**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).
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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).
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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).
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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).
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No abstract.
Forde, E.B. Severe weather. The Science Teacher, 71(4):42-44 (2004).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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No abstract.
Marks, F.D. Hurricanes. In Encyclopedia of Atmospheric Sciences, Elsevier Science Ltd., London, UK, 942-966 (2003).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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No abstract.
Aberson, S.D. Two years of operational hurricane synoptic surveillance. Weather and Forecasting, 17(5):1101-1110 (2002).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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No abstract.
Katsaros, K.B. Hurricane research inside the storm. Atmosphériques, 13:22-23 (2002).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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No abstract.
Enfield, D.B. Changes in sea surface temperatures influence rain patterns. Environmental Review, 8(11):1-8 (2001).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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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).
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The U.S. Weather Research Program identified landfalling tropical cyclones as a major focus for research in the coming years. In 1998, the Hurricane Research Division (HRD) of NOAA's Atlantic Oceanographic and Meteorological Laboratory coordinated experiments with other agencies and university groups in Hurricanes Bonnie, Earl, and Georges. On these flights, airborne Doppler radar data were collected to combine with WSR-88D radar data in three-dimensional analyses to document evolution of tropical cyclones as they make landfall, and to provide data for testing WSR-88D tropical cyclone algorithms. Hurricane Bonnie made landfall in near Wilmington, North Carolina as a Category 2 hurricane on 26 August. There were two HRD missions near the time of landfall. The first flight concentrated on examining the structure of the spiral rainbands and the second flight surveyed the hurricane as it interacted with the coast. During the flights, there was a vigourous rainband ~180 km northeast of the center with several mesocyclones (as identified on the Morehead City WSR-88D) that later produced confirmed tornadoes on land. Both NOAA aircraft had to deviate around strong cells in this band, between 1540 and 1830 UTC, and those deviations resulted in small Doppler analysis boxes enclosing some of the mesocyclones. A companion paper (Spratt et al.) uses dropsondes and adjacent radiosondes to describe the local environment in which the Bonnie mesocylones were embedded, and in this paper we will present windfield analyses, from combining WSR-88D and airborne Doppler radar data, that provide the three dimensional structure of the mesocyclones. The Doppler data are too coarse to resolve actual tornadoes, but the parent mesoscale circulations are clearly resolved.
Dunion, J.P., S.H. Houston, M.D. Powell, C.S. Velden, and P.G. Black. Using surface adjusted GOES low-level cloud-drift winds to improve the estimation of tropical cyclone outer wind radii. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 488-489 (2000).
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No abstract.
Enfield, D.B., and A.M. Mestas-Nunez. Global modes of ENSO and non-ENSO SST variability and their associations with climate. In: El Niño and the Southern Oscillation: Multiscale Variability and Global and Regional Impacts, H.F. Diaz and V. Markgraf (eds.). Cambridge University Press (ISBN 0521621380), 89-112 (2000).
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In this chapter we review much of the recent work by others regarding the nature of the global modes of sea surface temperature (SST) variability and the SST involvement in interannual to multidecadal climate variability. We also perform our own analysis of global SST so as to describe and separate the SST variability associated with El Niño-Southern Oscillation (ENSO) from the low-frequency modes not associated with ENSO (non-ENSO). ENSO is a global phenomenon with significant phase propagation between basins, which we preserve and describe using complex empirical orthogonal function (CEOF) analysis, and subsequently remove from the global SST data. A second CEOF analysis of the residuals reveals three non-ENSO modes of low-frequency variability that are identified with and related to signals described in the reviewed literature: (1) a secular trend representing the global warming signal with associated superimposed decadal variability; (2) an interdecadal mode with maximal realization in the extratropical North Pacific; and (3) a multidecadal mode with maximal realization in the extratropical North Atlantic. Regression- and SVD-based analyses of the relationships between the SST data and a high-quality precipitation data set demonstrate for the interannual-to-decadal time scales of the western hemisphere tropics that (a) tropical Atlantic SSTA is comparable to the Pacific ENSO in its relevance to regional rainfall and is not redundant with respect to ENSO; and (b) non-ENSO variability explains a significant fraction of the total covariance between the two variables. We are led to conclude that present operational climate predictions can be significantly improved by extending numerical SST predictions from the Pacific to the world ocean and by enabling these models to emulate the observed non-ENSO modes of global variability.
Enfield, D.B., and A.M. Mestas-Nunez. Tropospheric direct circulations associated with the climatic components of SST variability in the equatorial Pacific. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, J49-J50 (2000).
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No abstract.
Esenkov, O.E. A numerical study of the dynamics of the Somali Current system. Ph.D. Thesis, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 140 pp. (2000).
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The evolution of surface circulation, salinity budget, and processes at intermediate depth in the northwestern Indian Ocean were studied with the open boundary version of the Miami Isopycnic Coordinate Ocean Model (MICOM). Under climatological wind and thermodynamic forcing, the model develops solutions that are in good agreement with global MICOM results and with observations. When the observed winds (Legler et al., 1989) force the model, interannual variability of the surface fields increases significantly. However, coalescence of the two large eddies in the end of the summer monsoon, which was observed in some years, does not occur in the model. To identify what processes facilitate the merger, a series of experiments was performed with modified model parameters and forcing fields. The eddies coalesced when half-slip, rather than no-slip, boundary conditions were used. In this case, less positive vorticity was produced at the coast, resulting in a reduced blocking effect on the propagation of the southern eddy. Socotra Island, which is submerged in the standard model, hinders movement of the northern anticyclone, leading to stronger interaction between the eddies and their subsequent merging. A more realistic coalescence occurs in an experiment where winds are held constant after reaching the peak summer value. Freshwater fluxes from the east and south were previously considered important for the salinity budget in the Arabian Sea, where evaporation exceeds precipitation; however, the model demonstrated that only cross-equatorial transport of low-salinity water in the upper 400 m is essential. About 86% of this water is advected below the surface layer at the western boundary. The strongest interaction between the mixed layer and the oceanic interior occurs during the summer in the coastal upwelling regions off Somalia. Forty-three percent of all upwelled water comes from depths between 100 m and 200 m, thus signifying the importance of mid-depth circulation and water mass distribution for the surface processes. Both observations and model solutions demonstrate strong annual cycle and alongshore variability of coastal subsurface circulation. A cross-equatorial northward flow below the surface, which exists throughout the year, is disconnected from currents farther north. A southward undercurrent north of 5°N is present during the winter monsoon. Water for the current is supplied by flows from the north and northeast. The former originates in the Persian Gulf and carries higher-salinity water, while the latter contribution is mainly from the Gulf of Aden. Separation of the southward undercurrent near 4°N is not caused by its interaction with a topographical ridge, as was previously suggested. Agreement with the observations north of 5°N improves when Socotra Island is present in the model.
Feuer, S.E., M.L. Black, and J.L. Franklin. The asymmetric wind structure of tropical cyclones in various shear environments. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 450-451 (2000).
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No abstract.
Ffield, A., K. Vranes, A.L. Gordon, R.D. Susanto, and S.L. Garzoli. Temperature variability within the Makassar Strait. Geophysical Research Letters, 27(2):237-240 (2000).
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Recent mooring observations of ocean temperature provide the first high-resolution, long-term record of temperature variability in the Makassar Strait of the Indonesian Seas. The mooring observation span the entire cycle of the strong 1997/1998 El Niño. A high correlation (r = 0.67) is found between variability in the average thermocline temperature, to variability in the southward Makassar volume transport: during high (low) volume transport, the average temperature of the thermocline is also high (low). In addition, from nearly 15 years of XBT data, the Makassar thermocline temperature is shown to be highly correlated (r = 0.77) to SOI. This reveals that the Makassar temperature field, when coupled with the throughflow, transmits the equatorial Pacific El Niño and La Niña temperature fluctuations into the Indian Ocean. The ENSO variability in the internal energy transport is calculated: 0.63 PW during the La Niña months of December 1996 through February 1997, and 0.39 PW during the El Niño months of December 1997 through February 1998.
Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D. Fratantoni, P. Richardson, and G.J. Goni. CTD/O2, LADCP, and XBT measurements collected aboard the R/V Seward Johnson, February-March 1999: North Brazil Current Rings Experiment, cruise 2 (NBC-2). NOAA Data Report, OAR-AOML-37, 291 pp. (2000).
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Summaries of conductivity-temperature-depth (CTD/O2), lowered acoustic Doppler current profiler (LADCP), and expendable bathythermograph (XBT) measurements and hydrographic data acquired on an oceanographic research cruise during the winter of 1999 aboard the Harbor Branch Oceanographic Institution ship R/V Seward Johnson are presented. Data acquisition and processing systems are described, and calibration procedures are documented. Station location, CTD/O2, LADCP, XBT summary data listings, and profiles are included for each station.
Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D. Fratantoni, P. Richardson, and G.J. Goni. CTD/O2, LADCP, and XBT measurements collected aboard the R/V Seward Johnson, February-March 2000: North Brazil Current Rings Experiment, cruise 3 (NBC-3). NOAA Data Report, OAR-AOML-38 (PB2001-100486), 258 pp. (2000).
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Summaries of conductivity-temperature-depth (CTD)/O2, lowered acoustic Doppler current profiler (LADCP) measurements, and hydrographic data acquired on an oceanographic research cruise during the winter of 2000 aboard the Harbor Branch Oceanographic Institution ship R/V Seward Johnson are presented. Data acquisition and processing systems are described, and calibration procedures are documented. Station location, CTD/O2, LADCP summary data listings, and profiles are included for each station.
Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D. Fratantoni, P. Richardson, and G.J. Goni. CTD/O2, LADCP, and XBT measurements collected aboard the R/V Seward Johnson, November-December 1998: North Brazil Current Rings Experiment, cruise 1 (NBC-1). NOAA Data Report, OAR-AOML-39 (PB2001-101653), 274 pp. (2000).
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Summaries of conductivity-temperature-depth (CTD/O2), lowered acoustic Doppler current profiler (LADCP), expendable bathythermograph (XBT) measurements, and hydrographic data acquired on an oceanographic research cruise during the fall of 1998 aboard the Harbor Branch Oceanographic Institution ship R/V Seaward Johnson are presented. Data acquisition and processing systems are described, and calibration procedures are documented. Station location, CTD/O2, LADCP, XBT summary data listings, and profiles are included for each station.
Franklin, J.L., M.L. Black, and K. Valde. Eyewall wind profiles in hurricanes determined by GPS dropwindsondes. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 446-447 (2000).
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No abstract.
Gamache, J.F., M.L. Black, and H.E. Willoughby. Radial variation of azimuthally averaged flow across the hurricane core as observed with airborne Doppler radar. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 416-417 (2000).
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No abstract.
Garzoli, S.L., and G.J. Goni. Combining altimeter observations and oceanographic data for ocean circulation and climate studies. In Satellites, Oceanography, and Society, D. Halpern (ed.). Elsevier Oceanographic Series (ISBN 0444505016), 63, 79-95 (2000).
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Calibrating Topography Experiment (TOPEX)/Poseidon (T/P) altimeter data to inverted echo sounder measurements is one of the methodologies developed to advance the study of the South Atlantic Ocean. The mass transport of the main boundary currents can be monitored using dynamic height time series obtained from altimeter-derived sea surface height anomalies. A two-layer model yields upper-layer thickness and surface dynamic height of the ocean in areas of strong vertical stratification to identify and track anticyclonic rings, such as those shed from the Agulhas retroflection, which play an important role in the interocean exchange of heat and mass. Interannual variability of boundary currents, derived from analysis of the first five years of T/P data, is discussed. A combination of T/P data and in-situ observations provides significant contributions to the study of ocean dynamics for climate applications.
Godin, O.A., D. Yu Mikhin, and D.R. Palmer. Monitoring of ocean currents in the coastal zone. Izvestiya Atmospheric and Oceanic Physics, 36(1):131-142 (2000).
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A method proposed recently for remote monitoring of currents in coastal regions of the ocean is discussed and compared to alternative approaches. The new method, which is referred to as the method of matched nonreciprocity (MMN), represents further development of conventional acoustic tomography of currents as applied to shallow-sea conditions. In measurements of currents, low-frequency acoustic waves are employed as sounding signals. The MMN makes it possible to obtain real-time current charts in a region extending horizontally to tens or hundreds of kilometers and covering the whole depth of the water from the surface of the ocean to its bottom. Such charts are important in solving major scientific problems, in particular, monitoring of climate changes and verification of global-circulation models. It is shown that the MMN is free of limitations inherent in the monitoring methods proposed previously. The MMN is based on recent advances in the theory and mathematical modeling of acoustic propagation in inhomogeneous moving media and also in the use of the matched-field method for solving tomographic inverse problems. The physical basis of the MMN is a choice of an acoustic-field characteristic for measurements, which must be sensitive to current profiles and insensitive to both acoustic-speed variations and bottom topography. As a result, the MMN leads to a stable solution of the inverse problem for the vertical distribution of current velocity. The development of methods for current acoustic tomography is considered from the standpoint of their applicability to monitoring ocean dynamics in coastal regions. Possible applications of the MMN to solving other oceanographic problems are also discussed.
Goldenberg, S.B. Intraseasonal predictability of Atlantic basin hurricane activity. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 59-60 (2000).
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No abstract.
Goldenberg, S.B., C.W. Landsea, and G.D. Bell. Summary of the 1999 Atlantic hurricane season: A climatic perspective. Proceedings, 24th Annual Climate Diagnostics and Prediction Workshop, Tucson, AZ, November 1-5, 1999. National Weather Service, 1-4 (2000).
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No abstract.
Goni, G.J., L.K. Shay, P.G. Black, S.D. Jacob, T.M. Cook, J.J. Cione, and E.W. Uhlhorn. Role of the upper ocean structure on the intensification of Hurricane Bret from satellite altimetry. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, J5-J6 (2000).
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No abstract.
Hendee, J.C. A data-driven soft real-time expert system for producing coral bleaching alerts. Ph.D. Thesis, Nova Southeastern University, 131 pp. (2000).
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In the Florida Keys there are many physical, chemical, and biological events of interest and concern to personnel of the Florida Keys National Marine Sanctuary, marine biologists, oceanographers, fishermen, and divers. Large volumes of continuously-generated meteorological and oceanographic data from instruments in the SEAKEYS (Sustained Ecological Research Related to Management of the Florida Keys Seascape) network help to understand these events. However, since no one has the time to look at every printout of data from every station, every day, seven days a week, it is highly desirable to have an automated system that can monitor parameters of interest and produce specialized alerts of specific events, as indicated by prescribed or abnormal ranges, or combinations of parameters. A soft real-time expert system was developed to produce such alerts based on data input from the SEAKEYS network. The prototype system collected data from the Sombrero Reef station in the network and produced automated e-mail and World-Wide Web alerts when conditions were thought to be conducive to, or predictive of, coral bleaching, which occurs under environmental conditions stressful to corals. Configuration of the system included a point system for three coral bleaching models (high sea temperature only, high sea temperature plus low winds, high sea temperature plus low winds plus low tide). The approach is an important development in the use of knowledge-based systems to solve environmental problems, as it provides for knowledge synthesis (in the form of data summaries) from any environmental ASCII data stream or table, be it real-time or not.
Hendee, J.C. An environmental information synthesizer for expert systems: A framework for use in near real-time detection of harmful algal blooms. Proceedings, 17th International Conference of The Coastal Society: Coasts at the Millennium, Portland, OR, July 9-12, 2000. The Coastal Society, 233-241 (2000).
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As an enhancement to the SEAKEYS environmental monitoring network in the Florida Keys National Marine Sanctuary, software called the Environmental Information Synthesizer for Expert Systems (EISES) has been utilized together with a specially developed expert system to model and report the near real-time sensing of environmental conditions conducive to the onset of a harmful algal bloom (HAB, e.g., "red tide"). Actual near real-time in-situ fluorometry data was matched with wind speeds and photosynthetically active radiation at the Long Key SEAKEYS station in Florida Bay to simulate the onset of an HAB. These incidences were e-mailed to the knowledge engineer as they occurred, and could in the future be e-mailed to regulatory agencies, or posted to a Web site, as is done with a similarly developed expert system for coral bleaching. This approach shows promise with the future remote detection of HAB pigment data via in-situ or satellite sensors.
Jacob, S.D., L.K. Shay, P.G. Black, and S.H. Houston. Upper ocean response to hurricane wind asymmetries. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, J66-J67 (2000).
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No abstract.
Jacobs, S.D., L.K. Shay, A.J. Mariano, and P.G. Black. The 3D oceanic mixed layer response to Hurricane Gilbert. Journal of Physical Oceanography, 30(6):1407-1429 (2000).
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Upper-ocean heat and mass budgets are examined from three snapshots of data acquired during and after the passage of Hurricane Gilbert in the western Gulf of Mexico. Measurements prior to storm passage indicated a warm core eddy in the region with velocities of O(1) m s-1. Based upon conservation of heat and mass, the three-dimensional mixed layer processes are quantified from the data. During and subsequent to hurricane passage, horizontal advection due to geostrophic velocities is significant in the eddy regime, suggesting that prestorm oceanic variability is important when background flows have the same magnitude as the mixed layer current response. Storm-induced near-inertial currents lead to large vertical advection magnitudes as they diverge from and converge toward the storm track. Surface fluxes, estimated by reducing flight-level winds to 10 m, indicate a maximum wind stress of 4.2 N m-2 and a heat flux of 1200 W m-2 in the directly forced region. The upward heat flux after the passage of the storm has a maximum of 200 W m-2 corresponding to a less than 7 m s-1 wind speed. Entrainment mixing across the mixed layer base is estimated using three bulk entrainment closure schemes that differ in their physical basis of parameterization. Entrainment remains the dominant mechanism in controlling the heat and mass budgets irrespective of the scheme. Depending on the magnitudes of friction velocity, surface fluxes and/or shear across the mixed layer base, the pattern and location of maximum entrainment rates differ in the directly forced region. While the general area of maximum entrainment is in the right-rear quadrant of the storm, the shear-induced entrainment scheme predicts a narrow region of cooling compared to the stress-induced mixing scheme and observed SST decreases. After storm passage, the maximum contribution to the mixed layer dynamics is associated with shear-induced entrainment mixing forced by near-inertial motions up to the third day as indicated by bulk Richardson numbers that remained below criticality. Thus, entrainment based on a combination of surface fluxes, friction velocity, and shear across the entrainment zone may be more relevant for three-dimensional ocean response studies.
Jones, R.W., and H.E. Willoughby. Linear motion of a two-layer baroclinic hurricane in shear. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 83-84 (2000).
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No abstract.
Kang, W.-J., J.H. Trefy, T.A. Nelsen, H.R. Wanless. Direct atmospheric inputs versus runoff fluxes of mercury to the lower Everglades and Florida Bay. Environmental Science and Technology, 34(19):4058-4063 (2000).
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Age-dated sediments from the lower Everglades and Florida Bay provide a record of inputs of excess Hg from direct atmospheric input versus runoff. Direct atmospheric fluxes of excess Hg to sediments in the lower Everglades and Florida Bay, calculated using a mass balance model for excess 210Pb, currently average 24 ± 9 µg m-2 yr-1 and are comparable with recent results from bulk atmospheric deposition. In contrast, present-day runoff fluxes of excess Hg to area sediments are variable, ranging from about 4-160 µg m-2 yr-1. The runoff flux now carries 60-80% of the total flux of excess Hg to the sediments in areas near river sloughs but less than 20% of the total flux of excess Hg in more remote areas of Florida Bay. These results show the greater importance of runoff relative to direct atmospheric deposition for Hg inputs to many areas of the lower Everglades and immediately adjacent Florida Bay. Thus, the choice of future water management strategies can play an important role in controlling Hg inputs to the lower Everglades and portions of Florida Bay.
Kaplan, J., and M. DeMaria. Large-scale characteristics of rapidly intensifying tropical cyclones in the North Atlantic basin. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 232-233 (2000).
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No abstract.
Katsaros, K.B. The paradigm for research on atmosphere-ocean interaction at the cusp between the 20th and 21st centuries. Bulletin of the American Meteorological Society, 81(4):837-838 (2000).
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No abstract.
Katsaros, K.B., and R.T. Pinker. Algorithm improvement for novel applications in earth science research. Proceedings, First Meteosat Second Generation Research Announcement of Opportunity Workshop, Bologna, Italy, May 17-19, 2000. European Space Agency, ESA SP-452, 103-106 (2000).
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No abstract.
Katsaros, K.B., P. Vachon, P.G. Black, P.P. Dodge, and E.W. Uhlhorn. Wind fields from SAR: Could they improve our understanding of storm dynamics? John Hopkins APL Technical Digest, 21(1):86-93 (2000).
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Four hurricane images obtained by RADARSAT are examined for what they reveal about the storms. Features seen include strong variations in backscatter from the surface in and around convective cells associated with rain cells and rainbands, coupled with increased backscatter in regions of high wind outflow. Long linear features of scale 3-6 km are observed in three of the four hurricanes, probably from secondary circulations in the atmospheric boundary layer (roll vortices). They occur between convective rainbands, where the descending motion could produce a well-defined boundary layer. Although the origins of and the mechanisms producing the features are still not clear, the high resolution, wide-swath coverage modes of synthetic aperture radar provide new observations and present important questions for further research.
Kelly, P.S., K.M.M. Lwiza, R.K. Cowen, and G.J. Goni. Low-salinity pools at Barbados, West Indies: Their origin, frequency, and variability. Journal of Geophysical Research, 105(C8):19,699-19,708 (2000).
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A vertical array of conductivity-temperature sensors moored off the west coast of Barbados, West Indies, from May 1996 to November 1997 revealed a heterogeneous and variable salinity pattern punctuated by six intrusions of low-salinity water (<34.5 psu) into the region. A typical intrusion extended to 30 m depth and lasted ~25 days, although one intrusion extended to 47 m and lasted 94 days. Water samples taken during an intrusion in May 1997 have Radium 228/226 activity ratios of approximately 1, consistent with previous measurements in Barbados of water that originated in the Amazon River mixing zone. The Amazon water likely was translated to Barbados in rings spawned from the North Brazil Current. Analysis of sea height anomaly derived from the TOPEX/Poseidon satellite supports this conclusion and reveals that, contrary to previous studies, rings are shed throughout the year, mostly during spring. The intrusions of low-salinity water and their associated velocities dramatically changed the already variable flow in our study area. We believe the complex salinity and flow we observed represented the disorganized remnants of rings that were at or near the ends of their lives. The changes we observed in the velocity and water structure are interesting in their own right as evidence of the Barbados region as a mixing zone and for their influence on recruitment of larval fishes to the reef along the island's west coast.
King, D.B., J.H. Butler, S.A. Montzka, S.A. Yvon-Lewis, and J.W. Elkins. Implications of methyl bromide supersaturations in the temperate North Atlantic Ocean. Journal of Geophysical Research, 105(D15):19,763-19,769 (2000).
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Methyl bromide saturation anomalies measured in the springtime North Atlantic and summertime North Pacific Oceans during 1998 revealed persistent supersaturations in the temperate waters of the northeastern Atlantic but undersaturtions in tropical waters of both oceans. A comparison of data from this study with those from a previous cruise to the northeastern Atlantic suggests that methyl bromide is cycled seasonally in these waters and perhaps in all temperate open-ocean waters. This means that the calculated net flux of methyl bromide into the oceans is slightly less negative than previously reported. With these new insights we estimate that the global air-sea flux of methyl bromide ranges from -11 to -20 Gg yr-1. Data combined from this and three previous cruises support a flux dependence upon sea surface temperature, as reported recently by Groszko and Moore (1998). Whereas sea surface temperature can account for 40-70% of the observed variability in methyl bromide globally, it is able to reproduce only a small fraction of the observed seasonal cycle in the temperate northeastern Atlantic. The development of reliable predictions of air-sea fluxes of methyl bromide will require information on additional variables as well.
King, D.B., J.H. Butler, S.A. Montzka, S.A. Yvon-Lewis, and J.W. Elkins. Correction to "Implications of methyl bromide supersaturations in the temperate North Atlantic Ocean." Journal of Geophysical Research, 105(D20):24,713-24,714 (2000).
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No abstract.
Knaff, J.A., and Landsea, C.W. Application of the El Niño-Southern Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme. Experimental Long-Lead Forecast Bulletin, 9(3):48-50 (2000).
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No abstract.
Landsea, C.W. Climate variability of tropical cyclones: Past, present, and future. In Storms (Volume 1), R.A. Pielke, Sr. and R.A. Pielke, Jr. (eds.). Routledge, New York (ISBN 041517239X), 220-241 (2000).
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No abstract.
Landsea, C.W. El Niño-Southern Oscillation and the seasonal predictability of tropical cyclones. In El Niño and the Southern Oscillation: Multiscale Variability and Global and Regional Impacts, H.F. Diaz and V. Markgraf (eds). Cambridge University Press (ISBN 0521621380), 149-181 (2000).
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Perhaps the most dramatic effect that El Niño has upon the climate system is in changing tropical cyclone characteristics around the world. This chapter reviews how tropical cyclone frequency, intensity, and areas of occurrence are altered in all of the cyclone basins by the phases of El Niño-Southern Oscillation (ENSO). In addition to ENSO, other global (such as the stratospheric Quasi-Biennial Oscillation) and local factors (such as sea surface temperature, monsoon intensity and rainfall, sea level pressures, and tropospheric vertical shear) can also help modulate tropical cyclone ariability. Understanding how these various factors relate to tropical cyclone activity can be challenging due to the fairly short (on the scale of only tens of years) record of reliable data. Despite this limitation, many of the factors that have been linked to tropical cyclones, the foremost of which being ENSO, have substantial lead relationships and can be utilized to provide seasonal forecasts of tropical cyclones. Details of methodologies that have been developed for the North Atlantic, northwest Pacific, south Pacific and Australian basin tropical cyclones are presented, as well as the real-time forecasting performance of Atlantic hurricanes as issued by Professor William Gray.
Landsea, C.W., and J.A. Knaff. Application of the El Niño-Southern Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme. Experimental Long-Lead Forecast Bulletin, 9(1):32-34 (2000).
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No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niño-Southern Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme. Experimental Long-Lead Forecast Bulletin, 9(2):31-33 (2000).
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No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niño-Southern Oscillation CLImatology PERsistence (CLIPER) forecasting scheme. Experimental Long-Lead Forecast Bulletin, 9(4):48-50 (2000).
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No abstract.
Landsea, C.W., and J.A. Knaff. How much "skill" is there in forecasting El Niño? Weatherzine, 23:2-4 (2000).
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No abstract.
Landsea, C.W., and J.A. Knaff. How much "skill" was there in forecasting the strong 1997-1998 El Niño and 1998-2000 La Niña events? Proceedings, 25th Annual Climate Diagnostics and Prediction Workshop, Palisades, NY, October 23-27, 2000. NOAA/Climate Prediction Center and the International Research Institute for Climate Prediction, 4-7 (2000).
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No abstract.
Landsea C.W., and J.A. Knaff. How much skill was there in forecasting the very strong 1997-1998 El Niño? Bulletin of the American Meteorological Society, 81(9):2107-2120 (2000).
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The very strong 1997-1998 El Niño was the first major event in which numerous forecasting groups participated in its real-time prediction. A previously developed simple statistical tool, the El Niño-Southern Oscillation Climatology and Persistence (ENSO-CLIPER) model, is utilized as a baseline for determination of skill in forecasting this event. Twelve statistical and dynamical models were available in real time for evaluation. Some of the models were able to outperform ENSO-CLIPER in predicting either the onset or the decay of the 1997-1998 El Niño, but none were successful at both for a medium-range two season (6-8 months) lead time. There were no models, including ENSO-CLIPER, able to anticipate even one-half of the actual amplitude of the El Niño's peak at medium-range (6-11 months) lead. In addition, none of the models showed skill (i.e., lower root-mean-square error than ENSO-CLIPER) at the zero season (0-2 months) through the two season (6-8 months) lead times. No dynamical model and only two of the statistical models (the canonical correlation analysis [CCA] and the constructed analog [ANALOG]) outperformed ENSO-CLIPER by more than 5% of the root-mean-square error at the three season (9-11 months) and four season (12-14 months) lead time. El Niño impacts were correctly anticipated by national meteorological centers one-half year in advance, because of the tendency for El Niño events to persist into and peak during the boreal winter. Despite this, the zero to two season (0-8 month) forecasts of the El Niño event itself were no better than ENSO-CLIPER and were in that sense, not skillful, a conclusion that remains unclear to the general meteorological and oceanographic communities.
Landsea, C.W., C. Anderson, N. Charles, G. Clark, J. Fernandez-Partagas, P. Hungerford, C. Neumann, and M. Zimmer. The Atlantic hurricane database re-analysis project: Results for 1851-1885. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 542-543 (2000).
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No abstract.
Lawrence, J.R., S.D. Gedzelman, and J.F. Gamache. Tropical cyclogenesis and stable isotope ratios of water. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 260-261 (2000).
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No abstract.
Lee, K., F.J. Millero, R.H. Byrne, R.A. Feely, and R. Wanninkhof. The recommended dissociation constants for carbonic acid seawater. Geophysical Research Letters, 27(2):229-232 (2000).
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A coherent representation of carbonate dissociation constants and measured inorganic carbon species is essential for a wide range of environmentally important issues such as oceanic uptake of anthropogenic CO2 and carbon cycle depictions in ocean circulation models. Previous studies have shown varying degrees of discordance between calculated and measured CO2-system parameters. It is unclear if this is due to errors in thermodynamic models or in measurements. In this work, we address this issue using a large field data set (15,300 water samples) covering all ocean basins. Our field data, obtained using laboratory-calibrated measurement protocols, are most consistent with calculated parameters using the dissociation constants of Mehrbach et al. (1973) as refit by Dickson and Millero (1987). Thus, these constants are recommended for use in the synthesis of the inorganic carbon data collected during the global CO2 survey during the 1990s and for characterization of the carbonate system in seawater.
Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global relationships of total inorganic carbon with temperature and nitrate in surface seawater. Global Biogeochemical Cycles, 14(3):979-994 (2000).
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High quality total inorganic carbon (CT) measurements made in the major ocean basins as part of the Joint Global Ocean Flux Study (JGOFS), the National Oceanic and Atmospheric Administration/Ocean Atmosphere Carbon Exchange Study (NOAA/OACES), and the Department of Energy/World Ocean Circulation Experiment (DOE/WOCE) programs are related to sea surface temperature (SST) and nitrate (NO3-). A simple two-parameter function with SST and NO3- of the form NCT = a + b SST + c SST2 + d NO3 - fits salinity (S)-normalized surface CT (NCT = CT × 35/S) data for different parts of the oceans within an area-weighted error of ±7 µmol kg-1 (1 sigma). Estimated values of NCT using the derived algorithms with NO3- and SST are compared with values calculated from the surface partial pressure of CO2 (pCO2SW) (Takahashi et al., 1997) and total alkalinity (AT) (Millero et al., 1998) fields using thermodynamic models. Comparisons of the estimated values of NCT with measurements not used to derive the same algorithms, and comparisons with the values calculated from global AT and pCO2SW fields, give a realistic uncertainty of ±15 µmol kg-1 in estimated CT. The derived correlations of NCT with SST and NO3- presented here make it possible to estimate surface CT over the ocean from climatological SST, S, and NO3- fields.
Lee, W.-C., and F.D. Marks. An objective method to determine tropical cyclone center near landfall from WSR-88D data: The GBVTD-simplex algorithm. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 310-311 (2000).
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No abstract.
Lee, W.-C., and F.D. Marks. Tropical cyclone kinematic structure retrieved from single Doppler radar observations, Part II: The GBVTD-simplex center finding algorithm. Monthly Weather Review, 128(6):1925-1936 (2000).
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This paper is the second of a series and focuses on developing an algorithm to objectively identify tropical cyclone (TC) vorticity centers using single-Doppler radar data. The first paper dealt with the formulation of a single-Doppler radar TC wind retrieval technique, the ground-based velocity-track-display (GBVTD), and the results are verified using analytical TCs. It has been acknowledged that the quality of the GBVTD-retrieved TC circulation strongly depends on accurately knowing its center position. However, existing single-Doppler radar center finding algorithms are limited to estimate centers for axisymmetric TCs. The proposed algorithm uses a simplex method to objectively estimate the TC vorticity center by maximizing GBVTD-retrieved mean tangential wind. When tested with a number of axisymmetric and asymmetric analytical TCs, the accuracy of the TC centers estimated by the GBVTD-simplex algorithm is approximately equal to 340 m from the true center. When adding 5 m s-1 random noise to the Doppler velocities, the accuracy of the TC centers is nearly unchanged at 350 m. When applying the GBVTD-simplex algorithm to Typhoon Alex (1987), the estimated uncertainty varies between 0.1 and 2 km. When the overall velocity gradient is weak, the uncertainties in the retrieved TC centers are usually large. The GBVTD-simplex algorithm sometimes has problems finding a solution when a large sector of Doppler radar data is missing in conjunction with weak velocity gradients. The GBVTD-simplex algorithm significantly reduces the uncertainties in estimating TC center position compared with existing methods and improves the quality of the GBVTD-retrieved TC circulation. The GBVTD-simplex algorithm is computationally efficient and can be easily adapted for real-time applications.
Lee, W.-C., B. J.-D. Jou, P.-L. Chang, and F.D. Marks. Tropical cyclone kinematic structure retrieved from single-Doppler radar observations. Part III: Evolution and structures of Typhoon Alex (1987). Monthly Weather Review, 128(12):3982-4001 (2000).
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This paper is the third of a series that focuses on the applications of the ground-based velocity track display (GBVTD) technique and the GBVTD-simplex center finding algorithm developed in the previous two papers to a real tropical cyclone (TC). The evolution and structure of Typhoon Alex (1987), including full tangential winds, mean radial winds, one component of the mean flow, and their derived axisymmetric angular momentum and perturbation pressure fields are reconstructed from 16 volume scans (6.5 h of data with a 2-h gap) from the Civil Aeronautic Administration (CAA) Doppler radar while Typhoon Alex moved across the mountainous area in northern Taiwan. This analysis retrieves a plausible and physically consistent three-dimensional primary circulation of a landfalling TC using a single ground-based Doppler radar. Highly asymmetric wind structures were resolved by the GBVTD technique where the maximum relative tangential wind at z = 2 km evolved from 52 m s-1 (before landfall), to less than 40 m s-1 (after landfall), to less than 35 m s-1 (entering the East China Sea). Alex's eye began to fill with precipitation while its intensity decreased rapidly after landfall, a characteristic of circulations disrupted by terrain. The mean radial wind field revealed a layer of low-level inflow in agreement with past TC observations. The outward slope of the eyewall reflectivity maximum was consistent with the constant angular momentum contours within the eyewall. After Alex entered the East China Sea, its circulation became more axisymmetric. The axisymmetric perturbation pressure field was retrieved using the gradient wind approximation which, when used in conjunction with one or more surface pressure measurements within the analysis domain, can estimate the central pressure. The retrieved perturbation pressure fields at two time periods were compared with surface pressures reported in northern Taiwan. Considering the assumptions involved and the influence of terrain, good agreement (only 1V2-mb deviation) was found between them. This agreement indicates the relative quality of the GBVTD-retrieved axisymmetric circulation and suggests GBVTD-retrieved quantities can be useful in operational and research applications.
Lonfat, M., F.D. Marks, and S. Chen. A study of the rain distribution in tropical cyclones using TRMM/TMI. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 480-481 (2000).
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No abstract.
Luo, J., P.B. Ortner, D. Forcucci, and S.R. Cummings. Diel vertical migration of zooplankton and mesopelagic fish in the Arabian Sea. Deep-Sea Research, Part II, 47(7-8):1451-1473 (2000).
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Acoustic (153 kHz ADCP and 12 kHz hull-mounted transducers) data and MOCNESS (MOC01 and MOC10) net tow samples collected in the Arabian Sea during the Spring Intermonsoon (April/May) and Southwest Monsoon (August) in 1995 documented substantial diel migrations of fish and zooplankton despite the year-round presence of an oxygen minimum (<0.2 ml l-1 at 125-150 m). Fish and zooplankton layers were distinguished by comparing 12 kHz sonar and 153 kHz ADCP backscatter data, which indicated that the strongly migrating layers were predominantly composed of fishes. Fish vertical migration speeds were independently estimated from the slopes of the volume scattering layers and from the vertical velocity components of the ADCP, yielding average speeds of 4 and 3 cm s-1 and maximum speeds of 13 and 10 cm s-1, respectively. A few migrating zooplankton layers were identified with an average speed of about 2 cm s-1 and maximum speeds as high as 8 cm s-1. Migration depths for both zooplankton and fish differed somewhat amongst stations and appeared to be related to local hydrographic conditions (principally the vertical gradients in DO and water temperature). Zooplankton displacement volumes at individual sites suggested that zooplankton biomass during the Southwest Monsoon could be as much as fivefold greater than during the Spring Intermonsoon. This observation was confirmed for the region in general by first deriving a relationship between ADCP backscatter intensity and daytime zooplankton biomass and then comparing the latter between cruises using daytime ADCP data taken along a 1500 km transect that extended from the coast of Somalia to the center of the northern basin.
Marks, F.D., L. Selevan, and J.F. Gamache. WSR-88D derived rainfall distributions in Hurricane Danny (1997). Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 298-299 (2000).
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No abstract.
McAdie, C.J., and P.P. Dodge. Maximum sustained winds in Hurricane Irene as measured by the Miami WSR-88D. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 212-213 (2000).
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No abstract.
McArthur, C., R. Ferry, and J.R. Proni. Amenities monitoring for dredged material disposal management. Proceedings, 17th Conference of the Coastal Society: Coasts at the Millennium, Portland OR, July 9-12, 2000. The Coastal Society, 6 pp. (2000).
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Valuable amenities are present throughout U.S. coastal waters, from coral reefs, to oyster beds, to coastal fisheries. In essentially every case in which navigation and/or maintenance dredging is contemplated, the issues of potential impact of dredging activities on nearby amenities arise. In order to evaluate that potential impact, long-term monitoring of amenities is required. Key management issues related to amenities include: (1) reduction or elimination of dredging impacts; (2) scheduling ("windows") for dredging and dredged material disposals; (3) monitoring of transport to, and effects upon amenities; and (4) compliance with defined procedures for dredging activities. While the data needed for management decisions may vary from location to location, certain basic measurement needs appear almost universally: (1) characterization and quantification of dredged sediments arriving at amenities sites; (2) determination of "natural" sediment ranges at amenities sites; (3) photosynthetic light reductions; (4) sediment resuspension and transport; and (5) other sources of materials of potential impact to amenities sites. Dredging and disposal must also be considered in the context of temporal "windows." In the Miami Offshore Disposal Site project, data for management of dredging activities is coordinated between the disposal and amenities (coral reef) sites where dumping windows are determined by realtime current meter data, indicating potential transport to the reef site. In the Pacific Northwest, "curtains" of dredge-related sediment may inhibit upstream spawning activities of valued fisheries resources and thus they are subject to similar temporal windows.
Melo, N., F.E. Muller-Karger, S.C. Estrada, R. Perez de los Reyes, I.V. del Rio, P.C. Perez, and I.M. Arenal. Near-surface phytoplankton distribution in the western Intra-Americas Sea: The influence of El Niño and weather events. Journal of Geophysical Research, 105(C6):14,029-14,043 (2000).
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The space-time variation of phytoplankton pigments in the vicinity of the island of Cuba is examined using digital images obtained with the Coastal Zone Color Scanner (CZCS) sensor, flown aboard the Nimbus-7 satellite from 1978 to 1986. The results are compared to historical in-situ hydrographic observations. A marked seasonality in pigment concentration is observed in waters around Cuba, with an average of 0.07 mg m-3 in summer (April-September) and 0.13 mg m-3 during winter (October-March). The range of variation in pigment concentration is larger in the Gulf of Mexico relative to that in the western Caribbean Sea. Four biogeographical areas are identified based on groups of pixels with similar patterns of time variability. Area I: southwest of Cuba, Yucatan Channel, and Florida Strait; Area II: central Gulf of Mexico; Area III: east of Cuba; and Area IV: central Caribbean Sea, south of Jamaica and Hispaniola. Two major factors led to anomalies in the seasonal cycle of pigment concentrations. During the 1982-1983 El Niño-Southern Oscillation (ENSO) event, positive anomalies are observed in pigment concentration in the northwestern Caribbean and in the Gulf of Mexico. This is due to intense mixing of the water column driven by the higher frequency of cold fronts during winter and associated strong winds. The 1982-1983 El Niño therefore had a fertilizing effect on this region. Another positive anomaly was observed during non-ENSO years, specifically during 1980-1981. This anomaly is associated with a higher frequency of hurricanes and extra-tropical low-pressure systems.
Mestas-Nunez, A.M. Orthogonality properties of rotated empirical modes. International Journal of Climatology, 20(12):1509-1516 (2000).
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The properties (spatial orthogonality and temporal uncorrelatedness) of orthogonally-rotated empirical modes depend on the normalization of the modes prior to rotation. It is shown here that these properties also depend on how the empirical modes are formulated. The preferred convention is one that allows us to reconstruct the data from the unrotated or rotated modes. When the empirical modes are normalized so that the spatial eigenvectors are unit length (i.e., EOFs), the rotated modes preserve spatial orthogonality but are no longer temporally uncorrelated. Relaxing the temporal orthogonality in this way does not prejudice conclusions that can be inferred regarding the temporal couplings of the rotated modes.
Mestas-Nunez, A.M., and D.B. Enfield. El Niño-Southern Oscillation: Canonical and non-canonical aspects. Proceedings, 24th Annual Climate Diagnostics and Prediction Workshop, Tucson, AZ, November 1-5, 1999. National Weather Service, 111-114 (2000).
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The main goal of this paper is to investigate and compare the atmospheric signatures associated with the canonical ENSO and residual components of the SST anomaly variability in the eastern tropical Pacific. An expanded version of this paper will appear in the Journal of Climate (Mestas-Nuñez and Enfield, 2001).
Molinari, R.L., and J.F. Festa. Effect of subjective choices on the objective analysis of sea surface temperature data in the tropical Atlantic and Pacific Oceans. Oceanologica Acta, 23(1):3-14 (2000).
