distances of
5-10 km in both the horizontal and vertical, affect much larger
areas than updrafts in the other regions, and exhibit a pronounced
outward slope of 45 degrees with height. The only other updrafts
that appear to slope outward are rainband updrafts at 7.5 km.
Downdrafts are significantly correlated over smaller areas than
the updrafts and exhibit little or no slope. The eyewall region is
the primary location for well-organized updrafts and downdrafts.
Comparisons are made of radius-height profiles of reflectivity and
vertical velocity in hurricanes that contain widely different eyewall
structure. The composite spatial structure of updrafts and downdrafts
in the lower and upper troposphere in each of the four regions are
presented. The role of the eyewall updrafts to the maintenance of
the hurricane's intensity are discussed.
Black, M.L., R.W. Burpee, and F.D. Marks. Vertical motion
asymmetries in the hurricane eyewall. Preprints, 27th Conference on
Radar Meteorology, Vail, CO, October 9-13, 1995. American
Meteorological Society, Boston, 574-576 (1995).
No abstract.
Black, P.G., and L.K. Shay. Observed sea surface temperature
variability in tropical cyclones: Implications for structure and
intensity change. Preprints, 21st Conference on Hurricanes and
Tropical Meteorology, Miami, FL, April 24-28, 1995. American
Meteorological Society, Boston, 603-604 (1995).
No abstract.
Black, P.G., S.H. Houston, D. Lipscombe, and J. Parrish. AFRES-NOAA
intercomparison flight of 13 April 1994. Minutes, 49th Interdepartmental
Hurricane Conference, Miami, FL, February 14-17, 1995. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-5 (1995).
An intercomparison flight between an Air Force Reserve (AFRES)
aircraft and a National Oceanic and Atmospheric Administration
(NOAA) aircraft took place on 13 April 1994. This mission resulted
from a recommendation made at the 48th Interdepartmental Hurricane
Conference. The AFRES and NOAA aircraft each recorded most
flight-level meteorological, as well other data related to the
flight (e.g., true air speed, heading, etc.), at
1-sec intervals. In addition to these high-resolution data, the
1-min averages of these data were sent from each aircraft via
satellite to the National Hurricane Center in real-time. All of
these 1-sec and 1-min data have been compared and there was
generally good agreement between the measured variables. The wind
data were in very good agreement at the higher wind speeds in the
midtroposphere, except in turns where the angle-of-attack measurement
is not fully included in the AFRES wind measurement. Methods for
improvements in the wind calculations are discussed and additional
intercomparison flights during 1995 are recommended.
Black, P.G., J.R. Proni, J.C. Wilkerson, and C.E. Samsury. Classification
of convective and stratiform regions in oceanic tropical and subtropical
mesoscale convective systems using underwater acoustic methods.
Preprints, 27th Conference on Radar Meteorology, Vail, CO, October
9-13, 1995. American Meteorological Society, Boston, 237-239 (1995).
No abstract.
Black, P.G., R. McIntosh, C. Swift, J. Carswell, K. St. Germain, I.
Popstefanija, and M. Goodberlet. Ocean surface wind, stress, and rain
rate measurements in tropical cyclones from concurrent airborne microwave
scatterometer and radiometer observations. Preprints, 27th Conference on
Radar Meteorology, Vail, CO, October 9-13, 1995. American
Meteorological Society, Boston, 623-625 (1995).
No abstract.
Black, R.A., and J. Hallett. The relationship between the evolution
of the ice phase hydrometeors with altitude and the establishment of
strong electric fields in Hurricane Claudette. Preprints, Conference
on Cloud Physics, Dallas, TX, January 1995. American Meteorological
Society, Boston (1995).
No abstract.
Black, R.A., H.B. Bluestein, and M.L. Black. Unusually strong
vertical motions in a Caribbean hurricane. Preprints, 21st
Conference on Hurricanes and Tropical Meteorology, Miami, FL, April
24-28, 1995. American Meteorological Society, Boston, 260-262 (1995).
No abstract.
Broecker, W.S., S. Sutherland, W. Smethie, T.-H. Peng, and G. Ostlund.
Oceanic radiocarbon: Separation of the natural and bomb components.
Global Biogeochemical Cycles, 9(2):263-288 (1995).
An improved method has been developed for the separation of the
natural and bomb components of the radiocarbon in the ocean. The
improvement involves the use of a very strong correlation between
natural radiocarbon and dissolved silica. This method is applied to
radiocarbon measurements made on samples collected during the
Geochemical Ocean Sections Study (GEOSECS), Transient Tracers in
the Ocean (TTO) and South Atlantic Ventilation Experiment (SAVE)
expeditions. On the basis of this new separation we provide not
only an estimate of the global inventory of bomb 14C
inventory and penetrations along thermocline isopycnals in the
North Atlantic Ocean but also between the times of the GEOSECS
(1972-1973) and TTO (1980-1982) surveys and in the South Atlantic
Ocean between the times of the GEOSECS (1973) and SAVE (1987-1989)
surveys. In addition, we show that the bomb tritium to bomb
C ratio (expressed in the tritium units [TU] 81
units/100%) for waters entering the thermocline of the northern
hemisphere is about nine times higher than for those entering the
southern hemisphere thermocline. This contrast offers long-term
potential as an indicator of inter-hemispheric transport of upper
ocean waters.
Butler, J.H., J.M. Lobert, S.A. Yvon, and L.S. Geller. The distribution
and cycling of halogenated trace gases between the atmosphere and ocean.
In The Expedition ANTARKTIS XII of RV Polarstern in 1994/1995 Reports
of Legs ANT XII/1 and 2, G. Kattner and K. Fütterer (eds.),
Ber. Polarforsch., 168:27-39 (1995).
No abstract.
Cantillo, A.Y., L. Pikula, J. Beattie, E. Collins, K. Hale, and T.
Schmidt. Natural and anthropogenic events impacting Florida Bay, 1910-1994
time line. NOAA Technical Memorandum, NOS ORCA-90, 510 pp. (1995).
Florida Bay is a coastal lagoon, on average less than 3 m deep,
approximately 1,000 square miles in area, located between the south
Florida mainland and the Florida Keys. In recent years, adverse
environmental changes have been noted in the Bay. Currently, a
multi-agency multi-year effort is underway to restore the ecosystem of
south Florida, including that of Florida Bay. To assist in determining
the Bay's former condition and to catalogue changes, events that may have
affected or have occurred in the Bay are described, listed, and graphically
displayed in a common time scale. The time coverage begins in 1910 with
construction activities along the Florida Keys, and in what later became
the Everglades National Park. Included are global scale atmospheric,
geological, and astronomical phenomena such as El Niño events, volcanic
eruptions, and solar activity that may affect local weather. On local
scales, documented are: dieoffs of species such as seagrasses, sponges,
and fishes; environmental occurrences of algal blooms, coral reef
degradation, fishery catch changes, and soil subsidence; and human
activities such as population increases and construction. Awareness of
the environmental importance of the Bay is documented in legislation
affecting environmental regulations nationwide and in the Bay area; and
environmental programs and studies performed currently and in the past by
federal, state, municipal, academic, and civic organizations.
Carleton, A.M., L.A. McMurdie, K.B. Katsaros, H. Zhao, N.M. Mognard, and
C. Claud. Satellite-derived features and associated atmospheric
environments of Southern Ocean mesocyclone events. Global Atmosphere
and Ocean System, 3(2-3):208-248 (1995).
Mesoscale cyclones in cold air outbreaks are generated frequently over
the southern oceans poleward of about 50°S. Polar orbiting
satellites sensing in visible and IR wavelengths supply cloud information
from which processes important in mesocyclone development have been
inferred. However, direct retrieval of the integrated cloud liquid water
(ICLW) and water vapor (IWV) contents, precipitation occurrence, and
surface wind speeds associated with mesocyclones, is possible using
microwave radiometry. We present three mesocyclone cases, analyzed using
data from the DMSP (Defense Meteorological Satellite Program) SSM/I
(Special Sensor Microwave/Imager), supplemented with data from the Geosat
radar altimeter and the TOVS (TIROS-N Operational Vertical Sounder). The
mesocylones possess different IR cloud signatures, but have common
features in the microwave: low to moderate ICLW, low IWV, light rain, and
strong to gale-force surface winds. Mesocyclones appear predominantly
baroclinic (TOVS); however, the role of sea-air interactions cannot be
ruled out. These case investigations confirm the value of multiple
satellite systems for mesoscale studies in remote ocean areas.
Carsey, T.P., M.L. Farmer, C.J. Fischer, A. Mendez, A.A. Pszenny,
V.B. Ross, P.-Y. Whung, M. Springer-Young, and M.P. Zetwo.
Atmospheric chemistry measurements from the 1992 ASTEX/MAGE cruise.
NOAA Data Report, ERL AOML-26 (PB95-179552) 90 pp. (1995).
No abstract.
Chen, H., R.H. Wanninkhof, R. Feely, and D. Greeley. Measurements
of fugacity of carbon dioxide in seawater: An evaluation of a
method based on infrared analysis. NOAA Technical Memorandum, ERL
AOML-85 (PB95-271029), 54 pp. (1995).
An analysis system is described to measure the fugacity of
CO2 (fCO2)1 in 500 mL of
seawater (discrete samples) by infrared analysis. The unit
has been used on oceanographic research cruises sponsored by
the Ocean-Atmosphere Carbon Exchange Study (OACES) of NOAA since
1991 for a total of approximately 10,000 measurements. The
precision of the analyses based on replicate samples during
routine analysis is 0.2%. Precision is primarily limited by
sample storage, and the difference between headspace gas and
water CO2 concentrations prior to equilibration.
The precision and accuracy of the instrument is estimated in
several different ways. A preliminary side by side test of
two different discrete fCO2 systems using an infrared
(IR) analyzer and a gas chromatograph (GC) shows a variability
of 0.8% without significant bias. For surface waters the
discrete measurements are compared with measurements from
a continuous flowing underway system which was deployed on all
cruises. Select comparisons with fCO2 calculated
from spectrophotometric pH and DIC (Total Dissolved Inorganic
Carbon) measurements are performed. These comparisons are
limited by uncertainty in the magnitude and the temperature
dependence of the carbon and borate dissociation constants.
Indirect comparisons are made with pCO2 measurements
of Drs. Takahashi and Chipman of LDEO in the South Atlantic and
equatorial Pacific (EqPac). Although the measurements were
performed months (for the EqPac study in 1992) to years (for the
South Atlantic study in 1989 and 1991) apart, some inferences can
be made by normalizing the fCO2 values and by performing
the comparison in property space. The comparison indicates that
the precision of our system is comparable to that of the LDEO
system. The surface values obtained from the LDEO system during
EqPac are 1.5 to 3% lower. There is inconclusive evidence that
some of the subsurface LDEO pCO2 values are lower as
well. However, the comparison of subsurface values for the North
Atlantic Deep Water in the South Atlantic study shows good agreement.
Because of the current uncertainty in dissociation constants, there
is no a priori way to determine which value is correct.
Cione, J.J., and S. Raman. A numerical investigation of surface-induced
mesocyclogenesis near the Gulf Stream. Tellus, 47A:815-833 (1995).
No abstract.
Cione, J.J., S. Raman, L.J. Pietrafesa, X. Li, R.A. Neuherz, and K.
Keeter. Operational utilization of the Atlantic Surface Cyclone
Intensification Index (ASCII). Proceedings, American Meteorological
Society Regional Training Symposium for Operational Forecasters in the
Carolinas and Virginia, Raleigh, North Carolina, November 6-8 1995.
American Meteorological Society, Boston (1995).
No abstract.
Clark, J.F., P. Schlosser, R.H. Wanninkhof, H.J. Simpson, W.S.F.
Schuster, and D.T. HO. Gas transfer velocities for SF6
and 3He in a small pond at low wind speeds. Geophysical
Research Letters, 22(2):93-96 (1995).
Gas transfer velocities for two gases, SF6 (sulfur
hexafluoride) and 3He, were determined in a small pond
by injecting a mixture of these gases into the water and monitoring
the decline of their concentrations over the next eight days. For
wind speeds between 1.5-2.5 m s-1, no variations of gas
transfer velocity with wind speed could be resolved with our data.
Gas transfer velocities at wind speeds greater than 3 m s-1
were substantially larger and consistent with other lake tracer
experiments. From the ratio of gas transfer velocities for
SF6 and 3He, we calculated the Schmidt
number exponent to be 0.57 ± 0.07.
Claud, C., K.B. Katsaros, N.M. Mognard, and N.A. Scott. Synergetic
satellite study of a rapidly deepening cyclone over the Norwegian Sea:
13-16 February 1989. Global Atmosphere and Ocean System, 3(1):1-34
(1995).
In oceanic regions, conventional meteorological observations are often
insufficient for following the progression of atmospheric depressions,
which generally leads to poor prediction in terms of strength and
location. Since observations from polar-orbiting satellites probe nearly
every region of the earth about twice a day, they can be used to track
the propagation and evolution of weather systems and potentially improve
the forecasts. The synoptic and mesoscale aspects of a rapidly
intensifying cyclone, which persisted over the northern Atlantic Ocean
and the Norwegian Sea for four days in February 1989, are presented. A
combination of three instruments was used: the TIROS-N Operational
Vertical Sounder (TOVS; 19 infrared, 1 visible and 4 microwave channels),
the Special Sensor Microwave/Imager (SSM/I; a passive microwave
radiometer with 7 channels), and an active radar altimeter (Geosat). The
combination of TOVS and SSM/I provides a rough estimation of the air-sea
fluxes, which are of the same order of magnitude as for rapidly
intensifying storms found previously over other maritime areas. This case
study confirms the value of using a combination of satellite instruments
for studying weather systems in data-sparse maritime areas.
Crane, M.L., R.H. Smith, M.H. Bushnell, W.D. Wilson, and S. Tosini.
NSWC moored ADCP data, 1994 (Straits of Florida, 26°04.00'N,
80°03.50'W). CD-ROM, NODC-59, National Oceanographic Data Center,
Washington, D.C. (1995).
This database contains acoustic Doppler current profiler (ADCP) data
collected during 1994 on the eastern shelf of Florida. The data were
collected at 10-minute intervals by a bottom mounted 300-kHz ADCP
unit (from RD Instruments, San Diego, CA), and is offshore Ft.
Lauderdale, Florida, at a depth of 140 m. This instrument is positioned
at approximately 26°04.0'N by 80°03.5'W. The unit is
supported by the United States Naval Surface Warfare Center (NSWC),
which receives binary data directly from the ADCP by way of a
submerged cable. Following negotiations in 1993, a cooperative
effort was established between the National Oceanic and Atmospheric
Administration (NOAA) and the Naval Surface Warfare Center to forward
the binary ADCP data collected by NSWC to the NOAA Atlantic
Oceanographic and Meteorological Laboratory (AOML) in Miami, Florida.
Since April 1994, AOML has been receiving the binary data from NSWC.
Dagg, M.J., and P.B. Ortner. Zooplankton grazing and the fate of
phytoplankton in the northern Gulf of Mexico. Proceedings, 1994
Synthesis Workshop, Baton Rouge, LA, April 26-28, 1994. Louisiana
Sea Grant Program, 21-27 (1995).
The copepod community consumes a significant fraction of the
phytoplankton production that is stimulated by riverine nutrient
inputs in the northern Gulf of Mexico. In addition, there is
strong evidence that Appendicularians are important consumers of
small particles (including pico-phytoplankton). The primary fate
of phytoplankton production in this river-dominated shelf is to
be grazed by zooplankton.
Dammann, W.P., and J.R. Proni. Fort Pierce, Florida dredge material
discharge study. Contract Report RM-CW-94-0033, U.S. Army Corps of
Engineers, 6 pp. (1995).
No abstract.
Darling, R.W.R., S.H. Houston, and H.E. Willoughby. Parametric
models of hurricane surface winds for storm surge calculations.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society,
Boston, 454-456 (1995).
No abstract.
Dodge, P.P., F.D. Marks, J.F. Gamache, J.S. Griffin, and N.F.
Griffin. EVTD radar analyses of the inner core of Hurricane Olivia
(1994). Preprints, 27th Conference on Radar Meteorology, Vail, CO,
October 9-13, 1995. American Meteorological Society, Boston, 299-301
(1995).
No abstract.
Dodge, P.P., F.D. Marks, J.F. Gamache, J.S. Griffin, Jr., and
N.F. Griffin. The evolution of the inner core of Hurricane Olivia
(1994) from EVTD Doppler radar analyses. Preprints, 21st Conference
on Hurricanes and Tropical Meteorology, Miami, FL, April 24-28, 1995.
American Meteorological Society, Boston, 463-465 (1995).
On 24 and 25 September 1994, the Hurricane Research Division (HRD)
and the Aircraft Operations Center (AOC) of NOAA conducted experiments
in eastern Pacific Hurricane Olivia, 1400-1500 km southwest of Puerto
Vallarta. Each day two aircraft flew simultaneously through the center
at altitudes of 3 and 4.3 km, recording radar data for dual-Doppler
estimates of the wind field. The experiment required a strong hurricane,
and Olivia certainly met that requirement. On 24 September the minimum
sea-level pressure (MSLP) dropped from 954 mb to 948 mb in 3.5 h and the
maximum flight level winds increased from 50 m s-1 to 61 m
s-1 on the last pass through the center. The next day Olivia
had deepened further to 926 mb, and maximum flight level winds were 65-70
m s-1 on almost every pass. The radius of maximum winds
contracted from 20 km to 12 km during the two days of the experiment.
Each aircraft collected Doppler data in 15 passes through the storm
on the 24th and the 25th. Eventually the Doppler data from both aircraft
will be analyzed with dual-Doppler algorithms to yield a time series of
three-dimensional wind fields, but in this paper we use the Extended
Velocity Track Display (EVTD) technique to estimate the evolution of the
mesoscale features of the windfield. EVTD provides a coarser estimate
than the full dual-Doppler solution, but the computation is much faster.
Indeed, data from one aircraft can be used to estimate the windfield in
real-time; EVTDs computed on the upper aircraft during Olivia show that
the azimuthally averaged tangential winds increased on the first day
from 50-55 m s-1 to over 60 m s-1 on the last pass.
EVTD analyses on the second day show that the winds remained 60-65 m
s-1 throughout the flight. HRD plans to send such analyses
from reconnaissance aircraft to the National Hurricane Center during the
1995 hurricane season. In the single-aircraft EVTDs, data from
successive passes are combined and filtered to give a time series of
three-dimensional wind estimates. Orthogonal legs with simultaneous
radar data from both aircraft permit us to construct "true EVTD" analyses
that are closer to true dual-Doppler wind analyses than the single-aircraft
EVTDs. We will use the Olivia data to compare these two types of EVTD
analysis.
Dupuis, H., A. Weill, K.B. Katsaros, and P.K. Taylor. Turbulent heat
fluxes by profile and inertial dissipation methods: Analysis of the
atmospheric surface layer from shipboard measurements during the
SOFIA/ASTEX and SEMAPHORE experiments. Ocean-Atmosphere
Interactions, 1065-1074 (1995).
Heat flux estimates obtained using the inertial dissipation method, and
the profile method applied to radiosonde soundings, are assessed with
emphasis on the parameterization of the roughness lengths for temperature
and specific humidity. Results from the inertial dissipation method show
a decrease of the temperature and humidity roughness lengths for
increasing neutral wind speed, in agreement with previous studies. The
sensible heat flux estimates were obtained using the temperature
estimated from the speed of sound determined by a sonic anemometer. This
method seems very attractive for estimating heat fluxes over the ocean.
However, allowance must be made in the inertial dissipation method for
non-neutral stratification. The SOFIA/ASTEX and SEMAPHORE results show
that, in unstable stratification, a term due to the transport terms in
the turbulent kinetic energy budget, has to be included in order to
determine the friction velocity with better accuracy. Using the profile
method with radiosonde data, the roughness length values showed large
scatter. A reliable estimate of the temperature roughness length could
not be obtained. The humidity roughness length values were compatible
with those found using the inertial dissipation method.
Enfield, D.B., and J.E.Harris. A comparative study of tropical
Pacific sea surface height variability: Tide gauges vs. the NMC
data-assimilating OGCM, 1982-1992. Journal of Geophysical
Research, 110:8661-8675 (1995).
To help assess the effectiveness of the model-based analysis and
prediction procedures at the National Meteorological Center (NMC),
we compare the seasonal and nonseasonal components of sea level from
44 tide gauges in the tropical Pacific with those of the dynamic
heights output by two 11-year model reanalyses (1982-1992), at the
same locations, which differ mainly in their wind forcing. Both
reanalyses assimilate ocean thermal data and incorporate most of the
procedures used by NMC in producing operational ocean analyses and
experimental coupled model climate forecasts. The reanalyses
reproduce the broad patterns of annual amplitude and phase, and of
seasonal and nonseasonal variance, except for severe underestimates
along the eastern boundary, especially north of the equator. The
annual cycles and interannual departures of zonal flow indices
estimated from selected island pairs near the dateline show good
correspondence for the North Equatorial Countercurrent (NECC) and
somewhat flawed and noisy comparisons for the North Equatorial
Current (NEC) and South Equatorial Current (SEC). The reanalyses
also reproduce the large scale time and space patterns of nonseasonal
variability in the first three empirical orthogonal functions (EOFs),
which together explain about 65% of the anomalous variability and
characterize the El Niño/Southern Oscillation cycle. The first
two EOF modes describe the westward migration of three ENSO episodes
and the third mode appears to capture differences between episodes.
However, the reanalysis based on the anomalous winds generated by the
NMC medium range forecast model shows significant discrepancies in the
large scale spatial and temporal variability. These discrepancies
disappear in the reanalysis based on departures of the FSU analyzed
wind fields. Hence, the wind forcing critically affects the reanalysis
in spite of the assimilation of ocean thermal data. Future improvements
in the atmospheric model to produce a more realistic evolution of the
wind field can therefore lead to significantly better model integrations,
in the analysis and initialization mode (with data assimilation) as
well as in the coupled model forecast mode.
Feely, R.A., R.H. Wanninkhof, C. Cosca, H. Chen, M. Steckley, and
P. Murphy. Distributions of fCO2 in the eastern
equatorial Pacific during and after the 1992-1993 El Niño:
Global fluxes of carbon and its related substances in the coastal
sea-ocean-atmosphere system. Proceedings, IGBP Symposium, Sapporo,
Japan, November 1994. Hokkaido University, 360-367 (1995).
As part of the U.S. JGOFS Equatorial Pacific Process Study, measurements
of fCO2 were determined for the atmosphere and in the surface
waters of the central and eastern equatorial Pacific during the spring
and autumn of 1992 and 1993, and the spring of 1994 after the 1992-1993
ENSO event. Surface water fCO2 data indicate significant
differences between the springtime El Niño conditions and the
autumn post-El Niño conditions. The autumn fugacity
(DELTA fCO2) maxima were approximately 15-55 µatm
higher than in the spring. The lower surface DELTA fCO2
values in the spring data set were the result of: (1) advection of
CO2-depleted water from the west at the equator near
170°W; and (2) reduced upwelling and lower DELTA fCO2
distributions as consequence of lighter zonal winds in the eastern
Pacific from 140°W to 110°W. In the spring of 1993 elevated
sea surface temperatures were observed in spring of 1992. In spring
1994 sea surface temperatures were near the climatological mean and
fCO2 levels were 70-90 µatm higher than the 1992
levels. These results clearly indicate that the largest sustained
fCO2 variations in the eastern equatorial Pacific occur
during ENSO events.
Feely, R.A., R.H. Wanninkhof, C.E. Cosca, P.P. Murphy, M.F. Lamb,
and M.D. Steckley. CO2 distributions in the equatorial
Pacific during the 1991-1992 ENSO event. Deep-Sea Research II,
42(2-3):365-386 (1995).
As part of the U.S. JGOFS Equatorial Pacific Process Study, measurements
of CO2 species concentrations were made in the atmosphere and
in the surface waters of the central and eastern equatorial Pacific
during the boreal spring and autumn of 1992. Surface water
fCO2 data indicate significant differences between the
springtime El Niño conditions and the autumn post-El Niño
conditions. The autumn fugacity (DELTA fCO2) maxima were
approximately 15-55 µatm higher than in the spring. The lower
surface DELTA fCO2 values in the spring data set were the
result of: (i) advection of CO2-depleted water from the west
at the equator near 170°W; and (ii) reduced upwelling and lower
DELTA fCO2 distributions as a consequence of lighter zonal
winds in the eastern Pacific from 140°W to 110°W. Assuming
the springtime data are representative of the El Niño conditions
and the autumn data are representative of the post-El Niño
conditions, it is estimated that the net annual CO2 flux
during the 1991-1992 ENSO period is 0.3 Gt C. Over 60% of this flux
occurred during the four-month period in the autumn when DELTA
fCO2 values were close to normal. The net annual reduction
of the ocean-atmosphere CO2 flux during the 1991-1992 El
Niño is estimated to be on the order of 0.5-0.7 Gt C.
Feuer, S.E., and J. Kaplan. Tropical cyclone intensity change and
environmental kinematic structure in Omega dropwindsonde data sets.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
362-364 (1995).
Since 1982, the Hurricane Research Division (HRD) of the NOAA/Atlantic
Oceanographic and Meteorological Laboratory has conducted airborne
experiments to collect environmental data from Atlantic basin tropical
cyclones. These synoptic-flow experiments (SFEs) are performed aboard
one or two NOAA WP-3D aircraft, from which Omega dropwindsondes (ODWs)
are released within 1000 km of the storm center over a 9-10 h period.
As the ODWs descend, kinematic and thermodynamic soundings are obtained
from flight level (400-500 mb) down to the surface. Through 1992, HRD
has acquired 16 SFE data sets. Three-dimensional wind analyses have
been produced using the HRD nested objective analysis algorithm. For
each SFE case, post-processed ODW winds, along with rawinsonde, NOAA,
and USAF reconnaissance aircraft, surface ship, commercial aircraft, and
GOES satellite observations, were analyzed with a two-dimensional, cubic
spline-based routine at 10 mandatory levels. Consistent filtering
parameters were applied to all of the data sets. Raw observations
were thoroughly scrutinized; erroneous ones were subjectively removed.
Cross-sections of the analyzed wind fields were subsequently examined,
and adjustments were made to ensure vertical continuity between the
analysis levels. The resultant wind fields accurately depict the
environment surrounding the tropical cyclones beyond 300 km from the
storm center. We have successfully composited the analyzed wind fields
to examine the mean kinematic, synoptic-scale structure of the tropical
cyclones in our data set. Composites of various diagnostic quantities
have been made for the full set of SFE cases, as well as stratified
subgroupings. These composited fields are being used to compare the
mean large-scale structure of storms with different intensification
rates. Results will be presented at the conference.
Ffield, A., R.L. Molinari, W.D. Wilson, and R.H.Wanninkhof. Repeat
hydrography along WHP lines 15°W, 17°N, and 11°W.
International WOCE Newsletter, 20:23-24 (1995).
No abstract.
Finley, S.V., P.J. Fitzpatrick, J.A. Knaff, and C.W. Landsea. A
systematic bias in the Aviation model's forecast of the Atlantic
TUTT: Implications for tropical cyclone forecasting. Preprints,
21st Conference on Hurricanes and Tropical Meteorology, Miami, FL,
April 24-28, 1995. American Meteorological Society, Boston, 238-240
(1995).
No abstract.
Fitzpatrick, P.J., J.A. Knaff, C.W. Landsea, and S.V. Finley. A
systematic bias in the Aviation model's forecast of the Atlantic
tropical upper tropospheric trough: Implications for tropical
cyclone forecasting. Weather and Forecasting,
10(2):433-446 (1995).
This study uncovers what appears to be a systematic bias in the
National Meteorological Center's Aviation (AVN) model at 200 mb over
the Caribbean Sea. In general, the 48 h forecast in the vicinity of
the Tropical Upper Tropospheric Trough (TUTT) underpredicts the
magnitude of the westerly 200-mb winds on the order of 5-10 m
s-1. This unrealistic weakening of the TUTT and associated
cold lows by the AVN model results in erroneous values of the vertical
(850-200 mb) wind shear. These systematic errors are in the same order
of magnitude as the minimum shear threshold for tropical cyclone
genesis and development. Thus, 48-h tropical cyclone formation and
intensity forecasts based upon the AVN model are often incorrect in
the vicinity of the TUTT. Knowing the correct future upper wind regime
is also crucial for track forecasting of more intense tropical cyclones,
especially in cases of recurvature. It is shown that simple persistence
or climatology of the 200-mb winds south of a TUTT axis is superior to
the AVN model's 48-h forecast. Until this bias in the AVN is successfully
removed, the tropical cyclone forecaster for the Atlantic basin should be
aware of this systematic error and make subjective changes in his/her
forecasts. For 200-mb west winds greater than or equal to 10 m
s-1, forecasts based on persistence are best, while for west
winds less than 10 m s-1, half climatology and half
persistence is the preferable predictor. If the TUTT is weak such that
200-mb easterly winds occur, climatology tends to be the best predictor
as it nudges the forecast back to a normal westerly wind regime.
Gamache, J.F. Preliminary three-dimensional analyses of dual-platform
airborne Doppler observations of intense convection in eastern Pacific
Hurricane Olivia (1994). Preprints, 21st Conference on Hurricanes and
Tropical Meteorology, Miami, FL, April 24-28, 1995. American
Meteorological Society, Boston, 254-256 (1995).
On 24 and 25 September 1994, coordinated two-aircraft airborne Doppler
missions were flown into eastern Pacific Hurricane Olivia. The storm
was located approximately 1500 km west-southwest of Puerto Vallarta,
Mexico, the base of operations. The purpose of the experiment was to
study the evolution of a tropical cyclone's reflectivity structure and
three-dimensional wind field. On the first day the hurricane had a
fairly slowly changing precipitation structure, dropping central pressure,
and increasing winds. The precipitation structure on the second day
evolved from symmetric to asymmetric, the winds appeared to be fairly
constant, and the central pressure was increasing. The environmental
shear appeared to change from easterly during the first day to
southwesterly during the second day. During the 3.5 hours on station
of 24 September, the extrapolated minimum surface pressure dropped from
954 mb in the first pass to 948 mb on the last pass. Real-time EVTD
(Extended Velocity Track Display) analyses showed the mean tangential
wind maximum increasing from 50-55 m s-1 on the first pass
to over 60 m s-1 on the last pass, and the radius of maximum
winds contracting from 20 km to 16 km. This is the most rapid deepening
of a tropical cyclone observed during a coordinated airborne Doppler
mission. When the aircraft re-entered the storm the next day the radius
of maximum winds had decreased to 12 km, the extrapolated minimum surface
pressure was 926 mb, and EVTD revealed the azimuthally-averaged tangential
winds to be between 60-65 m s-1. These wind speeds were
maintained while the aircraft were on station; however, the extrapolated
minimum surface pressure dropped to 925 mb on the second pass, but
increased to 935 mb by the eighth and final pass, about 3.5 hours later.
It is possible that some of this increased pressure is associated with
the strong asymmetric convection occurring near the end of the mission
that might have produced a wind and pressure field that were temporarily
out of balance. During several penetrations on the 24th and 25th, there
were elevated reflectivity maxima that are indicative of large graupel
and vertical winds probably in excess of 10 m s-1. The
three-dimensional wind fields observed during each of the hurricane
penetrations will eventually be analyzed; however, during the conference
the wind fields associated with the strong convective events and elevated
reflectivity maxima will be emphasized.
Gamache, J.F., F.D. Marks, and F. Roux. Comparison of three
airborne Doppler sampling techniques with airborne in-situ wind
observations in Hurricane Gustav (1990). Journal of Atmospheric
and Oceanic Technology, 12(1):171-181 (1995).
Three different airborne Doppler radar sampling strategies were tested
in Hurricane Gustav (1990) on 29 August 1990. The two new strategies
were the fore-aft scanning technique (FAST) and airborne dual-platform
Doppler sampling. FAST employs radar scans in cones pointing alternately
fore and aft of the vertical plane that is perpendicular to the flight
track. The airborne dual-platform sampling uses two Doppler radars,
each aboard a separate aircraft. The Doppler radars scan strictly in
the vertical plane normal to the flight track. The aircraft fly
simultaneously along different, preferably perpendicular, tracks. The
third strategy tested in Hurricane Gustav was single-platform sampling,
which uses one Doppler radar on one aircraft that flies two consecutive,
usually orthogonal, flight tracks. The antenna scans in the plane normal
to the flight track. The third technique had been used previously in
hurricanes and other disturbed weather. The rms differences between the
aircraft in-situ winds and the Doppler winds derived near the aircraft
by single-platform sampling, dual-platform sampling, and FAST are found
to be 7.8, 5.1, and 2.5 m sec-1, respectively. These results
suggest that in hurricanes dual-platform, flat-plane sampling and FAST
both enable substantial improvements in the accuracy and temporal
resolution of airborne Doppler wind fields over those obtained from
single-platform, flat-plane scanning. The FAST results should be
applicable to dual-beam sampling, which began in 1991. The actual rms
errors of Doppler winds from the flight tracks, at levels well above
flight level, and in highly sheared environments may be significantly
higher than the above differences.
Garzoli, S.L., A. Gordon, and C. Duncombe Rae. Benguela Current sources
and transports. U.S. WOCE Report, 17-19 (1995).
No abstract.
German, C., B.A. Barreiro, N.C. Higgs, T.A. Nelsen, E.M. Ludford, and
M.R. Palmer. Seawater-metasomatism in hydrothermal sediments (Escanaba
Trough, northeast Pacific). Chemical Geology, 119:175-190 (1995).
Hydrothermal sediments from the NESCA vent-field, Escanaba Trough,
are enriched in a number of typical "vent-fluid" metals for which
fluid data for the same, sediment-hosted, site exhibit anomalous
depletion. These results are consistent with cooling of rising
fluids and precipitation of various metal sulfide, sulfate, and
oxide phases in-situ with the sediment column, prior to expulsion
of the fluids from the seabed. Significant enrichments of Mg and U,
elements which are quantitatively removed from high-temperature vent
fluids, are also observed in the Escanaba Trough sediments, however.
Enrichments of these elements cannot derive from simple conductive
cooling of the rising vent-fluids but, instead, are believed to
result from extensive seawater-metasomatism as relatively fresh
unreacted seawater is heated from below by hot sediments and/or
percolating vent-fluids in the upper levels of the circulation system.
Calculated seawater/sediment interaction ratios range from -5:1 to
2500:1 of seawater per gram of sediment. Pb, Sr, and Nd isotope
distributions for the Escanaba sediments are consistent with combined
sediment-fluid and seawater-sediment interactions. Pb isotope ratios
for hydrothermal and background sediments coincide with local sulfide
deposits but are much more radiogenic than local MORB. This indicates
not only that complete isotopic re-equilibration must occur between
the hot, rising fluids and the host sediments but, in addition, that
sediment composition appears to dominate the Pb isotopic composition of
these fluids. Sr and Nd isotope ratios in the hydrothermally
altered sediments, which are distinct from background ratios, coincide
closely with modern seawater values, providing confirmatory evidence
that extensive interactions must also have occurred between these
hydrothermal sediments and relatively fresh, unreacted seawater.
Goldenberg, S.B., and L.J. Shapiro. A new look at the relationship
between El Niño, west African rainfall, and North Atlantic tropical
cyclone activity. Preprints, 21st Conference on Hurricanes and Tropical
Meteorology, Miami, FL, April 24-28, 1995. American Meteorological
Society, Boston, 585-587 (1995).
In previous studies, El Niño events have been shown to be
associated with decreased tropical cyclone activity in the Atlantic
basin. Studies have also established a strong association between
increased (decreased) rainfall over west Africa (specifically the
west Sahel) and increased (decreased) Atlantic basin activity. The
primary physical mechanism for both of these associations appears to be
an equatorially-confined Walker-cell-type circulation which acts to
modify the vertical shear over the main tropical cyclone development
region; reduced (increased) shear contributing to increased (decreased)
Atlantic basin tropical cyclone activity. Recent studies have identified
two types of El Niño events and different phases of atmospheric
coupling likely controlling the teleconnection between the equatorial
east Pacific sea-surface temperature (SST) anomalies and west African
monsoonal rainfall amounts. The probably non-homogeneous physical
mechanisms for the teleconnections would suggest a stratification of the
years to better resolve the different physical mechanisms responsible for
the associations between El Niño events, west African rainfall
fluctuations, and variability in Atlantic basin tropical cyclone activity.
The grouping of all of the years of data together for previous studies
possibly gives an overly-simplistic picture of the relationships. This
study will present results of the application of various stratification
methodologies to the present problem. El Niño-associated equatorial
eastern Pacific SST anomalies are typically largest in the spring, out
of phase with the summer Atlantic hurricane season. Other investigators
have found a delayed atmospheric response to eastern Pacific SST anomalies.
Results will also be presented that include a closer examination of lag
(predictive) relationships between eastern Pacific SSTs and both the
circulation anomalies and tropical cyclone activity. Particular attention
will be given to those features, such as vertical shear, that impact the
character of the hurricane season.
Goni, G.J., G. Podesta, O.B. Brown, and J. Brown. Mesoscale ocean
variability signal recovered from altimeter data in the southwest
Atlantic Ocean: A comparison of orbit error correction in three
GEOSAT data sets. Bolm Inst. Oceanogr., S. Paulo, 43(2):101-110
(1995).
Orbit error is one of the largest sources of uncertainty in studies of
ocean dynamics using satellite altimeters. The sensitivity of GEOSAT
mesoscale ocean variability estimates to altimeter orbit precision in
the southwest Atlantic is analyzed using three GEOSAT data sets derived
from different orbit estimation methods: (a) the original GDR data
set, which has the lowest orbit precision; (b) the GEM-T2 set,
constructed from a much more precise orbital model; and (c) the
Sirkes-Wunsch data set, derived from additional spectral analysis of
the GEM-T2 data set. Differences among the data sets are investigated
for two tracks in dynamically dissimilar regimes of the southwestern
Atlantic Ocean, by comparing (a) distinctive features of the average
power density spectra of the sea height residuals, and (b) space-time
diagrams of sea height residuals. The variability estimates produced
by the three data sets are extremely similar in both regimes after
removal of the time-dependent component of the orbit error using a
quadratic fit. Our results indicate that altimeter orbit precision
with appropriate processing plays only a minor role in studies of
mesoscale ocean variability.
Hansen, D.V., and H.F. Bezdek. Testing winds against other variables
from COADS. Proceedings, International COADS Winds Workshop, Kiel,
Germany, May 31-June 2, 1994. U.S. Department of Commerce, 85-90 (1995).
No abstract.
Hendee, J.C. Ocean Profiler: Software for the at-sea merging of
oceanographic data. NOAA Technical Memorandum, ERL AOML-86 (PB96-128186),
13 pp. (1995).
Ocean Profiler is a computer program (software) that was constructed to
meet the needs of oceanographers working at sea to build a master
database of parameters as the data are generated. This report represents
the technical manual for the operation of the software. Descriptions are
provided for the loading, importing, and exporting of data files. Editing
of data, adding of stations and fields to the database, deleting and
cleaning up of data records, and replacing of certain values with others
are features supported by the software. A Remote Bulletin Board System
and an FTP site for downloading, a World-Wide Web location, and an e-mail
address are provided for additional support for the software.
Hendee, J.C. Operations manual for PELAGOS: An expert system for
quality control and feature recognition of oceanographic data from
the open ocean. NOAA Technical Memorandum, ERL AOML-87 (PB96-131255),
63 pp. (1995).
An expert system was developed to aid oceanographers and data managers in
the quality control and feature recognition of oceanographic data from
the open ocean. Oceanographic data collected from the open ocean are
screened for proper ranges against data collected from the same area
during former cruises. Calculations are also performed on the data as a
cross-check of certain parameters against others. The system developed
runs on the PC, the Macintosh, and a UNIX workstation. The system is
easily configurable to report only oceanographic parameters of interest.
Data are read from, and output to, ASCII files. Source code is provided,
and a list of avenues for further development is presented.
Houston, S.H., and M.D. Powell. Real-time surface wind analyses in
support of marine warnings in tropical cyclones. Preprints, Second
International Workshop on Wind and Earthquake Engineering for Offshore
Coastal Facilities, Berkeley, CA, January 17-19, 1995. University of
California at Berkeley, 323-328 (1995).
Real-time analyses of tropical cyclone wind observations are generated
by the Hurricane Research Division (HRD) on an experimental basis. This
paper describes analyses that apply to nearshore and offshore commercial
activities affected by tropical cyclones. These products can help
determine the extent of tropical storm and hurricane force winds for
marine warnings. They can also be used as input to storm surge and wave
models, as well as for estimating peak wind gusts associated with tropical
cyclones.
Houston, S.H., W.A. Schaffer, M.D. Powell, and J. Chen. Comparisons of
SLOSH parametric and HRD analyzed surface wind fields in recent hurricanes.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
619-621 (1995).
In recent years, the Hurricane Research Division (HRD) has developed new
techniques to analyze the surface wind fields in tropical cyclones based
on all available surface wind observations, including aircraft
flight-level observations adjusted to the surface. As part of NOAA's
Coastal Ocean Program research on coastal hazards, the Techniques
Development Laboratory (TDL) and HRD are evaluating wind fields used as
input to the National Weather Service's (NWS) Sea, Lake, and Overland
Surge from Hurricanes (SLOSH) model through comparisons with HRD's surface
wind field analyses. The SLOSH model-computed water levels are used
primarily by government and emergency management officials to plan for
the evacuation of populations from coastal areas prone to flooding from
storm surge produced by tropical cyclones. The model was developed for
real-time forecasting of hurricane storm surges on continental shelves,
across inland water bodies, and along coastlines. The values used to
initiate the SLOSH model are each tropical cyclone's position, size, and
intensity. Using these input parameters, a wind field is computed by
SLOSH, which is used as the primary forcing mechanism for the oceanographic
processes. Previously, the SLOSH model has been tested for hurricane
landfalls along the U.S. coastlines and has been found to have an accuracy
of ±20% when the hurricane is adequately described. Hurricane wind
field cases examined in this study include Hugo (1989) at landfall in
South Carolina, Bob (1991) at landfall in New England, Andrew (1992) at
landfall in south Florida and Louisiana, as well as the closest approach
of Bob (1991) and Emily (1993) to the North Carolina Outer Banks.
Huang, H., J.R. Proni, and J.J. Tsai. Comment on "Probabilistic
approach to initial dilution of ocean outfalls," by H. Huang, J.R.
Proni, and J.J. Tsai. Water Environment Research, 67:880-881
(1995).
No abstract.
Johns, E. Sources of the Florida Current: Results from NOAA's
Subtropical Atlantic Climate Study. Proceedings, Chapman Conference on
the Circulation of the Intra-Americas Sea, La Parguera, Puerto Rico,
January 22-26, 1995. IOC Workshop Report No. 111, Intergovernmental
Oceanographic Commission, AIII.5 (1995).
The Florida Current is a major component of the Atlantic's thermohaline
circulation, which is believed to play a significant role in controlling
the global climate. To quantify the net heat flux of the Florida
Current, recirculating flow, which would not lead to a net heat flux,
must be distinguished from cross-equatorial flow which carries
significant interhemispheric exchanges of mass, heat, and salt. Previous
studies using historical data have indicated that some 45% of the
transport of the Florida Current, primarily in the <24°C and
7-12°C temperature ranges, originates in the southern hemisphere
(Schmitz and Richardson, Deep- Sea Res., vol. 38, suppl., 1991).
However, the available historical data are somewhat limited in space and
time. Herein, we examine the transport and water masses of the Florida
Current and surrounding inflows to the Caribbean Sea using more recent
data, in an effort to further refine and quantify our understanding of
its source waters. Using shipboard hydrographic and direct velocity data
collected as part of NOAA's Subtropical Atlantic Climate Study between
1984 and 1991, we have examined the volume transport and water mass
properties of the Florida Current, the northern passages into the
Caribbean Sea (Windward, Mona, and Anegada), and across the Caribbean Sea
along 63°30'W. The transport analysis suggests that the circulation
into the Caribbean Sea is different than reported in earlier studies,
with a greater proportion of the flow entering through the northern
passages (Windward, Mona, and Anegada) and a smaller amount through the
more southern passages of the Lesser Antilles. Distributions of
salinity, oxygen, and silica indicate that the conclusions of earlier
studies about the sources of the Florida Current are generally correct.
However, there are indications in our more recent data that the freshest
waters of the Florida Current in the 17-24°C range do not enter the
Caribbean through any of the passages but rather are formed in the Gulf
of Mexico by mixing and freshwater input. In addition, the silica
distributions suggest that the main thermocline waters of the Florida
Current, which in the earlier studies were considered to be primarily of
northern origin, may also include a significant component from the south.
Jones, R.W., M. DeMaria, and C.R. Hagelberg. A comparison of data
assimilation techniques in barotropic track forecasts of west Pacific
typhoons. Preprints, 21st Conference on Hurricanes and Tropical
Meteorology, Miami, FL, April 24-28, 1995. American Meteorological
Society, Boston, 141-142 (1995).
Recently, Bennett et al. (1993) reported results of data
assimilation with a generalized inverse method that was applied to
10 cases for track forecasting of Pacific typhoons using a nondivergent
barotropic model. DeMaria and Jones (1993) reported similar experiments
in the Atlantic basin using the method of model fitting or "adjoint
method." In contrast with DeMaria and Jones, who found many cases where
the results of assimilation were not as good as the control forecasts
with no assimilation, Bennett et al. found reduced track forecast errors
for all 10 cases. Results will be presented for typhoon track forecasts
using the data of Bennett et al. together with the model fitting
strategy of DeMaria and Jones. The generalized inverse method results
will be compared with the adjoint method results.
Kaplan, J. An examination of the role of large-scale forcing on the
rapid intensification of Hurricane Emily (1987). Preprints, 21st
Conference on Hurricanes and Tropical Meteorology, Miami, FL, April
24-28, 1995. American Meteorological Society, Boston, 332-334 (1995).
Hurricane Emily (1987) intensified rapidly to hurricane strength just
prior to crossing the island of Bermuda around 1200 UTC on 25 September.
This period of rapid intensification was not anticipated by numerical
guidance or operational forecasters. Consequently, insight into the
physical processes that facilitated Emily's intensification are of
interest both to the research and operational communities. During the
24 h period leading up to Emily's rapid intensification, the Hurricane
Research Division (HRD) of the Atlantic Oceanographic and Meteorological
Laboratory (AOML) conducted two synoptic-flow experiments (SFEs) within
Emily's (1987) large-scale environment. SFEs have been conducted by the
HRD for the past 13 years and are designed to collect wind and
thermodynamic data within approximately a 1000 km radius of tropical
cyclones by deploying Omega dropwindsondes from research aircraft flying
near 400 mb. The data collected during these SFEs have been combined
with other available conventional (e.g., rawinsonde, satellite,
and ship) data sources and analyzed using the HRD nested analysis scheme.
The analyses have been performed at the mandatory levels over a 2000 km
× 2000 km domain centered on Emily. These analyses are being used
to investigate the change in storm structure prior to the rapid
intensification of Emily. The possible role that an upper-level trough
to the northwest of Emily may have played in Emily's rapid intensification
are also being investigated, since previous studies have suggested that
interactions between upper-level troughs and tropical cyclones appear to
be positively correlated with intensification provided that other
environmental factors (e.g., vertical wind shear and sea-surface
temperature) remain favorable. The interaction between Emily and the
upper-level trough is being examined by evaluating the forcing terms in
the secondary circulation equation (e.g., fluxes of momentum,
heat, and moisture) to determine if the changes in these quantities are
consistent with the structural changes and intensification observed in
Emily. Results from these investigations will be presented at the
conference.
Kaplan, J., and M. DeMaria. A simple empirical model for predicting the
decay of tropical cyclone winds after landfall. Journal of Applied
Meteorology, 34(11):2499-2512 (1995).
An empirical model for predicting the maximum wind of landfalling
tropical cyclones is developed. The model is based upon the observation
that the wind speed decay rate after landfall is proportional to the wind
speed. Observations also indicate that the wind speed decays to a small,
but nonzero, background wind speed. With these assumptions, the wind
speed is determined from a simple two-parameter exponential decay model,
which is a function of the wind speed at landfall and the time since
landfall. A correction can also be added that accounts for differences
between storms that move inland slowly and storms that move inland
rapidly. The model parameters are determined from the National Hurricane
Center best track intensities of all U.S. landfalling tropical cyclones
south of 37°N for the period 1967-1993. Three storms that made
landfall in Florida prior to 1967 were also included in the sample.
Results show that the two parameter model explains 91% of the variance of
the best track intensity changes. When the correction that accounts for
variations in the distance inland is added, the model explains 93% of the
variance. This model can be used for operational forecasting of the
maximum winds of landfalling tropical cyclones. It can also be used to
estimate the maximum inland penetration of hurricane force winds (or any
wind speed threshold) for a given initial storm intensity. The maximum
winds at an inland point will occur for a storm that moves inland
perpendicular to the coastline. Under this assumption, the maximum wind
at a fixed point becomes a function of the wind speed at landfall and the
translational speed of motion. For planning purposes, maps of the
maximum inland wind speed can be prepared for various initial storm
intensities and speeds of motion. The model can also be applied to the
entire wind field of an individual storm to provide a two-dimensional
field of the maximum wind during a given storm. Examples of each of
these applications are presented.
Katsaros, K.B., and W.T. Liu. Microwave radiometers for studies of the
ocean and the marine atmosphere. In Oceanographic Applications of
Remote Sensing, M. Ikeda and F.W. Dobson (eds.). CRC Press, Boca
Raton, 257-269 (1995).
Measurements of oceanographic and marine meteorological parameters by
microwave instruments on satellites started in the 1960s on several
Russian satellites. In this chapter we discuss microwave radiometers
only, leaving out discussion of sounders and active microwave sensors
(radars). The list of microwave radiometers on satellites is quite long.
We give a short recapitulation of the experience gained with the early
microwave radiometers in space, and then concentrate on the
characteristics of the current operational system, the Special Sensor
Microwave/Imager (SMM/I), on satellites in the Defense Meteorological
Satellite Program (DMSP). Some characteristics of the atmosphere with
respect to microwave radiation and emission characteristics of the sea
surface are recalled. The instrument, its sampling characteristics, and a
few applications are then discussed, followed by a selected bibliography
containing review articles that pursue the subject in greater depth.
Keeling, R.F., and T.-H. Peng. Transport of heat, CO2,
and 02 by the Atlantic's thermohaline circulation.
Philosophical Transactions of the Royal Society of London B,
348:133-142 (1995).
We estimate transport of heat, CO2, and O2 by
the Atlantic's thermohaline circulation using an approach based on
differences in the chemical and physical characteristics of North
Atlantic Deep Water (NADW), Antarctic Intermediate Water (AAIW), and
the northward return flow across the equator. The characteristics of
the return-flow waters are constrained by imposing conservation
of phosphate in the North Atlantic as a whole. Based on a total
equatorial return flow of 13 × 106 m3
s-1, we find that the Atlantic north of the equator is a
source of 7.7 ± 1.4 × 1014 W to the atmosphere, a
sink of 0.51 ± 0.21 × 1014 mol of O2,
and preindustrially was a sink of 0.33 ± 0.15 ×
1014 mol of CO2. Uptake of O2 and
CO2 by the North Atlantic is driven mainly by thermal, as
opposed to biological, processes.
Klein, B., R.L. Molinari, T.J. Muller, and G. Seidler. A
transatlantic section at 14.5°N: Meridional volume and heat
fluxes. Journal of Marine Research, 53:929-957 (1995).
Two high-resolution hydrographic sections occupied during February and
March 1989 in the western and eastern basins of the North Atlantic at
14.5°N are combined to study the water mass structure and meridional
mass and heat transports. Absolute velocities were determined using
these data and an earlier section at 8°N in a linear inverse
analysis. Mass balance for several layers representing the main water
masses in the region and a zero net divergence for the sum of geostrophic
and Ekman transport between the two sections are assumed. Using the
annual mean of Ekman transports (13.6 Sv, 14.5°N), (15.2 Sv,
8°N) based on the climatology by Isemer and Hasse (1985), the annual
average fluxes for the sections at 8°N and 14.5°N have been
calculated. For the annual mean the strength of the meridional
overturning cell at 14.5°N amounts to 15.9 Sv with an associated
heat transport of 1.22 PW. A similar value can be obtained at 8°N
where the annual mean heat transport reaches 1.18 PW and the overturning
cell measures 15 Sv. The total northward heat transport is strongly
dominated by the wind-driven Ekman heat transport. In-situ values
of heat transport using the actual wind-driven transports for the
respective months yield even higher estimates. Heat transport at
14.5°N rises to 1.37 × 0.42 PW (February) and the maximum is
now at the 8°N section, 1.69 × 0.52 PW (May). Comparisons of
our results with another tropical section at 11°N occupied
concurrently demonstrate the large variabiltiy in heat transport related
to changes in the wind field. Due to extremely weak winds in the eastern
Atlantic and a resulting low Ekman transport, the in-situ value of
heat transport through this section ranged between 0.30 × 0.18 PW
and 0.59 × 0.18 PW depending on the value chosen for the Ekman
transport. The lower of the two heat transport estimates results from
calculations with the acutal observed winds and the other using a monthly
climatological mean. That even the computations with the climatological
monthly mean give such a low heat transport points to additional changes
in the baroclinic structures between 11°N and 14.5°N.
Lamb, M.F., T.P. Lantry, J.C. Hendee, K.E. McTaggart, P.P. Murphy, R.A.
Feely, R.H. Wanninkhof, F.J. Millero, R.H. Byrne, E.T. Peltzer, and D.
Frazel. Chemical and hydrographic measurements from the equatorial
Pacific during boreal autumn 1992. NOAA Data Report ERL PMEL-56
(PB95-274809), 173 pp. (1995).
In the boreal autumn of 1992, NOAA's Climate and Global Change Program
sponsored a major cooperative effort with the U.S. JGOFS Program in the
central and eastern equatorial Pacific to investigate the unique role of
equatorial processes on CO2 cycling during and following the
1991-1992 ENSO event. Data were collected meridionally along four
transects, generally between 10°N and 10°S. The first leg (Leg
3) included the 140°W and 125°W transects; the second leg (Leg
4) sampled along 110°W, and the third leg (Leg 5) included stations
along 95°W and three short transects extending westward from the
Peru coast. Chemical parameters sampled included fCO2, DIC,
TAlk, pH, TOC, and nutrients. Ancillary measurements of salinity,
temperature, and dissolved oxygen (DO) were also taken. Descriptions of
sampling methods and data summaries are given in this report.
Landsea, C.W. SHIFOR94: Atlantic basin tropical cyclone intensity
forecasting. Australian Physical Oceanography and Australian Meteorological
and Oceanography Society Joint Conference, Lorne, Australia, February 20-22,
1995. APOC/AMOS, 69 (1995).
Intensity forecasting of tropical cyclones has always been extremely
difficult, with most basins showing little to no skill even at 24 h
predictions. Any additional objective aid that can provide skillful
guidance for the forecaster would be useful. SHIFOR94 is a
climatology-persistence based empirical forecasting technique that is
to be used for the Atlantic basin. It is fundamentally different than
Jarvinen, Neumann, and Pike's SHIFOR (Statistical Hurricane Intensity
FORecasting) in that, in addition to the usual predictors of current
intensity, location, motion, and Julian date, use is made of climatological
vertical shear, sea surface temperatures, and sub-surface sea temperatures.
CLIPER, the climatology-persistence statistical track model, is run to
provide future positions and appropriate climatological values of the above
parameters. Results have been found that suggest decreases in 24 h
intensity forecasts by 10 to 20% over the use of simple climatology and
persistence (i.e., SHIFOR). These improvements correspond to 0.5
to 1.0 m s-1 decrease in errors that average near 6 m
s-1 with SHIFOR. Note that "official" forecasts issued by
the U.S. National Hurricane Center at the 24 h mark average only slightly
better with errors of 5.5 m s-1. Investigations are also
undertaken to determine whether the use of seasonal predictors utilized
for hurricane activity (e.g., ENSO, QBO, etc.) can provide
any improvement in the day-to-day intensity forecasting by their inclusion
in this model. Lastly, plans of extending this model to 72 h (and possibly
120 h) and its possible application toward Australian basin tropical
cyclone forecasting are discussed.
Landsea, C.W. SHIFOR94: Atlantic tropical cyclone intensity forecasting.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
365-367 (1995).
No abstract.
Lantry, T.P., M.F. Lamb, J.C. Hendee, R.H. Wanninkhof, R.A. Feely,
F.J. Millero, R. Byrne, E.T. Peltzer, W.D. Wilson, and G.A. Berberian.
Chemical and hydrographic measurements from the equatorial Pacific
during boreal spring 1992. NOAA Data Report, ERL AOML-27 (PB95-227773),
133 pp. (1995).
From February 24 to May 19, 1992, the National Oceanic and Atmospheric
Administration's (NOAA) Climate and Global Change Program sponsored a
major cooperative effort with the U.S. Joint Global Ocean Flux Study
(U.S. JGOFS) to study the role of equatorial processes on CO2
cycling in the central and eastern equatorial Pacific during the 1991-1992
El Niño Southern Oscillation (ENSO) event. The NOAA Ship Malcolm
Baldrige performed four transequatorial sections in the region and this
report presents hydrographic and chemical data from that cruise, including
tables of the following data from each station: hydrography from each
CTD cast at the bottle trip depths, dissolved oxygen, fCO2, DIC,
pH, TAlk, nutrients, and TOC. Descriptions of the sampling techniques and
analytical methods used in the collection and processing of these data are
also presented.
MacIntyre, S., R.H. Wanninkhof, and J.P. Chanton. Chapter 3: Trace
gas exchange across the air-water interface in fresh water and coastal
marine environments. In Biogenic Trace Gases: Measuring Emissions
from Soil and Water, P.A. Matson and R.C. Harriss (eds.). Blackwell
Science, Cambridge, 52-97 (1995).
No abstract.
Marks, F.D., and H.A. Friedman. 1995 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 138 pp. (1995).
No abstract.
Mayer, D.A., J.F. Festa, R.L. Molinari, and D.W. Behringer. Model and
observed upper layer temperature structure of the gyres of the Atlantic
Ocean. Proceedings, ACCP Principal Investigators Meeting, Miami, Florida,
May 2-4, 1995. University Corporation for Atmospheric Research, 205 pp.
(1995).
No abstract.
McAdie, C.J., P.P. Dodge, and S.H. Houston. Mesoscale features of
Tropical Storm Beryl (15-16 August 1994) as detected by the WSR-88D.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society,
Boston, 320-322 (1995).
The spatial resolution of the WSR-88D, in conjunction with the Doppler
velocities it provides, makes it possible to examine the mesoscale
features contained within the parent circulation of the tropical cyclone.
Tropical Storm Beryl, which made landfall on 16 August 1994, near Panama
City, Florida, was observed by the WSR-88D at Eglin AFB. Among the few
tropical cyclones observed by this new radar to date, this was the first
for which digital data was recorded, although not until near the time of
landfall. Among the mesoscale features observed is a well-defined
mesocyclone. The velocity couplet is found on the upwind extremity
of a rainband, and is associated with a Bounded Weak Echo Region. The
mesocylone occurs offshore, about 1 h prior to landfall. This is
believed to the first time the WSR-88D has detected a mesocyclone within
a parent tropical cyclone circulation. As earlier work suggests (Parrish
et al., 1982), the passage of an intense rainband seems to
correlate with the time maximum gusts are recorded at surface observing
sites. An effort is made in the present case to relate the Doppler
velocities aloft with winds reported by both C-MAN and the conventional
reporting network.
Millero, F.J., W. Yao, K. Lee, J.-Z. Zhang, and D.M. Campbell. The
carbonate system near the Galapagos Islands. University of Miami
Technical Report, RSMAS-95-001, 104 pp. (1995).
During the IRONEX cruise and theh PlumEX experiments around the Galapagos
Islands, measurements were made on the components of the carbonate
system. The carbonate parameters pH, TA (total alkalinity),
TCO2 (total carbon dioxide), and fCO2
(fucacity of CO2) were determined. The pH measurements
(± 0.002) were made using spectrophotometric techniques, the TA
(± 2 µmol kg-1) measurements were made by
potentiometric titrations, the TCO2 (± 2 µmol
kg-1) were determined by coulometry and the
fCO2 in the surface waters (± 2 µatm) was
determined using an infrared detector. A significant decrease of the
surface TCO2 (7 µmol kg-1) and
fCO2 (11 µatm) in the Fe patch was detected within
48 hours of the iron release. This decrease, however, did not continue.
A good correlation was found between TCO2, pH, and
fCO2 with temperature in the surface waters around the
Galapagos Islands. The effect of high primary production on the
CO2 system in the downstream plume is overshadowed by the
upwelling waters with high CO2.
Millero, F.J., J.-Z. Zhang, K. Lee, J. Aicher, S. Mane, S. Olivella, D.O.
Medina, and P.A. Steinberg. Ph and total alkalinity measurements in the
North Atlantic. University of Miami Technical Report, RSMAS-95-004, 81
pp. (1995).
This report gives the results of our pH (spectrophotometry and
potentiometry), total alkalinity (TA), and total inorganic carbon dioxide
(TCO2) measurements made in the North Atlantic during the
Joint Global Ocean Flux Study (JGOFS) sponsored by the National Oceanic
and Atmospheric Administration (NOAA). Measurements of TA on 91 samples
of Certified Reference Materials (CRMs) with the three cells at sea
indicate that the systems have a reproducibility of ± 3 µmol/kg
in TA. The resulting pH, TA, and TCO2 are thought to be
precise to ± 0.002 (spectrophotometry) and ± 0.01
(potentiometry) in pH, ± 3 µmol kg-1 in
TCO2, and ± 3 µmol kg-1 in TA. Our
titration results will be combined with NOAA measurements of
TCO2 (coulometry) and fCO2 to characterize
the CO2 system in the North Atlantic.
Mognard, N.M., and K.B. Katsaros. Statistical comparison of the special
sensor microwave imager/and the Geosat altimeter wind speed measurements
over the ocean. Global Atmosphere Ocean System, 2(4):291-299 (1995).
Wind speed data from quasi-simultaneous measurements obtained by the
Special Sensor Microwave/Imager (SSM/I) and the Geosat altimeter acquired
over the world ocean are compared. Under good atmospheric conditions, the
standard deviation of wind speed differences are only 1.2 m/s, but can
reach 1.7 m/s. To assess the cause of the larger differences, integrated
cloud water content and the presence of precipitation are computed using
SSM/I multifrequency algorithms, and significant wave heights are
measured along the altimeter tracks. The atmospheric and sea state
measurements derived from the two satellite sensors show that differences
between the two wind speed estimates are mostly caused by the
interference of the atmosphere with the ocean surface emission and
reflection in the microwave frequencies used. Significant wave height
has no discernible effect on the satellite wind speed estimates.
Mognard, N.M., and K.B. Katsaros. Weather patterns over the ocean
observed with the special sensor microwave/imager and the Geosat
altimeter. Global Atmosphere Ocean System, 2(4):301-323 (1995).
A combination of quasi-simultaneous measurements of atmospheric and sea
state parameters by the Special Sensor Microwave/Imager (SSM/I) and the
Geosat altimeter are analyzed in diverse weather patterns such as
anticyclones, atmospheric fronts, and in a hurricane. Estimates of
integrated water vapor and integrated cloud liquid water content, an
index for the scattering by large ice particles, the presence of
precipitation, and the ocean surface wind speed are derived using SSM/I
multifrequency algorithms. Significant wave height and ocean surface wind
speed are calculated along the altimeter tracks. Variations in the
atmospheric and sea state measurements derived from the two satellite
sensors are analyzed. In regions of precipitation, where there are no
SSM/I wind estimates, the altimeter sea state estimates give the location
and measurement of the wind speed gradients as well as measurements of
significant wave height variations. The synergetic use of microwave
passive and active satellite sensors yields new and complementary
insights into the structure of the lower atmosphere across different
weather conditions.
Nelsen, T.A., P. Blackwelder, T. Hood, C. Zarikian, J.H. Trefry, S.
Metz, B. Eadie, and B. McKee. Retrospective analysis of NECOP area
sediments: Biogenic, inorganic and organic indicators of anthrogenic
influences since the turn of the century. Proceedings, 1994 Synthesis
Workshop, Baton Rouge, LA, April 26-28, 1994. Louisiana Sea Grant
Program, 90-101 (1995).
Surface and cored sediments from the NECOP study area were analyzed
for physical (coarse-grain texture, composition), biological
(foraminifera), and chemical (organic and inorganic) properties.
Results of analyses for surface samples indicated spatial patterns
of benthic foraminifera dictated by sediment accumulation rate and
regions of seasonal hypoxia. The latter also correlated well with
the distribution of surface authigenic glauconite. Temporal
variability, determined from core samples, indicated transitions
in benthic foraminifera community structure with upcore increases
in hypoxia tolerant assemblages. Transitions in glauconite abundance,
organic carbon, and other chemical parameters strongly correlated
temporally with increases in fertilizer application in the United States.
Niiler, P.P., A.S. Sybrandy, K. Bi, P.M. Poulain, and D.S. Bitterman.
Measurements of the water-following capability of holey-sock and TRISTAR
drifters. Deep-Sea Research I, 42(11/12):1951-1964 (1995).
Since 1985, a number of measurements have been made in deep water to
determine the water-following characteristics of mixed layer drifters with
both holey-sock and TRISTAR drogues at 15 m depth. The measurements were
done by attaching two neutrally buoyant vector measuring current meters
(VMCMs) to the top and the bottom of the drogues and deploying the drifters
in different wind and upper ocean shear conditions for periods of 2-4 h.
The average velocity of the VMCM records was taken to be a quantitative
measure of the slip of the drogue through the water, observed to be
0.5-3.5 cm s-1. The most important hydrodynamic design parameter
which influenced the slip of the drogue was the ratio of the drag area of
the drogue to the sum of the drag areas of the tether and surface floats:
the drag area ratio R. The most important environmental parameters
which affected the slip were the wind and the measured velocity difference
across the vertical extent of the drogue. A model of the vector slip as a
function of R, vector wind and velocity difference across the drogue
was developed and a least squares fit accounts for 85% of the variance of
the slip measurements. These measurements indicated that to reduce the
wind produced slip below 1 cm s-1 in 10 m s-1 wind
speed, R > 40. Conversely, if the daily average wind is known to
5 m s-1 accuracy, the displacement of the R = 40 drifter
can be corrected to an accuracy of 0.5 km day-1.
Ooyama, K.V. A thermodynamic foundation for modeling the moist
atmosphere. Part II: Tests of microphysics in the formation of
squall lines. Preprints, 21st Conference on Hurricanes and Tropical
Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological
Society, Boston, 219-221 (1995).
It was proposed (Ooyama, 1990) that the separation of dynamics and
thermodynamics by their primary roles would simplify the design of
numerical models of the moist atmosphere. The dynamics is to predict
temporal changes in the spatial distribution of conservative properties,
such as mass, momentum and energy, while the thermodynamics is to
diagnose the state of each chemical component of the matter in the
atmosphere. In particular, the pressure that affects the motion of
the matter is treated strictly as a thermodynamic state variable.
The theory originally covered only reversible thermodynamic processes.
It is now extended to include Kessler type microphysics of precipitation.
A numerical model of the moist atmosphere in a vertical two-dimensional
plane has been developed to test the extended theory. The model is
nonhydrostatic, and comprises six prognostic variables: two velocity
components, and four density variables for the dry air, the total water
substance, the total entropy (air and water), and the precipitating water.
The spatial numerics is spectral by the SAFER method, and the
time-integration is by the semi-implicit method. To control side-lobe
oscillations due to Gibbs' phenomena at the cloud boundaries, nonlinear
diffusion is employed with variable coefficients which are derived from
the deformation of a high-passed motion field. The model has been tested
in numerical experiments for the simulation of long-lived squall lines,
following the theoretical guide by Rotunno et al. (1988), and the
results generally agree with their theory. The basic state in the
experiments is a typical tropical atmosphere with enhanced relative
humidity, and with a constant wind (U) everywhere except in a bottom
layer of about 2 km in height. Within the bottom layer, the wind decreases
gradually toward zero at the ground. A warm bubble initiates an initial
convective cell, and its rain-loaded, evaporatively-cooled downdraft
generates a pool of cold air that spreads in a thin layer above the ground.
New cells and more downdrafts are generated in succession near the leading
(down-shear) edge of the cold pool, perpetuating the dynamic system of a
squall line. Although new cells may rise on either side of downdrafts,
there is a favored side which depends on U. If U is faster than the
spreading speed of the cold pool, new cells rise more often behind the
downdraft of an earlier cell than in front, so that the squall line as
a system travels slower than U. If the reverse is true, the favored side
is switched and the squall line travels faster than U. The paper will
also discuss other problems of general interest, which have been noted in
the test.
Ortner, P.B., and M.J. Dagg. Nutrient-enhanced coastal ocean
productivity in the Gulf of Mexico. EOS, Transactions, American
Geophysical Union, 76(10):97, 109 (1995).
No abstract.
Ortner, P.B., T.N. Lee, P.J. Milne, R.G. Zika, M.E. Clarke, G.P.
Podesta, P.K. Swart, P.A. Tester, L.P. Atkinson, and W.R. Johnson.
Mississippi River flood waters that reached the Gulf Stream.
Journal of Geophysical Research, 100(C7):13,595-13,601 (1995).
Distributions of physical, biological, and chemical parameters in Florida
Keys coastal waters seaward of the reef track were surveyed on September
9-13, 1993, as part of a coordinated multi-disciplinary study of surface
transport processes. A band of low-salinity water was observed along the
shoreward side of the Florida Current over the downstream extent of the
survey from Miami to Key West. Biological and chemical indicators within
the band, together with its large volume, satellite imagery, and a surface
drifter trajectory suggested the recent Mississippi River flood as the source.
Palmer, D.R. Acoustic imaging of underwater plumes. Acoustical
Imaging, 21:241-255 (1995).
We review the research that has been done to acoustically image
naturally occurring underwater plumes. Since our interest is in
the use of acoustical techniques to study fluxes of material and
heat across the ocean-seafloor interface, the review is limited to
studies of those plumes that result from vents located on the seafloor.
The review was undertaken to gain perspectives that might help in
our efforts to image black-smoker hydrothermal plumes in the deep
ocean. Specifically, we wanted to identify common themes in hardware
development, experimental design, and data analysis and interpretation.
After describing the general structure of an underwater plume and
discussing the advantages of sonar imaging, we survey the individual
experimental efforts. These include observations of offshore and
deep-ocean hydrocarbon plumes, buoyant plumes from a submarine spring,
and buoyant and neutrally-buoyant hydrothermal plumes. We then make
some general statements about the characteristics of imaging sonars and
their platforms, sonar calibration, scattering mechanisms, and the
potential for Doppler measurements. Finally, we discuss the importance
of in-situ observations. We argue that acoustical imaging can complement
but cannot replace in situ measurements. In fact, it is not extreme to
adopt the point of view that the primary purpose of acoustical imaging of
underwater plumes is to support the collection of in-situ data.
Palmer, D.R., L. Krige, G. Brundrit, and K. Metzger. ATOC-FACT
arrival-time differences. Journal of the Acoustical Society of
America, 97:3265 (1995).
No abstract.
Peng, T.-H. Chapter 14: Future climate surprises. In Future Climates
of the World: A Modeling Perspective, A. Henderson-Sellers (ed.).
Elsevier Science, Amsterdam, 517-535 (1995).
No abstract
Peng, T.-H., and W.S. Broecker. Estimate of interhemispheric ocean
carbon transport based on CO2 and nutrient distribution.
In Ecological Time Series, T.M. Powell and J.H. Steele (eds.).
Chapman and Hall, New York, 28-47 (1995).
No abstract.
Powell, M.D., S.H. Houston, and I. Ares. Real-time damage assessment
in hurricanes. Minutes, 49th Interdepartmental Hurricane Conference,
Miami, FL, February 14-17, 1995. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A-23 (1995).
The ultimate cost of a disaster is related to the amount of time
taken for a community to recover; a faster, more organized recovery
will help to mitigate the losses associated with a tropical cyclone.
Real-time information on the actual areas impacted by a hurricane's
eyewall and strongest winds should help minimize confusion and assist
recovery management at the earliest stages of a disaster. The ability
of Geographic Information Systems to link meteorological field
information to damage statistics from infrastructure databases makes
damage assessment modeling a possibility. In a project co-sponsored by
Florida Power and Light Corporation, several meteorological products
are being evaluated for use in estimating structural damage severity.
Geo-referenced statistics on the damaged facilities in 16 subareas
affected by Hurricane Andrew in south Florida were available for
categories of uniform structures. Damage to these facilities was
correlated with quantities derived from meteorological fields believed
to be associated with damage. The goal of this work is to construct a
model that can estimate facility damage in real time as the storm is
in progress. Comparisons of damage in these areas to poststorm surveys
completed by several groups suggest that significant damage in the Florida
City-Homestead area may have been related to the range of wind directions
experienced during the storm. Hence, wind steadiness is an important
predictor in the prototype damage assessment model. Other predictors are
discussed and the potential cost effectiveness of this modeling approach
is examined. Beyond the electrical utility industry, other segments of
the infrastructure could benefit from a similar approach. With models
available for all segments of the infrastructure, a preliminary indication
of the impact of the disaster would be possible while the storm is in
progress or immediately afterward instead of waiting days for visual
assessments to be completed. Scenarios for the impact of hurricanes on
a community could also be created by applying the damage model to a
historical or model-simulated wind field and a given radar reflectivity
structure.
Powell, M.D., S.H. Houston, and I. Ares. Real-time damage assessment
in hurricanes. Preprints, 21st Conference on Hurricanes and Tropical
Meteorology, Miami, FL, April 24-28, 1995. American Meteorological
Society, Boston, 500-502 (1995).
The ultimate cost of a disaster is related to the amount of time
taken for a community to recover; a faster, more organized recovery
will help to mitigate the losses associated with a tropical cyclone.
Real-time information on the actual areas impacted by a hurricane's
eyewall and strongest winds should help minimize confusion and assist
recovery management at the earliest stages of a disaster. The
ability of Geographic Information Systems to link meteorological
field information to damage statistics from infrastructure databases
makes damage assessment modeling a possibility. In a project
co-sponsored by Florida Power and Light Corporation, several
meteorological products are being evaluated for use in estimating
structural damage severity. Geo-referenced statistics on the damaged
facilities in 16 subareas affected by Hurricane Andrew in south Florida
were available for categories of uniform structures. Damage to these
facilities was correlated with quantities derived from meteorological
fields believed to be associated with damage. The goal of this work
is to construct a model that can estimate facility damage in real time
as the storm is in progress. Comparisons of damage in these areas to
poststorm surveys completed by several groups suggests that significant
damage in the Florida City-Homestead area may have been related to the
range of wind directions experienced during the storm. Hence, wind
steadiness is an important predictor in the prototype damage assessment
model. Other predictors are discussed and the potential cost
effectiveness of this modeling approach is examined. Beyond the
electrical utility industry, other segments of the infrastructure could
benefit from a similar approach. With models available for all segments
of the infrastructure, a preliminary indication of the impact of the
disaster would be possible while the storm is in progress or immediately
afterward instead of waiting days for visual assessments to be completed.
Scenarios for the impact of hurricanes on a community could also be
created by applying the damage model to a historical or model-simulated
wind field and a given radar reflectivity structure.
Proni, J.R., J.J. Tsai, and J.F. Craynock. Acoustic profiling of
disposed dredge material in the 6-mile MUD dumpsite, New York.
Contract Report 68-C8-0105, U.S. Environmental Protection Agency,
17 pp. (1995).
No abstract.
Prospero, J.M., and P.B. Ortner, Co-covenors. Report: South Florida
Coastal Ocean Ecosystem Workshop, Miami, FL, February 27-28, 1995.
Cooperative Institute for Marine and Atmospheric Research, 164 pp.
(1995).
The South Florida Coastal Ocean Ecosystem (SoFCOE) encompasses
Florida Bay, the coral reefs of the Florida Keys, and the ocean
margins of the unique Everglades ecosystem. All these regions
are interconnected; they are also closely linked to, and affected
by, the waters of the Straits of Florida, the Gulf of Mexico, and
the Caribbean Sea through the effects of various current systems.
Over the past few decades, the SoFCOE has undergone great changes
due to altered freshwater flow through South Forida, sharply increased
human population in South Florida, including the Florida Keys, and
intensified sports and commercial fishing. These changes have
resulted in extensive degradation in many locations. Continued
rapid growth in the region could greatly exacerbate these stresses.
Major efforts have been initiated to protect and restore these
environments and, as a result, the SoFCOE is emerging as a key study
area for improving methods and principles of management and protection
of regional coastal resources that are of national interest.
Pujals, G., C. Bakker, M.D. Powell, and S.H. Houston. Demonstration
of object-oriented software for real-time acquisition and presentation
of meteorological fields in hurricanes. Preprints, 21st Conference on
Hurricanes and Tropical Meteorology, Miami, FL, April 24-28, 1995.
American Meteorological Society, Boston, 303-305 (1995).
NOAA scientists at the Hurricane Research Division (HRD) in Miami
have been developing a real-time surface wind analysis system. The
purpose is to provide forecasters with diagnostic information regarding
the extent of hurricane force and tropical storm force winds at various
radii. This information can then be used in marine advisories and for
determining hurricane and tropical storm warnings for tropical cyclones
making landfall. The system consists of utilities, tasks, and
applications that acquire, process, examine, and analyze meteorological
data. First, Unix-based scripts are used to bring in the most recent
data automatically from marine and land-based surface observations,
aircraft flight level data, and gridded fields. These data are then
processed to a common framework and examined with HRD's Quality Control
software package. We then incorporate the storm track to choose time
intervals and mesh sizes for storm-relative analysis, as well as the
weighting factors and additional analysis parameters for each mesh.
Once all the desired parameters are set, a run file is created based
on these parameters. The file, in turn, runs the analysis. The
output parameters are then displayed graphically. An electronic
poster will present the steps involved in bringing in data automatically.
Examples of these steps will be shown for Hurricane Andrew's landfall
on south Florida. Wind data from surface observations received in real
time and after the fact are shown in the Quality Control application.
Comparisons between the surface observation and the aircraft measured
winds from flight level, as well as after adjustments to the surface,
are also shown. The graphical interface for choosing meshes and filter
wavelengths is shown, and finally, surface wind analyses are presented.
Samsury, C.E., M.L. Black, and R.E. Orville. The relationship of
cloud-to-ground lightning with radar reflectivity and vertical
velocity in Hurricanes Bob (1991) and Emily (1993). Preprints,
21st Conference on Hurricanes and Tropical Meteorology, Miami,
FL, April 24-28, 1995. American Meteorological Society, Boston,
257-259 (1995).
In-situ flight-level and radar data from the NOAA WP-3D aircraft,
digitized data from NWS radars, and cloud-to-ground (CG) lightning
data from the National Lightning Detection Network are analyzed for
a study of the electrification of Hurricanes Bob (1991) and Emily
(1993). The data were collected over 12-18 h as both storms passed
just east of Cape Hatteras, North Carolina. Hurricanes Bob and Emily
had maximum sustained winds of 100 kts but differed greatly in
reflectivity structure and lightning characteristics. In Emily, the
highest reflectivities were near the eyewall with much lower
reflectivity outside the eyewall. Emily had very few CG lightning
flashes, averaging less than 10 h-1. In addition, 30% of
the flashes detected were positive, a larger percentage than in any
storm noted in the literature. In contrast to Emily, Bob contained
convectively-active rainbands that had several hundred mostly
negative flashes. Most of the flashes were located near regions of
highest reflectivity, similar to results of other studies. Results
from this and previous research suggest that CG lightning in hurricanes,
regardless of polarity, occurs almost exclusively in regions of high
reflectivity. In addition, the existence of convective rainbands or
lack thereof critically impacts the amount of CG lightning associated
with hurricanes. An impetus for this study was to increase knowledge
of hurricane CG lightning characteristics, such as multiplicity
(strokes/flash) and polarity. Most importantly, in addition to
determining the location of CG lightning relative to the storm center
as done with other hurricanes, this research expands on the limited
previous work. In this study, the relationship between vertical
velocity, radar reflectivity, and CG lightning is investigated.
Flight-level and Doppler-derived vertical velocities, and horizontal
and vertical radar reflectivity data from airborne and land-based
radars are used to analyze the microphysical environment associated
with the CG lightning in hurricanes. These data are also used to
study the correlation between lightning and hurricane intensification.
Schmid, C., H. Schäfer, G. Podestá, and W. Zenk. The Vitória eddy and
its relation to the Brazil Current. Journal of Physical
Oceanography, 25(11):2532-2546 (1995).
In late austral summer 1991, a cyclonic thermocline eddy was detected in
the subtropical western South Atlantic off the Brazilian shelf near the
city of Vitória. This Vitória eddy was tracked for 55 days by surface
drifters drogued at 100 m depth. The drifters had been deployed in the
western boundary current regime by FS Meteor as part of a
basin-wide surface current study. The analysis of a combined CTD/XBT
section across the Vitória eddy, together with drifter data and satellite
images of the thermal surface structure, revealed the unexpected
complexity of the region. The eddy interacted not only with the local
topography and the Brazil Current, located further offshore, but also
with an extended upwelling regime north of Cabo Frio. The hydrographic
and kinematic properties and anomalies of the Vitoria eddy are analyzed
and compared with similar vortices described elsewhere in the literature.
Serafy, J.E., S. Lutz, T.R. Capo, P.B. Ortner, and P. Lutz. Anchor
tags affect swimming performance and growth of juvenile red drum
(Sciaenops ocellatus). Marine Behavior and Physiology
(UK), 27(3):1-7 (1995).
Swimming efficiency and growth of anchor-tagged red drum (Sciaenops
ocellatus) juveniles were compared with untagged controls. The
O2 consumption of fish swimming at different speeds was
measured in a Blaska-type respirometer. Daily growth rates of tagged
and untagged red drum were compared over 42 days of feeding fixed
rations of live mosquitofish (Gambusia affinis) to siblings held
individually in 380 L tanks. At swimming speeds of <1.0 body
lengths per second (bl s-1), no differences in O2
consumption were found. However, at speeds of 1.5-2.5 bl s-1,
tagged red drum O2 consumption was significantly greater (by
36-39%) than that of untagged fish (anova, P <0.05), indicating a
substantially impaired swimming efficiency. Daily growth rates of
tagged an untagged fish also differed significantly (P < 0.02).
