Listing of Recent AOML Publications

**In Press**

Enfield, D.B. Evolution and historical perspective of the 1997-1998 El Niño-Southern Oscillation event. Bulletin of Marine Science (in press).

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.

Rogers, R.F., and J.M. Fritsch. Surface cyclogenesis from convectively-driven amplification of mid-level mesoscale convective vortices. Monthly Weather Review, in press.

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. **2001**

Enfield, D.B., and A.M. Mestas-Nuñez. Interannual to multidecadal climate variability and its relationship to global sea surface temperatures. In: Interhemispheric Climate Linkages, V. Markgraf (ed.). Academic Press, 17-29 (ISBN 0124726704) (2001).

As a benchmark to help profile paleoclimates across the Americas we develop an overview of what is known of modern climate variability on a planetary scale, with emphasis on climate manifestations in the Western Hemisphere. From instrumental observations taken as early as the mid-19th century, we look at both atmospheric and oceanic variables and consider their relationships on timescales ranging from interannual to multidecadal. We focus on three of the most important climate modes: the interannual El Niño-Southern Oscillation (ENSO), the interdecadal Pacific Decadal Oscillation (PDO), and the multidecadal North Atlantic Oscillation (NAO). The variable of greatest interest is sea surface temperature (SST) because it is arguably the least understood of the atmospheric boundary conditions for prehistoric climates and yet one of the most critical for effecting atmospheric model simulations of those climates. The analysis begins by computing a global distribution of the trend in SST, which turns out to be highly non-uniform, with characteristics that may reflect low-frequency changes in shallow water mass formation. We then compute a global, canonical mode for ENSO that preserves the amplitude and phase structures of interannual ENSO variability worldwide. The ranking of the modal amplitudes of ENSO events differs from the absolute amplitudes obtained by indexing SST data directly. This reflects the importance of the (non-ENSO) decadal-multidecadal climate modes in modifying the intensity of ENSO-related ocean warmings. Comparing the global mode between the ends of the 19th and 20th centuries, we see essentially no difference in amplitudes and frequency of ENSO on the global warming timescale, although such changes have occurred on shorter, multidecadal timescales. Upon removal of the global ENSO mode from the data, the residual variability is subjected to two different analyses that extract very similar spatio-temporal patterns of SST for the PDO- and NAO-like climate modes. The climate variations with longer timescales (PDO, NAO) together account for about the same amount of variance as ENSO, globally, and in some regions, e.g., the northeastern North Pacific, may rival ENSO in their climate and marine impacts. The NAO, in particular, involves an Atlantic-Pacific connection that may arise through fluctuations in the polar vortex, an aspect which may also characterize previous climates. In our discussion, we speculate on what might be learned from the instrumental record regarding possible characteristics of ancient climates, especially regarding the possibility that ENSO may have been considerably different or even absent in the mid-Holocene.

Kaplan, J., and M. DeMaria. On the decay of tropical winds after landfall in the New England area. Journal of Applied Meteorology, 40(2):280-286 (2001).

A version of the Kaplan and DeMaria empirical model for predicting the decay of tropical cyclone 1-min maximum sustained surface winds after landfall is developed for the New England region. The original model was developed from the National Hurricane Center (NHC) best-track wind estimates for storms that made landfall in the United States south of 37°N from 1967 to 1993. In this note, a similar model is developed for U.S. storms north of 37°N, which primarily made landfall in New York or Rhode Island and then moved across New England. Because of the less frequent occurrence of New England tropical cyclones, it was necessary to include cases back to 1938 to obtain a reasonable sample size. In addition, because of the faster translational speed and the fairly rapid extratropical transition of the higher-latitude cases, it was necessary to estimate the wind speeds at 2-h intervals after landfall, rather than every 6 h, as in the NHC best track. For the model development, the estimates of the maximum sustained surface winds of nine landfalling storms (seven hurricanes and two tropical storms) at 2-h intervals were determined by an analysis of all available surface data. The wind observations were adjusted to account for variations in anemometer heights, averaging times, and exposures. Results show that the winds in the northern model decayed more (less) rapidly than those of the southern model, when the winds just after landfall are greater (less) than 33 knots. It is hypothesized that this faster rate of decay is due to the higher terrain near the coast for the northern sample and to the more hostile environmental conditions (e.g., higher vertical wind shear). The slower decay rate when the winds fall below 33 knots in the northern model might be due to the availability of a baroclinic energy source as the storms undergo extratropical transition.

Liu, W.T., and K.B. Katsaros. Air-sea fluxes from satellite data. In Ocean Circulation and Climate: Observing and Modeling the Global Ocean, G. Siedler, J. Church, and J. Gould (eds.). Academic Press, 173-180 (2001).

No abstract.

Mestas-Nuñez, A.M., and D.B. Enfield. Eastern equatorial Pacific SST variability: ENSO and non-ENSO components and their climatic associations. Journal of Climate, 14(3):391-402 (2001).

Using an updated Kaplan et al. global SST anomaly (SSTA) dataset (1870-1999), we construct a canonical representation of El Niño-Southern Oscillation (ENSO). When this canonical ENSO is subtracted from the data, we are left with a residual (non-ENSO) dataset for SSTA that includes inter-seasonal to multi-decadal variability. Over the eastern equatorial Pacific (NINO3) the canonical ENSO accounts for about 79% of the total SSTA variability, while the residual, dominated by decadal time scales, accounts for the rest. In particular, about 40-50% of the amplitudes of the strong 1982-83 and 1997-98 El Niño events were accounted for by the residual variability. The non-ENSO variability is characterized by the known shift from cold to warm eastern tropical Pacific in the mid-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-Nuñez, A.M., D.B. Chelton, and D.B. Enfield. North Pacific circulation variability from TOPEX/POSEIDON sea level observations. Proceedings, 5th Pacific Ocean Remote Sensing Conference (PORSEC), Goa, India, December 5-8, 2000. National Institute of Oceanography, 1:263-267 (2001).

We analyze seven years (October 1992-October 1999) of sea level observations from the TOPEX/POSEIDON (T/P) satellite altimeter data to investigate the large-scale ocean circulation variability of the North Pacific from seasonal to interannual time scales. We focus in the mid-latitude western regions and use the T/P observations to estimate the barotropic volume transport variability of the Kuroshio, Oyashio, and Kuroshio Extension currents. We base our transport variability estimates on altimetric sea level differences, and our results agree well with simple wind-driven Sverdrup theory and with a global numerical ocean model simulation.

Wang, C. A unified oscillator model for the El Niño-Southern Oscillation. Journal of Climate, 14(1):98-115 (2001).

The delayed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflective oscillator have been proposed to interpret the oscillatory nature of the El Niño-Southern Oscillation (ENSO). All of these oscillator models assume a positive ocean-atmosphere feedback in the equatorial eastern and central Pacific. The delayed oscillator assumes that the western Pacific is an inactive region and wave reflection at the western boundary provides a negative feedback for the coupled system to oscillate. The western Pacific oscillator emphasizes an active role of the western Pacific in ENSO. The recharge-discharge oscillator argues that discharge and recharge of equatorial heat content cause the coupled system to oscillate. The advective-reflective oscillator emphasizes the importance of zonal advection associated with wave reflection at both the western and eastern boundaries. Motivated by the existence of these different oscillator models, a unified oscillator model is formulated and derived from the dynamics and thermodynamics of the coupled ocean-atmosphere system. Consistent with ENSO anomaly patterns observed in the tropical Pacific, this oscillator model considers sea surface temperature anomalies in the equatorial eastern Pacific, zonal wind stress anomalies in both the equatorial central Pacific and the equatorial western Pacific, and thermocline depth anomalies in the off-equatorial western Pacific. If the western Pacific wind-forced response is neglected, thermocline and zonal wind stress anomalies in the western Pacific are decoupled from the coupled system, and the unified oscillator reduces to the delayed oscillator. If wave reflection at the western boundary is neglected, the unified oscillator reduces to the western Pacific oscillator. The mathematical form of the recharge-discharge oscillator can also be derived from this unified oscillator. Most of the physics of the advective-reflective oscillator are implicitly included in the unified oscillator, and the negative feedback of wave reflection at the eastern boundary is added to the unified oscillator. With appropriate model parameters chosen to be consistent with those of previous oscillator models, the unified oscillator model oscillates on interannual time scales. **2000**