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Many subjective choices are required to perform an objective interpolation (OI) analysis of environmental variables. Herein, we consider the effects on the statistical analysis of sea surface temperature (SST) using (1) a structure function or covariance analysis, (2) different analytical expressions to represent the statistics of the raw data, and (3) different historical SST data sets. The historical data sets are the well-sampled Comprehensive OceanAtmospheric Data Set (COADS) and the poorly sampled historical expendable bathythermograph (XBT) data set. Results from these analyses are used to generate error maps for a poorly-sampled, two month XBT array and a proposed well-sampled profiling float array. For the relatively data-rich COADS analysis, decorrelation scales are the same using either the structure function or covariance analyses. Results differ for the data-poor XBT analysis. Representative decorrelation scales in the Pacific (Atlantic) are about 11-14 (6-10) degrees in the zonal direction and 4-7 (3-6) degrees in the meridional direction. As COADS SST data are less precise than XBT SST data, error and signal variances are greater for the former. The choice of analytical fit to the raw data (needed to generate error maps) has a dramatic effect on the resulting uncertainty fields. Gaussian fits, because of their parabolic shape near the origin, result in smaller errors than exponential fits for the same observing array. Finally, the proposed float array can achieve the accuracies needed to resolve satisfactory upper layer heat content changes over larger areas than the present XBT network.
Morisseau-Leroy, N., M.K. Solomon, and J. Basu. Oracle 8i: Java Component Programming. Osborne McGraw-Hill (ISBN 0072127376), 697 pp. (2000).
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No abstract.
Murillo, S.T., W.-C. Lee, and F.D. Marks. Evaluating the GBVTD-tropical center finding simplex algorithm. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 312-313 (2000).
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The GBVTD simplex algorithm has been tested using axisymmetric and asymmetric analytic tropical cyclones by Lee et al. (1999). The algorithm objectively identifies the tropical cyclone center by maximizing the GBVTD-derived mean tangential wind field. Lee and Marks (1999) applied the GBVTD simplex algorithm to Typhoon Alex (1987). However, a true center was not available to verify the accuracy of the algorithm. This study applies the GBVTD simplex algorithm to Hurricane Danny (1997). The estimated storm track derived by the algorithm is compared to radar and aircraft storm fixes. The derived track is in good agreement with the true storm track within 2 km. Results will be presented that show how the GBVTD simplex algorithm improves the quality of the GBVTD retrieved wind analysis.
Murnane, R.J., C. Barton, E. Collins, J. Donnelly, J. Elsner, K. Emanuel, I. Ginis. S. Howard, C.W. Landsea, K. Liu, D. Malmquist, M. McKay, A. Michaels, N. Nelson, J. O'Brien, D. Scott, and T. Webb. Model estimates of hurricane wind speed probabilities. EOS, Transactions, American Geophysical Union, 81(38):433, 438 (2000).
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No abstract.
Nelsen, T.A., S.J. Stamates, B.J. Elkind, W.P. Dammann, and J.R. Proni. Field evaluation of the temporal and spatial variations in total suspended matter and current fields at Chesapeake Bay Site 104 and contiguous areas. Final Report, U.S. Army Corps of Engineers, MIPR No. W81W3@00604995, 47 pp. (2000).
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No abstract.
Nolan, D.S., M.T. Montgomery, and P.D. Reasor. Studies of the wavenumber one instability in hurricane-like vortices. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 29-30 (2000).
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No abstract.
Ooyama, K.V. A dynamic and thermodynamic foundation for modeling the moist atmosphere with classical thermodynamics and parameterized microphysics. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 561-562 (2000).
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No abstract.
Otero, S., N. Morisseau-Leroy, N. Carrasco, and M.D. Powell. A distributed real-time hurricane wind analysis system. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 197-198 (2000).
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No abstract.
Parrish, J.R., M.L. Black, S.H. Houston, P.P. Dodge, and J.J. Cione. The structure of Hurricane Irene over South Florida. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 456-457 (2000).
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No abstract.
Peng, T.-H., and F. Chai. Modeling the carbon cycle in the equatorial Pacific Ocean. Proceedings, Marine Environment: The Past, Present, and Future, Kaohsiung, Taiwan, January 26-28, 1999. Sueichan Press, 240-255 (2000).
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An ocean ecosystem model of the equatorial Pacific Ocean has been developed with new and export productivity regulated by Si and Fe to synthesize and analyze data collected during the JGOFS process-study-oriented survey cruises in 1992. The data also include those obtained by NOAA/OACES cruises in concert with the JGOFS EqPac process study. The circulation model is based on the Modular Ocean Model of the NOAA/GFDL ocean general circulation model. The ecosystem model is originally formulated by Chai et al. (1996), and is now expanded to consist of nine components describing two sizes of phytoplankton, two sizes of zooplankton, two detritus pools, and three dissolved nutrients: silicate, nitrate, and ammonium. The carbonate chemistry is parameterized in the model to evaluate the variations of pCO2 and, hence, the CO2 flux across the air-sea interface. At this initial stage, a test case by using a 1D model is performed to simulate low-silicate, high-nitrate, and low-chlorophyll conditions in the equatorial Pacific, and to investigate how the carbon system behaves in this ecosystem structure. The model includes the vertical upwelling and diffusion processes. The modeled upwelling rate and vertical diffusivity, from a 3D circulation model, were initially averaged for the region with latitudes 5°S to 5°N, and longitude 180° to 90°W, the "cold tongue" of the equatorial Pacific. Temperature is used to calibrate model upwelling and vertical diffusion rates. Comparison of model results with the observations made during the NOAA/OACES EqPac 1992 expeditions indicates that the vertical profiles of DIC, NO3, and Si(OH)4 are consistent with the measurements made in the fall season when the ocean was in a normal non-El Niño condition. A tight fit of profiles between model and observation is not possible because of spatial variations of the observed values. A 3D simulation is required, which is in progress. The 1D model CO2 evasion rate is estimated to be 2.9 mol/m2/yr, which is consistent with the range of estimates from measurements made during non-El Niño conditions.
Powell, M.D. Tropical cyclones during and after landfall. In Storms (Volume 1), R. Pielke, Sr. and R. Pielke, Jr. (eds.). Routledge, New York (ISBN 041517239X), 196-219 (2000).
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No abstract.
Proni, J.R. Using acoustical methods to study and monitor the discharge of sewage and dredged-material in the coastal ocean. Proceedings, Fifth European Conference on Underwater Acoustics (ECUA 2000), Lyon, France, July 10-13, 2000. European Acoustics Association, Volume 1, 755-760 (2000).
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Acoustical backscatter has been shown to be very effective in the study and monitoring of sewage efffluent and dredged material released into the coastal waters. Acoustical detection of a detrainment phenomenon in discharge plumes shows the extreme sensitivity of effluent distributions to small water column density changes. Acoustic measurements, as part of an ensemble of sensor systems, reveal turbidity changes occurring at environmentally valuable biological communities such as coral reefs and oyster beds. Examples of acoustic observations are presented.
Protat, A., Y. Lemaitre, D. Bouniol, and R.A. Black. Microphysical observations during FASTEX from airborne Doppler radar and in-situ measurements. Physics and Chemistry of the Earth, Part B: Hydrology, Oceans, and Atmosphere, 25(10-12):1097-1102 (2000).
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A major objective of FASTEX is to document the three-dimensional dynamic and microphysical structure of the North-Atlantic frontal cyclones in their mature stage at different scales of motion. In this paper, we combine the airborne Doppler radar and microphysical 2D-C and 2D-P probes data to recover the 3D microphysical and radiative properties of the IOP16 and IOP12 frontal cyclones (terminal fall velocity, cloud and precipitation water contents, precipitation fall rate, effective radius). The first step is to derive statistical relationships between the microphysical quantities and reflectivity from the 2D-P and 2D-C probes. Then, the Doppler-derived 3D reflectivity field is combined with these statistical relationships to access the 3D microphysical fields.
Quilfen Y., A. Bentamy, P. Delecluse, K.B. Katsaros, and N. Grima. Prediction of sea level anomalies using ocean circulation model forced by scatterometer wind and validation using TOPEX/Poseidon data. IEEE Transactions on Geoscience and Remote Sensing, 38(4):1871-1884 (2000).
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Uncertainties in the surface wind field have long been recognized as a major limitation in the interpretation of results obtained by oceanic circulation models. It is especially true in the tropical oceans, where the response to wind forcing is very strong on short time scales. The purpose of this paper is to show that these uncertainties can be greatly reduced by using spaceborne wind sensors that provide accurate measurements on a global basis. Surface winds over the global oceans have been measured by scatterometry since the launch of the European Remote Sensing Satellite (ERS-1) in August 1991 by the European Space Agency, Noordwijk, The Netherlands, and is currently provided by ERS-2, launched in April 1995. The ground-track wind vectors are processed to compute mean weekly surface winds onto a 1° square grid at the Institut Francais de Recherche pour l'Exploitation de la Mer (IFREMER), Plouzane, France. These winds are validated by comparison with the buoy array in the tropical Pacific Ocean, showing good agreement. In order to further evaluate this wind field, the three-dimensional ocean model OPA7 developed at Laboratoire d'Océanographie Dynamique et de Climatologie, Paris, France, is forced over the tropical oceans by the ERS-derived wind stress fields and by fields from the atmospheric model "Arpege/Climat." Selected ocean parameters are defined in order to validate the ocean model results with measurements of the tropical ocean and global atmosphere (TOGA) buoys in the Pacific Ocean. The ability of the model to describe the short scale (a few weeks to a few years) oceanic variability is greatly enhanced when the satellite-derived surface forcing is used. In this paper, we present further comparison of the ocean model results with the TOPEX-Poseidon altimeter measurements. Simulated and measured sea level variability are described over the three tropical oceans. The annual and semi-annual signals, as well as the interannual variability, partly linked to the El Niño-Southern Oscillation (ENSO) phenomenon, are well simulated by the OPA7 model when the satellite winds are used. Furthermore, it shows that the objective method, kriging technique, used to interpolate the mean ERS wind fields, dramatically reduces the effects of the satellite bandlike sampling. In the last part of this paper, we focus on the relationship between the wind stress anomalies and the sea level anomalies in the case of the 1997-1998 El Niño event. It clearly shows that sea level anomalies in the eastern and western parts of the Pacific are strongly linked to wind stress anomalies in the central Pacific. The forthcoming scatterometers aboard the METOP and ADEOS satellites will provide a much better coverage. It will enable the wind variability spatial and temporal scales to be resolved better, in order that wind uncertainties no longer blur the interpretation of ocean circulation numerical model results.
Reasor, P.D., and M.T. Montgomery. 3D alignment and co-rotation of weak, TC-like vortices via linear vortex Rossby waves. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 268-269 (2000).
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No abstract.
Reasor, P.D., M.T. Montgomery, F.D. Marks, and J.F. Gamache. Low-wavenumber structure and evolution of the hurricane inner core observed by airborne dual-Doppler radar. Monthly Weather Review, 128(6):1653-1680 (2000).
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The asymmetric dynamics of the hurricane inner-core region is examined through a novel analysis of high temporal resolution, three-dimensional wind fields derived from airborne dual-Doppler radar. Seven consecutive composites of Hurricane Olivia's (1994) wind field with 30-min time resolution depict a weakening storm undergoing substantial structural changes. The symmetric and asymmetric mechanisms involved in this transformation are considered separately. To zeroth order the weakening of the primary circulation is consistent with the axisymmetric vortex spindown theory of Eliassen and Lystad for a neutrally-stratified atmosphere. Vertical shear, however, increased dramatically during the observation period, leading to a strong projection of the convection onto an azimuthal wavenumber 1 pattern oriented along the maximum vertical shear vector. Recent theoretical ideas elucidating the dynamics of vortices in vertical shear are used to help explain this asymmetry. The role of asymmetric vorticity dynamics in explaining some of the physics of hurricane intensity change motivates a special focus on Olivia's vorticity structure. It is found that an azimuthal wavenumber 2 feature dominates the asymmetry in relative vorticity below 3-km height. The characteristics of this asymmetry deduced from reflectivity and wind composites during a portion of the observation period show some consistency with a wavenumber 2 discrete vortex Rossby edge wave. Barotropic instability is suggested as a source for the wavenumber 2 asymmetry through a series of barotropic numerical simulations. Trailing bands of vorticity with radial wavelengths of 5-10 km are observed in the inner core approximately 20 km from the storm center, and may be symmetrizing vortex Rossby waves. Elevated reflectivity bands with radial scales comparable to those of the vorticity bands, also near 20-25-km radius, may be associated with these vorticity features.
Rogers, R.F. Surface-based modification of convectively-generated mesovortices and its implications for tropical cyclogenesis. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 151-152 (2000).
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No abstract.
Rogers, R.F., J.M. Fritsch, and W.C. Lambert. A simple technique for using radar data in the dynamic initialization of a mesoscale model. Monthly Weather Review, 128(7):2560-2574 (2000).
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A simple technique for using radar reflectivity to improve model initialization is presented. Unlike previous techniques, the scheme described here does not infer rain rates and heating profiles from assumed relationships between remotely-sensed variables and precipitation rates. Rather, the radar data are only used to tell the model when and where deep moist convection is occurring. This information is then used to activate the model's convective parameterization scheme in the grid elements where convection is observed. This approach has the advantage that the convective precipitation rates and heating profiles generated by the convective parameterization are compatible with the local (grid element) environment. The premise is that if convection is forced to develop when and where it is observed during a data assimilation period, convectively-forced modifications to the environment will be in the correct locations at the model initial forecast time and the resulting forecast will be more accurate. Three experiments illustrating how the technique is applied in the simulation of deep convection in a warm-season environment are presented: a control run in which no radar data are assimilated, and two additional runs where radar data are assimilated for 12 h in one run and 24 h in the other. The results indicate that assimilating radar data can improve a model's description of the mesoscale environment during the pre-forecast time period, thereby resulting in an improved forecast of precipitation and the mesoscale environment.
Rogers, R.F., S.S. Chen, J.E. Tenerelli, and M. Lonfat. A numerical study of the distribution of precipitation in Hurricane Bonnie (1998). Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 408-409 (2000).
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No abstract.
Sabine, C.L., R.H. Wanninkhof, R.M. Key, C. Goyet, and F.J. Millero. Seasonal CO2 fluxes in the tropical and subtropical Indian Ocean. Marine Chemistry, 72(1):33-53 (2000).
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Improved estimates of the variability in air-sea CO2 fluxes on seasonal and interannual time scales are necessary to help constrain the net partitioning of CO2 between the atmosphere, oceans, and terrestrial biosphere. Few direct measurements of the carbon system have been made in the main Indian Ocean basin. In the mid 1990s, several global carbon measurement programs focused on the Indian Ocean, greatly increasing the existing carbon database for this basin. This study examines the combined surface CO2 measurements from three major U.S. programs in the Indian Ocean: the global carbon survey cruises, conducted in conjunction with the World Ocean Circulation Experiment (WOCE); the NOAA Ocean-Atmosphere Carbon Exchange Study (OACES) Indian Ocean survey; and the Joint Global Ocean Flux Study (JGOFS) Arabian Sea Process Study. These data are fit with multiparameter linear regressions as a function of commonly-measured hydrographic parameters. These fits are then used with NCEP/NCAR reanalysis and Levitus 94 gridded values to evaluate the seasonal variability of surface seawater CO2 in the tropical and subtropical Indian Ocean and to estimate the magnitude of the Indian Ocean as a net sink for atmospheric CO2. The net annual flux for the Indian Ocean (north of 36°S) was -12.4 ± 0.5 × 1012 mol of carbon (equivalent to -0.15 Pg C) in 1995. The relatively small net flux results from the very different surface water pCO2 distributions and seasonal variations in the northern and southern Indian Ocean. The equatorial and northern hemisphere regions have values that are generally above atmospheric values. During the southwest monsoon, pCO2 values in the Arabian Sea coastal upwelling region are among the highest observed in the oceans. The upwelling is seasonal in nature, however, and only affects a relatively small area. The Indian Ocean equatorial region generally has values slightly above atmospheric. Unlike the Pacific and Atlantic Oceans, however, no clear equatorial upwelling signature was observed in 1995. The Southern Hemisphere Indian Ocean, which represents the largest region by area, generally has values below atmospheric. The strongest undersaturations are observed in the austral winter, with summer values reaching near or slightly above atmospheric.
Sabine, C.L., M.F. Lamb, J.L. Bullister, R.A. Feely, G.L. Johnson, R.M. Key, A. Kozyr, K. Lee, F.J. Millero, T.-H. Peng, and R.H. Wanninkhof. U.S. JGOFS team examines Pacific Ocean CO2 data quality. International WOCE Newsletter, 38:10-14 (2000).
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No abstract.
Sandrik, A., C.W. Landsea, and B. Jarvinen. The North Florida hurricane of 29 September 1896: A historical case of extreme inland high winds. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 547-548 (2000).
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No abstract.
Schmid, C., G. Siedler, and W. Zenk. Dynamics of intermediate water circulation in the subtropical South Atlantic. Journal of Physical Oceanography, 30(12):3191-3211 (2000).
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The circulation of the low-salinity Antarctic Intermediate Water in the South Atlantic and the associated dynamical processes are studied, using recent and historical hydrographic profiles, Lagrangian and Eulerian current measurements as well as wind stress observations. The circulation pattern inferred for the Antarctic Intermediate Water supports the hypothesis of an anticyclonic basin-wide recirculation of the intermediate water in the subtropics. The eastward current of the intermediate anticyclone is fed mainly by water recirculated in the Brazil Current and by the Malvinas Current. An additional source region is the Polar Frontal Zone of the South Atlantic. The transport in the meandering eastward current ranges from 6 Sv to 26 Sv (1 Sv = 106 m3 s-1). The transport of the comparably uniform westward flow of the gyre varies between 10 Sv and 30 Sv. Both transports vary with longitude. At the western boundary near 28°S, in the Santos Bifurcation, the westward current splits into two branches. About three quarters of the 19 Sv at 40°W go south as an intermediate western boundary current. The remaining quarter flows northward along the western boundary. Simulations with a simple model of the ventilated thermocline reveal that the wind-driven subtropical gyre has a vertical extent of over 1200 m. The transports derived from the simulations suggest that about 90% of the transport in the westward branch of the intermediate gyre and about 50% of the transport in the eastward branch can be attributed to the wind-driven circulation. The structure of the simulated gyre deviates from observations to some extent. The discrepancies between the simulations and the observations are most likely caused by the interoceanic exchange south of Africa, the dynamics of the boundary currents, the nonlinearity, and the seasonal variability of the wind field. A simulation with an inflow/outflow condition for the eastern boundary reduces the transport deviations in the eastward current to about 20%. The results support the hypothesis that the wind field is of major importance for the subtropical circulation of Antarctic Intermediate Water followed by the interoceanic exchange. The simulations suggest that the westward transport in the subtropical gyre undergoes seasonal variations. The transports and the structure of the intermediate subtropical gyre from the Parallel Ocean Climate Model (Semtner/Chervin model) agree better with observations.
Schott, F., C. Boning, H. Bryden, R.L. Molinari, P. Schlosser, C. Wunsch, and L. Stramma. 2000 Report of the WOCE North Atlantic Workshop. WOCE Report No. 169/2000, 110 pp. (2000).
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No abstract.
Schubert, W.H., S.A. Hausman, M. Garcia, K.V. Ooyama, and H.-C. Kuo. Potential vorticity in a moist atmosphere. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 563-564 (2000).
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No abstract.
Shay, L., G.J. Goni, and P.G. Black. Effects of a warm oceanic feature on Hurricane Opal. Monthly Weather Review, 128(5):1366-1383 (2000).
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On 4 October 1995, Hurricane Opal deepened from 965 to 916 hPa in the Gulf of Mexico over a 14-h period upon encountering a warm core ring (WCR) in the ocean shed by the Loop Current during an upper-level atmospheric trough interaction. Based on historical hydrographic measurements placed within the context of a two-layer model and surface height anomalies (SHA) from the radar altimeter on the TOPEX mission, upper-layer thickness fields indicated the presence of two warm core rings during September and October 1995. As Hurricane Opal passed directly over one of these WCRs, the 1-min surface winds increased from 35 to more than 60 m s-1, and the radius of maximum wind decreased from 40 to 25 km. Pre-Opal SHAs in the WCR exceeded 30 cm where the estimated depth of the 20°C isotherm was located between 175 and 200 m. Subsequent to Opal's passage, this depth decreased approximately 50 m, which suggests upwelling underneath the storm track due to Ekman divergence. The maximum heat loss of approximately 24 Kcal cm-2 relative to depth of the 26°C isotherm was a factor of 6 times the threshold value required to sustain a hurricane. Since most of this loss occurred over a period of 14 h, the heat content loss of 24 Kcal cm-2 equates to approximately 20 kW m-2. Previous observational findings suggest that about 10%-15% of upper-ocean cooling is due to surface heat fluxes. Estimated surface heat fluxes based upon heat content changes range from 2000 to 3000 W m-2 in accord with numerically simulated surface heat fluxes during Opal's encounter with the WCR. Composited AVHRR-derived SSTs indicated a 2°-3°C cooling associated with vertical mixing in the along-track direction of Opal except over the WCR where AVHRR-derived and buoy-derived SSTs decreased only by about 0.5°-1°C. Thus, the WCR's effect was to provide a regime of positive feedback to the hurricane rather than negative feedback induced by cooler waters due to upwelling and vertical mixing as observed over the Bay of Campeche and north of the WCR.
Shay, L.K., G.J. Goni, P.G. Black, S.D. Jacob, J.J. Cione, and E.W. Uhlhorn. Global analogues of deep warm upper ocean layers: Hurricane heat potential estimates. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, J3-J4 (2000).
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No abstract.
Spratt, S.M., F.D. Marks, P.P. Dodge, and D.W. Sharp. Examining the pre-landfall environment of mesovortices within a Hurricane Bonnie (1998) outer rainband. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 300-301 (2000).
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No abstract.
Tenerelli, J.E., S.S. Chen, M. Lonfat, R. Foster, and R.F. Rogers. Surface winds in Hurricane Floyd: A comparison between numerical simulations, aircraft data, and QuikScat satellite data. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 418-419 (2000).
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No abstract.
Uhlhorn, E.W., K.B. Katsaros, and M.D. Powell. Assimilation of scatterometer-derived winds into real-time tropical cyclone surface wind analyses. Preprints, 10th Conference on Satellite Meteorology and Oceanography, Long Beach, CA, January 9-14, 2000. American Meteorological Society, Boston, 214-215 (2000).
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No abstract.
Uhlhorn, E.W., P.G. Black, L.K. Shay, J.J. Cione, S.D. Jacob, and G.J. Goni. Warm core ocean features in the central and eastern Gulf of Mexico. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 147-148 (2000).
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No abstract.
Wainer, I., P. Gent, and G.J. Goni. Annual cycle of the Brazil-Malvinas confluence region in the National Center for Atmospheric Research climate system model. Journal of Geophysical Research, 105(C11):26,167-26,177 (2000).
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The objective of this study is to compare the mean and seasonal variability of the circulation in the southwest Atlantic with observations. The results used in the comparison are from the last 200 years of a 300-year control integration of the Climate System Model (CSM). The area of study includes the confluence region between the subtropical and subpolar waters represented by the Brazil and Malvinas Currents. The seasonal variation of transport and its relationship to changes in the wind stress forcing and in the sea surface temperature are examined and compared to available oceanographic observations. This study shows that a coarse resolution climate model, such as the CSM, can successfully reproduce major characteristics of the Brazil-Malvinas confluence seasonality, although the mesoscale features involving recirculation and meander dynamics are not resolved. The CSM transport values in the region of 38°S are consistent with hydrographically-derived values. The transport of the CSM Brazil Current is higher during austral summer and smaller during austral winter. Conversely, the Malvinas Current transport is weaker during austral summer and stronger during austral winter. This is also consistent with observations. The CSM seasonal cycle in transport associated with both the Brazil and Malvinas Currents and its meridional displacement is closely linked to the seasonal variations in the local wind stress curl. However, the displacement is much smaller in the model than in observations. The CSM results show that the latitudinal displacement of the 24°C and 17°C at the South American coast between austral summer and winter is 20° and 12°, respectively. This is very similar to the displacement seen in observations.
Walsh, E.J., C.W. Wright, D.C. Vandemark, W.B. Krabill, A.W. Garcia, S.H. Houston, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane directional wave spectrum spatial variation at landfall. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 327-328 (2000).
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No abstract.
Wang, C. A unified theory for the El Niño-Southern Oscillation. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, Florida, May 29-June 2, 2000. American Meteorological Society, Boston, J42-J43 (2000).
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No abstract.
Wang, C. On the atmospheric responses to tropical Pacific heating during the mature phase of El Niño. Journal of the Atmospheric Sciences, 57(22):3767-3781 (2000).
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The atmospheric heating and sea surface temperature (SST) anomalies during the mature phase of El Niño are observed to show both eastern and western Pacific anomaly patterns, with positive anomalies in the equatorial eastern/central Pacific and negative anomalies in the off-equatorial western Pacific. The detailed spatial patterns of the heating anomalies differ from the SST anomalies. The heating anomalies are more equatorially confined than the SST anomalies, and maxima of positive and negative heating anomalies are located farther to the west than the SST anomalies. The Gill/Zebiak atmospheric model assumes that the atmospheric initial heating has the same spatial patterns as the SST anomalies. This assumption results in some unrealistic model simulations for El Niño. When the model heating anomaly forcing is modified to resemble the observed heating anomalies during the mature phase of El Niño, the model simulations have been improved to: (1) successfully simulate equatorial easterly wind anomalies in the western Pacific; (2) correctly simulate the position of maximum westerly wind anomalies; and (3) reduce unrealistic easterly wind anomalies in the off-equatorial eastern Pacific. This paper shows that off-equatorial western Pacific negative atmospheric heating (or cold SST) anomalies are important in producing equatorial easterly wind anomalies in the western Pacific. These off-equatorial cold SST anomalies in the western Pacific also contribute to equatorial westerly wind anomalies observed in the central Pacific during the mature phase of El Niño. Although off-equatorial cold SST anomalies in the western Pacific are smaller than equatorial positive SST anomalies in the eastern Pacific, they are enough to produce atmospheric responses of comparable magnitude to the equatorial eastern Pacific. This is because the atmospheric mean state is convergent in the western Pacific and divergent in the equatorial eastern Pacific. By either removing the atmospheric mean convergence or removing off-equatorial cold SST anomalies in the western Pacific, the atmospheric responses show no equatorial easterly wind anomalies in the western Pacific. In the Gill/Zebiak model, the mean wind divergence field is an important background state, whereas the mean SST is secondary.
Wang, C., and R.H. Weisberg. The 1997-1998 El Niño evolution relative to previous Niño events. Journal of Climate, 13(2):488-501 (2000).
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The evolution of the 1997-1998 El Niño is described using NCEP sea surface temperature (SST) and outgoing longwave radiation (OLR) data, NCEP-NCAR reanalysis sea level pressure (SLP) fields, and FSU surface wind data. From November 1996 to January 1997, the eastern Pacific is characterized by equatorial cold SST and high SLP anomalies, while the western Pacific is marked by off-equatorial warm SST anomalies and off-equatorial anomalous cyclones. Corresponding to this distribution are high OLR anomalies in the equatorial central Pacific and low OLR anomalies in the off-equatorial far western Pacific. The off-equatorial anomalous cyclones in the western Pacific are associated with a switch in the equatorial wind anomalies over the western Pacific from easterly to westerly. These equatorial westerly anomalies then appear to initiate early SST warmings around the date line in January/February 1997 and around the far eastern Pacific in March 1997. Subsequently, both the westerly wind and warm SST anomalies, along with the low OLR anomalies, grow and progress eastward. The eastward propagating warm SST anomalies merge with the slower westward spreading warm SST anomalies from the far eastern Pacific to form large-scale warming in the equatorial eastern and central Pacific. The anomaly patterns in the eastern and central Pacific continue to develop, reaching their peak values around December 1997. In the western Pacific, the off-equatorial SST anomalies reverse sign from warm to cold. Correspondingly, the off-equatorial SLP anomalies in the western Pacific also switch sign from low to high. These off-equatorial high SLP anomalies initiate equatorial easterly wind anomalies over the far western Pacific. Like the equatorial westerly wind anomalies that initiate the early warming, the equatorial easterly wind anomalies over the far western Pacific appear to have a cooling effect in the east and, hence, help facilitate the 1997-1998 El Niño decay. The paper also compares the 1997-1998 El Niño with previous warm events, and discusses different ENSO mechanisms relevant to the 1997-1998 El Niño.
Wilkerson, J.C., and J.R. Proni. Monitoring tropical and subtropical rainfall over the ocean using underwater acoustic techniques. Proceedings, Fifth European Conference on Underwater Acoustics (ECUA 2000), Lyon, France, July 10-13, 2000. European Acoustics Association, Volume 1, 741-746 (2000).
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Measurements of underwater sound produced by rain were made at three U.S. coastal sites to determine feasibility and limitations of acoustic detection and classification of rainfall over water. In the study, concurrent radar observations were used to identify convective and stratiform regions of the precipitating clouds overhead. Acoustic-derived classifications of rain type, based on information in the 4-30 kHz frequency band, were in general agreement with radar-derived classifications. A correlation of 0.9 was found to exist between sound spectrum levels (in decibels) in the 4-10 kHz frequency band and rain rate, suggesting the use of acoustical methods for rainfall estimation. Testing of the acoustic technique in deep water is currently underway at the U.S. Navy Atlantic Undersea Test and Evaluation Center, Bahamas. Examples of acoustic spectra are presented.
Willoughby, H.E. and R.W. Jones. Are the beta gyres really normal modes? Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 187-188 (2000).
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No abstract.
Wilson, W.D., and K.D. Leaman. Transport pathways through the Caribbean: The tropical origins of the Gulf Stream. Current, 16(1):14-18 (2000).
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No abstract.
Wright, C.W., E.J. Walsh, D.C. Vandemark, W.B. Krabill, A.W. Garcia, S.H. Houston, M.D. Powell, P.G. Black, and F.D. Marks. Hurricane directional wave spectrum spatial variation in the open ocean. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, J1-J2 (2000).
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No abstract.
Yao, Q., S.L. Garzoli, R. Zantopp, and W.E. Johns. North Brazil Current Rings Experiment: Time series data report. NOAA Data Report (PB2001-106244), OAR-AOML-40, 104 pp. (2000).
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This data report presents the data collected through moored instrumentation during the North Brazil Current Rings Experiment, a joint effort between the University of Miami's Rosenstiel School of Marine and Atmospheric Science, NOAA's Atlantic Oceanographic and Meteorological Laboratory, the Woods Hole Oceanographic Institution, and Columbia University's Lamont Doherty Earth Observatory. The program is funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). The main goal of this program is to study the contribution of the North Brazil Current (NBC) rings to inter-hemispheric exchange of heat and salt and to determine their role in climate.
Yvon-Lewis, S.A. Methyl bromide in the atmosphere and ocean. IGACtivities Newsletter, 19:9-12 (2000).
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No abstract.
Zhang, J.-Z. Shipboard automated determination of trace concentrations of nitrite and nitrate in oligotrophic water by gas-segmented continuous flow analysis with a liquid waveguide capillary flow cell. Deep-Sea Research, Part I, 47(6):1157-1171 (2000).
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Incorporation of a liquid waveguide capillary flow cell to a gas-segmented continuous flow auto-analyzer significantly enhances the sensitivity of automated colorimetric analysis. Nanomolar concentrations of nitrite and nitrate in oligotrophic surface seawater can be accurately determined. The advantages of this technique are low detection limit, high precision, and automation for rapid analysis of a large number of samples. This technique has been successfully used on shipboard measurements of about 1000 seawater samples during a one-month cruise in North Atlantic.
Zhang, J.-Z. The use of pH and buffer intensity to quantify the carbon cycle in the ocean. Marine Chemistry, 70(1-3):121-131 (2000).
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The pH of seawater is governed by the content of total carbon dioxide and ionic equilibra between hydrogen ions and various inorganic carbon species in seawater. Buffer intensity is defined as a measure of the ability of seawater to accommodate the addition of acid or base without appreciable pH change. It can be calculated from pH and total carbon dioxide of seawater. pH data in conjunction with buffer intensity can be used to quantify the carbon cycle in the ocean. The total amount of acid that has been released or consumed by any biogeochemical processes can be calculated from the change in pH multiplied by buffer intensity of seawater, dCH = d(beta-pH). This approach has been used to quantify the remineralization process in the Antarctic Intermediate Water in the South Pacific. Based on the observational data (pH, total carbon dioxide, O2, and nutrient measurements on P18 cruise), calculated elemental remineralization ratios are 173, 107, and 14.3 for O/P, C/P and N/P, respectively. The dissolution of calcium carbonate accounts for 21.5% of carbon increased from the remineralization in the Antarctic Intermediate Water.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Comparison of open tubular cadmium reactors and packed cadmium columns in automated gas-segmented continuous flow nitrate analysis. International Journal of Environmental Analytical Chemistry, 76(2):99-113 (2000).
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Detailed procedures are provided for preparing packed cadmium columns to reduce nitrate to nitrite. Experiments demonstrated the importance of conditioning both open tubular cadmium reactor (OTCR) and packed copper-coated cadmium columns to achieve 100% reduction efficiency. The effects of segmentation bubbles in the OTCR upon reduction efficiency and baseline noise in nitrate analysis are investigated using an auto-analyzer. Metal particles derived from segmentation bubbles in OTCR result in i nterference with continuous flow analyses. Therefore, packed columns are recommended for determination of low level nitrate in natural waters.
Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. New production in oligotrophic waters: Estimation based on diel cycle of nitrate. Proceedings, Joint Global Ocean Flux Study (JGOFS) Open Science Conference, Bergen, Norway, April 13-17, 2000. JGOFS International Project Office, 76-77 (2000).
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New production can be estimated from accurate measurements of inventory change in nitrate at nM levels in the photic zone. A strong diel cycle was observed in nitrate concentrations in response to photosynthesis in the eastern North Atlantic during the GASEX-98 cruise. During a diel study, nitrate concentration was 92 nM in the morning and decreased to 12 nM by 6 p.m. It increased after dark, presumably due to the diffusive flux from the nitracline. Oxygen showed a similar diel cycle with a change in concentration of about 2 µM. The vertical eddy diffusivity was derived from temporal changes in concentrations of a deliberate tracer, SF6, below the mixed layer. Together with vertical nitrate distributions, the nitrate flux from nitracline throughout the nighttime can account for a nitrate concentration of 102 nM by morning, which is in good agreement with measured nitrate of 92 nM at 6 a.m. The new production estimated from changes of nitrate inventory in the photic zone during the day was 28 mmole C/m2 d. Increases in the mixed layer nitrate were observed during storm events that deepened the mixed layer and brought the nitrate to the surface. The storm-induced nitrate disappeared within two days, indicating a rapid uptake by phytoplankton. The relative importance of sporadic storm events versus daily diffusive flux in supply nitrate to new production can be estimated based on nitrate inventory changes in the photic zone.
Zhang, J.-Z., C.W. Mordy, L.I. Gordon, A. Ross, and H.E. Garcia. Temporal trends in deep ocean Redfield ratios. Science, 289:1839 (2000).
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No abstract.
**1999**
Aberson, S.D. Ensemble-based products to improve tropical cyclone forecasting. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 843-844 (1999).
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No abstract.
Aberson, S.D. Targeting and sampling strategies to improve hurricane forecasts. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 105-107 (1999).
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No abstract.
Aberson, S.D., and J.L. Franklin. Impact on hurricane track and intensity forecasts of GPS dropwindsonde observations from the first-season flights of the NOAA Gulfstream-IV jet aircraft. Bulletin of the American Meteorological Society, 80(3):421-428 (1999).
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In 1997, the Tropical Prediction Center (TPC) began operational Gulfstream-IV jet aircraft missions to improve the numerical guidance for hurricanes threatening the continental United States, Puerto Rico, and the Virgin Islands. During these missions, the new generation of Global Positioning System dropwindsondes were released from the aircraft at 150-200-km intervals along the flight track in the environment of the tropical cyclone to obtain profiles of wind, temperature, and humidity from flight level to the surface. The observations were ingested into the global model at the National Centers for Environmental Prediction, which subsequently served as initial and boundary conditions to other numerical tropical cyclone models. Because of a lack of tropical cyclone activity in the Atlantic basin, only five such missions were conducted during the inaugural 1997 hurricane season. Due to logistical constraints, sampling in all quadrants of the storm environment was accomplished in only one of the five cases during 1997. Nonetheless, the dropwindsonde observations improved mean track forecasts from the Geophysical Fluid Dynamics Laboratory hurricane model by as much as 32%, and the intensity forecasts by as much as 20% during the hurricane watch period (within 48 h of projected landfall). Forecasts from another dynamical tropical cyclone model (VICBAR) also showed modest improvements with the dropwindsonde observations. These improvements, if confirmed by a larger sample, represent a large step toward the forecast accuracy goals of TPC. The forecast track improvements are as large as those accumulated over the past 20-25 years, and those for forecast intensity provide further evidence that better synoptic-scale data can lead to more skillful dynamical tropical cyclone intensity forecasts.
Albrecht, B., T. Faber, A. Savtchenko, D. Churchill, F.D. Marks, and P.G. Black. Surface-based remote sensing of a landfalling tropical storm. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 489-492 (1999).
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No abstract.
Alfaro, E.J., and D.B. Enfield. The rainy season in Central America: An initial success in prediction. IAI Newsletter, 20:21-22 (1999).
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No abstract.
Amat, L.R., M.D. Powell, and S.H. Houston. A real-time, Internet-based application for the archival, quality control, and analysis of hurricane surface wind observations. Preprints, 15 International Conference on Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 573-576 (1999).
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No abstract.
Atlas, D., C.W. Ulbrich, F.D. Marks, E. Amitai, and C.R. Williams. Systematic variation of drop size and radar-rainfall relations. Journal of Geophysical Research, 104(D6):6155-6169 (1999).
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Time histories of the characteristics of the drop size distribution of surface disdrometer measurements collected at Kapingamarangi Atoll were partitioned for several storms using rain rate, R, reflectivity factor Z, and median diameter of the distribution of water content D0. This partitioning produced physically based systematic variations of the drop size distribution (DSD) and Z-R relations in accord with the precipitation types viewed simultaneously by a collocated radar wind profiler. These variations encompass the complete range of scatter around the mean Z-R relations previously reported by Tokay and Short (1996) for convective and stratiform rain and demonstrate that the scatter is not random. The systematic time or space variations are also consistent with the structure of mesoscale convective complexes with a sequence of convective, transition, and stratiform rain described by various authors. There is a distinct inverse relation between the coefficient A and the exponent of the Z-R relations which has been obscured in prior work because of the lack of proper discrimination of the rain types. Contrary to previous practice, it is evident that there is also a distinct difference in the DSD and the Z-R relations between the initial convective and the trailing transition zones. The previously reported Z-R relation for convective rain is primarily representative of the transition rain that was included in the convective class. The failure of present algorithms to distinguish between the initial convective and the trailing transition rains causes an erroneous apportionment of the diabatic heating and cooling and defeats the primary intent of discriminating stratiform from convective rains.
Baringer, M.O., and R.L. Molinari. Atlantic Ocean baroclinic heat flux at 24-26°N. Geophysical Research Letters, 26(3):353-356 (1999).
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The spatially varying, interior geostrophic baroclinic heat flux component of the total meridional oceanic heat flux near 24°N in the Atlantic Ocean is examined using four transatlantic hydrographic sections including the October 1957 Discovery II IGY section, the September 1981 Atlantis section, the August 1992 Hesperides section, t he February 1998 Ronald H. Brown section and the 1982 Levitus and the Lozier, Owens, Curry climatologies. The 1992 section is complemented by shorter western boundary sections obtained concurrently during the Trident cruise. We find an average southward baroclinic heat flux of 0.9 0.3 PW with an annual cycle amplitude of 0.3 PW. More than 90% of the annual cycle is captured within 30° of the western boundary.
Baringer, M.O., and J.F. Price. A review of the physical oceanography of the Mediterranean Outflow. Marine Geology, 155(1-2):63-82 (1999).
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The physical oceanography of the Mediterranean Sea is reviewed with particular emphasis on the Mediterranean outflow in the Gulf of Cadiz. In this region the dense Mediterranean water forms a high velocity bottom current that interacts strongly with the sea floor. The major energy source for the plume comes from the release of potential energy as the plume descends the continental slope, and the major energy sink is work against bottom stress, which is as large as 4 Pa where the plume begins to descend the continental slope. In this region the current makes a nearly inertial turn that would otherwise appear to be steered by the underlying topography. The Mediterranean plume entrains the overlying North Atlantic Central Water and thereby loses much of its density anomaly. The mixed Mediterranean water becomes neutrally buoyant in the lower portion of the North Atlantic thermocline near Cape St. Vincent. There are then two preferred transport modes having somewhat different temperature and salinity whose distinct characteristics can be found far into the open North Atlantic. The temperature, salinity and volume of the Mediterranean water in the Strait of Gibraltar and in the Gulf of Cadiz appear to be roughly constant since modern measurements have been made. The estimated westward transport of Mediterranean water has gone down considerably as direct measurement techniques have been applied. A recent estimate is that the westward transport of pure Mediterranean water is only about a half a Sv (1 Sv = 106 m3/s); the transport of mixed Mediterranean water in the western Gulf of Cadiz is larger by about a factor of three or four because of the entrainment of North Atlantic water.
Bentamy, A.P., P. Queffeulou, Y. Quilfen, and K.B. Katsaros. Ocean surface wind fields estimated from satellite active and passive microwave instruments. IEEE Transactions on Geoscience and Remote Sensing, 37(5):2469-2486 (1999).
