**2004**
Chave, A.D., D.S. Luther, and C.S. Meinen. Correction of motional electrical
field measurements for galvanic distortion. Journal of Atmospheric and
Oceanic Technology, 21(2):317-330 (2004).
Interactions between motional electric fields and lateral gradients in
electrical conductivity (e.g., seafloor topography) produce boundary
electric charges and galvanic (i.e., noninductive) secondary electric
fields that result in frequency-independent changes in the electric field
direction and amplitude that are specific to a single location. In this
paper, the theory of galvanic distortion of the motional electric field is
developed from first principles and a procedure to correct for it is then
derived. The algorithm is based on estimation of intersite transfer tensors
for the horizontal electric fields at the high frequencies where external
(ionospheric and magnetospheric) sources, not oceanic motionally induced
electric fields, dominate. A decomposition of each measured tensor is
derived that expresses it as the product of a set of distortion tensors and
the underlying, undistorted transfer tensor. The algorithm may be applied
simultaneously to a set of sites and assessed statistically, yielding the
undistorted electric field uniquely at each site except for a single
site-dependent multiplicative scalar, which must be obtained from other
data. Because the distortion is frequency independent, the same tensors
may be used to undistort the low-frequency, motional induction components
that are of interest in oceanography. This procedure is illustrated using
an electric field dataset collected in the Southern Ocean in 1995-97, which
is significantly distorted by galvanic processes.
Coale, K.H., K.S. Johnson, F.P. Chavez, K.O. Buesseler, R.T. Barber, M.A.
Brzezinski, W.P. Cochlan, F.J. Millero, P.G. Falkowski, J.E. Bauer, R.H.
Wanninkhof, R.M. Kudela, M.A. Altabet, B.E. Hales, T. Takahashi, M.R.
Landry, R.R. Bidigare, X. Wang, Z. Chase, P.G. Strutton, G.E. Friederich,
M.Y. Gorbunov, V.P. Lance, A.K. Hilting, M.R. Hiscock, M. Demarest, W.T.
Hiscock, K.F. Sullivan, S.J. Tanner, R.M. Gordon, C.N. Hunter, V.A. Elrod,
S.E. Fitzwater, J.L. Jones, S. Tozzi, M. Koblizek, A.E. Roberts, J.
Herndon, J. Brewster, N. Ladizinsky, G. Smith, D. Cooper, D. Timothy, S.L.
Brown, K.E. Selph, C.C. Sheridan, B.S. Twining, and Z.I. Johnson. Southern
Ocean Iron Enrichment Experiment: Carbon cycling in high and low Si waters.
Science, 304(5669):408-414 (2004).
The availability of iron is known to exert a controlling influence on
biological productivity in surface waters over large areas of the ocean and
may have been an important factor in the variation of the concentration of
atmospheric carbon dioxide over glacial cycles. The effect of iron in the
Southern Ocean is particularly important because of its large area and
abundant nitrate, yet iron-enhanced growth of phytoplankton may be
differentially expressed between waters with high silicic acid in the south
and low silicic acid in the north, where diatom growth may be limited by both
silicic acid and iron. Two mesoscale experiments, designed to investigate the
effects of iron enrichment in regions with high and low concentrations of
silicic acid, were performed in the Southern Ocean. These experiments
demonstrate iron's pivotal role in controlling carbon uptake and regulating
atmospheric partial pressure of carbon dioxide.
Dunion, J.P., and C.S. Velden. The impact of the Saharan air layer on
Atlantic tropical cyclone activity. Bulletin of the American
Meteorological Society, 85(3):353-365 (2004).
A deep well-mixed, dry adiabatic layer forms over the Sahara Desert and
Shale regions of North Africa during the late spring, summer, and early
fall. As this air mass advances westward and emerges from the northwest
African coast, it is undercut by cool, moist low-level air and becomes the
Saharan air layer (SAL). The SAL contains very dry air and substantial
mineral dust lifted from the arid desert surface over North Africa, and is
often associated with a midlevel easterly jet. A temperature inversion
occurs at the base of the SAL where very warm Saharan air overlies
relatively cooler air above the ocean surface. Recently developed
multispectral Geostationary Operational Environmental Satellite (GOES)
infrared imagery detects the SAL's entrained dust and dry air as it moves
westward over the tropical Atlantic. This imagery reveals that when the
SAL engulfs tropical waves, tropical disturbances, or preexisting tropical
cyclones (TCs), its dry air, temperature inversion, and strong vertical
wind shear (associated with the midlevel easterly jet) can inhibit their
ability to strengthen. The SAL's influence on TCs may be a factor in the TC
intensity forecast problem in the Atlantic and may also contribute to this
ocean basin's relatively reduced level of TC activity.
Forde, E.B. Severe weather. Science Scope, 27(7):33-35 (2004).
No abstract.
Forde, E.B. Severe weather. The Science Teacher, 71(4):42-44
(2004).
No abstract.
Garzoli, S.L., A. Ffield, W.E. Johns, and Q. Yao. North Brazil Current
retroflection and transports. Journal of Geophysical Research,
109(C1):1013, doi:10.1029/2003JC001775 (2004).
A subset of data collected as a part of a larger program, the North Brazil
Current Rings (NBCR) Experiment, is analyzed to study the variability of
the transport of the North Brazil Current (NBC) and its relation with the
shedding of rings. It is concluded that there is a direct relation between
the latitude of penetration, the number of rings shed, and the intensity
of the NBC. The data set consists of dynamic height time series derived
from three inverted echo sounders and a shallow pressure gauge deployed
along a section perpendicular to the South American coast between the
continent and 7°N, and between 48° and 45°W. Velocity and
hydrographic data collected during the NBCR cruises are also analyzed and
used to validate the results. The 15-month mean transport of the NBC is
16 ± 2 Sv. The 18-month mean of the retroflected southeastward flow is 22
± 2 Sv. Both flows display considerable variability. The retroflected
southeast flow reaches its maximum value during September 1999, near the
time when the climatological North Equatorial Countercurrent (NECC) reaches
its maximum strength and it is minimum when the climatological NECC reverses
or is not present in the basin. The mean difference between the NBC flow
and the retroflected flow during August-December 1999 when the NECC is
fully established is -7 Sv. The excess in the retroflected flow is due to
North Atlantic water joining the retroflected flow from the South
Atlantic. The combination of both flows constitutes the NECC.
Grigorieva, N.G., G.M. Fridman, and D.R. Palmer. Investigation of
near-axial interference effects for propagation in a ducted waveguide.
Proceedings, Sixth International Conference on Theoretical and
Computational Acoustics, Honolulu, HI, August 11-15, 2003.
World Scientific Publishing, 6 pp. (2004).
The observed time-of-arrival patterns from a number of long-range ocean
acoustic propagation experiments show early geometrical-like arrivals
followed by a crescendo of energy that propagates along the sound-channel
axis and is not resolved into individual arrivals. To describe in a simple
model case the interference of near-axial waves which resulted in forming
the so-called axial wave and propose formulas for the axial wave in more
general cases, the two-dimensional reference point source problem for the
parabolic index of refraction squared is investigated. The integral
representation for the exact solution is transformed in such a way to
extract ray summands corresponding to rays radiated from the source at
angles less than a certain angle, the axial wave, and a term corresponding
to a sum of all the rays having launch angles greater than the indicated
angle. Numerical results for the axial wave are obtained for parameters
corresponding to long-range ocean acoustic propagation experiments.
Guo, L., J.-Z. Zhang, and C. Gueguen. Speciation and fluxes of nutrients
(N, P, Si) from the upper Yukon River. Global Biogeochemical
Cycles, 18(1):GB1038, doi: 10.1029/2003GB002152 (2004).
Water samples were collected from the Yukon River near the Stevens Village
Station from May to September 2002 and analyzed for nutrients (N, P, and
Si) in dissolved, particulate, organic, and inorganic forms to examine
temporal variations in nutrient concentrations, fluxes, and phase
partitioning. Both NO3 and PO4 concentrations in the
Yukon River were much lower than those of world rivers, with an average
concentration of 2.43 ± 0.63 µM-N and 0.053 ± 0.040 µM-P,
respectively. Si(OH)4 concentrations were more comparable to
those of world rivers, with an average concentration of 82 ± 21
µM-Si. Integrated annual fluxes were 2.4 x 108
mole-NO3, 3.4 x 106 mole-PO4, and 8.7 x
109 mole-Si(OH)4, respectively. Nutrient discharge
during the river ice open season contributed 73 to 95% of the annual flux
depending on nutrient species. Within the total N pool transported by the
Yukon River, dissolved inorganic N comprised 7 ± 4% and particulate N made
up 25 ± 10%, while dissolved organic N (DON) was the dominant N species
(with an average of 67 ± 10%). In contrast, P was predominantly
partitioned in the particulate phase (with an average of 94 ± 6%), leaving
4 ± 5% of the total P in the dissolved organic phase and ~2 ± 1% in
the dissolved inorganic phase. The partitioning of N and P indicates that
the transformation between dissolved and particulate or inorganic and
organic phases may play a critical role in controlling the flux of
bioavailable nutrients and thus the nutrient dynamics in the Yukon River
Basin and its coastal region. Nutrient specific fluxes normalized to
drainage area in the Yukon River Basin were 0.57 mmole/m2/yr
for NO3, 0.012 mmole/m2/yr for PO4, and
~19 mmole/m2/yr for Si(OH)4, respectively. The
relatively low specific fluxes of NO3 and PO4 in the
Yukon River Basin reflect its pristine status or little anthropogenic
influence, whereas cold climate in the Arctic/subarctic region may be
responsible for its lower Si(OH)4 specific flux, in agreement
with a general trend of increasing Si specific flux with decreasing
latitude in global river systems. A warming climate and thus deeper
permafrost active layer in the Yukon River watershed would likely enhance
the export flux of nutrients into the Bering Sea.
Hansell, D.A., H.W. Ducklow, A.M. Macdonald, and M.O. Baringer. Metabolic
poise in the North Atlantic Ocean diagnosed from organic matters transport.
Limnology and Oceanography, 49(4):1084-1094 (2004).
Recently there has been discussion about the metabolic state of the ocean,
with arguments questioning whether the open ocean is net autotrophic or
net heterotrophic. Accurately determining the metabolic balance of a
marine system depends on fully defining the system being evaluated and on
quantifying the inputs and outputs to that system. Here, a net northward
transport of dissolved organic carbon (DOC) (across 24.5°N) of 3.3 ±
1.9 Tmol C yr-1 was determined using basin-wide transport
estimates of DOC. This flux, coupled with DOC inputs from the Arctic Ocean
(2.2 ± 0.8 Tmol C yr-1), the atmosphere (0.6 ± 0.08 Tmol C
yr-1), and rivers (3.1 ± 0.6 Tmol C yr-1), indicates
net heterotrophy in the North Atlantic (full depth, 24.5-72°N) of 9.2
± 2.2 Tmol C yr-1. This rate is small (<2%) compared to
autochthonous production (~494 Tmol C yr-1) and
consumption (production:respiration of 0.98), indicating that the North
Atlantic is essentially metabolically balanced and that autochthonous
production is remineralized within the basin. The upper layer of the
subtropical gyre has previously been reported to exhibit high rates of net
heterotrophy, but our analysis does not support those findings. Instead,
allochthonous inputs of organic carbon to the upper subtropical gyre are
an order of magnitude less than required by the elevated rates of net
heterotrophy reported. We find, too, that net mineralization of
allochthonous DOC within the basin could account for 10% of the
preindustrial inorganic carbon exported from the basin to the south. Two
factors, the import of organic matter and the unique thermohaline
circulation pattern of the North Atlantic, are primary in ensuring net
heterotrophy in the basin.
Harasti, P.R., C.J. McAdie, P.P. Dodge, W.-C. Lee, J. Tuttle, S.T. Murillo,
and F.D. Marks. Real-time implementation of single-Doppler radar analysis
methods for tropical cyclones: Algorithm improvements and use with WSR-88D
display data. Weather and Forecasting, 19(2):219-239 (2004).
The NOAA/NWS/NCEP/Tropical Prediction Center/National Hurricane Center has
sought techniques that use single-Doppler radar data to estimate the
tropical cyclone wind field. A cooperative effort with NOAA/Atlantic
Oceanographic and Meteorological Laboratory/Hurricane Research Division
and NCAR has resulted in significant progress in developing a method
whereby radar display data are used as a proxy for a full-resolution base
data and in improving and implementing existing wind retrieval and
center-finding techniques. These techniques include the ground-based
velocity track display (GBVTD), tracking radar echoes by correlation
(TREC), GBVTD-simplex, and the principal component analysis (PCA) methods.
The GBVTD and TREC algorithms are successfully applied to the Weather
Surveillance Radar-1988 Doppler (WSR-88D) display data of Hurricane Bret
(1999) and Tropical Storm Barry (2001). GBVTD analyses utilized circulation
center estimates provided by the GBVTD-simplex and PCA methods, whereas
TREC analyses utilized wind center estimates provided by radar imagery and
aircraft measurements. GBVTD results demonstrate that the use of the storm
motion as a proxy for the mean wind is not always appropriate and that
results are sensitive to the accuracy of the circulation center estimate.
TREC results support a previous conjecture that the use of polar
coordinates would produce improved wind retrievals for intense tropical
cyclones. However, there is a notable effect in the results when different
wind center estimates are used as the origin of coordinates. The overall
conclusion is that GBVTD and TREC have the ability to retrieve the intensity
of a tropical cyclone with an accuracy of ~2 m s-1 or
better if the wind intensity estimates from individual analyses are
averaged together.
Hendee, J.C. The Coral Reef Early Warning System (CREWS): Marine
environmental monitoring to support research and marine sanctuary
management.In The Effects of Combined Sea Temperature, Light, and
Carbon Dioxide on Coral Bleaching, Settlement, and Growth, J.C. Hendee
(ed.). NOAA Research Special Report, Silver Spring, MD, 23-25 (2004).
No abstract.
Katsaros, K.B., and A.V. Soloviev. Vanishing sea surface temperature
gradients at low wind speeds. Boundary-Layer Meteorology,
112(2):381-396 (2004).
Sea surface temperature (SST) is a result of multiple interactions in
air-sea processes. During days with strong insolation and low wind speed,
there may be uneven net heating of the water layer near the surface of the
ocean, when there are horizontal temperature gradients at the sea surface.
Cooling of the water caused by evaporation, sensible, or longwave radiative
heat loss would be greater from warm water compared to that from relatively
colder water. As a result, under low wind speed conditions and clear skies,
the horizontal SST discontinuities, occurring at fronts, eddies, or in storm
wakes, may diminish or even vanish. This phenomenon is illustrated here with
some field and modeling results. The dependence of the difference in warming
on the cold and warm side of SST discontinuities is explored for its
dependence on latitude and mean environmental conditions. The time dependence
is important for the impact on remote sensing of SST, and it is found to be
short enough that substantial masking of SST gradients can occur during the
first six hours of the diurnal heating cycle, but the effect would continue
to grow if calm and solar heating persist for several subsequent days. An
integrated effect of this uneven net heating is seen in the seasonal masking
of subsurface temperature gradients in the Gulf of Mexico and Florida Straits.
Lawrence, D., M.J. Dagg, H. Liu., S.R. Cummings, P.B. Ortner, and C.R.
Kelble. Wind events and benthic-pelagic coupling in a shallow subtropical
bay in Florida. Marine Ecology Progress Series, 266:1-13 (2004).
During the winter months (December to April), the southeast United States
is influenced by continental air masses from the north or northwest which
pass at approximately 4 to 7 d intervals. These wind events can cause
suspension of bottom sediments in Florida Bay. Over a 9 d period in March
2001, we examined the effects of a wind-mixing event on the pelagic system
within the northwest part of Florida Bay, where water depth is 2 to 3 m.
This event caused significant suspension of bottom materials, large
increases in NH4 and PO4, smaller increases in
NO3+NO2 and Si(OH)4, a decrease in
microzooplankton abundance, and an increase in benthic copepods in the water
column. As wind speeds declined, there was a rapid decline in
PO4 concentration, gradual declines in suspended sediment,
NH4 and Si(OH)4, an increase in chlorophyll
a (chl a) stock, an increase in phytoplankton growth and
productivity, an increase in microzooplankton grazing rate, and a settling
of the benthic harpacticoid community. No grazing response was apparent in
the mesozooplankton community. The wind event clearly injected dissolved and
particulate benthic materials into the water column, where they directly
stimulated the bacterioplankton, phytoplankton and microzooplankton
communities within 1 to 2 d after the event. The water column was strongly
net heterotrophic at this time, suggesting a large input of dissolved
organic matter from the bottom. Stimulation of the pelagic food web continued
at least until we completed our study 6 d after the event. By the end of our
study, the water column was net autotrophic.
Manzello, D. A decade of SEAKEYS data: SST trends and patterns. In The
Effects of Combined Sea Temperature, Light, and Carbon Dioxide on Coral
Bleaching, Settlement, and Growth, J.C. Hendee (ed.). NOAA Research
Special Report, Silver Spring, MD, 35-36 (2004).
No abstract.
McFarquhar, G.M., and R.A. Black. Observations of particle size and phase
in tropical cyclones: Implications for mesoscale modeling of microphysical
processes. Journal of the Atmospheric Sciences, 61(4):422-439
(2004).
Mesoscale model simulations of tropical cyclones are sensitive to
representations of microphysical processes, such as fall velocities of
frozen hydrometeors. The majority of microphysical parameterizations are
based on observations obtained in clouds not associated with tropical
cyclones, and hence their suitability for use in simulations of tropical
cyclones is not known. Here, representations of mass-weighted fall speed
Vm for snow and graupel are examined to show that
parameters describing the exponential size distributions and fall speeds
of individual hydrometeors [through use of relations such as
V(D) = aDb are identically important for
determining Vm. The a and b coefficients
are determined by the composition and shape of snow and graupel particles;
past modeling studies have not adequately considered the possible spread
of a and b values. Step variations in these coefficients,
associated with different fall velocity regimes, however, do not have a
large impact on Vm for observed size distributions in
tropical cyclones and the values of a and b used here,
provided that coefficients are chosen in accordance with the sizes where
the majority of mass occurs. New parameterizations for
Vm are developed such that there are no inconsistencies
between the diameters used to define the mass, number concentration, and
fall speeds of individual hydrometeors. Effects due to previous
inconsistencies in defined diameters on mass conversion rates between
different hydrometeor classes (e.g., snow, graupel, cloud ice) are
shown to be significant. In situ microphysical data obtained in Hurricane
Norbert (1984) and Hurricane Emily (1987) with two-dimensional cloud and
precipitation probes are examined to determine typical size distributions
of snow and graupel particles near the melting layer. Although well
represented by exponential functions, there are substantial differences in
how the intercept and slope of these distributions vary with mass content
when compared to observations obtained in other locations; most notably,
the intercepts of the size distributions associated with tropical cyclones
increase with mass content, whereas some observations outside tropical
cyclones show a decrease. Differences in the characteristics of the size
distributions in updraft and downdraft regions, when compared to
stratiform regions, exist, especially for graupel. A new representation
for size distributions associated with tropical cyclones is derived and
has significant impacts on the calculation of Vm.
Olsen, A., J.A. Trinanes, and R. Wanninkhof. Sea-air flux of
CO2 in the Caribbean Sea estimated using in situ and remote
sensing data. Remote Sensing of Environment, 89(3):309-325 (2004).
Empirical relationships between sea surface carbon dioxide fugacity
(fCO2sw) and sea surface temperature (SST)
were applied to data sets of remotely sensed SST to create
fCO2sw fields in the Caribbean Sea. SST data
sets from different sensors were used, as well as the SST fields created
by optimum interpolation of bias corrected AVHRR data. Empirical
relationships were derived using shipboard
fCO2sw data, in situ SST data, and SST data
from the remote sensing platforms. The results show that the application
of a relationship based on shipboard SST data, on fields of remotely
sensed SST yields biased fCO2sw values. This
bias is reduced if the fCO2sw-SST
relationships are derived using the same SST data that are used to create
the SST fields. The fCO2sw fields found to
best reproduce observed fCO2sw are used in
combination with wind speed data from QuikSCAT to create weekly maps of
the sea-air CO2 flux in the Caribbean Sea in 2002. The region
to the southwest of Cuba was a source of CO2 to the atmosphere
throughout 2002, and the region to the northeast was a sink during winter
and spring and a source during summer and fall. The net uptake of
CO2 in the region was doubled when potential skin layer effects
on fCO2sw were taken into account.
Ortner, P.B., S.R. Cummings, S.L. Smith, P. Lane, J. Lamkin, C. Yeung, and
D. Jones. Abundance and diel migrations of demersal mesozooplankton and
small reef fishes and their trophodynamic contribution to the coral reef
ecosystem: A pilot study. In The Effects of Combined Sea Temperature,
Light, and Carbon Dioxide on Coral Bleaching, Settlement, and Growth,
J.C. Hendee (ed.). NOAA Research Special Report, Silver Spring, MD, 27-28
(2004).
No abstract.
Pandya, R.E., D.R. Smith, M.K. Ramamurthy, P.J. Croft, M.J. Hayes, K.A.
Murphy, J.D. Mcdonnell, R.M. Johnson, and H.A. Friedman. 11th American
Meteorological Society Education Symposium. Bulletin of the American
Meteorological Society, 85(3):425-430 (2004).
The 11th American Meteorological Society (AMS) Education Symposium was held
from 13 to 15 January 2002 in Orlando, Florida, as part of the 82nd Annual
Meeting of the AMS. The theme of the symposium was "creating opportunities
in educational outreach in the atmospheric and related sciences." Drawing
from traditional strengths in meteorology and numerous national
recommendations, the presentations and posters of the symposium highlighted
three opportunities for reform. These opportunities build on partnerships
between diverse educational stakeholders, efforts to make science education
more like scientific practice, and strategies that place the atmospheric
sciences within a larger, multi-disciplinary context that includes
oceanography, hydrology, and earth-system science.
Powell, M.D., D. Bowman, D. Gilhousen, S.T. Murillo, N. Carrasco, and R.
St. Fleur. Tropical cyclone winds at landfall: The ASOS-C-MAN Wind Exposure
Documentation Project. Bulletin of the American Meteorological
Society, 85(6):845-851 (2004).
Photographs describing the wind exposure at automatic weather stations
susceptible to tropical cyclones are now available on web pages at the
National Climatic Data Center and the National Data Buoy Center. Given the
exposure for one of eight wind direction sectors, a user may estimate the
aerodynamic roughness and correct mean wind measurements to an
open-terrain exposure. The open-terrain exposure is consistent with the
tropical cyclone advisories and forecasts issued by the National Weather
Service, as well as building design wind load standards published by the
American Society of Civil Engineers.
Saltzman, E.S., M. Aydin, W.J. De Bruyn, D.B. King, and S.A.
Yvon-Lewis. Methyl bromide in pre-industrial air: Measurements from
an Antarctic ice core. Journal of Geophysical Research,
109(D5):D05301, doi:10.1029/2003JD004157 (2004).
This paper presents the first ice core measurements of methyl bromide
(CH3Br). Samples from a shallow Antarctic ice core (Siple
Dome, West Antarctica), ranging in mean gas dates from 1671 to 1942, had a
mean CH3Br mixing ratio of 5.8 ppt. These results extend the
existing historical record derived from air and Antarctic firn air to
about 350 years before present. Model simulations illustrate that the ice
core results are consistent with estimates of the impact of anthropogenic
activity (fumigation, combustion, and biomass burning) on the atmospheric
CH3Br burden, given the large current uncertainties in the
modern atmospheric CH3Br budget. A preindustrial scenario
assuming no fumigation, no combustion, and a 75% reduction in biomass
burning sources, yields a Southern Hemisphere mean mixing ratio of 5.8
ppt, in good agreement with the ice core results. There is a significant
imbalance between the known CH3Br sources and sinks in the
modern atmospheric CH3Br budget. The ice core data do not
sufficiently constrain the model to determine how much of the "unknown
source" was present in the preindustrial budget. The results do indicate
that most of the southern hemispheric component of this "unknown source"
is not anthropogenic.
Thacker, W.C., S.-K. Lee, and G.R. Halliwell. Assimilating 20 years of
Atlantic XBT data into HYCOM: A first look. Ocean Modelling,
7(1-2):183-210 (2004).
Expendable bathythermographic (XBT) data for the years 1972-1991 have been
assimilated into a Hybrid Coordinate Ocean Model (HYCOM) for the Atlantic
Ocean. Climatological salinity profiles were combined with the observed
temperature profiles to estimate companion potential-density profiles, which
are used to determine the observation-based local structure of the model's
hybrid layers. The model's density, temperature, and layer-interface-depth
fields were corrected monthly via optimal interpolation. Preliminary results
presented here show that the data have a major impact on the simulation,
correcting model biases, and that the corrections persist between monthly
assimilations.
Ward, B., R.H. Wanninkhof, P.J. Minnett, and M.J. Head. SkinDeEP: A
profiling instrument for upper-decameter sea surface measurements.
Journal of Atmospheric and Oceanic Technology, 21(2):207-222
(2004).
The Skin Depth Experimental Profiler (SkinDeEP) is an autonomous,
self-contained, hydrodynamic instrument capable of making repeated,
high-resolution profiles of temperature and conductivity within the
ocean's upper decameter. Autonomous profiling operation is accomplished
through SkinDeEP's ability to change its density: positive buoyancy is
achieved by pumping air from inside the body of the profiler into an
external, neoprene, inflatable sleeve; the instrument sinks when the
sleeve is deflated by returning the air to the interior. The sensors are
mounted some distance from the top endcap and data are recorded only
during the ascending phase of the profile so as to minimize disruption of
a naturally occurring scalar structure by the presence of the instrument.
Temperature and conductivity are measured with resolutions in the
submillimeter and millimeter ranges, respectively. Highly accurate and
slower sensors are installed for calibration purposes. These data are used
to study exchange processes at the air-sea interface and the structure of
the ocean just below.
Ward, B., R.H. Wanninkhof, W.R. McGillis, A.T. Jessup, M.D. DeGrandpre, J.E.
Hare, and J.B. Edson. Biases in the air-sea flux of CO2
resulting from ocean surface temperature gradients. Journal of Geophysical
Research, 109(C8):C08S08, doi:10.1029/2003JC001800 (2004).
The difference in the fugacities of CO2 across the diffusive
sublayer at the ocean surface is the driving force behind the air-sea flux
of CO2. Bulk seawater fugacity is normally measured several
meters below the surface, while the fugacity at the water surface, assumed
to be in equilibrium with the atmosphere, is measured several meters above
the surface. Implied in these measurements is that the fugacity values are
the same as those across the diffusive boundary layer. However, temperature
gradients exist at the interface due to molecular transfer processes,
resulting in a cool surface temperature, known as the skin effect. A warm
layer from solar radiation can also result in a heterogeneous temperature
profile within the upper few meters of the ocean. Here we describe
measurements carried out during a 14-day study in the equatorial Pacific
Ocean (GasEx-2001) aimed at estimating the gradients of CO2 near
the surface and resulting flux anomalies. The fugacity measurements were
corrected for temperature effects using data from the ship's
thermosalinograph, a high-resolution profiler (SkinDeEP), an infrared
radiometer (CIRIMS), and several point measurements at different depths on
various platforms. Results from SkinDeEP show that the largest cool skin
and warm layer biases occur at low winds, with maximum biases of -4% and
+4%, respectively. Time series ship data show an average CO2
flux cool skin retardation of about 2%. Ship and drifter data show significant
CO2 flux enhancement due to the warm layer, with maximums occurring
in the afternoon. Temperature measurements were compared to predictions based
on available cool skin parameterizations to predict the skin-bulk temperature
difference, along with a warm layer model.
Yvon-Lewis, S.A., D.B. King, R. Tokarczyk, K.D. Goodwin, E.S. Saltzman,
and J.H. Butler. Methyl bromide and methyl chloride in the Southern
Ocean. Journal of Geophysical Research, 109(C2):C02008,
doi:10.1029/2003JC001809 (2004).
Air and water concentrations of methyl bromide (CH3Br) and
methyl chloride (CH3Cl) were measured in the Southern Ocean
(latitudes 45°S-67°S, longitudes 144°E-139°E) from
late October through mid-December 2001. CH3Br and
CH3Cl were undersaturated with mean saturation anomalies of
-39±11% and -37±11% between 45°S and 65°S. The minimum
degradation rate constants needed to maintain these saturation anomalies
are consistent with the observed total degradation rate constants,
suggesting that there is no significant production of these gases in this
region. Near the Antarctic coast (south of 65°S), the saturation
anomalies for both gases decreased to approximately -80%, although CFC-11
measurements suggest these extreme anomalies are associated with enhanced
vertical mixing rather than degradation in the surface waters.
**2003**
Aberson, S.D. Targeted observations to improve operational tropical
cyclone track forecast guidance. Monthly Weather Review,
131(8):1613-1628 (2003).
Since 1997, the Tropical Prediction Center and the Hurricane Research Division
have conducted operational synoptic surveillance missions with a Gulfstream
IV-SP jet aircraft to improve numerical forecast guidance. Due to limited
aircraft resources, optimal observing strategies for these missions must be
developed. In the current study, the most rapidly growing modes are
represented by areas of large forecast spread in the NCEP bred-vector
ensemble forecasting system. The sampling strategy requires sampling of the
entire target region with regularly spaced dropwindsonde observations. Three
dynamical models were employed in testing the targeting and sampling
strategies. With the assimilation into the numerical guidance of all the
observations gathered during the surveillance missions, only the 12-h
Geophysical Fluid Dynamics Laboratory Hurricane Model forecast showed
statistically significant improvement. Assimilation of only the subset of
data from the subjectively found fully sampled target regions produced a
statistically significant reduction of the track forecast errors of up to 25%
within the critical first two days of the forecast. This is comparable with
the cumulative business-as-usual improvement expected over 18 yr.
Aberson, S.D., and C.R. Sampson. On the predictability of tropical cyclone
tracks in the northwest Pacific basin. Monthly Weather Review,
131(7):1491-1497 (2003).
A new northwest Pacific climatology and persistence (CLIPER) model is derived
with historical tropical cyclone tracks during the satellite and aircraft
reconnaissance era (1970-1995). The new CLIPER extends the forecasts from
three to five days and exhibits smaller forecast biases than the previous
CLIPER, although forecast errors are comparable. The new model is based on
more accurate historical tropical cyclone track data, and a simpler derivation
of the regression equations, than is the old model. Nonlinear systems analysis
shows that the predictability timescale in which the average errors increase
by a factor e is just over 15 h, which is about the same as that calculated
by similar methods near Australia and in the North Atlantic. This suggests
that five-day tropical cyclone track forecasts may be beneficial, assuming
small initial errors; therefore, a CLIPER model extended to five days is
needed as a baseline to measure the forecast skill.
Ball, W.P., R.R. Dickerson, B.G. Doddridge, J.W. Stehr, T.L. Miller, D.L.
Savoie, and T.P. Carsey. Bulk and size-segregated aerosol composition
observed during INDOEX 1999: Overview of meteorology and continental
impacts. Journal of Geophysical Research, 108(D10):8001,
doi:10.1029/2002JD002467 (2003).
Bulk and size-segregated aerosol samples were collected from the NOAA R/V
Ronald H. Brown as it cruised from Cape Town, South Africa, through
the Indian Ocean and into the Bay of Bengal and Arabian Sea (February to
April 1999; 33°S to 19°N). Throughout the Northern Hemisphere,
aerosol loading was greater than in the Southern Hemisphere. Samples collected
in air that had passed over India showed evidence of fossil fuel combustion,
biomass burning, and eolian material, with elemental carbon (EC) dominating
radiation absorption and the following relative contributions to the total
mass of aerosol particles: ash 29%, nss-sulfate 22%, sea salt 15%, nitrate
9%, organic material 8%, ammonium 6%, and EC 5%. Careful examination of the
coarse mode revealed substantial concentrations of nitrate, adequate to
acidify sea salt aerosols north of the Intertropical Convergence Zone. Air
that had passed over Arabia showed little evidence of biomass burning but had
more acidity, mineral dust, and higher nitrate to sulfate ratios than air
from India. High concentrations of mineral dust played a major role in
radiation absorption; mean contributions to aerosol mass in Arabian air were:
ash 38%, nss-sulfate 10%, sea salt 33%, nitrate 5%, organic material 4%,
ammonium 1%, and EC 1%. From the ship we measured an average bulk aerosol
concentration of 20 µg m-3 in the marine boundary layer of
the northern Indian Ocean.
Bentamy, A., K.B. Katsaros, A.M. Mestas-Nunez, W.M. Drennan, E.B. Forde,
and H. Roquet. Satellite estimates of wind speed and latent heat flux over
the global oceans. Journal of Climate, 16(4):637-656 (2003).
Surface fluxes of momentum, freshwater, and energy across the air-sea
interface determine oceanic circulation and its variability at all time
scales. The goal of this paper is to estimate and examine some ocean surface
flux variables using satellite measurements. The remotely sensed data come
from the European Remote Sensing (ERS) satellite scatterometer on ERS-2, NASA
scatterometer (NSCAT), and several Defense Meteorological Satellite Program
(DMSP) radiometers [Special Sensor Microwave Imager (SSM/I)] on board the
satellites F10-F14. The sea surface temperature comes from daily analysis
calculated from Advanced Very High Resolution Radiometer (AVHRR) measurements.
This study focuses on the nine-month period (October 1996-June 1997) of the
NSCAT mission. To ensure high quality of the merged surface parameter fields,
comparisons between different satellite estimates for the same variable have
been performed, and bias corrections have been applied so that they are
compatible with each other. The satellite flux fields are compared to in situ
observations from buoys and ships globally and in different regions of the
ocean. It is found that the root-mean-square (rms) difference with weekly
averaged wind speeds is less than 2.5 m s-1 and the correlation
coefficient is higher than 0.8. For weekly latent heat flux, the rms
difference between satellite and buoys does not exceed 30 W
m-2. The comparisons with weekly ship latent heat flux estimates
gives an rms difference approaching 40 W m-2. Comparisons are
also made between satellite fields and atmospheric analyses from the European
Centre for Medium-Range Weather Forecasts (ECMWF) and reanalyses from the
National Centers for Environmental Prediction-National Center for Atmospheric
Research (NCEP-NCAR). The wind speeds and latent heat fluxes from these
atmospheric analyses compare reasonably well with the satellite estimates.
The main discrepancies are found in regions and seasons of large air-sea
temperature difference and high wind speed, such as the Gulf Stream during
the winter season.
Bitterman, D.S., R.H. Smith, W.D. Wilson, N. Melo, and T.N. Lee. Florida
Bay shallow water surface drifter. Joint Conference on the Science and
Restoration of the Greater Everglades and Florida Bay Ecosystem from
Kissimmee to the Keys, Palm Harbor, FL, April 13-18, 2003. University
of Florida Office of Conferences and Institutes, 56-58 (CD-ROM) (2003).
No abstract.
Black, M.L., F.D. Marks, R.F. Rogers, L.K. Shay, B.A. Albrecht, and H.E.
Willoughby. The relationship between environmental wind shear and the
distribution of vertical velocities and precipitation in the hurricane
eyewall. Preprints, 31st Conference on Radar Meteorology,
Seattle, WA, August 6-12, 2003. American Meteorological Society, Boston,
1016-1019 (2003).
No abstract.
Black, R.A., G.M. Heymsfield, and J. Hallett. Extra large particle images
at 12 km in a hurricane eyewall: Evidence of high-altitude supercooled
water? Geophysical Research Letters, 30(21):2124,
doi:10.1029/2003GL017864 (2003).
The conventional wisdom about hurricanes suggests that updrafts are weak
and supercooled water is scarce in the eyewall, and almost non-existent at
temperatures colder than about -5°C (Black and Hallett, 1986). However,
there is evidence that some hurricanes are different. Questions about the
existence of high-altitude supercooled cloud water cannot be answered with
only the instruments aboard the typical propeller-driven aircraft. During
the summer of 1998, the NASA DC-8 aircraft made penetrations of the
intensifying eyewall of Hurricane Bonnie at 12 km MSL, collecting the
first truly high-altitude two-dimensional particle imagery in a hurricane.
The similarity of the splash images in Hurricane Bonnie to those from
raindrops obtained at higher temperatures in other hurricanes suggests
that the large images obtained by the DC-8 were soft, low density graupel,
rather than hard, high-density graupel particles or frozen raindrops. This
implies that these particles grew to several millimeters in diameter at
altitude, rather than simply advecting from lower, warmer altitudes. This
growth in turn requires the presence of deeply supercooled cloud droplets.
Thermal emission from supercooled water aloft increases the microwave
brightness temperatures, giving a misleading impression that there is much
less ice aloft than actually exists. The extra attenuation from the
occasional presence of large graupel at these altitudes reduces the
ability of microwave sensors to see precipitation at lower altitudes. Both
of these effects impede efforts to accurately quantify condensate mass
remotely from radiometric data such as that provided by the TRMM
satellite.
Boebel, O., J.R.E. Lutjeharms, C. Schmid, W. Zenk, T. Rossby, and C.
Barron. The Cape Cauldron: A regime of turbulent inter-ocean exchange.
Deep-Sea Research, Part II, 50(1):57-86 (2003).
Combining in-situ Lagrangian intermediate depth velocity measurements from
the KAPEX (Cape of Good Hope Experiments) float program with sea surface
height data, this study reviews the inter-ocean exchange mechanisms around
southern Africa. In the southeastern Cape Basin, a highly energetic field
of coexisting anticyclonic and cyclonic eddies is documented. Agulhas
rings of typically 200 km diameter are observed to merge, split, deform,
and to reconnect to the Agulhas Retroflection. Concomitant, slightly
smaller cyclones are observed to drift across the northwestward migration
path of the Agulhas rings. These cyclones, with typical diameters of 120
km, are formed within the Cape Basin along the African shelf, inshore of
the Agulhas Current, and in the subantarctic region south of Africa. The
data suggest the annual formation of three to six long-lived Agulhas Rings
that eventually cross 5°E longitude, while approximately twice the
number of rings occur in the southeastern Cape Basin. Within this region,
cyclones outnumber anticyclones by a factor of 3:2. Both cyclones and
anticyclones extend through the upper thermocline into the intermediate
depth layer. Mean drifts of anticyclones are 3.8 ± 1.2 cm s-1
to the northwest, while cyclones follow a west-southwestward route at 3.6
± 0.8 cm s-1. Transport estimates suggest that the intermediate
depth layer in the southeastern Cape Basin is primarily supplied from the
east (approximately 9 Sv), with minor direct inflow from the Atlantic to
the west and south. Cyclone/anticyclone interaction is surmised to result
in vigorous stirring and mixing processes in the southeastern Cape Basin,
which necessitates a review of the traditional concept of Indo-Atlantic
inter-ocean exchange. We propose to limit the concept of "isolated Agulhas
Rings embedded in a sluggish Benguela Drift" to the northwestern Cape
Basin and beyond, while linking this regime to the Agulhas Retroflection
proper through a zone of turbulent stirring and mixing in the southeastern
Cape Basin, named for the first time the "Cape Cauldron" hereinafter.
Brenes, C.L., J.E. Coen, D.B. Chelton, D.B. Enfield, S. Leon, and D.
Ballestero. Wind driven upwelling in the Gulf of Nicoya, Costa Rica.
International Journal of Remote Sensing, 24(5):1127-1133 (2003).
Using satellite sensor data and information from local meteorological
stations, a transient upwelling event in the Gulf of Nicoya, Costa Rica, has
been observed during the period 6-8 March 1997 in coincidence with strong
upwelling in the Gulf of Papagayo. Strong north-easterlies funneled through
two mountain passes are responsible for this feature, observed intermittently
between November and March.
Burkert, J., M.D. Andres-Hernandez, L. Reichert, J. Meyer-Arnek, B.
Doddridge, R.R. Dickerson, J. Muhle, A. Zahn, T.P. Carsey, and J.P.
Burrows. Trace gas and radical diurnal behavior in the marine boundary
layer during INDOEX 1999. Journal of Geophysical Research,
108(D8):8000, doi:10.1029/2002JD002790 (2003).
Selected trace gas mixing ratios (i.e., peroxy radicals
(RO*2 = HO2 + SIGMA-RO2), nonmethane
hydrocarbons (NMHCs), O3, CO, HCHO, and NO) and photolysis rate
coefficients of j(NO2) and j(O(1D)) were measured in
the marine boundary layer (MBL) over the Indian Ocean. The measurements
were performed during February, March, and April 1999 as a part of the
Indian Ocean Experiment (INDOEX) on board the research vessel R/V
Ronald H. Brown. During the campaign, air parcels having different
origins and consequently variable compositions were encountered, but all
air masses, including those heavily polluted with NMHCs and aerosols, were
in the regime of rapid photochemical ozone destruction. The influence of
aerosols on the photolysis frequencies was investigated by comparison of
measurements and results from the radiative transfer model PHOTOST: the
high optical depth (up to 0.6) and low single scattering albedo of the
aerosol reduces the UV flux at the surface substantially downwind of India
and Arabia causing, for instance, a reduction in j(O(1D)) by up
to 40%. The diurnal behavior of the trace gases and parameters in the MBL
has been investigated by using a time-dependent zero-dimensional chemical
model. Significant differences between the diurnal behavior of
RO*2 derived from the model and observed in measurements were
identified. The measured HCHO concentrations differed from the model
results and are best explained by some missing chemistry involving low
amounts of Cl. Other possible processes describing these two effects are
presented and discussed.
Chung, S.-N., K. Lee, R.A. Feely, C.L. Sabine, F.J. Millero, R.H.
Wanninkhof, J.L. Bullister, R.M. Key, and T.-H. Peng. Calcium carbonate
budget in the Atlantic Ocean based on water column inorganic carbon
chemistry. Global Biogeochemical Cycles, 17(4):1093,
doi:10.1029/2002GB002001 (2003).
Recent independent lines of evidence suggest that the dissolution of
calcium carbonate (CaCO3) particles is substantial in the upper
ocean above the calcite 100% saturation horizon. This shallow-water
dissolution of carbonate particles is in contrast with the current
paradigm of the conservative nature of pelagic CaCO3 at shallow
water depths. Here we use more than 20,000 sets of carbon measurements in
conjunction with CFC and 14C data from the WOCE/JGOFS/OACES
global CO2 survey to estimate in-situ dissolution rates of
CaCO3 in the Atlantic Ocean. A dissolution rate is estimated
from changes in alkalinity as a parcel of water ages along an isopycnal
surface. The in-situ CaCO3 dissolution increases rapidly at the
aragonite 100% saturation horizon. Estimated dissolution rates north of
40°N are generally higher than the rates to the south, which is
partly attributable to the production of exported CaCO3 being
higher in the North Atlantic than in the South Atlantic. As more
CaCO3 particles move down the water column, more particles are
available for in-situ dissolution. The total water column CaCO3
dissolution rate in the Atlantic Ocean is determined on an annual basis by
integrating estimated dissolution rates throughout the entire water column
and correcting for alkalinity input of approximately 5.6 x 1012
mol C yr-1 from CaCO3-rich sediments. The resulting
water column dissolution rate of CaCO3 for the Atlantic Ocean
is approximately 11.1 x 1012 mol C yr-1. This
corresponds to about 31% of a recent estimate (35.8 x 1012 mol
C yr-1) of net CaCO3 production by Lee (2001) for
the same area. Our calculation using a large amount of high-quality water
column alkalinity data provides the first basin-scale estimate of the
CaCO3 budget for the Atlantic Ocean.
Cione, J.J., and E.W. Uhlhorn. Sea surface temperature variability in
hurricanes: Implications with respect to intensity change. Monthly
Weather Review, 131(8):1783-1796 (2003).
Scientists at NOAA's Hurricane Research Division recently analyzed the
inner-core upper-ocean environment for 23 Atlantic, Gulf of Mexico, and
Caribbean hurricanes between 1975 and 2002. The interstorm variability of
sea surface temperature (SST) change between the hurricane inner-core
environment and the ambient ocean environment ahead of the storm is
documented using airborne expendable bathythermograph (AXBT) observations
and buoy-derived archived SST data. The authors demonstrate that differences
between inner-core and ambient SST are much less than poststorm, "cold wake"
SST reductions typically observed (i.e., 0-2°C versus
4-5°C). These findings help define a realistic parameter space for
storm-induced SST change within the important high-wind, inner-core
hurricane environment. Results from a recent observational study yielded
estimates of upper-ocean heat content, upper-ocean energy extracted by the
storm, and upper-ocean energy utilization for a wide range of tropical
systems. Results from this analysis show that, under most circumstances,
the energy available to the tropical cyclone is at least an order of
magnitude greater than the energy extracted by the storm. This study also
highlights the significant impact that changes in inner-core SST have on
the magnitude of air-sea fluxes under high-wind conditions. Results from
this study illustrate that relatively modest changes in inner-core SST
(order 1°C) can effectively alter maximum total enthalpy (sensible
plus latent heat) flux by 40% or more. The magnitude of SST change (ambient
minus inner core) was statistically linked to subsequent changes in storm
intensity for the 23 hurricanes included in this research. These findings
suggest a relationship between reduced inner-core SST cooling
(i.e., increased inner-core surface enthalpy flux) and tropical cyclone
intensification. Similar results were not found when changes in storm
intensity were compared with ambient SST or upper-ocean heat content
conditions ahead of the storm. Under certain circumstances, the variability
associated with inner-core SST change appears to be an important factor
directly linked to the intensity change process.
Crusius, J., and R.H. Wanninkhof. Gas transfer velocities measured at low
wind speed over a lake. Limnology and Oceanography,
48(3):1010-1017 (2003).
The relationship between gas transfer velocity and wind speed was evaluated
at low wind speeds by quantifying the rate of evasion of the deliberate
tracer, SF6, from a small oligotrophic lake. Several possible
relationships between gas transfer velocity and low wind speed were
evaluated by using 1-min-averaged wind speeds as a measure of the
instantaneous wind speed values. Gas transfer velocities in this data set
can be estimated virtually equally well by assuming any of three widely
used relationships between k600 and winds referenced to 10-m
height, U10: (1) a bilinear dependence with a break in the slope
at ~3.7 m s-1, which resulted in the best fit; (2) a power
dependence; and (3) a constant transfer velocity for U10
< ~3.7 m s-1, with a linear dependence on wind speed at
higher wind speeds. The lack of a unique relationship between transfer
velocity and wind speed at low wind speeds suggests that other processes,
such as convective cooling, contribute significantly to gas exchange when
the wind speeds are low. All three proposed relationships clearly show a
strong dependence on wind for winds >3.7 m s-1 which, coupled with
the typical variability in instantaneous wind speeds observed in the field,
leads to average transfer velocity estimates that are higher than those
predicted for steady wind trends. The transfer velocities predicted by the
bilinear steady wind relationship for U10 < ~3.7 m
s-1 are virtually identical to the theoretical predictions for
transfer across a smooth surface.
Darrow, B.P., J.J. Walsh, G.A. Vargo, R.T. Masserini, K.A. Fanning, and
J.-Z. Zhang. A simulation study of the growth of benthic microalgae
following the decline of a surface phytoplankton bloom. Continental
Shelf Research, 23(14-15):1265-1283 (2003).
The West Florida continental shelf is an oligotrophic system for most of the
year. An episodic chlorophyll plume has previously been observed in satellite
imagery on the northern portion of the shelf during the spring months. The
fate of the plume upon its decline in the late spring and early summer is
unknown. Decreased chlorophyll levels and sustained nutrient stocks may be
explained by sediment/water-column interactions, including the presence of
benthic microalgae. A one-dimensional model, consisting of 16 state variables,
is constructed to simulate the decline of a surface chlorophyll bloom in the
northeastern Gulf of Mexico as measured during the Florida Shelf Lagrangian
Experiment (FSLE). Results from a baseline simulation of two FSLE studies
suggest that remineralized nutrients from the declining bloom are taken up by
heterotrophic bacteria in the water-column and by benthic microalgae in
the sediments. Perturbation experiments imply that low light levels, due
to increased CDOM, do not have significant effects on the benthic
microfloral community at mid-shelf locations.
Dunion, J.P., C.W. Landsea, S.H. Houston, and M.D. Powell. A reanalysis
of the surface winds for Hurricane Donna of 1960. Monthly Weather
Review, 131(9):1992-2011 (2003).
Hurricane Donna, the only major hurricane to strike the United States during
the 1960 Atlantic hurricane season, passed over the middle Florida Keys near
Sombrero Key before making landfall southeast of Naples, near Goodland,
Florida, on 10 September at approximately 1600 UTC. This study makes detailed
retrospective surface wind analyses of Hurricane Donna utilizing the National
Oceanic and Atmospheric Administration (NOAA) Hurricane Research Division's
(HRD) H*Wind surface wind analysis system. Analyses were produced at intervals
of 6 h between 1800 UTC 9 September and 1200 UTC 11 September 1960 while the
hurricane was close to and over Florida. These analyses depict the storm
track as well as the distribution and extent of tropical storm force, 50 kt
(25.7 m s-1), and the hurricane-force wind radii throughout this
time period and include new methodologies for adjusting aircraft flight-level
data to the surface in the tropical cyclone core environment. Algorithms were
developed to account for the effects of eyewall tilt and the warm core
structure typical of tropical cyclones. Additional methods were developed
using global positioning system (GPS) dropwindsondes (sondes) to more
accurately adjust boundary layer winds to equivalent surface winds. The
Kaplan-DeMaria Inland Wind Decay Model was also used for the first time to
adjust landfall data being input into the H*Wind system. These data were used
to generate low-weighted background fields that helped generate postlandfall
wind field analyses of Hurricane Donna. Finally, swaths of peak winds,
duration of hurricane- and major hurricane-force winds, and wind steadiness
were produced to facilitate damage assessment. The information provided by
these objective analyses is significantly more detailed than the more limited
descriptions of peak winds, storm position, and minimum central pressure
available in the National Hurricane Center's (NHC) hurricane database
archive (HURDAT).