ABERSON, S.D. A tropical cyclone ensemble forecasting system for the North Atlantic Basin. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(48):F585, NG12A-05 (2000). A real-time, 41-member VICBAR orthonormalized bred-mode ensemble forecasting system has been run once per day during the 1998 and 1999 hurricane seasons, and twice per day during the 2000 hurricane season, in the North Atlantic basin. VICBAR is a movable, nested-mesh shallow-water model using the National Centers for Environmental Prediction Aviation and Medium-Range Forecast Models as both initial and time-dependent boundary conditions. The numerics are based on cubic b-splines so as to eliminate discontinuities on the mesh boundaries. The deterministic run has provided skillful forecasts competitive with other track forecast models since 1989. The 850-200 hPa mass-weighted flow is combined with a vortex representative of the tropical cyclone including an asymmetry for the initial motion. Within 1500 km of the storm center, the forecast is wholly barotropic; more than 2500 km away from the storm center, the forecast is entirely that of the global model, with a transition region between the two circles. Forecasts extend to 120 h. This is the first ensemble forecasting system available for tropical cyclone track prediction in the Atlantic. Global models are either unable to skillfully forecast tracks, or, in some ensemble forecasting systems, the tropical regions are not perturbed. The three-year sample will be evaluated to show the value of the ensemble forecasting system, whether the ensemble spans the reality of the track, whether the ensemble mean provides an improved forecast over individual ensemble members and the control forecast, and whether the system can provide probabilistic forecasts of events such as landfall. Further uses of the ensemble, such as providing information for operational hurricane targeting missions with the National Oceanic and Atmospheric Administration's Gulfstream-IV jet aircraft, and for ensemble-based data assimilation schemes, add to the potential value of the ensemble.

Atlas, D., C.W. Ulbrich, F.D. Marks, R.A. Black, E. Amitai, P.T. Willis, and C.E. Samsury. Partitioning tropical oceanic convective and stratiform rains by draft strength. Journal of Geophysical Research, 105(D2):2259-2267 (2000).

The discrimination of convective from stratiform tropical oceanic rains by conventional radar-based textural methods is problematic because of the small size and modest horizontal reflectivity gradients of the oceanic convective cells. In this work, the vertical air motion measured by an aircraft gust probe is used as a discriminator which is independent of the textural methods. A threshold draft magnitude approximately equal to 1 m s^-1 separates the two rain types. Simultaneous airborne in-situ observations of drop size distributions (DSD) made during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) were used to compute Z, R, and other integral parameters. The data were quality controlled to minimize misclassifications. The convective and stratiform rains, observed just below the melting level but adjusted to surface air density, are characterized by power law Z-R relations (Z = 129R^1.38 [convective]) and 224R^1.28 [stratiform]). However, at R < 10 mm h^-1, the convective population is essentially coincident with the small-drop size, small-Z portion of the stratiform population. Tokay and Short (1996) found a similar result when their algorithm did not separate the rain types unambiguously at R < 10 mm h^-1. The physical reasons for the wide variability of the drop size spectra and Z-R points in stratiform rain and their overlap with that of convective rain are proposed. The subtle distinctions in the microphysical properties and the Z-R relations by rain type could not be found by Yuter and Houze using the same airborne DSD data set as that in this work and a radar-based textural classification algorithm.

Beal, L.M., R.L. Molinari, T.K. Chereskin, and P.E. Robbins. Reversing bottom circulation in the Somali Basin. Geophysical Research Letters, 27(16):2565-2568 (2000).

Two sets of direct velocity measurements were taken, concurrent with hydrographic data, in the bottom waters of the northern Somali Basin in June and September 1995. The velocities indicate a temporal flow reversal in the bottom circulation, which is consistent with the changing density structure between the sections. In June, there is evidence of a southward Deep Western Boundary Current with a transport of 5 Sv. By September, flow close to the boundary is northward, with a transport of 2.6 Sv. Furthermore, the deep density gradient across the interior of the Somali Basin also changes between occupations, implying a cyclonic circulation in June and anticyclonic flow in September. Rossby wave activity is high in this region during the southwest monsoon, yet there is also evidence of a strong barotropic component to the Great Whirl in September, which may cause the reversal in the abyssal circulation.

Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black. Environmental influences on the rapid intensification of Hurricane Opal (1995) over the Gulf of Mexico. Monthly Weather Review, 128(2):322-352 (2000).

Hurricane Opal intensified rapidly and unexpectedly over the Gulf of Mexico between 1800 UTC 3 October 1995 and 1000 UTC 4 October 1995. During this period, the storm central pressure decreased from 963 to 916 hPa and sustained winds reached 68 m s-1. Analyses that include high-resolution GOES-8 water vapor winds and European Centre for Medium-Range Weather Forecasts (ECMWF) and National Centers for Environmental Prediction (NCEP) gridded datasets are employed to examine the rapid intensification phase of Opal. Opal first reached tropical storm strength on 29V30 September 1995 as it interacted with a trough while situated over the Yucatan Peninsula. Opal deepened moderately (20 hPa) in the 24 h ending 1200 UTC 2 October as it achieved minimal hurricane strength and as it turned northeastward. The deepening occurred in conjunction with an environmental flow interaction as determined by an Eliassen balanced vortex outflow calculation. As Opal accelerated toward the Gulf coast by 1200 UTC 3 October, it approached the equatorward jet-entrance region of a progressive synoptic-scale trough. The trough tail extended southwestward toward the lower Texas coast. As the poleward portion of the trough moved eastward, the equatorward end of the trough lagged behind, stretched meridionally, and partially fractured as it encountered a deformation region over the northwest Gulf. Enhanced outflow and increased divergence in the upper troposphere poleward of Opal was associated with the deformation zone and the partially fractured trough tail. An analysis of the 300-200-hPa layer-averaged divergence and 6-h divergence change based on an analysis of the water vapor winds shows a significant increase in the magnitude and equatorward extension of the divergence core toward Opal that begins at 1200 UTC 3 October and is most apparent by 1800 UTC 3 October and 0000 UTC 4 October. This divergence increase is shown to precede convective growth in the eyewall and the onset of rapid intensification and is attributed to a jet-trough-hurricane interaction in a low-shear environment. Calculations of balanced vortex outflow based on the ECMWF and NCEP gridded datasets confirms this interpretation. A crucial finding of this work is that the jet-trough-hurricane interaction and explosive intensification of Opal begins near 0000 UTC 4 October when the storm is far from its maximum potential intensity (MPI), and the 850-200-hPa shear within 500 km of the center is weak (2-3 m s^-1). In this first stage of rapid intensification, the winds increase by almost 15 m s^-1 to 52 m s^-1 prior to the storm reaching an oceanic warm-core eddy. The second stage of rapid intensification occurs between 0600 and 1000 UTC 4 October when Opal is over the warm-core eddy and sustained winds increase to 68 m s^-1. During this second stage, conditions are still favorable for a jet-trough-hurricane interaction as demonstrated by the balanced vortex outflow calculation. Opal weakens rapidly after 1200 UTC 4 October when the storm is near its MPI, the shear is increasing, and the eye is leaving the warm-core eddy. This weakening occurs as Opal moves closer to the trough. It is suggested that an important factor in determining whether a storm-trough interaction is favorable or unfavorable for intensification is how far a storm is from its MPI. The results suggest that a favorable storm-trough interaction ("good trough") can occur when a storm is far from its MPI. It is suggested that although the ECMWF (and to lesser extent NCEP) analyses reveal the trough-jet-hurricane interaction through the balanced vortex outflow calculation, that the failure of the same models to predict the rapid intensification of Opal can be attributed to the inability of the model to resolve the eye and internal storm structure and the associated influence of the trough-jet-hurricane interaction on the diabatically driven storm secondary circulation. The analyses also indicate that the high spatial and temporal resolution of the GOES-8 water vapor winds reveal important mesoscale details of the trough-jet-hurricane interaction that would otherwise be hidden.