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This study examines the consistency of surface wind speeds estimated from the European Remote Sensing Satellite (ERS-1) scatterometer, ERS-1 altimeter, and the special sensor microwave/imager (SSM/I). The goal is to combine these wind estimates to produce surface wind fields. With this in mind, a comparison with buoy wind measurements and comparison among the three sensors is performed. According to the in-situ data, the rms errors of the three wind estimates are all within 2 m/s. The differences between the remotely-sensed and buoy wind speeds are studied according to atmospheric and oceanic variables, and their impact is shown. A large data base is obtained from the comparisons among the three sensor winds. The rms values of the differences between the scatterometer and the altimeter and between the scatterometer and the SSM/I are 1.67 and 1.45 m/s, respectively. There is no global bias between the scatterometer and the SSM/I, but between the scatterometer and the altimeter wind speeds, the bias is about 0.3 m/s. Furthermore, it is shown that the difference between the scatterometer and the altimeter wind estimates is dependent on the significant wave height, while the difference between the scatterometer and the SSM/I winds is dependent on the integrated water vapor content. The comparison enables some corrections to be made for consistency and combining products. The use of combining scatterometer, altimeter, and SSM/I wind estimates is illustrated by two examples.
Berberian, G.A., and A.Y. Cantillo. Oceanographic conditions in the Gulf of Mexico and Straits of Florida: Fall 1976. NOAA Data Report, OAR AOML-36 (PB2000-106209), 64 pp. (1999).
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NOAA conducted an investigation in the Gulf of Mexico and the Straits of Florida of oceanographic conditions and nutrients and trace metal levels in seawater during September and October 1976 aboard the NOAA Ship Researcher. This report lists the chemical data obtained from 118 stations. Collection and analyses methodologies, as well as results, are described.
Bishop, C.H., S. Majumdar, I. Szunyogh, Z. Toth, and S.D. Aberson. Using ensembles to simulate the impact of targeted observations. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 117-118 (1999).
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No abstract.
Black, M.L. Recent observations of the hurricane eyewall: Unusual and complex structure. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 313-316 (1999).
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No abstract.
Black, M.L., and J.L. Franklin. Recent observations of the convective structure associated with low-level wind maxima in the hurricane eyewall. Preprints, 29th International Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society, Boston, 370-373 (1999).
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No abstract.
Black, R.A., and J. Hallett. Electrification of the hurricane. Journal of the Atmospheric Sciences, 56(12):2004-2028 (1999).
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A survey of reports of electrical activity in hurricanes and typhoons from flight notes and personal experience (18 years, >230 eyewall penetrations for R. A. Black; ~20 years for J. Hallett, plus that of others at the Hurricane Research Division), and perusal of flight notes dating from 1980, show that lightning in and within 100 km or so of the eyewall is usually sparse. However, occasionally, significant electrical activity (>one flash per minute) occurs in or near the eyewall. National Oceanic and Atmospheric Administration WP-3D aircraft penetrations through a number of storms relate the lightning occurrence to strong vertical velocity (>10 m s-1) and the presence of supercooled liquid cloud droplets extending to temperatures below 20°C. Specific measurements of cloud properties during eyewall penetrations show that the supercooled cloud water content increases with upward velocities > ~5.0 m s-1, as does the presence of large (>2 mm) supercooled drops. Measurements at temperatures >-13°C show that the transition of supercooled cloud water to ice along an outward radial in all systems is associated with local electric fields (occasionally >20 kV m-1) and negative charge above positive charge. In systems with stronger vertical velocity there is a larger region of supercooled cloud extending to lower temperatures where charge separation may occur, as judged by the presence of regions containing graupel, small ice, and cloud droplets. The ratio of ice to supercooled water increases radially outward from the eyewall and depends upon altitude (temperature). The spatial distribution of charge is further influenced by the relation of vertical velocity to the radial flow, with the upper charge regions tending to be advected outward. In symmetrical, mature hurricanes, supercooled water usually occurs only in regions at temperatures above about -5°C. The upward transport of supercooled cloud water is limited by a balance between water condensed in the eyewall updraft and its erosion by ice in downdrafts descending in the outward regions of the eyewall. This ice originates from both primary and secondary ice nucleation in the updraft. This is consistent with an exponential increase in ice concentration, as the rate at which the ice particle concentrations increase depends on the production of secondary particles by preexisting graupel, some of which ultimately grow into new graupel, and its outward transport in the anvil flow aloft. Penetrations at temperatures as low as -15°C show the presence of electric fields consistent with specific laboratory-derived criteria for charge separated during ice-graupel collisions, given that a liquid water-dependent sign reversal temperature may occur. Such a reversal may result from either a changing temperature in the vertical, a changing cloud liquid water content in the horizontal, or a combination of the two. Since cloud-to-ground (CG) lightning can be observed with remote detection networks that provide the polarity and frequency of CG lightning, there is potential that hurricane evolution may be detected remotely and that lightning may be usable as an indicator of a change in the storm intensity and/or track.
Boebel, O., C. Schmid, and W. Zenk. Kinematic elements of Antarctic Intermediate Water in the western South Atlantic. Deep-Sea Research, Part II, 46(1-2):355-392 (1999).
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The northward flowing Antarctic Intermediate Water (AAIW) is a major contributor to the large-scale meridional circulation of water masses in the Atlantic. Together with bottom and thermocline water, AAIW replaces North Atlantic Deep Water that penetrates into the South Atlantic from the north. On the northbound propagation of AAIW from its formation area in the southwestern region of the Argentine Basin, the AAIW progresses through a complex spreading pattern at the base of the main thermocline. This paper presents trajectories of 75 subsurface floats, seeded at AAIW depth. The floats were acoustically tracked, covering a period from December 1992 to October 1996. Discussions of selected trajectories focus on mesoscale kinematic elements that contribute to the spreading of AAIW. In the equatorial region, intermittent westward and eastward currents were observed, suggesting a seasonal cycle of the AAIW flow direction. At tropical latitudes, just offshore the intermediate western boundary current, the southward advection of an anticyclonic eddy was observed between 5°S and 11°S. Farther offshore, the flow lacks an advective pattern and is governed by eddy diffusion. The westward subtropical gyre return current at about 28°S shows considerable stability with the mean kinetic energy to eddy kinetic energy ratio being around one. Farther south, the eastward deeper South Atlantic Current is dominated by large-scale meanders with particle velocities in excess of 60 cm s-1. At the Brazil-Falkland Current Confluence Zone, a cyclonic eddy near 40°S, 50°W seems to act as injector of freshly mixed AAIW into the subtropical gyre. In general, much of the mixing of the various blends of AAIW is due to the activity of mesoscale eddies, which frequently reoccupy similar positions.
Boebel O., C. Schmid, G. Podesta, and W. Zenk. Intermediate water in the Brazil-Malvinas Confluence Zone: A Lagrangian view. Journal of Geophysical Research, 104(C9):21,063-21,082 (1999).
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The subsurface flow within the subantarctic and subtropical regions around the Brazil-Malvinas Confluence Zone is studied, using daily hydrographic and kinematic data from four subsurface floats and a hydrographic section parallel to the South American shelf. The trajectories are mapped against sea-surface flow patterns as visible in concurrent satellite sea-surface temperature images, with focus on the November 1994 and October/November periods. The unprecedented employment of Lagrangian-S diagrams enables us to trace the advection of patches of fresh Antarctic Intermediate Water (AAIW) from the Confluence Zone into the subtropical region. The fresh AAIW consists of a mixture of subtropical AAIW and Malvinas Current core water. Within the subtropical gyre, these patches are discernible for extended periods and drift over long distances, reaching north to 34.26°S and east to 40.26°W. The cross-frontal migration of quasi-isobaric floats across the Confluence Zone from the subtropical to the subantarctic environment is observed on three occasions. The reverse process, float migration from a subpolar to a subtropical environment was observed once. These events were located near 40.26°S, 50.26°W, the site of a reoccurring cold core feature. Subsurface float and SST data comparison reveals similarities with analogous observations made in the Gulf Stream (Rossby, 1996) where cross-frontal processes were observed close to meander crests. The limited number of floats of this study and the complex structure of the Brazil-Malvinas Confluence Zone, however, restricts the analysis to a description of two events.
Boebel, O., R.E. Davis, M. Ollitrault, R.G. Peterson, P.L. Richardson, C. Schmid, and W. Zenk. Direct observations of the western South Atlantic intermediate depth circulation. Geophysical Research Letters, 26(21):3329-3332 (1999).
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The subsurface oceanic circulation is an important part of the Earth climate system. Subsurface currents traditionally are inferred indirectly from distributions of temperature and dissolved substances, occasionally supplemented by current meter measurements. Neutrally-buoyant floats, however, now enable us to obtain for the first time directly measured intermediate depth velocity fields over large areas such as the western South Atlantic. Here, our combined data set provides unprecedented observations and quantification of key flow patterns, such as the Subtropical Gyre return flow (12 Sv; 1 Sverdrup = 106 m3 s-1), its bifurcation near the Santos Plateau and the resulting continuous narrow and swift northward intermediate western boundary current (4 Sv). This northward flowing water passes through complex equatorial flows and finally enters into the North Atlantic.
Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black. Environmental influences on the rapid intensification of Hurricane Opal (1995) over the Gulf of Mexico. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 983-984 (1999).
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No abstract.
Bourles, B., R.L. Molinari, E. Johns, W.D. Wilson, and K.D. Leaman. Upper layer currents in the western tropical North Atlantic (1989-1991). Journal of Geophysical Research, 104(C1):1361-1376 (1999).
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Shipboard Acoustic Doppler Current Profiler (ADCP) measurements and hydrographic observations of temperature, salinity, and dissolved oxygen are used to examine the upper water column flow field in the North Brazil Current (NBC) retroflection region of the western tropical Atlantic Ocean. Observations are presented from six cruises, one conducted in August 1989 and the other five conducted during the Western Tropical Atlantic Experiment (WESTRAX) between January 1990 and September 1991. The upper water column is divided into two layers, an upper thermocline layer located between the surface and the 24.5 sigma theta isopycnal surface, and a lower subthermocline layer located between the 24.5 and 26.75 isopycnals. In the upper layer the NBC retroflects north of the equator to form the eastward flowing North Equatorial Counter Current (NECC). During the six cruises the retroflection appeared complete. However, data coverage did not extend shoreward of the 200 m isobath, so the possibility of a continuous flow over the shelf still remains. There were also indications of several NBC rings which had apparently separated from the NBC retroflection and drifted to the northwest towards the eastern Caribbean Sea. North of the NBC retroflection and the NECC, the North Equatorial Current (NEC) flows west as the southern limb of the subtropical gyre. Part of the NEC is observed to retroflect cyclonically to join the eastward NECC flow. In the lower layer, beneath the NBC, the North Brazil Undercurrent (NBUC) retroflects to feed the eastward North Equatorial Undercurrent (NEUC). To the north, a deeper component of the NEC recurves to also contribute to the NEUC.
Boutin, J., J. Etcheto, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, H.Y. Inoue, M. Ishii, R.D. Ling, P.D. Nightingale, N. Metzl, and R.H. Wanninkhof. Satellite sea surface temperature: A powerful tool for interpreting in-situ pCO2 measurements in the equatorial Pacific Ocean. Tellus B, 51(2):490-508 (1999).
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In order to determine the seasonal and interannual variability of the CO2 released to the atmosphere from the equatorial Pacific, we have developed pCO2-temperature relationships based upon shipboard oceanic CO2 partial pressure measurements, pCO2, and satellite sea surface temperature, SST, measurements. We interpret the spatial variability in pCO2 with the help of the SST imagery. In the eastern equatorial Pacific, at 5°S, pCO2 variations of up to 100 µatm are caused by undulations in the southern boundary of the equatorial upwelled waters. These undulations appear to be periodic with a phase and a wavelength comparable to tropical instability waves, TIW, observed at the northern boundary of the equatorial upwelling. Once the pCO2 signature of the TIW is removed from the Alize II cruise measurements in January 1991, the equatorial pCO2 data exhibit a diel cycle of about 10 µatm with maximum values occurring at night. In the western equatorial Pacific, the variability in pCO2 is primarily governed by the displacement of the boundary between warm pool waters, where air-sea CO2 fluxes are weak, and equatorial upwelled waters which release high CO2 fluxes to the atmosphere. We detect this boundary using satellite SST maps. East of the warm pool, DELTA-P is related to SST and SST anomalies. The 1985-1997 CO2 flux is computed in a 5° wide latitudinal band as a combination of DELTA-P and CO2 exchange coefficient, K, deduced from satellite wind speed, U. It exhibits up to a factor 2 seasonal variation caused by K-seasonal variation and a large interannual variability, a factor 5 variation between 1987 and 1988. The interannual variability is primarily driven by displacements of the warm pool that makes the surface area of the outgassing region variable. The contribution of DELTA-P to the flux variability is about half of the contribution of K. The mean CO2 flux computed using either the Liss and Merlivat (1986) or the Wanninkhof (1992) K-U parameterization amounts to 0.11 GtC yr-1 or to 0.18 GtC yr-1, respectively. The error in the integrated flux, without taking into account the uncertainly on the K-U parameterization, is less than 31%.
Bove, M.C., J.B. Elsner, C.W. Landsea, X. Niu, and J.J. O'Brien. Effect of El Niño on U.S. landfalling hurricanes, revisited. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 278-281 (1999).
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No abstract.
Broecker, W.S., S. Sutherland, and T.-H. Peng. A possible 20th-century slowdown of Southern Ocean deep water formation. Science, 286(5442):1132-1135 (1999).
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Chlorofluorocarbon-11 inventories for the deep Southern Ocean appear to confirm physical oceanographic and geochemical studies in the Southern Ocean, which suggests that no more than 5 × 106 cubic meters per second of ventilated deep water is currently being produced. This result conflicts with conclusions based on the distributions of the carbon-14/carbon ratio and a quasi-conservative property, PO4, in the deep sea, which seem to require an average of about 15 × 106 cubic meters per second of Southern Ocean deep ventilation over about the past 800 years. A major reduction in Southern Ocean deep water production during the 20th century (from high rates during the Little Ice Age) may explain this apparent discordance. If this is true, a seesawing of deep water production between the northern Atlantic and Southern Oceans may lie at the heart of the 1500-year ice-rafting cycle.
Broecker, W.S., E. Clark, D.C. McCorkle, T.-H. Peng, I. Hajdas, and G. Bonani. Evidence for a reduction in the carbonate ion content of the deep sea during the course of the Holocene. Paleoceanography, 14(6):744-752 (1999).
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The paleo carbonate ion proxy proposed by Broecker et al. (1999) is applied in a search for trends in the Holocene acidity of waters in the transition zone between North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). A clear signal emerges that the carbonate ion content of waters in this zone declined during the last 8000 years. In order to determine whether this decline represents a strengthening of the northward penetrating tongue of low CO3 content AABW or a global reduction of CO3 ion, measurements were made on a core from the Ontong Java Plateau in the western equatorial Pacific. Evidence for a similar decline in CO3 ion over the course of the Holocene was obtained, lending support of the latter explanation. Such a drop is consistent with the recent finding by Indermuhle et al. (1999) that the CO2 content of the atmosphere (as recorded in the Taylor Dome Antarctica ice core) rose by 20 to 25 ppm during the last 8000 years.
Campos, E., A. Busalacchi, S.L. Garzoli, J. Lutjeharms, R. Matano, P. Nobre, D.B. Olson, A. Piola, C. Tanajura, and I. Wainer. The South Atlantic and the climate. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1, 16 pp. (1999).
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As a contribution to the OCEANOBS99 objectives, we give a brief description of the present knowledge of the South Atlantic and identify some key processes and areas which need to be monitored in order to understand the role of that part of the ocean in the global climate. Included are suggestions of strategies for a first approximation towards an ocean climate monitoring system in the South Atlantic.
Checkley, D.M., P.B. Ortner, F.E. Werner, L.R. Settle, and S.R. Cummings. Spawning habitat of the Atlantic menhaden in Onslow Bay, North Carolina. Fisheries Oceanography, 8(2):22-36 (1999).
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The Continuous, Underway Fish Egg Sampler (CUFES) was used to sample pelagic eggs of the Atlantic menhaden (Brevoortia tyrannus) from a 3-m depth off North Carolina in winter 1993-1994 and 1994-1995. Simultaneous measurements were made of temperature, salinity, and the concentration of chlorophyll a. The maximal concentration of eggs was 346 eggs m-3. Eggs were highly aggregated in patches which occurred between the Gulf Stream and mid-shelf fronts (17-23°C, 36.0-36.4 ppm). Unexpectedly, eggs were found almost exclusively in water of 20-60 m (mode 20 m) bottom depth. Thus, spawning appears related to bathymetry as well as hydrography. Variograms for egg concentration indicated a mean (± SE) patch scale of 3.6 ± 1.7 km and a high degree of spatial variance explained by CUFES sampling. Lagrangian modeling of particles moving in response to tides, winds, and a prescribed flow from the north indicated that the region of observed, maximal occurrence of eggs is favorable for the retention of eggs and larvae on the shelf adjacent to inlets used to enter nursery areas.
Cione, J.J., P.G. Black, and S.H. Houston. Cooling and drying within the hurricane near-surface environment? Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1027-1030 (1999).
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No abstract.
Cook, S.K. Vertical thermal structure of midshelf waters: Water temperatures and climatological conditions south of New England, 1974-1983. NOAA Technical Report, NMFS-134, 43 pp. (1999).
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No abstract.
DeMaria, M., and J. Kaplan. An updated Statistical Hurricane Intensity Prediction Scheme (SHIPS) for the Atlantic and eastern North Pacific basins. Weather and Forecasting, 14(3):326-337 (1999).
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Updates to the Statistical Hurricane Intensity Prediction Scheme (SHIPS) for the Atlantic basin are described. SHIPS combines climatological, persistence, and synoptic predictors to forecast intensity changes using a multiple regression technique. The original version of the model was developed for the Atlantic basin and was run in near-real time at the Hurricane Research Division beginning in 1993. In 1996, the model was incorporated into the National Hurricane Center operational forecast cycle, and a version was developed for the eastern North Pacific basin. Analysis of the forecast errors for the period 1993-1996 shows that SHIPS had little skill relative to forecasts based upon climatology and persistence. However, SHIPS had significant skill in both the Atlantic and east Pacific basins during the 1997 hurricane season. The regression coefficients for SHIPS were rederived after each hurricane season since 1993 so that the previous season's forecast cases were included in the sample. Modifications to the model itself were also made after each season. Prior to the 1997 season, the synoptic predictors were determined only from an analysis at the beginning of the forecast period. Thus, SHIPS could be considered a "statistical-synoptic" model. For the 1997 season, methods were developed to remove the tropical cyclone circulation from the global model analyses and to include synoptic predictors from forecast fields, so the current version of SHIPS is a "statistical-dynamical" model. It was only after the modifications for 1997 that the model showed significant intensity forecast skill.
Dickerson, R.R., K.P. Rhoads, T.P. Carsey, S.J. Oltmans, J.P. Burrows, and P.J. Crutzen. Ozone in the remote marine boundary layer: A possible role for halogens. Journal of Geophysical Research, 104(D17):21,385-21,395 (1999).
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On the spring 1995 cruise of the National Oceanic and Atmospheric Administration research vessel Malcolm Baldrige, we measured very large diurnal variations in ozone concentrations in the marine boundary layer. Average diurnal variations of about 32% of the mean were observed over the tropical Indian Ocean. We simulated these observations with the Model of Chemistry in Clouds and Aerosols, a photochemical box model with detailed aerosol chemistry. The model was constrained with photolysis rates, humidity, aerosol concentrations, NO, CO, and O3 specified by shipboard observations and ozonesondes. Conventional homogeneous chemistry, where ozone photolysis to O(1D) and HOx chemistry dominate ozone destruction, can account for a diurnal variation of only about 12%. On wet sea-salt aerosols (at humidities above the deliquesence point), absorption of HOBr leads to release of BrCl and Br2, which photolyze to produce Br atoms that may provide an additional photochemical ozone sink. After eight days of simulation, these Br atoms reach a peak concentration of 1.2 × 107 cm-3 at noon and destroy ozone through a catalytic cycle involving BrO and HOBr. Reactive Br lost to HBr can be absorbed into the aerosol phase and reactivated. The model predicts a diurnal variation in O3 of 22% with aerosol-derived Br reaction explaining much, but not all, of the observed photochemical loss. The lifetime of ozone under these conditions is short, about two days. These results indicate that halogens play an important role in oxidation processes and the ozone budget in parts of the remote marine boundary layer.
Digby, S., T. Antczak, R. Leben, G. Born, S. Barth, R. Cheney, D. Foley, G.J. Goni, G. Jacobs, and L. Shay. Altimeter data for operational use in the marine environment. Proceedings, Oceans '99 MTS/IEEE Conference, Seattle, WA, September 13-16, 1999. Marine Technology Society, 605-613 (1999).
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TOPEX/Poseidon has been collecting altimeter data continuously since October 1992. Altimeter data have been used to produce maps of sea surface height, geostrophic velocity, significant wave height, and wind speed. This information is of proven use to mariners as well as to the scientific community. Uses of the data include commercial and recreational vessel routing, ocean acoustics, input to geographic information systems developed for the fishing industry, identification of marine mammal habitats, fisheries management, and monitoring ocean debris. As with sea surface temperature data from the Advanced Very High Resolution Radiometer (AVHRR) in the late 1980s and early 1990s, altimeter data from TOPEX/Poseidon and ERS-1 and -2 are in the process of being introduced to the marine world for operational maritime use. It is anticipated that over the next few years companies that specialize in producing custom products for shipping agencies, fisheries, and yacht race competitors will be incorporating altimeter data into their products. The data are also being incorporated into weather and climate forecasts by operational agencies both in the United States and Europe. This paper will discuss these products, their uses, operational demonstrations, and means of accessing the data.
Dodge, P.P., R.W. Burpee, and F.D. Marks. The kinematic structure of a hurricane with sea-level pressure less than 900 mb. Monthly Weather Review, 127(6):987-1004 (1999).
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A National Oceanic and Atmospheric Administration aircraft recorded the first Doppler radar data in a tropical cyclone with a minimum sea level pressure (MSLP) <900 mb during a reconnaissance mission in Hurricane Gilbert on 14 September 1988, when its MSLP was ~895 mb. A previous mission had found an MSLP of 888 mb, making Gilbert the most intense tropical cyclone yet observed in the Atlantic basin. Radar reflectivity identified the hurricane eye, inner and outer eyewalls, a stratiform region between the eyewalls, and an area outside the outer eyewall that contained a few rainbands but that had mostly stratiform rain. Pseudo-dual Doppler analyses depict the three-dimensional kinematic structure of the inner eyewall and a portion of the outer eyewall. The vertical profiles of tangential wind and reflectivity maxima in the inner eyewall are more erect than in weaker storms, and winds >50 m s-1 extended to 12 km, higher than has been reported in previous hurricanes. The inner eyewall contained weak inflow throughout most of its depth. In contrast, the portion of the outer eyewall described here had shallow inflow and a broad region of outflow. The stratiform region between the two eyewalls had lower reflectivities and was the only region where the vertically incident Doppler radar data seemed to show downward motion below the freezing level. Gilbert's structure is compared with other intense Atlantic and eastern North Pacific hurricanes with MSLP >900 mb. Storms with lower MSLP have higher wind speeds in both inner and outer eyewalls, and wind speeds >50 m s-1 extend higher in storms with lower MSLP. Hurricanes Gilbert and Gloria (1985), the strongest Atlantic hurricanes yet analyzed by the Hurricane Research Division, had different outer eyewall structures. Gloria's outer eyewall had a deep region of inflow, while Gilbert's inflow layer was shallow. This may explain differences in the subsequent evolution of the two storms.
Dodge, P.P., J.F. Gamache, S.H. Houston, and F.D. Marks. Windfields in landfalling hurricanes from multiple Doppler radar data: The 1998 hurricane season. Preprints, 29th International Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society, Boston, 273-275 (1999).
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No abstract.
Dodge, P.P., S.H. Houston, W.-C. Lee, J.F. Gamache, and F.D. Marks. Windfields in Hurricane Danny (1997) at landfall from combined WSR-88D and airborne Doppler radar data. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 61-62 (1999).
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No abstract.
Donnelly, W.J., J.R. Carswell, R.E. McIntosh, P.S. Chang, J.C. Wilkerson, F.D. Marks, and P.G. Black. Revised ocean backscatter models at C and Ku-bands under high wind conditions. Journal of Geophysical Research, 104(C5):11,485-11,498 (1999).
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A series of airborne scatterometer experiments designed to collect C and Ku-band ocean backscatter data in regions of high ocean surface winds has recently been completed. Over 100 hours of data were collected using the University of Massachusetts C and Ku-band scatterometers, CSCAT and KUSCAT. These instruments measure the full azimuthal normalized radar cross section (NRCS) of a common surface area of the ocean simultaneously at four incidence angles. Our results demonstrate limitations of the current empirical models, CMOD4, SASSII and NSCAT1, that relate ocean backscatter to the near surface wind at high wind speeds. The discussion focuses on winds in excess of 15 m/sec in clear atmospheric conditions. The scatterometer data is collocated with measurements from ocean data buoys and GPS dropsondes, and a Fourier analysis is performed as a function of wind regime. A three-term Fourier series is fit to the backscatter data, and a revised set of coefficients is tabulated. These revised models, CMOD4HW and KUSCAT1, are the basis for a discussion of the NRCS at high wind speeds. Our scatterometer data show a clear over prediction of the derived NRCS response to high winds based on the CMOD4, SASSII and NSCAT1 models. Furthermore, saturation of the NRCS response begins to occur above 15 m/sec. Sensitivity of the upwind and crosswind response is discussed with implications towards high wind speed retrieval. wind speed retrieval.
Ellsberry, R.L., and F.D. Marks. The Hurricane Landfall Workshop summary. Bulletin of the American Meteorological Society, 80(4):683-685 (1999).
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No abstract.
Enfield, D.B., and E.J. Alfaro. The dependence of Caribbean rainfall on the interaction of tropical Atlantic and Pacific Oceans. Journal of Climate, 12(7):2093-2103 (1999).
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Seasonally-stratified analyses of rainfall anomalies over the Intra-Americas Sea and surrounding land areas and of onset and end dates of the Central American rainy season show that the variability of the tropical Atlantic sea surface temperature anomaly (SSTA) is more strongly associated with rainfall over the Caribbean and Central America than is tropical eastern Pacific SSTA. Seasonal differences include the importance of antisymmetric configurations of tropical Atlantic SSTA in the dry season but not in the rainy season. Both oceans are related to rainfall, but the strength of the rainfall response appears to depend on how SSTA in the tropical Atlantic and eastern Pacific combine. The strongest response occurs when the tropical Atlantic is in the configuration of a meridional dipole (antisymmetric across the ITCZ) and configuration of a meridional dipole (antisymmetric across the ITCZ) and the eastern tropical Pacific is of opposite sign to the tropical North Atlantic. When the tropical North Atlantic and tropical Pacific are of the same sign, the rainfall response is weaker. The rainy season in lower Central America tends to start early and end late in years that begin with warm SSTs in the tropical North Atlantic, and the end dates are also delayed when the eastern equatorial Pacific is cool. This enhancement of date departures for zonally antisymmetric configurations of SSTA between the North Atlantic and Pacific is qualitatively consistent with the results for rainfall anomalies.
Enfield, D.B., and A.M. Mestas-Nunez. Multiscale variabilities in global sea surface temperatures and their relationships with tropospheric climate patterns. Journal of Climate, 12(9):2719-2733 (1999).
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El Niño-Southern Oscillation (ENSO) is a global phenomenon with significant phase propagation within and between basins. We capture and describe this in the first mode of a complex empirical orthogonal function (CEOF) analysis of sea surface temperature anomaly (SSTA) from the mid-19th century through 1991. We subsequently remove the global ENSO from the SSTA data, plus a linear trend everywhere, in order to consider other global modes of variability uncontaminated by the intra- and inter-basin effects of ENSO. An ordinary EOF analysis of the SSTA residuals reveals three non-ENSO modes of low-frequency variability that are related to slow oceanic and climate signals described in the literature. The first two modes have decadal-to-multidecadal time scales with high loadings in the Pacific. They bear some spatial similarities to the ENSO pattern but are broader, more intense at high latitudes, and differ in the time domain. A CEOF analysis confirms that they are not merely the phase-related components of a single mode and that all three modes are without significant phase propagation. The third mode is a multidecadal signal with maximal realization in the extratropical North Atlantic southeast of Greenland. It is consistent with studies that have documented connections between North Atlantic SSTA and the tropospheric North Atlantic Oscillation (NAO). All three SSTA modes have mid-tropospheric associations related to previously classified Northern Hemisphere teleconnection patterns. The relationships between SSTA modes and tropospheric patterns are consistent with the ocean-atmosphere interactions discussed in previous studies to explain low-frequency climate oscillations in the North Pacific and North Atlantic sectors. The first three leading modes of non-ENSO SSTA are most related, respectively, to the tropospheric patterns of the Pacific North American (PNA), the North Pacific (NP) and the Arctic Oscillations (AO), respectively. The 500 hPa pattern associated with the third SSTA mode also bears similarities to the NAO in its Atlantic sector. This North Atlantic mode has a region of high, positive SSTA loadings in the Gulf of Alaska, which appear to be connected to the North Atlantic SSTA by a tropospheric bridge effect in the AO.
Enfield, D.B., A.M. Mestas-Nunez, D.A. Mayer, and L. Cid-Serrano. How ubiquitous is the dipole relationship in tropical Atlantic sea surface temperatures? Journal of Geophysical Research, 104(C4):7841-7848 (1999).
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Several kinds of analysis are applied to the departures of sea surface temperatures from climatology (SSTA, 1856-1991) to determine the degree to which SSTA of opposite sign in the tropical North and South Atlantic occur. Antisymmetric ("dipole") configurations of SSTA on basin scales are not ubiquitous in the tropical Atlantic. Unless the data are stratified by both season and frequency, inherent dipole behavior cannot be demonstrated. Upon removing the global ENSO signal in SSTA (which is symmetric between the North and South Atlantic) from the data, the regions north or south of the intertropical convergence zone have qualitatively different temporal variabilities and are poorly correlated. Dipole configurations do occur infrequently (12-15% of the time), but no more so than expected by chance for stochastically-independent variables. Non-dipole configurations that imply significant meridional SSTA gradients occur much more frequently, nearly half of the time. Cross-spectral analysis of seasonally averaged SSTA indices for the North and South Atlantic show marginally significant coherence with antisymmetric phase in two period bands: 8-12 years for the boreal winter-spring, and 2.3 years for the boreal summer-fall. Antisymmetric coherence is optimal for a small sub-region west of Angola in the South Atlantic, with respect to SSTA of basin scale in the tropical North Atlantic. Dipole variability, even where optimal, explains only a small fraction of the total variance in tropical Atlantic SSTA (<7%).
Enfield, D.B., A.M. Mestas-Nunez, D.A. Mayer, and L. Cid-Serrano. The dipole in tropical Atlantic SST: Common? Random? Intrinsic? Proceedings, 23rd Annual Climate Diagnostics and Prediction Workshop, Miami, Florida, October 26-30, 1998. National Weather Service, 223-226 (1999).
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In this paper we clarify the confusing and apparently contradictory views regarding tropical Atlantic dipole variability. The issue is revisited by using a recently reconstructed 136-year SST anomaly (SSTA) analysis for the globe (Kaplan et al., 1998; henceforth, K98). An expanded analysis will appear in the Journal of Geophysical Research-Oceans (Enfield et al., 1999).
Esenkov, O.E., and B. Cushman-Roisin. Modeling of two-layer eddies and coastal flows with a particle method. Journal of Geophysical Research, 104(C5):10,959-10,980 (1999).
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An existing particle-in-cell (PIC) numerical code is applied to lens-like anticyclonic vortices and buoyant coastal currents. A first series of experiments with initially elongated eddies reveals that motions induced in the lower layer act to increase the rate of rotation of the structure; eccentricity reduction, if any, produces a final vortex of aspect ratio between 1.8 and 1.9, in accordance with a theoretical prediction. A second series of experiments determines the maximal separation distance that can exist between two identical and circular vortices before they spontaneously merge; this distance is a function of the vortex size and ambient stratification. In a third series of experiments, vortex interactions across layers are considered; results similar to those obtained with two-layer point vortices (hetons) are obtained. Finally, the PIC method is generalized to simulate the finite-amplitude instability of a buoyant geostrophic current flowing along a vertical coastal wall.
Etcheto, J., J. Boutin, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, R.D. Ling, P.D. Nightingale, and R.H. Wanninkhof. Air-sea CO2 flux variability in the equatorial Pacific Ocean near 100°W. Tellus B, 51(3):734-747 (1999).
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The interannual variability of the CO2 partial pressure (pCO2) in the surface layer of the east equatorial Pacific Ocean near 100°W is studied and compared with the sea surface temperature (SST) monitored from satellites. This variability is shown to be correlated with the SST anomaly rather than with the temperature itself. The pCO2OC variability is related to the variability of the upwelling systems (the equatorial upwelling and the upwelling along the American coast), the main influence being from the coastal upwelling via the surface water advected from the east. A method is derived to interpolate the pCO2OC measurements using the SST satellite measurements. By combining the result with the exchange coefficient (K) deduced from the wind speed provided by satellite-borne instruments, we deduce the air-sea CO2 flux and, for the first time, we continuously monitor its temporal variation. The variability of this flux is mainly due to the variability of K, with a clear seasonal variation. The flux obtained using the Liss and Merlivat (1986) relationship averaged from April 1985 to June 1997 in the region 97.5°-107.5°W, 0-5°S is 1.67 mole m-2 yr-1 of CO2, leaving the ocean with an estimated accuracy of 30%.
Etcheto, J., J. Boutin, D.C.E. Bakker, Y. Dandonneau, R.A. Feely, H.Y. Inoue, M. Ishii, R.D. Ling, L. Merlivat, P.D. Nightingale, N.Metzl, and R.H. Wanninkhof. pCO2 in the equatorial Pacific and Atlantic Oceans: Determination of air-sea CO2 flux using satellite-borne instruments. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 119-125 (1999).
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No abstract.
Feely, R.A., M.F. Lamb, D.J. Greeley, and R.H. Wanninkhof. Comparison of the carbon system parameters at the global CO2 survey crossover locations in the North and South Pacific Ocean between 1990-1996. Technical Report, ORNL/CDIAC-115, Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, 73 pp. (1999).
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As a collaborative program to measure global ocean carbon inventories and provide estimates of the anthropogenic carbon dioxide (CO2) uptake by the oceans, the National Oceanic and Atmospheric Administration and the U.S. Department of Energy have sponsored the collection of ocean carbon measurements as part of the World Ocean Circulation Experiment and Ocean-Atmosphere Carbon Exchange Study cruises. The cruises discussed here occurred in the North and South Pacific from 1990 through 1996. The carbon parameters from these 30 crossover locations have been compared to ensure a consistent global data set emerges from the survey cruises. The results indicate that for dissolved inorganic carbon, fugacity of CO2, and pH, the agreement at most crossover locations are well within the design specifications for the global CO2 survey, whereas in the case of total alkalinity, the agreement between crossover locations is not as close.
Feely, R.A., C.L. Sabine, R.M. Key, and T.-H. Peng. CO2 survey synthesis results: Estimating the anthropogenic carbon dioxide sink in the Pacific Ocean. U.S. JGOFS News, 9(4):1-4 (1999).
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Our results to date suggest that the cumulative amount of anthropogenic CO2 in the global ocean is somewhere between 105 and 118 PgC through the year 1996. These results can be utilized as a constraint on other global carbon model simulations, similar to Princeton/Geophysical Fluid Dynamics Laboratory Ocean Biogeochemical Model and National Center for Atmospheric Research model simulations. As we refined and complete the estimates of the oceanic uptake of anthropogenic CO2, the results will be compared to CO2 uptake estimates for the atmosphere and terrestrial biosphere.
Feely, R.A., R.H. Wanninkhof, T. Takahashi, and P. Tans. Influence of El Niño on the equatorial Pacific contribution to atmospheric CO2 accumulation. Nature, 398(6728):597-601 (1999).
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The equatorial ocean is an important CO2 source to the atmosphere, contributing annually 0.7-1.5 Pg of carbon as CO2, as much as 80% of which is attributed to the equatorial Pacific. This source is known to change significantly by ENSO events. To better understand the regional and interannual variability of CO2 fluxes from the equatorial Pacific, field measurements of the partial pressure of CO2 (pCO2) have been made in the equatorial Pacific region since 1992. Here, we report that during the 1991-1994 ENSO period the net annual sea-to-air flux of CO2 was 0.3 PgC from the fall of 1991 to the fall of 1992, 0.6 PgC in 1993, and 0.7 PgC in 1994. These fluxes are 30%-80% of the 0.9 PgC observed during the non-El Niño year of 1996. The total reduction of the sea-to-air CO2 flux during the 1991-1994 El Niño is estimated to be 0.8-1.2 PgC, which accounts for 16-36% of the atmospheric anomaly (the difference between the annual atmospheric CO2 increase in PgC yr-1 and the long-term average increase of 3.18 PgC yr-1) observed over the same period.
Feely, R.A., C.L. Sabine, R.M. Key, T.-H. Peng, and R.H. Wanninkhof. The U.S. global CO2 survey in the North and South Pacific Ocean. Preliminary synthesis results. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 193-198 (1999).
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As a collaborative program to measure global ocean carbon inventories and provide estimates of the anthropogenic CO2 uptake in the oceans, the National Oceanic and Atmospheric Administration, the U.S. Department of Energy, and the National Science Foundation have co-sponsored the collection of ocean carbon measurements as part of the World Ocean Circulation Experiment (WOCE) and Ocean-Atmospheric Carbon Exchange Study (OACES). The cruises discussed here occurred in the North and South Pacific from 1990 through 1996. The new estimates for anthropogenic CO2, employing the DELTA-C* method of Gruber et al. (1996), indicate that the largest buildup of anthropogenic CO2 occurs in subtropical waters. Along 155°W, anthropogenic CO2 penetrates to a maximum depth of 900 m at about 37°N in the North Pacific and 1300 m at about 48°S in the South Pacific. Strong shoaling of anthropogenic CO2 occurs southward of 50°S and northward of 48°N. The anthropogenic CO2 inventories from the observations are smaller than the Princeton Ocean Biogeochemical Model (POBM) model estimates, primarily because the Princeton model produces too much deep convective mixing of anthropogenic CO2 in the Southern Ocean. The NCAR Climate System Ocean model, which has very different physics and biological parameterizations, appears to do a better job of reproducing the general patterns in the data-based section.
Fine, R.A., L. Merlivat, W. Roether, W.M. Smethie, and R.H. Wanninkhof. Observing tracers and the carbon cycle. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1, 14 pp. (1999).
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A program for repeated sampling of tracers and variables essential for quantitative understanding of the carbon cycle is recommended within CLIVAR/GOOS. The program is critical to our monitoring and understanding of climate change, both natural and anthropogenic. The objectives are: quantification of changes in the rates and spatial patterns of oceanic carbon uptake, fluxes, and storage of anthropogenic CO2; detection and possible quantification of changes in water mass renewal and mixing rates; and provision of a stringent test of the time integration of models' natural and anthropogenic climate variability. The strategy is to put in place a global observing network for tracers and CO2 to document the continuing large-scale evolution of these fields. Hydrographic lines are advocated, although it is realized that there has to be a limit on these observations due to logistical and resource constraints. Thus, there is the need to supplement these observations with time series and autonomous measurements to provide detail in the temporal evolution of the fields.
Franklin, J.F., M.L. Black, and S.E. Feuer. Wind profiles in hurricanes determined by GPS dropwindsondes. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 167-168 (1999).
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No abstract.
Gamache, J.F. Airborne Doppler observations of intensity change in eastern Pacific Hurricane Guillermo. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 325-328 (1999).
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No abstract.
Garzoli, S.L., P.L. Richardson, C.M. Dumcombe Rae, D.M. Fratantoni, G.J. Goni, and A.J. Roubicek. Three Agulhas rings observed during the Benguela Current Experiment. Journal of Geophysical Research, 104(C9):20,971-20,986 (1999).
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A field program to study the circulation of the Benguela Current and its extension into the southeastern Atlantic Ocean has completed the survey and instrument deployment phase. We report here new observations of three Agulhas rings north and west of Cape Town, South Africa. Three mesoscale anticyclonic rings initially identified by means of TOPEX/POSEIDON altimetry were surveyed with expendable bathythermographs (XBTs), conductivity-temperature-depth-oxygen (CTDO) profiles, direct current measurements from a lowered acoustic Doppler current profiler (LADCP), a hull-mounted acoustic Doppler current profiler (ADCP), and satellite-tracked surface drifters. Characteristics of the rings are presented and their origins are discussed. Two are typical Agulhas rings surveyed at different times after their generation; the third Agulhas ring has an anomalous watermass structure whose most likely origin is the Subtropical Front.
Garzoli, S.L., D.B. Enfield, G. Reverdin, G. Mitchum, R.H. Weisberg, P. Chang, and J. Carton. COSTA: A Climate Observing System for the Tropical Atlantic. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1, 19 pp. (1999).
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This paper summarizes the discussions that took place during the COSTA (Climate Observing System for the Tropical Atlantic) workshop held in Miami, Florida during May 1999. The main objective of the workshop was to coordinate the present efforts in the region and to set the scientific basis for an extended and more permanent observing system. The intent of the COSTA workshop, based in the CLIVAR (global) and ACVE (basin) experience, was to formulate the basis for an extended and more permanent (regional) tropical Atlantic observing system, building on the present existing monitoring programs and process studies, and the current scientific underlayment. The first part of this paper establishes the importance and the role of the tropical Atlantic in climate fluctuations and their impact in society. This is followed by a description of the climate variability in the Atlantic sector, its relationship to tropical Atlantic variability, especially sea surface temperature (SST), and to the North Atlantic Oscillation and meridional overturning circulation. The possible mechanisms behind tropical Atlantic SST fluctuations and their relation to climate is also discussed, highlighting, in particular, the role of surface fluxes in the off-equatorial regions, the equatorial ocean-atmosphere interactions, and their relationships to movements of the Inter-Tropical Convergence Zone. The second part of this paper summarizes the scientific discussions and recommendations from the working groups who centered their discussions in the following themes: (1) SST and surface fluxes; (2) sea level and subsurface structure; (3) circulation; and (4) modeling and data assimilation. Finally, the present status of the observing system and a summary of recommendations is presented.