Esenkov, O.E., D.B. Olson, and R. Bleck. A study of the circulation and
salinity budget of the Arabian Sea with an isopycnic coordinate ocean
model. Deep-Sea Research, Part II, 50(12-13):2091-2110 (2003).
The evolution of surface circulation and salinity budget are studied with
the open-boundary version of the Miami Isopycnic Coordinate Ocean Model
(MICOM) that uses a global MICOM simulation as a boundary condition. Under
climatological wind and thermodynamic forcing, the model develops solutions
that are in good agreement with the climatologically forced global MICOM
results and with observations. When the observed winds force the model,
interannual variability of the surface fields increases significantly.
However, coalescence of the two large eddies off Somalia in the end of the
summer monsoon suggested in earlier observations does not occur in the model.
To identify what processes facilitate or restrict the merger, a series of
experiments was performed with modified model parameters and forcing fields.
The eddies coalesced when half-slip, rather than no-slip, boundary conditions
were used. In this case, less positive vorticity was produced at the coast,
resulting in reduced blocking effect on the propagation of the southern eddy.
The Socotra Island, which is submerged in the standard model, hinders a
northward movement of the Great Whirl, leading to a stronger interaction
between the eddies, which results in their subsequent merging. A more
realistic coalescence occurs in an experiment where winds are held constant
after reaching the peak summer value. Freshwater fluxes from the east and
south are important for the salinity budget in the Arabian Sea, where
evaporation exceeds precipitation. The only significant cross-equatorial
transport of low-salinity water occurs in the upper 400 m in the model. Most
of this water is advected below the surface mixed layer at the western
boundary. The strongest interaction between the mixed layer and the oceanic
interior occurs during the summer in the coastal upwelling regions off Somalia.
Almost half of all upwelled water comes from depths between 100 and 200 m,
thus signifying the importance of mid-depth circulation and water mass
distribution for the surface processes.
Fram, M.S., B.A. Bergamaschi, K.D. Goodwin, R. Fujii, and J.F.
Clark. Processes affecting the trihalomethane concentrations associated
with the third injection, storage, and recovery test at Lancaster, Antelope
Valley, California, March 1998 through April 1999. U.S. Geological Survey,
Water-Resources Investigations Report 03-4062, 72 pp. (2003).
The formation and fate of trihalomethanes (THM) during the third injection,
storage, and recovery test at Lancaster, Antelope Valley, California, were
investigated as part of a program to assess the long-term feasibility of using
injection, storage, and recovery as a water-supply method and as a way to
reduce water-level declines and land-subsidence in the Antelope Valley. The
program was conducted by the U.S. Geological Survey in cooperation with the
Los Angeles County Department of Public Works and the Antelope Valley-East
Kern Water Agency. The water used for injection, storage, and recovery must
be disinfected before injection and thus contains THMs and other disinfection
byproducts. THMs (chloroform, CHCl3, bromodichloromethane,
CHCl2Br, dibromochloromethane, CHClBr2, and bromoform,
CHBr3) are formed by reaction between natural dissolved organic
carbon that is present in water and chlorine that is added during the
disinfection step of the drinking water treatment process. THMs are
carcinogenic compounds, and their concentrations in drinking water are
regulated by the U.S. Environmental Protection Agency. During previous cycles
of the Lancaster program, extracted water still contained measurable
concentrations of THMs long after continuous pumping had extracted a greater
volume of water than had been injected. This raised concerns about the
potential long-term effect of injection, storage, and recovery cycles on
ground-water quality in Antelope Valley aquifers. The primary objectives of
this investigation were to determine (1) what controlled continued THM
formation in the aquifer after injection, (2) what caused the persistence of
THMs in the extracted water, even after long periods of pumping, (3) what
controlled the decrease of THM concentrations during the extraction period,
and (4) the potential for natural attenuation of THMs in the aquifer.
Franca, C., I. Wainer, A.R. de Mesquita, and G.J. Goni. Planetary equatorial
trapped waves in the Atlantic Ocean from TOPEX/Poseidon altimetry. In
Interhemispheric Water Exchange in the Atlantic Ocean, G.J.
Goni and P. Malanotte-Rizzoli (eds.). Elsevier Oceanography Series, 68
(ISBN 0444512675), 213-232 (2003).
Planetary equatorial waves are important mechanisms for the adjustment of
the tropical oceans. The identification and role of planetary equatorial
waves in the tropical Atlantic is investigated by taking advantage of
unprecedented accuracy, coverage and resolution of the TOPEX/POSEIDON
altimeter data, from 1992 to 1999. This is accomplished by projecting the
sea level height anomalies, obtained from the altimetry for the tropical
Atlantic basin onto the linear equatorial meridional waves, first
baroclinic mode. Results presented here show the existence of equatorial
Kelvin and Rossby modes, as well as their significant reflection off the
African coast.
Franklin, J.L., M.L. Black, and K. Valde. GPS dropwindsonde wind profiles in
hurricanes and their operational implications. Weather and
Forecasting, 18(1):32-44 (2003).
The recent development of the global positioning system (GPS) dropwindsonde
has allowed the wind and thermodynamic structure of the hurricane eyewall to
be documented with unprecedented accuracy and resolution. In an attempt to
assist operational hurricane forecasters in their duties, dropwindsonde data
have been used in this study to document, for the first time, the mean
vertical profile of wind speed in the hurricane inner core from the surface
to the 700-hPa level, the level typically flown by reconnaissance aircraft.
The dropwindsonde-derived mean eyewall wind profile is characterized by a
broad maximum centered 500 m above the surface. In the frictional boundary
layer below this broad maximum, the wind decreases nearly linearly with the
logarithm of the altitude. Above the maximum, the winds decrease because of
the hurricane's warm core. These two effects combine to give a surface wind
that is, on average, about 90% of the 700-hPa value. The dropwindsonde
observations largely confirm recent operational practices at the National
Hurricane Center for the interpretation of flight-level data. Hurricane wind
profiles outside of the eyewall region are characterized by a higher level
of maximum wind, near 1 km, and a more constant wind speed between 700 hPa
and the top of the boundary layer. Two factors that likely affect the
eyewall profile structure are wind speed and vertical motion. A minimum in
surface wind adjustment factor (i.e., relatively low surface wind
speeds) was found when the wind near the top of the boundary layer was
between 40 and 60 m s-1. At higher wind speeds, the fraction of
the boundary layer wind speed found at the surface increased, contrary to
expectation. Low-level downdrafts and enhanced vertical motion generally were
also associated with higher relative surface winds. These results may be of
interest to engineers concerned with building codes, to emergency managers
who may be tempted to use high-rise buildings as a "refuge of last resort"
in coastal areas, and to those people on locally elevated terrain. The top
of a 25-story coastal high-rise in the hurricane eyewall will experience a
mean wind that is about 17% higher (or one SaffirSimpson hurricane-scale
category) than the surface or advisory value. For this reason, residents
who must take refuge in coastal high-rises should generally do so at the
lowest levels necessary to avoid storm surge.
Garraffo, Z.D., W.E. Johns, E.P. Chassignet, and G.J. Goni. North Brazil
Current rings and transport of southern waters in a high resolution
numerical simulation of the North Atlantic. In Interhemispheric Water
Exchange in the Atlantic Ocean, G.J. Goni and P. Malanotte-Rizzoli
(eds.). Elsevier Oceanography Series, 68 (ISBN 0444512675), 375-409 (2003).
Output from a very high resolution (1/12 deg.) North Atlantic simulation
with the Miami Isopycnic Coordinate Ocean Model (MICOM) is analyzed in a
region of the Tropical Atlantic characterized by the presence of the North
Brazil Current (NBC) retroflection and North Brazil Current rings. The
model mean and seasonal circulations present a good qualitative agreement
with observations. Quantitatively, the modeled NBC in summer and fall does
not completely retroflect into the North Equatorial Counter Current, and
the model upper 100 m NBC is more intense than the observed values by 3-4
Sv. The modeled NBC generates a variety of rings, which we classify as
"shallow," "intermediate," "deep," and "subsurface." An average of 8.3
rings of all types are generated per year, of which 6 are surface
intensified, in good agreement with altimetry (5.7 rings per year, Goni
and Johns, 2001). The transport of southern origin water by the rings was
estimated using two methods. First, the transport was computed
kinematically from the rings' volume, resulting in an average transport of
6.6 Sv. Second, an estimation of southern water transport based on an
explicit calculation of water mass content was done, resulting in an
average transport of 7.5 Sv. The rings' contribution represents ~40%
of the total meridional transport from the surface to the intermediate water
layers. Possible mechanisms operating in the model ring generation are
briefly discussed.
Garzoli, S.L., and J. Servain. CLIVAR workshop on tropical Atlantic
variability. Geophysical Research Letters, 30(5):8001,
doi:10.1029/2002GL016823 (2003).
No abstract.
Garzoli, S.L., A. Ffield, and Q. Yao. North Brazil Current rings and the
variability in the latitude of the retroflection. In Interhemispheric
Water Exchange in the Atlantic Ocean, G.J. Goni and P.
Malanotte-Rizzoli (eds.). Elsevier Oceanography Series, 68
(ISBN 0444512675), 357-373 (2003).
An array of 14 inverted echo sounders (IES) were deployed as part of the
North Brazil Current Rings (NBCR) experiment to study the dynamics of the
ocean in the region. Synoptic maps of dynamic height were produced from
the data collected with the IES. After validating these maps with
hydrographic data collected during the four NBCR cruises, they were
analyzed to determine the variability of the latitude of retroflection of
the North Brazil Current (NBC) and the number of rings shed during this
process. Results from this analysis indicate that there is no obvious
seasonality in the variability of the latitude of penetration of the NBC
and, with the exception of one event, each time that the NBC reaches its
northward position a ring is shed at the retroflection. A total of 11
rings were shed during the period of the observations November 1998 to
June 2000. The mean diameter of the rings was estimated to be
approximately 390 km, and the mean speed of propagation 12.4 km/day. The
rings transported an average of 8 Sv (1 Sv = 106 m3
s-1) of water and 0.54 PW of heat per year. These estimates are
much larger than previous results, both in the number of rings shed per year
and in the contribution of the rings to the inter-hemispheric exchange of
mass and heat.
Gedzelman, S., E. Hindman, X. Zhang, J. Lawrence, J.F. Gamache, M.L. Black,
R.A. Black, J.P. Dunion, and H.E. Willoughby. Probing hurricanes with stable
isotopes of rain and water vapor. Monthly Weather Review,
131(6):1112-1127 (2003).
Rain and water vapor were collected during flights in Hurricanes Olivia
(1994), Opal (1995), Marilyn (1995), and Hortense (1995) and analyzed for
their stable isotopic concentrations, or ratios,
H218O:H2O and HDO:H2O. The
spatial patterns and temporal changes of isotope ratios reflect details of a
hurricane's structure, evolution, microphysics, and water budget. At all
flight levels over the sea (850-475 hPa) the lowest isotope ratios occur in
or near regions of stratiform rains between about 50 and 250 km from the eye.
Isotope ratios are higher in the eyewall and were particularly high in the
crescent-shaped eyewall of Hurricane Opal at a time when no rain was falling
over a large area near the storm center. In Hurricane Olivia, isotope ratios
decreased from 24 to 25 September after vertical and radial circulation
weakened. A two-layer isotope model of a radially symmetric hurricane
simulates these features. The low isotope ratios are caused by fractionation
in extensive, thick, precipitating clouds with predominantly convergent
low-level flow accompanied by removal of heavy isotopes by falling raindrops.
Evaporation and isotope equilibration of sea spray increase isotope ratios of
the ambient vapor and produce a deuterium excess or enrichment of D relative
to 18O that increases with decreasing relative humidity and
increasing wind speed. Model results show that sea spray supplies the eyewall
with up to 50% of its water vapor and is largely responsible for its high
isotope ratios.
Goni, G.J., and W.E. Johns. Synoptic study of warm rings in the North
Brazil Current retroflection region using satellite altimetry. In
Interhemispheric Water Exchange in the Atlantic Ocean, G.J. Goni
and P. Malanotte-Rizzoli (eds.). Elsevier Oceanography Series, 68 (ISBN
0444512675), 335-356 (2003).
Ten years of altimeter data are used in conjunction with temperature and
salinity data within a two-layer reduced gravity approximation to
investigate the shedding and translation of North Brazil Current rings.
Space-time diagrams of sea height anomalies and residues along the
altimeter groundtracks show large seasonal and interannual variability.
Results presented here confirm previous estimates that indicate a shedding
rate of 3 to 7 rings per year with no marked seasonal variability but with
very strong year-to-year variability. Additionally, eddies not shed by the
retroflection travel through the region as well. Most of the rings pass
very near of Barbados, affecting the environment in the region, of which
seven rings during the study period are seen to enter into the Caribbean
Sea. A link is found in this study between long-term surface temperature
changes in the tropical Atlantic and the number of rings shed at the NBC
retroflection, where periods of time with warmer surface temperatures are
associated to a higher number of rings shed.
Goni, G.J., and J.A. Trinanes. Ocean thermal structure monitoring could
aid in the intensity forecast of tropical cyclones. EOS, Transactions,
American Geophysical Union, 84(51):573-578 (2003).
No abstract.
Goni, G.J., P.G. Black, and J.A. Trinanes. Using satellite altimetry to
identify regions of hurricane intensification. AVISO Newsletter,
9:19-20 (2003).
No abstract.
Halliwell, G.R., R.H. Weisberg, and D.A. Mayer. A synthetic float analysis
of upper-limb meridional overturning circulation interior ocean pathways in
the tropical/subtropical Atlantic. In Interhemispheric Water Exchange in
the Atlantic Ocean, G.J. Goni and P. Malanotte-Rizzoli (eds.).
Elsevier Oceanography Series, 68 (ISBN 0444512675), 93-136 (2003).
Synthetic floats are released in an ocean general circulation model to study
fluid pathways followed by the upper limb of the meridional overturning
circulation from the subtropical South Atlantic to the subtropical North
Atlantic. The floats are designed to track this fundamentally
three-dimensional, non-isentropic flow while sampling water properties and
all terms of the equation governing the vertical component of relative
vorticity. The low-resolution ocean simulations demonstrate how upper-limb
flow navigates the complex, time-dependent system of wind-driven gyres.
Pathways that extend into the interior North Atlantic before entering the
Caribbean Sea are emphasized over the more direct western boundary route.
A large number of floats are released in the southern hemisphere to verify
the importance of such interior pathways in the model and document key events
that occur along them. Upper limb water first approaches the equator in a
modified inertial western boundary layer. Equatorial processes
(visco-inertial boundary layer dynamics, upwelling, heating) are necessary
to reset water properties and permit fluid to permanently cross the equator,
typically requiring eastward retroflection into the EUC. After upwelling at
the equator, fluid that does not advect northward or southward into the
interior returns to the western boundary and turns northward in a frictional
western boundary layer. The generation of negative relative vorticity by
planetary vorticity advection can break the boundary layer constraint and
permit retroflection into the NECC near 5°N from late spring through
fall. Once in the interior, this fluid advects northward into the southern
subtropical gyre in a flow governed by Ekman dynamics. There the fluid
subducts and advects southwestward to enter the Caribbean Sea under the
influence of layered thermocline dynamics. The importance of interior
pathways is confirmed, although we note that fluid parcels generally take
complex paths and frequently make multiple attempts to enter the northern
hemisphere or multiple treks around gyres.
Hendee, J.C., and R. Berkelmans. Expert system generated coral bleaching
alerts for Myrmidon and Agincourt reefs, Great Barrier Reef, Australia.
Proceedings, 9th International Coral Reef Symposium, Bali,
Indonesia, October 23-27, 2000. Indonesian Institute of Sciences,
1099-1104 (2003).
No abstract.
Houston, S.H., and M.D. Powell. Surface wind fields for Florida Bay
hurricanes. Journal of Coastal Research, 19(3):503-513 (2003).
The surface wind fields of several tropical cyclones which impacted
Florida Bay and the surrounding coastal areas were reconstructed by the
Hurricane Research Division (HRD) of the national Oceanographic and
Atmospheric Administration. These cyclones provided the forcing for
significant changes in water levels, waves, and currents, resulting in
sediment transport, deposition, and other physical processes affecting the
Bay. In addition, tropical cyclones had direct and indirect effects on
plant and animal life in the Bay and the surrounding coastal areas, such
as the Florida Keys and Everglades. The HRD wind fields are being made
available in gridded form for use in hindcasts, which may help researchers
to estimate the potential impacts of future tropical cyclones on the south
Florida ecosystem, especially in relation to Florida Bay. The tropical
cyclones investigated represent vastly different scenarios for the type of
events that might be expected over extreme south Florida. The
reconstructed storms range in intensity from Tropical Storm Gordon of 1994
to the Labor Day Hurricane of 1935 (the United States' most intense
hurricane at landfall). This paper summarizes the methods used to
reconstruct tropical cyclone surface wind fields and provides examples of
their circulation features and wind swaths. Comparisons of winds to
observed damage are also presented for three major hurricanes. The wind
fields for all of these tropical cyclones are being made available to
researchers as graphical products and gridded data sets on a Web site
maintained by HRD (www.aoml.noaa.gov/hrd).
Jiang, M.-S., F. Chai, R.C. Dugdale, F.P. Wilkerson, T.-H. Peng, and R.T.
Barber. A nitrate and silicate budget in the equatorial Pacific Ocean: A
coupled physical-biological model study. Deep-Sea Research, Part
II, 50(22-26):2971-2996 (2003).
A coupled physical-biological model was developed to simulate the
low-silicate, high-nitrate, and low-chlorophyll (LSHNLC) conditions in the
equatorial Pacific Ocean and used to compute a detailed budget in the
Wyrtki box (5°N-5°S, 180-90°W) for the major sources and
cycling of nitrogen and silicon in the equatorial Pacific. With the
incorporation of biogenic silicon dissolution, NH4 regeneration
from organic nitrogen and nitrification of ammonia in the model, we show
that silicon recycling in the upper ocean is less efficient than nitrogen.
As the major source of nutrients to the equatorial Pacific, the Equatorial
Undercurrent provides slightly less Si(OH)4 than NO3
to the upwelling zone, which is defined as 2.5°N-2.5°S. As a
result, the equatorial upwelling supplies less Si(OH)4 than
NO3 into the euphotic zone in the Wyrtki box, having a Si/N
supply ratio of about 0.85 (2.5 vs. 2.96 mmol m-2
day-1). More Si(OH)4 than NO3 is taken up
with a Si/N ratio of 1.17 (2.72 vs. 2.33 mmol m-2
day-1) within the euphotic zone. The difference between
upwelling supply and biological uptake is balanced by nutrient
regeneration and horizontal advection. Excluding regeneration, the net
silicate and nitrate uptakes are nearly equal (1.76 vs. 1.84 mmol
m-2 day-1). However, biogenic silica export
production is slightly higher than organic nitrogen (1.74 vs. 1.59 mmol
m-2 day-1) following a 1.1 Si/N ratio. In the
central equatorial Pacific, low silicate concentrations limit diatom
growth; therefore, non-diatom new production accounts for most of the new
production. Higher silicate supply in the east maintains elevated diatom
growth rates and new production associated with diatoms dominate upwelling
zone. In contrast, the new production associated with small phytoplankton
is nearly constant or decreases eastward along the equator. The total new
production has a higher rate in the east than in the west, following the
pattern of surface silicate. This suggests that silicate regulates the
diatom production, total new production, and thereby carbon cycle in this
area. The modeled mean primary production is 48.4 mmol Cm-2
day-1, representing the lower end of direct field measurements,
while new production is 15.0 mmol Cm-2 day-1, which
compares well with previous estimates.
Johns, E., P.B. Ortner, R.H. Smith, C.R. Kelble, S.R. Cummings, J.C.
Hendee, N. Melo, T.N. Lee, and E.J. Williams. New interdisciplinary
oceanographic observations in the coastal waters adjacent to Florida Bay.
Joint Conference on the Science and Restoration of the Greater Everglades
and Florida Bay Ecosystem from Kissimmee to the Keys, Palm Harbor, FL,
April 13-18, 2003. University of Florida Office of Conferences and
Institutes, 45-47 (CD-ROM) (2003).
No abstract.
Johns, W.E., R.J. Zantopp, and G.J. Goni. Cross-gyre transport by North
Brazil Current rings. In Interhemispheric Water Exchange in the Atlantic
Ocean, G.J. Goni and P. Malanotte-Rizzoli (eds.). Elsevier Oceanography
Series, 68 (ISBN 0444512675), 411-441 (2003).
Recent observations collected as part of the North Brazil Current Rings
Experiment are used to assess the role played by NBC rings in tropical to
subtropical cross-gyre transport in the Atlantic Ocean. During the course
of the 20 month experiment, four different NBC Rings were surveyed by
ships and 12 additional rings were identified by moored current meters and
temperature/salinity recorders. Of the total of 16 rings observed, four
were subsurface-intensified rings with little or no surface signal. Except
for these subsurface rings, generally good agreement was found in the
identification of NBC rings during the experiment by various techniques
including satellite altimetry, ocean color, and inverted echo sounders.
The observations of water properties in the ring cores provided by the
in-situ temperature and salinity measurements are used to estimate the
trapped core volumes of South Atlantic water in the rings. Based on these
new measurements we estimate a ring formation rate of 8-9 rings per year,
with no apparent seasonal variation in the formation rate. However, the
surface rings show a seasonal cycle in their vertical penetration and
associated trapped core volumes. Deeper rings tend to occur in fall and
early winter, while shallower rings occur in spring and summer. The
subsurface rings are usually smaller in diameter than the surface rings
(average radius of maximum velocity 100 km versus 130 km), but have a
thicker layer of trapped South Atlantic water and consequently a larger
transport per ring. The average ring-induced transport including all ring
types is about 1.1 Sv per ring, leading to an estimate of 9.3 Sv for the
total annualized ring transport. This value is nearly twice that of most
previous estimates, and suggests that NBC rings could account for more
than half of the northward transport in the warm limb of the Atlantic
meridional overturning cell.
Jurado, J.L., G.L. Hitchcock, and P.B. Ortner. The roles of freshwater
discharge, advective processes, and silicon cycling in the development of
diatom blooms in coastal waters of the southwestern Florida Shelf and
northwestern Florida Bay (1999-2001). Joint Conference on the Science
and Restoration of the Greater Everglades and Florida Bay Ecosystem from
Kissimmee to the Keys, Palm Harbor, FL, April 13-18, 2003. University
of Florida Office of Conferences and Institutes, 119-121 (CD-ROM) (2003).
No abstract.
Kaplan, J., and M. DeMaria. Large-scale characteristics of rapidly
intensifying tropical cyclones in the North Atlantic basin. Weather and
Forecasting, 18(6):1093-1108 (2003).
The National Hurricane Center (NHC) and Statistical Hurricane Intensity
Prediction Scheme (SHIPS) databases are employed to examine the large-scale
characteristics of rapidly intensifying Atlantic basin tropical cyclones. In
this study, rapid intensification (RI) is defined as approximately the 95th
percentile of over-water 24-h intensity changes of Atlantic basin tropical
cyclones that developed from 1989 to 2000. This equates to a maximum sustained
surface wind speed increase of 15.4 m s-1 (30 kt) over a 24-h
period. It is shown that 31% of all tropical cyclones, 60% of all hurricanes,
83% of all major hurricanes, and all category 4 and 5 hurricanes underwent RI
at least once during their lifetimes. The mean initial (t = 0 h)
conditions of cases that undergo RI are compared to those of the non-RI
cases. These comparisons show that the RI cases form farther south and west
and have a more westward component of motion than the non-RI cases. In
addition, the RI cases are typically intensifying at a faster rate during the
previous 12 h than the non-RI cases. The statistical analysis also shows that
the RI cases are further from their maximum potential intensity and form
in regions with warmer SSTs and higher lower-tropospheric relative humidity
than the non-RI cases. The RI cases are also embedded in regions where the
upper-level flow is more easterly and the vertical shear and upper-level
forcing from troughs or cold lows is weaker than is observed for the non-RI
cases. Finally, the RI cases tend to move with the flow within a higher layer
of the atmosphere than the non-RI cases. A simple technique for estimating
the probability of RI is described. Estimates of the probability of RI are
determined using the predictors for which statistically significant
differences are found between the RI and non-RI cases. Estimates of the
probability of RI are also determined by combining the five predictors that
had the highest individual probabilities of RI. The probability of RI
increases from 1% to 41% when the total number of thresholds satisfied
increases from zero to five. This simple technique was used in real time for
the first time during the 2001 Atlantic hurricane season as part of the
Joint Hurricane Testbed (JHT).
Katsaros, K.B. Book review, Atmosphere-Ocean Interactions, Volume
1, W. Perrie (ed.). Oceanography, 16(4):106-108 (2003).
No abstract.
Katsaros, K.B. Satellite versus in-situ measurements at the air-sea
interface. In Handbook of Weather, Climate and Water: Dynamics, Climate,
Physical Meteorology, Weather Systems, and Measurements, T.D. Potter
and B.R. Colman (eds.). John Wiley and Sons, 885-893 (2003).
In this chapter we explore the trade-offs in selecting surface in-situ versus
satellite platforms to measure properties near or at the air-sea interface.
The most obvious difference between the two observing platforms is sampling
coverage in time and space. A surface platform can obtain continuous
measurements at a point, while a polar-orbiting satellite instrument samples,
at most, twice per day depending on the swath width of the sensor. A
geostationary satellite can sample the surface as frequently as every 15
minutes (once per hour is typical), but the high altitude (38,000 km) limits
the resolution that is achievable for some sensors. To focus the discussion,
we compare the following two variables commonly measured by both in-situ and
satellite systems: the sea surface temperature (SST) and surface wind speed,
U, or wind vector, [overline] U.
Katsaros, K.B., A.M. Mestas-Nunez, A. Bentamy, and E.B. Forde. Wind bursts
and enhanced evaporation in the tropical and subtropical Atlantic Ocean.
In Interhemispheric Water Exchange in the Atlantic Ocean, G.J. Goni
and P. Malanotte-Rizzoli (eds.). Elsevier Oceanography Series, 68 (ISBN
0444512675), 463-474 (2003).
Satellite-derived estimates of weekly latent heat flux for the tropical
and subtropical Atlantic Ocean (40°S to 40°N) were calculated
for a one-year period from September 30, 1996 to September 28, 1997 (52
weeks). The oceanic variables required to estimate evaporation (sea surface
temperature, surface wind speed, and surface air humidity) were obtained
from sensors on several polar-orbiting satellites including the European
Remote Sensing satellite 2 (ERS-2), the NASA scatterometer (NSCAT), and
the Special Sensor Microwave/Imager (SSM/I). During this period, high
values of the weekly satellite estimates of wind speed and latent heat
flux were found over the northeast and southeast trade wind regions. In
these regions, the 52-week average fields showed wind speeds greater than
about 7 m s-1 and associated evaporation rates greater than 120
W m-2. The annual cycle dominates the temporal evolution of sea
surface temperature but is hardly noticeable in wind speed and latent heat
flux, which are dominated by large 3-4 week fluctuations. The most significant
event during our period of study was a strong northeast trade wind burst that
originated near the northwest African coast in early February 1997. It
persisted for five weeks as it crossed the North Atlantic Ocean and finally
dissipated in the Caribbean Sea in early March 1997. In the southeast trade
region, a similar but less intense period of higher flux was observed during
July 1997. These large-scale wind bursts illustrate the strong role that the
Atlantic trade winds play in enhancing evaporation.
Kelble, C.R., G.L. Hitchcock, P.B. Ortner, and J.N. Boyer. A recent study
of the light environment in Florida Bay. Joint Conference on the Science
and Restoration of the Greater Everglades and Florida Bay Ecosystem from
Kissimmee to the Keys, Palm Harbor, FL, April 13-18, 2003. University of
Florida Office of Conferences and Institutes, 48-50 (CD-ROM) (2003).
No abstract.
Knaff, J.A., N. Wang, M. DeMaria, M. Zehr, J.S. Griffin, and F.D.
Marks. A demonstration of real-time transmission and display of GOES imagery
aboard the NOAA P-3 aircraft during the 2002 hurricane season.
Preprints, 12th Conference on Satellite Meteorology and
Oceanography and 3rd Conference on Artificial Intelligence
Applications to Environmental Science, Long Beach, CA, February 8-13,
2003. American Meteorological Society, Boston, 5 pp. (CD-ROM) (2003).
No abstract.
Kollias, P., B.A. Albrecht, and F.D. Marks. Cloud radar observations of
vertical drafts and microphysics in convective rain. Journal of
Geophysical Research, 108(D2):4053, doi:10.1029/2001JD002033
(2003).
Observations of convective precipitation using a 94-GHz cloud radar are
presented. Due to Mie scattering, the Doppler power spectra collected at
vertical incidence contains characteristics of the scatterers (hydrometeors).
These characteristics are used for the retrieval of the vertical air motion
and the associated raindrop size distribution in an attempt to accurately map
the time-height structure of the vertical air motion and raindrop fields
within intense convective precipitation. The data provide strong evidence of
the interaction between draft intensity and raindrop size distribution and
highlight the variability of convective precipitation at small scales.
Horizontal sorting of the raindrops caused by the air motion is documented.
Signal attenuation measured at 94 GHz is shown to be well correlated to
rainfall rates. The observations demonstrate the capability of 94-GHz cloud
radars for studies of precipitation processes at low altitudes even under
intense convective conditions.
Landsea, C.W., C. Anderson, N. Charles, G. Clark, J.P. Dunion, J.
Fernandez-Partagas, P. Hungerford, C. Neumann, and M. Zimmer. The Atlantic
hurricane database re-analysis project: Results for the first 60 years,
1851-1910. Preprints, 14th Symposium on Global Change and Climate
Variations, Long Beach, CA, February 9-13, 2003. American
Meteorological Society, Boston, 36 pp. (CD reprint) (2003).
No abstract.
Langdon, C., W.S. Broecker, D.E. Hammond, E. Glenn, K. Fitzsimmons, S.G.
Nelson, T.-H. Peng, I. Hajdas, and G. Bonani. Effect of elevated
CO2 on the community metabolism of an experimental coral reef.
Global Biogeochemical Cycles, 17(1):1011, doi:10.1029/2002GB001941
(2003).
The effect of elevated pCO2 on the metabolism of a coral reef
community dominated by macroalgae has been investigated utilizing the
large 2650 m3 coral reef mesocosm at the Biosphere-2 facility
near Tucson, Arizona. The carbonate chemistry of the water was manipulated
to simulate present-day and a doubled CO2 future condition.
Each experiment consisted of a one-two month preconditioning period
followed by a seven-nine day observational period. The pCO2
was 404 ± 63 µatm during the present-day pCO2 experiment
and 658 ± 59 µatm during the elevated pCO2 experiment.
Nutrient levels were low and typical of natural reefs waters
(NO3- 0.5-0.9 µM, NH4+
0.4 µM, PO43- 0.07-0.09 µM). The
temperature and salinity of the water were held constant at 26.5 ±
0.2°C and 34.4 ± 0.2 ppt. Photosynthetically available irradiance was
10 ± 2 during the present-day experiment and 7.4 ± 0.5 mol photons
m-2 d-1 during the elevated pCO2
experiment. The primary producer biomass in the mesocosm was dominated by
four species of macroalgae: Haptilon cubense, Amphiroa fragillisima,
Gelidiopsis intricata, and Chondria dasyphylla. Algal biomass was 10.4
mol C m-2 during the present-day and 8.7 mol C m-2
and during the elevated pCO2 experiments. As previously
observed, the increase in pCO2 resulted in a decrease in
calcification from 0.041 ± 0.007 to 0.006 ± 0.003 mol CaCO3
m-2 d-1. Net community production (NCP) and dark
respiration did not change in response to elevated pCO2. Light
respiration measured by a new radiocarbon isotope dilution method exceeded
dark respiration by a factor of 1.2 ± 0.3 to 2.1 ± 0.4 on a daily basis
and by 2.2 ± 0.6 to 3.9 ± 0.8 on an hourly basis. The 1.8-fold increase
with increasing pCO2 indicates that the enhanced respiration in
the light was not due to photorespiration. Gross production (GPP) computed
as the sum of NCP plus daily respiration (light + dark) increased
significantly (0.24 ± 0.03 vs. 0.32 ± 0.04 mol C m-2
d-1). However, the conventional calculation of GPP based on the
assumption that respiration in the light proceeds at the same rate as the
dark underestimated the true rate of GPP by 41-100% and completely missed
the increased rate of carbon cycling due to elevated pCO2. We
conclude that under natural, undisturbed, nutrient-limited conditions
elevated CO2 depresses calcification, stimulates the rate of
turnover of organic carbon, particularly in the light, but has no effect
on net organic production. The hypothesis that an increase pCO2
would produce an increase in net production that would counterbalance the
effect of decreasing saturation state on calcification is not supported by
these data.
Lee, K., S.-D. Choi, G.-H. Park, R.H. Wanninkhof, T.-H. Peng, R.M. Key,
C.L. Sabine, R.A. Feely, J.L. Bullister, F.J. Millero, and A. Kozyr. An
updated anthropogenic CO2 inventory in the Atlantic Ocean.
Global Biogeochemical Cycles, 17(4):1116, doi:1029/2003GB002067
(2003).
This paper presents a comprehensive analysis of the basin-wide inventory
of anthropogenic CO2 in the Atlantic Ocean based on
high-quality inorganic carbon, alkalinity, chlorofluorocarbon, and
nutrient data collected during the World Ocean Circulation Experiment
(WOCE) Hydrographic Program, the Joint Global Ocean Flux Study (JGOFS),
and the Ocean-Atmosphere Carbon Exchange Study (OACES) surveys of the
Atlantic Ocean between 1990 and 1998. Anthropogenic CO2 was
separated from the large pool of dissolved inorganic carbon using an
extended version of the DELTA-C* method originally developed by Gruber
et al. (1996). The extension of the method includes the use of an
optimum multiparameter analysis to determine the relative contributions
from various source water types to the sample on an isopycnal surface.
Total inventories of anthropogenic CO2 in the Atlantic Ocean
are highest in the subtropical regions at 20°-40°, whereas
anthropogenic CO2 penetrates the deepest in high-latitude
regions (>40°N). The deeper penetration at high northern latitudes is
largely due to the formation of deep water that feeds the Deep Western
Boundary Current, which transports anthropogenic CO2 into the
interior. In contrast, waters south of 50°S in the Southern Ocean
contain little anthropogenic CO2. Analysis of the data
collected during the 1990-1998 period yielded a total anthropogenic
CO2 inventory of 28.4 ± 4.7 Pg C in the North Atlantic
(equator-70°N) and of 18.5 ± 3.9 Pg C in the South Atlantic
(equator-70°S). These estimated basin-wide inventories of
anthropogenic CO2 are in good agreement with previous estimates
obtained by Gruber (1998), after accounting for the difference in
observational periods. Our calculation of the anthropogenic CO2
inventory in the Atlantic Ocean, in conjunction with the inventories
calculated previously for the Indian Ocean (Sabine et al., 1999)
and for the Pacific Ocean (Sabine et al., 2002), yields a global
anthropogenic CO2 inventory of 112 ± 17 Pg C that has
accumulated in the world oceans during the industrial era. This global
oceanic uptake accounts for approximately 29% of the total CO2
emissions from the burning of fossil fuels, land-use changes, and cement
production during the past 250 years.
Lee, T.N., E. Williams, E. Johns, R.H. Smith, and N. Melo. Circulation and
exchange processes within Florida Bay interior basins. Joint Conference on
the Science and Restoration of the Greater Everglades and Florida Bay
Ecosystem from Kissimmee to the Keys, Palm Harbor, FL, April 13-18, 2003.
University of Florida Office of Conferences and Institutes, 26-28 (CD-ROM)
(2003).
No abstract.
Lee, W.-C., F.D. Marks, and C. Walther. Airborne Doppler radar data
analysis workshop. Bulletin of the American Meteorological Society,
84(8):1063-1075 (2003).
The Airborne Doppler Radar Data Analysis Workshop, sponsored by the
Atmospheric Technology Division (ATD) of the National Center for Atmospheric
Research (NCAR), was the first to focus on analyzing airborne Doppler radar
data. The workshop (held 13-16 March 2000 at NCAR) aimed to (1) summarize
the current airborne Doppler radar data analysis techniques, and (2) promote
the use of airborne Doppler radar data in the atmospheric sciences community.
The workshop also intended to encourage new users to analyze this Doppler
data and to provide a forum for experienced users to exchange ideas and
discuss problems related to analyzing the data. It also provided a forum to
train the users in planning future airborne Doppler radar programs. Graduate
students, recent PhDs, faculty and researchers participantsthe leading experts
in the fieldcovered the theory of airborne Doppler radar, experiment design,
standard data analysis procedures and software, and recently developed
analysis techniques. Eight working groups were organized among the
participants to analyze preselected airborne Doppler radar datasets collected
in past experiments using the standard software available from NCAR. Each
working group used standard data analysis procedures to obtain dual-Doppler
radar winds from raw airborne Doppler radar data.
Lirman, D., B. Orlando, S. Macia, D. Manzello, L. Kaufman, P. Biber,
and T. Jones. Coral communities of Biscayne Bay, Florida and adjacent
offshore areas: Diversity, abundance, distribution, and environmental
correlates. Aquatic Conservation: Marine and Freshwater Ecosystems,
13(2):121-135 (2003).
Hardbottom habitats of Biscayne Bay, a shallow lagoon adjacent to the city
of Miami, Florida, contain a limited number of coral species that represent a
small subset of the species found at nearby offshore hardbottom and reef
habitats of the Florida Reef Tract. Although the physical characteristics of
this basin make it a marginal environment for coral growth, the presence of
dense populations of Siderastrea radians and Porites furcata
indicate that these, as well as other corals that are found at lower
densities, are able to tolerate extreme and fluctuating conditions. Three
factors, temperature, sedimentation, and salinity, appear to limit coral
abundance, diversity, and distribution within Biscayne Bay. Temperatures
exhibit high frequencies of extreme high and low values known to cause coral
stress and mortality elsewhere. Similarly, sedimentation rates are very high
and sediment resuspension caused by currents, storms, and boating activities
commonly bury corals under sediment layers. Sediment burial was shown
experimentally to influence growth and mortality of S. radians. The
salinity of Biscayne Bay is influenced by freshwater inputs from canal,
sheetflow, and groundwater sources that create a near-shore environment with
low mean salinity and high salinity fluctuation. Coral communities along
this western margin have the lowest coral density and species richness.
Chronic exposure to low salinity was shown experimentally to cause a decrease
in the growth of S. radians. The location of Biscayne Bay, downstream
of a large restoration effort planned for the Everglades watershed,
highlights the need to understand the relationship between the physical
environment and the health of benthic communities. The data presented here
provide the type of scientific information needed so that management
decisions can take into account the potential impacts of human activities on
the health of coral populations that are already near their tolerance limits
for temperature, salinity, and sedimentation.
Liu, K.-K., T.-H. Peng, P.-T. Shaw, and F.-K. Shiah. Circulation and
biogeochemical processes in the East China Sea and the vicinity of Taiwan:
An overview and a brief synthesis. Deep-Sea Research, Part II,
50(6-7):1055-1064 (2003).
The East China Sea shelf (including the Yellow Sea and the Bohai Sea) is a
very challenging system for hydrodynamic and biogeochemical studies due to
its complicated physical and chemical forcing. It receives much attention
because of its capacity for absorbing atmospheric CO2 in spite of
large riverine fluxes of terrigenous carbon. This volume reports field
observations and modeling studies during the Kuroshio Edge Exchange Processes
and ensuing projects, which are a part of the continental margins study in
the Joint Global Ocean Flux Study. A three-dimensional numerical model has
been developed to simulate the climatological circulation in the East China
Sea. The model result is supported by observations in the seas around Taiwan.
The significance of inflow from the Taiwan Strait is emphasized. Geochemical
tracers prove useful in understanding the water and material transport.
Biogeochemical studies suggest very efficient recycling of organic carbon by
bacterial and protozoan consumption in the shelf water, but a finite amount of
particulate organic carbon with a significant terrigenous fraction is
exported from the shelf. The fine-grained sediments in the inner shelf
appear to be an important source of organic carbon for export. Future
studies are needed to improve our understanding of key physical and
biogeochemcial processes, to develop coupled physical-biogeochemical
models, and to catch and survey the elusive spring algal bloom. A
tantalizing goal of our ongoing effort is to document or even to predict
future changes in the East China Sea shelf caused by the operation of the
Three-Gorge Dam, which is under construction in the middle reach of the
Yangtze River.
Lumpkin, R. Decomposition of surface drifter observations in the Atlantic
Ocean. Geophysical Research Letters, 30(14):1753,
doi:10.1029/2003GL017519 (2003).
Surface drifter observations are decomposed into mean, seasonal (annual and
semiannual), and eddy components via Gauss-Markov estimation. This approach
helps separate seasonal fluctuations and mean values in the
observationally-sparse tropical and South Atlantic, where monthly mean
values cannot be calculated at the spatial scale of the major currents. In
some regions, large differences are found between these means and those
obtained by simple binned averaging. The differences are attributed to
inhomogeneous sampling of seasonal variability, and to the inherent bias
of Lagrangian observations towards periods of low velocity. The analysis
reveals strong seasonal variations of some surface currents, including a
significant late spring reversal of the western North Equatorial
Counter-Current.
Lumpkin, R., and K. Speer. Large-scale vertical and horizontal circulation
in the North Atlantic Ocean. Journal of Physical Oceanography,
33(9):1902-1920 (2003).
Observations of large-scale hydrography, air-sea forcing, and regional
circulation from numerous studies are combined by inverse methods to
determine the basin-scale circulation, average diapycnal mixing, and
adjustments to air-sea forcing of the North Atlantic Ocean. Dense overflows
through the Denmark Strait and Faroe Bank channels are explicitly included
and are associated with strong vertical and lateral circulation and mixing.
These processes in the far northern Atlantic play a fundamental role in the
meridional overturning circulation for the entire ocean, accompanied by an
upper cell of mode-water and intermediate-water circulation. The two cells
converge roughly at the mean depth of the midocean ridge crest. The Labrador
Sea Water layer lies within this convergence. South of the overflow region,
model-derived mean diapycnal diffusivities are O(10-5
m2 s-1) or smaller at the base of the thermocline,
and diapycnal advection is driven primarily by air-sea transformation on
outcropping layers.
Macdonald, A.M., M.O. Baringer, R. Wanninkhof, K. Lee, and D.W.R. Wallace.
A 1998-1992 comparison of inorganic carbon and its transport across
24.5°N in the Atlantic. Deep-Sea Research, Part II,
50(22-26):3041-3064 (2003).
In January and February 1998, when an unprecedented fourth repetition of
the zonal hydrographic transect at 24.5°N in the Atlantic was
undertaken, carbon measurements were obtained for the second time in less
than a decade. The field of total carbon along this section is compared to
that provided by a 1992 cruise which followed a similar path (albeit in a
different season). Consistent with the increase in atmospheric carbon
levels, an increase in anthropogenic carbon concentrations of 8 ± 3
mol kg-1 was found in the surface layers. Using an inverse
analysis to determine estimates of absolute velocity, the flux of
inorganic carbon across 24.5° is estimated to be -0.74 ± 0.91
and -1.31 ± 0.99 Pg Cyr-1 southward in 1998 and 1992,
respectively. Estimates of total inorganic carbon flux depend strongly
upon the estimated mass transport, particularly of the Deep Western
Boundary Current. The 1998 estimate reduces the large regional divergence
in the meridional carbon transport suggested by previous studies and
brings into question the idea that the tropical Atlantic constantly
outgasses carbon, while the subpolar Atlantic sequesters it. Uncertainty
in the carbon transports themselves, dominated by the uncertainty in the
total mass transport estimates, are a hindrance to determining the "true"
picture. The flux of anthropogenic carbon (C*ANTH) across the
two transects is estimated as northward at 0.20 ± 0.08 and 0.17
± 0.06 Pg Cyr-1 for the 1998 and 1992 sections,
respectively. The net transport of C*ANTH across 24.5°N is
strongly affected by the difference in concentrations between the
northward flowing shallow Florida Current and the mass balancing, interior
return flow. The net northward transport of C*ANTH is opposite
the net flow of total carbon and suggests, as has been found by others,
that the pre-industrial southward transport of carbon within the Atlantic
was stronger than it is today. Combining these flux results with estimates
of atmospheric and riverine inorganic carbon input, it is determined that
today's oceanic carbon system differs from the pre-industrial system in
that today there is an uptake of anthropogenic carbon to the south that is
advected northward and stored within the North Atlantic basin.
Manzello, D., and D. Lirman. The photosynthetic resilience of Porites
furcata to salinity disturbance. Coral Reefs, 22(4):537-540
(2003).
No abstract.
Marks, F.D. Hurricanes. In Encyclopedia of Atmospheric Sciences,
Elsevier Science Ltd., London, UK, 942-966 (2003).
No abstract.
Marks, F.D. Hurricanes. In Handbook of Weather, Climate and Water:
Dynamics, Climate, Physical Meteorology, Weather Systems, and
Measurements, T.D. Potter and B.R. Colman (eds.). John Wiley and Sons,
641-676 (2003).
No abstract.
Marks, F.D. State of the science: Radar view of tropical cyclones. In
Radar and Atmospheric Science: A Collection of Essays in Honor of David
Atlas, R.M. Wakimoto and R.C. Srivastava (eds.). Meteorological Monograph,
Volume 30, No. 52, American Meteorological Society, Boston, 33-74 (2003).
No abstract.
Mayer, D.A., M.O. Baringer, and G.J. Goni. Comparison of hydrographic and
altimeter based estimates of sea level height variability in the Atlantic
Ocean. In Interhemispheric Water Exchange in the Atlantic Ocean,
G.J. Goni and P. Malanotte-Rizzoli (eds.). Elsevier Oceanography Series,
68 (ISBN 0444512675), 23-48 (2003).
Our ability to understand the means by which mass and heat are exchanged
between the tropics and subtropics is seriously compromised when using
only sea level data because the exchange processes span a wide range of
variability across the different dynamical regimes in our domain.
Expendable bathythermograph (XBT) profiles and TOPEX/Poseidon (T/P)
altimeter data are compared to temperature anomalies (TA) and to dynamic
height anomalies (DHA) for the period 1993 through 1997 to determine how
much can be inferred about the internal field of mass from sea level
changes. Our focus is on the annual cycle along two well-sampled XBT
sections on the western and eastern sides of the Atlantic Ocean from
10°S to 40°N. XBT profiles were matched (time/location) to Sea
height anomalies (SHA) derived from T/P data, 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, unless there is a strong relationship between SHA and DHA and
an understanding of the details of how temperature variability affects DHA.
These relationships can be problematic if SHA are small. This occurs in
zones of transition in the vicinity of troughs where small fluctuations in
SHA belie the true nature of water column variability. These areas separate
the mid-latitudes where surface buoyancy fluxes dominate from those in the
equatorial region where ocean dynamics cause thermocline effects that
dominate the forcing of sea level. Thus, the variability of SHA in transition
regions tends to be small because both surface and thermocline variability
may be significant but compensating in nature. This emphasizes how important
direct observations (in-situ data) can be in interpreting SHA correctly.
Strong relationships between SHA and DHA are suggested where more than half
of the SHA variance in the annual cycle can be accounted for by DHA
(approximately 30% of the positions along the two XBT sections). These
relationships between SHA and DHA for residual variability (obtained by
removing the annual cycle) are weak. 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 near 50°W, 8°N. 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.
Meinen, C.S., and D.S. Luther. Comparison of methods of estimating mean
synoptic current structure in "stream coordinates" reference frames with
an example from the Antarctic Circumpolar Current. Deep-Sea Research,
Part I, 50(2):201-220 (2003).
Stream coordinates techniques, that is, methods of deriving the mean
"synoptic" structures of narrow meandering ocean currents from Eulerian
measurements, have been in use for nearly two decades and have resulted in
improvements in our understanding of the dynamics and transports of such
currents. A two-year experiment in the Sub-Antarctic Front (SAF) southwest
of Tasmania, involving overlapping arrays of inverted echo sounders and
horizontal electric field recorders, has provided an opportunity to test
various stream coordinates methods. The methods differ significantly in how
well, or even if, they can reveal divergence or convergence of the meandering
current, and whether they accurately reproduce the current's horizontal
structure and transport. Cross-stream distance was determined either via a
frozen-field assumption or as the distance to an optimally interpolated (OI)
origin contour; downstream direction was determined either as the local
direction which maximized the vertical shear of horizontal velocity or as
the tangent line to the OI mapped core contour. All combinations of these
distance and direction definitions were tested. The use of a frozen field
assumption in determining cross-stream distance yields overly smooth
along-stream velocity cross-sections and overestimated transports. The
vertical shear definition of downstream direction results in a false rotation
of cross-stream flows into along-stream flows near the flanks of the current.
The preferred methods define the horizontal location of the front with
two-dimensional arrays of instruments (e.g., inverted echo sounders or
moored current meters). Methods employing the assumptions of a meandering
"frozen-field" baroclinic structure or the use of the local vertical shear
of the horizontal velocity to determine the downstream direction should be
avoided, if possible, particularly in the SAF.
Meinen, C.S., D.S. Luther, D.R. Watts, A.D. Chave, and K.L. Tracey. Mean
stream coordinates structure of the Subantarctic Front: Temperature, salinity,
and absolute velocity. Journal of Geophysical Research,
108(C8):3263, doi:10.1029/2002JC001545 (2003).