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, 16 pp. (2000).

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.

Chai, F., R. Dugdale, R.T. Baraber, M. Jiang, and T.-H. Peng. Ecosystem modeling in the equatorial Pacific upwelling region. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS29, OS11P-06 (2000).

The equatorial Pacific Ocean is the dominant oceanic source of carbon dioxide to the atmosphere, an annual net flux of 1.0 Pg carbon. This net sea-to-air flux of carbon is the result of a complex interplay between physical and biological processes in the region. A physical-biogeochemical model has been developed and used to investigate physical variations, ecosystem responses, and biogeochemical consequences. The ecosystem model, embedded into a three-dimensional circulation model, is capable of reproducing the low silicate, high nitrate, low chlorophyll (LSHNLC) conditions in the equatorial Pacific upwelling region. Linkage of the ecosystem components to the carbon system provides a model estimated sea-to-air flux of carbon which is comparable with the observations. The ecosystem responses to the tropical instability waves have been documented to exam the transition from a "balanced" to "bloom" state of phytoplankton production. The physical-biogeochemical model results show a consistent decrease of the sea-to-air CO₂ flux during El Niño events.

Cione, J.J., P.G. Black, and S.H. Houston. Surface observations in the hurricane environment. Monthly Weather Review, 128(5):1550-1561 (2000).

Composite analyses of marine surface observations from 37 hurricanes between 1975 and 1998 show that the difference between the sea surface temperature and the surface air temperature significantly increases just outside the hurricane inner core. This increase in the sea-air contrast is primarily due to a reduction in surface air temperature and is more likely to occur when sea temperatures are at least 27°C. Results show that 90% of the observed cooling occurs 3.25°-1.25° latitude from the hurricane center, well outside the region of strongest surface winds. Since surface pressure only decreases 3 mb over this interval, the 2°C drop in air temperature is not a result of adiabatic expansion. For the subset of observations that contained moisture measurements, surface specific humidity decreased 1.2 g kg^-1 4.5°-1.75° latitude from the storm center. This finding suggests that the observed reduction in surface air temperature is not simply a result of near-surface evaporation from sea spray or precipitation. An alternate explanation may be that outside the hurricane inner core, unsaturated convective downdrafts act to dry and evaporatively cool the near-surface environment. Between 3.25° and 1.25° radius, composite analyses show that low-level inflow is not isothermal, surface moisture is not constant, and the near-surface environment is not in thermodynamic equilibrium with the sea. Calculations based on these observations show that theta_e 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.

Cosca, C.E., R.A. Feely, R.H. Wanninkhof, J. Boutin, J. Etcheto, and M.J. McPhaden. Seasonal and interannual variations of the fCO₂-SST relationships in the equatorial Pacific. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS28, OS11O-11 (2000).

In order to utilize satellite temperature data for determining high-resolution variations of CO₂ distributions in the equatorial Pacific, we have developed seasonal and interannual fCO₂-SST relationships from shipboard data. The data were gathered onboard the NOAA ships Baldridge, Discoverer, and Ka'imimoana from 1992 through 1998 as a companion project to the biannual deployment of the TAO moorings. The cruises during the 6-year period included 55 10°S to 10°N crossings of the equatorial Pacific between 95°W and 165°E, and spanned two major ENSO events (1992-1994 and 1997-1998). Data were collected during the warm boreal spring season (February through June) and during the cooler boreal fall season (July through December) of each year, making it possible to examine the interannual and seasonal variability of the fCO₂-SST relationship. A linear fit through all 55 data sets yields an inverse correlation between SST and fCO₂, with an R² of 0.583 and an RMS of 28.4 µatm. When separated, there is a significant difference between the regression lines for El Niño versus non-El Niño data sets. During non-El Niño periods, we observed seasonal differences in the fCO₂-SST relationship. The regression lines through the spring and fall data sets have higher R² and lower RMS values than the composite non-El Niño regression line, and the slopes are significantly different at the 95% confidence level. The slope for the fall season is less negative than during spring, suggesting higher biological productivity occurred during the fall non-El Niño seasons. The regression line for the composite El Niño data, which shows no significant seasonal variability, has a slope very similar to the non-El Niño spring slope, indicating less influence by biological processes. These relationships have been combined with satellite-based temperature data to provide a composite time-space map of DELTA-fCO₂ in the equatorial Pacific.

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, 32:515-543 (2000).

A particle-in-cell (PIC) numerical method developed for the study of shallow-water dynamics, when the moving fluid layer is laterally confined by the intersection of its top and bottom surfaces, is described. The effect of ambient rotation is included for application to geophysical fluids, particularly open-ocean buoyant vortices in which the underlying density interface outcrops to the surface around the rim of the vortex. Extensions to include the dynamical effect of a second moving layer (baroclinicity) and the presence of a lateral rigid boundary (sidewall) are also described. Although the method was developed for oceanographic investigations, applications to other fluid mechanics problems would be straightforward.

Enfield, D.B., and A.M. Mestas-Nuñez. Global modes of ENSO and non-ENSO SST variability and their associations with climate. In: El Niño and the Southern Oscillation: Multiscale Variability and its Impacts on Natural Ecosystems and Society, H.F. Diaz and V. Markgraf (eds.). Cambridge University Press, 89-112 (ISBN 0521621380) (2000).

In this chapter we review much of the recent work by others regarding the nature of the global modes of sea surface temperature (SST) variability and the SST involvement in interannual to multidecadal climate variability. We also perform our own analysis of global SST so as to describe and separate the SST variability associated with El Niño-Southern Oscillation (ENSO) from the low-frequency modes not associated with ENSO (non-ENSO). ENSO is a global phenomenon with significant phase propagation between basins, which we preserve and describe using complex EOF (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.

Esenkov, O.E. A numerical study of the dynamics of the Somali Current system. Ph.D. Thesis, University of Miami/Rosenstiel School of Marine and Atmospheric Science, 140 pp. (2000).

The evolution of surface circulation, salinity budget, and processes at intermediate depth in the northwestern Indian Ocean were studied with the open boundary version of the Miami Isopycnic Coordinate Ocean Model (MICOM). Under climatological wind and thermodynamic forcing, the model develops solutions that are in good agreement with global MICOM results and with observations. When the observed winds (Legler et al., 1989) force the model, interannual variability of the surface fields increases significantly. However, coalescence of the two large eddies in the end of the summer monsoon, which was observed in some years, does not occur in the model. To identify what processes facilitate the merger, a series of experiments was performed with modified model parameters and forcing fields. The eddies coalesced when half-slip, rather than no-slip, boundary conditions were used. In this case, less positive vorticity was produced at the coast, resulting in reduced blocking effect on the propagation of the southern eddy. The 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 the Socotra Island is present in the model.

Feely, R.A., C.E. Cosca, R.H. Wanninkhof, M.J. McPhaden, C.S. Meinen, J. Boutin, and J. Etcheto. The role of ENSO on the phasing of the CO₂ signal in the equatorial Pacific. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS279, OS42J-02 (2000).