Goldenberg, S.B., and C.W. Landsea. Relationships between decadal-scale fluctuations in vertical shear from NCEP/NCAR reanalysis data and Atlantic basin tropical cyclone activity. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1089-1091 (1999).
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No abstract.
Goni, G.J. Transport estimates of the Kuroshio Current from satellite altimeter data. In Ecosystem Dynamics of the Kuroshio Oyashio Transition Region, M. Terazaki, K. Ohtani, T. Sugimoto, and Y. Watanabe (eds.). Japan Marine Science Foundation, Tokyo, 1-8 (1999).
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The Kuroshio, together with the Gulf Stream, its counterpart in the North Atlantic, are the two major western boundary currents in the northern hemisphere. These currents have been viewed as the principal channel of water exchange between the equatorial regions, where heat is added to the oceans to be later removed in the polar regions. The transport of the Kursohio current remains one of the largest uncertainties in the meridional heat flux estimate across the North Pacific subtropical gyre. Estimates of the Kuroshio mean transports vary from 21 Sv to 33 Sv (1 S v =106 m3 s-1). Some characteristics of the dynamics of this current and its variability will be also briefly addressed in this work. One very important issue in ocean dynamics is to constantly monitor the subsurface thermal structure and transport of a western boundary current. This work presents a methodology that uses a combination of satellite altimetry-derived sea height anomaly and inverted echosounder-derived hydrographic data to estimate the thickness of the ocean upper layer and baroclinic transport. The estimates reveal that during the end of 1996 and beginning of 1997 the Kuroshio Current presents an anomalous behavior.
Goni, G.J., M.M. Huber, and L.K. Shay. TOPEX/POSEIDON-derived Atlantic Ocean hurricane heat content estimates. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, American Meteorological Society 79th Annual Meeting, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1037-1042 (1999).
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No abstract.
Graber, H.C., M.A. Donelan, S. Atakturk, W.M. Drennan, and K.B. Katsaros. Marine flux-profile relations from an air-sea interaction spar buoy. Proceedings, Symposium on the Wind-Driven, Air-Sea Interface, Sydney, Australia, January 10-15, 1999, M. Banner (ed.). The University of New South Wales, 317-324 (1999).
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The Air-Sea Interaction Spar (ASIS) is a new autonomous spar buoy designed to permit long-term measurements of processes at the air-sea interface. During a two-month deployment in the Gulf of Mexico in April/May 1997, the buoy recorded waves as high as 3.5 m and wind speeds up to 20 m/s. The ASIS buoy was instrumented to measure high resolution wave directional properties, wind stress, and four level profiles of wind speed, temperature, and humidity. These data are used to examine marine flux-profile relations and to explore the effect of a thick wave boundary layer on the validity of Monin-Obukhov similarity theory.
Gray, J. National Oceanic and Atmospheric Administration research and operation priorities. In Proceedings, South Florida Measurement Center Workshop: Establishment of a Center for Innovative Oceanography in the 21st Century, Dania, FL, February 24-26, 1999. National Science Foundation, 207-213 (1999).
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No abstract.
Grima, N., A. Bentamy, K.B. Katsaros, Y. Quilfen, P. Delecluse, and C. Levy. Sensitivity of an oceanic general circulation model forced by satellite wind stress fields. Journal of Geophysical Research, 104(C4):7967-7989 (1999).
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Satellite wind and wind stress fields at the sea surface, derived from the scatterometers on European Remote Sensing satellites 1 and 2 (ERS-1 and ERS-2) are used to drive the ocean general circulation model (OGCM) "OPA" in the tropical oceans. The results of the impact of ERS winds are discussed in terms of the resulting thermocline, current structures, and sea level anomalies. Their adequacy is evaluated on the one hand by comparison with simulations forced by the Arpege-Climat model and on the other hand by comparison with measurements of the Tropical Atmosphere-Ocean (TAO) buoy network and of the TOPEX/Poseidon altimeter. Regarding annual mean values, the thermal and current responses of the OGCM forced by ERS winds are in good agreement with the TAO buoy observations, especially in the central and eastern Pacific Ocean. In these regions the South Equatorial Current, the Equatorial Undercurrent, and the thermocline features simulated by the OGCM forced by scatterometer wind fields are described. The impact of the ERS-1 winds is particularly significant to the description of the main oceanic variability. Compared to the TAO buoy observations, the high-frequency (a few weeks) and the low-frequency of the thermocline and zonal current variations are described. The correlation coefficients between the time series of the thermocline simulated by ERS winds and that observed by the TAO buoy network are highly significant; their mean value is 0.73, over the whole basin width, while it is 0.58 between Arpege model simulation and buoy observations. At the equator the time series of the zonal current simulated by the ERS winds, at three locations (110°W, 140°W, and 165°E) and at two depths, are compared to the TAO current meter and acoustic Doppler current profiler (ADCP) measurements. The mean value of the significant correlation coefficients computed with the in-situ measurements in 0.72 for ERS, while it is 0.51 for the Arpege-Climat model. Thus, ERS wind fields through the OGCM generate more realistic current variations than those obtained with Arpege climate winds, and they are particularly efficient in capturing abrupt changes ("wind bursts") which may be important regarding ocean dynamics.
Hansen, D.V., and W.C. Thacker. Estimation of salinity profiles in the upper ocean. Journal of Geophysical Research, 104(C4):7921-7934 (1999).
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A new algorithm is presented for estimating salinity profiles in the upper ocean from measurements of temperature profiles and surface salinity. In application to the eastern tropical Pacific the method replicates a large fraction of the variability of salinity in the upper few tens of meters and provides modest to substantial improvement at nearly all levels. Estimated salinity profiles are able to characterize barrier layers, regions formed by a halocline within the thermal mixed layer. The rms error of geopotential-height calculations based on estimated salinity profiles is reduced more than 50 percent by this method relative to methods not using surface salinity. Even without the surface salinity measurement some reduction of error in geopotential heights can be obtained relative to previous methods.
Hock, T.F., and J.L. Franklin. The NCAR GPS dropwindsonde. Bulletin of the American Meteorological Society, 80(3):407-420 (1999).
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The National Center for Atmospheric Research (NCAR), in a joint effort with the National Oceanic and Atmospheric Administration (NOAA) and the German Aerospace Research Establishment, has developed a dropwindsonde based on the Global Positioning System (GPS) satellite navigation. The NCAR GPS dropwindsonde represents a major advance in both accuracy and resolution for atmospheric measurements over data-sparse oceanic areas of the globe, providing wind accuracies of 0.52 m s-1 with a vertical resolution of ~5 m. One important advance over previous generations of sondes is the ability to measure surface (10 m) winds. The new dropwindsonde has already been used extensively in one major international research field experiment (Fronts and Atlantic Storm Track Experiment), in operational and research hurricane flights from NOAA's National Weather Service and Hurricane Research Division, during NCAR's SNOWBAND experiment, and in recent CALJET and NORPEX El Niño experiments. The sonde has been deployed from a number of different aircraft, including NOAA's WP-3Ds and new Gulfstream IV jet, the Air Force C-130s, NCAR's Electra, and a leased Lear-36. This paper describes the characteristics of the new dropwindsonde and its associated aircraft data system, details the accuracy of its measurements, and presents examples from its initial applications.
Houston, S.H., and M.D. Powell. Hurricanes and tropical storms in Florida Bay. Florida Sea Grant College Program, FLSGP-G-99-016, 2 pp. (1999).
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No abstract.
Houston, S.H., W.A. Shaffer, M.D. Powell, and J. Chen. Comparisons of HRD and SLOSH surface wind fields in hurricanes: Implications for storm surge modeling. Weather and Forecasting, 14(5):671-686 (1999).
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Surface wind observations analyzed by the Hurricane Research Division (HRD) were compared to those computed by the parametric wind model used in the National Weather Service Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model's storm surge computations for seven cases in five recent hurricanes. In six cases, the differences between the SLOSH and HRD surface peak wind speeds were 6% or less, but in one case (Hurricane Emily of 1993) the SLOSH computed peak wind speeds were 15% less than the HRD. In all seven cases, statistics for the modeled and analyzed wind fields showed that for the region of strongest winds, the mean SLOSH wind speed was 14% greater than that of the HRD and the mean inflow angle for SLOSH was 19° less than that of the HRD. The radii beyond the region of strongest winds in the seven cases had mean wind speed and inflow angle differences that were very small. The SLOSH computed peak storm surges usually compared closely to the observed values of storm surge in the region of the maximum wind speeds, except Hurricane Emily where SLOSH underestimated the peak surge. HRD's observation-based wind fields were input to SLOSH for storm surge hindcasts of Hurricanes Emily and Opal (1995). In Opal, the HRD input produced nearly the same computed storm surges as those computed from the SLOSH parametric wind model, and the calculated surge was insensitive to perturbations in the HRD wind field. For Emily, observation-based winds produced a computed storm surge that was closer to the peak observed surge, confirming that the computed surge in Pamlico Sound was sensitive to atmospheric forcing. Using real-time, observation-based winds in SLOSH would likely improve storm surge computations in landfalling hurricanes affected by synoptic and mesoscale factors that are not accounted for in parametric models (e.g., a strongly sheared environment, convective asymmetries, and stably stratified boundary layers). An accurate diagnosis of storm surge flooding, based on the actual track and wind fields, could be supplied to emergency management agencies, government officials, and utilities to help with damage assessment and recovery efforts.
Houston, S.H., G. Forbes, A. Chiu, W.-C. Lee, and P.P. Dodge. Super Typhoon Paka's (1997) surface winds. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1032-1033 (1999).
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No abstract.
Huang, H., R.E. Fergen, J.J. Tsai, and J.R. Proni. Evaluation of mixing zone models: CORMIX, PLUMES, and OMZA with field data from two Florida ocean outfalls. Proceedings, Second International Symposium on Environmental Hydraulics, Hong Kong, China, December 16-18, 1998. Environmental Hydraulics, pp. 249-254 (1999).
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This paper presents an evaluation of three mixing zone models: CORMIX, PLUMES, and OMZA using field data from two Florida ocean outfalls: Hollywood and Miami-Central outfalls. The hollywood outfall has a single port outlet and the Miami-Central outfall has a multiport diffuser. Both outfalls discharge secondary effluent. For the nearfield, all of the three models predict realistic initial dilutions for the tests at the outfall except three cases in CORMIX predictions and two cases in PLUMES predictions (out of 20 cases). For the nearfield and farfield combined, CORMIX significantly overestimates dye concentrations for the tests at the Hollywood outfall but underestimates dye concentrations within the 300 m to 400 m range for the tests at the Miami-Central outfall. PLUMES predictions agree reasonably well with the filed data for the range from 300 m to 800 m but do not agree well within the 300 m range for the tests at both outfalls. OMZA predictions agree well with the field data within the 800 m range for the test at both outfalls.
Huber, M.M., L.K. Shay, and G.J. Goni. The Atlantic Ocean's role on intensity change. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, American Meteorological Society 79th Annual Meeting, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 36-39 (1999).
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No abstract.
Humphrey, J.C., S.L. Vargo, J.C. Ogden, and J.C. Hendee. SEAKEYS 1999: Florida Keys monitoring initiative. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Program and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 240-241 (1999).
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The Sustained Ecological Research Related to the Management of the Florida Keys Seascape (SEAKEYS) program was organized in 1991 by the Florida Institute of Oceanography (FIO) with initial funding from the John D. and Catherine T. MacArthur Foundation, and continuing funding from the South Florida Ecosystem Restoration, Prediction and Monitoring (SFERPM) program, administered by the National Oceanic and Atmospheric Administration (NOAA). The SEAKEYS environmental monitoring program, which is basically an oceanographic extension to the meteorologically-oriented Coastal-Marine Automated Network of NOAA, has accumulated an unparalleled long-term database of meteorological and oceanographic data from the Florida Straits and Florida Bay. During 1998, the SEAKEYS network was upgraded with more precise oceanographic sensors, and selected stations were augmented with fluorometers, transmissometers, and water-level sensing equipment. A seventh monitoring station, a cooperative effort between FIO and the University of South Florida's Department of Marine Science (USF/DMS), was completed in Northwest Florida Bay at 25°05'00"N, 81°05'30"W during summer, 1998. This station also contains a full suite of meteorological and oceanographic instrumentation and also transmits its data hourly via a NOAA GOES satellite. The Northwest Florida Bay station is the northwestern most station in the SEAKEYS network, as well as the southernmost link in the West Florida Coastal Ocean Monitoring and Prediction System of USF/DMS. Turbulent weather was prominent during 1998 in the Florida Keys. Severe conditions reported by the SEAKEYS stations included the Ground Hog Day Storm, Hurricane Georges, and Tropical Storm Mitch. In most cases the SEAKEYS stations contained the only instruments to measure the meteorological and oceanographic measurements accompanying these events in the Florida Keys. The Long Key station measured the highest winds (119 mph) in South Florida during the Ground Hog Day Storm of February 2, 1998. On September 25, 1998 the eye of Hurricane Georges passed over Key West at 1150 EDT as wind speeds dropped from 85.2 mph to 9.6 mph. The eye moved across the Dry Tortugas station at 1610 EDT with barometric pressures dropping to 974.4 mb. Winds gusted to hurricane force only after the eye passed at 2100 EDT. Georges' most severe winds in the Florida Keys gusted to 113 mph at Sombrero Reef, with a sustained wind speed of 94 mph. Long Key, Molasses Reef, and Fowey Rocks received gusts of tropical storm force. The tide station at Sombrero Reef reported a storm water level of 2.87 feet above mean lower low water. This contrasted with below normal levels reported at a station on Florida Bay. Hurricane Mitch passed northwest of the Florida Keys on the evening of November 4, 1998, bringing peak winds of 62.4 mph at Molasses Reef and sustained gale force winds until the following afternoon. Numerous localized tornadoes spawned by this storm caused extensive damage in the Upper Keys. Daily near real-time SEAKEYS data are available to researchers via NOAA's Coral Health and Monitoring Program (CHAMP) Web site at http://www.coral.noaa.gov, while historical data are available at http://www.neptune.noaa.gov. The Coral Reef Early Warning System (CREWS), which utilizes the near real-time data from six SEAKEYS stations, is an online expert system which monitors environmental conditions on the reef that are theoretically conducive to coral bleaching. If these conditions occur, alerts are sent via email to researchers and posted to the Web at http://www.coral.noaa.gov/sferpm/seakeys/es.
Jodoin, C. Detection of direct-sequence spread-spectrum signals in a multipath fading environment. Master's Thesis, Florida Atlantic University, Boca Raton, FL, 120 pp. (1999).
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In this thesis, we study the effect of Rice fading on the performance of Global Positioning System (GPS) receivers. The field-theoretic foundation of pseudo-random-noise (PRN) codes, their implementation, and their use in generating unique navigation messages in the GPS receiver is reviewed. The processing of the spread-spectrum signals within the digital delay locked loop (DDLL) in the receiver is also considered. In particular, we derive numerical expressions that can be easily evaluated for the probability error and the mean-time to lose-lock, for a DDL operating in an additive white Gaussian noise (AWGN) channel in the presence of Rice fading. The results obtained generalize results in the literature for the Rayleigh fading environment.
Johns, E., W.D. Wilson, and T.N. Lee. Surface salinity variability of Florida Bay and southwest Florida coastal waters. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 169-171 (1999).
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No abstract.
Johns, E., W.D. Wilson, and R.L. Molinari. Direct observations of velocity and transport in the passages between the Intra-Americas Sea and the Atlantic Ocean, 1984-1996. Journal of Geophysical Research, 104(C11):25,805-25,820 (1999).
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Shipboard acoustic Doppler current profiler observations of the velocity in the upper 200 m of the water column collected during 1984-1996 using the National Oceanic and Atmospheric Administration R/V Malcolm Baldrige are used to examine the velocity structure and transport in the passages between the Atlantic Ocean and the Intra-Americas Sea (IAS). Data were colected during 23 cruises along the following sections: across the Straits of Florida, in the Northwest Providence Channel (NWPC), across the northern passages into the Caribbean Sea (Windward, Mona, and Anegada), across the eastern Caribbean along 63°30'W, thereby forming a closed quadrangle, and in the Grenada Passage. The Florida Current, the eastern Caribbean, and the Grenada Passage share a similar mean velocity structure characterized by high-velocity, surface intensified flows with strong vertical and horizontal shears. The northern Caribbean passages (NWPC, Windward, Mona, and Anegada) share a different common mean velocity structure, with subsurface velocity maxima directed into the IAS, and surface-intensified counterflows along one side of each paassage. On average, there is a transport balance in the upper 200 m between waters entering and exiting the IAS, with the 16.5 ± 2.4 Sv (1 Sv = 106 m3 s-1) transport of the Florida Current at 27°N comprised of 0.4 ± 0.8 Sv from the NWPC, 2.2 ± 1.5 Sv from the Windward Passage, 2.8 ± 2.1 and 2.4 ± 2.8 Sv from the Mona and Anegada passages, respectively, and 9.5 ± 4.7 Sv across the eastern Caribbean, for a total of 17.3 Sv. The four passages north of 17°N (from NWPC to Anegada Passage) have a combined transport of 7.8 Sv, nearly half of the transport of the Florida Current in the upper 200 m. Of the 9.5 Sv flowing through the eastern Caribbean between 11°N and 17°N, 4.9 ± 2.6 Sv, or more than half, come from the Grenada Passage. This is significant to the subject of cross-equatorial exchange of mass, heat, and salt, as the Grenada Passage is where the highest transport of waters originating in the southern hemisphere is thought to enter the Caribbean.
Jones, R.W., and M. DeMaria. Further studies of the optimization of a hurricane track prediction model using the adjoint equations. Monthly Weather Review, 127(7):1586-1598 (1999).
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The method of model fitting, or adjoint method, is applied to a barotropic hurricane track forecast model described by DeMaria and Jones using a large sample of forecast cases. The sample includes all Atlantic tropical cyclones that reached hurricane intensity during the 1989-1993 hurricane seasons (141 72-h forecasts of 17 storms). The cases considered by DeMaria and Jones are a subset of the present sample. Model-fitting calculations using strong, weak, strong followed by weak, or weak followed by strong model constraints are discussed for data assimilation periods varying from 6 to 72 h. Generally, the best track forecasts occur for shorter assimilation periods and for weak constraints, although only the 12-h assimilation with the weak constraint has less track error than the control forecast without assimilation, and only for the 12-h forecast. The principle reason for this lack of improvement is that the fit of the model to the observed track is good at the middle of the assimilation period, but not very good at the end where the forecast begins. When a future track position at 6 h is included in the assimilation, in order to improve the track fit at the synoptic data time, the resulting track errors average about 10% smaller than the control forecast. The control forecast may also be improved in the same way. In that case, the best assimilation forecasts have 2.5% smaller track errors than the modified control forecasts.
Jones, R.W., and H.E. Willoughby. Results of generalizing a semispectral shallow-water barotropic hurricane tracking model into a two-layer baroclinic model. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 747-750 (1999).
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No abstract.
Kaplan, J., and M. DeMaria. Climatological and synoptic characteristics of rapidly intensifying tropical cyclones in the North Atlantic basin. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 592-595 (1999).
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No abstract.
Landsea, C.W., and J.A. Knaff. Application of the El Niño-Southern Oscillation CLImatology and PERsistence (CLIPER) forecasting scheme. Experimental Long-Lead Forecast Bulletin, 8(4):34-36 (1999).
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No abstract.
Landsea, C.W., R.A. Pielke, A.M. Mestas-Nunez, and J.A. Knaff. Atlantic basin hurricanes: Indices of climatic changes. Climatic Change, 42(1):89-129 (1999).
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Accurate records of basin-wide Atlantic and U.S. landfalling hurricanes extend back to the mid 1940s and the turn of the century, respectively, as a result of aircraft reconnaissance and instrumented weather stations along the U.S. coasts. Such long-term records are not exceeded elsewhere in the tropics. The Atlantic hurricanes, U.S. landfalling hurricanes, and U.S. normalized damage time series are examined for interannual trends and multidecadal variability. It is found that only weak linear trends can be ascribed to the hurricane activity and that multidecadal variability is more characteristic of the region. Various environmental factors including Caribbean sea level pressures and 200 mb zonal winds, the stratospheric Quasi-Biennial Oscillation, the El Niño-Southern Oscillation, African West Sahel rainfall, and Atlantic sea surface temperatures, are analyzed for interannual links to the Atlantic hurricane activity. All show significant, concurrent relationships to the frequency, intensity, and duration of Atlantic hurricanes. Additionally, variations in the El Niño-Southern Oscillation are significantly linked to changes in U.S. tropical cyclone-caused damages. Finally, much of the multidecadal hurricane activity can be linked to the Atlantic Multidecadal Mode, an empirical orthogonal function pattern derived from a global sea surface temperature record. Such linkages may allow for prediction of Atlantic hurricane activity on a multidecadal basis. These results are placed into the context of climate change and natural hazards policy.
Landsea, C.W., C.A. Anderson, G. Clark, J. Fernandez-Partagas, P. Hungerford, C. Neumann, and M. Zimmer. The Atlantic hurricane database re-analysis project. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 394-397 (1999).
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No abstract.
Lapitan, R.L., R.H. Wanninkhof, and A.R. Mosier. Methods for stable gas flux determination in aquatic and terrestrial systems. In Approaches to Scaling of Trace Gas Fluxes in Ecosystems, A.F. Bouwman (ed.), Elsevier, Amsterdam, 27-66 (1999).
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A general description of the current approaches for measuring trace gas fluxes in aquatic and terrestrial systems is presented in this paper. Our aim is to provide an overview of the current methodologies employed in trace gas flux measurements and the most recent advancements made; with emphasis on the uncertainties observed and potential areas for future developments required to further minimize these uncertainties brought about by spatial and temporal variabilities of fluxes in the field. The increase in sensitivity and improved response time of analytical devices for measuring trace gases within the last five years, such as advancements in laser spectroscopy, have significantly improved the effectiveness of the current methods of measuring these gases in aquatic and terrestrial systems. Systematic errors in trace gas flux estimates have also been reduced with the refinements in estimates of the gas transfer velocity,k, through the use of tracers in the two systems. Footprint corrections of micrometeorological flux measurements in terrestrial systems have provided a better means of identifying the spatial sources of trace gases, and thus, have increased the scope of inference from trace gas flux measurements. Despite these improvements, however, flux measurement errors still remain high. Experimental and sampling designs that can efficiently and effectively deal with the spatial and temporal variabilities in trace gas flux measurements to the minimum are of utmost priority. The same can be said of the modeling procedures; that is, there is a need for an effective method that can reduce instead of propagate potential errors in scaling from field plot to regional or global scales.
Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global distribution of total inorganic carbon in surface water. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 493-496 (1999).
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No abstract.
Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely. Interannual variations in oceanic uptake of anthropogenic carbon dioxide for the period of 1982-1995. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 31-34 (1999).
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No abstract.
Lee, T.N., E. Williams, E. Johns, and W.D. Wilson. First year results from enhanced observations of circulation and exchange processes in western Florida Bay and connecting coastal waters, including effects of El Niño and Hurricane Georges. 1999 Florida Bay and Adjacent Marine System Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 145-147 (1999).
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No abstract.
Majumdar, S.J., S.D. Aberson, C.H. Bishop, and Z. Toth. Real time hurricane track targeting using a VICBAR ensemble. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 755-756 (1999).
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No abstract.
Marks, F.D., P.P. Dodge, and C. Sandin. WSR-88D observations of hurricane atmospheric boundary layer structure at landfall. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1051-1054 (1999).
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No abstract.
Marks, F.D., P.P. Dodge, and C. Sandin. WSR-88D observations of hurricane atmospheric boundary layer structure at landfall. Preprints, 29th International Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society, Boston, 374-377 (1999).
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No abstract.
McGillis, W., J. Edson, and R.H. Wanninkhof. Direct air-sea flux measurements of carbon dioxide over the North Atlantic Ocean and the comparison to indirect methods. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22,1999. Center for Global Environmental Research (CGER-I037-99), 367-377 (1999).
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To date, large uncertainties in the extent of the CO2 flux between the atmosphere and ocean have prevented us from accurately quantifying how the increasing atmospheric CO2 burden partitions between the ocean and the terrestrial biosphere. This limits our ability to accurately predict future atmospheric CO2 levels. We have recently designed a direct CO2 flux measurement system that considerably improves our estimates of air-sea gas exchange. The system measures the direct air-sea flux of CO2 in the atmospheric boundary layer using eddy correlation (direct covariance). It was successfully deployed during the large scale experiment to study air-sea gas fixes, GASES98, which was conducted in the CO2 sink region of the North Atlantic during May/June of 1998. The seasonal algal bloom caused air-sea pCO2 differences of between -80 to ~100 µatm. This large concentration gradient generated large signals for accurate measurement of the CO2 flux using a close path CO2 sensor. In addition to the CO2 gas flux, the comprehensive atmospheric flux measurement suite included momentum, heat, and moisture fluxes. Atmospheric flux and air-sea gas concentration measurements were performed for over 500 hours, providing more than 1000 observations. Wind speeds between 1 and 16 m/s were experienced over the range of these observations. Preliminary flux estimates from our system compare extremely well with previous estimates of the gas transfer velocity for wind speeds below 7 m/s. At higher wind speeds, the transfer velocities obtained from our system are as much as 20-50% higher than those estimated by empirical relationships. Based on accurate air-sea CO2 coefficients obtained by our investigation and atmospheric and surface ocean pCO2 data obtained to date, estimates of the global ocean CO2 sink are now feasible. Our findings will also provide better predictions of the seasonal and interannual variability of sea-air CO2 flux observed in various global regions.
McPhaden, M.J., T. Delcroix, K. Hanawa, Y. Kuroda, G. Meyers, J. Picaut, and M.S. Swenson. The ENSO observing system. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1, 14 pp. (1999).
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This paper reviews the status of the ENSO (El Niño-Southern Oscillation) observing system, with emphasis on the Pacific Ocean during the recent 1997-1998 El Niño and subsequent La Niña. Contributions of this system to detection, monitoring, forecasting, and understanding of ENSO-related climate swings will be described. Recommended enhancements and extensions to the observing system will also be presented.
McTaggart, K.E., G.C. Johnson, C.I. Fleurant, and M.O. Baringer. CTD/O2 measurements collected on a Climate and Global Change cruise along 24°N in the Atlantic Ocean (WOCE section A6) during January-February 1998. NOAA Data Report, ERL PMEL-68 (PB99-155194), 368 pp. (1999).
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Summaries of CTD/O2 measurements and hydrographic data acquired on a Climate and Global Change cruise during the winter of 1998 aboard the NOAA ship Ronald H. Brown are presented. The majority of these data were collected along 24.5°N from 23.5°W to 69°W. Completing the transatlantic section are data collected along a northeast-southwest dogleg off the coast of Africa, and along a second, short, zonal section along 26.5°N off the coast of Abaco Island from 69°W to 77°W, jogging north along 27°N in the Straits of Florida to 80°W. Data acquisition and processing systems are described and calibration procedures are documented. Station location, meteorological conditions, CTD/O2 summary data listings, profiles, and potential temperature-salinity diagrams are included for each cast. Section plots of oceanographic variables and hydrographic data listings are also given.
Mestas-Nunez, A.M., and D.B. Enfield. Rotated global modes of non-ENSO sea surface temperature variability. Journal of Climate, 12(9):2734-2746 (1999).
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A varimax rotation was applied to the EOF modes of global SST derived by Enfield and Mestas-Nuñez (1999). The SST anomaly record is more than a century long, with a global complex EOF representation of ENSO and a linear trend removed at every grid point. The rotated EOF modes capture localized centers of variability that contribute to the larger scale spatial patterns of the unrotated modes. The first rotated EOF represents a multidecadal signal with larger response in the North Atlantic. The second rotated EOF represents an interdecadal uctuation with larger response in the eastern North Pacific and out of phase fluctuations of smaller amplitude in the central North Pacific. The third rotated EOF captures interdecadal fluctuations in the eastern tropical Pacific with a dominant peak that coincides with the 1982-83 ENSO. The fourth rotated EOF has an interdecadal to multidecadal nature with larger response in the central equatorial Pacific and quasi-symmetric out of phase response in the western North and South Pacific. The fifth mode represents multidecadal fluctuations with large response at about 40°N in the North Pacific. The sixth mode has interannual to interdecadal time scales with largest response confined to the South Atlantic. Our rotated modes are dominated by intra- rather than interocean uctuations supporting the hypothesis that the non-ENSO variability is more regional than global in nature. Analyses of sea level pressure and surface wind stress show that in general the non-ENSO rotated EOFs are consistent with an ocean response to local atmospheric forcing. An exception is the eastern tropical Pacific mode which is more consistent with an atmospheric response to changes in the ocean SST.
Mestas-Nunez, A.M., and D.B. Enfield. Rotated global modes of non-ENSO sea surface temperature. Proceedings, 23rd Annual Climate Diagnostics and Prediction Workshop, Miami, Florida, October 26-30, 1998. National Weather Service, 162-165 (1999).
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No abstract.
Molinari, R.L. Lessons learned from operating global ocean observing networks. Bulletin of the American Meteorological Society, 80(7):1413-1420 (1999).
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The Global Ocean Observing System Center (GOOSC) at the National Oceanic and Atmospheric Administration's (NOAA) Atlantic Oceanographic and Meteorological Laboratory operates two global observing networks, a drifting buoy array, and a Voluntary Observing Ship network. The arrays provide in real time surface atmospheric and subsurface oceanographic data needed by NOAA weather and climate forecasters. The data are used in delayed mode to verify model simulations of the ocean and atmosphere, to provide in situ calibration/validation data for remote sensing observations, and to increase understanding of the dynamics of the ocean and atmosphere. The operational and research lessons learned in the operation of the GOOSC are reviewed. Operationally, it was learned that, because of costs, international participation is required to maintain global networks; data management methodology is a critical component of operations; and integrated observing systems using multiple platforms provide more accurate products. Scientifically, it was learned, for example, that accurate characterizations of the salinity field must be available in model simulations. As more data become available it is found that scales of important phenomena such as equatorial upwelling are smaller, and high-frequency signals can impact on the mean structure of the upper ocean. These findings must be considered when designing effective sampling strategies.
Molinari, R.L., S.L. Garzoli, and R.W. Schmitt. Equatorial currents at 1000 m in the Atlantic Ocean. Geophysical Research Letters, 26(3):361-364 (1999).
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Twenty-seven Profiling ALACE (PALACE) floats were deployed in the equatorial Atlantic during July-August 1997. The floats were ballasted to drift at 1000 m for 10 to 14 days, return to the surface while obtaining a temperature profile, transmit data via satellite, and then after one day return to 1000 m. One-year float paths are now available. Floats deployed on the equator were launched into a deep westward jet. The jet extends some 1-2° north of the equator, with eastward motion observed in floats to the north of 2°N. The equatorial current reverses in the central basin to the east in mid-October and then back to the west in mid-February. Flow to the north also reverses. The short space and time scales contrast with earlier work based on fewer floats that inferred space scales of some 5 -10 in latitude and time scales greater than one year. The new results are consistent with models that indicate that equatorial Rossby waves are the cause of the reversing currents.
Morisseau-Leroy, N., M.K. Solomon, G.P. Momplaisir, T. Kurian, and E. Griffin. Oracle 8I SQLJ Programming. Osborne McGraw-Hill (ISBN 0072121602), 557 pp. (1999).
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No abstract.
Murillo, S.T., and J.J. O'Brien. The influence of ENSO on eastern Pacific tropical cyclones. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 437-438 (1999).
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No abstract.
Murillo, S.T., P.P. Dodge, W.-C. Lee, and F.D. Marks. Using the GBVTD technique in nowcasting hurricane windfields using the WSR-88D. Preprints, 29th International Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society, Boston, 276-277 (1999).
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No abstract.
Murillo, S.T., W.-C. Lee, K. Hondl, P.P. Dodge, C. McAdie, and F.D. Marks. Implementation of the GBVTD technique in nowcasting hurricane wind fields using the WSR-88D. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 311-312 (1999).
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No abstract.
Nelsen, T.A., and J.R. Proni. Distribution and movement of discharged dredged material at the San Juan Ocean Disposal site. Final Report to the U.S. Army Corps of Engineers, MIPR No. W32CS580843181, 57 pp. (1999).
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No abstract.
Nelsen, T.A., and J.R. Proni. Signatures contained in suspended particulate matter with application to coastal-ocean environmental studies. In Coastal Engineering and Marine Developments, C. Brebbia and P Anagnostopoulos (eds.). WIT Press, Southampton, 328-346 (1999).
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Suspended particulate matter (SPM) samples from the New York Bight Apex collected during a sewage-dump experiment were analyzed for chemical as well as physical parameters such as particle-size distributions. The latter provided a signature of the SPMs' sewage component that allowed differentiation from other components. These results were applied to a series of eight Water Column Characterization (WCC) cruises in this area. Co-analysis of WCC and sewage dump particle-size distributions by factor analysis and Distribution Component Analysis revealed patterns that allowed differentiation of sewage-derived components for all WCC samples. From this, a long-termed budget of SPM components, including sewage-derived materials, was constructed. Given this, we conclude that useful tools are available for developing signatures of anthropogenic components of SPM plumes which are independent of study sites or subject materials. These signatures can be applied to understand the sources, pathways, and sinks of such materials in the coastal ocean, as well as constructing long-termed budgets thereof. Ultimately such estimates can be critical to waste management strategies and decisions in an ever more anthropogenically-impacted coastal ocean.
Nelsen, T.A., G. Garte, C.M. Featherstone, P.L. Blackwelder, T. Hood, C. Alvarez-Zarikian, P. Swart, H.R. Wanless, L. Tedesco, C. Souch, J. Pachut, and J. Arthur. Understanding long-term rainfall, freshwater flow, and salinity patterns with concomitant responses of benthic microfauna, stable isotopes, and pollen in Oyster and Florida Bays. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 189-190 (1999).
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Salinity records exhibited variability from the decadal scale to the monthly scale that can be accounted for by changing patterns in regional rainfall. Changes in salinity, both near the outflow of the Shart River Slough at Oyster Bay, and in central Florida Bay near Jimmy Key, show a direct response to regional rainfall on these time scales. Moreover, regional rainfall, represented by the 80+ year record at Homestead, Florida, proved representative of the study area and indicated high correlation with flow into Shark River Slough prior to major watershed construction instigated in the early 1960s. During subsequent periods of water management strategies, enacted from the mid-1960s to present, results indicate essentially no correlation between regional ranfall and flow during the Monthly Allocation Plan. In contrast, correlations most closely paralleled pre-construction, apparently more natural condtions, during the Rainfall Plan. Investigated characteristics for the benthic microfaunal community (foraminifers and ostracods) such as stable isotopes, abundance, and community diversity, exhibited changes and trends that apparently more closely paralleled natural rather than anthropogenic influences over the whole period of record. At both Jimmy Key and Oyster Bay, foraminifer and ostracod data indicate direct correlation to rainfall patterns for temporal scales ranging from decadal down to the limit-of-resolution of our geochronology. An exception to this natural influence was observed from the late-1940s to mid-1950s during which time a dual transition occurred in the sediments adjacent to the Shark River Slough in Oyster Bay. Organic carbon content permanently declined from above- to below-average with concurrent onset of major increases in foraminifer and ostracod abundances. These events temporally conicided with the construction of the Everglades Agricultural Area, which impounded 700,000 acres of organic-rich swampland. These effects were not observed for sediments representing the same time period at Jimmy Key. Stable isotope (delta 18O, delta 13O) trends alone for ostracods and foraminifers at Oyster Bay and Jimmy Key showed mixed signals, with most data suggesting upcore trends to less fresh, more marine conditions. However, when long-term trends for relative abundance of salinity-sensitive species were examined, for the same time periods and locations, they confirmed a statistically valid upcore trend toward less fresh, more marine conditions at both Oyster and Florida Bay study sites. This trend was coincident with a weak decline in regional rainfall over the same time span. Changes in the stable isotopic values of these microfauna indicated, to the limits of our geochronology, direct responses to regional rainfall. Such responses more closely paralleled rainfall than freshwater runoff, even adjacent to the outflow of the Shark River Slough. At Oyster Bay, istracod stable isotope (delta18O) trends correlated better with variabions in regional rainfall than with freshwater outflow from the adjacent Shark River Slough. Crashes in microfaunal abundances at Oyster Bay and more gradual declines at Jimmy Key were salinity related. This abundance drop was concurrent with an equally dramatic drop in community diversity. The latter was characterized by survivor-mode dominance by two microfaunal species and occurred over a period of drought at both sites and the related reduced flow from Shart River Slough. A non-traditional use of pollen allowed evaluation of the degree of paleo-flushing from Shark River Slough that not only correlated well with existing flow and rainfall records but suggests validity as a flushing proxy for pre-record eras. Analysis of regional pollen indicated taxa associations that allowed discrimination of pollen zonations from coastal mangrove to upland slough environments. This, in turn, allowed reconstruction in the sediment record of historical periods of major to minor flushing from Shark River Slough.
Ooyama, K.V. Boundary-layer parameterization in a cloud-resolving model using the radical thermodynamic formulation. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 150-152 (1999).
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No abstract.
Ortner, P.B., L.B. Crowder, and D.E. Hoss. The South Atlantic Bight Recruitment Experiment: Introduction and overview. Fisheries Oceanography, 8(2):1-6 (1999).
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The South Atlantic Bight Recruitment Experiment (SABRE) brought together an interdisciplinary team of scientists to conduct research to enhance our understanding of the relationship between variation in environmental factors and the variable recruitment of "estuarine dependent" fishes within the South Atlantic Bight. The project sought to develop a new fusion of government and academic scientists, each possessing unique skills, to address the difficult problem of recruitment variability in fishes. This fusion required the development of appropriate and, at that time, novel management and administrative strategies. SABRE initially focused on recruitment dynamics of Atlantic menhaden, Brevoortia tyrannus, in the South Atlantic Bight, but expanded over time to include several estuarine-dependent species and much of the Middle Atlantic Bight as well. The project was conducted from 1991 to 1997 and resulted in a substantial improvement in our understanding of the life history and ecology of Atlantic menhaden and the potential constraints upon its recruitment. SABRE also contributed to our understanding of the physical oceanography of the western North Atlantic shelf and adjacent coastal inlets and the implications of physical dynamics upon the potential pathways for larval transport.
Ortner, P.B., M.J. Dagg, G.S. Kleppel, and C.R. Tomas. Grazing by zooplankton in Florida Bay waters. Florida Sea Grant College Program, FLSGP-G-99-012, 2 pp. (1999).
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No abstract.
Palmer, D.R. Parabolic approximations for global acoustic propagation modeling. NOAA Technical Memorandum, NOAA-TM-ERL-AOML-94 (PB99-171571), 54 pp. (1999).
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Motivated by the difficulty in using the splitting matrix method to obtain parabolic approximations to complicated wave equations, we have developed an alternative method. It is three-dimensional, does not a priori assume a preferred direction or path of propagation in the horizontal, determines spreading factors, and results in equations that are energy conserving. It is an extension of previous work by several authors relating parabolic equations to the horizontal ray acoustics approximation. Unlike previous work, it applies the horizontal ray acoustics approximation to the propagator rather than to the Green's function or the homogenous field. The propagator is related to the Green's function by an integral over the famous "fifth parameter" of Fock and Feynman. Methods for evaluating this integral are equivalent to narrow-angle approximations and their wide-angle improvements. When this new method is applied to simple problems, it gives the standard results. In this paper, it is described by applying it to a problem of current interest: the development of a parabolic approximation for modeling global underwater and atmospheric acoustic propagation. The oceanic or atmospheric waveguide is on an Earth (or other heavenly body) that is modeled as an arbitrary convex solid of revolution. The method results in a parabolic equation that is energy conserving and has a spreading factor that describes field intensification for antipodal propagation. Significantly, it does not have the singularities in its range-sliced version possessed by many parabolic equations developed for global propagation. The work is generalized to allow for refracted geodetics and the possibility that the depth dependence of the pressure field can be described by adiabatic normal modes.
Peng, T.-H., and F. Chai. Modeling the carbon cycle in the equatorial Pacific Ocean. Proceedings, Second International Symposium on CO2 in the Ocean, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 183-189 (1999).
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As part of the U.S. JGOFS SMP program, we have developed an ocean ecosystem model of the equatorial Pacific Ocean with new and export productivity regulated by Si and Fe to synthesize and to analyze data collected during the process-study-oriented survey cruises in 1992. The circulation model is based on the Modular Ocean Model of the NOAA/GFDL ocean general circulation model. The ecosystem model consists of nine components describing two size phytoplankton, two size zooplankton, two detritus pool, and three dissolved nutrients: silicate, nitrate, and ammonium. The carbonate chemistry is parameterized in the model to evaluate the variations of pCO2, and hence the CO2 flux across the air-sea interface. At this initial stage, a test case by using a 1D model is performed to simulate low-silicate, high-nitrate, and low-chlorophyll conditions in the equatorial Pacific, and to investigate how the carbon system behaves in this ecosystem structure. The model includes the vertical upwelling and diffusion processes. The upwelling rate and vertical diffusivity were initially averaged for the region 5°S to 5°N, 180°W to 90°W, the "cold tongue" of the equatorial Pacific from the parameter values of 3D model simulations. Temperature is used to calibrate model upwelling and vertical diffusion rates. Comparison of model results with the observations made during the NOAA/OACES EqPac 1992 expeditions indicates that the vertical profiles of DIC, NO3 and Si(OH)4 are consistent with the measurements made in the fall season when the ocean was in a normal non-El Niño condition. A tight fit of profiles between model and observation is not possible because of spatial variations of the observed values. A 3D simulation is required, which is in progress. The 1D model CO2 evasion rate is estimated to be 2.9 mol/m2/yr, which is within the range of estimates from measurements made during non-El Niño conditions.
Peng, T.-H., J.-J. Hung, R.H. Wanninkhof, and F.J. Millero. Carbon budget in the East China Sea in spring. Tellus B, 51(2):531-540 (1999).