The mean synoptic structure of the northern, strongest branch of the Antarctic
Circumpolar Current southwest of Tasmania, at the Subantarctic Front (SAF), is
estimated by a stream coordinates analysis of data from overlapping arrays of
Inverted Echo Sounders (IESs) and Horizontal Electric Field Recorders deployed
during the 1995-1997 Sub-Antarctic Flux and Dynamics Experiment. The stream
coordinates are derived from a daily objective mapping of the temperature
field obtained from combining the IES travel time measurements with an
empirical look-up table constructed from the extensive hydrography acquired
during WOCE. Full-water-column stream-coordinates sections of temperature,
salinity, and absolute velocity are presented and compared with prior
observations. The along-stream current has a single peak with surface
velocities reaching about 50 cm s-1. The vertical structure of
the along-stream velocity is roughly consistent with a combined external and
first internal normal mode description that is adapted to the buoyancy
frequency as it varies across the front, although there are some significant
differences. The cross-stream structure of along-stream velocity is very
nearly symmetric about the jet axis, but the lateral shear magnitude is
slightly larger on the cold side of the SAF. Separating the baroclinic and
barotropic currents reveals that the SAF currents are diffluent, primarily
baroclinically, in the cross-stream direction. Baroclinic cross-stream
diffluence of approximately 0.23 Sv per km (Sv = 106
m3 s-1), or about 16 Sv per degree of longitude at
51°S. The 2-year mean total SAF transport is 75 Sv (for a 220 km width);
the barotropic contribution is small (8 Sv) but not negligible.
Melo, N., T.N. Lee, E.J. Williams, D. Smith, M. Framinan, R.H. Smith, and
E. Johns. A movie of Florida Bay sea level response to local wind
forcing. Joint Conference on the Science and Restoration of the Greater
Everglades and Florida Bay Ecosystem from Kissimmee to the Keys, Palm
Harbor, FL, April 13-18, 2003. University of Florida Office of Conferences
and Institutes, 59-60 (CD-ROM) (2003).
No abstract.
Mo, Q., A.G. Detwiler, J. Hallett, and R.A. Black. Horizontal structure
of the electric field in the stratiform region of an Oklahoma mesoscale
convective system. Journal of Geophysical Research, 108(D7):4225,
doi:10.1029/2001JD001140 (2003).
This analysis combines vertical electric field components Ez
observed by two research aircraft flying horizontally at two levels, with
vertical soundings of thermodynamic parameters and Ez made by five
balloons, to produce a quasi-three-dimensional view of the space charge
distribution in the trailing stratiform cloud region behind a mesoscale
convective system (MCS) that developed in central Oklahoma late in the
afternoon of 2 June 1991. The balloons were launched serially at one-hour
intervals from two sites separated by 80 km along a north-south line as the
MCS moved eastward, yielding two east-west time-height cross-sections of the
Ez structure within the quasi-steady state trailing stratiform
region behind the MCS. The balloon measurements are consistent with a
vertical stack of five rearward- and downward-sloping horizontal sheets of
charge of alternating polarity, beginning at the bottom with a negative
charge layer below the 0°C level and a positive layer near the 0°C
level. This structure persisted for more than 2 hours. The two aircraft flew
back and forth along a north-south line through the balloon launch sites
during the balloon launch period. Aircraft measurements demonstrated that the
vertical electric field (Ez) at constant altitude varied in the
north-south direction. The peak magnitudes of Ez deduced from
the airborne instrument systems agreed with the magnitudes deduced from
the balloon measurements at the aircraft altitudes of 4.5 km and 5.8 km AGL.
Rapid reversals in polarity of Ez with peak magnitude >50 kV
m-1 observed by the aircraft at 4.5 km, just above the 0°C
level, confirms the thin concentrated positive charge layer observed there
by balloons and suggests that this charge layer is undulating above and
below 4.5 km altitude, at least in the north-south direction. Microphysically,
this layer contained large aggregates and pockets of low cloud liquid water
concentration. At the 5.8 km level, the polarity of Ez was always
positive but the magnitude varied from zero to 25 kV m-1.
Aircraft-observed Ez at both altitudes varied on horizontal scales
of ~10 km or greater at both levels, suggesting that the charge density
derived using the one-dimensional infinite-layer Gauss's law approximation
applied to the balloon soundings of Ez is valid in this study.
These observations show that layers of charge can persist for hours as they
advect rearward in a storm-relative sense, possibly due to continuing in situ
charge separation, and/or due to weak dispersion, slow recombination, and slow
settling of charge attached to low mobility low terminal velocity ice
hydrometeors.
Molinari, R.L., and A.M. Mestas-Nunez. North Atlantic decadal variability
and the formation of tropical storms and hurricanes. Geophysical
Research Letters, 30(10):1541, doi:10.1029/200GL016462 (2003).
Both the annual number of Atlantic tropical storms forming south of
23.5°N and of Atlantic major hurricanes increased between the 1970s-1980s
and 1995-2000. These increases are coincident with a multi-decadal warming in
North Atlantic SST, suggesting that the high activity of 1995-2000 may persist
for the next ~10 to 40 years. However, during 1950-2000 strong decadal
oscillations are superimposed on the multi-decadal changes in both SST and
tropical storms (positive SST anomalies, increased storm activity). We appear
to be entering a negative phase of the decadal SST signal implying that
tropical storm and, most likely, major hurricane activity may be reduced in
the next several years rather than remain at the very high 1995-2000 level
when both signals were in their positive phase. Tropical storm activity during
2001 and 2002 is less than expected only from the multi-decadal signal but
for 2002 the main cause may be El Niño.
Molinari, R.L., S. Bauer, D.P. Snowden, G.C. Johnson, B. Bourles, Y. Gouriou,
and H. Mercier. A comparison of kinematic evidence for tropical cells in the
Atlantic and Pacific Oceans. In Interhemispheric Water Exchange in the
Atlantic Ocean, G.J. Goni and P. Malanotte-Rizzoli (eds.). Elsevier
Oceanography Series, 68 (ISBN 0444512675), 269-286 (2003).
Kinematic evidence for the existence of Tropical Cells (TC) in the Atlantic
Ocean is offered. Mean sections of meridional velocity, its horizontal
divergence and vertical velocity are estimated from 12 available sections
centered at about 35°W. Of the 12 sections, six were occupied in March
and April, thus there is a boreal spring bias to the observations. Equatorial
upwelling and off-equatorial downwelling, between 3°N and 6°N,
represent the southern and northern boundaries of a northern hemisphere TC.
Uncertainties for the estimates of average quantities are large. However,
favorable comparisons with observational representations of Pacific TCs
provide support for the existence of a northern hemisphere Atlantic TC.
Owens, B.F., and C.W. Landsea. Assessing the skill of operational Atlantic
seasonal tropical cyclone forecasts. Weather and Forecasting,
18(1):45-54 (2003).
Since 1984, William Gray of Colorado State University and a team of
researchers have been issuing seasonal tropical cyclone forecasts for the
North Atlantic Ocean. Prior to this, little work had been done in the area of
long-term tropical cyclone forecasting because researchers saw minimal
potential skill in any prediction models and no obvious benefits to be
gained. However, seasonal forecasts have been attracting more attention as
economic and insured losses from hurricane-related catastrophes rose sharply
during recent decades. Initially, the forecasts issued by Gray consisted of
output from simple statistical prediction models. Over time, the models
became increasingly more complex and sophisticated, with new versions being
introduced in 1992, 1993, 1994, 1996, and 1997. In addition, based on a
combination of experience with the statistical models and other qualitative
considerations such as examinations of analog years, the statistical forecasts
were modified to create adjusted seasonal forecasts. This analysis assessed
the skill demonstrated, if any, of both the statistical and adjusted forecasts
over the benchmarks of climatology and persistence and examined whether the
adjusted forecasts were more accurate than the statistical forecasts. The
analysis indicates that, over the past 18 years, both the statistical and
adjusted forecasts demonstrated some skill over climatology and persistence.
There is also evidence to suggest that the adjusted forecast was more skillful
than the statistical model forecast.
Palmer, D.R. On the interpretation of measurements of acoustic backscatter
from dredged-material plumes. Journal of Marine Environmental
Engineering, 7(2):125-152 (2003).
During the Mobile, Alabama Field Data Collection Project (MFDCP), a barge
repeatedly released dredging material at an ocean dumpsite near Mobile Bay
while a research ship tracked the resulting underwater plumes. This ship was
equipped with high-frequency sonar systems and equipment for measuring water
properties and collecting sediment and water samples. Ogushwitz has presented
an analysis of the relationship between particle concentration in the plumes,
as measured from water sampling, and sonar echo strength. To explain the
great variability in echo strength measurements, Ogushwitz listed a number of
possible sources of variability which we group into four categories:
experimental design, plume characteristics, ambient ocean conditions, and
instrumentation effects. Ogushwitz argued that one of these sources of
variability, the tumbling of the irregularly shaped particles that comprised
the plumes, could result in up to 7 dB variability in echo strength. The
argument is based on the short-wavelength or geometrical acoustics result
that the backscattered intensity is proportional to the geometrical area of
the target particle as seen by the incident sonar beam. This argument is
somewhat inconsistent, however, since it is known that the scattering took
place in the long-wavelength or Rayleigh region. New analytic techniques have
been developed since the publication of Ogushwitz's results that allow us to
obtain a more accurate determination of the maximum variability in echo
strength that can be attributed to particle shape. In this paper, we develop
a formalism for applying these techniques to MFDCP. We find tumbling of
irregularly shaped particles in the plume can only lead to a variability in
the backscattered intensity of from 0.9 dB below the intensity for scattering
from spheres to 3.8 dB above the intensity for spheres. We also use this
formalism to discuss several of the sources of variability in Ogushwitz's
list and their significance for estimating particle concentration from
backscattered intensity. The discussion is framed in terms of the insonified
volume determined by the sonar characteristics and defined such that at any
specific time the received pressure field is the sum of the fields scattered
by particles in this volume. The random distribution of the particles in the
insonified volume leads to a Rayleigh distribution for the backscattered
intensity. Ping-to-ping variability of the mean concentration of particles
in the insonified volume can be used to characterize plume type. For dredging
material plumes, this variability makes it very difficult, if not impossible,
to obtain quality estimates of particle concentration based on knowledge of
the acoustic intensity. In addition to this inverse scattering problem, we
discuss the value of the images of plumes obtained from single-ping data or
data averaged over a few pings. Despite their qualitative nature, these
images have several valuable uses. We point out that quantitative plume
images would have additional uses and that there does not seem to be any
obstacle in developing, for a given experimental situation, a formalism for
creating them.
Peng, T.-H., R. Wanninkhof, and R.A. Feely. Increase of anthropogenic
CO2 in the Pacific Ocean over the last two decades. Deep-Sea
Research, Part II, 50(22-26):3065-3082 (2003).
The multiple-parameter linear regression method (Monitoring global ocean
carbon inventories, Ocean Observing System Development Panel, Texas A&M
University, College Station, TX, 1995, 54 pp; Global Biogeochem.
Cycles, 13 (1999) 179) is used to compare inorganic carbon data from
the GEOSECS CO2 survey in the Pacific Ocean in 1973 to the
WOCE/JGOFS global CO2 survey in the 1990s. A model of total
dissolved inorganic carbon (DIC) as a function of five variables (AOU,
theta, S, Si, and PO4) has been developed from the recent
CO2 survey data (namely CGC91 and CGC96) in the Pacific Ocean.
After correcting for a systematic DIC offset of -30.3 ± 7 mol
kg-1 from the GEOSECS data, the residual DIC based on this
model as computed from GEOSECS data has been used to estimate the
anthropogenic CO2 penetration in the Pacific Ocean. In the
Northeast Pacific, we obtained an increase of CO2 of 21.3
± 7.9 mol m-2 over the period from GEOSECS in 1973 to
CGC91 in 1991. This gives a mean anthropogenic CO2 uptake rate
of 1.3 ± 0.5 mol m-2 yr-1 over this 17 year
time period. In the South Pacific, north of 50°S between 180°
and 120°W region, the integrated anthropogenic CO2
inventory is estimated to be 19.7 ± 5.7 mol m-2 over the
period from GEOSECS in 1974 to CGC96 in 1996. The equivalent mean
CO2 uptake rate is estimated to be 0.9 ± 0.3 mol
m-2 yr-1 over the 22 years. These results are
compared with the isopycnal method (Nature, 396 (1998) 560) to
estimate the anthropogenic CO2 signal in the Northeast Pacific
(30°N, 152°W) at the crossover region between CGC91 and GEOSECS.
The results of the isopycnal method are consistent with those derived from
the MLR method. Both methods show an increase in anthropogenic
CO2 inventory in the ocean over two decades that is consistent
with the increase expected if the ocean uptake has kept pace with the
atmospheric CO2 increase.
Pielke, R.A., J. Rubiera, C. Landsea, M.L. Fernandez, and R.
Klein. Hurricane vulnerability in Latin America and the Caribbean: Normalized
damage and loss potentials. Natural Hazards Review, 4(3):101-114
(2003).
In late October 1998, the remnants of Hurricane Mitch stalled over Honduras
and Nicaragua, killing more than 10,000 people and causing as much as $8.5
billion in damage. While Central America and the Caribbean have a history of
natural disasters, the fatalities and destruction caused by Mitch were the
greatest in at least several decades, prompting many questions including:
What accounts for the extent of these losses? Is Mitch a harbinger of future
disasters in the region? and What might be done in response? This paper seeks
to shed light on these questions by examining the historical and geographic
context of hurricane vulnerability in Latin America and the Caribbean. The
paper examines trends in economic and other societal factors that increase
vulnerability to hurricanes in Central America and the Caribbean and includes
a case study of normalized hurricane losses in Cuba made possible by newly
collected damage data published herein. The paper places its findings into
the context of policies related to climate change and natural hazards.
Powell, M.D., P.J. Vickery, and T.A. Reinhold. Reduced drag coefficient
for high wind speeds in tropical cyclones. Nature, 422:279-283
(2003).
The transfer of momentum between the atmosphere and the ocean is described
in terms of the variation of wind speed with height and a drag coefficient
that increases with sea surface roughness and wind speed. But direct
measurements have only been available for weak winds; momentum transfer
under extreme wind conditions has therefore been extrapolated from these
field measurements. Global Positioning System sondes have been used since
1997 to measure the profiles of the strong winds in the marine boundary layer
associated with tropical cyclones. Here we present an analysis of these data,
which show a logarithmic increase in mean wind speed with height in the
lowest 200 m, maximum wind speed at 500 and a gradual weakening up to a
height of 3 km. By determining surface stress, roughness length, and neutral
stability drag coefficient, we find that surface momentum flux levels off as
the wind speeds increase above hurricane force. This behavior is contrary to
surface flux parameterizations that are currently used in a variety of modeling
applications, including hurricane risk assessment and prediction of storm
motion, intensity, waves, and storm surges.
Richardson, P.L., and S.L. Garzoli. Characteristics of intermediate water
flow in the Benguela Current as measured with RAFOS floats. Deep-Sea
Research, Part II, 50(1):87-118 (2003).
Seven floats (not launched in rings) crossed over the mid-Atlantic Ridge in
the Benguela extension with a mean westward velocity of around 2 cm/s between
22°S and 35°S. Two Agulhas rings crossed over the mid-Atlantic Ridge
with a mean velocity of 5.7 cm/s toward 285°. This implies they
translated at around 3.8 cm/s through the background velocity field near
750 m. The boundaries of the Benguela Current extension were clearly defined
from the observations. At 750 m, the Benguela extension was bounded on the
south by 35°S and the north by an eastward current located between
18°S and 21°S. Other recent float measurements suggest that this
eastward current originates near the Trindade Ridge close to the western
boundary and extends across most of the South Atlantic, limiting the Benguela
extension from flowing north of around 20°S. The westward transport of
the Benguela extension was estimated to be 15 Sv by integrating the mean
westward velocities from 22°S to 35°S and multiplying by the 500 m
estimated thickness of intermediate water. Roughly 1.5 Sv of this are
transported by the ~3 Agulhas rings that cross the mid-Atlantic
Ridge each year (as observed with altimetry). This value of the Benguela
extension transport is the first one to have been obtained from long-term
(two-year) observations and across the full width of the Benguela
extension.
Rogers, R.F., S. Chen, J. Tenerelli, and H.E. Willoughby. A numerical
study of the impact of vertical shear on the distribution of rainfall in
Hurricane Bonnie (1998). Monthly Weather Review, 131(8):1577-1599
(2003).
Despite the significant impacts of torrential rainfall from tropical cyclones
at landfall, quantitative precipitation forecasting (QPF) remains an unsolved
problem. A key task in improving tropical cyclone QPF is understanding the
factors that affect the intensity and distribution of rainfall around the
storm. These include the storm motion, topography, and orientation of the
coast, and interactions with the environmental flow. The combination of these
effects can produce rainfall distributions that may be nearly axisymmetric or
highly asymmetric and rainfall amounts that range from 1 or 2 cm to >30 cm.
This study investigates the interactions between a storm and its environmental
flow through a numerical simulation of Hurricane Bonnie (1998) that focuses on
the role of vertical wind shear in governing azimuthal variations of rainfall.
The simulation uses the high-resolution nonhydrostatic fifth-generation
Pennsylvania State University-NCAR Mesoscale Model (MM5) to simulate the storm
between 0000 UTC 22 August and 0000 UTC 27 August 1998. During this period
significant changes in the vertical shear occurred in the simulation. It
changed from strong west-southwesterly, and across track, to much weaker
south-southwesterly, and along track. Nearly concurrently, the azimuthal
distribution of convection changed from a distinct wavenumber-1 pattern to
almost azimuthally symmetric by the end of the time period. The strongest
convection in the core was generally located on the downshear left side of the
shear vector when the shear was strong. The azimuthal distributions and
magnitudes of low-level radial inflow, reflectivity, boundary layer
divergence, and low-level vertical motion all varied consistently with the
evolution of the vertical shear. Additionally, the vortex showed a generally
downshear tilt from the vertical. The magnitude of the tilt correlated well
with changes in magnitude of the environmental shear. The accumulated rainfall
was distributed symmetrically across the track of the storm when the shear was
strong and across track, and it was distributed asymmetrically across the
track of the storm when the shear was weak and along track.
Sandrik, A., and C.W. Landsea. Chronological listing of tropical cyclones
affecting north Florida and coastal Georgia, 1565-1899. NOAA Technical
Memorandum, NOAA-TM-NWS-SR-244 (PB2003-104513), 74 pp. (2003).
This chronology is a portion of an ongoing re-analysis project for
tropical cyclone events along the Georgia and northeast Florida coasts,
including inland north Florida and southeast Georgia. The domain for this
study ranges from Savannah, Georgia in the north to Flagler Beach, Florida
in the south, the adjacent coastal waters, the inland cities (and their
surrounding areas) of Palatka, Gainesville, and Lake City in Florida and
Waycross, Georgia. The number of hurricanes and principle areas affected
after 1900 are considered to be fairly accurate, but are the subject of a
reevaluation by the Hurricane Research Division (HRD) in Miami, Florida
(Landsea et al., 1999, 2003). The intention of this study is to
accurately extend the historical hurricane landfall data base for the study
area back as far as possible, but at a minimum to 1800.
Schmid, C., Z.D. Garraffo, E. Johns, and S.L. Garzoli. Pathways and
variability at intermediate depths in the tropical Atlantic. In
Interhemispheric Water Exchange in the Atlantic Ocean, G.J. Goni
and P. Malanotte-Rizzoli (eds.). Elsevier Oceanography Series, 68 (ISBN
0444512675), 233-268 (2003).
Oceanographic and meteorological data, as well as model results, are analyzed
to study the pathways and the temporal variability of the intermediate depth
(800-1100 m) flow in the tropical Atlantic (9°S to 7°N). The mean
flow is dominated by zonal currents which interact with the western boundary
current. These currents frequently experience reversals of the zonal and
meridional flow. The primary focus in the analysis of the variability is on
the region around 6°S. The observations reveal temporal variability on
mesoscale, annual, and interannual time scales. Several westward propagating
signals can be identified, with propagation velocities between 5 and 7 cm
s-1. Two zonal length scales (500-700 km and more than 2000 km)
are observed. It is hypothesized that these are due to planetary waves. A
comparative analysis of observations and model velocities reveals striking
similarities in their time and length scales. Sample spectra of the model
velocities show a dominant peak of the spectral energy density at a wave
length between 500 km and 1100 km. Additionally, a longer wave with a zonal
wave length of about 5000 km is present, which can not be resolved by the
spectral analysis. In the time space the spectral analysis for the zonal
and meridional velocity reveals coinciding peaks at periods of 45 days, 66
days, and one year. For the latter two periods, the energy for the two
velocity components are quite similar. An analytical planetary wave solution
shows that a superposition of a mesoscale and an annual planetary wave in
sufficient to reproduce a large part of the variability found in the
observations and the model. The wave with an annual period is most likely
due to the annual cycle of the wind field.
Schmid, C., O. Boebel, W. Zenk, J.R.E. Lutjeharms, S.L. Garzoli, P.L.
Richardson, and C. Barron. Early evolution of an Agulhas ring.
Deep-Sea Research, Part II, 50(1):141-166 (2003).
Rings shed at the Agulhas retroflection are an integral part of interoceanic
exchange south of Africa. There is clear evidence of westward ring translation
from the northern Cape Basin across the South Atlantic Ocean. Early ring
development and translation from the southern to the northern Cape Basin,
however, are obscured by an intensely variable kinematic field close to the
spawning site. In this study, unique in-situ observations, obtained in March
to September 1997, are analyzed to improve the understanding of the early
development of a juvenile Agulhas ring. In March, the ring was surveyed near
37°S, 16°E, approximately four months after its generation. Its
strength and size were in the upper range typical for Agulhas rings, and its
trapping depth extended down to at least 1600 dbar according to geostrophic
velocities and RAFOS trajectories in the ring. Between March and September,
the ring propagated in a general northwestward direction; however, RAFOS
trajectories and MODAS sea-surface steric height fields revealed a large
variability of the translation speed (3 cm s-1 to more than 20
cm s-1) and direction. In September 1997, the mature ring was
examined near 31°S, 9°E. By this time, its available heat and salt
anomaly were reduced by about 30% and its available potential energy was
reduced by about 70%. This indicates that a significant loss of the ring
characteristics occurred on the way from the southern to the northern Cape
Basin. One-third of this loss is due to changes at intermediate depth
(between 800 and 1600 m).
Schott, F.A., M. Dengler, P. Brandt, K. Affler, J. Fischer, B. Bourles, Y.
Gouriou, R.L. Molinari, and M. Rhein. The zonal currents and transports
at 35 W in the tropical Atlantic. Geophysical Research Letters,
30(7):1349, doi:10.1029/2002GL016849 (2003).
The total of 13 existing cross-equatorial shipboard current profiling
sections taken during the WOCE period between 1990 and 2002 along
35°W are used to determine the mean meridional structure of the
zonal top-to-bottom circulation between the Brazilian coast, near
5°S, and 5°N and to estimate mean transports of the individual
identified shallow, intermediate and deep current branches. One of the
results is that, on the equator, a mean westward Equatorial Intermediate
Current below the Equatorial Undercurrent exists.
Snowden, D.P., and R.L. Molinari. Subtropical cells in the Atlantic
Ocean: An observational summary. In Interhemispheric Water Exchange in
the Atlantic Ocean, G.J. Goni and P. Malanotte-Rizzoli (eds.).
Elsevier Oceanography Series, 68 (ISBN 0444512675), 287-312 (2003).
In this paper, we survey the observational literature pertaining to the
shallow meridional overturning circulation cells connecting the subduction
regions of the subtropical North and South Atlantic Ocean with the upwelling
regions on and near the equator. These subtropical cells (STCs) exist in
both hemispheres, but they are not symmetric about the equator. The southern
hemisphere STC has a structure consistent with the cannonical feature
(i.e., subduction in the southern hemisphere subtropics, transport
of the subducted water to the Equatorial Undercurrent, upwelling on the
equator, and return of the upwelled water to the subtropics). However,
there is no clear evidence to indicate that water subducted in the northern
hemisphere subtropics reaches the equator. Rather, pathways of water
subducted in the subtropical North Atlantic have been observed to the North
Equatorial Countercurrent. Upwelling regions for these northern hemisphere
water masses are not yet defined. Characteristics of the STCs which must be
more fully explored (e.g., temporal variability, transports, mixing)
in order to understand their impacts on the regional climate variability of
the tropical Atlantic Ocean are identified.
Thacker, W.C. Data-model-error compatibility. Ocean Modelling,
5(3):233-247 (2003).
During data assimilation, differences between observations and their model
counterparts should be consistent with the error statistics that govern how
the model is to be corrected. The concept of incompatibility distance between
observations and their model counterparts is introduced as a way of detecting
inconsistencies, and formulae are presented for estimating the probability of
encountering greater incompatibility. Observations can be examined one-by-one
to insure that their confidence intervals are not widely separated from those
of the model counterparts. They can be further examined in pairs to detect
whether contrasts across fronts are consistent with assumptions about error
correlations.
Tokarczyk, R., K.D. Goodwin, and E.S. Saltzman. Methyl chloride and methyl
bromide degradation in the Southern Ocean. Geophysical Research
Letters, 30(15):1808, doi:10.1029/2003GL017459 (2003).
This study presents shipboard measurements of the loss rate constants of
methyl bromide and methyl chloride in surface seawater in the Southern Ocean,
using a 13C stable isotope incubation technique. The measurements
were made during October-December 2001, on a cruise track extending from
Hobart, Tasmania to Buchanan Bay (Mertz Glacier) at the coast of Antarctica
(46-67°S, 138-145°E). Significant loss rates were measured for both
compounds, even in very cold waters where chemical loss rates were negligible.
These observations are attributed to biological uptake, and they explain the
tendency for high latitude waters to be undersaturated with respect to
atmospheric methyl bromide and methyl chloride. These observations are the
first open ocean measurements demonstrating the biological degradation of
methyl chloride.
Tokarczyk, E.S. Saltzman, R.M. Moore, and S.A. Yvon-Lewis. Biological
degradation of methyl chloride in coastal seawater. Global
Biogeochemical Cycles, 17(2):1057, doi:10.1029/2002GB001949 (2003).
Methyl chloride (CH3Cl) is the most abundant halocarbon in the
atmosphere, and constitutes a significant fraction of the total atmospheric
halogen burden. Chemical reactions of CH3Cl in seawater are
slow, and it has been believed that the oceans are not an important sink
for this compound. However, direct measurements of CH3Cl
degradation rates in coastal seawater (Bedford Basin, Nova Scotia), using a
stable isotope incubation technique, indicate rapid loss attributed to
microbial activity. A series of weekly measurements from March 2000 to May
2001 yielded degradation rates ranging from 0-30% d-1, with an
annual mean of 7.4% d-1. If biological uptake of
CH3Cl occurs throughout the oceans at similar rates, the mean
partial atmospheric lifetime of CH3Cl with respect to oceanic
removal could be a few years, rather than several decades as previously
thought. This rapid removal would make the oceans a major sink for
CH3Cl and lower the overall atmospheric lifetime of
CH3Cl from the current estimate of 1.3 to about 1.0 years.
Measurements of the degradation rate of CH3Cl in open ocean waters
are needed in order to quantify the oceanic uptake rate.
Trinanes, J.A., and G.J. Goni. A web application to distribute and
visualize altimeter-related products. AVISO Newsletter, 9:21-22
(2003).
No abstract.
Trinanes, J.A., and G.J. Goni. Implementation of a multi-scale system for
environmental data distribution. In Remote Sensing of Fisheries and
Prediction of Toxic Tides, F. Pose (ed.). Institute of University
Studies, Spain, 79-111 (2003).
No abstract.
Uhlhorn, E.W., and P.G. Black. Verification of remotely sensed sea surface
winds in hurricanes. Journal of Atmospheric and Oceanic Technology,
20(1):99-116 (2003).
Surface winds in hurricanes have been estimated remotely using the
Stepped-Frequency Microwave Radiometer (SFMR) from the NOAA WP-3D aircraft
for the past 15 years. Since the use of the GPS dropwindsonde system in
hurricanes was first initiated in 1997, routine collocated SFMR and GPS
surface wind estimates have been made. During the 1998, 1999, and 2001
hurricane seasons, a total of 249 paired samples were acquired and compared.
The SFMR equivalent 1-min mean, 10-m level neutral stability winds were found
to be biased high by 2.3 m s-1 relative to the 10-m GPS winds
computed from an estimate of the mean boundary layer wind. Across the range
of wind speeds from 10 to 60 m s-1, the rms was 3.3 m
s-1. The bias was found to be dependent on storm quadrant and
independent of wind speed, a result that suggests a possible relationship
between microwave brightness temperatures and surface wave properties. Tests
of retrieved winds' sensitivities to sea surface temperature, salinity,
atmospheric thermodynamic variability, and surface wind direction indicate
wind speed errors of less than 1 m s-1 above 15 m
s-1.
Wallace, D.W.R., and R.H. Wanninkhof. Ocean-atmosphere exchange and
earth-system biogeochemistry. In Marine Science Frontiers for
Europe, G. Wefer, F. Lamy, and F. Mantoura (eds.). Springer, Berlin,
107-129 (2003).
No abstract.
Wang, C., and D.B. Enfield. A further study of the tropical Western
Hemisphere warm pool. Journal of Climate, 16(10):1476-1493 (2003).
Variability of the tropical Western Hemisphere warm pool (WHWP) of water
warmer than 28.5°C, which extends seasonally over parts of the eastern
North Pacific, the Gulf of Mexico, the Caribbean, and the western tropical
North Atlantic (TNA), was previously studied by Wang and Enfield using the da
Silva data from 1945-1993. Using additional datasets of the NCEP-NCAR
reanalysis field and the NCEP SST from 1950-1999, and the Levitus
climatological subsurface temperature, the present paper confirms and extends
the previous study of Wang and Enfield. The WHWP alternates with northern
South America as the seasonal heating source for the Walker and Hadley
circulations in the Western Hemisphere. During the boreal winter a strong
Hadley cell emanates northward from the Amazon heat source with subsidence
over the subtropical North Atlantic north of 20°N, sustaining a strong
North Atlantic anticyclone and associated northeast (NE) trade winds over its
southern limb in the TNA. This circulation, including the NE trades, is
weakened during Pacific El Niño winters and results in a spring warming of
the TNA, which in turn induces the development of an unusually large summer
warm pool and a wetter Caribbean rainy season. As the WHWP develops in the
late boreal spring, the center of tropospheric heating and convection shifts
to the WHWP region, whence the summer Hadley circulation emanates from the
WHWP and forks into the subsidence regions of the subtropical South Atlantic
and South Pacific. During the summers following El Niño, when the warm pool
is larger than normal, the increased Hadley flow into the subtropical South
Pacific reinforces the South Pacific anticyclone and trade winds, probably
playing a role in the transition back to the cool phase of ENSO. Seasonally,
surface heat fluxes seem to be primarily responsible for warming of the
WHWP. Interannually, all of the data sets suggest that a positive
ocean-atmosphere feedback through longwave radiation and associated
cloudiness seems to operate in the WHWP. During the winter preceding a
large warm pool, there is a strong weakening of the Hadley cell that
serves as a "tropospheric bridge" for transferring El Niño effects to the
Atlantic sector and inducing warming of the warm pool. Associated with the
warm SST anomalies is a decrease in 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 sea surface, which then reinforces SST anomalies. This
data-inferred hypothesis of the longwave radiation feedback process needs
to be further investigated for its validation in the WHWP.
Wanninkhof, R.H., T.-H. Peng, B. Huss, C.L. Sabine, and K. Lee. Comparison
of inorganic carbon system parameters measured in the Atlantic Ocean from
1990 to 1998 and recommended adjustments. Oak Ridge National Laboratory
Data Report, ORNL/CDIAC-140, 43 pp. (2003).
As part of the global synthesis effort sponsored by the Global Carbon Cycle
project of the National Oceanic and Atmospheric Administration (NOAA) and U.S.
Department of Energy, a comprehensive comparison was performed of inorganic
carbon parameters measured on oceanographic surveys carried out under the
auspices of the Joint Global Ocean Flux Study and related programs. Many of
the cruises were performed as part of the World Hydrographic Program of the
World Ocean Circulation Experiment and the NOAA Ocean-Atmosphere Carbon
Exchange Study. Total dissolved inorganic carbon (DIC), total alkalinity
(TAlk), fugacity of CO2, and pH data from 23 cruises were checked
to determine whether there were systematic offsets of these parameters
between cruises. The focus was on the DIC and TAlk state variables. Data
quality and offsets of DIC and TAlk were determined by using several different
techniques. One approach was based on crossover analyses, where the
deep-water concentrations of DIC and TAlk were compared for stations on
different cruises that were within 100 km of each other. Regional
comparisons were also made by using a multiple-parameter linear regression
technique in which DIC or TAlk was regressed against hydrographic and nutrient
parameters. When offsets of greater than 4 µmol/kg were observed
for DIC and/or 6 µmol/kg were observed for TAlk, the data taken on
the cruise were closely scrutinized to determine whether the offsets were
systematic. Based on these analyses, the DIC data and TAlk data of three
cruises were deemed of insufficient quality to be included in the
comprehensive basinwide data set. For several of the cruises, small
adjustments in TAlk were recommended for consistency with other cruises in
the region. After these adjustments were incorporated, the inorganic carbon
data from all cruises, along with hydrographic, chlorofluorocarbon, and
nutrient data, were combined as a research-quality product for the scientific
community.
**2002**
Aberson, S.D. Operational targeting of hurricane tracks in the Atlantic:
Processes and procedures. Proceedings, Second Workshop on Landfalling
Typhoons in the Taiwan Area, Taipei, Taiwan, April 25-26, 2002.
National Science Council, 53-67 (2002).
NOAA has been conducting operational targeting of dropwindsonde observations
to improve tropical cyclone track forecasts since 1997. During the first two
years, however, the impact of the observations was minimal, with only a
slight improvement in track forecasts. However, with improvements to models,
data assimilation, and targeting techniques, the forecasts for Hurricane
Michelle in late 2001 were improved by 45 to 60% in the NCEP global model.
This talk will present the basic premise behind targeting and the various
targeting techniques available, and the process used in the U.S. to
accomplish the targeting missions.
Aberson, S.D. Tropical cyclone track predictability limits. Preprints,
25th Conference on Hurricanes and Tropical Meteorology, San Diego, CA,
April 29-May 3, 2002. American Meteorological Society, Boston, 220-221
(2002).
No abstract.
Aberson, S.D. Two years of operational hurricane synoptic surveillance.
Weather and Forecasting, 17(5):1101-1110 (2002).
In 1997, the National Hurricane Center and the Hurricane Research Division
began operational synoptic surveillance missions with the Gulfstream IV-SP
jet aircraft to improve the numerical guidance for hurricanes that threaten
the continental United States, Puerto Rico, the Virgin Islands, and Hawaii.
During the first two years, 24 missions were conducted. Global positioning
system dropwindsondes were released from the aircraft at 150-200 km intervals
along the flight track in the environment of each tropical cyclone to obtain
profiles of wind, temperature, and humidity from flight level (nearly 150
hPa) to the surface. The observations were processed and formatted aboard
the aircraft and sent to NCEP to be ingested into the Global Data
Assimilation System, which subsequently served as initial and boundary
conditions for a number of numerical models that forecast the track and
intensity of tropical cyclones. The current study is an attempt to mimic
this process to assess the impact of these operational missions on the
numerical guidance. Although the small number of missions flown in 1997
showed error reductions of as much as 32%, the improvements seen in the
two-year sample are not promising. The additional dropwindsonde data from
the synoptic surveillance missions provided statistically significant
improvements in the GFDL forecasts only at 12 h. The "VBAR" and Global
Forecast System (AVN) forecasts were not significantly improved at any
forecast time. Further examination suggests that the AVN synthetic vortex
procedure, combined with difficulty in the quantification of the current
storm-motion vector operationally, may have caused the mediocre improvements.
Forecast improvements of 14-24% in GFDL forecasts are shown in the subset
of cases in which the synthetic vortex data do not seem to be a problem.
Improvements in the landfall forecasts are also seen in this subset of
cases. A reassessment of tropical cyclone vortex initialization schemes
used by forecast centers and numerical modelers may be necessary.
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 to comment by S.E. Yuter
and R.A. Houze, Jr. "On partitioning tropical oceanic convective and
stratiform rains by draft strength." Journal of Geophysical
Research, 107(D1):4006, doi:10.1029/2001JD000658 (2002).
No abstract.
Bauer, S., M.S. Swenson, and A. Griffa. Eddy mean flow decomposition and
eddy diffusivity estimates in the tropical Pacific Ocean: 2. Results.
Journal of Geophysical Research, 107(C10):3154, doi:
10.1029/2000JC000613 (2002).
Eddy diffusivity of the surface velocity field in the tropical Pacific Ocean
was estimated using satellite-tracked drifting buoys (1979 through mid-1996).
The tropical Pacific surface current system is characterized by
nonstationarity, strong meridional shear, and an energetic mesoscale velocity
field. Eddy diffusivity may be defined as the integral of the autocovariance
of Lagrangian eddy velocities, requiring both stationary and homogeneous
statistics of the eddy field. Eddy velocities were obtained by removing a
splined mean field to eliminate mean shear from observations binned (1)
spatially to group data that have similar dispersion characteristics and (2)
temporally to create stationary eddy statistics. Zonal diffusivity estimates
are up to seven times larger than meridional diffusivity estimates in the
high eddy energy regions. This anisotropy is associated with the meridional
mesoscale wave motion (i.e., by equatorial and tropical instability
waves) that increases eddy variance but does not lead to a proportional
increase in water parcel diffusion because of the coherent character of the
trajectory motion, at least for initial time lags. Simple autoregressive
models of first and second order are used to describe and classify the
resulting eddy statistics. An independent confirmation of the diffusivity
estimate in the central/eastern Pacific was obtained by comparing tracer
flux divergence computed from a parameterization using diffusivity estimates
of our analysis with that from direct eddy Reynolds stress flux divergence.
Our results show that diffusivity can be estimated for regions not considered
previously either because of sparse data or the complexities of the
velocity field.
Bender, M., S. Doney, R.A. Feely, I. Fung, N. Gruber, D.E. Harrison, R.
Keeling, J.K. Moore, J. Sarmiento, E. Sarachik, B. Stephens, T. Takahashi,
P. Tans, and R.H. WANNINKHOF. A large-scale CO2 observing
plan: In situ oceans and atmosphere (LSCOP). National Technical
Information Service, Springfield, VA, 201 pp. (2002).
This report recommends a strategy for making observations of carbon
dioxide (CO2) and related properties in the atmosphere and
oceans, over large spatial scales and long timescales. It also recommends
process studies of air-sea gas exchange, in order to obtain more accurate
estimates of CO2 transfer between the atmosphere and oceans.
Models are essential tools for understanding the distributions and fluxes
of CO2 in the atmosphere and oceans. We recommend observations
and modeling efforts to enhance the skills of models used for this
purpose. An ultimate product of the observations, modeling efforts, and
complementary process studies will be improved projections of the
trajectory of the atmospheric CO2 increase. The report's
recommendations are summarized in Table E-1. These recommendations are
prepared in the context of the U.S. Carbon Cycle Science Plan (CCSP), with
the goal of advancing our ability to address the two fundamental questions
that the CCSP posed: (1) what has happened to the carbon dioxide that has
already been emitted by human activities (past anthropogenic
CO2); and (2) what will be the future atmospheric
CO2 concentration trajectory resulting from both past and
future emissions? The importance of answering these questions is evident.
A recent National Research Council report, Climate Change Science,
documents the consensus scientists have reached that human emissions of
greenhouse gases are increasingly affecting world climate. The President's
speech to the nation on global climate change expressed concern about
greenhouse warming at the highest levels of government and committed the
United States to confront the issue. These documents recommend conducting
the research necessary to understand the environmental behavior of
biogenic greenhouse gases, of which carbon dioxide is the most
significant. This research will lead toward the knowledge required to
accurately project carbon removal rates from the atmosphere to the land
biosphere and the oceans. This report presents a plan for large-scale
U.S.-sponsored observations of CO2 in the oceans and
atmosphere. This plan represents an implementation plan for the
CO2 observations component of the CCSP. We recommend
observations to track the fate of fossil fuel-derived CO2, to
characterize fluxes of CO2 from the atmosphere to the land
biosphere and oceans over large scales of space and time, and to achieve
process-level understanding of physical and biological controls on those
fluxes now and in the future. Complementary small-scale process studies of
the land and ocean biospheres are needed for a comprehensive understanding
of carbon fluxes and distributions. No specific recommendations for such
programs are offered here, because they are being planned independently.
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.
Berkelmans, R., J.C. Hendee, P.A. Marshall, P.V. Ridd, A.R. Orpin, and D.
Irvine. Automatic weather stations: Tools for managing and monitoring
potential impacts to coral reefs. Marine Technology Society
Journal, 36(1):29-38 (2002).
With recent technological advances and a reduction in the cost of automatic
weather stations and data buoys, the potential exists for significant
advancement in science and environmental management using high-resolution,
near real-time data to predict biological and/or physical events. However,
real-world examples of how this potential wealth of data has been used in
environmental management are few and far between. We describe in detail two
examples where near real-time data are being used for the benefit of science
and management. These include a prediction of coral bleaching events using
temperature, light, and wind as primary predictor variables, and the
management of coastal development where dynamic discharge quality limits are
maintained with the aid of wind data as a proxy for turbidity in receiving
waters. We argue that the factors limiting the use of near real-time
environmental data in management are frequently not the availability of the
data, but the lack of knowledge of the quantitative relationships between
biological/physical processes or events and environmental variables. We
advocate renewed research into this area and an integrated approach to
the use of a wide range of data types to deal with management issues in
an innovative, cost-effective manner.
Black, M.L., J.F. Gamache, F.D. Marks, C.E. Samsury, and H.E.
Willoughby. Eastern Pacific Hurricanes Jimena of 1991 and Olivia of
1994: The effect of vertical shear on structure and intensity. Monthly
Weather Review, 130(9):2291-2312 (2002).
Shear is a key inhibitor of tropical cyclone intensification. Although its
signature is readily recognized in satellite imagery and theoretical or
modeling studies provide some insight, detailed observations have been
limited. Airborne radar and in-situ observations in Hurricanes Jimena of 1991
and Olivia of 1994 are a step toward better understanding. Each storm was
observed on two consecutive days. Initially, both had small eyes, 16-18 km
radius, and maximum winds of 57 m s-1 over sea surface
temperatures (SST) >28°C in easterly environmental shear. Jimena
maintained constant intensity or weakened gradually for 2 days in 13-20 m
s-1 easterly shear. Olivia intensified in 8 m s-1
shear on the first day. Overnight, the shear diminished to reverse and became
westerly. On the second day, Olivia weakened as the shear increased to
>15 m s-1 from the west, the storm moved over cooler SST, and
became surrounded by dryer air. As convection weakened and the outer rainbands
ceased to be effective barriers, relative flow due to the environmental
shear penetrated more deeply into the vortex core. In both storms, shear
controlled the convective structure. Convection organized itself into
axisymmetric rings as Olivia intensified in weak shear. When both storms
encountered stronger shear, radar reflectivity and vertical motion had
strong wavenumber-1 components. Highest reflectivity lay generally to the
left of the shear. Most radar echoes and updrafts formed in the downshear
quadrant of the storm and advected around the eye with 60-80% of the
swirling wind, consistent with vortex Rossby wave propagation. The
buoyant updrafts accelerated and reflectivity increased as they passed
through the left-of-shear semicircle. On the upshear side, the updrafts
rose through the 0°C isotherm, and hydrometeors fell out or froze.
Reflectivity declined as the echoes transformed into lower-tropospheric
downdrafts overlain by glaciated upper-tropospheric updrafts in the
right-of-shear semicircle. In relatively weak shear, clusters of echoes
could be tracked completely around the eye. Each time the clusters passed
through the downshear and left-of-shear quadrants, new echoes would form.
In strong shear, all echoes were short lived, and none could be tracked
around the eye. Echoes appeared downshear of the center and completed
their life cycles on the left side of the shear vector where the
composite reflectivities were greatest.
Black, M.L., E.W. Uhlhorn, S.E. Feuer, W.P. Barry, and L.K. Shay. The
relationship between GPS dropsonde wind profiles and sea-surface temperature
in Hurricane Bret (1999). Preprints, 25th Conference on Hurricanes and
Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 551-552 (2002).
No abstract.
Black, R.A., and G.M. Heymsfield. Extra large particle images at 40,000
ft in a hurricane eyewall: Evidence of partially frozen raindrops?
Preprints, 11th Conference on Cloud Physics, Ogden, UT, June 3-7,
2002. American Meteorological Society, Boston, 3 pp. (2002).
No abstract.
Bosart, L.F., P.G. Black, J.L. Evans, J.E. Molinari, C.S. Velden, and M.J.
Dickinson. The double transition of Hurricane Michael (2000): Baroclinic to
tropical to baroclinic. Preprints, 25th Conference on Hurricanes and
Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 503-504 (2002).
No abstract.
Burpee, R.W., and P.G. Black. Ocean mixed layer thermal changes induced
by moving tropical cyclones, Part I: Analyses of inner core observations
obtained by research aircraft. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 571-572 (2002).
No abstract.
Cecil, D.J., G.M. Heymsfield, F.J. LaFontaine, M.G. Bateman, E.J. Zipser,
and F.D. Marks. Precipitation structures observed in CAMEX hurricanes.
Preprints, 25th Conference on Hurricanes and Tropical Meteorology,
San Diego, CA, April 29-May 3, 2002. American Meteorological Society,
Boston, 63-65 (2002).
No abstract.
Chai, F., R.C. Dugdale, T.-H. Peng, F.P. Wilkerson, and R.T.
Barber. One-dimensional ecosystem model of the equatorial Pacific upwelling
system. Part I: Model development and silicon and nitrogen cycle.
Deep-Sea Research, Part II, 49(13-14):2713-2745 (2002).
A one-dimensional ecosystem model was developed for the equatorial Pacific
upwelling system, and the model was used to study the nitrogen and silicon
cycle in the equatorial Pacific. The ecosystem model consisted of 10
components (nitrate, silicate, ammonium, small phytoplankton, diatom,
micro- and meso-zooplankton, detrital nitrogen and silicon, and total
CO2). The ecosystem model was forced by the area-averaged
(5°S-5°N, 90°W-180°, the Wyrtki Box) annual mean
upwelling velocity and vertical diffusivity obtained from a three-dimensional
circulation model. The model was capable of reproducing the low-silicate,
high-nitrate, and low-chlorophyll (LSHNLC) conditions in the equatorial
Pacific. The linkage to carbon cycle was through the consumption of
assimilated nitrate and silicate (i.e., new productions). Model
simulations demonstrated that low-silicate concentration in the equatorial
Pacific limits production of diatoms, and it resulted in low percentage of
diatoms, 16%, in the total phytoplankton biomass. In the area of
5°S-5°N and 90°W-180°, the model produced an estimated
sea-to-air CO2 flux of 4.3 mol m-2 yr-1,
which is consistent with the observed results ranging of 1.0-4.5 mol
m-2 yr-1. The ammonium inhibition played an important
role in determining the nitrogen cycle in the model. The modeled surface
nitrate concentration could increase by a factor of 10 (from 0.8 to 8.0 mmol
m-3) when the strength of the ammonium inhibition increased from
psi = 1.0 to 10.0 (mmol m-3)-1. The effects of
both micro- and meso-zooplankton grazing were tested by varying the micro- and
meso-zooplankton maximum grazing rates, G1max and
G2max. The modeled results were quite sensitive to the
zooplankton grazing parameters. The current model considered the role of
iron implicitly through the parameters that determine the growth rate of
diatoms. Several iron-enrichment experiments were conducted by changing the
parameter alpha (the initial slope of the photosynthetic rate over
irradiance at low irradiance), KSi(OH)4 (half-saturation
concentration of silicate uptake by diatom), and µ2max (the
potential maximum specific diatom growth rate) in the regulation terms of
silicate uptake by diatom. Within the first five days in the modeled
iron-enrichment experiment, the diatom biomass increased from 0.08 to 2.5
mmol m-3, more than a factor of 30 increase. But the diatom
populations crashed two weeks after the experiment started, due to exhaustion
of available silicate and increased mesozooplankton population. The modeled
iron-enrichment experiments produced several ecological behaviors similar to
these observed during the IronEx-2.
Chereskin, T.K., W.D. Wilson, and L.M. Beal. The Ekman temperature and salt
fluxes at 8°30'N in the Arabian Sea during the 1995 southwest monsoon.
Deep-Sea Research, Part II, 49(7-8):1211-1230 (2002).
The Arabian Sea Ekman transport is an important component of the meridional
overturning circulation of the Indian Ocean. Chereskin et al.
(Geophys. Res. Lett., 24 (1997), 2541) presented direct estimates of
the Ekman transport across latitude 8°30'N in the Arabian Sea for June
and September during the 1995 southwest monsoon. In this paper, we use these
measurements to determine the Ekman depth and the resultant heat and salt
fluxes. In June, at the monsoon onset, the Ekman temperature and salt fluxes
were estimated to be southward, 2.4 ± 0.4 PW and 0.71 ± 0.1 ×
109 kgs-1. The transport-weighted Ekman temperature and
salinity were 29.0 ± 0.5°C and 35.31 ± 0.03 psu, not
significantly different from surface values, 29.2°C and 35.28 psu,
respectively. In September at the end of the monsoon, the Ekman temperature
and salt fluxes had decreased in magnitude but were still southward, 0.77
± 0.4PW and 0.27 ± 0.1 × 109 kgs-1.