Recent modeling studies, based upon inversions of atmospheric CO₂, delta¹³C, and O₂/N₂ records from Cape Grim, Tasmania by Rayner et al. (1999), have suggested a decrease in the equatorial Pacific Ocean source of CO₂ to the atmosphere which precedes the SOI by about seven to ten months. In order to test this model result, we have utilized satellite temperature data to obtain high-resolution variations of fCO₂ distributions in the eastern equatorial Pacific based on shipboard fCO₂-SST relationships. The data were gathered onboard the NOAA ships Baldridge, Discoverer, and Ka'imimoana from 1992 through 1998 as a companion project to the biannual deployment of the TAO moorings. The results indicate rapid drops in surface water fCO₂ at 110°W, 125°W and 140°W several months ahead of the peak SST anomalies associated with the 1986-1887, 1991-1992, and 1997-1998 warm ENSO events. These rapid changes in fCO₂ are inversely correlated with the integrated volume of the warm water above the 20°C isotherm in the eastern equatorial Pacific. During the onset phase of warm ENSO events, the propagation of Kelvin waves from west to east along the equatorial waveguide results in a deepening of the thermocline and a rapid decrease in surface water fCO₂. The phasing of the beginning of the decrease in fCO₂ is approximately six to eight months ahead of the minimum in the SOI index. During strong El Niño events, such as the 1997-2998 ENSO event, seawater fCO₂ values decrease by as much as 125 µatm over the course of a few weeks, indicating a rapid decrease in the outgassing of CO₂ near the equator. These results help to explain the dramatic decrease in the growth rate of CO₂ in the atmosphere that occurs at the beginning of each ENSO event.

Feely, R.A., C.L. Sabine, R.H. Wanninkhof, R.M. Key, G.C. Johnson, F.J. Millero, K. Lee, T.-H. Peng, J.L. Bullister, A. Kozyr, and M.F. Lamb. Synthesis of global ocean CO₂ survey data. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(48):F691, OS72E-01 (2000).

The synthesis of the global ocean CO₂ survey data is proceeding by ocean basin. Between 1991 and 1998, investigators analyzed dissolved inorganic carbon (DIC) and one or more other carbon system parameters (TAlk, pCO₂, or pH) on WOCE/JGOFS/OACES cruises in the Indian, Pacific, and Atlantic Oceans. The analysis of the Indian Ocean data is published in Sabine et al., GBC, 13, 179-198, 1999) and can be obtained at: http://cdiac.esd.ornl.gov/oceans/glodap/index.html. DIC and TAlk were measured on all cruises, with an estimated overall accuracy of 2-4 µmol kg^-1, respectively. For the Pacific Ocean, investigators from 15 different laboratories and four countries analyzed at least two of the four measurable ocean carbon parameters. Several different lines of evidence were used to examine the consistency among data sets and recommend adjustments. The analysis included comparison of calibration techniques, results from certified reference material analyses, precision of at-sea replicate analyses, agreement between shipboard analyses and replicate shore-based analyses, comparison of deep water values at locations where two or more cruises overlapped or crossed, consistency with other hydrographic parameters, and internal consistency with multiple carbon parameter measurements. With the adjustments recommended here, the data can be combined to generate a Pacific Ocean data set with over 36,000 unique sample locations. The best data coverage was for DIC, which has an estimated overall accuracy of ~3 µmol kg^-1 after the recommended adjustments. TAlk, the second most common carbon parameter, has an estimated overall accuracy of ~5 µmol kg^-1. The data have been integrated into a unified, internally-consistent data set and the physical and chemical controls of the basinwide distributions of DIC and TAlk will be discussed. The synthesis of the Atlantic data is just getting underway and will be conducted in association with the European Carbon Dioxide in the North Atlantic Ocean (CARINA) Project, with a projected completion date of mid-2002.

Ffield, A., K. Vranes, A.L. Gordon, R.D. Susanto, and S.L. Garzoli. Temperature variability within Makassar Strait. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS17, OS11I-05 (2000).

The Indonesian throughflow impacts the global climate system by carrying warm Pacific water from about 5°N, through the Indonesian Seas, into the Indian Ocean at 12°S. As part of the U.S./Indonesian Arlindo program, recent mooring observations of ocean temperature provide the first high-resolution, long-term record of temperature variability in the Makassar Strait of the Indonesian Seas. The mooring observations span the entire cycle of the strong 1997/1998 El Niño, and they reveal the complexity of the Makassar Strait thermocline with significant short and long period temperature variations as a function of both depth and time. A high correspondence (r = 0.67) is found between variability in the average thermocline temperature, to variability in the southward Makassar volume transport: during high (low) volume transport, the average temperature of the thermocline is also high (low). In addition, during the measurement period, the Makassar thermocline temperature corresponds strongly (r = -0.87) to NINO3. This implies that the Makassar temperature field, when coupled with the throughflow, transmitted the equatorial Pacific El Niño and La Niña temperature fluctuations into the Indian Ocean with potential consequences to the climate system. The Makassar mooring temperature observations are related to 15 years of regional XBT data to better estimate the semi-annual, annual (monsoonal), and interannual (ENSO) characteristics of the mooring temperature observations, and of the Makassar Strait thermocline in general. The potential of Makassar XBT measurements to efficiently monitor the Makassar throughflow as part of the developing global monitoring system is assessed.

Ffield, A., K. Vranes, A.L. Gordon, R.D. Susanto, and S.L. Garzoli. Temperature variability within the Makassar Strait. Geophysical Research Letters, 27(2):237-240 (2000).

Recent mooring observations of ocean temperature provide the first high-resolution, long-term record of temperature variability in the Makassar Strait of the Indonesian Seas. The mooring observation span the entire cycle of the strong 1997/1998 El 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.

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, 14 pp. (2000).

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.

Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D. Fratantoni, P. Richardson, and G.J. Goñi. CTD/O₂, LADCP, and XBT measurements collected aboard the R/V Seward Johnson, February-March 1999: North Brazil Current Rings Experiment, cruise 2 (NBC-2). NOAA Data Report, OAR-AOML-37, 291 pp. (2000).

Summaries of conductivity-temperature-depth (CTD/O₂), lowered acoustic Doppler current profiler (LADCP), and expendable bathythermograph (XBT) measurements and hydrographic data acquired on an oceanographic research cruise during the winter of 1999 aboard the Harbor Branch Oceanographic Institution ship R/V Seward Johnson are presented. Data acquisition and processing systems are described, and calibration procedures are documented. Station location, CTD/O₂, LADCP, XBT summary data listings, and profiles are included for each station.

Fleurant, C.I., W.D. Wilson, W. Johns, S.L. Garzoli, R.H. Smith, D. Fratantoni, P. Richardson, and G.J. Goñi. 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, 274 pp. (2000).

Summaries of conductivity-temperature-depth (CTD/O₂), lowered acoustic Doppler current profiler (LADCP), expendable bathythermograph (XBT) measurements, and hydrographic data acquired on an oceanographic research cruise during the fall of 1998 aboard the Harbor Branch Oceanographic Institution ship R/V Seaward Johnson are presented. Data acquisition and processing systems are described, and calibration procedures are documented. Station location, CTD/O₂, LADCP, XBT summary data listings, and profiles are included for each station.

Garraffo, Z.D., W.E. Johns, E.P. Chassignet, and G.J. Goñi. Impact of North Brazil Current rings on the eastern Caribbean. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS69, OS12P-04 (2000).

The influence of North Brazil Current (NBC) rings on the eastern Caribbean is investigated using new results from a high-resolution North Atlantic model simulation, ship surveys, drifters, and Topex/Poseidon (T/P) altimetry. North Brazil Current rings are large (~400-km diameter) anticyclonic eddies that periodically pinch off from the North Brazil Current Retroflection and propagate northwestward toward the Lesser Antilles, carrying with them water masses and biogenic materials from the equator and Amazon regions. Results from the high-resolution MICOM North Atlantic model and from five years of T/P altimetry now suggest that approximately five NBC rings are formed each year, nearly twice what had been previously documented. New shipboard surveys obtained as part of an intensive 1998-2000 in-situ study of NBC rings have shown that these rings can have highly varying vertical structures, ranging from shallow (<200 m) to deep (>1000 m) features, and even subsurface intensified rings with maximum swirl velocities in the thermocline. A similar range of features is produced in the MICOM-simulated rings. The model results and altimetry suggest that the strongest and deepest reaching NBC rings are the ones most likely to travel well northward along the Lesser Antilles arc before breaking up and dispersing their waters. The passage of the rings along the island arc and their interaction with the island topography strongly influences flow and transport variations through the Lesser Antilles passages.