Tagged fish grew at a mean rate of 0.95 mm d-1, and 1.45 g
d-1, while untagged fish (controls) grew at 1.14 mm
d-1 and 1.62 g d-1. Results suggest that
internal anchor tags, which weighed less than 1% of fish body weight,
represented a hydrodynamic drag burden that reduced swimming performance
and growth. These effects may decrease growth and/or survival in the
wild and thus bias estimates of biological parameters in stock assessment
and enhancement studies.
Thacker, W.C. Statistical modeling for numerical modelers.
GKSS-Forschungszentrum, 7-80 (1995).
This report contains the material that formed the basis for a series
of lectures presented at the GKSS Research Center during the summer of
1994. The audience consisted primarily of meteorologists and oceanographers
who were familiar with numerical modeling typical of numerical weather
prediction, and the intent of the lectures was to provide an overview of
ideas and techniques of statistical modeling within the context of
predicting the seasonal-to-interannual climate. Because of the large
numbers of variables needed to characterize climatic fields and the
opposing requirement that statistical models have a relatively small
number of predictors, emphasis is placed on the use of indices constructed
as linear combinations of field variables as predictors.
Tsai, J.J., H. Huang, and J.R. Proni. Acoustic observations of bottom
surge from dredged material discharge in the open ocean. Chemistry
and Ecology, 10:71-85 (1995).
Bottom surges generated from dredged material discharges in the open
ocean have been observed using high frequency acoustic concentration
profilers in several field studies during the past five years. The
locations, water depths, bottom slopes, oceanographic conditions, and
the dredged material composition differed from study to study.
Observed surges at three dredged material disposal sites may develop
more than one surge peak for a single discharge. For water depths of
the order of 10 m, surge height of the leading peak was estimated to
be about one quarter of the water depth. For water of greater depth,
of the order of 100 m, surge height reached 70 m, about 70% of the water
depth. Surge height is established instantaneously when dredged
material hits the bottom, and remains relatively constant as the surge
advances horizontally. Total surge length reached 150 m for water
depths of 10 m when measured from the impact point to the leading edge.
For water depths of more than 100 m, the surge length reached more than
100 m. Length of the leading surge peak was as large as 45 m at this
water depth. Dimensional analysis was applied to relate the surge
height of the leading surge peak to discharge parameters and oceanographic
conditions. Results showed that the ratio of surge height to water depth
was proportional to 1/10 power of the ratio of discharge volume to the
third power of water depth.
Wanninkhof, R.H., R.A. Feely, D.K. Atwood, G.A. Berberian, W.D.
Wilson, P.P. Murphy, and M.F. Lamb. Seasonal and lateral variations
in carbon chemistry of surface water in the eastern equatorial Pacific
during 1992. Deep-Sea Research II, 42(2-3):387-409 (1995).
During the (boreal) spring and fall of 1992, the NOAA Ocean-Atmosphere
Carbon Exchange Study did an intensive survey of upper water column
(<1000 m) chemistry in the eastern equatorial Pacific from
110°W to 170°W. The spring-time conditions were influenced
by an El Niño that had disappeared before the fall cruises. This
contributed to a large seasonal contrast in surface temperature, carbon,
nutrient concentrations, and thermocline depth. Nitrate, total inorganic
carbon, and fugacity of CO2 values were significantly lower
in the spring, while sea surface temperatures south of the equator were
higher. The seasonal change in surface water chemistry at the equator
is due to changes in upwelling of nutrient and carbon-enriched water.
Oxygen and CO2 anomalies at the surface point to approximately
a three-fold increase in upwelling of thermocline water in the fall
compared to the spring. The large-scale spatial variations in the
surface chemistry patterns remained unchanged between spring and fall.
There was a westward decrease in surface-water carbon and nitrate
concentrations and a strong north to south asymmetry with higher carbon
and nitrate values south of the equator. This pattern is attributed to
input of carbon and nutrients with the South Equatorial Current from the
east. Using velocities obtained from surface drifter tracks, along with
reasonable gas exchange estimates and a "Redfield analysis" to account
for export biological production, this westward decrease in carbon and
nutrients can be quantitatively accounted for in the region from 0°
to 3°S and 110°W to 140°W in the spring. In the fall the
calculated concentration decrease is greater than observed, which is
attributed to input from local equatorial upwelling along the pathway
of water transit.
Willis, P.T., and J. Hallett. The cloud microphysical and electrical
characteristics of a stratiform melting layer. Preprints, Conference
on Cloud Physics, Dallas, TX, January 15-20, 1995. American
Meteorological Society, Boston, 240-245 (1995).
This paper examines the microphysical characteristics and the structure
of the electric field in a region of stratiform precipitation. The
data were obtained in an aircraft advecting spiral descent, during which
it attempted to stay with the trajectory of the dominant particles as
they fell and melted (-5°C to 10°C) in a stratiform precipitation
region in Hurricane Jimena (eastern Pacific, 24 September 1991). The
evolution of the hydrometeors through the melting layer from PMS image
data is presented. Hydrometeor size distributions, and example particle
images, are shown for levels above the melting layer and for layers
through the melting layer. The temperature profile through the melting
layer displays an expected nearly isothermal layer 250 m deep near
0°C, and a second near-isothermal layer at 3°C. The measured
5 cm and 3 cm radar reflectivity factor profiles through the melting
layer are presented. The vertical profiles of the measured electric
field, the vertical component and one horizontal component, are
presented. Field strengths of approximately 25 kv m-1 are
found just above the melting layer. Changes in the structure of the
electric field are compared to the microphysical characteristics through
the melting layer. The melting layer characteristics are compared to
the mid-latitude profiles shown in other studies.
Willis, P.T., R.A. Black, F.D. Marks, and D. Baumgardner. Airborne
rain drop size distributions in TOGA-COARE. Preprints, 21st Conference
on Hurricanes and Tropical Meteorology, Miami, FL, April 24-28, 1995.
American Meteorological Society, Boston, 431-433 (1995).
Details of rain drop size distributions are important in understanding
precipitation formation processes in tropical cloud systems, and in the
quantitative interpretation of radar data, as well as other remote
sensing data. Describing the evolution of raindrop spectra and fitting
observed distributions with suitable analytical functions is a cloud
physics problem of considerable practical importance. This is
particularly true for tropical clouds and cloud systems.
Parameterizations of drop size distributions have wide application
in modeling and remote sensing applications. For this study a large
sample of TOGA COARE airborne imaging drop spectrometer data from the
NCAR Electra aircraft was reduced into approximately 15,000 six second
(~0.7 km spatial scale) drop size distributions. Mean drop size
distributions have been computed for these drop size distributions sorted
into rainfall rate categories. Functional fits to these mean drop size
distributions are computed (Willis, 1984; Willis and Tattelman, 1989).
Exponential and gamma distribution function fits to these mean drop size
distributions are explored using several fitting methods. These data are
further sorted into subsets by elevation, and by whether the precipitation
is stratiform or convective. Mean drop size distributions for these
subsets are also computed for categories of rainfall rate. Radar
reflectivity-rainfall rate relationships (Z-R), overall and
for a convective/stratiform sorting, are derived from the drop size
distribution data set. These Z-R relations are compared to
other relations commonly used for convection and other clouds.
Willoughby, H.E. Eye thermodynamics. Preprints, 21st Conference on
Hurricanes and Tropical Meteorology, Miami, FL, April 24-28, 1995.
American Meteorological Society, Boston, 357-358 (1995).
Central sea-level pressures of the most intense tropical cyclones
are approximately 10% lower than ambient. An adiabatic descent of
3 km in the eye is enough to produce the vertically-integrated
30°C warming necessary for the low hydrostatic pressure. In
balanced models, convective entrainment of air from the eye into
the eyewall causes the subsidence. Balanced models also predict,
and observations confirm, that the eye contracts during intensification.
Eye soundings show warm and dry air aloft, separated by an inversion
from cloudy air below that follows a moist adiabat almost to the
surface. I hypothesize that the air above the inversion has remained
in the eye since it was enclosed when the eyewall formed. Loss of
mass through entrainment into the eyewall is balanced by shrinking of
the eye's volume with little detrainment aloft from the eyewall into
the eye. The air sinks as mass below it is drawn outward from the
bottom of the eye. Dew point depressions at the inversion are
10-30°C rather than the approximately 100°C that would occur
if the air originated at the tropopause. The moist air below the
inversion derives primarily from frictional inflow under the eyewall
and secondarily from descent induced by evaporation of condensate mixed
across the inside edge of the eyewall. The moist air's residence time
in the eye is much shorter than that of the dry air above the inversion.
The depth of the inversion is determined by the balance between
frictional inflow and loss through entrainment into the eyewall. The
convective bubbles in the eyewall are buoyant with respect to the air
around the eye, but not with respect to the eye itself. Collectively,
they act as a "heat pump" that does work on the eye by forcing thermally
indirect descent. When the convection is intense, net entrainment lowers
the inversion, warming and drying the eye. When the convection weakens,
net frictional inflow raises the inversion, cooling the eye and filling
it with clouds. This interpretation suggests that convection intensifies
tropical cyclones through induced adiabatic warming of the eye sounding,
not through vertical mixing that acts to adjust the eyewall sounding
toward thermodynamic equilibrium with the sea.
Willoughby, H.E. Normal-mode initialization of barotropic vortex motion
models. Journal of the Atmospheric Sciences, 52(24):4501-4514
(1995).
An important limitation of numerical hurricane track forecasts is the
difficulty in coaxing the vortex to assume the correct initial motion.
Results from a semispectral, barotropic, linear model suggest a remedy.
When the model is initialized from axisymmetry and rest in a quiescent
environment on a northern hemisphere beta plane, the vortex moves toward
the northwest. The asymmetric streamfunction field is a dipole such that
flow between the cyclonic and anticyclonic gyres advects the vortex.
This asymmetry appears to reflect a free oscillation because the
asymmetric structure, and the induced motion, persists for a long time in
the absence of forcing. When the beta effect is turned off, the motion
continues on an f plane, and the dipole can be rotated and scaled to
produce any desired initial motion. In the normal-mode interpretation, a
vortex with cyclonic circulation throughout accelerates poleward rapidly
because the beta effect forces a neutral mode at zero frequency. A vortex
with angular momentum reduced to zero by encirclement of the cyclonic
core with an annulus of anticyclonic flow experiences weaker forcing of a
mode at the most anticyclonic orbital frequency of the axisymmetric
circulation. Although the latter mode has a weak barotropic instability,
acceleration along the curving track is slow, so that this vortex is
promising for track forecasting. By careful choice of vortex position
and the normal-mode asymmetry's amplitude and orientation at some time
before the beginning of the forecast calculation, it is possible to
"preinitialize" the vortex to pass through a target initial position at
the initial time with an arbitrarily chosen initial velocity. In
completely cyclonic vortices that have asymptotic decay of the swirling
flow with radius, radial wave energy propagation damps the mode at zero
frequency. Experimentation with a variety of axisymmetric vortex
structures suggest that, with this single qualification, existence of the
previously described modes is a general property of barotropic vortices
scaled to resemble hurricanes.
Willoughby, H.E. Normal-mode initialization of barotropic vortex-motion
models. Minutes, 49th Interdepartmental Hurricane Conference, Miami,
FL, February 14-17, 1995. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C., A-19
(1995).
A serious limitation of both barotropic and baroclinic hurricane track
forecast models is the difficulty in coaxing the vortex to assume the
correct initial motion. Results from a semispectral, shallow-water
barotropic, vortex-following, linear model suggest a way around this
difficulty. When this model is initialized from axisymmetry and rest
in a quiescent environment on a northern-hemisphere beta plane, the
vortex moves toward the northwest because wavenumber-one normal modes
with nearly zero frequency are excited. The modal streamfunction fields
are dipoles such that flow between their cyclonic and anticyclonic gyres
moves the vortex by advection. Because the modes are free oscillations,
their asymmetric structures and the motions they induce can persist for
long times even in the absence of forcing. If the beta effect is turned
off, the motion continues on an f plane. The modal streamfunctions can
be rotated and scaled to produce any desired initial motion. A vortex
with cyclonic circulation throughout accelerates poleward too rapidly
because the beta effect forces a neutral mode at zero frequency. A
vortex with angular momentum reduced to zero by encirclement of the
cyclonic core with an annulus of anticyclonic circulation experiences
weaker forcing of a mode whose frequency is the most anticyclonic
orbital frequency of the symmetric circulation. Although this mode has
a weak barotropic instability, acceleration along the curving track is
slower so that the latter vortex is more promising for track forecasting.
By careful choice of vortex position and the normal-mode's amplitude and
orientation at some time before the beginning of the forecast calculation,
it is possible to "preinitialize" the vortex to pass through a target
initial position at the initial time with an arbitrarily chosen initial
velocity. If the preinitialization begins early enough, start-up
transients die away by the initial time and acceleration away from the
desired target velocity is slow.
Wilson, W.D., W.E. Johns, and M.D. Hendry. Measurements of current
structure and transport in the Windward Islands Passages: 1991-1993.
Proceedings, Chapman Conference on the Circulation of the Intra-Americas
Sea, La Parguera, Puerto Rico, January 22-26, 1995. IOC Workshop Report
No. 111, Intergovernmental Oceanographic Commission, AIII.5-AIII.6 (1995).
The Windward Islands Passages Monitoring Program has been designed to
obtain inexpensive regular measurements of transport and water mass
characteristics in the major southern passages to the Caribbean towards
the goal of understanding the interhemispheric exchange of upper ocean
waters in the western tropical Atlantic. Many present theories of North
Atlantic circulation have the southward cross-equatorial Deep Western
Boundary Current flow compensated by a northward transport of upper ocean
South Atlantic water. This scenario is supported by the work of Schmitz
and Richardson (1991, hereafter SR91), which contains a reanalysis of
hydrographic and current measurements made in the southern passages in
March and April of 1970 (Stalcup and Metcalf, 1972). Their analysis
indicated that of 19 × 106 m3/s (1 ×
106 m3/s = 1 Sv) entering the Caribbean through
the three southernmost passages, 13 Sv were of South Atlantic origin. To
better resolve the mean flow and the percentage of waters of South
Atlantic origin, a Barbados Coast Guard vessel, the HMBS Trident,
which makes regular patrols through the islands, has been equipped to
collect standard hydrographic measurements (CTD and water samples) and
velocity profiles using a lowered ADCP. Since the program's inception
in December 1991, a total of ten cruises have been made, with repeat
section occupations in Grenada, St. Vincent, St. Lucia, and Dominica
Passages. Whenever possible, geostrophic velocity estimates have been
referenced with upper layer measured currents to estimate full passage
transports. The structure of the observed velocity and transport fields
is similar to that described by SR91; however, mean transports are
significantly smaller. Total westward transport through the three
southernmost passages ranges from approximately 3 to 17 Sv with a mean
value of 10 Sv, with no clear annual cycle apparent as yet in the data.
Time series of current profiles collected in July 1994 in the Grenada and
St. Vincent passages have been analyzed and used to predict and remove
the barotropic tidal component from the transport data in these two
passages, which account for 85% of the transport. The transports and
their vertical structure are also consistent with recent results from a
high-resolution numerical model of the North Atlantic which includes
forcing by a simulated thermohaline circulation at the northern and
southern boundaries (Johns et al., 1995). Salinity and dissolved
oxygen measurements are presently being analyzed to determine water mass
origins. Without the benefit of this analysis, exact estimates of the
transport of South Atlantic water are impossible, but the low mean total
transport numbers strongly suggest that significantly less than 13 Sv
of upper ocean South Atlantic transport is occurring at the western
boundary south of 15°N.
Wilson, W.D., W.E. Johns, J.A. Routt, and M.D. Hendry. Windward
Islands Passages Monitoring Program: Physical oceanographic data
collected on cruises WI-04, HMBS Trident, 7-13 December 1992,
WI-05, HMBS Trident, 7-12 February 1993, and WI-06, HMBS
Trident, 24-28 March 1993. NOAA Technical Memorandum, ERL
AOML-84 (PB95-208674), 116 pp. (1995).
No abstract.
Yvon, S.A., and J.H. Butler. Global mean wind speed from COADS:
Implications for the calculation of gas transfer velocities. EOS,
Transactions, American Geophysical Union, 76(46):F107 (1995).
No abstract.
Yvon, S.A., and J.H. Butler. Uncertainties in the effect of the ocean
on the atmospheric lifetime of methyl bromide. EOS, Transactions,
American Geophysical Union, 76(17):S162 (1995).
No abstract.
Yvon, S.A., J.H. Butler, J.M. Lobert, and L.S. Geller. Depth profiles
of methyl bromide and CFC-12 in the Atlantic Ocean. EOS,
Transactions, American Geophysical Union, 76(17):S168 (1995).
No abstract.
**1994**
Aberson, S.D. The accuracy of tropical cyclone prediction.
Minutes, 48th Interdepartmental Hurricane Conference,
Miami, FL, February 15-18, 1994. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington,
D.C., A54-A56 (1994).
No abstract.
Aberson, S.D., and M. DeMaria. Verification of a nested barotropic
hurricane track forecast model (VICBAR). Monthly Weather
Review, 122(12):2804-2815 (1994).
A nested analysis and barotropic hurricane track forecast model
(VICBAR) was run for tropical cyclone cases in the North Atlantic
basin during the 1989-1993 hurricane seasons. VICBAR is compared
to the other operational hurricane track forecast models and is
shown to perform as well as each of these. VICBAR forecasts are
stratified by initial date, intensity, and location to assess the
variability of model performance. VICBAR produces the best forecasts
for hurricane cases, for cases initiated earliest in the hurricane
season, for cases moving the most slowly northward, and for those
moving westward. The forecasts with the largest errors are examined
to illustrate the limitations of the model and to determine whether
these cases can be identified operationally.
Atlas, D., and P.G. Black. The evolution of convective storms from
their footprints on the sea as viewed by synthetic aperture radar
from space. Bulletin of the American Meteorological Society,
75(7):1183-1190 (1994).
SEASAT synthetic aperture radar (SAR) echoes from the sea have
previously been shown to be the result of rain and winds produced
by convective storms; rain damps the surface waves and causes
echo-free holes, while the diverging winds associated with the
downdraft generate waves and associated echoes surrounding the holes.
Gust fronts are also evident. Such a snapshot from 8 July 1978 has
been examined in conjunction with ground-based radar. This leads to
the conclusion that the SAR storm footprints resulted from storm
processes that occurred up to an hour or more prior to the snapshot.
A sequence of events is discerned from the SAR imagery in which new
cell growth is triggered in between the converging outflows of two
pre-existing cells. In turn, the new cell generates a mini-squall
line along its expanding gust front. While such phenomena are well
known over land, the spaceborne SAR now allows important inferences
to be made about the nature and frequency of convective storms over
the oceans. The storm effects on the sea have significant implications
for spaceborne wind scatterometry and rainfall measurements. Some of
the findings herein remain speculative because of the great distance
to the Miami weather radar--the only source of corroborative data.
Baringer, M.O., and R.A. Fine. Deep circulation in the western
subtropical North Atlantic from Trident. Proceedings, Principal
Investigators Meeting, Princeton, New Jersey, May 9-11, 1994.
Atlantic Climate Change Program, 135-137 (1994).
No abstract.
Baringer, M.O., and R.A. Fine. Deep circulation in the western
subtropical North Atlantic from Trident. EOS, Transactions,
American Geophysical Union, 75(44):396 (1994).
The new Trident data set provides nutrients and transient tracers to
describe and quantify the recirculations of the coldest waters in the
subtropical North Atlantic. As part of the ACCP Trident cruise during
August 3-31, 1992, approximate zonal sections from the western boundary
to the Mid-Atlantic Ridge (MAR) were obtained along nominal latitudes of
22.5°N and 26.5°N which included hydrography, nutrients, CFCs,
tritium/helium, and spot velocity measurements using LADCP and Pegasus
profilers. These data confirm the net northward flow of 5 Sv of AABW
with its associated high silica, low CFC, low salinity signature of
southern source waters. Waters colder than 1.5°C with the low
potential vorticity signature of Antarctic Bottom Water (AABW) enters the
subtropical North Atlantic along our 22.5°N section with 9 Sv of
southern waters below 1.8°C flowing northward between the western
flank of the Mid-Atlantic Ridge and about 60°W. This northward
flowing bottom water branches to the north of 22.5°N and
recirculates to the east and west of Bermuda around the Hatteras and Solm
Abyssal Plains in approximately equal parts. Northeast of Bermuda it
mixes with North Atlantic Deep Water (NADW) as hypothesized by McCartney
(1994; Schmitz and McCartney, 1993) and again returns southward across
the 26.5°N section near Bermuda as a slightly warmer
(1.7-1.8°C) water mass. This is confirmed by the near linear mixing
relationship found in this recirculating water between the low F11, high
Si AABW and the high F11, low Si NADW. This modified AABW/NADW then
flows northward again to the west of Bermuda around the Hatteras Abyssal
Plain, upwells and finally joins the southward flowing Deep Western
Boundary Current (DWBC) at the Blake Bahama Outer Ridge. Along the
western boundary the southward flow is associated with recirculation of
this low potential vorticity (PV) water that has upwelled and joined the
DWBC. This water is identified as a slightly warmer (1.9°C) low PV
transport mode. Below 1.9°C, the CFC/silica concentrations are
inversely correlated (Smethie, 1993). Transport estimates show a net
northward flow of 5 Sv AABW consistent with the tracer patterns, which
provide considerable detail about the circulation. The transport
estimates indicate that there is intense recirculation of the deep flows
at Abaco (order of 35 Sv) and other locations. The intense
recirculations generate no net export of MNADW. Although the circulation
patterns are substantially different in detail across these two
latitudes, the net transports are remarkably similar, confirming the
continuous nature of the DWBC and the large scale of these abyssal
recirculations. CFCs and silica confirm the modified nature of the low
PV water flowing around Bermuda, additionally they suggest a secondary
mixing history of AABW that is observed in the DWBC. AABW appears to
have mixed with older NADW around Bermuda but within the DWBC itself the
mixing history suggests the more direct connection between high CFC
"younger" DWBC water and AABW (also suggested by Smethie, 1993).
Bitterman, D.S., and W.D. Wilson. A compact CTD system with programmable
controller for obtaining in-situ water samples. Proceedings, IEEE Oceans
'93 Conference, Victoria, British Columbia, October 18-22, 1993. Institute
of Electrical and Electronic Engineers, Volume I, 144-148 (1994).
No abstract.
Black, P.G., and S.H. Houston. Comparison of NOAA and Air
Force wind measurements in Hurricane Emily near Cape Hatteras.
Minutes, 48th Interdepartmental Hurricane Conference, Miami,
FL, February 15-18, 1994. Office of the Federal Coordinator
for Meteorological Services and Supporting Research, Washington,
D.C., A33-A41 (1994).
No abstract.
Black, R.A., H.B. Bluestein, and M.L. Black. Unusually strong
vertical motions in a Caribbean hurricane. Monthly Weather
Review, 122(12):2722-2739 (1994).
Unusually strong updrafts and downdrafts in the eyewall of
Hurricane Emily (1987) during its rapidly deepening phase are
documented by both in-situ aircraft measurements and a vertically
pointing Doppler radar. Updrafts and downdrafts as strong as 24
and 19 m s-1, respectively, were found. Mean updrafts
and downdrafts were approximately twice as strong as those found
in other hurricanes. Updrafts had approximately the same width
as downdrafts. The most vigorous updrafts were located in the
front quadrants of the storm, and most of the strongest downdrafts
were found in the rear quadrants. The downdrafts could not be
explained in terms of evaporative or melting cooling or
precipitation drag. Evidence is presented that moist symmetric
instability initiated by precipitation loading may have been
responsible for the strong downdrafts.
Broecker, W.S., and T.-H. Peng. Stratospheric contribution to the
global bomb radiocarbon inventory: Model versus observation. Global
Biogeochemical Cycles,, 8:377-384 (1994).
An attempt is made, through modeling, to account for the decline in the
14C/C ratio in atmospheric CO2 after its
bomb-test-induced peak in 1963. The model suggests that as of 1964 about
one-third of the bomb 14C remained in the stratosphere and
that it was released to the troposphere with an e-folding time of
about seven years. By contrast, measurements carried out in the
stratosphere suggest that at that time the excess was closer to one
quarter of the total and that the e-folding time for its decline
was 3 ± 1 years. The anomaly between model and observation cannot be
attributed solely to an inadequacy in the representation of the
terrestrial biosphere. Rather, it must reflect either an inadequacy in
the ocean model or in the measured stratospheric inventories.
Brundit, G., L. Krige, D.R. Palmer, A. Forbes, and K. Metzger.
Acoustic thermometry of ocean climate: Feasibilty, Ascension-Cape
Town. Proceedings, Second European Conference on Underwater
Acoustics, Copenhagen, Denmark, July 4-8, 1994. Commission of the
European Communities Federation of Acoustic Societies of Europe,
Brussels, Luxembourg, Volume 2, 1019-1024 (1994).
No abstract.
Burpee, R.W., S.D. Aberson, P.G. Black, M. DeMaria, J.L. Franklin,
J.S. Griffin, S.H. Houston, J. Kaplan, S.J. Lord, F.D. Marks,
M.D. Powell, and H.E. Willoughby. Real-time guidance provided by
NOAA's Hurricane Research Division to forecasters during Emily of
1993. Bulletin of the American Meteorological Society,
75(10):1765-1783 (1994).
The Hurricane Research Division (HRD) is NOAA's primary component for
research on tropical cyclones. In accomplishing research goals, many
staff members have developed analysis procedures and forecast models
that not only help improve the understanding of hurricane structure,
motion, and intensity change, but also provide operational support
for forecasters at the National Hurricane Center (NHC). During the
1993 hurricane season, HRD demonstrated three important real-time
capabilities for the first time. These achievements included the
successful transmission of a series of color radar reflectivity
images from the NOAA research aircraft to NHC, the operational
availability of objective mesoscale streamline and isotach analyses
of a hurricane surface wind field, and the transition of the
experimental dropwindsonde program on the periphery of hurricanes
to a technology capable of supporting operational requirements.
Examples of these and other real-time capabilities are presented
for Hurricane Emily.
Carsey, T.P., M.L. Farmer V.B. Ross, M. Springer-Young, and M.P. Zetwo.
Trace gas aerosol species in the boundary layer of the North Atlantic
during September 1993. EOS, Transactions, American Geophysical
Union, 74:95 (1994).
No abstract.
Cione, J.J., and S. Raman. A three-dimensional numerical investigation of
surface-induced coastal cyclogenesis near the Gulf Stream. Proceedings,
Life Cycles of Extratropical Cyclones International Symposium, Bergen,
Norway, June 27-July 1, 1994. Vol III, 52-55 (1994).
No abstract.
Cione, J.J., and S. Raman. Two-dimensional numerical simulations of
Gulf Stream-enhanced offshore cold advection. Preprints, 6th Conference
on Mesoscale Processes, Portland, Oregon, July 18-22 1994. American
Meteorological Society, Boston, 270-273 (1994).
No abstract.
Clark, J.F., R.H. Wanninkhof, P. Schlosser, and H.J. Simpson.
Gas exchange rates in the tidal Hudson River using a dual tracer
technique. Tellus, 46B:274-285 (1994).
Gas exchange rates have been determined in the tidal Huson River by
injecting two inert gases, 3He and sulfur hexafluoride
(SF6), and monitoring their decline with time. Their
distributions along the main axis of the river were approximately
Gaussian and maximum concentrations of excess 3He and
SF6 observed during each transect decreased from about
6500 × 10-16 cm3 STP g-1 and
250 ppt (part per trillion by volume), respectively, to values close
to atmospheric equilibrium concentration were observed. After three
days of mixing, tracer concentrations in bottom samples were 0-19%
greater than in surface samples. Gas transfer velocities were
calculated from the temporal change in the depth-averged excess
3He/SF6 ratio from stations having maximum
tracer concentrations. They ranged from 1.5 to 9.0 cm h-1
and correlated well with mean wind speed.
Commons, D.N., J.R. Proni, and R. Fergen. Coastal oceanographic
characteristics and their impact on marine biotoxicity studies
during the SEFLOE II. Fourth Environmental Toxicology and Risk
Assessment Symposium, Montreal, Quebec, Canada, April 11, 1994.
American Society for Testing and Materials, 73-91 (1994).
A study, called the Southeast Florida Outfall Experiment II
(SEFLOE II), was conducted from February 1991 through August 1992
at four open ocean outfalls to determine their effluent dispersion
characteristics in the coastal ocean. The objectives of SEFLOE II
were to assess the effect of the Florida Current and its associated
spin-off eddies upon initial dilution and farfield dilution of the
surfacing wastewater plumes in order to facilitate evaluation of
mixing zone parameters, comparison of laboratory bioassay results
to actual field bioassay results, evaluation of indicator bacteria
die-off and dilution characteristics, and analysis of nutrient
reductions as a function of distance and time. This paper deals
with the impact of coastal oceanographic characteristics upon the
biotoxicity aspect of the study. During the SEFLOE II study, a total
of 1,727 acute bioassays (1,424 static acute screening bioassays and
303 static acute definitive bioassays) and 109 short-term chronic
bioassays were analyzed. Plant whole effluent toxicity (WET)
bioassays at different dilutions and time intervals were directly
compared to bioassays analyzed on samples taken from the outfall
dispersion plumes. These ocean bioassay results were then
evaluated with contemporaneous current direction and speed data
to determine initial and farfield dilutions and calculate actual
Eulerian and Lagrangian exposure times. In all ocean bioassay tests
no potential acute toxicity was demonstrated. SEFLOE II is a major
investigation of the impact of a major ocean current on outfall
plume behavior. The bioassay comparison indicated that standard
bioassay methodology does not adequately take into consideration
the substantial differences in dilution ratios and typical
exposure times between laboratory analyses and actual
environmental field conditions. The results of the study appear
to indicate that a new look needs to be taken at bioassay
methodology, especially for ocean outfalls based upon the initial
and farfield mixing conditions.
Refer all requests for SEFLOE II report to:
Hazen and Sawyer, PC
4000 Hollywood Boulevard
Hollywood, FL 33021
(305) 987-0066 (Voice)
(305) 987-2947 (Fax)
Commons, D.N., J.R. Proni, H. Huang, W.P. Dammann, B.M.
Goldenberg, J.G. Monson, and R.E. Fergen. Real world toxicity
testing of an open ocean discharger. 66th Annual Conference and
Exposition, Surface Water Quality and Ecology, Anaheim, CA,
October 3-7, 1993. Water Environment Federation, Volume VII,
15-26 (1994).
A study, called the Southeast Florida Outfall Experiment II (SEFLOE
II), was conducted from February 1991 through August 1992 at
four open ocean outfalls. The objective of the study was to
assess the effect of the Florida Current and coastal oceanographic
characteristics upon the surfacing effluent plumes. During the study,
the results from laboratory bioassays on plant effluent samples were
compared with results from bioassays on contemporaneous ocean
dispersion plume samples. Acute bioassay species used were the mysid
Mysidopsis bahia and the estuarine fish Menidia beryllina.
The mysid Mysidopsis bahia, and the estuarine fish Menidia
beryllina, the sea urchin Arbacia punctulata, and the
macroalga Champia parvula were the species used in short-term
chronic bioassays during the SEFLOE II study. The results of these
comparisons indicate a disparity between exposure times and dilutions
in laboratory bioassays, and those exposure times and dilutions were
actually demonstrated in the receiving waters.
Daneshzadeh, Y.-H., J.F. Festa, and S.M. Minton. Procedures used
at AOML to quality control real time XBT data collected in the
Atlantic Ocean. NOAA Technical Memorandum, ERL AOML-78 (PB94-173283),
50 pp. (1994).
Quality control (QC) procedures developed and implemented at AOML
for the examination of real time XBT data are presented. The
steps required to QC XBT data are outlined in a "cookbook" format.
The methods employed are primarily subjective, as many of the stages
involve interactive input from the user.
DeMaria, M., and S.D. Aberson. Development of a nested spectral
hurricane model. In Research Activities in Atmospheric and
Oceanic Modelling, G.J. Boer (ed.). CAS/JSC Working Group
on Numerical Experimentation, Report No. 19, WMO/TD-No. 592,
5.36 (1994).
No abstract.
DeMaria, M., and J. Kaplan. A statistical hurricane intensity
prediction scheme (SHIPS) for the Atlantic basin. Weather
and Forecasting, 9(2):209-220 (1994).
A statistical model for predicting intensity changes of Atlantic
tropical cyclones at 12, 24, 36, 48, and 72 h is described. The
model was developed using a standard multiple regression technique
with climatological, persistence, and synoptic predictors. The
model developmental sample includes all of the named Atlantic
tropical cyclones from 1989 to 1992, with a few additional cases
from 1982 to 1988. The sample includes only the times when storms
were over the ocean. The four primary predictors are (1) the
difference between the current storm intensity and an estimate of
the maximum possible intensity determined from the sea surface
temperature, (2) the vertical shear of the horizontal wind, (3)
persistence, and (4) the flux convergence of eddy angular momentum
evaluated at 200 mb. The sea surface temperature and vertical
shear variables are averaged along the track of the storm during
the forecast period. The sea surface temperatures along the storm
track are determined from monthly climatological analyses linearly
interpolated to the position and date of the storm. The vertical
shear values along the track of the storm are estimated using the
synoptic analysis at the beginning of the forecast period. All
other predictors are evaluated at the beginning of the forecast
period. The model is tested using a jackknife procedure where
the regression coefficients for a particular tropical cyclone are
determined with all of the forecasts for that storm removed from
that sample. Operational estimates of the storm track and initial
storm intensity are used in place of best track information in the
jackknife procedure. Results show that the average intensity errors
are 10%-15% smaller than the errors from a model that uses only
climatology and persistence (SHIFOR), and the error differences at
24, 36, and 48 h are statistically significant at the 99% level.
DeMaria, M., and J. Kaplan. Sea surface temperature and the maximum
intensity of Atlantic tropical cyclones. Journal of Climate,
7(9):1324-1334 (1994).
An empirical relationship between climatological sea surface
temperature (SST) and the maximum intensity of tropical cyclones
in the North Atlantic basin is developed from a 31-year sample
(1962-1992). This relationship is compared with the theoretical
results described by Emanuel. The theoretical results are in
agreement with the observations over a wide range of SST,
provided that the tropopause temperature is assumed to be a
function of SST. Each storm is examined to determine how close
the observed intensity comes to the maximum possible intensity
(MPI). Results show that only about 20% of Atlantic tropical
cyclones reach 80% or more of their MPI at the time when they are
the most intense. On average, storms reach about 55% of their
MPI. Storms that are farther west and farther north tend to
reach a larger fraction of their MPI. Storms are also more
likely to reach a larger fraction of their MPI in August-November
than in June-July. There is considerable interannual variability
in the yearly average of the ratio of the observed maximum
intensity to the MPI.
DeMaria, M., C.A. Mattocks, and M.D. Powell. Report, First South
Florida Atmospheric Modeling Workshop, Miami, FL, November 29, 1994.
U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, 17 pp. + figs. (1994).
The first South Florida Atmospheric Modeling Workshop was held
at the Atlantic Oceanographic and Meteorological Laboratory (AOML)
on Tuesday, November 29, 1994. Attendance was about 30 people
involved in various aspects of geophysical modeling. The primary
purpose of the workshop was to facilitate the exchange of information
between various groups involved in atmospheric, oceanographic, and
hydrological modeling of the south Florida area. Much of this work
is related to the NOAA-sponsored Florida Bay research program.
Formal talks were given in the morning and early afternoon,
followed by a lively discussion session. A synopsis of each talk
and the discussion are included below.
Donoso, M.C., J.E. Harris, and D.B. Enfield. Upper ocean thermal
structure of the eastern tropical Pacific. NOAA Technical Report,
ERL 450-AOML 36 (PB95-171781), 226 pp. (1994).
A rigorous quality control (QC) procedure developed to assure
the research quality of upper ocean thermal data, mainly from
expendable bathythermographs, is described in detail. The QC
scheme takes into account recommendations from different data
centers and is carried out completely by oceanographers. The
region of interest corresponds to the tropical Pacific from
30ºN to 30ºS and from the dateline to the west coast
of the Americas. For a 15 year period (1979-1993) 212,891 stations
from five data sources (National Oceanographic Data Center,
Joint Environmental Data Analysis Center, southeast Pacific,
Navy declassified, and Tropical Ocean and Global Atmosphere
Subsurface Data Center) were originally processed, of which
113,589 profiles were kept after rejecting duplicates and
submitting the data to the scientific QC process. The accepted
temperature-depth profiles were binned into boxes of 2 latitude
by 5 longitude. The climatology and bimonthly thermal fields
(sea surface temperature, temperature at 50 m, temperature at
100 m, temperature of the 0-400 m layer, 20ºC isotherm depth,
and 15ºC isotherm depth) are mapped.
Drennan, W.M., M.A. Donelan, N. Madsen, K.B. Katsaros, E.A. Terray, and
C.N. Flagg. Directional wave spectra from a SWATH ship at sea.
Journal of Atmospheric and Oceanic Technology, 11(4):1109-1116 (1994 ).
During the Surface Wave Dynamics Experiment (SWADE), the SWATH ship
Frederick G. Creed was equipped with an array of wave staffs for
the estimation of wave directional spectra. This paper reports on the
first such estimates taken from a ship at sea. An algorithm for removing
the effects of the ship motion, including those resulting from the
Doppler shifting of observed frequencies, is presented along with some
results from the SWADE experiment. A comparison with directional wave
spectra taken from a nearby buoy shows the fidelity of the method.
Enfield, D.B., and D.A. Mayer. Inter-American rainfall response to
tropical Atlantic and Pacific SST variability. EOS, Transactions,
American Geophysical Union, 1994 Fall Meeting, paper #031E-5 (1994).
No abstract.
Feely, R.A., R.H. Wanninkhof, C.E. Cosca, M.J. McPhaden, R.H.
Byrne, F.J. Millero, F.P. Chavez, T. Clayton, D.M. Campbell,
and P.P. Murphy. The effect of tropical instability waves on
CO2 species distributions along the equator in the
eastern equatorial Pacific during the 1992 ENSO event.
Geophysical Research Letters, 21(4):277-280 (1994).
Tropical instability waves have been shown to have a major impact
on the variability of temperature and nutrients along the equatorial
wave guide. In order to assess the impact of these features on
carbon species distributions during an ENSO event, sea surface
temperature, salinity, sigma-t, nitrate, CO2 fugacity,
total inorganic carbon, total alkalinity, and pH along the equator
were measured from 130°W to 100°W during 8-15 May 1992.
Concurrent moored measurements of surface currents and temperature
were also made at 0°, 110°W. Results indicate that
tropical instability waves, with periods of 15-20 days and zonal
wavelengths of 700-800 km, controlled the observed spatial
variability of the CO2 species, nitrate, and hydrographic
parameters at the equator.
Forde, E.B., J.C. Hendee, and R.H. Wanninkhof. Hydrographic, carbon
dioxide, nutrient, and productivity measurements from the South Atlantic
during July and August of 1991. NOAA Data Report, ERL AOML-24
(PB94-180668), 96 pp. (1994).
From July 11 to September 2, 1991, the National Oceanic and
Atmospheric Administration's (NOAA) Carbon Dioxide (CO2)
and Radiatively Important Trace Species (RITS) programs participated
in an oceanographic research cruise conducted aboard the NOAA ship
Malcolm Baldrige. This report presents the research from that
cruise that was conducted for the CO2 program, which has
recently been renamed the Ocean-Atmosphere Carbon Exchange Study
(OACES). During leg 1 of this cruise (Fortaleza, Brazil to Montevideo,
Uruguay), 33 CTD hydrographic casts and 17 Go-Flo hydrographic
(productivity) casts were conducted. Samples were also collected
while underway on leg 1, for the determination of the fugacity of
CO2 (fCO2) of the air and surface water. Leg
2 (Montevideo, Uruguay to Fortaleza, Brazil) collected 21 days of
underway fCO2 measurements, conducted five CTD hydrographic
casts, and nine Go-Flo hydrographic (productivity) casts.
This report contains tables of the following data: hydrography
from each CTD cast at the bottle trip depths (including salinity,
oxygen and nutrients), discrete carbon parameters, underway carbon
parameter values, and data from productivity casts. Descriptions of the
sampling techniques and analytical methods used in the collection and
processing of these data are also presented in this report.
Franklin, J.L., S.J. Lord, S.D. Aberson, and M. DeMaria. The impact
of ODW data on track forecasts of Hurricane Emily. Minutes, 48th
Interdepartmental Hurricane Conference, Miami, FL, February 15-18,
1994. Office of the Federal Coordinator for Meteorological Services
and Supporting Research, Washington, D.C., A57-A67 (1994).
The NOAA/Hurricane Research Division conducted two synoptic-flow
experiments in Hurricane Emily on 30 and 31 August 1993, as Emily
was approaching the U.S. eastern seaboard. On the 30th, two P-3
aircraft released 44 ODWs in the storm environment, concentrating
on the area north of the hurricane, to measure the location and
structure of a high pressure ridge responsible for Emily's westward
motion. Data from 36 ODWs were encoded and successfully transmitted
to NMC and NHC. At the request of NHC, a second mission was conducted
on the 31st. While all of the ODW messages were successfully
transmitted to NHC and NMC in real time, software problems at NMC
prevented roughly one-third of the ODWs from reaching the objective
track forecast models for the 0000 UTC 30 August forecast cycle.
Afterwards, the software problems were fixed and NMC reran the Global
Spectral Model (AVN), once using the full ODW data set, and again
using none of the ODW data, to assess the ODWs' true value. By
accurately specifying the strength and structure of the high-pressure
ridge north of the hurricane, the ODWs improved the forecast with a
more accurate initial direction and a recurvature that closely
paralleled the actual path of Emily. Forecast errors in the global
model were reduced by up to 66%. The ODW impact was also evaluated
using VICBAR, HRD's barotropic track model. The impact of the Emily
ODWs on VICBAR was small, about 10%. This is because VICBAR uses a
large bogus vortex that overwhelms the impact of any data within
several hundred kilometers of the center. Results for the 31st
are not yet available; however, the data were used subjectively by
the hurricane forecasters. On this day the ODWs showed that Emily
was about to pass the longitude of the mid-tropospheric high center.
With this knowledge, forecasters were able to confidently predict
that Emily would recurve without affecting the northeastern states.
Garzoli, S.L., and C. Giulivi. What forces the variability of the
southwestern Atlantic boundary currents? Deep-Sea Research,
41(10):1527-1550 (1994).
A marked variability in the location of the front originating at the
confluence of the Brazil and Malvinas Currents has been observed from
both surface and subsurface observations. Modeling experiments using
climatological winds predict a seasonal variability on the latitude of
separation of the Brazil Current from the coast. During the Confluence
program (November 1988-February 1990) and from data collected with an
array of inverted echo sounders, the location of the confluence front
and its variability was established. In this paper, the observed
oceanic variability is analyzed simultaneously with the wind product
from the European Center for Medium Weather Forecast (ECMWF) obtained
for the period of the observations. The ECMWF data is validated
against in-situ indirect wind magnitude observations obtained from a
sub-array of the Confluence deployments. The large-scale anomalies
are explored through the comparison with the climatological wind
fields obtained from Hellerman and Rosenstein (1983), Journal of
Physical Oceanography, 13:1093-1104. From the analysis it is
concluded that the main source of variability of the Confluence front
is the local wind forcing. There is a variability in the location of
the front due to the seasonal cycle of the winds in the South Atlantic.
In addition to this seasonal variability, the latitude of separation
of the Brazil Current from the coast presents a marked interannual
variability that is forced from anomalous wind patterns south of the
Confluence. There is no apparent correlation between wind-forced
pulses in the Antarctic Circumpolar Current and the observed anomalous
northward penetration of the Malvinas Current.
Garzoli, S.L., A.L. Gordon, and D. Pillsbury. Initial results from the
BEST cruises. WOCE Notes, 6(1):10-11, 15 (1994).
No abstract.
Gould, W.J., Y. Desaubies, B.M. Howe, D.R. Palmer, F. Schott, and
C. Wunsch. Acoustic thermometry in the Atlantic: A report to SCOR
WG 96. Scientific Committee on Oceanic Research, International
Council of Scientific Unions, 18 pp. (1994).
No abstract.
Gould, W.J., Y. Desaubies, B.M. Howe, D.R. Palmer, F. Schott, and C.
Wunsch. Acoustic thermometry in the Atlantic. Proceedings, Second
European Conference on Underwater Acoustics, Copenhagen, Denmark,
July 4-8 1994. Commission of the European Communities Federation of
Acoustic Societies of Europe, Brussels, Luxenbourg, Volume 2, 105-107
(1994).
No abstract.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Predicting
Atlantic basin seasonal tropical cyclone activity by 1 June. Weather
and Forecasting, 9(1):103-115 (1994).
This is the third in a series of papers describing the potential for the
seasonal forecasting of Atlantic basin tropical cyclone activity. Earlier
papers by the authors describe seasonal prediction from 1 December of the
previous year and from 1 August of the current year; this work demonstrates
the degree of predictability by 1 June, the "official" beginning of the
hurricane season. Through three groupings consisting of 13 separate
predictors, hindcasts are made that explain 51%-72% of the variability as
measured by cross-validated agreement coefficients for eight measures of
seasonal tropical cyclone activity. The three groupings of predictors
include (1) an extrapolation of quasi-biennial oscillation of 50- and
30-mb zonal winds and the vertical shear between the 50- and 30-mb zonal
winds (three predictors); (2) west African rainfall, sea level pressure,
and temperature data (four predictors); and (3) Caribbean basin and El
Niño-Southern Oscillation information including Caribbean 200-mb
zonal winds and sea level pressures, equatorial eastern Pacific sea
surface temperatures and Southern Oscillation index values, and their
changes in time (six predictors). The cross validation is carried out
using least sum of absolute deviations regression that provides an
efficient procedure for the maximum agreement measure criterion.
Corrected intense hurricane data for the 1950s and 1960s have been
incorporated into the forecasts. Comparisons of these 1 June forecast
results with forecasts results from 1 December of the year previous and
1 August of the current year are also given.
Hacker, P., E. Firing, W.D. Wilson, R.L. Molinari, and M.H. Bushnell.
Direct current velocity measurements during the Trident cruise in the
subtropical western North Atlantic, August 1992. Proceedings,
Principal Investigators Meeting, Princeton, New Jersey, May 9-11,
1994. Atlantic Climate Change Program, 162-165 (1994).
No abstract.
Hendee, J.C. Data management for the Nutrient Enhanced Coastal
Ocean Productivity program. Estuaries, 17(4):900-903 (1994).
The Nutrient Enhanced Coastal Ocean Productivity (NECOP) Data
Management Program (NDMP) is designed to ensure tracking of samples
and archival of all NECOP data in uniform formats, thus allowing
ready access to data by NECOP investigators and the scientific
community at large. The NDMP may broadly be described as possessing
several functions: oceanographic sample tracking, data review and
formatting, data dissemination, formation and supply of data products,
and data transmittal to the National Oceanographic Data Center
(NODC). Figure 1 gives an outline of data flow through the data
manager, and is described below.
Hendee, J.C. Object-oriented database management system and
their application to oceanography. Earth System Monitor,
4(4):6-9 (1994).
No abstract.
Houston, S.H., and M.D. Powell. Observed and modeled wind
and water-level response from Tropical Storm Marco (1990).
Weather and Forecasting, 9(3):427-439 (1994).
The Hurricane Research Division (HRD) analyzes surface wind
fields in tropical storms and hurricanes using surface wind
observations and aircraft flight-level wind measurements in
the vicinity of the storms. The analyzed surface wind fields
for Tropical Storm Marco (1990) were compared with the wind
fields used for input in the National Weather Service's Sea,
Lake, and Overland Surge from Hurricanes (SLOSH) model. The HRD
wind fields were also used to determine the wind speeds and
directions corresponding tothe storm surge at tide gauges along
Florida's west coast. The observed storm surge at the gauges
was compared with the storm surge computed by the SLOSH model.
Time series of the SLOSH model winds were compared with the
time series based on the analyzed wind field at each tide gauge,
because in most cases there were no wind observations available
at these gauges. The comparisons of the analyzed and modeled winds
and the observed and modeled storm surge show that the SLOSH model
reasonably represented the extreme storm tide effects on two basins
with relatively complicated coastlines. However, SLOSH overestimated
surface winds in areas of offshore flow, resulting in predictions of
excessive negative surge. It is suggested that real-time storm
surge model calculations, based on input from real-time surface
wind analyses, have potential for the support of emergency management
response and infrastructure recovery efforts during and immediately
following landfall.
Houston, S.H., and M.D. Powell. Surface wind fields in hurricanes
during the 1993 season. Minutes, 48th Interdepartmental Hurricane
Conference, Miami, FL, February 15-18, 1994. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A42-A43 (1994).
Surface wind fields were analyzed by NOAA's Hurricane Research
Division (HRD) both in real-time and after the fact for the 1993
Atlantic hurricane season. The real-time wind fields were provided
to forecasters at the National Hurricane Center (NHC) for
Hurricanes Emily and Gert as each storm approached the coast. In
the case of Emily, the storm remained offshore, but passed within
37 km of Cape Hatteras, North Carolina during 31 August to 1
September. For Gert, real-time surface wind analyses included
several hours prior to and during the landfall of the storm south
of Tampico, Mexico on 20 September. In addition to the Hurricane
Emily real-time surface wind field analyses, post-storm analyses
of the storm's circulation have been done. These latest Emily
wind fields include additional surface observations which were not
available in real-time.
Huang, H., J.R. Proni, and J.J. Tsai. Probabilistic approach to
initial dilution of ocean outfalls. Water Environment Research,
6:787-793 (1994).
This paper presents a probabilistic approach to develop initial
dilution criteria or standards for ocean outfall design and environmental
impact assessment of effluent discharges. In contrast to a currently
used "worst case" approach, in which a particular combination of
parameters affecting initial dilution is specified and an associated
initial dilution is calculated using a deterministic dilution model,
the probabilistic approach provides a framework for combining data
for the parameters which are often available in the form of time
series or described in statistics; the result of the probabilistic
approach is a description of initial dilution as a function of
cumulative or exceedance probability, from which the exposure
risk level to marine environment can be estimated and criteria
or standards can be defined. The proposed methodology basically
consists of implementing a probabilistic method with a deterministic
initial dilution model. The probabilistic method could be time
domain simulation, Monte Carlo simulation, or first-order
uncertainty analysis; while the deterministic initial dilution
model could be a mathematical model, a physical model, or an empirical
equation. A case study is presented of the Miami-Central Outfall on
the east coast of south Florida to compare the probabilistic approach
with the "worst case" approach. In this case study, time domain
simulation using actual data sets was employed to generate a time
series of initial dilutions (dilutions were calculated using a
semi-empirical equation). Some statistics of initial dilution were
then obtained from the simulated dilution time series. It is found
that for this case study the "worst case" dilution is 17.3 (minimum
surface or near-surface dilution) and the associated cumulative
probability of 5.4%.
Jones, R.W., and M. DeMaria. Data assimilation for tropical
cyclone prediction models. In Research Activities in
Atmospheric and Oceanic Modelling, G.J. Boer (ed.). CAS/JSC
Working Group on Numerical Experimentation, Report No. 19,
WMO/TD-No. 592, 1.33 (1994).
No abstract.
Johnson, G.C., T.B. Sanford, and M.O. Baringer. Stress on the
Mediterranean Outflow Plume: Part 1. Velocity and water property
measurements. Journal of Physical Oceanography,
24:2072-2083 (1994).
In September 1988, six sections were occupied across the Mediterranean
outflow plume in the Gulf of Cadiz, within 100 km of the Strait of Gibraltar.
Vertical profiles of temperature and salinity were collected at CTD stations.
Velocity and temperature profiles were collected with XCPs at a subset of
these stations. At the channel base, the plume undergoes geostrophic
adjustment and turns northwest to flow along the continental slope. There
it decelerates and spreads gradually down the slope as friction slows the
current and allows it to cross isobaths. Within the plume, downstream
velocity and density increase rapidly in the interfacial layer with depth
to the velocity maximum, or nose, -150 m above the bottom. Below the nose,
in the bottom layer, downstream velocity decreases rapidly toward the bottom
but the stratification is weak. Ekman-like veering occurs in the interfacial
layer. Local bottom stresses on the plume are estimated by fitting the
near-bottom velocity profiles to a log-layer model. These stresses are
compared with bulk estimates of total stresses from momentum budget residuals
(Baringer, 1993) and of interfacial stresses from combining the mean
vertical shear with bulk turbulent dissipation estimates. The downstream
pattern of the sum of the local bottom stresses and the bulk interfacial
stresses agrees well in magnitude and distribution with that of the bulk
total stresses. The largest stresses reach a mean of 5 Pa where the plume
is flowing rapidly westward down a channel after exiting the strait,
thinning and accelerating. These stresses are an order of magnitude larger
than mean wind-stress values over the ocean gyres and exceed most bottom
stress estimates in other regions.
Kaplan, J., and M. DeMaria. Preliminary results from a simple
model for predicting tropical cyclone winds over land. Minutes,
48th Interdepartmental Hurricane Conference, Miami, FL, February
15-18, 1994. Office of the Federal Coordinator for Meteorological
Services and Supporting Research, Washington, D.C., A110-A112
(1994).
No abstract.
Katsaros, K.B. ERS-I studies at the Department of Oceanography from
Space. Proceedings, Oceans '94 Conference, Brest, France, September
13-16, 1994. Institute of Electrical and Electronics Engineers, New
York, vol. 1, I.94-I.98 (1994).
The Department of Oceanography from Space at Institut Francais de
Recherche pour l'Exploitation de la Mer (IFREMER) was established in 1991
just before the launch of the first European Research Satellite ERS-I. It
encompasses a research team (The Laboratory of Oceanography from Space)
and a French Processing and Archiving Facility, the French PAF, for the
ERS data also known as Centre ERS d'Archivage et de Traitement - CERSAT).
The work of the two research groups of the Laboratory of Oceanography
from Space, dealing with Atmosphere-Ocean Interaction and Sea Ice, is
described and the objectives of our future endeavors are presented. The
CERSAT and its organization are presented in a poster paper at this
conference.
Katsaros, K.B., J. DeCosmo, R.J. Lind, R.J. Anderson, S.D. Smith, R.
Kraan, W. Oost, K. Uhlig, P.G. Mestayer, S.E. Larsen, M.H. Smith, and G.
DeLeeuw. Measurements of humidity and temperature in the marine
environment during the HEXOS main experiment. Journal of Atmospheric
and Oceanic Technology, 11(4):964-981 (1994).
Accurate measurement of fluctuations in temperature and humidity are
needed for determination of the surface evaporation rate and the air-sea
sensible heat flux using either the eddy correlation or inertial
dissipation method for flux calculations. These measurements are
difficult to make over the ocean, and are subject to large errors when
sensors are exposed to marine air containing spray droplets. All
currently available commercial measurement devices for atmospheric
humidity require frequent maintenance. Included in the objectives of the
Humidity Exchange over the Sea program were testing and comparison of
sensors used for measuring both the fluctuating and mean humidity in the
marine atmosphere at high wind speeds and development of techniques for
the protection of these sensors against contamination by oceanic
aerosols. These sensors and droplet removal techniques are described and
comparisons between measurements from several different systems are
discussed in this paper.
Kendall, A.W., L.S. Incze, and P.B. Ortner. Vertical distribution
of eggs and larvae of walleye pollock (Theragra chalcogramma)
in Shelikof Strait, Gulf of Alaska. Fisheries Bulletin,
92:540-554 (1994).
The vertical distribution of walleye pollock eggs and larvae
in Shelikof Strait, Gulf of Alaska, was investigated using data
from 36 Multiple Opening-Closing Net and Environmental Sensing
System (MOCNESS) tows taken in April and May, 1986-1988. Most
eggs were found from below 150 m to near bottom at depths of 300 m,
but were progressively shallower later in the season. Eggs in middle
stages of development were shallower than younger or older eggs. The
vertical distribution of eggs was positively related to observed
differences in seawater temperature but showed no relationship to
density. Larvae hatch at incubation depth and quickly rise to the
upper 50 m of the water column where they remain during larval
development. Larger larvae ( 7-10 mm standard length [SL]) undergo
limited diel vertical migration within the upper 50 m. They are deepest
during the day, shallowest at dusk, slightly deeper at night, and even
deeper at dawn. Their mean depths of occurrence were between 21 and
37 m at all times. At these depths, prey (copepod nauplii)
generally were at densities sufficient for larval pollock growth
in laboratory studies. Pronounced thermoclines and pycnoclines
were present in the part of the water column inhabited by the larvae
in late May. Larvae appear to remain below the upper mixed layer
during periods of increased turbulence, but at depths during daytime
where light was sufficient for feeding, and where prey densities
were adequate.
Kenyon, T.N., and M.C. Pazos. Data from drifting buoys deployed
in the equatorial Pacific between April 1, 1987 and June 30, 1988.
NOAA Technical Report, ERL AOML-25 (PB94-219177), 174 pp. (1994).
No abstract.
Landsea, C.W., W.M. Gray, P.W. Mielke, and K.J. Berry. Forecasting
seasonal Sahelian rainfall by 1 December of the previous year.
Proceedings, International Conference on Monsoon Variability and
Prediction, Trieste, Italy, WMO/TD No. 619. World Meteorological
Organization, 496-503 (1994).
No abstract.
Landsea, C.W., W.M. Gray, P.W. Mielke, and K.J. Berry. Seasonal forecasting
of Atlantic hurricane activity. Weather, 49:273-284 (1994).
No abstract.
Lawler, A.J., R.E. Fergen, A. Fairey, and J.F. Craynock. Comparison of
acoustical and dye monitoring techniques for in-harbor mixing of
Charleston's Plum Island Wastewater Treatment Plant effluent.
Proceedings, Conference on Challenges and Opportunities in the
Marine Environment, Washington, D.C., September 7-9, 1994. Marine
Technology Society, 740-747 (1994).
The City of Charleston Plum Island Wastewater Treatment Plant
(WWTP) discharges effluent through a multiport diffuser, designed for
rapid initial dilution, into the Charleston Harbor. The original
permit conditions for the Plum Island WWTP were based on initial
dilution values determined by the EPA "initial dilution" model UPLUME.
However, the City conducted a field study to determine actual instream
waste concentration. A conventional dye study was performed by
injecting a known amount of dye into the effluent and measuring the
concentration of dye in the harbor. The second technology used was an
innovative technique using acoustical backscatter data corrected to
eliminate the background signal generated within the water column that
is not related to the wastewater plume. Field data was used to determine
an average initial dilution and farfield dilution during worst case
(minimum mixing) conditions. Correlation of the two techniques provided
validation of the acoustical methodology as an accurate measurement system
for the determination of the dilution of the wastewater with distance
from the outfall. In addition, the acoustic measurement gives continuous
values, not just that of a given sampling point, and allows the entire
plume configuration to be depicted pictorially. This allows the
characterization of the microstructure in the rising plume and farfield
plume that is not available with other techniques.
Lawler, A.J., R.E. Fergen, A. Fairey, and J.F. Craynock. Comparison
of acoustical and dye monitoring techniques for in-harbor mixing of
Charleston's Plum Island Wastewater Treatment Plant effluent. 66th
Annual Conference and Exposition, Surface Water Quality and Ecology,
Anaheim, CA, October 3-7, 1993. Water Environment Federation, Volume
VII, 235-245 (1994).
The City of Charleston Plum Island Wastewater Treatment Plant
(WWTP) discharges effluent through a multiport diffuser, designed for
rapid initial dilution, into the Charleston Harbor. The original
permit conditions for the Plum Island WWTP were based on initial
dilution values determined by the EPA "initial dilution" model UPLUME.
However, the City conducted a field study to determine actual instream
waste concentration. A conventional dye study was performed by
injecting a known amount of dye into the effluent and measuring the
concentration of dye in the harbor. The second technology used was
an innovative technique using acoustical backscatter data corrected
to eliminate the background signal generated within the water column
that is not related to the wastewater plume. Field data was used to
determine an average initial dilution and farfield dilution during
worst case (minimum mixing) conditions. Correlation of the two
techniques provided validation of the acoustical methodology as an
accurate measurement system for the determination of the dilution
of the wastewater with distance from the outfall. In addition, the
acoustic measurement gives continuous values, not just that of a given
sampling point, and allows the entire plume configuration to be depicted
pictorially. This allows the characterization of the microstructure in
the rising plume and farfield plume that is not available with other
techniques.
Lee, W.-C., P.P. Dodge, F.D. Marks, and P.H. Hildebrand. Mapping
of airborne Doppler radar data. Journal of Atmospheric and
Oceanic Technology, 11(2):572-578 (1994).
Two sets of equations are derived to (1) map airborne Doppler radar
data from an aircraft-relative coordinate system to an earth-relative
coordinate system, and (2) remove the platform motion from the
observed Doppler velocities. These equations can be applied to data
collected by the National Oceanic and Atmospheric Administration
WP-3D system, the National Center for Atmospheric research ELDORA
system, and other airborne radar systems.
Lee, W.-C., F.D. Marks, and R.E. Carbone. Velocity track
display: A technique to extract real-time tropical cyclone
circulations using a single airborne Doppler radar. Journal
of Atmospheric and Oceanic Technology, 11(2):337-356 (1994).
The concept and formulation of a real-time Doppler radar wind
field analysis technique, velocity track display (VTD), is presented.
The VTD algorithm is a harmonic analysis method similar to the
velocity-azimuth display technique for ground-based radars; however,
it is designed to deduce the primary circulation properties of
atmospheric vortices such as tropical cyclones. When an aircraft
equipped with a Doppler radar scanning in a track-orthogonal plane
penetrates a cyclonic circulation, VTD decomposes Doppler velocities
on cylindrical rings into tangential, radial, and the mean
cross-track component of the wind velocity. Obtaining estimates
of the vortex circulation requires data from only one aircraft flight
leg instead of two in the pseudo-dual Doppler radar method. As a
test, the VTD technique was applied to two orthogonal legs ("figure
4" pattern) in Hurricane Gloria (1985). The entire computation was
completed about 15 min after the end of each flight leg with little
or no human interaction. The reconstructed hurricane vortex
structure (the mean tangential wind, mean radial wind, and the total
tangential wind) is consistent with those documented in the
literature by elaborate techniques that demand extensively interactive
decisions and intensive computations. The output consists of
about 4,000 Fourier coefficients, which can be transmitted from
an aircraft to a forecast center via geosynchronous satellite link in
real-time for further analysis and as initialization for tropical
cyclone models. A version of VTD was run successfully on board a
NOAA WP-3D during the 1991 hurricane season.
Lighthill, J., G. Holland, W. Gray, C.W. Landsea, G. Craig, J. Evans, Y.
Kurihara, and C. Guard. Global climate change and tropical cyclones.
Bulletin of the American Meteorological Society, 75(11):2147-2157
(1994).
This paper offers an overview of the authors' studies during a
specialized international symposium (Mexico, 22 November-1 December
1993) where they aimed at making an objective assessment of whether
climate changes, consequent on an expected doubling of atmospheric
CO2 in the next six or seven decades, are likely to increase
significantly the frequency or intensity of tropical cyclones (TCs).
Out of three methodologies available for addressing the question
they employ two, discarding the third for reasons set out in the
appendix. In the first methodology, the authors enumerate reasons
why, in tropical oceans, the increase in sea surface temperature
(SST) suggested by climate change models might be expected to affect
either (i) TC frequency, because a well-established set of six
conditions for TC formation include a condition that SST should
exceed 26°C, or (ii) TC intensity, because this is indicated by
thermodynamic analysis to depend critically on the temperature at
which energy transfer to air near the sea surface takes place.
Careful study of both suggestions indicates that the expected
effects of increased SST would be largely self-limiting, (i) because
the other five conditions strictly control how far the band of
latitudes for TC formation can be further widened, and (ii)
because intense winds at the sea surface may receive their energy
input at a temperature significantly depressed by evaporation of
spray, and possibly through sea surface cooling. In the second
methodology, the authors study available historical records that
have very large year-to-year variability in TC statistics. They
find practically no consistent statistical relationships with
temperature anomalies; also, a thorough analysis of how the El
Niño-Southern Oscillation cycle influences the frequency and
distribution of TCs shows any direct effects of local SST changes
to be negligible. The authors conclude that, even though the
possibility of some minor indirect effects of global warming on
TC frequency and intensity cannot be excluded, they must effectively
be "swamped" by large natural variability.
Maddox, R.A., and H.F. Bezdek. Surface wind-pressure gradient
relationships in central Florida. Monthly Weather Review,
122(11):2596-2602 (1994).
An extended series of surface observations is used to compare observed
surface winds with winds computed using the geostrophic relationship.
These computations are done for both steady and unsteady wind regimes.
Large differences are found in the comparisons of observed to computed
winds. The differences exhibit pronounced seasonal and diurnal
variability that appear to reflect both boundary layer stability and
small-scale wind and pressure fields--for example, those attending
land--sea breezes and thunderstorms. The results of this study may
be useful to those engaged in studying global data sets and to modelers,
who are continually challenged to improve the treatment of parameterization
of turbulent processes. However, it is not obvious that any simple
parameterization can be applied to obtain an accurate estimate of the
surface wind in central Florida, given only the large-scale pressure
gradient or a model-predicted wind above the surface as input. The
use of the pressure field to estimate surface winds is an uncertain
exercise at best.
Marks, F.D., and H.A. Friedman. 1994 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 138 pp. (1994).
No abstract.
Martin, J.H., K.H. Coale, K.S. Johnson, S.E. Fitzwater, R.M. Gordon,
S.J. Tanner, C.N. Hunter, V.A. Elrod, J.L. Nowicki, T.L. Coley, R.T.
Barber, S. Lindley, A.J. Watson, K. Van Scoy, C.S. Law, M.I.
Liddicoat, R. Ling, T. Stanton, J. Stockel, C. Collins, A. Anderson,
R. Bidigare, M. Ondrusek, M. Latasa, F.J. Millero, K. Lee, W. Yao,
J.-Z. Zhang, G. Friederich, C. Sakamoto, F. Chavez, K. Buck, Z. Kolber,
R. Greene, P. Falkowski, S.W. Chisholm, F. Hoge, R. Swift, J. Yungel,
S. Turner, P. Nightingale, A. Hatton, P. Liss, and N.W. Tindale.
Testing the iron hypothesis in ecosystems of the equatorial Pacific
Ocean. Nature, 371:123-129 (1994).
The idea that iron might limit phytoplankton growth in large regions of
the ocean has been tested by enriching an area of 64 km2 in
the open equatorial Pacific Ocean with iron. This resulted in a doubling
of plant biomass, a threefold increase in chlorophyll and a fourfold
increase in plant production. Similar increases were found in a
chlorophyll-rich plume downstream of the Galapagos Islands, which was
naturally enriched in iron. These findings indicate that iron
limitation can control rates of phytoplanton productivity and biomass
in the ocean.
Mayer, D.A., and R.H. Weisberg. On the observational basis for
ENSO modeling using COADS. EOS, Transactions, American Geophysical
Union, 75(44):360 (1994).
With 30 years of data from COADS, anomalies of SST, zonal and
meridional wind stress (taux, tauy) and sea
level pressure (Pb) fields are examined over a global
domain from 20°S-20°N. Important regions of covariability
among the data have been identified and are discussed in the context
of eastern and western Pacific variability. Maximum correlation,
cross-correlation and EOF analyses are equivalent in capturing simple
statistical relationships between a zonal pressure gradient
index and the rest of the data (SST, taux, and
tauy). Greatest variability resides in the central and
eastern Pacific for SST and in the west-central Pacific for
taux and tauy. The latter is characterized
by a large meridional asymmetry with most of the variability north
of the equator. Both taux and tauy have much
smaller correlation scales than those for SST, i.e., regional
scales are degraded owing to large wavenumber bandwidths. This
variability is represented by reference time series from the
maximum correlation analysis and canonical time series from the first
EOF modes. All of these time sequences are statistically
indistinguishable but are specific to significantly different
correlation regions with different spatial scales. Data in regions
identified by EOF modes above the first are not simply related to data
elsewhere and in many cases appear to be chaotic. Important regions
are not always associated with maximum variability. An important
example is the disproportionate influence that minimum variability
of SST has on Pb over the warm pool in the far western
Pacific and reflects the distinctly different background states
characterized by incipient instability in the west and relative stability
in the east. A model that considers only simple thermodynamics and
a hydrostatic atmosphere shows that only 1 Wm-2 of
condensation heating in the lower troposphere is required to change
the surface pressure by 1 mb/mo. This is consistent with observed
excitation rates for Pb during ENSO episodes. Linear
regression analyses between anomalies of SST and Pb
in the eastern and western Pacific suggest that the coupling
coefficient may be larger in the west by a factor of two despite
the SST anomalies being large in the east by a factor of five.
McCartney, M.S., and M.O. Baringer. The Subantarctic Mode Water--Antarctic
Intermediate Water connection in the South Pacific Ocean. EOS,
Transactions, American Geophysical Union, 75(3):204 (1994).
No abstract.
Mestas-Nunez, A.M., D.B. Chelton, M.H. Freilich, and J.G. Richman. An
evaluation of ECMWF-based climatological wind stress fields. Journal of
Physical Oceanography, 24(7):1532-1549 (1994).
A new mean monthly wind stress climatology based on seven years
(1980-1986) of operational weather analyses by the European Centre for
Medium-Range Weather Forecasts (ECMWF) has been derived by Trenberth
et al. This climatology (referred to here as the TLO climatology)
potentially represents a significant improvement over climatologies
derived only from conventional wind observations. An attempt is made here
to quantify the absolute accuracy of the TLO climatology by comparison
with global wind stress fields constructed from vector winds measured by
the SEASAT-A Satellite Scatterometer (SASS) during 1978. From a simulated
SASS data set, it is shown that the magnitudes of the SASS stresses must
be increased by about 7% to account for a systematic error that can be
attributed to the scatterometer spatial- and temporal-sampling
characteristics. After applying this correction, differences between the
TLO climatology and SASS winds in the tropics are most likely related to
known limitations of the ECMWF analyses. At latitudes south of 50°S,
interannual variability and uncertainties in the operational weather
analyses are o large that it is not possible to evaluate the TLO
climatology on the basis of comparisons with SASS data. Outside of these
equatorial and high southern latitude bands, the TLO stresses are shown
to be systematically stronger than SASS by almost 50%. It is found that
this difference can be entirely accounted for if the 1980-1986 ECMWF
1000-mb analyses are not interpreted as 10-m winds, as they were in
constructing the TLO climatology. This conclusion is supported by an
independent comparison of the synoptic ECMWF wind speed estimates with
coincident buoy observations.
Millero, F.J., J.-Z. Zhang, E. Peltola, M. Roche, S. Olivella, M. De
Alessi, and B. Vargas. Total alkalinity measurements in the South
Pacific. University of Miami Technical Report, RSMAS-94-003, 207 pp. (1994).
In spring 1994, we participated in one CO2 cruise in the South
Pacific during the Joint Global Ocean Flux Study (JGOFS) sponsored by the
National Oceanic and Atmospheric Administration (NOAA). This report
gives the results of our pH, total alkalinity (TA), and total inorganic
carbon dioxide (TCO2) measurements made in the South Pacific
during the cruise. The results were obtained by a potentiometric
titration of seawater samples with HCl. Measurements on 116 samples of
Certified Reference Material with the three cells at sea indicate that
the systems have a reproducibility of ± 3.3 µmol
kg-1 in TA. The resulting pH, TA, and TCO2 are
thought to be precise to ± 0.01 in pH, ± 3 µmol/kg in TA,
and ± 3 µmol/kg in TCO2. Our titration results will
be combined with the NOAA measurements of TCO2 and
fCO2 to characterize the CO2 system in this
region.
Millero, F.J., J.-Z. Zhang, D.M. Campbell, W. Yao, K. Lee, M. Helmer, S.
Mane, S. Olivella, S. Cass, D.G. Purkerson, J. Aicher, P.A. Steinberg,
and D. Medina. Total alkalinity measurements in the eastern equatorial
Pacific. University of Miami Technical Report, RSMAS-94-005, 229 pp. (1994).
In 1992, we made measurements on the carbonate system on two cruises
(spring and fall) in the eastern equatorial Pacific during the Joint
Global Ocean Flux Study (JGOFS) sponsored by the National Oceanic and
Atmospheric Administration (NOAA). This report gives the results of our
pH, total alkalinity (TA), and total inorganic carbon dioxide
(TCO2) measurements made during the spring and fall cruises.
The results were obtained by a potentiometric titration of seawater with
HCl acid. Measurements on the Certified Reference Materials during the
cruise with the three cells indicate that the systems have a
reproducibility of ± 2-4 µmol kg-1 in TA. The
titration values of TCO2 determined on the Certified Reference
Materials and the samples collected at sea were about 20 ± 6
µmol kg-1 (spring) and 17 ± 6 µmol
kg-1 (fall) too high. This offset in TCO2 is
independent of depth and is due to the non-Nernstian Behavior of the
electrodes. The measured values of pH, TA, and TCO2 are
thought to be precise too ± 0.01 in pH, ± 3 µmol
kg-1 in TA, and ± 5 µmol kg-1 in
TCO2. These results will be combined with NOAA's AOML and
PMEL groups to characterize the CO2 system in this region.
Molinari, R.L., and E. Johns. Upper layer temperature structure of the
western tropical Atlantic. EOS, Transactions, American Geophysical
Union, 75(3):224 (1994).
No abstract.
Molinari, R.L., and E. Johns. Upper layer temperature structure
of the western tropical Atlantic. Journal of Geophysical
Research, 99:18,225-18,233 (1994).
Mean monthly topographies of the 20°C and 10°C isothermal
surfaces are used to describe the vertical displacements of the
upper and lower thermocline in the western tropical Atlantic. The
isotherm topographies are generated from expendable bathythermograph
data collected between 1966 and 1993. The topographies confirm, and
extend closer to the coast, earlier findings that demonstrate large
spatial and temporal variability in the region. For example, the
ridge and trough systems observed previously in the interior are shown,
and their extension to the western boundary is described. In particular,
it is shown that the ridge associated with the North Equatorial
Countercurrent (NECC) extends from the interior northwestward along the
western boundary, reaching farther north along the boundary in the
upper thermocline than in the lower thermocline. South of the equator
the northwestern corner of the countercurrent trough is apparent on
the lower surface but not on the upper. The annual and semiannual
harmonics of the vertical isotherm displacements account on the
average for about 60% of the total variance on both surfaces. The
horizontal structure of the first harmonic amplitude is similar for
both surfaces, showing maximum amplitude along the axis of the NECC
ridge. Minimum amplitudes are observed to the north along the axis of
the NECC ridge. Minimum amplitudes are observed to the north along the
axis of the countercurrent trough. These distributions are similar to
the pattern of the first harmonic amplitude of the wind stress curl,
supporting earlier studies of curl forcing of near-surface current
features.
Molinari, R.L., and W.D. Wilson. Absolute velocity properties of
the Deep Western Boundary Current at 26.5°N. EOS,
Transactions, American Geophysical Union, 75(44):396 (1994).
The Deep Western Boundary Current (DWBC) is an important component of
meridional oceanic heat flux in the subtropical North Atlantic. Direct
velocity observations obtained from sensors deployed from research
vessels have been collected in the DWBC from 1985 to 1994. Both Pegasus,
a free-fall acoustically tracked unit, and a lowered acoustic Doppler
current profiler (LADCP) were used. Intercomparisons of total water
column velocity profiles obtained during an August 1992 cruise show
differences between the two sensors of only 0.1 m s-1 in
depth-averaged velocity components and 0.02-0.04 m s-1 in shear
observations. A section was repeatedly occupied east of Abaco Island, the
Bahamas, at 26.5°N. Prior to 1992, on average, the DWBC was
characterized by a mid-depth (1500 to 2500 m) meridional speed core of
about 0.2 m s-1. During the majority of these cruises, the
DWBC core was typically some 50 km offshore, with some excursions to
about 100 km offshore. During 1992, the mid-depth DWBC core was located
some 150 km offshore. This core remained some 100-150 km offshore during
June and September 1993 cruises. During April and July 1994, the core
was found at its historical position 50 km offshore. Considerable
variability is observed in total transport below 800 m within 400 km of
the boundary. On all but the June 1994 cruise, transport was approximately
40 Sv. During June 1994, transport was only 10 Sv. Significant changes
in vertical shear structure also are observed. When the DWBC core is
located onshore, a level of no motion is typically located at 800 m. When
offshore, the meridional velocity component can be unidirectional from
top to bottom, complicating the task of computing geostrophic velocities
from only density observations.
Molinari, R.L., D. Battisti, K. Bryan, and J. Walsh. Atlantic
Climate Change Program. Bulletin of the American Meteorological
Society, 75(7):1191-1199 (1994).
The Atlantic Climate Change Program (ACCP) is a component of
NOAA's Climate and Global Change Program. ACCP is directed at
determining the role of the thermohaline circulation of the Atlantic
Ocean on global atmospheric climate. Efforts and progress in four
ACCP elements are described. Advances include: (1) descriptions of
decadal and longer term variability in the coupled
ocean-atmosphere-ice system of the North Atlantic; (2) development
of tools needed to perform long-term model runs of coupled
simulations of North Atlantic air-sea interaction; (3) definition of
mean and time-dependent characteristics of the thermohaline circulation;
and (4) development of monitoring strategies for various elements of the
thermohaline circulation.
Nelsen, T.A., P. Blackwelder, T. Hood, B. McKee, N. Romer, C.
Alvarez-Zarikian, and S. Metz. Timed-based correlation of
biogenic, lithogenic, and authigenic sediment components with
anthropogenic inputs in the Gulf of Mexico NECOP study area.
Estuaries, 17(4):873-885 (1994).
Hypotheses related to variability in seasonal hypoxic conditions,
coastal nutrient enhancement, and offshelf transport of carbon on the
Louisiana continental shelf were tested by characterization of biogenic,
lithogenic, and authigenic components from two shelf and one Mississippi
Canyon sediment cores. The authigenic-phase glauconite occurs above
detection limits only in the core from the hypoxic area. A major
increase in glauconite concentration was coincident with the onset
(~1940) of the increased use of commercial fertilizers in the United
States. In the same hypoxic-area core, benthic foraminifera species
diversity decreases upcore from approximately the turn of the century
to the present in a manner concurrent with glauconite and fertilizer
increases. A subset of opportunistic benthic foraminifera species,
known to become more prominent in stressed environments (i.e.,
hypoxic), increased upcore from ~52% of the total population at core
bottom to ~90% at core top. These benthic foraminifera population
and diversity changes were not apparent in a "control" core outside
the area of documented hypoxia. Seaward of the shelf, in the
Mississippi Canyon, coincident increases in sediment accumulation
rate, percentages of coarse fraction and of organic carbon at core
top indicate increased offshelf transport of carbon and other
components. Quartz percentages indicate that episodic down-canyon
transport has been active to core bottom (prior to the mid 1800s).
Nystuen, J.A., J.R. Proni, C.A. Lauter, Jr., J.M. Bufkin, U. Rivero,
M. Boland, and J.C. Wilkerson. APL disdrometer evaluation. NOAA
Technical Memorandum, ERL AOML-83 (PB95-181681), 48 pp. (1994).
The Ocean Acoustics Division at the Atlantic Oceanographic and Meteorological
Laboratory has evaluated a new disdrometer design developed by the Applied
Physics Laboratory of John Hopkins University. Modified electronics have been
added to the data processing circuitry to reduce temperature sensitivity and
increase the dynamic range of the instrument. Calibration was performed
using water drops from 0.6-5.5 mm diameter impacting the sensor head at
terminal velocity. Field comparison to a Joss-Waldvogel disdrometer shows
equal performance characteristics at low rainfall rates and slightly better
performance for rainfall rates above 100 mm/hr. Engineering circuit
design details and physical design of
the calibration apparatus are described.
Oost, W.A., C.W. Fairall, J.B. Edson, S.D. Smith, R.J. Anderson, J.A.M.
Wills, K.B. Katsaros, and J. DeCosmo. Flow distortion calculations and
their application to HEXMAX. Journal of Atmospheric and Oceanic
Technology, 11:357-365 (1994).
No abstract.
Ooyama, K.V. Another way of modeling the tropical cyclone.
Proceedings, International Meeting on Numerical Prediction of
Tropical Cyclones, Tokyo, Japan, January 17-21, 1994. Japan
Meteorological Agency, Tokyo, 233-237 (1994).
No abstract.
Ooyama, K.V. Hurricane track and intensity predictions at HRD.
Proceedings, International Meeting on Numerical Prediction of
Tropical Cyclones, Tokyo, Japan, January 17-21, 1994. Japan
Meteorological Agency, Tokyo, 85-89 (1994).
No abstract.
Palmer, D.R. Application of isoperimetric inequalities to the
problem of acoustic scattering from irregularly shaped objects.
Journal of the Acoustical Society of America, 95:3020-3021
(1994).
It is of general interest to determine the extent that acoustic
remote sensing can estimate physical properties of particulates
suspended in the ocean. One question that can be asked is how
well the concentration of particulates can be determined from
measurements of the backscattered acoustic intensity. When it
applies, Rayleigh scattering theory provides the relationship
between the concentration and the intensity. The assumption is
always made in application of the theory that the individual
scatterers can be regarded as spheres. While this assumption is
intuitively reasonable, it is desirable to have error estimates.
In this work, bounds are derived for the error that can occur in
mass-concentration estimates due to the spherical-scatterer
assumption. These bounds are obtained using the theory of
isoperimetric inequalities and are rigourous; depending only on
the validity of Rayleigh scattering theory. The formalism is
applied to the problem of estimating the concentration of
particulates in black smoker hydrothermal plumes.
Palmer, D.R. ATOC-FACT arrival-time differences. ATOC
Occasional Notes, No. 17, 5 pp. (1994).
No abstract.
Petty, G.W., and K.B. Katsaros. The response of the SSM/I to the marine
environment. Part 2: A parameterization of the effect of the sea surface
slope distribution on emission and reflection. Journal of Atmospheric
and Oceanic Technology, 11(3):617-628 (1994).
Based on a geometric optics model and the assumption of an isotropic
Gaussian surface slope distribution, the component of ocean surface
microwave emissivity variation due to large-scale surface roughness is
parameterized for the frequencies and approximate viewing angle of the
Special Sensor Microwave/Imager. Independent geophysical variables in the
parameterization are the effective (microwave frequency dependent) slope
variance and the sea surface temperature. Using the same physical model,
the change in the effective zenith angle of reflected sky radiation
arising from large-scale roughness is also parameterized. Independent
geophysical variables in this parameterization are the effective slope
variance and the atmospheric optical depth at the frequency in question.