The transport-weighted temperature, 25.8 ± 0.5°C, was 1.1°C
colder than the surface value, and the transport-weighted salinity, 35.83
± 0.03 psu, was not significantly different from the surface value of
35.86 psu. For this pair of sections, the top of the pycnocline appeared
to be a better approximation for the Ekman depth than either the mixed
layer or a fixed depth, and our estimates of the Ekman heat and salt
fluxes were integrated from the surface to the top of the pycnocline.
Although uncertainty in the Ekman mass transport dominates the error in
the Ekman heat and salt fluxes, determining the Ekman depth is also
important in estimating the Ekman contribution to the heat budget of the
tropical Indian Ocean. A decrease in Ekman temperature by 1.1°C
resulted in a 5% decrease in the temperature transport estimated for
September.
Cione, J.J., and E.W. Uhlhorn. Upper ocean heat content and energy extracted
by the storm: Analytical look. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 631-632 (2002).
No abstract.
Cook, T.M., L.K. Shay, S.D. Jacob, C.W. Wright, P.G. Black, and E.W.
Uhlhorn. Surface wave effects on the ocean mixed layer response to
Hurricane Bonnie. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 633-634 (2002).
No abstract.
Dodge, P.P., M.L. Black, J.L. Franklin, J.F. Gamache, and F.D.
Marks. High-resolution observations of the eyewall in an intense
hurricane: Bret on 21-22 August 1999. Preprints, 25th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 607-608 (2002).
No abstract.
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., R.T. Barber, F. Chai, T.-H. Peng, and F.P.
Wilkerson. One-dimensional ecosystem model of the equatorial Pacific
upwelling system. Part II: Sensitivity analysis and comparison with JGOFS
EqPac data. Deep-Sea Research, Part II, 49(13-14):2747-2768 (2002).
A one-dimensional model of the equatorial Pacific upwelling ecosystem that
incorporates two phytoplankton components, two grazers, and three nutrients,
Si(OH)4, NO3, and NH4 (Chai et al.,
Deep-Sea Res., II (2002) 2713-2745), was designed to consider the
effects of Si(OH)4 limitation on the diatom growth and ecosystem
functioning. Model output was obtained for a range of source concentrations
of Si(OH)4, 3-15 mmol m-3, coinciding with the range
measured at 120 m depth during JGOFS EqPac. NO3 was held at 12
mmol m-3, reflecting the relatively greater concentrations of
NO3 compared to Si(OH)4 in the JGOFS data. The model
was shown to function as a chemostat-like system with the loss rates,
provided largely from zooplankton grazing, controlling growth rates of
the phytoplankton. When different source concentrations of
Si(OH)4 were applied, surface concentrations of
Si(OH)4 varied within a narrow range compared to
NO3 as would occur in a chemostat with limiting
Si(OH)4 and non-limiting NO3 in the feed water.
Vertical profiles of nutrients compared well with field data. Model results
are compared with field data for new and total nitrogen production and export
of N, Si, and C, and with other models, although none consider
Si(OH)4 specifically. The model suggests that the stability of
the equatorial system with its narrow range of biological and chemical
variables is conferred by the action of diatoms providing food for
mesozooplankton whose grazing also depletes the picoplankton. Diatoms
increase with source Si(OH)4 concentrations, and picoplankton
population and NO3 consumption decrease, resulting in a
maximum surface TCO2 and increased CO2 flux to the
atmosphere at intermediate source Si(OH)4 concentrations. Diatoms
function in the equatorial system as a silica pump to export silica. This
means that sedimented biogenic silica under the equatorial upwelling area
should be viewed as an amplifier of changes in surface properties, with
important consequences to paleoequatorial productivity.
Dugdale, R.C., A.G. Wischmeyer, F.P. Wilkerson, R.T. Barber, F. Chai,
M.-S. Jiang, and T.-H. Peng. Meridional asymmetry of source nutrients to
the equatorial Pacific upwelling ecosystem and its potential impact on
ocean-atmosphere CO2 flux: A data and modeling approach.
Deep-Sea Research, Part II, 49(13-14):2513-2531 (2002).
Si(OH)4, NO3, and TCO2 are shown to be
distributed asymmetrically in a north/south direction about the equatorial
Pacific using data from WEPOCS III and JGOFS EqPac cruises. Equatorial
SiOH4 concentrations are shown to be the product of both
geochemical and physical interactions with chemical processes occurring in
at least three regions remote from the equatorial Pacific, and physical
delivery processes from the equatorial undercurrent (EUC) to the surface
layer varying over a range of time scales. The EUC was partitioned into
upper and lower portions, the upper providing source water to the central
upwelling area and the lower crossing the Pacific without upwelling and
thought to reenter the surface along the coast of Peru and to the eastern
equatorial upwelling area. The source waters from the North Pacific, the
north equatorial countercurrent (NECC) and from the South Pacific, the New
Guinea coastal undercurrent (NGCUC) also were partitioned according to
source for the upper and lower EUC. Mean concentrations and ranges of
nutrients for each source partition were obtained from field data. Current
flow and advective data output from a three-dimensional physical model were
used with the field nutrient data to calculate nutrient fluxes into the EUC.
Although the inflow of water from the north and south were approximately
equal, the stronger asymmetric distribution of Si(OH)4
compared to NO3 resulted in identifying the South Pacific source
as only 30% of the total supply of Si(OH)4 to the EUC and the
cause of a low Si(OH)4:NO3 condition. These results
suggest a coupling between Southern Ocean productivity, equatorial
productivity, and the efflux of CO2 to the atmosphere from the
equatorial upwelling system.
Dunion, J.P., and M.D. Powell. Improvements to the NOAA Hurricane Research
Division's surface reduction algorithm for inner core aircraft flight-level
winds. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 581-582 (2002).
No abstract.
Dunion, J.P., and C.S. Velden. Application of surface-adjusted GOES
low-level cloud-drift winds in the environment of Atlantic tropical
cyclones. Part I: Methodology and validation. Monthly Weather
Review, 130(5):1333-1346 (2002).
Beginning with the 1997 hurricane season, the Cooperative Institute for
Meteorological Satellite Studies at the University of Wisconsin-Madison
began demonstrating the derivation of real-time Geostationary Operational
Environmental Satellite (GOES) low-level cloud-drift winds in the vicinity
of Atlantic tropical cyclones. The winds are derived from tracking low-level
clouds in sequential, high-resolution GOES visible channel imagery. Since
then, these data have been provided to the National Oceanic and Atmospheric
Administration (NOAA) Hurricane Research Division (HRD) for evaluation in
their real-time tropical cyclone surface wind objective analyses (H*Wind)
that are disseminated to forecasters at the NOAA National Hurricane Center on
an experimental basis. These wind analyses are proving useful as guidance
to support forecasters' tropical cyclone advisories and warnings. The
GOES satellite wind observations often provide essential near-surface
coverage in the outer radii of the tropical cyclone circulation where
conventional in-situ observations (e.g., ships and buoys) are
frequently widely spaced or nonexistent and reconnaissance aircraft do not
normally fly. The GOES low-level cloud-tracked winds are extrapolated to the
surface using a planetary boundary layer model developed at HRD for
hurricane environments. In this study, the unadjusted GOES winds are
validated against wind profiles from the newly deployed global
positioning system dropwindsondes, and the surface-adjusted winds are
compared with collocated in-situ surface measurements. The results show
the ability of the GOES winds to provide valuable quantitative data in
the periphery of tropical cyclones. It is also shown that the current
scheme employed to extrapolate the winds to the surface results in small
biases in both speed and direction. Nonlinear adjustments to account for
these biases are presented.
Dunion, J.P., and C.S. Velden. Satellite applications for tropical
wave/tropical cyclone tracking. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 132-133 (2002).
No abstract.
Dunion, J.P., and C.S. Velden. Satellite applications for tropical
wave/tropical cyclone tracking. Preprints, 11th Conference on Satellite
Meteorology and Oceanography, Madison, WI, April 29-May 3, 2002.
American Meteorological Society, Boston, 314-317 (2002).
No abstract.
Dunion, J.P., S.H. Houston, C.S. Velden, and M.D. Powell. Application of
surface adjusted GOES low-level cloud-drift winds in the environment of
Atlantic tropical cyclones. Part II: Integration into surface wind
analyses. Monthly Weather Review, 130(5):1347-1355 (2002).
The Cooperative Institute for Meteorological Satellite Studies at the
University of Wisconsin-Madison recently (1997 season) began providing
real-time Geostationary Operational Environmental Satellite (GOES) low-level
cloud-drift winds in the vicinity of tropical cyclones on an experimental
basis to the National Oceanic and Atmospheric Administration's (NOAA)
Hurricane Research Division (HRD). The cloud-drift winds are derived from s
equential high-resolution GOES visible channel imagery. These data were
included in many of HRD's real-time tropical cyclone surface wind objective
analyses, which were sent to NOAA's National Hurricane Center and the Central
Pacific Hurricane Center on an experimental basis during the 1997-2001
hurricane seasons. These wind analyses were used to support the forecasters'
tropical cyclone advisories and warnings. The satellite wind observations
provide essential low-level coverage in the periphery of the tropical
cyclone circulation where conventional in-situ observations (e.g.,
ships, buoys, and Coastal-Marine Automated Network stations) are often widely
spaced or nonexistent and reconnaissance aircraft do not normally fly.
Though winds derived from microwave channels on polar-orbiting satellites
provide valuable surface wind data for HRD surface wind analyses, their
swath coverage and orbital passes are limited spatially and temporally.
GOES low-level visible (GLLV) winds offer nearly continuous spatial and
temporal coverage in the western Atlantic and eastern Pacific basins. The
GLLV winds were extrapolated to the surface using a planetary boundary
layer model developed at HRD. These surface-adjusted satellite data were
used in real-time surface wind analyses of 1998 Hurricane Georges, as
well as in post-storm analyses of 1996 Hurricane Lili and 1997 Tropical
Storm Claudette. The satellite observations often helped to define the
spatial extent of the 17.5 m s-1 (34 kt) surface wind radii and
also redefined the 25.7 m s-1 (50 kt) wind radius for one case.
Examples of the impact of these data on real-time hurricane surface wind
fields provided to the NHC will be discussed.
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.
Esenkov, O.E., and D.B. Olson. A numerical study of the Somali coastal
undercurrents. Deep-Sea Research, Part II, 49(7-8):1253-1277
(2002).
Subsurface circulation in the western Arabian Sea is studied with an open
boundary version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The
model solution demonstrates a strong annual cycle and significant alongshore
variability of subsurface circulation. Based on the dynamics and water
properties, three regions are identified along the coast. A cross-equatorial
current, which exists throughout the year, carries low-salinity water
northwards. Comparison of the model results with observations in the
equatorial region demonstrates that the model reproduces the annual cycle and
transport of the currents remarkably well. Although it underestimates the
speed of the undercurrent core by about a factor of two, increasing the
horizontal resolution from 0.35° to 0.225° improves agreement
with the measurements. A spring southward undercurrent between 5°N
and the equator owes its existence to the wind forcing in the Arabian Sea.
Water with higher salinity values, found in the coastal region north of
5°N, is advected by a southward undercurrent that is present between
October and March. The existence of the undercurrent is caused by flows from
the east and northeast. The latter originates in the Persian Gulf and
provides about 75% of water for the coastal undercurrent. The annual Rossby
wave generated in the interior of the domain contributes to the formation of
the current in the fall. The third region is an area near 4°N, where
the southward undercurrent separates, as velocity and salinity fields suggest.
Subsurface circulation north of 5°N is disconnected from flows near the
equator during most of the year. The model circulation is not sensitive to
the details of coastal bottom topography. In contrast, the presence of the
Socotra Island, which is absent in the model, leads to a more realistic
solution in that the southward undercurrent north of 5°N is present
throughout the spring. Interannual variability of the model subsurface fields
increases significantly when observed, rather than climatological, wind
forcing is used. The most dramatic changes occur in the coastal and equatorial
regions.
Etherton, B.J., and S.D. Aberson. Assimilation of GPS dropwindsonde data
using a VICBAR ensemble. Preprints, 25th Conference on Hurricanes and
Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 218-219 (2002).
No abstract.
Evans, J.L., C.S. Velden, L.F. Bosart, J.E. Molinari, and P.G.
Black. Hurricane Michael: The "two-way TC." Preprints, 25th Conference
on Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 505-506 (2002).
No abstract.
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.
Feely, R.A., C.L. Sabine, K. Lee, F.J. Millero, M.F. Lamb, D. Greeley,
J.L. Bullister, R.M. Key, T.-H. Peng, A. Kozyr, T. Ono, and C.S.
Wong. In-situ calcium carbonate dissolution in the Pacific Ocean. Global
Biogeochemical Cycles, 16(4):1144, doi:10.1029/2002GB001866 (2002).
Over the past several years, researchers have been working to synthesize
the WOCE/JGOFS global CO2 survey data to better understand
carbon cycling processes in the oceans. The Pacific Ocean data set has
over 35,000 sample locations with at least two carbon parameters, oxygen,
nutrients, CFC tracers, and hydrographic parameters. In this paper, we
estimate the in-situ CaCO3 dissolution rates in the Pacific
Ocean water column. Calcium carbonate dissolution rates ranging from
0.01-1.1 mol kg-1 yr-1 are observed in intermediate
and deep water beginning near the aragonite saturation horizon. In the
North Pacific Intermediate Water between 400 and 800 m, CaCO3
dissolution rates are more than seven times faster than observed in middle
and deep water depths (average = 0.051 mol kg-1
yr-1). The total amount of CaCO3 that is dissolved
within the Pacific is determined by integrating excess alkalinity
throughout the water column. The total inventory of CaCO3 added
by particle dissolution in the Pacific Ocean, north of 40°S, is 157
Pg C. This amounts to an average dissolution rate of approximately 0.31 Pg
C yr-1. This estimate is approximately 74% of the export
production of CaCO3 estimated for the Pacific Ocean. These
estimates should be considered to be upper limits for in situ carbonate
dissolution in the Pacific Ocean, since a portion of the alkalinity
increase results from inputs from sediments.
Feely, R.A., J. Boutin, C.E. Cosca, Y. Dandonneau, J. Etcheto, H.Y. Inoue,
M. Ishii, C. Le Quere, D.J. Mackey, M. McPhaden, N. Metzl, A. Poisson, and
R.H. Wanninkhof. Seasonal and interannual variability of CO2
in the equatorial Pacific. Deep-Sea Research, Part II,
49(13-14):2443-2469 (2002).
As part of the JGOFS field program, extensive CO2 partial-pressure
measurements were made in the atmosphere and in the surface waters of the
equatorial Pacific from 1992 to 1999. For the first time, we are able to
determine how processes occurring in the western portion of the equatorial
Pacific impact the sea-air fluxes of CO2 in the central and eastern
regions. These eight years of data are compared with the decade of the 1980s.
Over this period, surface-water pCO2 data indicate significant
seasonal and interannual variations. The largest decreases in fluxes were
associated with the 1991-1994 and 1997-1998 El Niño events. The lower sea-air
CO2 fluxes during these two El Niño periods were the result of the
combined effects of interconnected large-scale 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; (2)
deepening of the thermocline by propagating Kelvin waves in the eastern
Pacific; and (3) the weakening of the winds in the eastern half of the basin.
These processes serve to reduce pCO2 values in the central and
eastern equatorial Pacific towards near-equilibrium values at the height of
the warm phase of ENSO. In the western equatorial Pacific there is a small
but significant increase in seawater pCO2 during strong El Niño
events (i.e., 1982-1983 and 1997-1998) and little or no change during
weak El Niño events (1991-1994). The net effect of these interannual
variations is a lower-than-normal CO2 flux to the atmosphere from
the equatorial Pacific during El Niño. The annual average fluxes indicate
that during strong El Niños the release to the atmosphere is 0.2-0.4
Pg Cyr-1 compared to 0.8-1.0 Pg Cyr-1 during non-El
Niño years.
Feuer, S.E., J.F. Gamache, M.L. Black, F.D. Marks, and J.B. Halverson. A
multiple aircraft experiment in Hurricane Humberto (2001), Part I: Wind
fields. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 206-207 (2002).
No abstract.
Fram, M.S., J.K. Berghouse, B.A. Bergamaschi, R. Fujii, K.D. Goodwin, and
J.F. Clark. Water-quality monitoring and studies of the formation and
fate of trihalomethanes during the third injection, storage, and recovery
test at Lancaster, Antelope Valley, California, March 1998 through April
1999. U.S. Geological Survey, Open-File Report 02-102, 48 pp. (2002).
The U.S. Geological Survey, in cooperation with the Los Angeles County
Department of Public Works and the Antelope Valley-East Kern Water Agency,
conducted three cycles of injection, storage, and recovery tests to
evaluate the feasibility of artificially recharging ground water in the
Lancaster area of Antelope Valley, California. During the third cycle
(March 1998 through April 1999), the tests included investigations of the
formation and fate of trihalomethanes in the aquifer. Trihalomethanes are
disinfection by-products formed by reaction between natural dissolved
organic carbon that is present in water and chlorine that is added during
the drinking-water-treatment process. This report includes a discussion of
the design of the investigation; descriptions of the sampling, analytical,
and experimental methods used in the investigation; and a presentation of
the data collected. During the third cycle, 60 million gallons of
chlorinated water was injected into the aquifer through well 7N/12W-27P2
in the Los Angeles County Department of Public Works well field in
Lancaster between April 15 and June 16, 1998. One hundred fifty million
gallons of water was extracted from the same well between June 30, 1998,
and April 29, 1999. Water-quality samples were collected during the entire
cycle from the well and from a nearby set of nested piezometers, and were
analyzed for residual chlorine, dissolved organic carbon, trihalomethane,
major anion, and dissolved solid concentrations; ultraviolet absorbance
spectra; and a number of field water-quality parameters. A statistical
analysis was done to evaluate the analytical precision of the residual
chlorine, dissolved organic carbon, trihalomethane, and ultraviolet
absorbance measurements on these samples. The formation of trihalomethanes
in the injection water was examined in laboratory experiments:
Trihalomethane concentrations in samples of injection water were monitored
during a storage period, and trihalomethane formation potential in the
presence of excess chlorine was measured. The role of mixing between
injection water and ground water and the conservative or non-conservative
behavior of trihalomethanes was studied by adding a conservative tracer,
sulfur hexafluoride, to the injection water and monitoring its
concentration in the extraction water. The potential for biodegradation of
trihalomethanes by aquifer bacteria was assessed in laboratory
experiments: Microcosms containing ground water or extraction water and
sediment or concentrated bacteria were spiked with trihalomethanes, and
the amount of trihalomethanes was monitored during an incubation period.
The potential for sorption of trihalomethanes to aquifer sediments was
assessed in laboratory experiments: Mixtures of sediment and water were
spiked with trihalomethanes, and then the trihalomethane concentrations
were measured after an equilibration period.
Gamache, J.F., P.D. Reasor, H.E. Willoughby, M.L. Black, and F.D.
Marks. Observations of the evolution of precipitation and kinematic
structure in a hurricane as it encountered strong westerly shear.
Preprints, 25th Conference on Hurricanes and Tropical Meteorology,
San Diego, CA, April 29-May 3, 2002. American Meteorological Society,
Boston, 547-548 (2002).
No abstract.
Goni, G.J., and M.O. Baringer. Surface currents in the tropical Atlantic
across high density XBT line AX08. Geophysical Research Letters,
29(24):2218, doi:10.1029/2002GL015873 (2002).
Three temperature sections that cross the tropical Atlantic obtained from
high density XBT transects are used to identify the major surface currents
and to compute their water mass transports. The dynamic heights are computed
using XBT temperature profiles with salinity derived from historical T-S
relationships. The values of dynamic height estimated from altimeter data
used in conjunction with climatological dynamic height fields are within 3 cm
of the XBT-derived values. The error in XBT-derived dynamic height introduced
by using historical T-S relationships instead of actual salinity values are
estimated to be of the order of 1.5 cm. Dynamic height estimates using the
actual salinity values underestimate those obtained using historical T-S
relationships. The structure exhibited in the dynamic height and
altimeter-derived sea height fields do not reveal all the upper ocean
currents, making these temperature sections presented here critical for
computing transports and identifying currents in this region.
Harasti, P.R., W.-C. Lee, J.D. Tuttle, C.J. McAdie, P.P. Dodge, S.T.
Murillo, and F.D. Marks. Operational implementation of single-Doppler
radar algorithms for tropical cyclones. Preprints, 25th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 487-488 (2002).
No abstract.
Hendee, J.C., G. Liu, A. Strong, J. Sapper, D. Sasko, and C. Dahgren. Near
real-time validation of satellite sea surface temperature products at
Rainbow Gardens Reef, Lee Stocking Island, Bahamas. Proceedings,
Seventh International Conference on Remote Sensing for Marine and Coastal
Environments, Miami, FL, May 20-22, 2002. Veridian Systems Division,
CD-ROM, 9 pp. (2002).
The National Oceanic and Atmospheric Administration's (NOAA) Coral Reef Watch
program is installing in-situ monitoring stations at strategic coral reef
areas for purposes of establishing long-term data sets, providing near
real-time information products, and surface-truthing NOAA satellite sea
surface temperature (SST) products used for coral bleaching predictions
("hot spots"). The suite of stations, which transmit data hourly, together
with custom artificial intelligence software that analyzes the data, is
called the Coral Reef Early Warning System (CREWS) network. At each CREWS
station, local maintenance and calibration of the sea temperature sensor
ensures high quality data. Local collaborators also provide feedback on the
presence and progress of coral bleaching and thus validate coral bleaching
predictions made by HotSpot and CREWS information products. Near Rainbow
Gardens Reef, where the first CREWS station was installed, additional in-situ
data loggers were deployed to compare with CREWS and satellite SST data for
both the relatively shallow Great Bahama Bank and much deeper Exuma Sound.
During summer 2001, CREWS successfully transmitted daily email satellite SST
and in-situ temperature comparisons, which showed good agreement. Logger
data were used to validate and interpret the satellite SST and CREWS station
readings.
Heymsfield, G.M., J.B.Halverson, M.L. Black, F.D. Marks, E.J. Zipser, L.
Tian, L. Belcher, P. Bui, and E. Im. Structure of the highly sheared
Tropical Storm Chantal during CAMEX-4. Preprints, 25th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 202-203 (2002).
No abstract.
Hitchcock, G.L., P. Lane, S. Smith, J. Luo, and P.B. Ortner. Zooplankton
spatial distributions in coastal waters of the northern Arabian Sea,
August 1995. Deep-Sea Research, Part II, 49(12):2403-2423 (2002).
The spatial distribution of zooplankton biomass was surveyed in coastal waters
of the northern Arabian Sea during the 1995 Southwest Monsoon (August) on
cruise MB 95-06 of the NOAA Ship Malcolm Baldrige. Vertical patterns of
displacement volumes from a limited set of paired day-night MOCNESS tows
suggest there was little diel vertical migration in the coastal waters off
the southern Arabian Peninsula. Zooplankton biomass varied from 5.2 to 15.1
gdwm-2 (178-517 mMC m-2) in the upper 200-300 m of
Omani coastal waters. Distributions of acoustic backscatter were mapped in
eight daytime acoustic Doppler current profiler transects in coastal waters
off Oman and Somalia. Several transects contained maxima in acoustic
backscatter that coincided with cool, fresh surface features that were
several tens of kilometers wide. Although there was considerable scatter in
the relationship between acoustically determined biomass (ADB) of zooplankton
and surface temperature, there was a trend of increased biomass in the cool
surface temperatures of the Omani upwelling zone. Acoustic transects crossed
two filaments that extended seaward from upwelling centers off Oman and
Somalia. Estimated zooplankton ADB exported from the upwelling zones in the
surface features was on the order of 300 kgdws-1. The physical
and biological characteristics of filaments maintain zooplankton associated
with upwelling areas, such as Calanoides carinatus, as they are
advected offshore from coastal upwelling zones.
Houston, S.H., and M.D. Powell. Sensitivity study of HRD's H*WIND surface
wind analyses for tropical cyclones. Preprints, 25th Conference
on Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 583-584 (2002).
No abstract.
Jiang, H., P.G. Black, E.W. Uhlhorn, P.A. Leighton, E.J. Zipser, and F.D.
Marks. Optimal rain rate estimation in tropical cyclones: Validation of
SFMR remote sensing rain rates. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 475-476 (2002).
No abstract.
Johns, W.E., T.L. Townsend, D.M. Fratantoni, and W.D. Wilson. On the
Atlantic inflow to the Caribbean Sea. Deep-Sea Research, Part I,
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.
Jones, R.W., and H.E. Willoughby. Nonlinear motion of a two-layer baroclinic
hurricane in shear. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American Meteorological
Society, Boston, 134-135 (2002).
No abstract.
Jury, M.R., D.B. Enfield, and J.-L. Melice. Tropical monsoons around
Africa: Stability of El Niño-Southern Oscillations associations and links
with continental climate. Journal of Geophysical Research,
107(C10):3151, doi: 10.1029/2000JC000507 (2002).
Interannual fluctuations of monsoons around Africa and the stability of
associations with the El Niño-Southern Oscillation (ENSO) and African rainfall
are studied. The statistical analysis employs sea surface temperature (SST),
surface and upper winds, and surface pressure averaged over key monsoon areas
of the tropical Atlantic and Indian Oceans. The time series span the period
1958-1998, and wavelet analysis is applied to localize relationships in time,
as well as in frequency, and enable us to examine how the amplitude and time
delay at interannual scales varies through the record. Comparisons are made
with Niño3 SST and other known ENSO signals in the African hemisphere. It is
found that upper zonal winds over the tropical Atlantic are an integral part
of the global ENSO. Zonal winds are associated with SST changes in the
equatorial east Atlantic, which are antiphase to those in the west-central
Indian Ocean. A composite analysis of warm and cool events in the Indian Ocean
reveals that evaporation, radiative fluxes, and wind curl interact
constructively. Anticyclonic curl (depression of isotherms) leads warm events,
while cool events may initiate from oceanic advection and are sustained by
evaporative fluxes. Rainfall fluctuations across Africa are analyzed, and
three coherent areas are identified: West (Sahel-Guinea), Southern
(Kalahari-Zambezi), and East (Kenya-Tanzania). Multivariate regression
algorithms are fitted to the continuous filtered rainfall series over the
period 1958-1988. Using three monsoon indices in a multivariate model,
about 40% of the variance is explained at zero lag. An influential variable
for most African rainfall areas is the zonal wind over the tropical Atlantic.
The north-south SST gradient in the tropical Atlantic modulates rainfall in
West Africa as expected. At six-month lead, surface pressure in the north
Indian Ocean is a key determinant for West African climate. For southern
African rainfall, SST in the southwest Indian Ocean and monsoon indices in
the west-central Indian Ocean play significant roles. East African rainfall
fluctuations are linked with zonal winds in the east Indian Ocean. The
findings address current Climate Variability and Predictability program
(CLIVAR) priorities for understanding how continental climate interacts with
ENSO and other regional modes of variability.
Kaplan, J., and M. DeMaria. Estimating the probability of rapid
intensification using the SHIPS model output: Some preliminary results.
Preprints, 25th Conference on Hurricanes and Tropical Meteorology,
San Diego, CA, April 29-May 3, 2002. American Meteorological Society,
Boston, 124-125 (2002).
No abstract.
Katsaros, K.B. Hurricane research inside the storm. Atmosphériques,
13:22-23 (2002).
No abstract.
Katsaros, K.B., E.B. Forde, A.M. Mestas-Nunez, and A. Bentamy. Wind and
evaporation patterns in the tropical Pacific Ocean from satellite data.
Proceedings, Sixth Pan Ocean Remote Sensing Conference (PORSEC),
Bali, Indonesia, September 3-6, 2002. Agency for Marine and Fisheries
Research, Volume 2, 527-533 (2002).
Using one year (October 1996-September 1997) of weekly sea surface
temperatures (SSTs) determined from Advanced Very High Resolution Radiometer
(AVHRR) data, gridded surface wind fields based on several satellite sensors,
and estimates of surface humidity based on the Special Sensor
Microwave/Imager (SSM/I), we examine the patterns of variability in wind and
evaporation rate in the tropical Pacific Ocean during the months preceding
the 1997-1998 El Niño. Enhanced surface wind and associated evaporation rates
were found to occur for periods of a few weeks in the northern hemisphere
trade wind region. The developing warming in the eastern Pacific Ocean
eliminated the cool tongue gradually, such that it disappeared by July 2,
1997, and there was no longer a minimum in evaporation in that region. The
enhanced strong evaporation associated with the Indian monsoon is clearly
seen in the Bay of Bengal and the Arabian Sea during the week of June
16, 1997.
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.
Kiesling, T.L., E. Wilkinson, J. Rabalais, P.B. Ortner, M.M. McCabe, and
J.W. Fell. Rapid identification of adult and naupliar stages of copepods
using DNA hybridization methodology. Marine Biotechnology, 4(1):30-39
(2002).
Larval stages of common marine invertebrates and their ecological roles
within their respective communities are frequently ignored because they are
hard to identify. Morphological characters are often insufficient to
differentiate between genera, much less species. To overcome the obstacles
associated with species identification of copepod larvae, we developed a
microtiter plate-based hybridization assay. Species-specific probes based on
rDNA sequences were bound to microplates and used to capture target DNA. A
novel method of linking the probes to the plate with poly-T tail ensured the
probes were positioned above the plate surface and available for
hybridization; this significantly increased the sensitivity of the assay.
Target DNA extracted from individual copepods was amplified with
biotin-labeled primers. The labeled target DNA bound to the probe specific
for that species and produced a colorimetric change in the assay. The assay
can be rapidly performed on freshly caught or ethanol preserved samples and
the results visually interpreted.
King, D.B., J.H. Butler, S.A. Yvon-Lewis, and S.A. Cotton. Predicting
oceanic methyl bromide saturation from SST. Geophysical Research
Letters, 29(24):2199, doi:10.1029/2002GL016091 (2002).
Data collected from the North Pacific Ocean during September and October 1999
were combined with data from other cruises to assess seasonal differences in
the relationships between sea surface temperature (SST) and methyl bromide
(CH3Br) saturation. We now are able to reproduce observed
saturation anomalies substantially better with the revised, seasonal
CH3Br-SST equations than with those that were independent of
season. The effect is most noticeable in temperate waters where data combined
on an annual basis proved insufficient. The estimated, net global air-sea flux
of CH3Br remains negative at -10 to -18 Gg yr-1,
which is consistent with extrapolations from observations.
Kollias, P., B.A. Albrecht, and F.D. Marks. Why Mie? Bulletin of the
American Meteorological Society, 83(10):1471-1483 (2002).
This article demonstrates an innovative method for the observation of vertical
air motion and raindrop size distribution in precipitation using a 94-GHz
Doppler radar. The method is particularly appealing since it is based on
fundamental physics, the scattering of microwave radiation by large particles
(Mie scattering). The technique was originally proposed in 1988 by Dr. Roger
Lhermitte, who ironically pioneered the development of 94-GHz Doppler radars
for the study of nonprecipitating clouds. Since then, no real effort for the
evaluation and demonstration of the technique was undertaken. In this article,
observations from stratiform rain are presented to illustrate the potential
and accuracy of the method. The retrievals from this technique provide
vertical air motion to an accuracy of 5-10 cm s-1. Despite
attenuation, the Doppler velocity measurements remain unbiased and the data
revealed high-resolution kinematical and microphysical structures within the
stratiform precipitation for the first time. This article will hopefully
expose the potential of this technique to the meteorological community and
will serve as another example of the visionary contributions that Dr.
Lhermitte has made to radar meteorology.
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., C. Anderson, N. Charles, G. Clark, J.P. Dunion, J.
Fernandez-Partagas, P. Hungerford, C. Neumann, and M. Zimmer. The
Atlantic hurricane database re-analysis project documentation for the
1851-1910 alterations and additions to the HURDAT database. Preprints,
25th Conference on Hurricanes and Tropical Meteorology, San Diego, CA,
April 29-May 3, 2002. American Meteorological Society, Boston, 460-461
(2002).
No abstract.
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.
Lee, K., D.M. Karl, R. Wanninkhof, and J.-Z. Zhang. Global estimates of net
carbon production in the nitrate-depleted tropical and subtropical oceans.
Geophysical Research Letters, 29(19):1907, doi:10.1029/2001GL014198
(2002).
Nitrate availability is generally considered to be the limiting factor for
oceanic new production and this concept is central in our observational and
modeling efforts. However, recent time-series observations off Bermuda and
Hawaii indicate a significant removal of total dissolved inorganic carbon
(CT) in the absence of measurable nitrate. Here we estimate net
carbon production in nitrate-depleted tropical and subtropical waters with
temperatures higher than 20°C from the decrease in the salinity
normalized CT inventory within the surface mixed layer. This
method yields a global value of 0.8 ± 0.3 petagrams of carbon per year (Pg C
yr-1, Pg = 1015 grams), which equates to a significant
fraction (20-40%) of the recent estimates (20-4.2 Pg C yr-1)
of total new production in the tropical and subtropical oceans (Emerson
et al., 1997; Lee, 2001). The remainder is presumably supported by
upward flux of nutrients into the euphotic zone via eddy diffusion and
turbulent mixing processes or lateral exchange. Our calculation provides the
first global-scale estimate of net carbon production in the absence of
measurable nitrate. We hypothesize that it is attributable to dinitrogen
(N2) fixing microorganisms, which can utilize the inexhaustible
dissolved N2 pool and thereby bypass nitrate limitation.
Li, Y.-H., and T.-H. Peng. Latitudinal change of remineralization ratios in
the oceans and its implication for nutrient cycles. Global
Biogeochemical Cycles, 16(4):1130, doi:10.1029/2001GB001828 (2002).
A new three-end-member mixing model is introduced to obtain remineralization
ratios of organic matter in the water column. Remineralization ratios
(P/N/Corg/-O2) of organic matter in the deep water
column change systematically from the northern Atlantic to the Southern
Oceans, then to the equatorial Indian and the northern Pacific oceans, more
or less along the global ocean circulation route of deep water. Average
remineralization ratios of organic matter for the northern Atlantic Ocean are
P/N/Corg/-O2 = 1/(16 ± 1)/(73 ± 8)/(137 ± 7), and
for the Southern Oceans P/N/Corg/-O2 = 1/(15 ±
1)/(80 ± 3)/(133 ± 5). Those values are similar to the traditional Redfield
ratios of P/N/Corg/-O2 = 1/16/106/138 for marine
plankton, except for the low Corg/P ratio. Average remineralization
ratios for the equatorial Indian Ocean are
P/N/Corg/-O2 = 1/(10 ± 1)/(94 ± 5)/(130 ± 7), and for
the northern Pacific Ocean P/N/Corg/-O2 = 1/(13 ±
1)/(124 ± 11)/(162 ± 11). The apparent low N/P ratio for both ocean basins
suggests that organic nitrogen was converted partly into gaseous
N2O and N2 by bacteria through
nitrification/denitrification processes in a low-oxygen or reducing
microenvironment of organic matter throughout the oxygenated water column.
The actual N/P ratio of remineralized organic matter is probably around 15
± 1. The -O2/Corg ratio of remineralized organic
matter also decreases systematically along the global ocean circulation route
of deep water, indicating changes in relative proportions of biomolecules
such as lipids, proteins, nucleic acids, and carbohydrates. No temporal
trends of remineralization ratios are detected when comparing the results
obtained by GEOSECS and WOCE data sets.
Lirman, D., D. Manzello, and S. Macia. Back from the dead: The resilence
of Siderastrea radians to severe stress. Coral Reefs,
21(3):291-292 (2002).
No abstract.
Liu, Q., S.J. Lord, N. Surgi, H.L. Pan, and F.D. Marks. Hurricane
initialization using reconnaissance data in GFDL hurricane forecast
model. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 267-268 (2002).
No abstract.
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.
Marks, F.D., G. Kappler, and M. DeMaria. Development of a tropical cyclone
rainfall climatology and persistence (R-CLIPER) model. Preprints, 25th
Conference on Hurricanes and Tropical Meteorology, San Diego, CA,
April 29-May 3, 2002. American Meteorological Society, Boston, 327-328
(2002).
No abstract.
Mayrinck, C.E., P.P. Dodge, F.D. Marks, S.H. Houston, and J.F.
Gamache. Evolution of the coastal windfield during the landfall of
Hurricane Floyd (1999). Preprints, 25th Conference on Hurricanes and
Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 337-338 (2002).
No abstract.
Meinen, C.S., D.S. Luther, D.R. Watts, K.L. Tracey, A.D. Chave, and J.
Richman. Combining inverted echo sounder and horizontal electric field
recorder measurements to obtain absolute velocity profiles. Journal of
Atmospheric and Oceanic Technology, 19(10):1653-1644 (2002).
Profiles of absolute velocity are difficult to obtain in the ocean,
especially over long periods of time at the same location. This paper
presents a method of estimating full water column absolute horizontal
velocity profiles as a function of time by combining historical hydrography
with the measurements from two separate instruments, the inverted echo
sounder (IES) and the horizontal electric field recorder (HEFR). Hydrography
is used to construct temperature, salinity, and specific volume anomaly
characteristics as functions of the independent variables pressure and
seafloor-to-sea-surface round-trip acoustic travel time (tau). Each IES
measured tau is combined with these two-dimensional characteristics to
estimate the profile of specific volume anomaly, which then is integrated
vertically to obtain profiles of geopotential height anomaly (DELTA-phi).
Profiles of DELTA-phi from adjacent IES sites are differenced to yield
vertical profiles of relative geostrophic velocity. Horizontal electric
fields arising from the vertically averaged horizontal water velocity
provide the requisite referencing of the IES-derived relative velocities.
Comparisons are presented between HEFR+IES absolute velocities in the
Southern Ocean near 51°S, 143.5°E and absolute velocities
determined via hydrography, acoustic Doppler current profiler, and current
meter.
Miller, L.G., and K.D. Goodwin. Halocarbon biogeochemistry.
Biogeochemistry, 60(2):119-120 (2002).
No abstract.
Millero, F.J., D. Pierrot, K. Lee, R. Wanninkhof, R.A. Feely, C.L. Sabine,
R.M. Key, and T. Takahashi. Dissociation constants for carbonic acid
determined from field measurements. Deep-Sea Research, Part I,
49(10):1705-1723 (2002).
A number of workers have recently shown that the thermodynamic constants
for the dissociation of carbonic acid in seawater of Mehrbach et
al. are more reliable than measurements made on artificial seawater.
These studies have largely been confined to looking at the internal
consistency of measurements of total alkalinity (TA), total inorganic
carbon dioxide (TCO2) and the fugacity of carbon dioxide
(fCO2). In this paper, we have examined the field measurements
of pH, fCO2, TCO2, and TA on surface and deep waters
from the Atlantic, Indian, Southern and Pacific oceans to determine the
pK1, pK2, and pK2-pK1. These
calculations are possible due to the high precision and accuracy of the
field measurements. The values of pK2 and
pK2-pK1 over a wide range of temperatures
(-1.6-38°C) are in good agreement (within ±0.005) with the results of
Mehrbach et al. The measured values of pK1 at 4°C
and 20°C are in reasonable agreement (within ±0.01) with all the
constants determined in laboratory studies. These results indicate, as
suggested by internal consistency tests, that the directly measured values
of pK1+pK2 of Mehrbach et al. on real
seawater are more reliable than the values determined for artificial
seawater. It also indicates that the large differences of
pK2-pK1 (0.05 at 20°C) in real and artificial
seawater determined by different investigators are mainly due to
differences in pK2. These differences may be related to the
interactions of boric acid with the carbonate ion. The values of
pK2-pK1 determined from the laboratory measurements
of Lee et al. and Lueker et al. at low fCO2 agree
with the field-derived data to ±0.016 from 5°C to 25°C. The
values of pK2-pK1 decrease as the fCO2 or
TCO2 increases. This effect is largely related to changes in
the pK2 as a function of fCO2 or TCO2.
The values of fCO2 calculated from an input of TA and
TCO2, which require reliable values of
pK2-pK1, also vary with fCO2. The field
data at 20°C has been used to determine the effect of changes of
TCO2 on pK2 giving an empirical relationship:
pK2TCO2 = pK2-1.6 x 10-4
(TCO2-2050) which is valid at TCO2 > 2050 µmol
kg-1. This assumes that the other dissociation constants such
as KB for boric acid are not affected by changes in
TCO2. The slope is in reasonable agreement with the laboratory
studies of Lee et al. and Lueker et al. (-1.2 x
10-4 to -1.9 x 10-4). This equation eliminates the
dependence of the calculated fCO2 on the level of
fCO2 or TCO2 in ocean waters (sigma = 29.7 µatm
in fCO2). An input of pH and TCO2 yields values of
fCO2 and TA that are in good agreement with the measured values
(±22.3 µatm in fCO2 and ±4.3 µmol kg-1 in
TA). The cause of the decrease in pK2 at high fCO2 is
presently unknown. The observed inconsistencies between the measured and
computed fCO2 values may be accounted for by adding the effect
of organic acid (~8 µmol kg-1) to the interpretation
of the TA. Further studies are needed to elucidate the chemical reactions
responsible for this effect.
Molinari, R.L., R. Lusic, S.L. Garzoli, M.O. Baringer, and G.J.
Goni. Benchmarks for Atlantic Ocean circulation. CLIVAR Exchanges,
7(3/4):6-9 (2002).
No abstract.
Morrison, I.J., F.D. Marks, and S. Businger. WSR-88D observations of
boundary layer rolls during hurricane landfall. Preprints, 25th
Conference on Hurricanes and Tropical Meteorology, San Diego, CA, April
29-May 3, 2002. American Meteorological Society, Boston, 341-342 (2002).
No abstract.
Murillo, S.T., W.-C. Lee, F.D. Marks, and P.P. Dodge. Examining structural
changes and circulation center of Hurricane Danny (1997) using a
single-Doppler radar wind retrieval technique. Preprints, 25th
Conference on Hurricanes and Tropical Meteorology, San Diego, CA, April
29-May 3, 2002. American Meteorological Society, Boston, 485-486 (2002).
No abstract.
Nogues-Paegle, J., C.R. Mechoso, R. Fu, E.H. Berbery, W.C. Chao, T.-C. Chen,
K. Cook, A.F. Diaz, D.B. Enfield, R. Ferreira, A.M. Grimm, V. Kousky, B.
Liebmann, J. Marengo, K. Mo, J.D. Neelin, J. Paegle, A.W. Robertson, A.
Seth, C.S. Vera, and J. Zhou. Progress in Pan American CLIVAR research:
Understanding the South American monsoon. Meteorologica,
27(1-2):3-32 (2002).
A review of recent findings on the South American Monsoon System (SAMS) is
presented. SAMS develops over a large extension of land mass crossed by the
equator with surface conditions that vary from the world's largest tropical
forest in Amazonia to a high desert in the Altiplano. The high Andes
mountains to the west effectively block air exchanges with the Pacific
Ocean, but plentiful moisture transport from the Atlantic maintains intense
precipitation that is strongest over central Brazil. There is also abundant
precipitation over the subtropical plains of South America in association
with moisture transport from tropical latitudes. Furthermore, midlatitude
systems are important modulators of the tropical precipitation. The
combination of all these factors results in a unique seasonal evolution of
convection and rainfall. The findings presented emphasize the system's
complexity, and highlight the importance of the South American continent as
the core of atmospheric linkages with the adjacent oceans. A discussion on
directions for research on SAMS is also presented. There are still
outstanding questions on the relative roles played on the system evolution
by the orography, local and remote heat sources, and sea surface
temperature anomalies. Other remaining questions address the impact of
Amazon-deforestation on water and energy cycles over the two largest river
basins of South America (Amazon and La Plata).
Nuissier, O., R.F. Rogers, and F. Roux. An initialization technique using
airborne Doppler radar observations for numerical simulations of Hurricane
Bret (21-23 August 1999). Preprints, 25th Conference on Hurricanes and
Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 403-404 (2002).
No abstract.
Ooyama, K.V. The cubic-spline transform method: Basic definitions and tests
in a 1D single domain. Monthly Weather Review, 130(10):2392-2415
(2002).
The purpose of the paper is to describe the technical details of a numerical
method that combines the cubic-spline representation of spatial variables in
a finite domain with the logistics of the spectral transform method for the
time integration of nonlinear meteorological equations. The reason for
developing the method lies in its application to two-way interacting nested
models of the atmosphere. When compared with the gridpoint representation,
the cubic-spline representation allows direct evaluation of derivatives in
the model equations, and leads to a substantial reduction of shortwave
dispersion of advecting and propagating waves. When compared with the Fourier
spectral representation, the cubic B-splines as basis functions provide
simple but exact means of implementing a variety of boundary conditions that
are needed at the domain interfaces, as well as at natural boundaries. A sharp
(sixth order) low-pass filter, which is built into the cubic-spline transform,
effectively eliminates adverse nonlinear accumulation of small-scale errors
near the resolution limit. These features, critically important to noise-free
nesting, are defined and analyzed in this paper in the simpler context of a
single 1D domain. The actual procedures for two-way interactive nesting will
be presented in a subsequent paper.
Palmer, D.R. A parabolic approximation method with application to global
wave propagation. Journal of Mathematical Physics, 43(4):1875-1905
(2002).
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 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. We then discuss two extensions of the method; first
to propagation along refracted geodesics and second to a description
involving discrete, local, normal modes.
Peterson, R.E., P.G. Black, and V. Pudov. Russian/FSU tropical cyclone
research: The last 25 years. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 513-514 (2002).
No abstract.
Powell, M.D., and S.D. Aberson. Accuracy of United States tropical
cyclone landfall forecasts in the Atlantic basin, 1976-2001. Preprints,
25th Conference on Hurricanes and Tropical Meteorology, San Diego, CA,
April 29-May 3, 2002. American Meteorological Society, Boston, 301-302
(2002).
No abstract.
Reasor, P.D., and M.T. Montgomery. Understanding the dynamics of vertically
sheared hurricanes. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American Meteorological
Society, Boston, 317-318 (2002).
No abstract.
Rogers, R.F., R.A. Black, and D.-L. Zhang. A preliminary investigation
of a common microphysical parameterization and its applicability to tropical
cyclone simulations. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 436-437 (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.
Rogers, R.F., S. Chen, J.E. Tenerelli, and H.E. Willoughby. The role of
vertical shear in determining the distribution of accumulated rainfall in
high-resolution numerical simulations of tropical cyclones. Preprints,
25th Conference on Hurricanes and Tropical Meteorology, San Diego, CA,
April 29-May 3, 2002. American Meteorological Society, Boston, 319-320
(2002).
No abstract.
Rona, P.A., D.R. Jackson, K.G. Bemis, C.D. Jones, K. Mitsuzawa, D.R.
Palmer, and D. Silver. Acoustic advances study of sea floor hydrothermal
flow. EOS, Transactions, American Geophysical Union, 83(44):497,
501-502 (2002).
No abstract.
Sabine, C.L., R.A. Feely, R.M. Key, J.L. Bullister, F.J. Millero, K. Lee,
T.-H. Peng, B. Tilbrook, T. Ono, and C.S. Wong. Distribution of anthropogenic
CO2 in the Pacific Ocean. Global Biogeochemical Cycles,
16(4):1083, doi:10.1029/2001GB001639 (2002).
This work presents an estimate of anthropogenic CO2 in the Pacific
Ocean based on measurements from the WOCE/JGOFS/OACES global CO2
survey. These estimates used a modified version of the DELTA C* technique.
Modifications include a revised preformed alkalinity term, a correction for
denitrification, and an evaluation of the disequilibrium terms using an
optimum multiparameter analysis. The total anthropogenic CO2
inventory over an area from 120°E to 70°W and 70°S to
65°N (excluding the South China Sea, the Yellow Sea, the Japan/East Sea,
and the Sea of Okhotsk) was 44.5 ± 5 Pg C in 1994. Approximately 28 Pg C was
located in the Southern Hemisphere and 16.5 Pg C was located north of the
equator. The deepest penetration of anthropogenic CO2 is found at
about 50°S. The shallowest penetration is found just north of the
equator. Very shallow anthropogenic CO2 penetration is also
generally observed in the high-latitude Southern Ocean. One exception to this
is found in the far southwestern Pacific where there is evidence of
anthropogenic CO2 in the northward moving bottom waters. In the
North Pacific, a strong zonal gradient is observed in the anthropogenic
CO2 penetration depth with the deepest penetration in the western
Pacific. The Pacific has the largest total inventory in all of the southern
latitudes despite the fact that it generally has the lowest average inventory
when normalized to a unit area. The lack of deep and bottom water formation
in the North Pacific means that the North Pacific inventories are smaller
than the North Atlantic.
Schaefer, J.K., K.D. Goodwin, I.R. McDonald, J.C. Murrell, and R.S.
Oremland. Leisingera methylohalidivorans gen. nov., sp. nov.,
a marine methylotroph that grows on methyl bromide. International
Journal of Systematic and Evolutionary Microbiology,
52(3):851-859 (2002).
A marine methylotroph, designated strain MB2T, was isolated for its ability
to grow on methyl bromide as a sole carbon and energy source. Methyl chloride
and methyl iodide also supported growth, as did methionine and glycine
betaine. A limited amount of growth was observed with dimethylsulfide. Growth
was also noted with unidentified components of the complex media marine broth
2216, yeast extract, and casamino acids. No growth was observed on methylated
amines, methanol, formate, acetate, glucose, or a variety of other substrates.