Garzoli, S.L., and G.J. Goñi. Combining altimeter observations and oceanographic data for ocean circulation and climate studies. In Satellites, Oceanography, and Society, D. Halpern (ed.). Elsevier Oceanographic Series, 63:79-95 (2000).

Calibrating Topography Experiment (TOPEX)/Poseidon (T/P) altimeter data to inverted echo sounder measurements is one of the methodologies developed to advance the study of the South Atlantic Ocean. The mass transport of the main boundary currents can be monitored using dynamic height time series obtained from altimeter-derived sea surface height anomalies. A two-layer model yields upper-layer thickness and surface dynamic height of the ocean in areas of strong vertical stratification to identify and track anticyclonic rings, such as those shed from the Agulhas retroflection, which play an important role in the interocean exchange of heat and mass. Interannual variability of boundary currents, derived from analysis of the first five years of T/P data, is discussed. A combination of T/P data and in-situ observations provides significant contributions to the study of ocean dynamics for climate applications.

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 Pacific. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, 19 pp. (2000).

This paper summarizes the discussions that took place during the COSTA (Climate Observing System for the Tropical Pacific) 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.

Goñi, G.J., S.M. Sainz-Trapaga, and T. Sugimoto. Transport estimates and variability of the Kuroshio Extension Current from satellite altimetry data. AGU 2000 Western Pacific Geophysics Meeting, Tokyo, Japan, June 27-30, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(22):WP77-WP78, OS32B-06 (2000).

Satellite altimetry observations of sea level in combination with historical vertical profiles of ocean density and dynamical modeling provide an excellent tool to understand the global meso- and large-scale ocean circulation. A two-layer dynamical model is used in conjunction with six years of TOPEX/POSEIDON (T/P) altimeter-derived sea height anomaly to monitor the upper ocean transport in a region east of Japan from 1993 to 1998. The key objective of this work is to estimate the upper layer thickness and investigate the baroclinic transport variability along a selected T/P groundtrack, in which a two-year time series of the 14°C isotherm derived from inverted echo sounders is available. The upper layer thickness field is used to monitor the Kuroshio Extension front, which is found to fluctuate between 33.7°N and 36.5°N. The across-track upper layer velocity and baroclinic transports are used to monitor the Kuroshio Extension axis. Estimates in this work reveal that the axis fluctuates between 32.1°N and 35.9°N. Two events are identified, one in 1996 and another in 1997, with unusual southern paths of the Kuroshio Extension axis, and related to large variations in baroclinic transport values. It is speculated that these extreme southern excursions of the axis may be compensating for large changes in relative vorticity and upper layer thickness.

Hendee, J.C. A data-driven soft real-time expert system for producing coral bleaching alerts. Ph.D. Thesis, Nova Southeastern University, 131 pp. (2000).

In the Florida Keys there are many physical, chemical, and biological events of interest and concern to personnel of the Florida Keys National Marine Sanctuary, marine biologists, oceanographers, fishermen, and divers. Large volumes of continuously-generated meteorological and oceanographic data from instruments in the SEAKEYS (Sustained Ecological Research Related to Management of the Florida Keys Seascape) network help to understand these events. However, since no one has the time to look at every printout of data from every station, every day, seven days a week, it is highly desirable to have an automated system that can monitor parameters of interest and produce specialized alerts of specific events, as indicated by prescribed or abnormal ranges, or combinations of parameters. A soft real-time expert system was developed to produce such alerts based on data input from the SEAKEYS network. The prototype system collected data from the Sombrero Reef station in the network and produced automated e-mail and World-Wide Web alerts when conditions were thought to be conducive to, or predictive of, coral bleaching, which occurs under environmental conditions stressful to corals. Configuration of the system included a point system for three coral bleaching models (high sea temperature only, high sea temperature plus low winds, high sea temperature plus low winds plus low tide). The approach is an important development in the use of knowledge-based systems to solve environmental problems, as it provides for knowledge synthesis (in the form of data summaries) from any environmental ASCII data stream or table, be it real-time or not.

Hendee, J.C. An environmental information synthesizer for expert systems: A framework for use in near real-time detection of harmful algal blooms. Proceedings, 17th International Conference of The Coastal Society: Coasts at the Millennium, Portland, OR, July 9-12, 2000. The Coastal Society, 233-241 (2000).

As an enhancement to the SEAKEYS environmental monitoring network in the Florida Keys National Marine Sanctuary, software called the Environmental Information Synthesizer for Expert Systems (EISES) has been utilized together with a specially developed expert system to model and report the near real-time sensing of environmental conditions conducive to the onset of a harmful algal bloom (HAB, e.g., "red tide"). Actual near real-time in-situ fluorometry data was matched with wind speeds and photosynthetically active radiation at the Long Key SEAKEYS station in Florida Bay to simulate the onset of an HAB. These incidences were e-mailed to the knowledge engineer as they occurred, and could in the future be e-mailed to regulatory agencies, or posted to a Web site, as is done with a similarly developed expert system for coral bleaching. This approach shows promise with the future remote detection of HAB pigment data via in-situ or satellite sensors.

Jacobs, S.D., L.K. Shay, A.J. Mariano, and P.G. Black. The 3D oceanic mixed layer response to Hurricane Gilbert. Journal of Physical Oceanography, 30(6):1407-1429 (2000).

Upper-ocean heat and mass budgets are examined from three snapshots of data acquired during and after the passage of Hurricane Gilbert in the western Gulf of Mexico. Measurements prior to storm passage indicated a warm core eddy in the region with velocities of O(1) m s^-1. Based upon conservation of heat and mass, the three-dimensional mixed layer processes are quantified from the data. During and subsequent to hurricane passage, horizontal advection due to geostrophic velocities is significant in the eddy regime, suggesting that prestorm oceanic variability is important when background flows have the same magnitude as the mixed layer current response. Storm-induced near-inertial currents lead to large vertical advection magnitudes as they diverge from and converge toward the storm track. Surface fluxes, estimated by reducing flight-level winds to 10 m, indicate a maximum wind stress of 4.2 N m^-2 and a heat flux of 1200 W m^-2 in the directly forced region. The upward heat flux after the passage of the storm has a maximum of 200 W m^-2 corresponding to a less than 7 m s^-1 wind speed. Entrainment mixing across the mixed layer base is estimated using three bulk entrainment closure schemes that differ in their physical basis of parameterization. Entrainment remains the dominant mechanism in controlling the heat and mass budgets irrespective of the scheme. Depending on the magnitudes of friction velocity, surface fluxes and/or shear across the mixed layer base, the pattern and location of maximum entrainment rates differ in the directly forced region. While the general area of maximum entrainment is in the right-rear quadrant of the storm, the shear-induced entrainment scheme predicts a narrow region of cooling compared to the stress-induced mixing scheme and observed SST decreases. After storm passage, the maximum contribution to the mixed layer dynamics is associated with shear-induced entrainment mixing forced by near-inertial motions up to the third day as indicated by bulk Richardson numbers that remained below criticality. Thus, entrainment based on a combination of surface fluxes, friction velocity, and shear across the entrainment zone may be more relevant for three-dimensional ocean response studies.

Kang, W.-J., J.H. Trefy, T.A. Nelsen, H.R. Wanless. Direct atmospheric inputs versus runoff fluxes of mercury to the lower Everglades and Florida Bay. Environmental Science and Technology, 34(19):4058-4063 (2000).