Both of the above model-based parameterizations are intended for use in
conjunction with empirical parameterizations relating effective slope
variance and foam coverage to near-surface wind speed. These empirical
parameterizations are the subject of a separate paper.
Powell, M.D. The consensus standard for surface wind characterization:
Origin and implications for hurricane research and forecasting.
Minutes, 48th Interdepartmental Hurricane Conference, Miami, FL,
February 15-18, 1994. Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington, D.C.,
A22-A32 (1994).
No abstract.
Price, J.F., and M.O. Baringer. Overflows and deep water
production by marginal seas. Progress in Oceanography
33:161-200 (1994).
Outflows of dense water from marginal seas provide a continuous
renewal of the deep open ocean. Much of this water comes from
one of four major outflows (Mediterranean Sea, Weddell Sea, and two
from the Norwegian-Greenland Sea) that each have a characteristic
property signature. Here we examine some of the processes that set
these properties by reviewing historical data and by an analysis of
numerical simulations. Our simulation model makes several of the
streadtube approximations of Smith (1975), but goes on to include
a Froude number-dependent parameterization of entrainment, a
parameterization of broadening due to bottom drag, and it can accept
real bottom topography and oceanic temperature and salinity profiles.
This model is able to simulate some of the main features of each of
the outflows, including the source to product water conversion process.
The numerical simulation of the Mediterranean outflow is initialized
at the west end of the Strait of Gibraltar (T=13.4°C and S=37.8
ppt) and allowed to flow freely into the Gulf of Cadiz. Within the
first 50 km the outflow descends to about 600 m depth and accelerates
to a maximum speed of about 1.2 m/s. This raises the Froude number
above 1, and causes very strong entrainment of fresher, overlying
North Atlantic Central Water. Entrainment more than doubles the volume
transport and reduces the temperature and salinity to 12.4°C
and 36.5 ppt, which reduces the density by about 1 kg/m3.
Entrainment stops where the Coriolis force turns the outflow parallel
to the local topography. The Mediterranean outflow continues on to
Cape St. Vincent as a nearly geostrophic current that slowly descends
the continental slope until becoming neutrally buoyant at a depth of
about 1000 m, roughly consistent with the observed outflow. The other
three outflows show a somewhat similar pattern in that strong
entrainment generally occurs over short segments of the path where
the bottom topography is relatively steep, typically just beyond the
shelf-slope break. These outflows lose much less of their density
anomaly (about 0.03 kg/m3 in the Weddell Sea case, about
0.1 kg/m3 in the Denmark Strait case, and about 0.2
kg/m3 in the Faeroe Bank Channel case) and continue to
the bottom in their respective basins. They lose much less of their
initial density primarily because there is less density contrast
between these outflows and the overlying oceanic water; they reach
the bottom primarily because the oceanic water column in polar and
subpolar seas is very weakly stratified. This and other results
indicate that the properties of the oceanic water column are of
great importance in determining the product water of a marginal
sea outflow.
Proni, J.R., H. Huang, and W.P. Dammann. Initial dilution of
southeast Florida ocean outfalls. Journal of Hydraulic
Engineering, 120:1409-1425 (1994).
Initial dilutions of four ocean outfalls (the Miami-Central,
Miami-North, Hollywood, and Broward outfalls) on the east coast
of south Florida were determined from dye and salinity studies.
In the dye studies, continuous injections of the red dye
Rhodamine-WT into effluent were conducted; dye concentrations
were measured using a deck-mounted fluorometer with a ship-towed
sampler and from grab water samples. In the salinity studies,
temperature and conductivity were measured using a towed
conductivity-temperature-depth device (CTD); salinity deficit
was taken as a tracer to determine initial dilution. Results show
that initial dilutions determined from both methods are consistent.
Data for initial dilution and for environmental and effluent
parameters are interpreted using the dimensional analysis method.
A comparison is made between the present data and data from
previous studies. Data for Hollywood and Broward outfalls
(single-port discharges) are consistent with previous data. Data
for Miami-Central and Miami-North outfalls (multiport diffuser
discharges) are not consistent with data for single-port
discharges. A value of C1 = 0.15 for the asymptotic
solution for the buoyancy-dominated nearfield is suggested.
Pszenny, A.A., T.P. Carsey, P.-Y. Whung, M.P. Zetwo, M.L. Farmer, and
C.J. Fischer. Measurements of various chemical concentrations in the
marine boundary layer during the 1992 ASTEX/MAGE experiment. EOS,
Transactions, American Geophysical Union, 75:89 (1994).
No abstract.
Quilfen, Y., K.B. Katsaros, and B. Chapron. Remote sensing of extreme
events with satellite microwave sensors. Proceedings, Oceans '94
Conference, Brest, France, September 13-16, 1994. Institute of
Electrical and Electronics Engineers, New York, I-64-I-69 (1994).
Unprecedented views of surface wind and wave fields in tropical cyclones
(TC) are now provided respectively by the C-band (5.3 GHz) scatterometer
and Synthetic Aperture Radar (SAR) on the European Remote Sensing
Satellite-1 (ERS-1). Indeed, their signals at C-band are able to
penetrate the thick convective clouds of these storms, observing the wind
fields and directional wave spectra with good accuracy. Patterns of
sea-state and surface wind are described and compared with the
forecasting model of the European Centre for Range Medium Weather
Forecasts. It shows that this kind of strong mesoscale event is often
missed by the model, mainly due to the lack of input data and because TC
physics are not well understood. The use of microwave data allow greater
confidence and greater temporal and spatial coverage for monitoring TCs
over the open ocean. The combination of observations of different
parameters by several sensors is necessary for two reasons: (1) in order
to improve the understanding of feedback mechanism between the surface
wind and heat fluxes that govern the development and behavior of TC's;
(2) in order to know how the different parameters interact to modify the
radar measurements (e.g., influence of sea-state and atmospheric
water content on scatterometer wind measurements, knowledge of the wind
vector to resolve ambiguities in the wave directional spectrum as
measured by the SAR). Improvements of the actual scatterometer system are
discussed in order to define the best system for tropical cyclone
monitoring in the future.
Quilfen, Y., K.B. Katsaros, and B. Chapron. Surface wind fields
structures in tropical hurricanes surveyed by ERS-1 scatterance meters
and relationships with waves and atmospheric precipitations.
Proceedings, New Frontiers in Oceanic Remote Sensing, Paris, France,
December 17, 1993. Institut Oceanographique, Monaco, 13-22 (1994).
Signals emitted by satellite microwave radars are not affected by the
various precipitations, with special consideration at the rain. This is
specially true for the "Active Microwave Instrument" aboard the satellite
ERS-1 that emit signals in the C band (5.3 GHz). The functions of this
instrument are both as a scatterance meter of the wind and as a synthetic
aperture radar. It allows wind and waves imagery in the ocean surface,
even in regions where hurricanes and precipitations are very important. A
Special Sensor Microwave/Imager aboard a U.S. Department of Defense
satellite gives a survey of rainfall intensity, and gives also a
description of convective structures that may be related to the
divergence field of surface winds.
Rogers, R.F., J.M. Fritsch, and J.S. Kain. A new trigger function for
mesoscale convective systems. Preprints, 10th Conference on Numerical
Weather Prediction, Portland, OR, July 18-22, 1994. American
Meteorological Society, Boston, 105-107 (1994).
No abstract.
Saltzman, E.S., S.A. Yvon, D.J. Cooper, T.S. Bates, and A.M. Thompson.
Atmospheric dimethylsulfide cycling at a tropical South Pacific station
(12°S, 135°W): A comparison of field data and model results.
EOS, Transactions, American Geophysical Union, 75(16):82 (1994).
No abstract.
Schott, F., J. Reppin, E. Johns, and W.D. Wilson. Cross-equatorial warm
water transfer in the western tropical Atlantic. EOS, Transactions,
American Geophysical Union, 75(3):224 (1994).
No abstract.
Thacker, W.C., and R. Lewandowicz. Dynamics of information and
uncertainty. Tellus, 46A:651-670 (1994).
The question of what information might be inferred from a set of
data is posed in terms of the uncertainties of model variables
determined by a least-squares fit. When a dynamical model is
fitted to asynoptic data, the uncertainty can be characterized by
a region in the model's phase space surrounding the point
associated with the best fit. Changes in the shape and orientation
of this region as it evolves indicate how information is redistributed
dynamically among the model variables, much as kinetic and potential
energy might be redistributed. These ideas are illustrated within
the context of single and double oscillator systems. Information
about the state of a shallow-water model is shown to depend sensitively
on the sampling interval of fictitious altimetric data.
Thacker, W.C., and R. Raghunath. The rigid lid's contribution to
the ill-conditioning of oceanic inverse problems. Journal of
Geophysical Research, 99(C5):10,131-10,141 (1994).
Fitting oceanographic general circulation models to data is a
difficult computational undertaking. This paper addresses difficulties
stemming from the rigid lid approximation. Adjusting the barotropic
stream function to achieve the fit, in effect, requires the solution
of a hidden elliptical equation, the resolution-dependent difficulty
of the elliptical problem manifest in the optimization problem.
Adjusting the independent (subsurface) baroclinic velocity variables
also contributes to the ill-conditioning of the least squares
computation, but Lagrange multipliers can be used to adjust all
baroclinic velocity variables (surface and subsurface) symmetrically.
Similarly, Lagrange multipliers can be used to adjust the total
velocity variables, thereby circumventing the use of barotropic
stream function and baroclinic velocities; determining the multipliers
at each optimization iteration requires the solution of an
elliptical partial differential equation, the solution of which can
be thought of as a preconditioning transformation.
Trefry, J.H., S. Metz, T.A. Nelsen, R.P. Trocine, and B.J. Eadie.
Transport of particulate organic carbon by the Mississippi River
and its fate in the Gulf of Mexico. Estuaries, 17(4):839-849
(1994).
This study was designed to determine the amount of particulate
organic carbon (POC) introduced to the Gulf of Mexico by the
Mississippi River and assess the influence of POC inputs on the
development of hypoxia and burial of organic carbon on the
Louisiana continental shelf. Samples of suspended sediment and
supporting hydrographic data were collected from the river and
>50 sites on the adjacent shelf. Suspended particles collected
in the river averaged 1.8 ± 0.3% organic carbon. Because of
this uniformity, POC values (in µmol l-1) correlated
well with concentrations of total suspended matter. Net transport
of total organic carbon by the Mississippi-Atchafalaya River system
averaged 0.48 × 1012 moles y-1 with 66%
of the total organic carbon carried as POC. Concentrations of POC
decreased from as high as 600 µmol l-1 in the river
to <0.8 µmol l-1 in offshore waters. In contrast,
the organic carbon fraction of the suspended matter increased from
<2% of the total mass in the river to >35% along the shelf
at >10 km from the river mouth. River flow was a dominant factor
in controlling particle and POC distributions; however, time-series
datashowed that tides and weather fronts can influence particle movement
and POC concentrations. Values for apparent oxygen utilization (AOU)
increased from -60 µmol l-1 to >200 µmol
l-1 along the shelf on approach to the region of chronic
hypoxia. Short-term increases in AOU were related to transport
of more particle-rich waters. Sediments buried on the shelf
contained less organic carbon than incoming river particles. Organic
carbon and delta 13C values for shelf sediments indicated
that large amounts of both terrigenous and marine organic carbon are
being decomposed in shelf waters and sediments to fuel observed hypoxia.
Vaughan, S.L., and R.L. Molinari. Water mass variability in the Deep
Western Boundary Current: A comparison of results based on differencing
along isobars and isopycnals. EOS, Transactions, American
Geophysical Union, 75(44):396 (1994).
Changes in hydrographic properties between synoptic sections separated in
time can be estimated by differencing along either isobaric or isopycnal
surfaces. A time series of hydrographic data is available from 10 years
of repeat occupations of a section transversing the Deep Western Boundary
Current (DWBC) at 26.5°N. The series illustrates the potential
problems associated with using difference sections computed along
isobaric surfaces to assess changes in large scale water mass
characteristics. The magnitudes of differences along isobaric surfaces
were considerably greater than those calculated along isopycnal surfaces
between the same years. For June 1993 minus March 1987, for example,
maximum potential temperature (theta) and salinity (S) differences were
.25°C and .02 in the isobaric sections and .07°C and .01 in the
isopycnal sections. Most of the differences in the isobaric sections
were apparently due to vertical motion of the isopycnals and not to
actual changes in water mass characteristics. A method developed by
Bindoff and McDougall (JPO, 24, 1994) for distinguishing differences due
to changes in processes at the water mass source region (warming or
freshening) from vertical movement of the isopycnals ("heave") was
applied to several pairs of sections from the Abaco time series. Terms
representing changes in theta and S along both isobars and isopycnals
were calculated for the three cores of the DWBC, as defined by freon
concentrations, and plotted against one another. The high freon upper
(3.2-5.0°C) and deep (1.8-2.4°C) cores consist mainly of
recently ventilated high latitude water while the middle low freon core
(2.4-3.2°C) consists mainly of recirculated interior Atlantic
water. In the upper and middle layers, initial results were inconclusive,
but in the deep layer, in several pairs of sections, the dominance of the
"heave" process was evident along with some suggestion of changes in the
source regions.
Wakimoto, R.M., and P.G. Black. Damage survey of Hurricane Andrew
and its relationship to the eyewall. Bulletin of the American
Meteorological Society, 75(2):189-200 (1994).
A damage map documenting Hurricane Andrew's destructive landfall
over southern Florida is presented. Vectors that represent the
direction of winds causing damage to trees and structures are
shown along with an F-scale rating in order to assess the strength
of the near-surface winds. It is hypothesized that increased surface
roughness once the hurricane made landfall may have contributed to a
surface wind enhancement resulting in the strongest winds ever
estimated (F3) for a landfall hurricane. This intense damage
occurred primarily during the "second" period of strong winds
associated with the east side of the eyewall. For the first time,
a well-defined circulation in the damage pattern by the second
wind was documented. A superposition of radar data from Miami
and Key West on top of the damage map provides the first detailed
examination of the relationship between the eyewall and the
surface flow field as estimated from the damage vectors.
Wang, C., and R.H. Weisberg. Equatorially trapped waves of a coupled
ocean-atmosphere system. Journal of Physical Oceanography,
24(9):1978-1998 (1994).
Equatorially trapped waves of a simplified coupled ocean-atmosphere
system are described by applying the formalism for conventional
equatorially trapped waves with the assumption that the zonal wind stress
and sea surface temperature perturbations are proportional. In this
system, inertial-gravity and Rossby-gravity waves are unaffected by
coupling whereas Rossby and Kelvin waves are affected, and in the
low-frequency limit, these Rossby and Kelvin waves transform to slow
westward and eastward propagating wave modes, respectively. The primary
modifications by air-sea coupling are a decrease in phase speed and an
increase in meridional scale. The properties of these coupled waves are
useful in discussing several features, observed and modeled, relative to
the evolution of the El Niņo-Southern Oscillation.
Wang, C., and R.H. Weisberg. On the "slow mode" mechanism in
ENSO-related coupled ocean-atmosphere models. Journal of Climate,
7(11):1657-1667 (1994).
A linear perturbation, coupled ocean-atmosphere model is revisited for
further insights into El Niņo-Southern Oscillation phenomenon. The model
oscillates as a slow, eastward propagating mode interpreted as a
divergence mode, whose energetics are controlled by the ocean. Growth
requires that the work performed by the wind stress minus the work
required to effect the ocean divergence exceeds the loss terms. The
intrinsic scale of the atmosphere relative to the basin width is
important. For sustainable oscillations, the ocean basin must be large
enough so that oppositely directed divergence can develop on opposite
sides of the basin. The global aspect of the atmospheric pressure field
suggests that continental heating may provide either a direct source
affecting adjacent oceans, or a connection between oceans. The important
model parameters are the coupling and warming coefficients and the ocean
Kelvin wave speed. The importance of the Kelvin wave speed derives from
its specification of the background buoyancy state for the ocean. Upon
further simplification, an analytical solution gives simialr parameter
dependence as found numerically and shows that growth requires both large
zonal wavelength and a zonal phase lag between the anomalies of wind
stress and SST.
Watson, A.J., C.S. Law, K.A. Van Scoy, F.J. Millero, W. Yao,
G.E. Friederich, M.I. Liddicoat, R.H. Wanninkhof, R.T. Barber,
and K.H. Coale. Minimal effect of iron fertilization on
sea-surface carbon dioxide concentrations. Nature,
371:143-145 (1994).
No abstract.
Williams, R.G., and J.R. Proni. Acoustic remote sensing of
wastewater outflow. Seventh International Symposium on Acoustic
Remote Sensing and Associated Technologies of the Atmosphere and
Oceans, Boulder, CO, October 4, 1994. Boundary-Layer
Meteorology, Proceedings Volume, I-43-I-49 (1994).
The Ocean Acoustics Division of NOAA's Atlantic Oceanographic and
Meteorological Laboratory has been monitoring water currents in the
vicinity of a Miami municipal wastewater outfall three miles offshore
Virginia Key, Florida. An array of Aanderaa impeller-and-vane
current meters has been used to monitor current patterns for over
one year to determine pathways for the transport of the effluent
plume extending outward from the diffuser. NOAA's National Ocean
Service deployed a bottom-mounted 1200 kHz RD Instruments' acoustic
Doppler current profiler (ADCP) adjacent to the diffuser, at 20 m
depth. Mean profiles of current velocity and relative acoustic
backscatter were obtained at a vertical resolution of 1 meter, using
15-minute averages of 256 individual pings. Temporal patterns of
discharge were obtained from the ADCP; spatial patterns were obtained
by towing a 200 kHz acoustic echo sounder over the diffuser. The
correlation matrix computed from these data provides useful information
for delineating the plume in time and space. Additional bottom-mounted
ADCPs and acoustic tracklines would allow mapping of the plume from the
diffuser site to any nearby site of concern, thereby permitting
assessment of any possible environmental impact. This technology can
be readily applied to other sites in the U.S. and abroad.
Willis, P.T., J. Hallett, R.A. Black, and W. Hendricks. An aircraft
study of rapid precipitation development and electrification in a
growing convective cloud. Atmospheric Research, 33:1-24 (1994).
The rapid initial precipitation growth and initial electrification of
a convective cloud, growing as a new cell on the upshear side of
a cloud system in Florida, is traced from radar data and aircraft
penetrations at the -7°C to -10°C level. This study
combines radar, microphysical, and electrical measurements so that
an examination of the interactions between the cloud dynamics,
microphysics, and electrification is possible. The first pass
(-7°C) was characterized by a strong 23 m/s updraft, all
liquid cloud water, no precipitation, and no significant
electrification. In the 300 s between the two penetrations,
precipitation developed very rapidly from <15 dBZ to >45
dBZ, and the vertical component of the electric field increased from
below the measurement threshold to -25 kv/m. The second penetration,
which started at -7°C and ended at -10°C, was still exclusively
updraft, but with lesser peak velocities and a more complex structure;
i.e., no downdraft, but with relative minima in the updraft. The
microphysics of the second pass displayed a segment of exclusively cloud
liquid water (no precipitation size hydrometeors), a small segment of all
liquid precipitation size hydrometeors, a small region of mixed
hydrometeors and an extensive region of graupel hyrdometeors, ranging
in size from 100 µm to several mm. High cloud liquid water coexisted
with the liquid and graupel by hydrometeors in the strong updrafts. The
electrification was observed to occur exclusively in the segments
of the cloud pass where graupel were observed. Within this graupel
region, where the graupel often coexisted with supercooled cloud liquid
water, a significant electric field occurred only at relative minima in
the updraft. These relative velocity minima were also minima in the
cloud liquid water content. The observed updraft velocities in these
relative minima were close to balance velocities for the observed larger
graupel hydrometeors. The strongest updrafts, where the formation and
the riming growth of graupel was the greatest (maxima in cloud liquid water
content), were not the locations of significant electrification at this
flight level.
Willoughby, H.E. Nonlinear motion of a shallow water barotropic
vortex. Journal of Atmospheric Science, 51(24):3722-3744 (1994).
Nonlinear motions of a shallow water barotropic vortex on a beta
plane differ substantially from the analogous linear motions.
The nonlinear model described here, in which wavenumber 1-3
asymmetries interact with each other and the mean vortex, predicts
that an initially completely cyclonic vortex will accelerate toward
the north-northwest, reaching a speed of 2.5 m s-1 at 48
h. During the rest of the 240-h calculation, the speed varies by
<0.5 m s-1 as the direction turns from north-northwest
to northwest. The vortex accelerations are in phase with temporal
changes of vortex-relative angular momentum (LR). The
turning back of track coincides with a transition of the wavenumber
1 asymmetry from a single dipole to double dipole. The latter structure
appears to be another orthogonal solution of the second-order radial
structure equation for a neutral linear normal mode. The corresponding
linear model, in which forces only wavenumber 1, shows only the
single dipole structure and straight north-northwest accelerating
motion that reaches a speed of 9 m s-1 at 240 h. The
slower motion in the nonlinear model stems from wave-induced changes
in the axisymmetric vortex and vacillation between the orthogonal and
modal structures. A nonlinear calculation with zero initial
LR on a beta plane follows a curving path dictated by a
barotropically unstable linear mode for the first 144 h. Subsequently,
the double dipole structure for that mode appears as the track turns
toward the northwest and the speed accelerates from 1 to 2 m
s-1. A spatially uniform geostrophic environment on an
f plane causes vortex motion by advection and by propagation. The
potential vorticity (PV) gradient due to the current acts as much
as beta does. Although the PV gradient is typically 0.1 of that
due to beta, the induced propagation toward high potential vorticity
is 1/2-1/4 of that on a beta plane because superposition of the vortex
on a geopotential gradient amplifies the PV gradient's effect. In
a quiescent environment on an f plane, initial asymmetries that project
onto the normal modes induce long-lasting motion that retains about
half its speed to 240 h. If the initial speed is <2 m
s-1, vacillation between orthogonal modal structures may
cause dramatic turns and accelerations of the vortex track.
Willoughby, H.E. Nonlinear shallow-water vortex motion. In
Research Activities in Atmospheric and Oceanic Modelling,
G.J. Boer (ed.). CAS/JSC Working Group on Numerical Experimentation
Report No. 19, WMO/TD-No. 592, 5.37 (1994).
No abstract.
Willoughby, H.E. The Twentieth Conference on Hurricanes and
Tropical Meteorology. Bulletin of the American Meteorological
Society 75(4):601-611 (1994).
No abstract.
Wilson, W.D. Deep ocean current profiling with a lowered
broadband acoustic Doppler current profiler. Proceedings,
Oceans '94 Conference, Brest, France, October 1994. Institute of
Electrical and Electronics Engineers, New York, 660-665 (1994).
An RD Instruments 150 kHz broadband acoustic Doppler current
profiler (ADCP) has been mounted on a CTD frame and used to measure
current velocity shear below the instrument during casts as deep as
5500 m. By using processing techniques similar to those described
by Firing and Gordon for (1) a 300 kHz narrowband ADCP and Fischer
and Visbeck and (2) a 150 kHz narrowband ADCP, as well as some more
recently developed algorithms, the raw profiles are merged with CTD
data, corrected, edited, integrated, and averaged to produce unreferenced
profiles of current velocity. Using GPS navigation data and the measured
velocities, the profiles are referenced to produce absolute velocity
profiles for both the upcasts and downcasts. This paper describes data
collection and processing procedures, instrument settings, and
modifications made to the standard self-contained instrument to
accommodate an external, rechargeable battery pack. The absolute
velocity profiles obtained compare favorably with simultaneous Pegasus
measurements. During five such comparisons made on a cruise in the
equatorial Atlantic Ocean in June 1993, depth-averaged eastward and
northward velocity components agreed to an average of 0.3 cm
s-1 with an rms difference of 0.7 cm s-1;
absolute velocity comparisons between the instruments compare
favorably. The lowered ADCP (LADCP) provides full water column
absolute velocity profiles, coincident with CTD measurements, with
the accuracy of a Pegasus profiler. It has the advantage of not
requiring any extra shiptime and being independent of auxiliary
bottom-mounted hardware. For use in this application, the RD
Instruments high-powered 150 kHz broadband ADCP used seems to have
advantages over both the 150 and 300 kHz narrowband instruments.
Wilson, W.D., E. Johns, and R.L. Molinari. Upper ocean circulation
in the tropical North Atlantic Ocean in August 1989. EOS,
Transactions, American Geophysical Union, 75(3):224 (1994).
No abstract.
Wilson, W.D., E. Johns, and R.L. Molinari. Upper layer circulation
in the western tropical North Atlantic Ocean during August 1989.
Journal of Geophysical Research, 99(C11):22,513-22,523 (1994).
Shipboard acoustic Doppler current profiler (ADCP) current velocity
and CTD temperature, salinity, and dissolved oxygen measurements are
used to map the flow field above the sigmatheta = 26.8
isopycnal (approximately the upper 300 m of the water column) in the
North Brazil Current (NBC) retroflection region (0° to 14°N,
60° to 40°W) during August of 1989. The water column is
divided into a near surface, upper thermocline layer (above
sigmatheta = 24.5), and a main to sub-thermocline layer
(sigmatheta = 24.5 to sigmatheta = 26.8). In the
upper layer, the eastward flowing North Equatorial Countercurrent (NECC)
is composed of 16 × 106 m3/s of NBC transport
that has retroflected from the coast between 6°N and 8°N, and
8 × 106 m3/s of North Equatorial Current
(NEC) transport returning eastward. An anticyclonic eddy with a
10 × 106 m3/s transport lies northwest of
the NBC retroflection. No throughflow is observed along the boundary,
and only a small portion of the observed NEC transport (1.5 ×
106 m3/s) enters the Caribbean Sea. In the lower
layer, the NBC transports 8 × 106 m3/s into
the subthermocline North Equatorial Undercurrent (NEUC). In addition,
15 × 106 m3/s joins the NEUC from the north.
At 44°W the subsurface core of the NEUC lies south of the
near-surface core of the NECC. Nearly half of the NEUC transport is
made up of a mixed water type with salinity-oxygen (S-O2)
characteristics intermediate to the characteristics of the original
component transports. There is no evidence of continuous NBC flow into
the Caribbean Sea in the lower level. The closed eddy to the north of
the retroflection, however, contains water masses with South Atlantic
S-O2 properties.
Wilson, W.D., W.E. Johns, and M.D. Hendry. Measurements of current
structure and transport in the Windward Islands Passages: 1991-1993.
Proceedings, Principal Investigators Meeting, Princeton, New Jersey,
May 9-11, 1994. Atlantic Climate Change Program, 168-172 (1994).
No abstract.
Wilson, W.D., W.E. Johns, M.D. Hendry, and J.A. Routt. Windward
Island Passages Monitoring Program: Physical oceanographic data
collected on cruise WI-91-01, HMBS Trident, 15-21 December 1991.
NOAA Technical Memorandum, ERL AOML-76 (PB94-129079), 62 pp. (1994).
No abstract.
Wilson, W.D., W.E. Johns, J.A. Routt, and M.D. Hendry.
Windward Island Passages Monitoring Program: Physical oceanographic
data collected on cruises WI-02, HMBS Trident, 6-10 May 1992 and
WI-03, HMBS Trident, 19-23 September 1992. NOAA Technical
Memorandum ERL, AOML-79 (PB94-194131), 107 pp. (1994).
No abstract.
Yvon, S.A., E.S. Saltzman, and D.J. Cooper. The budget of sulfur
dioxide in the tropical South Pacific marine boundary layer (12°S,
135°W). EOS, Transactions, American Geophysical Union,
75(16):82 (1994).
No abstract.
Zhang, J.-Z., and F.J. Millero. Investigation of metal sulfide
complexes in seawater using cathodic stripping square wave
voltammetry. Analytica Chimica Acta, 284:497-504 (1994).
Cathodic stripping square wave voltammetry has been used to detect
H2S in seawater over a wide range of concentrations (nM to
mM). The addition of metal ions to the solutions was found to depress
the signal. This depression was attributed to the formation of metal
sulfide complexes [MHS+, M(HS)2]. Stability
constants for the formation of sulfide complexes with Cd2+,
Cu2+, Cu+, Pb2+, Zn2+,
Co2+, Fe2+, Mn2+, Ni2+,
and Hg2+ have been estimated in sea water at pH 8.0 and
25°C using this method. The stability constants of cadmium
sulfide complexes (log betaCdHS = 6.3 and
log betaCd(HS)2 = 12.7) were found to be in reasonable
agreement with previous measurements. The values of log
betaCuHS = 7.0 and log betaCu(HS)2 = 13.0;
log betaPbHS = 7.1 and log betaPb(HS)2 = 13.5;
log betaZnHS = 6.0 and log betaZn(HS)2 = 13.7;
log betaFeHS = log betaCo(HS) = log
betaNiHS = 5.3 and log betaMn(HS) = 6.7 were
also obtained. Correction for the formation of strong chloro
complexes for Hg2+ and Cu+ in seawater gave
measured values close to the literature values. The results have
been used to determine the speciation of HS- in surface
seawater and of a number of metal ions in various anoxic basins.
Zhang, J.-Z., and F.J. Millero. Kinetics of oxidation of hydrogen
sulfide in natural waters. In Environmental Geochemistry of
Sulfide Oxidation, C.N. Alpers and D.W. Blowes (eds.). ACS
Symposium Series 550, American Chemical Society, Washington, D.C.,
393-409 (1994).
Recently we have studied the oxidation of H2S with
O2 in natural waters as a function of pH (4 to 10),
temperature (278.15 to 338.15 K), and salinity (0 to 36). The
major products formed from the oxidation of H2S were
SO32-, S2O32-,
and SO42-. A kinetic model was developed to
predict the distribution of the reactants and products over a wide
range of conditions. Dissolved and particulate metals have a
significant effect on the rates of oxidation and the product
formation. Field measurements made in the Black Sea, Framvaren
Fjord, Chesapeake Bay, and Cariaco Trench are in reasonable
agreement with the values predicted from laboratory studies at
the same concentration of Fe2+.
**1993**
Aberson, S.D., M. DeMaria, and R.E. Kohler. A four year (1989-1992)
sample of a nested barotropic hurricane track forecast model
(VICBAR). Preprints, 20th Conference on Hurricanes and Tropical
Meteorology, San Antonio, TX, May 10-14, 1993. American
Meteorological Society, Boston, 292-295 (1993).
No abstract.
Bergamasco, A., P. Malanotte-Rizzoli, W.C. Thacker, and R.B. Long.
The seasonal steady circulation of the eastern Mediterranean determined
with the adjoint method. Deep-Sea Research, 40(6):1269-1298
(1993).
In this paper we use a rather unconventional approach to determine the
steady seasonal circulation of the eastern Mediterranean. Traditional
calculations rely either on prognostic models spun-up with different
forcing functions or on inverse methods having rather simple dynamics.
In the present applications one of the most sophisticated inverse
techniques, the adjoint method of control theory, is used to find the
model state that is optimally consistent with the model dynamics, with
a prescribed climatology and is steady in time. The model used is the
GFDL primitive equation model in its fully time-dependent non-linear
version forced by seasonal wind-stress fields that are kept steady for
each calculation. The prescribed climatology consists of the seasonal
hydrographies of the temperature and salinity fields. Steadiness upon
the seasonal time scale is required as a term in the cost function of
the adjoint that penalizes the tendencies of the prognostic variables.
This use of the adjoint method reconstructs the steady seasonal
wind-driven circulation in an ocean with a prescribed baroclinic
structure. As such, it is equivalent to a prognostic spin-up
calculation with steady winds and the robust diagnostic applied,
i.e., adding a term that relaxes the temperature and salinity
fields to the seasonal climatologies with a time constant of three
months. To assess the "success" of these calculations, the success of
the inversion must be quantified. The examination of the final data
misfits and steady state residuals shows that steady state has indeed
been reached. The steady-state residuals are always much smaller than
the data misfits and both of them are always small, well below the one
standard deviation value for each field. Thus, we can assess that a
meaningful solution had indeed been attained. To assess further if
these solutions are reasonable, we have carried out for comparison
robust diagnostic calculations with a time constant of three months.
The circulations thus obtained are extremely similar to the adjoint
solutions in reproducing the overall patterns as well as the individual
sub-basin scale gyres and interconnecting currents and meandering
jets. The circulations obtained with the two approaches are also equally
strong. However, both the adjoint and the robust diagnostic results
produce an overall barotropic transport that is one order of magnitude
bigger than that observed. They also both show anomalously strong vortex
structures in regions of sharp topographic breaks connecting the deep
interior to the shelves, for which no observational evidence is available.
These unrealistic features can be explained by taking into account that
with the short time scale of three months used in both approaches biased
solutions may be obtained. These biases are due to inconsistencies between
the rough topography used and the smooth climatologies, that lead to a
misrepresentation of the important JEBAR effect. This explanation is
supported by a further robust diagnostic calculation in which the time
constant is increased in the deep layers that gives a circulation
intensity much more realistic.
Bitterman, D.S., and D.V. Hansen. Evaluation of sea surface
temperature measurements from drifting buoys. Journal of
Atmospheric and Oceanic Technology, 10(1):89-96 (1993).
Three drift-buoy designs have been deployed since 1988 in substantial
numbers in the tropical Pacific Ocean by United States participants as
part of the Tropical Ocean Global Atmosphere (TOGA) Pan Pacific
Surface Current Study. These include the Low Cost Tropical Drifter
designed and built at the Atlantic Oceanographic and Meteorological
Laboratory, the Low Cost Drifter (LCD) designed and built by the
Massachusetts Institute of Technology Draper Laboratories, and the
Ministar Drifter designed and built at the Scripps Institution of
Oceanography and built by Technocean Inc., San Diego, California, which
has subsequently become known as the World Ocean Climate Experiment
standard drifter. This report contains an evaluation of the performance
of the sea surface temperature measurement system carried by these
buoy designs. Based on comparisons of the monthly mean SST derived
from the available XBT and CTD casts and on intercomparisons among
each of the buoy types, all three designs appear to include a warm
bias in the surface temperatures they report. The LCD showed a larger
mean bias and diurnal variation from solar heating than the other two
buoy types. This difference is probably due to the location chosen
for its sensor, resulting in poor thermal contact with the surrounding
water.
Black, M.L. Comparisons of tropical cyclone intensity with eyewall
vertical velocities. Preprints, 20th Conference on Hurricanes and
Tropical Meteorology, San Antonio, TX, May 10-14, 1993. American
Meteorological Society, Boston, 520-523 (1993).
No abstract.
Black, M.L., and P.P. Dodge. Time-lapse radar images of
Hurricanes Hugo (1989) and Andrew (1992). Preprints, 26th
International Conference on Radar Meteorology, Norman, OK,
May 24-28, 1993. American Meteorological Society, Boston,
97-99 (1993).
No abstract.
Black, P.G., and A.V. Litinetski. Mesoscale fields in Hurricane Gilbert
according to data measurements by airborne meteorological laboratories.
Meteorology and Hydrology (in Russian), 2:27-37 (1993).
No abstract.
Black, R.A., J. Hallett, and C.P.R. Saunders. Aircraft studies of
precipitation and electrification in hurricanes. Preprints, Conference
on Atmospheric Electricity, St. Louis, MO, October 4-8, 1993. American
Meteorological Society, Boston, J20-J25 (1993).
No abstract.
Black, R.A., P.T. Willis, and J. Hallett. The development of ice
particles and the establishment of electric fields in a maritime
tropical cumulus cloud. Preprints, 20th Conference on Hurricanes
and Tropical Meteorology, San Antonio, TX, May 10-14, 1993.
American Meteorological Society, Boston, 81-84 (1993).
No abstract.
Bliven, L.F., J.-P. Giovanangeli, R.H. Wanninkhof, and B. Chapron.
A laboratory study of friction-velocity estimates from scatterometry:
Low and high regimes. International Journal of Remote Sensing,
14(9):1775-1785 (1993).
Measurements from scatterometers pointing at wind-waves in three
large wave-tanks are examined to study fetch effects and the
correlation with wind friction-velocity u*. Time-series
measurements were made at 13, 35, and 95 m with a Ka-band
scatterometer aimed upwind at 30° incidence angle and vertical
polarization. Average normalized radar cross-section sigma-o values
from all fetches follow a common trend for sigma-o as a function of
u*, so the fetch dependence is negligible. An empirical
power-law model yields a high correlation between sigma-o and
u*, but because systematic anomalies arise, we re-examine
a turbulence approach that delineates low and high regimes with
a transition at u* of approximately 25 cm s-1.
Using this criteria, the data are well represented by a two-section
power-law relationship between sigma-o and u*.
Broecker, W.S., and T.-H. Peng. Evaluation of the 13C constraint
on the uptake of fossil fuel CO2 by the ocean. Global
Biogeochemical Cycles, 7(3):619-626 (1993).
The proposal by Quay et al. (1992) that the time histories of
13C in atmospheric CO2 and oceanic SIGMA
CO2 provide a constraint on the magnitude of uptake of fossil
fuel CO2 by the ocean is examined. Our analysis suggests that,
while the potential is there, the data base is too inaccurate to permit a
distinction to be made among the carbon budgets currently on the table.
Examples are given to demonstrate that the twenty or so percent
uncertainties in the size of the effective exchange reservoir and in the
magnitudes of the temporal changes in the 13C/12C
ratio in atmospheric CO2 and ocean SIGMA CO2 are
just too large to permit a reliable estimate of oceanic uptake of fossil
fuel CO2. We conclude that tracer-verified ocean general
circulation models offer much better estimates than that based on the
13C budget.
Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles. Eldigio Press,
Lamont-Doherty Earth Observatory, Columbia University, Palisades, New
York, 251 pp. (1993).
No abstract.
Broecker, W.S., and T.-H. Peng. Interhemispheric transport of carbon
through the ocean. In The Global Carbon Cycle, M. Heimann (ed.).
Springer-Verlag, Berlin, 551-570 (1993).
No abstract.
Broecker, W.S., and T.-H. Peng. What caused the glacial to interglacial
CO2 change? In The Global Carbon Cycle, M. Heimann
(ed.). Springer-Verlag, Berlin, 95-115 (1993).
Scenarios put forward to explain the 80 µatm glacial to interglacial
change in atmospheric CO2 content are evaluated. The
conclusion is that no single mechanism is adequate. Rather, contributions
from temperature, sea ice, biological pumping, nutrient deepening, and
CaCO3 cycling must be called upon. The observation that the
13C/12C ratio for Antarctic foraminifera was 0.9
± 1o/oo lower during glacial than during
interglacial time constitutes a huge fly in the ointment for all
scenarios proposed to date.
Broecker, W.S., Y. Lao, M. Klas, E. Clark, G. Bonani, S. Ivy, and
T.-H. Peng. A search for an Early Holocene CaCO3
preservation event. Paleoceanography, 8(3):333-339 (1993).
No abstract.
Broecker, W.S., G. Ostlund, S. Sutherland, T.-H. Peng, T. Takahashi,
and W. Smethie. Radiocarbon Atlas, Volume I: Thermocline of the
Atlantic Ocean. Lamont-Doherty Earth Observatory, Palisades, New
York (1993).
No abstract.
Broecker, W.S., G. Ostlund, S. Sutherland, T.-H. Peng, T. Takahashi,
and W. Smethie. Radiocarbon Atlas, Volume II: Thermoclines of the
Pacific and Indian Oceans. Lamont-Doherty Earth Observatory,
Palisades, New York (1993).
No abstract.
Brundrit, G., L. Krige, D.R. Palmer, J. Penrose, A. Forbes, and
K. Metzger. Acoustic thermometry of ocean climate: Feasibility,
Ascension-Cape Town. Second International Meetingon Global Acoustic
Monitoring of the Ocean, Brest, France, June 20-22, 1993. Institut
Francais de Recherche Pour l'Exploitation de la Mer (IFREMER), 8-10
(1993).
No abstract.
Cione, J.J., S. Raman, and L.J. Pietrafesa. The effect of Gulf
Stream-induced baroclinicity on U.S. east coast winter cyclones. Monthly
Weather Review, 121:421-430 (1993).
No abstract.
Claud, C., N.M. Mognard, K.B. Katsaros, A. Chedin, and N.A. Scott.
Satellite observations of a polar low over the Norwegian Sea by Special
Sensor Microwave Imager, Geosat, and TIROS-N Operational Vertical
Sounder. Journal of Geophysical Research, 98(C8):14,487-14,501
(1993).
Many polar lows are generated at the boundary between sea ice and the
ocean, in regions of large temperature gradients, where in situ
observations are rare or nonexistent. Since satellite observations are
frequent in high-latitude regions, they can be used to detect polar lows
and track their propagation and evolution. The Special Sensor
Microwave/Imager (SSM/I) providing estimates of surface wind speed,
integrated cloud liquid water content, water vapor content, and
precipitation size ice-scattering signal over the ocean; the Geosat radar
altimeter measuring surface wind speed and significant wave height; and
the TIROS-N Operational Vertical Sounder (TOVS) allowing the
determination of temperature and humidity profiles in the atmosphere have
been used in synergy for a specific case which occurred in the Norwegian
Sea on January, 23-24 1988. All three instruments show sharp atmospheric
gradients associated with the propagation of this low across the ocean,
which permit the detection of the polar low at a very early stage and
tracking it during its development, propagation, and decay. The wind
speed gradients are measured with good qualitative agreement between the
altimeter and SSM/I. TOVS retrieved fields prior to the formation of the
low confirm the presence of an upper level trough, while during the
mature phase baroclinicity can be observed in the 1000-500 hPa
geopotential thicknesses. Comparisons between satellite-retrieved
products and analyses of the operational Norwegian limited area model
(150- and 50- km mesh) highlight the importance of satellites for the
monitoring of such mesoscale phenomena.
Clayton, T., P. Murphy, M.F. Lamb, F.J. Millero, R.H. Byrne, R.H.
Wanninkhof, and R.A. Feely. The internal consistency of CO2
measurements in the equatorial Pacific. Marine Chemistry,
44(2-4):269-280 (1993).
During a recent NOAA JGOFS equatorial Pacific cruise, all four
analytical parameters of the carbonate system were measured: pH,
total alkalinity (TA), total carbon dioxide (TCO2), and
the fugacity of carbon dioxide (fCO2). The measurements
made during leg 2 on surface waters have been used to examine the
internal consistency of the carbon dioxide system in these waters.
The internal consistency of the measurements was examined by using
various inputs of the measured parameters (pH-TA, pH-TCO2,
pH-fCO2, fCO2-TCO2, and
TA-TCO2) to calculate the components of the CO2
system. The results indicate that the measurements have an internal
consistency of ±0.003-0.006 in pH, ±5-7 µmol kg-1
in TCO2, and ±6-9 µAtm in fCO2 if reliable
constants are used for the dissociation of carbonic acid in seawater.
These results indicate that our present understanding of the thermodynamics
of the carbonate system in seawater is close to the present accuracy in
measuring the various parameters of the system (±0.0002 in pH, ±4
µmol kg-1 in TA, ±2 µmol kg-1
in TCO2, and ±2 µAtm in fCO2).
Commons, D.N., J.R. Proni, H. Huang, W.P. Dammann, B.M. Goldenberg, J.G.
Monsoon, and R.E. Fergen. Real world toxicity testing of an open ocean
discharger. Proceedings, 66th Annual Conference and Expedition, Anaheim,
CA, October 3-7, 1993. Water Environment Federation, 26 pp. (1993).
A study, called the Southeast Florida Outfall Experiment II (SEFLOE II),
was conducted from February 1991 through August 1992 at four open ocean
outfalls. The objective of the study was to assess the effect of the
Florida Current and coastal oceanographic characteristics upon the
surfacing effluent plumes. During the study, the results from laboratory
bioassays on plant effluent samples were compared with results from
bioassays on contemporaneous ocean dispersion plume samples. Acute
bioassay species used were the mysid Mysidopsis bahia and the
estuarine fish Menidia beryllina. The sea urchin Arbacia
punctulata and the macroalga Champia parvula were the species
used in short-term chronic bioassays during the SEFLOE II study. The
results of this comparison indicate a disparity between exposure times
and dilutions in laboratory bioassays, and those exposure times and
dilutions actually demonstrated in the receiving waters.
DeMaria, M., and R.W. Jones. Optimization of a hurricane track
forecast model with the adjoint model equations. Monthly
Weather Review, 121(6):1730-1745 (1993).
The method of model fitting, or "adjoint method," is tested in a
barotropic hurricane track forecast model. The model vorticity
field at the beginning of an assimilation period is adjusted to
minimize a cost function that is defined as the squared difference
between the model vorticity and the vorticity from a sequence of
analyses separated by 12 h. After the cost function is minimized,
the model vortex closely follows the observed storm track during
the assimilation period, indicating that information about the past
track of the storm is being included in the model solution. Track
forecasts using the assimilation procedure are compared with control
forecasts where the model is initialized with a single analysis at
the end of the assimilation period. Results from a series of 18
forecasts for Hurricane Hugo (1989) show that within a 12-h
assimilation period the average track forecast errors are smaller
than those of the control forecasts out to about 48 h. The forecast
errors using a 24-h assimilation period are larger than the errors with
a 12-h assimilation period. The method described by Derber in which
a forcing term that minimizes the cost function is added to the
vorticity equation is applied to extend the length of the assimilation
period. The forcing function has very localized extrema in the vicinity
of the vortex because the scale of the vortex is comparable with the
distance that the vortex moves during the assimilation period. This
localized forcing interferes with the subsequent motion of the storm
during the forecast period. The magnitude of the localized forcing is
reduced if the vorticity at the beginning of the assimilation period
is first adjusted, and then the forcing term is added to further
reduce the cost function. When the combined procedure is used, the
average track errors are smaller than the errors in the control
simulations out to 72 h. Forecasts from four additional storms from
the 1989 Atlantic hurricane season are also presented. In two of these
cases, the assimilation degrades the control forecasts. The
degradation appears to be related to errors in the operational
estimates of the storm positions and to poor first-guess fields used
in the analyses.
DeMaria, M., and J. Kaplan. Verification of a statistical hurricane
intensity prediction model. Preprints, 20th Conference on Hurricanes
and Tropical Meteorology, San Antonio, TX, May 10-14, 1993. American
Meteorological Society, Boston, 303-304 (1993).
No abstract.
DeMaria, M., J.J. Baik, and J. Kaplan. Upper-level eddy angular
momentum fluxes and tropical cyclone intensity change. Journal
of the Atmospheric Sciences, 50(8):1133-1147 (1993).
The eddy flux convergence of relative angular momentum (EFC) at
200 mb was calculated for the named tropical cyclones during the
1989-1991 Atlantic hurricane seasons (371 synoptic times). A period
of enhanced EFC within 1500 km of the storm center occurred about
every five days due to the interaction with upper-level troughs in
the midlatitude westerlies or upper-level, cold lows in low
latitudes. Twenty-six of the 32 storms had at least one period
of enhanced EFC. In about one-third of the cases, the storm
intensified just after the period of enhanced EFC. In most of the
cases in which the storm did not intensify, the vertical shear
increased, the storm moved over cold water, or the storm became
extratropical just after the period of enhanced EFC. A
statistically-significant relationship (at the 95% level) was found
between the EFC within 600 km of the storm center and the
intensity change during the next 48 h. However, this relationship
could only be determined using a multiple regression technique that
also accounted for the effects of vertical shear and sea surface
temperature variations. The EFC was also examined for the ten storms
from the 1989-1991 sample that had the largest intensification rates.
Six of the ten periods of rapid intensification were associated with
enhanced EFC. In the remaining four cases the storms were intensifying
rapidly in a low-shear environment without any obvious interaction
with upper-level troughs.
Dodge, P.P., M.L. Black, P.A. Leighton, B.A. Christoe, F.D. Marks, and
R.W. Burpee. Time-lapse radar images of Hurricane Andrew's
landfalls. Preprints, 20th Conference on Hurricanes and Tropical
Meteorology, San Antonio, TX, May 10-14, 1993. American Meteorological
Society, Boston, 163-166 (1993).
No abstract.
Dodge, P.P., and R.W. Burpee. Characteristics of rainbands, radar
echoes, and lightning near the North Carolina coast during GALE.
Monthly Weather Review, 121(7):1936-1955 (1993).
Characteristics of mesoscale rainbands and echoes in radar reflectivity
data recorded during the field phase of the Genesis of Atlantic Lows
Experiment (GALE) are presented. The primary sources of data were radar
microfilm and manually-digitized radar (MDR) reports from the operational
National Weather Service (NWS) radars at Cape Hatteras (HAT) and
Wilmington (ILM), North Carolina. The data set also included
cloud-to-ground lightning flashes that were recorded by the network
operated by the State University of New York at Albany. The analyses
included rainbands of at least 90-km length with lifetimes of at least
2 h. Nearly all of the rainbands were within 400 km of synoptic-scale
or coastal fronts. Warm-sector rainbands predominated. Rainbands were
classified by the location of their initial detection relative to the
land, coastal shelf, and Gulf Stream. Rainbands were initially
identified more frequently over the Gulf Stream and less often over
the coastal shelf than the corresponding fractional areas monitored
by the radars. Statistical tests determined significant differences in
the sample means of the MDR and lightning data between the Gulf
Stream and land regions that were largely a consequence of many more
hours with MDR and lightning over the Gulf Stream. Composites relative to
the beginning and ending of the rainband cases indicated that
differences between the Gulf Stream and land were small shortly after the
initial detection of rainbands and large just before the detection of
rainbands. The largest Gulf Stream-land disparities occurred, on the
average, during low-level cold and dry advection at HAT. Trunk and Bosart
reported a convective echo maximum over the Gulf Stream near HAT and
discussed physical processes that can account for the convective maximum.
Analysis of one idealized distribution of convection, however, supports
the likely role of sampling limitations of the NWS radar network in
determining the location of the convective echo maximum near HAT.
Fine, R.A., E. Johns, and R.L. Molinari. Deep Western Boundary Current
structure in the region of the Blake-Bahama outer ridge. Proceedings,
Principal Investigators Meeting of the Atlantic Climate Change Program,
Miami, FL, March 9-11, 1992. NOAA Climate and Global Change Program,
Special Report No. 7, 137-142 (1993).
No abstract.
Franklin, J.L., S.J. Lord, S.E. Feuer, and F.D. Marks. Multi-scale
objective kinematic analyses and the motion of Hurricane Gloria (1985).
Preprints, 20th Conference on Hurricanes and Tropical Meteorology,
San Antonio, TX, May 10-14, 1993. American Meteorological Society, Boston,
537-540 (1993).
No abstract.
Franklin, J.L., S.J. Lord, S.E. Feuer, and F.D. Marks. The kinematic
structure of Hurricane Gloria (1985) determined from nested analyses of
dropwindsonde and Doppler radar data. Monthly Weather Review,
121(9):2433-2451 (1993).
A set of three-dimensional, filtered, multiple-nested objective
analyses has been completed for the wind field of Hurricane
Gloria for 0000 UTC 25 September 1985. At this time Gloria
was one of the most intense hurricanes ever observed in the
Atlantic basin, with a minimum sea level pressure of 919 mb.
The nested analyses, based on observations from airborne
Doppler radar and Omega dropwindsondes, simultaneously
describe eyewall and synoptic-scale features, and are the most
comprehensive analyses of a single hurricane constructed to
date. The analyses have been used to document the multiscale
kinematic structure of Gloria and to investigate the relationship
between the kinematic fields and the motion of the vortex. The
analyses indicate that the vortex was unusually barotropic. The
radius of maximum wind (RMW) was nearly vertical below 500
mb, with a slight inward slope with heights between 750 and
550 mb. The strongest azimuthal mean tangential winds were
found well above the boundary layer, near 550 mb, where the
RMW was smallest. We speculate that this unusual structure
was associated with a concentric eye cycle. A persistent
asymmetry in the distribution of eyewall convection was associated
with the vertical shear of the environmental flow. The vortex
moved approximately 2.5 m s-1 faster than
the deep layer mean flow averaged at 667 km radius from
the center. Barotropic models have predicted a relationship
between the relative motion of the vortex and the gradients
of absolute vorticity in the cyclone's environment; however,
the predicted relationship was not found in Gloria. The vortex
also did not move with the mean flow in the immediate vicinity
of the center; the motion of the hurricane was most consistent
with the 300-850 mb layer mean flow well outside the eyewall,
at a radius of 65 km. The analyses suggest that the environmental
flow near the center had been distorted by eyewall convection,
with the scale of the distortion determined by the local Rossby
radius of deformation.
Friedman, H.A. 1993 Hurricane Field Program Plan. U.S. Department
of Commerce, NOAA/Atlantic Oceanographic and Meteorological Laboratory,
Miami, Florida (published for limited distribution), 121 pp. (1993).
No abstract.
Gamache, J.F. The angular momentum of the hurricane inner core as
observed by airborne Doppler radar. Preprints, 20th Conference on
Hurricanes and Tropical Meteorology, San Antonio, TX, May
10-14, 1993. American Meteorological Society, Boston, 533-536
(1993).
No abstract.
Gamache, J.F. The effect of global positioning satellites upon the
accuracy of dual-aircraft Doppler observations. Preprints, 26th
International Conference on Radar Meteorology, Norman, OK, May 24-28,
1993. American Meteorological Society, Boston, 402-403 (1993).
No abstract.
Gamache, J.F., R.A. Houze, Jr., and F.D. Marks. Dual-aircraft
investigation of the inner core of Hurricane Norbert. Part III:
Water budget. Journal of the Atmospheric Sciences,
50(19):3221-3243 (1993).
The hydrometeor water budget of Hurricane Norbert on 24 September 1984
is computed using two microphysical retrieval techniques. Three-dimensional
distributions of condensation, evaporation, precipitation, and
advection of cloud and precipitation are computed, and a bulk water
budget is computed as the volume integral of these distributions. The
role of the microphysical retrievals is to provide the three-dimensional
distribution of cloud water content, since it cannot be determined with the
equipment available. Both retrieval methods use the steady-state
continuity equation for water. The first method determines precipitation
formation mechanisms from the radar-reflectivity and Doppler wind fields.
The cloud water content is determined, through microphysical modeling,
to be the amount necessary to explain the rate of precipitation formation.
The second method (that of Hauser et al.) solves the water continuity
equations as a boundary value problem, while also employing microphysical
modeling. This method is applied in three dimensions for the first time.
Asymmetries in the water budget of Hurricane Norbert were important,
apparently accounting for nearly half of the net condensation. The most
condensation and heaviest precipitation was to the left of the storm track,
while the strongest evaporation was to the rear of the storm. Many of the
downdrafts were unsaturated because they were downwind of the precipitation
maximum where little water was available for evaporation. Since
evaporation in the downdrafts was significantly less than the condensation
in their counterpart updrafts, net condensation (bulk condensation-bulk
evaporation) was significantly greater than would be implied by the net
upward mass flux. Much of the vapor required to account for the greater
bulk condensation appears to have come from enhanced sea surface
evaporation under the dry downdraft air to the right of the storm track.
The net outflow of condensate from the storm inner core was quite small,
although there were appreciable outward and inward horizontal fluxes at
certain locations. A maximum of ice outflow to the left of the storm
track in front of the storm corresponded well to the ice particle
trajectories that Houze et al. suggested were feeding the stratiform
precipitation found farther outward from the storm center.
Garzoli, S.L. Geostrophic velocity and transport variability in the
Brazil-Malvinas Confluence. Deep-Sea Research, 40(7):1379-1403
(1993).
This paper presents the results from a study of the dynamics of the
Brazil-Malvinas Confluence in the southwestern Atlantic based on data
collected with an array of inverted echo sounders. Dynamic height series
were obtained at 10 different sites for a period of 15 months. The
data are analyzed in terms of dynamic height, geostrophic velocities,
and transports. The large variability previously inferred from
satellite observations is observed in the dynamic height field of the
surface, relative to 100 m, and is attributed to changes in the latitude
of separation, the meandering of the Confluence front towards the east,
and eddy generation. The eddy circulation observed is both cyclonic
and anticyclonic. These eddies are observed both between the southward
edge of the Brazil Current and the northward edge of the Malvinas
Current and superimposed to the main flows. The diameter of the eddies
is two to three times the Rossby radius of deformation. The highest
observed values of the geostrophic velocities (102 cm/s at 36.5°S
and -61 to -62 cm/s at 37.6°S) are associated with the large shear
in frontal situations. The northward penetration of the Malvinas Current
occurs during 1988 and 1990 during the southern hemisphere winter. This is
in agreement with results from a previous deployment, satellite
observations, and model results. The Brazil Current transport is at
35.2°S and 36.5°S, -24 Sv towards the south and -20 Sv between
37.7°S and 38°S (reference 1000 m). The transport of the Brazil
Current return at 35.2°S is of the same value as the southward flow:
24 Sv. For the Malvinas Current, the estimates indicate a northward
transport of 5 Sv at 37.7°S (reference 1000 m). These values are
considered as a lower limit. The array captured only about half the flow
due to the location of the deployments, and only the baroclinic component.
The transport should be at least doubled to compensate the value obtained
for the Malvinas return flow at the same latitudes, -24 Sv.
Goldenberg, S.B., and L.J. Shapiro. Relationships between tropical
climate and interannual variability of North Atlantic tropical cyclones.
Preprints, 20th Conference on Hurricanes and Tropical Meteorology,
San Antonio, TX, May 10-14, 1993. American Meteorological Society,
Boston, 102-105 (1993).
No abstract.
Gray, W.M., and C.W. Landsea. Examples of the large modification in U.S.
east coast hurricane spawned destruction by prior occurring west African
rainfall conditions. ICSU/WMO International Symposium on Tropical Cyclone
Disasters, October 12-16, 1992, Beijing, China. J. Lighthill, Z. Zhemin,
G. Holland, and K. Emanuel (eds.), Peking University Press, 182-189 (1993).
This paper discusses the surprisingly strong prediction (by 1 August)
relationship which exists between west African rainfall and U.S. hurricane
spawned destruction along the U.S. east coast and peninsula Florida for
the period 1950-1991. Ninety-eight percent of such damage occurs after
this data. Over four-fifths of east coast hurricane-spawned damage
occurs during the highest third rainfall years. The last quarter century
western Sahel drought has caused a large reduction in U.S. east coast
hurricane damage.
Gray, W.M., and C.W. Landsea. West African rainfall and Atlantic basin
intense hurricane activity as proxy signals for Atlantic conveyor belt
circulation strength. Preprints, 4th Symposium on Global Change,
Anaheim, CA. American Meteorological Society, Boston (1993).
No abstract.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Predicting Atlantic
basin seasonal tropical cyclone activity by 1 August. Weather and
Forecasting, 8(1):73-86 (1993).
More than 90% of all seasonal Atlantic tropical cyclone activity occurs
after 1 August. A strong predictive potential exists that allows seasonal
forecasts of Atlantic basin tropical cyclone activity to be issued by 1
August, prior to the start of the active portion of the hurricane season.
Predictors include June-July meteorological information of the
stratospheric quasi-biennial oscillation (QBO), west African rainfall, the
El Niño-Southern Oscillation (ENSO), as well as sea level pressure
anomalies (SLPA), and the upper-tropospheric zonal-wind anomalies (ZWA) in
the Caribbean basin. Use of a combination of these global and regional
predictors provides a basis for making cross-validated (jackknifed) 1
August hindcasts of subsequent Atlantic seasonal tropical cyclone activity
that show substantial skill over climatology. This relationship is
demonstrated in 41 years of hindcasts of the 1950-1990 seasons. It is
possible to independently explain more than 60% of the year-to year
variability associated with intense (category 3-4-5) hurricane activity.
This is significant because over 70% of all United States tropical cyclone
damage comes from intense hurricanes, and over 98% of intense hurricane
activity occurs after 1 August. Empirical evidence suggests that least
sum of absolute deviations (LAD) regression yields substantially more
improved cross-validated results than an analogous procedure based on
ordinary least sum of squared deviations (OLS) regression. This
improvement surprisingly occurs even with the squared Pearson
product-moment correlation coefficient for which one might anticipate
OLS regression to yield better cross-validated results than LAD regression.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Summary of author's
seasonal Atlantic basin tropical cyclone activity predictions by 1 June and
comparison with other forecast times of 1 December and 1 August.
Preprints, 20th Conference on Hurricanes and Tropical Meteorology,
San Antonio, TX, May 10-14, 1993. American Meteorological Society, Boston,
240-243 (1993).
No abstract.
Hallett, J., W. Hendricks, R.A. Black, C.P.R. Saunders, and I. Brooks.
Aircraft observations of precipitation development and hydrometeor
charge in Florida cumuli. Proceedings, Conference on Atmospheric
Electricity, St. Louis, MO, October 4-8, 1993. American Meteorological
Society, Boston, 785-790 (1993).
No abstract.
Houston, S.H., and M.D. Powell. Surface wind fields during
Hurricane Bob's (1991) landfall in New England. Preprints, 20th
Conference on Hurricanes and Tropical Meteorology, San Antonio,
TX, May 10-14, 1993. American Meteorological Society, Boston,
139-142 (1993).
No abstract.
Houston, S.H., F.D. Marks, and P.G. Black. A ship passes through
Hurricane Andrew's eye. Mariners Weather Log, 37(1):64-69
(1993).
No abstract.
Jensen, R.E., S.H. Houston, C.L. Vincent, and M.D. Powell.
Evaluation of a third generation wave model for the U.S. Atlantic
coast. Ocean Wave Measurement and Analysis, Proceedings, Second
International Symposium, New Orleans, LA, July 25-28, 1993.
American Society of Civil Engineers, New York, 433-447 (1993).
No abstract.
Johns, E., and A.M. Wilburn. Hydrographic observations in the western
tropical and subtropical North Atlantic Ocean: Atlantic Climate Change
Program (ACCP) and Western Tropical Atlantic Experiment (WESTRAX)
during 1990. NOAA Data Report, ERL AOML-22 (PB93-184760), 102 pp. (1993).
No abstract.
Johns, E., and A.M. Wilburn. Hydrographic observations in the
western tropical and subtropical North Atlantic Ocean: Atlantic
Climate Change Program (ACCP) and Western Tropical Atlantic
Experiment (WESTRAX) during 1991. NOAA Data Report, ERL AOML-23
(PB93-184778), 82 pp. (1993).
No abstract.
Jones, R.W., and M. DeMaria. Further results of variational data
assimilation with a barotropic hurricane track forecast model.
Preprints, 20th Conference on Hurricanes and Tropical Meteorology,
San Antonio, TX, May 10-14, 1993. American Meteorological Society,
Boston, 333-336 (1993).
No abstract.
Kaplan, J., and W.M. Frank. The large-scale inflow-layer structure
of Hurricane Frederic (1979). Monthly Weather Review,
121(1):3-20 (1993).
Aircraft rawinsonde, satellite, ship, and buoy data collected over a 40-h
period were composited to analyze the inflow-layer structure of Hurricane
Frederic (1979) within a radius of 10° latitude of the storm center.
To improve the quality of the composite analyses, the low-level,
cloud-motion winds (CMW's) employed in this study were assigned a
level of best fit (LBF). A LBF was assigned to each CMW by determining
the level at which the closest agreement existed between CMW and
ground-truth wind data (e.g., rawinsonde, aircraft, ship, and
buoy). The CMW's were then adjusted vertically to uniform analysis
levels, combined with ground-truth wind data, and objectively analyzed.
These objectively analyzed wind fields were used to obtain
kinematically-derived fields of vorticity, divergence, and vertical
velocity. An angular-momentum budget was also computed to obtain
estimates of surface drag coefficients. The low-level CMW's in this
study were found to have LBF's ranging from 300 to 4000 m. It was shown
that judicious use of this knowledge leads to substantial improvements in
the estimates of the radial flow, but relatively insignificant
improvement in the estimates of the rotational component of the wind.
These results suggest that the common practice of assigning all low-level
CMW's in a tropical cyclone environment to a constant level of 900-950 mb
(approximately 500-1000 m) is probably appropriate for computations that
depend primarily upon the rotational wind component. These
findings, however, also indicate that failure to account for variations
in LBF's of low-level CMW's could result in substantial errors in
calculations that are sensitive to the radial wind. The kinematic
analyses showed that the asymmetric wind structure observed previously
in studies of Frederic's inner core extends out to at least 10°
latitude radius. Frederic was characterized by strong northeast-southwest
radial flow through the storm and a pronounced northwest-southeast
asymmetry of the tangential wind field at each analysis level. Analysis
of Frederic's surface 560 m angular-momentum budget showed that the mean
value of the surface drag coefficient beyond 2° radius was
approximately 1.8 × 10-3.
Katsaros, K.B., M.A. Donelan, and W.M. Drennan. Flux measurements from
a SWATH ship in SWADE. Journal of Marine Systems, 4(2-3):117-132
(1993).
The Surface Wave Dynamics Experiment (SWADE) took place east of the U.S.
coast in the winter of 1990-1991. A major objective of the research
program is to refine our understanding of the relationship between fluxes
to the sea surface and the sea state as determined from directional wave
spectra. Simultaneous measurements of turbulent fluxes of mass, momentum
and energy between sea and air, with the directional wave spectra, were
required to meet this objective. In this article we describe the process
of obtaining turbulent flux measurements from a small water-plane-area
twin hull (SWATH) ship.
Lamb, M.F., R.A. Feely, L.D. Moore, and D.K. Atwood. Total
CO2 and nitrate measurements in the southwest Pacific
during austral autumn (1990). NOAA DR ERL PMEL-42 (PB93-188415),
68 pp. (1993).
During austral autumn of 1990, total CO2 and nitrate
measurements were made in the South Pacific as part of the
Climate and Global Change (C&GC) program. Data were collected during
two legs. Sampling for Leg 1 began along 170°W from 15°S to
60°S, then angled northwest toward New Zealand across the Western
Boundary Current. Leg 2 included a reoccupation of some stations
between 30°S and 15°S on 170°W, and measurements from
15°S to 5°N along 170°W. Ancillary measurements of
salinity were also taken. Descriptions of sampling and methods and
data summaries are given in this report.
Landsea, C.W. A climatology of intense (or major) Atlantic hurricanes.
Monthly Weather Review, 121(6):1703-1713 (1993).
The variability of intense (or major) hurricanes in the Atlantic basin is
investigated on both intraseasonal and interannual time scales. Differences
are highlighted in characteristics between intense hurricanes and the weaker
minor hurricanes and tropical storms. Intense hurricanes show a much more
peaked annual cycle than do weaker tropical cyclones. Ninety-five percent
of all intense hurricane activity occurrs during August to October. In
addition, over 80% of all intense hurricanes originate from African easterly
waves, a much higher proportion than is observed for weaker cyclones. Of
all classes of Atlantic basin tropical cyclones, the intense hurricanes
display the greatest year-to-year variability. The incidence of intense
hurricanes also has decreased during the last two decades. A small portion
of this decreased activity appears to be due to an overestimation of
hurricane intensity during the period spanning the 1940s through the 1960s.
After adjusting for this bias, however, a substantial downward trend in
intense hurricane activity during recent years is still apparent. Given
that intense hurricanes are responsible for more than 70% of all
destruction caused by tropical cyclones in the United States, an
understanding is needed of the physical mechanisms for these observed
variations of intense hurricane activity.
Landsea, C.W., W.M. Gray, P.W. Mielke, and K.J. Berry. Forecasting
seasonal Sahelian rainfall by 1 December of the previous year.
Proceedings, 18th Annual Climate Diagnostics Workshop, Boulder,
CO. NOAA, 394-397 (1993).
No abstract.
Landsea, C.W., W.M. Gray, P.W. Mielke, and K.J. Berry. Predictability of
seasonal Sahelian rainfall by 1 December of the previous year and 1 June
of the current year. Preprints, 20th Conference on Hurricanes and
Tropical Meteorology, San Antonio, TX, May 10-14, 1993. American
Meteorological Society, Boston, 473-476 (1993).
No abstract.
Lee, T.N., W. Johns, R. Zantopp, and E. Johns. Moored measurement
of the thermohaline circulation and meridional heat flux in the western
subtropical Atlantic at 26.5°N. Proceedings, Principal
Investigators Meeting of the Atlantic Climate Change Program, Miami,
FL, March 9-11, 1992. NOAA Climate and Global Change Program, Special
Report No. 7, 143-153 (1993).
No abstract.
Marks, F.D., D. Atlas, and P.T. Willis. Probability-matched
reflectivity-rainfall relations for a hurricane from aircraft
observations. Applied Meteorology, 32(6):1134-1141 (1993).
The probability-matching method (PMM) was used to determine the
relation between the distribution of equivalent reflectivity Ze
measured by an airborne C-band radar and that for concurrently measured
rain rate R by a disdrometer on the same aircraft in the eyewall and
outer bands of Hurricane Anita in 1977. When the PMM is applied to
the disdrometer population of Z's and R's, one finds that the Z-R
relations differ significantly from those obtained by linear regression
of their logarithms. Such regression relations are deceptive. When PMM
is applied to the set of Ze's and R's, we get a family of
Ze-R relations as a function of range which differ
significantly from the traditional disdrometer-based Z-R relation for
hurricanes by Jorgensen and Willis (JW). These new relations are
approximate power laws with slope (exponent) which decrease with
increasing range. At ranges less than 35 km the reflectivity in the
eyewall exceeds that in the outer bands and is consistent with the
expectation from the disdrometer-based relations. At greater ranges
the converse is true due to beamwidth averaging over a broader beam
and different vertical profiles of reflectivity in the eyewall and
outer bands. We also devise a method to obtain an "effective zero
range" Ze-R relation. This differs from the JW relation
by -8.2 dBZ and reflects an error in the radar calibration. This
approach is a novel way to calibrate an airborne meteorological radar.
The methods may be used with any type of rainstorm and provide a
means of using airborne radar and disdrometer systems for air-truthing
rainfall measurements from space.
Mayer, D.A., and R.H. Weisberg. A description of COADS surface
meteorological fields and the implied Sverdrup transports for the
Atlantic Ocean from 30°S to 60°N. Journal of Physical
Oceanography, 23:2201-2221 (1993).
Using COADS data spanning 1947-1988, we describe the regional
nature of the Atlantic Ocean wind-driven circulation between
30°S-60°N, and its annual and interannual variability.
The Sverdrup stream function defines the circulation gyres. Our
focus is on three central gyres: the northern hemisphere anticyclonic
subtropical gyre, the cyclonic tropical gyre just north of the equator,
and the clockwise equatorial gyre straddling the equator. This stream
function, computed with constant drag coefficient and air density,
compares favorably with that from other climatologies. In the Straits
of Florida, differences between the annual cycle in Sverdrup transport
and observations may be due to regional winds farther north. In the
tropical gyre, the Sverdrup circulation argues against a continuous
western boundary current transporting water from the equatorial region
into the Caribbean in boreal winter. Instead, the interior Sverdrup
circulation implies a southeastward flowing boundary current, bringing
to question the mechanisms for the known inter-hemisphere and inter-gyre
exchanges of heat and mass. A conceptual model is proposed involving
two stages. First, the western boundary current closing the clockwise
equatorial gyre is instrumental in storing heat and mass between the
North Equatorial Countercurrent ridge and the North Equatorial Current
trough in boreal summer. Transport farther north, across the tropical
gyre and into the subtropical gyre, in boreal winter is then
accomplished by Ekman transport, as the seasonal change in wind stress
torque deepens the thermocline, thus allowing for vortex stretching
and northward Sverdrup transport over the region of warmest waters.
Once in the subtropical gyre, the Ekman transport continues to be
northward despite the fact that the Sverdrup transport reverses to be s
outhward. Annual and interannual variability is addressed by examining
the spectrum of curl and its regional distribution. Outside the tropics
and the Sargasso Sea, interannual exceeds annual variability by at least
a factor of 1.5. A pentadal analysis in the subtropical gyre indicates
that wind stress curl was not a major factor in the density structure
differences reported between 1955-1959 and 1970-1974, and, hence, these
require other explanations.
McCreary, J.P., P.K. Kundu, and R.L. Molinari. A numerical
investigation of dynamics, thermodynamics, and mixed-layer processes
in the Indian Ocean. Progress in Oceanography, 31:181-244 (1993).
A 2½-layer thermodynamic numerical model is used to study the
dynamics, thermodynamics, and mixed-layer physics of the Indian
Ocean circulation. A surface mixed layer of temperature Tm
is imbedded in the upper layer of the model, and entrainment and
detrainment in the mixed layer are determined by wind stirring and
surface cooling. There is also detrainment wd through
the base of the upper layer that models subduction. Monthly
climatological data, including air temperature Ta and
specific humidity qa, are used to force the model, and
model sea surface temperature (SST), Tm, is used to
determine the sensible and latent heat fluxes. With a few notable
exceptions, our main run solution compares well with observed current
and SST data; this is particularly true for Tm, which
typically differs from observed SST by less than 0.5-1.0°C. Our
analyses focus on three topics: the relative importance of remote
versus local forcing, the thermodynamic processes that determine the
model SST field, and the development of meridional circulation cells.
There are a number of examples of remotely forced circulations in our
main run. During the spring a northeastward countercurrent flows
against the prevailing winds along the Somali coast north of 4°N,
and from October through February a southwestward Somali Undercurrent
is present from the tip of Somalia to 3°N; both of these flows
result in part from forcing during the previous Southwest Monsoon.
From March through May there is another southwestward Somali
Undercurrent south of 7°N, generated primarily by the propagation
of a Rossby wave from the west coast of India. The currents
along the west coast of India are either strongly influenced or
dominated by remote forcing from the Bay of Bengal throughout the
year. A northeastward flow is well established along the east coast
of India in March, long before the onset of the Southwest Monsoon; it
is remotely forced either by upwelling favorable, alongshore winds
elsewhere within the Bay of Bengal or by negative wind curl in the
western Bay. Finally, the Agulhas Current is strengthened considerably
in a solution that includes throughflow from the Pacific Ocean. To
investigate the relative importance of thermodynamic processes, we
carried out a series of test calculations with various terms dropped
from the Tm equation. There is little effect of
Tm when the sensible heat flux is set to zero, or
when the solar radiation field is replaced by a spatially smoothed
version. When temperature advection is deleted, Tm is
most strongly affected near western boundaries since isotherms are
no longer shifted there by the swift currents; the annual-mean,
surface-heat-flux field Q is also changed, with Q becoming more
positive (negative) to compensate for the absence of warm (cold)
currents. Without entrainment cooling, Tm never cools
during the summer in the intense upwelling regions in the northern
ocean, and the annual-mean heat gain through the ocean surface (the
area integral of Q over the basin) reverses to become a net heat loss.
In individual tests without entrainment cooling, with
Ta=Tm, and with qa set to 80% of
its saturated value qs, model SST warms near the northern
and southern boundaries during their respective winters by about
1°C, indicating that several processes contribute to wintertime
cooling. The Tm field degrades considerably in a single
test run with both Ta=Tm and qa=0.8
qs, so that one or the other of these external forcing
fields is required to be able to simulate SST accurately. The
annual-mean circulation has two meridional circulation cells. In the
Tropical Cell, water subducts in the southern ocean, flows equatorward
in the lower layer of the western-boundary current, and is entrained
back into the upper layer in the open-ocean upwelling regions in the
southern ocean. In the Cross-Equatorial Cell, the subducted water
crosses the equator near the western boundary, where it is entrained
in the regions of intense coastal upwelling in the northern ocean.
The strength of the cells is directly related to the assumed
magnitude of the subduction rate wd, but their structure
is not sensitive to the particular parameterization of wd
used.
McLeish, W.L., J.R. Proni, S.J. Stamates, W.P. Dammann, and J.F.
Craynock. Nearshore current measurements for the SEFLOE II project,
1991-1992. NOAA Technical Memorandum, ERL AOML-75 (PB93-227676),
106 pp. (1993).
A compilation of current measurements in 25-m water depth off southeast
Florida is presented.
Millero, F.J., J.-Z. Zhang, K. Lee, and D.M. Campbell. Titration
alkalinity of seawater. Marine Chemistry, 44:153-165 (1993).
The titration system is described that was used to measure the total
alkalinity of seawater (TA) during the Joint Global Ocean Flux Study
(JGOFS) sponsored by the National Oceanic and Atmospheric Administration
(NOAA) in the equatorial Pacific. It consists of a piston titrator, a
pH meter, and a glass thermostated cell. Since the new pH meters and
titrators have RS232 interfaces, the system can be easily connected to
a personal computer. The computer programs used to carry out the
titration and to determine TA, pHsw (pH on the seawater
scale), and TCO2 from the full titration curve are described.
A typical titration takes 20 min and consists of 25 points. Six
separate titration cells were calibrated to be used on three systems
at sea. The reliability of the electrodes was examined by titrations
of 0.7 m NaCl with HCl at a pH near 3 and using seawater buffers at a
pH near 8. Although most electrodes did not have Nernstian behavior
over the entire pH range, all gave precise values of TA for a given
solution. The individual cells were calibrated using standard
Na2CO3 and seawater standards prepared in our
laboratory and Certified Reference Material (CRM) provided by Dickson.
The cells gave reliable values of TA, but the values of pHsw
were low (0.02) and values of TCO2 were high (20 µmol
kg-1) due to the non-Nernstian behavior of the electrodes
at a pH near 8.0. If the slope determined from the buffers is used,
the titrations yield reliable values of TA, TCO2, and
pHsw. Measurements on Dickson standards with the three
cells at sea indicate that the systems have a reproducibility of
± 2-4 µmol kg-1 (fall) and 20 ± 6 µmol
kg-1 (spring) too high. This offset in TCO2 is
independent of depth and is due to the non-Nernstian behavior of the
electrodes. The offset is not due to unknown protolytes.
Millero, F.J., J.-Z. Zhang, S. Fiol, S. Sotolongo, R.N. Roy, K. Lee,
and S. Mane. The use of buffers to measure the pH of seawater.
Marine Chemistry, 44:143-152 (1993).
The pH of seawater can be measured in the field using potentiometric
and spectrophotometric methods. The use of pH standards or buffers
is an important aspect of the calibration of both methods in a
laboratory on a common concentration scale. The buffers can also be
used to monitor the performance of pH meter and spectrophotometer
during a cruise. A procedure is described for the determination of
the pH of seawater, where the proton concentration is expressed as
moles kg-H2O-1 using seawater buffers. The
buffers are prepared in synthetic seawater in the laboratory by the
methods outlined by Bates and coworkers. We have prepared four buffers
(Bis, Tris, Morpholine, and 2-Amino-pyridine) that cover a pH range
from 6.8 to 8.8. The EMF values of the buffers were measured with a
H2, Pt/AgCl, Ag electrode system after their preparation
and bottling for use at sea. The measured EMF values were found to be
in good agreement (± 0.05 mV) with the original measurements of
Bates and coworkers from 0 to 45°C. The measured pH of these
buffers are in good agreement (± 0.001 pH units) with the values
calculated from the equations of Dickson on the total pH scale based
on Bates et al. Studies are underway to access the long-term
stability of these buffers. We have also used these buffers to
calibrate systems used to make potentiometric and spectrophotometric
measurements of pH on seawater relative to the H2, Pt/Ag,
AgCl electrode from 5 to
45°C.
Molinari, R.L., E. Johns, R. Raghunath, W.E. Johns, and R.J.
Zantopp. The Deep Western Boundary Current from 29°N to
the equator. Proceedings, Principal Investigators Meeting of
the Atlantic Climate Change Program, Miami, FL, March 9-11,
1992. NOAA Climate and Global Change Program, Special Report
No. 7, 155-156 (1993).
No abstract.
Murray, J.W., M.W. Leinen, R.A. Feely, J.R. Toggweiler, and R.H.
Wanninkhof. Equatorial Pacific: A process study in the central
equatorial Pacific. Oceanography, 5(3):134-143 (1993).
No abstract.
Napp, J.M., P.B. Ortner, D.V. Holliday, and R.E. Pieper. Biomass
spectra Gulf Stream epizooplankton communities. Deep-Sea
Research, 40(3):445-459 (1993).
Zooplankton biovolume data from a multi-frequency acoustic profiling
system were used to construct biovolume-size spectra for the Gulf
Stream and the southern California Bight. These spectra were linear
through most, but not all, of the size range sampled (0.025-4.00 mm,
ESR). Analysis of covariance was sometimes a useful tool to distinguish
among spectra taken at different times and places. Difference spectra
offered an alternative method of visualizing disparities between spectra.
We compared our acoustically-derived spectra from the Gulf Stream
with those obtained from other oceans with different samplers and those
obtained in the same waters with a different sampler. The results
indicate that differences attributable to sampler bias within the same
system presently make it difficult, if not impossible, to interpret
comparison from different samplers in different ecosystems.
Palmer, D.R. Tropical Atlantic network design considerations.
Proceedings, Second International Meeting on Global Acoustic
Monitoring of the Ocean, Brest, France, June 20-22, 1993. Institut
Francais de Recherche Pour l'Exploitation de la Mer (IFREMER), 32-34
(1993).
No abstract.
Palmer, D.R., T.M. George, J.J. Wilson, L.D. Weiner, J.A. Paisley,
R. Mathiesen, R.R. Pleshek, and R.R. Mabe. Reception at Ascension
Island, South Atlantic, of the transmissions from the Heard Island
Feasibility Test. NOAA Technical Memorandum, ERL AOML-73 (PB93-176261),
29 pp. (1993).
The objective of the Heard Island Feasibility Test was to ensonify
the global ocean with a single source to determine the feasibility
of acoustically measuring the extent of ocean warming. Underwater
acoustic signals were transmitted from a ship in the southern Indian
Ocean and monitored at listening stations throughout the world. At
Ascension Island, about 9,200 km from the source ship, all transmissions
from the Heard Island Feasibility Test were recorded on at least eight
hydrophones and, for many transmissions, on 11 hydrophones. The depths
of most of these hydrophones are near the depth of the sound channel
axis but some are considerably deeper. All are bottom mounted.
Signal-to-noise ratios were found to be surprisingly high. Averaged
over the CW transmissions and in a 1 Hz band, signal-to-noise ratios
for the axial hydrophones south of the island range from about 19 to
30 db, adjusted to a source level of 220 db (referenced to 1 µPa
at 1 m). The average signal-to-noise ratio for a hydrophone at a depth
approximately 0.8 km below the axis is about 16 db, suggesting acoustic
energy was not restricted to a narrow interval in depth centered about
the sound channel axis. The travel time of the earliest arrival was
found to be about 1 h, 44 min, 17 s. A late, reverberative signal was
observed for at least 22 min after termination of the direct signal.