Growth on methyl bromide and methyl iodide resulted in their oxidation to
CO2 with stoichiometric release of bromide and iodide,
respectively. Strain MB2T exhibits growth optima at NaCl and
Mg2+ concentrations similar to that of seawater.
Phylogenetic analysis of the 16S rDNA sequences placed this strain in the
alpha subgroup of the Proteobacteria in proximity with the Ruegeria
and Roseobacter genera. We propose that strain MB2T be designated
Leisingera methylohalidivorans, gen. nov., sp. nov. (ATCC
accession number BAA-92).
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. The vertical alignment
of an incipient tropical cyclone. Preprints, 25th Conference on Hurricanes
and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002. American
Meteorological Society, Boston, 399-400 (2002).
No abstract.
Seki, M.P., R. Lumpkin, and P. Flament. Hawaii cyclonic eddies and blue
marlin catches: The case study of the 1995 Hawaiian International Billfish
Tournament. Journal of Oceanography, 58(5):739-745 (2002).
The combination of prevailing northeasterly tradewinds and island topography
results in the formation of vigorous, westward propagating cyclonic eddies in
the lee of the Hawaiian Islands on time scales of 50-70 days. These mesoscale
(~102 km) features are nowhere more conspicuous or spin up
more frequently than in the Alenuihaha Channel between the Island of Maui and
the Big Island of Hawaii. Cyclonic eddies in subtropical waters such as those
around Hawaii vertically displace the underlying nutricline into the
overlying, nutrient-depleted euphotic zone creating localized biologically
enhanced patches. Insight into how these eddies may directly influence
pelagic fish distribution is provided by examination of recreational fish
catch data coinciding with the presence of eddies on the fishing grounds. We
highlight the 1995 Hawaii International Billfish Tournament in which a
cyclonic eddy dominated the ocean conditions during the week-long event and
the fish catch distribution differed significantly from the average historical
tournament catch patterns. On the tournament fishing grounds, well-mixed
surface layers and strong current flows induced by the eddy's presence
characterized the inshore waters where the highest catches of the prized
Pacific blue marlin (Makaira mazara) occurred, suggesting possible
direct (e.g., physiological limitations) or indirect (e.g.,
prey availability) biological responses of blue marlin to the prevailing
environment.
Sharp, R.J., M.A. Bourassa, J.J. O'Brien, K.B. Katsaros, and E.B.
Forde. Early detection of tropical cyclones using SeaWinds-derived
vorticity for the 2001 hurricane season. Preprints, 25th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 401-402 (2002).
No abstract.
Shay, L.K., S.D. Jacob, T.M. Cook, M.M. Mainelli, S.R. White, P.G. Black,
G.J. Goni, and R.E. Cheney. Hurricane heat potential variability from
in-situ and radar altimetry measurements. Preprints, 25th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 575-576 (2002).
No abstract.
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.
Suvorov, A.M., A.Kh. Khaliulin, E.A. Godin, and D.R. Palmer. An evaluation
of the influence of interannual variability on climate analysis. Second
International Conference on Oceanography of the Eastern Mediterranean and
Black Sea, Ankara, Turkey, October 14-18, 2002. Middle East Technical
University Publication, 444-445 (2002).
Most of the existing methods for calculating climate products from temperature
and salinity data do not take into account interannual variability. As an
illustration, most of the existing temperature and salinity data for the Black
Sea were collected in the period from 1900 to 1995. In fact, more than 50% of
these data were collected in the 1970s and 1980s. Without taking into account
interannual variability, climate products calculated from these data can only
reflect conditions during this brief period. For five areas of the Black Sea
where existing data are plentiful, we have analyzed data for four levels
below the cold intermediate layer where seasonal variability can be ignored.
The analysis shows the existence of a pronounced interannual variability. Our
results illustrate a dependence of the obtained results upon the method used
for calculating the climate products.
Takahashi, T., S.C. Sutherland, C. Sweeney, A. Poisson, N. Metzl, B.
Tillbrook, N. Bates, R.H. Wanninkhof, R.A. Feely, C.L. Sabine, J.
Olafsson, and Y. Nojiri. Global sea-air CO2 flux based on
climatological surface ocean pCO2 and seasonal biological and
temperature effects. Deep-Sea Research, Part II,
49(9-10):1601-1622 (2002).
Based on about 940,000 measurements of surface-water pCO2
obtained since the International Geophysical Year of 1956-1959, the
climatological, monthly distribution of pCO2 in the global
surface waters representing mean non-El Niño conditions has been obtained
with a spatial resolution of 4° × 5° for a reference year
1995. The monthly and annual net sea-air CO2 flux has been
computed using the NCEP/NCAR 41-year mean monthly wind speeds. An annual
net uptake flux of CO2 by the global oceans has been
estimated to be 2.2 (+22% or 19%) Pg Cyr-1 using the (wind
speed)2 dependence of the CO2 gas transfer
velocity of Wanninkhof (J. Geophys. Res. 97 (1992) 7373). The
errors associated with the wind-speed variation have been estimated using
one standard deviation (about ±2 m s-1) from the mean
monthly wind speed observed over each 4° × 5° pixel area
of the global oceans. The new global uptake flux obtained with the
Wanninkhof (wind speed)2 dependence is compared with those
obtained previously using a smaller number of measurements, about 250,000
and 550,000, respectively, and are found to be consistent within
±0.2 Pg Cyr-1. This estimate for the global ocean uptake
flux is consistent with the values of 2.0 ± 0.6 Pg Cyr-1
estimated on the basis of the observed changes in the atmospheric
CO2 and oxygen concentrations during the 1990s (Nature
381 (1996) 218; Science 287 (2000) 2467). However, if the (wind
speed)3 dependence of Wanninkhof and McGillis (Geophys.
Res. Lett. 26 (1999) 1889) is used instead, the annual ocean uptake
as well as the sensitivity to wind-speed variability is increased by
about 70%. A zone between 40° and 60° latitudes in both the
northern and southern hemispheres is found to be a major sink for
atmospheric CO2. In these areas, poleward-flowing warm waters
meet and mix with the cold subpolar waters rich in nutrients. The
pCO2 in the surface water is decreased by the cooling effect
on warm waters and by the biological drawdown of pCO2 in
subpolar waters. High wind speeds over these low pCO2 waters
increase the CO2 uptake rate by the ocean waters. The
pCO2 in surface waters of the global oceans varies seasonally
over a wide range of about 60% above and below the current atmospheric
pCO2 level of about 360 µatm. A global map showing the
seasonal amplitude of surface-water pCO2 is presented. The
effect of biological utilization of CO2 is differentiated from
that of seasonal temperature changes using seasonal temperature data. The
seasonal amplitude of surface-water pCO2 in high-latitude
waters located poleward of about 40° latitude and in the equatorial
zone is dominated by the biology effect, whereas that in the temperate
gyre regions is dominated by the temperature effect. These effects are
about six months out of phase. Accordingly, along the boundaries between
these two regimes, they tend to cancel each other, forming a zone of
small pCO2 amplitude. In the oligotrophic waters of the
northern and southern temperate gyres, the biology effect is about 35
µatm on average. This is consistent with the biological export flux
estimated by Laws et al. (Glob. Biogeochem.Cycles 14 (2000)
1231). Small areas such as the northwestern Arabian Sea and the eastern
equatorial Pacific, where seasonal upwelling occurs, exhibit intense
seasonal changes in pCO2 due to the biological drawdown of
CO2.
Taylor, M.A., E.B. Enfield, and A.A. Chen. Influence of the tropical
Atlantic versus the tropical Pacific on Caribbean rainfall. Journal of
Geophysical Research, 107(C9):3127, doi:10.1029/2001JC001097 (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 Niño/La Niña 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 sea surface temperature (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.
Thacker, W.C., and O.E. Esenkov. Assimilating XBT data into HYCOM.
Journal of Atmospheric and Oceanic Technology, 19(5):709-724 (2002).
A scheme is presented for assimilating expendable bathythermographic data
into HYCOM, an oceanic circulation model featuring a hybrid vertical
coordinate. The scheme is fully multivariate, using observations of
temperature to correct density, pressure, salinity, and momentum, in addition
to temperature. Central to the scheme is the estimation of companion profiles
of salinity and potential density. The potential density profiles are used to
estimate the thicknesses of the model's layers, so that layer-averaged values
of potential density and potential temperature can be computed. These derived
data and the derived layer thicknesses are assimilated via optimal
interpolation. Salinity corresponding to the corrected potential density and
potential temperature fields is determined by the equation of state of
seawater, and corrections to the momentum field are computed geostrophically
from the corrections to the pressure field. The scheme is illustrated using
data from March 1995 in the Atlantic Ocean.
Uhlhorn, E.W., and J.J. Cione. Real-time simulation of hurricane inner-core
ocean cooling as a gauge for intensity change. Preprints, 25th Conference
on Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3,
2002. American Meteorological Society, Boston, 658-659 (2002).
No abstract.
Walsh, E.J., C.W. Wright, D. Vandemark, L.F. Bliven, E.W. Uhlhorn, P.G.
Black, and F.D. Marks. Rain rate measurements in Hurricane Humberto using
the airborne NASA scanning radar altimeter. Preprints, 25th Conference on
Hurricanes and Tropical Meteorology, San Diego, CA, April 29-May 3, 2002.
American Meteorological Society, Boston, 208-209 (2002).
No abstract.
Walsh, E.J., C.W. Wright, D. Vandemark, W.B. Krabill, A.W. Garcia, S.H.
Houston, S.T. Murillo, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane
directional wave spectrum spatial variation at landfall. Journal of
Physical Oceanography, 32(6):1667-1684 (2002).
The NASA Scanning Radar Altimeter (SRA) flew aboard one of the NOAA WP-3D
hurricane research aircraft to document the sea surface directional wave
spectrum in the region between Charleston, South Carolina, and Cape Hatteras,
North Carolina, as Hurricane Bonnie was making landfall near Wilmington,
North Carolina, on 26 August 1998. Two days earlier, the SRA had documented
the hurricane wave field spatial variation in open water when Bonnie was 400
km east of Abaco Island, Bahamas. Bonnie was similar in size during the two
flights. The maximum wind speed was lower during the landfall flight (39 m
s-1) than it had been during the first flight (46 m
s-1). Also, Bonnie was moving faster prior to landfall (9.5 m
s-1) than when it was encountered in the open ocean (5 m
s-1). The open ocean wave height spatial variation indicated
that Hurricane Bonnie would have produced waves of 10 m height on the
shore northeast of Wilmington had it not been for the continental shelf.
The gradual shoaling distributed the wave energy dissipation process
across the shelf so that the wavelength and wave height were reduced
gradually as the shore was approached. The wave height 5 km from shore
was about 4 m. Despite the dramatic differences in wave height caused by
shoaling and the differences in the wind field and forward speed of the
hurricane, there was a remarkable agreement in the wave propagation
directions for the various wave components on the two days. This suggests
that, in spite of its complexity, the directional wave field in the
vicinity of a hurricane may be well behaved and lend itself to be modeled
by a few parameters, such as the maximum wind speed, the radii of the
maximum and gale force winds, and the recent movement of the storm.
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 Niño. 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 Niño
can affect the TNA through the Walker and Hadley circulations, favoring the
TNA warming in the subsequent spring of the Pacific El Niño 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
Niño-Southern Oscillation. Journal of Climate, 15(4):399-419 (2002).
Atmospheric circulation cells associated with the El Niño-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 Niño 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.
White, S.R., M.M. Mainelli, S.D. Jacob, and L.K. Shay. Hurricane heat
potential estimates from monthly versus seasonal temperature and salinity
data. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American Meteorological
Society, Boston, 128-129 (2002).
No abstract.
Willoughby, H.E. Aircraft observations of Hurricane Floyd. Proceedings,
Second Workshop on Landfalling Typhoons in the Taiwan Area, Taipei,
Taiwan, April 25-26, 2002. National Science Council, 35-51 (2002).
The 1995 through 2001 hurricane seasons produced 27 "major" hurricanes, in
categories 3, 4, or 5 on the Saffir-Simpson scale. Only three of the major
hurricanes that formed during the last six seasons reached U.S. shores with
category 3 or greater intensity. This experience contrasts with a long-term
expectation that about a third of Atlantic major hurricanes (i.e.,
9 of the 27) would make U.S. landfall. Hurricane Floyd of 1999 is
representative of the anticlimatic late 20th century major hurricanes. Like
most of these storms, it formed from an African Wave. It intensified rapidly
east of the Bahamas, reaching a minimum central pressure of 921 hPa on 13
September 1999. This pressure was nearly in equilibrium with the actual
ocean surface temperature under the storm at that time. Subsequently, Floyd
weakened through a concentric eyewall replacement, reintensified somewhat,
and then weakened as a result of large-scale shear and less favorable
thermodynamic conditions to category 2 before landfall in eastern North
Carolina. Floyd's most serious impact was torrential rainfall that claimed
75 lives through drowning in the northeastern U.S., the largest mortality in
a hurricane since Agnes in 1972. Intensive observations from instrumented
aircraft, including flight-level data, radar, dropsondes, and
air-expendable bathythermographs are the key to understanding of the
factors that caused Floyd's rapid intensification and more gradual weakening.
Willoughby, H.E., and M.E. Rahn. A new parametric model of hurricane wind
profiles. Preprints, 25th Conference on Hurricanes and Tropical
Meteorology, San Diego, CA, April 29-May 3, 2002. American Meteorological
Society, Boston, 553-554 (2002).
No abstract.
Wilson, D.W., W.E. Johns, and S.L. Garzoli. Velocity structure of North
Brazil Current rings. Geophysical Research Letters,
29(8):10.1029/2001GL013869 (2002).
High-resolution shipboard surveys of four North Brazil Current rings are
presented, which are the first such dedicated surveys to be made of these
features. Of the four rings surveyed, three fundamentally different types of
ring structures are found: (1) a shallow, surface-trapped structure with
velocities confined to the top 200 m (two rings); (2) a deep-reaching
structure with significant swirl velocities (~0.2 m/s) extending to
2000 m (one ring); and (3) a thermocline-intensified structure with almost
no detectable surface signature (one ring). The results of this study
indicate that North Brazil Current rings can have highly variable vertical
structures, and that assessing their overall role in cross gyre exchange in
the tropical Atlantic will require a careful combination of remote sensing
and in-situ observations.
Yvon-Lewis, S.A., and J.H. Butler. Effect of oceanic uptake on atmospheric
lifetimes of selected trace gases. Journal of Geophysical Research,
107(D20):4414, doi:10.1029/2001JD001267 (2002).
We have calculated from a 2° x 2° grid of oceanic properties the
contribution of oceanic loss to the overall lifetimes of a number of
anthropogenic and naturally produced trace gases involved in global
warming and stratospheric ozone depletion. The model, originally developed
for atmospheric methyl bromide, can be used for any well-mixed trace gas
where the seawater degradation rate constants and solubilities are known.
Of the gases tested, it is clear that known oceanic chemical degradation
processes alone are not significant sinks for most HFCs and HCFCs. Chemical
degradation in the oceans is a substantial sink for COS (28%) and
COCl2 (8%) and a minor sink for CH3Cl (<2%) and
CH3I (2.5%), and it should be considered when determining
atmospheric lifetimes and sink strengths for these gases. Biological
degradation processes are likely to increase the oceanic uptake rates of
many gases.
Yvon-Lewis, S.A., J.H. Butler, E.S. Saltzman, P.A. Matrai, D.B. King, R.
Tokarczyk, R.M. Moore, and J.-Z. Zhang. Methyl bromide cycling in a warm-core
eddy of the North Atlantic. Global Biogeochemical Cycles,
16(4):1141, doi:10.1029/2002GB001898 (2002).
We conducted a detailed investigation of the evolution of methyl bromide
concentrations, degradation rates, and ventilation rates for 26 days in a
naturally contained, warm-core eddy of the North Atlantic Ocean. This is the
first study of the oceanic cycling of methyl bromide in a natural, contained
system with a complete suite of supporting measurements of physical and
chemical variables. Methyl bromide concentrations in the mixed layer ranged
from 2.3 to 4.2 nmol m-3, degradation rates ranged from 0.1 to 0.9
nmol m-3 d-1, net sea-to-air exchange rates ranged
from 0 to 0.5 nmol m-3 d-1, and net loss rates through
the thermocline were less than 0.1 nmol m-3 d-1. From a
mass balance for methyl bromide in the mixed layer, we calculated production
rates ranging from <0.1 to 1.3 nmol m-3 d-1. The median
of this range, 0.48 nmol m-3 d-1, is higher than the
~0.15 nmol m-3 d-1 necessary to maintain the
reported global oceanic emission of 56 Gg yr-1. This is reasonable,
because our study area was supersaturated in methyl bromide, whereas the
ocean as a whole is undersaturated.
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.
Zhang, J.-Z., G.A. Berberian, and R. Wanninkhof. Long-term storage of
natural water samples for dissolved oxygen determination. Water
Research, 36(16):4165-4168 (2002).
A method for preserving natural water samples for dissolved oxygen analysis
is recommended. The conventional method of using greased glass stoppers has
been found to cause a 12% increase in oxygen concentration over a one-month
period as a result of evaporation of water sample through micro-gaps and
concurrent intrusion of air into the water sample bottles. Sealing the sample
bottles with water has been found to be the optimal storage method. It permits
a 100.2 ± 0.3% recovery of dissolved oxygen concentration from storage
seawater samples over four months.
**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 ±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.
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. Proceedings, 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, 20 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.
Dunion, J.P., C.S. Velden, and J.R. Rhome. Satellite applications for
tropical wave/tropical cyclone tracking. Preprints, 18th Conference on
Weather Analysis and Forecasting, Ft. Lauderdale, FL, July 30-August 2,
2001. American Meteorological Society, Boston, 436-438 (2001).
No abstract.
Enfield, D.B. Changes in sea surface temperatures influence rain
patterns. Environmental Review, 8(11):1-8 (2001).
No abstract.
Enfield, D.B. Evolution and historical perspective of the 1997-1998 El
Niño-Southern Oscillation event. Bulletin of Marine Science,
69(1):7-25 (2001).
The ocean thermal history of the 1997-98 El Niño 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
Niña) 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 Niño 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., 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 1860-180
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
Niño-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 Niño/La Niña conditions, with environmental
changes in Florida Bay and the Florida Keys National Marine Sanctuary.
Jarrell, J.D., M. Mayfield, E.N. Rappaport, and C.W. Landsea. Deadliest,
costliest, and most intense United States hurricanes from 1900 to 2000
(and other frequently requested hurricane facts), updated October 2001.
NOAA Technical Memorandum, NOAA-TM-NWS-TPC-3 (PB2002-100134), 44 pp.
(2001).
This version of the "Deadliest, Costliest, and Most Intense United States
Hurricanes from 1900 to 2000" extends the work of Herber et al.
(1997) through the 2000 season. It also includes an estimate of the monetary
loss that historical hurricanes could exact on the current property-at-risk
in the same location.
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 Niño-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 Niño-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 Niño-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 Niño-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 10(4):41-43 (2001).
No abstract.
Lee, K. Global net community production estimated from the annual cycle
of surface water total dissolved inorganic carbon. Limnology and
Oceanography, 46(6):1287-1297 (2001).
Global net community production is determined, for the first time, from
the decrease in salinity (S)-normalized total dissolved inorganic carbon
(NCT = CT x 35/S) inventory in the surface mixed
layer corrected for changes due to net air-sea CO2 exchange and
diffusive carbon flux from the upper thermocline. Changes in the mixed
layer NCT inventory are estimated using a derived annual cycle
of NCT and global records of the mixed layer depth. The annual
NCT cycle is deduced from regional algorithms relating
NCT to sea surface temperature (SST) and nitrate
(NO3-), along with global records of seasonal mean
SST and NO3-, and from the monthly mean surface
partial pressure of CO2 and total alkalinity fields using
thermodynamic models. The two methods show similar regional trends and
yield global net community production estimates of 6.7 and 8.0 Gt C (1 Gt
C = 1 x 1012 kg carbon), respectively. The two global estimates
are not significantly different and represent an eight-month period of
1990 (warming period) during which the mixed layer NCT
concentration decreases. However, the estimates do not account for net
community production during a four-month cooling period. Ratios of net
community production during the warming and cooling periods are estimated
from multiyear sediment trap data at the Hawaii Ocean Time-series (228N,
1588W) and Ocean Weather Station P (50°N, 145°W) sites. Global
extrapolation of these ratios yields annual rates of net community
production of 9.1 ± 2.7 and 10.8 ± 2.7 Gt C yr-1.
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.
McAdie, C.J., P.R. Harasti, P.P. Dodge, W.-C. Lee, S.T. Murillo, and
F.D. Marks. Real-time implementation of tropical cyclone-specific radar
data processing algorithms. Preprints, 30th International Conference on
Radar Meteorology, Munich, Germany, July 19-24, 2001. American
Meteorological Society, Boston, 466-468 (2001).
No abstract.
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 Niño-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 Niño 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 ±0.7
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.
Murillo, S.T., W.-C. Lee, F.D. Marks, and P.P. Dodge. Using a single-Doppler
radar wind retrieval technique to examine structural changes in Hurricane
Danny (1997). Preprints, 30th International Conference on Radar
Meteorology, Munich, Germany, July 19-24, 2001. American Meteorological
Society, Boston, 148-149 (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.H. 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. Proceedings, 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.
Reasor, P.D., M.T. Montgomery, F.D. Marks, and J.G. Gamache. Studies of
tropical cyclone vorticity dynamics using airborne Doppler-derived wind
fields. Preprints, 30th International Conference on Radar
Meteorology, Munich, Germany, July 19-24, 2001. American Meteorological
Society, Boston, 142-144 (2001).
No abstract.
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.
Rogers, R.F., S.S. Chen, J.E. Tenerelli, and H.E. Willoughby. A numerical
study of the impact of vertical shear on the distribution of rainfall in
Hurricane Bonnie (1998). Preprints, Ninth Conference on Mesoscale
Processes, Ft. Lauderdale, FL, July 30-August 2, 2001. American
Meteorological Society, Boston (2001).
No abstract.
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.
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 Niño. Though the bulk of the array was deployed in late 1997, the
effects of the 1997/1998 El Niño 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 Niño-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
Niño-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(5):674-691 (2001).
The El Niño-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.
Wanninkhof, R.H., and P. Liss. SOLAS requirements for the improvement of
ocean-atmosphere flux fields. Proceedings, Intercomparison and
Validation of Ocean-Atmosphere Flux Fields Workshop, Potomac, MD,
May 21-24, 2001. WCRP-115-WMO/TD-No. 1083, 8-9 (2001).
No abstract.
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.
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(1-2):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. 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.
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. 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. 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.
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.
Cushman-Roisin, B., O.E. Esenkov, and B.J. Mathias. A
particle-in-cell-method for the solution of two-layer shallow-water
equations. International Journal of Numerical Methods in Fluids,
32(5):515-543 (2000).
A particle-in-cell (PIC) numerical method developed for the study of
shallow-water dynamics, when the moving fluid layer is laterally confined
by the intersection of its top and bottom surfaces, is described. The effect
of ambient rotation is included for application to geophysical fluids,
particularly open-ocean buoyant vortices in which the underlying density
interface outcrops to the surface around the rim of the vortex. Extensions
to include the dynamical effect of a second moving layer (baroclinicity) and
the presence of a lateral rigid boundary (sidewall) are also described.
Although the method was developed for oceanographic investigations,
applications to other fluid mechanics problems would be straightforward.
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.
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).
No abstract.
Esenkov, O.E. A numerical study of the dynamics of the Somali Current
system. Ph.D. Thesis, University of Miami, Rosenstiel School of Marine
and Atmospheric Science, 140 pp. (2000).
The evolution of surface circulation, salinity budget, and processes at
intermediate depth in the northwestern Indian Ocean were studied with the
open boundary version of the Miami Isopycnic Coordinate Ocean Model (MICOM).
Under climatological wind and thermodynamic forcing, the model develops
solutions that are in good agreement with global MICOM results and with
observations. When the observed winds (Legler et al., 1989) force
the model, interannual variability of the surface fields increases
significantly. However, coalescence of the two large eddies in the end of
the summer monsoon, which was observed in some years, does not occur in
the model. To identify what processes facilitate the merger, a series of
experiments was performed with modified model parameters and forcing fields.
The eddies coalesced when half-slip, rather than no-slip, boundary conditions
were used. In this case, less positive vorticity was produced at the coast,
resulting in a reduced blocking effect on the propagation of the southern
eddy. Socotra Island, which is submerged in the standard model, hinders
movement of the northern anticyclone, leading to stronger interaction
between the eddies and their subsequent merging. A more realistic coalescence
occurs in an experiment where winds are held constant after reaching the
peak summer value. Freshwater fluxes from the east and south were previously
considered important for the salinity budget in the Arabian Sea, where
evaporation exceeds precipitation; however, the model demonstrated that
only cross-equatorial transport of low-salinity water in the upper 400 m is
essential. About 86% of this water is advected below the surface layer at
the western boundary. The strongest interaction between the mixed layer and
the oceanic interior occurs during the summer in the coastal upwelling
regions off Somalia. Forty-three percent of all upwelled water comes from
depths between 100 m and 200 m, thus signifying the importance of mid-depth
circulation and water mass distribution for the surface processes. Both
observations and model solutions demonstrate strong annual cycle and
alongshore variability of coastal subsurface circulation. A cross-equatorial
northward flow below the surface, which exists throughout the year, is
disconnected from currents farther north. A southward undercurrent north of
5°N is present during the winter monsoon. Water for the current is
supplied by flows from the north and northeast. The former originates in the
Persian Gulf and carries higher-salinity water, while the latter contribution
is mainly from the Gulf of Aden. Separation of the southward undercurrent
near 4°N is not caused by its interaction with a topographical ridge,
as was previously suggested. Agreement with the observations north of
5°N improves when Socotra Island is present in the model.
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).
No abstract.
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 Niño. 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 Niño and La Niña temperature fluctuations into the Indian
Ocean. The ENSO variability in the internal energy transport is
calculated: 0.63 PW during the La Niña months of December 1996 through
February 1997, and 0.39 PW during the El Niño 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), 274 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.
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).
No abstract.
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.
Godin, O.A., D. Yu Mikhin, and D.R. Palmer. Monitoring of ocean currents
in the coastal zone. Izvestiya Atmospheric and Oceanic Physics,
36(1):131-142 (2000).
A method proposed recently for remote monitoring of currents in coastal
regions of the ocean is discussed and compared to alternative approaches.
The new method, which is referred to as the method of matched nonreciprocity
(MMN), represents further development of conventional acoustic tomography of
currents as applied to shallow-sea conditions. In measurements of currents,
low-frequency acoustic waves are employed as sounding signals. The MMN makes
it possible to obtain real-time current charts in a region extending
horizontally to tens or hundreds of kilometers and covering the whole depth
of the water from the surface of the ocean to its bottom. Such charts are
important in solving major scientific problems, in particular, monitoring of
climate changes and verification of global-circulation models. It is shown
that the MMN is free of limitations inherent in the monitoring methods proposed
previously. The MMN is based on recent advances in the theory and
mathematical modeling of acoustic propagation in inhomogeneous moving
media and also in the use of the matched-field method for solving
tomographic inverse problems. The physical basis of the MMN is a choice of
an acoustic-field characteristic for measurements, which must be sensitive
to current profiles and insensitive to both acoustic-speed variations and
bottom topography. As a result, the MMN leads to a stable solution of the
inverse problem for the vertical distribution of current velocity. The
development of methods for current acoustic tomography is considered from
the standpoint of their applicability to monitoring ocean dynamics in
coastal regions. Possible applications of the MMN to solving other
oceanographic problems are also discussed.
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).
No abstract.
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., 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.
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.
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.
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).
No abstract.
Katsaros, K.B. The paradigm for research on atmosphere-ocean interaction
at the cusp between the 20th and 21st centuries. 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.
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.
Knaff, J.A., and Landsea, C.W. Application of the El Niño-Southern
Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme.
Experimental Long-Lead Forecast Bulletin, 9(3):48-50 (2000).
No abstract.
Landsea, C.W. Climate variability of tropical cyclones: Past, present,
and future. In Storms (Volume 1), R.A. Pielke, Sr. and R.A.
Pielke, Jr. (eds.). Routledge, New York (ISBN 041517239X), 220-241
(2000).
No abstract.
Landsea, C.W. El Niño-Southern Oscillation and the seasonal predictability
of tropical cyclones. 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), 149-181 (2000).
Perhaps the most dramatic effect that El Niño 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 Niño-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 Niño-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 Niño? Weatherzine, 23:2-4 (2000).
No abstract.
Landsea, C.W., and J.A. Knaff. How much "skill" was there in forecasting the
strong 1997-1998 El Niño and 1998-2000 La Niña events? Proceedings, 25th
Annual Climate Diagnostics and Prediction Workshop, Palisades, NY,
October 23-27, 2000. NOAA/Climate Prediction Center and the International
Research Institute for Climate Prediction, 4-7 (2000).
No abstract.
Landsea C.W., and J.A. Knaff. How much skill was there in forecasting
the very strong 1997-1998 El Niño? Bulletin of the American
Meteorological Society, 81(9):2107-2120 (2000).
The very strong 1997-1998 El Niño was the first major event in which
numerous forecasting groups participated in its real-time prediction. A
previously developed simple statistical tool, the El Niño-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 Niño, 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 Niño'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 Niño impacts were correctly anticipated by
national meteorological centers one-half year in advance, because of the
tendency for El Niño events to persist into and peak during the boreal
winter. Despite this, the zero to two season (0-8 month) forecasts of the
El Niño 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., 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.
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.
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, Part 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., 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).
No abstract.
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.
Melo, N., 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 Niño-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 Niño
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.
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 Niño-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-Nuñez 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.
Murnane, R.J., C. Barton, E. Collins, J. Donnelly, J. Elsner, K. Emanuel,
I. Ginis. S. Howard, C.W. Landsea, K. Liu, D. Malmquist, M. McKay, A.
Michaels, N. Nelson, J. O'Brien, D. Scott, and T. Webb. Model estimates of
hurricane wind speed probabilities. EOS, Transactions, American
Geophysical Union, 81(38):433, 438 (2000).
No abstract.
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).
No abstract.
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 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
consistent with the range of estimates from measurements made during non-El
Niño conditions.
Powell, M.D. Tropical cyclones during and after landfall. In Storms
(Volume 1), R. Pielke, Sr. and R. Pielke, Jr. (eds.). Routledge, New York
(ISBN 041517239X), 196-219 (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.
Protat, A., Y. Lemaitre, D. Bouniol, and R.A. Black. Microphysical
observations during FASTEX from airborne Doppler radar and in-situ
measurements. Physics and Chemistry of the Earth, Part B: Hydrology,
Oceans, and Atmosphere, 25(10-12):1097-1102 (2000).
A major objective of FASTEX is to document the three-dimensional dynamic
and microphysical structure of the North-Atlantic frontal cyclones in their
mature stage at different scales of motion. In this paper, we combine the
airborne Doppler radar and microphysical 2D-C and 2D-P probes data to recover
the 3D microphysical and radiative properties of the IOP16 and IOP12 frontal
cyclones (terminal fall velocity, cloud and precipitation water contents,
precipitation fall rate, effective radius). The first step is to derive
statistical relationships between the microphysical quantities and
reflectivity from the 2D-P and 2D-C probes. Then, the Doppler-derived 3D
reflectivity field is combined with these statistical relationships to
access the 3D microphysical fields.
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 Niño-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 Niño 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.
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).
No abstract.
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).
No abstract.
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 ± 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., 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.
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.
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).
No abstract.
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 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 Niño-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 Niño. Journal of the Atmospheric Sciences,
57(22):3767-3781 (2000).
The atmospheric heating and sea surface temperature (SST) anomalies
during the mature phase of El Niño 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 Niño. When the model heating anomaly forcing is modified to
resemble the observed heating anomalies during the mature phase of El
Niño, 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 Niño. 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., and R.H. Weisberg. The 1997-1998 El Niño evolution relative to
previous Niño events. Journal of Climate, 13(2):488-501 (2000).
The evolution of the 1997-1998 El Niño 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 Niño decay. The paper also
compares the 1997-1998 El Niño with previous warm events, and discusses
different ENSO mechanisms relevant to the 1997-1998 El Niño.
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. 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. 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.
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.
Yvon-Lewis, S.A. Methyl bromide in the atmosphere and ocean. IGACtivities
Newsletter, 19:9-12 (2000).
No abstract.
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., 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.
Alfaro, E.J., and D.B. Enfield. The rainy season in Central America: An
initial success in prediction. IAI Newsletter, 20:21-22 (1999).
No abstract.
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.
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.
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.
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 Niño 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.
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.
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(2):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.
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., J.F. Gamache, S.H. Houston, and F.D. Marks. Windfields in
landfalling hurricanes from multiple Doppler radar data: The 1998 hurricane
season. Preprints, 29th International Conference on Radar
Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American
Meteorological Society, Boston, 273-275 (1999).
No abstract.
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. 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).
Esenkov, O.E., and B. Cushman-Roisin. Modeling of two-layer eddies and
coastal flows with a particle method. Journal of Geophysical
Research, 104(C5):10,959-10,980 (1999).
An existing particle-in-cell (PIC) numerical code is applied to lens-like
anticyclonic vortices and buoyant coastal currents. A first series of
experiments with initially elongated eddies reveals that motions induced in
the lower layer act to increase the rate of rotation of the structure;
eccentricity reduction, if any, produces a final vortex of aspect ratio
between 1.8 and 1.9, in accordance with a theoretical prediction. A second
series of experiments determines the maximal separation distance that can
exist between two identical and circular vortices before they spontaneously
merge; this distance is a function of the vortex size and ambient
stratification. In a third series of experiments, vortex interactions
across layers are considered; results similar to those obtained with
two-layer point vortices (hetons) are obtained. Finally, the PIC method is
generalized to simulate the finite-amplitude instability of a buoyant
geostrophic current flowing along a vertical coastal wall.
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 Niño on the equatorial Pacific contribution to atmospheric
CO2 accumulation. Nature, 398(6728):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 Niño year of 1996. The total reduction of the
sea-to-air CO2 flux during the 1991-1994 El Niño 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.
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.
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., 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.
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., 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.
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.
Hock, T.F., and J.L. Franklin. The NCAR GPS dropwindsonde. Bulletin of
the American Meteorological Society, 80(3):407-420 (1999).
The National Center for Atmospheric Research (NCAR), in a joint effort with
the National Oceanic and Atmospheric Administration (NOAA) and the German
Aerospace Research Establishment, has developed a dropwindsonde based on the
Global Positioning System (GPS) satellite navigation. The NCAR GPS
dropwindsonde represents a major advance in both accuracy and resolution for
atmospheric measurements over data-sparse oceanic areas of the globe,
providing wind accuracies of 0.52 m s-1 with a vertical resolution
of ~5 m. One important advance over previous generations of sondes is
the ability to measure surface (10 m) winds. The new dropwindsonde has
already been used extensively in one major international research field
experiment (Fronts and Atlantic Storm Track Experiment), in operational and
research hurricane flights from NOAA's National Weather Service and Hurricane
Research Division, during NCAR's SNOWBAND experiment, and in recent CALJET
and NORPEX El Niño experiments. The sonde has been deployed from a number of
different aircraft, including NOAA's WP-3Ds and new Gulfstream IV jet, the
Air Force C-130s, NCAR's Electra, and a leased Lear-36. This paper describes
the characteristics of the new dropwindsonde and its associated aircraft
data system, details the accuracy of its measurements, and presents examples
from its initial applications.
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.
Jodoin, C. Detection of direct-sequence spread-spectrum signals in a
multipath fading environment. Master's Thesis, Florida Atlantic University,
Boca Raton, FL, 120 pp. (1999).
In this thesis, we study the effect of Rice fading on the performance of
Global Positioning System (GPS) receivers. The field-theoretic foundation
of pseudo-random-noise (PRN) codes, their implementation, and their use in
generating unique navigation messages in the GPS receiver is reviewed. The
processing of the spread-spectrum signals within the digital delay locked
loop (DDLL) in the receiver is also considered. In particular, we derive
numerical expressions that can be easily evaluated for the probability error
and the mean-time to lose-lock, for a DDL operating in an additive white
Gaussian noise (AWGN) channel in the presence of Rice fading. The results
obtained generalize results in the literature for the Rayleigh fading
environment.
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.
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, 8(4):34-36 (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(1):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 Niño 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., 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.
Marks, F.D., P.P. Dodge, and C. Sandin. WSR-88D observations of hurricane
atmospheric boundary layer structure at landfall. Preprints, 29th
International Conference on Radar Meteorology, Montreal, Quebec,
Canada, July 12-16, 1999. American Meteorological Society, Boston, 374-377
(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.
McPhaden, M.J., T. Delcroix, K. Hanawa, Y. Kuroda, G. Meyers, J. Picaut,
and M.S. Swenson. The ENSO observing system. 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).
This paper reviews the status of the ENSO (El Niño-Southern Oscillation)
observing system, with emphasis on the Pacific Ocean during the recent
1997-1998 El Niño and subsequent La Niña. Contributions of this system to
detection, monitoring, forecasting, and understanding of ENSO-related climate
swings will be described. Recommended enhancements and extensions to the
observing system will also be presented.
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., P.P. Dodge, W.-C. Lee, and F.D. Marks. Using the GBVTD
technique in nowcasting hurricane windfields using the WSR-88D.
Preprints, 29th International Conference on Radar Meteorology,
Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society,
Boston, 276-277 (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. 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(2):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, NOAA-TM-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., 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 Niña, El Niño, 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 Niño-Southern Oscillation phenomena.
This paper compares the historical record of La Niña and El Niño 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 Niña
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.
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).
No abstract.
Shapiro, L.J., and J.L. Franklin. Potential vorticity asymmetries and
tropical cyclone motion. Monthly Weather Review, 127(1):124-131
(1999).
A set of nine synoptic-flow cases, incorporating Omega dropwindsonde
observations for six tropical storms and hurricanes, is used to deduce the
three-dimensional distribution of potential vorticity (PV) that contributed
to the deep-layer mean (DLM) wind that steered the cyclones. A piecewise
inversion technique, the same as that previously applied by Shapiro to
Hurricane Gloria of 1985, is used to derive the DLM wind induced by pieces
of anomalous PV restricted to cylinders of different radii centered on each
cyclone. The cylinder of PV that induces a DLM wind that best matches the
observed DLM wind near the center of each cyclone is evaluated. It is found
that the results can be loosely placed into two categories describing the
spatial scale of the PV anomalies that influenced the cyclone's motion. Four
of the cases, including Hurricane Gloria, had "local" control, with a good
match (to within 40%) between the observed DLM wind near the cyclone center
and the DLM wind attributable to a cylinder of PV with a given radius of
1500 km. Further decomposition of the PV anomaly into upper (400 mb and
above) and lower levels (500 mb and below) indicates the dominance of
upper-level features in steering two of the cyclones (Hurricanes Gloria of
1985 and Andrew of 1992), while Hurricane Debby of 1982 was steered by more
barotropic features. These results supplement those found in other studies.
Five of the cases, by contrast, had "large-scale" control, with no cylinder
of radius 2000 km having a good match between the induced and observed DLM
wind. Hurricanes Emily of 1987 and 1993 fell into this category, as did
Hurricane Josephine of 1984. Implications of the results for guiding
in-situ wind measurements to improve hurricane track forecasts are discussed.
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, 41-42 (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(8):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 Niño-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 Niño-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 Niño-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 Niño-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. 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.
Watson, A.I., K.M. Stellman, K.J. Gould, and P.P. Dodge. Local applications
of the WSR-88D hourly digital precipitation product at the National Weather
Service office in Tallahassee, Florida. Preprints, 29th International
Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16,
1999. American Meteorological Society, Boston, 232-235 (1999).
No abstract.
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.
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.
**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., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of
tropical cyclone intensity. Preprints, Symposium on Tropical Cyclone
Intensity Change, 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, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 290-292 (1998).
No abstract.
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 and Symposium
on the Research Foci of the U.S. Weather Research Program, 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):15,939-15,958
(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, 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, Phoenix, AZ, January 11-16, 1998.
American Meteorological Society, Boston, 161-168 (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, 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 Niña 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 Niña 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. Eldigio Press,
Palisades, New York, 278 pp. (1998).
No abstract.
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,
NOAA-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, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 141-145 (1998).
No abstract.
Cione, J.J., R.A. Neuherz, S. Raman, L.J. Pietrafesa, K. Keeter, and X.
Li. The use of pre-storm boundary-layer baroclinicity in determining and
operationally implementing the Atlantic Surface Cyclone Intensification
Index. Boundary-Layer Meteorology, 89(2):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.
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.
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, 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 (National Center
for Atmospheric Research, Boulder, CO), 40 pp. (1998).
No abstract.
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 research ships. Analytica
Chimica Acta, 377(2-3):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. Technical Report, Lamont-Doherty Earth Observatory,
LDEO-98-1, 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.
Friedman, H.A., and D.J. Garcia. Tropical cyclone public awareness
programmes: Preparing for the twenty-first century. Preprints, Seventh
Symposium on Education, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 166-168 (1998).
No abstract.
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, Phoenix, AZ, January 11-16, 1998. American
Meteorological Society, Boston, 169-171 (1998).
No abstract.
Godin, O.A., D. Yu. Mikhin, and D.R. Palmer. Ocean current monitoring in
the coastal zone. NOAA Technical Memorandum, NOAA-TM-ERL-AOML-93
(PB99-120255), 26 pp. (1998).
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.
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.
Gray, J. Commentary: Major ocean programs, National Oceanic and
Atmospheric Administration. Marine Technology Society Journal,
32(3):85-87 (1998).
Ocean researchers from academia and federal agencies were called together
by the National Academy of Sciences (NAS)/National Research Council (NRC)
to think about the large ocean research programs that exist today, their
history, lessons learned, and advice for future ocean research endeavors.
As a scientist and manager with the National Oceanic and Atmospheric
Administration (NOAA), I was asked to contribute my thoughts regarding
NOAA's role and benefits of such research programs as the World Ocean
Circulation Experiment (WOCE), Joint Global Ocean Flux Study (JGOFS),
GLOBal ocean ECosystem dynamics (GLOBEC), Ocean Drilling Program (ODP),
Tropical Ocean and Global Atmospheric/Tropical Atmosphere Ocean array
(TOGA/TAO), CLImate VARiability and predictability (CLIVAR), Ridge
Interdisciplinary Global Experiment (RIDGE), Earth Sciences History (ESH),
and ARCtic System Science (ARCSS). I encourage everyone to read the
NAS/NRF report.
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., 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, Phoenix,
AZ, January 11-16, 1998. American Meteorological Society, Boston,
241-244 (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., 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, Phoenix, AZ, January 11-16, 1998. American Meteorological
Society, Boston, 139-140 (1998).
No abstract.
Huang, H., R.E. Fergen, J.R. Proni, and J.J. Tsai. Initial dilution
equations for buoyancy-dominated jets in current. Journal of Hydraulic
Engineering, 124(1):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, 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.
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,
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.
Landsea, C.W., and R.A. Pielke. Trends in U.S. hurricane losses,
1925-1995. Preprints, Ninth Symposium on Global Change Studies,
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, 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, 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 Niño) to cold episode conditions (La
Niña) 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.
Lee, K., and W.M. Sackett. The high temperature titration of biogenic
silica. Deep-Sea Research, Part I, 45(6):1015-1028 (1998).
A new method has been developed for measuring biogenic silica (amorphous)
in marine sediments. It is based on the Hogbom-Urey reaction
CaCO3+SiO2 (biogenic silica)->CaSiO3
(wollastonite)+CO2. The reaction is carried out in evacuated
sealed glass tubes with added excess reagent grade calcite at 500°C
for 3 d. The product CO2 is measured in a calibrated manometer.
The dependence of the reaction on time, temperature, product
CO2 pressure, and other factors is examined.
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(6707):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 L.K. Shay. Landfalling tropical cyclones: Forecast
problems and associated research opportunities. Preprints, 16th
Conference on Weather Analysis and Forecasting and Symposium on
the Research Foci of the U.S. Weather Research Program, 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.
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., 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.
Millero, F.J., K. Lee, and M. Roche. Distribution of alkalinity in the
surface waters of the major oceans. Marine Chemistry,
60(1-2):111-130 (1998).
In recent years the total alkalinity (TA) of seawater has been measured
with high precision (~ ±2 µmol kg-1) in the Atlantic,
Pacific, and Indian oceans. In this paper, we have analyzed the surface
alkalinity of the major ocean basins using these measurements as well as
those obtained during the GEOSECS and TTO studies. The salinity normalized
alkalinity (NTA=TA x 35/S) in subtropical gyres between 30°S and
30°N is remarkably invariable except in upwelling areas (e.g.,
the eastern equatorial Pacific). The NTA increases toward high latitudes
(>40°) and is inversely proportional to sea surface temperature
(SST). This increase in NTA with latitude (or decreasing temperature) is
attributed to the upward transport of deep waters with higher NTA due to
the dissolution of CaCO3(s). The distribution of surface NTA in
the major ocean basins shows that the major basins can be divided into
regions where different trends of NTA are observed and boundaries between
the regions are similar to those of the major ocean currents. The linear
behavior of NTA (~ ±5 µmol kg-1) with respect to SST
makes it possible to provide regional maps of NTA. These maps can be used
to estimate TA in surface waters in large areas of the ocean from values
of SST and salinity (S). By combining the estimates of TA using SST and S
(from the Climatological Atlas of the World Ocean) with underway
fCO2 measurements (by ships, moorings, and satellites),
it is possible to map the detailed distribution of TCO2 for
surface waters over a large area of the ocean. Calculations of
TCO2 from measurements of fCO2, SST, and S in
the subtropical Pacific Ocean agree with the coulometrically measured
values to ±5 µmol kg-1.
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,
Part 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 µmol kg-1)
and fCO2 (11 µatm) 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 µmol 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 ± 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.
Millero, F.J., A.G. Dickson, G. Eischeid, C. Goyet, P. Guenther, K.M.
Johnson, R.M. Key, K. Lee, D. Purkerson, C.L. Sabine, R.G. Schottle,
D.R.W. Wallace, E. Lewis, and C.D. Winn. Assessment of the quality of the
shipboard measurements of total alkalinity on the WOCE hydrographic
program Indian Ocean CO2 survey cruises, 1994-1996. Marine
Chemistry, 63(1-2):9-20 (1998).
In 1995, we participated in a number of WOCE Hydrographic Program cruises
in the Indian Ocean as part of the Joint Global Ocean Flux Study (JGOFS)
CO2 survey sponsored by the Department of Energy (DOE). Two
titration systems were used throughout this study to determine the pH,
total alkalinity (TA), and total inorganic carbon dioxide
(TCO2) of the samples collected during these cruises. The
performance of these systems was monitored by making closed cell titration
measurements on Certified Reference Materials (CRMs). A total of 962
titrations were made on six batches of CRMs during the cruises. The
reproducibility calculated from these titrations was ±0.007 in pH,
±4.2 µmol kg-1 in TA, and ±4.1 µmol
kg-1 in TCO2. The at-sea measurements on the CRMs
were in reasonable agreement with laboratory measurements made on the same
batches. These results demonstrate that the CRMs can be used as a
reference standard for TA and to monitor the performance of titration
systems at sea. Measurements made on the various legs of the cruise agreed
to within 6 µmol kg-1 at the 15 crossover points. The
overall mean and standard deviation of the differences at all the
crossovers are 2.1 ± 2.1 µmol kg-1. These crossover
results are quite consistent with the overall reproducibility of the CRM
analyses for TA (±4 µmol kg-1) over the duration of
the entire survey. The TA results for the Indian Ocean cruises provide a
reliable data set that, when combined with TCO2 data, can
completely characterize the carbonate system.
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, 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.
Montgomery, M.T., and J.L. Franklin. An assessment of the balance
approximation in hurricanes. Journal of the Atmospheric Sciences,
55(12):2193-2200 (1998).
The validity of the traditional balance approximation for the asymmetric
flow above the boundary layer generally in hurricanes is examined here.
Scaling considerations of the divergence equation show that the validity
of the balance approximation hinges on the smallness of the nondimensional
product. The first term represents the ratio of asymmetric horizontal
divergence to asymmetric vertical vorticity for azimuthal wavenumber,
n, while the second term represents a Rossby number based upon the
azimuthal mean tangential wind and absolute vertical vorticity of the
hurricane vortex. Wind observations of Hurricane Gloria (1985) indicate
that this product is not at all small in the near-vortex region (several
hundred kilometers beyond the radius of maximum tangential winds) where
asymmetric convergence forced by surface friction and cumulus convection
is typically large. Although the Gloria observations represent only a
single case, there are dynamical reasons to expect this product to be 0(1)
just above the hurricane boundary layer in steadily translating
hurricanes. The meteorological relevance of these results to the problem
of balance dynamics in hurricanes is briefly discussed.
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 ±0.2°C and the
voltages were corrected for pressure differences between calibration and
sampling.
Nicholls, N., C.W. Landsea, and J. Gill. Recent trends in Australian
region tropical cyclone activity. Meteorology and Atmospheric
Physics, 65(3-4):197-205 (1998).