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Results of total dissolved inorganic carbon (DIC) and total alkalinity (TA) measurements made in the East China Sea (ECS) during a geochemical expedition of KEEP (Kuroshio Edge Exchange Processes) program in May of 1996 show that ECS is a CO2 sink during the spring season. The mean difference of fCO2 (fugacity of CO2) between the atmosphere and surface water is calculated to be 28 µatm, and the resulting net CO2 invasion flux is 2.1 mol/m2/yr, which gives about 0.03 GtC/yr of CO2 uptake in this continental shelf in spring. This study supports the notion that shelf regions can be a significant CO2 sink. The riverine alkalinity, which discharges into ECS, is estimated to be 1,743 µmol/kg on the basis of a linear relationship between TA and salinity. The observed salinity-normalized alkalinity in ECS is higher than that in the open sea, and this excess alkalinity is estimated to be 42 µmol/kg. With the known rate of the Changjiang discharge, this excess TA gives a mean residence time of 1.2 years for the continental shelf water in the ECS. The DIC in the ECS is also found to be higher than that in the open sea. This excess DIC is estimated to be about 76 ± 70 µmol/kg, which is equal to a net carbon input to ECS of 3.9 ± 3.6 mol/m2/yr. Based on the riverine alkalinity input, the equivalent riverine carbon flux from Changjiang discharge is estimated to be about 1.8 mol/m2/yr. With net CO2 invasion flux of 2.1 ± 2.8 mol/m2/yr, the remaining 0 ± 4.6 mol/m2/yr could come from remineralization of organic matter derived from biological pump in the shelf or terrestrial sources. Although this preliminary carbon budget implies that gas exchange and riverine input are the main sources of excess carbon in ECS, the contribution of biological carbon flux can not be ruled out because of the large uncertainty associated with these estimates.
Pielke, R.A., and C.W. Landsea. La Niña, El Niño, and Atlantic hurricane damages in the United States. Bulletin of the American Meteorological Society, 80(10):2027-2034 (1999).
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Hurricanes result in considerable damage in the United States. Previous work has shown that Atlantic hurricane landfalls in the United States have a strong relationship with the El Niño-Southern Oscillation phenomena. This paper compares the historical record of La Niña and El Niño events defined by eastern Pacific sea surface temperature with a data set of hurricane losses normalized to 1997 values. A significant relationship is found between the ENSO cycle and U.S. hurricane losses, with La Niña years exhibiting much more damage. Used appropriately, this relationship is of potential value to decision makers who are able to manage risk based on probabilistic information.
Pielke, R.A., C.W. Landsea, R.T. Musulin, and M. Downton. Evaluation of catastrophe models using a normalized historical record: Why it is needed and how to do it. Journal of Risk and Insurance, 18:177-194 (1999).
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No abstract.
Powell, M.D. Hurricanes at landfall. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 107-108 (1999).
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No abstract.
Powell, M.D., and S.H. Houston. Comments on "A multiscale numerical study of Hurricane Andrew (1992). Part I: Explicit simulation and verification." Monthly Weather Review, 127(7):1706-1710 (1999).
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No abstract.
Powell, M.D., T.A. Reinhold, and R.D. Marshall. GPS sonde insights on boundary layer wind structure in hurricanes. Proceedings, 10th Conference on Wind Engineering, Copenhagen, Denmark, June 21-24, 1999. ICWE, 307-314 (1999).
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No abstract.
Powell, M.D., P.G. Black, S.H. Houston, and T.A. Reinhold. GPS sonde insights on boundary layer structure in hurricanes. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 881-884 (1999).
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No abstract.
Proni, J.R., and T.A. Nelsen. Integrated measurements of sewage effluent and dredged material discharges. In Coastal Engineering and Marine Developments, C. Brebbia and P Anagnostopoulos (eds.). WIT Press, Southampton, 368-379 (1999).
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A series of measurements to characterize sewage effluent discharge plumes and dredged material discharge plumes were carried out in coastal ocean waters off the coast of Puerto Rico in April 1998. A multiple sensor suite including an acoustic backscatter profiler, a towed optical backscatter containing CTD device, a vertical cast CTD having an optical transmissometer and oxygen sensors, and an acoustic Doppler current profiler (ADCP) was utilized to determine the subsurface plume spatial distribution and dilution. The sewage effluent plumes resulted from discharges at several diffusers located approximately one or more miles from the coastline. Using the multiple sensor systems listed above, it was possible to relate measurements made at water locations distant from the diffuser to plumes emanating from various parts of the diffuser under study. That is, a "connectivity" was established so that quantities inherent in the effluent discharge could be used for dilution calculations. Typical "initial" dilutions observed were on the order of 60:1. Using inherent tracers, such as plume salinity, effluent plume distributions were determined out to several hundred meters from the diffuser. "Macro" scale comparisons of multiple sensor outputs were carried out with good general agreement on plume distributions. Comparisons between in-situ "contact" sensors, e.g., temperature and salinity probes, and in-situ remote sensor probes, e.g., optical and acoustic backscatter, optical transmissivity (transmissometry), were made with good agreement resulting.
Proni, J.R., and T.A. Nelsen. Puerto Rico outfall/dredged material disposal studies: April 13-26, 1998. Contract EPA/IAG DW13937869-01-04 (Final report). U.S. Environmental Protection Agency, 74 pp. (1999).
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No abstract.
Quilfen, Y., A. Bentamy, K.B. Katsaros, and G. Lorand. Estimation of ocean-atmosphere turbulent fluxes from satellite measurements. Proceedings, 1999 International Geoscience and Remote Sensing Symposium (IGARSS '99), Hamburg, Germany, June 28-July 2, 1999. Institute of Electrical and Electronic Engineers, 2 pp. (1999).
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No abstract.
Reasor, P.D., M.T. Montgomery, and F.D. Marks. The asymmetric structure of Hurricane Olivia's inner core. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 301-304 (1999).
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No abstract.
Rodbell, D.T., G.O. Seltzer, D.M. Anderson, M.B. Abbott, D.B. Enfield, and J.H. Newman. A high-resolution ~15,000 year record of El Niño driven alluviation in southwestern Ecuador. Science, 283:516-520 (1999).
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Debris flows have deposited inorganic laminae in an alpine lake 75 kilometers east of the Pacific Ocean, in Ecuador. These storm-induced events are dated by radiocarbon, and the age of laminae that are less than 200 years old matches the historic record of El Niño events. From about 15,000 to about 7,000 calendar years before the present, the periodicity of clastic deposition is greater than or equal to 15 years; thereafter, there is a progressive increase in frequency to periodicities of 2-8.5 years. This is the modern El Niño periodicity, which was established about 5,000 calendar years before present. This may reflect the onset of a steeper zonal sea surface temperature gradient, which was driven by enhanced trade winds.
Roemmich, D., O. Boebel, Y. Desaubies, H. Freeland, B. King, P.-Y. Letraon, R.L. Molinari, W.B. Owens, S. Riser, U. Send, K. Takeuchi, and S. Wijffels. Argo: The global array of profiling floats. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1, 12 pp. (1999).
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A broad-scale global array of temperature/salinity (T/S) profiling floats, known as Argo, is planned as a major component of the ocean observing system, with deployment scheduled to begin in 2000. Conceptually, Argo builds on the existing upper-ocean thermal networks, extending their spatial and temporal coverage, depth range and accuracy, and enhancing them through addition of salinity and velocity measurements. The name Argo is chosen to emphasize the strong complementary relationship of the global float array with the Jason altimeter mission. For the first time, the physical state of the upper ocean will be systematically measured and assimilated in near real time. Objectives of Argo fall into several categories. Argo will provide a quantitative description of the evolving state of the upper ocean and the patterns of ocean climate variability, including heat and freshwater storage and transport. The data will enhance the value of the Jason altimeter through measurement of subsurface vertical structure (T(z), S(z)) and reference velocity, with sufficient coverage and resolution for interpretation of altimetric sea surface height variability. Argo data will be used for initialization of ocean and coupled forecast models, data assimilation, and dynamical model testing. A primary focus of Argo is seasonal to decadal climate variability and predictability, but a wide range of applications for high-quality global ocean analyses is anticipated. The initial design of the ARGO network is based on experience from the present observing system, on newly gained knowledge of variability from the TOPEX/Poseidon altimeter, and on estimated requirements for climate and high-resolution ocean models. Argo will provide 100,000 T/S profiles and reference velocity measurements per year from about 3000 floats distributed over the global oceans at 3-degree spacing. Floats will cycle to 2000 m depth every 10 days, with a 4-5 year lifetime for individual instruments. All Argo data will be publicly available in near real-time via the GTS, and in scientifically quality-controlled form with a few months delay. Global coverage should be achieved during the Global Ocean Data Assimilation Experiment, which together with CLIVAR and GCOS/GOOS, provide the major scientific and operational impetus for Argo. The design emphasizes the need to integrate Argo within the overall framework of the global ocean observing system. International planning for Argo, including sampling and technical issues, is coordinated by the Argo Science Team. Nations presently having Argo plans that include float procurement or production include Australia, Canada, France, Germany, Japan, the U.K., and the U.S.A., plus a European Union proposal. Combined deployments from these nations may exceed 700 floats per year as early as 2001. Broad participation in Argo by many nations is anticipated and encouraged either through float procurement, logistical support for float deployment, or through analysis and assimilation of Argo data.
Rogers, R.F. Amplification of warm-core vortices by convective redevelopment: A key component of tropical cyclogenesis. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 929-932 (1999).
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No abstract.
Rogers, R.F., and J.M. Fritsch. Amplification of warm-core vortices by convective redevelopment: A key component of tropical cyclogenesis. Preprints, Eighth Conference on Mesoscale Processes, Boulder, CO, June 28-July 1, 1999. American Meteorological Society, Boston, 55-60 (1999).
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No abstract.
Shapiro, L.J., and J.L. Franklin. Potential vorticity asymmetries and tropical cyclone motion. Monthly Weather Review, 127(1):124-131 (1999).
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A set of nine synoptic-flow cases, incorporating Omega dropwindsonde observations for six tropical storms and hurricanes, is used to deduce the three-dimensional distribution of potential vorticity (PV) that contributed to the deep-layer mean (DLM) wind that steered the cyclones. A piecewise inversion technique, the same as that previously applied by Shapiro to Hurricane Gloria of 1985, is used to derive the DLM wind induced by pieces of anomalous PV restricted to cylinders of different radii centered on each cyclone. The cylinder of PV that induces a DLM wind that best matches the observed DLM wind near the center of each cyclone is evaluated. It is found that the results can be loosely placed into two categories describing the spatial scale of the PV anomalies that influenced the cyclone's motion. Four of the cases, including Hurricane Gloria, had "local" control, with a good match (to within 40%) between the observed DLM wind near the cyclone center and the DLM wind attributable to a cylinder of PV with a given radius of 1500 km. Further decomposition of the PV anomaly into upper (400 mb and above) and lower levels (500 mb and below) indicates the dominance of upper-level features in steering two of the cyclones (Hurricanes Gloria of 1985 and Andrew of 1992), while Hurricane Debby of 1982 was steered by more barotropic features. These results supplement those found in other studies. Five of the cases, by contrast, had "large-scale" control, with no cylinder of radius 2000 km having a good match between the induced and observed DLM wind. Hurricanes Emily of 1987 and 1993 fell into this category, as did Hurricane Josephine of 1984. Implications of the results for guiding in-situ wind measurements to improve hurricane track forecasts are discussed.
Smith, N.R., D.E. Harrison, R. Bailey, O. Alves, T. Delcroix, K. Hanawa, B. Keeley, G. Meyers, R.L. Molinari, and D. Roemmich. The role of XBT sampling in the ocean thermal network. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1, 26 pp. (1999).
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This paper evaluates the present role of the XBT program and proposes a strategy for the future under the assumption that there are other direct and indirect contributions to sampling the temperature and salinity of the ocean. Since the focus is on XBT sampling, the paper restricts its scope to the upper ocean, mostly above 1000 m. The conclusions of the paper are based on a study and workshop that were convened specifically to look at the design of the ship-of-opportunity network and to look at options for its implementation in the future under the assumption that Argo happens. The paper also addresses issues related to data distribution and management. The primary conclusion is that the network of the future should place greatest emphasis on line sampling, at intermediate to high densities, and assume that a proposed profiling float array, Argo, will largely take over the role formerly occupied by area (broadcast) sampling. It is argued that line sampling exclusively addresses several needs of the ocean observing system that cannot easily be addressed by other forms of sampling. Further, it is argued that such a mode complements other in-situ components such as moorings and floats, as well as remotely-sensed surface topography. A new network is outlined with a strategy for implementation that ensures continuity between existing and planned networks. We conclude the data management system that was established around the SOOP program requires substantial renovation if it is to adequately address the needs of the data gatherers and suppliers, and the data users (modelers, scientists, operational applications).
Smith, R.H. IASlinks.org: Online management and distribution of oceanographic and meteorological data for the Gulf of Mexico and Caribbean Sea. Proceedings, First Biennial Intra-Americas Sea Initiative (IASI) Science Meeting, Panama City, Panama, November 9-11, 1999. University of Miami, 41-42 (1999).
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There is a growing recognition of the connectivity among oceanic processes within the Gulf of Mexico and Caribbean Sea region (Intra-Americas Sea). Recent technological breakthroughs in communication, specifically the Internet, provide a common denominator for scientific collaboration and data exchange among the region's institutions and government agencies that collect data and utilize data products. The growing need for regional scale models requires that interaction between research endeavors take place, enabling the creation of larger, regional data sets and a more unified approach to understanding the oceanography, climate, and ecology of the Intra-Americas Sea. The Internet web site, http://IASlinks.org, hosted by NOAA/AOML in Miami, Florida, has been developed to facilitate the sharing of resources, results, and data sets relevant to research conducted throughout the Intra-Americas Sea region. The site is presently designed with indices describing the different types of research and the different institutions, agencies, and personnel involved, with regular highlights of specific regional research topics; it is our hope that the site will continue to expand, becoming a more complete representation of observational programs presently underway in and around the Gulf of Mexico and Caribbean Sea. The usefulness of a venue such as IASlinks.org will continue to be realized as scientists and operational observing systems throughout the Intra-Americas Sea make more of their data available over the Internet. In particular, the Internet as a medium for data exchange will play a pivotal role in the forthcoming IOCARIBE-GOOS regional observing system. IASlinks will complement the IASI web site, which will emphasize research programs, education, and training. This collaborative atmosphere, where scientific information and resources are shared with one another, will provide investigators working in the region the ability to tackle larger questions regarding climate, circulation, the propagation of species, and the connectivity of regional marine environments.
Swenson, M.S., and D.V. Hansen. Tropical Pacific Ocean mixed-layer budget: The Pacific cold tongue. Journal of Physical Oceanography, 29(1):69-82 (1999).
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Data from satellite-tracked drifting buoys and VOS/XBT profiles for the years 1979-1995 were used to evaluate the seasonal cycle of how major oceanic processes redistribute heat in the cold tongue region of the tropical Pacific. The most active processes for the annual cycle are local heat storage and heat export by entrainment of upwelling and by mean meridional advection. Heat export by zonal advection, however, is not negligible, and meridional eddy heat fluxes associated with tropical instability waves effect a negative feedback that offsets a considerable fraction of that produced by the mean meridional advection. All of these processes mimic the essentially one cycle per year of the surface wind stress, as do those of the depths of both the bottom of the surface mixed layer and the thermocline. Because it is associated with poleward Ekman transports, upwelling, and baroclinic adjustment near the equator, the zonal wind stress component appears to be the more important. The meridional wind stress, while weaker in the annual mean, has a larger annual variation and, therefore, has equal influence on the annual variation of the scalar stress and perhaps the mixed layer thickness. The Monin-Obukov length is found to underestimate the mixed layer thickness very considerably. Finally, we produce the first estimates of the seasonal cycle of eddy heat flux convergence, which plays a significant role in the evolution of the cold tongue, and show that the eddy heat flux convergence can be quantitatively modeled as eddy diffusion with a diffusivity derived from single-particle buoy statistics.
Takahashi, T., R.H. Wanninkhof, R.A. Feely, R.F. Weiss, D.W. Chipman, N. Bates, J. Olafsson, C.Sabine, and S.C. Sutherland. Net sea-air CO2 flux over the global oceans: An improved estimate based on the sea-air pCO2 difference. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 9-15 (1999).
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No abstract.
Tedesco, L.P., C. Souch, J. Pachut, J.A. Arthur, H.R. Wanless, P.L. Blackwelder, T. Hood, C. Alvarez-Zarikian, J. Trefry, W.J. Kang, S. Metz, and T.A. Nelsen. The signature of hurricane sedimentation in the lower Everglades/Florida Bay ecosystem: Recognition of sedimentologic, geochemical, and microfaunal indicators. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 194-195 (1999).
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Winter storm and hurricane resuspension and transport processes are responsible for building the bulk of the sediment sequence in the accreting bank flanks in both northwest Oyster Bay (Whitewater Bay) and Florida Bay. Repetitive resuspension by winter storms provides fine silt-sized carbonate, siliceous and organic laminae as thin event laminae, mostly a millimeter or less in thickness. As these repetitive winter storms produce similar wind and transport sequences in an area, the constituent composition and mineralogy of the laminae are similar. Vertical profiles of excess 210Pb activity in sediments from northwest Oyster Bay, Jimmy Key, and First National Bank showed that sedimentation at these sites has been in steady state during the last 40 years. However, two to three discontinuities of short duration (<2 years) in the decay profiles of excess 210Pb activities were observed in the sedimentary records from northwest Oyster Bay, Jimmy Key, and First National Bank. Based on excess 210Pb-based ages, the discontinuities occurred at about 1960, 1948, and 1935, dates coincident with major hurricanes passing through Florida Bay: Donna in September 1960 (category 4); an unnamed hurricane in September 1948 (category 3); and the Great Labor Day Hurricane in September 1935 (category 5). Hurricane layers from 1935, 1948, 1960 (Donna), and 1992 (Andrew) in Oyster Bay are identified by a sharp surface on which sand-sized shell, carbonate peloids, and organic detritus are concentrated and overlain by a white, fine sand to silt layer, 0.5-2 cm in thickness. Sedimentologic and geochemical data on discontinuity surfaces show that the base of each hurricane layer is an erosional surface from which several centimeters of sediment was eroded. This is expected as the upper 3-10 cm of the sediment in these accreting flanks is a very soft zone with as much as 80% water content that could easily be removed. Discontinuities of 210Pb profiles and, therefore, erosion were more pronounced in open water sites such as Jimmy Key and First National Bank (3-20 cm thick) relative to the more protected, mangrove coastline surrounded environment of northwest Oyster Bay (~2 cm thick). Major hurricanes (categories 4 and 5) are devastating to the red and black mangrove communities, causing destruction to 50-100% of the forest in the eye wall of the storm. This loss is reflected in the organic detritus content of sediments in cores from northwest Oyster Bay and other areas surrounded by extensive mangrove coastlines. Prior to a major hurricane, the macro-organic detritus is mainly partly decayed fragments of mangrove leaves released from the adjacent forests. Defoliation, uprooting, and death of the forest during and following the storm result in a change in the amount and composition of organic detritus in sediments. Organic detritus is composed of fine root hairs for a period of 5-10 years following the event. This reflects an extended period of erosion and release of root-hair detritus from the disrupted and decaying mangrove peat substrate. Organic detritus gradually decreases and becomes dominated by leaf detritus as the forest recovers. Hurricane-related signals in the microfaunal assemblage data (benthic ostracods and foraminifers) are both site- and event-specific. The two hurricanes that significantly modified the microfaunal assemblages from Jimmy Key and northwest Oyster Bay are the Labor Day Hurricane of 1935 and Hurricane Donna (1960). Hurricane Donna resulted in peaks in relative abundance of atypical benthic foraminifer species at both sites. At Jimmy Key, the species comprising this peak were derived from elsewhere within Florida Bay. In contrast, in northwest Oyster Bay, species were comprised of continental shelf species transported from the Gulf of Mexico by Donna's last winds. An example of hurricane-specific effects can be seen in the differing signals recorded by the 1935 and 1960 hurricanes at Jimmy Key. The 1960 hurricane left a distinct lag-type deposit, whereas the 1935 hurricane sediments were essentially barren of microfauna. High organic carbon influx and subsequent oxygen depletion associated with these hurricane events appear to be recorded in the microfaunal assemblages as well.
Thacker, W.C. Principal predictors. International Journal of Climatology, 19(8):821-834 (1999).
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Principal predictors are linear combinations of variables from one set that efficiently describe the collective variability of those from a second set. Their defining eigenproblem is similar to that of canonical-correlation analysis, and when the two sets are taken to be the same, principal predictors reduce to principal components. Within the context of a forecast model for the circulation in the Gulf of St. Lawrence, they are shown to be capable of providing a low-dimensional characterization of high-resolution model dynamics.
Uhlhorn, E.W., P.G. Black, and A.F. Hasler. Evolution of mesoscale flow in a mature tropical cyclone as determined from satellite imagery. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 200-203 (1999).
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No abstract.
Vachon, P.W., and K.B. Katsaros. Atmospheric cyclones from spaceborne SAR. Backscatter, 10(4):14-19 (1999).
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No abstract.
Vachon, P.W., K.B. Katsaros, P.G. Black, and P.P. Dodge. RADARSAT synthetic aperture radar measurements of some 1998 hurricanes. Proceedings, 1999 International Geoscience and Remote Sensing Symposium (IGARSS '99), Hamburg, Germany, June 28-July 2, 1999. Institute of Electrical and Electronic Engineers, 1631-1633 (1999).
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The RADARSAT synthetic aperture radar (SAR) acquired C-band and HH polarization images over four 1998 hurricanes: Bonnie, Danielle, Georges, and Mitch. We present the SAR images and discuss their quantitative use in understanding hurricane morphology. The SAR provides a complementary "view from below" that is most beneficial when considered in the context of more conventional hurricane observations.
Wang, C., R.H. Weisberg, and J.I. Virmani. Western Pacific interannual variability associated with the El Niño-Southern Oscillation. Journal of Geophysical Research, 104(C3):5131-5149 (1999).
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Observations of sea surface temperature (SST), sea level pressure (SLP), surface wind, and outgoing longwave radiation (OLR) show that the El Niño-Southern Oscillation (ENSO) displays western Pacific anomaly patterns in addition to eastern Pacific anomaly patterns. During the warm phase of ENSO, warm SST and low SLP anomalies in the equatorial eastern Pacific and low OLR anomalies in the equatorial central Pacific are accompanied by cold SST and high SLP anomalies in the off-equatorial western Pacific and high OLR anomalies in the off-equatorial far western Pacific. Also, while the zonal wind anomalies over the equatorial central Pacific are westerly, those over the equatorial far western Pacific are easterly. The nearly out-of-phase behavior between the eastern and western tropical Pacific is also observed during the cold phase of ENSO, but with anomalies of opposite sign. These western Pacific interannual anomaly patterns are robust features of ENSO, independent of data sets. It is argued that equatorial easterly (westerly) wind anomalies over the far western Pacific during the warm (cold) phase of ENSO are initiated by off-equatorial western Pacific cold (warm) SST anomalies, and that these winds are important for the evolution of ENSO. An atmosphere model is employed to demonstrate that small off-equatorial western Pacific cold (warm) SST anomalies (compared to those in the east) are sufficient to produce equatorial easterly (westerly) wind anomalies as observed over the far western Pacific. The coupled ocean-atmosphere model of Zebiak and Cane is then modified to investigate the evolution of the western Pacific interannual anomaly patterns in a coupled ocean-atmosphere system, by including a meridional structure to the subsurface temperature parameterization in the western Pacific. The modified model produces both western and eastern Pacific interannual anomaly patterns.
Wang, C., R.H. Weisberg, and H. Yang. Effects of the wind speed-evaporation-SST feedback on the El Niño-Southern Oscillation. Journal of the Atmospheric Sciences, 56(10):1391-1403 (1999).
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The thermodynamical process of latent heat flux is added to an analogical delayed oscillator model of the El Niño-Southern Oscillation (ENSO) that mainly considers equatorial ocean dynamics and produces regular, non-phase-locked oscillations. Latent heat flux affects the model sea surface temperature (SST) variations by a positive feedback between the surface wind speed and SST operating through evaporation which is called the wind speed-evaporation-SST feedback. The wind speed-evaporation-SST feedback in which the atmosphere interacts thermodynamically with the ocean through surface heat flux differs from the conventional zonal wind stress-SST feedback in which the atmosphere interacts dynamically with the ocean through momentum flux. The combination of equatorial ocean dynamics and thermodynamics produces relatively more realistic model oscillations. When the annual cycle amplitude of the zonal wind in the wind speed-evaporation-SST feedback is gradually increased, the model solution undergoes a transition from periodic to chaotic and then to periodic oscillations for some ranges of the parameters, whereas for other ranges of the parameters the transition goes from periodic to quasi-periodic and then to periodic oscillations. The route to chaos is the intermittency route. Along with such irregularity, the nonlinear interactions between the annual and interannual cycles operating through the wind speed-evaporation-SST feedback also produce a phase-locking of ENSO to the seasonal cycle. The model ENSO onset and peak occur in the boreal winter and spring, respectively, consistent with the observed phase-locking of ENSO in the far eastern Pacific. It is shown that ENSO decadal or interdecadal variability may result from the nonlinear interactions between the annual and interannual cycles in the tropics.
Wanninkhof, R.H. Recent advances in determining air-sea CO2 fluxes. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 101-104 (1999).
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Uncertainties in inverse calculations to determine regional carbon fluxes between the atmospheric, oceanic, and terrestrial reservoirs (Fan et al., 1998) have clearly indicated the need to improve our oceanic carbon flux estimate. There have been significant advances in several aspects of air-sea flux determinations to address this question, including direct estimates of fluxes by co-variance and gradient measurements in the air-boundary layer, extrapolation routines using remote sensing products, and a rapidly increasing observational database of air-sea partial pressure differences. The gas fluxes are commonly expressed as F = k s DELTA-pCO2 where F is the air-sea flux CO2 (mol m-2 day-1), k is the gas transfer velocity (m day-1), s is the solubility (mol m3 µatm-1) and DELTA-pCO2 is the air-water partial pressure difference (µatm). This overview discusses recent research aimed at improving estimates of F, k, and DELTA-pCO2.
Wanninkhof, R.H., and W.M. McGillis. A cubic relationship between air-sea CO2 and wind speed. Geophysical Research Letters, 26(13):1889-1892 (1999).
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Using recent laboratory and field results we explore the possibility of a cubic relationship between gas exchange and instantaneous (or short-term) wind speed, and its impact on global air-sea fluxes. The theoretical foundation for such a dependency is based on retardation of gas transfer at low to intermediate winds by surfactants, which are ubiquitous in the world's oceans, and bubble-enhanced transfer at higher winds. The proposed cubic relationship shows a weaker dependence of gas transfer at low wind speed and a significantly stronger dependence at high wind speed than previous relationships. A long-term relationship derived from such a dependence, combined with the monthly CO2 climatology of Takahashi (1997), leads to an increase in the global annual oceanic CO2 uptake from 1.4 Gigaton C yr-1 to 2.2 Gigaton C yr-1. Although a cubic relationship fits within global bomb-14C oceanic uptake constraints, additional checks are warranted, particularly at high wind speeds where the enhancement is most pronounced.
Wanninkhof, R.H., E. Lewis, R.A. Feely, and F.J. Millero. The optimal carbonate dissociation constants for determining pCO2 from alkalinity and total inorganic carbon. Marine Chemistry, 65(3-4):291-301 (1999).
-J-
In many numerical ocean chemistry models total dissolved inorganic carbon (DIC) and total alkalinity (TA) are transported between subsurface boxes, and partial pressure pCO2 is calculated from TA and DIC in the surface box in order to account for air-sea exchange of carbon dioxide. The conversion is commonly performed by solving the thermodynamic relationships for equilibria between carbonate, bicarbonate, and aqueous CO2 using apparent carbonate dissociation constants. Four independent determinations of the constants have been performed for seawater in the past 50 years. These results have been corrected, refit, and combined by others, creating a virtual cottage industry of laboratory and field verification and cross checks. Here we show that, based on extensive field observations in three major ocean basins, the calculated surface pCO2 from TA and DIC corresponds best with the measured pCO2 of the constants proposed by Mehrbach et al.
Wanninkhof, R.H., S. Doney, T.-H. Peng, J.L. Bullister, K. Lee, and R.A. Feely. Comparison of methods to determine the anthropogenic CO2 invasion into the Atlantic Ocean. Tellus B, 51(2):511-530 (1999).
-J-
A comparison of different methods of estimating anthropogenic CO2 into the Atlantic Ocean through the center of the basin between 62°N and 42°S is performed using referenced high quality total dissolved inorganic carbon (DIC) data. The specific anthropogenic input is determined utilizing analytical procedures as described in Gruber et al. (1996), and Chen and Millero (1979) to correct for remineralization and to estimate preanthropogenic endmembers. These estimates are compared with results of the Princeton ocean biogeochemical model (OBM). The results show the specific inventories of anthropogenic carbon agreeing to within 20% but with different uptake patterns. The differences are largely caused by differing assumptions about mixing and winter outcrop endmembers. The same photosynthetic quotients (Redfield ratios) were used each methods. Varying these constants within the range of literature values causes changes in specific inventories of similar magnitude as the different methodologies. Comparison of anthropogenic CO2 uptake and chlorofluorocarbon ages, and preanthropogenic photosynthetic quotients utilizing the analytical methods suggest that anthropogenic CO2 penetration is too shallow following the procedure according to Gruber et al. (1996), and too deep using those of Chen and Millero (1979) in the North Atlantic. The results support previous observations that the uptake of CO2 in the North Atlantic is disproportionate to its surface area. This is caused by a combination of deep water formation and deep winter mixed layers.
Watson, A.I., K.M. Stellman, K.J. Gould, and P.P. Dodge. Local applications of the WSR-88D hourly digital precipitation product at the National Weather Service office in Tallahassee, Florida. Preprints, 29th International Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society, Boston, 232-235 (1999).
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No abstract.
Willis, P.T. The WSR-88D tropical Z-R relationship in south Florida. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 237-240 (1999).
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No abstract.
Willoughby, H.E. Hurricane heat engines. Nature, 401:649-650 (1999).
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No abstract.
Willoughby, H.E. Vortex tracking semispectral hurricane models. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 662-665 (1999).
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No abstract.
Wilson, W.D. Atlantic western boundary currents. Proceedings, South Florida Measurement Center Workshop: Establishment of a Center for Innovative Oceanography in the 21st Century, Dania, FL, February 24-26, 1999. National Science Foundation, 131-140 (1999).
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No abstract.
Wilson, W.D., E. Johns, R.H. Smith, T.N. Lee, and E. Williams. Interaction of freshwater riverine discharges from the Everglades with the Gulf of Mexico and Florida Bay: Preliminary results from a moored array and shipboard surveys. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 175-177 (1999).
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No abstract.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Laboratory glassware as a contaminant in silicate analysis of natural water samples. Water Research, 33(12):2879-2883 (1999).
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When glassware is used for the storage of water samples, reagents, and standard solutions, dissolution of silicate from the glass containers can contaminate the samples. Experimental results demonstrate that dissolution from glassware can introduce micromolar silicate within a few hours. The extent of dissolution depends upon contact time, salinity, and pH of the solution, and the size and shape of the containers.
Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Optimization of performance and minimization of silicate interference in continuous flow phosphate analysis. Talanta, 49(2):293-304 (1999).
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Specific reaction conditions for automated continuous flow analysis of phosphate are optimized in regard to minimizing coating and silicate interference, while maintaining high sensitivity. Use of Sb in the reagent increases sensitivity and yields absorbances with little temperature dependence. Coating can be minimized by using a final solution at a pH >0.5. At final pH of 0.78, there is maximum interference from silicate in the sample. We recommend, therefore, as an optimal reaction condition with minimal silicate interference, the use of Sb, a final solution pH of 1.00, room temperature for the reaction, and a [H+]/Mo ratio of 70. An equation is provided to correct silicate interference in high precision phosphate determination.
**1998**
Aberson, S.D. Five-day tropical cyclone track forecasts in the North Atlantic basin. Weather and Forecasting, 13(4):1005-1015 (1998).
-J-
Statistical analyses of the most recent 40 years of hurricane tracks (1956-1995) are presented, leading to a version of the North Atlantic climatology and persistence (CLIPER) model that exhibits much smaller forecast biases but similar forecast errors compared to the previously used version. Changes to the model involve the inclusion of more accurate historical tropical cyclone track data and a simpler derivation of the regression equations. Nonlinear systems analysis shows that the predictability timescale in which the average errors increase by a factor e is approximately 2.5 days in the Atlantic basin, which is larger than that found by similar methods near Australia. This suggests that five-day tropical cyclone track forecasts may have some benefit, and, therefore, a version of CLIPER extended to five days to be used as a baseline to measure this skill is needed.
Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of tropical cyclone intensity. Preprints, Symposium on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 150-153 (1998).
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No abstract.
Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of tropical cyclone tracks. Preprints, 12th Conference on Numerical Weather Prediction, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 290-292 (1998).
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No abstract.
Alfaro, E., L. Cid, and D.B. Enfield. Relationships between the start and end date of the rainy season in Central America and the tropical Atlantic and Pacific Oceans. Investigaciones Marinas, 26:59-69 (1998).
-J-
In recent years, several studies have shown that anomalies in the sea surface temperature of the tropical Atlantic and Pacific Oceans are related to variations in the intensity and timing of the rainy season in Central America. In order to study anomalous behavior of the rainy season over Central America, tropical Atlantic and Pacific Oceans indices are used to produce correlation series with the starting and ending date (IELL and TELL) of the rainy season. The North Atlantic (ATN) and SOI-Niño3 indices show the main correlations with the IELL and the TELL respectively.
Amat, L.R., M.D. Powell, and S.H. Houston. WANDA: HRD's real-time tropical cyclone "Wind Analysis Distributed Application." Preprints, 16th Conference on Weather Analysis and Forecasting and Symposium on the Research Foci of the U.S. Weather Research Program, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, J29-J31 (1998).
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No abstract.
Asher, W.E., and R.H. Wanninkhof. The effect of bubble-mediated gas transfer on purposeful dual gaseous-tracer experiments. Journal of Geophysical Research, 103(C5):10,555-10,560 (1998).
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For air-water gas exchange across unbroken surfaces, the only gas-dependent parameter affecting the transfer velocity is the molecular diffusivity of the transferring species. In contrast, bubble-mediated transfer processes can cause the transfer velocity to depend on both molecular diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual-gaseous tracer gas transfer experiments. Bubble effects also complicate the estimation of transfer velocities for other gases from the transfer velocity calculated using the dual-tracer data. Herein, a method for incorporating the effects of bubble-mediated gas transfer processes on the transfer velocity is presented. This new procedure is used to analyze the data from two recent dual-tracer gas transfer experiments. Transfer velocities that include the effect of bubbles are calculated using the data from two previous oceanic dual-gaseous tracer experiments. Comparing these transfer velocities with transfer velocities calculated by neglecting the effect of bubbles shows that bubble-mediated transfer increased the transfer velocity of helium 3 by 5% at a wind speed of 10.6 m s-1. However, when using the transfer velocities form helium 3 to calculate transfer velocities for carbon dioxide under the same conditions, including the effect of bubbles, decreases the transfer velocity of carbon dioxide by 18%. This shows that bubble-mediated transfer does not have a large effect on the analysis of dual-tracer data, but it is important in relating transfer velocities determined using helium 3 and sulfur hexafluoride to transfer velocities of more soluble gases at wind speeds above 10 m s-1.
Asher, W.E., and R.H. Wanninkhof. Transient tracers and air-sea gas transfer. Journal of Geophysical Research, 103(C8):15,939-15,958 (1998).
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This paper provides a review of the physics and chemistry associated with air-sea gas transfer of transient atmospheric trace gases and the available laboratory and field measurement techniques used to study air-water gas transfer. The mechanistic principals and their relation to the measurement techniques are used to show that the error associated with estimating air-sea transfer velocities of transient tracers from transfer velocities measured using proxy tracers can be significant if an incorrect dependence of the transfer velocity on molecular diffusivity is assumed. Bubble-mediated transfer processes are also demonstrated to have a significant effect on the parameterization of the transfer velocity.
Atakturk, S.S., and K.B. Katsaros. Estimates of surface humidity and wind speed obtained from satellite data in the stratocumulus regime in the Azores region. In Remote Sensing of the Pacific Ocean by Satellites, R.A. Brown (ed.). Southwood Press, Marrickville, Australia, 16-22 (1998).
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No abstract.
Bauer, S., M.S. Swenson, A. Griffa, A.J. Mariano, and K. Owens. Eddy-mean flow decomposition and eddy-diffusivity estimates in the equatorial Pacific. Journal of Geophysical Research, 103(C13):30,855-30,872 (1998).
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The ocean-atmospheric dynamics of the tropical Pacific Ocean create longitudinally coherent zonal flow () with strong meridional shear () in the large-scale mean and energetic mesoscale (O(100 km)) component. Parameterization of the effects of the mesoscale field depends on the separation of the large-scale mean and mesoscale eddy components in order to compute meaningful eddy diffusivity estimates in flow regimes that demonstrate strong currents and strong shear. Large gradients in the large-scale mean have precluded diffusivity estimation by traditional binning techniques. In this first of two publications, a method is developed for using Lagrangian data to estimate the diffusivity addressing the inhomogeneity of the mean flow. The spatially dependent estimate of the mean field is computed with a least squares bicubic smoothing spline interpolation scheme with an optimized roughness parameter which guarantees minimum energy in the fluctuation field at low frequencies. Numerical simulations based on a stochastic model of a turbulent shear flow are used to validate our approach in a conceptually simple but realistic scenario. The technique is applied to near-surface drifter observations obtained from 1979-1996 from two dynamically distinct time-space regions of the tropical Pacific Ocean. The first region, in the SEC, is characterized by a linear zonal shear mean flow and an approximately exponential autocovariance structure in the residuals. The residual velocity variance is s2 ~ 130 cm2 s-2 for both components and horizontal diffusivities are 7 × 107 cm2 s-1, and 3 × 10 cm2 s-1. The second region, in the NECC and the NEC, has a mean flow with a strong zonal shear and a weak northward velocity. The autocovariance is approximately exponential for the zonal component while the meridional component has a negative lobe at about 10 days probably due to the presence of instability waves. The variance is approximately tripled compared to the SEC region estimate while the meridional diffusivity estmate is nearly the same magnitude. The zonal diffusivity is estimated to be 15 × 107 cm2 s-1.
Black, P.G., and L.K. Shay. Observations of tropical cyclone intensity change due to air-sea interaction processes. Preprints, Symposium on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 161-168 (1998).
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No abstract.
Boebel, O., C. Duncombe Rae, S.L. Garzoli, J. Lutjeharms, P. Richardson, T. Rossby, C. Schmid, and W. Zenk. Float experiment studies interocean exchanges at the tip of Africa. EOS, Transactions, American Geophysical Union, 79(1):7-8 (1998).
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No abstract.
Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black. Environmental influences on the rapid intensification stage of Hurricane Opal (1995) over the Gulf of Mexico. Preprints, Symposium on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 105-112 (1998).
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No abstract.
Bove, M.C., J.J. O'Brien, J.B. Eisner, C.W. Landsea, and X. Niu. Effect of El Niño on U.S. landfalling hurricanes, revisited. Bulletin of the American Meteorological Society, 79(11):2477-2482 (1998).
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Changes in the frequency of U.S. landfalling hurricanes with respect to the El Niño-Southern Oscillation (ENSO) cycle are assessed. Ninety-eight years (1900-1997) of U.S. landfalling hurricanes are classified, using sea surface temperature anomaly data from the equatorial Pacific Ocean, as occurring during an El Niño (anomalously warm tropical Pacific waters), La Niña (anomalously cold tropical Pacific waters), or neither (neutral). The mean and variance of U.S. landfalling hurricanes are determined for each ENSO phase. Each grouping is then tested for Poisson distribution using a chi-squared test. Resampling using a "bootstrap" technique is then used to determine the 5% and 95% confidence limits of the results. Last, the frequency of major U.S. landfalling hurricanes (sustained winds of 96 kt or more) with respect to ENSO phase is assessed empirically. The results indicated that El Niño events show a reduction in the probability of a U.S. landfalling hurricane, while La Niña shows an increase in the chance of a U.S. hurricane strike. Quantitatively, the probability of two or more landfalling U.S. hurricanes during an El Niño is 28%, of two or more landfalls during neutral conditions is 48%, and of two or more landfalls during La Niña is 66%. The frequencies of landfalling major hurricanes show similar results. The probability of one or more major hurricane landfall during El Niño is 23% but is 58% during neutral conditions and 63% during La Niña.
Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles. Eldigio Press, Palisades, New York, 278 pp. (1998).
-B-
No abstract.
Broecker, W.S., S.L. Peacock, S. Walker. R. Weiss, E. Fahrbach, M. Schroeder, U. Mikolajewicz, C. Heinze, R. Key, T.-H. Peng, and S. Rubin. How much deep water is formed in the Southern Ocean? Journal of Geophysical Research, 103(C8):15,833-15,843 (1998).
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Three tracers are used to place constraints on the production rate of ventilated deep water in the Southern Ocean. The distribution of the water mass tracer PO4* ("phosphate star") in the deep sea suggests that the amount of ventilated deep water produced in the Southern Ocean is equal to or greater than the outflow of North Atlantic Deep Water from the Atlantic. Radiocarbon distributions yield an export flux of water from the North Atlantic which has averaged about 15 Sv over the last several hundred years. CFC inventories are used as a direct indicator of the current production rate of ventilated deep water in the Southern Ocean. Although coverage is as yet sparse, it appears that the CFC inventory is not inconsistent with the deep water production rate required by the distributions of PO4* and radiocarbon. It has been widely accepted that the major part of the deep water production in the Southern Ocean takes place in the Weddell Sea. However, our estimate of the Southern Ocean ventilated deep water flux is in conflict with previous estimates of the flux of ventilated deep water from the Weddell Sea, which lie in the range 1-5 Sv. Possible reasons for this difference are discussed.
Bryan, G.H., R.F. Rogers, and J.M. Fritsch. Cloud-scale resolution simulations in moist absolutely unstable layers. Preprints, Eighth Pennsylvania State University/National Center for Atmospheric Research's Mesoscale Model Users Workshop, Boulder, CO. National Center for Atmospheric Research, 59-62 (1998).