An unexpected combination of phase stability and amplitude variability
was observed in the received signals. Continuing analysis of the
Ascension data set is likely to provide considerable information about
the characteristics of acoustic signals that have propagated global
distances.
Peng, T.-H. Possible reduction of atmospheric CO2 by iron
fertilization in the Antaractic Ocean. In A Global Warming Forum:
Scientific, Economic, and Legal Overview, R.A. Geyer (ed.). CRC
Press, Boca Raton, 263-285 (1993).
No abstract.
Peng, T.-H., and T. Takahashi. Ocean uptake of carbon dioxide. In
Heat Transfer in Turbulent Flows, R.A. Amano, R.H. Pletcher,
S.A. Sherif, R.G. Watts, and A.N. Anand (eds.). American Society of
Mechanical Engineers, 117-134 (1993).
Factors controlling the capacity of the ocean for taking up anthropogenic
CO2 include carbon chemistry, distribution of alkalinity,
pCO2 and total concentration of dissolved CO2,
sea-air pCO2 difference, gas exchange rate across the sea-air
interface, biological carbon pump, ocean water circulation and mixing,
and dissolution of carbonate in deep sea sediments. A general review of
these processes is given and models of ocean-atmosphere system based on
our understanding of these regulating processes are used to estimate the
magnitude of CO2 uptake by the ocean. We conclude that the
ocean can absorb up to 35% of the fossil fuel emission. Direct
measurements show that 55% of CO2 from fossil fuel burning
remains in the atmosphere. The remaining 10% is not accounted for by
atmospheric increases and ocean uptake. In addition, it is estimated that
an amount equivalent to 30% of recent annual fossil fuel emissions is
released into the atmosphere as a result of deforestation and farming. To
balance global carbon budget, a sizable carbon sink besides the ocean is
needed. Storage of carbon in terrestrial biosphere as a result of
CO2 fertilization is a potential candidate for such missing
carbon sinks.
Peng, T.-H., E. Maier-Reimer, and W.S. Broecker. Distribution of
32Si in the world ocean: Model compared to observation.
Global Biogeochemical Cycles, 7(2):463-474 (1993).
Calculations of the 32Si/SiO2 ratio obtained in
ocean models are compared with measurements of this ratio made as part
of the GEOSECS program (Somayajulu et al., 1987, 1991). A major
difference is found; while the models predict threefold to fivefold
higher ratios in the deep Atlantic Ocean than in the deep Pacific and
Indian Oceans, no such difference is seen in the measurements. This
points to a flaw in the measurements. Our modeling results suggest that
the most interesting application for this 120-year half-life cosmogenic
isotope is as a monitor of upwelling. However, considering the expense
and difficulty associated with 32Si measurements, such
studies may prove impractical.
Powell, M.D. Wind forecasting for yacht racing at the 1991 Pan
American Games. Bulletin of the American Meteorological
Society, 74(1):5-16 (1993).
The U.S. Sailing Team competed successfully at the 1991 Pan
American Games despite having no previous experience with the
sailing conditions off Havana, Cuba. One of the key factors
in the team's success was meteorological support in the form of
wind climate analysis; application of sea breeze forecasting
typical of the south Florida area, modified by tropical weather
systems; and effective preregatta briefing.
Powell, M.D. Wind measurement and archival under the automated
surface observing system (ASOS): User concerns and opportunity
for improvement. Bulletin of the American Meteorological
Society, 74(4):615-623 (1993).
The National Weather Service, as a part of its modernization
effort, is implementing the Automated Surface Observing System
(ASOS). Much discussion has occurred about various aspects of
ASOS versus the current system of manual and automated observations.
Based upon a study of the ASOS specifications and an informal
survey of potential ASOS wind data users, defects of the wind
sampling and archival strategy chosen for ASOS are discussed in
terms of their impact on various user groups. Limitations
include: (1) hourly observation average periods that do not
conform to international recommendations for wind reporting made
by the World Meteorological Organization; (2) no regular archival
of high-resolution data--potentially valuable research data are
destroyed if not identified within a 12-h period; and (3) no
emergency power for operation in severe weather conditions. An
alternative sampling and archiving strategy is recommended that
benefits a wider cross section of users, without detracting from
aviation and forecast service requirements, at a cost of less than
1% of the original ASOS portion of the National Weather Service's
modernization budget.
Powell, M.D., and S.H. Houston. Analysis of surface wind fields
in Hurricane Andrew. Preprints, 7th National Conference on Wind
Engineering, UCLA, CA, June 27-30, 1993. Wind Engineering
Research Council, College Station, 523-532 (1993).
No abstract.
Powell, M.D., and S.H. Houston. Surface wind field analyses in
Hurricane Andrew. Preprints, 20th Conference on Hurricanes and
Tropical Meteorology, San Antonio, TX, May 10-14, 1993. American
Meteorological Society, Boston, 58-61 (1993).
No abstract.
Powell, M.D., S.H. Houston, and T.A. Reinhold. Standardizing
wind measurements for documentation of surface wind fields in
Hurricane Andrew. Proceedings, Conference on Hurricanes of 1992,
Miami, FL, December 1-3, 1993. American Society of Civil
Engineers, New York, Volume VI, 1-13 (1993).
No abstract.
Price, J.F., M.O. Baringer, R.G. Lueck, G.C. Johnson, I. Ambar, G.
Parilla, A. Cantos, M.A. Kennelly, and T.B. Sanford. The Mediterranean
Outflow. Science, 259:1277-1282 (1993).
No abstract.
Proni, J.R., J.F. Craynock, and J.J. Tsai. Miami Harbor Dredge
Material Disposal Project: Total suspended solids measurements.
Contract Report W81EWF-2-C228, U.S. Army Corps of Engineers,
Jacksonville, FL, 72 pp. (1993).
No abstract.
Pszenny, A.A.P., C.J. Fischer, A. Mendez, and M.P. Zetwo. Direct
comparison of cellulose and quartz fiber filters for sampling
submicrometer aerosols in the marine boundary layer.
Atmospheric Environment, 27A:281-284 (1993).
Lodge (1986) and Harrison et al. (1987) called attention
to the possibility that Whatman 41 filter material (hereafter W41)
may not retain particles with 100% efficiency under all conditions.
Subsequently, several groups have presented evidence confirming
that W41 has imperfect collection efficiency but that for most
applications the losses are tolerably small (Harrison, 1987;
Lowenthal and Rahn, 1987; Watts et al., 1987). This is not
always the case, however (Kitto and Anderson, 1988). W41 has been
used often for "final" filters in cascade impactors when mass-size
distributions of inorganic species in marine boundary layer (MBL)
aerosols are to be determined (e.g., McDonald et al.,
1982; Savoie and Prospero, 1982; Duce et al., 1983; Keene
et al., 1990; Pszenny, 1992). Because the upstream impaction
stages remove virtually all aerosols larger than about 0.5 µm
diameter and, therefore, the majority of total MBL aerosol mass,
and because MBL fine-particle mass concentrations are usually
relatively low, it bears checking whether collection inefficiency
artifacts may be important under these conditions. To our knowledge
such a check has not been reported previously. In this short
contribution we report the results of a direct comparison of W41
with Pallflex Tissuquartz 2500 QAT-UP quartz fiber (hereafter QTZ)
used as final filters in high-volume cascade impactors sampling
open-ocean surface air.
Rogers, R.F., and R.E. Davis. The effect of coastline curvature on the
weakening of Atlantic tropical cylcones. International Journal of
Climatology, 13, 287-299 (1993).
This study attempts to determine the relationship between the curvature
of the coastline and the filling (increase in central pressure) of
hurricanes and tropical storms by comparing both the rate of filling and
the total filling for storms striking convex, concave, and linear
coastlines. The USA and Mexican coastline was approximated by a
subjective smoothing procedure, and the coastal curvature corresponding
to each landfalling Atlantic tropical cyclone from 1900 to 1979 was
measured and grouped into one of the three curvature categories.
Storm-filling rates and total amounts of filling were determined before
and after landfall by computing the change in wind speed for various
Saffir-Simpson hurricane intensity categories. The averages of these
variables within each strength and curvature grouping were compared in
order to determine if they were statistically different. Storms were
also compared in order to determine if stronger storms fill a greater
total amount than weaker storms, regardless of the coastline's curvature.
Concave coasts were found to be associated with storms filling both more
rapidly and by a greater amount than convex coasts for weak hurricanes
and strong tropical storms, and they were associated with storms that
filled by a greater amount for hurricanes of moderate strength. This
most likely results from the lower water-to-land ratios associated with
storms striking concave coasts and the reduction in latent and sensible
heat fluxes from the surface. Also, stronger storms were found to fill
more rapidly and by a greater total amount than weaker storms, and storms
striking the East Coast generally filled more rapidly and by a greater
total amount than storms striking the Gulf Coast or Florida.
Rona, P.A., and D.R. Palmer. Acoustic imaging beneath the sea.
In Physics News in 1992, P.F. Schewe and B.P. Stein (eds.).
American Institute of Physics, New York, 1-2 (1993).
No abstract.
Rona, P.A., and D.R. Palmer. Imaging plumes beneath the sea.
Journal of the Acoustical Society of America, 93(1):569-570
(1993).
No abstract.
Saltzman, E.S., S.A. Yvon, and P.A. Matrai. Low level atmospheric sulfur
dioxide measurements using HPLC/fluorescence. Journal of Atmospheric
Chemistry, 17:73-90 (1993).
An automated technique for measuring SO2 in ambient air has
been developed. Air is passed through a gas/liquid exchange coil with an
aqueous absorber solution containing 10 µM formaldehyde and 0.84 mM
Na2EDTA. The SO2 rapidly equilibrates with
bisulfite (HSO3-) and sulfite
(SO3-2) in the aqueous solution. The aqueous S(IV)
is subsequently reacted with o-phthaldehyde in the presence of excess
ethanolamine to form a fluorescent isoindole in a continuous flow
stream. This derivative is then separated using reversed phase HPLC and
detected via fluorescence with excitation and emission wavelengths at 330
and 380 nm, respectively. The lower limit of detection is 7 pptv
(S/N=3), with a measurement period of eight minutes per sample. The
instrument response is linear over several orders of magnitude.
Shapiro, L.J., and S.B. Goldenberg. Intraseasonal oscillations
over the Atlantic. Journal of Climate, 6(4):677-699 (1993).
Winds at low (near-surface) and 200-mb levels from National
Hurricane Center objective analyses are used to elucidate the
dynamics of the tropical and subtropical intraseasonal
oscillations for the North Atlantic/northeast Pacific regions,
including over the continents, for the years 1980-1989. The
intraseasonal oscillations are broken into three bands, with
long (50-85 day), intermediate (30-55 day), and short (13-29 day)
periods. Winter and summer seasons are analyzed separately. A
complex empirical orthogonal function technique is used to derive
the dominant modes of intraseasonal variability over the region,
including their propagation characteristics. Statistically-distinct
modes of variability are found only during the winter and only for
the long-period and short-period bands. The dominant mode of coupled
200-mb, low-level, long-period variability during winter has a
dipole structure. It has a substantial equivalent barotropic
component in the subtropics, as well as a baroclinic structure
consistent with quasigeostrophic midlatitude systems. Negative
outgoing longwave radiation anomalies tend to be in phase with a
low-level convergence/upper-level divergence couplet, which lies
approximately one-quarter wavelength to the east of the cyclonic
vorticity centers. The long-period oscillations during 1981-1988
are dominated by three events, with periods between about 60 and 70
days. There is a negative correlation, explaining about 50% of the
variance, between the magnitude of the mode and an index of El
Niño based on sea surface temperatures in the eastern equatorial
Pacific. The dominant modes of short-period variability during winter
appear as zonally-oriented wave trains similar to those found by
previous investigators of global-scale fluctuations. Rotation of
the modes of 200-mb variability effectively separates them into
their propagating and standing components. Approximately one-half
of the variance in the meridional wind near teleconnection centers
of action is found in the eastward propagating component. The dominant
mode of coupled 200-mb/low-level variability propagates to the east,
and has a vertical structure similar to that in the long-period band.
It has a predominant period near 18 days.
Siegenthaler, U., and T.-H. Peng. Summary of workshop on radiocarbon
distributions as a constraint for global carbon cycle modeling. In
The Global Carbon Cycle, M. Heimann (ed.). Springer-Verlag,
Berlin, 570-574 (1993).
No abstract.
Snyder, R.L., W.C. Thacker, K. Hasselmann, S. Hasselmann,
and G. Barzel. Implementation of an efficient scheme for
calculating nonlinear transfer from wave-wave interactions.
Journal of Geophysical Research, 98(C8):14,507-14,525
(1993).
Nonlinear transfer from wave-wave interactions is an important
term in the action-balance equation governing the evolution of the
surface-gravity-wave field. Computation of this term, however,
has hitherto been so consuming of computer resources that its full
representation has not been feasible in nonparametric
two-dimensional computer models of this equation. This paper describes
the implementation of a hybrid computational scheme, incorporating a
simplification first proposed by Thacker into the EXACT-NL Boltzmann
integration scheme of Hasselmann and Hasselmann. This hybrid scheme
retains EXACT-NL's symmetry, precision, and two-stage structure, but,
by transferring a spectrum-independent preintegration from the second
stage to the first, dramatically accelerates the resulting second-stage
computation, enabling a relatively efficient and precise determination
of nonlinear transfer in two-dimensional wave models. Physically, this
preintegration collects together in single hybrid interactions, multiple
interactions belonging to identical spectral-band quadruplets. Thus,
all possible interactions are represented, and these interactions are
represented in a uniquely efficient manner consistent with the spectral
representation. We compute the coefficients in the resulting second-stage
hybrid sum by essentially sorting and pre-summing the coefficients
generated by a piecewise-constant first-stage EXACT-NL computation,
using a variant of EXACT-NL that replaces the gather-scatter operations
with a simpler bin-assignment procedure and employs a somewhat simpler
set of integration variables. By exploiting the natural scaling of the
integrand and partially pre-summing prior to sorting, we are able to
further improve the efficiency of this computation for the deep-water
case and to refine its integration-grid resolution almost to convergence.
In wave-model computations of nonlinear transfer, vectorization on the
spatial grid points of the model and selective truncation of the hybrid
sum potentially reduce the working computation time for a single model
time step to well under one Cray Y-MP single-processor CPU second per
hundred grid points, while preserving a remarkably faithful
representation of the full transfer.
Thompson, A.M., J.E. Johnson, A.L. Torres, A.C. Kelly, E. Atlas, J.
Greenberg, N.M. Donahue, S.A. Yvon, E.S. Saltzman, B.G. Heikes, B.W.
Mosher, A.A. Shashkov, and V.I. Yegorov. Ozone observations and a model
of marine boundary layer photochemistry during SAGA-3. Journal of
Geophysical Research, 98:16,955-16,968 (1993).
A major purpose of the third joint Soviet-American Gases abd Aerosols
(SAGA 3) oceanographic cruise was to examine remote tropical marine
O3 and photochemical cycles in detail. On leg 1, which took
place between Hilo, Hawaii, and Pago-Pago, American Samoa, in February
and March 1990, shipboard measurements were made
of O3, CO,
CH4, nonmethane hydrocarbons (NMHC), NO, dimethyl sulfide
(DMS), H2S, H2O2, organic peroxides, and
total column O3. Postcruise analysis was performed for alkyl
nitrates and a second set of nonmethane hydrocarbons. A latitudinal
gradient in O3 was observed on SAGA 3, with O3
north of the intertropical convergence zone (ITCZ) at 15-20 parts per
billion by volume (ppbv) and less than 12 ppbv south of the ITCZ but
never =3 ppbv as observed on some previous equatorial Pacific cruises
(Piotrowicz et al., 1986; Johnson et al., 1990). Total
column O3 (230-250 Dobson units (DU)) measured from the
Akademik Korolev was within 8% of the corresponding total ozone
mapping spectrometer (TOMS) satellite observations and confirmed the
equatorial Pacific as a low O3 region. In terms of number and
constituents measured, SAGA 3 may be the most photochemically complete
at-sea experiment to date. A one-dimensional photochemical model gives
a self-consistent picture of O3-NO-CO-hydrocarbon interactions
taking place during SAGA 3. At typical equatorial conditions, mean
O3 is 10 ppbv with a 10-15% diurnal variation and maximum
near sunrise. Measurements of O3, CO, CH, NMHC,
and H2O constrain model calculated OH to 9 × 105
cm-3 for 10 ppbv O3 at the equator. For DMS
(300-400 parts per trillion by volume (pptv)) this OH abundance requires
a sea-to-air flux of 6-8 × 109 cm-2
s-1, which is within the uncertainty range of the flux deduced
from SAGA 3 measurements of DMS in seawater (Bates et al., this
issue). The concentrations of alkyl nitrates on SAGA 3 (5-15 pptv total
alkyl nitrates) were up to 6 times higher than expected from currently
accepted kinetics, suggesting a largely continental source for these
species. However, maxima in isopropyl nitrate and bromoform near the
equator (Atlat et al., this issue) as well as for nitric oxide
(Torres and Thompson, this issue) may signify photochemical and
biological sources of these species.
Tsai, J.J., J.R. Proni, W.P. Dammann, and J.R. Craynock.
Acoustic detection of particulates from dredged material discharges
in the oceanic dredged material disposal site for the Calcasieu Bar
Channel, Gulf of Mexico, August 19-29, 1991. Contract Report
DWI-35-54001, U.S. Environmental Protection Agency, Narragansett,
RI, 32 pp. (1993).
A study of the behavior of dredged material discharged in the
Calcasieu Ocean Dredged Material Disposal Site using acoustical
remote sensing techniques in combination with other measurement
systems has provided substantial information on the dispersion
and general behavior of such discharges. Information was obtained
on discharged material plume structure, particulate transport, and
water column residual. Features observed during the study include
increasing plume width during the convective descent, possible bottom
surges, and persistent near-bottom nepheloid layers. Residual water
column dredged material concentrations were observed for times in
excess of one hour and twenty minutes after discharge. Residual water
column concentrations appear to diminish slowly and may persist for
long periods of time. Determination of the general movement of water
column residual material is made possible through use of the
acoustic technique.
Velden, C., S. Nieman, S.D. Aberson, and J.L. Franklin. Tracking
motions from satellite water vapor imagery: Quantitative applications
to hurricane track forecasting. Preprints, 20th Conference on
Hurricanes and Tropical Meteorology, San Antonio, TX, May 10-14,
1993. American Meteorological Society, Boston, 193-196 (1993).
No abstract.
Wakimoto, R.M., and P.G. Black. Damage survey of Hurricane Andrew
and its relationship to the radar-detected eyewall. Preprints, 20th
Conference on Hurricanes and Tropical Meteorology, San Antonio, TX,
May 10-14, 1993. American Meteorological Society, Boston, 54-57
(1993).
No abstract.
Wanninkhof, R.H., and K. Thoning. Measurement of fugacity of
CO2 in surface water using continuous and discrete
sampling methods. Marine Chemistry, 44(2-4):189-204
(1993).
Instrumentation and methodology is described which is used for
measurement of the fugacity (or partial pressure) of carbon dioxide
(fCO2 or pCO2) in surface seawater. Two
separate instruments were developed for the measurements. One is
an underway system which measures the mixing ratio of CO2,
XCO2, in a headspace in equilibrium with surface
seawater continuously pumped into a 24 l-equilibrium chamber. The
other is a discrete system in which 460 ml aliquots of water are
equilibrated with a 120 ml headspace. Both systems use a
non-dispersive infrared analyzer as detector. In the underway
instrument the average XCO2 in the headspace of an
equilibration chamber is measured at near in-situ temperature over
20 min each hour. At a cruising speed of 13 knots this translates
into a space averaged fCO2 value over 8 km. The underway
system is ideally suited for mapping of the surface water fugacity
over large geographic regions. Samples from the discrete instrument
are analyzed at 20°C. The primary function of the system is
for measurement of CO2 and other (carbon) parameters
sub-sampled from the same aliquot. To calculate the fCO2
in water for in-situ conditions from the mixing ratio in the
headspace of the flask of the discrete system, small carbon mass
balance and, sometimes significant, temperature corrections have to
be applied. Comparison of 100 surface values obtained in the South
Atlantic using the underway and discrete systems shows that the
average difference of pCO2 values for the two systems
ranges from -4.3 µatm to -8.6 µatm, depending on the
temperature correction, with a standard deviation of 4 µatm.
The differences show scatter of up the 15 µatm which we
attribute to a mismatch between the point samples for the discrete
system and the integrated samples for the underway system.
Wanninkhof, R.H., W.E. Asher, R. Weppernig, H. Chen, P. Schlosser,
C. Langdon, and R. Sambrotto. Gas transfer experiment on Georges
Bank using two volatile deliberate tracers. Journal of
Geophysical Research, 98(C11):20,237-20,248 (1993).
A gas exchange experiment was performed on Georges Bank using the
deliberate tracers sulfur hexafluoride (SF6) and helium
3 (3He). The concentrations of the tracers were
measured in the water column over a period of 10 days. During this
time the patch grew from an 8-km-long injection streak to an area of
about 500 km2. The gas transfer velocity was determined
from the change in the ratio of the tracers over time scaled to the
ratio of their Schmidt numbers. A near-linear relationship between
gas exchange and wind speed was observed based on four experimental
points covering a wind speed range from 3 to 11 m/s. The results
fall in the upper part of the range of gas transfer-wind speed
relationships developed to date. Wind speeds during the experiment
obtained from anemometers on the ship, on a free floating drifter,
and on a fixed mooring showed significant differences. With the
ability to measure gas transfer velocities over the ocean on time
scales of several days, accurate wind speed/stress measurements are
imperative to obtain a robust relationship between gas transfer and
wind speed.
Willis, P.T., J. Hallett, W. Hendricks, and R.A. Black. Hydrometeor
development and structure of a convective cell. Preprints, 20th
Conference on Hurricanes and Tropical Meteorology, San Antonio, TX,
May 10-14, 1993. American Meteorological Society, Boston, 74-77
(1993).
No abstract.
Willoughby, H.E. Mature structure and evolution. In Global
Perspectives on Tropical Cyclones (chapter 2 in preliminary
edition), E.L. Elsberry (ed.). World Meteorological Organization,
Geneva, 62 pp. (1993).
No abstract.
Willoughby, H.E. Nonlinear shallow-water vortex motion. Preprints,
20th Conference on Hurricanes and Tropical Meteorology, San Antonio,
TX, May 10-14, 1993. American Meteorological Society, Boston,
J38-J40 (1993).
No abstract.
Yvon, S.A., and E.S. Saltzman. A time-dependent photochemical box model
for atmospheric chemistry (PBMAC). RSMAS Technical Report 93-008, University
of Miami, Miami, Florida, 78 pp. (1993).
No abstract.
Yvon, S.A., E.S. Saltzman, D.J. Cooper, and V. Koropalov. Atmospheric
hydrogen sulfide over the equatorial Pacific (SAGA-3). Journal of
Geophysical Research, 98:16,979-16,983 (1993).
Atmospheric H2S concentrations were measured over the
equatorial Pacific on Leg 1 of the SAGA-3 cruise during February and
March of 1990. Five north-south transects were made across the equator
between Hawaii and American Samoa. The concentrations ranged from below
the detection limit of 0.4 ± 0.5 (1 sigma) to 14.4 ppt with an
average value of 3.6 ± 2.3 ppt (1 sigma, n=72). The highest
concentrations were found on the easternmost two transects just south of
the equator. The average concentration of 3.6 ppt observed on this
cruise is the lowest reported value for background atmospheric
H2S over the tropical oceans. A lack of correlation between
222Rn and H2S rules out a significant continental
source. Model calculations indicate that the oceanic source of
H2S in this region is in the range of 9 to 21 ×
10-8 moles m-3 day-1. From this flux,
the concentration of free sulfide (H2S + S=) in the
surface mixed layer of the ocean is estimated to be in the range of 32 to
67 pmol liter-1. In the atmosphere, the oxidation of
H2S produces SO2 at a rate of 2.1 to 4.4 ×
10-11 moles m-3 day-1 which is only a
small fraction of that estimated from the oxidation of DMS in this
region. A diurnal cycle was not observed in the H2S data
recorded during this cruise.
Zhang, J.-Z., and F.J. Millero. The chemistry of the anoxic waters
in the Cariaco Trench. Deep-Sea Research, 40(5):1023-1041
(1993).
The Cariaco Trench has been widely used as a natural laboratory for
the study of anaerobic processes since the deep waters were found to
be anoxic in 1954. In the summer of 1990 on a cruise of the R.V.
Thomas Washington, we had the opportunity to measure a number
of chemical parameters (salinity, H2S, O2, pH,
TCO2, NH4+, PO43-,
SiO2, SO32-, and
S2O32-) in the eastern and western
basins of the Cariaco Trench. The oxic-anoxic interface was
located at 330 m in both basins. The concentrations of H2S,
NH4+, PO43-, and
SiO2 in the deep waters of the Cariaco Trench have
increased with time. The linear extrapolations of H2S
and NH4+ with time indicate that the trench
was oxic around 1915. This turnover may be related to earthquakes
that occurred in 1900 and 1929. The ratio of C/N/P/S in the anoxic
waters was found to be close to 106:16:1:53, the ratio predicted from
the oxidation of phytoplankton by sulfate. Micromolar concentrations of
SO32- and S2O32-
were found below the interface in the intermediate waters. These
intermediates appear to be due to the oxidation of H2S by
the sinking of oxygenated surface waters. The rates of oxidation of
H2S with oxygen also were measured in the Cariaco Trench
waters at 25°C. Measurements were made on surface waters, deep
waters, and mixtures of deep and surface waters. Oxidation rates were
found to be 10 times faster in the deep waters than for surface
seawater with added H2S due to Fe2+ in the
deep waters. The intermediates SO32- and
S2O32- formed during the oxidation
of H2S were also determined. A simple kinetic model was
used to fit the results.
Zhang, J.-Z., and F.J. Millero. The products from the oxidation of
H2S in seawater. Geochimica et Cosmochimica Acta,
57:1705-1718 (1993).
The oxidation of sulfide in seawater is an overall second-order reaction,
first-order with respect to both sulfide and oxygen. The major products
formed from the oxidation of H2S with O2 have been
measured in water and seawater as a function of pH (4-10), temperature
(10-45°C), and salinity (0-36). The major products formed from
the oxidation of H2S were SO32-,
S2O32-, and
SO42-. The pH dependence of the product
distribution has been attributed to the effect of pH on the rate of
the individual reaction steps. A kinetic model was developed to
account for the distribution of the reactants and products. The model
is based on the following overall reactions:
H2S + O2 (k1) -->
Products (SO3),
H2SO3 + O2 (k2
--> Products (SO4), and
H2S + H2SO3 + O2
k3 --> Products (S2O3).
Rate constants were determined for the oxidation of HS- and
formation of SO32- (k1), for
the oxidation of SO32- and production of
SO42- (k2) and for the formation
of S2O32- from HS- and
SO32- (k3). These values of
k1, k2, and k3
as a function of pH, temperature, and salinity can predict the
concentrations of the measured reactants and products within
experimental error. The effect of metals (Fe3+,
Fe2+, Mn2+, Cu2+, and Pb2+)
and oxides (alpha-FeOOH and MnO2) on the product
distribution has also been examined. The field measurements from
the Framvaren Fjord (Norway) and Cariaco Trench (Venezuela) are in
reasonable agreement with the laboratory results at the same
concentration of Fe2+ as in the anoxic basins.
**1992**
Aberson, S.D., and M. DeMaria. VICBAR: 1991 verification and plans for
1992. Minutes, 46th Annual Interdepartmental Hurricane Conference,
Homestead Air Force Base, FL, January 14-17, 1992. Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-20 (1992).
No abstract.
Asher, W.E., P.J. Farley, R.H.Wanninkhof, E.C. Monahan, and
T.S. Bates. Laboratory and field measurements concerning the
correlation of fractional area foam coveraging with air/sea gas
transport. In Precipitation Scavenging and Atmosphere-Surface
Exchange, Vol. 2, The Semonin Volume: Atmosphere Surface Exchange
Processes, S.E. Schwartz and W.G.N. Slinn (eds.). Hemisphere,
Washington, D.C., 815-828 (1992).
Laboratory results have demonstrated that bubble plumes are a
very efficient air/water gas transport mechanism. Because
breaking waves generate bubble plumes, it may be possible to
correlate air/sea gas transport velocities with whitecap coverage.
This correlation may then allow transport velocities to be
predicted from measurements of apparent microwave brightness
temperature through the increase in sea surface microwave emissivity
associated with breaking waves. In order to develop this
remote-sensing based method for predicting air/sea gas fluxes,
the whitecap simulation tank at Battelle/Marine Sciences Laboratory
was used to measure transport velocities for oxygen, helium,
sulfur hexafluoride, and dimethyl sulfide. This allowed the gas
exchange process to be studied as a function of fractional area
bubble plume coverage, molecular diffusivity (or Schmidt number),
and water temperature. Using these results, an empirical model
has been developed that permits prediction of the transport
velocity in the Whitecap Simulation Tank from bubble plume
coverage and Schmidt number. The implications of these results
to the analysis of in situ dual-tracer air/sea gas transport data
are also discussed.
Atwood, D.K., J.C. Hendee, and A. Mendez. An assessment of
global warming stress on Caribbean coral reef ecosystems.
Bulletin of Marine Science, 51(1):118-130 (1992).
There is evidence that stress on coral reef ecosystems in the
Caribbean region is increasing. Recently, numerous authors
have stated that major stress results from "abnormally high"
seasonal sea surface temperatures (SST) and have implicated
global warming as a cause, stating that recent episodes of
coral bleaching result therefrom. However, an analysis of
available SST data sets shows no discernible warming trend
that could cause an increase in coral bleaching. Given the
lack of long-term records synoptic with observations of coral
ecosystem health, there is insufficient evidence available to
label temperatures observed in coincidence with recent regional
bleaching events as "abnormally" high.
Black, M.L., and H.E. Willoughby. The concentric eyewall cycle
of Hurricane Gilbert. Monthly Weather Review,
120(6):947-957 (1992).
Hurricane Gilbert of 1988 formed an outer eyewall as it
intensified rapidly toward a record minimum pressure of
888 hPa in the western Caribbean. The outer eyewall
strengthened and contracted, while the inner eyewall showed
some signs of weakening before landfall on the Yucatan
Peninsula. Remarkably, both eyewalls survived passage over
land, but the storm was much weaker when it entered the
Gulf of Mexico. Although the primary cause of weakening
was passage over land, the effect of the contracting outer
eyewall may have contributed. Later, the outer eyewall
completely replaced the inner eyewall. Subsequently, it
contracted steadily but slowly as Gilbert maintained nearly
constant intensity over the cooler waters of the Gulf before
final landfall on the mainland of Mexico.
Black, P.G., and A.V. Litinetski. Flight-level and surface
wind observations in Hurricane Gilbert from AN-12 "Cyclone" and
WP-3D "Orion" aircraft. Proceedings, 5th International Symposium
on Tropical Meteorology, Obninsk, Russia, May 27-31, 1992.
USSR State Committee on Hydrometeorology, 20-31 (1992).
No abstract.
Black, P.G., S. Carson, R. McIntosh, K. St. Germain, C.C. Swift,
and J. Wilkerson. The NOAA WP-3D capability for surface wind
measurement using UMASS dual active/passive remote sensing and
its application to present and future hurricane reconnaissance.
Minutes, 46th Annual Interdepartmental Hurricane Conference,
Homestead Air Force Base, FL, January 14-17, 1992. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-30 (1992).
No abstract.
Broecker, W.S., and T.-H. Peng. Interhemispheric transport of carbon
dioxide by ocean circulation. Nature, 356:587-589 (1992).
Although anthropogenic emissions of carbon dioxide have today created a
greater atmospheric CO2 concentration in the Northern than in
the Southern Hemisphere, a comparison of interhemispheric CO2
profiles from 1980 and 1962 led Keeling and Heimann to conclude that,
before the Industrial Revolution, natural CO2 sources and
sinks acted to set up a reverse (south to north) gradient which drove
about one gigatonne of carbon each year through the atmosphere from the
Southern to the Northern Hemisphere. At steady state, this flux must have
been balanced by a counter flow of carbon from north to south through the
ocean. Here we present a means to estimate this natural flux by a
separation of oceanic carbon anomalies into those created by biogenic
processes and those created by CO2 exchange between the ocean
and atmosphere. We find that before the Industrial Revolution, deep water
formed in the northern Atlantic Ocean carried about 0.6 gigatonnes of
carbon annually to the Southern Hemisphere, providing support for Keeling
and Heimann's proposal. The existence of this oceanic carbon pump also
raises questions about the need for a large terrestrial carbon sink in
the Northern Hemisphere, as postulated by Tans et al. to balance
the present global carbon budget.
Burpee, R.W., and P.P. Dodge. Analyses of visible satellite
imagery of the south Florida sea breeze circulation. Preprints,
5th Conference on Mesoscale Processes, Atlanta, GA, January
5-10, 1992. American Meteorological Society, Boston, 77-80 (1992).
No abstract.
Burpee, R.W., J.S. Griffin, F.D. Marks, and J.L. Franklin.
Real-time airborne analysis of aircraft data supporting operational
hurricane forecasting. Minutes, 46th Annual Interdepartmental Hurricane
Conference, Homestead Air Force Base, FL, January 14-17, 1992.
NOAA Office of the Federal Coordinator for Meteorological Services
and Supporting Research, Washington, D.C., A-29 (1992).
No abstract.
Carsey, T.P., and M.L. Farmer. Active nitrogen gases in the North
Atlantic boundary layer during ASTEX. EOS, Transactions, American
Geophysical Union, 73:84 (1992).
No abstract.
Cione, J.J., L.J. Pietrafesa, S. Raman, and J. Churchill. The influence
of Gulf Stream position on offshore storm intensification. Proceedings,
American Geophysical Union Conference, New Orleans, Louisiana, January
27-31, (1992).
No abstract.
Claud, C., K.B. Katsaros, G.W. Petty, A. Chedin, and N.A. Scott. A cold
air outbreak over the Norwegian Sea observed with the TIROS-N operational
vertical sounder (TOVS) and the special sensor microwave/imager (SSM/I).
Tellus, 44A(2):100-118 (1992).
Until recently, the scarcity of meteorological observations over polar
areas has limited studies of high-latitude weather systems, but now data
from polar orbiting satellites offer a new opportunity to observe and
describe these systems. TOVS data have been used successfully for
delineating synoptic and sub-synoptic systems, since they provide the
vertical temperature structure of the atmosphere; SSM/I observations have
proved valuable for analyzing storms through water vapor and rain
determinations. These positive results prompted us to analyze
simultaneous TOVS and SSM/I observations obtained during a cold air
outbreak over the Norwegian Sea. After a description of the instruments
and the retrieval schemes, the mutually supporting information from these
two independent instruments is discussed. Implications for the monitoring
of polar lows are presented.
Craynock, J.F., W. McLeish, and J.R. Proni. Acoustical
characterization of an effluent plume in the Charleston Harbor
estuarine system. Contract Report 91-0036866, Commissioners
of Public Works of the City of Charleston, South Carolina,
22 pp. (1992).
A study of the effluent discharge from the City of Charleston Plum Island
plant into the Ashley River/Charleston Harbor was carried out on January
14-15, 1992. Advanced acoustical methods, dye injection methods, and other
advanced technologies were used in the study. The plumes originating from
the risers of the outfall discharge line were observed to rise to the river
surface while merging, such inter-plume merging beginning at about 2-3 m
below the river surface. The plume dilution was about 17 to 1, i.e.,
plume dye concentration was about one-seventeenth the whole effluent dye
concentration in the plant. Dye concentration measurements, made in the
direction of current flow during a flood tide, indicated an effective
dilution of about 50 to 1 at a distance of approximately 200 m from the
discharge riser locations. Further up the river about 2-3 km from
the discharge, at the Bascule Bridge and in the Wappoo Creek area, no dye
was detected and acoustical reflectivity data indicated an absence of
effluent material. Acoustical measurements were made in a direction
downriver of the discharge point, where dyed plume material had not yet
reached, and opposite to the direction of the ongoing flood tide. Effective
dilutions ranging from 40 to 1 to 150 to 1 were observed in this region
southeast of the discharge. The detection of two extraneous plumes,
possibly natural springs, were made in the downriver portion of the study.
Dagg, M.J., and P.B. Ortner. Mesozooplankton grazing and the
fate of carbon in the northern Gulf of Mexico. Proceedings, NECOP
Workshop on Nutrient Enhanced Coastal Ocean Productivity, Chauvin,
Louisiana, October 2-3, 1991. Texas A&M University Press, College
Station, 117-121 (1992).
Grazing of the mesozooplankton community (organisms >200
µm) on phytoplankton was measured in two regions of the
continental shelf west of the Mississippi River delta. Grazing
by individual organisms was measured experimentally and scaled
to the community by application of abundance and distribution
data collected on several temporal and spatial scales by
various methods. One of the principal fates of phytoplankton
production stimulated by nutrient enrichment from the Mississippi
River is to be grazed by the mesozooplankton community.
Dammann, W.P., and J.R. Proni. Chapter 6: Sediment plume measurements
within acoustic concentration profiler. In Report 1: Dredged Material
Plume Survey Data Report, N.C. Kraus (ed.). U.S. Army Corp of Engineers,
Technical Report DRP-91-3, 311-345 (1992).
No abstract.
Davis, R.E., and R.F. Rogers. A synoptic climatology of severe storms in
Virginia. The Professional Geographer, 44, 319-332 (1992).
A synoptic climatology is developed for Virginia using 21 years of late
spring and summer surface and upper air observations. The climatology is
produced by applying a combination of principal components analysis and
cluster analysis such that each day is classified into one of a distinct
number of synoptic situations. Days on which at least one severe storm
occurred in Virginia are merged with the synoptic climatology. A
majority of severe storms are associated with one synoptic situation
distinguished by moderate instability and a high moisture content.
DeMaria, M., S.D. Aberson, K.V. Ooyama, and S.J. Lord. A nested
spectral model for hurricane track forecasting. Monthly Weather
Review, 120(8):1628-1643 (1992).
A numerical method for including a wide range of horizontal
scales of motion is tested in a barotropic hurricane track forecast
model. The numerical method uses cubic B-spline representations of
variables on nested domains. The spline representation is used for the
objective analysis of observations and the solution of the prediction
equations (shallow-water equations on a Mercator projection). This
analysis and forecasting system is referred to as VICBAR. The VICBAR
model was tested in near real-time during the 1989 and 1990 Atlantic
hurricane seasons. For the 1989 season, VICBAR had skill comparable with,
or greater than, that of the operational track forecast models. For
the 1990 season, VICBAR had skill comparable with that of the
operational track forecast models, except at 72 h when QLM (a
three-dimensional mesoscale model) had greater skill than VICBAR.
During both 1989 and 1990, VICBAR had considerably more skill for
forecasts of hurricanes than for forecasts of tropical storms. For the
1990 season, VICBAR was generalized to include time-dependent boundary
conditions from a global forecast model. These boundary conditions
improve the VICBAR forecasts, especially for the longer range forecasts
(60-72 h). The skill of the VICBAR is sensitive to the choice of the
background field used in the objective analysis and the fields used to
apply the boundary conditions. The use of background fields and boundary
condition fields from a 12 h old global model forecast significantly
reduced the VICBAR skill relative to the use of fields from the
current global forecast.
Eadie, B.J., J.A. Robbins, P. Blackwelder, S. Metz, J.H. Trefry,
B. McKee, and T.A. Nelsen. A retrospective analysis of nutrient
enhanced coastal ocean productivity in sediments from the Louisiana
continental shelf. Proceedings, NECOP Workshop on Nutrient Enhanced
Coastal Ocean Productivity, Chauvin, LA, October 2-3, 1991. Texas
A&M University Press, College Station, 7-14 (1992).
Sediments have been collected and analyzed to obtain evidence in
support of the argument that anthropogenic nutrient loading has
led to changes in coastal water quality and increased productivity.
Cores representing approximately 100 years of input show unmistakable
signs of increased accumulation of organic carbon beginning early in
the 1900's. Organic tracers show that virtually all of this increase
appears to be of marine origin. At two sites within the plume/hypoxia
region, preliminary estimates are that 50% to 70% more organic carbon
is presently accumulating than at the turn of the century. These
preliminary interpretations provide strong support for the central
themes of the NECOP program. Analysis and interpretation of further
supporting information is continuing.
Enfield, D.B. Historical and prehistorical overview of El
Niño/Southern Oscillation. In El Niño: Historical
and Paleoclimatic Aspects of the Southern Oscillation, H.F.
Diaz and V. Markgraf (eds.). Cambridge University Press,
Cambridge, 95-117 (1992).
This paper presents a thumbnail sketch of what El Niño/Southern
Oscillation (ENSO) is, how it may have existed (or not) in previous
epochs, and its relation to paleoclimatic studies. El Niño is a
recurrent aperiodic, interannual (2-5 years) warming of the tropical
Pacific Ocean, with an associated atmospheric counterpart, the Southern
Oscillation. The two synchronous phenomena appear to occur as the
result of an unstable interaction between ocean and atmosphere and
vacillate between two contrasting states. They are of very large
spatial scale and involve remote interannual climatic perturbations
beyond the equatorial Pacific region of intense interaction. These
"teleconnections" are one of the primary ways in which El
Niño-like fluctuations during historical and prehistorical epochs
have been preserved in surrogate records by biospheric and geological
processes. Analyses of historical, proxy, and geological
information suggest that: (1) ENSO has existed intermittently, as
today, over at least the last 5,000 years; and (2) its statistics are
probably nonstationary during that period, although apparently not in
relation to variations of the background climate, such as the Little
Ice Age. Evidence as to the existence of ENSO prior to 5,000 BP is
mainly geological and as yet equivocal. Strategies for paleoclimatic
research in this area are discussed in regard to several possible
scenarios.
Festa, J.F., and R.L. Molinari. An evaluation of the WOCE volunteer
observing ship-XBT network in the Atlantic. Journal of Atmospheric
and Oceanic Technology, 9:305-317 (1992).
A volunteer observing ship (VOS)-expendable bathythermograph
(XBT) network has been proposed for the Atlantic Ocean to
satisfy World Ocean Circulation Experiment (WOCE) objectives
in the upper water column. These objectives include measuring
changes in upper-layer temperature. An evaluation of the
proposed WOCE XBT network to resolve variability in sea
surface temperature (SST), temperature distribution at
150 m (T150), and average temperature of the upper 400 m
(T400L) between 25°S and 35°N is performed.
A sampling design study based on an optimum interpolation
(OI) of the historical XBT data set is used to construct
uncertainty distributions for various XBT networks. The OI
technique requires statistical representations of the variability
(in the form of structure functions) of the three variables that
are derived from the historical database. The structure functions
and various sampling grids are used to construct uncertainty
maps. Two seasons are used in the analysis of SST. In both
seasons, uncertainties in mapped SST values for the proposed
WOCE grid range from 0.3°C to 0.4°C in regions of
adequate data coverage. Errors are larger along the boundary.
Uncertainties in the T150 fields are larger (0.5°-0.7°)
because of the smaller scales of spatial variability at depth.
Errors in T400L range from 0.3°C to 0.4°C. The effects
of alternative observing strategies on the error maps are shown.
Finally, error maps derived from the XBT network as it exists
today (i.e., incomplete) are given. The maps indicate that
monthly resolution is not available from the incomplete network.
Fine, R.A., E. Johns, and R.L. Molinari. Deep Western Boundary
Current structure in the region of the Blake Bahama Outer Ridge.
EOS, Transactions, American Geophysical Union, 72(51):32
(1992).
No abstract.
Friedman, H.A., and C.A. Arnhols. 1992 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 116 pp.
(1992).
No abstract.
Froelich, P.N., V. Blanc, R.A. Mortlock, S.N. Chillrud, W. Dunstan,
A. Udomkit, and T.-H. Peng. River fluxes of dissolved silica to the
ocean were higher during glacials: Ge/Si in diatoms, rivers, and
oceans. Paleoceanography, 7(6):739-767 (1992).
Two centric marine diatom species, Thalassiosira oceanica and
Thalassiosira antarctica, were grown in batch cultures to
determine the incorporation of germanium (Ge) and silicon (Si) into
siliceous shells (opal). The results were modeled as Ge/Si "isotope"
fractionation. During exponential growth, diatoms take up and incorporate
Ge/Si from solution without major discrimination against Ge. During
stationary phase growth near silica limitation, the Antarctic species
(T. antarctica) discriminates slightly against Ge but integrated
(Ge/Si)opal produced over the latter portion of the growth
cycle is indistinguishable from the initial solution ratio. These results
confirm experiments using radioactive 68Ge that showed absence
of fractionation during diatom silica uptake (Azam and Volcani, 1981), in
contrast to two-box ocean models that invoke 50% Ge discrimination by
diatoms to explain the observed "excess" surface ocean germanium
concentration (Murnane and Stallard, 1988; Froelich et al., 1989)
and late Pleistocene ocean sediment (Ge/Si)opal records
(Mortlock et al.,1991). Runs of a 10- box ocean Ge and Si model
(PANDORA) with 50% discrimination reproduce the excess surface ocean Ge
but introduces curvature into the deep ocean Ge versus Si relationship
that is not observed in the oceans. Thus, 50% fractionation is not
supported by either cultures or models. If diatoms do not fractionate
Ge/Si, then late Pleistocene (Ge/Si)opal variations in piston
cores are caused not by changes in local biosiliceous production and
silica utilization (Mortlock et al., 1991) but rather by whole
ocean changes in (Ge/Si)seawater. The marine
(Ge/Si)opal record of the last 450 kyr can be modeled as
transient oceanic responses to instantaneous continental climate
transitions of consistent with the chemical weathering model of Murnane
and Stallard (1990). Glacial periods are characterized by lower
continental weathering intensity, lower (Ge/Si)riv, and
two-fold higher dissolved silica river fluxes. Marine (Ge/Si)
opal records thus contain a history of ocean silica chemistry that
reflect rapid global changes in continental weathering.
Galloway, J.N., J.E. Penner, C.S. Atherton, J.M. Prospero, H.
Rodhe, R.S. Artz, Y.J. Balkanski, H.G. Bingemer, R.A. Brost, S.
Burgermeister, G.R. Carmichael, J.S. Chang, R.J. Charlson, S.
Cober, W.G. Ellis, Jr., C.J. Fischer, J.M. Hales, D.R. Hastie, T.
Iversen, D.J. Jacob, K. John, J.E. Johnson, P.S. Kasibhatla, J.
Langner, J. Lelieveld, H. Levy, III, R. Lipschultz, J.T. Merrill,
A.F. Michaels, J.M. Miller, J.L. Moody, J. Pinto, A.A.P. Pszenny,
P.A. Spiro, L. Tarrason, S.M. Turner, and D.M. Whelpdale. Sulfur
and nitrogen levels in the North Atlantic Ocean's atmosphere: A
synthesis of field and modeling results. Global Biogeochemical
Cycles, 6(2):77-100 (1992).
In April 1990, 42 scientists from eight countries attended a workshop at
the Bermuda Biological Station for Research to compare field measurements
with model estimates of the distribution and cycling of sulfur and nitrogen
species in the North Atlantic Ocean's atmosphere. Data sets on horizontal
and vertical distributions of sulfur and nitrogen species and their
rates of deposition were available from ships' tracks and island
stations. These data were compared with estimates produced by
several climatological and event models for two case studies: (1)
sulfate surface distributions and deposition; and (2) nitrate surface
distributions and deposition. Highlights of the conclusions of the
case studies were that the measured concentrations and model results
of nitrate and non-seasalt sulfate depositions appeared to be in
good agreement at some locations but in poor agreement for some
months at other locations. The case studies illustrated the need
for the measurement and modeling communities to interact not only
to compare results, but also to cooperate in improving the designs
of the models and the field experiments.
Garraffo, Z., S.L. Garzoli, W. Haxby, and D.B. Olson. Analysis of a
general circulation model. Part 2: Distribution of kinetic energy in
the South Atlantic and Kuroshio/Oyashio systems. Journal of
Geophysical Research-Oceans, 97(C12):20,139-20,153 (1992).
The energy of the model transient eddies at 37.5 m is compared with
GEOSAT altimeter observations for the South Atlantic Ocean and for
the Kuroshio system. The model shows areas of transient motions
overlapping the ones obtained from GEOSAT altimeter data. For the
South Atlantic Ocean, the modeled eddy kinetic energy is smaller than
the one observed with GEOSAT, by a factor of 3 for area average on
the whole South Atlantic region, and by a factor of 4 for its western
boundary. On the Agulhas system, transient eddy activity develops in the
region where the Agulhas Current retroflects. In the western South
Atlantic, the modeled eddy activity is concentrated on the Confluence
front; observed variability along a more extended region following
the topography is not resolved in the model. For the Kuroshio region,
the energy level of the modeled transient motions is comparable with
GEOSAT observations, but the model eddy activity is more concentrated
in the Kuroshio Current and not in the Kuroshio extension. The
observations show the opposite. For the South Atlantic Ocean, a
comparison is also done between model eddy kinetic energy (defined
as including standing and transient eddy contributions) with values
obtained from surface driftnets. The analysis shows differences in
the western boundary, and good agreement across the South Atlantic
Ocean between 35°S and 45°S. In this formulation, the model
mean energy level is smaller than that observed with drifters from
the First GARP Global Experiment; differences might be due to an
overestimation in the values obtained with the drifters.
Garzoli, S.L. The Atlantic Equatorial Countercurrent: Models and
observations. Journal of Geophysical Research-Oceans,
97(C11):17,931-17,946 (1992).
An analysis of the dynamic height and volume transport variability of
the North Equatorial Countercurrent (NECC) in the western tropical
Atlantic (west of 38°W) is presented. The study is based upon a
subset of the data (16 month-long series of dynamic height obtained
with an array of inverted echo sounders) collected in the tropical
Atlantic during 1987 and 1988 as part of the National Science
Foundation/Tropical Ocean-Global Atmosphere array. Results are
compared with those from a previous work in the center of the basin
(28°W); a wind product for 1987-1988 is jointly analyzed for
further interpretation of the results. In order to obtain transports
from the echo sounder data, which do not provide information on the
vertical structure of the geostrophic velocities, the product from
the Community Model Experiment (CME) is analyzed. In this way the
present work follows the objectives: to provide a description of
the dynamics of the NECC in a region where maximum reversal is
predicted, compare the results with those in the center of the basin,
and to validate the product of the CME model.
Garzoli, S.L., Z. Garraffo, G. Podesta, and O.B. Brown. Analysis of
a general circulation model product. Part 1: Frontal systems in the
Brazil/Malvinas and Kuroshio/Oyashio regions. Journal of
Geophysical Research-Oceans, 97(C12):20,117-20,138 (1992).
In the present paper, the product of the Semtner and Chervin general
circulation model (GCM) is compared with available observations in the
frontal areas of the Brazil/Malvinas and the Kuroshio/Oyashio confluences.
The dimensionality of the systems studied is reduced by using the
empirical orthogonal functions (EOF) and frontal density methods. The
two sets of data utilized to validate the model are the sea surface
temperature (SST) from the satellite observations and temperature
fields product from the GCM at levels 1 (12.5 m), 2 (37.5 m) and 6
(160 m). Comparisons are made between the dominant empirical modes
and the locus of maximum probability for observations and model product.
The model reproduces intense thermal fronts at the surface and in the
upper layers. In the upper layer (level 1) they are induced by the
internal dynamics of the model and not by the restoring of the model
to climatology alone. The variability of these fronts is less pronounced
in the model than in the observations. The dominant period in the
observations is annual with contributions of semiannual and high
frequency oscillations. In the model, the dominant variability is
also annual at all analyzed levels. A semiannual oscillation
contributed to a lower degree and is related to eddies that, in the
model, have an annual and semiannual periodicity.
Gray, W.M., and C.W. Landsea. African rainfall as a precursor of
hurricane-related destruction on the U.S. east coast. Bulletin of
the American Meteorological Society, 73:1352-1364 (1992).
This paper describes a predictive relationship between west African rainfall
and U.S. hurricane-spawned destruction, which is based on information for
the 42-year period 1949-1990. It is shown that above-average rainfall
during the previous year along the Gulf of Guinea, in combination with
above-average rainfall in the western Sahel during June and July, is
linked to hurricane-spawned destruction along the U.S. east coast occurring
after 1 August, which is 10-20 times greater than in years when pre-August
precipitation for these west African regions is below average. Similar
hurricane-spawned damage along the U.S. Gulf coast shows only a negligible
relationship with African rainfall. Hurricane-caused deaths for both U.S.
coastal regions also show a similar association with west African rainfall.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Predicting Atlantic
seasonal hurricane activity 6-11 months in advance. Weather and
Forecasting, 7:440-455 (1992).
A surprisingly strong long-range predictive signal exists for Atlantic-basin
seasonal tropical cyclone activity. This predictive skill is related to two
measures of west African rainfall in the prior year and to the phase of the
stratospheric quasi-biennial oscillation of zonal winds at 30 mb and 50 mb,
extrapolated ten months into the future. These predictors, both of which are
available by 1 December, can be utilized to make skillful forecasts of
Atlantic tropical cyclone activity in the following June-November season.
Using jackknife methods to provide independent testing of datasets, it is
found that these parameters can be used to forecast nearly half of the
season-to-season variability for seven indices of Atlantic seasonal tropical
cyclone activity as early as late November of the previous year.
Griffin, J.S., R.W. Burpee, F.D. Marks, and J.L. Franklin.
Real-time airborne analysis of aircraft data supporting operational
hurricane forecasting. Weather and Forecasting, 7(3):480-490
(1992).
The Hurricane Research Division (HRD) has developed a technique
for real-time airborne analysis of aircraft data from reconnaissance
and research flights in tropical cyclones. The technique uses an
onboard workstation that analyzes flight-level observations, radar
reflectivity patterns, radial Doppler velocities, and vertical
soundings from Omega dropwindsondes (ODWs). Many of the workstation
analyses are in storm-relative coordinates that depend upon interactive
identification of the cyclone center from the radar reflectivity data.
Displays of the lower fuselage reflectivity, composited for 1-2 h,
provide an overall perspective of the horizontal patterns of
precipitation and a framework for interpretation of thermodynamic and
kinematic observations. The workstation runs algorithms for estimation
of the horizontal wind field in the hurricane core using radial
velocities measured by the airborne Doppler radar during one or more
penetrations of the storm center. Interactive software also supports
real-time processing of ODW wind and thermodynamic data, objective
editing of bad data, and automatic dissemination of mandatory and
significant-level data in the standard dropwindsonde code. Plans for
the 1992 hurricane season include transmission of subsets of the data
to the National Hurricane Center (NHC) through the Geostationary
Operational Environmental Satellite (GOES) communications system and
display of the aircraft analyses for the forecasters at NHC. With
the implementation of these plans, NHC will receive two-dimensional
analyses of the mesoscale precipitation and wind structure of the
storm core and more frequent estimates of the location and recent
motion of tropical cyclones.
Griffin, J.S., R.W. Burpee, F.D. Marks, and J.L. Franklin.
Real-time airborne analysis of flight-level and radar data supporting
operational hurricane forecasting. Preprints, 8th International
Conference on Interactive Information and Processing Systems for
Meteorology, Oceanography, and Hydrology, Atlanta, GA, January 5-10,
1992. American Meteorological Society, Boston, 241-246 (1992).
No abstract.
Hallett, J., W. Hendricks, and P.T. Willis. Evolution of
precipitation spectra in a developing convective cloud.
Preprints, 11th International Conference on Clouds and
Precipitation, Montreal, Canada, August 17-21, 1992.
American Meteorological Society, Boston, 216-219 (1992).
No abstract.
Hansen, D.V. Comments on "The significance of half-inertial
flow in the eastern equatorial Pacific." Journal of Physical
Oceanography, 22(7):811-813 (1992).
It is shown that the instability waves regularly observed in the
tropical Pacific and Atlantic Oceans do not necessarily contain
oscillations of half the local inertial frequency. Rather, it is
hypothesized that the flow approaches the half-inertial conditions
only at times when the instability waves develop sufficient
baroclinic intensity to saturate the geostrophic vorticity limit
of the gradient wind equation for anticyclonic flow.
Houston, S.H., and M.D. Powell. Hurricane Bob's surface wind
fields during landfall in New England. Minutes, 46th Annual
Interdepartmental Hurricane Conference, Homestead Air Force
Base, FL, January 14-17, 1992. NOAA Office of the Federal
Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-33 (1992).
No abstract.
Houze, R.A., Jr., F.D. Marks, and R.A. Black. Dual-aircraft
investigation of the inner core of Hurricane Norbert. Part II: Mesoscale
distribution of ice particles. Journal of the Atmospheric Sciences,
49(11):943-962 (1992).
Horizontal fields of cloud microphysical parameters, vertical air motion,
and horizontal wind at the 6 km level in Hurricane Norbert (1984) were
obtained by mapping and interpolating data collected on board a WP-3D
aircraft along numerous flight tracks executed within the central region
of the storm. Although the storm was characterized by a strong vortex of
winds reaching peak values >50 m s-1 all around the
storm, the precipitation was concentrated on the southwest side of the storm.
A sloping eyewall was located within 20-30 km of the eye. Stratiform
precipitation dominated the region outside the eyewall. A band of maximum
stratiform precipitation was located 60-70 km southwest of the storm center.
The ice particles at flight level tended to be relatively large both in the
eyewall and in the outer band of stratiform precipitation. Particles were
smaller and more numerous (100-300 l-1) in the zone between the
eyewall and outer stratiform band. These particles occurred on the outside
edges of the eyewall convective updrafts, indicating that they may have been
produced by splintering in association with graupel formation in the
updrafts. The large particles in the eyewall tended to be graupel. In the
outer stratiform region, characterized by weak, average vertical air motion
and an absence of strong convective drafts, the predominant particle type
was aggregates. The region of large graupel particles in the eyewall
coincided with the radius of maximum tangential wind and was apparently
produced by the azimuthal advection of the graupel particles. Since graupel
particles fall rapidly, they were not susceptible to advection out of the
weaker radial wind component. On the other hand, some of the more slowly
falling, less dense aggregates produced in the eyewall region were evidently
advected radially as well as azimuthally, thus accounting for the location
of the outer region of maximum stratiform precipitation intensity.
Johns, E., R.L. Molinari, and W.D. Wilson. Upper layer circulation
in the western tropical Atlantic inferred from climatological
temperature and salinity distributions. EOS, Transactions,
American Geophysical Union, 72(51):21 (1992).
No abstract.
Kaplan, J., and M. DeMaria. An operational statistical
hurricane intensity prediction scheme (SHIPS) for the Atlantic
basin. Minutes, 46th Annual Interdepartmental Hurricane Conference,
Homestead Air Force Base, FL, January 14-17, 1992. Office of the
Federal Coordinator for Meteorological Services and Supporting Research,
Washington, D.C., A-22 (1992).
No abstract.
Katsaros, K.B., and S.S. Atakturk. Air-sea interaction and remote
sensing. NASA Contract Rept. (NASA-CR-190913), 12 pp. (1992).
The first part of the proposed research was a joint effort between our
group and the Applied Physics Laboratory (APL), University of Washington.
The author's own research goal is to investigate the relation between the
air-sea exchange processes and the sea state over the open ocean and to
compare these findings with previous results obtained over a small body
of water namely, Lake Washington. The goals of the APL researchers are
to study (1) the infrared sea surface temperature (SST) signature of
breaking waves and surface slicks, and (2) microwave and acoustic
scattering from water surface. The task of the group in this joint effort
is to conduct measurements of surface fluxes (of momentum, sensible heat,
and water vapor) and atmospheric radiation (longwave and shortwave) to
achieve our research goal as well as to provide crucial complementary
data for the APL studies. The progress of the project is summarized.
Landsea, C.W., and W.M. Gray. The strong association between western
Sahelian monsoon rainfall and intense Atlantic hurricanes. Journal of
Climate, 5(5):435-453 (1992).
Seasonal variability of Atlantic basin tropical cyclones is examined with
respect to the monsoon rainfall over west Africa. Variations of intense
hurricanes are of the most interest, as they are responsible for over
three-quarters of United States tropical cyclone spawned destruction,
though they account for only one-fifth of all landfalling cyclones. Intense
hurricanes have also shown a strong downward trend during the last few
decades. It is these storms that show the largest concurrent association
with Africa's western Sahelian June-September rainfall for the years
1949-1990. Though the Sahel is currently experiencing a multidecadal
drought, the relationship between Atlantic tropical cyclones and western
Sahelian rainfall is not dependent on the similar downward trends in both
datasets. A detrended analysis confirms that a strong association still
exists, though reduced somewhat in variance explained. Additionally,
independent data from the years 1899 to 1948 substantiate the existence of
the tropical cyclone-western Sahelian rainfall association. The fact that
the Sahel periodically experiences multidecadal wet and dry regimes suggests
that the current Sahelian drought, which began in the late 1960s, could be a
temporary condition that may end in the near future. When this occurs, the
Atlantic hurricane basin--especially the Caribbean islands and the United
States east coast--will likely see a large increase in intense hurricane
activity associated with abundant Sahelian rainfall similar to the period
of the late 1940s through the 1960s.
Landsea, C.W., W.M. Gray, P.W. Mielke, and K.J. Berry. Long-term variations
of western Sahelian monsoon rainfall and intense U.S. landfalling
hurricanes. Journal of Climate, 5(5):1528-1534 (1992).
Western Salelian rainfall during the primary rainy season of June through
September is shown to be significantly associated with concurrent intense
U.S. landfalling hurricanes during the last 92 years. The most intense
hurricanes (i.e., Saffir-Simpson scale category 3, 4, or 5) have an
especially strong relationship with Sahelian rainfall, whereas weaker
hurricanes show little or no association. The hurricane-Sahelian rainfall
association is most evident along the U.S. east coast but is negligible in
the U.S. Gulf coast region.
Landsea, C.W., W.M. Gray, P.W. Mielke, and K.J. Berry. Seasonal forecasting
of Atlantic basin tropical cyclones by 1 June. Proceedings, 17th Annual
Climate Diagnostics Workshop, Norman, OK. NOAA, 388-390 (1992).
No abstract.
Marks, F.D. Kinematic structure of the hurricane inner core as
revealed by airborne Doppler radar. Preprints, 5th Conference on
Mesoscale Processes, Atlanta, GA, January 5-10, 1992. American
Meteorological Society, Boston, 127-132 (1992).
No abstract.
Marks, F.D., R.A. Houze, and J.F. Gamache. Dual-aircraft
investigation of the inner core of Hurricane Norbert. Part I:
Kinematic structure. Journal of the Atmospheric Sciences,
49(11):919-942 (1992).
A dedicated experiment to study the details ofthe important
physical processes and scale interactions operative within
the eyewall regions of Hurricane Norbert was carried out on
24-25 September. The two National Oceanic and Atmospheric
Administration (NOAA) Aircraft Operations Center (AOC) WP-3D
research aircraft were used for the study. One aircraft,
equipped with airborne Doppler radar, flew repeated radial
penetrations in and out of the eye, mapping the three-dimensional
wind field over the region surrounding the eyewall. This data
set provides the first complete mapping of the three-dimensional
wind field of the hurricane inner core. The three-dimensional
wind field within 40 km of the storm center was derived from a
"pseudo" dual-Doppler analysis in each quadrant of the
storm. The vertical wind components were derived from the mass
continuity equation and the horizontal wind field. The
Doppler-derived wind fields for the four quadrants were combined
to form a storm composite wind field that was 75 × 75 km on
a side and centered on the storm circulation center. The
wind-field altitude extended from 0.5-12 km. The Norbert wind
field was asymmetric, and the asymmetry varied with altitude.
The tangential wind maximum sloped upwind with increasing altitude,
from the left of the track (azimuths 147°-327°) at 1 km
altitude to the right of the storm track (azimuths 327°-147°)
at 3 km altitude. The radial wind at 1 km altitude had inflow in
front of the storm (327° azimuth) and outflow behind. This
pattern in the radial flow disappeared at 3 km altitude, where the
radial flow switched from inflow in the rear of the storm to outflow
in the front. The vertical velocity maximum was to the left of the
storm track at all levels. The maximum sloped downwind with
increasing altitude (along the upper boundary of the reflectivity
maximum) from in front of, and to the left of, the track at 2 km
altitude, to behind and to the right of the track at 8 km altitude.
To investigate the nature of the wind-field asymmetry, a technique
was devised to partition the horizontal wind components into a
horizontal mean wind as a function of the altitude and a
perturbation wind. The cylindrical nature of the wind
field permitted further partitioning of the perturbation wind
into the mean vortex (a function of radius and height-wave number
0) and a perturbation from the mean vortex (including any higher
order wave numbers). The wind partitioning was used to describe
the structure of the mean vortex and its interaction with the
environmental flow. The partition of the horizontal wind pointed
out the complex interactions of the wind components in determining
storm motion and in forcing mesoscale convergence/divergence
patterns that resulted in the vertical velocity asymmetry.
Maul, G.A., D.V. Hansen, and N.J. Bravo. A note on sea level
variability
at Clipperton Island from GEOSAT and in-situ observations. IUGG
Geophysical Monograph Series 69, 11:145-154 (1992).
During the 1986-1989 Exact Repeat Mission (ERM) of GEOSAT, in-situ
observations of sea level at Clipperton Island (10°N/109°W) and
satellite-tracked, free-drifting drogued buoys in the eastern tropical
Pacific Ocean are concurrently available. A map of the standard deviations
of GEOSAT sea surface heights (2.9 years) shows a variance maximum along
~12°N from Central America, past Clipperton to ~160°W.
Seafloor pressure gauge observations from a shallow (10 m depth) site on
Clipperton Island and an ERM crossover point in deep water nearby show
a correlation of r = 0.76 with a residual of ±6.7 cm RMS.
Approximately 17% of the difference (GEOSAT minus sea level) is characterized
by a 4 cm amplitude 0° phase annual harmonic, which is probably caused by
unaccounted-for tropospheric water vapor affecting the altimeter and/or ERM
orbit error removal. Wintertime anticyclonic mesoscale eddies advecting past
Clipperton Island each year have GEOSAT sea surface height and
in-situ sea level signals of more than 30 cm, some of which are
documented by the satellite-tracked drifters. Meridional profiles of the
annual harmonic of zonal geostrophic current from GEOSAT and from the
drifters both show synchronous maxima in the North Equatorial Countercurrent
and the North Equatorial Current. Other Clipperton sea level maxima seen
during late spring of each year may involve anticyclonic vortices formed
along Central America the previous winter.
Mestas-Nunez, A.M., D.B. Chelton, and R.A. deSzoeke. Evidence of
time-dependent Sverdrup circulation in the South Pacific from the SEASAT
scatterometer and altimeter. Journal of Physical Oceanography,
22(8):934-943 (1992).
SEASAT scatterometer and altimeter data are analyzed to investigate
time-dependent Sverdrup dynamics in the Southern Ocean (40°S to
60°S) over seasonal time scales. Sverdrup dynamics are shown to be
inadequate to describe the circulation in the South Atlantic and Indian
oceans. The Sverdrup circulation in the South Pacific is reasonable north
of 55°S. The changes in Sverdrup circulation from July to September
1978 indicate an eastward acceleration along 55°S and westward
acceleration along 40°S, suggesting a southward shift in the
subpolar eastward flow. Sea level in the South Pacific is estimated for
July and September 1978 from scatterometer vector wind data based on
Sverdrup dynamics assuming a flat-bottom ocean with barotropic flow. The
changes in Sverdrup sea level are compared with the changes in sea level
observed by the altimeter for the same time period. Both estimates
indicate a rise in sea level along a zonal band centered at about
50°S. This sea level rise inferred from both the scatterometer and
altimeter data is supported by a similar rise in sea level observed from
tide gauge measurements at two locations in New Zealand. The spatial
correlation between the two satellite estimates of sea level change is
about 0.5. This agreement suggests that time-dependent Sverdrup dynamics
may account for about 1/4 of the spatial variance of sea level change in
the South Pacific over the three-month SEASAT mission.
Mielke, P.W., K.J. Berry, W.M. Gray, and C.W. Landsea. Cross-validated
prediction models for 1 December and 1 August forecasts of seasonal
tropical cyclone activity in the Atlantic basin. Preprints, 12th
Conference on Probability and Statistics in Atmospheric Sciences,
Toronto, Canada. American Meteorological Society, Boston (1992).
No abstract.
Miller, D.K., and K.B. Katsaros. Satellite-derived surface latent heat
fluxes in a rapidly intensifying marine cyclone. Monthly Weather
Review, 120(7):1093-1107 (1992).
The aim of this article is to estimate surface latent heat fluxes in the
vicinity of a rapidly deepening cyclone before and during its period of
most rapid intensification. This is done with a bulk parameterization
scheme and remotely sensed input data. A method for estimating the
difference in specific humidity between the surface and a 10-m height is
investigated using the Special Sensor Microwave/Imager (SSM/I)-observed
integrated water vapor field and a sea surface temperature analysis. The
surface latent heat flux fields generally have estimated errors below 40%
south of 40°N and outside the region of high integrated water vapor
values associated with frontal bands. The method of estimating surface
latent heat fluxes for the case study was found to be usable in most
regions of the northwest Atlantic Ocean except for those locations
directly adjacent to coastlines in instances of offshore flow and in the
vicinity of surface fronts (DBO).
Millero, F.J., and J.-Z. Zhang. Total alkalinity measurements in
the South Atlantic. Data Report, University of Miami, 63 pp. (1992).
This report gives the results of our pH, total alkalinity (TA), and total
inorganic carbon dioxide (TCO2) measurements made in the South
Atlantic from June 11 to August 6, 1991 on the NOAA R/V Malcolm
Baldridge. The results were obtained by a potentiometric titration
of seawater samples with HCl. The resulting pH, TA, and TCO2
are thought to be precise to ± 0.01 in pH, ± 3 µmol/kg in TA,
and ± 5 µmol/kg in TCO2. These results will be combined
with the NOAA's measurements made by Rik Wanninkhof to characterize the
CO2 system in this region.
Molinari, R.L., and E. Johns. Upper layer circulation in
the western tropical Atlantic inferred from climatological
temperature and salinity distributions. EOS, Transactions,
American Geophysical Union, 72(51):21 (1992).
No abstract.
Molinari, R.L., R.A. Fine, and E. Johns. The Deep Western
Boundary Current in the tropical North Atlantic Ocean.
Deep-Sea Research, 39:1967-1984 (1992).
Tracer and CTD data collected on four cruises to the western
tropical North Atlantic Ocean during 1987-1989 are used to
describe the Deep Western Boundary Current (DWBC). The study
area extends along the boundary and east to the Mid-Atlantic
Ridge from 14.5°N to just north of the equator. Two cores
of recently ventilated (with respect to the chlorofluorocarbon
F11) northern hemisphere water are advected through the
area. A shallow core is centered at about 1,500 m and a deeper
core at about 3,500 m. The upper core of high F11 (bounded by
the 3.2°C and 4.7°C potential temperature isotherms)
is typically located inshore of the deeper currents,and
transports were computed relative to a zero reference velocity
on the 4.7°C potential temperature surface. Total transport
below the 4.7°C surface for the most intense portion of the
DWBC is 26 Sv (1 Sv = 106 m3/s). Of this
total, 17 Sv is contained in the two recently ventilated high
F11 cores. The Ceara Rise blocks equatorward flow in the DWBC
below the 1.8°C potential temperature surface, causing the
coldest waters to recirculate back to the north.
Molinari, R.L., E. Johns, W.E. Johns, and R. Zantopp. A
comparison of observed and simulated representations of the
North Atlantic Deep Western Boundary Current. EOS,
Transactions, American Geophysical Union, 72(51):39 (1992).
No abstract.
Peng, T.-H. Possible effects of ozone depletion on global carbon
cycle. Radiocarbon, 34(3):772-779 (1992).
The increase of UV-B radiation resulting from ozone depletion is
considered to have damaging effects on marine ecosystems. A cutback of
marine productivity would tend to reduce the oceanic uptake of
atmospheric CO2. Box models of the global oceans based on the
distribution of bomb-produced 14C are used to evaluate the
possible effects of ozone depletion on the atmospheric CO2
concentration. The maximum effect presumably takes place if the ozone
hole reduces the marine productivity to zero in the Antarctic Ocean. In
a business-as-usual scenario of future CO2 emissions, the
atmospheric CO2 partial pressure (pCO2) would
increase by an additional 37 µatm over the course of the next
century. This increase corresponds to 4.6% of the projected atmospheric
pCO2 in the year 2090. However, if the damaging effect caused
by the destruction of the stratospheric ozone layer is assumed to lower
the productivity over the Antarctic Ocean by 10%, the atmospheric
pCO2 would rise by less than 3 µatm over the expected
atmospheric level in the next century.
Peng, T.-H., and W.S. Broecker. Reconstruction of radiocarbon
distribution in the glacial ocean. In Radiocarbon After Four
Decades: An Interdisciplinary Perspective, R.E. Taylor, A. Long,
and R.S. Kra (eds.). Springer-Verlag, New York, 75-92 (1992).
No abstract.
Peng, T.-H., W.S. Broecker, and H.G. Ostlund. Dynamic Constraints on
CO2 Uptake by an Iron-Fertilized Antarctic, Modeling The
Earth System, D. Ojima (ed.). Global Change Institute, Volume 3,
77-106 (1992).
No abstract.
Petty, G.W., and K.B. Katsaros. Morning-evening differences in global
and regional oceanic precipitation as observed by the SSM/I. Purdue
University Press, 4 pp. (1992).
For the present preliminary analysis of oceanic rainfall statistics,
global oceanic SSM/I data were simply scanned for pixels which exhibited
a 37 GHz polarization difference (vertically polarized brightness
temperatures minus horizontally polarized brightness temperatures) of
less than 15 K. Such a low polarization difference over the open ocean is
a completely unambiguous indication of moderate to intense precipitation.
Co-located brightness temperatures from all seven channels of the SSM/I
were saved for each pixel so identified. Bad scans and geographically
mislocated block of data were objectively identified and removed from the
resulting data base. The authors collected global oceanic rainfall data
for two time periods, each one month in length. The first period (20
July-19 August 1987) coincides with the peak of the Northern Hemisphere
summer. The second period (13 January-12 February 1988) coincides with
the Northern Hemisphere winter.
Pikula, L., and S. Elswick. Ecosystems of the Florida Keys: A bibliography.
Library and Information Services Division, Current References (92-1),
National Oceanographic Data Center, 189 pp. (1992).
No abstract.
Post, W.M., F. Chavez, P.J. Mulholland, J. Pastor, T.-H. Peng, K.
Prentice, and T. Web. Climate feedbacks in the global carbon
cycle. In The Science of Global Change: The Impacts of Human
Activities on the Environment, D.A. Dunnette and R.J. O'Brien
(eds.). American Chemical Society, 392-412 (1992).
Increasing atmospheric CO2 is likely to produce chronic
changes in global climate, as it may have done in the geologic past.
Future CO2-induced changes in temperature and precipitation
distribution changes could equal or exceed the changes which have
occurred over the past 160,000 years and have affected the global carbon
cycle. We consider ocean and terrestrial processes that could involve
large change in carbon fluxes (>2 Pg C·yr-1) or changes
in storage in large carbon pools (>200 Pg C) resulting from
CO2-induced climate changes. These include (1) air-sea
exchange of CO2 in response to changes in temperature and
salinity; (2) climate-induced changes in ocean circulation; (3) changes
in oceanic new production and regeneration of organic debris caused
directly by climate change; (4) altered oceanic nutrient supply needed
to support new production due to climate-induced alteration of ocean
circulation and river discharge; (5) CaCO3 compensation in
sea water; (6) altered river nutrient flux and effects on coastal
organic matter production and sediment accumulation; (7) seasonal
balance between GPP and decomposition-respiration in terrestrial
ecosystems in response to changes in temperature and precipitation; (8)
successional processes in terrestrial ecosystems and formation of new
plant associations in response to climatic change; (9) effects on soil
nutrient availability, which amplifies ecosystem responses to climate
change; (10) and responses of northern forests, tundra, and peatlands
which have, until recently, been a sink for CO2. The
potential effect of these processes on the rate of atmospheric
CO2 concentration changes are estimated where possible, but
not much quantitative information at a global scale is known, so
uncertainty in these estimates is high. Each of these secondary
feedbacks, however, has the potential of changing atmospheric
CO2 concentration in magnitude similar to the effects of the
direct human processes (fossil fuel burning and land clearing)
responsible for the concern about global warming in the first place. It
is, therefore, urgent that these uncertainties be resolved. Lines of
research to accomplish this are suggested.
Powell, M.D. Surface wind speeds in hurricanes. Proceedings,
ASCE Structures, Congress X, San Antonio, TX, April 13-15, 1992.
American Society of Civil Engineers, New York, 246-249 (1992).
No abstract.
Powell, M.D., and S.H. Houston. A comparison of surface wind
sampling strategies in hurricanes. Minutes, 46th Annual Interdepartmental
Hurricane Conference, Homestead Air Force Base, FL, January
14-17, 1992. NOAA Office of the Federal Coordinator for
Meteorological Services and Supporting Research, Washington,
D.C., A-32 (1992).
No abstract.
Richardson, P.L., S. Arnault, S.L. Garzoli, and J.G. Bruce. Annual
cycle of the Atlantic North Equatorial Countercurrent. Deep-Sea
Research, 39(6):997-1014 (1992).
An analysis of numerous meridional XBT sections near 28°W reveals
that the geostrophic North Equatorial Countercurrent (NECC) continues
to flow eastward throughout the year, fastest in fall and slowest in
spring. Drifting buoys and historical ship drifts show that the
near-surface Countercurrent reverses each spring even when systematic
errors due to windage are taken into account. The seasonally fluctuating
winds drive an Ekman surface current that is eastward in fall, adding
to the geostrophic current, and westward in spring, countering and
overwhelming the geostrophic current. The reversal of the Countercurrent
in spring occurs in the near-surface layer and is driven by the
Northeast Trades. Thus, the near-surface velocity in the Countercurrent
is determined by a competition between local wind stress and the larger
field of wind stress curl, both of which have large seasonal variations
in the tropical Atlantic.
Rona, P.A., H. Bougault, J.L. Charlou, P. Appriou, T.A. Nelsen,
J.H. Trefry, G.L. Eberhart, A. Barone, and H.D. Needham.
Hydrothermal circulation, serpentinization and degassing at a
rift valley-fracture zone intersection: Mid-Atlantic Ridge near
15°N, 45°W. Geology, 20(9):783-786 (1992).
A hydrothermal system characterized by high ratios of methane to
both manganese and suspended particulate matter was detected in
seawater sampled at the eastern intersection of the rift valley
of the Mid-Atlantic Ridge with the Fifteen-Twenty Fracture Zone.
This finding contrasts with low ratios in black smoker-type
hydrothermal systems that occur within spreading segments.
Near-bottom water sampling coordinated with SeaBeam bathymetry
and camera-temperature tows detected the highest concentrations
of methane at fault zones in rocks with the appearance of
altered ultramafic units in a large dome that forms part of the
inside corner high at the intersection. The distinct chemical
signatures of the two types of hydrothermal systems are inferred
to be controlled by different circulation pathways related to
reaction of seawater primarily with ultramafic rocks at
intersections of spreading segments with fracture zones but
with mafic rocks within spreading segments.
Smith, S.D., R.J. Anderson, W.A. Oost, C. Kraan, N. Maat, J. DeCosmo,
K.B. Katsaros, K.L. Davidson, K. Bumke et al. Sea surface wind
stress and drag coefficients: The HEXOS results. Boundary-Layer
Meteorology, 60(1-2):109-142 (1992).
Turbulent fluxes have been measured in the atmospheric surface layer from
a boom extending upwind from the Dutch offshore research platform
Meetpost Noordwijk (MPN) during HEXMAX (Humidity Exchange over the Sea
Main Experiment) in October-November 1986. We started out to study eddy
flux of water vapor, but discrepancies among simultaneous measurements made
with three different anemometers led us to develop methods to correct eddy
correlation measurements of wind stress for flow distortion by nearby
objects. We then found excellent agreement among the corrected wind
stress data sets from the three anemometers on the MPN boom and with eddy
correlation measurements from a mast on a tripod. Inertial-dissipation
techniques gave reliable estimates of wind stress from turbulence
spectra, both at MPN and at a nearby ship. The data cover a range of wave
ages and the results yield new insights into the variation of sea surface
wind stress with sea state; two alternative formulas are given for the
nondimensional surface roughness as a function of wave age.
Thacker, W.C. Oceanographic inverse problems. Physica D,
60:16-37 (1992).
Oceanographic inverse problems are generalizations of the concept
of linear regression to encompass the fitting of numerical models
based on the partial-differential equations of fluid dynamics to
oceanic data by adjusting surface fluxes, initial conditions,
and/or transport parameters. The limited resolution of the data
requires some sort of regularizing assumptions similar to those
needed for spatial interpolation. Computationally, they are
nonlinear-least-squares problems involving very many variables.
These problems can be ill-conditioned due to the indirect nature
of the observations, to the way the dynamics enter, and to the
effect of the regularizing assumptions. Solving such large
optimization problems requires efficient computation of derivatives
of functions defined by computational codes. The adjoint method
provides derivatives with respect to all the code's many adjustable
inputs for roughly the same cost as computing a single model
simulation. Although computationally difficult, model fitting
offers the promise of dynamically consistent multivariate analyses
of oceanographic data.
Trefry, J.H., R.P. Trocine, S. Metz, T.A. Nelsen, and N. Hawley.
Suspended particulate matter on the Louisiana shelf:
Concentrations, composition and transport pathways. Proceedings,
NECOP Workshop on Nutrient Enhanced Coastal Ocean Productivity,
Chauvin, LA, October 2-3, 1991. Texas A&M University Press, College
Station, 126-130 (1992).
The concentrations, composition and transport pathways of
suspended particulate matter and particulate organic carbon
(POC) have a direct bearing on the development and persistence
of shelf hypoxia, as well as on the global cycling of carbon.