Age-dated sediments from the lower Everglades and Florida Bay provide a record of inputs of excess Hg from direct atmospheric input versus runoff. Direct atmospheric fluxes of excess Hg to sediments in the lower Everglades and Florida Bay, calculated using a mass balance model for excess ²¹⁰Pb, currently average 24 ± 9 µg m^-2 yr^-1 and are comparable with recent results from bulk atmospheric deposition. In contrast, present-day runoff fluxes of excess Hg to area sediments are variable, ranging from about 4-160 µg m^-2 yr^-1. The runoff flux now carries 60-80% of the total flux of excess Hg to the sediments in areas near river sloughs but less than 20% of the total flux of excess Hg in more remote areas of Florida Bay. These results show the greater importance of runoff relative to direct atmospheric deposition for Hg inputs to many areas of the lower Everglades and immediately adjacent Florida Bay. Thus, the choice of future water management strategies can play an important role in controlling Hg inputs to the lower Everglades and portions of Florida Bay.

Katsaros, K.B. Millennium perspectives. Bulletin of the American Meteorological Society, 81(4):837-838 (2000).

No abstract.

Katsaros, K.B., and R.T. Pinker. Algorithm improvement for novel applications in earth science research. Proceedings, First Meteosat Second Generation Research Announcement of Opportunity Workshop, Bologna, Italy, May 17-19, 2000. European Space Agency, ESA SP-452, 103-106 (2000).

No abstract.

Katsaros, K.B., P. Vachon, P.G. Black, P.P. Dodge, and E.W. Uhlhorn. Wind fields from SAR: Could they improve our understanding of storm dynamics? John Hopkins APL Technical Digest, 21(1):86-93 (2000).

Four hurricane images obtained by RADARSAT are examined for what they reveal about the storms. Features seen include strong variations in backscatter from the surface in and around convective cells associated with rain cells and rainbands, coupled with increased backscatter in regions of high wind outflow. Long linear features of scale 3-6 km are observed in three of the four hurricanes, probably from secondary circulations in the atmospheric boundary layer (roll vortices). They occur between convective rainbands, where the descending motion could produce a well-defined boundary layer. Although the origins of and the mechanisms producing the features are still not clear, the high resolution, wide-swath coverage modes of synthetic aperture radar provide new observations and present important questions for further research.

Kelly, P.S., K.M.M. Lwiza, R.K. Cowen, and G.J. Goñi. Low-salinity pools at Barbados, West Indies: Their origin, frequency, and variability. Journal of Geophysical Research, 105(C8):19,699-19,708 (2000).

A vertical array of conductivity-temperature sensors moored off the west coast of Barbados, West Indies, from May 1996 to November 1997 revealed a heterogeneous and variable salinity pattern punctuated by six intrusions of low-salinity water (<34.5 psu) into the region. A typical intrusion extended to 30 m depth and lasted ~25 days, although one intrusion extended to 47 m and lasted 94 days. Water samples taken during an intrusion in May 1997 have Radium 228/226 activity ratios of approximately 1, consistent with previous measurements in Barbados of water that originated in the Amazon River mixing zone. The Amazon water likely was translated to Barbados in rings spawned from the North Brazil Current. Analysis of sea height anomaly derived from the TOPEX/Poseidon satellite supports this conclusion and reveals that, contrary to previous studies, rings are shed throughout the year, mostly during spring. The intrusions of low-salinity water and their associated velocities dramatically changed the already variable flow in our study area. We believe the complex salinity and flow we observed represented the disorganized remnants of rings that were at or near the ends of their lives. The changes we observed in the velocity and water structure are interesting in their own right as evidence of the Barbados region as a mixing zone and for their influence on recruitment of larval fishes to the reef along the island's west coast.

Kiesling, T.L., J. Fell, and P.B. Ortner. Rapid molecular identification of copepods froma plankton tow. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS234, OS41F-04 (2000).

Florida Bay is a 1000 square mile subtropical lagoon located between the Florida Keys and the Florida mainland. Like other estuarine systems, Florida Bay serves as a nursery ground for commercially and recreationally important species of fish. Despite the fact that the primary source of food for many first-feeding larval fish is copepod nauplii, the trophodynamic role of the zooplankton community in Florida Bay has historically been ignored. There is currently a multi-agency effort underway to describe the Florida Bay zooplankton community. Along with traditional sorting methods, molecular methods are being designed to identify and quantify juvenile stages of copepods so that their trophodynamic role can be more accurately defined. We have developed a microtiter plate based hybridization assay to identify copepod species in a mixed sample. With this method, species-specific probes based on DNA sequence are used to identify the copepod species. This method is superior to other PCR-based identification procedures, which require several PCR reactions using several species-specific primers to determine the identity of the DNA. Our technique requires one PCR reaction, which creates an amplicon using universal primers that target a region containing the probe sequences. This amplicon can be tested with a macroarray of several different probes on a single plate. This is especially important when dealing with the limited amounts of DNA that are extracted from these small metazoans. We isolated eight of the most common species of copepods found in Florida Bay, extracted their DNA and sequenced the large subunit of ribosomal DNA for each species. The rDNA sequences were compared and species-specific probes were designed based on base pair differences. Each probe was immobilized to the wells of a microtiter plate. The plates were hybridized with amplified and labeled target DNA from a mixed sample of copepods. If the DNA from the species in question was present in the DNA mix, it would bind to the species-specific probe. The labeled target DNA, once bound to the probe, can be detected via a colorimetric assay. With this method, We were able to identify each of six species of copepods from mixed samples. Testing is now proceeding with the juvenile forms of the copepods. Efforts are also underway to make the method quantitative.

King, D.B., J.H. Butler, S.A. Montzka, S.A. Yvon-Lewis, and J.W. Elkins. Implications of methyl bromide supersaturations in the temperate North Atlantic Ocean. Journal of Geophysical Research, 105(D15):19,763-19,769 (2000).

Methyl bromide saturation anomalies measured in the springtime North Atlantic and summertime North Pacific Oceans during 1998 revealed persistent supersaturations in the temperate waters of the northeastern Atlantic but undersaturtions in tropical waters of both oceans. A comparison of data from this study with those from a previous cruise to the northeastern Atlantic suggests that methyl bromide is cycled seasonally in these waters and perhaps in all temperate open-ocean waters. This means that the calculated net flux of methyl bromide into the oceans is slightly less negative than previously reported. With these new insights we estimate that the global air-sea flux of methyl bromide ranges from -11 to -20 Gg yr^-1. Data combined from this and three previous cruises support a flux dependence upon sea surface temperature, as reported recently by Groszko and Moore (1998). Whereas sea surface temperature can account for 40-70% of the observed variability in methyl bromide globally, it is able to reproduce only a small fraction of the observed seasonal cycle in the temperate northeastern Atlantic. The development of reliable predictions of air-sea fluxes of methyl bromide will require information on additional variables as well.

King, D.B., J.H. Butler, S.A. Montzka, S.A. Yvon-Lewis, and J.W. Elkins. Correction to "Implications of methyl bromide supersaturations in the temperate North Atlantic Ocean." Journal of Geophysical Research, 105(D20):24,713-24,714 (2000).

No abstract.

Lamb, M.F., C.L. Sabine, R.M. Key, J.L. Bullister, F.J. Millero, R.H. Wanninkhof, T.-H. Peng, A. Kozyr, and R.A. Feely. Dissolved inorganic carbon crossover points in the Pacific Ocean. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS122, OS22F-03 (2000).

Between 1991 and 1996, carbon measurements were made on 25 U.S. WOCE, U.S. JGOFS, and NOAA OACES cruises in the Pacific Ocean. These cruises were co-sponsored by the National Science Foundation, the U.S. Department of Energy, and NOAA's Climate and Global Change Program. Although at least two carbon parameters were measured on all of the cruises, dissolved inorganic carbon (DIC) was the only parameter common to all of the cruises. The measurements were collected over six years by ten different laboratories. Together, these data comprise the most comprehensive high-precision survey of carbon distributions in the Pacific Ocean with a greater than ten-fold increase in the number of samples analyzed than for the GEOSECS expedition of the early 1970s. As a part of the JGOFS Synthesis and Modeling Project, we have been working to combine these data into an internally consistent, unified data set. Additional DIC data collected by international investigators have also been included, where possible, to fill in holes in the U.S. survey program. In an effort to ensure the accuracy and internal consistency of these data, we have compared the deep water (>2000 m) DIC values measured on different cruises in areas where two or more cruises overlapped or crossed (within ~100 km). Data from each of the comparison stations were plotted against the density anomaly referenced to 3000 dbar (sigma 3). Polynomial fits of the data from each cruise were evaluated at evenly-spaced intervals over the density range common to both sets of stations. These results, together with information on the calibration procedures, analyses of Certified Reference Materials (CRMs), the quality of duplicate analyses, internal consistency with other carbon parameters, and with large-scale correlations with hydrographic parameters, were used to suggest minor adjustments to some of the cruises to optimize the internal consistency of the data. Our results show that a unified Pacific data set of over 30,000 samples can be achieved with an estimated precision and accuracy of ±2 µmol/kg.

