**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 dev