More than 120 CTD-transmissometer profiles and >400 particle
samples were collected from the Mississippi River and adjacent
Gulf of Mexico on cruises during July-August 1990 and February
1991. River-flow is a dominant factor in controlling particle
distributions; however, time-series data show that tides and
weather fronts can greatly influence concentrations and movement
of suspended matter. Results from chemical analyses show that
concentrations of POC range from >80 µmol/L (>1 mg/L)
at near river locations to <0.8 µmol/L (<0.01 mg/L)
in some deep offshore waters. The organic fraction of the
suspended matter increases from <5% of the total mass near
the river mouth to >90% along the shelf at about 10 km from
the river. The C/N molar ratio in suspended particles from
throughout the shelf is near uniform at 6. Plumes of particle-rich
water at outer shelf depths of about 100 m, along with transport
in near-bottom nepheloid layers, carry a POC burden that can be
traced tens of kilometers offshore.
Tsai, J.J., J.R. Proni, W.P. Dammann, and N.C. Kraus. Dredged
material disposal at the edge of the Florida Current. Chemistry
and Ecology, 6:169-187 (1992).
A field data collection project was undertaken to investigate the
short-term fate of dredged material discharged in the designated
Miami Ocean Dredged Material Disposal Site (ODMDS) before dredging of
the Miami River and the Miami Harbor Turning Basin begins. The
designated ODMDS is located in relatively deep water for discharge sites
with typical bottom depth of 150 m and is also located in the western
boundary region of the Gulf Stream current off Miami. Acoustical
backscattering, current, particulate, temperature, and salinity data
were gathered over a three-day period from April 24, 1990 through
April 26, 1990. The major generic features of shallow-water discharge
plumes were observed to be present: (a) the presence of a rapid
convective descending plume portion; (b) impact of that plume portion
with the ocean bottom and concomitant generation of bottom surge; (c)
rapid horizontal width growth of the descending plume through
entrainment; and (d) retention of a residual plume portion within the
water column. A well-mixed upper water column layer extending to a
depth of 40 to 60 m below the surface of the ocean permitted
measurements of the plume entrainment coefficient free from bottom
boundary, water column density gradient, and vertical current shear
effects which are usually present in relatively shallow, e.g.,
less than 40 m bottom depth, coastal ocean discharge studies.
Entrainment coefficient estimates obtained in this study were between
0.5 to 0.7. The residual water plume material was tracked over
one-half hour during each of eight discharge events and was transported
in a north-northeast direction.
Tziperman, E., W.C. Thacker, R.B. Long, and S.-M. Hwang. Oceanic
data analysis using a general circulation model. Part 1:
Simulations. Journal of Physical Oceanography,
22(12):1434-1457 (1992).
This paper deals with the solution of inverse problems involving
complex numerical models of the oceanic general circulation and
large data sets. The goal of these inverse problems is to find values
for model inputs consistent with a steady circulation and, at the
same time, consistent with the available data. They are formulated as
optimization problems, seeking values for the model's inputs that minimize
a cost function measuring departure from steady state and from data.
The two main objectives of this work are (1) to examine the feasibility
of solving inverse problems involving a realistic numerical model of the
oceanic general circulation, and (2) to understand how the optimization
uses various data to calculate the desired model parameters. The model
considered here is similar to the primitive equations model of Bryan
(1969) and of Cox (1984), the principal difference being that here the
horizontal momentum balance is essentially geostrophic. The model's inputs
calculated by the optimization consist of surface fluxes of heat, water,
and momentum, as well as the eddy-mixing parameters. In addition, optimal
estimates for the hydrography are obtained by requiring the hydrography
to be consistent with both other types of data and the model's dynamics.
In the examples presented here, the data have been generated by the
model from known inputs; in some cases simulated noise has been added.
The cost function is a sum of terms quadratic in the differences
between the data and their model counterparts and terms quadratic in the
temperature and salinity time rate of change as evaluated using the
model equations. The different inverse problems considered differ in the
choice of the model inputs calculated by the optimization and in the
data used in the cost function. Optimal values of the model's inputs
are computed using a conjugate-gradient minimization algorithm, with
the gradient computed using the so-called adjoint method. In examples
without added noise, solutions for the model inputs were found
efficiently and accurately. This was not the case when simulated data
with randomly generated noise were used. Amplification of noise was
especially felt in regions of deep water formation due to the strong
vertical mixing in these regions. Away from deep water formation
regions, the performance of the optimization with noisy data was still
not satisfactory, possibly due to bad conditioning of the problem. The
conditioning of the optimization and the difficulties due to the noise
amplification are further discussed in part 2 of this work using real
oceanographic data for the North Atlantic Ocean.
Tziperman, E., W.C. Thacker, R.B. Long, S.-M. Hwang, and S.R.
Rintoul. Oceanic data analysis using a general circulation model,
Part 2: A North Atlantic model. Journal of Physical
Oceanography, 22(12):1458-1485 (1992).
A general circulation model (GCM) and North Atlantic climatological
data of temperature, salinity, wind stress, evaporation minus
precipitation, and air-sea heat fluxes are used to examine the
possibility of solving inverse problems using a full-scale numerical
GCM and real oceanographic data, combined through an optimization
approach. In this study several solutions for the model inputs and
the structure of the cost function as a function of the model inputs
are examined to demonstrate two of the main difficulties confronting
such large-scale nonlinear inverse problems (about 30,000 unknowns and
a similar number of constraints for the problem examined here). The
first is the possible existence of local minima of the cost function,
which prevents the convergence of the optimization to the global
minimum representing the desired optimal solution for the model inputs.
The second difficulty, which seems the dominant one for many of the
problems examined in this part as well as in part 1, is the ill
conditioning of the inverse problem. Simple model equations are used
to analyze the conditioning of the optimization problem and to analyze
the role of both dissipation and waves in the model dynamics in
conditioning the problem. The analysis suggests what might be an
improved formulation of the cost function resulting in better
conditioning of the problem. The relation between the optimization
approach and the robust diagnostic method of Sarmiento and Bryan
(1982) is explicitly demonstrated, and the solution obtained by
combining the two methods is used to examine the performance of the
GCM used here for the North Atlantic Ocean.
Wanninkhof, R.H. Relationship between gas exchange and wind speed
over the ocean. Journal of Geophysical Research,97:7373-7381
(1992).
Relationships between wind speed and gas transfer, combined with
knowledge of the partial pressure difference of CO2 across
the air-sea interface are frequently used to determine the CO2
flux between the ocean and the atmosphere. Little attention has been
paid to the influence of variability in wind speed on the calculated gas
transfer velocities and the possibility of chemical enhancement of
CO2 exchange at low wind speeds over the ocean. The effect
of these parameters is illustrated using a quadratic dependence of gas
exchange on wind speed which is fit through gas transfer velocities
over the ocean determined by the natural-14C disequilibrium
and the bomb-14C inventory methods. Some of the variability
between different data sets can be accounted for by the suggested
mechanisms, but much of the variation appears due to other causes.
Possible causes for the large difference between two frequently-used
relationships between gas transfer and wind speed are discussed. To
determine fluxes of gases other than CO2 across the air-water
interface, the relevant expressions for gas transfer, and the temperature
and salinity dependence of the Schmidt number and solubility of several
gases of environmental interest, are included in an appendix.
Willis, P.T., J. Hallett, and R.A. Black. Cloud and hydrometeor
microphysics at -3°C in a vigorous Florida convective updraft.
Preprints, 11th International Conference on Clouds and Precipitation,
Montreal, Canada, August 17-21, 1992. American Meteorological Society,
Boston, 436-439 (1992).
No abstract.
Willoughby, H.E. Linear motion of a shallow-water barotropic vortex
as an initial-value problem. Journal of the Atmospheric
Sciences, 49(21):2015-2031 (1992).
This paper revisits calculation of motion for a shallow-water
barotropic vortex with fixed mean axisymmetric structure. The
algorithm marches the linear primitive equations for the wavenumber
1 asymmetry forward in time using a vortex motion extrapolated from
previous calculations. Periodically, it examines the calculated
asymmetry for the apparent asymmetry due to mispositioning of the
vortex center, repositions the vortex to remove the apparent
asymmetry, and passes the corrected vortex motion on to the next
cycle. This approach differs from the author's earlier variational
determination of the steady-state motion after initial transients
had died away. The steady-state approach demonstrated that the
vortex had normal modes at zero frequency and, when an annulus of
weak anticyclonic flow encircled the cyclonic inner vortex, at the
most anticyclonic rotation frequency of the mean flow. Forcing of
the former model led to too rapid steady-state poleward motion on
a beta plane. At least for the linear problem, the key to more
realistic simulation of motion and structure is the normal modes'
transient response to diverse forcing: environmental potential
vorticity gradients, embedded sources and sinks of mass, and
initial asymmetries. The beta effect and other environmental
potential vorticity gradients excite the normal modes to induce an
acceleration of the vortex center toward and to the left of the
direction to maximum environmental vorticity. Times ~100 days
would be required to reach the too fast motions predicted in the
earlier work. A rotating mass source-sink pair drives the vortex
along a cycloidal track, but does not force the normal modes. A
nonrotating source-sink forces a motion from the source toward the
sink and excites the normal modes, leading to motion that persists
after the forcing has ceased. Similarly, initial asymmetries that
project onto the normal modes maintain themselves for times >10
days, leading to persistent vortex propagation that evolves
as the complex normal-mode frequencies dictate. Understanding of
these normal modes can contribute to better tropical cyclone motion
forecasts through better initialization of numerical track prediction
models.
Wilson, W.D., and E. Johns. Shipboard ADCP current measurements
in the North Brazil Current retroflection region. EOS,
Transactions, American Geophysical Union, 72(51):21 (1992).
No abstract.
Yvon, S.A., E.S. Saltzman, and D.J. Cooper. Measurements of atmospheric
DMS, SO2 and H2S over the equatorial Pacific Ocean
during IGAC/MAGE. EOS, Transactions, American Geophysical Union,
73(43):81 (1992).
No abstract.
**1991**
Aberson, S.D., and M. DeMaria. A nested barotropic hurricane track
forecast model (VICBAR). Extended Abstracts, 19th Conference on
Hurricanes and Tropical Meteorology, Miami, FL, May 6-10, 1991.
American Meteorological Society, Boston, 81-86 (1991).
No abstract.
Barnes, G.M., J.F. Gamache, M.A. LeMone, and G.J. Stossmeister. A
convective cell in a hurricane rainband. Monthly Weather Review,
119(3):776-794 (1991).
On 10 October 1983 the two NOAA WP-3D aircraft completed a mision designed
to provide airborne Doppler radar data for a convective cell embedded in
a weak rainband on the trailing side of Hurricane Raymond. Comparisons
of the wind field produced from the pseudo-dual Doppler radar technique
with in-situ wind measurements suggest that the larger convective-scale
features may be resolved if the sampling time is kept to a minimum. The
convective cell was found to move downband faster than any environmental
winds, but slightly slower than the winds found in the reflectivity core
that delineates the cell. In the core of the cell the tangential wind
is increased and the radial inflow turns to outflow with respect to the
circulation center. The flow field demonstrates that the downband
stratiform portion of a rainband is not from cells currently active,
since the updraft detrains upwind relative to the cell, but rather it is
due to the fallout from ice particles placed into the upper troposphere
by clouds that have since dissipated. The mass flux of this cell is
estimated to be 5%-10% of the mass flux accomplished by an eyewall of
a moderate tropical cyclone. This finding supports the concept that
large, convective-active rainbands have a major effect on the subcloud
layer air flowing toward the eyewall.
Barnes, G.M., and M.D. Powell. The inflow thermodynamics of Hurricane
Gilbert. Extended Abstracts, 19th Conference on Hurricanes and
Tropical Meteorology, Miami, FL, May 6-10, 1991. American Meteorological
Society, Boston, 486-489 (1991).
No abstract.
Beryulev, G.P., P.B. Black, and A.V. Litinetski. Intercomparison of wind
and temperature data from the research aircraft WP-3D and AN-12BC in
Hurricane Gilbert, 1988. Extended Abstracts, 19th Conference on
Hurricanes and Tropical Meteorology, Miami, FL, May 6-10, 1991.
American Meteorological Society, Boston, 587-588 (1991).
No abstract.
Black, M.L., R.W. Burpee, and F.D. Marks. Vertical motions in tropical
cyclones determined with airborne Doppler radial velocities. Extended
Abstracts, 19th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, May 6-10, 1991. American Meteorological Society, Boston,
409-411 (1991).
No abstract.
Black, P.B., and F.D. Marks. The structure of an eyewall meso-vortex
in Hurricane Hugo (1989). Extended Abstracts, 19th Conference on
Hurricanes and Tropical Meteorology, Miami, FL, May 6-10, 1991.
American Meteorological Society, Boston, 579-582 (1991).
No abstract.
Broecker, W.S., A. Virgilio, and T.-H. Peng. Radiocarbon age of the
deep Atlantic revisited. Geophysical Research Letters, 18(1):1-3
(1991).
No abstract.
Brown, M.G., F.D. Tappert, and G.J. Goni. An investigation of
sound ray dynamics in the ocean volume using an area preserving
mapping. Wave Motion, 14(1):93-99 (1991).
An area preserving mapping which describes sound ray propagation in a
simple range-dependent model of the ocean sound channel is derived and
studied. The unbounded ocean model has a bilinear sound speed profile in
which the vertical sound speed gradient above the sound channel axis
varies sinusoidally in range. It is assumed that the scale of the
range-dependent perturbation is small compared to a typical upper loop
length of a ray. The explicit mapping which results gives successive
iterates of range and upgoing ray angle at the sound channel axis
(rn, thetan) - (rn+1, theta
n+1). The degree of stochasticity of the mapping is governed by
a single dimensionless parameter, epsilon, the strength of the
range-dependent perturbation. Iterates of the mapping indicate that some
ray trajectories are chaotic (i.e., exhibit extreme sensitivity to
initial conditions) for perturbations comparable in strength to those
produced by internal waves in the ocean. The chaotic nature of these rays
is confirmed by the calculation of positive Lyapunov exponents.
Burpee, R.W., and P.G. Black. Strong surface winds and mesoscale convective
systems in the unnamed tropical storm of 1987. Extended Abstracts, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May 6-10,
1991. American Meteorological Society, Boston, 412-415 (1991).
No abstract.
Burpee, R.W., J.S. Griffin, J.L. Franklin, and F.D. Marks. Airborne
analysis of observations from a NOAA P-3 in support of operational
hurricane forecasting. Preprints, 7th International Conference on
Interactive Information and Processing Systems for Meteorology,
Oceanography, and Hydrology, New Orleans, LA, January 13-18, 1991.
American Meteorological Society, Boston, 195-197 (1991).
No abstract.
Burpee, R.W., J.S. Griffin, J.L. Franklin, and F.D. Marks. Airborne
analysis of observations from a P-3 aircraft in support of operational
hurricane forecasting. Proceedings, 4th Interagency Airborne Geoscience
Workshop, La Jolla, CA, January 29-February 1, 1991. NASA, Washington,
D.C., 123-124 (1991).
No abstract.
Carsey, T.P. Marine tropospheric hydrocarbons: An intercomparison
exercise. NOAA Data Report, ERL AOML-21 (PB91-223735), 31 pp. (1991).
No abstract.
Carsey, T.P., M.S. Gallagher, M.L. Farmer, and C.S. Moore. PAN in the
equatorial Pacific boundary layer. EOS, Transactions, American
Geophysical Union, 72:107 (1991).
No abstract.
Charlou, J.L., H. Bougault, P. Appriou, T.A. Nelsen, and
P.A. Rona. Different TDM/CH4 hydrothermal plume
signatures: TAG site 26°N and serpentinized ultrabasic
diapir at 15°05'N on the Mid-Atlantic Ridge.
Geochimica et Cosmochimica Acta, 55(12):3209-3222 (1991).
As a part of the 1988 NOAA VENTS Program, CH4 and
Mn tracers were used to identify and compare hydrothermal plumes
found above the TAG field (26°N) and in the rift valley at
15°N close to the eastern intersection of the ridge axis with
the 15°20'N Fracture Zone at the Mid-Atlantic Ridge (MAR).
Active hydrothermal venting was confirmed at TAG, based on
elevated concentrations of total dissolved Mn (TDM up to 30
nmol/kg), high CH4 concentrations (up to 200 nL/L),
and elevated nephelometry signals. Plumes of a different
composition were identified at 15°N with high CH4
concentrations (up to 400 nL/L), low total dissolved Mn concentrations
(TDM <1 nmol/kg), and no significant nephelometry signal. The
different properties of these tracers and the different tracer ratios
can be used to deduce vent fluid characteristics and compare one
hydrothermal area to another. TDM/CH4 and
nephel/CH4 ratios at TAG are of the same order of
magnitude as those observed at other spreading axis hydrothermal
fields. At 15°N, the low TDM/CH4 ratio provides
evidence of fluid circulation into ultrabasic rocks and offers a
potentially useful and single method of exploring for hydrothermal
activity associated with serpentinization. Mantle degassing through
hydrothermal activity associated with serpentinization is an
important process with respect to chemical and thermal exchanges
between the upper mantle and the ocean. Different ratios of
hydrothermal tracers (i.e., TDM/CH4) provide a
useful framework for identifying subseafloor processes along
mid-oceanic ridges.
Cione, J.J., S. Raman, and L.J. Pietrafesa. Effects of marine boundary
layer baroclinicity induced by the Gulf Stream on east coast winter
storms. Preprints, 5th Conference on Meteorology and Oceanography of
the Coastal Zone, Miami, Florida, May 6-9, 1991. American Meteorological
Society, Boston, 113-117 (1991).
No abstract.
Dammann, W.P., J.R. Proni, J.F. Craynock, and R. Fergen. Oceanic
wastewater outfall plume characteristics measured acoustically.
Chemistry and Ecology, 5:75-84 (1991).
A study, called SEFLOE, of the dispersion characteristics of several
wastewater outfalls was conducted off the coast of southeast Florida
(USA). In this study, the feasibility of utilizing high frequency
(20 kHz and 200 kHz) acoustic echoes to characterize the dilution
characteristics of the effluent wastewater was examined. It is
hypothesized that the background corrected acoustic backscattered
intensity may be used to guide chemical/biological sampling, and that
one or more plume subfields may be revealed by the scattering strength
field. Data from SEFLOE have indicated that the wastewater plume
field is divided into regions of higher concentration spatially
separated by regions of lower concentration; we call these regions of
higher concentration "boluses." When the water column is density
stratified, subsurface plumes may peel off of the main rising plume
and remain at equilibrium on a density gradient.
DeMaria, M., and R.W. Jones. Optimization of a hurricane
track forecast model using the adjoint model equations.
Preprints, 9th Conference on Numerical Weather Prediction,
Denver, CO, October 14-18, 1991. American Meteorological Society,
Boston, 547-550 (1991).
No abstract.
DeMaria, M., and J. Kaplan. A statistical model for predicting tropical
cyclone intensity change. Extended Abstracts, 19th Conference on
Hurricanes and Tropical Meteorology, Miami, FL, May 6-10, 1991.
American Meteorological Society, Boston, 521-525 (1991).
No abstract.
Dodge, P.P., R.W. Burpee, and F.D. Marks. Airborne Doppler radar
analyses of the core of Hurricane Gilbert. Extended Abstracts, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May 6-10,
1991. American Meteorological Society, Boston, 551-552 (1991).
No abstract.
Enfield, D.B., and L. Cid. Low-frequency changes in El
Niño/Southern Oscillation. Journal of Climate,
4:1137-1146 (1991).
Although there are indications from numerical models that El
Niño/Southern Oscillation (ENSO) may be an internal mode
of the coupled Pacific Ocean/atmosphere system, sensitive to
climatic background parameters, it has not yet been possible to
find significant changes in ENSO variability between the Little
Ice Age and the present. Yet, a number of authors have found
qualitative indications in anecdotal and proxy records of shorter,
century-scale variations in the return-interval statistics for El
Niño episodes. To objectively determine what
nonstationarities exist, we statistically examine the El Niño
occurrences since 1525, compiled by Quinn et al. (1987).
We have stratified the return intervals both for strong events and
for all events according to two null hypotheses: (1) return
intervals are stationary over periods of 200-500 years; and
(2) the intervals are stationary on a centenary time scale,
between epochs of contrasting solar variability. Two-parameter
Weibull distributions are fit to subsamples of the data using an
optimized bootstrap procedure, and the scale parameters are
compared between groups. At the 95% significance level, only
the null hypothesis for high/low solar levels and strong El
Niño events can be rejected. The corresponding
hypothesis for all events rejects at the 90% level, while
overall stationarity cannot be rejected at any reasonable level,
for either class of events. The significant results are that: (a)
the El Niño recurrence rate is stationary with respect
to long-term climate changes; (b) return intervals of strong
El Niño events are significantly nonstationary at
centenary time scales; and (c) events of all intensities exhibit
the same nonstationarity but less clearly. There is too little
data to reject the possibility that the association with solar
epochs is coincidental; however, we have advanced this
hypothesis to explain such a connection.
Feuer, S.E., and J.L. Franklin. Nested analyses of Hurricane Gloria
from dropwindsonde and Doppler radar data. Extended Abstracts, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May 6-10,
1991. American Meteorological Society, Boston, 130-133 (1991).
No abstract.
Frazel, D.W., G.A. Berberian, J. McElroy, and G.L. Hitchcock.
Radiatively Important Trace Species (RITS) 1990: Tropical Pacific
Ozone Minimum Expedition--nutrient, chlorophyll-a, and primary
productivity data. NOAA Data Report, ERL AOML-19 (PB91-178087),
40 pp. (1991).
During the period of January 3-February 18, 1990, a multifaceted
oceanographic research cruise called the RITS 1990 Tropical
Pacific Ozone Minimum Expedition was made on the NOAA ship
Malcolm Baldrige in the equatorial Pacific Ocean. The
objective of the cruise was to study processes controlling
radiatively important trace species in the region of the tropical
Pacific ozone minimum in the central equatorial Pacific Ocean.
Measurements from hydrocasts for nutrients, phytoplankton biomass,
and primary productivity were made during this period. This report
represents the hydrographic, nutrient, and biological data from this
cruise.
Friedman, H.A., and C.A. Arnhols. 1991 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 118 pp. (1991).
No abstract.
Gamache, J.F. Inner core budget studies of Hurricane Norbert (1984).
Extended Abstracts, 19th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, May 6-10, 1991. American Meteorological
Society, Boston, 545-550 (1991).
No abstract.
Gamache, J.F., F. Roux, and F.D. Marks. Comparison of three methods
to deduce three-dimensional wind fields in a hurricane with airborne
Doppler radar. Preprints, 25th International Conference on Radar
Meteorology, Paris, France, June 24-28, 1991. American Meteorological
Society, Boston, 462-465 (1991).
No abstract.
Goni, G.J. Chaos in underwater acoustics. In Ocean Variability
and Acoustic Propagation, J. Potter and A. Warn-Varnas (eds.).
Kluwer Academic Publishers, The Netherlands, 139-160 (1991).
No abstract.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Potential forecast
skill for Atlantic seasonal hurricane variability. Extended Abstracts,
19th Conference on Hurricanes and Tropical Meteorology, Miami, FL, May
6-10, 1991. American Meteorological Society, Boston, 89-95 (1991).
No abstract.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Strong extended
range seasonal predictive potential for Atlantic hurricane activity.
Proceedings, 16th Annual Climate Diagnostics Workshop, Los
Angeles, CA. NOAA, 412-416 (1991).
No abstract.
Griffin, J.S., R.W. Burpee, J.L. Franklin, and F.D. Marks. Preliminary
results of airborne analysis of observations in support of operational
hurricane forecasting. Extended Abstracts, 19th Conference on Hurricanes
and Tropical Meteorology, Miami, FL, May 6-10, 1991. American
Meteorological Society, Boston, 144-147 (1991).
No abstract.
Houston, S.H., and M.D. Powell. Effects of Tropical Storm Marco (1990)
on Florida's west coast. Preprints, 5th Conference on Meteorology and
Oceanography of the Coastal Zone, Miami, FL, May 6-9, 1991. American
Meteorological Society, Boston, 131-133 (1991).
No abstract.
Jones, R.W., and M. DeMaria. A variational method for including
persistence in a hurricane track forecast model. Preprints, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May
6-10, 1991. American Meteorological Society, Boston, 331-334 (1991).
No abstract.
Kaplan, J., and J.L. Franklin. The relationship between the motion of
Tropical Storm Florence (1988) and its environmental flow. Extended
Abstracts, 19th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, May 6-10, 1991. American Meteorological Society, Boston,
93-97 (1991).
No abstract.
Lagos, P., D.V. Hansen, and A. Herman. Climatological atlas of the
subsurface thermal structure of the eastern tropical South Pacific
Ocean. NOAA Technical Report, ERL 444-AOML-34, 303 pp. (1991).
Monthly climatological maps of objectively analyzed fields of temperature
are presented at standard oceanographic observation levels from the
surface to 300 m depth on a 1° latitude-longitude grid in the region
between the equator and 20°S and between the South American coast
and 90°W. The temperature data used in this study were from
bathythermograph measurements obtained from 1952 to 1987 from Peruvian
and other research vessels; they were made available by research
institutions in Peru and the United States and by the National
Oceanographic Data Center and the Fleet Numerical Oceanographic Center.
The data set was blended with recent data to form a data base
containing 14,000 observations. The method of analysis consists of
optimally interpolating the value at each mapping grid point, using
observations taken at known nearby locations. This method, known as
Kriging, is a best linear unbiased estimator that also yields an estimate
of the uncertainty of each interpolated value. A brief discussion of the
major characteristic features of the temperature fields is given,
including a comparison of the SST results with results from other SST
climatologies.
Landsea, C.W. Intense Atlantic hurricanes and their concurrent/predictive
relationships to west African rainfall. Extended Abstracts, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May
6-10, 1991. American Meteorological Society, Boston, 165-169 (1991).
No abstract.
Landsea, C.W. West African monsoonal rainfall and intense hurricane
associations. Colorado State University, Department of Atmospheric
Science Paper No. 484, 272 pp. (1991).
No abstract.
Landsea, C.W., and W.M. Gray. Concurrent multidecadal variations of west
African monsoonal rainfall and intense Atlantic hurricane activity.
Extended Abstracts, 5th Conference on Climate Variations, Denver,
CO. American Meteorological Society, Boston, 38-41 (1991).
No abstract.
Landsea, C.W., and W.M. Gray. Predictability of intense Atlantic
hurricanes and western Sahel rainfall from west African rainfall.
Proceedings, 16th Annual Climate Diagnostics Workshop, Los
Angeles, CA. NOAA, 417-422 (1991).
No abstract.
Lee, W.-C., and F.D. Marks. Real-time display of mean
three-dimensional hurricane structure using the VTD technique.
Preprints, 25th International Conference on Radar Meteorology,
Paris, France, June 24-28, 1991. American Meteorological
Society, Boston, 470-473 (1991).
No abstract.
Lee, W.-C., F.D. Marks, and R. Carbone. Real-time display of mean
three-dimensional hurricane structure using the VTD technique. Extended
Abstracts, 19th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, May 6-10, 1991. American Meteorological Society, Boston,
445-450 (1991).
No abstract.
Lhermitte, R., and P.T. Willis. Small Doppler radar as a precipitation
gauge. Preprints, 25th International Conference on Radar Meteorology,
Paris, France, June 24-28, 1991. American Meteorological Society,
Boston, 778-781 (1991).
No abstract.
Marks, F.D., and R.A. Houze. Kinematic structure of the eyewall of
Hurricane Emily (1987) as determined from an airborne Doppler radar.
Extended Abstracts, 19th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, May 6-10, 1991. American Meteorological
Society, Boston, 437-440 (1991).
No abstract.
Marks, F.D., D. Atlas, and P.T. Willis. Probability matched Z-R
relations for hurricanes from aircraft observations. Preprints, 25th
International Conference on Radar Meteorology, Paris, France, June
24-28, 1991. American Meteorological Society, Boston, 778-781 (1991).
No abstract.
Mayer, D.A., and G.A. Maul. Refinement of the statistical
relationship between Straits of Florida sea level difference
and Florida-Bahamas cable voltages. Journal of Geopysical
Research, 96(C3):4971-4972 (1991).
Analyses of a composite 6.5-year record of Bahamas minus Miami sea
level difference (SLD) and Florida-Bahamas volume transport determined
from submarine cable voltages (CABLE) support the hypothesis advanced
by Maul et al. (1990) that SLD is the better variable for
monitoring volume transport than western side sea level alone. In
the subseasonal frequency band BW1 (393-1-
182-1 cycles per day), modeled CABLE, when using SLD,
accounts for 79% of the variance of observed CABLE. Further, the
phase relationships of modeled CABLE with respect to SLD in BW1
represent approximately a simple time shift in that SLD leads CABLE
by a little more than two weeks.
McMurdie, L.A., and K.B. Katsaros. Satellite-derived integrated
water-vapor distribution in oceanic midlatitude storms: Variation with
region and season. Monthly Weather Review, 119(3):589-605 (1991).
With the atmospheric water-vapor content information available from the
SEASAT and Nimbus-7 Scanning Multichannel Microwave Radiometers (SMMR),
differences in water-vapor distribution between cyclonic storms in
different regions of the global ocean can be examined in more detail than
previously possible from radiosondes. SMMR-derived integrated water vapor
is a robust and dependable variable of the same accuracy as integrated
radiosonde soundings. In this study, maximum and minimum water-vapor
content in the vicinity of cold fronts of 80 storms that occurred in the
North Atlantic, North Pacific, and Southern oceans are compared. North
Atlantic storms were found to have significantly higher maximum and
minimum water-vapor content near cold fronts on average than North
Pacific or Southern ocean storms for both the warm and cold seasons.
These differences are attributed to warmer sea surface temperatures and
air temperatures in the North Atlantic, and higher baroclinity and
consequently stronger upward motion in North Atlantic storms.
Additionally, some of the differences may be attributed to the fact that
the North Atlantic storms generally occur at lower latitudes than the
storms in the other regions. Furthermore, the North Pacific storms were
found to have significantly higher maximum and minimum water-vapor
content near cold fronts on average than the Southern Ocean storms for
both the warm and cold seasons. These differences are attributable to
warmer sea surface temperatures in the North Pacific during the warm
season, and to less moisture transport by Southern Ocean storms and the
poleward location of the Southern Ocean storms compared to North Pacific
storms during the cold season. Two examples of water-vapor content in a
South Atlantic storm are given to contrast with the Southern Ocean cases.
The South Atlantic storm had much higher maximum water-vapor content near
the cold front than most Southern Ocean storms (DBO).
McPhaden, M.J., D.V.Hansen, and P.L. Richardson. A comparison of ship
drift, drifting buoy, and current meter mooring velocities in the Pacific
South Equatorial Current. Journal of Geophysical Research,
96(C1):775-781 (1991).
In this note we compare mean seasonal cycles of zonal and meridional
velocity in the Pacific South Equatorial Current based on current meter
mooring data, drifting buoy data, and ship drift data. Monthly averages
of ship drift and drifting buoy data were computed over 2° latitude
by 10° longitude rectangles centered at the positions of multiyear
current meter moorings near 0°, 110°W, and 0°, 140°.
All three representations of the flow field show the basic character
of the annual mean and its variations, provided that the sampling
characteristics associated with each measurement technique are taken
into account. In particular, we find that more than 15 days of drifter
data (regardless of year) are required on a 2° latitude by
10° longitude basis to produce monthly mean estimates that agree
with moored estimates to within about 5-10 cm s-1 rms.
We also infer that windage affects climatological monthly mean ship
drift velocities, although uncertainties in the data limit a precise
determination of the windage magnitude. An upper bound appears to be
about 3% of the surface wind speed, though the actual effect of windage
may be considerably smaller.
Nelsen, T.A., and E.B. Forde. The structure, mass, and interactions
of the hydrothermal plumes at 26°N on the Mid-Atlantic Ridge.
Earth and Planetary Science Letters, 106:1-16 (1991).
Water-column surveys by combined nephelometer/CTD (NCTD) tows
contributed to the 1985 discovery of the first black smokers on
the Mid-Atlantic Ridge. Subsequent regional water-column mapping
has helped define the extent, mass, and interactions of the suspended
particulate matter phase (SPM) of the hydrothermal plumes emanating
from the known and other nearby sources. The results of 29 NCTD
cast/tows, covering 23-30 km2 of ridge segment,
indicate the presence of as many as two additional sources based
on SPM concentration gradients and plume-top doming over source
areas. Plume doming, documented here for the first time from
field observations, conforms strikingly with laboratory experiments
and can serve as a marker for source field location. A comparison
of the plumes' SPM with potential temperature and salinity
distributions indicates close correlation in water-column anomaly
patterns for each, confirming modification of the regional
potential temperature and salinity structure for hydrothermal
plumes, which is expressed by wide separation and sloping of
isotherms and isohalines.
Ooyama, K.V. A dynamic test of the diagnostic pressure calculation.
Extended Abstracts, 19th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, May 6-10, 1991. American Meteorological
Society, Boston, 171 (1991).
No abstract.
Oxburgh, R., W.S. Broecker, and R.H. Wanninkhof. The carbon
budget of Mono Lake. Global Biogeochemical Cycles,
5:359-372 (1991).
Radiocarbon measurements suggest that 14C-free
carbon enters from beneath Mono Lake at a rate of about 1
mol/m2/yr. An input of this magnitude should
be manifested in the inorganic carbon budget of the lake and,
with this in mind, we have devised a model to reconstruct
the evolution of the partial pressure of CO2
(pCO2) over the past 150 years. This
encompasses a period (1945 to present) during which major
diversions of source water via the Los Angeles aqueduct
have been in effect, significantly increasing the salinity of
the lake, and hence its pCO2. The model has
been constrained by experimental characterization of the
carbonate chemistry of the lake water, by the temperature
dependence of pCO2 for the lake water, and
by pCO2 measurements made on the lake
water in 1966, 1969, 1981, and 1989. Our calculations suggest
that prior to 1945 the pCO2 of about 3.3
mol/m2/yr is required. Volcanic activity
beneath the lake is a probable source of this input.
Palmer, D.R., T.M. Georges, and R.M. Jones. Classical chaos and the
sensitivity of the acoustic field to small-scale ocean structure.
Computer Physics Communications, 65:219-233 (1991).
Ray theory is usually the basis of data inversion schemes for acoustic
remote sensing of the ocean. Chaotic ray paths are expected to be present
whenever the ocean environment possesses small-scale, range-dependent
structure. We are studying the implications of their presence for data
inversion schemes. Using numerical simulations we consider ray-path
characteristics for acoustic remote sensing of the Florida Current. We
find small-scale bathymetric structure results in chaotic ray paths
and an exponential proliferation of eigenrays. As a result, for each
feature in the time-of-arrival pattern, there is associated not a single
eigenray but a group, thereby limiting the spatial resolution of a remote
sensing system.
Peng, T.-H. Indication of changes in ocean ventilation rates in
14C/12C record of tree-ring and of deep sea
sediment. Proceedings, Interaction of the Global Carbon and Climate
Systems Symposium, Lake Arrowhead, California, October 24-28,
1988. University of California, 15-1-15-12 (1991).
No abstract.
Peng, T.-H. Oceanic CO2 uptake and future atmospheric
CO2 concentration. In Air-Water Mass Transfer: Selected
Papers from the Second International Symposium on Gas Transfer at
Water Surfaces. ASCE, New York, 618-636 (1991).
The global pattern of water column inventories of bomb-produced
14C suggests that an upwelling of bomb 14C-free
water takes place in the Antarctic, northern Pacific, and equatorial
regions, whereas a downwelling of bomb 14C-rich surface waters
occurs in the temperate oceans and northern Atlantic. A global model of
the closed ocean- atmosphere system is constructed on the basis of these
dynamic flows for the purpose of estimating the oceanic uptake of excess
CO2. To produce a close match between the historical pattern
of atmospheric CO2 predicted by the model and that observed in
the Siple ice core and the Mauna Loa record requires that a net release
of 90 × 1015 g of carbon from the terrestrial ecosystem
be posited for the period 1800- 1990, in addition to fossil fuel
CO2 input. It is estimated that the ocean takes up, on average
2.4-2.6 × 1015 g of anthropogenic carbon each year. This
net flux of CO2 into the ocean is equivalent to 44% of the
estimated total for anthropogenic CO2 emissions. The model
uses four scenarios of future CO2 emissions from fossil fuel
consumption and tropical deforestation to predict atmospheric
CO2 concentrations. Although the resulting patterns of
predicted CO2 levels are similar to those in the report given
by the Intergovernmental Panel on Climate Change (IPCC), the uptake of
CO2 from fossil fuel in the model is more efficient than that
in the general box-diffusion models used by IPCC; that is, all
predictions from the model are lower than those given by IPCC.
Peng, T.-H., and W.S. Broecker. Dynamical limitations on the Antarctic
iron fertilization strategy. Nature, 349(6306):227-229 (1991).
Martin et al. have proposed an ingenious means by which the rise
in atmospheric CO2 content generated by the burning of fossil
fuels and deforestation might be partially compensated. The idea is that
plant production in the nutrient-rich surface waters of the Antarctic
could be stimulated by the addition of dissolved iron, thereby reducing
the CO2 partial pressure in these waters and allowing
CO2 to flow from the atmosphere into the Antarctic Ocean. We
have used a box model calibrated with transient tracer data to examine
the dynamical aspects of this proposal, and conclude that after 100
years of totally successful fertilization the CO2 content of
the atmosphere would be lowered by only 10 ± 5% below what it would
have been in the absence of fertilization. So if after 100 years the
CO2 content of the atmosphere were 500 µatm without
fertilization, it would be between 425 and 475 µatm with full
fertilization. In other words, if our model calibration is correct, even
if iron fertilization worked perfectly it would not significantly reduce
the atmospheric CO2 content.
Peng, T.-H., and W.S. Broecker. Factors limiting the reduction of
atmospheric CO2 by iron fertilization. Limnology and
Oceanography, 36(8):1919-1927 (1991).
A limit on the reduction in atmospheric CO2 partial pressure
(pCO2) in the next century resulting from purposeful Fe
fertilization of the Antarctic Ocean is estimated with an
advection-diffusion model calibrated with transient tracer distributions.
To evaluate the possible increase in atmospheric CO2 with and
without fertilization, we adopt a "business-as-usual" scenario of
anthropogenic CO2 emission. Such increase is computed from the
atmospheric pCO2 in the ocean-atmosphere total C system as it
responds to this emission scenario. Assuming completely successful Fe
fertilization, we calculate an 8% atmospheric CO2 reduction
for a case with a 3 cm2 s-1 vertical diffusivity
and 17.4 Sv upwelling flux, as derived from distribution of
bomb-14C in the ocean. Hence, if atmospheric pCO2
reaches 800 µatm in the next century, the maximum possible reduction
is ~64 µatm. Doubling of upwelling flux to 34.8 Sv results in a
reduction of 96 µatm. If we assume the surface area of the Antarctic
Ocean is 16% of the total ocean area instead of 10% as used in the
standard case, the reduction is ~71 µatm. These results are
independent of the respiration function adopted. As we hold the surface
water PO4 content at a near-zero value, it makes no difference
at what depth the organic material is oxidized (or whether it falls to
the bottom and accumulates). Changes in the gas exchange rate over the
Antarctic Ocean also do not have a significant effect on the magnitude of
atmospheric CO2 drawdown. Doubling the gas exchange rate in
the Antarctic region after fertilization results in a reduction of 68
µatm. Doubling of vertical diffusivity to 6 cm2
s-1 in Antarctic deep water yields a reduction of 75
µatm. The key parameters are the rate of upwelling in the Antarctic
and the fate of this upwelled water. The length of the productive season
influences the extent of pCO2 reduction. For 8 months of
productive fertilization our model yields a reduction of 60 µatm,
for 4 months a reduction of 50 µatm, and for 2 months a reduction of
40 µatm. The maximum O2 consumption in our standard case
is estimated to be 133 µmol kg-1 at a depth of 600 m.
However, O2 consumption depends on the reoxidation function in
the subsurface water. If the organic flux reoxidizes completely in the
upper 2000 m, the maximum consumption of O2 at 500 m could
teach 500 µmol kg-1. Hence, depending on the reoxidation
function, an anoxic Antarctic thermocline could result from Fe
fertilization. Both calculations regarding the seasonality of production
and those regarding oxygen reduction are highly sensitive to parameters
over which we have little control. They are included only to emphasize
their potential importance.
Piotrowicz, S.R., H.F. Bezdek, G.R. Harvey, M. Springer-Young,
and K.J. Hanson. On the ozone minimum over the equatorial
Pacific Ocean. Journal of Geophysical Research,
96(D10):18,679-18,687 (1991).
Since 1977, several ship and aircraft expeditions to the equatorial
Pacific have reported extremely low (10 ppbv) or undetectable
levels of ozone within the marine boundary layer. Of necessity,
field programs from mobile platforms are limited in both their
temporal and spatial coverage. However, a 10-year record of
observations at the geophysical monitoring for climatic change
site in American Samoa suggests that low ozone mixing ratios
are a common occurrence and may reflect a spatially
variable but permanent region of low ozone in the equatorial
Pacific. The spatial and temporal limits of this feature, as well
as some aspects of the intensity of the minimum, appear to be
maintained by the large-scale atmospheric circulations of the
equatorial Pacific. Perturbations in the large-scale circulations,
as well as episodic events, are reflected in observations of
ozone in the equatorial Pacific. Variations in the large-scale
zonal circulation patterns (i.e., Walker circulation)
of the equatorial Pacific appear to have a major influence on
the spatial distribution of ozone across the equatorial
Pacific. The relative importance of variations in large-scale
meridional circulation patterns on the distribution of ozone in
the tropical Pacific is uncertain; however, they may be important
at latitudes somewhat removed from the equator such as at
American Samoa.
Post, W.M., V.H. Dale, D.L. DeAngelis, L.K. Mann, P.J. Mulholland,
R.V. O'Neill, T.-H. Peng, and M.P. Farrell. Formulating energy
policies related to fossil fuel use: Critical uncertainties in the
global carbon cycle. Proceedings, 1990 Southeast Climate
Symposium, Global Change: A Southern Perspective, October 1990,
77-95 (1991).
No abstract.
Powell, M.D. Surface wind distribution of Hurricane Hugo in the Carolinas.
Extended Abstracts, 19th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, May 6-10, 1991. American Meteorological
Society, Boston, 441-444 (1991).
No abstract.
Powell, M.D., P.P. Dodge, and M.L. Black. The landfall of Hurricane Hugo
in the Carolinas: Surface wind distribution. Weather and
Forecasting, 6(3):379-399 (1991).
Hurricane Hugo struck Charleston, South Carolina, on 22 September 1989 as
the most intense hurricane to affect the United States since Camille in
1969. The northeastern eyewall, which contained the maximum winds measured
by reconnaissance aircraft shortly before landfall, moved inland over a
relatively unpopulated area and there were few fatalities. However, no
observations were available to document the surface wind distribution in
this part of the storm as it continued inland. To improve specification
of surface winds in Hugo, empirically adjusted aircraft winds were
combined with coastal, offshore, and inland surface observations and
were input to the Ooyama objective analysis algorithm. The wind analysis
at landfall was then compared with subsequent analyses at 3 and 6 h after
landfall. Reconstruction of the surface wind field after landfall
suggests that the maximum (~13 min mean) surface wind at the
coast was 50 m s-1 in the Bulls Bay region, ~40 km
northeast of Charleston. Surface roughness over land caused wind speeds
to drop off rapidly just inland of the coast to only 50% of values
measured by reconnaissance aircraft at the same location relative to
the storm over water. Despite relatively rapid increases in the central
sea-level pressure and decreases in the mean circulation as Hugo
progressed inland, hurricane-force wind gusts extended Hugo's damage
pattern well past Charlotte, North Carolina, ~330 km inland.
Accurate determination of surface wind distribution in landfalling
hurricanes is dependent upon the spatial density and quality of surface
wind measurements and techniques to adjust reconnaissance flight-level
winds to the surface. Improvements should allow forecasters to prepare
more accurate warnings and advisories and allow more thorough
documentation of poststorm effects. Empirical adjustments to
reconnaissance aircraft measurements may replace surface data voids
if the vertical profile of the horizontal wind is known. Expanded use
of the airborne stepped-frequency microwave radiometer for remote
sensing of ocean surface winds could fill data voids without relying
upon empirical methods or models. A larger network of offshore,
coastal, and inland surface platforms at standard (10 m) elevations
with improved sampling strategies is envisioned for better resolution
of hurricane wind fields. A rapid-response automatic station network,
deployed at prearranged coastal locations by local universities with
meteorology and/or wind engineering programs, could further supplement
the fixed platform network and avoid the logistical problems posed by
sending outside teams into threatened areas.
Roux, F., and F.D. Marks. Eyewall evolution in Hurricane Hugo deduced
from successive airborne Doppler observations. Preprints, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May 6-10,
1991. American Meteorological Society, Boston, 558-563 (1991).
No abstract.
Roux, F., F.D. Marks, and J.F. Gamache. Three-dimensional circulation
in a hurricane from airborne Doppler radar data: Extended velocity track
display. Preprints, 25th International Conference on Radar
Meteorology, Paris, France, June 24-28, 1991. American Meteorological
Society, Boston, 466-469 (1991).
No abstract.
Roy, R.N., J.-Z. Zhang, and F.J. Millero. The ionization of sulfurous
acid in Na-Mg-Cl solutions at 25°C. Journal of Solution
Chemistry, 20(4):361-373 (1991).
The stoichiometric pK1* and
pK2* for the ionization of sulfurous acid has
been determined from EMF measurements in NaCl solutions with varying
concentrations of added MgCl2 (m = 0.1, 0.2, and 0.3) from
I = 0.5 to 6.0 molal at 25°C. These experimental results have
been treated using both the ion pairing and Pitzer's specific
ion-interaction models. The Pitzer parameters for the interaction
of Mg2+ with SO2 and HSO3-
yielded lambda = 0.085 ± 0.004, beta(0) = 0.35 ±
0.02, beta(1) = 1.22 ± 0.04, and Cphi =
-0.072 ± 0.007. The Pitzer parameters beta(0) =
-2.8 ± 0.4, beta(1) = 12.9 ± 2.9, and
beta(2) = -201 ± 57 have been determined for the
interactions of Mg2+ with SO32-.
The calculated values of pK1* and
pK2* using Pitzer's equations reproduce the
measured values to within ± 0.04 pK units. The ion pairing
model with log KMgSO3 = 2.36 ± 0.02 and
log gammaMgSO3 = 0.1021, reproduces the experimental
values of pK2* to ± 0.01. These results
demonstrate that treating the data by considering the formation of
MgSO3 yields a better fit of the experimental measurements
with fewer adjustable parameters. With these derived coefficients
obtained from the Pitzer equations and the ion pairing model, it is
possible to make reliable estimates of the activity coefficients of
HSO3- and SO32- in
seawater, brines, and marine aerosols containing Mg2+
ions.
Roy, R.N., J.-Z. Zhang, M.A. Sibblies, and F.J. Millero. The
pK2* for the dissociation of
H2SO3 in NaCl solutions with added
Ni2+, Co2+, Mn2+, and
Cd2+ at 25°C. Journal of Solution
Chemistry, 20(5):467-478 (1991).
The pK2* for the dissociation of sulfurous acid
from I = 0.5 to 6.0 molal at 25°C has been determined from EMF
measurements in NaCl solutions with added concentrations of
NiCl2, CoCl2, MnCl2, and
CdCl2 (m = 0.1). These experimental results have been
treated using both the ion pairing and Pitzer's specific
ion-interaction models. The Pitzer parameters for the interactions
of M2+ with SO32- yielded
beta(0)NiSO3 = -5.5,
beta(1)NiSO3 = 5.8, and
beta(2)NiSO3 = -138
beta(0)CoSO3 = -12.3,
beta(1)CoSO3 = 31.6, and
beta(2)CoSO3 = -562
beta(0)MnSO3 = -8.9,
beta(1)MnSO3 = 18.7, and
beta(2)MnSO3 = -353
beta(0)CdSO3 = -7.2,
beta(1)CdSO3 = 13.8, and
beta(2)CdSO3 = -489
The calculated values of pK2* using Pitzer's
equations reproduce the measured values to within ± 0.01 pK
units. The ion pairing model yielded
log KNiSO3 = 2.88 and log gammaNiSO3 = 0.11I
log KCoSO3 = 3.08 and log gammaCoSO3 = 0.05I
log KMnSO3 = 3.00 and log gammaMnSO3 = 0.04I
log KCdSO3 = 3.29 and log gammaCdSO3 = 0.17I
for the formation of the complex MSO3. The stability
constants for the formation of MSO3 complexes were found
to correlate with the literature values for the formation of MSO4
complexes.
Shay, L.K., P.B. Black, J.D. Hawkins, R.L. Elsberry, and A.J. Mariano.
Sea surface temperature response to Hurricane Gilbert. Preprints, 19th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, May 6-10,
1991. American Meteorological Society, Boston, 574-578 (1991).
No abstract.
Tappert, F.D., G.J. Goni, and M.G. Brown. Weak chaos in an
area-preserving mapping for sound ray propagation. Physics
Letters A, 153(4-5):181-185 (1991).
No abstract.
Thacker, W.C. Automatic differentiation from an oceanographer's
perspective. Proceedings, Workshop on Automatic Differentiation
of Algorithms, Breckenridge, CO, January 6-8, 1991. Society of
Industrial and Applied Mathematics, Philadelphia, 191-201 (1991).
An automatic differentiator is a tool that, when given code for
evaluating a function, generates additional code for evaluating
its derivatives. Within an oceanographic context, the
function-defining code often involves the numerical solution of
a system of partial-differential equations, and the corresponding
derivative-evaluating code involves the solution of the adjoint
system. Because the task of preparing the adjoint code is tedious,
time-consuming, and error-prone, an automatic differentiator that
could serve as an automatic adjoint generator would be most valuable.
To be practical, its design should reflect the fact that, for
oceanographic applications, efficient use of storage is crucial.
In handwritten adjoint codes, data compression is realized by saving
expressions rather than values. This expression-saving approach can
be automated. The design of the automatic differentiator would
resemble that of a compiler, and compiler-building tools could be
used to construct it.
Tsai, J.J., and J.R. Proni. Dredged material disposal at the edge of the
Florida Current. First International Ocean Pollution Symposium,
Mayaguez, Puerto Rico, April 28-May 3, 1991. University of Puerto Rico,
Mayaguez, 80 (1991).
A field data collection project was undertaken to evaluate the potential
environmental impact of dumping in the designated Miami Ocean Dredged
Material Disposal Site before the actual dredging of Miami River and
Miami Harbor Turning Basin. Strong Gulf Stream current and relatively
deep water depth at the disposal site make the study unique and
important. Acoustic remote sensing techniques with current measurements
from acoustic Doppler current profiler and in-situ oceanographic
measurements were used to monitor the physical processes and the
dispersive characteristics. Results indicate that during the period of
observations of the study, materials were transported north-northeast
away from sensitive reef areas and penetrated the strong pycnoclines to
reach the bottom in the first few minutes. For the first time,
intercomparison among all field data and numerical prediction provides
dispersive characteristics of dredged material disposal at the western
edge of the Florida Current.
Tziperman, E., W.C. Thacker, and K. Bryan. Computing the
steady oceanic circulation using an optimization approach.
Dynamics of Atmospheres and Oceans, 16:379-403
(1991).
The traditional method for computing steady oceanic circulation
has been by stepping an oceanic model forward in time until
transients are damped by friction. An alternative method, which has
the potential for being more economical, is to minimize the sum of
the squares of the residuals of the steady model equations. A variety
of algorithms might be considered for computing the minimum;
attention here is focused on preconditioned conjugate-gradient
descent with the gradient computed using an adjoint model. The
choice of variables, i.e., the preconditioning transformation
used in the optimization process, is found to be critical to the
efficiency of the method. An appropriate preconditioning
transformation can be suggested by a heuristic analysis similar to
that commonly used to test the stability of numerical models.
The method is demonstrated within the context of the barotropic
vorticity equation, and results indicate that the method can be at
least as efficient as time-stepping.
Willis, P.T., and J. Hallett. Microphysical measurements from an aircraft
ascending with a growing isolated maritime cumulus tower. Journal of
the Atmospheric Sciences, 48(2):283-300 (1991).
The development of precipitation in the top of an isolated marine cumulus
is traced by four rapid penetrations with an instrumented aircraft between
400 and 1000 m below the visible top of the growing tower. The
hydrometeor distribution evolves from the first appearance of a few
large supercooled drops [0.45 l-1, D > 0.5 m] to
well-developed precipitation (largely ice) in 500 s. This development
results from accretion and coalescent growth in the cloud top volume,
not from advection by the updraft of large drops from below. Large
supercooled drops precede the appearance of ice at -9°C near the
cloud top. The cloud and precipitation water budgets are computed and
compared with observed values, which indicate that, once precipitation
is well-developed, the convective tower cannot maintain itself as a
steady-state entity. The budget computations demonstrate a sensitivity
of cloud evolution to the ice particle density.
Willis, P.T., and A.J. Heymsfield. Trajectories of hydrometeors in
Hurricane Emily. Extended Abstracts, 19th Conference on Hurricanes
and Tropical Meteorology, Miami, FL, May 6-10, 1991. American
Meteorological Society, Boston, 192-197 (1991).
No abstract.
Willis, P.T., F.D. Marks, and J. Hallett. Tracing the interactions
of precipitation evolution and cloud dynamics using airborne Doppler radar
and in-situ data. Preprints, 25th International Conference on Radar
Meteorology, Paris, France, June 24-28, 1991. American Meteorological
Society, Boston, 916-919 (1991).
No abstract.
Willoughby, H.E. Reply. Journal of the Atmospheric Sciences,
48(9):1209-1212 (1991).
No abstract.
Willoughby, H.E. Semispectral models of moving hurricane-like vortices.
Preprints, 19th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, May 6-10, 1991. American Meteorological Society, Boston,
383-384 (1991).
No abstract.
Yvon, S.A., D.J. Cooper, E.S. Saltzman, and P.K. Quinn. Measurements of
atmospheric DMS and SO2 over the northeast Pacific Ocean
during PSI-3. EOS, Transactions, American Geophysical Union,
72(44):104 (1991).
No abstract.
Zhang, J.-Z., and F.J. Millero. The rate of sulfite oxidation in
seawater. Geochimica et Cosmochimica Acta, 55:677-685 (1991).
The rate of oxidation of sulfide, S(IV), in seawater was
measured as a function of pH (4.0-8.5), temperature (15-45°C),
and salinity (0-35). The observed rate constant, k, in seawater
at a pH = 8.2 was found to be second order with respect to
S(IV) and half order with respect to oxygen:
-d [S(IV)]/dt =
k[S(IV)]2
[O2]0.5.
The resulting values of k (M-1.5 min-1)
have been fitted to a function of ionic strength, I, and
temperature, T(K):
log k = 19.54 - 5069.47/T + 14.74I0.5
- 2.93I - 2877.0I0.5/T,
and the standard error is 0.05 in log k. The energy of
activation was found to be a function of salinity and has a value of
140 ± 6 kJ mol-1 at S = 35. The rates measured
in 0.57 M NaCl were found to be higher than the rates in seawater.
Measurements made in the major sea salts indicate that Ca2+,
Mg2+, and SO42- added to NaCl cause
the decrease. Measurements made in artifical seawater (Na+,
Mg2+, Ca2+, Cl-, and
SO42-) were found to be in good agreement with
the measurements in real seawater. The rate increased from pH 4 to
a maximum at pH 6.5 and decreased at higher pH. The effect of Ph on
the rates was attributed to the rate-determining step involving the
combination of HSO3- and SO32-.
This yields:
k = k alpha HSO3 -
alpha SO32-
where alphai is the molar fraction of species i.
Values of k equal to 6.66 ± 0.06 and 6.17 ± 0.17
were found for NaCl and seawater, respectively. The larger range of
k in seawater is due to it being a function of pH. The
addition of Mn2+ was found to increase the rate apparently
due to the formation of MnSO3. Additions of Fe3+
and Fe2+ have a catalytic effect only before they hydrolyze
to colloidal iron.
**1990**
Baringer, M.O., and J.F. Price. A simple model of the descending
Mediterranean outflow plume. Proceedings, NATO Advanced Research
Institute on the Physical Oceanography of Sea Straits, L.J. Pratt (ed.),
Kluwer Academic Publishers, 298-308 (1990).
No abstract.
Bitterman, D.S., P.P. Niiler, Y. Aoustin, and A. de Chaffaut. Drift
buoy intercomparison results. NOAA Data Report, ERL AOML-17, 52 pp.
(1990).
Detailed tests were carried out aboard the NOAA ship Oceanographer
to measure the slippage of several drift buoy designs used in the TOGA
Pan Pacific Surface Current study. These included the AOML low-cost
tropical drifter, the Scripps Institution of Oceanography Ministar
drifter, the MIT Draper Laboratory low-cost drifter, and the IFREMER
(Brest, France) thermistor chain buoy. The results of six tests carried
out under varying wind and sea conditions are included.
Black, R.A. Radar reflectivity -- ice water content relationships for
use above the melting level in hurricanes. Journal of Applied
Meteorology, 29(9):955-961 (1990).
Regression of equations linking radar reflectivity (Ze)
and ice water content (IWC) were calculated from airborne radar and particle
image data that were collected above the melting level in two hurricanes.
The Ze-IWC equation from the stratiform areas of Hurricane
Norbert (1984) is similar to the composite equation for thunderstorm anvils
derived by Heymsfield and Palmer. The Ze-IWC equation
from the convective regions of Hurricane Irene (1981) has essentially the
same exponent, but a significantly greater coefficient than that from Norbert.
The higher density of the graupel and rounded ice in the Hurricane Irene data
accounts for the difference in the coefficients. The hurricane
Ze-IWC relations have smaller exponents than most of those
from midlatitude clouds, which indicates that small ice particles may be more
prevalent in these two hurricanes than in midlatitude clouds.
Black, R.A., and J. Hallett. Electric field and microphysical
measurements in vigorous hurricane eyewalls. Preprints,
Conference on Cloud Physics, San Francisco, CA, July 23-27,
1990. American Meteorological Society, Boston, 662-665 (1990).
No abstract.
Broecker, W.S., T.-H. Peng, J. Jouzel, and G. Russell. The magnitude
of global fresh-water transports of importance to ocean circulation.
Climate Dynamics, 4:73-79 (1990).
Water-vapor transport from low to high latitudes in a given ocean and
from one ocean to another must be compensated by a net flow of salt
through the sea. A comparison is presented which shows that water-vapor
fluxes derived from meteorological information, from an atmospheric
general circulation model and from a radiocarbon-calibrated ocean box
model are in first-order agreement.
Broecker, W.S., T.-H. Peng, S. Trumbore, G. Bonani, and W. Wolfli.
The distribution of radiocarbon in the glacial ocean. Global
Biogeochemical Cycles, 4:103-117 (1990).
Accelerator mass spectrometric radiocarbon measurements on benthic
foraminifera shells, picked from samples on which concordant ages were
obtained on the shells of two species of planktonic foraminifera, reveal
that the age of deep water in the equatorial Atlantic during glacial time
was 675 ± 80 years (compared to today's age of 350 years) and that
the age of deep water in the South China Sea was 1670 ± 105 years
(compared to today's value of 1600 years). These results demonstrate
that the 1.3 to 1.5 times higher radiocarbon content of carbon in glacial
surface waters of the Caribbean Sea reconstructed by Bard et al.
(1990) was primarily the result of a higher global inventory of
radiocarbon rather than a decrease in rate of mixing between surface and
deep waters of the ocean. The results are also consistent with the
conclusion by Boyle and Keigwin (1987) that the flow of North Atlantic
Deep Water was considerably weakened during glacial time, allowing deep
waters of Antarctic origin to push much further north into the Atlantic
than they do today.
Chelton, D.B., A.M. Mestas-Nunez, and M.H. Freilich. Global wind
stress and Sverdrup circulation from the SEASAT scatterometer. Journal
of Physical Oceanography, 20(8):1175-1205 (1990).
Three months of vector wind observations from the SEASAT-A satellite
scatterometer (SASS) are used to construct gridded fields of monthly
average wind stress and wind stress curl over the global ocean. These
fields are examined to identify features either poorly resolved or not
present in wind stress fields constructed from conventional data.
Particular attention is focused on the spatial structures in the high
southern latitudes and the tropical regions. The SASS wind stress fields
are compared globally with the Hellerman and Rosenstein climatological
monthly average surface wind stress fields and with monthly averages of
wind stress computed from contemporaneous 1000 mb wind analyses produced
by the National Meteorological Center. The potential for satellite
scatterometry improving the present knowledge of the global wind stress
field and making important contributions to ocean modeling is demonstrated
by comparison of global maps of the Sverdrup circlation computed from
three-month average SASS and Hellerman and Rosenstein climatological wind
stress curl fields. Except for the region south of about 35°S, the
two estimates of Sverdrup circulation are generally very similar. The
transports of the western boundary currents calculated from the
climatological wind stress fields are consistently higher because the
drag coefficient used by Hellerman and Rosenstein is too large by
approximately 19%. In the Antarctic Circumpolar Current region, the
difference between the two estimates of zonal transport is very large,
even disagreeing in direction in the region south of Australia and New
Zealand. Historical hydrographic data suggest a tendency, albeit less
extensive, for the westward Sverdrup transport indicated by the SASS
data, suggesting the possibility of deficiencies in the climatological
wind stress fields.
DeMaria, M., and R.W. Jones. The use of aircraft observations in a
hurricane track forecast model. Preprints, International Symposium
on Assimilation of Observations in Meteorology and Oceanography,
Clermont-Ferrand, France, July 9-13, 1990. American Meteorological
Society, Boston, 191-195 (1990).
No abstract.
Dodge, P.P., J.S. Griffin, F.D. Marks, and R.W. Burpee.
Interactive analysis of NOAA P-3 aircraft data in support of
operational hurricane forecasting. Preprints, Sixth International
Conference on Interactive Information and Processing Systems for
Meteorology, Oceanography, and Hydrology, Anaheim, CA, February
4-9, 1990. American Meteorological Society, Boston, 245-247 (1990).
No abstract.
Franklin, J.L., C.S. Velden, J. Kaplan, and C.M. Hayden. Some
comparisons of VAS and dropwindsonde data over the subtropical
Atlantic. Monthly Weather Review, 118(9):1869-1887 (1990).
Omega dropwindsonde and other in-situ (INS) data collected during the
NOAA/Hurricane Research Division's (HRD) field program are used as a
ground truth data set for the evaluation of VISR Atmospheric Sounder
(VAS) soundings over the subtropical Atlantic. The experiments were
coordinated with the Cooperative Institute for Meteorological Satellite
Services at the University of Wisconsin. The focus of this study is
to determine whether soundings derived from VAS radiances are an
improvement over the first-guess data used as a starting point in the
sounding retrieval process. First-guess inputs for this study are
provided by NMC's Regional Analysis and Forecast System (RAFS)
nested-grid model (NGM). In a case study, an objective algorithm is
used to analyze the INS, VAS, and first-guess data at and below 500 mb
from an HRD experiment on 1-2 September 1988. The case study is
supplemented by a statistical investigation of data composited from
other HRD experiments. In particular, we examine VAS estimates of
horizontal temperature and moisture gradients to see if they represent
improvements over the first guess. The temperature and moisture
descriptions in the vicinity of a 500 mb cold low were improved by
the VAS in the case study; however, VAS temperature gradients were
found to be generally less accurate than those of the first guess.
Temperature gradients from the VAS were also consistently stronger
than INS or first-guess gradients. The composite study found that
large-scale VAS moisture gradients were better than those of the first
guess. Other results indicate a preferred mode for VAS modifications
to the guess; the primary impact of the VAS radiances on the first
guess was to improve the description of the phasing of horizontal
features. The VAS representation of the amplitude of features,
however, was not consistently an improvement. This suggests that in
tropical applications, VAS data may be most suitable for subjective
forecasting uses; if VAS data are to be used in numerical weather
prediction, strongest weight should be given to the representation
of the location of weather features (troughs, ridges, etc.),
and relatively weak weight should be given to the representation of
the strength of these features.
Frazel, D.W., and G.A. Berberian. Distributions of chlorophyll and
primary productivity in relation to water column structure in the
eastern North Atlantic Ocean. Global Biogeochemical Cycles,
4(3):241-251 (1990).
Latitudinal variations in the megascale (103 km) distribution
of biological properties are described in relation to water column
structure between 60°N and 7°N in the eastern North Atlantic
Ocean. Stations were occupied along a meridional transect of stations
at 20°W in August-September 1988, during the third leg of the
National Oceanic and Atmospheric Administration Global Change Expedition.
An additional transect to the south (38°N to 7°N) was
occupied to extend the total range of latitudinal observations.
Chlorophyll-a concentrations were highest in the northern latitudes
(<2.51 mg m-3), decreasing to >0.2 mg m-3 in
the vicinity of the subtropical gyre, south of 40°N. The nitracline
was associated with a shoaling of the pycnocline in the northern
latitudes. At 7°N, high chlorophyll concentrations (approximately
0.5 mg m-3) and enhanced primary productivity (375.5 mg C
m-2 d-1) were associated with a lens of fresh
Amazon River Water.
Friedman, H.A. "Adopt-a-meteorologist" as an educational resource for
teachers. Weather Tips (newsletter of the American Meteorological
Society Education Office, prototype issue), 3 (1990).
No abstract.
Friedman, H.A. Hurricane names. Weather Tips (newsletter of the
American Meteorological Society Education Office, prototype issue),
1-2 (1990).
No abstract.
Friedman, H.A., and C.A. Arnhols. 1990 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 108 pp. (1990).
No abstract.
Gallagher, M.S., T.P. Carsey, and M.L. Farmer. Peroxyacetyl nitrate in
the North Atlantic marine boundary layer. Global Biogeochemical
Cycles, 4(3):297-308 (1990).
An automated system utilizing packed column gas chromatography and
electron capture detection for the determination of peroxyacetyl nitrate
(PAN) is described. The system was calibrated with a cryogenic PAN
sublimation device, a molybdenum catalyst, and a chemiluminescent
nitric oxide detector. Computer control of the analysis resulted in
an analytical precision level of ~1%. A total of 1,178 PAN
measurements were made from August 6 to September 5, 1988, in the
marine boundary layer during the GCE/CASE/WATOC cruise (66°N to
7°N). Overall, PAN concentrations were highest at high latitudes
(up to 40 ppt); PAN levels in the lower latitudes of the cruise track
were usually <10 ppt. A number of episodes of elevated PAN are
described which were characterized by elevated radon concentrations
and a discernible diurnal cycle in the PAN concentration. These higher
PAN levels are attributed to air masses with some continental influence,
and to the enhanced stability of PAN at the cooler temperatures
characteristic of the sub-Arctic region. In aged air masses of marine
origin, PAN concentrations were significantly less and did not display
diel changes; this is interpreted as a measure of the "background" PAN
signal.
Gamache, J.F. Microphysical observations in summer MONEX convective
and stratiform clouds. Monthly Weather Review,
118(6):1238-1249 (1990).
Two-dimensional images of ice particles observed by a NOAA WP-3D
research aircraft during the Summer Monsoon Experiment (SMONEX) are
examined. These images were obtained in the temperature interval from
-25°C to 0°C. The particle structures and size distributions
found in convective and stratiform clouds are compared. Branched
crystals were located predominantly in stratiform clouds while
column-shaped crystals were located commonly in both stratiform and
convective clouds. Stratiform clouds, particularly those observed at
temperatures warmer than -7°C, had a much greater percentage
concentration of large ice particles (>0.8 mm in diameter), and many
of these ice particles were aggregates or branched crystals. The
importance of aggregation and deposition above the melting level in
stratiform clouds is strongly suggested by these findings. Ice
particle number concentrations measured with the cloud probe were
often very high in convective clouds, with a maximum value of
approximately 800 L-1. The average convective-cloud
concentration was approximately 230 L-1, while the average
concentration in the stratiform clouds was approximately
20 L-1. Liquid water was almost completely absent in the
convective updrafts, at temperatures between -10°C and
-22°C. This suggests that the convective updrafts may have
been nearly completely glaciated, and the microphysics were
dominated by deposition. The high particle concentrations in the
convective updrafts suggest that the updrafts may provide most of
the ice particles found in the stratiform cloud. Significant
modification in particle structures and size distributions has
occurred, however, by the time these suspended particles fall out of
the stratiform clouds. These modifications appear to arise from
aggregation and deposition.
Garzoli, S.L., and C. Simionato. Baroclinic instabilities and forced
oscillations in the Brazil/Malvinas confluence front. Deep-Sea
Research, 37(6A):1053-1074 (1990).
Observations collected at the confluence between the Brazil and
Malvinas Currents are analyzed to study the high-frequency oscillations
in the range of periods from 55 to 2 days. The variability in time
and space of the thermohaline front originates at the confluence. The
meandering of the Brazil Current after the encounter and the presence
of an abrupt shelf break create the conditions for the generation of
baroclinic and internal waves. Analysis of time-series of dynamic
height, wind magnitude, and position of the front indicates the
following: in the band from 20 to 55 day periods, two waves propagate
with similar characteristics but in the opposite direction; neither
of these waves appears to be forced by the wind. The westward-propagating
wave (T=37.4 days) is related to the position of the front and is assumed
to be forced by its north-south displacement. The eastward-propagating
wave (T=29.1 days) has the characteristics of a topographic Rossby wave.
Georges, T.M., and D.R. Palmer. Applications of ocean acoustic
remote sensing to climate monitoring. NOAA Technical Memorandum,
ERL WPL-85, 9 pp. (1990).
No abstract.
Giese, G.S., D.C. Chapman, P.B. Black, and J.A. Fornshell. Causation
of large-amplitude coastal seiches on the Caribbean coast of Puerto
Rico. Journal of Physical Oceanography, 20(9):1449-1458 (1990).
Sea-level oscillations at supertidal frequency with amplitudes of the
order of the mean tidal range have been reported from the Caribbean coast
of Puerto Rico. Analysis of a 10-year time series of digital tide data
from Magueyes Island, Puerto Rico, demonstrates that sea-level variance
at the fundamental normal mode (seiche) frequency of the shelf has a
pronounced fortnightly distribution with a maximum occurring 6-7 days
after new and full moon. The seiche variance also shows a bimodal
seasonal distribution with an inverse relationship to easterly wind
stress. It is argued that the seiches are excited by internal waves
generated by strong tides in the southeastern Caribbean. Support is
provided by airborne radar imagery showing sea-surface patterns
suggesting the presence of internal waves near the southern Aves
Ridge, and by the results of two field experiments, carried out during
times when large-amplitude seiches were expected, to research for
evidence of internal wave forcing near the shelf break. During the
first experiment, large negative-amplitude, pulse-like internal waves
were recorded 6 km seaward of the shelf break during a period of
strong seiche activity. Such pulses were not observed during the
second experiment. However, high-frequency temperature variance
2.3 km seaward of the shelf break, possibly resulting from internal
surf, increased with depth and reached a maximum 6-7 days following
new moon, again suggesting the presence of internal waves. The 10-year
time series analysis shows that large tides are necessary, but not
sufficient, to generate high seiche activity. This is supported by
the two field experiments; during the first, large-amplitude seiches
occurred as expected, while during the second experiment they did not.
We suggest that this behavior is related to variations in
stratification, which, in turn, alter the energy transfer from tides to
seiches.
Gray, W.M., C.W. Landsea, P.W. Mielke, and K.J. Berry. Forecasting Atlantic
seasonal hurricane variability. Proceedings, 15th Annual Climate
Diagnostics Workshop, Asheville, NC. NOAA, 456-461 (1990).
No abstract.
Hallett, J., and P.T. Willis. Development of precipitation in isolated
maritime cumulus. Preprints, Conference on Cloud Physics, San
Francisco, CA, July 23-27, 1990. American Meteorological Society, Boston,
74-79 (1990).
No abstract.
Hansen, C., K.B. Katsaros, S.A. Kitaigorodskii, and S.E. Larsen. The
dissipation range of wind-wave spectra observed on a lake. Journal of
Physical Oceanography, 20(9):1264-1277 (1990).
No abstract.
Hansen, D.V. Subsurface current and temperature patterns in the western
tropical Pacific. Proceedings, U.S.-PRC International TOGA Symposium,
Beijing, China, November 15-17, 1988. China Ocean Press, Beijing,
121-127 (1990).
No abstract.
Hansen, D.V., and G.A. Maul. Anticyclonic current rings in the eastern
tropical Pacific Ocean. Journal of Geophysical Research,
96(C4):6965-6979 (1990).
Observations from satellite-tracked drifting buoys, XBT and CTD data, and
GEOSAT altimeter data are used to describe anticyclonic eddies that occur
in small numbers off the Pacific coast of Central America. These eddies
are similar in many respects to the well-known, warm-core rings that are
observed north of the Gulf Stream off the Atlantic coast of North America,
except that they occur in an environment that also is warm, and they
contain considerably greater kinetic energy. It is hypothesized that
they are formed as a result of conservation of potential vorticity when
the North Equatorial Countercurrent (NECC) turns northward upon
approaching the eastern boundary during its autumnal maximum. The rings
so formed have a strongly nonlinear character which causes them to
propagate westward between 9°N and 14°N with a speed in excess
of that of long Rossby waves. Due to a relatively small available
potential energy content, these rings have a dissipation time scale of
about six months and perhaps end by collision with and reabsorption
into the NECC. The rings account for the observed enhancement of
surface kinetic energy, and probably for the seaward transport of
waters enriched in copper.
Houze, R.A., Jr., B.F. Smull, and P.P. Dodge. Mesoscale organization
of springtime rainstorms in Oklahoma. Monthly Weather Review,
118(3):613-654 (1990).
Radar reflectivity and rain gage data obtained during six springtimes
indicates the types of mesoscale organization that occur in association
with major rain events in Oklahoma (at least 25 mm of rain in 24 h over
an area exceeding 12,500 km2). In these storms, the primary
rain area is found to be a contiguous region of precipitation tens to
hundreds of kilometers in scale that consists partly of deep convection
and partly of stratiform rain. The patterns of rain formed by the
convective and stratiform areas comprise a continuous spectrum of
mesoscale structures. About two-thirds of the cases examined exhibited
variations on the type of organization in which convective cells arranged
in a moving line are followed by a region of stratiform rain. Storm
organization was graded according to the degree to which it matched an
idealized model of this "leading-line/trailing-stratiform" structure.
The precipitation pattern was further graded according to whether its
structure was relatively symmetric with respect to an axis normal to
and passing through the midpoint of the line, or asymmetric, in which
case the storm was biased toward having stronger, more discrete
convective structure at the upwind (south or southwestern) end of the
line and/or the most extensive stratiform precipitation behind the
downwind (north to northeastern) end of the line. About one-third of the
cases examined displayed much more chaotic, unclassifiable arrangements
of convective and stratiform areas. Among the cases with
leading-line/trailing-stratiform structure, severe weather was most
frequent in systems with (1) a strong degree of
leading-line/trailing-strataiform structure, in which a solid, relatively
uniform, arc-shaped line had stratiform rain centered symmetrically
behind it, and (2) a weaker degree of leading-line/trailing-stratiform
structure in which a southwest-northeast line was biased toward having
narrow, intensely convective, irregularly spaced cell structure at its
southwestern (upwind) end and stratiform rain confined to the region
behind the broader northeastern (downwind) portion of the line. Although
all mesoscale organization types were characterized by all types of
severe weather, the type (2) cases were the most prolific category in
terms of tornado and hail production, while type (1) cases were prone
to be associated with flooding. The chaotic, unclassifiable cases,
which exhibited no line organization, had just as much severe weather
as the cases with line organization, but were more likely to produce
hail and somewhat less likely to produce tornadoes and flooding than
the systems with line structure. Major rain events occurred whenever
a mesoscale convective complex (MCC) was dissipating or merely skirting
the area. However, 75% of the major rain events occurred under cloud
shields that failed to meet the MCC criteria explicitly, although they
often resembled MCCs qualitatively. No particular type of mesoscale
radar-echo organization was favored when cloud shields meeting the
MCC criteria were observed. A slight preference for the more chaotic
type of organization was suggested; however, the data sample is not
large enough for this finding to be regarded as conclusive. Mean
soundings and hodographs generally show no sign of a low-level jet in
environments associated with chaotically arranged rain areas that
lacked any line structure. On the other hand, a low-level jet and
resulting curved hodograph were typically associated with cases in which
line organization was evident. The wind shear in the low to
midtroposphere, the bulk Richardson number, and other familiar parameters
characterizing squall line environments are consistent with results
from recent modeling studies. When leading-line/trailing-stratiform
structure was present, the cross-line shear in the environment was of a
magnitude associated with model simulations in which a rearward sloping
updraft circulation favorable to trailing-stratiform anvil formation
quickly develops. The along-line componentt of shear was greater when
the squall system structure was of the asymmetric type and the degree
of leading-line/trailing-stratiform structure was not as strong,
i.e., in those mesoscale systems favoring tornado occurrence.
Katsaros, K.B., U. Hammarstrand, and G.W. Petty. Atmospheric water
parameters in mid-latitude cyclones observed by microwave radiometry and
compared to model calculations. NASA Tech. Pap., 30 pp. (1990).
Existing and experimental algorithms for various parameters of
atmospheric water content such as integrated water vapor, cloud water,
precipitation, are used to examine the distribution of these quantities
in mid latitude cyclones. The data was obtained from signals given by
the special sensor microwave/imager (SSM/I) and compared with data from
the NIMBUS scanning multichannel microwave radiometer (SMMR) for North
Atlantic cyclones. The potential of microwave remote sensing for
enhancing knowledge of the horizontal structure of these storms and to
aid the development and testing of the cloud and precipitation aspects of
limited area numerical models of cyclonic storms is investigated.
Marks, F.D., and P.G. Black. Close encounter with an intense
mesoscale vortex within Hurricane Hugo (September 15, 1989). Extended
Abstracts, 4th Conference on Mesoscale Processes, Boulder, CO, June
25-29, 1990. American Meteorological Society, Boston, 114-115 (1990).
No abstract.
Maul, G.A., K. Hanson, and H.F. Bezdek. A note on determining potential
anthropogenic signals in sea level: An example from Florida and
juxtaposed areas. In Towards an Integrated System for Measuring
Long-Term Changes in Global Sea Level, H.F. Eden (ed.). Joint
Oceanographic Institutions, Inc., Washington, D.C., 17-25 (1990).
No abstract.
Maul, G.A., D.A. Mayer, and M.H. Bushnell. Statistical relationships
between local sea level and weather with Florida-Bahamas cable and
Pegasus measurements of Florida Current volume transport.
Journal of Geophysical Research, 95(C3):3287-3296 (1990).
Straits of Florida sea level is studied as a measure of Florida Current
volume transport because sea level provides an independent time series
both (1) for detecting changes in the calibration of the Florida-Bahamas
submarine cable which has been operating since 1982, and (2) as a measure
of the strength of the Gulf Stream system dating to the 1930's when cable
measurements were not available. Accordingly, tide gauge records from
Haulover Beach (Miami) and Lake Worth, Florida, and from Cat Cay and
Settlement Point, The Bahamas, together with Miami weather and cable
voltage, are correlated with each other and with discrete volume transport
estimated from all Pegasus data taken during the intensive 1982-1984
Subtropical Atlantic Climate Studies (STACS) observations. Time domain
linear correlation coefficients between these 132 Pegasus values and
cable voltage observations, Cat Cay minus Haulover Beach sea level, and
Haulover Beach sea level only, are 0.91, 0.55, and -0.76, respectively, but
for the 1982-1988 time series, Cat Cay minus Haulover Beach is better
correlated with cable observations (0.62) than is Haulover Beach alone
(-0.44). Frequency domain modeling computations reveal that the sea level
and cable data are organized in such a way that most of their energy lies
below frequencies of 30-1 cycles per day (cpd). In a subseasonal
band (up to and including the semiannual frequency) 49% of the cable
energy and 59% of the Haulover Beach energy can be accounted for using
30-day low-passed data. A subseasonal frequency response function has been
tentatively identified that relates both Florida sea level and
Bahamas-Florida sea level difference to cable observations and can
successfully account for more than 60% of the observed cable variance
(standard error is ±1 × 106 m3
s-1). Further, negative Florida sea level only and
Bahamas-Florida sea level difference have different phase relationships
with cable observations; it is suggested that steric effects could be
responsible for the phase shifts.
Mayer, D.A., R.L. Molinari, and R.H. Weisberg. Analysis of volunteer
observing ship temperature fields in the tropical Atlantic Ocean.
Oceanologica Acta, 13(3):257-264 (1990).
Volunteer observing ship data collected during the FGGE year in 1979
and data from in situ moorings deployed during the SEQUAL/FOCAL
experiment in 1983-1984 are used to estimate the dominant temporal and
spatial scales of SST variability in the equatorial Atlantic Ocean.
Two-dimensional Fourier transforms show that enhanced energy levels
in a wave number and frequency band of 1924-1-825-1
cycles/km and 37-1-21-1 cycles/day respectively,
are associated with organized SST structures with wave-like
oscillations that are consistent with barotropic instabilities. The
oscillations appear on the equator between 1°S and 1°N
eastward of 25°W shortly after the springtime intensification
of the easterly wind stress and persist into August. They are
characterized by a westward phase propagation of about 50 cm
s-1 and a pattern that progresses eastward at approximately
30 cm s-1.
Molinari, R.L., E. Johns, and J.F. Festa. The annual cycle of
meridional heat flux in the Atlantic Ocean at 26.5°N.
Journal of Physical Oceanography, 20(3):476-482
(1990).
Total meridional heat flux through a zonal oceanic section
at 26.5°N in the Atlantic Ocean is computed from
hydrographic, direct current, and surface wind observations.
The oceanic current and temperature fields are decomposed
into depth-averaged and depth-dependent (including Ekman
and geostrophic) components to perform the calculation. The
mean annual heat flux is estimated to be 1.21 ± 0.34
PW. Mean monthly values of net heat flux are alsocomputed
from the data. The annual cycle of net heat flux determined
from these values ranges from a minimum of 0.69 PW in
February to a maximum of 1.86 PW in July. Thus, in contrast
to an earlier estimate of the annual cycle of oceanic heat flux
derived indirectly from surface energy fluxes and upper-layer
heat content changes, there is no net southward heat flux during
the fall. Results from a simulation of the circulation of the North
Atlantic give an annual cycle of heat flux similar to our calculation
with a summer maximum and winter minimum. However, the
simulated mean value and range of the annual cycle are less than
observed.
Molinari, R.L., D. Olson, and G. Reverdin. Surface current distributions
in the tropical Indian Ocean derived from compilations of surface buoy
trajectories. Journal of Geophysical Research, 95(C5):7217-7238
(1990).