Lamb, M.F., C.L. Sabine, R.A. Feely, F.J. Millero, R.H. Wanninkhof, R.M. Key, G.C. Johnson, K. Lee, T.-H. Peng, A. Kozyr, J.L. Bullister, and D. Greeley. Consistency and proposed adjustments of Pacific Ocean CO₂ survey data. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(48):F700, OS11B-10 (2000).

Between 1991 and 1996, carbon measurements were made on 24 WOCE/JGOFS/OACES survey cruises in the Pacific Ocean. This combined database will be used to determine the distribution and inventory of carbon parameters in the Pacific Ocean, and will enhance our understanding of the ocean carbon cycle, including estimates of the anthropogenic CO₂ uptake by the oceans. Of the four measurable carbon parameters, (dissolved inorganic carbon (DIC), total alkalinity (TAlk), fugacity of CO₂ (fCO₂), and pH), DIC was measured on all the cruises, and TAlk was the second most measured. We examined the data where cruises overlapped using several independent techniques, and have proposed adjustments that will result in a consistent, unified data set. Based on our results, we recommend DIC adjustments for P16N, P17N, and P2, and TAlk adjustments for P8S, P17C, P17N, P2 and P31. Details of our proposed adjustments are posted at http://cdiac.esd.ornl.gov/oceans/glodap/index.html. This CO₂ data set represents the most comprehensive high-precision survey of carbon distributions in the Pacific Ocean since the GEOSECS expedition, and provides an order of magnitude improvement in the quality and quantity of Pacific DIC and Talk data. With the proposed adjustments, DIC and TAlk have an estimated overall accuracy of ~3 and 5 µmol kg^-1 respectively.

Landsea C.W., and J.A. Knaff. How much skill was there in forecasting the very strong 1997-1998 El Niño? Bulletin of the American Meteorological Society, 81(9):2107-2120 (2000).

The very strong 1997-1998 El Niño was the first major event in which numerous forecasting groups participated in its real-time prediction. A previously developed simple statistical tool, the El Niño-Southern Oscillation Climatology and Persistence (ENSO-CLIPER) model, is utilized as a baseline for determination of skill in forecasting this event. Twelve statistical and dynamical models were available in real time for evaluation. Some of the models were able to outperform ENSO-CLIPER in predicting either the onset or the decay of the 1997-1998 El Niño, but none were successful at both for a medium-range two season (6-8 months) lead time. There were no models, including ENSO-CLIPER, able to anticipate even one-half of the actual amplitude of the El Niño's peak at medium-range (6-11 months) lead. In addition, none of the models showed skill (i.e., lower root-mean-square error than ENSO-CLIPER) at the zero season (0-2 months) through the two season (6-8 months) lead times. No dynamical model and only two of the statistical models (the canonical correlation analysis [CCA] and the constructed analog [ANALOG]) outperformed ENSO-CLIPER by more than 5% of the root-mean-square error at the three season (9-11 months) and four season (12-14 months) lead time. El Niño impacts were correctly anticipated by national meteorological centers one-half year in advance, because of the tendency for El Niño events to persist into and peak during the boreal winter. Despite this, the zero to two season (0-8 month) forecasts of the El Niño event itself were no better than ENSO-CLIPER and were in that sense, not skillful, a conclusion that remains unclear to the general meteorological and oceanographic communities.

Leaman, K.D., W.D. Wilson, and Z.D. Garraffo. Physical variability of surface currents in the the Panama-Colombia Gyre: Nature, causes, and comparisons with a high-resolution numerical model. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS33, OS11R-09 (2000).

As part of the National Oceanographic Partnership Program Year of the Ocean (YOTO) contribution, a total of 32 WOCE surface drifters have to date been launched in the southwestern Caribbean Sea using vessels of the Colombian Navy. These deployments consist of groups of eight surface drifters launched nominally every three to four months on a line between Cartagena and San Andres Island. All drifters have been drogued at a depth of 15 m and are designed to report surface positions and temperatures. This launch program is planned to continue through at least the next year with launches of six floats roughly every three months. These drifter tracks can be found at Web pages for the NOPP drifters (www.drifters.doe.gov), the IAS oceanography page (IASlinks.org), or the Intra-Americas Sea Initiative page (www.rsmas.miami.edu/groups/IASI/IASIhome.htm). The purpose of these deployments is to explore the structure and variability of a prominent circulation feature in the southwestern Caribbean known as the Panama-Colombia Gyre (PCG). This cyclonic gyre has been revealed by the drifter tracks obtained so far to be a permanent feature of the circulation but one that shows considerable seasonal and shorter-term variability as well. Retention times for drifters launched in the PCG are order several months. Very few drifters from the open Caribbean find their way into the PCG; however, a large number of PCG drifters exit the PCG at various locations and times, and a significant number of these become trapped in shelf waters south of Cuba. This latter fact has implications for biological problems of larval transport and interconnectivity of coastal habitats. Observed drifter tracks are compared to numerical surface drifters "deployed" in a high-resolution isopycnic-coordinate numerical model. Similar seasonal variability is observed in both real and numerical drifter trajectories; in particular, a deformation of the flow field in late summer has been observed in the model, as well as in two sequential years of drifter observations. Over longer periods, numerical drifter concentrations in the PCG decrease until a balance is achieved between northward Ekman advection and diffusion of drifters from the interior.

Lee, K., J.-Z. Zhang, and R. Wanninkhof. Carbon export in nitrate-depleted tropical and subtropical oceans: Implication of nitrogen fixation. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(48):F693, OS72E-12 (2000).

The export of carbon from surface waters to the interior of the ocean is a central mechanism controlling the net uptake of carbon dioxide from the atmosphere. Existing estimates of the vertical carbon export vary greatly in regional and global comparisons. We estimate the biologically-mediated vertical carbon export, referred to as "new production," from the mean annual cycle of total inorganic carbon concentration normalized to salinity (NDIC = DIC × 35/S) in the mixed layer. It is assumed that the decrease in NCT from early spring to fall is solely caused by biological uptake and subsequent transport out of the upper oceans. Seasonal drawdown of NDIC in the mixed layer is quantified from regional algorithms relating NDIC to sea surface temperature (SST) and nitrate (NO₃^-) combined with seasonal changes in climatological SST and NO₃^- fields, and separately from the surface partial pressure of CO₂ and alkalinity fields using thermodynamic models. The two independent methods show similar regional trends and yield global new production values of 7.5 GtC/yr and 8.6 GtC/yr, respectively. A significant fraction of the global total, 0.8-1.1 GtC/yr, is exported in the absence of measurable nitrate levels in the oligotrophic tropical and subtropical oceans. This estimate is a direct indication of carbon export supported by nitrogen fixation. The value constitutes a significant fraction (30-50%) of the total new production in the oligotrophic oceans.

Lee, K., F.J. Millero, R.H. Byrne, R.A. Feely, and R. Wanninkhof. The recommended dissociation constants for carbonic acid seawater. Geophysical Research Letters, 27(2):229-232 (2000).