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No abstract.
Butler, J.H., J.W. Elkins, S.A. Montzka, T.M. Thompson, T.H. Swanson, A.D. Clarke, F.L. Moore, D.F. Hurst, P.A. Romashkin, S.A. Yvon-Lewis, J.M. Lobert, M. Dicorleto, G.S. Dutton, L.T. Lock, D.B. King, R.E. Dunn, E.A Ray, M. Pender, P.R. Wamsley, and C. M. Volk. Nitrous oxide and halocompounds. In Climate Monitoring and Diagnostics Laboratory Summary Report No. 24, D.J. Hofmann, J.T. Peterson, and R.M. Rosson (eds.). National Technical Information Services, Springfield, VA, 91-121 (1998).
-C-
No abstract.
Castle, R.D., R.H. Wanninkhof, J.L. Bullister, S.C. Doney, R.A. Feely, B.E. Huss, E. Johns, F.J. Millero, K. Lee, D. Frazel, D. Wisegarver, D. Greeley, F. Menzia, M. Lamb, G. Berberian, and L.D. Moore. Chemical and hydrographic profiles and underway measurements from the eastern North Atlantic during July and August of 1993. NOAA Data Report, NOAA-ERL-AOML-32 (PB98-131865), 82 pp. (1998).
-T-
From July 4-August 30, 1993, the National Oceanic and Atmospheric Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES) and Radiatively Important Trace Species (RITS) programs participated in an oceanographic research cruise aboard the NOAA ship Malcolm Baldrige. The objectives of the OACES component were to determine the source and sink regions of CO2 in the equatorial and North Atlantic during the summer and to establish a baseline of total carbon inventory in the region. Data were collected from 5°S to Iceland along a nominal longitude of 20°W. This report presents only the OACES-related data from legs 1, 2A, and 2B, including hydrography, nutrients, carbon species, dissolved oxygen, total inorganic carbon, chlorofluorocarbons, total alkalinity, pH, and salinity. Included are contour plots of the various parameters and descriptions of the sampling techniques and analytical methods used in data collection.
Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark. A new look at the diurnal variation of global oceanic precipitation from the ocean TOPography EXperiment (TOPEX) and the TOPEX Microwave Radiometer (TMR). International Journal of Remote Sensing, 19(1):171-180 (1998).
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New results on the diurnal variation of global oceanic precipitation are obtained by using one year's TOPEX (ocean TOPography EXperiment) and TMR (TOPEX Microwave Radiometer) data, derived from the dual-frequency (Ku and C band) capacity of the altimeter and the non-Sun-synchronous orbit of the satellite. The diurnal variation is characterized by a three-maximum structure which peaks at 00:00, 08:00, and 16:00 local time. The midnight-morning-afternoon maxima and dawn-noon-evening minima pattern seems to correlate with the results of most previous studies and to offer a unified picture of the diurnal variation of oceanic rainfall. A slight daytime (06:00-18:00) preference of oceanic precipitation appears to be significant in all seasons with the day/night ratio varying from 1.032 to 1.141 and the annual mean being 1.082. Examination of the geographical distribution of the timing of diurnal variation shows that the majority of the world oceans favor an afternoon maximum and an evening minimum. Moreover, the northern hemisphere is more coherent in reaching its maximum, while the southern hemisphere in reaching its minimum. In addition, the mechanisms responsible for the diurnal variations are discussed.
Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark. Identification of possible wave damping by rain using TOPEX and TMR data. Remote Sensing of Environment, 63(1):40-48 (1998).
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A global picture of wave damping by rain (WDBR), a phenomenon familiar to seafarers for centuries, has been so far unavailable owing to the fact that neither rules nor tools exist for its systematic measurement. The situation has changed following the launch of the first dual-frequency (5.3 GHz and 13.6 GHz) radar altimeter TOPEX, along with the three-frequency (18 GHz, 21 GHz, and 37 GHz) radiometer TMR (TOPEX Microwave Radiometer). In this study, a scheme for detecting possible WDBR using TOPEX/TMR data is proposed. The geographical distribution of identified WDBR is consistent with the simultaneous presence of high sea state and intensive rainfall. Frequent occurrences of WDBR are observed in the midlatitude of the two hemispheres, particularly in the Pacific Ocean. In contrast, WDBR rarely occurs in the majority of the tropical and subtropical oceans. The global seasonality of WDBR is found to be weak as a result of the hemispheric phase opposition of sea state and rainfall in their annual variations. Knowledge of spatial distribution and temporal variation of WDBR is useful in dealing with potential systematic biases in satellite wind and wave measurements due to rain/sea interaction. It would have been interesting to compare the WDBR with coincident estimates of global rainfall from the SSM/I (Special Sensor Microwave/Imager).
Cione, J.J., and P.G. Black. Surface thermodynamic observations within the tropical cyclone inner core. Preprints, Symposium on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 141-145 (1998).
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No abstract.
Cione, J.J., R.A. Neuherz, S. Raman, L.J. Pietrafesa, K. Keeter, and X. Li. The use of pre-storm boundary-layer baroclinicity in determining and operationally implementing the Atlantic Surface Cyclone Intensification Index. Boundary-Layer Meteorology, 89(2):211-224 (1998).
-J-
The lateral motion of the Gulf Stream off the eastern seaboard of the United States during the winter season can act to dramatically enhance the low level baroclinicity within the coastal zone during periods of offshore cold advection. The relative close proximity of the Gulf Stream current off the mid-Atlantic coast can result in the rapid and intense destabilization of the marine atmospheric boundary layer directly above and shoreward of the Gulf Stream within this region. This airmass modification period oftentimes precedes either wintertime coastal cyclogenesis or the cyclonic re-development of existing mid-latitude cyclones. A climatological study investigating the relationship between the severity of the pre-storm, cold advective period, and subsequent cyclogenic intensification was undertaken by Cione et al. in 1993. Findings from this study illustrate that the thermal structure of the continental airmass, as well as the position of the Gulf Stream front relative to land during the pre-storm period (i.e., 24-48 h prior to the initial cyclonic intensification), are linked to the observed rate of surface cyclonic deepening for storms that either advected into or initially developed within the Carolina-southeast Virginia offshore coastal zone. It is a major objective of this research to test the potential operational utility of this pre-storm low level baroclinic linkage to subsequent cyclogenesis in an actual National Weather Service (NWS) coastal winter storm forecast setting. The ability to produce coastal surface cyclone intensity forecasts recently became available to North Carolina State University researchers and NWS forecasters. This statistical forecast guidance utilizes regression relationships derived from a nine-season (January 1982- April 1990), 116-storm study conducted by Cione et al. (1993). During the period between February 1994 and February 1996, the Atlantic Surface Cyclone Intensification Index (ASCII) was successfully implemented in an operational setting by the NWS at the Raleigh-Durham forecast office for 10 winter storms. Analysis of these ASCII forecasts will be presented.
Doney, S.C., J.L. Bullister, and R.H. Wanninkhof. Climatic variability in upper ocean ventilation rates diagnosed using chlorofluorocarbons. Geophysical Research Letters, 25(9):1399-1402 (1998).
-J-
The chlorofluorocarbon CFC-12 (CCl2-F2) distributions from two occupations of a meridional hydrographic section in the eastern North Atlantic are used to describe the oceanic penetration of CFCs and change in the integrated ventilation patterns over the five years from 1988 to 1993. The CFC-12 water-column inventories increased by 30-40%, despite a slowing atmospheric growth rate (14%), because of continuing uptake by undersaturated subsurface water masses whose response is lagged by the ventilation time-scales. After removing the long-term CFC temporal trend using a tracer age based normalization technique, we observe a distinct dipole pattern in upper ocean ventilation, with reduced convection in the subpolar gyre and enhanced production of saline subtropical underwater in 1993. These differences are discussed in relation to interannual variability in atmospheric surface forcing, upper ocean anomalies, and convection patterns associated with the North Atlantic Oscillation.
Durand, P., H. Dupuis, D. Lambert, B. Bénech, A. Druilhet, K.B. Katsaros, P.K. Taylor, and A. Weill. Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments. Journal of Geophysical Research, 103(C11):25,125-25,136 (1998).
-J-
Two major campaigns (Surface of the Oceans, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphére, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were conducted in 1992 and 1993, respectively, in the Azores region. Among the various platforms deployed, instrumented aircraft and ship allowed the measurement of the turbulent flux of sensible heat, latent heat, and momentum. From coordinated missions we can evaluate the sea surface fluxes from (1) bulk relations and mean measurements performed aboard the ship in the atmosphere surface layer and (2) turbulence measurements aboard aircraft, which allowed the flux profiles to be estimated through the whole atmospheric boundary layer and therefore to be extrapolated toward the sea surface level. Continuous ship fluxes were calculated with bulk coefficients deduced from inertial-dissipation measurements in the same experiments, whereas aircraft fluxes were calculated with eddy-correlation technique. We present a comparison between these two estimations. Although momentum flux agrees quite well, aircraft estimations of sensible and latent heat flux are lower than those of the ship. This result is surprising, since aircraft momentum flux estimates are often considered as much less accurate than scalar flux estimates. The various sources of errors on the aircraft and ship flux estimates are discussed. For sensible and latent heat flux, random errors on aircraft estimates, as well as variability of ship flux estimates, are lower than the discrepancy between the two platforms, whereas the momentum flux estimates cannot be considered as significantly different. Furthermore, the consequence of the high-pass filtering of the aircraft signals on the flux values is analyzed; it is weak at the lowest altitudes flown and cannot therefore explain the discrepancies between the two platforms but becomes considerable at upper levels in the boundary layer. From arguments linked to the imbalance of the surface energy budget, established during previous campaigns performed over land surfaces with aircraft, we conclude that aircraft heat fluxes are probably also underestimated over the sea.
Eads, L.J., H.A. Friedman, and D.J. Garcia. From humble beginnings as the Inner City Marine Project to selection as a National School of Excellence. Preprints, Seventh Symposium on Education, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 162-165 (1998).
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The evolution of the MAST Academy (Maritime and Science Technology High School), a Dade County Magnet School of Choice, from its predecessor, the Inner City Marine Project (ICMP), is described. ICMP originated after Dade County experienced civil unrest in the Black community in 1984. At that time, Dr. Linda J. Eads, currently MAST Academy's principal, was assigned to design a program in maritime education which emphasized career exploration for minorities. The ICMP operated from the District Office of the Dade County Public Schools and targeted elementary and middle schools in the inner city with high minority populations. When the MAST Academy opened its doors in 1991, the ICMP became the MAST Academy Outreach Department which continued to provide programs for the targeted schools. The MAST Academy presently carries on the tradition of the ICMP by providing high school students with specialized marine-theme science and technology courses. In 1996, the MAST Academy was selected as a U.S. Department of Education National Blue Ribbon School of Excellence.
Ellis, G., P. Swart, M. Lutz, C. Alvarez-Zarikian, P. Blackwelder, T.A. Nelsen, H. Wanless, and J. Trefry. The stable isotope composition of foraminifera, ostracods, and organic material in a dated core from Whitewater Bay. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 2 pp. (1998).
-P-
No abstract.
Ellsberry, R.L., and F.D. Marks. U.S. Weather Research Program Hurricane Landfall Workshop Report. Technical Note, NCAR/TN-442 (National Center for Atmospheric Research, Boulder, CO), 40 pp. (1998).
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No abstract.
Feely, R.A., R.H. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P. Murphy. A new automated underway system for making high precision pCO2 measurements onboard research ships. Analytica Chimica Acta, 377(2-3):185-191 (1998).
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We have developed a new temperature-controlled, automated underway system for making atmospheric and surface ocean pCO2 measurements onboard research vessels equipped with an uncontaminated seawater intake system. Uncontaminated seawater is supplied to a showerhead plexiglass equilibrator at the rate of approximately 50 liters/minute. After about 3 minutes, the air trapped in the equilibrator is equilibrated with seawater. This air is sampled six times per hour. In addition, atmospheric air is sampled three times per hour from the intake on the bow flagstaff through 3/8" DekabonTM tubing to the underway system. The CO2 measurements are made with a differential, non-dispersive, infrared analyzer LiCorTM (model 6252). The underway system operates on an hourly cycle with the first quarter of each hour devoted to calibration with three CO2 standards, each measured for 5 minutes. A second order polynomial calibration curve is calculated from the voltage values of the standards. The remaining time in each hour is used to measure equilibrator air (15 min), bow air (15 min), and equilibrator air once again (15 min). To date, we have successfully used the underway pCO2 system on 12 cruises of the NOAA Ship Ka'imimoana in the equatorial Pacific. The analytical precision of the system is approximately 0.3-0.4 ppm for seawater and for air.
Ffield, A., C.I. Fleurant, R.L. Molinari, and W.D. Wilson. NOAA Ship Malcolm Baldrige 1995 cruises: MB95-02, MB95-04, and MB95-07 hydrographic data. Technical Report, Lamont-Doherty Earth Observatory, LDEO-98-1, 310 pp. (1998).
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No abstract.
Fleurant, C.I., and R.L. Molinari. Comparison of bottle salinity and bottle oxygen values from WHP repeat lines I7N, I1W, I8N, and I8S. International WOCE Newsletter, 33:27-29 (1998).
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No abstract.
Friedman, H.A., and D.J. Garcia. Tropical cyclone public awareness programmes: Preparing for the twenty-first century. Preprints, Seventh Symposium on Education, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 166-168 (1998).
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No abstract.
Garcia, D.J., H.A. Friedman, and L.J. Eads. MAST Academy outreach: Serving the community with marine theme programs. Preprints, Seventh Symposium on Education, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 169-171 (1998).
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No abstract.
Godin, O.A., D. Yu. Mikhin, and D.R. Palmer. Ocean current monitoring in the coastal zone. NOAA Technical Memorandum, NOAA-TM-ERL-AOML-93 (PB99-120255), 26 pp. (1998).
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A new technique has recently been put forward for real-time monitoring of ocean currents in the coastal zone. The acoustic technique, called matched non-reciprocity tomography (MNT), is being developed to extend traditional ocean acoustic tomography to the coastal zone. It should provide maps of the current field extending out tens of kilometers in range and throughout the water column. These maps will have applications to several important scientific problems such as measuring ocean circulation and upwelling and monitoring global climate change. Alternative approaches for monitoring currents in the coastal zone are surveyed and their limitations when compared with the MNT approach are discussed. Non-reciprocity tomography is based on recent progress in the theory of acoustic propagation in moving media and in the use of matched-field processing to solve tomographic inverse problems. The MNT technique can be viewed as an application of matched-field processing to a judiciously selected acoustic observable that is sensitive to flow velocity, but insensitive to sound speed and bathymetric variations, and leads to robust inversions for the depth-dependence of the velocity. The development of non-reciprocity tomography is reviewed in this article in the context of extended opportunities the technique offers in monitoring ocean dynamics in the coastal zone by acoustic means. Applications of the MNT technique to problems not directly related to coastal current monitoring are also noted.
Goodwin, K.D., J.K. Schaefer, and R.S. Oremland. Bacterial oxidation of dibromomethane and methyl bromide in natural waters and enrichment cultures. Applied and Environmental Microbiology, 64(12):4629-4636 (1998).
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Bacterial oxidation of 14CH2Br2 and 14CH3Br was measured in freshwater, estuarine, seawater, and hypersaline-alkaline samples. In general, bacteria from the various sites oxidized similar amounts of 14CH2Br2 and comparatively less 14CH3Br. Bacterial oxidation of 14CH3Br was rapid in freshwater samples compared to bacterial oxidation of 14CH3Br in more saline waters. Freshwater was also the only site in which methyl fluoride-sensitive bacteria (e.g., methanotrophs or nitrifiers) governed brominated methane oxidation. Half-life calculations indicated that bacterial oxidation of CH2Br2 was potentially significant in all of the waters tested. In contrast, only in freshwater was bacterial oxidation of CH3Br as fast as chemical removal. The values calculated for more saline sites suggested that bacterial oxidation of CH3Br was relatively slow compared to chemical and physical loss mechanisms. However, enrichment cultures demonstrated that bacteria in seawater can rapidly oxidize brominated methanes. Two distinct cultures of nonmethanotrophic methylotrophs were recovered; one of these cultures was able to utilize CH2Br2 as a sole carbon source, and the other was able to utilize CH3Br as a sole carbon source.
Gray, J. Commentary: Major ocean programs, National Oceanic and Atmospheric Administration. Marine Technology Society Journal, 32(3):85-87 (1998).
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Ocean researchers from academia and federal agencies were called together by the National Academy of Sciences (NAS)/National Research Council (NRC) to think about the large ocean research programs that exist today, their history, lessons learned, and advice for future ocean research endeavors. As a scientist and manager with the National Oceanic and Atmospheric Administration (NOAA), I was asked to contribute my thoughts regarding NOAA's role and benefits of such research programs as the World Ocean Circulation Experiment (WOCE), Joint Global Ocean Flux Study (JGOFS), GLOBal ocean ECosystem dynamics (GLOBEC), Ocean Drilling Program (ODP), Tropical Ocean and Global Atmospheric/Tropical Atmosphere Ocean array (TOGA/TAO), CLImate VARiability and predictability (CLIVAR), Ridge Interdisciplinary Global Experiment (RIDGE), Earth Sciences History (ESH), and ARCtic System Science (ARCSS). I encourage everyone to read the NAS/NRF report.
Hasler, A.F., K. Palaniappan, C. Kambhammetu, P.G. Black, E.W. Uhlhorn, and D. Chesters. High-resolution wind fields within the inner core and eye of a mature tropical cyclone from GOES 1-min images. Bulletin of the American Meteorological Society, 79(11):2483-2496 (1998).
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Mesoscale wind fields have been determined for a mature hurricane with high spatial and temporal resolution, continuity, and coherency. These wind fields, near the tropopause in the inner core and at low levels inside the eye, allow the evolution of mesoscale storm features to be observed. Previously, satellite-derived winds near hurricanes have been determined only at some distance from the eye over a typical time period of 1V2 h. Hurricane reconnaissance aircraft take 30 min to 1 h to complete an inner-core pattern. With the long observation periods of these previous methods, steady-state conditions must be assumed to give a complete description of the observed region. With the advent of 1-min interval imagery, and fourfold improvement of image dynamic range from NOAA's current generation of GOES satellites, there is a new capability to measure inner-core tropical cyclone wind fields near the tropopause and within the eye, enabling mesoscale dynamical processes to be inferred. These measurements give insights into the general magnitude and structure of the hurricane vortex, along with very detailed measurements of the cloud-top wind's variations in response to convective outbursts. This paper describes the new techniques used to take advantage of the GOES satellite improvements that, in turn, allowed the above innovations to occur. The source of data for this study is a nearly continuous 12-h sequence of 1-min visible images from NOAA GOES-9 on 6 September 1995. These images are centered on Hurricane Luis with maximum winds of 120 kt (CAT4) when it was 250 km northeast of Puerto Rico. A uniform distribution of long-lived cirrus debris with detailed structure is observed in the central dense overcast (CDO), which has been tracked using the 1-min images. The derived wind field near the tropopause at approximately 15 km in the CDO region has a strong closed circulation with speeds up to 25 m s-1, which pulses in response to the convective outbursts in the eyewall. Cloud displacements are computed at every pixel in every image, resulting in a quarter-million uVv winds in each of 488 hurricane images observed at 1- to 4-min intervals over 12 h. For analysis and presentation, these ultradense wind fields are reduced to 8- or 16-km grids using a 7-min time base by smoothing displacement vectors in space and time. Cloud structures were tracked automatically on a massively parallel processing computer, but with manual spot-checking. Manual tracking has been used to follow CDO structure over long time periods, up to 90 min for a small test sample. Cloud tracking for the wind fields presented here is accomplished using a Massively Parallel Semi-Fluid Motion Analysis (MPSMA) automatic technique. This robust deformable surface-matching algorithm has been implemented on the massively parallel Maspar supercomputer. MPSMA automatic tracking typically follows a feature for 7 min. For this time base the error of these winds is estimated to be 1.5 m s-1. However, systematic navigation and height assignment errors in the moderately sheared hurricane environment must still be considered. Spatial and temporal smoothing of the wind field have been performed to reduce systematic navigation errors and small-scale turbulent noise. The synthesis used here to compute the wind fields gives an order of magnitude reduction in the amount of data presented compared to the amount of data processed. Longer tracking could give higher accuracy but would smooth out the smaller-scale spatial and temporal features that appear dynamically significant. The authors believe that the techniques described in this paper have great potential for further research on tropical cyclones and severe weather as well as in operational use for nowcasting and forecasting. United States and foreign policymakers are urged to augment the GOES, GMS, FY2, and Meteosat geostationary satellite systems with dual imaging systems such that 1-min observations are routinely taken.
Hendee, J.C. An expert system for marine environmental monitoring in the Florida Keys National Marine Sanctuary and Florida Bay. Proceedings, 2nd International Conference on the Coastal Environment, Cancun, Mexico, September 8-10, 1998. Computational Mechanics Publications/WIT Press, Southampton, 57-66 (1998).
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The National Oceanic and Atmospheric Administration's (NOAA, U.S. Department of Commerce) Atlantic Oceanographic and Meteorological Laboratory (AOML) works cooperatively with the Florida Institute of Oceanography (FIO) in the implementation of the SEAKEYS (Sustained Ecological Research Related to Management of the Florida Keys Seascape) network, which is situated along 220 miles of coral reef tract within the Florida Keys National Marine Sanctuary (FKNMS). This network is itself actually an enhanced framework of seven Coastal-Marine Automated Network (C-MAN) stations for long-term monitoring of meteorological parameters (wind speed, wind gusts, air temperature, barometric pressure, relative humidity). To the C-MAN network, SEAKEYS adds oceanographic parameters (sea temperature, photosynthetically active radiation, salinity, fluorometry, optical density) to the stations. As a recent enhancement to the SEAKEYS network, an expert system shell is being employed to provide daily interpretations of near real-time acquired data for the benefit of scientists, fishermen, and skin divers. These interpretations are designed to be automatically emailed to Sanctuary managers and to the FIO maintainers of the network. The first set of interpretations include those dealing with environmental conditions conducive to coral bleaching. Other marine environmental interpretations are slated to follow.
Hendee, J.C., C. Humphrey, and T. Moore. A data-driven expert system for producing coral bleaching alerts. Proceedings, 7th International Conference on the Development and Application of Computer Techniques to Environmental Studies, Las Vegas, Nevada, November 10-12, 1998. Computational Mechanics Publications/WIT Press, Southampton, 139-147 (1998).
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As a recent enhancement to the SEAKEYS (Sustained Ecological Research Related to Management of the Florida Keys Seascape) environmental monitoring network, an expert system shell was employed to provide daily interpretations of near real-time acquired combinations of meteorological and oceanographic parameters as they meet criteria generally thought to be conducive to coral bleaching. These interpretations were automatically posted to the World-Wide Web and emailed to Florida Keys National Marine Sanctuary managers and scientists so they could witness and study bleaching events as they might happen, and so that a model could be developed with greater precision in identifying physical factors conducive to coral bleaching. The expert system, as a model, was successful in showing that certain assumptions by experts regarding coral bleaching apparently do not hold at Sombrero Reef.
Henderson-Sellers, A., H. Zhang, G. Berz, K. Emanuel, W. Gray, C.W. Landsea, G. Holland, J. Lighthill, S.-L. Shieh, P. Webster, and K. McGuffie. Tropical cyclones and global climate change: A post-IPCC assessment. Bulletin of the American Meteorological Society, 79(1):19-38 (1998).
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The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but there is no clear evidence of long-term trends. Efforts have been initiated to use geological and geomorphological records and analysis of oxygen isotope ratios in rainfall recorded in cave stalactites to establish a paleoclimate of tropical cyclones, but these have not yet produced definitive results. Recent thermodynamical estimation of the maximum potential intensities (MPI) of tropical cyclones shows good agreement with observations. Although there are some uncertainties in these MPI approaches, such as their sensitivity to variations in parameters and failure to include some potentially important interactions such as ocean spray feedbacks, the response of upper-oceanic thermal structure and eye and eyewall dynamics do appear to be an objective tool with which to predict present and future maxima of tropical cyclone intensity. Recent studies indicate the MPI of cyclones will remain the same or undergo a modest increase of up to 10%-20%. These predicted changes are small compared with the observed natural variations and fall within the uncertainty range in current studies. Furthermore, the known omissions (ocean spray, momentum restriction, and possibly also surface to 300-hPa lapse rate changes) could all operate to mitigate the predicted intensification. A strong caveat must be placed on analysis of results from current GCM simulations of the "tropical-cyclone-like" vortices. Their realism, and hence prediction skills (and also that of "embedded" mesoscale models), is greatly limited by the coarse resolution of current GCMs and the failure to capture environmental factors that govern cyclone intensity. Little, therefore, can be said about the potential changes of the distribution of intensities as opposed to maximum achievable intensity. Current knowledge and available techniques are too rudimentary for quantitative indications of potential changes in tropical cyclone frequency. The broad geographic regions of cyclogenesis and, therefore, also the regions affected by tropical cyclones are not expected to change significantly. It is emphasized that the popular belief that the region of cyclogenesis will expand with the 26 C SST isotherm is a fallacy. The very modest available evidence points to an expectation of little or no change in global frequency. Regional and local frequencies could change substantially in either direction, because of the dependence of cyclone genesis and track on other phenomena (e.g., ENSO) that are not yet predictable. Greatly improved skills from coupled global ocean-atmosphere models are required before improved predictions are possible.
Hitchcock, G., G.A. Vargo, T. Lee, E. Johns, E. Williams, and J. Jurado. The influence of circulation on nutrient distributions in western Florida Bay. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 98-99 (1998).
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No abstract.
Hood, T., C. Alvarez-Zarikian, P. Blackwelder, P. Swart, T.A. Nelsen, H.R. Wanless, J.H. Trefry, and L. Tedesco. The sediment record as a monitor of natural and anthropogenic changes in the lower Everglades/Florida Bay ecosystem. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 33-34 (1998).
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No abstract.
Houston, S.H., and M.D. Powell. Reconstruction of surface wind fields for hurricanes affecting Florida Bay. Preprints, Second Conference on Coastal Atmospheric and Oceanic Prediction and Processes, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 241-244 (1998).
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No abstract.
Houston, S.H., and M.D. Powell. Surface wind fields in hurricanes. Proceedings, Third International Symposium, Waves '97, Virginia Beach, VA, November 3-7, 1997. American Society of Civil Engineers (ASCE), 1391-1399 (1998).
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No abstract.
Houston, S.H., M. Lawrence, S. Spisak, and S.T. Murillo. A verification of National Hurricane Center forecasts of surface wind speed radii in hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 139-140 (1998).
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No abstract.
Huang, H., R.E. Fergen, J.R. Proni, and J.J. Tsai. Initial dilution equations for buoyancy-dominated jets in current. Journal of Hydraulic Engineering, 124(1):105-108 (1998).
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Initial dilution of submerged, single, round, buoyancy-dominated jets in a current is considered. Two simple semi-empirical equations, one for centerline dilution and the other for minimum surface dilution, are presented. These equations are derived based on the continuity equation for the buoyant jet flow with a hypothesis that shear entrainment and forced entrainment can be added. Available laboratory and field data are used to determine the constants in the equations. Unlike asymptotic equations which apply for the limiting flow regimes, the proposed equations span all flow regimes, from the buoyancy-dominated near field (BDNF), to the transition, and to the buoyancy-dominated far field (BDFF), providing continuous predictions for dilutions.
Jameson, A.R., A.B. Kostinski, and R.A. Black. The texture of clouds. Journal of Geophysical Research, 103(D6):6211-6220 (1998).
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Using a precise definition of clustering, it is shown that in two tropical cumulus clouds, droplets appear to be bunched over distances ranging from at least a kilometer or more down to several centimeters. A statistical framework is proposed for quantifying clustering in terms of a Poisson probability mixture. While these observations require further substantiation in many different clouds, droplet clustering may play a role in diverse phenomena from the coalescence growth of raindrops to the scattering of radiation by clouds.
Kaplan, J., and M. DeMaria. Climatological and synoptic characteristics of rapidly intensifying tropical cyclones in the North Atlantic basin. Preprints, Symposiuim on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 119-123 (1998).
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No abstract.
Katsaros, K.B. Microwave remote sensing with radiometers. In Remote Sensing of the Pacific Ocean by Satellites, R.A. Brown (ed.). Southwood Press, Marrickville, Australia, 13-15 (1998).
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No abstract.
Landsea, C.W., and R.A. Pielke. Trends in U.S. hurricane losses, 1925-1995. Preprints, Ninth Symposium on Global Change Studies, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 210-212 (1998).
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No abstract.
Landsea, C.W., J. Kaplan, and M. DeMaria. The differing roles of the large-scale environment in the intensity changes of recent Atlantic hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 113-114 (1998).
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No abstract.
Landsea, C.W., N. Nicholls, and J. Gill. Australian region tropical cyclones: Recent trend and interannual predictions. Preprints, Ninth Conference on Interaction of the Sea and Atmosphere, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 1-4 (1998).
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No abstract.
Landsea, C.W., G.D. Bell, W.M. Gray, and S.B. Goldenberg. The extremely active 1995 Atlantic hurricane season: Environmental conditions and verification of seasonal forecasts. Monthly Weather Review, 126(5):1174-1193 (1998).
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The 1995 Atlantic hurricane season was a year of near-record hurricane activity with a total of 19 named storms (average is 9.3 for the base period 1950-1990) and 11 hurricanes (average is 5.8), which persisted for a total of 121 named storm days (average is 46.6) and 60 hurricane days (average is 23.9), respectively. There were five intense (or major) Saffir-Simpson category 3, 4, or 5 hurricanes (average is 2.3 intense hurricanes) with 11.75 intense hurricane days (average is 4.7). The net tropical cyclone activity, based upon the combined values of named storms, hurricanes, intense hurricanes and their days present, was 229% of the average. Additionally, 1995 saw the return of hurricane activity to the deep tropical latitudes: seven hurricanes developed south of 25°N (excluding all of the Gulf of Mexico) compared with just one during all of 1991-1994. Interestingly, all seven storms that formed south of 20°N in August and September recurved to the northeast without making landfall in the United States. The sharply increased hurricane activity during 1995 is attributed to the juxtaposition of virtually all of the large-scale features over the tropical North Atlantic that favor tropical cyclogenesis and development. These include extremely low vertical wind shear, below-normal sea level pressure, abnormally warm ocean waters, higher than average amounts of total precipitable water, and a strong west phase of the stratospheric quasi-biennial oscillation. These various environmental factors were in strong contrast to those of the very unfavorable conditions that accompanied the extremely quiet 1994 hurricane season. The favorable conditions for the 1995 hurricane season began to develop as far back as the previous winter. Their onset well ahead of the start of the hurricane season indicates that they are a cause of the increased hurricane activity, and not an effect. The extreme duration of the atmospheric circulation anomalies over the tropical North Atlantic is partly attributed to a transition in the equatorial Pacific from warm episode conditions (El Niño) to cold episode conditions (La Niña) prior to the onset of the hurricane season. Though the season as a whole was extremely active, 1995's Atlantic tropical cyclogenesis showed a strong intraseasonal variability with above-normal storm frequency during August and October and below normal for September. This variability is likely attributed to changes in the upper-tropospheric circulation across the tropical North Atlantic, which resulted in a return to near-normal vertical shear during September. Another contributing factor to the reduction in tropical cyclogenesis during September may have been a temporary return to the near-normal SSTs across the tropical and subtropical North Atlantic, caused by the enhanced tropical cyclone activity during August. Seasonal hurricane forecasts for 1995 issued at Colorado State University on 30 November 1994, 5 June 1995, and 4 August 1995 correctly anticipated an above-average season, but underforecast the extent of the extreme hurricane activity.
Lee, K., and W.M. Sackett. The high temperature titration of biogenic silica. Deep-Sea Research, Part I, 45(6):1015-1028 (1998).
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A new method has been developed for measuring biogenic silica (amorphous) in marine sediments. It is based on the Hogbom-Urey reaction CaCO3+SiO2 (biogenic silica)->CaSiO3 (wollastonite)+CO2. The reaction is carried out in evacuated sealed glass tubes with added excess reagent grade calcite at 500°C for 3 d. The product CO2 is measured in a calibrated manometer. The dependence of the reaction on time, temperature, product CO2 pressure, and other factors is examined.
Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely. Low interannual variability in recent oceanic uptake of atmospheric carbon dioxide. Nature, 396(6707):155-158 (1998).
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An improved understanding of the partitioning of carbon between the atmosphere, terrestrial biosphere, and ocean allows for more accurate predictions of future atmospheric CO2 concentrations under various fossil-fuel CO2 emission scenarios. One of the more poorly quantified relevant processes is the interannual variability in the uptake of fossil-fuel CO2 from the atmosphere by the terrestrial biosphere and ocean. Existing estimates, based on atmospheric measurements, indicate that the oceanic variability is large. Here we estimate the interannual variability in global net air-sea CO2 flux using changes in the observed wind speeds and the partial pressure of CO2 (pCO2) in surface seawater and the overlying air. Changes in seawater pCO2 are deduced from interannual anomalies in sea surface temperature and the regionally and seasonally varying temperature-dependence of seawater pCO2, assuming that variations in sea surface temperature reflect seawater pCO2 changes caused by thermodynamics, biological processes, and water mixing. The calculated interannual variability in oceanic CO2 uptake of 0.4 Gt C yr-1(2 sigma) is much less than that inferred from the analysis of atmospheric measurements. Our results suggest that variable sequestration of carbon by the terrestrial biosphere is the main cause of observed year-to-year variations in the rate of atmospheric CO2 accumulation.
Lee, T.N., E. Johns, W.D. Wilson, and E. Williams. Florida Bay circulation and exchange study. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 43-44 (1998).
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No abstract.
Marks, F.D., and L.K. Shay. Landfalling tropical cyclones: Forecast problems and associated research opportunities. Preprints, 16th Conference on Weather Analysis and Forecasting and Symposium on the Research Foci of the U.S. Weather Research Program, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 520-523 (1998).
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No abstract.
Marks, F.D., L.K. Shay, and PDT-5 (Fifth Prospectus Development Team). Landfalling tropical cyclones: Forecast problems and associated research opportunities. Report of the Fifth Prospectus Development Team to the U.S. Weather Research Program. Bulletin of the American Meteorological Society, 79(8):305-323 (1998).
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The Fifth Prospectus Development Team of the U.S. Weather Research Program was charged to identify and delineate emerging research opportunities relevant to the prediction of local weather, flooding, and coastal ocean currents associated with landfalling U.S. hurricanes specifically, and tropical cyclones in general. Central to this theme are basic and applied research topics, including rapid intensity change, initialization of and parameterization in dynamical models, coupling of atmospheric and oceanic models, quantitative use of satellite information, and mobile observing strategies to acquire observations to evaluate and validate predictive models. To improve the necessary understanding of physical processes and provide the initial conditions for realistic predictions, a focused, comprehensive mobile observing system in a translating storm-coordinate system is required. Given the development of proven instrumentation and improvement of existing systems, three-dimensional atmospheric and oceanic data sets need to be acquired whenever major hurricanes threaten the United States. The spatial context of these focused three-dimensional data sets over the storm scales is provided by satellites, aircraft, expendable probes released from aircraft, and coastal (both fixed and mobile), moored, and drifting surface platforms. To take full advantage of these new observations, techniques need to be developed to objectively analyze these observations, and initialize models aimed at improving prediction of hurricane track and intensity from global-scale to mesoscale dynamical models. Multinested models allow prediction of all scales from the global, which determine long-term hurricane motion to the convective scale, which affect intensity. Development of an integrated analysis and model forecast system optimizing the use of three-dimensional observations and providing the necessary forecast skill on all relevant spatial scales is required. Detailed diagnostic analyses of these data sets will lead to improved understanding of the physical processes of hurricane motion, intensity change, the atmospheric and oceanic boundary layers, and the air-sea coupling mechanisms. The ultimate aim of this effort is the construction of real-time analyses of storm surge, winds, and rain, prior to and during landfall, to improve warnings and provide local officials with the comprehensive information required for recovery efforts in the hardest hit areas as quickly as possible.
Mayer, D.A., and R.H. Weisberg. El Niño-Southern Oscillation-related ocean-atmosphere coupling in the western equatorial Pacific. Journal of Geophysical Research, 103(C9):18,635-18,648 (1998).
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Using 43 years of Comprehensive Ocean-Atmosphere Data Set (COADS) and related data for the period 1950-1992, an examination is made into the regional dependence of ocean-atmosphere coupling in relation to the El Niño-Southern Oscillation (ENSO). The cross correlation between sea surface temperature (SST) and sea level pressure (SLP) anomalies over the global tropics shows two patterns of significant negative correlation consistent with a local hydrostatic response of SLP to SST: (1) the eastern Pacific, where the correlation is symmetric about and largest on the equator; and (2) the western Pacific, where symmetric regions of negative correlation are found off the equator, separated by a region of positive correlation on the equator. Anomalies within these two patterns vary out of phase with each other. While the SLP anomalies on both sides of the basin are of similar magnitude, the SST anomalies in the east are much larger than those in the west. Despite this disparity in the SST anomaly magnitudes between the eastern and western Pacific, we argue that the ocean-atmosphere couplings in the western and west-central Pacific are important for ENSO. The off-equator SST anomalies in the west enhance the SLP anomalies there and they appear to initiate easterly wind anomalies over the far western Pacific during the peak El Niño phase of ENSO. As these easterlies evolve, their effect upon the ocean tends to oppose that of the westerly wind anomalies found over the west-central Pacific. These competing effects suggest a mechanism that may contribute to coupled ocean-atmosphere system oscillations. The west-central equatorial Pacific (the region separating the eastern and western patterns), while exhibiting large momentum and heat flux exchanges, shows minimum correlation between SST and SLP. Thus, neither the SST and SLP anomaly magnitudes nor the correlation between them are alone indicative of ocean-atmosphere coupling, and the regional dependence for such coupling in relation to ENSO appears more complicated than mechanistic interpretations of ENSO would suggest.
Mayer, D.A., R.L. Molinari, and J.F. Festa. The mean and annual cycle of upper layer temperature fields in relation to Sverdrup dynamics within the gyres of the Atlantic Ocean. Journal of Geophysical Research, 103(C9):18,545-18,566 (1998).
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Using 28 years of expendable bathythermograph data (1967-1994), we describe the mean and annual cycle of the upper ocean temperature fields in the Atlantic from 30°S to 50°N in the context of the basin-scale wind-driven gyres (Sverdrup stream function field) which provide a framework for describing the oceanographic measurements. We examine the circulation field implied by the temperature distributions which are used as a proxy for the field of mass. Similarities between the temperature and stream function fields increase with depth. In the lower to subthermocline depths of the tropical and equatorial gyres, the zonal currents form a closed circulation. A Southeastward Boundary Current is suggested near and below 150 m that provides closure for the tropical gyre, and the equatorial gyre axis is southward of that suggested by the stream function field. Higher in the water column, the North Equatorial Countercurrent (NECC) may be a surface manifestation of the North Equatorial Undercurrent (NEUC) where the latter can be interpreted as the southern limb of the tropical gyre. Because there are large vertical shears in the tropics, the equatorial gyre is not clearly indicated in the vertically integrated temperature field but appears below about 200 m. Here, the South Equatorial Undercurrent (SEUC) can be interpreted as the eastward flowing northern limb of the equatorial gyre and is opposite in direction to the westward flowing South Equatorial Current above. Both the NEUC and SEUC are analagous to currents in the Pacific that are governed by non-Sverdrup dynamics. Despite the shortcomings of the data, the mean annual cycle appears to be relatively stable, and we have discounted the possibility that in regions where it represents a significant percentage of the total variance, it is changing slowly over the 28 years of record. The wind-forcing fields, which undergo large meridional movements (5-6 of latitude) during their annual cycle, with some exceptions, have essentially no counterpart in gyre movements between their seasonal extremes. Most of the variability associated with the annual cycle is confined to the upper 300 m. Greatest variability, where ranges exceed 6°C, occurs in the northwestern Atlantic in late winter and early spring. During this time of year south of the Gulf Stream and below about 100 m, water temperatures exhibit a systematic phase lag with depth. The next largest area of variability, where ranges can also exceed 6°C, resides in the tropical western basin between the equator and 10°N just below 100 m. In the eastern basin, ranges decrease and shoal. Additionally, the phase fields are consistent with the intensification and relaxation of the tropical ridge-trough system where the NECC disappears in March in the west but the NECC/NEUC complex is strongest in September.
McElligott, S., R.H. Byrne, K. Lee, R.H. Wanninkhof, F.J. Millero, and R.A. Feely. Discrete water column measurements of CO2 fugacity and pHT in seawater: A comparison of direct measurements and thermodynamic calculations. Marine Chemistry, 60(1-2):63-73 (1998).
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The NOAA Equatorial Pacific CO2 system data set (~2500 water samples) has been evaluated to assess the internal consistency of measurements and calculations involving CO2 fugacity and pHT. This assessment represents the first large scale field comparison of pHT and fCO2 data. Comparisons of direct discrete CO2 fugacity (fCO2) measurements with CO2 fugacity calculated from total inorganic carbon (CT), total alkalinity (AT), and spectrophotometric pH (pHT = -log[H+]T) indicate that a variety of improvements are needed in the parameter measurements and thermodynamic relationships used to relate fCO2, CT, AT, and pHT in seawater. CO2 fugacity calculated from CT and pHT or AT and pHT agree with direct measurements to no better than 1%. Comparisons of measured fugacity, fCO2 (measured), and CO2 fugacity calculated from CT and pHT, fCO2 (CT, pHT), indicate that the precision of fCO2 calculations is good relative to direct measurements. In contrast, due to the extreme sensitivity of fCO2 and [H+]T calculations to relatively small errors in both CT and AT, CO2 fugacity, as well as [H+]T, calculated from CT and AT are very imprecise and render comparisons with direct measurements of little use. Consequently, precise calculations of fCO2 require the use of direct pHT measurements.