Three different satellite-tracked drifting buoy data sets are compiled
and used to generate a monthly climatology of surface currents in the
tropical Indian Ocean. Buoys were deployed between 1975 and 1987. The
data density is maximum on and near the equator and decreases poleward.
Drift characteristics of the different buoy configurations are compared
using a structure function analysis. The differences in windage effects
are consistent with the buoy designs and small compared with the signals
studied. The currents in the tropical Indian Ocean during boreal winter
and spring can be characterized as two counterrotating gyres. A
southern clockwise rotating gyre is bounded on the south by the South
Equatorial Current (SEC) and on the north during winter by the Equatorial
Countercurrent (ECC) and during spring by the Equatorial Jet (EJ). A
northern counterclockwise rotating gyre is bounded on the south by the
ECC and EJ, depending on season, and on the north by the North Equatorial
Current (NEC). The two gyre systems break down during boreal summer.
During this season, the SEC is located closer to the equator, and the
NEC is replaced by the eastward flowing Indian Monsoon Current (IMC).
The western boundary circulation becomes more complicated from late
spring through early autumn with the observation of two intense smaller
scale gyres. The large-scale southern gyre reappears during boreal
autumn with the reappearance of the EJ. The northern gyre begins to
reappear in December, with the reversal of the IMC and the reappearance
of the NEC. The monthly buoy speeds are compared with a monthly
climatology generated from ship drift reports. Differences between
the two climatologies are, in general, small except in regions of few
trajectories. The annual cycles in amplitudes and phases of the major
currents in the region are thus comparable.
Ooyama, K.V. A thermodynamic foundation for modeling the moist atmosphere.
Journal of the Atmospheric Sciences, 47(21):2580-2593 (1990).
With advances in numerical modeling of the atmosphere, we have experienced
that the return to the first principles of physics often enables a model
to cope more easily with the complexities of the real atmosphere. The
return to the primitive equations of motion from historical balance
approximations is an example. This paper proposes a way to return to the
"primitive" form of moist thermodynamics, in which prediction is made
strictly in terms of conservative properties, such as mass and entropy.
There is no conservation law that would apply directly to temperature or
pressure. These intensive properties, therefore, should be diagnostically
determined by thermodynamics, from the predicted conservative properties.
The scope of the paper is limited to the thermodynamics of reversible
processes. Irreversible processes, which would make a model alive with
real weather, are not discussed here, since each of them requires a
separate empirical treatment. It is shown, however, that the proposed
formulation of thermodynamics facilitates modularization of various
approximations within a model, and among models. For example, both the
hydrostatic and nonhydrostatic models can be built under an identical
design, differing only in the manner of calculating vertical motion.
The proposed formulation is extended to include the ice phase within
reversible thermodynamics. Also discussed are numerical problems in the
spatial representation of thermodynamic discontinuities, which are
caused by the phase transition of water substance.
Palmer, D.R. Book review, "Elastic wave propagation," North-Holland
Series in Applied Mathematics and Mechanics, Vol. 35, M.F. McCarthy
and M.A. Hayes (eds.). Journal of the Acoustical Society of
America, 88:1665 (1990).
No abstract.
Palmer, D.R., and P.A. Rona. Comment on "Acoustic Doppler current
profiler observations of a mid-ocean ridge hydrothermal plume."
Journal of Geophysical Research, 95(C4):5409-5412 (1990).
No abstract.
Palmer, D.R., T.M. Georges, and R.M. Jones. Chaos in underwater
acoustics. Proceedings, Fifth International Symposium on Acoustic
Remote Sensing of the Atmosphere and Oceans, S.P. Singal (ed.). New
Delhi, India, February 6-9, 1990, Tata McGraw-Hill, 210-215 (1990).
During numerical simulations of acoustic propagation in a weakly
range-dependent, deterministic ocean, we find conditions that produce
chaotic ray paths. Chaos is an instability which results from the
nonlinear nature of the differential equations which determine the
ray paths, rather than from externally imposed noise or randomness.
It places a fundamental limitation on the range to which an acoustic
field can be predicted. We also discuss some new methods for
identifying chaotic rays which have advantages over the standard
methods. Finally, we note the existence of chaotic rays for
propagation in the Straits of Florida.
Palmer, D.R., T.M. Georges, and R.M. Jones. Classical chaos and the
sensitivity of the acoustic field to small-scale ocean structure.
Proceedings, First International Conference on Computational Physics,
Boulder, CO, June 11-15, 1990, North Holland, 8-15 (1990).
Ray theory is usually the basis of data inversion schemes for acoustic
remote sensing of the ocean. Chaotic ray paths are expected to be
present whenever the ocean environment possesses small-scale,
range-dependent structure. We are studying the implications of their
presence for data inversion schemes. Using numerical simulations we
consider ray-path characteristics for acoustic remote sensing of the
Florida Current. We find small-scale bathymetric structure results in
chaotic ray paths and an exponential proliferation of eigenrays. As a
result, for each feature in the time-of-arrival pattern, there is
associated not a single eigenray but a group, thereby limiting the
spatial resolution of a remote sensing system.
Peng, T.-H. Climate change and atmospheric CO2 variations.
Proceedings of the Geological Society of China, 33(4): 391-409
(1990).
A strong correlation between climate change and atmospheric CO2
variations was revealed through measurements of paleoatmospheric
CO2 in air bubbles trapped in polar ice layers. It was shown
that the atmospheric CO2 increased from 200 to 280 ppm as
climate changed from glacial to intergalcial conditions. Many hypotheses
have been proposed to explain the cause of these atmospheric
CO2 changes. In most early hypotheses the marine biological
activity was considered to be the main mechanism for transferring carbon
within ocean-atmosphere-biosphere reservoirs. Unfortunately, these
hypotheses have inherent problems of deficient O2 concentration
in glacial deep waters and changes of nutrient content accompanying
climate change that are contrary to deep sea sediment records. However,
two important factors became clear: (1) the ultimate source of the
CO2 change must lie in the sea, and (2) the most critical
waters of the ocean are those at the surface in the polar region. Based
on these factors and a recent requirement for an alkalinity increase
derived from the observed nutrient deepening in the glacial Atlantic, a
polar alkalinity hypothesis was proposed. The hypothesis suggests that
the major cause for the 80-ppm change in CO2 was a 75-µeq
· kg-1 drop in the salinity-normalized alkalinity of
Antarctic surface waters at the close of glacial time. This drop stemmed
in part from the reinitiation of the Atlantic conveyor circulation system
(i.e., North Atlantic Deep Water) and in part from the shallowing
of the ocean's nutrient maximum.
Peng, T.-H., T.L. Ku, J. Southon, C. Measures, and W.S. Broecker.
Factors controlling the distribution of 10Be and
9Be in the ocean. In From Mantle to Meteorites, A Garland
of Perspectives: A Festschrift for Devendra Lal, K. Gopalan, V.K.
Gaur, B.L.K. Somayajulu and J.D. Macdougall (eds.). Indian Academy of
Sciences, Bangalore, India, 201-204 (1990).
Observations show that while the concentration of 9Be in the
deep sea is geographically uniform, that of 10Be increases
from Atlantic to Antarctic to Pacific. Using a geochemical ocean box
model calibrated by the radiocarbon distribution in the sea, we show
that this situation requires (1) that 9Be be added
preferentially to the Atlantic Ocean and (2) that the residence time for
beryllium in the sea be comparable to the oceanic mixing time. Both
requirements are consistent with what is known regarding the
geochemistry of beryllium.
Peng, T.-H., W.M. Post, D.L. DeAngelis, V.H. Dale, and M.P. Farrell.
Atmospheric carbon dioxide and the global carbon cycle: The key
uncertainties. In Environmental Problems and Solutions,
T.N. Veziroglu (ed.). Hemisphere Pub. Corp., New York, 17-38 (1990).
No abstract.
Piotrowicz, S.R., C.J. Fischer, and R.S. Artz. Ozone and carbon monoxide
over the North Atlantic during a boreal summer. Global Biogeochemical
Cycles, 4(2):215-224 (1990).
Ozone mixing ratios observed on a cruise from the east coast of North
America to Bermuda, to Iceland, to the Azores, and terminating in
Barbados in a boreal summer exhibit wide variability. Increases above
a North Atlantic background of 10-20 ppbv appear to be associated with
transport from terrestrial systems. In the central gyre of the North
Atlantic and in the tropical North Atlantic, ozone mixing ratios below
10 ppbv are commonly observed when the air being sampled does not have
a recent (10 days) history of terrestrial input. Carbon monoxide mixing
ratios within the boundary layer vary latitudinally from an average of
124 ppbv in the westerlies to 88 ppbv in the tropical North Atlantic.
Variability in the distribution of CO appears to be dominated by
transport from terrestrial source regions.
Post, W.M., T.-H. Peng, W.R. Emanuel, A.W. King, V.H. Dale, and D.L.
DeAngelis. The global carbon cycle. American Scientist,
78:310-326 (1990).
No abstract.
Powell, M.D. Boundary layer structure and dynamics in outer hurricane
rainbands. Part I: Mesoscale rainfall and kinematic structure.
Monthly Weather Review, 118(4):891-917 (1990).
Results of hurricane boundary layer experiments conducted in outer
rainbands of Hurricanes Josephine (1984) and Earl (1986) are presented.
Comparisons of precipitation and kinematic structures in these storms
and in Hurricane Floyd (1981) indicate that principal rainbands have
common characteristic mesoscale and convective-scale features in the
boundary layer. The two-dimensional mesoscale structure suggests that
these rainbands are made up of a linear aggregate of cellular
reflectivity elements (on the inner, upshear side of the band) and
stratiform rain (on the outer downshear side). The bands are oriented
perpendicular to the shear above the boundary layer and cells move
downband at about 85% of the density-weighed mean wind speed of the
0.2-6 km layer. The boundary layer windfield is strongly influenced
by the rainband with alongband and crossband wind maxima located on the
outer side of the band axis, and minima 4-8 km to the inner side.
Maximum crossband convergence and cyclonic shear vorticity are also
found to the inner side of the rainband axis. Updrafts and downdrafts
are preferentially located on the inner side of the band axis, with
some downdrafts spreading out at the surface. The band-relative
positions of the updraft and perturbation pressure minimum suggest
that the minimum may be produced by interaction of the wind shear and
the updraft. Outer hurricane rainbands show many similarities to
tropical squall lines; major differences are associated with propagation
and the structure of the leading and trailing edges.
Powell, M.D. Boundary layer structure and dynamics in outer hurricane
rainbands. Part II: Downdraft modification and mixed-layer recovery.
Monthly Weather Review, 118(4):918-938 (1990).
Recent aircraft boundary layer measurements in the vicinity of principal
hurricane rainbands have confirmed that convective downdrafts are capable
of transporting cool, dry, low equivalent potential temperature air to
the surface, wher the mixed layer is eliminated. The incorporation of
this air into convection near the core of the storm may weaken the storm,
depending upon the scale of the disturbance and the processes governing
the recovery of the air while it is flowing toward the eyewall. This
paper examines the thermodynamic characteristics of the boundary layer
in outer convective hurricane rainbands, providing evidence for downdraft
modification mechanisms and determining the extent to which disturbed
boundary layer air may be restored on its trajectory to the storm.
Powell, M.D. Observations of boundary layer structure and mesoscale
wind fields in a midlatitude marine rainband during GALE. Extended
Abstracts, 4th Conference on Mesoscale Processes, Boulder, CO, June
25-29, 1990. American Meteorological Society, Boston, 55-56 (1990).
No abstract.
Powell, M.D., and P.G. Black. Meteorological aspects of Hurricane Hugo's
landfall in the Carolinas. Shore and Beach, 58(4):3-10 (1990).
No abstract.
Powell, M.D., and P.G. Black. The relationship of hurricane
reconnaissance flight-level wind measurements to winds measured
by NOAA's oceanic platforms. Journal of Wind Engineering and
Industrial Aerodynamics, 36:381-392 (1990).
A well-known problem in hurricane forecasting and in the administration
of hazardous weather warnings and advisories concerns what adjustments
to make to flight-level reconnaissance wind observations in order to
make them representative of sustained surface winds. To solve this
problem, a study was initiated comparing NOAA reconnaissance flight-level
winds to 10 m level observations from NOAA's oceanic buoys and platforms.
A data base was created that consisted of comparisons made whenever the
aircraft observation was: (1) within 10 km radial separation from the
surface platform (in a storm-relative coordinate system); (2) within
±4 h of the surface observation time; and (3) within ±2 h of
the surface observation time. The data base contains all storms flown
by NOAA aircraft in the vicinity of the Atlantic and Gulf of Mexico buoy
network over the 11-year period from 1975-1986. Comparisons from these
criteria are discussed in terms of the ratio of the buoy-measured wind
speed (VB) to the aircraft-measured wind speed VA.
Results indicate that the 10 m level surface winds over water were
within 55%-85% of the winds measured by the reconnaissance aircraft.
The ratio VB/VA depended strongly on the low-level
atmospheric stability as indicated by the buoy air-sea temperature.
Provost, C., V. Garcon, and S.L. Garzoli. Sea level variability in the
Brazil and Malvinas Confluence region. Advances in Space Research,
9(7):7387-7392 (1990).
No abstract.
Shapiro, L.J., and K.V. Ooyama. Barotropic vortex evolution on a beta
plane. Journal of the Atmospheric Sciences, 47(2):170-187
(1990).
A barotropic, primitive equation (shallow water) model is used on the
beta plane to investigate the influence of divergence, total relative
angular momentum (RAM), and advective nonlinearities on the evolution of
a hurricane-like vortex. The multinested numerical model is based on
the spectral application of a finite element representation. The
undisturbed fluid depth is taken to be 1 km. Scaling of the vorticity
equation, in conjunction with a Bessel function spectral decomposition,
indicates that divergence should have a very small effect on the
hurricane motion. Simulations with an initially symmetric cyclonic
vortex in a resting environment confirm this analysis, and contradict
previous published studies on the effect of divergence in a barotropic
model. During a 120 h simulation, the cyclonic vortex develops
asymmetries that have an influence far from the initial circulation.
The total RAM within a large circle centered on the vortex decreases
with time, and then oscillates about zero. For circles with radii
<1000 km, the total RAM approaches, but does not reach, zero. An
angular momentum budget indicates that the horizontal angular momentum
flux tends to counteract the net Coriolis torque on the vortex. If the
total RAM of the initial symmetric vortex is zero, the weak far-field
asymmetries are essentially eliminated. The motion of the vortex is
not, however, related to the RAM in any simple way. Within a few days
the near-vortex asymmetries reach a near-steady state. The asymmetric
absolute vorticity (AAV) is nearly uniform within ~350 km of the
vortex center. The homogenization of AAV, which occurs within the
closed vortex gyre, is likely due to shearing by the symmetric wind,
combined with removal of energy at the smallest scales. The
homogenization effectively neutralizes the planetary beta effect, as
well as the vorticity associated with an environmental wind.
Thacker, W.C. Large least-squares problems and the need for automating
the generation of adjoint codes. In Computational Solution of
Nonlinear Systems of Equations, E.L. Allgower and K. Georg (eds).
American Mathematical Society, Lectures in Applied Mathematics,
26:645-677 (1990).
Some important least-squares problems that arise in oceanography
and meteorology are large because they are based on systems of
partial-differential equations. The function to be minimized is
defined with the aid of a computer code, so the equations stating
that the gradient should vanish are not available explicitly. It
is possible to construct a second code that evaluates the gradient
for a computational effort approximately equal to that of evaluating
the function. Since the gradient code can be derived from the
function code by following a well-defined set of rules, it should
be possible to construct a compiler-like utility to do this task
automatically. Such a compiler should find wide applicability, not
only within oceanography and meteorology, but for optimization problems
in general, as well as for solving systems of nonlinear equations
and for checking the sensitivity of outputs of complicated codes
to their inputs.
Wilburn, A.M., E. Johns, and M.H. Bushnell. Current velocity
and hydrographic observations in the southwestern North
Atlantic Ocean: Subtropical Atlantic Climate Study (STACS),
1989. NOAA Data Report, ERL AOML-18, 97 pp. (1990).
No abstract.
Willis, P.T., and A.J. Heymsfield. Microphysical trajectories in
tropical cyclones. Preprints, Conference on Cloud Physics, San
Francisco, CA, July 23-27, 1990. American Meteorological Society,
Boston, 666-671 (1990).
No abstract.
Willoughby, H.E. Gradient balance in tropical cyclones. Journal
of the Atmospheric Sciences, 47(2):265-274 (1990).
Analysis of a large inventory of in-situ observations from research
aircraft shows that the gradient wind approximates the axisymmetric
swirling flow in the free atmosphere within 150 km of the centers of
Atlantic hurricanes and tropical storms. In the middle and lower
troposphere, the rms difference between azimuthal mean swirling and
gradient winds is typically <1.5 m s-1 with zero bias.
This balance prevails only for the azimuthal mean, not locally, nor
is balance to be expected in either the surface friction layer or the
upper tropospheric outflow layer, where the radial flow is comparable
with the swirling flow. It is theoretically possible that axisymmetric
supergradient flow may occur in response to rapid radial acceleration
where the radial flow slows in the friction layer beneath the eyewall
or where it converges into intense diabatically-forced updrafts.
Nevertheless, the observations in the free lower and midtroposphere
show that systematic departures of the azimuthal mean vortex from
balance are too small to measure.
Willoughby, H.E. Linear normal modes of a moving, shallow-water
barotropic vortex. Journal of the Atmospheric Sciences,
47(17):2141-2148 (1990).
Calculations with a linear semispectral model of a moving
tropical-cyclone-like barotropic vortex (Willoughby, 1988) show that
a vortex with cyclonic circulation throughout exhibits unphysically
fast poleward motion on a beta plane, but a vortex with enough
anticyclonic circulation at its periphery to make the total relative
angular momentum (LR) small moves slowly. The high poleward
speed arises because the vortex has a linear normal mode at zero
frequency, where the beta effect forces asymmetric perturbations.
Advection of planetary vorticity by the axisymmetric circulation
forces this normal mode at a rate proportional to LR.
Because the governing equations are third-order in time, as many as
three linear normal modes are possible. A completely cyclonic vortex
has three repeated stable normal modes at zero frequency, whereas one
with small LR has a single stable mode at zero frequency
and a conjugate pair of barotropically unstable modes. The frequency
of the unstable modes lies at the most anticyclonic rotation frequency
of the axisymmetric circulation, and the growth rate is slow; the
e-folding time is typically 75 days. If the fluid is made very
shallow, the stable normal mode moves away from zero frequency. In
this situation, the beta effect fails to force the resonance, and the
vortex propagates westward much as a planetary Rossby wave does. In
this model, meridional motion of vortices with LR = 0 always
acts to adjust LR toward zero through conservation of
absolute angular momentum. Since the asymmetric perturbations are
Rossby waves that propagate upon the radial gradient of mean relative
vorticity, the mode at zero frequency experiences critical--radius
absorption where the mean swirling wind is zero--at the boundary
between cyclonic and anticyclonic mean circulation and at the edge
of the vortex. Regardless of the sign of LR, the wave
momentum convergence is concentrated at these critical radii and
weakens the circulation while expanding it spatially. When
LR = 0, waves emanating from the cyclonic and anticyclonic
circulations interfere destructively, so that the vortex radiates no
angular momentum to its environment.
Willoughby, H.E. Temporal changes of the primary circulation in tropical
cyclones. Journal of the Atmospheric Sciences, 47(2):242-264
(1990).
More than 900 radial profiles of in-situ aircraft observations collected
in 19 Atlantic hurricanes and tropical storms over 13 years confirm that
the usual mechanism of tropical cyclone intensification involves
contracting maxima of the axisymmetric swirling wind. Radar shows that
annuli of convective echoes accompany the wind maxima. These features,
called convective rings, exist and move inward because latent heat released
in the rings leads to descent, adiabatic warming, and rapid isobaric
height falls in the area they enclose. The radial change in rate of
isobaric height fall is concentrated at the inner edge of the wind
maximum, causing the gradient wind to increase there and the maximum to
contract. Vigorous convection organized in rings invariably causes
well-defined, inward-moving wind maxima, but when convection is weak,
the rings are also weak or even absent. In this case, the swirling wind
may be nearly constant with radius and change slowly in time. Hurricanes
that have a single, vigorous, axisymmetric ring strengthen rapidly.
Although a series of minor convective rings may support steady
strengthening, development is more generally episodic. When asymmetric
convection erupts near the center of tropical storms or weak hurricanes,
it may cause intensification to falter and the cyclone tracks to
become irregular. In intense hurricanes, outer convective rings may
form around the pre-existent eyewalls, contract, and strangle the
original eyewalls, halting intensification or causing weakening.
Yvon, S.A., E.S. Saltzman, D.J. Cooper, A.M. Thompson, P. Newman, J.E.
Johnson, and A.L. Torres. Atmospheric H2S measurements in
the equatorial Pacific from the SAGA-3 cruise. EOS, Transactions,
American Geophysical Union, 71(43):1226 (1990).
No abstract.
**1989**
Bitterman, D.S., and D.V. Hansen. Direct measurements of current shear in
the tropical Pacific Ocean and its effect on drift buoy performance.
Journal of Atmospheric and Oceanic Technology, 6(2):274-279 (1989).
Measurements of ocean surface currents derived from drift buoy trajectories
are subject to errors caused by slippage of the buoy relative to the
surrounding water. This slippage error is caused by a number of forces
acting on the buoy and drogue element, one of which is the current shear
in the water. Idealized model calculations are used to exemplify some
effects of vertical current shear on drogues, and on the performance of
drogued buoy systems in current shear. It is shown that shear enhances
the performance of drogues, and that long drogues should perform better
than short drogues in shear, but shear also can induce slippage by adding
drag force to the buoy hull. To establish environmental design parameters,
average and rms current shear values between 9.7 m and 22.5 m depth were
computed from Doppler acoustic current profiler measurements from the
tropical Pacific Ocean. Largest values of shear (~0.25 s-1
rms) were found near the equator in the eastern Pacific as expected.
Elsewhere, the shear was generally less than 0.02 s-1, mostly
less than 0.01 s-1. Average values of shear were generally
less than 0.007 s-1.
Black, M.L. Signal loss of WSR-57 radars as a function of range in
tropical cyclones. Preprints, 24th Conference on Radar Meteorology,
Tallahassee, FL, March 27-31, 1989. American Meteorological Society,
Boston, 514-517 (1989).
No abstract.
Black, M.L., and F.D. Marks. Concentric eyewalls in Hurricane Gilbert
(1988). Extended Abstracts, 18th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, May 16-19, 1989. American Meteorological
Society, Boston, 224-225 (1989).
No abstract.
Black, P.G., L.K. Shay, R.L. Elsberry, and J.D. Hawkins. Response of the
Gulf of Mexico to Hurricane Gilbert. Extended Abstracts, 18th Conference
on Hurricanes and Tropical Meteorology, San Diego, CA, May 16-19, 1989.
American Meteorological Society, Boston, 226-227 (1989).
No abstract.
Broecker, W.S., and T.-H. Peng. The cause of the glacial to
interglacial CO2 change: A polar alkalinity hypothesis.
Global Biogeochemical Cycles, 3(3):215-239 (1989).
In an attempt to create a scenario for the cause of the glacial to
interglacial CO2 change recorded in air trapped in polar ice,
we call on an increase in the alkalinity of polar surface waters. In this
way we circumvent a major deficiency of the polar nutrient scenarios of
Sarmiento and Toggweiler (1984), Siegenthaler and Wenk (1984), and Knox
and McElroy (1984). Namely, our scenario does not require a drop in the
nutrient content of polar surface waters in conformity with the
demonstration by Boyle (1988a,b) that the cadmium content of planktonic
foraminifera from polar regions did not decrease from late glacial to
Holocene time. The rise in alkalinity required by our model is a natural
consequence of the demise, during glacial time, of North Atlantic Deep
Water as a major force in ocean circulation and of the nutrient maximum
deepening of Boyle (1988b). Rather than being original, our hypothesis
builds on the concept basic to the polar nutrient hypotheses, namely that
the CO2 partial pressure in polar waters controls that for
both the atmosphere and warm surface ocean. It also requires the
alkalinity increase in surface waters produced by Boyle's nutrient
deepening.
Burpee, R.W., and M.L. Black. Temporal and spatial variations near the
centers of two tropical cyclones. Monthly Weather Review,
117(10):2204-2218 (1989).
The Hurricane Research Division collected radar reflectivity data with
a portable recorder that was attached to the WSR-57 radar at National
Weather Service offices as Hurricane Alicia of 1983 and Elena of 1985
approached the U.S. coastline. The reflectivity data were used to
compute rain rates for the eyewall region, including the rain-free eye
and the rainbands in the annular area outside the eyewall, but within
75 km of the center of the eye. Area- and time-averaged rain rates (R)
in the eyewall region were 5.2 and 6.0 mm h-1, respectively,
for Alicia and Elena. The corresponding averages in the rainband region
were 2.8 and 3.4 mm h-1. The rain rates include reflectivity
corrections that were based upon the variation of average returned
power with range in four hurricanes. Precipitation was convective in
the eyewall region and largely stratiform in the rainband region.
Comparison with published results from other tropical cyclones suggests
that the corrected R's in the eyewall region are underestimated, but
are within a factor of 1.6 of the actual amount. The R's in the
rainband region, however, are similar to those from other studies.
Alicia's eyewall region represented ~15% of the computational
area and contributed ~25% of the total rain rate within 75 km of
the center of the eye. Elena's eyewall region comprised ~22% of
the area and contributed ~33% of the area-averaged rain rate.
The area-averaged rain rate (R) in the eyewall region of both
hurricanes varied by up to 4 mm in 1-2 h. In Alicia, the variations
of R were caused by the growth and decay of mesoscale convective
areas with reflectivity >38 dBZ that achieved maximum areas of
500-800 km2. In Elena, life cycles of individual
convective cells with maximum reflectivities >48 dBZ also accounted
for large changes in the eyewall R. In both hurricanes, the time
series of R in the rainband regions were less variable than the eyewall
R because the rainband regions included larger areas than the eyewall
and had a smaller percentage of area with convective activity. For
several hours, the maximum rain rates in the eyewall and rainband
regions of Alicia occurred in the left-front quadrant relative to the
storm motion. Then the maximum rain rate in the eyewall region
shifted to the right-front quadrant and the maximum in the rainband
region moved to the right of the storm track. In Elena, the maximum
rain rates in the eyewall and rainband regions were in the right-front
quadrant throughout the computational period. About 55% of the
precipitation in Elena's eyewall region occurred in the right-front
quadrant. In both hurricanes, the maximum rain rate in the rainband
region was generally oriented to the right of that in the eyewall region.
Burpee, R.W., M.L. Black, and F.D. Marks. Vertical motions measured
by airborne Doppler radar in the core of Hurricane Elena. Preprints,
18th Conference on Hurricanes and Tropical Meteorology, San Diego,
CA, May 16-19, 1989. American Meteorological Society, Boston, 69-70 (1989).
No abstract.
Carbone, R.E., and F.D. Marks. Velocity track display (VTD): A
real-time application for airborne Doppler radar data in hurricanes.
Extended Abstracts, 18th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, May 16-19, 1989. American Meteorological
Society, Boston, 11-12 (1989).
No abstract.
Carder, K.L., R.G. Steward, G.R. Harvey, and P.B. Ortner. Marine humic
and fulvic acids: Their effects on remote sensing of ocean chlorophyll.
Limnology and Oceanography, 34(1):68-81 (1989).
Marine humic and fulvic acids were concentrated from about 1,400 liters
of seawater from the Gulf of Mexico, and specific absorption coefficients
were measured for each from 240 to 675 nmi. Spectral absorption
coefficients were then calculated for Gulf of Mexico stations where
earlier data on humic and fulvic acid concentrations were available.
Marine humic and fulvic acid values have low molecular weights consistent
with extrapolations from soil-derived curves of their specific absorption
coefficients versus molecular weight. Marine fulvic and humic acids
appear to account for most, if not all, water color or Gelbstoff in the
offshore regions of the Gulf of Mexico. Based on a remote-sensing
reflectance model, it appears that the increase in the
Gelbstoff:chlorophyll ratio for waters adjacent to and downstream from
regions of high primary productivity accounts for much of the
deviation found for such waters from the global chlorophyll algorithm
of the Coastal Zone Color Scanner.
Clarke, T.L., J.R. Proni, and L.C. Huff. Joint CGS-AOML acoustical bottom
echo-formation research II: Field experiment results and recommendations
for echo-sounder design. NOAA Technical Memorandum, ERL AOML-67, 71 pp.
(1989).
Field experiments were conducted to test and verify a mathematical model
that has been developed to assess the effects of bottom roughness and
material properties on bottom echo shape. The physical basis of the
model is reviewed and model output is presented. The experiments were
conducted in lower Chesapeake Bay and involved taking high resolution
acoustic data at a number of frequencies and taking supporting sediment
samples. A unique, high-resolution bottom profiler was used to measure
bottom roughness profiles for input to the model. While model predictions
were in general agreement with the data, fine structure was observed in
the echoes that could not be explained by the existing model. An extension
to the model has been developed that is able to account for this
structure. The essential ingredient of this extension is to consider
bottom surface scattering as arising from a number of statistically
independent patches within the transducer beam. This revised model
should lead to improved predictions of bottom echo waveforms for
echo-sounder design. The algorithm developed for removing ship motion
from the observations suggests a design for a new type of echo-sounder
detector circuit based on an energy threshold. This circuit could be
easily implemented with modern digital signal processing (DSP) circuits,
and it might be suitable for retro-fitting to existing echo-sounders.
Dodge, P.P. The precipitation structure of Hurricane Elena. Preprints,
24th Conference on Radar Meteorology, Tallahassee, FL, March 27-31, 1989.
American Meteorological Society, Boston, 522-524 (1989).
No abstract.
Enfield, D.B. El Niño, past and present. Reviews of
Geophysics, 27(1):159-187 (1989).
El Niño events--anomalous warmings of the tropical Pacific with
associated climatic and economic impacts around the globe--have occurred
at several year intervals since before written records began with the logs
of Francisco Pizarro in 1525. In this review, the history of El
Niño research is traced from its beginnings through the key
innovations of Bjerknes and Wyrtki to the unusual 1982-1983 event.
Research research is then reviewed, with detailed discussions of the
key processes: instability growth and vacillation between climate states.
Throughout the paper there are adjunct discussions of extraregional
teleconnections, ecological impacts, and research on El Niño in
the ancient record. The final section discusses the present paradigm
for vacillations between El Niño and non-El Niño states and
speculates on the possible chaotic nature of El Niño. El Niño
and its atmospheric counterpart, the Southern Oscillation, appear to
occur as an internal cycle of positive and negative feedbacks within
the coupled ocean-atmosphere climate system of the tropical Pacific,
although hypotheses based on external forcing also exist. All events
are preceded by westerly wind anomalies on the equator near the date
line. Baroclinic equatorial Kelvin waves are generated, propagating
eastward toward South America where they depress the thermocline and
raise sea level, while the deep, upper ocean reservoir of warm water in
the western Pacific is depleted. Sea surface temperature (SST) anomalies
in the cool eastern Pacific occur primarily because the normal source
of cold water is depressed below the reach of mixing and upwelling
processes. In the central equatorial Pacific, eastward advection by
anomalous zonal flows is the principal mechanism. Nonlinear heat transfer
to the lower atmosphere creates a positive ocean-atmosphere feedback
resulting in the unstable growth of anomalies along the equator. Much
of the present research aims at determining how the ocean-atmosphere
system vacillates between the El Niño and non-El Niño states.
Coupled models suggest that a longer time scale, negative-feedback
process produces the transitions: at the apex of an El Niño
development an anomalous atmospheric convection above the areas of
reduced upper layer thickness in the off-equatorial ocean, which slowly
propagate westward to the western boundary as Rossby waves and back to
the central equatorial Pacific as upwelling Kelvin waves, re-establishing
the normal cooling process. A similar negative feedback of opposite
sign completes the second half of an oscillation, returning again to
the El Niño state. However, the notion that El Niño/Southern
Oscillation variability results only from an internal feedback process
is still highly contentious and a number of external forcing mechanisms
have been proposed.
Franklin, J.L., C.S. Velden, C.M. Hayden, and J. Kaplan. A comparison
of VAS and ODW data around a subtropical cold low. Preprints, 4th
Conference on Satellite Meteorology, San Diego, CA, May 16-19, 1989.
American Meteorological Society, Boston, 141-144 (1989).
No abstract.
Friedman, H.A., and C.A. Arnhols. 1989 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 100 pp. (1989).
No abstract.
Gallagher, M.S., T.P. Carsey, and M.L. Farmer. Peroxyacetyl nitrate
measurements in the North Atlantic. EOS, Transactions, American
Geophysical Union, 70:1041 (1989).
No abstract.
Gamache, J.F. Retrieval of thermodynamic and microphysical variables
from airborne Doppler observations in Hurricane Norbert (1984).
Preprints, 24th Conference on Radar Meteorology, Tallahassee, FL,
March 27-31, 1989. American Meteorological Society, Boston, 525-528 (1989).
No abstract.
Gamache, J.F. The eyewall water budget of Hurricane Norbert (1984) as
determined from airborne Doppler radar. Extended Abstracts, 18th
Conference on Hurricanes and Tropical Meteorology, San Diego, CA, May
16-19, 1989. American Meteorological Society, Boston, 73-74 (1989).
No abstract.
Garzoli, S.L., and Z. Garraffo. Transports, frontal motions, and eddies
at the Brazil-Malvinas Currents Confluence. Deep-Sea Research,
36(5A):681-703 (1989).
Three inverted echo sounders were deployed to study the dynamics of
the western South Atlantic Brazil-Malvinas Confluence region. Using a
simple model, the location of the thermal front is obtained from the
time series of the depth of the thermocline. Results show that the
main motion of the front is an east-west displacement for distances
of about 100 km; the observed period occurs with a periodicity of 12
months and is related to a variability in the latitude of maximum
northward penetration of the Malvinas Current. Motions of the front,
with a period of 1-2 months, are probably related to a north-south
variation of the latitude of return of the Brazil Current.
Garzoli, S.L., and P.L. Richardson. Low-frequency meandering of the
Atlantic North Equatorial Countercurrent. Journal of Geophysical
Research-Oceans, 94(C2):2079-2090 (1989).
Four 19-month time series of indirect measurements of dynamic height
were obtained in the tropical Atlantic along 28°W at 0°,
3°N, 6°N, and 9°N with three inverted echo sounders and
one current meter mooring. The series were analyzed to study the
time-latitude variability of the North Equatorial Countercurrent
(NECC). The eastward flow associated with the NECC was present at
28°W from 3°N to 9°N during most of the observed
period except in March-April 1983 and April-May 1984, periods that
coincided with the onset of the wind at the equator. The amplitude
of the NECC's annual cycle was maximum at 6°N and was larger in
1983 than in 1984. The analysis of the time-latitude variability of
differences in dynamic height shows a long-period meridional shift of
the NECC. The core of the current attains its northernmost location
during August-September in both years and its southernmost location
during March-April in 1983 and March in 1984. The location of the
core is directly related to the position of the intertropical
convergence zone. From the time series of dynamic height obtained
from the indirect measurements, geostrophic velocities and transports
were estimated and compared with direct observations of currents
and values obtained from hydrographic casts.
Goni, G.J., F.D. Tappert, and M.G. Brown. Numerical experiments
in the standard mapping. RSMAS Technical Report 89-005 (1989).
No abstract.
Hansen, D.V. Physical aspects of the El Niño event of 1982-1983.
In Global Ecological Consequences of the 1982-1983 El
Niño-Southern Oscillation, P.W. Glynn (ed.). Elsevier
Oceanography Series (1989).
El Niño events are marked by the appearance of anomalously warm
ocean waters and unusual rainfall in normally arid coastal regions of
Ecuador and Peru. During the past century such events have occurred at
about four-year intervals on average, and nine of the events have been
described as strong or very strong. In the spring of 1982 the heavy
rainfall that normally characterizes the Indo-Pacific archipelago began
to shift eastward toward the central Pacific. During the following year
the region of anomalous rainfall traversed the ocean to the coast of
South America, in phase with anomalous winds, currents, and sea surface
temperatures. At the peak of the event in the eastern tropical Pacific,
Peru and Ecuador experienced record-setting rainfall leading to flooding
and avalanches, near surface ocean currents reversed from their normal
direction, sea surface temperature rose to 5°C or more above
normal, the thermocline plunged to 100 m or more below normal, and sea
level rose to nearly half a meter above normal. Upon reaching the coast,
many of the oceanic perturbations propagated poleward along the
continental margins in both hemispheres, carrying the signs and effects
of El Niño to middle and high latitudes in the Pacific. The
magnitude of this event made it the "event of the century" in most
variables, and the event of several centuries in some. The magnitude of
perturbation of the atmosphere in the tropical Pacific sector certainly
carried anomalies also in distant regions of the atmosphere, and thereby
secondarily in other parts of the ocean. At greater distance, however,
it becomes increasingly difficult to distinguish between anomalies
resulting from El Niño and those arising from other kinds of
variations of the atmospheric circulation.
Hansen, D.V., and A. Herman. A seasonal isotherm depth climatology for
the eastern tropical Pacific. NOAA Technical Report, ERL 434 AOML-33,
35 pp. (1989).
A seasonal climatology of the depths of the 10°C, 15°C, and
20°C isotherms in the eastern tropical Pacific is presented. The
analyses used Kriging, which is a method for optimal interpolation of
data fields. The data set consisted of 10,505 expendable bathythermograph
(XBT) and conductivity-temperature-depth (CTD) stations collected during
non-El Niño years. Results are presented on shaded contour maps
with values overprinted at 2° intervals. The method of analysis
also yields an estimate of the uncertainty of each interpolated point.
Hansen, D.V., and A. Herman. Evolution of isotherm depth anomalies
in the eastern tropical Pacific Ocean during the El Niño event
of 1982-1983. Journal of Geophysical Research,
94(C10):14,461-14,473 (1989).
Subsurface temperature data collected from research vessels, aircraft,
and vessels of opportunity are used to describe the evolution of the
major El Niño event in the tropical Pacific from September 1982
through September 1983. Optimum interpolation is used to create six
analysis mas of the anomalous depths of the 20°C, 15°C, and
10°C isothermal surfaces. The regions analyzed is 20°N to
20°S and 140°W to the coast of the Americas. Each analysis
is based on data accumulated over about a month, and the analysis
periods are separated by about a month. The depths of the 20°C
isotherm are used to compute zonal thermoclinic transports across
100°W of the North and South Equatorial Currents and the North
Equatorial Countercurrent.
Hansen, D.V., and A. Herman. Temporal sampling requirements for surface
drifting buoys in the tropical Pacific. Journal of Atmospheric and
Oceanic Technology, 6(4):599-607 (1989).
Drifting buoy data from the eastern tropical Pacific Ocean are used to
evaluate the degradation of sea surface temperature and current information
incurred by reducing the number of transmissions from drifting buoys
using the ARGOS system for position finding. Buoy locations are
interpolated at uniform time intervals using an optimum interpolation
method known as Kriging, which provides also an estimate of the rms
position error. It is found that the published standard for surface
current measurement for the TOGA Program (5 cm s-1) can be
met with transmissions on one day of three in the Southern Hemisphere.
Due to stronger mesoscale variability in the Northern Hemisphere, the
standard would be jeopardized by reducing transmissions even to one day
of two. The standard for observation of sea surface temperature
(0.1°C) can be met in either hemisphere with transmissions on one
day of four. The Lagrangian decorrelation times for the Northern
Hemisphere region of the eastern tropical Pacific are estimated as
four days in the meridional direction, and 14 days in the zonal direction.
It is recommended that transmissions be made on one day of three, and
the time scale for the TOGA standard be revised accordingly.
Hirsh, M.A., and H.A. Friedman. Creating an awareness of the hurricane
problem in at-risk coastal communities of south Florida. Preprints,
Second International Conference on School and Popular Meteorological and
Oceanographic Education, Crystal City, Virginia, July 12-16, 1989.
American Meteorological Society, Boston, 160-162 (1989).
No abstract.
Houde, E.D., P.B. Ortner, L. Lubbers, and S.R. Cummings. Test of a
camera-net system to determine abundance and heterogeneity in anchovy
egg distributions. Rapports et Proces-Verbaux des Reunions Cons.
Int. Explor. Mer., 191:112-118 (1989).
A prototype, in-situ camera-net system was deployed in Chesapeake Bay
to test its ability to estimate abundances and delineate fine-scale
vertical and horizontal distributions of bay anchovy Anchoa
mitchilli eggs and larvae. Hydrographic variables were measured
synoptically by electronic sensors on the system. Comparison catch
data were obtained by simultaneous deployment of a conventional
plankton net. The camera subsampled 1.9% of the water that entered
the system and photographed part of the catch at 2-m intervals along
the tow. Densities of anchovy eggs, which averaged 99.0 m-3
during six trial tows, were estimated at 1, 5, and 10 m depths. Anchovy
larvae were uncommon (0.34 m-3) and not sampled effectively.
The system detected increasing egg abundances between the surface and
10 m depth and horizontal patchiness over 10-100 m distances. In the
configuration used, the system has potential where mean egg or larval
densities exceed ca. 5 m-3. Its advantages are that it can
(1) reduce the need to collect and sort plankton samples, (2) provide
photographic data for image analysis, and (3) synoptically assess
fine-scale distributions of ichthyoplankton, environmental variables,
and co-occurring predators and prey.
Johns, E., and R.L. Molinari. Recent current and watermass
observations along the western boundary of the tropical North
Atlantic Ocean. EOS, Transactions, American Geophysical
Union, 70(15):360 (1989).
No abstract.
Johns, E., D.R. Watts, and H.T. Rossby. A test of geostrophy
in the Gulf Stream. Journal of Geophysical Research,
94(C3):3211-3222 (1989).
In July 1982 two detailed sections of density and absolute velocity were
taken across the Gulf Stream northeast of Cape Hatteras to conduct an
accurate test of geostrophy in a strong current. The sections, which were
taken about four days apart, were each completed within 48 hours, using
one ship to make closely spaced (12 km) conductivity-temperature-depth
measurements to 2000 m, and a second ship to simultaneously take Pegasus
absolute velocity profiles to the ocean bottom. The Gulf Stream path and
curvature were also surveyed. The dynamically inferred velocity profiles
were made absolute by matching their velocities to the Pegasus profiles at
2000 m. The geostrophic method (properly referenced) underestimated the
observed velocities by 10-25 cm s-1 in the core of the current
above 500 m where speeds exceeded 150 cm s-1. The
difference is a factor of 2, larger than the sampling and measurement errors
in corresponding parts of the current, estimated to be 5-10 cm
s-1, well within the uncertainties of the method. The
transport above 2000 m is less sensitive to curvature effects; it agrees to
within 3 Sv before and 1 Sv after correcting for curvature, or approximately
2% of the total 93 Sv transport. The deep velocity field below 1000 m had
significant changes (10-20 cm s-1) in structure, and even
reversals, in the four days between the sections, with cross-stream scales
of 50-100 km. This deep variability, attributed to topographic Rossby
waves, introduces more than 10 Sv uncertainty in defining the total
volume transport of the Gulf Stream.
Katsaros, K.B., G.W. Petty, I. Bhatti, and D. Miller. Application of
special sensor microwave/imager data for analysis of cyclonic storms in
midlatitudes over the sea. Contract Report 00014-86-K-0453. Naval
Environmental Prediction Research Facility, Monterey, CA, 42 pp. (1989).
This report is concerned with currently operating microwave radiometer,
the Special Sensor Microwave/Imager (SSM/I) on the F8 satellite in the
Defense Meteorological Satellite Program (DMSP). This sensor employs
three frequencies with similar characteristics as the ones giving
atmospheric water data on SMMR, but not at exactly the same frequencies.
For this reason we needed to test the algorithms for identifying fronts
with data from this new sensor. In addition, the SSM/I has two channels
at 85 GHz which are sensitive to scattering caused by large ice particles
and graupel in the clouds. We found that an index of this scattering
gives a unique view of the deep clouds in frontal zones. We also tested
cloud liquid water and wind algorithms developed for SSM/I, and found
good qualitative agreement with conventional data.
Landsea, C.W., H.E. Willoughby, and J.M. Masters. Analysis of Hurricane
Gilbert at its maximum intensity. Extended Abstracts, 18th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, May 16-19, 1989.
American Meteorological Society, Boston, 222-223 (1989).
No abstract.
Leaman, K.D., E. Johns, and H.T. Rossby. The average distribution of
volume transport and potential vorticity with temperature at three
sections across the Gulf Stream. Journal of Physical Oceanography,
19(1):36-51 (1989).
Average cross sections of downstream velocity and temperature, obtained
using PEGASUS current profilers at three locations along the Gulf Stream,
have been partioned into 2.5°C temperature intervals to examine the
distribution of transport increase versus temperature between the two
southern sections (27° and 29°N) and off Cape Hatteras
(73°W). Between 27° and 29°N the total transport of the
Florida Current over the sections increased only by about 3 ×
106 m3 s-1 (3 Sv) but the current
broadens by about 50%. By Cape Hatteras, the transport has increased
nearly three-fold to 93.7 Sv, of which two-thirds of the increase is
contained in the 19.5°-17.0°C ("18°") layer and in water
colder than the 7°C "sill" temperature found at 27°N.
Cross-stream distributions of layer transport, potential vorticity, and
thickness are estimated. At each section, the 10 × 10-7
m-1 s-1 contour tends to be a boundary (independent
of temperature) between the region of relatively uniform layer potential
vorticity on the anticyclonic (offshore) side of the current and an area
with high lateral potential vorticity gradients on the cyclonic (onshore)
side. In the colder (<7°C) waters off Cape Hatteras, layer
potential vorticity also tends to be uniform at ~5 ×
10-7 m-1 s-1. Layer potential
vorticity in the 18° layer is quite uniform with minimum values
~3.5 × 10-7 m-1 s-1
at 27° and 29°N and somewhat less off Cape Hatteras, which
is close to where 18°C water is formed in the wintertime. At Cape
Hatteras this same layer shows a peak in transport/unit width at the point
where the layer begins to thin as one moves into the Gulf Stream core
from the southeast. A simple model based on conservation of layer
potential vorticity is proposed to describe this transport structure.
Liao, Q., and M.C. Pazos. Drifting buoy data from western tropical Pacific
for the period February 1, 1986 through February 28, 1989. NOAA Data
Report, ERL AOML-14, 125 pp. (1989).
No abstract.
Long, R.B., and W.C. Thacker. Data assimilation into a numerical
equatorial ocean model, Part 1: The model and the assimilation
algorithm. Dynamics of Atmospheres and Oceans, 13:379-412
(1989).
Numerical modeling provides a powerful tool for the study of the
dynamics of oceans and atmospheres. However, the relevance of modeling
results can only be established by reference to observations of the
system being modeled. Typical oceanic observation sets are sparse,
asynoptic, of mixed type and limited reliability, generally inadequate
in some respects, and redundant and inconsistent in others. An optimal
procedure for interfacing such data sets with a numerical model is the
so-called adjoint method. This procedure effectively assimilates the
observations into a run of the numerical model by finding that solution
to the model equations that best fits all observations made within
some specified space-time interval. The method requires the construction
of the adjoint of the numerical model, a process made practical for
models by finding that solution to the model equations that best fits
all observations made within some specified space-time interval. The
method requires the construction of the adjoint of the numerical model,
a process made practical for models of realistic complexity by the work
of Thacker and Long (1988). In the present paper, the first of two
parts, we illustrate the application of Thacker and Long's approach
by constructing a data-assimilating version of an equatorial ocean
model incorporating the adjoint method. The model is subsequently run
for five years to near-steady state, and exhibits many of the features
known to be characteristic of equatorial oceanic flows. Using the
last 54 days of the run as a control, a set of simulated sea level and
subsurface density observations are collected, then successfully
assimilated to demonstrate that the procedure can recover the control
run, given a generous amount of data. In part 2 we conduct a sequence
of numerical experiments to explore the ability of more limited sets of
observations to fix the state of the modeled ocean; in the process, we
examine the potential value of sea level data obtained via satellite
altimetry.
Long, R.B., and W.C. Thacker. Data assimilation into a numerical
equatorial ocean model, Part 2: Assimilation experiments. Dynamics
of Atmospheres and Oceans, 13:413-439 (1989).
A sequence of numerical experiments is conducted using a linear,
semi-spectral equatorial ocean model and an advanced data assimilation
scheme. The numerical model is based on decomposition of the oceanic
fields into Kelvin and Rossby waves belonging to the baroclinic modes
of a stratified equatorial ocean. The assimilation procedure finds that
solution to the model equations that best fits, in the generalized
least-squares sense, all observations made within some specified
space-time interval. All experiments are of the "identical twin"
type; synthetic data are generated by sampling the observable fields
produced by a control run of the model, then the data are assimilated
using the same model. The sequence of numerical experiments serves
two purposes: to demonstrate the performance of the assimilation
procedure in the context of a fully three-dimensional, time-varying
equatorial ocean model, and to examine the utility of specified data
sets, and in particular, observations of sea level, in estimating the
state of the equatorial ocean. The results indicate that the
assimilation procedure works very well when sufficient data are
provided. However, sea level data alone are not sufficient and must
be supplemented with subsurface observations if more than a few
baroclinic modes are allowed in the model ocean. The required amount
of supplementary subsurface data (in the form of density profiles in
these experiments) can be reduced by imposing smoothness constraints
on the recovered model solution.
Lyons, W.A., M.G. Venne, P.G. Black, and R.C. Gentry. Hurricane
lightning: A new diagnostic tool for tropical storm forecasting?
Extended Abstracts, 18th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, May 16-19, 1989. American Meteorological
Society, Boston, 113-114 (1989).
No abstract.
Marks, F.D. Kinematic structure of the inner core of hurricanes as
viewed by airborne Doppler radar. Proceedings, Third Interagency
Airborne Geosciences Workshop, La Jolla, CA, February 21-24, 1989.
American Meteorological Society, Boston, IV-79-IV-81 (1989).
No abstract.
Marks, F.D. Radar observations of tropical weather systems. In
Radar in Meteorology, D. Atlas (ed.). American Meteorological
Society, Boston, 1024 pp. (1989).
No abstract.
Marks, F.D. Three-dimensional structure of the eyewall of Hurricane
Emily (1987) as determined from an airborne Doppler radar. Extended
Abstracts, 18th Conference on Hurricanes and Tropical Meteorology, San
Diego, CA, May 16-19, 1989. American Meteorological Society, Boston,
71-72 (1989).
No abstract.
Marks, F.D., and S.J. Lord. Kinematic structure of Hurricane Gloria
as viewed by airborne Doppler radar and Omega dropwindsondes. Preprints,
24th Conference on Radar Meteorology, Tallahassee, FL, March 27-31, 1989.
American Meteorological Society, Boston, 529-532 (1989).
No abstract.
Maul, G.A., D.A. Mayer, M.H. Bushnell, and K. Hanson. Volume transport
fluctuations in the Gulf Stream system modeled from Florida sea level
records, 1931-1988. Proceedings, Chapman Conference on the Physics of
the Gulf of Mexico. EOS, Transactions, American Geophysical Union,
12 (1989).
No abstract.
Maul, G.A., J.R. Proni, M.H. Bushnell, and J.L. Mitchell. Oceanic
dynamic height anomaly from GEOSAT: A conceptual model for short
collinear orbit segments. Marine Geodesy, 12:259-285 (1989).
A method is derived for extracting oceanic dynamic height anomaly from
collinear (exact repeat mission) GEOSAT short (~1,000 km long) orbit
segments. The procedure requires at least one year of simultaneous
in-situ observations and involves: (1) computing with respect to the
ellipsoid, a mean sea surface height (SSH) profile solely from altimetry;
(2) linear least-squares removal of tilt and bias from individual SSH
profiles with respect to the mean profile; (3) determining an
independent mean dynamic height anomaly profile from hydrographic data
along the orbit segment; (4) demeaning the tilt-and-bias removed
individual SSH profiles and addition of the mean in-situ dynamic
height anomaly; and (5) correcting for concurrently observed dynamic
height anomaly at two or more suborbital points during satellite transit.
Analysis of the concept suggests root sum squared errors of
±5 cm, which can be reduced by smoothing and longer term
measurements along the same orbit segment. A one-year comparison
between two orbit segments at an open ocean crossover point shows
differences of ±2 cm, and comparison with six months of
simultaneous in-situ data shows corrections of ±3 cm are required.
Space-time plots of demeaned tilt-and-bias removed GEOSAT SSH profiles,
compared with similarly processed NMC/CAC numerical circulation model
calculations, show good agreement with variability in the South
Equatorial Current/North Equatorial Countercurrent system in the eastern
Pacific Ocean, and suggest that further development of the concept is
warranted.
McCreary, J.P., H.S. Lee, and D.B. Enfield. The response of the coastal
ocean to strong offshore winds: With application to circulation in the
Gulfs of Tehuantepec and Papagayo. Journal of Marine Research,
47:81-109 (1989).
Two ocean models are used to investigate the response of the coastal
ocean to strong offshore winds: a linear 1 1/2-layer model, and a
non-linear 1 1/2-layer model that allows entrainment of cool water into
the surface layer. The models are forced by wind stress fields similar
in structure to the intense wintertime, mountain-pass jets (~20
dyne/cm2) that appear in the Gulfs of Tehuantepec and Papagayo
for periods of three to ten days. Solutions are arranged in a hierarchy
of increasing dynamical complexity in order to illustrate the important
physical processes. They compare favorably with observations in several
ways. Some properties of solutions are the following. While the wind
strengthens, there is an ageostrophic current (not Ekman drift) that is
directed offshore. This offshore drift forces coastal upwelling, thereby
lowering the local sea level and sea surface temperature (SST). Although
the drop in sea level at the coast can be large and rapid (of the order
of 20 cm at the peak of a wind event), none of this signal propagates
poleward as a coastally-trapped wave. While the wind weakens, the
ageostrophic current is directed onshore, and consequently the coastal
ocean readjusts toward its initial state. Throughout the wind event,
cyclonic and anticyclonic gyres spin up offshore on either side of the
jet axis due to Ekman pumping. Entrainment cools SST offshore on and
to the right (looking onshore) of the jet axis, and virtually eliminates
the cyclonic gyre. The advection terms intensify the anticyclonic gyre
and give it a more circular shape. After a wind event, the anticyclonic
gyre propagates westward due to beta. Its propagation speed is enhanced
over that of a linear Rossby wave due to the nonlinear terms associated
with the increased thickness at the center of the gyre and with the
divergence of momentum flux.
Millero, F.J., J.P. Hershey, G. Johnson, and J.-Z. Zhang. The solubility
of SO2 and the dissociation of H2SO3 in
NaCl solutions. Journal of Atmospheric Chemistry, 8:377-389 (1989).
The pK1* and pK2* of
H2SO3 have been determined in NaCl solutions as a
function of ionic strength (0.1 to 6 m) and temperature (5 and
25°C). The extrapolated values in water were found to be in good
agreement with literature data. The experimental results have been used
to determine the Pitzer interaction parameters for SO2,
HSO3-, and SO32- in NaCl
solutions. The resultant parameters for NaHSO3 and
Na2SO3 were found to be in reasonable agreement
with the values for NaHSO4 and Na2SO4.
It thus seems reasonable to assume that the interactions of
Mg2+ and Ca2+ with HSO3- and
SO32- can be estimated from the values with
HSO4- and SO42- until
experimental values are available. Measurements of
pK1* and pK2* in artificial seawater
were found to be in good agreement with the calculated values using the
derived Pitzer parameters. It is, thus, possible to make reasonable
estimates of the activity coefficients HSO3- and
SO32- ions and pK1* and
pK2* for the ionization of H2SO3
in marine aerosols.
Ortner, P.B., L.C. Hill, and S.R. Cummings. Zooplankton community
structure and copepod species composition in the northern Gulf of Mexico.
Continental Shelf Research, 9(4):387-402 (1989).
Zooplankton community structure and copepod species composition are
analyzed in samples obtained during spring and winter from three areas
of the northern Gulf of Mexico: near the Mississippi River outflow, off
Cape San Blas, and in the central Gulf of Mexico. Samples from different
regions were distinguishable in correspondence analysis of dominant
species and/or functional groups. The near-surface communities of the
Mississippi and central Gulf were particularly distinct while Cape
San Blas was intermediate in both structure and specific character.
Saltier waters directly beneath the Mississippi plume yielded samples
similar to those from near-surface waters well offshore. At the same
time near-surface waters off the Mississippi and off Cape San Blas to the
west were distinguishable even during spring when the outflow from the
Mississippi was at its annual peak. These differences are consistent with
the discharge and flow patterns of the Mississippi River plume and the
northern Gulf and with systematic differences in such parameters as
temperature, salinity, and chlorophyll concentration. The implications
of these observations upon the feeding environments of the larvae of
commercially significant fish species are addressed since both zooplankton
prey and larval predators appear to be particularly abundant in the
Mississippi River plume environs.
Ooyama, K.V. Thermodynamics in the primitive form for modeling the
moist atmosphere. Extended Abstracts, 18th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, May 16-19, 1989. American
Meteorological Society, Boston, 157-158 (1989).
No abstract.
Peng, T.-H. Changes in ocean ventiliation rates over the last 7000
years based on 14C variations in the atmosphere and oceans.
Radiocarbon, 31(3):481-492 (1989).
Changes in the ocean ventilation rate may be one of the causes for a net
decrease of 100o/oo DELTA 14C in
atmospheric CO2 over the last 8000 years. Ocean ventilation
rates of the past can be derived from the 14C record preserved
in planktonic and benthic foraminifera in deep-sea sediments. Results of
14C dating using accelerator mass spectrometry on deep sea
sediments from the South China Sea show that the age differences between
planktonic (G sacculifer) and benthic foraminifera increase from
1350 yr ca 7000 yr ago to 1590 yr at present. An 11-box geochemical model
of global ocean circulation was used for this study. Both
tree-ring-determined atmospheric 14C values and foraminifera
14C age differences are used as constraints to place limits on
patterns of changes in ocean ventilation rates and in atmospheric
14C production rates. Results indicate: (1) 14C
production rates in the atmosphere may have decreased by as much as 30%
between 7000 and 3000 yr ago, and may have increased again by ca 15% in
the past 2000 yr; and (2) the global ocean ventilation rate may not have
been at steady state over the last 7000 yr, but may have slowed by as
much as 35%.
Peng, T.-H., W.M. Post, D.L. DeAngelis, V.H. Dale, and M.P. Farrell.
Atmospheric carbon dioxide and the global carbon cycle. The key
uncertainties. In Alternative Energy Sources VIII, Volume 2:
Research and Development, T.N. Veziroglu (ed.). Hemisphere Pub.
Corp., New York, 707-728 (1989).
No abstract.
Peterson, D.H., D.R. Cayan, J.F. Festa, F.H. Nichols, R.A. Walters, J.
V. Slack, S.E. Hager, and L.E. Schemel. Climate variability in an
estuary: Effects of riverflow on San Francisco Bay. In: Aspects of
Climate Variability in the Pacific and Western Americas, D.H.
Peterson, editor, Geophysical Monograph 55, 419-442 (1989).
No abstract.
Piotrowicz, S.R., R.A. Rasmussen, K.J. Hanson, and C.J. Fischer. Ozone
in the boundary layer of the equatorial Atlantic Ocean. Tellus,
41B:314-322 (1989).
Shipboard (~7) ozone and carbon monoxide measurements made in the
equatorial Atlantic Ocean south of the inter-tropical convergence zone
between 5°N and 10°S and 10°-30°W in August and
September of 1986 exhibited variability in excess of a factor of 2.
Ozone mixing ratios ranged from <25 to over 50 ppbv while carbon monoxide
mixing ratios ranged from <50 to over 120 ppbv along the western edge
of the equatorial Atlantic in spite of the fact that the prevailing
surface winds were from the east to southeast at between 5 and 15 m/sec.
Ozone and carbon monoxide mixing ratios were generally lower and
exhibited less variability in the eastern tropical Atlantic where a
lighter, south to southeasterly wind regime predominated. Isobaric
trajectory analyses indicated that the high ozone and carbon monoxide
mixing ratios appear to be related to long-range transport off of the
African continent. Time series analysis of the ozone data indicates a
diel cycle in ozone mixing ratios with a morning maximum and afternoon
minimum.
Powell, M.D. Boundary-layer kinematic structure in outer hurricane
rainbands. Extended Abstracts, 18th Conference on Hurricanes and
Tropical Meteorology, San Diego, CA, May 16-19, 1989. American
Meteorological Society, Boston, 67-68 (1989).
No abstract.
Powell, M.D. Boundary-layer structure and dynamics in outer hurricane
rainbands. Preprints, 24th Conference on Radar Meteorology,
Tallahassee, FL, March 27-31, 1989. American Meteorological Society,
Boston, 533-536 (1989).
No abstract.
Proni, J.R., and W.P. Dammann. Observations of acoustic backscatter from
oceanic wastewater outfalls. Journal of the Acoustical Society of
America, 85:S42 (1989).
Narrow beam echo sounders were used to characterize the spatial
distribution of wastewater plume material from six ocean outfalls in
the south Florida area. Volume scattering strengths were computed
and plotted as a function of depth and horizontal distance for 200 kHz
echoes. Reduction in peak scattering strength with increased range
from the outfall locations correlated well with reduction in
concentration of Rhodamine-WT dye introduced into the undiluted
wastewater at a concentration of 1 ppm. Sound power reflection
coefficients ranging from 10-5 to 10-9 were
observed for these wastewater plumes. The data presented demonstrates
the degree to which the sound power reflection coefficient for a
distribution of scatterers is dependent upon the concentration of
those scatterers, and shows the utility of the acoustical method in
watermass characterization.
Proni, J.R., W.P. Dammann, J.F. Craynock, and R. Fergen.
Oceanic wastewater plume characteristics measured acoustically.
Program and Abstracts, Eighth International Ocean Disposal Symposium,
Dubrovnik, Yugoslavia, October 9-13, 1989. Inter-University
Center of Postgraduate Studies, 18-19 (1989).
The measurement of oceanic wastewater plume features is complex
and the obtaining of samples of plume material is difficult. A
study, called SEFLOE, has been conducted on wastewater outfalls
off the coast of southeast Florida (USA). The wastewater plume field
F(r,0,z,t) is considered to be comprised of a set of subfields
fi(r,0,z,t), i.e., F(r,0,z,t) =
F(fi, ..., fi, ..., fn);
likewise, the oceanic water column field W(r,0,z,t),
into which the wastewater plume is injected, is considered to be
comprised of a set of subfields; i.e., W(r,0,z,t) = W(W1,
..., wi, ..., wn). In this study, the
feasibility of utilizing high-frequency acoustics to provide an estimator
field I(r,0,z,t) for one or more of the wastewater plume subfields
fi(r,0,z,t) is examined. It is hypothesized that the
water-column background corrected acoustical backscattered
intensity I(r,0,z,t) where I(r,0,z,t) = <If(r,0,z,t)> -
<Iw(r,0,z,t)> may be used to guide
chemical/biological sampling and the physical structure of at least one
wastewater plume subfield is revealed by the structure of I(r,0,z,t)
(the brackets denote a measured quantity). Data from SEFLOE have indicated
that the wastewater plume field is divided into regions of higher
concentration, spatially separated by regions of lower concentration;
we call these regions of higher concentration "boluses." When the water
column is density stratified, a "peeling-off" effect of the outer
portions of the rising wastewater plume is observed. The outer
portions "peel-off" into a vertical series of subsurface plumes at
different depths within the water column. The rate of dilution with
range for a purely surficial plume which existed in January 1988 is
compared within the rate of dilution with range of subsurface plume
which existed in June of 1988. In the surface plume, a much slower
dilution rate is observed for acoustical, dye and fecal streptococcal
subfields, while a somewhat slower dilution rate was observed for the
fecal coliform. In the subsurface plume, a much slower dilution rate
is observed. In addition to dilution with range, mean value, standard
deviation and the peak-to-mean values are presented as a function of
range for a specific ship transect.
Ramos, P.A., and D.R. Palmer. Comments on the Deep Six Sound Channel.
Journal of the Acoustical Society of America, 85:1767 (1989).
Some features of the Deep Six Sound Channel [J.C. Miller, J. Acoust.
Soc. Am., 71:859-862 (1982)], which may be important to those who
wish to use the model in various applications, are noted and discussed.
Rao, R.R., R.L. Molinari, and J.F. Festa. Evolution of the climatological
near-surface structure of the tropical Indian Ocean. Part I: Description
of mean montthly mixed layer depth and sea-surface temperature, surface
current, and surface meteorological fields. Journal of Geophysical
Research, 94(C8):10,801-10,815 (1989).
Mean monthly mixed layer depth (MLD), sea-surface temperature (SST), and
surface current climatologies are generated for the tropical Indian Ocean.
In addition, surface meteorological climatologies are produced for those
variables which could influence the evolution of the MLD and SST fields.
Only the MLD climatology is described in detail, as climatologies for the
other variables have appeared previously in the literature. The sum of
the annual and semi-annual harmonics account for greater than 75% of
the energy in the MLD time series over most of the basin. The amplitude
of the annual signal is greater than 20 m between 10°S and
25°S, with deepest MLDs observed during the southern hemisphere
winter. The south-central Arabian Sea, between the equator and 10°N,
and the northern Arabian Sea are also regions of larger annual harmonic
amplitude (>15 m). The amplitude of the semi-annual harmonic is largest
in the central Arabian Sea (>25 m). Deepest MLDs are observed there
during the height of the two monsoon seasons. Correlation coefficients
are computed between MLD and SST and several other oceanographic and
meteorological variables to explore possible causal relationships. Net
energy flux through the sea surface can account for 75% of the variance
in the SST and MLD time series over most of the region south of the
equator. Large coefficients are also observed in the northwestern
Arabian Sea. Correlations between SST and MLD and surface currents are,
in general, small throughout the region with maxima observed in the
central Arabian Sea, in the vicinity of the South Equatorial Current
and in the extreme eastern equatorial Indian Ocean. These correlations
are examined in more detail in Part II of this study in which simple
models of mixed layer dynamics are employed.
Rappaport, E.N., and P.G. Black. The utility of special sensor
microwave/imager data in the operational analysis of tropical cyclones.
Extended Abstracts, 18th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, May 16-19, 1989. American Meteorological
Society, Boston, J21-J24 (1989).
No abstract.
Rosenfeld, L.K., R.L. Molinari, and K.D. Leaman. Observed and modeled
annual cycle of transport in the Straits of Florida and east of Abaco
Island, the Bahamas (26.5°N). Journal of Geophysical Research,
94(C4):4867-4878 (1989).
Direct velocity observations were collected with a free-fall acoustic
velocity profiler along an east-west section extending 65 km offshore
of Abaco Island, the Bahamas (26.5°N). The section, which includes
five stations, was occupied 14 times between September 1984 and September
1987. The two inshore stations were located on the continental slope,
and the three offshore stations were located over the abyssal plain (at
depths approaching 4,700 m). The average total section transport between
the surface and 2,500 m (the portion of the water column best sampled) was
10 Sv (1 Sv = 106 m3/s) to the south.
The range of transports is 40 Sv with maximum northward transport observed
during April 1985 (5.3 Sv) and maximum southward transport observed during
April 1986 (34.8 Sv). The average flow above 800-900 m is to the north at
the four westernmost stations and is to the south below 800-900 m and over
most of the easternmost station. The southward flow includes the Deep
Western Boundary Current. Strong vertical shears extend to 1,100 m. An
approximation for the upper layer (above 1,100 m) baroclinic transport has
a mean of 12.2 Sv to the north and a range of 15 Sv. Results from a
two-layer and a one-and-a-half-layer wind-driven model are compared with
the annual cycles of total and upper layer transport, as determined from
the observations. The barotropic transport from the two-layer model has a
range of the order of ±10 Sv, with a winter maximum and fall minimum.
The range of the baroclinic transport from the one-and-a-half-layer model
is an order of magnitude smaller and of opposite sign. Although there are
similarities between the observations and the results of both models, the
small signal-to-noise ratio precludes definitive confirmation of the annual
cycle. The situation east of the Bahamas, where the two models give very
different predictions, is compared with the Straits of Florida, where
both models predict an annual cycle similar to that observed for the total
transport. The roles played by topography and local and remote wind forcing
in producing these results are discussed.
Shay, L.K., R.L. Elsberry, and P.G. Black. Vertical structure of the
ocean current response to a hurricane. Journal of Physical
Oceanography, 19(5):649-669 (1989).
During the passage of Hurricane Norbert in 1984, the Hurricane Research
Division of NOAA conducted a planetary boundary-layer experiment that
included the deployment of airborne expendable current profilers (AXCP).
A total of 16 AXCPs provided, for the first time, high-resolution vertical
profiles of currents and temperatures in hurricanes wind conditions.
This study focuses on the vertical structure of the near-inertial
baroclinic currents excited by the passage of this hurricane. The
transient, hurricane-induced currents are isolated from the AXCP
profiles in Norbert by subtracting a spatially-averaged current. Near
the center of Hurricane Norbert, the WKBJ-scaled vertical wavenumber
spectra are a decade greater than the Garrett-Munk spectra (GM75).
The first ten linear, baroclinic-free modes are calculated from the
spatially-averaged, Brunt-Väisälä frequency. To allow
a more direct comparison with the AXCP observations in the high-wind
regime, the near-inertial response for the three-dimensional velocities
is simulated by superposing a hurricane-like wind stress field onto the
first ten baroclinic modes. About 70% of the current variance in
Hurricane Norbert can be explained by a sum of only the first four
near-inertial modes. Most of the ocean current variability can be
accounted for by the wind stress curl, although the direct effect of the
wind stress and the stress divergence do contribute to the observed current
variance within 30-60 km from the storm. However, these last two effects
rapidly diminish after one inertial period. Although the energy input by the
hurricane forcing is spread over all of the vertical wavelengths, most
of the energy is contained in the gravest four vertical modes which then
govern the dynamics in the wake region.
Thacker, W.C. Fitting models to inadequate data by enforcing spatial and
temporal smoothness. Journal of Geophysical Research,
93(C9):10,655-10,665 (1989).
When observations are too sparse to determine the state of a dynamical
model, it is necessary to make use of prior knowledge or prejudice. The
approach discussed here is to require that the model state be the best
smooth fit to the sparse data. The requirement of smoothness is enforced
by introducing bogus data, which correspond to hypothetical observations
that properties such as slope, curvature, or temporal tendency of model
fields have zero values within some specified accuracy. The bogus data
serve to increase the effective ratio of data to model degrees of
freedom. The concept of bogus data allows a bias toward smoothness to be
incorporated easily into the adjoint method for fitting time-dependent
models to asynoptic data. Computational examples using a simple
three-wave model show that reasonable fits can be obtained even when
the number of real data is considerably less than the number of model
degrees of freedom.
Thacker, W.C. The role of the Hessian matrix in fitting models to
measurements. Journal of Geophysical Research, 94:6177-6196
(1989).
A numerical model can be fit to data by minimizing a positive quadratic
function of the differences between the data and their model counterparts.
The rate at which algorithms for computing the best fit to data converge
depends on the size of the condition number and the distribution of
eigenvalues of the Hessian matrix, which contains second derivatives of
this quadratic function. The inverse of the Hessian can be identified
as the covariance matrix that establishes the accuracy to which the model
state is determined by the data; the reciprocals of the Hessian's
eigenvalues representing the variances of linear combinations of variables
determined by its eigenvectors. The aspects of the model state that are
most difficult to compute are those about which the data provide the
least information. A unified formalism is presented in which the model
may be treated as either strong or weak constraints, and methods for
computing and inverting the Hessian matrix are discussed. Examples of
the uncertainties in the best-fit analyses using an oceanographic model
are given for several different sets of hypothetical data.
Tziperman, E., and W.C. Thacker. An optimal control/adjoint equations
approach to studying the oceanic general circulation. American
Meteorological Society, 19:1471-1485 (1989).
An efficient procedure is presented for analyzing oceanographic
observations with the aid of a general circulation model. Poorly known
model parameters, such as eddy mixing coefficients, surface forcing and
tracer boundary fluxes, can be calculated by fitting model results to
observations. Optimal estimates for all model fields, including the
observed ones, can then be computed by running the model with the
best-fit values of the calculated parameters. Information about the
resolution and the error-covariances of the model parameters can be
computed. This information is shown to be very valuable for critically
evaluating how well the data determine the parameter's values. An
adjoint model, similar in structure to the numerical model, uses
information on model-data misfit to improve estimates of the unknown
model parameters, and improve the fit to observations. The procedure
is illustrated using simulated data and a simple, barotropic, nonlinear,
quasi-geostrophic model. Examples are discussed in which friction
parameters, wind forcing, and the steady-state circulation are
determined from simulated vorticity and streamfunction observations.
Venne, M.G., W.A. Lyons, C.S. Keen, P.G. Black, and R.C. Gentry.
Explosive supercell growth: A possible indicator of tropical storm
intensification? Preprints, 24th Conference on Radar Meteorology,
Tallahassee, FL, March 27-31, 1989. American Meteorological Society,
Boston, 545-548 (1989).
No abstract.
Wilburn, A.M., E. Johns, and M.H. Bushnell. Current velocity and
hydrographic observations in the southwestern North Atlantic Ocean:
Subtropical Atlantic Climate Study (STACS), 1988. NOAA Data
Report, ERL AOML-13, 83 pp. (1989).
No abstract.
Willis, P.T., and A.J. Heymsfield. Hurricane microphysical trajectories.
Extended Abstracts, 18th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, May 16-19, 1989. American Meteorological
Society, Boston, 75-76 (1989).
No abstract.
Willis, P.T., and A.J. Heymsfield. Structure of the melting layer in
mesoscale convective system stratiform precipitation. Journal of the
Atmospheric Sciences, 46(13):2008-2025 (1989).
This study examines the aircraft observations and theoretical evolution
of particles above, through, and below the melting layer in the
stratiform region associated with a mesoscale convective system (MCS).
The aircraft data were obtained from an advecting spiral descent where
the descent rate approximately corresponded to the typical hydrometeor
fall speeds. The microphysical and thermodynamic measurements not only
allowed us to characterize the particle evolution, but also enabled us
to compare them with the theoretical evolution of the particles in the
melting layer and to quantify the associated heating and cooling rates.
Even though complete melting requires a fairly deep layer, most of the
mass melts, and thus most of the cooling occurs, in a thin layer above
the location of the radar bright band. Based upon the magnitude of
vertical velocity fluctuations, the layers below the melting layer appear
to be decoupled from those above. The ice water content above the
melting layer is two to three times the liquid water content below the
melting layer. The production of a few, very large, aggregates is
dramatic after the onset of melting, due in part to a melting-induced
increase in the terminal velocity difference between similar-sized
hydrometeors. The radar reflectivity maximum (bright band) is due to
these relatively few, very large, aggregates that survive to warmer
temperatures. The reflectivity maximum is depressed well below the
isothermal layer and the level where most of the ice mass is melted.
Above the melting layer, small crystals are replenished by a
fragmentation or breakup process.
Willis, P.T., and P. Tattleman. Drop-size distributions associated with
intense rainfall. Journal of Applied Meteorology, 28(1):3-15
(1989).
The probability of occurrence of extreme rainfall rates is reviewed. The
drop-size distributions associated with a range of high rainfall rates
are examined using data from tropical storms and hurricanes. Mean
drop-size distributions are presented for a range of high rainfall rates,
as well as a Gamma-distribution fit to the entire set of normalized
drop-size distributions. This fit forms the basis for a model drop-size
distribution for intense rain. The goodness of fit of the model is
examined by comparing it with independent drop-camera measurements of
high-rain-rate distributions from several geographic locations. The
slope of exponential fits to the distributions are examined for
constancy with rainfall rate and are generally found to decrease with
increasing rainfall rate.
Willoughby, H.E., W.P. Barry, and M.E. Rahn. Real-time monitoring of
Hurricane Gilbert. Extended Abstracts, 18th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, May 16-19, 1989. American
Meteorological Society, Boston, 220-221 (1989).
No abstract.
Willoughby, H.E., J. Masters, and C.W. Landsea. A record minimum sea
level pressure observed in Hurricane Gilbert. Monthly Weather
Review, 117(12):2824-2828 (1989).
On 13 September 1988, Hurricane Gilbert attained an extreme minimum sea
level pressure, estimated to be 885 hPa from aircraft reconnaissance
reports at the time. Postseason analysis indicates that the flight-level
pressure, P, upon which this figure is based requires correction
upward. In typhoons with sea level pressure <900 hPa, comparison
between sea level pressures measured by dropsonde and those estimated
by the same method used in Gilbert indicates that, in addition to the
error in P, the estimation has a bias toward low pressure. Although
the aircraft did not release a dropsonde in the eye at minimum pressure,
it is possible to calculate hydrostatic sea level pressures by assuming
a variety of plausible thermal structures below flight level. With
corrected P, both the statistical extrapolation with its bias removed
and the hydrostatic calculations show that a revised value of
888 ± 2 hPa is closer to the true minimum sea level pressure. The
standard deviation of the various approximations means that the
probability is <3% that the actual minimum failed to reach a value
below 892 hPa, the old record for a hurricane in the Atlantic Basin
set by the Labor Day Hurricane of 1935.
Wilson, W.D., and A. Leetmaa. Acoustic Doppler current profiling in the
equatorial Pacific in 1984. Journal of Geophysical Research,
93(C11):13,947-13,966 (1989).
Hydrographic data and acoustic Doppler current profiles collected from
150°W to 85°W in the equatorial Pacific during 1984 showed
significant seasonal changes in the temperature and velocity fields. On
the equator, the surface current was eastward in April up to 80 cm
s-1, reversing to westward at 100 cm s-1 by November.
Over the same period, the Equatorial Undercurrent (EUC) transport decreased,
the equatorial zonal pressure gradient (ZPG) increased, and the depth of
the mixed layer and EUC core deepened. Off the equator at 150°W, the
North Equatorial Countercurrent (NECC) was absent in April/May but
pronounced in October/November. Superimposed on this seasonal variability
were smaller-scale (roughly 1,000 km wavelength) correlated fluctuations
in the upper ocean temperature and velocity fields. We identify these
structures with the 20- to 30-day instability waves (Legeckis, 1977).
The coincident high-resolution velocity and temperature data allowed the
calculation of Reynold's stresses due to the waves and resultant heat
and momentum flux estimates as well as details of of the vertical phase
structure. Barotropic instability at the northern edge of the EUC is a
likely source of energy for these waves. Estimated EUC transport
decreased from 50 in April to 25 × 106 m3
s-1 in November while the westward wind stress doubled and
the 0-/400-dbar ZPG quadrupled. The data were used to estimate terms
in the momentum balance in the upper 150 m, and it was found that
nonlinear terms were often at least as important as the integrated
ZPG in balancing the surface wind stress. East of 120°W, the
eastward advection of eastward momentum, UUx, was particularly
important. These momentum equation terms were used to estimate a
profile of the coefficient of vertical eddy viscosity; it was similar
to profiles estimated by bulk methods and by parameterization by
Richardson number.
Wood, V.T., and F.D. Marks. Hurricane Gloria: Simulated land-based
Doppler velocities reconstructed from airaborne Doppler radar measurements.
Extended Abstracts, 18th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, May 16-19, 1989. American Meteorological
Society, Boston, 115-116 (1989).
No abstract.
Vazquez, F., J.-Z. Zhang, and F.J. Millero. Effect of metals on the rate
of the oxidation of H2S in seawater. Geophysical Research
Letters, 16(12):1363-1366 (1989).
Recent measurements on the oxidation of H2S in the Black Sea
yielded rates that were ten times faster than expected. To determine if
this increase was due to trace metals, measurements have been made on the
oxidation of H2S in seawater with added transition metals.
Below a concentration level of 100 nM, none of the metals except for
Fe2+ affect the rate of oxidation. At higher concentrations
the rates increase for all the metals except Zn2+. The
increase in the rates followed the order:
Fe2+ > Pb2+ > Cu2+ > Fe3+ >
Cd2+ > Ni2+ > Co2+ > Mn2+.
The increase in the rates below sulfide precipitation appears to be
related to the formation of MHS+ ion pairs that have a higher
rate of oxidation than HS-. Only Fe2+ and
Mn2+ have concentrations high enough to be effective in
influencing the rate of oxidation of H2S in the waters of
anoxic basins and sediments. The estimated rates of oxidation of
H2S in the Black Sea using the laboratory measurements were
found to be in reasonable agreement with the measured values. Since
CuHS+ has a higher rate of oxidation than HS-, it
cannot be used to explain the stability of H2S in oxic
seawaters. A more likely choice is ZnHS+.
**1988**
Bitterman, D.S. The NOAA-AOML drift buoy program. Proceedings,
International Service ARGOS Users Conference and Exhibit, Greenbelt,
MD, September 15-17, 1987, 107-116 (1988).
No abstract.
Black, P.G. Hurricane-ocean interaction near the subtropical front.
Preprints, 7th Conference on Ocean-Atmosphere Interaction, Anaheim,
CA, January 31-February 5, 1988. American Meteorological Society,
Boston, J60 (1988).
No abstract.
Black, P.G., R.L. Elsberry, and L.K. Shay. Airborne surveys of ocean
current and temperature perturbations induced by hurricanes. In
Advances in Underwater Technology, Ocean Science, and Offshore
Engineering, Vol. 16, Oceanology '88. Graham and Trotman, London,
51-58 (1988).
No abstract.
Black, P.G., R.L. Elsberry, L.K. Shay, R.M. Partridge, and J.D. Hawkins.
Atmospheric boundary-layer and oceanic mixed-layer observations in
Hurricane Josephine obtained from air-deployed drifting buoys and
research aircraft. Journal of Atmospheric and Oceanic Technology,
5(6):683-698 (1988).
Three drifting buoys were successfully air dropped ahead of Hurricane
Josephine. This deployment resulted in detailed simultaneous measurements
of surface wind speed, surface pressure, and subsurface ocean temperature
during and subsequent to storm passage. This represents the first time
that such a self-consistent data set of surface conditions within a
tropical cyclone has been collected. Subsequent NOAA research aircraft
overflights of the buoys, as part of a hurricane planetary boundary-layer
experiment, showed that aircraft wind speeds, extrapolated to the 20 m
level, agreed to within ±2 m s-1, pressures agreed to
within ±1 mb, and sea-surface temperatures agreed to within
±0.8°C of the buoy values. Ratios of buoy peak 1 min wind
(sustained wind) to 1/2 h mean wind >1.3 were found to coincide with
eyewall and principal rainband features. Buoy trajectories and subsurface
temperature measurements revealed the existence of a series of mesoscale
eddies in the subtropical front. Buoy data revealed storm-generated,
inertia-gravity-wave motions superposed upon mean current fields, which
reached a maximum surface speed >1.2 m s-1 immediately
following storm passage. A maximum mixed-layer temperature decrease
of 1.8°C was observed to the right of the storm path. A temperature
increase of 3.5°C at 100 m and subsequent decrease of 4.8°C
following storm passage indicated a combination of turbulent mixing,
upwelling, and horizontal advection processes.