The number of tropical cyclones observed in the Australian region (south
of equator; 105-160°E) has apparently declined since the start of
reliable (satellite) observations in the 1969/1970 season. However, the
number of more intense cyclones (with minimum pressures dropping to 970
hPa or lower) has increased slightly. The numbers of weak (minimum pressures
not dropping below 990 hPa) and moderate systems (minimum pressures between
970 and 990 hPa) have declined. Possible reasons for these different
trends are discussed. The decline in the number of weaker cyclones may at
least partly reflect improved understanding of the nature of some weak
systems. The decline in the number of cyclones more intense than 990 hPa
primarily reflects the downward trend in the Southern Oscillation Index
(SOI). Previous work has demonstrated that the number of tropical cyclones
observed in the Australian region each cyclone season is related to the
value of the SOI prior to the start of the cyclone season. This relationship
is clearest with the number of moderate cyclones. The SOI is only weakly
related to the number of intense or weak cyclones. The increase in the number
of intense cyclones is not attributable to the trend in the SOI. Nor is there
clear reason, at present, to suspect that it is artificial (i.e.,
due to changes in observing or analysis techniques).
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, Phoenix, AZ, January 12-16,
1998. American Meteorological Society, Boston, 421-424 (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.
Ozgokmen, T.M., and O.E. Esenkov. Asymmetric fingers induced by the
nonlinear equation of state. Physics of Fluids, 10(8):1882-1890
(1998).
The impact of the nonlinearity in the equation of state associated
with the change in the thermal expansion coefficient with temperature on
the structure of fingers growing from an interface between two mixed
layers is investigated using a numerical model. It is shown that the
nonlinearity acts to enhance the buoyancy force acting on the descending
fingers with respect to that acting on the ascending fingers, resulting in
narrower and faster-growing descending fingers than ascending fingers. The
results are discussed with emphasis on the vertical variability of
properties along the fingers.
Ozgokmen, T.M., O.E. Esenkov, and D.B. Olson. A numerical study of layer
formation due to fingers in double-diffusive convection in a
vertically-bounded domain. Journal of Marine Research,
56(2):463-487 (1998).
The evolution of fingers in a double-diffusive system is investigated using
numerical integration of two-dimensional equations of motion for an
incompressible, Boussinesq fluid. The computational domain is periodic in
the horizontal direction and is closed with no-flux boundary conditions in
the vertical direction. The main result of this study is the evolution of
the system from initially linear profiles for both fast and slow diffusing
components to a layered state characterized by a finger zone sandwiched
between two mixed layers. The horizontal boundaries in this system play
an important role in the development of the layered state. At the top and
bottom boundaries, light and heavy finger fluxes accumulate leading to the
formation of mixed layers exhibiting larger-scale eddies. In the
quasi-equilibrium state, the finger zone is characterized by broken wiggly
fingers which do not extend across the entire interface. The salinity flux
at the mid-depth of the domain is approximately proportional to the 4/3
power of the salinity difference between the mixed layers, except for the
initial phase and for the run-down phase.
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., R. Key, and H.G. Ostlund. Temporal variations of bomb
radiocarbon in the Pacific Ocean. Marine Chemistry,
60(1-2):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(6711):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 µmol/kg/yr, as compared with
background DIC of ~2000 µmol/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 ±
4.5 µmol/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 and Symposium on the Research Foci of
the U.S. Weather Research Program, 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.
Rogers, S.M., and S.H. Houston. Hurricane surge and wave conditions:
Research needs. Proceedings, Third International Symposium,
Waves '97, Virginia Beach, VA, November 3-7, 1997. American Society
of Civil Engineers, 1414-1424 (1998).
For many years, coastal engineers have recognized the importance
of reliable wave height and frequency information in the design of major
coastal structures. Over time, research by government agencies, such as
the U.S. Army Corps of Engineers and NOAA, and private interests such as
the offshore oil industry has made a substantial investment in wave gages,
wave hindcasting, and wave forecasting. Design needs for breakwaters,
jetties, coastal protection, offshore oil facilities, and similar
large-scale projects have driven the acquisition of better wave data. Our
ability to optimize design wave conditions has improved significantly and
with ongoing research is likely to continue to improve in the future.
Most designers and researchers would expect wave data is most important
for large coastal projects. However, in the United States the most
frequent application of design wave conditions is for the design of single
family homes and other coastal buildings. Each day hundreds of coastal
buildings in communities around the U.S. begin construction in Coastal
High Hazard Areas (or V-zones) as identified by the National Flood
Insurance Program (NFIP) and the Federal Emergency Management Agency
(FEMA). The NFIP prepares flood hazard maps specifying minimum flood
elevation standards that include wave height predictions during a 100-year
storm surge, generally occurring during a hurricane or other severe
coastal storm. The NFIP uses several relatively simple models for
shoreline erosion, wave setup, wave runup and depth-limited linear waves.
Given the uncertainties inherent in any 100-year surge model, the simple
models are not unreasonable, including the use of depth limited, linear
waves. For many years we have been measuring water marks along the coast
following severe coastal storms with the goal of measuring the storm
surge, still water elevation, and/or wave height maximum. This paper will
report on case studies of U.S. hurricanes from U.S. hurricanes describing
the discrepancies between even the most reliable still water marks and the
lower limit of wave damage at the same locations. It is reassuring that
our ability to predict offshore wave conditions has improved. However, it
is clear that we have little understanding of the water-levels and wave
conditions during hurricanes where we need them the most; that is, flooded
building sites that are normally dry land. Some of the discrepancies can
be explained by measurement errors, wave setup, wave runup, and localized
setup in confined spaces and other factors, but no rational theory can
explain local variations. In short, we may have a good wave gage record
somewhere offshore and many post-storm water marks, but we have little
idea what water elevations and wave conditions occurred in flooded
building sites near the beach.Two problems result. First, small buildings
are usually designed to avoid waves by being elevated on piling
foundations. Without a reasonable understanding of the wave conditions,
buildings will be improperly elevated for cost-effective designs (i.e.,
either too high or too low). A second potentially more serious problem is
that the high water marks will eventually be used to calibrate the
underlying storm surge models on which all design conditions are based.
Our lack of understanding increases the risk of improperly calibrating the
storm surge models, which are also used to predict flood elevations much
further inland than those areas affected by waves. The authors believe
that there is a substantial need for wave and water-level measurements
near coastal building sites which are flooded during hurricanes and other
design-level storms. The frequent application of wave predictions is to
design cost-effective, storm-resistant buildings. The deployment of
multiple, self contained wave gages at preselected sites near coastal
buildings that are expected to be flooded during a landfalling hurricane
is now a practical research goal with recent improvements in
instrumentation. It is time to stop guessing the wave and water-level
conditions and produce some real measurements.
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 Niño) 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, Phoenix, AZ, January 11-16,
1998. American Meteorological Society, Boston, 131-138 (1998).
No abstract.
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.
Thomas, G.G., R. Benway, S.K. 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.
Valdimarsson, H., S.-A. Malmberg, and M.H. Bushnell. SVP drifters in
Icelandic waters, 1995-1997: Preliminary results. Technical Session, 13th
Data Buoy Cooperation Panel Meeting, La Reunion, October 1997. DBCP
Technical Publication 12, 91-101 (1998).
No abstract.
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 µatm 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.
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.
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.
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. 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.
Barnston, A.G., M. Chelliah, and S.B. Goldenberg. Documentation of a
highly ENSO-related SST region in the equatorial Pacific.
Atmosphere-Ocean, 35(3):367-383 (1997).
A new ENSO SST index is documented that is strongly correlated to the core
ENSO phenomenon. The SST anomaly in much of the east-central and eastern
tropical Pacific is closely related to ENSO. However, the anomaly from
approximately the centre of the eastern half of the equatorial Pacific
westward to near the date line is suggested to be most strongly
ENSO-related when data spanning the most recent several decades are used.
This is the case both with respect to the (1) strength of association with
other oceanic/atmospheric ENSO-related anomalies (both simultaneously and
as a time-delayed predictand), and (2) impact on remote worldwide climate
anomalies. This observational insight was lacking in the early 198Os when
the four "Niño" regions were developed. While a firmer dynamical
foundation for this regional preference still needs to be established, the
region straddling Niño 3 and Niño 4 may be regarded as an appropriate
general SST index of the ENSO state by researchers, diagnosticians, and
forecasters. A dataset of this index, called "Niño 3.4"
(5°N-5°S, 120-170°W) is maintained on the Internet, shown in
the Climate Diagnostics Bulletin, and provided in the Appendix of
this note.
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).
No abstract.
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 (1997).
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, 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).
Bushnell, M.H., and W.S. Krug. Global Drifter Center support for the
International Buoy Program in the Indian Ocean. Final Report, Second
WMO/DBCP International Indian Ocean Buoy Program Meeting, Perth,
Australia, July 1997. Australian Bureau of Meteorology, Annex V,
15-20 (1997).
No abstract.
Cantillo, A.Y., and G.A. Berberian. MESA New York Bight Project water
column chemistry data cruises No. 6-12 of the NOAA Ship Ferrel,
April-November 1997. NOAA Technical Memorandum, ERL-AOML-92
(PB98-140759), 74 pp. (1997).
During the period April-November 1974, seven oceanographic cruises,
denoted WCC 6-12, were conducted by the NOAA Ship Ferrel to obtain samples
of sea water and suspended particulates from the New York Bight Apex for
chemical analyses. This report presents the chemical data obtained from
these samples.
Carsey, T.P., D.D. Churchill, M.L. Farmer, C.J. Fischer, A.A.P. 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(3-4):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).
No abstract.
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.
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, Part 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 Niño
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
Niño period was about 25% higher than the severe El Niño 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), 88 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.
Franklin, J.L., H.L. Cole, T.F. Hock, D.K. Lauritsen, K.D. Norris,
and E.F. Chamberlain. GPS dropwindsondes and the NOAA G-IV jet aircraft:
New opportunities for forecasting and research. Preprints, 22nd
Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO,
May 19-23, 1997. American Meteorological Society, Boston, 135-136 (1997).
No abstract.
Gallagher, M.S., D.B. King, P.-Y. Whung, and E.S. Saltzman. Performance
of the HPLC/fluorescence SO2 detector during the GASIE instrument
intercomparison experiment. Journal of Geophysical Research,
102(D13):16,247-16,254 (1997).
Sulfur dioxide (SO2) in synthetic air and diluted ambient air
was measured as part of the Gas-Phase Sulfur Intercomparison Experiment
(GASIE) using the high performance liquid chromatography
(HPLC)/fluorescence technique. SO2 was analyzed by
equilibrating the gaseous sample with aqueous SO2, sulfite, and
bisulfite, then converting the aqueous S(IV) to an isoindole derivative.
The derivative was separated by reversed phase HPLC and detected via
fluorescence. The system was calibrated with mixtures of SO2 in
zero air prepared from an SO2 permeation device through a
two-stage dilution system. The instrument has a 4-minute sample
integration time and a measurement period of 9 minutes. During the GASIE
intercomparison, the lower limit of detection averaged 3.6 parts per
trillion by volume (pptv). The precision of replicate measurements over
the entire intercomparison period was better than 5% at the 20 pptv level.
Instrument performance was unaffected by the interferent gases included in
the GASIE protocol (H2O, O3, NOx, DMS,
CO, CO2, and CH4). During diluted ambient air tests,
the HPLC/fluorescence technique exhibited an approximately 10% reduction
in response relative to some other techniques. The cause of this apparent
calibration change is not understood.
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).
No abstract.
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 REEs 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).
No abstract.
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., C. Wiebinga, and P.B. Ortner. CTD hydrographic data
from the Global Ocean Ecosystem Dynamics (GLOBEC) Indian Ocean cruises.
University of Miami Technical Report, RSMAS-97-006, 69 pp. (1997).
No abstract.
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(1-4):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 B, 49(2):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), 66 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.
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.
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).
No abstract.
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 A, 49(5):622-623 (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.
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.
Martin, D., M. Tsivou, B. Bonsang, C. Abonnel, T.P. Carsey, M.
Springer-Young, and A.A.P. 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(D5):6003-6015 (1997).
Gas phase hydrogen peroxide (H2O2) was measured in
surface air on the NOAA ship Malcolm Baldrige from June 8-27, 1992
(Julian days 160-179), during the Atlantic Stratocumulus Transition
Experiment/Marine Aerosol and Gas Exchange experiment in the eastern
subtropical North Atlantic region. Average H2O2
mixing ratios observed were 0.63 ± 0.28 ppbv, ranging between detection
limit and 1.5 ppbv. For the entire experiment, only weak or no
correlation was found between H2O2 mixing ratio and
meteorological parameters (pressure, temperature, humidity, or UV
radiation flux), as well as with tracers of continental air masses (CO,
black carbon, radon). The average daily H2O2 cycle
for the entire period exhibits a maximum of 0.8 ± 0.3 ppbv near sunset and
a minimum of 0.4 ± 0.2 ppbv 4-5 hours after sunrise. Several clear
H2O2 diurnal variations have been observed, from
which a first-order removal rate of about 1 x 10-5
s-1 for H2O2 can be inferred from
nighttime measurements. This rate compares well with those deduced from
measurements taken at Cape Grim (Tasmania, 41°S) and during the
Soviet-American Gas and Aerosol III experiment (equatorial Pacific Ocean).
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), 80 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 ± 1.2 µmol
kg-1 (N = 115). The potentiometric measurements on CRM gave a
reproducibility of ± 2.7 µmol kg-1 in TCO2, ±
3.2 µmol kg-1 in TA, and ± 0.007 in pH (N = 177). The
surface measurements of pH and normalized TA were quite uniform
throughout the year (pH = 8.084 ± 0.016, NTA = 2288 ± 5 µmol
kg-1); normalized TCO2 was more variable
(NTCO2 = 1949 ± 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).
No abstract.
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.
Saltzman, E.S., P.-Y. Whung, and P.A. Mayewski. Methanesulfonate in the
Greenland Ice Sheet Project 2 ice core. Journal of Geophysical
Research, 102(C12):26,649-26,657 (1997).
In this paper we present measurements of methanesulfonate in the Greenland
Ice Sheet Project 2 (GISP2) ice core. Methanesulfonate is an atmosphere
oxidation product of dimethylsulfide. The GISP2 methanesulfonate record
contains information about the atmosphere loading of biogenic sulfur over
the past 110 kyr and its relationship to climate change. The GISP2 data set
supports the inferences made from the Renland ice core from Greenland that
the glacial atmosphere over Greenland had reduced concentrations of
biogenic sulfur compared with the present day (Hansson and Saltzman, 1993).
We conclude that the flux of biogenic sulfur from the North Atlantic Ocean
must have been lower during glacial times and speculate that this decrease
may have been related to differences in phytoplankton speciation. The data
suggest that changes in direct radiative forcing from biogenic sulfur
aerosols would act as negative feedback to the glacial/interglacial climate
cycles in this region.
Shapiro, L.J., and J.L. Franklin. Potential vorticity and hurricane motion.
Preprints, 22nd Conference on Hurricanes and Tropical Meteorology,
Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston,
156-157 (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.
Stecher, H.A., G.W. Luther, D.L. MacTaggart, S.O. Farwell, D.R. Crosley, W.D.
Dorko, P.D. Goldan, N. Beltz, U. Krischke, W.T. Luke, D.C. Thornton, R.W.
Talbot, B.L. Lefer, E.M. Scheuer, R.L. Benner, J. Wu, E.S. Saltzman, M.S.
Gallagher, and R.J. Ferek. Results of the Gas-Phase Intercomparison
Experiment (GASIE): Overview of experimental setup, results and general
conclusions. Journal of Geophysical Research, 102(D13):16,219-16,236
(1997).
Seven techniques for the field measurement of trace atmospheric
SO2 were compared simultaneously over one month in 1994 using
samples produced in situ by dynamic dilution. Samples included
SO2 in dry air, in humid air, and in air with potentially
interfering gases added. In addition, two days of comparison using diluted
ambient air were conducted. Six of the seven techniques compared well, with
good linear response and no serious interferences but with a range of
calibration differences of about 50%.
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(9):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(1):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., 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 Niño-Southern Oscillation. Geophysical Research Letters,
24:779-782 (1997).
A data-based hypothesis is presented on the mechanism of the El
Niño-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 Niño-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 Niña
conditions in 1988 through the peak El Niño 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 Niña 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 Niño. 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, Part I,
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 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.
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.
**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 o
f 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.
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. Hurricanes. The MacMillan Encyclopedia of Earth
Science, Vol. 1, 467-471 (1996).
No abstract.
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., 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.
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(1):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 (PB97-135446), 83 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.
DeMaria, M. A history of hurricane forecasting for the Atlantic basin,
1920-1995. In Historical Essays on Meteorology, 1919-1995, J.R.
Fleming (ed.). American Meteorological Society, Boston, 263-305 (1996).
The history of hurricane forecasting for the Atlantic basin from 1920-1995
is reviewed. The focus is on the forecast problem of estimating storm
tracks and intensities, although other aspects of the hurricane warning
process are mentioned when appropriate. Technological advances including
in the implementation of the upper-air network in the late 1930s, the
establishment of routine aircraft reconnaissance in the 1940s, the advent
of numerical weather prediction beginning in the 1950s, and the availability
of satellite observations starting in the 1960s, and their impact on
hurricane forecasting are reviewed. Organizational changes in the hurricane
forecast offices and the interaction between the research and forecast
communities are also described. Specific forecast cases are presented to
illustrate the improvements and limitations of hurricane forecasting. The
outlook for the future is also discussed.
DeMaria, M. The effect of vertical shear on tropical cyclone intensity
change. Journal of the Atmospheric Sciences, 53(14):2076-2087
(1996).
The effect of vertical shear on tropical cyclone intensity change is
usually explained in terms of "ventilation" where heat and moisture at
upper levels are advected away from the low-level circulation, which
inhibits development. A simple two-level diagnostic balance model is used
to provide an alternate explanation of the effect of shear. When the
upper layer wind in the vortex environment differs from that in the lower
layer, the potential vorticity (PV) associated with the vortex circulation
becomes tilted in the vertical. The balanced mass field associated with
the tilted PV pattern requires an increased midlevel temperature
perturbation near the vortex center. It is hypothesized that this
midlevel warming reduces the convective activity and inhibits the storm
development. Previous studies have shown that diabatic heating near the
storm center acts to reduce the vertical tilt of vortex circulation.
These studies have also shown that there is an adiabatic process which
acts to reduce the vertical tilt of a vortex. The effectiveness of the
adiabatic process depends on the Rossby penetration depth, which increases
with latitude, horizontal scale, and vortex amplitude. Large-scale
analyses from the 1989-1994 Atlantic hurricane seasons are used to show
that high-latitude, large, and intense tropical cyclones tend to be less
sensitive to the effect of vertical shear than low-latitude, small, and
weak storms.
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.
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,
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.
Enfield, D.B., and D.A. Mayer. Relationships of western hemisphere rainfall
to tropical Atlantic and Pacific SST variability. Preprint Volume, 8th
Conference on Air-Sea Interaction and Symposium on the Global
Ocean-Atmosphere-Land System (GOALS), Atlanta, GA, January 28-February
2, 1996. American Meteorological Society, Boston, 390-394 (1996).
No abstract.
Ffield, A., and A.L. Gordon. Tidal mixing signatures in the Indonesian
Seas. Journal of Physical Oceanography, 26(9):1924-1937 (1996).
Expressions of low-frequency tidal periods are found throughout the
Indonesian Seas' temperature field, supporting the hypothesis that vertical
mixing is enhanced within the Indonesian Seas by the tides. The thermal
signatures of tidal mixing vary mostly at the fortnightly and monthly tidal
periods due to nonlinear dynamics redistributing tidal energy into these
periods. Away from the coasts, the largest tidal mixing signatures are
observed in sea surface temperature within the Scram and Banda Seas. Most
of the Indonesian Throughflow passes through the Banda Sea where strong
vertical mixing modifies the thermocline by transferring surface heat and
freshwater to deeper layers before the upper water column is exported to the
Indian Ocean. Modulation of vertical eddy fluxes within the Indonesian Seas
by fortnightly and monthly tides may act to regulate ocean-atmosphere fluxes.
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.
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, 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. Are we seeing the beginning of a long-term upturn in
Atlantic basin major activity? Catastrophe Reinsurance: Predictions
and Protections, New York City, NY, November 7-8, 1996. American
Conference Institute, section 3, 33 pp. (1996).
No abstract.
Goldenberg, S.B. Where we are at in forecasting seasonal Atlantic basin
tropical cyclone activity. Final Report, Expert Meeting on Public Weather
Services and Hurricane Disaster Preparedness, Port-of-Spain, Trinidad
and Tobago, December 11-15, 1995. South African Weather Bureau, 5 pp.
(1996).
Most of the tropical cyclones in the North Atlantic basin (including the
North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico) form from easterly
(African) wave disturbances. Although the number of easterly waves in the
tropical Atlantic tends to be fairly steady from year to year, the fraction
of these that develop into tropical cyclones exhibits substantial interannual
variability. Not only the number, but also the strength and location of the
Atlantic basin tropical cyclones vary greatly from year to year. The Atlantic
basin, unlike the east and west Pacific basins, in the mean, is not
particularly favorable for tropical cyclone development. Year-to-year changes
in the large-scale environment have a substantial influence on the overall
activity of each Atlantic hurricane season. The search for conditions that
result in the development or nondevelopment of the waves into tropical
cyclones has been the subject of numerous studies, some of which have
attempted to relate the variability to fluctuations in the tropical and
global climate. Some of the climatic indicators that have been associated
with fluctuations in Atlantic basin hurricane activity include sea-surface
temperature (SST) anomalies for the equatorial central and eastern Pacific
(i.e., El Niño activity), SSTs for the tropical Atlantic, rainfall variations
over west Africa, the stratospheric Quasi-Biennial Oscillation (QBO), and
vertical wind shear over the tropical Atlantic. Various studies have examined
some of these indicators in an attempt to establish the actual physical
mechanisms responsible for the associations with tropical cyclone activity.
Other work has used selected parameters to predict Atlantic basin activity as
much as 6-11 months in advance. Information will be presented describing the
various parameters and their possible physical association with Atlantic
hurricane activity. Current methodology used by other investigators to make
seasonal predictions of activity and a discussion of their past performance
will be presented with a special emphasis on implications for the Caribbean.
The extended-range forecast for the 1996 Atlantic seasonal hurricane activity
and Wverifications for the 1995 seasonal forecast will be discussed. The
strengths and weaknesses of the current state of seasonal forecasting will be
presented. The implications of fluctuations in hurricane activity on the
multi-decadal scale will also be discussed.
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.
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, 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.
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, Part 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.
Harris, J.E., D.B. Enfield, and N. Bravo. Altimetric assessment of the NMC
ocean model. AVISO Newsletter, 4:18-20 (1996).
No abstract.
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), 69 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), 35 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., 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).
No abstract.
Huang, H., R.E. Fergen, J.R. Proni, and J.J. Tsai. Probabilistic
analysis of ocean outfall mixing zones. Journal of Environmental
Engineering, 122(5):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.
Huebert, B.J., A.A.P. Pszenny, and B. Blomquist. The ASTEX/MAGE Experiment.
Journal of Geophysical Research, 101(D2):4319-4329 (1996).
The Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas
Exchange (ASTEX/MAGE) was a multinational experiment designed to study the
relationship between marine chemistry, aerosols, clouds, and air/sea
exchange. Several aircraft, ships, and island sites supported measurements
of marine boundary layer chemistry in both pristine and polluted North
Atlantic air masses in the vicinity of the Azores in June of 1992. The
International Global Atmospheric Chemistry (IGAC) Program's MAGE activity
organized the chemical experiments in ASTEX because such experiments are
beyond the capabilities of any one platform, discipline, or nation working
alone. One highlight of ASTEX/MAGE was the development of a Lagrangian
experimental strategy. It offered a unique way of constraining fluxes and
reaction rates by observing the effect those processes have on a tagged
parcel of air.
Jensen, T.L., S.M. Kreidenweis, Y. Kim, H. Sievering, and A.A.P.
Pszenny. Aerosol distributions in the North Atlantic marine boundary layer
during Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas
Exchange (ASTEX/MAGE). Journal of Geophysical Research,
101(D2):4455-4467 (1996).
Marine boundary layer aerosol size distributions observed during June 1992
are described. Measurements were made from on board the National Oceanic
and Atmospheric Administration ship Malcolm Baldrige in support of
the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas
Exchange field experiment in the area surrounding 32°N latitude and
25°W longitude. Measurements obtained from three instruments, the
differential mobility particle sizer, the active scattering aerosol
spectrometer probe, and the forward scattering spectrometer probe, were
used to investigate the contributions of the different aerosol modes to
total number, surface area, and volume concentrations. It was observed
that aerosol populations in air masses that appear to have originated from
remote marine areas have a bimodal number distribution with total number
concentrations ranging from 200 to 800 particles cm-3. In air
masses that have been affected by anthropogenic emissions, the aerosol
size distributions become monomodal and total number concentrations
increase to 500 to 1800 cm-3. The data also suggest that air
mass boundaries can be very sharp and that there may be some mesoscale
variability in the aerosol population within an air mass.
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(13):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.
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.
Mayewski, P.A., M.S. Twickler, S.I. Whitlow, L.D. Meeker, Q. Yang, J.
Thomas, K. Kreutz, P.M. Grootes, D.L. Morse, E.J. Steig, E.D. Waddington,
E.S. Saltzman, P.-Y. Whung, and K.C. Taylor. Climate change during last
deglaciation in Antarctica. Science, 272(5268):1636-1638 (1996).
Greenland ice core records provide clear evidence of rapid changes in
climate in a variety of climate indicators. In this work, rapid climate
change events in the Northern and Southern hemispheres are compared on the
basis of an examination of changes in atmospheric circulation developed
from two ice cores. High-resolution glaciochemical series, covering the
period 10,000 to 16,000 years ago, from a central Greenland ice core and a
new site in east Antarctica display similar variability. These findings
suggest that rapid climate change events occur more frequently in
Antarctica than previously demonstrated.
McCartney, M.S., R.G. Curry, and H.F. Bezdek. North Atlantic's
transformation pipeline chills and redistributes subtropical water.
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 ± 2.7 µmol kg-1 in TA, ± 2.9 µmol
kg-1 in TCO2 and ± 0.005 in pH. The TA measurements made on
CRM at sea (2131 ± 3 µmol kg-1) were in good agreement
with the laboratory measurements (2130 ± 1.4 µmol kg-1).
The normalized values of TA (NTA = 2375 ± 5 µmol kg-1)
and normalized TCO2 (NTCO2 = 2230 ± 10 µmol
kg-1) were quite uniform for the surface waters. The deep
waters had similar carbonate properties (pH = 7.60 ± 0.02, TA = 2355 ± 10
µmol kg-1, TCO2 = 2240 ± 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. 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 I: Global Environmental Change,
Vol. 36, 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. Acoustic rainfall analysis: Rainfall drop size distribution
using the underwater sound field. Journal of Atmospheric and Oceanic
Technology, 13(1):74-84 (1996).
Rainfall estimation is difficult, especially in oceanic regions where
land-based techniques are unavailable. Fortunately, rain produces a loud
and unique sound underwater that can be used to detect and quantify
rainfall. Laboratory studies of the sound generated by individual
raindrops have provided the basis for a formal inversion of the naturally
generated underwater ambient sound field. Field measurements of
subtropical rainfall at the Atlantic Oceanographic and Meteorological Lab
Rain Gauge Facility are used to demonstrate the forward (predicting the
sound field given the rainfall drop size distribution) and the inverse
problem (estimating the drop size distribution given the sound field).
This acoustical rainfall analysis (ARA) algorithm was tested for several
dozen rainfall events spanning six months and was found to provide
excellent estimates of rainfall rate, rainfall accumulation, and rainfall
reflectivity (the quantity sensed by radars). High temporal resolution
(order 510 s) variations in drop size distribution within the rain can be
studied using ARA.
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.
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.
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).
No abstract.
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 Oceanic Technology,
13(4):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.
Shapiro, L.J. The motion of Hurricane Gloria: A potential vorticity
diagnosis. Monthly Weather Review, 124(11):2497-2508 (1996).
Multilevel, multinested analyses of Hurricane Gloria of 1985 are the most
comprehensive kinematic data set yet developed for a single hurricane. A
piecewise inversion technique is used with these analyses and the nonlinear
balance equation to deduce the three-dimensional distribution of potential
vorticity (PV) that contributed to the deep-layer mean (DLM) flow that
steered Hurricane Gloria toward the northwest. The background state is taken
to be the azimuthally averaged winds in balance with a geopotential
distribution on an f plane. Advantage is taken of the near-linearity
of the weak asymmetries near the hurricane's core and of PV in the
environment. Thus, ad hoc aspects of the linearization required by other
investigators are effectively eliminated. Removal of the hurricane vortex
and the use of a climatological mean background state are avoided as well.
The insensitivity of the results to the imposed lateral boundary condition is
also demonstrated. Wind anomalies attributable to pieces of anomalous PV
restricted to cylinders of different radii centered on the hurricane are
evaluated. The DLM wind that steered Gloria to the northwest is primarily
attributable to PV anomalies confined within a cylinder of radius 1000 km
and levels 500 mb and above, including positive anomalies associated with
a cold low over Cuba. The vector difference between the hurricane's
observed motion and the DLM wind at Gloria's center attributable to these
PV anomalies is 1.0 m s-1, explaining more than five-sixths of
the hurricane's 6.2 m s-1 motion. Implications for measurements
required to establish short-term changes of the environmental steering flow
are considered. Difficulties in the interpretation of results are discussed
for PV anomalies that are confined to noncircular regions; the implication
for other studies is considered as well.
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, and T.P. Carsey. Carbon monoxide
gradients in the marine boundary layer of the North Atlantic Ocean.
Journal of Geophysical Research, 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.
Swenson, M.S., and P.P. Niiler. Statistical analysis of the surface
circulation of the California Current. Journal of Geophysical
Research, 101(C10):22,631-22,645 (1996).
We use a set of mixed-layer drifting buoy trajectories from the California
Current (20°N-40°N) during 1985-1990 to obtain statistically
reliable estimates of the mean currents, the mean variance field, and the
geographically varying diffusivity, integral timescales, and integral
space scales. Typical values for the diffusivity are 1.1-8.7 ×
107 cm2 s-1, while the timescales and
space scales are 2.1-7.1 days and 16-59 km, respectively. The variance
field displays a strong westward gradient out to 125°W, and
diffusivity shows a tendency to decrease toward the southwest part of the
domain. Significant anisotropy is found in the variance field near the
coastal boundary and at 30°N, 130°W, which is the region where
the subarctic and northern subtropical fronts approach the California
Current. The antisymmetric component of the diffusivity tensor indicates
that cyclonic eddies dominate the mesoscale signature of drifters in this
region. We seek simple parameterizations to relate the scales of motion
of the random velocity field to the diffusivity by testing least-square
fits. We found no cases for which these two hypotheses could be
distinguished. For the meridional component the linear regressions are
not successful, which suggests that the meridional departure velocities
result from a flow regime that is significantly organized by, for example,
waves or coherent structures. A subset of the drifters measured
temperature along their tracks, and we use the resultant data to produce
the first direct estimates of the horizontal eddy heat flux divergence
based on Lagrangian estimates. In addition, we separately compute the
"eddy diffusivity" parameterization of the eddy heat flux divergence using
our diffusivity estimates and a sea surface temperature climatology. The
two independent terms agree well, which provides a measure of reassurance
about the difusivity estimates. The eddy heat flux divergence in the
California Current is very small (<5 W m-2) and does not appear
to be significant in the long-term heat budget of the upper ocean in this
region.
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 A, 48:584-592 (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., 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.
Willoughby, H.E., and P.G. Black. Hurricane Andrew in Florida: Dynamics
of a disaster. Bulletin of the American Meteorological Society,
77(3):543-652 (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.
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(D3):6911-6918 (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, D.J. Cooper, T.S. Bates, and A.M.
Thompson. 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(D3):6899-6910 (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(D1):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.
**1995**
Abbott, M.R., K.H. Brink, C.R. Booth, D. Blasco, M.S. Swenwon, C.O. Davis,
and L.A. Codispoti. Scales of variability of bio-optical properties as
observed from near-surface drifters. Journal of Geophysical
Research, 100(C7):13,345-13,367 (1995).
A drifter equipped with bio-optical sensors and an automated water sampler
was deployed in the California Current as part of the coastal transition
zone program to study the biological, chemical, and physical dynamics of
the meandering filaments. During deployments in 1987 and 1988, measurements
were made of fluorescence, downwelling irradiance, upwelling radiance, and
beam attenuation using several bio-optical sensors. Samples were collected
by an automated sampler for later analysis of nutrients and phytoplankton
species composition which, in turn, were associated with the meandering
circulation. Variance spectra of the bio-optical parameters revealed
fluctuations on both diel and semidiurnal scales, perhaps associated with
solar variations and internal tides, respectively. Offshore, inertial-scale
fluctuations were apparent in the variance spectra of temperature,
fluorescence, and beam attenuation. Although calibration samples can help
remove some of these variations, these results suggest that the use of
bio-optical data from unattended platforms such as moorings and drifters
must be analyzed carefully. Characterization of the scales of phytoplankton
variability must account for the scales of variability in the algorithms
used to convert bio-optical measurements into biological quantities.
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).
No abstract.
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.
Bakker, C. Development of object-oriented software for real-time
presentations and quality control of wind data in hurricanes.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
86-88 (1995).
No abstract.
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).
No abstract.
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., 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., 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.
Burpee, R.W., J.L. Franklin, S.J. Lord, and R.E. Tuleya. The performance of
hurricane track guidance models with and without Omega dropwindsondes.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
6-8 (1995).
No abstract.
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.
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.
Churchill, D.D., S.H. Houston, and N.A. Bond. The Daytona Beach wave of
3-4 July 1992: A shallow-water gravity wave forced by a propagating squall
line. Bulletin of the American Meteorological Society,
76(1):21-32 (1995).
An unexpected runup of the ocean along Daytona Beach, Florida, on 3-4 July
1992 was associated with at least one large ocean wave. The wave, which
reached a height of about 3 m above normal tide, injured 75 people and
damaged property along Daytona Beach. Analyses of meteorological and
oceanographic observations are consistent with the hypothesis that a squall
line generated a long water wave. The critical evidence is that the
propagation speed of the squall line matched the shallow-water wave speed
that prevailed along the direction of motion of the squall line. The squall
line exerted force on the ocean for at least 3 h. The issues of recurrence
and public safety are discussed.
Cione, J.J., and S. Raman. A numerical investigation of surface-induced
mesocyclogenesis near the Gulf Stream. Tellus A, 47:815-833 (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.
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). National Oceanographic Data Center, Washington, D.C.,
CD-ROM, NODC-59 (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.
DeMaria, M. Another look at the effect of vertical shear on tropical
cyclone intensity change. Preprints, 21st Conference on Hurricanes and
Tropical Meteorology, Miami, FL, April 24-28, 1995. American
Meteorological Society, Boston, 323-325 (1995).
No abstract.
DeMaria, M. Evaluation of hydrostatic height-coordinate formulation of
the primitive equations for atmospheric modeling. Monthly Weather
Review, 123(12):3576-3589 (1995).
The hydrostatic form of the primitive equations described by Ooyama is
evaluated by comparing nonhydrostatic and hydrostatic integrations of a
dry axisymmetric model with a specified entropy (heat) source. In this
formulation, pressure is a diagnostic variable, so that the hydrostatic
approximation can be included simply by replacing the vertical momentum
equation with a diagnostic vertical velocity equation. This diagnostic
equation is a one-dimensional (height) second-order elliptic equation that
can be solved using a direct method. Results show that hydrostatic
solutions are very sensitive to the accuracy of the method used to solve
the diagnostic vertical velocity equation. However, this sensitivity can
be eliminated by adding an extra term to the diagnostic equation that
ensures that the solution does not drift away from hydrostatic balance due
to numerical approximation. When the extra term is added, this formulation
of the primitive equations allows for the design of a numerical model in
height coordinates that can be used in hydrostatic and nonhydrostatic
regimes.
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, 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).
No abstract.
Enfield, D.B., and J.E.Harris. A comparative study of tropical Pacific sea
surface height variability: Tide gauges vs. the National Meteorological
Center data-assimilating ocean general circulation model, 1982-1992.
Journal of Geophysical Research, 100(C5):8661-8676 (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.D. 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, Part 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).
No abstract.
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.
Franklin, J.L. Searching for beta gyres in Omega dropwindsonde data sets.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
55-57 (1995).
No abstract.
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).
No abstract.
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.R., 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(1-4):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).
No abstract.
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.
Harvey, G.R. Petroleum hydrocarbon oxidation products in the marine
atmosphere. Marine Pollution Bulletin, 30(6):425-426 (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),
18 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),
68 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.
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).
No abstract.
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).
No abstract.
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.
Katz, E.J., A. Busalacchi, M.H. Bushnell, F. Gonzalez, L. Gourdeau, M.
McPhaden, and J. Picaut. A comparison of coincidental time series of the
ocean surface height by satellite altimeter, mooring, and inverted echo
sounder. Journal of Geophysical Research, 100(C12):25,101-25,108
(1995).
Altimetric measurements of sea surface height at two locations in the
western tropical Pacific Ocean are compared to estimates of the dynamic
sea surface height computed from cotemporal surface-to-bottom
temperature/salinity measurements on moorings and acoustic travel time
measured by bottom-moored inverted echo sounders. The results show
statistically high correlation between the in-situ measurements at periods
greater than five days and between the altimeter and in-situ measurements
at periods greater than 20 days. The rms difference between any two modes
of observation is consistently between 2-3 cm.
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(1324):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.
Kim, Y., H. Sievering, J. Boatman, D. Wellman, and A.A.P. Pszenny. Aerosol
size distribution and aerosol water content measurements during Atlantic
Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange.
Journal of Geophysical Research, 100(D11):23,027-23,038 (1995).
Aerosol size distribution data measured during the June 1992 Marine
Aerosol and Gas Exchange experiment are analyzed to investigate the
characteristics of fine marine aerosol particles measured over the North
Atlantic near the Azores Islands. Measured aerosol size distribution data
were corrected using the corrected size calibration data based on the
optical properties of particles being measured. The corrected size
distribution data were then approximated with either one or two lognormal
size distributions, depending on air mass conditions. Under clean air mass
conditions <3 µm diameter aerosol size distributions typically
exhibited two modes, consisting of an accumulation mode and the small end
of the sea-salt particle mode. However, under the influence of continental
polluted air masses, the aerosol size distribution was dominated by <1
µm diameter particles in a single mode with an increased aerosol
concentration. Aerosol water content of accumulation mode marine aerosols
was estimated from differences between several series of ambient and dried
aerosol size distributions. The average aerosol water fraction was 0.31,
which is in good agreement with an empirical aerosol growth model
estimate. The average rate of SO4= production in the
accumulation mode aerosol water by H2O2 oxidation
was estimated to be <7 × 10-10 mol L-1
s-1, which is an insignificant contributor to the observed
non-sea-salt SO4= in the accumulation mode.
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 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),
134 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. 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.
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).
No abstract.
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.
Montgomery, M.T., and L.J. Shapiro. Generalized Charney-Stern and Fjortof
theorems for rapidly rotating vortices. Journal of the Atmospheric
Sciences, 52(10):1829-1833 (1995).
A generalized Charney-Stern theorem for rapidly rotating (large Rossby
number) baroclinic vortices, such as hurricanes, is derived based on the
asymmetric balance (AB) approximation. In the absence of dissipative
processes, a symmetrically stable baroclinic vortex is shown to be
exponentially stable to nonaxisymmetric perturbations if a generalized
potential vorticity gradient on theta surfaces remains single signed
throughout the vortex. The generalized potential vorticity gradient
involves the sum of an interior potential vorticity gradient associated
with the symmetric vortex and surface contributions associated with the
vertical shear of the tangential wind. The AB stability formulation is
then shown to yield Fjortof's theorem as a corollary. In the modern view
of shear instabilities the theorems admit simple interpretation. The
Charney-Sterm theorem represents a necessary condition for the existence
of counterpropagating Rossby waves associated with the radial potential
vorticity gradient, while Fjortof's theorem represents a necessary condition
for these waves to phase lock and grow in strength. Potential application
of these results as well as limitations of the slow-manifold approach are
briefly discussed.
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 TRISTARdrifters. Deep-Sea Research, Part 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).
No abstract.
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.
Pasteur, E.C., R. Mulvaney, D.A. Peel, E.S. Saltzman, and P.-Y. Whung. A
340 year record of biogenic sulphur from the Weddell Sea area, Antarctica.
Annals of Glaciology, 21:169-174 (1995).
Detailed records of methanesulphonic acid (MSA) and non-sea-salt sulphate
(nss SO42-) have been obtained from ice cores
drilled on Dolleman Island on the east coast of the Antarctic Peninsula
(70°35.2'S, 60°55.5'W). Annual average concentrations of MSA are
presented for the period 1652-1992. Over this time span, the mean annual
concentration of MSA is 0.69 µ = l-1 (sigma = 0.33, n =
340), the range is 0.13-2.35 µ = l-1, and the
MSA/nss-SO42- ratio is 0.22. The high MSA
concentration reflects the proximity of the Weddell Sea, believed to be a
region of high marine phytoplankton production. The overall mean
nss-SO42- concentration is about 66% of the total
sulphate deposited in the snowfall. Low-frequency variations of MSA and
oxygen-isotope signals correlate closely, indicating that they may be
modulated by similar atmospheric processes. Positive correlations are
observed between the oxygen-isotope signature and both MSA (r = 0.41) and
nss-SO42- (r = 0.50), significant at the 99% level.
A small negative correlation can be seen between both species and the
annual duration of sea ice at Scotia Bay, Laurie Island in the South
Orkneys, since 1902 (MSA r = 0.23, and nss-SO42- r =
0.29; significant at 95% confidence). No significant link between high MSA
concentrations and El Niño events is observed at this location.
Peng, T.-H. 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.
Picaut, J., A.J. Busalacchi, M.J. McPhaden, E.J. Katz, L. Gourdeau, F.I.
Gonzalez, E.C. Hackert, and M.H. Bushnell. Open-ocean validation of
TOPEX/POSEIDON sea level in the western equatorial Pacific. ORSTOM Report
No. 5, 76 pp. (1995).
During the verification phase of the TOPEX/POSEIDON radar altimeter mission
a rigorous open-ocean validation experiment was conducted in the western
equatorial Pacific Ocean. From August-September 1992 to February-March
1993 two TOGA-TAO moorings at 2°S-156°E (1739 m depth) and
2°S-164.4°E (4400 m depth) were outfitted with additional
temperature, salinity, and pressure sensors to measure precisely the
dynamic height from the surface to the bottom at 5-min intervals directly
beneath two TOPEX/POSEIDON crossovers. Bottom pressure gauges and inverted
echo sounders were deployed as well. A pre-deployment design study using
full depth CTD casts, subsequently confirmed by post-deployment analyses,
indicated this suite of instruments was capable of measuring sea surface
height fluctuations to within 1-2 cm. The validation experiment also
benefited from the comprehensive set of ocean-atmosphere measurements that
were made in the region during the TOGA-COARE intensive observation period
of November 1992-February 1993. The surface relative to bottom dynamic
height fluctuations observed in-situ during the 6-7 month experiment had a
standard deviation of 5 cm with excursions of order ±15 cm. Energetic
steric sea level variability was found to exist on short time scales of
order hours to a few days, most notably the quasi-permanence of strong
semi-diurnal internal tides. Such internal tides were noted to induce
changes in surface dynamic height with a standard deviation of 2 dyn cm.
At the shallower of the two sites, 2°S-156°E, a possible nonlinear
rectification of the internal tide was observed occasionally to change the
dynamic height by as much as 30 cm over less than an hour. On time scales
longer than the 10 day repeat of the TOPEX/POSEIDON satellite, the
low-frequency fluctuations of dynamic height were related to interannual
variations corresponding to the 1991-1993 ENSO, to the seasonal cycle and to
intraseasonal variations associated with the 40-60 day oscillations of the
equatorial zonal wind field. Instantaneous comparisons between the 1 sec
TOPEX/POSEIDON altimeter retrievals and the 5-min dynamic height were
performed with regard to several tide models, the barotropic tide measured
in-situ, ECMWF surface air pressure, and the surface air pressure measured
in-situ. Depending on the choice of altimeter and of the environmental
corrections applied to the altimeter data, the rms differences between the
satellite and the in-situ measurements of sea level were as low as 3.3 cm
at 2°S-156°E and 3.7 cm at 2°S-164.4°E. When additional
satellite data in the general vicinity of the mooring are included, and
after the use of a 30-day low-pass filter, the satellite and in-situ data
were found to be highly correlated, with correlation coefficients of about
0.95 and rms differences around 1.8 cm.
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).
No abstract.
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).
No abstract.
Samsury, C.E., and E.J. Zipser. Secondary wind maxima in hurricanes:
Air-flow and relationship to rainbands. Monthly Weather Review,
123(12):3502-3517 (1995).
Aircraft flight-level data from 787 radial legs in 20 hurricanes are
analyzed to identify the composite kinematic structure in the hurricane
eyewall, and especially with secondary horizontal wind maxima (SHWM) that
occur outside the eyewall. Similar to previous studies, analysis of the
flight-level wind data in the eyewall reveals radial convergence near the
radius of maximum wind (RMW), and the highest frequency of updrafts and the
largest upward mass transport radially inward of the RMW. More than 20% of
the flight legs contain substantial secondary horizontal wind maxima of
specified strength and length. The kinematic structure associated with SHWM
is similar to that of the hurricane eyewall with radial convergence near
the radius of maximum wind and a preferred location for maximum upward
motions and upward mass transport just inside the RMW. Statistical analysis
confirms the similarity in characteristics between radial and vertical
velocities of the eyewall and near the SHWM. In addition, for both the
eyewalls and the SHWM, the radial velocity composite results show that the
radial mass transport in the planetary boundary layer must be largely
confined to the lowest 1000 m. Lower fuselage radar reflectivity data from
13 of the hurricanes are used to assess whether the outer wind maxima are
associated with rainbands, and vice versa. In the radial legs with SHWM
for which radar data were available, the secondary horizontal wind maximum
was frequently associated with a mesoscale reflectivity feature (rainband).
In contrast, many rainbands, more than 70%, were without wind maxima. The
results from this study show that to some extent an outer eyewall or rainband
with SHWM can act as a barrier to inflow to the inner wall. Additionally,
it is possible that thermodynamic modification of inflow air may occur as a
result of convective-scale vertical motions associated with a rainband. In
those cases when an outer rainband encircles the eyewall, it is possible that
these factors act together with subsidence to weaken the inner eyewall.
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).
No abstract.
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.
Shapiro, L.J., and J.L. Franklin. Potential vorticity in Hurricane Gloria.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology,
Miami, FL, April 24-28, 1995. American Meteorological Society, Boston,
524-525 (1995).
No abstract.
Shapiro, L.J., and J.L. Franklin. Potential vorticity in Hurricane Gloria.
Monthly Weather Review, 123(5):1465-1475 (1995).
Potential vorticity (PV) analyses for Hurricane Gloria of 1985 are derived
from nested objective wind analyses of Omega dropwindsonde and airborne
Doppler radar data. The analyses resolve eyewall-scale features in the
inner vortex core and embed analyses of these features within the
larger-scale environment. Since three-dimensional geopotential height
fields required for evaluation of PV are not available in the core, they
are derived using the balance equation. In the process of deriving the
heights, the degree of gradient balance is evaluated. The 500-mb tangential
winds in the core, averaged azimuthally on the four cardinal points, are
close to gradient balance outside the radius of maximum wind. The resulting
depiction of PV is the first presented for a real hurricane. Due to data
deficiencies immediately outside the Doppler region, as well as inside the
eye, smoothing of the wind data using a filter with a minimum 25-km spatial
scale is required to derive a balanced geopotential height distribution
consistent with a statically stable vortex. The large-scale PV distribution
evidences asymmetries in the middle and upper troposphere that appear to be
associated with Gloria's translation to the northwest. Eyewall-scale PV in
the core, and PV of the azimuthally-averaged vortex, are also presented.
Sievering H., E. Gorman, T. Ley, A.A.P. Pszenny, M. Springer-Young, J.
Boatman, Y. Kim, C. Nagamoto, and D. Wellman. Ozone oxidation of sulfur
in sea-salt aerosol particles during the Azores Marine Aerosol and Gas
Exchange experiment. Journal of Geophysical Research,
100(D11):23,075-23,082 (1995).
Sea-salt aerosol particles in the lowest tens of meters above the ocean are,
typically, more than three-fourths water on a volume basis. Calculations
herein indicate that aqueous-phase conversion of sulfur dioxide dissolved
in the water associated with sea-salt particles (sea-salt aerosol water)
support the production of 2-8 nmol m-3 of nonsea-salt sulfate
(nssSO4=) during the Marine Aerosol and Gas Exchange
(MAGE) experiment intensives. This production is based on ozone oxidation
of dissolved SO2 in sea-salt aerosol water and accounts for
sulfur gas and ozone mass transfer limitations as a function of sea-salt
particle size. Measurements show that 1-15 nmol m-3 of
nssSO4= was actually present in the sea-salt particle
mode except for four enhanced concentration cases due to continental sulfur
input. The range in predicted as well as observed
nssSO4= produced by ozone oxidation of sulfur dioxide,
being in the sea-salt particle mode with observed volume geometric median
diameter of 3.5-5 µm, is dry, deposited at a fairly rapid rate. The
remainder, being large-particle cloud condensation nuclei, may contribute
little to cloud albedo over the global oceans. The two papers following
this one, Kim et al. (this issue) on aerosol size distribution and
water content and Parfai et al. (this issue) on compositional
variations of sea-salt-mode aerosol particles observed by electron
microscopy, complement and support results presented here. All three
present results of the MAGE experiment and precede a forthcoming special
of the Journal of Geophysical Research-Atmospheres on MAGE (B.
Huebert, guest editor).
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(1-2):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.
Vaughan, S.L., and K.D. Leaman. The role of small-scale cells in the
Mediterranean convection process. Journal of Physical Oceanography,
25(10):2423-2436 (1995).