Millero, F.J., K. Lee, and M. Roche. Distribution of alkalinity in the surface waters of the major oceans. Marine Chemistry, 60(1-2):111-130 (1998).
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In recent years the total alkalinity (TA) of seawater has been measured with high precision (~ ±2 µmol kg-1) in the Atlantic, Pacific, and Indian oceans. In this paper, we have analyzed the surface alkalinity of the major ocean basins using these measurements as well as those obtained during the GEOSECS and TTO studies. The salinity normalized alkalinity (NTA=TA x 35/S) in subtropical gyres between 30°S and 30°N is remarkably invariable except in upwelling areas (e.g., the eastern equatorial Pacific). The NTA increases toward high latitudes (>40°) and is inversely proportional to sea surface temperature (SST). This increase in NTA with latitude (or decreasing temperature) is attributed to the upward transport of deep waters with higher NTA due to the dissolution of CaCO3(s). The distribution of surface NTA in the major ocean basins shows that the major basins can be divided into regions where different trends of NTA are observed and boundaries between the regions are similar to those of the major ocean currents. The linear behavior of NTA (~ ±5 µmol kg-1) with respect to SST makes it possible to provide regional maps of NTA. These maps can be used to estimate TA in surface waters in large areas of the ocean from values of SST and salinity (S). By combining the estimates of TA using SST and S (from the Climatological Atlas of the World Ocean) with underway fCO2 measurements (by ships, moorings, and satellites), it is possible to map the detailed distribution of TCO2 for surface waters over a large area of the ocean. Calculations of TCO2 from measurements of fCO2, SST, and S in the subtropical Pacific Ocean agree with the coulometrically measured values to ±5 µmol kg-1.
Millero, F.J., W. Yao, K. Lee, J.-Z. Zhang, and D.M. Campbell. Carbonate system in the waters near the Galapagos Islands. Deep-Sea Research, Part II, 45(6):1115-1134 (1998).
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During the IRONEX cruise in the equatorial Pacific Ocean, the carbonate parameters TA (total alkalinity), TCO2 (total inorganic carbon), pH, and fCO2 (fugacity of CO2), were determined both in a small (8 × 8 km) patch of water fertilized with Fe and in the waters around the Galapagos Islands. The CO2 parameters, along with hydrographic properties, were found to be uniform in the surface waters of the study area before the addition of iron. A significant decrease of the surface TCO2 (7 µmol kg-1) and fCO2 (11 µatm) in the patch was detected within 48 h of the iron release. This decrease, however, did not continue and was lower than expected from the complete utilization of NO3- due to the addition of iron. The shipboard iron a ddition experiments (3 nM fe) resulted in a continual decrease of TCO2 (up to 48 µmol kg-1) and complete consumption of the nutrients. A good correlation was found between TCO2, pH, and fCO2 with temperature in the surface waters around the Galapagos Islands. The salinity (S = 35) normalized alkalinities were quite uniform (NTA = 2310 ± 9 mol kg-1) throughout the region. The effect of high primary production on the CO2 system in the downstream plume is overshadowed by the upwelling waters with high CO2.
Millero, F.J., D.G. Purkerson, P. Steinberg, E. Peltola, K. Lee, C. Edwards, J. Goen, and M.P. Roche. The carbon dioxide system in the Ross Sea during the JGOFS Southern Ocean Process Study. University of Miami Technical Report, RSMAS-98-001, 159 pp. (1998).
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In the austral summer of 1996 and austral fall of 1997, we participated in the Joint Global Ocean Flux Study (JGOFS) supported by the National Science Foundation (NSF) in the Southern Ocean aboard the R/V Nathaniel B. Palmer. The first cruise was a survey across the Antarctic Convergence Zone from Port Lyttelton, New Zealand to the Ross Sea and back. The Process 1 and 3 cruises were in the Ross Sea. The first process cruise originated in Port Lyttelton, New Zealand and ended in McMurdo Station, Antarctica. The third process cruise originated and ended in Port Lyttelton, New Zealand. This report gives the results of our pH, total alkalinity (TA), and total inorganic carbon dioxide (TCO2) measurements made during these cruises. The pH, TCO2, and TA results were obtained by potentiometric titration of seawater samples with hydrochloric acid (HCl), while the TCO2 was determined by coulometry. Spectroscopic pH measurements were also made. Measurements of pH, TA, and TCO2 were made on certified reference material (CRM) throughout the cruises to assess the quality of the measurements. The reproducibility of these CRM measurements by potentiometric titration were ±1.6 µmol kg-1 in TA, ±2.2 µmol kg-1 in TCO2, and ±0.005 in pH. The reproducibility in TCO2 by coulometry were ±1 µmol kg-1 and ±0.001 in the spectroscopic values of pH. The at sea measurements agreed with the assigned values of ±2 µmol kg-1 in TA, ±5 µmol kg-1 in TCO2, and ±0.002 in pH. All the measurements done at sea were adjusted for these differences. The values of pH, TA, and TCO2 for the measurements in the Ross Sea are examined for the process studies along with surface nutrients and pCO2.
Millero, F.J., A.G. Dickson, G. Eischeid, C. Goyet, P. Guenther, K.M. Johnson, R.M. Key, K. Lee, D. Purkerson, C.L. Sabine, R.G. Schottle, D.R.W. Wallace, E. Lewis, and C.D. Winn. Assessment of the quality of the shipboard measurements of total alkalinity on the WOCE hydrographic program Indian Ocean CO2 survey cruises, 1994-1996. Marine Chemistry, 63(1-2):9-20 (1998).
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In 1995, we participated in a number of WOCE Hydrographic Program cruises in the Indian Ocean as part of the Joint Global Ocean Flux Study (JGOFS) CO2 survey sponsored by the Department of Energy (DOE). Two titration systems were used throughout this study to determine the pH, total alkalinity (TA), and total inorganic carbon dioxide (TCO2) of the samples collected during these cruises. The performance of these systems was monitored by making closed cell titration measurements on Certified Reference Materials (CRMs). A total of 962 titrations were made on six batches of CRMs during the cruises. The reproducibility calculated from these titrations was ±0.007 in pH, ±4.2 µmol kg-1 in TA, and ±4.1 µmol kg-1 in TCO2. The at-sea measurements on the CRMs were in reasonable agreement with laboratory measurements made on the same batches. These results demonstrate that the CRMs can be used as a reference standard for TA and to monitor the performance of titration systems at sea. Measurements made on the various legs of the cruise agreed to within 6 µmol kg-1 at the 15 crossover points. The overall mean and standard deviation of the differences at all the crossovers are 2.1 ± 2.1 µmol kg-1. These crossover results are quite consistent with the overall reproducibility of the CRM analyses for TA (±4 µmol kg-1) over the duration of the entire survey. The TA results for the Indian Ocean cruises provide a reliable data set that, when combined with TCO2 data, can completely characterize the carbonate system.
Molinari, J., S. Skubis, D. Vollaro, F. Alsheimer, and H.E. Willoughby. Potential vorticity analysis of tropical cyclone intensification. Journal of the Atmospheric Sciences, 55(6):2632-2644 (1998).
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The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive potential vorticity anomaly was examined. The intensification mechanism proposed earlier for mature Hurricane Elena appears to be valid for Danny as well, despite significant differences in the synoptic-scale environment and in the stage of the tropical cyclone prior to the interaction. Both storms experienced rapid pressure falls as a relatively small-scale positive upper potential vorticity anomaly began to superpose with the low-level tropical cyclone center. The interaction is described in terms of a complex interplay between vertical wind shear, diabatic heating, and mutual advection among vortices at and below the level of the outflow anticyclone. Despite this complexity, the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions.
Molinari, R.L., H.F. Bezdek, M. Latif, and A. Groetzner. A comparison of modeled and observed mean and decadal time-scale Atlantic air-sea structure. Proceedings, Atlantic Climate Variability Meeting, Palisades, New York, September 24-26, 1997. University Corporation for Atmospheric Research, 78-79 (1998).
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No abstract.
Molinari, R.L., R.A. Fine, W.D. Wilson, R.G. Curry, J. Abell, and M.S. McCartney. The arrival of recently formed Labrador Sea Water in the Deep Western Boundary Current at 26.5°N. Geophysical Research Letters, 25(13):2249-2252 (1998).
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The Deep Western Boundary Current (DWBC) of the North Atlantic is a principal conduit between the formation region for Labrador Sea Water (LSW) and the oceanic interior to the south. Time series (1985-1997) of hydrographic properties obtained in the DWBC at 26.5°N show that prior to 1994, temperature, salinity, and transient tracer properties within the LSW density range showed little indication of recently formed parcels. Properties characteristic of a newer version of LSW (cooler, fresher, and higher tracer concentrations) were observed beginning in 1994 and continuing through 1997. Longer time series of temperature and salinity, developed from a regional data base, show both the 1994 and a 1980-1981 event in the Abaco region. Both events are consistent with anomalies in the Labrador Sea that occurred some 10 years earlier. The 10-year transit time from the Labrador Sea to 26.5°N is less than the 18-year transit time inferred from earlier studies.
Montgomery, M.T., and J.L. Franklin. An assessment of the balance approximation in hurricanes. Journal of the Atmospheric Sciences, 55(12):2193-2200 (1998).
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The validity of the traditional balance approximation for the asymmetric flow above the boundary layer generally in hurricanes is examined here. Scaling considerations of the divergence equation show that the validity of the balance approximation hinges on the smallness of the nondimensional product. The first term represents the ratio of asymmetric horizontal divergence to asymmetric vertical vorticity for azimuthal wavenumber, n, while the second term represents a Rossby number based upon the azimuthal mean tangential wind and absolute vertical vorticity of the hurricane vortex. Wind observations of Hurricane Gloria (1985) indicate that this product is not at all small in the near-vortex region (several hundred kilometers beyond the radius of maximum tangential winds) where asymmetric convergence forced by surface friction and cumulus convection is typically large. Although the Gloria observations represent only a single case, there are dynamical reasons to expect this product to be 0(1) just above the hurricane boundary layer in steadily translating hurricanes. The meteorological relevance of these results to the problem of balance dynamics in hurricanes is briefly discussed.
Murphy, P.P., R.A. Feely, and R.H. Wanninkhof. On obtaining high-precision measurements of oceanic pCO2 using infrared analyzers. Marine Chemistry, 62(1-2):103-115 (1998).
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Assessments of ocean carbon uptake using the air-sea disequilibrium of CO2 require very high quality measurements of pCO2 in the atmosphere and in surface seawater. These measurements are often collected and analyzed using infrared detectors. Laboratory data are presented here which suggest that errors of the order of several parts per million in xCO2 can result if the analyzer temperature and pressure are not carefully matched during calibration and sampling. Field data were examined to address questions about the importance of measuring analysis temperature and pressure under more extreme conditions, sample averaging, and calibration frequency. The results indicate that calibration frequency can be minimized without significant compromises in data quality if the analyzer temperatures and pressures are suitably monitored and/or controlled. Daily calibrations gave results to within 0.4 ppm of the results obtained by hourly calibration when the temperature of the analyzer was controlled to ±0.2°C and the voltages were corrected for pressure differences between calibration and sampling.
Nicholls, N., C.W. Landsea, and J. Gill. Recent trends in Australian region tropical cyclone activity. Meteorology and Atmospheric Physics, 65(3-4):197-205 (1998).
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The number of tropical cyclones observed in the Australian region (south of equator; 105-160°E) has apparently declined since the start of reliable (satellite) observations in the 1969/1970 season. However, the number of more intense cyclones (with minimum pressures dropping to 970 hPa or lower) has increased slightly. The numbers of weak (minimum pressures not dropping below 990 hPa) and moderate systems (minimum pressures between 970 and 990 hPa) have declined. Possible reasons for these different trends are discussed. The decline in the number of weaker cyclones may at least partly reflect improved understanding of the nature of some weak systems. The decline in the number of cyclones more intense than 990 hPa primarily reflects the downward trend in the Southern Oscillation Index (SOI). Previous work has demonstrated that the number of tropical cyclones observed in the Australian region each cyclone season is related to the value of the SOI prior to the start of the cyclone season. This relationship is clearest with the number of moderate cyclones. The SOI is only weakly related to the number of intense or weak cyclones. The increase in the number of intense cyclones is not attributable to the trend in the SOI. Nor is there clear reason, at present, to suspect that it is artificial (i.e., due to changes in observing or analysis techniques).
Niyogi, D.S., J.J. Cione, and S. Raman. Gulf Stream influence on the North Carolina mesoclimate. Preprints, 2nd Conference on Coastal Atmospheric and Oceanic Prediction, Phoenix, AZ, January 12-16, 1998. American Meteorological Society, Boston, 421-424 (1998).
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No abstract.
Ortner, P.B., M.J. Dagg, G.S. Kleppel, R. Brenner, and C. Tomas. Trophic pathways in the pelagic environment of Florida Bay. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 143-145 (1998).
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No abstract.
Ozgokmen, T.M., and O.E. Esenkov. Asymmetric fingers induced by the nonlinear equation of state. Physics of Fluids, 10(8):1882-1890 (1998).
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The impact of the nonlinearity in the equation of state associated with the change in the thermal expansion coefficient with temperature on the structure of fingers growing from an interface between two mixed layers is investigated using a numerical model. It is shown that the nonlinearity acts to enhance the buoyancy force acting on the descending fingers with respect to that acting on the ascending fingers, resulting in narrower and faster-growing descending fingers than ascending fingers. The results are discussed with emphasis on the vertical variability of properties along the fingers.
Ozgokmen, T.M., O.E. Esenkov, and D.B. Olson. A numerical study of layer formation due to fingers in double-diffusive convection in a vertically-bounded domain. Journal of Marine Research, 56(2):463-487 (1998).
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The evolution of fingers in a double-diffusive system is investigated using numerical integration of two-dimensional equations of motion for an incompressible, Boussinesq fluid. The computational domain is periodic in the horizontal direction and is closed with no-flux boundary conditions in the vertical direction. The main result of this study is the evolution of the system from initially linear profiles for both fast and slow diffusing components to a layered state characterized by a finger zone sandwiched between two mixed layers. The horizontal boundaries in this system play an important role in the development of the layered state. At the top and bottom boundaries, light and heavy finger fluxes accumulate leading to the formation of mixed layers exhibiting larger-scale eddies. In the quasi-equilibrium state, the finger zone is characterized by broken wiggly fingers which do not extend across the entire interface. The salinity flux at the mid-depth of the domain is approximately proportional to the 4/3 power of the salinity difference between the mixed layers, except for the initial phase and for the run-down phase.
Peltola, E., R. Wanninkhof, R. Molinari, B.E. Huss, R. Feely, J. Bullister, J.-Z. Zhang, F. Chavez, A. Dickson, A. Ffield, D. Hansell, F. Millero, P. Quay, R. Castle, G. Thomas, R. Roddy, T. Landry, M. Roberts, H. Chen, D. Greeley, K. Lee, M. Roche, J.A. Goen, F. Millero, K. Buck, M. Kelly, F. Menzia, A. Huston, T. Waterhouse, S. Becker, and C. Mordy. Chemical and hydrographic measurements during the Indian Ocean I8 repeat cruise (IR8N) in September and October 1995. NOAA Data Report, ERL AOML-34 (PB99-126948), 176 pp. (1998).
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This document contains data and metadata from the I8 repeat cruise in the Indian Ocean cruise in 1995 from Fremantle, Australia to Male in the Maldives. From September 22 to October 25, 1995, the National Oceanic and Atmospheric Administration (NOAA) sponsored an oceanographic research cruise conducted aboard the NOAA Ship Malcolm Baldrige. This report presents the analytical and quality control procedures and data from the cruise that was conducted for the Ocean-Atmosphere Carbon Exchange Study (OACES). Samples were taken at 101 stations. The data presented in this report includes hydrography, nutrients, total dissolved inorganic carbon dioxide (DIC), fugacity of carbon dioxide (fCO2), total alkalinity (TA), pH, total organic carbon and nitrogen data (TOC/TON), chlorofluorocarbons, 13C, and biological parameters.
Peng, T.-H., R. Key, and H.G. Ostlund. Temporal variations of bomb radiocarbon in the Pacific Ocean. Marine Chemistry, 60(1-2):3-14 (1998).
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The natural and anthropogenic components of the radiocarbon measurements from seawater samples can be successfully separated by an improved method, which is based on a very well-defined relationship between natural radiocarbon and dissolved silica observed mainly during the GEOSECS survey for waters beneath 1000 m depth. This relationship is further reconfirmed by the 14C measurements from large volume samples taken in the deep waters in the Pacific Ocean during the recent WOCE survey program. Analysis of upper ocean 14C measurements made along 152°W, and north of 20°'N, in the northeastern Pacific Ocean during the NOAA's CGC91 cruise, which is a part of the WOCE survey program, indicates that the bomb 14C inventory in this part of the ocean has increased by 22% since the GEOSECS measurements made in 1974. This increase is consistent with the model prediction of 25% for the northern hemisphere ocean. Change of the surface water bomb 14C values during this period is insignificant. This feature is also consistent with the model simulation. Results of this new analysis will provide useful information of the temporal variations of bomb 14C inventory in the ocean, in addition to the spatial distribution, which can be used as powerful constraints in calibrating the global ocean carbon cycle models, especially those based on three dimensional ocean general circulation models, for estimating the uptake of CO2 by the ocean.
Peng, T.-H., R.H. Wanninkhof, J.L. Bullister, R.A. Feely, and T. Takahashi. Quantification of decadal anthropogenic CO2 uptake in the Indian Ocean based on dissolved inorganic carbon measurements. Nature, 396(6711):560-563 (1998).
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The increase of total dissolved inorganic carbon (DIC) in the ocean caused by the uptake of fossil fuel CO2 is estimated mostly by ocean models. These model estimates need to be verified using field measurements. However, the direct detection of the anthropogenic CO2 signal in the ocean has been hampered by the relatively small annual increase in DIC in seawater (~1 µmol/kg/yr, as compared with background DIC of ~2000 µmol/kg) and by lack of high-precision measurements in the past. With the recent improvement in DIC analyses techniques, it has now become possible to detect the anthropogenic CO2 signal on decadal time scales. Here we report a significant increase in DIC between the GEOSECS survey in 1978 and the recent NOAA-OACES survey in 1995 in the Indian Ocean. The anthropogenic CO2 signal is 12 ± 4.5 µmol/kg at ~300 m (potential density, sigmatheta = 26.6) and the signal decreases on denser isopycnal horizons down to undetectable near ~1000 m (sigmatheta = 27.2). The data are used to illustrate the isopycnal analysis and corrections necessary to determine the anthropogenic CO2 increase over time. The work can be used as a guide for future observational strategies to assess uptake of anthropogenic CO2.
Pielke, R.A., and C.W. Landsea. Normalized hurricane damages in the United States: 1925-1995. Weather and Forecasting, 13(3):621-631 (1998).
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Hurricanes are the costliest natural disasters in the United States. Understanding how both hurricane frequencies and intensities vary from year to year, as well as how this is manifested in changes in damages that occur, is a topic of great interest to meteorologists, public and private decision makers, and the general public alike. Previous research into long-term trends in hurricane-caused damage along the U.S. coast has suggested that damage has been quickly increasing within the last two decades, even after considering inflation. However, to best capture the year-to-year variability in tropical cyclone damage, consideration must also be given toward two additional factors: coastal population changes and changes in wealth. Both population and wealth have increased dramatically over the last several decades and act to enhance the recent hurricane damages preferentially over those occurring previously. More appropriate trends in the United States hurricane damages can be calculated when a normalization of the damages are done to take into account inflation and changes in coastal population and wealth. With this normalization, the trend of increasing damage amounts in recent decades disappears. Instead, substantial multidecadal variations in normalized damages are observed: the 1970s and 1980s actually incurred less damages than in the preceding few decades. Only during the early 1990s does damage approach the high level of impact seen back in the 1940s through the 1960s, showing that what has been observed recently is not unprecedented. Over the long term, the average annual impact of damages in the continental United States is about $4.8 billion (1995 $), substantially more than previous estimates. Of these damages, over 83% are accounted for by the intense hurricanes (Saffir-Simpson categories 3, 4, and 5), yet these make up only 21% of the U.S.-landfalling tropical cyclones.
Powell, M.D., and S.D. Aberson. How well do we forecast the position and time of hurricane landfall? Preprints, 16th Conference on Weather Analysis and Forecasting and Symposium on the Research Foci of the U.S. Weather Research Program, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 9-12 (1998).
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No abstract.
Powell, M.D., and S.H. Houston. Surface wind fields of 1995 Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne at landfall. Monthly Weather Review, 126(5):1259-1273 (1998).
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Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne were the most destructive hurricanes of 1995. At landfall, Luis and Marilyn contained maximum sustained winds (marine exposure) estimated at near 60 and 46 m s-1, respectively. The strongest landfalling storm of the 1995 season, Luis, decreased in intensity from a category 4 to 3 on the Saffir-Simpson scale shortly before the eyewall crossed the Islands of Antigua, Barbuda, St. Kitts-Nevis, St. Barthelemy, St. Martin, and Anguilla. Hurricane Marilyn strengthened as it approached the U.S. Virgin Islands, with St. Thomas bearing the brunt of the north and south eyewall winds of 46 m s-1 (marine exposure) and St. Croix being affected by the relatively weak western eyewall peak winds of 35-40 m s-1 (marine exposure). For Luis and Marilyn, only surface winds with marine exposures were analyzed because of unknown small-scale interactions associated with complex island terrain with 500-1000-m elevations. Wind engineering studies suggest that wind acceleration over blunt ridges can increase or "speed up" winds by 20%-80%. Topographic effects were evident in damage debris analyses and suggest that an operational method of assessing terrain-induced wind gusts (such as a scaled down mesoscale model) is needed. After landfall as a marginal hurricane over central Florida, Hurricane Erin regained strength over the Gulf of Mexico with a well-defined radar reflectivity structure. Erin struck the Florida panhandle near Navarre Beach with maximum sustained surface winds of 35-40 m s-1 affecting the Destin-Ft. Walton area. Hurricane Opal made landfall in nearly the identical area as Erin, with maximum sustained surface winds of 40-45 m s-1, having weakened from an intensity of nearly 60 m s-1 only 10 h earlier. Opal was characterized by an asymmetric structure that was likely related to cold front interaction and an associated midlevel southwesterly jet. Roxanne struck Cozumel, Mexico, with sustained surface winds (marine exposure) of 46 s-1, crossed the Yucatan, and meandered in the southwest Gulf of Mexico for several days. While in the Bay of Campeche, Roxanne's large area of hurricane-force winds disabled a vessel, which led to the drowning deaths of five oil industry workers. High-resolution wind records are critical to preserving an accurate extreme wind climatology required for assessment of realistic building code risks. Unfortunately, power interruptions to Automated Surface Observing Stations (ASOS) on the U.S. Virgin Islands (St. Croix, St. Thomas) and Destin, Florida, prevented complete wind records of the eyewall passages of Marilyn and Opal, respectively.
Powell, M.D., and S.K. Rinard. Marine forecasting at the 1996 centennial olympic games. Weather and Forecasting, 13(3):764-782 (1998).
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A team of meteorologists from the United States, Canada, and Australia provided marine weather support to the sailing events of the 1996 Centennial Olympic Games, held in Wassaw Sound near Savannah, Georgia. The team conducted research on the weather and climate and developed a set of forecast products designed to inform athletes, volunteers, and race managers of the wind, tidal current, wave, and weather behavior expected each day during the pre-Olympic and Olympic periods. The Olympic period proved to be a challenge with thunderstorms delaying, abandoning, or postponing races on half of the days. Thunderstorm development and movement was linked to the timing and strength of the sea breeze as well as the direction and speed of the gradient wind. Numerous thunderstorm warnings were issued with the assistance of the WSR-88D radar and the Warning Decision Support System. Frequent lightning was a legitimate safety concern due to the long distances between race courses and lack of suitable shelter; fortunately no one was injured during the lightning episodes. Forecasters benefited from access to a variety of monitoring tools and models including real-time Olympic buoy wind and current time series displays; satellite and radar imagery animation; 2-, 8-, and 10-km resolution mesoscale models; a live video feed of race coverage; and communications with forecasters aboard patrol craft offshore. Official wind forecasts, mesoscale models, and a simple vector addition model performed better than climatology and persistence as defined by mean vector error and rms wind direction error. Climatology was difficult to beat on the basis of wind speed error.
Powell, M.D., S.H. Houston, L.R. Amat, and N. Morisseau-Leroy. The HRD real-time hurricane wind analysis system. Journal of Wind Engineering and Industrial Aerodynamics, 77&78:53-64 (1998).
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The HRD real-time wind analysis system is currently undergoing evaluation in the operational forecasting environment of the National Hurricane Center. The system is an object-oriented, distributed, three-tiered client-server application that assimilates disparate observations and processes the data into a common framework for exposure, height, and averaging time. The data are then examined collectively or by type, quality controlled, and passed on to a scale-controlled objective analysis algorithm. Several products are derived from the analysis wind field and storm track, yielding effective tools for disaster assessment, emergency management, and recovery.
Proni, J.R., and J.C. Wilkerson. Underwater acoustic monitoring for satellite rainfall estimation validation. Proceedings, 6th International Conference for Precipitation, Mauna Lani Bay, Hawaii, June 29-July 1, 1998. NASA/NOAA, 2-10 (1998).
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Application of underwater acoustic techniques to the monitoring of rainfall over water is demonstrated at four acoustically distinct ocean sites based on information in the 4-30 kHz frequency band. Rainfall detection and classification as to type (convective or stratiform) are possible because underwater sound spectral characteristics of rain are different from the normally prevailing underwater background noise in the ocean, and because there are distinct differences in the sound levels and spectral shapes of the acoustic signature of the two rain types. Rain type classification is determined by an acoustic discriminant, DR, which is defined as the difference in the average spectral levels between the 10-30 and 4-10 kHz bands. Rainfall estimation potential is based on the high correlation between sound spectral levels in decibels (in the 4-10 kHz frequency band) and radar reflectivity dBz. Data obtained from a spatially distributed 12-hydrophone array on the ocean floor, at a depth of 1.5 km, demonstrates the potential of monitoring rainfall at the sea surface on spatial (420 km2) and temporal (five samples/minute) scales suitable for validating precipitation estimates from remote sensors carried on geostationary and polar orbiting satellites.
Proni, J.R., and J.C. Wilkerson. Wind-generated acoustic spectral effects in the surf zone in the presence and absence of rainfall at Duck, North Carolina. Proceedings, 16th International Congress on Acoustics and 135th Meeting of the Acoustical Society of America, Seattle, Washington, June 20-26, 1998. Journal of the Acoustical Society of America, 103(5):2865-2866 (1998).
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Concurrent underwater sound, wind, radar, and rainfall measurements were made on November 5, 1992, off Duck, North Carolina. A wind speed increment from 5 m/s to 13 m/s in 90 seconds resulted in a reduction in the rainfall sound spectrum level beginning at about 50 kHz and extending downward in frequency with time to about 10 kHz. The reduction in rainfall-generated sound spectrum level with time is thought to be due to sound absorption by the evolving wind-generated bubble field.
Proni, J.R., C. McArthur, and G. Schuster. Adaptive dredged material discharge for the Port of Miami. Proceedings, Ports '98, Long Beach, California, March 8-11, 1998. American Society of Civil Engineers, 1249-1257 (1998).
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In a joint effort of the U.S. Army Corps of Engineers, the U.S. Environmental Protection Agency, the National Oceanic and Atmospheric Administration, the State of Florida, the Port of Miami, and the University of Miami, a novel, environmentally adaptively controlled procedure was developed, wherein a vital port expansion and maintenance dredging operation was carried out while affording maximum protection to sensitive coral reefs. After establishing the existence and spatial disposition of a residual water column discharge plume, via acoustic backscattering methods, a real-time current measurement system was established at the offshore dredged material disposal site to be utilized. Dredged material discharges then proceeded on a schedule in conformity with the ambient currents, so that material transport to the coral reefs of concern was minimized.
Quilfen, Y., B. Chapron, T. Elfouhaily, K.B. Katsaros, and J. Tournadre. Observations of tropical cyclones by high-resolution scatterometry. Journal of Geophysical Research, 103(C4):7767-7786 (1998).
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Unprecedented views of surface wind fields in tropical cyclones (hereafter TCs) are provided by the European Remote Sensing Satellite (ERS) C-band scatterometer. Scatterometer measurements at C band are able to penetrate convective storms clouds, observing the surface wind fields with good accuracy. However, the resolution of the measurements (50 × 50 km2) limits the interpretation of the scatterometer signals in such mesoscale events. The strong gradients of the surface wind existing at scales of a few kilometers are smoothed in the measured features such as the intensity and location of the wind maxima and the position of the center. Beyond the ERS systems, the scatterometers on-board the ADEOS and METOP satellites, designed by the Jet Propulsion Laboratory and by the European Space Agency, respectively, will be able to produce measurements of the backscattering coefficient at about 25 × 25 km2 resolution. A few sets of ERS-1 orbits sampling TC events were produced with an experimental 25 × 25 km2 resolution. Enhancing the resolution by a factor of 2 allows location of the wind maxima and minima in a TC with a much better accuracy than at 50 km resolution. In addition, a better resolution reduces the geophysical noise (variability of wind speed within the cell and effect of rain) that dominates the radiometric noise and, hence, improves the definition of the backscattering measurements. A comprehensive analysis of the backscattering measurements in the case of high winds and high sea states obtained within TCs is proposed in order to refine the interpretation of the wind vector derived from a backscattering model that is currently only calibrated up to moderate winds (<20 m/s) in neutral conditions. Observations of the TOPEX-POSEIDON dual-frequency altimeter are also used for that purpose. Patterns of the surface winds in TCs are described and characteristic features concerning asymmetries in the maximum winds and in the divergence field are discussed.
Rogers, S.M., and S.H. Houston. Hurricane surge and wave conditions: Research needs. Proceedings, Third International Symposium, Waves '97, Virginia Beach, VA, November 3-7, 1997. American Society of Civil Engineers, 1414-1424 (1998).
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For many years, coastal engineers have recognized the importance of reliable wave height and frequency information in the design of major coastal structures. Over time, research by government agencies, such as the U.S. Army Corps of Engineers and NOAA, and private interests such as the offshore oil industry has made a substantial investment in wave gages, wave hindcasting, and wave forecasting. Design needs for breakwaters, jetties, coastal protection, offshore oil facilities, and similar large-scale projects have driven the acquisition of better wave data. Our ability to optimize design wave conditions has improved significantly and with ongoing research is likely to continue to improve in the future. Most designers and researchers would expect wave data is most important for large coastal projects. However, in the United States the most frequent application of design wave conditions is for the design of single family homes and other coastal buildings. Each day hundreds of coastal buildings in communities around the U.S. begin construction in Coastal High Hazard Areas (or V-zones) as identified by the National Flood Insurance Program (NFIP) and the Federal Emergency Management Agency (FEMA). The NFIP prepares flood hazard maps specifying minimum flood elevation standards that include wave height predictions during a 100-year storm surge, generally occurring during a hurricane or other severe coastal storm. The NFIP uses several relatively simple models for shoreline erosion, wave setup, wave runup and depth-limited linear waves. Given the uncertainties inherent in any 100-year surge model, the simple models are not unreasonable, including the use of depth limited, linear waves. For many years we have been measuring water marks along the coast following severe coastal storms with the goal of measuring the storm surge, still water elevation, and/or wave height maximum. This paper will report on case studies of U.S. hurricanes from U.S. hurricanes describing the discrepancies between even the most reliable still water marks and the lower limit of wave damage at the same locations. It is reassuring that our ability to predict offshore wave conditions has improved. However, it is clear that we have little understanding of the water-levels and wave conditions during hurricanes where we need them the most; that is, flooded building sites that are normally dry land. Some of the discrepancies can be explained by measurement errors, wave setup, wave runup, and localized setup in confined spaces and other factors, but no rational theory can explain local variations. In short, we may have a good wave gage record somewhere offshore and many post-storm water marks, but we have little idea what water elevations and wave conditions occurred in flooded building sites near the beach.Two problems result. First, small buildings are usually designed to avoid waves by being elevated on piling foundations. Without a reasonable understanding of the wave conditions, buildings will be improperly elevated for cost-effective designs (i.e., either too high or too low). A second potentially more serious problem is that the high water marks will eventually be used to calibrate the underlying storm surge models on which all design conditions are based. Our lack of understanding increases the risk of improperly calibrating the storm surge models, which are also used to predict flood elevations much further inland than those areas affected by waves. The authors believe that there is a substantial need for wave and water-level measurements near coastal building sites which are flooded during hurricanes and other design-level storms. The frequent application of wave predictions is to design cost-effective, storm-resistant buildings. The deployment of multiple, self contained wave gages at preselected sites near coastal buildings that are expected to be flooded during a landfalling hurricane is now a practical research goal with recent improvements in instrumentation. It is time to stop guessing the wave and water-level conditions and produce some real measurements.
Roubicek, A.J., S.L. Garzoli, P.L. Richardson, C.M. Dumcombe Rae, and D.M. Fratantoni. Benguela Current Experiment, R/V Seward Johnson Cruise SJ9705, Cape Town, September 4, 1997-Recife, September 30, 1997. NOAA Data Report, ERL AOML-33 (PB98-164775), 215 pp. (1998).
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The main objective of this program is to study the pathways, velocity, transport, and variability of the Benguela Current and its extension with emphasis on tracking floats in the intermediate water. It is expected that the results of this program will make a significant contribution towards the understanding of inter-ocean (Indian to Atlantic) and inter-basin (South and North Atlantic) exchange of intermediate water and its role in heat and mass exchanges. This program is a component of KAPEX (Cape of Good Hope Experiment), a joint U.S., German, and South African experiment. In March 1997, a German cruise on the Polarstern led by W. Zenk and O. Boebel launched 35 RAFOS floats and five sound sources (including one of the U.S. sources near 20°S, 4°E) in the general area west and southwest of Cape Town. During August 1997, a U.S. cruise on the R/V Seward Johnson led by T. Rossby launched three sound sources east and southeast of Cape Town; 50 RAFOS floats will be launched in the Agulhas Current starting in November 1997. During the Benguela Current Experiment cruise on the RV Seward Johnson in September 1997, 32 RAFOS floats and two sound sources were launched in the general area west and northwest of Cape Town. During KAPEX, over 100 RAFOS floats and nine sound sources will measure ocean trajectories for the first time in the Agulhas Current, in its rings which enter the South Atlantic, and in the Benguela Current and its extension, which is the source of water moving northward through the Atlantic in the meridional overturning circulation cell. In addition, temperature, salinity, and velocity profiles will document the water mass and velocity structure of the Benguela Current, its extension, and several Agulhas rings.
Shapiro, L.J., and S.B. Goldenberg. Atlantic sea surface temperatures and tropical cyclone formation. Journal of Climate, 11(4):578-590 (1998).
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It has long been accepted that interannual fluctuations in sea surface temperature (SST) in the Atlantic are associated with fluctuations in seasonal Atlantic basin tropical cyclone frequency. To isolate the physical mechanism responsible for this relationship, a singular value decomposition (SVD) is used to establish the dominant covarying modes of tropospheric wind shear and SST, as well as horizontal SST gradients. The dominant SVD mode of covarying vertical shear and SST gradients, which comprises equatorially confined near-zonal vertical wind shear fluctuations across the Atlantic basin, is highly correlated with both equatorial eastern Pacific SST anomalies (associated with El Niño) and west African Sahel rainfall. While this mode is strongly related to tropical storms, hurricanes, and major hurricane frequency in the Atlantic, it is not associated with any appreciable Atlantic SST signal. By contrast, the second SVD mode of covarying vertical shear and horizontal SST gradient variability, which is effectively uncorrelated with the dominant mode, is associated with SST fluctuations concentrated in the main tropical cyclone development region between 10°N and 20°N. This mode is significantly correlated with tropical storm and hurricane frequency but not with major hurricane frequency. Statistical tests confirm the robustness of the mode, and lag correlations and physical reasoning demonstrate that the SST anomalies are not due to the developing tropical cyclones themselves. Anomalies of SST and vertical shear during years where the mode has substantial amplitude confirm the resemblance of the individual fields to the modal structure, as well as the association of hurricane development with the warmer SSTs. Although SSTs are of secondary importance to vertical shear in modulating hurricane formation, explaining only 10% of the interannual variability in hurricane frequency over the 50% explained by vertical shear, the results support the conclusion that warmer SSTs directly enhance development. The lack of correlation with major hurricanes implies that the underlying SSTs are not a significant factor in the development of these stronger systems.
Shay, L., G.J. Goni, F.D. Marks, J.J. Cione, and P.G. Black. Role of warm ocean features on intensity change: Hurricane Opal. Preprints, Symposium on Tropical Intensity Change, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 131-138 (1998).
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No abstract.
Swart, P., K.S. White, D.B. Enfield, P. Milne, and R.E. Dodge. Stable oxygen isotopic composition of corals from the Gulf of Guinea as indicators of periods of extreme precipitation conditions in the sub-Sahara. Journal of Geophysical Research, 103(C12):27,885-27,891 (1998).
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Analyses of scleractinian coral skeletons from the Gulf of Guinea in the eastern Atlantic reveal that the corals from this region can be used to identify periods of severe drought and above average precipitation in the Subsahara. Data presented in this paper show a positive correlation between the magnitude of the Sahel drought and the d18O values of the Principe coral skeleton. The explanation for this positive correlation is that the salinity of the Gulf of Guinea is strongly influenced by the outflow of the Niger and Zaire Rivers. The outflow of these rivers is also correlated with the fluorescence of the Principe coral. These periods of high freshwater input correlate with periods of higher rainfall in the Subsahara and have affected the d18O values of the coral skeleton. The correlations between Principe coral d18O values and Atlantic NATL (r = -0.34), the dipole (r = -0.45), and the latitudinal position of the ITCZ (r = -0.37) illustrate that the d18O values in the Principe coral reflect climate dynamics of the region that affect the precipitation patterns in the Subsahara.
Thomas, G.G., R. Benway, S.K. Cook, Y.-H. Daneshzadeh, and W.S. Krug. Surface salinity and temperature from ships of opportunity. Proceedings, Ocean Community Conference '98, Baltimore, MD, November 16-19, 1998. Marine Technology Society, 160-165 (1998).
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Thermosalinograph (TSG) data collected aboard both NOAA research vessels and ships participating in the National Oceanic and Atmospheric Administration's (NOAA) Volunteer Observing Ship (VOS) program plays an important role in the study of meridional circulation in the world's oceans. Sea surface temperature (SST) and sea surface salinity (SSS) are valuable measurements in our attempt to understand the interaction between the world's oceans and global climate. The ability to collect and calibrate these data sets to insure a high standard of data quality is necessary to validate their use in NOAA's Global Ocean Observing System (GOOS) Center data base at the Atlantic Oceanographic and Meteorological Laboratory (AOML) located in Miami, Florida.
Valdimarsson, H., S.-A. Malmberg, and M.H. Bushnell. SVP drifters in Icelandic waters, 1995-1997: Preliminary results. Technical Session, 13th Data Buoy Cooperation Panel Meeting, La Reunion, October 1997. DBCP Technical Publication 12, 91-101 (1998).
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No abstract.
Wang, C., and R.H. Weisberg. Climate variability of the coupled tropical-extratropical ocean atmosphere system. Geophysical Research Letters, 25(21):3979-3982 (1998).
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Observations show that tropical and extratropical Pacific SST anomalies vary out-of-phase, and that the atmospheric meridional Hadley and zonal Walker Circulations are related to these variations. A tropical-extratropical model is constructed to show oscillations consistent with observations. The positive feedback introduced by the Walker Circulation causes tropical warming so that the air rises and flows toward the subtropics where it sinks. When the sinking air approaches the sea surface, it flows both equatorward and poleward enhancing tropical easterly and extratropical westerly winds, respectively. Enhanced extratropical westerlies increases wind speed and hence evaporation, resulting in extratropical cooling. The Walker and Hadley Circulations thus result in tropical warming and extratropical cooling, respectively. The tropical warming and extratropical cooling increase the meridional SST difference and hence the meridional heat transport which erodes the tropical warming and extratropical cooling. Enhanced tropical easterlies due to the Hadley Circulation cools the tropical ocean through ocean dynamics. These negative feedbacks help the system to switch from warm to cold phases, and vice versa.
Wang, C., and R. H. Weisberg. Observations of meridional scale frequency dependence in the coupled tropical ocean-atmosphere system. Journal of Geophysical Research, 103(C2):2811-2816 (1998).
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It is generally observed in models of the coupled tropical ocean-atmosphere system that the meridional scales for oscillations at interannual periods are larger than an oceanic equatorial Rossby radius of deformation. Using nine years of the high-resolution Optimum Interpolation sea surface temperature (SST) product of the NOAA/NCEP, analyses are made on the frequency dependence of the observed meridional scales, with emphasis on the latitudinal structures in the central Pacific at 140°W. On the relatively short intraseasonal and seasonal time scales the SST variations are found to occur over a meridional scale of the oceanic equatorial Rossby radius of deformation suggested by conventional equatorially trapped wave theory. In contrast to this, on the longer annual and interannual time scales the meridional scales are found to increase beyond the oceanic equatorial Rossby radius of deformation. A physical explanation for this meridional scale increase with decreasing frequency in the coupled tropical ocean-atmosphere system is discussed.
Wanninkhof, R.H., and R.A. Feely. fCO2 dynamics in the Atlantic, Pacific, and South Indian Oceans. Marine Chemistry, 60(1-2):15-31 (1998).
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Subsurface fugacities of CO2 (fCO2(20)) can be used in combination with total dissolved inorganic carbon (DIC) to precisely calculate total alkalinity. Thus, it can be used to determine dissolution of calcium carbonate (hard tissue) and remineralization of organic material (soft tissue), to quantify saturation constants of calcite and aragonite in seawater, and to characterize water masses. fCO2(20) is a good tracer of biological transformation since it is thermodynamically related to the other inorganic carbon system parameters and it has a dynamic range from 200 to 2000 µatm in the world's ocean. Precision of fCO2 measurements is better than 0.3% and the values are well calibrated using compressed gas reference standards. Increases of fCO2(20) are observed as the water masses age during movement from the Atlantic to the Indian and South Pacific Oceans. As an example of the determination of the ratio of soft tissue remineralization to hard tissue dissolution from fCO2(20) and DIC, the trends along the 27.2 isopyncal for the subtropical gyres of the three basins are investigated. Little CaCO3 dissolves along this isopycnal in the Atlantic and the South Pacific while the soft tissue remineralization to hard tissue dissolution ratio in the Indian Ocean is 4.5:1. The difference in this ratio along the 27.2 isopycnal appears to be a combination of the calcite and aragonite saturation levels and the supply of aragonite tests.