Broecker, W.S., D. Oppo, T.-H. Peng, W. Curry, M. Andree, W. Wolfli,
and G. Bonani. Radiocarbon-based chronology for the
180/160 record for the last deglaciation.
Paleoceanography, 3(4):509-515 (1988).
A radiocarbon-calibrated box model for today's ocean suggests that a lag
of about 1750 years should exist between the arrival of the mid-point of
the deglaciation 18O signal in the deep Atlantic Ocean and
its arrival in the deep Pacific Ocean. In order to assess the actual
lag, we have carried out accelerator radiocarbon measurements on two
cores from the Atlantic Ocean and one core from the Pacific Ocean.
Although the results are not definitive, there is a suggestion that the
actual time lag was about 1000 years.
Broecker, W.S., R.H. Wanninkhof, G. Mathieu, T.-H. Peng, S. Stine,
S. Robinson, A. Herczeg, and M. Stuiver. The radiocarbon budget for
Mono Lake: An unsolved mystery. Earth and Planetary Science
Letters, 88:16-26 (1988).
Since 1957 the 14C/C ratio of the dissolved inorganic carbon
in Mono Lake has risen by about 60%. The magnitude of this increase is
about four times larger than that expected from the invasion of
bomb-produced 14C from the atmosphere. We have eliminated the
following explanations: (1) measurement error; (2) an unusually high
physical exchange rate for non-reactive gases; (3) inorganic enhancement
of the CO2 exchange rate; and (4) biological enhancement of
the CO2 exchange rate. Clandestine disposal of waste
radiocarbon remains a dark-horse explanation. In the course of our
investigations we have uncovered evidence for at least one episodic
input of radiocarbon-free carbon to the lake over the last 1000 years.
We speculate that this injection was related to a hydrothermal event
resulting from sublacustrine volcanic activity.
Clarke, T.L., J.R. Proni, D.A. Seem, and J.J. Tsai. Joint CGS-AOML
acoustical bottom echo-formation research, I: Literature search and
initial modeling results. NOAA Technical Memorandum, ERL AOML-66
(PB88-202007), 73 pp. (1988).
A literature survey has found work dealing with the problem of
echo-formation for rough sedimentary bottoms. The main attempts at
practical application have been at frequencies lower than those used
for echo-sounding work. A model has been formulated that includes
the effect of surface scattering and volume scattering in a unified
manner. This model has been implemented on the AOML computer and
exercised for a variety of bottom types and echo-sounding frequencies.
Colin, C., and S.L. Garzoli. High-frequency variability of in-situ
wind, temperature, and current measurements in the equatorial Atlantic
during the FOCAL/SEQUAL experiment. Oceanologica Acta,
11(2):139-148 (1988).
The high-frequency variability of in-situ wind measurements in the
western (1°N, 29°W) and eastern (0°, 4°W) equatorial
Atlantic are described and for the first time compared. The data were
obtained from meteorological sensors placed respectively on St. Peter
and St. Paul Rocks and at the top of a surface buoy moored in the
Gulf of Guinea during the FOCAL/SEQUAL experiment from February 1983
to September 1984.
Dodge, P.P. A climatology of rainbands observed by coastal radars in
GALE. Reports of GALE/CASP Preliminary Analysis Workshop, Virginia
Beach, VA, November 2-6, 1987. GALE Project Office, NCAR, Boulder,
19-22 (1988).
No abstract.
Enfield, D.B. Is El Niño becoming more common? Oceanography,
1(2):23-27 (1988).
No abstract.
Fine, R.A., and R.L. Molinari. A continuous deep western boundary
current between Abaco (26.5°N) and Barbados (13°N).
Deep-Sea Research, 35:1441-1450 (1988).
No abstract.
Friedman, H.A., and C.A. Arnhols. 1988 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 120 pp. (1988).
No abstract.
Franklin, J.L., S.J. Lord, and F.D. Marks. Dropwindsonde and radar
observations of the eye of Hurricane Gloria (1985). Monthly Weather
Review, 116(5):1237-1244 (1988).
Two soundings from the eye of Hurricane Gloria (1985) during a period of
rapid deepening are described. The soundings were made by Omega
dropwindsondes (ODWs) during research flights of the NOAA Hurricane
Research Division on 24-25 September 1985. During the 4.7 h between the
two ODW drops, Gloria's minimum sea-level pressure fell from 932 to
922 mb. The ODWs indicate substantial warming due to dry adiabatic
descent from 580-660 mb. Descent rates are estimated to be about
11 cm s-1. Near 500 mb, ascent is indicated. Approximately
60% of the 10 mb pressure fall is associated with thermodynamic changes
below 500 mb.
Gamache, J.F., F.D. Marks, and R.A. Black. The bulk water budget of
Hurricane Norbert (1984) as determined from thermodynamic and
microphysical analyses retrieved from airborne Doppler radar. Preprints,
10th International Cloud Physics Conference, Bad Homburg, Federal
Republic of Germany, August 15-20, 1988. American Meteorological Society,
Boston, 711-713 (1988).
No abstract.
Georges, T.M., D.R. Palmer, R.M. Jones, and J.P. Riley. A survey of
acoustic techniques for monitoring El Niño. NOAA Technical
Memorandum, ERL WPL-149 (PB88-157615), 58 pp. (1988).
The challenge of understanding the El Niño-Southern Oscillation (ENSO)
cycle in the equatorial Pacific Ocean is a test of our abilities to
observe, model, and forecast the processes of global climate change.
The only viable technology for monitoring the structure, dynamics, and
energetics of the ocean interior on the space-time scales of the ENSO signal
appears to be acoustic remote sensing. We, therefore, examine how the
following acoustic techniques might be used to monitor ENSO-induced changes
in the upper ocean: (1) ocean acoustic tomography; (2) a long-range acoustic
thermometer; (3) passive monitoring of ambient acoustic noise level; (4) an
occulation technique that depends on bottom absorption; and (5) space-time
scintillation analysis. We computed the acoustic properties of ocean
models based on the 1982-1983 ENSO event and found out how sensitive
different acoustic measurables are to the temperature changes that
accompany a strong El Niño. In the eastern Pacific, for example,
the largest (and earliest) temperature increases occur between 40 and
100 m depth. For long-range (ducted) sound rays to pass through this
region without being absorbed by the bottom, the ocean must be at least
4 km deep. Pulse tomography, applied to vertical ocean slices, could
adequately sample the temperature and currents in the upper ocen if
appropriate receiving arrays were used. The passive listening scheme could
monitor changes in the ambient noise level with the onset of El
Niño, but it raised many questions about the natural variability
of the noise environment. An occulation scheme that uses a vertical
receiving array could economically monitor changes in average thermocline
depth. The long-range acoustic thermometer could monitor the heat content
of the equatorial ocean, a likely ENSO precursor. The horizontal
covariance of acoustic scintillations might be used to measure the
structure of transverse currents crossing a long acoustic path. If
problems in extending the theoretical model to longer ranges can be
solved, scintillation analysis could be used to monitor subsurface
equatorial currents that transport heat eastward along the equator.
Each technique examined offers some remote-sensing potential, but each
also poses problems to be solved before its relative advantages in cost,
coverage, or convenience over in-situ methods are clear.
Hansen, D.V., and C.A. Paul. Vertical motion in the eastern equatorial
Pacific inferred from drifting buoys. Oceanologica Acta,
6:27-32 (1988).
Surface current measurements have been obtained from the eastern tropical
Pacific Ocean by means of drifting buoys tracked by the NIMBUS and ARGOS
satellite systems since 1977. Near-equatorial divergence of Ekman
transport is indicated qualitatively by persistent avoidance of the
equator by drifters. Upwelling velocity and transport were estimated
from the horizontal divergence of surface current fields obtained by
optimum interpolation of overall and monthly composite data. The
estimated divergence is predominantly meridional. Average upwelling
velocity and transport in the region 1.5°N-1.5°S,
80°W-130°W are estimated to be 1.5 m da-1 and
32 × 106 m3 s-1. Seasonal
variation
of the estimated upwelling agrees closely in phase but is larger in
magnitude than that implied by the annual and semiannual constituents
of 14°C isotherm depth variations in the eastern equatorial Pacific.
Houze, R.A., F.D. Marks, and R.A. Black. Mesoscale patterns of ice
particle characteristics in Hurricane Norbert. Preprints, 10th
International Cloud Physics Conference, Bad Homburg, Federal Republic
of Germany, August 15-20, 1988. American Meteorological Society,
Boston, 708-710 (1988).
No abstract.
Lautenschlager, M., D.P. Eppel, and W.C. Thacker. Subgrid-parameterization
in helical flows. Beiträge zur Physik der Atmosphäre,
61(2):87-97 (1988).
A new parameterization for the turbulent momentum fluxes of an
incompressible flow is suggested. Assuming the turbulent field to carry
internal structure, the expansion of the subgrid fluxes in terms of
average vorticity leads, in addition to subgrid kinetic energy, to
subgrid helicity as an extra parameter to characterize this internal
structure. In a simple model the expansion coefficients are connected
to the resolution scale of the numerical grid model used. It is shown
that the new subgrid-helicity dependent terms act against diffusion as
they can transport additional rotation into the mean motion. In the limit
of vanishing turbulent helicity the new parameterization reproduces the
well-known diffusion parameterization of the turbulent fluxes.
Maul, G.A., J.R. Proni, and J.L. Mitchell. On the integration of
satellite altimeter data with in-situ oceanographic data to
provide precise profiles of absolute dynamic height anomaly. Proceedings,
PACON '88, Pacific Congress on Marine Science and Technology, OST2,
9-10 (1988).
In 1984, the U.S. National Academy of Science, and in 1985 the U.S.
National Science Foundation, issued reports on global observations and
understanding of the general circulation of the oceans, and on the
emergence of a unified ocean science. Both reports note that there are
certain critical areas in the ocean where horizontal fluxes must be
monitored: the Gulf Stream; the Kuroshio; East Australian, Brazil, and
Somali Currents; Norwegian and Mediterranean Seas outflows; through the
Drake Passage and across the equator at several Pacific and Atlantic
sites. These fluxes are required as boundary conditions in numerical
models, as verification data for forecasts and remote sensing, and as
time series signals to measure changes at climatically sensitive sites.
Results from the NOAA Subtropical Atlantic Climate Study (STACS) have
shown that volume flux is closely related to changes in sea surface
topography across one of the most important of these critical areas:
the Florida Current portion of the Gulf Stream system. This paper
investigates the role of satellite altimetry in precise determination
of the variations of absolute dynamic topography anomaly across
critical areas of the Gulf Stream system in the STACS region, and the
tropical Pacific in the Equatorial Pacific Ocean Climate Study (EPOCS)
region near 110°W. From error budgets for GEOSAT, ERS-1, and
TOPEX/POSEIDON, it is clear that satellite altimeters alone cannot
provide both the precision and accuracy required to determine absolute
dynamic topography anomaly across a critical ocean area. Conversely, for
both logistic and financial reasons, no in-situ measuring scheme
alone is reasonably able to observe horizontal fluxes, such as volume
transport on interannaul time scales. Some combination of remote sensing
and in-situ observations will provide the proper mix of
technologies; satellite altimetry coupled with independent measures of
sea level and/or dynamic height, supplemented by buoy, mooring, and
ship-of-opportunity data, is such a mixture. Based on experience with
GEOSAT, we are developing sampling strategies that use mixed data inputs
to create time series of absolute dynamic topography anomaly along short
(~1000 km) exact repeat mission (EER) tracks. RSS accuracies due
to media effects are estimated to be less than ± 5 dynamic
centimeters (dyn-cm) for the GEOSAT ERM when coupled with in-situ
observations. ERS-1 and TOPEX/POSEIDON promise to provide significant
improvements over this figure, and should allow monitoring volume
transport at the ±1 gigaliter per second (106
m3 sec-1) level in the subtropics, as well as
documenting oceanic equatorial waves and other tropical circulation
features such as those associated with ENSO events. In the open ocean,
inverted echo sounder/pressure gauge (IES/PG) assemblies have been
found to provide in-situ verification data that is accurate
within ±3 dyn-cm. However, on more careful examination of the
record, a seasonal dependence in the correlation between acoustic
travel time and dynamic height anomaly has been discovered. In the
equatorial Pacific Ocean, thermistor strings that measure the upper
500 m at 50 m intervals have been found to be as accurate as IES/PGs,
with the added benefit of real-time data transmission for nowcasting
purposes. In coastal regions, open ocean tide gauges and/or shallow
water pressure gauges are shown to provide calibration data at the
±1 dyn-cm precision level, but may have distorted amplitudes of
the tidal wave component of instantaneous sea level. This work is
conducted as part of the overall NOAA EPOCS and STACS efforts in climate,
and as such benefits from other aspects of these programs such as
numerical modeling at GFDL, in-situ observations from NOAA
ships and moorings, other satellite studies, sea-level/weather
stations, and cooperative efforts with several institutes and
universities. Using a space-time objective analysis, we show variability
in dynamic height derived from GEOSAT, to provide information that is
in agreement with in-situ observations, and that is precise at
±5 dyn-cm.
Metz, S., J.H. Trefry, and T.A. Nelsen. History and geochemistry of a
metalliferous sediment core from the Mid-Atlantic Ridge at 26°N.
Geochimica et Cosmochimica Acta, 52:2369-2378 (1988).
Fourteen thousand years of hydrothermal deposition are recorded in a
metalliferous sediment core recovered from the Trans-Atlantic Geotraverse
(TAG) Hydrothermal Field on the Mid-Atlantic Ridge at 26°N. An
estimated 26% to >96% of the sediment at this core site is hydrothermally
derived as determined from the CaCO3, Al, and Fe data. Layers
of essentially pure vent precipitates contain <3% CaCO3 and
<0.5% Al, with high concentrations of Fe (43%), Cu (4.1%), Zn (1.2%),
Mn (1.1%), V (480 ppm), Pb (175 ppm), Cd (32 ppm) and Hg (3.8 ppm).
Sediment accumulation rates vary from ~1 to >30 g/cm2/1,000
y throughout the core, a function of the intensity of hydrothermal inputs.
Distinct hydrothermal events are recorded at 6,000 and 8,500 y B.P. in
layers containing >90% vent-derived material. Vertical metal profiles and
interelement relationships in the core result from variable deposition
of oxides and sulfides, oxidation, and dissolution of sulfide phases and
scavenging of metals from seawater.
Molinari, R.L., and K.D. Leaman. Variability of Gulf Stream surface
currents in the Straits of Florida. Marine Weather Log,
31(3):10-13 (1988).
No abstract.
Molinari, R.L., and J. Morrison. The separation of the Yucatan Current
from the Campeche Bank and the intrusion of the Loop Current into the
Gulf of Mexico. Journal of Geophysical Research,
93(C9):10,645-10,654 (1988).
Data collected in the eastern Gulf of Mexico during 1974, 1975, and 1976
show that the penetration of the Loop Current into the Gulf is strongly
correlated with the location of the Yucatan Current on the Campeche Bank.
The Loop does not penetrate far into the Gulf when the Yucatan Current
separates from the bank in the vicinity of the Catoche Tongue (i.e.,
the eastern Campeche Bank). Deep Loop penetrations are correlated
with separations farther west on the bank. The angle of the Yucatan
Current at separation is also correlated with separations farther west
on the bank. The angle of the Yucatan Current at separation is also
correlated with the location of separation (i.e., smaller angles
relative to due east are correlated with separations from farther east
on the bank). Thus, small angles at separation are correlated with
shallow intrusions of the Loop. Historical temperature data collected in
the eastern Gulf are reviewed and support these correlations. Simple
conservation of potential vorticity considerations can explain the
correlation between the angle at separation and the penetration of the Loop.
Palmer, D.R., T.M. Georges, and R.M. Jones. New techniques for
investigating the properties of chaotic ray paths. Journal of the
Acoustical Society of America, 84:S91 (1988).
It has been established that acoustic ray paths in a range-dependent ocean
environment can exhibit chaotic behavior [Palmer et al., Geophys.
Res. Lett., 15:569-572 (1988)]. The usual techniques for identifying
chaotic rays are the examination of Poincaré sections and power
spectra of path depth, as well as the observation of exponential
sensitivity to initial conditions. These techniques are not always
useful, however, and are not directly related to observable signal
characteristics. Travel times, ray elevation angle at axis crossings,
and upper and lower turning point depths have practical relevance and
provide new insights into the character of chaotic rays. Since this
effort involved the numerical calculation of ray paths for both the
Helmholtz and parabolic equations, procedures were developed for comparing
results obtained for the two equations.
Palmer, D.R., M.G. Brown, F.D. Tappert, and H.F. Bezdek. Chaotic behavior
of ray trajectories in a range-dependent ocean environment. Journal of
the Acoustical Society of America, 83:S37 (1988).
It has been demonstrated that ray trajectories propagating in a
range-dependent ocean environment can exhibit chaotic behavior. A
particularly simple sound-speed model was considered consisting of the
Munk reference sound-speed profile to which is added a small range-dependent,
deterministic perturbation having a harmonic dependence on range and
decreasing exponentially with depth. Chaotic ray trajectories were
identified from an examination of Poincaré sections and power
spectra. The sensitivity of chaotic trajectories to initial conditions
and the consequent implications for predictability were investigated
by considering the evolution with range of a bundle of rays that
initially occupy a very small region in phase space. The largest
Lyapunov exponent was determined by considering the spread of the
bundle. Since the ray equations define a nonautonomous Hamiltonian
system with one degree of freedom, our results can be understood in
terms of recent contributions to the study of classical chaos.
Palmer, D.R., M.G. Brown, F.D. Tappert, and H.F. Bezdek. Classical chaos
in nonseparable wave propagation problems. Geophysical Research
Letters, 15(6):569-572 (1988).
Numerical calculations show that acoustic ray paths in a weakly
range-dependent, deterministic ocean model exhibit chaotic behavior,
that is, have an exponentially sensitive dependence on initial
conditions. Since the ray equations define a nonautonomous Hamiltonian
system with one degree of freedom, these results may be understood in
terms of recent advances in classical chaos. The Hamiltonian structure
of ray equations in general suggests that chaotic ray trajectories
will be present in all types of linear wave motion in geophysics when
variables do not separate, as in laterally inhomogeneous media.
Palmer, D.R., L.M. Lawson, Y.-H. Daneshzadeh, and D.W. Behringer.
Computational studies of the effect of an El Niño/Southern
Oscillation event on underwater sound propagation. In Computational
Acoustics: Algorithms and Applications, D. Lee, R.L. Sternberg, and
M.H. Schultz (eds.). Elsevier Science Publishers B.V. (North-Holland),
Amsterdam, 335-356 (1988).
Computer simulations of underwater sound propagation in the equatorial
Pacific have been undertaken using a recently-developed program called
ULETA. This program was developed to exploit the characteristics of
modern computing systems including the clustering of processors, command
languages that permit interactive processor communication, and the
availability of color graphics hardware and software. It has three
modes of operation: a ray-tracing mode; a continuous-wave mode in which
transmission loss as a function of depth and range is obtained for a
source radiating a single acoustic frequency; and a pulsed mode in which
the pressure resulting from a pulsed source is obtained at selected
locations as a function of time. The input data for the simulations
consisted of a series of sound-speed profiles which reflect the onset,
evolution, and cessation of the most recent El Niño/Southern
Oscillation (ENSO) event. The results of the computations indicate the
presence of a layer of ray-path instability in the ocean, extending from
about 50 m to 280 m in depth, which suddenly became very quiet during
the ENSO event. Sound which entered this layer or was generated within
it could not have traveled on for more than a few tens of kilometers
in range without striking the bottom and experiencing the usual severe
losses in intensity. While the existence of this layer provides an
opportunity to monitor ENSO events using underwater sound, it prevents
the straightforward application of the techniques of acoustic tomography
to study the dynamics of the ocean in the layer. This is unfortunate
since the major temperature anomalies occur within it.
Pazos, M.C. Drifting buoy data from the equatorial Pacific for the
period January 1, 1984 through May 31, 1985. NOAA Data Report, ERL
AOML-11 (PB88-212824), 100 pp. (1988).
No abstract.
Powell, M.D. Boundary-layer structure and dynamics in outer hurricane
rainbands. Ph.D. dissertation, Florida State University, Tallahassee,
227 pp. (1988).
Results of hurricane boundary-layer experiments conducted in outer
rainbands of Hurricanes Josephine (1984) and Earl (1986) are presented.
Comparisons of precipitation, kinematic, and thermodynamic structures in
these storms indicate that principal rainbands have common characteristic
mesoscale and convective-scale features in the boundary layer. The
two-dimensional mesoscale structure suggests that rainbands are made of
a linear aggregate of cellular reflectivity elements (on the inner,
upshear side of the band) and stratiform rain (on the outer downshear
side). The band is oriented perpendicular to the shear above the
boundary layer and cells move downband at about 80% of the maximum
wind. Alongband and crossband wind and equivalent potential temperature
maxima are located on the outer side of the band axis. Updrafts and
downdrafts are preferentially located on the inner side of the band
axis. Downdraft transport of cool and dry air from middle levels on the
inner side of the rainband was responsible for modifying mixed-layer
structure adjacent to the band on alongband scales of 100 km. An
undisturbed mixed layer of 500 m was present on the outer side of the
band. Application of a mixed-layer model to low-level flow trajectories
from the outer rainband to the eyewall indicates that under some
conditions, the mixed layer may not recover sufficiently and low
surface equivalent potential temperature air may reach the eyewall.
These conditions are associated with suppressed flow in a region of
positive divergence with moderate rainfall from a middle level anvil cloud.
Differential evaporation cooling over the transition layer drives
entrainment of dry air, resulting in a drier mixed layer (with lower
surface equivalent potential temperature). The model results suggest
that incomplete recovery may be responsible for transitional changes
in hurricane intensity.
Tappert, F.D., M.G. Brown, D.R. Palmer, and H.F. Bezdek. Chaos in
underwater acoustics. Journal of the Acoustical Society of America,
83:S36 (1988).
The problem of predicting sound propagation in range-dependent ocean
environments has been investigated, in which it is supposed that the
environment (volume and/or boundary) varies smoothly in range and is
exactly known with arbitrary precision. Although this problem as stated
is deterministic and not intrinsically stochastic, it has been
discovered from numerical and analytical studies of physically
realistic examples drawn from deep ocean propagation, shallow-water
propagation, and surface duct propagation, that ray path solutions
exhibit "classical chaos," namely, unpredictable and stochastic
behavior. Ray paths are found to have a continuous spectrum characteristic
of noisy stochastic processes, and ray paths are found to have an
exponentially sensitive dependence on initial conditions and environmental
parameters characteristic of chaotic processes. This phenomenon of chaos
in underwater acoustics is caused by the exponential proliferation of
catastrophes (caustics) due to the loss of control implied by the
nonseparability of variables in the eikonal equation. As a consequence,
even when the ocean environment is known exactly, there exists a
"predictability horizon" that limits the range to which acoustic fields
can be predicted.
Thacker, W.C. A cost-function approach to the assimilation of asynoptic
data. Journal of Scientific Computing, 2(2):137-158 (1988).
This paper describes a method for reconstructing a synoptic state by
fitting dynamics to asynoptic data. The best fit is defined by the
minimum of a quadratic cost function and dynamics are enforced through
the use of a penalty term. When the coefficient of the penalty term is
identified as the inverse of the variance of model error, the method
yields the same results as Kalman filtering, and in the limit of
infinitely large coefficients, the same as strong-constraint formalisms.
The self-adjoint nature of the equations for the best fit motivated
the use of a relaxation method for their solution. The method is
illustrated within the context of one-dimensional, linear, shallow-water
wave dynamics, where computational examples indicate that a synoptic
state is properly determined only if the asynoptic data are equivalent
to complete initial conditions.
Thacker, W.C., and R.B. Long. Fitting dynamics to data. Journal of
Geophysical Research, 93(C2):1227-1240 (1988).
A formalism is presented for fitting dynamic forecast models to asynoptic
data. Because of the importance of wind stress forcing in oceanic models
and of the inadequacies of wind stress observations, the formalism allows
an oceanic model to be fit to both oceanographic and meteorological data.
Within the context of this formalism the important question of whether an
asynoptic data set contains sufficient information to determine the model
state completely and unambiguously is discussed. Becuse the information
travels along wave characteristics, it is clear that for the data to be
sufficient to determine the model state, they must be distributed so
that every feature of the flow is seen at some time or another. Such
widespread coverage of the oceans requires a data collection system that
relies heavily on satellites. The formalism is illustrated using a highly
truncated model of the wind-driven equatorial ocean and computational
examples demonstrate how surface elevation and wind stress observations
might be used to recover the model state.
Wilburn, A.M., E. Johns, and M.H. Bushnell. Current velocity
and hydrographic observations in the southwestern North
Atlantic Ocean: Subtropical Atlantic Climate Study (STACS),
1987. NOAA Data Report, ERL AOML-12, 86 pp. (1988).
No abstract.
Willis, P.T., and A.J. Heymsfield. Melting-layer structure in MCC
stratiform precipitation. Preprints, 10th International Cloud Physics
Conference, Bad Homburg, Federal Republic of Germany, August 15-20,
1988. American Meteorological Society, Boston, 699-701 (1988).
No abstract.
Willoughby, H.E. Linear motion of a shallow-water, barotropic vortex.
Journal of the Atmospheric Sciences, 45(13):1906-1928 (1988).
A shallow-water barotropic model of tropical cyclone motion allows
calculation of linear wavenumber one perturbations on a maintained,
moving axisymmetric vortex. The perturbations are Rossby waves that
depend upon the radial gradient of axisymmetric relative vorticity
rather than the meridional gradient of absolute vorticity. Although
the motion of the vortex is a parameter for calculation of the
perturbations, the motion in a particular situation is determinate
because it minimizes the Lagrangian of the system. The motion in an
environmental current matches the current, except at frequencies where
the vortex is barotropically unstable. Imposed sources and sinks of
mass simulate the effects of convection. The "convectively-induced"
motions excite the barotropic instability plus a mode that depends upon
forcing at the Rossby wave critical radius. This mode has largest
amplitude and fastest vortex motion at the orbital frequency of the
axisymmetric flow where forcing is imposed. It seems to correspond with
the trochoidal motion of real tropical cyclones. For cyclonic frequencies
only, perturbation in the stream-function field resembles a solitary
Rossby wave and exhibits counterrotating gyres isolated from the
relative flow due to the vortex motion. The vortex motion on a beta
plane is largely meridional with speed proportional to the total
relative angular momentum of the vortex. When the vortex has cyclonic
circulation throughout, the northward motion is much too fast. This
unreasonable result highlights the importance of nonlinear processes
in tropical cyclone motion.
Willoughby, H.E. The dynamics of the tropical cyclone core.
Australian Meteorological Magazine, 36(3):183-191 (1988).
The core of a tropical cyclone occupies the inner 100-200 km of the vortex.
It is dominated by a cyclonic primary circulation in balance with a nearly
axisymmetric, warm core low-pressure anomaly. Superimposed on the primary
circulation are weaker asymmetric motions and an axisymmetric secondary
circulation. The asymmetries, which may be either internal gravity waves
or Rosby waves, modulate precipitation and cloud into trailing spirals.
The axisymmetric secondary circulation, driven by latent heat release and
surface friction, comprises the following parts: surface inflow that
extracts latent heat from the sea and replaces the frictional loss of
angular momemtum (M) to the sea; diabatically forced deep inflow that
supplies an excess of M above frictional loss; the eyewall, an outward
sloping locus of convective ascent; diabatically forced descent inside the
eye; and upper tropospheric inflow. The eyewall usually moves inward as a
result of differential adiabatic heating across the wind maximum.
Eyewall succession occurs in intense cyclones when two concentric
eyewalls are present and the outer replaces the inner. Because of their
semibalanced dynamics, the primary and sedondary circulations are
relatively simple and well understood. These dynamics are not valid
in the upper troposphere where the outflow is comparable to the swirling
flow, nor do they apply to the asymmetric motions. Since the
synoptic-scale environment appears to interact with the vortex core
in the upper troposphere by means of the asymmetric motions, future
research should emphasize this aspect of the tropical-cyclone dynamics.
**1987**
Atakturk, S.S., and K.B. Katsaros. Intrinsic frequency spectra of short
gravity-capillary waves obtained from temporal measurements of wave
height on a lake. Journal of Geophysical Research,
92(C5):5131-5141 (1987).
Intrinsic frequency spectra of water waves in the range of 6-17 Hz were
obtained as a function of both wind speed and wind stress from point
measurements of wave height. In a lake with a limited fetch there are two
types of surface motions causing Doppler shift in the frequencies of
short waves: orbital velocity of long waves and surface wind drift. The
former was estimated from long-wave amplitude by using a linear wave
theory. The two techniques were found to produce comparable results.
Experimental results showed that the spectral energy of short waves
rapidly increased in response to increasing winds and jumped up by an
order of magnitude when wave breaking occurred.
Baker, E.T., G.J. Massoth, R.W. Collier, J.H. Trefry, D. Kadko, T.A.
Nelsen, P.A. Rona, and J.E. Lupton. Evidence for high-temperature
hydrothermal venting on the Gorda Ridge, northeast Pacific Ocean.
Deep-Sea Research, 34(8):1461-1476 (1987).
The first water-column survey of the axial valley of the Gorda Ridge, a
slow- to medium-rate spreading center within 300 km of the coast of
Oregon and California, found strong evidence for ongoing hydrothermal
venting. At the northern end of the ridge, anomalously high concentrations
of helium-3, dissolved manganese, particulate iron, and methane confirmed
the hydrothermal origin of the above-bottom plumes identifiable as
maxima in light-attenuation profiles. The presence of excess radon-222
and the highly soluble hydrothermal precipitate anhydrite in the plumes
require a local vent source; the precipitation of anhydrite requires
fluid temperatures of at least 130°C. Indications of hydrothermal
activity elsewhere in the axial valley were inconclusive.
Barnes, G.M., G.J. Stossmeister, M.A. LeMone, and J.F. Gamache. A rainband
on the trailing side of a fast-moving hurricane. Preprints, 17th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, April
7-10, 1987. American Meteorological Society, Boston, 377-380 (1987).
No abstract.
Black, M.L., and R.W. Burpee. Temporal and spatial variations of
precipitation near the center of tropical cyclones. Preprints, 17th
Conference on Hurricanes and Tropical Meteorology, Miami, FL, April
7-10, 1987. American Meteorological Society, Boston, 170-173 (1987).
No abstract.
Black, P.G. New measurements within, around, and under tropical cyclones
using airborne microwave remote sensors and expendable probes. Program
Booklet, Second Airborne Science Workshop, Miami, FL, February 3-6,
1987. NASA, Washington, D.C., 29-30 (1987).
No abstract.
Black, P.G., and F.D. Marks. Environmental interactions associated
with hurricane supercells. Preprints, 17th Conference on Hurricanes and
Tropical Meteorology, Miami, FL, April 7-10, 1987. American
Meteorological Society, Boston, 416-419 (1987).
No abstract.
Bluestein, H.B., and F.D. Marks. A note on the structure of the
eyewall of Hurricane Diana (1984): Comparison of radar and visual
characteristics. Monthly Weather Review, 115(10):2542-2552
(1987).
Features seen in aerial and satellite photographs of the inside edge of
the eyewall of Hurricane Diana (1984) are compared with features seen in
digitized three-dimensional airborne radar reflectivity data. The
photographs show regularly spaced, upwind (downshear) tilted striations
in the northeast, east, and southeast sectors of the eyewall that are
nearly collocated with upwind (downshear) tilted axes of relative
reflectivity maxima of approximately 15 dBZ.
Broecker, W.S., and T.-H. Peng. The oceanic salt pump: Does it contribute
to the glacial-interglacial difference in atmospheric CO2
content? Global Biogeochemical Cycles, 1(3):251-259 (1987).
Sea ice formation drives salt from the surface to the deep sea. In so
doing, it lowers the salinity of polar surface waters. We show here that
this reduction in turn lowers the CO2 partial pressure of
polar surface waters and hence also of the atmosphere. We propose that
during glacial time when more sea ice existed, this pumping action may
have been stronger. If so, part of the glacial to interglacial
atmospheric CO2 content change observed in ice cores may have
been driven by the ocean's salt pump.
Broecker, W.S., and T.-H. Peng. The role of CaCO3
compensation in the glacial to interglacial atmospheric CO2
change. Global Biogeochemical Cycles, 1(1):15-29 (1987).
The only viable explanations put forth to date for the glacial to
interglacial change in atmospheric CO2 content suggested from
measurements of the CO2 content of gas extracted from ice
cores involve changes in the ocean's nutrient cycles. Any nutrient change
capable of creating the 80 µatm changes in atmosphere CO2
pressure suggested by the ice core results also creates significant
change in the deep ocean's CO3= content. Evidence
from deep sea sediments suggests that these CO3=
changes are compensated on the time scale of a few thousand years by
reductions or increases in the amount of CO3=
accumulating in deep sea sediments. This compensation process has two
important consequences. First, it significantly increases the magnitude
of the CO2 change per unit of nutrient forcing. Second, it
causes a delay in the response of the atmospheric CO2 change.
While the first of these consequences is a boon to those seeking to
explain the CO2 change, the second may prove to be a curse.
The ice core CO2 record shows no evidence of a significant lag
between the CO2 response and the polar warming. In any case
it is important that we improve our knowledge of the magnitude and timing
of the CaCO3 preservation events which mark the close of
episodes of glaciation and of the dissolution events which mark the onset
of these episodes.
Carsey, T.P. LISA: A new aerosol generation system for sampler
evaluation. Amer. Ind. Hyg. Assoc. J., 48:710-717 (1987).
No abstract.
Carsey, T.P., S.A. Shulman, and C.D. Lorberau. An investigation of
the performance of the 10-mm nylon cyclone. Applied Ind. Hyg.,
2:47-52 (1987).
No abstract.
Clarke, T.L., and J.R. Proni. A pattern recognition approach to remote
acoustic bottom characterization. In Progress in Underwater Acoustics,
H.M. Merklinger (ed.). Plenum Press, New York, 225-229 (1987).
The possibility of extracting useful bottom information from reflected
pulse waveforms at customary echo-sounding frequencies has been demonstrated
experimentally. The one-dimensional nature of the sediment property
continuum should also enable the use of remotely measured acoustical
sedimentary properties to predict navigationally important mechanical
characteristics. A convenient mathematical model has been developed to
assess the effects of bottom roughness and material properties on bottom
echo shape. The physical basis of the model is explained and model output
is presented. The ability of this model to easily generate sample echoes
from a wide range of bottom types permits a pattern recognition approach
to be taken to the problem of extracting information from the ehco signals.
An adaptive algorithm can be "trained" using model-generated echoes in the
same way speech recognition systems are "trained." The linear discriminant
algorithm can be trained to distinguish mud from gravel, but has
difficulty with mud versus fine sand. A commercially available voice
recognition system conversely has difficulty distinguishing sand from
gravel. More sophisticated algorithms will be needed for general bottom
discrimination.
Clarke, T.L., J.R. Proni, and L. Huff. High temporal resolution
observation of high-frequency acoustic bottom echoes. Journal of
the Acoustical Society of America, 82:S-122 (1987).
Acoustic bottom echoes at frequencies from 10 to 380 kHz were recorded
for a variety of bottom types in southern Chesapeake Bay. Short pulse
lengths and direct digital recording allowed temporal resolution of
100 µs to be achieved. Supporting measurements of sediment
characteristics and bottom roughness allowed comparison of the
measurements with theory. The field observations were in good
agreement with the theory after corrections for the interaction of
transducer beam patterns with bottom roughness were made.
Colin, C., and S.L. Garzoli. In-situ wind measurements and the ocean
response in the equatorial Atlantic during the FOCAL/SEQUAL experiment.
Journal of Geophysical Research-Oceans, 92(C4):3741-3750 (1987).
In-situ wind measurements collected as part of the Programme Francais
Ocean et Climat dans l'Atlantique Equatorial (FOCAL)/Seasonal Response
of the Equatorial Atlantic (SEQUAL) experiment (1983-1984) in the
western and eastern parts of the equatorial Atlantic basin are
described. They were obtained from meteorological stations placed at
St. Peter and St. Paul Rocks (SPP) (1°N, 29°W) and at the
top of a surface buoy moored in the Gulf of Guinea (0°N, 4°W).
From the wind observations the wind stress was inferred, and results
are compared with climatology. The seasonal variations of the
temperature both at the surface and below the surface at 28°W
and 4°W are interpreted in the light of the results of a
nonlinear multilevel model in the cases of a sudden increase and a
sudden relaxation of the trade winds.
Cornejo-Rodriguez, M.P., and D.B. Enfield. Propagation and forcing of
high-frequency sea level variability along the west coast of South
America. Journal of Geophysical Research, 92(C13):14,323-14,334
(1987).
Tide and wind data from coastal and island stations from Buenaventura,
Colombia (4°N), to Callao, Peru (12°S), have been analyzed for
the 1979-1984 time period to determine the propagation and forcing
characteristics of coastal sea level variability at periods of days to
weeks, as well as how they vary either with season or between the 1982-1983
El Niño-Southern Oscillation (ENSO) period and non-ENSO years.
During four non-ENSO years, the ensemble averaged cross spectra between
coastal sea level height (SLH) and local winds show weak evidence of local
forcing during the whole year without significant differences between the
austral summer and winter seasons, other than a greater energy in the
wind fluctuations at Talara during summer. Cross spectra between SLH
series from neighboring stations show evidence of poleward phase
propagation during winter seasons at speeds of about 20 m s-1
between La Libertad and Talara at periods of a week or more, and about
2.7 m s-1 between Talara and Callao at periods of 5-11 days,
but no propagation is found during summers. During the 1982-1983 ENSO there
is a large increase in SLH energy at most frequencies at all coastal
stations, but especially in the 8-11 day band, where energies are
enhanced by as much as an order of magnitude above non-ENSO levels. The
cross spectra between adjacent SLH stations indicate a nondispersive
poleward propagation of events during the 1982-1983 ENSO with phase
speeds of 2.2-3.5 m s-1 from La Libertad to Talara (periods
of a week or more) and 3.4-3.6 m s-1 from Talara to Callao
(3.5 days or more). As with the SLH energy, the coherence and phase
propagation were much stronger along the Peru coast in 1982-1983 than
during non-ENSO periods, especially in the 8-11 day band. The one-third
increase in phase speeds during the ENSO over the non-ENSO speeds is
found to be consistent with the anomalous depression of the density
structure during El Niño. Comparisons between coastal SLH and the
local alongshore wind suggest that locally forced SLH variability was
obscured during the 1982-1983 ENSO by noncoastally forced, but energetic
propagating fluctuations, which probably originated in the equatorial
waveguide.
Dammann, W.P., and C.A. Lauter. High-resolution acoustic bottom roughness
measurement in support of bottom echo interaction modeling. Journal of
the Acoustical Society of America, 82:S-123 (1987).
A high-resolution acoustic bottom profiler using an extremely narrow-beam,
three-megahertz echo sounder was developed at the Ocean Acoustics Division
of NOAA/AOML. The device was used to measure bottom roughness over a range
of scales from less than 1 cm to several meters. Roughness measurements
were made in the lower Cheasapeake Bay area over mud, fine to medium grain
sand, and course grain sand. The data produced were used to appraise the
performance of an acoustic echo formation model that predicts the effects
of marine bottom characteristics on a reflected acoustic pulse envelope.
Major aspects of the design and use of the system, procedures for
processing generated data, and examples of processed output are presented.
Dodge, P.P., M.L. Black, R.W. Burpee, and F.D. Marks. Time-lapse radar
imagery from landfalling hurricanes. Preprints, 17th Conference on
Hurricanes and Tropical Meteorology, Miami, FL, April 7-10, 1987.
American Meteorological Society, Boston, 166-169 (1987).
No abstract.
Enfield, D.B. Progress in understanding El Niño. Endeavor,
11(4):197-204 (1987).
Prior to the work of Jacob Bjerknes, the El Niño phenomenon was
regarded as an aperiodic climatic event confined to the Pacific coast
of South America. Spurred by a growing consciousness of the oceans' role
in global climate, there has been an explosion of El Niño research
in the last two decades. El Niño is now recognized to be an integral
part of a Pacific-wide ocean relaxation, with global climatic impacts
and economically important ecological consequences. However, we are still
groping for the final prize: the ultimate cause of this climate anomaly
and the ability to reliably predict its onset and intensity.
Enfield, D.B. The intraseasonal oscillation in eastern Pacific sea
levels: How is it forced? Journal of Physical Oceanography,
17(11):1860-1976 (1987).
Daily sea level and surface winds at eastern Pacific shore locations and
equatorial islands, together with gridded five-day averages of 850 mb
winds, have been analyzed for the 1979-84 period to determine how the
40-60 day intraseasonal oscillation of eastern Pacific sea levels is
forced, as described by Spillane et al. for 1971-75. The
oscillation was also present in 1980-84 from Callao, Peru, to San
Francisco, with maximum energy near 52-57 days and band limits of 43 and
65 days. During 1980-84, there was no evidence for forcing of the
large-scale oscillation in the eastern Pacific, although a local
contribution of forcing was superimposed on the remote signal at the
California stations. Interannual fluctuations in amplitude were evident
in the sea level time series, consistent with those of the corresponding
wind oscillation in the western equatorial Pacific. The oscillation was
best developed in both variables in 1980-82 and became weak or
nonexistent during the recovery phase of the 1982-83 El Niño,
similar to a weakening that occurred following the 1972-73 episode, noted
by Spillane et al. The sea level oscillations have the
characteristics of lowest baroclinic mode Kelvin waves that are primarily
forced by a similar, energetic oscillation in the winds in the western
equatorial Pacific. During the 1980-82 period a significant component of
the wind signal extended into the central Pacific and was associated with
sea level propagation speeds of about 5 m/s, suggesting a more extensive
forcing along the equatorial waveguide at that time. In 1982-84, when the
oscillation was weak, the sea level propagation was about 3 m/s,
consistent with the free propagation of lowest baroclinic mode Kelvin
waves in the central Pacific.
Enfield, D.B., M.P. Cornejo-Rodriguez, R.L. Smith, and P.M. Newberger.
The equatorial source of propagating variability along the Peru coast
during the 1982-1983 El Niño. Journal of Geophysical Research,
92(C13):14,335-14,346 (1987).
Using data obtained from tide gauges in South America, current meters along
the equator and the Peru coast, and an array of pressure gauges and inverted
echo sounders within and around the Galapagos archipelago, we have analyzed
the equatorial origin of coastal trapped waves observed by
Cornejo-Rodriguez and Enfield (this issue) along the Peru coast during
the intense 1982-1983 El Niño. The propagating fluctuations along
the coast were much stronger at that time either before or after the El
Niño, and the variability was not locally forced by coastal winds.
We find that the coastal variability was also more energetic during
previous El Niño occurrences. At periods of one to two weeks the
meridional component of currents on the equator was up to an order of
magnitude more energetic than the zonal fluctuations and was consistently
associated with sea level that fluctuates antisymmetrically between
hemispheres. At periods longer than two weeks the zonal velocity component
was more energetic and the cross-equatorial sea level variability was
symmetric. The meridional and zonal phase structures of cross spectra
involving the currents and sea level established the one- to two-week
equatorial fluctuations as mixed Rossby-gravity (Yanai) waves of low
wave number with infinite phase speed (standing oscillations) in the
middle of the band (10 days); the corresponding structures for longer
periods were consistent with non-dispersive Kelvin waves. Frequency
domain EOF modes of the sea level and current data established the mixed
Rossby-gravity waves as the principal source of the strong trapped wave
variability in the one- to two-week band along the Ecuador-Peru coast
during the 1982-1983 El Niño episode.
Fine, R.A., and R.L. Molinari. Observations of the Deep Western Boundary
Current in the subtropical North Atlantic Ocean. EOS, Transactions,
American Geophysical Union, 36(16):338 (1987).
No abstract.
Franklin, J.L., K.V. Ooyama, and S.J. Lord. Two improvements in
Omega windfinding techniques. Journal of Atmospheric and Oceanic
Technology, 4(1):214-219 (1987).
A one-dimensional local spline smoothing technique is applied to Omega
navigational signals for the purpose of windfinding. Wind profiles so
produced depend largely on two parameters of the smoothing procedure:
the nodal spacing, which determines the smallest resolvable scale, and a
filtering wavelength, which produces the necessary smoothing of the phase
data, and prevents representational distortion of any power from the
unresolved scales. Phase "noise" from stationary test sondes is
superimposed on synthetic Omega signals to compare wind profiles obtained
with this new procedure with profiles computed using other techniques.
It is shown that the effect of aircraft maneuvers on Omega wind accuracy
is not completely removed by the normal practice of evaluating all phase
derivatives at a common time. Additional improvements in accuracy of 2-3
m s-1 can be obtained by a "rate-aiding" technique using
aircraft navigational data.
Friedman, H.A., and C.A. Arnhols. 1987 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 120 pp. (1987).
No abstract.
Gamache, J.F. The bulk water budget of Hurricane Norbert (1984).
Preprints, 17th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 7-10, 1987. American Meteorological Society, Boston,
351-354 (1987).
No abstract.
Garzoli, S.L. Forced oscillations on the equatorial Atlantic basin
during the Seasonal Response of the Equatorial Atlantic Program
(1983-1984). Journal of Geophysical Research-Oceans, 92(C5):
5089-5100 (1987).
A subset of data from an array of eight inverted echo sounders and a
meteorological station deployed and maintained for 15 months in the
equatorial Atlantic as part of the Seasonal Response of the Equatorial
Atlantic Program are analyzed to determine the variability of forced
oscillations of the basin. The analysis is done to study both low-
and high-frequency variability. The most significant oceanic
oscillations in the inertial gravity band are centered at 5.2 and
3.5 days. From the study of their meridional structure it is concluded
that those oscillations correspond to forced inertial gravity waves
with meridional structures corresponding to the meridional numbers
n=1 and n=3, respectively.
Garzoli, S.L., and A. Bianchi. Time-space variability of the local
dynamics of the Malvinas-Brazil confluence as revealed by inverted
echo sounders. Journal of Geophysical Research,
92(C2):1914-1922 (1987).
Two inverted echo sounders have been deployed for approximately eight
months in the region of the confluence of western boundary currents in
the South Atlantic (37°58.7'S, 51°56.4'W and 37°29.3'S,
53°49.3'W). The confluence of the subtropical Brazil Current
with the sub-Antarctic Malvinas Current creates a strong, sharp
thermohaline front. From the time series obtained with the sounders,
two parameters are obtained and analyzed: dynamic height from the
surface relative to 800 m and the position of the front. The time
series of dynamic height indicates the presence of a cold intrusion
during November, the southward extension of the Brazil Current and
northward extension of the Malvinas Current during January, and a
simulataneous warming of the area at both moored locations (0.04
dyn m/month) from March through June.
Goldenberg, S.B., S.D. Aberson, and R.E. Kohler. An updated, fine-grid
version of the operational barotropic hurricane-track prediction model.
Preprints, 17th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 7-10, 1987. American Meteorological Society, Boston,
86-89 (1987).
No abstract.
Hansen, D.V., and C.A. Paul. Vertical motion in the eastern equatorial
Pacific inferred from drifting buoys. Proceedings, International Symposium
on Equatorial Vertical Motion, Paris, France, May 6-10, 1985.
Oceanological Acta, 27-32 (1987).
No abstract.
Johns, E. A comparison of observed and modelled transport
through the Windward Passage. EOS, Transactions, American
Geophysical Union, 68(50):1718 (1987).
No abstract.
Johns, E., and R.L. Molinari. Observations of current variability
northeast of the Bahamas. EOS, Transactions, American
Geophysical Union, 68(16):338 (1987).
No abstract.
Jones, R.W. A simulation of hurricane landfall with a numerical model
featuring latent heating by the resolvable scales. Monthly Weather
Review, 115(10):2279-2297 (1987).
A nested grid hurricane model is used to transport a strong vortex over a
straight coastline at about 4 m s-1. The track, at landfall,
of the vortex is about 20 km to the left of a control simulation without
land. Just before landfall, a 15 km amplitude trochoidal oscillation of
the vortex track occurs. This amplitude is nearly double that of similar
oscillations of the control simulation. About 10 h before landfall, a
spiral rainband nearly surrounds the vortex at radii of about 135 km.
This rainband has a weak secondary maximum in the tangential wind and is
the model analog of the secondary eyewalls observed by Willoughby et
al. in several hurricanes. The rainfall in spiral rainbands
diminishes during the 7 h before landfall. However, rainfall in the
inner core of the vortex is greater during landfall than in the control
simulation. The greatest rainfall accumulation is to the right of the
vortex. However, compared with the control simulation, rainfall is
greater to the left and less to the right of the vortex. This may be
the result of an increase of the relative radial inflow in the boundary
layer in the left-front quadrant near landfall. To the extent which is
possible, these characteristics of landfall are related to observations.
Katsaros, K.B., S.D. Smith, and W.A. Oost. HEXOS: Humidity Exchange Over
the Sea. A program for research on water-vapor and droplet fluxes from
sea to air at moderate to high wind speeds. Bulletin of the American
Meteorological Society, 68(5): 466-476 (1987).
HEXOS is an international program for the study of evaporation and
spray-droplet flux from sea to air. Present accomplishments of the
program include an investigation of processes near the air-sea interface
in a wind-wave simulation tunnel. The main field experiment, taking place
in the autumn of 1986 at and around the Noordwijk platform, includes
measurements of the fluxes of water vapor, spray droplets, sensible heat,
and momentum, as well as the structure of the planetary boundary layer
and the state of the sea.
Komar, P.D., and D.B. Enfield. Short-term sea-level changes and coastal
erosion. In Sea-Level Change and Coastal Evolution, D. Nummedal
(ed.). Society of Economic Paleontologists and Mineralogists,
41:17-27 (1987).
Investigations of the role of sea level in producing coastal erosion have
focused mainly on the long-term rise due to melting of glaciers and
thermal expansion of seawater. There are additional shorter term changes
in the local sea level produced by a variety of ocean processes.
Variations in the coastal currents, for example, can alter the water
level at the shoreline due to the geostrophic balance between the current
and the offshore sea-surface slope. Other factors which may alter local
sea level include changes in atmospheric pressure, winds blowing either
in the longshore or cross-shore directions, and the occurrence of
upwelling. Because the inclined continental shelf and slope act as a
wave guide, the fluctuations often become trapped and propagate over
longshore distances beyond where they are actually generated. In that
many of these processes are typically seasonal, the responding sea level
also has a pronounced seasonal cycle, but frequently there can be
significant fluctuations at periodicities of several days to a few weeks.
The magnitudes of such changes vary considerably with coastal location
but are typically on the order of 10 to 30 cm, achieving a maximum of
about 100 cm in the Bay of Bengal. The occurrence of an El Niño
in the equatorial Pacific is known to have considerable impact on the
erosion of the coasts of California and Oregon. This occurs because
associated with an El Niño are shifts in the storm paths and a
temporary rise in sea level. An El Niño is a breakdown of the normal
equatorial wind and current patterns. This breakdown releases water
which is normally set up in the western Pacific by the trade winds. The
release creates a "wave" of sea-level rise, which first propagates
eastward along the equator and then poleward along the eastern ocean
margin. Such "waves" have been measured in the tide records of the
western United States, amounting to some 20 to 60 cm and lasting for
several months. Such transient sea-level changes have likely played an
important role in coastal erosion.
Landsea, C.W. A quantitative comparison of two BASIN lidar images.
UCLA Undergraduate Science Journal, 4:49-56 (1987).
No abstract.
Leaman, K.D., and R.L. Molinari. Topographic modification of the Florida
Current by Little Bahama and Great Bahama Banks. Journal of Physical
Oceanography, 17(10):1724-1736 (1987).
The effect of local topography in modifying the structure and variability
of the Florida Current is examined using shipboard acoustic Doppler and
Pegasus acoustic current profiler data. Pegasus absolute velocity data
were obtained during 16 cruises in the Florida Current at 27°N as
part of the Subtropical Atlantic Climate Studies (STACS) program. The
ensemble average of all Pegasus velocity data shows that the effect of
the constriction imposed on the mean Florida Current by Little Bahama
Bank can be detected up to 30 km into the Straits of Florida. A simple
model is proposed to explain how this effect can produce the subsurface
maximum of northward flow commonly observed in the eastern Straits.
Pegasus and acoustic Doppler data obtained during the March 1984 STACS
cruise are used to describe the temporal and spatial variability of the
flow. It is shown that intermittent southward flow can exist in a band
10-15 km wide off Little Bahama Bank; one such event was detected during
this cruise. The Pegasus data suggest that these events are associated
with meandering of the Florida Current. These results may explain earlier
observations in satellite synthetic aperture radar images of small-scale
vortices moving southward across the mouth of Northwest Providence Channel.
Leaman, K.D., R.L. Molinari, and E. Johns. Velocity and transport
variability at 26.5°N east of Abaco Island, the Bahamas. EOS,
Transactions, American Geophysical Union, 68(16):338 (1987).
No abstract.
Leaman, K.D., R.L. Molinari, and P.S. Vertes. Structure and variability
of the Florida Current at 27°N: April 1982-July 1984. Journal of
Physical Oceanography, 17:565-583 (1987).
Results of a two-year field experiment as part of the Subtropical Atlantic
Climate Studies (STACS) program in the Straits of Florida are presented.
Temperature and absolute ocean current observations were obtained by
Pegasus acoustic current profilers over 16 cruises during which repeated
cross sections of the Florida Current were made at 27°N. Results are
shown for the mean velocity and temperature fields, the perturbation
horizontal kinetic energy and potential energy fields and for those
energy conversion terms that could be computed directly from the data.
The barotropic and baroclinic energy conversion terms, although small,
indicate that the flow is stable for both types of perturbations. A
large part of the variability is contributed by short time scales (one
week or less). The average and standard deviation of northward volume
transport by the Florida Current during these cruises was (31.7 ±
3.0) × 106 m3 s-1. Barotropic and
baroclinic contributions to the total heat flux across the North
Atlantic Ocean at 27°N are computed for each cruise and for the
two-year average of all cruises. With the use of previous estimates of
the midbasin baroclinic and Ekman heat fluxes, the total average
northward heat flux from the obsersvations is (1.29 ± 0.21) ×
1015 W. To compare STACS data with results from a recent
numerical model by Anderson and Corry, Florida Current transports are
resolved in a simple manner into barotropic and baroclinic modes.
Although the barotropic mode is considerably more variable than the
baroclinic, the basic annual signal obtained from the model also appears
in the STACS observations. In particular, a rapid transport decrease in
the fall with a secondary decrease in the spring are found in both model
and observations.
Marks, F.D., and R.A. Houze. Inner core structure of Hurricane Alicia
from airborne Doppler radar observations. Journal of the Atmospheric
Sciences, 44(9):1296-1317 (1987).
Airborne Doppler radar measurements are used to determine the horizontal
winds, vertical air motions, radar reflectivity, and hydrometeor fallspeeds
over much of the inner-core region (within 40 km of the eye) of Hurricane
Alicia (1983). The reconstructed flow field is more complete and detailed
than any obtained previously. The data show both the primary (azimuthal)
and secondary (radial-height) circulations. The primary circulation was
characterized by an outward sloping maximum of tangential wind. The
secondary circulation was characterized by a deep layer of radial inflow
in the lower troposphere and a layer of intense outflow above the 10 km
altitude. The rising branch of the secondary circulation was located in
the eyewall and sloped radially outward. Discrete convective-scale bubbles
of more intense upward motion were superimposed in this mean rising
current, and convective-scale downdrafts were located throughout and
below the core of maximum precipitation in the eyewall. Precipitation
particles in the eyewall rainshaft circulated 18-20 km downwind as they
fell, consistent with the typical upwind slope with increasing altitude
of eyewall precipitation cores. Outside the eyewall, the precipitation was
predominantly stratiform. A radar bright band was evident at the melting
level. Above the melting level, ice particles were advected into the
stratiform region from the upper levels of the eyewall and drifted
downward through a mesoscale region of ascent. Hypothetical precipitation
particle trajectories showed that as these particles fell slowly through
the mesoscale updraft toward the melting level, they were carried
azimuthally as many as 1 1/2 times around the storm. During this spiraling
descent, the particles evidently grew vigorously. The amount of water
condensed by the ambient mesoscale ascent exceeded that transported into
the stratiform region by the eyewall outflow by a factor of 3. As the
particles fell into the lower troposphere, they entered a mesoscale
region of subsidence, the top of which coincided with the radar bright
band.
Marks, F.D., and R.A. Houze. Three-dimensional structure of the
eyewall of Hurricane Norbert as determined from an airborne Doppler
radar. Preprints, 17th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, April 7-10, 1987. American Meteorological
Society, Boston, 347-350 (1987).
No abstract.
Maul, G.A., D.A. Mayer, and M.H. Bushnell. Relationships between local
sea level and weather with Florida-Bahamas cable and Pegasus measurements
of the Florida Current: 1982-1986. EOS, Transactions, American
Geophysical Union, 68(16):336-337 (1987).
No abstract.
Molinari, R.L. Air mass modification over the eastern Gulf of Mexico as a
function of surface wind fields and Loop Current position. Monthly
Weather Review, 115(3):645-652 (1987).
The effects of surface wind patterns and Loop Current position on surface
distribution of latent and sensible heat fluxes in the eastern Gulf of
Mexico are demonstrated. Mean monthly fields of these fluxes computed
from data collected during February 1975 and February 1976 are decomposed
into two different modes, a north-wind mode associated with winter
outbreaks of dry cold continental air masses and a trade-wind mode
associated with advection from the south of warm moist maritime air.
The distributions of sensible and latent heat fluxes are different for
each mode, with both heat fluxes considerably larger over the northern
Gulf, in particular, during times of the northerlies. However, during
these two months, trade-wind days are more numerous and the mean monthly
flux patterns reflect this preponderance. A simple model of the effect of
extreme Loop Current configurations and the associated sea surface
temperature distributions on air parcels traversing the Gulf below the
inversion layer is presented. Total changes in air parcel temperature
and specific humidity are shown to depend on the configuration of the
Loop Current parcels which traverse the Gulf and cross the U.S. coastline
between Louisiana and Florida during the time of a deep northern Loop
intrusion and have 1.3°C higher temperatures and 1.0 g kg-1
greater specific humidities than parcels which cross the Gulf during a
shallow Loop intrusion.
Molinari, R.L. A review of STACS results on Florida Current variability.
EOS, Transactions, American Geophysical Union, 68(16):337 (1987).
No abstract.
Molinari, R.L. Ocean-atmosphere relations. In McGraw-Hill Yearbook of
Science and Technology. McGraw-Hill, New York, 323-325 (1987).
No abstract.
Molinari, R.L., and D.V. Hansen. Observational studies of near-surface
thermal budgets in the tropics: Review, evaluation, and recommendations.
In Further Progress in Equatorial Oceanography E.J. Katz and J.M.
Witte (eds.). Nova University Press, For Lauderdale, 421-438 (1987).
No abstract.
Molinari, R.L., E. Johns, G.A. Maul, D.A. Mayer, J.C. Larsen, R. Fine,
K.D. Leaman, T.N. Lee, W.E. Johns, and F.A. Schott. Subtropical Atlantic
Climate Studies (STACS). Proceedings, IUGG XIX General Assembly,
3:1013 (1987).
No abstract.
Nelsen, T.A., and E.B. Forde. Spatial and compositional variability of
the hydrothermal plume at TAG: Mid-Atlantic Ridge. EOS, Transactions,
American Geophysical Union, 68(44):1325 (1987).
No abstract.
Ooyama, K.V. Numerical experiments of steady and transient jets with a
simple model of the hurricane outflow layer. Preprints, 17th Conference
on Hurricanes and Tropical Meteorology, Miami, FL, April 7-10, 1987.
American Meteorological Society, Boston, 318-320 (1987).
No abstract.
Ooyama, K.V. Scale-controlled objective analysis. Monthly Weather
Review, 115(10):2479-2506 (1987).
The major topic of this paper is the resolvable spatial scales that can
be analyzed by statistical interpolation of an undersampled data set. The
inquiry was motivated by the need to design the most appropriate
procedures for spatial analysis of the upper air sounding data from the
GARP Atlantic Tropical Experiment. A reliable representation of
horizontal scales in the analyzed wind fields was a matter of utmost
concern, since the derived fields of vorticity, divergence, and vertical
motion were also of vital interest. To achieve our goal, it was found
that the traditional premise of statistical interpolation had to be
reexamined. The main conclusions of this theoretical inquiry are: (1)
resolvable scales are determined by the geometrical distribution of
observing stations; (2) precise knowledge of the second-moment statistics
improves the analysis by de-aliasing the amplitude of resolvable scales,
but has no effect on the definition of resolvable scales; (3) residual
effects of unresolvable signals in the data are removable by a spatial
filter and must be so removed; and (4) spatial phases of de-aliased
resolvable scales may still be in error. On the basis of these findings,
the objective analysis procedures we have developed are targeted on the
best achievable analysis of resolvable scales. The procedures include
the following: an adequate estimate of "true" statistical fields from
the given ensemble of data, a search for the optimum spatial filter by
monitoring the targeted error variance, and a rational method of
desensitizing the analysis to statistically errant data. In order to
reduce the spatial phase error of propagating disturbances, the
procedures are extended to the analysis of the time-wise Fourier-transformed
data set (actually in the frequency-band analog). Since the wind is a
physical vector, the entire procedure for the wind analysis is given in
the tensor-invariant form, which is decidedly advantageous for very
practical reasons. For example, the tensor approach eliminates the
notorious ambiguity in normalization that is encountered in the
multivariate approach. The paper also describes, in the Appendix, a
method of filtered mechanical interpolation, which is specifically
designed, with a variety of optional boundary conditions, for application
to analysis in a finite domain.
Palmer, D.R., and R.A. Rona. The acoustics of "black smoker" hydrothermal
plumes. 113th Meeting of the Acoustical Society of America, Indianapolis,
Indiana, May 11-15, 1987. Journal of the Acoustical Society of
America, 81:S50 (1987).
High-temperature "black smoker" hydrothermal plumes occur when seawater
that has penetrated into the oceanic crust and assimilated heat from magma
is discharged from vents located at the axis of a mid-ocean ridge. The
acidic, metal-rich discharge mixes with alkaline, oxidizing seawater,and
a fine suspension of sulfide particles is precipitated and convected by
the flow. Vent fields have now been found at both fast and slow seafloor
spreading centers and may be an ubiquitous feature of mid-ocean ridges.
A review of the progress made in using underwater acoustics to study
black smoker plumes is presented. Both active and passive techniques are
being investigated. Active techniques involve a high-frequency monostatic
sonar mounted on a submersible. Analysis of the amplitude and phase of the
signal backscattered from the plume provides information about the
three-dimensional shape of the plume as well as estimates of the
flow-velocity field of the discharging fluid. Passive techniques use
bottom-mounted hydrophones to listen to the very low-frequency,
hydrodynamic noise generated by a plume. These noise signatures have
potential use in locating, characterizing, and monitoring plume sites and
in determining the contribution plume noise makes to the overall ambient
noise field in the ocean.
Peng, T.-H. Modeling the seasonal variations of surface water
CO2 in the high-latitude North Atlantic Ocean. Proceedings,
Marine Sciences Symposium, NSC Symposium Series No. 10,
199-209 (1987).
Seasonal variations in CO2 partial pressure (pCO2),
total dissolved CO2 (TCO2), O2,
nutrients (PO4, NO3, and SiO4), and
temperature in surface water have been monitored at two stations, one
located to the north and the other to the west of Iceland. Results of
observations show that during the summer, pCO2,
TCO2, and nutrients are the lowest, while the O2
concentration is the highest. This trend is reversed during the winter.
These seasonal variations are mainly the result of a deepening of the
mixed layer during the winter and stratification coupled with intense
biological activity during the summer. Photosynthetic utilization of the
nutrient constituents during the long daylight time of summer in a
strongly stratified and shallow surface mixed layer drives these changes.
Enhanced mixing of surface water with deeper water during the winter
brings the nutrient-rich deep water to the surface. Together with reduced
biological activity due to decreased daylight, this mixing brings about
higher concentrations of nutrient constituents and a higher
TCO2 and pCO2. A simple box model representing the
upper water column is devised to simulate the seasonal variations in the
properties of surface water. It is shown that the model prediction of the
seasonal variation of CO2 and O2 is consistent with
observations.
Peng, T.-H., and W.S. Broecker. C/P ratios in marine detritus.
Global Biogeochemical Cycles, 1(2):155-161 (1987).
Until reliable procedures have been developed to preserve the phosphorus
contained in particulate matter captured by in-situ pumps and sediment
traps and until these procedures are applied over a wide range of
locations and depths in the sea, indirect methods will have to be used to
determine the C/P ratio in marine detritus. We have taken two such
approaches: (1) the use of C/N ratios for particulates captured in the
upper thermocline in conjunction with O2/P and N/P ratios
obtained from deconvolutions of ocean chemical data and (2) regression
along isopycnals in the deep-sea waters free of fossil fuel
CO2. While neither approach yields a definitive answer, both
suggest that a value of 127 carbon atoms per phosphorus atom would be a
more appropriate interim value than that of 106 adopted long ago by A.C.
Redfield and his associates.
Peng, T.-H., T. Takahashi, W.S. Broecker, and J. Olafsson. Seasonal
variability of carbon dioxide, nutrients, and oxygen in the northern
North Atlantic surface water: Observations and a model. Tellus,
39B:439-458 (1987).
The seasonal variation of various surface water properties has been
monitored at a station located at about 120 miles south of the
Iceland-Greenland sill during the two-year period, March 1983 through
May 1985. These properties include the temperature, salinity,
mixed-layer depth, partial pressure of CO2 in seawater and
the concentrations of dissolved total CO2, oxygen, and
nutrients. It was observed that during the summer, the CO2
partial pressure and the concentrations of CO2 and nutrients
in surface water were lowest, while the oxygen concentration was
highest. This situation was reversed during the winter. The seasonal
variation is attributed mainly to the high photosynthetic utilization
rate of carbon and nutrients in a strongly stratified and shallow
surface mixed layer during the summer. The winter observations are
attributed to the upward transport of deep waters rich in total
CO2 and nutrients by deep convective mixing. In order to
account for the observed seasonal variation, a vertically
one-dimensional, two-box ocean model has been constructed. The vertical
mixing between the surface mixed layer and deep water is characterized
in terms of changes in the mixed layer thickness with time, and the
biological productivity is related to the solar insolation and nutrient
concentration in the mixed layer. Gas exchange of oxygen and
CO2 between the mixed layer and the atmosphere is taken into
consideration. When this model is calibrated using the observed
phosphate concentration in surface water, it yields seasonal variations
of carbon and oxygen values consistent with the observations, with an
exception of a large excursion of spring time values resulting from
phytoplankton blooms. It is shown that the spring bloom effect can be
simulated by a short-term reduction of the phosphate residence time and
of the gas exchange rate.
Powell, M.D. Boundary-layer structure in convective hurricane rainbands.
Preprints, 17th Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 7-10, 1987. American Meteorological Society, Boston,
373-376 (1987).
No abstract.
Powell, M.D. Changes in the low-level kinematic and thermodynamic structure
of Hurricane Alicia (1983) at landfall. Monthly Weather Review,
115(1):75-99 (1987).
Aircraft, land station, and buoy data were composited with respect to the
center of Hurricane Alicia (1983) for three 8 h periods corresponding to
prelandfall in the open Gulf of Mexico, landfall in the Galveston area,
and postlandfall in the vicinity of Houston. Comparison of the wind
analyses before, during, and after landfall emphasizes the land-sea
frictional asymmetry at landfall. In addition, other asymmetries in the
surface wind field and differences between the flight-level and the
surface wind fields are revealed. The asymmetric structure of the surface
wind field may be interpreted as having resulted from the combined effects
of land-sea roughness differences, background environmental flow, and
storm translation. The land-sea frictional difference acted to oppose
the mean vortex flow over land and reinforce it over water. The southwest
background environmental flow acted nearly parallel to the coastline,
producing surface inflow on the left side and outflow on the right side,
while the effect of the storm translation increased winds on the right
and decreased winds on the left. At landfall, the analysis revealed a
broad region of high wind speeds and a mesoscale divergence-convergence
couplet along the outer rainband axis just offshore on the northeast
(right) side of the storm. The outer rainband axis acted as an obstruction
to the surface flow, separating the warmer central core of the storm from
the environment through which the storm moved. In contrast to recent
numerical model studies, surface convergence was also noted on the left
side of the storm just offshore, despite outflow at flight level. Analyses
of temperature, dew point, and equivalent potential temperature indicate
that loss of the oceanic heat and moisture source, combined with advection
of drier air on the landward side of the storm, was responsible for cooling
and drying of the inflowing boundary layer air. Upon introduction of this
air into the core convection and vertical ascent, a decrease in the release
of latent heat could then lead to cooling in the middle levels of the
storm and a subsequent increase in the central sea-level pressure.
Powell, M.D., and P.N. Georgiou. Response of the Allied Bank Plaza Tower
during Hurricane Alicia (1983). Journal of Wind Engineering and
Industrial Aerodynamics, 26:231-254 (1987).
As Hurricane Alicia passed over Houston on August 19, 1983, a record lasting
approximately 90 minutes was obtained of the wind-induced accelerations of
the tallest building in the downtown area, the Allied Bank Plaza.
Coincidently, the building had been the subject of a detailed wind tunnel
model study several years earlier, the results of which included the
prediction of building accelerations as a function of wind speed and wind
direction. From the many wind observations made during Alicia's passage
inland, it was possible to reconstruct the wind speeds and directions
experienced at the Allied Bank Plaza site which overlapped the period of
the acceleration record. This reconstructed wind history was combined
with the wind tunnel test data to compute a time series of estimated
accelerations sustained by the building during Alicia's passage inland.
The resulting favorable comparison of actual and predicted accelerations
provides a valuable case study, illustrating the reliability of wind
tunnel modeling within the design process for tall buildings.
Sanford, T.B., P.B. Black, J.R. Haustein, J.W. Feeney, G.Z. Forristall,
and J.F. Price. Ocean response to a hurricane. Part I: Observations.
Journal of Physical Oceanography, 17(11):2065-2083 (1987).
The response of the ocean was investigated using aircraft-deployable
expendable current profilers (AXCP). The goals were to observe and
separate the surface wave and surface mixed-layer velocities under the
storms and to map the across-track and along-track velocity and
temperature response in the mixed layer and thermocline. Custom
instrumentation was prepared, including slower falling AXCPs, and
the AXCP equipment was installed on NOAA WP-3D aircraft. Research
flights were made into two 1984 hurricanes: Norbert, in the western
Pacific off Baja, California (19°N, 109°W); and Josephine, off
the west coast of the U.S. (29°N, 72°W). Thirty-one probes were
deployed in each hurricane. All but four AXCPs survived the 220-knot launch
and wave-zone impact (surface winds up to 75 knots) and produced basic
RF transmissions. About half the AXCPs provided temperature and velocity
profiles. Most velocity profiles exhibited strong surface wave contributions,
slab-like velocities in the SML, strong shears beneath the SML, and only weak
flows in the upper thermocline. Separation of the surface gravity wave
velocities from the steady and inertial motions was obtained by fitting
the profiles to steady flows and shears in three layers and to a single
surface wave at all levels. The velocity profiles displayed large
divergences to the horizontal SML velocities in the wake of the hurricanes.
The observations show a strong enhancement to the right of the storm as
expected from numerical simulations. The largest SML velocities were 1.1
m s-1 in Norbert and 0.73 m s-1 in Josephine.
Numerical simulations will be compared with the observations in Part II.
Shay, L.K., R.L. Elsberry, and P.B. Black. Mesoscale ocean temperature and
current patterns induced by hurricanes. Preprints, 17th Conference on
Hurricanes and Tropical Meteorology, Miami, FL, April 7-10, 1987.
American Meteorological Society, Boston, 388-392 (1987).
No abstract.
Spillane, M.C., D.B. Enfield, and J.S. Allen. Intraseasonal oscillations
in sea level along the west coasst of the Americas. Journal of Physical
Oceanography, 17:313-325 (1987).
Hourly observations of coastal sea level at stations from Peru to British
Columbia are analyzed for low frequency content. A space-time contour
plot of sea level, from four years of data during the 1971-75 period,
shows the meridional structure of the seasonal cycle and interannual
variability associated with the 1972-73 El Niño. Oscillations with
intraseasonal periods of 36-73 days are also evident, coherent over
alongshore distances of several thousand kilometers. Further
investigation using spectral methods and empirical orthogonal function
analysis in the frequency domain reveals, in particular, that
intraseasonal sea level variability has a peak in spectral density along
the coasts of South America, Central America and Mexico, with high
coherence from near the equator (Tumaco, 2°N) north to central
California (34°N) and south to at least Callao (12°S). Phase
propagation north of the equator is poleward at 150-200 kilometers/day.
Atmospheric pressure, alongshore wind stress and wind stress curl,
derived from Fleet Numerical Oceanography Center data for the Northern
Hemisphere, are used to assess the importance of local atmospheric
forcing. The low coherence between sea level and these fields in the
intraseasonal frequency band suggests that the observed oscillation may
be a coastally propagating response to remote processes in the equatorial
Pacific waveguide.
Tanner, A., C.T. Swift, and P.B. Black. Operational airborne remote sensing
of wind speeds in hurricanes. Preprints, 17th Conference on Hurricanes
and Tropical Meteorology, Miami, FL, April 7-10, 1987. American
Meteorological Society, Boston, 385-387 (1987).
No abstract.
Velden, C.S., and S.B. Goldenberg. The inclusion of high-density satellite
wind information in a barotropic hurricane forecast model. Preprints,
17th Conference on Hurricanes and Tropical Meteorology, Miami, FL,
April 7-10, 1987. American Meteorological Society, Boston, 90-93 (1987).
No abstract.
Wilburn, A.M., E. Johns, and M.H. Bushnell. Current velocity and
hydrographic observations in the Straits of Florida, the Caribbean
Sea, and offshore of the Antillean Archipelago: Subtropical Atlantic
Climate Study (STACS), 1984 and 1985. NOAA Data Report, ERL AOML-8,
1994 pp. (1987a).
No abstract.
Wilburn, A.M., E. Johns, and M.H. Bushnell. Current velocity and
hydrographic observations in the Straits of Florida, the Caribbean
Sea, and offshore of the Antillean Archipelago: Subtropical Atlantic
Climate Study (STACS), 1986. NOAA Data Report, ERL AOML-10, 247 pp.
(1987b).
No abstract.
Willis, P.T., and F.D. Marks. Convective-scale transports in a
mature hurricane. Preprints, 17th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, April 7-10, 1987. American Meteorological
Society, Boston, 343-346 (1987).
No abstract.
Willoughby, H.E. Tropical cyclone track prediction: Some theoretical
aspects. Preprints, 17th Conference on Hurricanes and Tropical
Meteorology, Miami, FL, April 7-10, 1987. American Meteorological
Society, Boston, 262-265 (1987).
No abstract.
Willoughby, H.E. Use of aircraft in hurricane research. Program Booklet,
Second Airborne Science Workshop, Miami, FL, February 3-6, 1987. NASA,
Washington, D.C., 83 (1987).
No abstract.
Willoughby, H.E., and W.P. Barry. Real-time data acquisition and analysis
in Hurricane Charley of 1986. Preprints, 17th Conference on Hurricanes
and Tropical Meteorology, Miami, FL, April 7-10, 1987. American
Meteorological Society, Boston, 341-342 (1987).
No abstract.
Zhang, J.-Z., H. Jiazhen, L. Bianling, and L. Faxi. The kinetics of
oxidation of hydrogen sulfide by dissolved oxygen in seawater. Donghai
Marine Science, 5(3):71-77 (1987).
The rate of oxidation of hydrogen sulfide by oxygen has been studied in
both a 0.5 M NaCl solution and in seawater over a range of pH and
temperature in the presence of metal sulfide precipitation. The results
indicate that maximum reaction rates in pH appear at about 7 and great
reactions rates in pH at between 9 and 12. The activation energy of the
reaction at pH 8.5 in 0.5 M NaCl solution was 25 kcal/mol. The visible
light did not affect the reaction rate obviously. The catalysis of FeS,
MnS, CuS, and NiS on the reaction has been observed in both the 0.5 M NaCl
solution and in seawater, but Mg2+, Al3+, and CdS
did not catalyze the reaction.
**1986**
Adams, W.L., and H.A. Friedman. 1986 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, Miami, Florida (published for limited
distribution), 116 pp. (1986).
No abstract.
Andree, M., H. Oeschger, W.S. Broecker, N. Beavan, M. Klas, A. Mix,
G. Bonani, H.J. Hoffman, M. Suter, W. Woelfli, and T.-H. Peng. Limits
on the ventilation rate for the deep ocean over the last 12,000 years.
Climate Dynamics, 1:53-62 (1986).
In this paper we present accelerator radiocarbon measurements on
hand-picked benthic and planktonic foraminifera separated from two deep
sea cores raised from the South China Sea. From the benthic-planktonic
age differences we are able to place limits on the extent to which the
ventilation rate of the deep Pacific Ocean has changed over the last
12,000 years. While much work remains to be done before any definitive
answers for the global oceans can be given, these results on cores with
sedimentation rates suitably high to avoid major corrections for
bioturbation effects suggest that the ventilation rate of the deep
Pacific Ocean has remained nearly the same throughout Holocene time.
Further, there is no suggestion that the rate was slower during the
period of major glacial retreat. These results confirm that the changes
in atmospheric 14C/C ratio over the last 10,000 years owe
their origin to radiocarbon production rate changes.
Bitterman, D.S., and D.V. Hansen. The design of a low cost tropical
drifter buoy. Proceedings, '86 Marine Data Systems International Symposium,
New Orleans, LA, April 30-May 2, 1986. The Marine Technology Society,
575-581 (1986).
Since 1979, the NOAA/Atlantic Oceanographic and Meteorological Laboratory
(NOAA/AOML) has been deploying satellite-tracked drift buoys in the tropical
Atlantic and Pacific Oceans in support of various long-term laboratory
field programs. In order to reduce the cost and eliminate the long
procurement lead times associated with commercially available buoys, a
simple, relatively inexpensive drift buoy was designed for use in these
equatorial areas. This paper describes the construction of the buoy, the
results of field tests of the drogue to directly measure its effectiveness
under various wind and sea conditions, and illustrates the results of buoy
deployments in the open ocean as part of the scientific program.
Black, P.G., F.D. Marks, and R.A. Black. Supercell structure in
tropical cyclones. Preprints, 23rd Conference on Radar Meteorology,
Snowmass, CO, September 22-26, 1986. American Meteorological Society,
Boston, JP255-JP259 (1986).
No abstract.
Black, P.G., R.A. Black, J. Hallett, and W.A. Lyons. Electrical activity
of the hurricane. Preprints, 23rd Conference on Radar Meteorology,
Snowmass, CO, September 22-26, 1986. American Meteorological Society,
Boston, J277-J280 (1986).
No abstract.
Black, P.G., R.W. Burpee, N.M. Dorst, and W.L. Adams. Appearance of the
sea surface in tropical cyclones. Weather and Forecasting,
1(1&2):102-107 (1986).
No abstract.
Black, R.A. Microphysical investigations above the melting level in
Hurricane Norbert (1984). Preprints, 23rd Conference on Cloud
Physics, Snowmass, CO, September 22-26, 1986. American Meteorological
Society, Boston, JP252-JP254 (1986).
No abstract.
Black, R.A., and J. Hallett. Observations of the distribution of ice in
hurricanes. Journal of Atmospheric Science, 43(8):802-822 (1986).
Observations of the type and distribution of particles above the 0°C
isotherm in three Atlantic hurricanes are presented. Supercooled drops,
graupel, columns, and aggregated snowflakes were observed. The supercooled
drops were found only in convective updrafts stronger than 5 m
s-1, but not all updrafts >5 m s-1 contained
appreciable liquid. Graupel was found in all updrafts at temperatures
<-2°C, and small columns were sometimes found in downdrafts.
Nonconvective rainbands contained 15-30 L-1 of snow composed
of columns and what appeared to be large aggregates. Other stratiform
regions contained 1-15 L-1 of medium and large aggregates;
columns were occasionally found there also but only within about 15 km
of convection. Hurricane convection is almost completely glaciated at
the -5°C level. It is suggested that the ice particles observed
at 6 km inside the convection result primarily from downward mixing
on both sides of the eyewall updraft of ice formed in the convective
areas at higher, colder levels. The ice in the stratiform areas is
believed to have fallen from the high-level (6 km and higher) eyewall
outflow.
Broecker, W.S., and T.-H. Peng. Carbon cycle: 1985. Glacial to
interglacial changes in the operation of the global carbon cycle.
Radiocarbon, 28(2A):309-327 (1986).
The hottest topic for those interested in the earth's carbon cycles is
the change in atmospheric CO2 content between glacial and
interglacial time. What caused it? What is its role in glacial cycles?
We evaluate here the hypotheses that have been put forward to explain
the CO2 change with evidence from deep sea sediments. We
conclude that all the hypotheses have serious drawbacks and that much
effort will have to be expended in gathering more data from ice cores
and ocean sediments before we will be pointed toward the correct
scenario. Also, thoughtful modeling aimed at depicting the ties between
pCO2, O2, 13C/12C,
14C/12C, and nutrient constituents in the sea for
various modes of circulation will have to be done before the evidence
from ocean cores can be properly interpreted.
Broecker, W.S., T.-H. Peng, and G. Ostlund. The distribution of
bomb tritium in the ocean. Journal of Geophysical Research,
91(C12):14,331-14,344 (1986).
A global picture of the water column inventories of bomb-produced tritium
is constructed from the GEOSECS data set. This picture is compared with
that obtained by combining the bomb tritium input function of Weiss and
Roether (1980) with the bomb radiocarbon calibrated lateral
redistribution model of Broecker et al. (1985). While differences
between the calculated and observed distribution exist, they are
surprisingly small. Tritium distributions calculated using the lateral
redistribution model provide predictions of the changes to be expected
in the next few decades. Such predictions are essential to the design of
sound strategies for continued monitoring of the tritium transient.