Data from the Gulf of Lions in the northwest Mediterranean in 1987 indicated
that the deep convection known to occur in that region was organized into
small-scale [O(1 km)] cells embedded in a larger-scale [0(50 km)] homogeneous
"patch." Velocities from current meters showed that during the period of
strong surface forcing a front of increased kinetic energy propagated
downward, finally reaching the bottom. An analytic expression for the depth
of penetration of this front as a function of time and surface buoyancy flux
was derived, using a simple one-dimensional model of the density profile,
which agreed well with the observations. An analytic expression for the
kinetic energy density was derived as a function of time, dissipation rate,
and rate of change of potential energy, assuming conservation of total
energy. Estimates of not volume transport were made from frequency
distributions of vertical velocity. Results indicate that the cells provided
the turbulence necessary to efficiently mix the water column vertically,
removing the existing weak but stable stratification. The cells were not
directly responsible for any net volume transport downward but did contribute
to the transport of fluid properties such as heat, energy, and chemical
tracer concentration.
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, Part 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).
No abstract.
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).
No abstract.
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).
No abstract.
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.
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),
112 pp. (1995).
During 1991, a collaborative program between the United States and Barbados
was established with the support of NOAA's Climate and Global Change
Atlantic Climate Change Program to conduct regular measurements of the
transport and water mass characteristics in the major southern passages to
the Caribbean Sea. This program involves the use of a Barbados Coast Guard
vessel, the HMBS Trident, which makes routine monthly patrols in the
area and has been equipped to collect standard hydrographic measurements
(CTDO2 profiles and water samples) and velocity profile
measurements using a downward-looking acoustic Doppler current profiler
(ADCP). The purpose of the program is to determine the quantity and
time-variability of South Atlantic surface, thermocline, and intermediate
waters flowing into the North Atlantic in compensation for southward
cross-equatorial transport of North Atlantic Deep Water, and to establish
an economical means for future monitoring of this transport loop. This
report contains data collected on cruises WI-04, WI-05, and WI-06 of this
program.
Yuter, S.E., R.A. Houze, B.F. Smull, F.D. Marks, J.R. Daugherty, and S.R.
Brodzik. TOGA COARE aircraft mission summary images: An electronic atlas.
Bulletin of the American Meteorological Society, 76(3):319-328
(1995).
An electronic atlas of research aircraft missions in TOGA COARE (Tropical
Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment) has
been prepared and is available on the Internet via World Wide Web browsers
such as Mosaic. These maps are in the form of time sequences of color imagery
assembled using the NCAR Zebra software. Initial versions of these maps were
prepared in the field at the TOGA COARE Honiara Operations Center to aid in
the evaluation of each aircraft mission immediately after it was flown. The
maps prepared in the field have been updated, corrected, and remapped at
standard scales and with common color schemes. They show the meteorological
setting of sampling by all seven aircraft participating in TOGA COARE--the
two NOAA WP-3D aircraft, the NCAR Electra, the FIAMS C-340, the UK C-130,
and the NASA DC-8 and ER-2--by overlaying flight tracks, GMS satellite
infrared data, and NOAA WP-3D airborne radar images. The map sequences are
combined with text of scientists' notes and other background information on
the research flights to form a summary of each aircraft mission. The
resulting aircraft mission summaries are intended as a road map to the COARE
aircraft dataset. They indicate where and when data were collected and the
meteorological context for those data. As an electronic document, the
atlas of aircraft mission summaries is available on demand, and it is
dynamic: as further information becomes available, the mission summaries
will continue to be added to and updated as appropriate, and new releases
will be issued periodically.
**1994**
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.
Atwood, D.K., A. Bratkovich, M.S. Gallagher, and G.L. Hitchcock. Introduction
to the dedicated issue. Estuaries, 17(4):729-731 (1994).
No abstract.
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.
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. (1994).
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.
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, 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.
Bogdanov, Yu.A., P.A. Rona, E.G. Gurvich, V.M. Kuptsov, N.A. Rimskij-Korsakov,
A.M. Sagalevich, and M.D. Hannington. Relict sulphide mounds of the TAG
hydrothermal field, Mid-Atlantic Ridge (26°N, 45°W).
Okeanologiya, 34(4):590-599 (1994).
The huge inactive cone-shaped hydrothermal Mir Mound discovered and surveyed
during the 23rd cruise of the R/V Akademik Mstislav Keldysh in 1991
has the base diameter of more than 700 m, the height of 50-70 m and the mass
of hydrothermal material of about 10 million tons. In plan, the sound may be
divided into two zones: the inner 400 m diameter zone with a dense "forest"
of high-temperature sulphide chimneys and the more ancient outer zone
(150-200 m) with lower temperature hydrothermal deposits of Fe and Mn
hydroxides, opal and sometimes sulphides, partly covered by carbonate
sediments. Radiocarbon dating showed that the formation of the mound had
begun over 25,000 years ago. Over this time, hydrothermal activity occurred
23-25, 12-16 and 4-8 thousand years ago. Bottom photography, side scanning,
and sediment analysis suggest the existence 2.5 km north of the Mir Mound of
another inactive hydrothermal mound of similar dimensions.
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, C.J. Fischer, A. Mendez, A.A.P. 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. (1994).
The report describes the results of the 1992 ASTEX/MAGE cruise aboard the
NOAA R/V Malcolm Baldrige. The cruise was designed to support
research sponsored by the NOAA Climate and Global Change Program under:
(1) the Marine Sulfur and Climate (MS&C) component of the Atmosphere and
Land-Surface Processes Core Project, and (2) the Radiatively Important
Trace Species (RITS) component of the Atmospheric Chemistry Core Project.
Chemical and meteorological measurements obtained on the cruise include
reduced sulfur gases, ozone, carbon monoxide, nitrogen oxides and
peroxyacetyl nitrate, rawinsondes, aerosol chemistry, microwave radiometry,
vertical wind profiles, heat and water momentum flux, non-methane
hydrocarbons, trace metals, aerosol size distributions, aerosol physical
properties, and surface water chlorophyll. The report contains a brief
description of the experimental apparatus and procedures employed, plus
graphic and tabular presentations of the data sets, for most of the data
from AOML/Ocean Chemistry Division investigators.
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 B, 46(4):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. Proceedings, 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.
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. Proceedings, 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).
The Atlantic Oceanographic and Meteorological Laboratory (AOML) is one of
several Research Science Centers participating in a global effort to
quality control oceanographic data collected from either research vessels
or volunteer observing ships (VOS). AOML efforts are currently focused on
XBT data collected in the Atlantic Ocean. The data being examined consists
of "real-time," delayed, historical and Navy declassified modes. 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. An evaluation of the hydrostatic version of a new formulation
of the primitive equations for atmospheric modeling. Preprints, 10th
Conference on Numerical Weather Prediction, Portland, OR, July 18-22,
1994. American Meteorological Society, Boston, 443-445 (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.
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.
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.
Gamo, T., H. Chiba, P. Fryer, J.-I. Ishibashi, T. Ishii, L.E. Johnson, K.
Kelly, H. Masuda, S. Ohta, A.-L. Reysenbach, P.A. Rona, T. Shibata, J.
Tamaoka, et al. Mariana 1992 diving surveys by Shinkai 6500
(Y9204 cruise): Revisits to the Mid-Mariana hydrothermal area and discovery
of hydrothermal vents in the southern Mariana region. Journal of Deep Sea
Research, 10:153-162 (1994).
We had ten dives of the submersible Shinkai 6500, together with its
mothership Yokosuka, of JAMSTEC in the mid-to southern Mariana areas during
November to December 1992. We revisited to the mid-Mariana Trough
hydrothermal site (Alice Springs Field: 18°13'N, 144°42'E) five
years after the discovery by the submersible Alvin in 1987. It was confirmed
that the site had maintained the similar hydrothermal activity during the
five years, because the highest fluid temperature (280°C), density of
biological vent communities, and chemical composition of the hydrothermal
endmember were compared well with those observed five years ago. In the
southern Mariana area, we dove to an inner trench wall to recover ultramafic
rocks originated from lower crust or upper mantle. Fresh basaltic lavas were
found to outcrop on the side of a southern Mariana forearc fault, suggesting
recent forearc volcanism related to the fault activity. In a transient zone
between the southern Mariana arc and backarc systems, basaltic rocks with
intermediate characteristics were recovered. It should be emphasized that a
new hydrothermal vent site with 202°C fluid was discovered at the summit
(depth: 1,470 m) of an arc seamount at (13°24'N, 143°55'E) in the
southern Mariana Trough.
Garzoli, S.L., and C. Giulivi. What forces the variability of the
southwestern Atlantic boundary currents? Deep-Sea Research, Part
I, 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.
Hansen, D.V., M.S. Swenson, and M.C. Pazos. The Drifter Data Assembly
Center. International WOCE Newsletter, 15:27-30 (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 to the 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.
Huang, H., J.R. Proni, and J.J. Tsai. Probabilistic approach to initial
dilution of ocean outfalls. Water Environment Research,
66(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%.
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(10):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.
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(3):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 Data
Report, ERL AOML-25 (PB94-219177), 180 pp. (1994).
This data report covers the entire life (through August 31, 1989) of free
drifting buoys released in the tropical Pacific Ocean by the Atlantic
Oceanographic and Meteorological Laboratory (AOML) between April 1, 1987 and
June 30, 1988. Excluded are those drifters released from Chinese research
vessels which were covered in a separate report (Qiyu and Pazos, 1989).
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. Proceedings, 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.
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(6493):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.
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. Journal of Geophysical Research,
99(C9):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., 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. Inter-comparison of automatic rain gauges in optical rain
gauge performance. Proceedings, Second Workshop on Optical Rain Gauge
Measurements, Greenbelt, MD, April 21-22, 1994, O.W. Thiele, N.J.
McPhaden, and D.A. Short (eds.). NASA Conference Publication 3288, 15-26
(1994).
No abstract.
Nystuen, J.A., J.R. Proni, C.A. Lauter, 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.
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.
Price, J.F., and M.O. Baringer. Outflows and deep water production by
marginal seas. Progress in Oceanography, 33(3):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(12):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.
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.
Rosenthal, S.L. Statistical aspects of the precipitation regimes at Miami
International Airport (MIA) and Palm Beach International Airport (PBI):
1961-1990. NOAA Technical Memorandum, ERL AOML-80 (PB94-194289),
40 pp. (1994).
Low-frequency components of the time series of mean annual precipitation for
1961-1990 at Miami International Airport (MIA) and Palm Beach International
Airport (PBI) are closely in phase. The data show a decadal-scale variation
with relatively high precipitation in the 1960s and 1980s and relatively low
precipitation in the 1970s. This fluctuation is concomitant with a
statistically significant decadal-scale fluctuation in tropical weather
system frequency. MIA precipitation is systematically related to tropical
weather system frequency on monthly and seasonal time scales but not so
precisely that one can conclude a cause and effect relationship exists.
Spectral analysis showed well marked peaks in the MIA and PBI spectra
(computed from annual precipitation totals) at a period of 15 years. Both
stations also showed considerable spectral intensity at a period of 10 years.
Cospectral calculations indicated that the covariance of the MIA and PBI
annual precipitation totals was primarily the result of fluctuations with
periods of 10 years or more. The annual numbers of cloudy days (NCLD),
thunderstorm days (NTWS), days with measurable precipitation (NP.01), and
the precipitation total for the rainiest day of the year (P24X) at MIA were
correlated with those from PBI. Positive correlations (significant at either
the 95% or 99% level) were obtained in all four cases. The time series of
annual values of NCLD showed statistically significant negative trends at
both stations. In contrast, the annual values of NP.01 showed positive
trends at these stations. Thus, the number of days with measurable rain at
these stations increased over these 30 years while the number of cloudy days
decreased. The time series of annual rainfall totals at both stations, when
smoothed with five-year running means, showed maxima in the decade of the
1960s. Analyses of year-month cross sections showed that these maxima were
the result of anomalously high rainfall in June and September-October during
the later half of that decade.
Rosenthal, S.L. Variability of surface-air temperature and precipitation at
Miami International Airport including relationships with tropical weather
system activity and El Niño: 1941-1990. NOAA Technical Memorandum, ERL
AOML-81 (PB94-216892), 38 pp. (1994).
The Miami International Airport (MIA) surface-air temperature and
precipitation data for the period 1941-1990 were examined to determine El
Niño's impact on the MIA climate. In this sample, El Niño years and the
years just prior to El Niño years are relatively warm and the years that
follow El Niño years are relatively cool. The MIA winter months in El
Niño years tend to be relatively rainy in comparison to those of non El
Niño years. The winter and spring of years preceding El Niño years tend
to be relatively dry.
Samsury, C.E., and R.E. Orville. Cloud-to-ground lightning in tropical
cyclones: A study of Hurricanes Hugo (1989) and Jerry (1989). Monthly
Weather Review, 122(8):1887-1896 (1994).
Cloud-to-ground lightning characteristics of two Atlantic tropical cyclones
of 1989, Hurricanes Hugo and Jerry, are presented. Statistics on the number
of flashes, location, polarity, peak currents, and multiplicity (number of
strokes per flash) are examined in an 18-hour period divided into pre-landfall
and post-landfall categories. Land-based and aircraft lower fuselage radar
data are also analyzed to determine the nature of the precipitation in which
lightning is detected. Jerry is found to be more electrically active than
Hugo, with 691 flashes detected compared with 33 flashes for Hugo. The
majority of these flashes, regardless of the polarity, are located in the
right front and right rear quadrants of the hurricanes, almost exclusively in
outer convective rainbands. One reason for the large difference in the number
of flashes between the two storms is the presence of many convective
rainbands in Jerry, compared to only a few in Hugo. More than 20% of the
flashes in each storm have a positive polarity. Median negative peak
currents of the first return strokes are 49 kA in Hugo and 40 kA in Jerry.
Median positive peak currents are 65 kA in Hugo and 52 kA in Jerry. The mean
multiplicity of the negative flashes is 1.7 in Hugo and 2.6 in Jerry. 20% of
the negative flashes detected in Jerry have a multiplicity of 4 or higher.
Smith, S.M., and G.L. Hitchcock. Nutrient enrichments and phytoplankton
growth in the surface waters of the Louisiana Bight. Estuaries,
17(4):740-753 (1994).
Nitrate concentrations have increased twofold in the Mississippi River
during the past three decades. The increased nitrogen loading to the
Louisiana shelf has been postulated as a factor leading to eutrophication
and the subsequent development of hypoxia west of the Mississippi River
delta. While ratios of nitrogen:phosphorus and nitrogen:silica are
relatively high in surface waters on the western Louisiana shelf, nitrogen
has been posed as the "limiting" nutrient in this region. Bioassays were
performed with nutrient additions to surface waters collected from the
Louisiana shelf to examine the potential for specific nutrient limitation.
Experiments were conducted in March and September 1991, and May 1992. The
growth responses of natural and cultured phytoplankton populations were
determined by measuring the time course of in vivo and 3-(3,4
dichlorophenyl)-1, 1-dimethylurea (DCMU)-induced fluorescence, as well as
initial and final chlorophyll a concentrations. The results suggest
that phosphate and silicate potentially limit phytoplankton growth during
the winter-spring, particularly at low salinities. In late summer, in
contrast, nitrogen limitation may be prominent at higher salinities.
Thacker, W.C., and R. Lewandowicz. Dynamics of information and uncertainty.
Tellus A, 46(5):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 data
showed 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.
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 Niño-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 Niño-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(6493):143-145 (1994).
It has long been hypothesized that iron concentrations limit phytoplankton
productivity in some parts of the ocean. As a result, iron may have played
a role in modulating atmospheric CO2 levels between glacial and
interglacial times, and it has been proposed that large-scale deposition
of iron in the ocean might be an effective way to combat the rise of
anthropogenic CO2 in the atmosphere. As part of an experiment
in the equatorial Pacific Ocean, we observed the effect on dissolved
CO2 of enriching a small (8 × 8 km) patch of water with
iron. We saw significant depression of surface fugacities of CO2
within 48 hours of the iron release, which did not change systematically
after that time. But the effect was only a small fraction (similar to 10%)
of the CO2 drawdown that would have occurred had the enrichment
resulted in the complete utilization of all the available nitrate and
phosphate. Thus artificial fertilization of this ocean region did not cause
a very large change in the surface CO2 concentration, in contrast
to the effect observed in incubation experiments, where addition of similar
concentrations of iron usually results in complete depletion of nutrients.
Although our experiment does not necessarily mimic all circumstances under
which iron deposition might occur naturally, our results do not support the
idea that iron fertilization would significantly affect atmospheric
CO2 concentrations.
Whung, P.-Y., E.S. Saltzman, and G.W. Gross. Uptake of methanesulfonate and
sulfate in ice. Antarctic Journal of the United States, 29(5):73-75
(1994).
Methanesulfonate (MSA) is an atmospheric oxidation product of dimethyl
sulfide; the latter is produced by phytoplankton in the surface ocean.
Because of its biogenic origin, MSA can be used as a biological tracer in
studies of atmospheric sulfur chemistry. The ratio of MSA to total
non-seasalt sulfur has been used as an indicator for various atmospheric
sulfur sources. Due to differences in physicochemical properties of MSA and
sulfate, postdepositional processes could alter this fraction. Specifically,
we address the question of whether there is a difference in the distribution
coefficients (Conc.ice/Conc.water) of MSA and of
sulfate. We also study the effect of ammonia on the uptake of MSA and
sulfate in ice.
Whung, P.-Y., E.S. Saltzman, M.J. Spencer, P.A. Mayewski, and N.
Gundestrup. Two-hundred year record of biogenic sulfur in a south
Greenland ice core (20D). Journal of Geophysical Research,
99(D1):1147-1156 (1994).
The concentration of methanesulfonic acid (MSA) was determined in a shallow
south central Greenland ice core (20D). This study provides a high-resolution
record of the DMS-derived biogenic sulfur in Greenland precipitation over the
past 200 years. The mean concentration of MSA is 3.30 ppb (sigma = 2.38 ppb,
n=1134). The general trend of MSA is an increase from 3.01 to 4.10 ppb between
1767 and 1900, followed by a steady decrease to 2.34 ppb at the present time.
This trend is in marked contrast to that of non-sea-salt sulfate
(nss SO42-), which increases dramatically after 1900
due to the input of anthropogenic sulfur. The MSA fraction
((MSA/(MSA+nss SO42-)) * 100) ranges from a mean of
15% in preindustrial ice to less than 5% in recent ice. These MSA fractions
suggest that approximately 15 to 40% of the sulfur in recent Greenland ice
is of biological origin. It is suggested that there is a significant
low-latitude component to the biogenic sulfur in the core and that variations
in the MSA fraction reflect changes in the relative strengths of low- and
high-latitude inputs. The data show no evidence for a strong dependence of
dimethyl sulfide (DMS) emissions on sea surface temperature during the last
century. There is also no indication that the yield of MSA from DMS oxidation
has been altered by increased NOx levels over the North Atlantic
during this period.
Williams, R.G., and J.R. Proni. Acoustic remote sensing of wastewater
outflow. Proceedings, Seventh International Symposium on Acoustic Remote
Sensing and Associated Technologies of the Atmosphere and Oceans,
Boulder, CO, October 4, 1994. Proceedings Volume, Boundary-Layer
Meteorology, I43-49 (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 the Atmospheric Sciences, 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. 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 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, J.A. Routt, and M.D. Hendry. Windward Islands
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).
During 1991, a collaborative program between the U.S. and Barbados was
established with support from the United States NOAA/CGC/ACCP to conduct
regular measurements of the transport and water mass characteristics in
the major southern passages to the Caribbean. This program involves the
use of a Barbados Coast Guard vessel (the HMBS Trident) that makes
routine patrols in this area, which has been equipped to collect standard
hydrographic measurements using a Conductivity-Temperature-Depth-dissolved
Oxygen (CTDO2) and velocity profile measurements on station
using a downward-looking acoustic Doppler current profiler (ADCP). The
purpose of the program is to determine the quantity and time-variability of
South Atlantic surface, thermocline, and intermediate waters flowing into the
North Atlantic in compensation for southward cross-equatorial transport of
North Atlantic Deep Water, and to establish an economical means for future
monitoring of this return flow. This report contains data from cruises
WI-02 and WI-03 conducted May 6-10, 1992 and September 19-23, 1992,
respectively.
Zhang, J.-Z., and F.J. Millero. Investigation of metal sulfide complexes
in seawater using cathodic stripping square wave voltammetry. Analytica
Chimica Acta, 284(3):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, Part II,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, J20-25 (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 sigmao values from all fetches follow a common
trend for sigmao as a function of u*, so the fetch
dependence is negligible. An empirical power-law model yields a high
correlation between sigmao 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
sigmao and u*.
Bougault, H., J.L. Charlou, Y. Fouquet, H.D. Needham, N. Vaslet, P. Appriou,
P. Jean Baptiste, P.A. Rona, L. Dmitriev, and S. Silantiev. Fast and slow
spreading ridges: Structure and hydrothermal activity, ultramafic topographic
highs, and CH4 output. Journal of Geophysical Research,
98:9643-9651 (1993).
Different parts of the world ridge system have quite different morphologies,
which reflect different constructional processes. It appears that hydrothermal
circulation at all spreading centers is an important exchange process between
the ocean and the newly formed oceanic crust. This hydrothermal circulation
may vary according to morphology and crustal composition and may also affect
ridge constructional processes. The TAG (26°N) and Snake Pit
(23°N) hydrothermal sites on the Mid-Atlantic Ridge (MAR) display
Mn/CH4 ratios in overlying seawater similar to those of
nonsedimented East Pacific Rise sites, i.e., about 0.2 mol/L. In
contrast, large methane anomalies with very low Mn/CH4 ratios
of 0.005 mol/L are associated with ultramafic topographic highs near
15°N, close to the axis and on ultramafic walls of the rift valley.
The association of ultramafic bodies and CH4 anomalies in seawater indicates
active serpentinization processes. CH4 is produced during
serpentinization according to the Fisher Tropsch reaction (Charlou et
al., 1991). Many ultramafic rock assemblages have been sampled on the
MAR away from fracture zones, in particular by the Deep Sea Drilling Project.
Changes of mechanical properties and of density of uplifted deep material in
the accreting plate boundary zone caused by serpentinization may play an
important role in the construction of slow-spreading ridges.
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. Proceedings, 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.
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.
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, 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.
Hanson, K., and G.A. Maul. Analysis of temperature, precipitation, and sea
level variability with concentration on Key West, Florida, for evidence of
trace-gas induced climate change. In Climatic Change in the
Intra-Americas Sea, G.A. Maul (ed.). Edward Arnold Publishers,
London, 193-213 (1993).
Meteorological and sea level data for Key West, Florida, have been examined
for evidence of changes during recent decades that may be attributed to
increasing trace gases in the atmosphere. The 136-year air temperature
record (1851-1986) gives the evidence that a slight warming has occurred,
but there has been no appreciable change since 1950. However, there are
questions of the reality of the warming because of the varied
temperature-observing conditions over the period of record. The 101-year
precipitation record (1886-1986) gives evidence that no significant change
in precipitation has occurred during the period of record. In addition to
Key West weather, sea level records from all 62 stations on file with the
Permanent Service for Mean Sea Level that cover the Caribbean Sea, Gulf of
Mexico, the Bahamas, and Bermuda have been examined for linear trends.
Average (±1 standard deviation) sea level rise is 0.4 cm/yr (±0.6 cm/yr)
for all stations (mean record length 20 years), and 0.3 cm/yr (±0.4 cm/yr)
for those stations with records 10 years in length. A regional maximum
+1.0 cm/yr is centered in the northwestern Gulf of Mexico, an area of
subsidence. Regional minima (approximately -0.3 cm/yr) occur in the
southwestern Gulf and in the Lesser Antilles, where there is diastrophism.
Average sea level rise at Key West, a site of tectonic stability, is 0.22
cm/yr (±0.01 cm/yr) for the period 1913-1986. Key West sea level seems
unrelated to local air temperature, barometric pressure, precipitation, and
records of coral growth, but is significantly lower than normal during the
year preceding a strong El Niño-Southern Oscillation event, and higher than
normal during the event itself. There is no evidence for accelerated sea
level rise at this site.
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. Proceedings,
Second International Symposium on Ocean Wave Measurement and Analysis,
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), 108 pp. (1993).
Data collected during the 1990 Atlantic Climate Change Program and the
Western Tropical Atlantic Experiment are presented. The goals of the
programs were to increase the understanding of the roles of the regional
circulation and ocean circulation in global climate. Salinity, ocean
temperature as a function of depth, and other hydrographic data were
collected from shipborne platforms.
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).
Data collected during the 1991 Atlantic Climate Change Program and the
Western Tropical Atlantic Experiment are presented. The goals of the
programs were to increase the understanding of the roles of regional
circulation and ocean circulation in global climate. Salinity, ocean
temperature as a function depth and other hydrographic data were collected
from shipborne platforms.
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 (CMWs) 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 CMWs 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 CMWs in this
study were found to have LBFs 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 CMWs 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 LBFs of
low-level CMWs 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.
Keene, W.C., J.R. Maben, A.A.P. Pszenny, and J.N. Galloway. Measurement
technique for inorganic chlorine gases in the marine boundary layer.
Environmental Science and Technology, 27(5):866-874 (1993).
A technique was developed to measure inorganic Cl gases in the marine
boundary layer. The inlet inertially removed coarse aerosol (>1 µm
diameter), and an in-line filter removed fine aerosol. A trace gas
concentrator positioned downstream incorporated an acidic mist chamber
which sampled HCl* (including HCl, NOCl, ClNO2, and
ClNO3), followed by an alkaline mist chamber which sampled
Cl2* (including Cl2 and a portion of HOCl). Mist
solutions were analyzed by ion chromatography. Estimated detection limits
for HCl* and Cl2* were 39 and 13 pptv, respectively. Standard
additions of calibration gases from permeation sources to ambient air were
recovered quantitatively within source uncertainties. The sampler appears
to discriminate against organic Cl gases. HCl* in coastal air near Miami
varied from <39 to 268 pptv with lower mixing ratios at night. Ambient
Cl2 varied from >13 to 127 pptv with highest mixing ratios
before dawn.
Keene, W.C., D.J. Jacob, A.A.P. Pszenny, R.A. Duce, J.J. Schultz-Tokos, and
J.N. Galloway. Comment on "Aqueous phase chemical processes in deliquescent
sea-salt aerosols: A mechanism that couples the atmospheric cycles of S and
sea salt" by W.L. Chameides and A.W. Stelson. Journal of Geophysical
Research, 98(D5):9047-9049 (1993).
Keene et al. (1990) measured substantial Cl deficits relative to sea
salt in coarse aerosol sampled over the North Atlantic Ocean. These deficits
were not balanced by NO3 or non-sea-salt (nnss)
SO2/4 in the aerosol and thus could not be explained
completely by acid-displacement reactions (Brimblecombe and Clegg, 1988) or
by reactions involving nonacidic N gases (Finlayson-Pitts et al.,
1989). To account for the unexplained Cl-deficits, Keene et al.
(1990) adopted from Behnke and Zetzsch (1989a,b) a stoichiometric description
of the action of O3 on sea-salt aerosol to produce
Cl2. They then developed and assessed a model for Cl cycling
in the gas phase. The quality of the Keene et al. (1990) data and
the validity of their interpretation have been questioned by Chameides and
Stelson (1992) who report not significant Cl volatilization in photochemical
model simulations of deliquescent sea-salt aerosol in the marine boundary
layer (MBL). We wish to comment on some aspects of the Chameides and Stelson
(1992) analysis in light of our previous work and that of others. Our
comments focuses on the quality of the Keene et al. (1990) data and
on mechanisms of Cl volatilization from sea-salt aerosol.
Lalou, C., J.-L. Reyss, E. Brichet, M. Arnold, G. Thompson, Y. Fouquet, and
P.A. Rona. New age data for Mid-Atlantic Ridge hydrothermal sites: TAG and
Snake Pit chronology revisited. Journal of Geophysical Research,
98(B6):9705-9713 (1993).
The chronologies of TAG and Snake Pit hydrothermal fields have been
established using 210Pb/Pb, 230Th/234U
and 14C dating. At the TAG field, a Mn-oxide record, indicative
of low temperature events, began at least 125,000 years and possibly 140,000
years ago with maximum intensities at 15,000, 7,000 and 4,000 years before
present. High-temperature events, giving rise to sulfide deposits, began
about 100,000 years ago and have been intermittent to the present day. A
presently active site has experienced intermittent pulses of activity every
4,000 to 6,000 years over the past 20,000 years. Decrease in activity is
often marked by low temperature aragonite precipitation in chimney conduits
at 4,000, 7,000 and 9,000 years ago. After a period of quiescence lasting
about 4,000 years, this site was reactivated about 50 years ago. The Snake
Pit field is much younger, and no sulfides older than 4,000 years have been
recovered. Relict sulfide deposits are dated between 2,000 and 4,000 years
old, indicating this site was active during a quiescent period at TAG.
Reactivation of Snake Pit took place about 80 years ago, and is presently
concurrent with that of TAG. Comparison with hydrothermal sites on the East
Pacific Rise suggests that on slow-spreading ridges the major fracture
systems focusing the hydrothermal discharge can be reactivated at intervals
and new deposits precipitated on top of older ones, while on faster-spreading
ridges each pulse of activity is separated in space and time resulting in
discrete deposits.
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.
Maul, G.A. Ecosystem and socioeconomic response to future climatic conditions
in the marine and coastal regions of the Caribbean Sea, Gulf of Mexico,
Bahamas, and the northeast coast of South America. Caribbean Environment
Programme, CEP Technical Report No. 22, 43 pp. (1993).
Global climate change, and particularly the impact of human activities on
Earth's biogeographic environment, is of enormous socioeconomic and
ecological importance. It is the regional effect of global change, however,
that weighs most heavily on individual lives because of the complexity of
local response to a world-wide phenomenon. This report summarizes the
opinion of a Task Team of 23 experts concerning the implications of climate
change in the Intra-Americas Seas (Gulf of Mexico-Caribbean
Sea-Bahamas-Bermuda-Guianas), of a global 1.5°C temperature and 20 cm
sea level rise by the year 2025. For some ecosystems in the region, the
effect of temperature rise is much more important than sea level rise, and
vice versa for others; for some neither is important; for others both are
important. Of the 14 ecosystems considered, the most heavily impacted are
expected to be deltas and beaches, both because of sea level rise; neither
are particularly vulnerable to a modest temperature rise. Estuaries, wetlands,
lagoons and seagrass beds will all be moderately affected by both the
1.5°C and 20 cm scenarios. The other two very important ecosystems,
mangroves and coral reefs, are expected to have a low-to-moderate
vulnerability to climate change per se, but both are expected to experience
extreme stress due to local anthropogenic activities such as deforestation,
coastal development, runoff, overfishing, and tourism. Seven socioeconomic
issues were also studied in the context of local response to global change;
tourism and the influence of tropical storms are considered most important
vis a vis levels of vulnerability. As with the ecosystems, some other
socioeconomic issues are more affected by sea level rise (e.g.,
settlements and structures, and cultural heritage) than temperature rise
(which mostly affects coastal zones, public health, and human migration).
In addition to evaluating the effects of 1.5°C and 20 cm global rises,
the Task Team discussed the potential local rates of temperature and sea
level rise and found that for the Intra-Americas Sea, less climatic change
is expected than for other areas of Earth, but that human population pressure
will significantly stress the region's environment. Finally, we report on
new computer-based, decision-making tools for evaluating the effects of
climate change, tools that will give decision makers quantitative information
upon which to base new policies for management.
Maul, G.A. Implications of future climate on the ecosystems and
socio-economic structure in the marine and coastal regions of the
Intra-Americas Sea. In Climatic Change in the Intra-Americas Sea,
G.A. Maul (ed.). Edward Arnold Publishers, London, 3-28 (1993).
Global climate change, and particularly the impact of human activities on
Earth's biogeographic environment, is of enormous socioeconomic and ecological
importance. It is the regional effect of global change, however, that weighs
most heavily on individual lives because of the complexity of local response
to a world-wide phenomenon. This report summarizes the opinion of a Task Team
of 23 experts concerning the implications of climate change in the
Intra-Americas Seas (Gulf of Mexico-Caribbean Sea-Bahamas-Bermuda-Guianas),
of a global 1.5°C temperature and 20 cm sea level rise by the year
2025. For some ecosystems in the region, the effect of temperature rise is
much more important than sea level rise, and vice versa for others; for some
neither is important; for others both are important. Of the 14 ecosystems
considered, the most heavily impacted are expected to be deltas and beaches,
both because of sea level rise; neither are particularly vulnerable to a
modest temperature rise. Estuaries, wetlands, lagoons and seagrass beds will
all be moderately affected by both the 1.5°C and 20 cm scenarios. The
other two very important ecosystems, mangroves and coral reefs, are expected
to have a low-to-moderate vulnerability to climate change per se, but both
are expected to experience extreme stress due to local anthropogenic
activities such as deforestation, coastal development, runoff, overfishing,
and tourism. Seven socioeconomic issues were also studied in the context of
local response to global change; tourism and the influence of tropical storms
are considered most important vis a vis levels of vulnerability. As with the
ecosystems, some other socioeconomic issues are more affected by sea level
rise (e.g., settlements and structures, and cultural heritage) than
temperature rise (which mostly affects coastal zones, public health, and
human migration). In addition to evaluating the effects of 1.5°C and
20 cm global rises, the Task Team discussed the potential local rates of
temperature and sea level rise and found that for the Intra-Americas Sea,
less climatic change is expected than for other areas of Earth, but that
human population pressure will significantly stress the region's environment.
Finally, we report on new computer-based, decision-making tools for
evaluating the effects of climate change, tools that will give decision
makers quantitative information upon which to base new policies for
management.
Maul, G.A., and S.R. Baig. Glossary of scientific terms. In Climatic
Change in the Intra-Americas Sea, G.A. Maul (ed.). Edward Arnold
Publishers, London, 369-381 (1993).
Scientists use terms that can make a treatise such as Climatic Change
in the Intra-Americas Seas inaccessible to non-specialists and, in
particular, to management and policy makers not trained in the natural
sciences. To overcome this difficulty, this glossary of terms covering some
aspects of oceanography, geodesy, meteorology, ecology, and climatology has
been included. The terms and abbreviations selected for inclusion are mostly
those that have appeared in the text; the meanings are meant to be scientific
rather than legal. We have freely paraphrased many of the definitions from
more recent sources (Baker et al., 1966; Bates and Jackson, 1980;
NOAA, 1988) without explicit acknowledgment in order to minimize text, and
we have also cross-referenced some of the older texts (Sverdrup et
al., 1942; Mitchell, 1948; Huschke, 1959). The reader is referred to
the several sources listed below for more information, but is cautioned that
terms and meanings change with time (Maul, 1988). For the future, it is
urged that a multi-lingual glossary be created for the region, one that
includes more information on socio-economic and public health terms.
Maul, G.A., and M.H. Bushnell. The relation between acoustic travel time
and dynamic height anomaly off Abaco Island, Bahamas. Proceedings,
Joint IAPSO-IOC Workshop on Sea Level Measurements and Quality Control,
Paris, France, October 12-13, 1992. Intergovernmental Oceanographic
Commission, Workshop Report No. 81, 88-96 (1993).
Inverted Echo Sounders (IESs) measure the round-trip acoustic travel time
from the IES to the sea surface. These relatively inexpensive
ocean-bottom-mounted instruments have been proposed for (a) monitoring
long-term change at a specific site of a dynamical variable of interest
(e.g., heat content, thermocline depth, dynamic height anomaly,
etc.), (b) for open-sea calibrating of satellite altimeters, and (c) for
studying the difference in sea level signals between a coastal tide gauge
and that offshore. For the purpose of sea level variations, particularly at
the centimeter level of accuracy, precise relations between the travel time
and dynamic height anomaly must be obtained. The usual assumption is that
there are constant linear regression coefficients between dynamic height
anomaly and travel time. Based on 77 hydrocasts over the depth range 0-3000
db during 1984-1987 in the offing of Abaco Island, Bahamas, the regression
coefficients between travel time and dynamic height have been found to vary
systematically from month to month. If not accounted for, this can add ±10
dynamic centimeters of additional uncertainty when applying IES data to
problems of sea level variability.
Maul, G.A., and D.M. Martin. Sea level rise at Key West, Florida, 1846-1992:
America's longest instrument record? Geophysical Research Letters,
20(18):1955-1959 (1993).
The continuous series of sea level at Key West, Florida, commenced in 1913,
but we have discovered sporadic measurements that date back to 1846. From
records at the U.S. Army Corps of Engineers and the U.S. Coast and Geodetic
Survey, the sea level series has been connected to a Summary (common) Datum.
Thus, a gappy record of monthly and annual mean heights (H[t]), perhaps the
United States' longest series over San Francisco (ca. 1854) or New York (ca.
1856), can be tested to ascertain if the rise in relative sea level at this
site is stationary. Applying first and second order least squares and
two-phase regression analyses, we find that dH/dt is 0.19 ± 0.01 cm/yr,
and that d2H/dt2 = [9.6 ± 8.6] 10-3
cm/yr2; the two-phase regression shows H[t] rising 0.15 ± 0.03
cm/yr before ca. 1925 and 0.23 ± 0.01 cm/yr afterwards. Neither the
second-order regression coefficient nor d2H/dt2 nor
the two-phase calculation are significant above the 75% confidence level,
but all three are weakly consistent with accelerated rise. For the epoch
1951-1987, Key West sea level, corrected for post-glacial rebound, is best
explained by concurrent measurements of 0-1,000 db dynamic height anomaly
change.
Maul, G.A., and F.M. Vukovich. The relationship between variations in the
Gulf of Mexico Loop Current and Straits of Florida volume transport.
Journal of Physical Oceanography, 22(3):785-796 (1993).
Twelve years of monthly mean positions of the northern boundary of the Loop
Current in the eastern Gulf of Mexico from satellite and in-situ data have
been compared with coincident 1977-1988 estimates of volume transport in the
Straits of Florida in the "sub-seasonal" frequency band 15-1 to
5-1 cycles per month. Volume transport estimated from Cuba minus
Florida sea level difference in this frequency band accounts for 69% of the
variance in volume transport estimated from the Florida-Grand Bahama Island
submarine cable. On average, the Loop Current has a dominant period of 11
months, whereas the volume transport is dominated by annual spectral energy;
little significant coherence squared occurs between them. The maximum
northward penetration of the Loop Current occurs on average in winter when
the volume transport is a minimum, but this is an artifact of the sampling
epoch. This negative relationship is most pronounced for 1979-1981 when
transport is characterized as unimodal, but for 1984-1985 and 1987 the Loop
Current and volume transport are more in phase, bimodal, and transport and
position tend to have more semiannual energy. In this "sub-seasonal band,"
the volume transport undergoes a significant change in the phase of its
annual cycle after 1985 as compared with 1977-1984. For the 12 years
considered in this study, the ensemble correlation between monthly position
of the Loop Current and volume transport is essentially zero.
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(10):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 southward. 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(3):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, J.F. Craynock, and W.P.
Dammann. Nearshore current measurements for the SEFLOE II project,
1991-1992. NOAA Technical Memorandum, ERL AOML-75 (PB93-227676),
111 pp. (1993).
The 1989 Southeast Florida Outfall Experiment (SEFLOE) was performed to
evaluate the dispersion and advection of wastewater from ocean outfalls
along the southeast Florida coast. The results showed that more comprehensive
current measurements were needed to interpret the wastewater dilution
measurements, and SEFLOE II was scheduled to include the additional data
collection. Continuous series of current measurements were obtained at four
outfalls both to support other measurements being collected during intensive
survey periods and to compile long-term statistics of the different characters
of ocean currents at the outfalls. Current meters were installed at two depths
on each mooring.
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., R.H. Byrne, R.H. Wanninkhof, R.A. Feely, T. Clayton, P.
Murphy, and M.F. Lamb. 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-TA, 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 TA,
±5-7 µmol kg-1 in TCO2 and ±69 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 (±0.002 in pH, ±4 µmol kg-1 in TA, ±2 µmol
kg-1 in TCO2 and ±2 µAtm in fCO2).
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, Part I,
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, and J.A.
Paisley. Reception at Ascension Island, South Atlantic, of the transmissions
from the Heard Island Feasibility Test. NOAA Technical Memorandum, ERL
AOML-73 (PB93-176261), 35 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(2):281-284
(1993).
Paired high-volume aerosol samples of 20-60-h duration were collected
using identical Sierra Model 235 cascade impactors during a July-September
1991 research cruise in the Atlantic Ocean. Whatman 41 cellulose fiber was
used for the final filter in one impactor and a quartz fiber filter was
used for the final filter in the other impactor during each of 17 sampling
intervals. A paired t-test of measured non-seasalt sulfate (NSS) mass
concentrations indicates that the retention efficiencies of the two
materials for this primarily submicrometer species are indistinguishable
under the conditions of our sampling. A paired t-test of ammonium
concentrations indicates slightly higher concentrations on Whatman 41,
suggesting, perhaps, a positive artifact due to sorption of ammonia vapor.
Pszenny, A.A.P., W.C. Keene, D.J. Jacob, S. Fan, J.R. Maben, M.P. Zetwo,
M. Springer-Young, and J.N. Galloway. Evidence of inorganic chlorine gases
other than hydrogen chlorine in marine surface air. Geophysical Research
Letters, 20(8):699-702 (1993).
We report the first measurements of inorganic chlorine gases in the marine
atmosphere using a new tandem mist chamber method. Surface air was sampled
during four days including one diel cycle in January 1992, at Virginia Key,
Florida. Concentrations of HCl* (including HCl, ClNO3,
ClNO2, and NOCl) were in the range 40 to 268 pptv and
concentrations of Cl2* (including Cl2 and any HOCl
not trapped in the acidic mist chamber) were in the range <26 to 254 pptv
Cl. Concentrations of Cl2* increased during the night, and
decreased after sunrise as HCl* concentrations increased by similar amounts.
The measurements suggest an unknown source of either HOCl or Cl2
to the marine atmosphere. Photochemical model calculations indicate that
photolysis of the observed Cl2* would yield a chlorine atom (Cl•)
concentration of order 104-105 cm-3.
Oxidation by Cl• would then represent a significant sink for alkanes
and dimethylsulfide (DMS) in the marine boundary layer. The cycling of
Cl• could provide either a source or a sink for O3, depending
on NOx levels.
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. New directions in seafloor hydrothermal research. Proceedings,
Workshop 1992 on Global Undersea Research Program, Yokosuka, Japan,
September 2-4, 1992. Japan Marine Science and Technology Center (JAMSTEC),
117-120 (1993).
Ten years ago members of a pioneering research community of marine geologists,
geophysicists, geochemists, and biologists met at a NATO Advanced Research
Institute to assess the initial studies of seafloor hydrothermal systems
(Rona et al., 1983). The prevailing view at that time (Edmond et
al., 1979; Von Damm et al., 1983), based on preliminary
investigations of newly discovered warm springs at the Galapagos spreading
center (Corliss et al., 1979) and hot springs at latitude 21°N
at the East Pacific Rise (RISE Project Group, 1980), was that black
smoker-type venting was the predominant type of venting, that the composition
of solutions venting as black smokers was uniform, and that these solutions
had worldwide influence on ocean chemistry and mineralization. The components
of a seafloor hydrothermal system are a large heat source in a permeable
medium and a fluid. Since magmatic heat sources in fractured basalt as a
permeable medium and seawater are present at seafloor spreading centers, it
was initially reasoned that the chemistry of hydrothermal solutions produced
by reaction of circulating seawater with basalt should be uniform. A
prominent geochemist went so far as to say at the 1982 meeting that further
studies of hot springs at seafloor spreading centers would be "stamp
collecting."
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.
Rona, P.A., and S.D. Scott. Preface: Seafloor hydrothermal mineralization:
New perspectives. Economic Geology, 88(8):1935-1976 (1993).
Seafloor hydrothermal mineralization is a product of the exchange of heat
and chemicals between the lithosphere and the oceans that is occurring along
the global system of divergent plate boundaries (seafloor spreading centers)
at mid-ocean ridges and behind volcanic island arcs, at the island arcs, and
at intraplate volcanic centers. This exchange process has changed our concept
of ocean basins within the past 15 years from passive sinks that only
received material transported from land to active sources of matter and
energy that significantly effect global chemical mass balances and budgets,
the thermal regime of the Earth, adaptation of life forms based on a food net
dependent on the Earth's internal chemical energy (chemosynthesis) rather
than sunlight (photosynthesis), and the formation of mineral deposits. A
number of papers have reviewed the chemical (Von Damm, 1990), thermal
(Lowell, 1991), biological (Childress, 1992), and mineralization (Cronan,
1980; Bonatti, 1981; Rona, 1984, 1988; Morrison and Thompson, 1986; Bäcker
and Lange, 1987; Gross and MacLeod, 1987, Scott, 1992) aspects of the global
seafloor hydrothermal exchange process, and the relation of the
mineralization to ancient deposits (Franklin et al., 1981; Mitchell
and Garson, 1981; Sawkins, 1984; Scott, 1985, 1987). The purpose of this
special issue is to present a cross section of papers at the cutting edge
of research on seafloor hydrothermal mineralization.
Rona, P.A., and G. Thompson. Introduction to Atlantic hydrothermal activity.
Journal of Geophysical Research, 98(B6):9621-9623 (1993).
Seafloor hydrothermal research has advanced rapidly from local to global
scope through a sequence of discoveries. Hydrothermal research at seafloor
spreading centers began in the mid-1960s with the discovery of hot
metalliferous brines and sediments ponded in deeps along the slow spreading
(half rate 1 cm yr-1) axis of the Red Sea (Charnock, 1964; Miller,
1964; Swallow and Crease, 1965; Miller et al., 1966; Hunt et
al., 1967; Bischoff, 1969). At the same time, a hydrothermal
metalliferous component was identified in sediments of the East Pacific Rise
(Skornyakova, 1965; Arrhenius and Bonatti, 1965; Bostrom and Peterson,
1966). Geophysicists recognized that heat flow measurements at spreading
centers could only be explained by convective cooling of the crust with
circulating seawater (Elder, 1967; Lister, 1972). In 1972 and 1973, warm
springs and low-temperature hydrothermal precipitates were discovered at
the TAG hydrothermal field on the slow-spreading (half rate 1.2 cm
yr-1) Mid-Atlantic Ridge near 26°N (Rona, 1973; Rona and
Scott, 1974; M.R. Scott et al., 1974; R.B. Scott et al.,
1974; Rona et al., 1975). Warm springs and chemosynthetic vent biota
were found in 1977 at the intermediate-spreading (half rate 3 cm
yr-1) Galapagos spreading center (Williams et al., 1974;
Lonsdale, 1977; Corliss et al., 1979). The existence and composition
of pure, high-temperature end-member hydrothermal solutions were predicted
by extrapolation of the composition of the low-temperature Galapagos
hydrothermal solutions that were mixed with seawater (Edmond et
al., 1979). Inactive massive sulfide deposits that had been formed by
high-temperature hot springs (CYAMEX Scientific Team, 1979) were found in
1978 at 21°N on the East Pacific Rise, which is spreading at an
intermediate rate (half rate 3 cm yr-1). Active high-temperature
hot springs with the predicted end-member solutions were found in 1979 with
the discovery of black smoker-type venting within kilometers of the
previously discovered relict massive sulfide deposits at the East Pacific
Rise 21°N site (RISE Project Group, 1980). In 1985, the first
high-temperature black smoker-type venting with massive sulfides and vent
biota in the Atlantic Ocean were discovered at the TAG hydrothermal field
(Rona, 1985a,b; Rona et al., 1986) and at the Snake Pit hydrothermal
field (Scientific Party, 1986) at 26°N and 23°N, respectively,
on the Mid-Atlantic Ridge. Additional hydrothermal sites continue to be found
at spreading centers in the northeast Pacific, the southeast Pacific, and the
Indian Ocean, as well as in back arc basins of the western Pacific, all
leading to recognition of seafloor hydrothermal activity as a global
phenomenon (Rona, 1988). The basic hydrothermal process is similar at the
different locations and consists of subseafloor circulation of seawater,
driven convectively by magmatic heat sources at or near spreading centers
and reaction of the heated seawater with permeable rocks of the crust and
sometimes the upper mantle. However, significant differences in solution
chemistry, heat transfer, mineralization, and biology are being found at
the different sites. The 11 papers presented in this special section on
Atlantic hydrothermal activity are part of the initial series of papers
which define chemical, physical, and biological characteristics of
hydrothermal systems based on detailed investigations at the TAG and Snake
Pit hydrothermal sites. These investigations include the initial intensive
dive series at Snake Pit (11 dives) by Deep Submergence Vehicle (DSV) Nautile
in 1988 (Mevel et al., 1989); at TAG (16 dives) and Snake Pit (three
dives) by DSV Alvin in 1990 (Mid-Atlantic Ridge Hydrothermal Research
Team, 1990); and by the two MIR submersibles in the TAG area in 1988 (18
dives) (Zonenshain et al., 1989; Lisitsyn et al., 1989) and
in 1991 (six dives) (see P.A. Rona et al., this issue). Earlier versions of
most of the papers were presented orally in two sessions at the fall 1990
American Geophysical Union meeting (Rona and Thompson, 1990; Thompson and
Rona, 1990).
Rona, P.A., Y.A. Bogdanov, E.G. Gurvich, N.A. Rimski-Korsakov, A.M.
Sagalevich, and M.D. Hannington. Relict hydrothermal mounds at the TAG
hydrothermal field, Mid-Atlantic Ridge, 26°N, 45°W. Journal of
Geophysical Research, 98:9715-9730 (1993).