White, S.R., J.D. McFadden, and J.L. Franklin. Atmospheric observations with the NOAA Gulfstream IV-SP. Preprints, 10th Symposium on Meteorological Observations and Instrumentation, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 38-41 (1998).
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No abstract.
Willoughby, H.E. Tropical cyclone eye thermodynamics. Monthly Weather Review, 126(12):3053-3067 (1998).
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In intense tropical cyclones, sea level pressures at the center are 50-100 hPa lower than outside the vortex, but only 10-30 hPa of the total pressure fall occurs inside the eye between the eyewall and the center. Warming by dry subsidence accounts for this fraction of the total hydrostatic pressure fall. Convection in the eyewall causes the warming by doing work on the eye to force the thermally indirect subsidence. Soundings inside hurricane eyes show warm and dry air aloft, separated by an inversion from cloudy air below. Dewpoint depressions at the inversion level, typically 850-500 hPa, are 10-30 K rather than the 100 K that would occur if the air descended from tropopause level without dilution by the surrounding cloud. The observed temperature and dewpoint distribution above the inversion can, however, be derived by 100 hPa of undilute dry subsidence from an initial sounding that is somewhat more stable than a moist adiabat. It is hypothesized that the air above the inversion has remained in the eye since it was enclosed when the eyewall formed and that it has subsided at most a few kilometers. The cause of the subsidence is the enclosed air's being drawn downward toward the inversion level as the air below it flows outward into the eyewall. Shrinkage of the eye's volume is more than adequate to supply the volume lost as dry air is incorporated into the eyewall or converted to moist air by turbulent mixing across the eye boundary. The moist air below the inversion is in thermodynamic contact with the sea surface. Its moisture derives from evaporation of seawater inside the eye, frictional inflow of moist air under the eyewall, and from moist downdrafts induced as condensate mixes into the eye. The moist air's residence time in the eye is much shorter than that of the dry air above the inversion. The height of the inversion is determined by the balance between evaporation, inflow, and inward mixing on one hand and loss to the eyewall updrafts on the other.
Zegowitz, V., and S.K. Cook. World Meteorological Organization-Volunteer Observing Ship Program. Proceedings, Ocean Community Conference '98, Baltimore, MD, November 16-19, 1998. Marine Technology Society, 6 pp. (1998).
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As one of our astute, well-informed political figures said recently, "What do we need the Weather Service for, we have the Weather Channel!" Just where DOES the data come from to make a good marine forecast? Even those of you who have wandered here by mistake are about to be exposed to a little bit of information about a big contributor to this process, the World Meteorological Organization (WMO) Voluntary Observing Ship (VOS) program.
Zhang, J.-Z., and P.B. Ortner. Effect of thawing conditions on the recovery of reactive silicic acid from frozen natural water samples. Water Research, 32(8):2553-2555 (1998).
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A method for thawing frozen samples for silicic acid analysis is recommended. The maximum recovery of silicic acid is achieved by thawing the frozen samples in a refrigerator (at 4°C) in the dark for at least four days. This method significantly improves the recovery of silicic acid from frozen fresh water samples. It also permits close to 100% recovery of reactive silicic acid from frozen seawater samples even after three months storage.
**1997**
Aberson, S.D. Adaptive observations in a hurricane environment. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 308-309 (1997).
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No abstract.
Aberson, S.D. The prediction of the performance of a nested barotropic hurricane track forecast model. Weather and Forecasting, 12(1):24-30 (1997).
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Linear multiple regression and discriminant analyses provide estimates of the errors of track forecasts from a nested barotropic hurricane track forecast model (VICBAR), which was run in the North Atlantic Basin during the 1989-94 hurricane seasons. Predictors are determined from the synoptic situation, the magnitude of atmospheric changes in the environment of the tropical cyclone, the consistency between current and past predictions, and the past performance of the model for each particular storm. This technique distinguishes cases in which VICBAR performs well from those for which it performs poorly and can provide skillful operational predictions of model performance to forecasts.
Acero-Schertzer, C.E., D.V. Hansen, and M.S. Swenson. Evaluation and diagnosis of surface currents in the NCEP ocean analyses. Journal of Geophysical Research, 102(C9):21,037- 21,048 (1997).
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Ensemble average currents from the 15 m depth level of the NCEP analyses of the tropical Pacific Ocean are evaluated against surface mixed layer current observations obtained from an extensive set of satellite-tracked drifting buoys. These averages display many climatological characteristics of the region, but are not intended to serve as a climatology because the data from the analyses are trimmed to match the time-space distribution of the observations. Substantial discrepancies between the analyses and the observations are revealed. First, the near-equatorial meridional currents and divergence have approximately twice the magnitude in the analyses as in the observations. This discrepancy is largely independent of whether temperature profile data are assimilated or not, and is attributed to the parameterization of vertical viscosity. Second, the zonal flow in both the NECC and the SEC is much stronger in the analyses than in the observations, especially in the western Pacific. This discrepancy is associated with assimilation of temperature profile data. It arises because salinity is an active variable in the underlying analysis model, but is not controlled by boundary fluxes or other observations. Under the uncontrolled influence of advection and strong horizontal diffusion, the salinity distribution becomes nearly homogeneous. Consequently, the analyses do not account for observed temperature-salinity correlations when density is computed following assimilation of temperature profile data. This leads to erroneous pressure gradients that drive excessively strong geostrophic currents and force large accelerations near the western boundary. Our results indicate that it is important to consider the consequences on the density structure of neglecting salinity during the assimilation of temperature data. We recommend that surface salinity observations from drifting buoys and volunteer observing ships be initiated to improve the ocean analyses.
Baringer, M.O., and J.F. Price. Mixing and spreading of the Mediterranean Outflow. Journal of Physical Oceanography, 27(8):1654-1677 (1997).
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Hydrographic and expendable current profiler (XCP) data taken during the Gulf of Cadiz Expedition on September 21-27, 1988 were analyzed to diagnose the mixing, spreading, and descent of the Mediterranean Outflow. The theta/S properties and the thickness and width of the outflow were very similar to that seen in earlier surveys (for example, by Heezen and Johnson, 1969). The transport of pure Mediterranean water (S=38.4) was estimated to be about half a Sv, which is considerably lower than historical estimates, most of which were indirect, but comparable to other recent estimates made from direct velocity observations. The total outflow transport was about 0.7 Sv at the west end of the Strait of Gibraltar, and increased to about 1.9 Sv within the western Gulf of Cadiz. This increase in transport occurred by entrainment of fresher North Atlantic Central Water (NACW), and the salinity anomaly of the outflow was rapidly eroded. The velocity-weighted salinity decreased to 36.7 within 60 km of the Strait, during the initial descent of the continental slope, and decreased by about another 0.1 before the deeper portion of the outflow began to float off of the bottom near Cape St. Vincent. Entrainment appears to have been correlated with the occurrence of bulk Froude numbers slightly greater than 1. In the western Gulf of Cadiz, where entrainment was much weaker, Froude numbers were well below 1. The outflow began in the eastern Strait of Gibraltar as a narrow (10 km wide) current having a very narrow range of theta/S properties (theta varies by < 0.5°C). The outflow broadened as it descended the continental slope of the northern Gulf of Cadiz, and reached a maximum width of 90 km in the western Gulf of Cadiz. The descent of the outflow was very asymmetric: the offshore and downslope edge of the flow descends rapidly, while the onshore and shallower edge of the outflow descends slowly. The northern, nearshore side remained considerably higher in the water column and thus entrained relatively warm and salty NACW. This caused the outflow to develop horizontal theta/S variability and, by about 100 km downstream, the across-stream variation in temperature on an isopycnal was more than 2°C. Much of the volume transport in the western Gulf of Cadiz was contained in two preferred modes, often called cores, apparently because of topographic steering effects. The deeper, offshore core had a central sigmatheta = 27.8, and the shallower nearshore core, which was still in contact with the bottom in the Gulf of Cadiz, had a central sigmatheta = 27.5.
Baringer, M.O., and J.F. Price. Momentum and energy balance of the Mediterranean Outflow. Journal of Physical Oceanography, 27(8):1678-1692 (1997).
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Hydrographic and expendable current profiler (XCP) data taken during the Gulf of Cadiz Expedition in September 1988 were analyzed to describe some aspects of the dynamics of the Mediterranean Outflow. During the initial descent of the continental slope, the outflow current executes a 90 degrees right turn that appears to be approximately inertial. The estimated geostrophic velocity greatly underestimated the actual current, and the estimated curvature Rossby number is about 0.5. A form of the Bernoulli function was evaluated to infer the total stress (entrainment stress and bottom drag) acting on the outflow. Total stress was as large as 5 Pa where the outflow begins to descend the continental slope and where currents were in excess of 1 m/s. The entrainment stress, estimated independently from property fluxes, reached a maximum of only about 1 Pa, which was less than the inferred bottom stress. By about 100 km downstream, the current was aligned approximately along the topography. The current amplitude and the estimated stress were much less, about 0.3 m/s and less than 0.5 Pa. The entrainment stress was very small in the region well downstream of the Strait. Bottom stress thus appears to be the crucial element in the dynamics of the Mediterranean Outflow, allowing or causing the outflow to descend some 1000 m into the North Atlantic. In the regions of strongest bottom stress the inferred drag coefficient was about 3 × 10- 3. Entrainment stress was much smaller by comparison, but the entrainment effect upon the density anomaly was crucial in eroding the density anomaly of the outflow.
Barnston, A.G., M. Chelliah, and S.B. Goldenberg. Documentation of a highly ENSO-related SST region in the equatorial Pacific. Atmosphere-Ocean, 35(3):367-383 (1997).
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A new ENSO SST index is documented that is strongly correlated to the core ENSO phenomenon. The SST anomaly in much of the east-central and eastern tropical Pacific is closely related to ENSO. However, the anomaly from approximately the centre of the eastern half of the equatorial Pacific westward to near the date line is suggested to be most strongly ENSO-related when data spanning the most recent several decades are used. This is the case both with respect to the (1) strength of association with other oceanic/atmospheric ENSO-related anomalies (both simultaneously and as a time-delayed predictand), and (2) impact on remote worldwide climate anomalies. This observational insight was lacking in the early 198Os when the four "Niño" regions were developed. While a firmer dynamical foundation for this regional preference still needs to be established, the region straddling Niño 3 and Niño 4 may be regarded as an appropriate general SST index of the ENSO state by researchers, diagnosticians, and forecasters. A dataset of this index, called "Niño 3.4" (5°N-5°S, 120-170°W) is maintained on the Internet, shown in the Climate Diagnostics Bulletin, and provided in the Appendix of this note.
Black, M.L., R.W. Burpee, and F.D. Marks. The asymmetric distribution of vertical motions and precipitation in the hurricane eyewall. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 100-101 (1997).
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No abstract.
Black, M.L., J.F. Gamache, H.E. Willoughby, C.E. Samsury, F.D. Marks, and R.W. Burpee. Airborne radar observations of shear-induced asymmetries in the convective structure of Hurricane Olivia (1994). Proceedings, 28th Conference on Radar Meteorology, September 9-12, 1997, Austin, TX. American Meteorological Society, Boston, 577-578 (1997).
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No abstract.
Black, P.G., J.R. Proni, J.C. Wilkerson, and C.E. Samsury. Oceanic rainfall detection and classification in tropical and subtropical mesoscale convective systems using underwater acoustic methods. Monthly Weather Review, 125(9):2014-2042 (1997).
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Measurements of the underwater sound produced by rain were made at three U.S. coastal sites in a study to determine the feasibility and limitations of the acoustic detection and classification of rainfall over water. In the analysis of the rain sound spectra, concurrent radar reflectivity observations were used to identify convective and stratiform regions of the precipitating clouds overhead. It was found that acoustic classifications of rainfall as to type, based on information in the 4-30 kHz frequency band, were in general agreement with radar-derived classifications. The classification technique is based on use of an acoustic discriminant, DR, defined as the difference in average spectral levels between the 10-30 kHz and 4-10 kHz bands. A high correlation was found between sound spectrum levels (in dB) in the 4-10 kHz frequency band and radar reflectivity, dBZ, suggesting the possible use of the 4-10 kHz band sound spectral level as a classification tool in the same way that radar reflectivity is used in classifying precipitation. Our results demonstrate the feasibility of the acoustic method for detecting and classifying rainfall at sea.
Black, R.A. Giant raindrops observed from large aircraft. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 494-495 (1997).
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No abstract.
Boebel, O., C. Schmid, and W. Zenk. Flow and recirculation of Antarctic Intermediate Water across the Rio Grande Rise. Journal of Geophysical Research, 102(C9):20,967-20,986 (1997).
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The flow of the low-salinity Antarctic Intermediate Water (AAIW) at 700-1150 m depth across the Rio Grande Rise and the lower Santos Plateau is studied under the auspices of the World Ocean Circulation Experiment (WOCE) in the context of the Deep Basin Experiment. Our data set consists of several hydrographic sections, a collection of 15 RAFOS float trajectories, and records from 14 moored current meters. The data were gathered during different intervals between 1990 and 1994. The inferred flow field strongly supports a basinwide anticyclonic recirculation cell in the subtropical South Atlantic underneath the wind-driven gyre. Its center, which appears to be southeast of the Rio Grande Rise, separates the eastward advection of AAIW below the South Atlantic Current from the westward flowing, recirculating AAIW. The two near-shelf limbs closing the circumference of AAIW flow are formed in the east by the deep Benguela Current, potentially modulated by salty inflow of Indian Ocean Intermediate Water, and in the west by the Brazil Current system. Further important circulation elements are the Brazil-Falkland (Malvinas) Confluence Zone at 40°S and an unnamed divergence at 28°S close to the 1000 m isobath. The resulting broad southward flow of AAIW augments the share of modified, i.e., saltier, intermediate water in the source region of the South Atlantic Current, while the smaller northward flow marks the source of a narrow equatorward Western Intermediate Boundary Current, ultimately leaving the South Atlantic. This shelf-trapped jet is clearly documented in hydrographic data from 19°S and in nearby current meter records. The jet contrasts a sluggish flow across this latitude east of 35°W. A continuous flow of AAIW from its subpolar region in the southwestern Argentine Basin all along the western slope toward the equator appears unlikely between 35°S and 25°S.
Bringi, V.N., K.Knupp, A. Detwiler, L. Liu, I.J. Caylor, and R.A. Black. Evolution of a Florida thunderstorm during the Convection and Precipitation Experiment: The case of August 9, 1991. Monthly Weather Review, 125(9):2131-2160 (1997).
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The relationships among kinematic, microphysical, and electric field properties within a multicell Florida thunderstorm are investigated using observations from three Doppler radar (one with multiple wavelength and polarization diversity capabilities), four instrumented penetrating aircraft, a surface-based electric field mill network, and other observation facilities. The storm was convectively active for about 1 h and at least five primary cells developed within the storm during this time, one of which went through three consecutive development cycles. The updrafts in this storm were 2-4 km wide, exhibited bubble-like evolution, and had lifetimes of 10-20 min. The maximum updraft determined by the multiple Doppler analysis was about
20 m s-1. A differential reflectivity (ZDR) "column," indicating regions containing millimeter-size raindrops, extending above the freezing level, was associated with each cell during its developing stages. This column reached altitudes exceeding 6 km (-8°C) in the stronger updrafts. As the ZDR columns reached maximum altitude, a "cap" of enhanced linear depolarization ratio (LDR) and enhanced 3-cm wavelength attenuation (A3) formed, overlapping the upper regions of the ZDR column. These parameters indicate rapid development of mixed-phase conditions initiated by freezing of supercooled raindrops. Lightning was observed only in the central and strongest convective cell. Electric fields exceeding 10 k V m-1 were noted during aircraft penetrations in this as well as several other cells that did not produce lightning. Fields exceeding 1 k V m-1 were noted by the instrumented aircraft at midcloud levels within a few minutes of development of mixed-phase conditions at these levels or aloft. The first intracloud lightning was detected by the surface field mill network within 5 min of development of mixed-phase conditions aloft in the first cycle of development in the central cell, and the first cloud-to-ground event was noted within 9 min of this development. Lightning continued through two additional cycles of updraft growth in this central region and diminished as the convection subsided after about 30 min. Aircraft-measured electric fields and lightning retrievals from the surface field meter network are consistent with a tendency for negative charge to accumulate above the 6.5 km (-12°C) level within regions of radar reflectivity maxima and for positive charge to accumulate in the anvil region well above 9 km (-30°C).
Bushnell, M.H., and W.S. Krug. Global Drifter Center support for the International Buoy Program in the Indian Ocean. Final Report, Second WMO/DBCP International Indian Ocean Buoy Program Meeting, Perth, Australia, July 1997. Australian Bureau of Meteorology, Annex V, 15-20 (1997).
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No abstract.
Cantillo, A.Y., and G.A. Berberian. MESA New York Bight Project water column chemistry data cruises No. 6-12 of the NOAA Ship Ferrel, April-November 1997. NOAA Technical Memorandum, ERL-AOML-92 (PB98-140759), 74 pp. (1997).
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During the period April-November 1974, seven oceanographic cruises, denoted WCC 6-12, were conducted by the NOAA Ship Ferrel to obtain samples of sea water and suspended particulates from the New York Bight Apex for chemical analyses. This report presents the chemical data obtained from these samples.
Carsey, T.P., D.D. Churchill, M.L. Farmer, C.J. Fischer, A.A.P. Pszenny, V.B. Ross, E.S. Saltzman, M. Springer-Young, and B. Bonsang. Nitrogen oxides and ozone production in the North Atlantic marine boundary layer. Journal of Geophysical Research, 102(D9):10,653-10,665 (1997).
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Measurements of reactive nitrogen gases (NO, NO2, NOy), as well as related chemical (O3, CO, aerosol black carbon, radon, selected nonmethane hydrocarbons) and meteorological parameters, were made on board the R/V Malcolm Baldrige prior to and subsequent to the 1992 ASTEX (Atlantic Stratocumulus Transition Experiment) in the North Atlantic Ocean during June and July 1992. Results showed indications of well-defined plumes from North America and Europe from both chemistry and back trajectory data. Elevated ozone concentrations were also observed in air masses from uninhabited continental regions. Chemical and meteorological data were incorporated into a simple photochemical model in which ozone destruction predominated over generation. The principal reaction leading to ozone destruction was O(1D) + H2O - 2OH.
Checkley, D.M., P.B. Ortner, L.R. Settle, and S.R. Cummings. A continuous, underway fish egg sampler (CUFES). Fisheries Oceanography, 6(2):58-73 (1997).
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We describe a method to sample the highly contagious distribution of pelagic fish eggs. CUFES, the continuous, underway fish egg sampler, consists of a submersible pump, concentrator, electronics, and sample collector. This system operates continuously and under nearly all sea conditions, providing a real-time estimate of the volumetric abundance of pelagic fish eggs at pump depth, usually 3 m. CUFES-derived estimates of volumetric abundance agree well with those from nets towed at pump depth and with a real abundance estimated from vertically-integrated plankton tows. CUFES has been used successfully to sample the eggs of menhaden, pinfish, sardine, and anchovy off the coasts of the eastern and western United States and South Africa. Two large patches of eggs of the Atlantic menhaden were sampled off North Carolina in winter 1993-1994, had a linear scale of 5-10 km, and were found in waters between the Gulf Stream and mid-shelf front. Spawning location may be related to bathymetry. CUFES is now being used to estimate spawner biomass by the Daily Egg Production Method. An optical plankton counter provided accurate estimates of the number of Atlantic menhaden eggs sampled by CUFES. Automation of egg counting in CUFES is under development.
Chelton, D.B., and A.M. Mestas-Nunez. The large-scale, wind-driven response of the North Pacific. International WOCE Newsletter, 25:3-6 (1997).
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In this note, we present the results of an investigation of the validity of the time-varying Sverdrup balance in the North Pacific based on analysis of three years of: (1) a simple flat bottom Sverdrup model; (2) the primitive equation global ocean circulation model developed by the Parallel Ocean Program (POP) at the Los Alamos National Laboratory; and (3) observations of sea surface height (SSH) by the TOPEX/POSEIDON (T/P) altimeter. The three-year period considered here is October 1992 through November 1995. We conclude that much of the large-scale, low-frequency variability in the North Pacific can be accounted for by simple Sverdrup dynamics.
Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark. Global oceanic precipitation: A joint view by TOPEX and the TOPEX microwave radiometer. Journal of Geophysical Research, 102(C5):10,457-10,471 (1997).
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The TOPEX/POSEIDEN mission offers the first opportunity to observe rain cells over the ocean by a dual-frequency radar altimeter (TOPEX) and simultaneously observe their natural radiative properties by a three-frequency radiometer (TOPEX microwave radiometer (TMR)). This work is a feasibility study aimed at understanding the capability and potential of the active/passive TOPEX/TMR system for oceanic rainfall detection. On the basis of past experiences in rain flagging, a joint TOPEX/TMR rain probability index is proposed. This index integrates several advantages of the two sensors and provides a more reliable rain estimate than the radiometer alone. One year's TOPEX/TMR data are used to test the performance of the index. The resulting rain frequency statistics show quantitative agreement with those obtained from the Comprehensive Ocean-Atmosphere Data Set (COADS) in the Intertropical Convergence Zone (ITCZ), while qualitative agreement is found for other regions of the world ocean. A recent finding that the latitudinal frequency of precipitation over the Southern Ocean increases steadily towards the Antarctic continent is confirmed by our result. Annual and seasonal precipitation maps are derived from the index. Notable features revealed include an overall similarity in rainfall pattern from the Pacific, the Atlantic, and the Indian Oceans and a general phase reversal between the two hemispheres, as well as a number of regional anomalies in terms of rain intensity. Comparisons with simultaneous Global Precipitation Climatology Project (GPCP) multisatellite precipitation rates and COADS rain climatology suggest that systematic differences also exist. One example is that the maximum rainfall in the ITCZ of the Indian Ocean appears to be more intensive and concentrated in our result compared to that of the GPCP. Another example is that the annual precipitation produced by TOPEX/TMR is constantly higher than those from GPCP and COADS in the extratropical regions of the northern hemisphere, especially in the northwest Pacific Ocean. Analyses of the seasonal variations of prominent rainy and dry zones in the tropics and subtropics show various behaviors such as systematic migration, expansion, and contraction, merging and breakup, and pure intensity variations. The seasonality of regional features is largely influenced by local atmospheric events such as monsoon, storm, or snow activities. The results of this study suggest that TOPEX and its follow-on may serve as a complementary sensor to the special sensor microwave/imager in observing global oceanic precipitation.
Chereskin, T.K., W.D. Wilson, H.L. Bryden, A. Ffield, and J. Morrison. Observations of the Ekman balance at 8°30'N in the Arabian Sea during the 1995 southwest monsoon. Geophysical Research Letters, 24(21):2541-2544 (1997).
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The Ekman transport is estimated from two sets of hydrographic and shipboard acoustic Doppler current profiler (ADCP) velocity observations made during June and September 1995, during the southwest monsoon in the Arabian Sea. Both sets of measurements were made along latitude 8°30'N, designated as World Ocean Circulation Experiment (WOCE) line I1W, from Somalia to Sri Lanka. The Ekman transport estimates calculated from ageostrophic velocity were southward: 17.6 ± 2.4 106 m3 s-1 in June and 7.9 ± 2.7 106 m3 s-1 in September. These direct estimates were in good agreement with those predicted by the Ekman balance using both shipboard and climatological winds. The vertical structure of the ageostrophic velocity and the stratification were quite different between the two occupations of the transect. The wind-driven momentum was confined to a very shallow layer in June (about 50 m) and the surface layer was strongly stratified, with a maximum salinity layer at depths between 50 and 70 m. The ageostrophic velocity penetrated much deeper in September (to about 160 m) and the pycnocline was correspondingly deeper. In both cases, the Ekman transport penetrated beneath the mixed layer, to the top of the pycnocline.
Cione, J.J., and S. Raman. The impact of SST gradients on propagating low-level mesovortices near the Gulf Stream. Preprints, Conference on Coastal Oceanic and Atmospheric Prediction, Atlanta, GA, January 28- February 2, 1996. American Meteorological Society, Boston, 204-211 (1997).
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No abstract.
DeMaria, M., and J. Kaplan. An operational evaluation of a statistical intensity prediction scheme (SHIPS). Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 280-281 (1997).
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No abstract.
Dietrich, D.E., C.A. Lin, A.M. Mestas-Nunez, and D.-S. Ko. A high resolution numerical study of Gulf of Mexico fronts and eddies. Meteorology and Atmospheric Physics, 64(3-4):187-201 (1997).
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The Gulf of Mexico (GOM) circulation is simulated using the DieCAST ocean model, with a horizontal resolution of 1/12 degree and 20 vertical layers. The results compare well with observations of both large and small scale features, including Loop Current frontal occlusions associated with frontal eddies. The simulation is carried out without any data assimilation. The frontal eddies tend to be spaced at about 90 degree intervals around the Loop Current, leading to a Loop Current head shaped like a square with rounded corners. The pattern rotates as eddies circle the Loop, and frontal eddies elongate as they squeeze through the Florida Strait. Major warm core eddies separate regularly from the Loop Current and propagate to the western GOM. Old warm core eddies in the western Gulf dissipate through bottom drag effects, which also generate cyclonic parasitic eddies. Newly arrived warm core eddies merge with old ones in the western GOM. Recently separated elongated Loop Current eddies can rotate and reattach temporarily to the Loop Current. The barotropic flow component develops eddies between the main separated warm core eddy and the Loop Current due to eastward dispersion, as the main eddy itself propagates westward into the Gulf.
Dodge, P.P., S.H. Houston, and J.F. Gamache. Three-dimensional windfields in Hurricane Fran (1996) at landfall. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 115-116 (1997).
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No abstract.
Dodge, P.P., S.H. Houston, and J.F. Gamache. Windfields in Hurricane Fran (1996) at landfall from combined WSR-88D and airborne Doppler radar data. Proceedings, 28th Conference on Radar Meteorology, Austin, TX, September 9-12, 1997. American Meteorological Society, Boston, 575-576 (1997).
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No abstract.
Donelan, M.A., W.M. Drennan, and K.B. Katsaros. The air-sea momentum flux conditions of wind sea and swell. Journal of Physical Oceanography, 27(10):2087-2099 (1997).
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During the Surface Wave Dynamics Experiment, direct measurements of momentum, heat, and water vapor fluxes were obtained from a mast on the foredeck of a SWATH (small water-plane area, twin hull) ship in deep water off the state of Virginia. Directional wave spectra were obtained simultaneously from a six or three-wire wave-staff array mounted at the bow of the ship. One hundred and twenty-six 17-minute runs of flux and wave data obtained with the ship steaming slowly into the wind are examined for the effects of the relative direction of the wind sea and background swell on the momentum transfer. The adequacy of the inertial dissipation method, which depends on the high-frequency turbulent fluctuations for evaluating the wind stress, is also examined for any effects of swell. The results show that the presence of counter- and cross-swells can result in drag coefficients that are much larger than the value for a pure wind sea. The eddy correlation and inertial dissipation methods for measuring wind stress are found to diverge during the complex sea conditions. The authors interpret the latter observations as an indication that the traditional inertial dissipation method, in which the pressure and transport terms in the kinetic energy balance equation are assumed to be in balance, may be unsuitable for use in a marine boundary layer disturbed by swell.
Drennan, W.M., M.A. Donelan, E.A. Terray, and K.B. Katsaros. On waves, oceanic turbulence, and their interaction. Geophysica, 33:17-28 (1997).
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No abstract.
Dupuis, H., P.K. Taylor, A. Weill, and K.B. Katsaros. Inertial dissipation method applied to derive turbulent fluxes over the ocean during the Surface of the Fluxes and Interactions with the Atmosphere/Atlantic Stratocumulus Transition Experiment (SOFIA/ASTEX) and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiments with low to moderate wind speeds. Journal of Geophysical Research, 102(C9):21,115-21,129 (1997).
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The transfer coefficients for momentum and heat have been determined for 10 m neutral wind speeds (U10n) between 0 and 12 m/s using data from the Surface of the Ocean, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiments. The inertial dissipation method was applied to wind and pseudo virtual temperature spectra from a sonic anemometer, mounted on a platform (ship) which was moving through the turbulence field. Under unstable conditions the assumptions concerning the turbulent kinetic energy (TKE) budget appeared incorrect. Using a bulk estimate for the stability parameter, Z/L (where Z is the height and L is the Obukhov length), this resulted in anomalously low drag coefficients compared to neutral conditions. Determining Z/L iteratively, a low rate of convergence was achieved. It was concluded that the divergence of the turbulent transport of TKE was not negligible under unstable conditions. By minimizing the dependence of the calculated neutral drag coefficient on stability, this term was estimated at about -0.65 Z/L. The resulting turbulent fluxes were then in close agreement with other studies at moderate wind speed. The drag and exchange coefficients for low wind speeds were found to be Cen × 103 = 2.79 U10n-1 + 0.66 (U10n < 5.2 m/s), Cen × 103 = Chn × 103 = 1.2 (U10n > 5.2 m/s), and Cdn × 103 = 11.7 U10n-2 + 0.668 (U10n < 5.5 m/s), which imply a rapid increase of the coefficient values as the wind decreased within the smooth flow regime. The frozen turbulence hypothesis and the assumptions of isotropy and an inertial subrange were found to remain valid at these low wind speeds for these shipboard measurements. Incorporation of a free convection parameterization had little effect.
Elfouhaily, T., B. Chapron, K.B. Katsaros, and D. Vandemark. A unified directional spectrum for long and short wind-driven waves. Journal of Geophysical Research, 102(C7):15,781-15,796 (1997).
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Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in-situ observations of Cox and Munk (1954), Jahne and Riemer (1990), and Hara et al. (1994) data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips (1985) and Kitaigorodskii (1973) at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.
Enfield, D.B., and D.A. Mayer. Tropical Atlantic sea surface temperature variability and its relation to El Niño-Southern Oscillation. Journal of Geophysical Research, 102(C1):929-945 (1997).
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Past analyses of tropical Atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics, across the Intertropical Convergence Zone (ITCZ). By analyzing an improved 43-year (1950-1992) record of SST (Smith et al., 1996) and other data derived from the Comprehensive Ocean-Atmosphere Data Set (COADS), it is shown that the regions north and south of the ITCZ are statistically independent of each other at the seasonal to interannual time scales dominating the data, confirming the conclusions of Houghton and Tourre (1992). Some dipole behavior does develop weakly during the boreal spring season, when there is a tendency for SST anomaly west of Angola to be opposite of that in the tropical North Atlantic. It is further shown that tropical Atlantic SST variability is correlated with Pacific El Niño-Southern Oscillation (ENSO) variability in several regions. The major region affected is the North Atlantic area of northeast trades west of 40°W along 10°N-20°N and extending into the Caribbean. There, about 50-80% of the anomalous SST variability is associated with the Pacific ENSO, with Atlantic warmings occurring 4-5 months after the mature phases of Pacific warm events. An analysis of local surface flux fields derived from COADS data show that the ENSO-related Atlantic warmings occur as a result of reductions in the surface northeast trade wind speeds, which in turn reduce latent and sensible heat losses over the region in question, as well as cooling due to entrainment. This ENSO connection is best developed during the boreal spring following the most frequent season of maximum ENSO anomalies in the Pacific. A region of secondary covariability with ENSO occurs along the northern edge of the mean ITCZ position and appears to be associated with northward migrations of the ITCZ when the North Atlantic warmings occur. Although easterly winds are intensified in the western equatorial Atlantic in response to Pacific warm events, they do not produce strong local changes in SST. Contrary to expectations from studies based on equatorial dynamics, these teleconnected wind anomalies do not give rise to significant correlations of SST in the Gulf of Guinea with the Pacific ENSO. As the teleconnection sequence matures, strong southeast trades at low southern latitudes follow the development of the North Atlantic SST anomaly and precede by several months the appearance of weak negative SST anomalies off Angola and stronger positive anomalies extending eastward from southern Brazil along 15°-30°S.
Faber, T., L.K. Shay, S.D. Jacob, S.H. Houston, and P.G. Black. Observed air-sea interactions during Hurricane Emily. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 433-434 (1997).
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No abstract.
Feely, R.A., R.H. Wanninkhof, C. Goyet, D.E. Archer, and T. Takahashi. Variability of CO2 distributions and sea- air fluxes in the central and eastern equatorial Pacific during the 1991-1994 El Niño. Deep-Sea Research, Part II, 44(9-10):1851-1867 (1997).
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As part of the U.S. JGOFS Program and the NOAA Ocean-Atmosphere Carbon Exchange Study (OACES), measurements of CO2 partial pressure were made in the atmosphere and in the surface waters of the central and eastern equatorial Pacific during the boreal spring and autumn of 1992, the spring of 1993, and the spring and autumn of 1994. Surface-water pCO2 data indicate significant diurnal, seasonal, and interannual variations. The largest variations were associated with the 1991-1994 ENSO event, which reached maximum intensity in the spring of 1992. The lower values of surface-water DELTApCO2 observed during the 1991-1994 ENSO period were the result of the combined effects of both remotely and locally forced physical processes. The warm pool, which reached a maximum eastward extent in January-February of 1992, began in September of 1991 as a series of westerly wind events lasting about 30 days. Each wind event initiated an eastward-propagating Kelvin wave which caused a deepening of the thermocline. By the end of January 1992 the thermocline was at its maximum depth, so that the upwelled water was warm and CO2-depleted. In April of the same year, the local winds were weaker than normal, and the upwelling was from shallow depths. These changes resulted in a lower-than-normal CO2 flux to the atmosphere. The results show that for the one-year period from the fall of 1991 until the fall of 1992, approximately 0.3 GtC were released to the atmosphere; 0.6 GtC were released in 1993, and 0.7 GtC in 1994, in good agreement with the model results of Ciais et al. (Science, 269, 1098-1102; J. Geophys. Res., 100, 5051-5070). The net reduction of the ocean-atmosphere CO2 flux during the 1991-1994 El Niño was on the order of 0.8-1.2 GtC. Thus, the total amount of CO2 sequestered in the equatorial oceans during the prolonged 1991-1994 El Niño period was about 25% higher than the severe El Niño of 1982-1983.
Festa, J.F., and R.L. Molinari. Comparison of thermal statistics derived from observational data sets in the tropical Atlantic and Pacific Oceans. NOAA Technical Memorandum, ERL AOML-91 (PB97-208177), 88 pp. (1997).
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Statistical analysis of surface and subsurface temperature data in the tropical Atlantic and Pacific Oceans is presented. The statistics were estimated from the Comprehensive Ocean-Atmospheric Data Set (COADS) and the historical expendable bathythermograph (XBT) observations. Spatial structure functions (semivariograms) for the anomaly fields of sea surface temperature and the temperature at 200 m and 400 m were estimated for a 2 degree by 2 degree grid in the tropical oceans. Dominant scales of spatial variability are identified and compared with other investigations.
Ffield, A., J. Toole, and W.D. Wilson. Seasonal circulation in the South Indian Ocean. Geophysical Research Letters, 24(22):2773-2776 (1997).
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Two World Ocean Circulation Experiment hydrographic cruises in March and June 1995, along with Topex-Poseidon altimeter data and National Meteorological Center wind data, are used to estimate seasonal changes in the South Indian Ocean subtropical gyre. Mean annual curves derived from the altimeter and wind data reveal strengthening of the anticyclonic gyre in March and September, and weakening in June and December. The seasonal changes correspond to variations in the wind field south of 30 S at the equinoxes and solstices. In addition, the wind-driven gyre is further north in July, and further south in March. These variations in strength and location of the South Indian Ocean gyre may influence inter-ocean transports south of Africa. Despite the inferred mean annual seasonal variations in the South Indian Ocean gyre, volume transports estimated in 1995 from the hydrographic data are close to mean values. Apparently, a mesoscale eddy in March disrupts the stronger fall gyre, whereas in June the weaker winter gyre is delayed by 1 month.
Franklin, J.L., H.L. Cole, T.F. Hock, D.K. Lauritsen, K.D. Norris, and E.F. Chamberlain. GPS dropwindsondes and the NOAA G-IV jet aircraft: New opportunities for forecasting and research. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 135-136 (1997).
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No abstract.
Gallagher, M.S., D.B. King, P.-Y. Whung, and E.S. Saltzman. Performance of the HPLC/fluorescence SO2 detector during the GASIE instrument intercomparison experiment. Journal of Geophysical Research, 102(D13):16,247-16,254 (1997).
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Sulfur dioxide (SO2) in synthetic air and diluted ambient air was measured as part of the Gas-Phase Sulfur Intercomparison Experiment (GASIE) using the high performance liquid chromatography (HPLC)/fluorescence technique. SO2 was analyzed by equilibrating the gaseous sample with aqueous SO2, sulfite, and bisulfite, then converting the aqueous S(IV) to an isoindole derivative. The derivative was separated by reversed phase HPLC and detected via fluorescence. The system was calibrated with mixtures of SO2 in zero air prepared from an SO2 permeation device through a two-stage dilution system. The instrument has a 4-minute sample integration time and a measurement period of 9 minutes. During the GASIE intercomparison, the lower limit of detection averaged 3.6 parts per trillion by volume (pptv). The precision of replicate measurements over the entire intercomparison period was better than 5% at the 20 pptv level. Instrument performance was unaffected by the interferent gases included in the GASIE protocol (H2O, O3, NOx, DMS, CO, CO2, and CH4). During diluted ambient air tests, the HPLC/fluorescence technique exhibited an approximately 10% reduction in response relative to some other techniques. The cause of this apparent calibration change is not understood.
Gamache, J.F. Evaluation of a fully three-dimensional variational Doppler analysis technique. Proceedings, 28th Conference on Radar Meteorology, Austin, TX, September 9-12, 1997. American Meteorological Society, Boston, 422-423 (1997).
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No abstract.
Gamache, J.F., H.E. Willoughby, M.L. Black, and C.E. Samsury. Wind shear, sea surface temperature, and convection in hurricanes observed by airborne Doppler radar. Preprints, 22nd Conference on Hurricanes and Tropical Meteorology, Ft. Collins, CO, May 19-23, 1997. American Meteorological Society, Boston, 121-122 (1997).
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No abstract.
Garzoli, S.L., G.J. Goni, A.J. Mariano, and D.B. Olson. Monitoring the upper southeastern Atlantic transports using altimeter data. Journal of Marine Research, 55(3):453-481 (1997).
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A large in-situ data set, collected in the southeastern Atlantic Ocean, is merged with the TOPEX/POSEIDON altimeter observations in order to verify the use of altimeter data in monitoring the transports of the Agulhas/Benguela system. Comparisons between altimeter observations and either moored current meters or inverted echo sounder measurements shows that the sea surface elevation anomaly is significantly correlated with the thermocline depth and the surface dynamic height, respectively. Knowing the least-squares regression parameters, it is possible to calculate the transports by using geostrophy and either a two-layer or a continuously-stratified model. The transports obtained from fits of dynamic height to altimeter sea surface height are similar to the ones calculated with the moored instruments. In the southern part of the area under analysis, around 35°S, close to the Agulhas retroflection, the transports obtained from the two-layer model are overestimated. Across the Benguela Current, at 30°S, transports are still overestimated but of the same order as the measured ones. In this part of the region, the two-layer model can be successfully used to calculate the total and barotropic transports of the Benguela Current. Analysis of the three years of geostrophic transport obtained from the altimeter data indicate that the mean Benguela Current transport does not change interannually more than 20%. However, the primary interannual variability derives from the source water that forms the Benguela Current.
German, C.R., D.L. Bourles, E.T. Brown, J. Hergt, S. Colley, N.C. Higgs, E.M. Ludford, T.A. Nelsen, R.A. Feely, G. Raisbeck, and F. Yiou. Hydrothermal scavenging on the Juan de Fuca Ridge: 230Thxs, 10Be, and REEs in ridge-flank sediments. Geochimica et Cosmochimica Acta, 61(19):4067-4078 (1997).
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We have investigated the geochemistry of a hydrothermally-enriched sediment core recovered from the western flank of the N.Cleft Segment, Juan de Fuca Ridge, 8 km west of the "MegaPlume" area previously identified near 45°N. The core contains varying biogenic, lithogenic, and hydrothermal components, as reflected in CaCO3, Al, and Fe contents, respectively. Horizons of pronounced hydrothermal input, in core-top sediments and at depth, exhibit increased concentrations of Fe, Cu, Zn, Pb, and shifts in Pb isotopic compositions toward nonradiogenic (MORB/hydrothermal) values. REE concentrations co-vary with hydrothermal Fe down-core, and shale-normalized REE distributions patterns exhibit both negative Ce-anomalies and positive Eu-anomalies, indicative of input from plume-particle fall-out. Unsupported 230Thxs activities down-core are consistent with continuous slow sediment accumulation rates of 0.54 cm/ky for 200 ky since the deposition of the deeper Fe-rich horizon. 10Be(0) and 9Be isotope concentrations also co-vary with hydrothermal Fe down-core and exhibit 10Be(0) 9Be ratios which approach that of Pacific Ocean deep water, indicative of a seawater-scavenging source. 10Be(0) 230Thxs(0) ratios throughout most of Core GC88-6 are greater than mean Pacific Ocean values, indicating that hydrothermal scavenging can lead to significant net removal of dissolved 10Be into ridge-flank sediments.
Goldenberg, S.B., C.W. Landsea, and L.J. Shapiro. Are we seeing the beginning of a long-term upturn in Atlantic basin major hurricane activity? Proceedings, Tropical Cyclone Symposium, Melbourne, Australia, December 9-13 1996. U.S. Office of Naval Research, 10 pp. (1997).
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No abstract.
Goldenberg, S.B., L.J. Shapiro,