Broecker, W.S., J.R. Ledwell, T. Takahashi, R. Weiss, L. Merlivat,
L. Memery, T.-H. Peng, B. Jahne, and K.O. Munnich. Isotopic versus
micrometeorologic ocean CO2 fluxes: A serious conflict.
Journal of Geophysical Research, 91(C9):10,517-10,527 (1986).
Eddy correlation measurements over the ocean give CO2 fluxes
an order of magnitude or more larger than expected from mass balance
measurements using radiocarbon and radon 222. In particular, Smith and
Jones (1985) reported large upward and downward fluxes in a surface zone
at supersaturations of 15% and attributed them to the equilibration of
bubbles at elevated pressures. They argue that even on the open ocean
such bubble injection may create steady state CO2
supersaturations and that inferences of fluxes based on air-sea
pCO2 differences and radon exchange velocities must be made
with caution. We defend the global average CO2 exchange rate
determined by three independent radioisotopic means: prebomb radiocarbon
inventories; global surveys of mixed layer radon deficits; and oceanic
uptake of bomb-produced radiocarbon. We argue that laboratory and lake
data do not lead one to expect fluxes as large as reported from the eddy
correlation technique; that the radon method of determining exchange
velocities is indeed useful for estimating CO2 fluxes; that
supersaturations of CO2 due to bubble injection on the open
ocean are negligible; that the hypothesis that Smith and Jones advance
cannot account for the fluxes that they report; and that the
pCO2 values reported by Smith and Jones are likely to be
systematically much too high. The CO2 fluxes for the ocean
measured to date by the micrometeorological method can be reconciled
with neither the observed concentrations of radioisotopes of radon and
carbon in the oceans nor the tracer experiments carried out in lakes and
in wind/wave tunnels.
Chelton, D.B., and D.B. Enfield. Ocean signals in tide gauge records.
Journal of Geophysical Research, 91:9081-9098 (1986).
Tide gauges are designed to measure changes in water level relative to
land. However, vertical motions of the earth's crust manifest themselves
as apparent water level changes in tide gauge records. These
crustally-induced changes are often small in amplitude relative to the
wide range of oceanic processes which affect water level in coastal
regions. Vertical crustal motion can best be studied by first removing
oceanic variability from the time series. In this paper we summarize the
major oceanic signals in tide gauge records. We take the approach that
the oceanic signals are unwanted "noise" in the data. Methods are
described for removing or at least reducing the various oceanic signals.
These oceanic signals span a broad range of time scales from tides to
interannual variability associated with the El Niño phenomenon and
secular sea level change from a number of oceanographic effects.
Chew, F., M.H. Bushnell, R.L. Molinari, K.D. Leaman, and S.A. Frisch.
A new type of meandering in the Florida Current near latitude 27°N.
EOS, Transactions, American Geophysical Union, 67(16):294 (1986).
No abstract.
Clarke, T.L., and J.R. Proni. Remote Acoustical Measurement of Ocean
Bottom Parameters: Current Practices and New Technology in Ocean
Engineering. OED, Vol. II, Book No. I00206, 145-148 (1986).
The use of acoustics in measuring ocean bottom characteristics has been
in progress a number of years. Three of the most widely studied acoustical
features have been returned pulse amplitude (genearlly peak amplitude),
pulse attenuation, and sub-bottom sound speed. Recently, overall returned
pulse shape has been examined as an acoustical feature for sediment
classification. An acoustical bottom and sub-bottom sound reflection and
scattering model has been developed in NOAA for the purpose of deriving
an improved definition of the bottom for charting purposes. A key
question being studied is what are those acoustic features relatable to
certain bottom physical features such as the shear modulus profile? A
discussion of a new application of coherent transverse Doppler to bottom
sound speed profile measurements and other profile measurements will be
given. A sensitivity analysis of sound speed versus backscattered
acoustical intensity will also be presented. Results of the NOAA model
will be presented for acoustical frequencies covering the interval from
10 kHz to 200 kHz for various bottom types. Two-dimensional, frequency-time,
intensity contours will be presented with particular attention to
describing and distinguishing specular reflection, bottom surface-scattering
and bottom volumetric scattering regimes. Comparison of typical fluid
mud structures with those of sand type bottoms will be given with a
discussion of certain esoteric "internal wave" induced "fluid mud like"
episodes. Confusion produced in standard echo-sounding systems by such
phenomena will be illustrated.
Clarke, T.L., S. Alper, J.R. Proni, and L. Huff. A definition of "ocean
bottom" and "ocean bottom depth." Proceedings, Oceans '85,
2:1212-1215 (1986).
The question of the definition of "ocean bottom" for charting and other
purposes has been discussed for many years. Intimately associated with
the question of the definition of "ocean bottom depth," acoustical
echo-sounding has been the dominant approach in making bottom depth
estimates. NOAA has undertaken an applied research program to determine
the maximum information content available in an acoustical echo from an
ocean bottom which may be used to characterize that bottom in terms of
texture, particulate type and engineering properties such as the shear
modulus of elasticity; the resulting information to be analyzed and
synthesized resulting in a scientific/engineering based definition of
"bottom" or "bottom-depth." Results shall be presented from a computer
model of acoustic information from different bottom types, e.g.,
of varying surface roughness, porosity, and so on. Initial model data
indicate that with appropriate choices of acoustic frequency,
bottom-roughness scattering can be less than bottom volumetric scattering,
thereby allowing inferences of bottom characterization and engineering
parameters.
Enfield, D.B. Zonal and seasonal variability of the equatorial Pacific
heat balance. Journal of Physical Oceanography, 16:1038-1054
(1986).
This study calculates a detailed climatological inventory of the oceanic
heat balance in the equatorial Pacific. The gridded climatology of Weare
et al. is used as an estimate of net surface heating. Zonal and
meridional/vertical advection are estimated in a manner similar to that
of Wyrtki, using the gridded climatologies for wind stress (Wyrtki and
Meyers) and sea surface temperature (Reynolds), plus estimates of zonal
transport. In addition, the meridional diffusion of heat into the cold
tongue has been estimated from the work of Hansen and Paul and the terms
of the heat balance have been resolved by ten-degree longitude zones and
by month of the year. The computed residual heat flux has been examined
for consistency with expectations about the remaining, vertical
diffusion process. The effects of using the alternate climatologies of
Esbensen and Kushnir and Reed for the net surface heating are also
calculated. The total advective heat flux divergence is calculated to be
-27 ą 7, -91 ą 17 and -48 ą 17 W m-2, respectively, in the
western, central and eastern equatorial Pacific with meridional
advection and upwelling removing about three times as much heat as zonal
advection. The advective contributions are in approximate agreement with
Wyrtki's "likely case" estimates for the 100°W-170°E longitude
zone. The contributions from zonal advection, meridional advection and
meridional diffusion are found to be greatest during the Boreal fall,
winter and fall-winter seasons, respectively. Depending on the
climatology used for the net surface heat gain, the assumption of a
uniform meridional diffusivity of 2 × 104 m2
s-1 leads to physically unrealistic residual flux divergences
that imply a heat gain from vertical turbulence in the central Pacific
or that vertical turbulence removes much more heat from the western and
eastern Pacific than from the central Pacific. Total neglect of the
meridional diffusion exacerbates the problems. Increasing the meridional
diffusivity to 6 × 104 m2 s-1 in
the central Pacific, consistent with direct estimates by Hansen and
Paul, gives zonally uniform, negative residuals that are physically
consistent with existing measurements of equatorial turbulence. With the
model so tuned, the "best guess" heat balance in the central Pacific
involves significant contributions from all terms, in the western
Pacific between surface heat gain from the atmosphere and losses due to
vertical diffusion, and in the eastern Pacific between surface gain and
losses due to meridional advection (upwelling) and vertical diffusion.
Friedman, H.A., and O.E. Thompson. First International Conference
on School and Popular Meteorological Education, Lady Margaret Hall,
Oxford University, July 2-4, 1984. Bulletin of the American
Meteorological Society, 67(4):422-425 (1986).
The First International Conference on School and Popular Meteorological
Education convened at Lady Margaret Hall, one of the colleges of Oxford
University. The conference, held from July 2-4, 1984, was organized by
the Royal Meteorological Society (RMS) and was cosponsored by the
American Meteorological Society (AMS) and the World Meteorological
Organization (WMO). The AMS Board of School and Popular Meteorological
and Oceanographic Education (BSPMOE) played an active, though relatively
minor, role in helping to structure the conference by developing interest
among potential participants in the United States, including educators,
meteorological instrument manufacturers and distributors, scientists,
school career counselors, representatives of the electronic and print
media, and publishers of meteorological and related textbooks and other
educational materials. The chairperson of the Conference Organizing
Committee was J.M. Walker, education secretary of RMS.
Gamache, J.F. Bulk water-budget components in Hurricane Norbert as
determined from airborne radar and Doppler observations. Preprints, 23rd
Conference on Radar Meteorology, Snowmass, CO, September 22-26, 1986.
American Meteorological Society, Boston, JP244-JP247 (1986).
No abstract.
Gamache, J.F. Particle characteristics in stratiform and convective clouds
observed during summer MONEX. Preprints, Conference on Cloud Physics,
Snowmass, CO, September 22-26, 1986. American Meteorological Society,
Boston, J143-J146 (1986).
No abstract.
Garzoli, S.L., and M.E. Clements. Indirect wind observations in the
southwestern Atlantic. Journal of Geophysical Research,
91(C9):10,551-10,556 (1986).
Two time series of wind speed have been inferred from ambient noise
measurements obtained with bottom deployed inverted echo sounders in the
southwestern Atlantic. The wind records from the two instruments,
deployed 181 km apart, show significant differences at low frequencies.
The mean speed for the recorded period is 10 m/s. The energy density
spectra of the inferred wind records show a decrease in energy with
frequency with a slope of -1.7 for frequencies between 0.22 and 20 cpd.
The analysis to the spectra from the time series at the two moored
locations shows differences in the band of 2-10 days. An increase in the
variance is detected in the offshore location at discrete periods
corresponding to atmospheric oscillations. These oscillations are
considerably less energetic in the continental shelf-slope regime but
are coherent in both locations.
Govoni, J.J., P.B. Ortner, F. Alyamani, and L.C. Hill. Selective feeding
of spot (Leiostomus xanthurus) and Atlantic croaker (Micropogonias
undulatus) larvae in the northern Gulf of Mexico. Marine Ecology
Progress Series, 28:175-183 (1986).
No abstract.
Hayes, S.P., D.W. Behringer, M. Blackmon, D.V. Hansen, N.C. Lau, A. Leetmaa,
S.G.H. Philander, E. Pitcher, C.S. Ramage, E.M. Rasmusson, E.S. Sarachik,
and B.A. Taft. The Equatorial Pacific Ocean Climate Studies (EPOCS) plans:
1986-1988. EOS, Transactions, American Geophysical Union, 67:442-444
(1986).
No abstract.
Jones, R.W. Mature structure and motion of a model tropical cyclone with
latent heating by the resolvable scales. Monthly Weather Review,
114(6):973-990 (1986).
The mature structure of a model tropical cyclone is presented with
emphasis on convection in the eyewall and spiral rainbands.
Representative patterns of rainband activity occur during the last two
days of a 13-day experiment and are shown for 288 h or day 12. These
model rainbands seem to be forced by a pair of quasi-stationary spiral
bands of upward motion that appear in the low troposphere and boundary
layer ahead of and behind the westward moving vortex. These forcing
bands, in turn, may be the result of a non-linear interaction of
azimuthal wavenumber one with itself. The convective band elements ahead
of the vortex do not reach the outflow layer, but are capped by a
mesoscale subsidence band in the upper troposphere. Elements behind the
vortex, however, reach the outflow layer and have greater precipitation
intensity. During the last two days of the experiment, three times as
much rain falls behind the vortex and outside of the inner core as falls
in front of the vortex. The mesoscale subsidence band that caps the
convection in bands in front of the vortex is the direct result of a
characteristic asymmetry of the 250 mb layer. This asymmetry forms
between simulation hours 60 to 84 and results from bands outside of
the inner core of the vortex. The model vortex structure, in
cross-section format, is compared with recent aircraft observations of
strong hurricanes (Jorgensen, 1984a,b), particularly Hurricane Allen on
5 August 1980. The model data represent a time and space average with
respect to real data. When this averaging is taken into account,
reasonable agreement is found between the model and Allen. The model
updraft maximum occurs inside of the radius of maximum wind and the
precipitation maximum is located outside of the maximum wind at lower
levels, in agreement with the real data. The time average motion of the
vortex is compared with the mass weighted mean environment current at
990 km radius. For periods of four days or more, the vortex speed agrees
with the current speed and the vortex path is mostly to the right of the
environment current. For 10 h averages, vortex speed deviations <12%
occur and show effects of vortex environment current interactions.
Katz, E.J., P. Hisard, J.-M. Verstraete, and S.L. Garzoli. Annual
change of sea surface slope along the equator of the Atlantic Ocean in
1983 and 1984. Nature, 322(6076):245-247 (1986).
The authors describe the sea surface slope derived from three
complementary methods: hydrographic stations, pressure gauges, and
inverted echo sounders. The latter two have the advantage of yielding
continuous time series, but depend on the hydrographic stations for an
absolute reference. Together, the three provide a detailed description
of the temporal variation of the sea surface slope which is then compared
to a wind-stress time series. The dominant signal, in both sea slope and
wind stress, is the annual cycle, although amplitude and phase vary
interannually. The annual increase in sea surface slope along the
equator in the western and central basins lags the onset of the southeast
trade wind. During the boreal winter of 1983-1984 a strong rise in sea
level occurred against the African coast, accompanied by a leveling of
the sea surface to the west. At the same time, an almost complete
relaxation of eastward wind stress on the equator was observed near
the center of the basin.
Marks, F.D. Three-dimensional wind structure of the eyewall of
Hurricane Norbert as determined from an airborne Doppler radar.
Preprints, 23rd Conference on Radar Meteorology, Snowmass, CO,
September 22-26, 1986. American Meteorological Society, Boston,
JP248-JP251 (1986).
No abstract.
Maul, G.A., J.R. Proni, W.P. Dammann, C.A. Lauter, M.H. Bushnell, and
D.A. Mayer. Inverted echo sounder/pressure gauge measurements under the
Gulf Stream in the offing of Cape Canaveral during the Florida Atlantic
Coast Transport Study (FACTS), Vol. 2. Submitted by Florida Institute of
Oceanography. Prepared for Minerals Management Service (U.S. Dept. of the
Interior), Contract 14-12-001-30082, 330-382 (1986).
Three inverted echo sounder/pressure gauges (IES/PGs) were placed at depths
of 140 m, 760 m, and 830 m under the Gulf Stream at latitude 29°N
off the Florida Atlantic coast from December 1984 to May 1985. The IES/PGs
were unusable due to excessive receiver gain. Volume backscattering from
below the surface caused the circuitry to record early returns rather
than those from the surface. An experiment in 215 m water depth at
27°N, from July to September 1985, successfully recorded travel times
to the surface after the receiver sensitivity was reduced by 30 db. The
unit, placed in 830 m water depth, recorded travel times that had a
non-Gaussian distribution function, but when processed by using all burst
samples in a 25-hour period, gave a 40-hour low passed signal with a net
decrease in travel time proportional to an increase in dynamic height of
5 dyn-cm for the five month record. Bottom pressure at the 140 m and
830 m water depth sites had net linear drifts of -178 mb and -77 mb
respectively over five months; low frequency comparisons with Florida
Current transport measured at the Jupiter, FL to Settlement, Point, Bahama
submarine cable were therefore excluded. Linear correlation of detrended
bottom pressure at the 140 m site were r = -0.33 with similarly detrended
cable transports; coherence squared above 0.65 occurred at 21, 9, and 3
days, all with a phase lag of about 245 degrees.
Mayer, D.A., and J.C. Larsen. Tidal transports in the Florida
Current and its relationship to tidal heights and cable voltages.
Journal of Physical Oceanography, 16(12):2199-2202 (1986).
A linear relationship between tidal height (sea level of tidal
frequencies) and tidal transport near 27°N in the Straits of
Florida is confirmed. Transport estimates from this relationship
for the O1 and M2 constituents are compared
with those computed from cable voltages across the Florida Current.
These estimates are independent in that the weighted tidal height
model (tidal-height transport relationship) was developed using
collective sets of current meter and velocity profiler data obtained
at different times of the year and in different locations. The
cable voltages, however, were calibrated using a quasi-synoptic
sectional integration of depth-averaged profiler data. Further, a
means is suggested by which changes in the cable calibration can
be detected.
McBride, J.L., and H.E. Willoughby. Comment: An interpretation of
Kurihara and Kawase's two-dimensional tropical-cyclone development model.
Journal of the Atmospheric Sciences, 43:3279-3283 (1986).
This comment presents a detailed examination of the published model results
of Kurihara and Kawase (1985) in an attempt to clarify the role of
wave-CISK in the development of tropical cyclones. Kurihara and Kawase's
model simulates the development of a tropical depression, although the
vertical structure differs significantly from observations. The physical
roles of vertical shear and nonlinear dynamics in the development in this
model are unclear. The authors propose that the nonlinear terms in the
equations promote rapid growth by increasing the "inertial stiffness." A
major concern, however, is that the enhanced development may occur because
the nonlinear terms excite modes with high horizontal wavenumbers. These
modes grow rapidly through wave-CISK. From considerations of the
climatological importance of horizontal shear to tropical-cyclone
development in nature, this model may be less relevant to tropical
cyclogenesis than one that allows horizontal shears of the environmental
flow. The authors discuss the model's response to changes in the vertical
shear of the basic state, which appears to have the opposite effect in
the model from what it has in nature.
Molinari, R.L. Subtropical Atlantic Climate Studies (STACS) revisited.
EOS, Transactions, American Geophysical Union, 67(5):59-60 (1986).
No abstract.
Molinari, R.L., J.F. Festa, and E. Marmolejo. Heat budget and climatic
atlas of the tropical Indian Ocean and Arabian Sea during FGGE (1979).
NOAA Technical Memorandum, ERL AOML-63, 76 pp. (1986).
Observations of surface oceanographic and meteorological fields collected
during the first GARP Global Experiment (FGGE) in the tropical western
Indian Ocean and Arabian Sea have been combined and averaged by month onto
a 2° by 2° grid. Monthly distributions of sea-surface
temperature, wind speed and direction, air temperature, specific humidity,
and cloud cover have been generated for the period from December 1978
through November 1979. Net short-wave and long-wave radiation, and
sensible and latent heat flux distributions have been generated from
these surface data using the bulk aerodynamic formulas. Standard errors
of the mean values have been computed along with monthly contoured plots
of each oceanographic and meteorological variable.
Molinari, R.L., J.F. Festa, and J. Swallow. Climatic atlas of mixed layer
and thermocline depth climatologies in the western Indian Ocean. NOAA
Technical Memorandum, ERL AOML-64 (PB86-154613), 40 pp. (1986).
Mean monthly distributions of the mixed layer depth (defined as the first
depth at which the temperature is 0.5°C less than the sea-surface
temperature) and thermocline depth (defined as the depth of the 20°C
isotherm) are derived from data collected between 1948 and 1981.
Approximately 50,000 data points are available to generate the
climatologies. Amplitude and phase distributions for the annual and
semi-annual signals are computed from the monthly time series. The
mixed layer depth distributions are compared to the thermocline depth
distributions to identify possible regions where thermocline displacements
influence mixed layer displacements.
Molinari, R.L., J.F. Festa, and J. Swallow. Evolution of the near-surface
thermal structure in the western Indian Ocean during FGGE, 1979.
Journal of Marine Research, 44:739-762 (1986).
The evolution of mixed layer temperature (taken as sea-surface temperature,
SST) in the western Indian Ocean north of 20°S and west of 80°E
during the First GARP Global Experiment (FGGE), 1979, is described and
modeled. The FGGE-year development in time and space of SST is compared
to the appropriate climatology. FGGE events occurred in phase with
climatology, but some amplitude anomalies were observed. Heat budget
computations for the surface mixed layer indicate that over 25% of the
region-studied energy fluxes through the sea surface can account for 80%
of the observed SST variance. South of the equator, 80% of the variance
is accounted for in 36% of the area and north, only 11%. Exceptions are
noted along the western boundary, in the central and eastern Arabian Sea,
and in a band south of the equator between 6°S and 12°S, east
of 60°E. The addition of entrainment through the base of the mixed
layer improves the heat budget estimates over most of the region, in
particular, along the Arabian coast. Near the northern part of the coast
of east Africa, however, inclusion of the effect of horizontal advection
gives more improvement. The breakdown of the heat budget computations in
the central and eastern Arabian Sea and in the band south of the equator
is attributed to a small signal in SST variance and few data in the
regions.
Molinari, R.L., S.L. Garzoli, E. Katz, E. Harrison, P. Richardson, and
G. Reverdin. A synthesis of the first GARP global experiment (FGGE) in
the equatorial Atlantic Ocean. Progress in Oceanography,
16(2):91-112 (1986).
A synthesis of near-surface oceanographic and surface meteorological data
collected during the First GARP Global Experiment (FGGE) is presented to
portray the oceanic response to the seasonal wind forcing for the period
December 1978 to November 1979, inclusive. Major wind events during FGGE
are in phase with events given in climatology. In particular, the
February-March-April relaxation and May enhancement of equatorial winds
occurs within one month of the mean event. Accordingly, the oceanic
responses, such as the May, June, July appearance of an equatorial cold
water tongue, the acceleration of the South Equatorial Current (SEC), and
the vertical displacementt of the equatorial thermocline occur at the
average time. Furthermore, the curl distribution in the vicinity of the
North Equatorial Countercurrent (NECC) during 1979 is similar to the
climatological distribution in terms of phase and amplitude, except for
a westward displacement in the position of the maximum curl. As predicted
from linear theory, the 1979 thermocline response across the NECC is in
phase with the climatological response with a westward displacement of
the maximum thermocline movement. Deeper than average equatorial
thermoclines and a weaker SEC may, in part, be responsible for the
anomalously warm sea-surface temperatures observed on the equator between
10°W and 30°W from June to November.
Nelsen, T.A., and J.H. Trefry. Pollutant-particle relationships in the
marine environment: A study of particles and their fate in a major
river-delta-shelf system. Rapports et Proces-Verbaux des Reunions,
186:115-127 (1986).
The Pollutant-Paraticle Relationships in the Marine Environment (P-PRIME)
program was designed to look at the association between partaicles
(lithogenic and biogenic) and selected heavy-metal pollutants for their
source-pathway-dispersal patterns and behavior from a major United States
river (Mississippi River) to the adjacent continental shelf. Data from
four cruises indicate the following: (a) the river's SPM concentration
varied on an hourly to seasonal scale; (b) suspended particulate matter
in the study area was composed of three distinct suites: a dominant
lithogenic suite and two subordinates, but distinct and seasonally
variable biogenic (phytoplankton) suites; (c) in order of abundance, the
offshore concentration of particulate matter is in the bottom nepheloid
layer, the surface turbid layer, and the midwater region; (d) in the
nearshore and midshelf zone, rapid removal of river-derived (lithogenic)
particles from the water column to the underlying sediments may be
"driven" by biopackaging; (e) 210 Pb sediment accumulation-rate support
the rapid removal and accumulation of river-derived sediments very near
the river mouth; (f) data for sediment pollutant Pb support the concept
of rapid sediment burial in the nearshore zone and also indicate no
losses of Pb from these particles. These findings indicate that modeling
and sediment transport of river/shelf systems such as the ones described
above must consider variability on the hourly to seasonal scale to provide
an accurate reflection of the natural system. Because of close coupling of
pollutants such as Pb with particles, even after burial, future studies
of the pathways and sinks of many pollutants can be, to a first
approximation, that of the river-derived particles.
Nelsen, T.A., G.P. Klinkhammer, J.H. Trefry, and R.P. Trocine. Real-time
observation and tracking of dispersed hydrothermal plumes using nephelometry:
Examples from the Mid-Atlantic Ridge. Earth and Planetary Science
Letters, 81:245-252 (1986).
As part of the 1984-1985 NOAA VENTS program on the Mid-Atlantic Ridge,
nephelometry was used to provide real-time detection and tracking of
dispersed hydrothermal plumes. At all nine 1984 study sites, hydrothermal
activity was detected by in-situ, real-time nephelometer
measurements and later confirmed by dissolved Mn and particulate Fe
measurements. These same techniques were employed in a site-specific
survey of the Trans-Atlantic Geotraverse (TAG) area in 1985 where large
water-column anomalies in turbidity and in dissolved Mn helped lead to
the discovery of high-temperature black smokers. The optical response
of the nephelometer was to hydrothermally-derived particulate matter.
Thus, strong correlations existed between the nephelometer readings and
total suspended matter (r = 0.98, n = 34), and particulate Fe (r = 88,
n = 32). In addition, digital nephelometer data correlated well
with dissolved Mn (r = 0.88, n = 78) throughout a large concentration
range (0.2-31.0 nmol/kg). These data provide good evidence for the utility of
in-situ nephelometer measurements for locating and surveying
plumes from hydrothermal events. It also appears possible, within limits,
to predict concentrations of in-situ total suspended matter, of
particulate Fe and of dissolved Mn.
Nelsen, T.A., S. Metz, J.H. Trefry, and A. Pimmel. Sedimentology and
composition of sediment near a black smoker field on the Mid-Atlantic
Ridge. EOS, Transactions, American Geophysical Union, 67:1022
(1986).
A 1.25 m core was recovered in 1985 from the Mid-Atlantic Ridge (26°N)
approximately 2 km north-northeast of the newly discovered black smokers
in the TAG Hydrothermal Field. Structural evidence within the core suggests
that it was recovered from the edge of a small infilling basin. Sediment
transport mechanisms for the hydrothermal materials appear to be both by
mass movement and grain-by-grain sedimentation. Sediment deposited by
the latter mechanism has accumulated at rates varying from 2-30 cm/1,000
years. Relative to mass movement transport, x-radiography reveals a
debris-flow deposit capped by an associated fine-grained turbidite. Upcore,
two course-grained turbidite deposits of hydrothermal material were
identified. These mass flow deposits account for approximately 44% of the
recovered sediment. The balance of the recovered sediment was deposited
in a grain-by-grain fashion with hydrothermal material dominating these
intervals. Hydrothermal input was pulsed, with events ranging from the
sub-millimeter scale to layers as thick as 25 cm. Within the top 12 cm,
representing approximately the last 4,000 years, interlayering of normal
pelagic sediments and hydrothermal material indicates either sporadic
deposition of, or intermittent venting of, hydrothermal material.
Superimposed on the above, chemical and mineralogical data show
considerable variability with time, as well as providing sustaining
evidence for the interpretations stated above.
Ooyama, K.V. A spectral prediction model on nested domains and its
application to asymmetric flow in the hurricane boundary layer.
Extended Abstracts, WMO/IUGG International Symposium on Short and
Medium-Range Numerical Weather Prediction, Tokyo, Japan, August
4-8, 1986. PSMP Report Series No. 19, 451-454 (1986).
No abstract.
Palmer, D.R., P.A. Rona, and M.J. Mottl. Acoustic imaging of
high-temperature hydrothermal plumes at seafloor spreading centers.
Journal of the Acoustical Society of America, 80(3):888-898
(1986).
We explore the possibility of using active sonar techniques to
acoustically image high-temperature "black smoker" hydrothermal plumes.
We examine recent sonar images of a hydrothermal vent field at 11°N
on the East Pacific Rise obtained from DSRV Alvin which may show the
presence of plumes. For vent fields on the East Pacific Rise, estimates
are obtained of the minimum detectable concentration of precipitates
as a function of the range between the sonar and the plume boundary.
These estimates are compared with measured concentrations. Some of the
anticipated advantages of acoustic imaging are discussed. We conclude
that acoustic imaging techniques have the potential of providing a
coherent framework for point sampling of physical and chemical properties
of hydrothermal plumes and for determining the dynamics of their injection
into the surrounding water mass.
Palmer, D.R., L.M. Lawson, Y.-H. Daneshzadeh, and D.W. Behringer. The
effect of an El Niño/Southern Oscillation event on underwater sound
propagation. 111th Meeting of the Acoustical Society of America,
Cleveland, OH, May 12-16, 1986. Journal of the Acoustical Society of
America, 79:S69 (1986).
No abstract.
Peng, T.-H. Land use change and carbon exchange in the tropics: II.
Estimates for the entire region--Comment. Environmental
Management, 10(5):573-575 (1986).
No abstract.
Peng, T.-H. The role of the ocean in the atmospheric CO2
problem. Science Monthly, 17(8):615-621 (in Chinese) (1986).
No abstract.
Peng, T.-H. Uptake of anthropogenic CO2 by lateral transport
models of the ocean based on the distribution of bomb-produced
14C. Radiocarbon, 28(2A):363-375 (1986).
The pattern of global water column inventories of bomb-produced
14C suggests that a sizeable portion of bomb 14C
that entered the Antarctic, northern Pacific, and tropical oceans has
been transported to adjacent temperate regions. Models of lateral
transport of surface water in the Atlantic, Indian, and Pacific Oceans
are based on this distribution pattern. Upwelling of
bomb-14C-free water from below takes place in the Antarctic,
northern Pacific, and tropical regions; downwelling of surface water
occurs in the temperature oceans and northern Atlantic. Uptake of excess
CO2 by these models is calculated using the observed Mauna Loa
pCO2 record as an input function. Results indicate that 35% of
fossil fuel CO2 is taken up by these model oceans during the
period 1958-1980. Considering the observed airborne fraction of 0.55, it
appears that ca 10% of the global fossil fuel CO2 is still
missing.
Peng, T.-H., and H.D. Freyer. Revised estimates of atmospheric
CO2 variations based on tree-ring 13C record.
In The Changing Carbon Cycle: A Global Analysis, J.R.
Trabalka and D.E. Reichle (eds.). Springer-Verlag, New York,
151-159 (1986).
No abstract.
Peterson, D.H., D.R. Cayan, and J.F. Festa. Interannual variability in
biogeochemistry of partially mixed estuaries: Dissolved silicate cycles
in northern San Francisco Bay. Estuarine Variability,
1986:123-138 (1986).
Much of the interannual variability in partially-mixed estuaries in
dissolved inorganic nutrient and dissolved oxygen patterns results from
an enhancement or reduction of their annual cycle (generally via climatic
forcing). In northern San Francisco Bay estuary the annual cycle of
dissolved silicate supply peaks in spring and the effect of phytoplankton
removal peaks in fall. Because riverine silicate sources are enhanced
in wet years and reduced in dry years, the annual silicate cycle is
modified accordingly. Effects of phytoplankton removal are reduced and
delayed in wet years and enhanced and advanced (seen earlier) in dry years.
Similar reasoning can apply to interpreting and understanding other
mechanisms and rates.
Piotrowicz, S.R., D.A. Boran, and C.J. Fischer. Ozone in the boundary
layer of the equatorial Pacific Ocean. Journal of Geophysical
Research, 91:13,113-13,119 (1986).
Shipboard (~7 m) ozone measurements made in the equatorial Pacific
Ocean between 20°N and 17°S and 140°W-160°W confirm
the existence of a distinct ozone minimum in the vicinity of the equator
in the late spring, its decline in the summer, and its absence in autumn.
This minimum could not be correlated with high biological activity in
surface waters. Coincident aircraft measurements of ozone from near sea
surface (50-100 m) to 2 km in altitude were made along 150°W at
stations at 10°N, 0°, 5°S, and 12°S in May-June 1984.
Aircraft data identified the existence of a distinct ozone maximum between
the lifting condensation level (LCL) or cloud base and the trade wind
inversion, with ozone mixing ratios amounting to 2-2.5 times the ozone
levels in the well-mixed subcloud layer. A gradient of decreasing ozone
with decreasing altitude extended from the LCL (or cloud base) to the
near-surface superadiabatic region but did not include it.
Powell, M.D. Airborne Doppler radar observations in the hurricane boundary
layer. Preprints, 23rd Conference on Radar Meteorology, Snowmass,
CO, September 22-26, 1986. American Meteorological Society, Boston,
JP260-JP263 (1986).
No abstract.
Reverdin, G., R.L. Molinari, and Y. Du Penhoat. Objective analysis of
thermocline depth distributions obtained in the tropical Atlantic Ocean
during FGGE, 1979. Deep-Sea Research, 33(1):43-53 (1986).
An objective analysis algorithm is applied to subsurface temperature data
collected in the tropical Atlantic Ocean from January to August 1979 to
obtain maps of 20°C isotherm topography. Throughout the eight-month
period anomalies were essentially aligned with the ridge-trough system
characteristic of the climatological thermocline distribution in the
region. The anomalies, as large as 30 m, increased the relief of the
1979 ridge-trough system relative to climatology. A simple diagnostic
calculation using the results from the algorithm and surface wind data
suggests that in the region of the North Equatorial Countercurrent the
thermocline responds to the effects of local Ekman pumping and the
divergence of geostrophic currents. Both effects are caused by the
seasonally varying surface winds.
Rona, P.A., G. Klinkhammer, T.A. Nelsen, J. H. Trefry, and H. Elderfield.
Black smokers, massive sulfides, and vent biota at the Mid-Atlantic Ridge.
Nature, 321:33-37 (1986).
No abstract.
Shang, E.C., L.M. Lawson, and D.R. Palmer. Source range information loss
in waveguides. Journal of the Acoustical Society of America,
79:958-963 (1986).
In a previous study (E.C. Shang, C.S. Clay, and Y.Y. Wang, J. Acoust.
Soc. Am., 78, 172 [1985]) a new method of passive source ranging in a
layered waveguide was proposed. This paper investigates the reduction
(loss) in range information due to phase fluctuations and to an inaccurate
description of the environment (waveguide mismatch). The effects of phase
fluctuations are investigated using a two-dimensional Gaussian
distribution function. A numerical normal mode code is used to study
the effects of waveguide mismatching. The loss in range information
caused by incorrect descriptions of both the bottom sediment type and
the sound speed profile in the water column is calculated. Examples are
given for a water depth of 100 m and frequencies in the range from
100-500 Hz.
Trefry, J.H., T.A. Nelsen, R.P. Trocine, S. Metz, and T.W. Vetter. Trace
metal fluxes through the Mississippi River delta system. Rapports et
Proces-Verbaux des Reunions, 186:277-288 (1986).
River deltas serve as an important sink for many continentally-derived
contaminants, thereby restricting their flux through the coastal zone.
We have investigated the geochemical cycling of several trace metals,
especially Cd, Mn, and Pb, in the Mississippi River delta-Gulf of Mexico
system to establish the efficiency of this deltaic sink. Greater than
90% of the Mississippi River trace metal load is associated with detrital
particles. As a result, dissolved metal concentrations are very low and
appear to be controlled in several instances by a predictable partitioning
between dissolved and particulate phases. To model this partitioning,
distribution coefficients (Kd) were calculated for several
metals using field and laboratory data. Much of the river-borne sediment
is deposited within 30-50 km of the river mouth. This is especially
evident in the sediment record for Pb which shows a sharp decrease in
the depth to which pollutant Pb is found with increasing distance
offshore. Sediment Pb profiles and river particulate Pb concentrations
also support a 40% decrease in the 1982-1983 Mississippi River burden of
pollutant Pb relative to the mid-1970's. Delta sediments are not always
the ultimate sink for trace metals. Remobilization of Mn and Cd to the
overlying water column leads to a 10-50% net loss of these metals from
the sediment. In contrast, the Pb cycle shows rapid, permanent removal
to the sediments. The Mississippi delta is thus a near-perfect filter
of Pb, and traps much, but not all, of the incoming fluxes of Cd and Mn.
The availability and potential reactivity of sediment trace metals were
elevated by leaching sediments with a series of buffers at pH 2.2-6.0.
Results show that Cu, Fe, and Pb have a much lower tendency towards
removal than Cd and Mn.
Willis, P.T. Characteristics of hurricane melting layers. Preprints, 23rd
Conference on Radar Meteorology, Snowmass, CO, September 22-26, 1986.
American Meteorological Society, Boston, JP264-JP267 (1986).
No abstract.
Wilson, W.D., C. Roffer, and D.S. Bitterman. The shipboard acoustic Doppler
current profiling program at AOML. EOS, Transactions, American
Geophysical Union, 67(44):1061 (1986).
No abstract.
Zhang, J.-Z., and M. Whitfield. Kinetics of inorganic redox reactions in
seawater. Marine Chemistry, 19:121-137 (1986).
The kinetics of the reaction between iodate and bisulfide ions have been
considered in seawater over a range of reactant concentrations and at
temperatures
from 5 to 35°C. The progress of the reaction in a closed vessel was
monitored by the potentiometric measurement of pH and pS2-.
In a series of experiments at reagent concentrations approaching those
observed in natural systems, samples were drawn off from the closed vessel
at regular intervals for polarographic analysis of iodate,
[IO3-], and total sulfide [ST]. The
stoichiometric measurements, together with observations on the products
formed, indicate that the initial reaction is:
5HS- + 2IO3- + 7H+ <-->
I2 + 5S + 6H2O
Measurements using both the potentiometric and polarographic data at
constant initial pH suggest an initial rate equation of the form:
(d[ST]0/dt)0 = k'
[IO3-]00.5
[ST]0
At 25°C, pH 8.2 and a salinity of 35 o/oo,
potentiometric measurements give k' = 162 mol-1
min-1 and polarographic measurements give k' = 105
mol-1 min-1. The reaction proceeds more rapidly
than the corresponding reaction of bisulfide ions with molecular oxygen
and it should, therefore, provide a significant source of molecular
iodine in circumstances where oxic and anoxic waters mix (e.g.,
when estuarine sediments are tidally stirred or during the intermittent
seasonal mixing of stratified fjord or lake systems).
**1985**
Benngio, B.L., and T.A. Nelsen. Technical note: Successful instrument array
deployments in soft mud bottoms adjacent to the Mississippi Delta.
Applied Ocean Research, 7(1):58-60 (1985).
An anchor design for instrument arrays was developed for use in the very
soft muddy sediments adjacent to the Mississippi Delta. Because of the
low sediment shear strengths and high sensitivities combined with large
dynamic loadings due to strong currents, problems in successful deployments
and recoveries were anticipated. A total of six deployments were attempted;
four were sediment trap arrays and two were current meter/transmissometer
arrays. All six deployments and recoveries were successful. The array
design presented herein is a safe, easy, and cost effective method for
deploying instrument arrays in areas where soft bottoms and strong currents
are a consideration.
Bennett, R.H., S.A. Bush, L. Lehman, P. Gritton, E.B. Forde, G.R. Harvey,
W.B. Sawyer, and M. Hulbert. Organic carbon and submarine sediment,
geotechnical property interrelations. Marine Geotechnology,
6:61-98 (1985).
Total organic carbon content (TOC) and selected geotechnical properties
were measured in submarine sediments of the U.S. central east coast and
the Mississippi Delta. TOC values in the near-surface Delta sediments were
approximately 1% (dry weight). TOC in surficial sediments from the U.S.
east coast outer continental shelf upper slope, and upper rise was
generally less than 1%, but between the upper slope and the upper rise,
values ranged from 1% to 3% and exceeded 3% in patches associated with
Norfolk and Washington Canyons. TOC displayed positive linear correlations
with water content, liquid limit, plastic limit, plasticity index, and
the amount (percent) of fine-grained material. Nevertheless, there appeared
to be no strong dependence of geotechnical properties on TOC in these
sediments. This was in accord with previously reported studies on
terrestrial soils with TOC values of less than 5%. Carbohydrate content
was strongly correlated with water content and plasticity index, suggesting
that measurement of individual components of the organic material may
provide more sensitive indications of the effects of organics on
geotechnical properties than measurement of bulk TOC. Selected
geotechnical properties and TOC content of U.S. continental margin surficial
sediments displayed regional trends related to water depth and
morphological setting. These trends are probably related to recent biological,
sedimentological, and oceanographic processes active on the outer shelf,
slope, and rise.
Bitterman, D.S. Use of ARGOS tracked drifting buoys in the equatorial
Pacific Ocean. 1984 Drifting Buoy Workshop, November 1984, Marine
Technology Society Gulf Coast Section, 109-111 (1985).
No abstract.
Black, P.G., R.L. Elsberry, L.K. Shay, and R.M. Partridge. Hurricane
Josephine (1984) surface winds and ocean response determined from
air-deployed drifting buoys and concurrent research aircraft data.
Preprints, 16th Conference on Hurricanes and Tropical Meteorology,
Houston, TX, May 14-17, 1985. American Meteorological Society, Boston,
22-24 (1985).
No abstract.
Black, P.G., R.C. Gentry, V.J. Cardone, and J. Hawkins. Seasat microwave
wind and rain observations in severe tropical midlatitude marine storms.
In Advances in Geophysics 27, Academic Press, New York, 197-277
(1985).
This overview presents initial results of studies concerning Seasat
measurements in and around tropical and severe midlatitude cyclones over
the open ocean and provides an assessment of their accuracy and usefulness.
Sensors flown on Seasat provided complementary measurements of surface wind
speed direction, rainfall rate, significant wave height and wave length,
and sea surface temperature. These measurements were made with the Seasat-A
Satellite Scatterometer (SASS), the Scanning Multichannel Microwave
Radiometer (SMMR), The Seasat altimeter, and the Seasat Synthetic Aperture
Radar (SAR). This is the first time that such a sophisticated array of
microwave instruments has been used to study tropical cyclones.
Black, R.A. Distribution of particle types above 6.0 km in two Atlantic
hurricanes. Preprints, 16th Conference on Hurricanes and Tropical
Meteorology, Houston, TX, May 14-17, 1985. American Meteorological
Society, Boston (1985).
No abstract.
Broecker, W.S., T.-H. Peng, and T. Takahashi. Reconstructions of past
atmospheric CO2 content from the chemistry of the
contemporary ocean: An evaluation. DOE Technical Report TR020, DOE/OR-857
(1985).
No abstract.
Broecker, W.S., C. Rooth, and T.-H. Peng. Ventilation of the deep
northeastern Atlantic. Journal of Geophysical Research,
90(C4):6940-6944 (1985).
Comparison of the 1973 GEOSECS expedition results from the deep eastern
basin of the North Atlantic with those for 1981 TTO expedition reveal no
firm evidence for change in NO3, PO4, or a
H4SiO4 concentration. While a 2-3 µmol/kg
difference is seen for O2, it is more likely experimental
than temporal in origin. The combined TTO-GEOSECS data sets reveal no
evidence for ventilation of the bottom waters of the eastern basin by
waters from the north.
Broecker, W.S., T.-H. Peng, G. Ostlund, and M. Stuiver. The
distribution of bomb radiocarbon in the ocean. Journal of
Geophysical Research, 90(C4):6953-6970 (1985).
Water column inventories are calculated for bomb radiocarbon at all the
stations occupied during the GEOSECS and NORPAX expeditions and for the
available TTO stations. The pattern of global inventories obtained in
this way suggests that a sizable portion of the bomb radiocarbon that
entered the Antarctic, the northern Pacific, and the tropical ocean has
been transported to the adjacent temperature zones. A strategy for
utilizing these inventory anomalies as constraints on global ocean
circulation models is presented. Essential to this strategy are the
improvement of our knowledge of the pattern of wind speed over the ocean,
the establishment of the wind speed dependence of the rate of gas
exchange between the atmosphere and sea, and the continued mapping of the
distribution of bomb-produced radiocarbon in the sea.
Burpee, R.W., R.E. Kohler, and D.G. Marks. An evaluation of Omega
dropwindsonde data in track forecasts of Hurricane Josephine. Preprints,
16th Conference on Hurricanes and Tropical Meteorology, Houston, TX, May
14-17, 1985. American Meteorological Society, Boston, 162-163 (1985).
No abstract.
Carsey, T.P. Quantitation of vanadium oxides in airborne dusts by x-ray
diffraction. Analytical Chemistry, 57:2125-2130 (1985).
No abstract.
Dodge, P.P., R.W. Burpee, and F.D. Marks. Convective-scale and
mesoscale structure of hurricanes during landfall. Preprints, 16th
Conference on Hurricanes and Tropical Meteorology, Houston, TX, May
14-17, 1985. American Meteorological Society, Boston, 7-8 (1985).
No abstract.
Emanuel, W.R., I. Y.-S. Fung, G.G. Killough, B. Moore, and T.-H.
Peng. Modeling the global carbon cycle and changes in the atmospheric
CO2 levels. In Atmospheric Carbon Dioxide and the
Global Carbon Cycle, J.R. Trabalka (ed.). DOE/ER-0239, 141-174
(1985).
No abstract.
Franklin, J.L., S.J. Lord, L.J. Shapiro, and K.V. Ooyama. An objective
analysis of Omega dropwindsonde data from Hurricane Debby (1982).
Preprints, 16th Conference on Hurricanes and Tropical Meteorology,
Houston, TX, May 14-17, 1985. American Meteorological Society, Boston,
186-187 (1985).
No abstract.
Friedman, H.A. Educational program encourages students to seek hurricane
precautions (instructional programs to encourage family involvement). In
Hurricane Awareness Workbook: Perspectives on Hurricane Preparedness
(a monograph). Federal Emergency Management Agency/National Oceanic and
Atmospheric Administration, Washington, D.C., A27-A28 (1985).
No abstract.
Friedman, H.A. Meteorological education as a window on science and
technology: Activities of the AMS Board of School and Popular
Meteorological and Oceanographic Education. Proceedings, First
International Conference on School and Popular Meteorological
Education, Oxford, England, July 2-4, 1984, J.M. Walker (ed.).
Royal Meteorological Society, Bracknell, Berkshire, United Kingdom,
6-9 (1985).
Many U.S. scientists and educators have long held the belief that our
educational system has failed to provide its students with the mathematics
and science skills needed to compete successfully in today's
technologically-oriented society or to maintain our nation's position of
technological leadership in the world. Only recently has this belief
motivated members of the meteorological profession, through the American
Meteorological Society (AMS) and other scientific organizations, to
undertake a number of educationally-related activities designed to reverse
the disturbing trend toward math and science illiteracy in the nation's
schools. The Board of School and Popular Meteorological and Oceanographic
Education (BSPMOE) has joined with other boards of the AMS Education and
Manpower Commission to develop a resource guide for use with school-aged
children and the general public. The guide is designed to help promote an
awareness of meteorology as a science and the importance of "weather" in
everyday life. We believe that such awareness will serve as a "window" on
mathematics, science, and technology, especially for school-aged children,
and will awaken their scientific curiosity, enhance their scientific
literacy, and heighten their enthusiasm for continued learning. The
activities, accomplishments, and programmatic goals of the BSPMOE are
discussed.
Friedman, H.A. School-based and community-wide education and public
information programs to increase tropical cyclone awareness and
preparedness. Proceedings, First International Conference on School
and Popular Meteorological Education, Oxford, England, July 2-4, 1984,
J.M. Walker (ed.). Royal Meteorological Society, Bracknell, Berkshire,
United Kingdom, 79-85 (1985).
Education and public information are recognized as critical elements in
the design, organization, and implementation of effective tropical cyclone
warning systems. Decision-makers and citizens must have a clear
understanding of the dangers associated with tropical cyclones. Otherwise,
even in nations that have a high level of preparedness, citizens are
likely to take all measures necessary to protect themselves, or to
mitigate against, the destructive effects of future landfalling storms.
In response to this recognition, a numer of education, public information,
and preparedness programs have been proposed or are now in progress. The
goals and strategies of three such programs, namely, (1) a cognitive and
effective learning model (CALM), to create an awareness of the hurricane
problem in at-risk coastal communities of south Florida (HRD/AOML-NOAA),
(2) Pan Caribbean Disaster Preparedness and Prevention Project (CARICOM,
UNDRO, WHO), and (3) Tropical Cyclone Programme Project No. 14: Public
Information and Education (WMO, UNDRO, LRCS), are discussed in this paper.
These efforts represent, respectively, programs with local, regional, and
international focus.
Friedman, H.A., and C.J. Nelson. 1985 Hurricane Field Program
Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and
Meteorological Laboratory, National Oceanic and Atmospheric Administration,
Miami, Florida (published for limited distribution), 109 pp. (1985)
No abstract.
Friedman, H.A., P. Stephens, J. Williams, and O.E. Thompson (eds.).
Guide to Establishing School and Public Educational Activities.
First edition (limited distribution), American Meteorological Society,
Boston, 21 pp. (1985).
The first edition of this guide to local AMS chapters and university
departments is designed to help develop school and public educational
outreach programs in their communities. The guide was produced cooperatively
by the AMS Board of School and Popular Meteorological and Oceanographic
Education and the Board on Women and Minorities. The authors invite readers
of this document to comment on its usefulness in conducting and implementing
community educational outreach programs. Formal publication of the guide
is planned.
Garzoli, S.L., and S.G.H. Philander. Validation of an equatorial
Atlantic simulation model using inverted echo sounder data. Journal
of Geophysical Research, 90(C5):9199-9201 (1985).
No abstract.
Goldenberg, S.B., S.D. Aberson, and R.E. Kohler. Incorporation of Omega
dropwindsonde data into SANBAR: An operational barotropic hurricane-track
forecast model. Preprints, 16th Conference on Hurricanes and Tropical
Meteorology, Houston, TX, May 14-17, 1985. American Meteorological
Society, Boston, 44-45 (1985).
No abstract.
Govoni, J.J., A.J. Chester, D.E. Hoss, and P.B. Ortner. An observation of
episodic feeding and growth of larval Leiostomus xanthurus in the
northern Gulf of Mexico. Journal of Plankton Research,
7(1):137-146 (1985).
Four cruises were conducted in the northern Gulf of Mexico over two
spawning seasons of the sciaenid fish Leiostomus xanthurus. On
only one occasion did unusually high densities of larvae and their
principal microzooplanktonic foods co-occur. Peak densities of larvae
and microzooplankton were observed in a thin lens of cool surface water
that characterized a hydrographic discontinuity, and all larvae contained
high numbers of food organisms in their guts. Instantaneous exponential
growth rates, estimated from measurements of otolith growth increments,
indicated accelerated growth on the day that larvae were collected. A
laboratory experiment verified that larval L. xanthurus responds
to an increased ration with accelerated growth that is detectable in
otoliths. Together these data suggest that the spatial distribution of
L. xanthurus larvae and their microzooplanktonic food is patchy
and that interactions of larvae and microzooplankton may be episodic.
Hansen, D.V. Eastern tropical Pacific thermocline topography during
1982-1983. In El Niño Atlas, 1982-1983, A. Leetmaa and J.
Witte (eds.), Chapter 12, Government Printing Office, 131-134 (1985).
No abstract.
Hansen, D.V. Large-scale aspects of oceanic and atmospheric conditions
associated with the 1982-1983 El Niño. Rev. Com. Perm. Pacifico
Sur, 15:49-65 (1985).
An unprecedented set of oceanic and atmospheric data are available to
complement those made in the ERFEN region for description of the El
Niño of 1982-1983. These data show that anomalies of sea level
atmospheric pressure, precipitation, and winds appeared in the western
Pacific Ocean as early as May 1982, and moved eastward across the ocean
to the coast of South America. These atmospheric anomalies were associated
with observed sea surface temperature and circulation anomalies in the
eastern Pacific Ocean. Movements of satellite-tracked drifting buoys
reveal that the South Equatorial Current near the equator flowed with
less than normal strength during the entire period from August 1982
through June 1983 and actually reversed dring December 1982 and from
mid-April through early June 1983. The temporal evolution of
near-equatorial water movements is similar to the sea surface temperature
and sea level anomalies observed east of the Galapagos Islands. By
December 1983, almost all of the anomalies associated with El Niño
had returned to near normal values.
Hansen, D.V., M.C. Pazos, and R. Allen. Movements of satellite-tracked
drifting buoys in the eastern equatorial Pacific during 1982-1983. In
El Niño Atlas, 1982-1983, A. Leetmaa and J. Witte (eds.),
Chapter 8, Government Printing Office, 89-102 (1985).
No abstract.
Hendee, J.C., and G. Mueller. Histology of the adenohypophysis of the
kelp greenling, Hexagrammus decagrammus (Hexagrammidae).
Journal of Fisheries Biology, 27(3):273-276 (1985).
No abstract.
Houze, R.A., F.D. Marks, R.A. Black, P.T. Willis, and J.F. Gamache.
Airborne Doppler and cloud microphysical measurements in Hurricane Norbert.
Preprints, 16th Conference on Hurricanes and Tropical Meteorology,
Houston, TX, May 14-17, 1985. American Meteorological Society, Boston,
5-6 (1985).
No abstract.
Katsaros, K.B., L.A. McMurdie, R.J. Lind, and J.E. deVault. Albedo of a
water surface, spectral variation, effects of atmospheric transmittance,
sun angle, and wind speed. Journal of Geophysical Research,
90(C4):7313-7321 (1985).
In this study, the authors examine the albedo's dependence on
transmittance (cloudiness) and solar altitude using observations obtained
from aircraft and a ship in the Joint Air-Sea Interaction (JASIN)
experiment, from a ship in the GARP Atlantic Tropical Experiment (GATE,
where GARP is the Global Atmospheric Research Program), and from an
instrumented mast located in Lake Washington (Seattle, Washington). These
results are then analyzed.
Lawson, L.M., D.A. Seem, D.R. Palmer, and Y.-H. Daneshzadeh. A computer
code for calculating acoustic ray paths with application to the Straits
of Florida. NOAA Technical Memorandum, ERL AOML-62, 142 pp. (1985).
Ocean acoustic tomography is an attractive candidate for monitoring the
heat transport in the Florida Current. The feasibility of this application
of tomography depends on the ability to identify individual ray paths.
Although experience shows that paths can be identified with deep ocean
propagation, the ray path structure in the Florida Straits is quite
different. There the sound speed is such that a ray path which travels
a modest distance necessarily experiences bottom bounces. To investigate
the question of ray path identification, a fast, specialized ray-tracing
program was developed. Using this code, we analyzed the fluctuations in
ray path geometry resulting from small perturbations in the bathymetry.
This report describes the computer code, documents the historical data,
and the numerous ray-tracings calculated for the Florida Straits.
Leetmaa, A., and W.D. Wilson. A diagnostic analysis of a 1982-1983 El
Niño simulation. EOS, Transactions, American Geophysical Union,
66(46):830 (1985).
No abstract.
Leetmaa, A., and W.D. Wilson. Ametek-Straza data from the eastern Pacific.
In El Niño Atlas, 1982-1983, A. Leetmaa and J. Witte (eds.),
Chapter 13, Government Printing Office, 135-148 (1985).
No abstract.
Leetmaa, A., and W.D. Wilson. Characteristics of near surface circulation
patterns in the eastern equatorial Pacific. Progress in Oceanography,
14:339-352 (1985).
Since June 1981 several CTD and velocity profiler sections have been made
across the equator at 85°W as part of the Equatorial Pacific Ocean
Climate Studies (EPOCS). Two of these sections, those in June 1981 and
December 1982, are discussed in order to characterize the circulation
patterns that occur when the ocean is forced by meridional wind stress.
In this area the winds are predominantly southerly. Use of an
Ametek-Straza acoustic Doppler backscatter profiler during the 1982
cruise gave velocity data to a depth of 270 m every 5.5 km along the
shiptrack. This allowed the shear and velocity fields to be examined
in greater detail than had been possible before. Large areas had shears
greater than 0.01 s-1 were observed. Greatest shears tended
to coincide with regions of large vertical density gradients. Comparisons
with geostrophic computations suggest that a large fraction of the shear
was geostrophic. Richardson number computations indicated that over 40%
of the area sampled by theCTD casts had values of less than 1 and about
5% had values less than one quarter. Values of less than one quarter
were concentrated in the mixed layer but were not confined to it. Below
the mixed layer, regions with low Richardson number were associated with
regions where the vertical density gradient was quasi-linear. Since such
regions were not confined to the vicinity of the equator, these
observations suggest shear mixing as an important mechanism over large
areas of the upper ocean. Within the top 40 m of the water column there
was a general tendency for motions in the mixed layer to be to the left
of the wind in the southern hemisphere and to the right in the northern
hemisphere. However, no clear examples were found of Ekman spirals. Most
of the veering was confined to the mixed layer which was of relatively
constant depth over the whole survey area. South of the equator a large
fraction of the shear across the base of the mixed layer appeared to be
geostrophic, whereas north of the equator, these shears were ageostrophic.
Estimates of the various terms in the momentum equation in the upper
ocean indicated that near the equator non-linear effects, such as
upwelling and northward advection, were as important as Coriolis forces,
pressure gradients, and wind stress. The pressure gradient, integrated
over the depth quarter, were concentrated in the mixed layer but were not
confined to it. Below the mixed layer, regions with low Richardson number
were associated with regions where the vertical density gradient was
quasi-linear. Since such regions were not confined to the vicinity of
the equator, these observations suggest shear mixing as an important
mechanism over large areas of the upper ocean. Within the top 40 m of the
water column there was a general tendency for motions in the mixed layer
to be to the left of the wind in the southern hemisphere and to the
right in the northern hemisphere. However, no clear examples were found
of Ekman spirals. Most of the veering was confined to the mixed layer
which was of relatively constant depth over the whole survey area. South
of the equator a large fraction of the shear across the base of the mixed
layer appeared to be geostrophic, whereas north of the equator, these
shears were ageostrophic. Estimates of the various terms in the momentum
equation in the upper ocean indicated that near the equator non-linear
effects, such as upwelling and northward advection, were as important as
Coriolis forces, pressure gradients, and wind stress. The pressure
gradient, integrated over the depth of the mixed layer, was larger than
the stress in the vicinity of the equator and the relative importance of
other terms varied from place to place. The horizontal scale of variation
was as small as 10 km. Near surface upwelling occurred in shallow cells
with horizontal dimensions of 100 km or less.
Lewis, J.M., C.M. Hayden, C.S. Velden, T.R. Stewart, S.J. Lord, S.B.
Goldenberg, and S.D. Aberson. The use of VAS winds and temperatures as
input to barotropic hurricane-track forecasting. Preprints, 16th
Conference on Hurricanes and Tropical Meteorology, Houston, TX, May
14-17, 1985. American Meteorological Society, Boston, 40-41 (1985).
No abstract.
Li, Y.-H., T.-H. Peng, and W.S. Broecker. A reply to the paper by
Austin and Green, "The role of baroclinic eddies in mixing tritium
into the oceanic gyres." Tellus, 37B:186-187 (1985).
No abstract.
Marks, F.D. Evolution of the structure of precipitation in Hurricane
Allen (1980). Monthly Weather Review, 113:909-930 (1985).
Reflectivity data from the airborne radar systems on board the three NOAA
aircraft were gathered during six consecutive days in Hurricane Allen of
1980. The data have been used to specify the horizontal and vertical
precipitation distribution within 111 km radius of the hurricane center.
The evolution of the structure and intensity of the precipitation in the
storm is described from representative time composite radar maps for seven
research flights made during the six-day period. The eyewall was
characterized by a narrow ring (12-15 km wide) of intense reflectivity
(42-47 dBZ) surrounding the center of the storm at a radius that varied
in time from 12-40 km. The eyewall had steep radial gradients of
reflectivity (4-5 dB km-1) and tilted radially outward in
height. The rain bands were characterized by areas of enhanced reflectivity
embedded in a region of stratiform rainfall that contained a distinct
bright band at the height of the 0°C isotherm. The most striking
changes in structure during the six-day period were the rapid contraction
in eyewall radius and the devleopment of a secondary ring of intense
reflectivity 80-100 km from the storm center. These changes in eye radius
appeared to be related to the vortex evolution, as discussed by
Willoughby and others. Changes in storm intensity, coincident with the
eyewall radius changes, seemed to have little effect on the total storm
rainfall or latent heat release. The maximum storm rainfall occurred when
the storm had a double eyewall structure. After the period of the double
eyewall, the mean rain rate in the eyewall increased as the storm
approached maximum intensity. However, coincident with the increase in
eyewall rain rate, the eyewall area decreased, resulting in little
change in the total storm rainfall. The sequence of time composites
provided the first opportunity to describe, quantitatively, the
precipitation distribution within 111 km of the center of a mature
hurricane that was away from land influences. The rainfall analysis showed
that the mean rain rates in the eyewall were a factor of 6 greater than
those outside the eyewall (11.3 mm h-1 versus 1.8 mm
h-1), but because the eyewall region encompassed such a small
area, it only contributed 40% of the total rainfall within a radius of
1° latitude of the storm center. The precipitation distribution
around the storm was asymmetric; more rainfall occurred ahead of the
storm than behind. In general, the maximum precipitation in the eyewall
region was within 15-20° of the storm track. The maximum rainfall
in the rainband region was 40-50° to the right of that in the eyewall.
Marmolejo, E., J.F. Festa, and R.L. Molinari. Heat budget and climatic
atlas of the equatorial Atlantic Ocean during FGGE (1979). NOAA Technical
Memorandum, ERL AOML-61, 76 pp (1985).
No abstract.
Maul, G.A., D.A. Mayer, and S.R. Baig. Comparisons between a
continuous three-year current-meter observation at the sill of the
Yucatan Strait, satellite measurements of Gulf Loop Current area,
and regional sea level. Journal of Geophysical Research,
90(C5):9089-9096 (1985).
From October 1977 through November 1980 a current-meter mooring was
maintained in the Yucatan Strait. The meter was moored halfway between
Mexico and Cuba, 145 m above the sill or in 1895 m of water. Motions
of low frequency (<14-1 cycles/day) are oriented
approximately parallel to the isobaths, 021°-030° true.
Net drift for three years is to the south-southwest at an average
velocity of 1.8 cm s-1. Sustained southward flows at
intervals of eight months, which persisted for several months each,
have average velocities of 5 cm s-1, with randomly spaced
bursts as high as 15 cm s-1. Energy in subtidal frequency
bands has significant peaks near 38-1 and 19-1
cycles/day, with a broad band of energy between 300-1 and
200-1 cycles/day. The latter peak is consistent with the
approximately eight-month interval between the southward flow events.
Comparison with weekly areal coverage of the Gulf Loop Current from
Geostationary Operational Environmental Satellite infrared observations
shows little covariation, except that eight months is typical of some
anticyclonic eddy generation. There is little coherence of sill depth
velocities with Naples sea level at subtidal frequencies, but with
Miami there is coherence at several frequencies, notably
38-1 and 19-1 cycles/day. In the higher
frequencies, the principal tidal motions are diurnal and are oriented
somewhat across the isobaths toward the northwest, 346°-349°
true, with counterrotating O1 and K1
constituents. No semidiurnal, inertial, or fortnightly energy is
observed above the background continuum.
Maul, G.A., F. Chew, M.H. Bushnell, and D.A. Mayer. Sea level variation
as an indicator of Florida Current volume transport: Comparisons with
direct measurements. Science, 227(4684):304-307 (1985).
Sea level measurements from tide gauges at Miami, Florida, and Cat Cay,
Bahamas, and bottom pressure measurements from a water depth of 50 m off
Jupiter, Florida, and a water depth of 10 m off Memory Rock, Bahamas,
were correlated with 81 concurrent direct volume transport observations
in the Straits of Florida. Daily-averaged sea level from either gauge on
the Bahamian side of the Straits was poorly correlated with transport.
Bottom pressure off Jupiter had a linear coefficient of determination of
r2 = 0.93, and Miami sea level, when adjusted for weather
effects, had r2 = 0.74; the standard errors of estimating
transports were ±1.2 × 106 cubic meters per second,
respectively. A linear multivariate regression, which combined bottom
pressure, weather, and the submarine cable observations between Jupiter
and the Bahamas, had r2 = 0.94 with a standard error of
estimating transport of ±1.1 × 106 cubic meters per
second. These results suggest that a combination of easily obtained
observations is sufficient to adequately monitor the daily volume
transport fluctuations of the Florida Current.
Molinari, R.L. Heat balances of the surface mixed layer in the equatorial
Atlantic and Indian Oceans during FGGE. In Proceedings, First
National Workshop on the Global Weather Experiment, National Academy
Press, 779-789 (1985).
No abstract.
Molinari, R.L., J.F. Festa, and E. Marmolejo. Evolution of sea-surface
temperature and surface meteorological fields in the tropical Atlantic
Ocean during FGGE, 1979: Part I. Description of surface fields and
computation of surface energy fluxes. Progress in Oceanography,
14:401-420 (1985).
Observations of surface oceanographic and meteorological fields collected
during the First GARP Global Experiment (FGGE) in the equatorial Atlantic
Ocean have been combined and averaged by month onto a 2° ×
2° grid. Monthly distributions of sea-surface temperature, wind
speed and direction, air temperature, specific humidity, and cloud cover
have been generated for the period from December 1978 through November
1979. Net short wave and long wave radiation, and sensible and latent
heat flux distributions have been generated from the surface data using
the bulk aerodynamic formulas. In 1979, large-scale patterns of all the
climatic and heat budget variables are very similar to distributions
determined from long-term climatological averages. Positive anomalies
of SST in the region of the equatorial cold water tongue represent
some region of systematic differences between the 1979 and climatological
distributions. The positive SST anomalies are, in general, coincident with
negative anomalies in the net oceanic heat gain. Negative heat gain
anomalies are primarily caused by positive wind speed anomalies, through
increased latent and sensible heat fluxes.
Molinari, R.L., J.F. Festa, and E. Marmolejo. Evolution of sea-surface
temperature in the tropical Atlantic Ocean during FGGE, 1979: Part II.
Oceanographic fields and heat balance of the mixed layer. Journal of
Marine Research, 43:67-81 (1985).
Surface meteorological and surface and subsurface oceanographic data
collected during 1979 are used to describe sea-surface temperature, mixed
layer depth, zonal current component, and net oceanic heat gain fields and
to estimate the terms in a heat balance relation for the mixed layer. The
terms are evaluated monthly on a 6° of latitude by 10° of
longitude grid which covers the equatorial Atlantic from 9°S to
9°N. The first balance tested is between changes in mixed layer
temperature and surface energy fluxes. These fluxes can account for more
than 75% of the variance in the original time series of the quadrangles
along 6°S. Variance reductions are less along 10° (order of 50%)
and 6°N (less than 25%). The addition of zonal advection improves
some of the predictions but not significantly. Low variance reductions
along 6°N, west of 20°W, are attributed to the uncertainties
in the estimates of observed temperature change and surface fluxes. The
small variance reductions east of 20°W, at 6°N and along 0°,
may be related to the neglect of coastal and equatorial upwelling and
meridional advection. A simple model is proposed which assumes an annual
cycle for the intensity of mixing across the base of the mixed layer, most
intense during summer, least intense during winter. Variance reductions
at 0°, 5°W increase from 20% to 60% with the inclusion of mixing.
Meridional advection may also account for a portion of the observed
variability in mixed layer temperature.
Molinari, R.L., W.D. Wilson, and K. Leaman. Volume and heat transports of
the Florida Current: April 1982 through August 1983. Science,
227(4684):295-297 (1985).
Absolute velocity and temperature profiles are used to estimate the volume
transport through the Straits of Florida and, in combination with historical
midbasin data, to estimate the total meridional heat flux through a section
at 27°N. The mean annual volume transport of the Florida Current from
April 1982 through August 1983 is 30.5 (+1) × 106 cubic
meters per second. The net northward heat flux through the 27°N section
is 1.2 (±0.1) × 1015 watts. The volume transport is
characterized by high values in the late spring and early summer and low
values in the late fall and early winter. There is a similar cycle in total
heat flux.
Molinari, R.L., G.A. Maul, F. Chew, W.D. Wilson, M.H. Bushnell, D.A. Mayer,
K. Leaman, F. Schott, T. Lee, R. Zantopp, J. Larsen, and T. Sanford.
Reports: Subtropical Atlantic Climate Studies: Introduction. Science,
227(4684):292-294 (1985).
This report is an introduction to the accompanying collection of reports
that present the results of a two-year period of intensive monitoring of
the Florida Current. Both direct observing systems (ship-deployed current
profilers and moored current meters) and indirect observing systems (coastal
tide gauge stations, bottom pressure gauge arrays, a submarine cable,
acoustic arrays, and radar installations) were used to measure temperature
and volume transport.
Oakley, S.A., I.W. Duedall, J.H. Parker, and J.R. Proni. Continuous
measurements of the dispersion of sewage sludge. In Wastes in the
Ocean, Volume 6, I.W. Duedall, D.R. Kester, P.K. Parke, and B.H.
Ketchum (eds.), Wiley, New York (1985).
No abstract.
Ooyama, K.V. The polar representation of tensor cross-spectra of winds.
Preprints, 16th Conference on Hurricanes and Tropical Meteorology,
Houston, TX, May 14-17, 1985. American Meteorological Society, 182-183
(1985).
No abstract.
Palmer, D.R., L.M. Lawson, D.A. Seem, and Y.-H. Daneshzadeh. Ray path
identification and acoustic tomography in the Straits of Florida. Journal
of Geophysical Research, 90(C3):4977-4989 (1985).
The Florida Current, which flows through the Straits of Florida, transports
a significant fraction of the heat which must be transferred from low to
high latitudes in order for the earth to remain in thermal balance. While
ocean acoustic tomography is an attractive candidate for monitoring this
heat transport, its use is dependent on being able to identify individual
ray paths. All published investigations of tomography have been concerned
with deep-ocean propagation where experience has shown that paths can be
identified. Propagation in the Straits is quite different from deep-ocean
propagation, however. The sound speed is such that a ray path which travels
modest distances necessarily experiences bottom bounces. It is not clear,
a priori, that paths can be identified in the Straits. We report the
results of an investigation of this question. Using a fast, specialized
ray-tracing program, we analyzed the fluctuations in ray path geometry
resulting from small perturbations in the bathymetry. We found that the
topographic features amplify these fluctuations to such a degree that
identification of individual rays becomes impossible after only a few
bottom bounces. Consequently, there is no adequate interpretive tool for
relating an acoustic signal recorded more than a few tens of kilometers
from a source to the heat transport, i.e., for carrying out the
tomographic inversion. We propose a way of overcoming this identification
problem based on the use of acoustic profilers.
Paul, C.A., and M.C. Pazos. Data for EPOCS/FGGE drifting buoys: February
1979 through October 1980. NOAA Data Report, ERL AOML-4, 157 pp. (1985).
No abstract.
Pazos, M.C., and C.E. Acero. Drifting buoy data from the equatorial
Pacific Ocean for the period November 1, 1981 through December 31, 1983.
NOAA Data Report, ERL AOML-7, 245 pp. (1985).
No abstract.
Peng, T.-H. Application of box models for geochemical modeling of
ocean. Journal of the National Bureau of Standards, 90:530
(1985).
No abstract.
Peng, T.-H. Atmospheric CO2 variations based on tree
ring 13C data. In The Carbon Cycle and Atmospheric
CO2: Natural Variations--Archean to Present, E.T.
Sundquist and W.S. Broecker (eds.). Geophysical Monograph 32, AGU,
123-131 (1985).
The reconstruction of atmospheric CO2 concentrations over the
last 150 years, based on a deconvolution of the tree-ring-based
13C record, is reviewed. Assuming that Freyer's latest
composite 13C record for the northern hemisphere represents
global changes in the 13C/12C ratio of atmospheric
CO2 induced by changes in atmospheric CO2
concentration due to deforestation, soil manipulation, and combustion of
fossil fuels, the deconvolution, using the modified box-diffusion model,
gives the following results: (1) the magnitude of the integrated
CO2 release from the terrestrial biosphere since 1800 is
about 90% of that from fossil fuel; (2) over the two-decade period
covered by the Mauna Loa atmospheric CO2 record, the input
from the forest-soil source is about 15% of that from fossil fuels; (3)
the 13C/12C trend and the atmospheric
CO2 anomaly over the last two decades have been dominated by
the input of fossil fueld CO2; and (4) the pre-1850
atmospheric CO2 content is estimated to be about 266 ppm.
The integrated amount of CO2 released from the terrestrial
biosphere between A.D. 1800 and 1980 is estimated to be 12 ×
1015 mol which is to be compared with the previous estimate
of 22 × 1015 mol on the basis of Freyer and Belacy's
(1983) 13C data. This indicates that tree-ring
13C-based estimates are volatile and further changes are
likely.
Peng, T.-H., and W.S. Broecker. PANDORA: An eleven-box geochemical
model of the world ocean. In Carbon Dioxide Transfer in the
Atmosphere-Ocean-Terrestrial System, R.S. Keir and W.H. Berger
(eds.). Scripps Institution of Oceanography, SIO Reference 85-31,
113-121 (1985).
No abstract.
Peng, T.-H., and W.S. Broecker. The utility of multiple tracer
distributions in calibrating models for uptake of anthropogenic
CO2 by the ocean thermocline. Journal of Geophysical
Research, 90(C4):7023-7035 (1985).
Two-dimensional thermocline ventilation models for the temperate North
Atlantic with differing circulation patterns were calibrated to yield a
tritium distribution similar to that observed during the GEOSECS survey.
These models were then run for 3He, bomb-produced
14C, radiokrypton, and freons. They were also run for the
uptake of fossil fuel CO2. While the models differ
significantly in their ability to match the observed 3He and
14C distributions, these differences are not large enough to
clearly single out one model as superior. This insensitivity of
tracer-to-tracer ratio to model design is reflected by the near identity
of the fossil fuel CO2 uptake by the various models. This
result suggests that the uptake of CO2 by the sea is limited
more by the rates of physical mixing within the sea than by gas exchange
across the sea surface. If so, then the hope that models employing
outcropping isopycnals will enhance the CO2 uptake by the sea
and thereby lead to a narrowing in the gap that exists for anthropogenic
CO2 budgets is not well founded. The interim strategy of using
reservoir models calibrated by tracer distributions appears to be sound.
Peterson, D.H., and J.F. Festa. Numerical simulation of phytoplankton
productivity in partially mixed estuaries. Estuarine, Coastal, and
Shelf Science, 19:563-589 (1985).
A two-dimensional steady-state model of light-driven phytoplankton
productivity and biomass in partially mixed estuaries has been developed.
Effects of variations in river flow, suspended sediment concentration,
phytoplankton sinking, self-shading, and growth rates on distributions of
phytoplankton biomass and productivity are investigated. Numerical
simulation experiments show that biomass and productivity are particularly
sensitive to variations in suspended sediment concentrations typical of
natural river sources and to variations in loss rates assumed to be
realistic but poorly known for real systems. Changes in the loss rate term
within the range of empirical error (such as from dark bottle incubation
experiments) cause phytoplankton biomass to change by a factor of two.
In estuaries with adequate light pentration in the water column, it could
be an advantage for phytoplankton to sink. Species that sink increase their
concentration and form a phytoplankton maximum in a way similar to the
formation of the estuarine turbidity maximum. When attenuation is severe,
however, sinking species have more difficultty in maintaining their
population.
Philander, G., D. Halpern, D.V. Hansen, R. Legeckis, L. Miller, C.A. Paul,
R. Watts, R. Weisberg, and M. Wimbush. Long waves in the equatorial
Pacific Ocean. EOS, Transactions, American Geophysical Union,
66(14):154 (1985).
Westward traveling waves with a period of three weeks and a wavelength of
1000 km appear in the central and eastern equatorial Pacific Ocean during
periods of intense trade winds and strong surface currents. Recent
measurements of the structure of these waves confirm that they are caused
by instabilities associated primarily with the latitudinal shear of the
surface currents.
Powell, M.D. Airborne Doppler radar observations of the hurricane boundary
layer. Preprints, 16th Conference on Hurricanes and Tropical
Meteorology, Houston, TX, May 14-17, 1985. American Meteorological
Society, 3-4 (1985).
No abstract.
Ratnaswamy, M., W.D. Wilson, and R.L. Molinari. Current velocity and
hydrographic observations in the Straits of Florida: Subtropical Atlantic
Climate Study (STACS), 1983-1984. NOAA Data Report, ERL AOML-5, 242 pp.
(1985).
No abstract.
Thompson, O.E., P. Stephens, H.A. Friedman, and D. Houghton. Annual
Report, 1984: Commission on Education and Manpower. American
Meteorological Society, Boston, Massachusetts (published for limited
distribution) (1985).
The various boards and committees of the AMS Commission on Education and
Manpower were active during 1984, conducting open meetings in conjunction
with the annual AMS meeting and transacting business by telephone and mail.
The various recommendations, initiatives, activities, and appointments are
briefly summarized in sections B-E of this report. Board annual reports
and publications of the commission are included as sections F-G and I-K,
respectively.
Trefry, J.H., R.P. Trocine, and J.R. Proni. Drilling-fluid discharges into
the northwestern Gulf of Mexico. In Wastes in the Ocean, Volume 4,
I.W. Duedall, D.R. Kester, P.K. Park, and B.H. Ketchum (eds.), Wiley, New
York, 196-222 (1985).
This chapter investigates the dispersion and fate of drilling-fluid
components discharged into the marine environmental with special focus
on the Texas Flower Garden Banks (Flower Gardens) area of the northwestern
Gulf of Mexico. Particulate Ba was found to be the best overall tracer of
drilling-fluid dispersion; however, routine monitoring of raw effluent for
dissolved and particulate Cr and Fe, total petroleum hydrocarbons, total
solids, and one other representative particulate trace metal (As, Cd, Hg,
or Pb) is also recommended. During field experiments, we observed: (1)
differential settling of the barite and clay components; (2) that the barite
component was less susceptible to resuspensoin than was normal sediment;
(3) that natural particle-rich layers can be distinguished from
drilling-related lenses; and (4) that the long-term, net directional
movement of the released fluids can be established. Near the coral reefs
of the Flower Gardens, drilling fluids are presently discharged to within
10 m of the bottom, a depth that is at least 100 m below the sea surface
and at least 80 m below the top of the reefs. Resuspension processes,
even during storms, do not carry bottom sediment, and thus the deposited
matter from drilling fluid, onto the living reef. Although the drilling
area to the north has higher than normal concentrations of Ba in the
sediment and in the suspended matter of the water column, no drilling-fluid
movement from that area to the Flower Gardens was observed. In fact,
Observed Ba enrichment in some surficial sediment samples taken 3-10 km
away from drilling areas may be due to a natural remobilization process.
Drilling-fluid-related increases in sedimentation rate and input of
different sediment types at the reef base remain as possible concerns.
Trefry, J.H., S.Metz, R.P. Trocine, and T.A. Nelsen. A decline in lead
transport by the Mississippi River. Science, 230(4724):439-441
(1985).
Inputs of pollutant lead to the Gulf of Mexico from the Mississippi River
have declined by about 40% within the past decade. This decrease has been
determined from annual lead loads of the Mississippi River and from the lead
record in Mississippi Delta sediments. The observed trend is consistent
with reduced consumption of lead in gasoline in the United States. More
than 90% of the riverborne lead is associated with suspended sediments.
Most of the particle-bound lead is deposited within 50 km of the river
mouth and is easily leached at pH values above 3.
Willis, P.T. Microphysics of a stratiform melting layer in Hurricane
Alicia. Preprints, 16th Conference on Hurricanes and Tropical
Meteorology, Houston, TX, May 14-17, 1985. American Meteorological
Society, Boston, 14-15 (1985).
No abstract.
Willis, P.T. Reply. Journal of the Atmospheric Sciences,
42:1349-1350 (1985).
No abstract.
Willis, P.T., and P. Tattleman. Model vertical profiles of extreme rainfall
rate, liquid water content, and drop-size distribution. Environmental
Research Papers, Air Force Geophysics Laboratory, No. 928, AFGL Technical
Report 85-022, Hanscom AFB, MA (1985).
This report provides a new model of hydrometeors and associated cloud-water
content from the surface to 20 km. The model profiles at altitude were
developed based on five surface rainfall rates: 36, 84, 168, 432, and
1872 mm/hr. The first three rates correspond to a frequency of occurrence
of 0.5%, 0.1%, and 0.01% of the time during the worst month in the most
severe area of the world for intense rainfall. The last two are the 42-
and 1-min world record rainfalls. The surface rainfall rates were
extrapolated aloft using results from previous studies. A large sample
of drop-size distributions from intense rainfall collected during
reconnaissance of Atlantic hurricanes/tropical storms was analyzed. The
data set was normalized and fit by a gamma distribution. This was used to
specify the drop-size distributions and liquid water content for rainfall
rates specified at the surface and aloft. Concurrent cloud-water content
was estimated. Results are presented at 2 km intervals.
Willoughby, H.E. Confirmatory observations of concentric eyes in hurricanes.
Preprints, 16th Conference on Hurricanes and Meteorology, Houston, TX,
May 14-17, 1985. American Meteorological Society, Boston, 1-2 (1985).
No abstract.
Willoughby, H.E., D.P. Jorgensen, R.A. Black, and S.L. Rosenthal.
Project STORMFURY: A scientific chronicle, 1962-1983. Bulletin
of the American Meteorological Society, 66:505-514 (1985).
Between 1962 and 1983, research in hurricane modification centered on an
ambitious experimental program, Project STORMFURY. The proposed modification
technique involved artificial stimulation of convection outside the eyewall
through seeding with silver iodide. The artificially invigorated convection,
it was argued, would compete with the convection in the original eyewall,
lead to reformation of the eyewall at larger radius, and thus produce a
decrease in the maximum wind. Since a hurricane's destructive potential
increases rapidly as its maximum wind becomes stronger, a reduction as small
at 10% would have been worthwhile. Modification was attempted in four
hurricanes on eight different days. On four of these days, the winds
decreased by between 10 and 30%. The lack of response on the other days
was interpreted to be the result of fault execution of the experiment or
poorly selected subjects. These promising results have, however, come into
question because recent observations of unmodified hurricanes indicate: (1)
that cloud seeding has little prospect of success because hurricanes contain
too much natural ice and too little supercooled water; and (2) that the
positive results inferred from the seeding experiments in the 1960s probably
stemmed from inability to discriminate between the expected effect of human
intervention and the natural behavior of hurricanes.
Wilson, W.D., C. Roffer, and G.G. Thomas. Pegasus current profiler
measurements collected for EPOCS, 1980-1983. NOAA Data Report, ERL
AOML-6, 178 pp. (1985).
Current velocity profiles recorded on nine AOML EPOCS (Equatorial Pacific
Ocean Climate Studies) cruises during 1980-1983 using the Pegasus profiler
are presented. The data were collected along several equatorial transects
from 85°W to 110°W. Station locations and current profiles are
shown for each cruise; the instrument and techniques of data acquisition
and processing are also described.