Two relict hydrothermal zones were delineated between water depths of 3,400
and 3,500 m at the lower part of the east wall of the rift valley of the
Mid-Atlantic Ridge in the TAG hydrothermal field using a deep-towed,
side-scan sonar tow and a camera-temperature tow along the northern 3 km of
the wall, and a submersible transect. Named the North and MIR relict zones,
they are located about 4 km and 2 km northeast, respectively, of the known
active high-temperature sulfide mound between water depths of 3,625 and
3,670 m on the rift valley floor near the base of the east wall. The North
zone extends about 2 km along the northern end of the lower east wall. The
zone includes two moundlike features up to 30 m high by 200 m in diameter
imaged by side-scan sonar within a 2-km-long line of discontinuous
hydrothermal deposits comprising inactive toppled and standing chimneys,
layered material, and patchy dark stains on sediment photographed by the
camera-temperature tow. Several other moundlike features were imaged with
the side-scan sonar outside of the photographic coverage. The MIR relict
hydrothermal zone 2 km south of the North zone, named after the MIR
submersible used to investigate it, consists of three subzones: (1) a
200-m-wide area of diverse types of hydrothermal materials exposed by normal
faulting at its western margin; (2) a 400-m-wide by 700-m-long central area
of discrete groups of toppled and standing inactive sulfide chimneys up to
25 m high on a substrate of red metalliferous sediment and carbonate lutite;
spires sampled on the highest chimneys are composed of coarse-grained,
recrystallized sulfides dominated by pyrite and chalcopyrite which contain
the first primary, free gold grains (2-3 µm diameter) found at a
hydrothermal site on a mid-ocean ridge; and (3) a 150-m-wide hummocky area
of layered hydrothermal material with the appearance of low temperature
precipitates and carbonate lutite with patchy dark stains at its eastern
margin. The active sulfide mound, the North zone, and the MIR zone are each
located on the fractured western margins of gentle, dome-shaped areas of
pillow flows typically 500 m in diameter interpreted as summits of volcanic
centers that may have supplied heat to drive adjacent hydrothermal activity.
The distribution and size of the active and inactive hydrothermal zones of
the TAG field, the chronology, and the characteristics of relict samples
recovered indicate a history of at least 100 x 103 years of
high-temperature hydrothermal episodes with multiple overprint stages of
mineralization accompanied by alteration.
Rona, P.A., M.D. Hannington, C.V. Raman, G. Thompson, M.K. Tivey, S.E.
Humphris, C. Lalou, and S. Peterson. Active and relict seafloor hydrothermal
mineralization at the TAG hydrothermal field, Mid-Atlantic Ridge.
Economic Geology, 88(8):1989-2017 (1993).
The TAG hydrothermal field is a site of major active and inactive
volcanic-hosted hydrothermal mineralization in the rift valley of the
slow-spreading Mid-Atlantic Ridge at 26°N. The TAG field occupies an
asymmetric area at least 5 km x 5 km of the floor and wall of the rift
valley between water depths of 2300 and 4000 m situated between 2 and 8 km
east of an axial high along the center of the spreading segment. The axial
high is the principal locus of present magmatic intrusions. The TAG field
contains three main areas of present and past hydrothermal activity: (1)
an actively venting high-temperature sulfide mound 200 m in diameter by 35
m high at a water depth of 3670 m on the floor of the rift valley near the
base of the east wall; (2) two former high-temperature vent areas known as
the MIR zone and the ALVIN zone containing multiple sulfide bodies that
are undergoing deformation and mass wasting during uplift on fault blocks
on the adjacent section of the lower east wall between water depths of
3400 m and 3600 m; and (3) a zone of low-temperature venting and
precipitation of Fe- and Mn-oxide deposits farther from the axial high and
higher on the east wall between water depths of 2300 m and 3100 m. The
active sulfide mound and the MIR and ALVIN zones are situated near the
margins of discrete volcanic centers. The volcanic centers occur at the
intersections between ridge axis-parallel normal faults and projected
axis-transverse transfer faults. The intersections of these active fault
systems may act as conduits both for magmatic intrusions from sources
beneath the axial high that build the volcanic centers and for
hydrothermal upwelling that taps the heat sources. Convective heat
transfer from a central black smoker vent complex (365°C; calculated
convective heat flux 225 ± 25 x 106W), white smoker vents
(<300°C), and widespread diffuse flow predominate on the active sulfide
mound. Values of conductive heat flow measured at the margins of the active
mound and the MIR zone appear to vary inversely with distance from adjacent
volcanic centers, supporting the inference that episodic intrusions at the centers
have driven hydrothermal circulation at the hydrothermal zones. A low in
magnetic intensity coincides with the entire TAG field. The low is modeled
as the combined effect of alteration pipes beneath the high-temperature
hydrothermal zones and thermal degmagnetization of a still hot but largely
solid intrusion beneath the axial high. Radiometric dating of sulfide
samples and manganese crusts in the hydrothermal zones and dating of
sediments intercalated with pillow lava flows in the volcanic center
adjacent to the active sulfide mound indicate multiple episodes of
hydrothermal activity throughout the field driven by heat supplied by
episodic intrusions over a period of at least 140 x 103 yr. The
sulfide deposits are built by juxtaposition and superposition during
relatively long residence times near episodic axial heat sources
counterbalanced by mass wasting in the tectonically active rift valley of
the slow-spreading oceanic ridge. Hydrothermal reworking of a relict
hydrothermal zone by high-temperature hydrothermal episodes has
recrystallized sulfides and concentrated the first visible primary gold
reported in a deposit at an oceanic ridge. Supergene reactions of older
sulfides with seawater produces secondary gold enrichment. Preservation of
the recrystallized sulfides is favored by silicification or an armoring of
oxides.
Rosenthal, S.L. Variability of the south Florida mean annual surface air
temperature during the last three decades. NOAA Technical Memorandum, ERL
AOML-77 (PB94-130721), 53 pp. (1993).
The oberved mean annual surface air temperature at Miami International
Airport (MIA) exceeded the 30-year (1961-1990) mean by 1.2 to 2.4 standard
deviations between 1989 and 1992. This was the result of a warming trend
that started in the late 1960s and accelerated sharply in the mid 1980s.
Unfortunately, the MIA surface temperature data cannot be taken at face
value. At times during these years, the site for measuring daily surface
maximum and minimum temperature was poorly positioned. There was a
significant relocation of the equipment in the late 1970s. There have been
three important changes of instrumentation from the original liquid in glass
extreme thermometers to a series of electronic hygrothermometers, culminating
in the installation of the less than ideal HO-83 in 1985. To determine the
impact of these activities, the MIA temperature data were compared with data
obtained at Palm Beach International Airport (PBI) and Page Field at Fort
Myers (FMY). The latter are the NWS first-order stations closest to MIA.
Comparisons were also made with data from nearby cooperative (COOP) stations
and with data from the FAA station at Fort Lauderdale International Airport
(FLL). Comparisons were also made with precipitation data from MIA, PBI and
FMY. At least part of the accelerated warming in the 1980s must be attributed
to a general south Florida warming during these years. However, MIA and PBI
warmed faster than their neighboring COOP stations during the late 1980s,
indicating that some artificial warming resulted from the HO-83 installations.
The MIA mean annual daily minimum temperatures show systematic fluctuations
but not a statistically-significant, long-term trend. These temperatures show
a sharp, temporally-local rise starting in the mid 1980s similar to the rise
found in the maximum temperatures which, therefore, provides support for the
contention that this warming event is, at least partially, a natural event
since previous investigators found no bias in the HO-83 minimum temperature
data. This conclusion is supported by the results of our precipitation
analyses. The MIA and FLL maximum temperatures both showed a warming trend
that started in the late 1980s, which lends support to the conclusion that
this trend is natural. The analyses support the contention that the MIA mean
annual daily minimum temperature warmed somewhat through the effects of
nearby jumbo jet operations and parking lot construction during the early
1970s. However, comparisons with other stations indicate that a general
natural warming process impacted south Florida during this period and that
the warming of MIA's mean annual daily minimum temperature was not entirely
a result of human activities. Regardless of the mechanisms that were
responsible, the trend ended abruptly in the early 1970s and these
temperatures thereafter fell to a new low point in the mid 1980s.
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.
Shapiro, L.J., and M.T. Montgomery. A three-dimensional balance theory for
rapidly rotating vortices. Preprints, 20th Conference on Hurricanes and
Tropical Meteorology, San Antonio, TX, May 10-14, 1993. American
Meteorological Society, Boston, J45-47 (1993).
No abstract.
Shapiro, L.J., and M.T. Montgomery. A three-dimensional balance theory for
rapidly rotating vortices. Journal of the Atmospheric Sciences,
50(19): 3322-3335 (1993).
A three-dimensional balance formulation for rapidly rotating vortices, such
as hurricanes, is presented. The asymmetric balance (AB) theory represents
a new mathematical framework for studying the slow evolution of rapidly
rotating fluid systems. The AB theory is valid for large Rossby numbers;
it makes no formal restriction on the magnitude of the divergence or
vertical advection, which need not be small. The AB is an ordered expansion
in the square of the ratio of orbital to inertial frequencies, the square of
a local Rossby number. The approximation filters gravity and inertial waves
from the system. Advantage is taken of the weak asymmetries near the vortex
core as well as the tendency for low azimuthal wavenumber asymmetries to
dominate. Linearization about a symmetric balanced vortex allows the
three-dimensional asymmetric dynamics to be deduced properly. The AB
formulation has a geopotential tendency equation with a three-dimensional
elliptic operator. The AB system has a uniformly valid continuation to
nonlinear quasigeostrophic theory in the environment. It includes the full
inertial dynamics of the vortex core, and reduces to Eliassen's formulation
for purely axisymmetric flow. It has a full set of conservation laws on
fluid parcels analogous to those for primitive equations, including
conservation of potential temperature, potential vorticity, three-dimensional
vorticity, and energy. A weakly nonlinear extension of the formulation in
the near-vortex region is presented. Appropriate physical applications for
the AB system, as well as its limitations, are discussed.
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.
Smith, S.M., J.N. McElroy, and G.L. Hitchcock. Chlorophyll-a and
phaeopigment concentrations in the Mississippi River plume and adjacent
shelf waters. NOAA Technical Memorandum, ERL AOML-74 (PB93-206407), 81 pp.
(1993).
The objective of this research project was to characterize the temporal and
spatial variability of phytoplankton biomass in the Mississippi River plume
and adjacent Louisiana shelf waters. Concentrations of chlorophyll-a
and phaeopigments were measured during three research cruises in this region
as part of NOAA's Nutrient Enhanced Coastal Ocean Productivity (NECOP)
program. The data include both surface and subsurface phytoplankton pigment
distributions during July 1990, March 1991, and May 1992.
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.
Tivey, M.A., P.A. Rona, and H. Schouten. Reduced crustal magnetization
beneath the active sulfide mound, TAG hydrothermal field, Mid-Atlantic Ridge
at 26&176;N. Earth and Planetary Science Letters, 115(1-4):101-115
(1993).
A detailed near-bottom magnetic field survey was carried out by the
submersible Alvin over the actively venting mound located within
the TAG (Trans-Atlantic Geotraverse) hydrothermal field on the Mid-Atlantic
Ridge at 26°08'N, 44°49'W. Three-dimensional analysis of these
data clearly shows a distinct zone of reduced magnetization directly beneath
the active mound. This magnetization low is consistent with the highly
altered upflow zone of a hydrothermal vent system that feeds the actively
venting mound structure. In contrast, the sea surface magnetic anomaly is
associated with a broad 2 x 8 km magnetization low elongated along the
axis, that includes both the active and inactive mounds. The short wavelength
(250 m), near-bottom magnetic anomaly over the active mound is far too small
to produce the long-wavelength (8 km) sea surface magnetic anomaly at TAG,
however, and even a collection of mounds with similar magnetic structure
cannot produce the magnetic moment needed to generate the sea surface
anomaly. Other hypotheses, including reversely-magnetized crust and
structurally-thinned crust, could account for the sea surface anomaly but
are considered unlikely. The existence of vigorous hydrothermal activity at
TAG and the lack of microseismic activity in the TAG area suggests that
thermal demagnetization is the prime contributor to the sea surface anomaly.
The thermal halo associated with a largely solid but still hot intrusion
would provide sufficient demagnetization on a kilometer scale to produce the
long-wavelength sea surface anomaly. Pervasive alteration at depth would
also be an important factor in the destruction of crustal magnetization and
is the only way that such a long wavelength magnetic signal could be
preserved in the crust. The overall model of crustal magnetization at a
hydrothermal field with discrete zones of demagnetization in the upper crust
and a broader zone of demagnetization at depth is consistent with studies of
hydrothermal systems in ophiolite suites. These studies show narrow
alteration pipes in the upper crust feeding the exhalative seafloor deposits
and pervasive alteration at depth which commonly have associated late-stage
intrusive bodies. While detailed magnetic surveys may provide some clues to
the location of oceanic hydrothermal upflow zones, only drilling will
ultimately test these hypotheses.
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
areequilibrated 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.
Washburn, L., M.S. Swenson, J.L. Largier, P.M. Kosro, and S.R. Ramp. Cross
shelf sediment transport by an anticyclonic eddy off northern California.
Science, 261(5128):1560-1564 (1993).
A combination of satellite imagery, shipboard profiles, drifter tracks, and
moored current observations reveals that an anticyclonic eddy off the coast
of northern California transported plumes of suspended sediments from the
continental shelf into the deep ocean. The horizontal scale of the eddy was
about 90 km, and the eddy remained over the continental shelf and slope for
about two months during the summer of 1988. The total mass of sediments
transported by the eddy was of order 100,000 metric tons. Mesoscale eddies
are recurrent features in this region and occur frequently in eastern
boundary currents. These results provide direct evidence that eddies export
sediments from continental shelves.
Wilde, P., and P.A. Rona. 29th International Geological Congress, Kyoto,
Japan, August 24-September 3, 1992. Scientific Information Bulletin,
18(2):95-105 (1993).
About 4,500 geologists and earth scientists from 85 countries, including
large contingents from the Commonwealth of Independent States and the
People's Republic of China, met in Japan for the 29th quadrennial meeting of
the International Geological Congress. A major theme was the requirement of
earth science involvement in identifying and handling not only resource
needs but also in dealing with environment concerns for public interest. Both
the end of the cold war, with its reunification of the global geological
community, and the general acceptance of plate tectonics as the major
terrestrial geological force made for a harmonious meeting more characterized
by historical summaries and evidence of broadening international cooperation
than by controversy or exciting new insights.
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, 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, J38-40 (1993).
No abstract.
Wilson, W.D., W.E. Johns, M.D. Hendry, and J.A. Routt. Windward Islands
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. (1993).
During 1991, a collaborative program between the U.S. and Barbados was
established with NOAA/CGC/ACCP support to conduct regular measurements of
the transport and water mass characteristics in the major southern passages
to the Caribbean. The program involves the use of a Barbados Coast Guard
vessel (the HMBS Trident) that makes routine (monthly) patrols in
this area, which has been equipped to collect standard hydrographic
measurements (CTD and water samples) and velocity profiles measurements
using a downward-looking ADCP. The purpose of the program is to determine
the quantity and time-variability of South Atlantic surface, thermocline,
and intermediate waters flowing into the North Atlantic in compensation
for southward cross-equatorial transport of North Atlantic Deep Water, and
to establish an economical means for future monitoring of this return
flow. The report contains data from cruise WI-91-01 conducted December
15-21, 1991.
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**
Asher, W.E., P.J. Farley, R.H.Wanninkhof, E.C. Monahan, and T.S.
Bates. Laboratory and field experiments on the correlation of fractional
area whitecap coverage with air/sea gas transport. In Precipitation
Scavenging and Atmosphere Surface Exchange, Volume 2, The Semonin Volume:
Atmosphere Surface Exchange Processes, S.E. Schwartz and W.G.N. Slinn
(eds.). Hemisphere Publishing Corporation, 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.
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.
Brown, B.E., W.A. Erb, and G.A. MAUL. Intra-Americas Sea Marine Science
Meeting of U.S. experts. NOAA Technical Memorandum, NMFS-SEFC-308, 125 pp.
(1992).
No abstract.
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.
Craynock, J.F., W.L. 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. 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 1900s. 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.
Elsberry, R.L., G.J. Holland, H. Gerrish, M. DeMaria, C.P. Guard, and K.
Emanuel. Is there any hope for tropical cyclone intensity prediction? -- A
panel discussion. Bulletin of the American Meteorological Society,
73(3):264-275 (1992).
The outlook for tropical cyclone intensity forecasts from operational and
research perspectives was discussed during a panel discussion at the 19th
Conference on Hurricanes and Tropical Meteorology. Whereas the operational
requirement at the National Hurricane Center is to predict maximum 1-min
sustained wind speeds at specific locations, the research community is
addressing the prediction of the maximum wind or minimum sea level pressure
in the storm. Commonality was found in the forecast strategies for
subjectively predicting storm intensity. The panelists suggested
improvements may be gained from additional observations, better conceptual
and theoretical models of storm structure and behavior, and enhancements in
statistical and numerical models. The discussion period brought out opposing
viewpoints on a number of topics. Both new observations and better use of
the existing observations were believed to be necessary. The limitations and
advantages of remotely sensed data for this problem were raised. The most
vigorous debates were on the physical processes, such as existence or
nonexistence of coupling between outer and inner core structure, and whether
convection is simply a response to forcing or is an essential contributor to
uncertainty in intensity forecasting. Several participants suggested that
uncertainties related to the sea surface temperature and its evolution also
contribute to the intensity forecast problem. Some specific suggestions for
improving intensity forecasts are given in terms of new observations, new
basic understandings, and new applied developments.
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(3):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.
Fiedler, P.C., F.P. Chavez, D.W. Behringer, and S.B. Reilly. Physical and
biological effects of Los Niños in the eastern tropical Pacific, 1986-1989.
Deep-Sea Research, Part I, 39(2):199-219 (1992).
The eastern tropical Pacific Ocean was surveyed in August-November 1986,
1987, 1988, and 1989 as part of a long-term program to monitor dolphin
stocks. Temperature, salinity, chlorophyll, and nutrients were monitored to
help interpret variability in dolphin stock estimates. The four surveys
reveal major environmental changes during the moderate 1987 El Niño and the
cold La Niña episode that followed in 1988. During the "onset" phase of El
Niño in fall 1986, surface temperatures were up to 1.5°C above normal
in equatorial water, but near normal in tropical water north of the equator.
The equatorial thermocline ridge was deepened by 10-30 m. During the
"mature" phase of El Niño in fall 1987, surface temperature anomalies were
up to +2.5°C in equatorial water and about +1°C in tropical water.
Thermocline topography was anomalously flat. Surface chlorophyll and nutrient
concentrations declined by 11-48% compared to 1986, with the greatest declines
occurring in coastal and equatorial upwelling systems and along the
countercurrent thermocline ridge. During La Niña in 1988, equatorial surface
temperatures were up to 2.5°C below normal and the equatorial thermocline
ridge was 10-50 m shallower than normal. Chlorophyll and nitrate
concentrations increased by 58-65% compared to 1987. In 1989, surface
temperature was within ±1°C of normal throughout the study area and
chlorophyll concentrations were similar to those observed in 1986. Changes
in nutrient availability and biological productivity during the El Niño/La
Niña cycle were caused by variations in both the rate of wind-driven
upwelling and in the nutrient content of subsurface water entrained by
upwelling.
Franklin, J.L., and M. DeMaria. The impact of Omega dropwindsonde
observations on barotropic hurricane track forecasts. Monthly Weather
Review, 120(3):381-391 (1992).
A scarcity of observations in the hurricane environment is one factor
believed to be limiting the improvement in hurricane track forecast accuracy.
Since 1982, the Hurricane Research Division (HRD) of the NOAA Atlantic
Oceanographic and Meteorological Laboratory has conducted 14 experiments to
determine the wind and thermodynamic fields within about 1000 km of tropical
cyclones in the Atlantic basin. During these synoptic-flow experiments,
Omega dropwindsondes (ODWs) are released from the two NOAA WP-3D research
aircraft over a 9-10 h period in the hurricane environment. The ODWs measure
pressure, temperature, humidity, and wind as they descend from flight level
(about 400 mb) to the surface. These data are then transmitted in real time
to the National Hurricane Center (NHC) and the National Meteorological Center
(NMC). Recently, a barotropic, nested, spectral hurricane track forecasting
model, VICBAR, has been developed at HRD and tested quasi-operationally
during the 1989 and 1990 hurricane seasons. Forecasts from this model have
compared favorably with other models run at NHC and NMC. In this study, the
VICBAR model is used to evaluate the impact of ODW data on track forecast
error for the 14 HRD synoptic-flow experiments. The ODW data produced highly
consistent reductions in track forecast errors in this sample of cases.
Forecast improvements due to single-level midtropospheric (aircraft) data
were significantly smaller than those due to the ODWs. At the important
verification times of 24-36 h (prior to landfall), when the decision to issue
a hurricane warning is being made, the ODWs reduced the model mean forecast
error by 12%-16%. These improvements, statistically significant at the 99%
level, are comparable to the total improvement in normalized NHC official
24 h forecast error occurring over the past 20-25 years.
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, 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, 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, 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.
Hitchcock, G., and T. Whitledge. Nutrient/pigment variability in the
Mississippi River plume and adjacent waters. Proceedings, NECOP Workshop
on Nutrient Enhanced Coastal Ocean Productivity, Chauvin, Louisiana,
October 2-3, 1991. Texas A&M University Press, College Station,
43-51 (1992).
The spatial distribution of salinity, temperature, pigments, and nutrients
was examined in the vicinity of the Mississippi River delta and contiguous
coastal waters in summer 1990 and spring 1991. The objectives were to document
spatial distributions by mapping parameters, and contrast these distributions
with temporal patterns near the mouth of Southwest Pass and to the west, near
hypoxic bottom waters. The temporal patterns are also compared to
observations taken while following a drifting surface instrument package
(with a sediment trap array). The mesoscale surface distributions in summer
1990 and spring 1991 show that localized regions of high nitrate exist west
of Southwest Pass. Additionally, a maximum in surface chlorophyll was
consistently southwest, or downplume, of the highest surface nitrate
concentrations. The surface salinity pattern, however, was not consistent
from summer to spring. In the summer observations, there was no coherent
pattern of low-salinity waters emanating from Southwest Pass; the position
of the low-salinity plume was too variable in time to derive a persistent
spatial pattern. This was supported by large variations (.10 psu in six hours) in surface salinity
while at a fixed position (28°55'N, 89°29'W) near the mouth of
Southwest Pass. Temporal variations in surface properties within the plume,
while following an instrumented surface drifter, show less variability in
surface properties in the Louisiana Bight. The observed time scales of the
plume and drifter motions suggest factors such as tides and inertial motions
are forcing mediating the variability in surface properties near Southwest
Pass.
Houze, R.A., 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.
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. Global temperature and sea level change. Physics and
Society, 21(5):6-8 (1992).
No abstract.
Maul, G.A. Temperature and sea level change. In Global Warming:
Physics and Facts, B.G. Levi, D. Hafemeister, and R.A. Scribner (eds.).
American Institute of Physics, New York, 78-112 (1992).
Instrumental measurements of air and sea temperature and of sea level are
rarely more than a century in length, and are characterized by numerous
observational inconsistencies. True "global" data sets do not exist, except
from satellite measurements during the last decade, primarily because most
of the 71% of Earth's surface covered by the oceans is not sampled. Surface
air-land temperature records are plagued by changes in measurement techniques,
location of thermometers, and microclimate changes, notably urbanization.
Surface marine air temperatures, too, are affected by changing ship design,
height of thermometers, and particularly, daytime biases. Sea surface
temperature data have similar difficulties, plus the added problems of
changed ship routes, and shifting from bucket to engine intake observations.
Sea levels from coastal tide gauges have notably shorter record-lengths than
temperature records, and often are dominated by diastrophism and subsidence
at the lowest frequencies. Determining statistically significant climatic
trends in any of these geophysical time series leads to uncertain results due
to natural variability such as El Niño-Southern Oscillation events.
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. In
Sea Level Changes: Determination and Effects, P.L. Woodworth, D.T.
Pugh, J.G. DeRonde, R.G. Warrick, and J. Hannah (eds.). Geophysical
Monograph Series, Volume 69, 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.
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., R.A. Fine, and E. Johns. The Deep Western Boundary Current
in the tropical North Atlantic Ocean. Deep-Sea Research, Part I,
39(11-12):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.
Murray, J.W., M.W. Leinen, R.A. Feely, J.R. Toggweiler, and R.H.
Wanninkhof. EqPac: A process study in the central equatorial Pacific.
Oceanography, 5(3):134-142 (1992).
EqPac is the United States-Joint Global Ocean Flux Study (US-JGOFS) process
study in the central equatorial Pacific. The first EqPac cruises sailed in
January 1992 during a moderately strong El Niño. This was fortuitous for our
studies of chemical and biological distributions because El Niño events are
difficult to predict, and the lead time for a project of this size is long.
There was virtually no previous upper-water-column chemical or biological
data for El Niño conditions in the central equatorial Pacific. Now an El Niño
has been studied in considerable detail, and it will be easy to sample the
extremes in environmental conditions by sampling non-El Niño conditions
(including La Niña) in 1993 and the years thereafter. The implementation of
EqPac illustrates how difficult it is to mount a large-scale interdisciplinary
study of the ocean when the interannual variability is large.
Peene, S.J., Y.P. Sheng, and S.H. Houston. Modeling tidal and wind-driven
circulation in Sarasota and Tampa Bays. Proceedings, International
Conference on Estuarine and Coastal Modeling, St. Petersburg, FL,
November 13-15, 1991. American Society of Civil Engineers, New York,
357-369 (1992).
As part of an effort to quantify the effects of hydrodynamics on water
quality within Sarasota Bay, Tampa Bay, and their adjoining waters, a field
and modeling study of circulation and transport is being conducted. This
paper presents some results from a simulation of barotropic circulation in
Tampa and Sarasota Bays during October 1990. Tropical Storm Marco passed
just west of the study area on October 11. At that time, NOAA was conducting
measurements of tides and currents at a number of stations in Tampa Bay, and
USGS had stations monitoring tides in Sarasota Bay. To simulate the
circulation, the recently enhanced CH3D model (Sheng, 1989), which was
originally developed for Chesapeake Bay, James River, and Lake Okeechobee,
was used. To allow sufficient lateral resolution in the vicinity of
shorelines and inlets, a boundary-fitted grid with a rather fine grid spacing
(between 200 and 1000 m) was generated for the region from Tampa Bay in the
north, south to Venice Inlet, and approximately 4 km into the Gulf of Mexico.
For the Tropical Storm Marco simulation, a wind field was generated by NOAA's
Hurricane Research Center using a two-dimensional least squares fitting
algorithm on surface and aircraft winds measured as the storm moved northward
along the Florida coast. Based on an objective comparison between simulated
and measured results, it is apparent that the model predicts the tidal and
wind-driven water surface elevation well, while the prediction of currents
is not as good due to the lack of resolution of the navigation channel in
the numerical grid.
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.
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.
Pszenny, A.A.P. Particle size distributions of methanesulfonate in the
tropical Pacific marine boundary layer. Journal of Atmospheric
Chemistry, 14(1-4):273-284 (1992).
Fourteen high-volume cascade impactor samples were collected during a
January-February 1990 research cruise in the tropical Pacific from Panama to
180°. Aqueous extracts of the samples were analyzed for methanesulfonate
(MSA), sulfate, and the seasalt tracer ion magnesium. The majority of
MSA-size distributions showed no pronounced maximum on submicrometer
particles, as has been observed elsewhere. Analysis of the data indicated
that MSA was distributed essentially uniformly with the effective surface
area of particles <0.5 µm in radius, which were primarily seasalt.
Relatively less MSA was found in smaller particles, which were primarily
sulfate. These results are consistent with those from theoretical and
laboratory experimental studies reported in the literature which suggest
that MSA produced from photochemical oxidation of dimethylsulfide condenses
on pre-existing particles in strong preference to nucleating into new
particles. This implies that MSA may not contribute appreciably to enhancing
cloud condensation nucleus populations in the remote tropical marine
atmosphere.
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.
Robinette, M., S.R. Piotrowicz, A.S. Artz, and T. Pizer. Meteorological
conditions over the South Atlantic Ocean during July and August of 1991.
NOAA Technical Memorandum, ERL AOML-70 (PB92-235738), 136 pp. (1992).
In the austral winter of 1991, the NOAA ship Malcolm Baldrige
conducted a research cruise in the South Atlantic Ocean investigating ozone,
carbon dioxide, and other related trace species which may be significant to
the earth's radiation balance. To better understand the environmental
conditions accompanying the acquired air samples, meteorological data were
collected on board ship using twice daily rawinsondes. The meteorological
data are presented using soundings and cross-sections along with synoptic
maps and back-trajectories developed during post-cruise analyses. The
synoptic maps illustrate the general meteorological conditions of the area
in terms of pressure distributions at mean sea-level while the
back-trajectories illustrate the flow of an air parcel due to the synoptic
conditions over the ten days prior to reaching the ship. Sounding data
obtained from rawinsonde launches on board ship present the vertical
structure of the atmosphere using four variables: temperature, relative
humidity, potential temperature, and wind. The cross-sections give an
overall view of the change in a parameter over a horizontal distance between
two points illustrating general outlines of the meteorological regimes
encountered.
Rona, P.A., and D.A. Trivett. Discrete and diffuse heat transfer at ASHES
vent field, Axial Volcano, Juan de Fuca Ridge. Earth and Planetary
Science Letters, 109(1-2):57-71 (1992).
Heat fluxes of discrete and diffuse components of hydrothermal discharge are
estimated from submersible measurements in the ASHES vent field located in
the caldera of Axial Volcano at the central Juan de Fuca Ridge. The discrete
component comprises discharge from individual vents and the diffuse component
comprises seepage from large areas of the seafloor. The investigation centered
on the high-temperature portion of the field, a 100 x 100 m area of fractured
lobate and sheet lava flows encompassing discrete discharge (<326°C)
from seven individual vents and diffuse flow from intervening areas. A total
of 4.4 ± 2 x 106W was estimated for the discrete heat flux based
on measurements of effluent temperature, flow rate, and orifice diameter at
all the known individual vents by DSV ALVIN in September 1987. A total of
15-75 x 106W was calculated with a standard plume model for the
diffuse flux based on a grid of temperature measurements at altitudes of 1 m
and 20 m above the study area using a 1 m long vertical array of temperature
sensors mounted at the front of DSV ALVIN's instrument platform. The study
indicates that: (1) the diffuse component rises separately from the discrete
component of hydrothermal discharge and is laterally advected by a prevailing
current below the discrete component; and (2) the diffuse component of
convective heat flux is approximately an order of magnitude greater than the
discrete component in the high-temperature portion of the ASHES vent field.
Rona, P.A., P.J. Meis, C.A. Beaverson, R.W. Embley, and C.G. Fox. Geologic
setting of hydrothermal activity at the northern Gorda Ridge. Marine
Geology, 106(3-4):189-201 (1992).
The northern end of the rift valley of the Gorda Ridge was investigated with
Sea Beam bathymetry, SeaMARC IA and II side-scan sonar, surface-towed
magnetics, and near-bottom, camera-temperature tows to determine the geologic
setting of large chemical anomalies in the water column indicative of intense
hydrothermal discharge comparable to anomalies associated with the Sea Cliff
hydrothermal field situated on the east wall of the rift valley 25 km to the
south. Water column and seafloor hydrothermal indicators and tectonic trends
converge on a seamount at 42°57.3'N, 126°33.0'W on a terrace 4.5
km east of the rift valley axis as the most likely source area for the
hydrothermal discharge. Comparison with the geologic setting of the Sea
Cliff hydrothermal field confirms the presence of an anomalous axis-oblique
tectonic trend that permeates the structure of the northern Gorda Ridge.
Additional sinistral offset along an axis-perpendicular structural trend at
the Sea Cliff field indicates a southward increase in deformation of the
northern Gorda Ridge along axis-transverse trends.
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.
Shapiro, L.J. Hurricane vortex motion and evolution in a three-layer model.
Journal of the Atmospheric Sciences, 9(2):140-153 (1992).
A three-layer, multinested numerical model is used to evaluate the asymmetric
evolution of a hurricane and its interaction with the large-scale environment.
The model uses a compressible fluid in isentropic coordinates. In 72 h the
hurricane vortex on a beta plane moves northwest at an average speed of 2.4 m
s-1. In the presence of a westerly zonal wind in the upper model
layer, the hurricane on an f plane moves to the southeast at an
average speed of 0.9 m s-1. A series of experiments establishes
that the southeastward drift in the presence of westerly shear is primarily
due to the southward isentropic gradient of background potential vorticity
(PV) in the middle model layer that is associated with the background
temperature field. The cyclonic circulation advects low PV air southward on
the west side of the vortex, inducing a negative isentropic PV anomaly to the
southwest. This anomaly is associated with a wind field that advects the
vortex to the southeast, just as the northward isentropic gradient of PV due
to the beta effect advects the hurricane to the northwest. The northward
gradient of background PV in the upper layer has little effect on the motion.
The westerly wind advects upper layer low PV outside the vortex core to the
east, inducing an anticyclonic anomaly that tends to advect the middle-layer
vortex to the north; this tendency is secondary to the motion. The role of
vertical transports of momentum due to cumulus convection on the hurricane
motion is also evaluated. Results are presented that generalize the
homogenization of asymmetric absolute vortex and oscillation in relative
angular momentum (RAM) found on the beta plane in a previous study with a
barotropic model. Outside the vortex core and within ~350 km of the
center, the asymmetries reach a near-steady state. The middle-layer
asymmetry is associated with a PV gradient that neutralizes the background
gradient due to planetary vortex or environmental temperature, thereby
insulating the symmetric vortex from distortion. Horizontal fluxes in the
presence of the planetary vortex gradient tend to counteract the development
of strong anticyclonic total RAM within a large circle about the vortex center.
Snyder, R.L., L.M. Lawson, and R.B. Long. Inverse modeling of the
action-balance equation. Part I: Source expansion and adjoint-model
equations. Journal of Physical Oceanography, 22(12):1540-1555
(1992).
In this paper a series of numerical experiments is defined to explore the
inverse modeling of the action-balance equation governing the evolution of
the surface gravity wave field, using the adjoint data-assimilation
model-optimization procedure of Thacker and Long. We begin by exploiting
power series, functional power series, and a variety of physical and
mathematical considerations to derive a systematic expansion of the source
terms in this equation for the deep-water case. This expansion, which
naturally incorporates a Thacker representation for the nonlinear transfer
from wave-wave interaction, defines a set of dimensionless expansion
coefficients to be determined by the inverse modeling and identifies the
simplified cases to be investigated in the numerical experiments. Dimensional
analysis determines a natural scaling for each term in this expansion and
suggests a general form for the whitecap dissipation term, which includes as
a special case the form proposed by Hasselmann, determining the first-order
contribution to his unknown spectrum-dependent coefficient to within a
multiplicative spectrum-independent constant. A general discussion of the
evolution of the simplified cases reveals a striking tendency to concentrate
action in a single band when whitecap dissipation has the Hasselmann form and
nonlinear transfer is ignored. A derivation of the adjoint-model equations is
included for one of the simplified cases and a general discussion of the
model-optimization procedure is given. In these equations, nonlinear transfer
is mirrored by a term of similar form, with Thacker's nonlinear transfer
coefficients replaced by a related set of adjoint coefficients and the
triple product of spectral intensities replaced by a product of two spectral
intensities and a Lagrange multiplier.
Springer-Young, M., S.R. Piotrowicz, and G.R. Harvey. Impact of an episodic
event on copper and zinc concentrations and speciation in surface waters of
the Gulf of Mexico. Deep-Sea Research, Part I, 39(6):953-964 (1992).
Electrochemical and chelation/extraction trace metal techniques are used to
develop an understanding of changes in copper and zinc concentrations and
speciation associated with a hydrographic and atmospheric event which
occurred during an eight-day station in the Gulf of Mexico. Changes in
copper and zinc concentrations and speciation coincided with physical
changes and biological productivity simulation. In normally oligotrophic
water masses it is possible that episodic events, such as inputs from
beneath the mixed layer or aeolian transport, may impact the interaction of
trace metals and marine biological processes.
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(1-2):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, and K. Bryan. Computing the steady oceanic
circulation using an optimization approach. Dynamics of Atmospheres and
Oceans, 16(5):379-403 (1992).
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.
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.
Velden, C.S., C.M. Hayden, W.P. Menzel, J.L. Franklin, and J.S. Lynch. The
impact of satellite-derived winds on numerical hurricane track forecasting.
Weather and Forecasting, 7(1):107-118 (1992).
While qualitative information from meteorological satellites has long been
recognized as critical for monitoring tropical cyclone activity, quantitative
data are required to improve the objective analysis and numerical weather
prediction of these events. In this paper, results are presented that show
that the inclusion of high-density, multispectral, satellite-derived
information into the analysis of tropical cyclone environmental wind fields
can effectively reduce the error of objective track forecasts. Two
independent analysis and barotropic track-forecast systems are utilized in
order to examine the consistency of the results. Both systems yield a 10%-23%
reduction in middle- to long-range track-forecast errors with the inclusion
of the satellite-wind observations.
Wanninkhof, R.H. Relationship between gas exchange and wind speed over the
ocean. Journal of Geophysical Research,97(5):7373-7382 (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.
Wooldridge, A.L., C.G.A. Harrison, M.A. Tivey, P.A. Rona, and H.
Schouten. Magnetic modeling near selected areas of hydrothermal activity
on the Mid-Atlantic and Gorda Ridges. Journal of Geophysical
Research, 97:10,911-10,926 (1992).
Sea surface magnetic and bathymetric data from two areas of observed
high-temperature hydrothermal activity in the Atlantic (trans-Atlantic
geotraverse, or TAG hydrothermal field) and Pacific (Sea Cliff hydrothermal
field) and two areas of inferred hydrothermal activity in the Atlantic
(Mid-Atlantic Ridge [MAR] at 15°N and 17°N) were studied to
determine the effect of vent activity on magnetization of the oceanic crust.
All of the sites examined show a low in the magnetic anomaly in varying
degrees. Magnetization lows within the axial marine magnetic anomaly have
been associated with some areas of active and relict high-temperature
hydrothermal venting. A three-dimensional magnetic inversion was performed
on magnetic and bathymetric data from the TAG hydrothermal area on the
Mid-Atlantic Ridge (26°N), and two-dimensional magnetic inversions were
done on individual profiles from the other study sites. The map from the TAG
area shows a "negative" in the crustal magnetization solution just to the
east of the median valley axis which encompasses the active hydrothermal
area. A low in magnetization continues up the eastern wall which suggests
alteration of the crust. A distinct low in magnetization is present within
the axial anomaly at the Sea Cliff hydrothermal field located on the eastern
wall of the Gorda Ridge. The magnetization low becomes less pronounced
farther south of the known vent field. Profiles from 15°N and
17°N on the Mid-Atlantic Ridge show magnetization lows over areas of
inferred hydrothermal activity. These lows are present over the eastern and
western walls of the median valley, respectively. The lows observed in the
axial marine magnetic anomaly in these four study sites all occur slightly
off axis, on crust that is at least 200,000 years old on the Mid-Atlantic
Ridge and at least 100,000 years old on the Gorda Ridge. On the basis of
magnetic modeling and measurements of rock magnetic properties, the most
probable cause of the low in the magnetization is alteration of the oceanic
crust with other subsidiary contributing factors which vary from site to
site. The magnetization low over TAG is most probably due to high-temperature
hydrothermal alteration of the crust and a thinner layer 2, with possible
contributions from reversal events and magma chamber/Curie isotherm effects.
The low near the Sea Cliff hydrothermal field on the Gorda Ridge is probably
the product of tectonically-controlled, low-temperature (non-hydrothermal)
alteration, high-temperature hydrothermal alteration, and magnetic reversal
events. At 15°N and 17°N on the MAR, the lows may be produced by
alteration of the crust due to possible hydrothermal activity.
**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.
Baik, J.-J., M. DeMaria, and S. Raman. Tropical cyclone simulations with the
Betts convective adjustment scheme. Part III: Comparisons with the Kuo
parameterization. Monthly Weather Review, 119(12):2889-2899 (1991).
Numerical simulations of tropical cyclones in an axisymmetric model with the
Betts convective adjustment scheme and the 1974 Kuo cumulus parameterization
are compared. It is shown that the storm with the Betts scheme has a slightly
more intense mature stage than the storm with the Kuo scheme. For both
schemes, the parameterized heating is dominant initially, while the
grid-scale heating is dominant at the mature stage. The storms begin to
intensify rapidly when the grid-scale heating extends through a deep layer.
The Betts scheme is more effective at removing water vapor and delays the
onset of grid-scale heating. This results in later development of the storm
with the Betts scheme. The storm evolution with both the Betts and Kuo
schemes is sensitive to the treatment of the evaporation of liquid water in
the grid-scale condensation scheme. This suggests that a prognostic equation
for liquid water should be used when simulating tropical cyclones with a model
resolution fine enough for grid-scale heating to be important.
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.
Chew, F., and M.H. Bushnell. Geostrophic departure, local turning, speed
change, and eddy flux: A new perspective. Journal of Physical
Oceanography, 21(11):1684-1689 (1991).
Conjunctions of meander passages and cross-stream eddy momentum fluxes are
common in western boundary currents. To explore the mechanism linking them,
we offer a diagnostic equation of their time-dependent motions. The equation
is embodied in the more explicit form of a hodograph with two characteristics:
a tilt and a veering/backing. The veering/backing is in response to the
changing geostrophic departure, and the tilt to the change in the speed of
the flow, which can be zero, positive, or negative. This direct approach to
the kinematic fieldits pattern and its changeled to a hypothesis on the
linkage that the cross-stream eddy momentum flux is driven by the downstream
pressure gradient force in the supergeostrophic segment of the meandering
flow.
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(12):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.
Franklin, J.L., and M. DeMaria. The impact of Omega dropwindsonde data on
hurricane track forecasts using the VICBAR model. Preprints, 9th
Conference on Numerical Weather Prediction, Denver, CO, October 14-18,
1991. American Meteorological Society, Boston, 404-407 (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.
Hannington, M., P. Herzig, S. Scott, G. Thompson, and P.A. Rona. Comparative
mineralogy and geochemistry of gold-bearing sulfide deposits on the mid-ocean
ridges. Marine Geology, 101(1-4):217-248 (1991).
A comparative study of the mineralogy and geochemistry of sulfide deposits on
mid-ocean ridges in the northeast Pacific and the Mid-Atlantic reveals common
characteristics associated with primary gold enrichment. Average gold
contents of 0.8 to 5 ppm Au occur in sulfides from Southern Explorer Ridge
and Axial Seamount (northeast Pacific) and from the TAG hydrothermal field
and Snakepit vent field (Mid-Atlantic Ridge). The enrichment of gold in
these deposits is consistently related to a phase of late-stage,
low-temperature (<300°C) venting. Concentrations >1 ppm Au occur
exclusively in pyritic assemblages and commonly with abundant Fe-poor
sphalerite and a suite of complex Pb-Sb-As sulfosalts. Amorphous silica and,
locally, barite or carbonate, are important constituents of the gold-rich
precipitates, but do not contain gold themselves. High-temperature
(350°C), black-smoker assemblages, consisting dominantly of pyrite,
chalcopyrite, pyrrhotite, isocubanite, and abundant anhydrite, are uniformly
gold-poor (<0.2 ppm Au). To the extent that individual sulfides can be
mechanically separated, chemical analyses by neutron activation indicate that
gold is most abundant in sphalerite (up to 5.7 ppm Au), but also occurs in
pyrite and marcasite. Samples of sphalerite with abundant inclusions of
fine-grained sulfosalts locally contain up to 18 ppm Au, suggesting that the
sulfosalts may be the repositories for gold. No free gold has been observed
at 4,000 x magnification of polished specimens, indicating that the gold is
present only as submicroscopic inclusions or as a chemical constituent within
the sulfides. Samples from gold-rich deposits in the northeast Pacific and
Mid-Atlantic are compared with similar but relatively gold-poor sulfides from
the Galapagos Rift and 13°N on the East Pacific Rise (EPR), and with
barren sulfides from 11°N EPR, 21°N EPR, the Endeavour Ridge,
and the Southern Juan de Fuca Ridge. Trace element analyses of more than
170 samples show that gold enrichment in almost all of the deposits is
associated with high concentrations of Ag, As, Sb, Pb, and Zn, and locally
with high Cd, Hg, Tl, and Ga. In contrast, gold is typically depleted in
samples with high Co, Se, and Mo. The close association of Au with Ag, As,
Sb, and Pb may reflect the common behavior of these metals as aqueous sulfur
complexes (e.g., [Au(HS)2-]) at low temperatures. Similar
mineralogical and geochemical associations are observed in sulfide deposits
from modern back-arc settings and in the ancient geologic record.
Hanson, K., and G.A. Maul. Florida precipitation and the Pacific El Niño,
1895-1989. Florida Scientist, 54(3/4):160-168 (1991).
This study identifies rainfall anomalies, timed with major El Niño events,
in seven climatic divisions of Florida. The study also determines the
statistical significance of these rainfall anomalies. The seasonal and
annual climatology of rainfall is presented for seven climatic divisions of
the State for the period 1895-1989. Periodogram analysis indicates five- to
six-year variability in rainfall throughout most of Florida, in particular,
during winter and spring. Superposed epoch analysis, utilizing only rainfall
during the year prior to and concurrent with a major El Niño, shows that
Statewide rainfall anomalies are timed with these Pacific events. The most
significant anomalies are: (1) below normal rainfall over all of the State
during winter and spring the year prior to an El Niño; and (2) above normal
rainfall over all of the State during winter and spring the second year of
an El Niño. Largest rainfall anomalies have occurred in the southern
climatic divisions of Florida. During winters of the second year of El Niño,
south Florida rainfall anomalies range from +76 to +94 mm (+3.0 to + 3.7
inches) depending on the climatic division. These anomalies are 45% to 66%
above normal winter rainfall, and are significant at the 0.999 level.
Herzig, P.M., M.D. Hannington, S.D. Scott, G. Maliotis, P.A. Rona, and G.
Thompson. Gold-rich seafloor gossans in the Troodos ophiolite and on the
Mid-Atlantic Ridge. Economic Geology, 86:1747-1755 (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.
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.
Moody, J.L., A.A.P. Pszenny, A. Gaudry, W.C. Keene, J.N. Galloway, and G.
Polian. Precipitation composition and its variability in the Southern
Indian Ocean: Amsterdam Island, 1980-1987. Journal of Geophysical
Research, 96(D11):20,769-20,786 (1991).
Event precipitation samples have been collected on Amsterdam Island
(37°47'S, 77°31'E) from May 1980 through January 1987 and
analyzed for SO4=, NO3-, C
Gamma , Na+, Mg++, K+, Ca++,
H+, HCOOt, and CH3COOt. The
objective of this paper is to assess the processes which influence
variability in the chemical composition of precipitation at this remote
marine site. Back trajectories and gas phase 222Rn measurements
were used to identify source regions and their relative contributions to
precipitation composition. The technique of cluster analysis was applied
to trajectory data as a method for determining to what degree different
atmospheric flow patterns influence variability in the observed composition.
The dominant source regions for chemical deposition were found to be
Madagascar and/or southeast Africa and the ocean region north and east of
Amsterdam Island. A strong seasonal signal in the precipitation composition
is illustrated. Processes which influence variability in the chemical
composition include the following: seasonality in the source strength of
biogenic precursors for non-sea-salt (nss) SO4=,
NH4+ and carboxylic acids; seasonality in
biomass-burning continental sources for the concentration of
NO3- and a portion of nss C Gamma; and variations
in source region driven by daily changes in meteorology, as well as seasonal
and annual differences in transport and removal patterns. In addition,
interannual differences in nss SO4= concentration
appear to be related to fluctuations in large-scale circulation patterns
as defined by the Southern Oscillation.
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(1-4):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.
Rona, P.A. Frontier of seafloor hydrothermal research. Proceedings, 11th
Meeting of U.S.-Japan Cooperative Program in Natural Resources, Tokyo,
Japan, September 26-27, 1991. Japan Science and Technology Agency,
325-345 (1991).
The back-arc basins in marginal seas behind volcanic island chains of the
central and western Pacific Ocean are at the frontier of new discoveries of
seafloor hydrothermal activity. Knowledge of the chemistry, physics, and
biology of the hydrothermal sites in these basins is essential to achieve a
global understanding of the role of seafloor hydrothermal processes in the
ocean environment, climate change, mineralization, and biologic adaptation.
Research approaches similar to those being utilized in investigations of
hydrothermal systems at oceanic ridges are needed to develop complementary
knowledge of hydrothermal systems in back-arc basins. These investigations
include solution chemistry, ore-forming processes, magnetic signatures of
hydrothermal activity, conductive and convective heat transfer, hydrothermal
plume behavior, and vent biota.
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.
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, 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.
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.
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. Journal of
Physical Oceanography, 19(10):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.
Dagg, M.J., P.B. Ortner, and F. Al-Yamani. Wintertime distribution and
abundance of copepod nauplii in the northern Gulf of Mexico. Fishery
Bulletin, 86(2):319-330 (1988).
No abstract.
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**
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.
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 ± 7, -91 ± 17 and -48 ± 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.
International Conference
on Marine Science in the Arabian Sea, M.F. Thompson and G.B. Dewey
(eds.), March 29-April 2, 1986. Van Nostrand Reinhold, pp. 67-77 (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.
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.