A coherent representation of carbonate dissociation constants and measured inorganic carbon species is essential for a wide range of environmentally important issues such as oceanic uptake of anthropogenic CO₂ and carbon cycle depictions in ocean circulation models. Previous studies have shown varying degrees of discordance between calculated and measured CO₂-system parameters. It is unclear if this is due to errors in thermodynamic models or in measurements. In this work, we address this issue using a large field data set (15,300 water samples) covering all ocean basins. Our field data, obtained using laboratory-calibrated measurement protocols, are most consistent with calculated parameters using the dissociation constants of Mehrbach et al. (1973) as refit by Dickson and Millero (1987). Thus, these constants are recommended for use in the synthesis of the inorganic carbon data collected during the global CO₂ survey during the 1990s and for characterization of the carbonate system in seawater.

Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global relationships of total inorganic carbon with temperature and nitrate in surface seawater. Global Biogeochemical Cycles, 14(3):979-994 (2000).

High quality total inorganic carbon (C_T) 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 NC_T = a + b SST + c SST² + d NO₃^- fits salinity (S)-normalized surface C_T (NC_T = C_T × 35/S) data for different parts of the oceans within an area-weighted error of ±7 µmol kg^-1 (1 sigma). Estimated values of NC_T using the derived algorithms with NO₃^- and SST are compared with values calculated from the surface partial pressure of CO₂ (pCO_2SW) (Takahashi et al., 1997) and total alkalinity (A_T) (Millero et al., 1998) fields using thermodynamic models. Comparisons of the estimated values of NC_T with measurements not used to derive the same algorithms, and comparisons with the values calculated from global A_T and pCO_2SW fields, give a realistic uncertainty of ±15 µmol kg^-1 in estimated C_T. The derived correlations of NC_T with SST and NO₃^- presented here make it possible to estimate surface C_T over the ocean from climatological SST, S, and NO₃^- fields.

Lee, W.-C., and F.D. Marks. Tropical cyclone kinematic structure retrieved from single Doppler radar observations, Part II: The GBVTD-simplex center finding algorithm. Monthly Weather Review, 128(6):1925-1936 (2000).

This paper is the second of a series and focuses on developing an algorithm to objectively identify tropical cyclone (TC) vorticity centers using single-Doppler radar data. The first paper dealt with the formulation of a single-Doppler radar TC wind retrieval technique, the ground-based velocity-track-display (GBVTD), and the results are verified using analytical TCs. It has been acknowledged that the quality of the GBVTD-retrieved TC circulation strongly depends on accurately knowing its center position. However, existing single-Doppler radar center finding algorithms are limited to estimate centers for axisymmetric TCs. The proposed algorithm uses a simplex method to objectively estimate the TC vorticity center by maximizing GBVTD-retrieved mean tangential wind. When tested with a number of axisymmetric and asymmetric analytical TCs, the accuracy of the TC centers estimated by the GBVTD-simplex algorithm is approximately equal to 340 m from the true center. When adding 5 m s^-1 random noise to the Doppler velocities, the accuracy of the TC centers is nearly unchanged at 350 m. When applying the GBVTD-simplex algorithm to Typhoon Alex (1987), the estimated uncertainty varies between 0.1 and 2 km. When the overall velocity gradient is weak, the uncertainties in the retrieved TC centers are usually large. The GBVTD-simplex algorithm sometimes has problems finding a solution when a large sector of Doppler radar data is missing in conjunction with weak velocity gradients. The GBVTD-simplex algorithm significantly reduces the uncertainties in estimating TC center position compared with existing methods and improves the quality of the GBVTD-retrieved TC circulation. The GBVTD-simplex algorithm is computationally efficient and can be easily adapted for real-time applications.

Lee, W.-C., B. J.-D. Jou, P.-L. Chang, and F.D. Marks. Tropical cyclone kinematic structure retrieved from single-Doppler radar observations. Part III: Evolution and structures of Typhoon Alex (1987). Monthly Weather Review, 128(12):3982-4001 (2000).

This paper is the third of a series that focuses on the applications of the ground-based velocity track display (GBVTD) technique and the GBVTD-simplex center finding algorithm developed in the previous two papers to a real tropical cyclone (TC). The evolution and structure of Typhoon Alex (1987), including full tangential winds, mean radial winds, one component of the mean flow, and their derived axisymmetric angular momentum and perturbation pressure fields are reconstructed from 16 volume scans (6.5 h of data with a 2-h gap) from the Civil Aeronautic Administration (CAA) Doppler radar while Typhoon Alex moved across the mountainous area in northern Taiwan. This analysis retrieves a plausible and physically consistent three-dimensional primary circulation of a landfalling TC using a single ground-based Doppler radar. Highly asymmetric wind structures were resolved by the GBVTD technique where the maximum relative tangential wind at z = 2 km evolved from 52 m s^-1 (before landfall), to less than 40 m s^-1 (after landfall), to less than 35 m s^-1 (entering the East China Sea). Alex's eye began to fill with precipitation while its intensity decreased rapidly after landfall, a characteristic of circulations disrupted by terrain. The mean radial wind field revealed a layer of low-level inflow in agreement with past TC observations. The outward slope of the eyewall reflectivity maximum was consistent with the constant angular momentum contours within the eyewall. After Alex entered the East China Sea, its circulation became more axisymmetric. The axisymmetric perturbation pressure field was retrieved using the gradient wind approximation, which, when used in conjunction with one or more surface pressure measurements within the analysis domain, can estimate the central pressure. The retrieved perturbation pressure fields at two time periods were compared with surface pressures reported in northern Taiwan. Considering the assumptions involved and the influence of terrain, good agreement (only 1V2-mb deviation) was found between them. This agreement indicates the relative quality of the GBVTD-retrieved axisymmetric circulation and suggests GBVTD-retrieved quantities can be useful in operational and research applications.

Lonfat, M., F.D. Marks, and S. Chen. Characterization of the rain distribution in tropical cyclones using TRMM/TMI-PR. AGU 2000 Spring Meeting, Washington, D.C., May 30-June 3, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(19):S237-S238, H42B-16 (2000).

The goals of this study are (1) to improve our understanding of tropical cyclone (TC) precipitation fields by developing a climatology of rainfall distribution and vertical profiles of hydrometeors and heating in TCs around the globe, and (2) to develop methodologies to validate operational and research model forecasts of TC rainfall distribution and structure. Surface rain estimates from the NASA Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR) were used to study the global TC rainfall distribution. From November 1997 to December 1998, 87 storms were observed, providing approximately 1200 events, ranging from tropical storm intensity to category 4 hurricanes. At the time of the satellite measurement, approximately 70% of the events were tropical storms, 25% were category 1-2 hurricanes, and 5% were category 3 or higher. Although the sample size for major hurricanes is smaller than other categories, we have more than 50 observations, which is an order of magnitude larger than previous studies. TMI was used to develop the climatology, as the instrument swath allows a more extended coverage of the storms than PR. For each event, we derive mean rain rates in 10-km rings around the TC center. Averaging these distributions produces rates up to 5 mm h^-1 close to the center. Rain rates decrease rapidly below 1 mm h^-1 by 200 km radius. We examine the rain rate distribution as a function of the storm intensity and geographical location. Close to the storm center, the mean rates are greater than 15 mm h^-1 for category 3 and higher hurricanes, and about 3 mm h^-1 for tropical storms. Rain distributions show strong asymmetries in the rain patterns between the different basins. PR data were used on several individual 1999 storm cases (Floyd and Bret) and compared to TMI distributions. This comparison pointed out a problem in version 4 of the TMI surface rain algorithm. We are also in the process of comparing our TC rain rate distributions with a high-resolution model simulation. Our study provides a broad description of hurricane precipitation distributions, which is of fundamental use as a climatological basis, notably for simulation purpose, and gives a feedback for TRMM/TMI algorithm improvement as well.

Luo, J., P.B. Ortner, D. Forcucci, and S.R. Cummings. Diel vertical migration of zooplankton and mesopelagic fish in the Arabian Sea. Deep-Sea Research, II, 47(7-8):1451-1473 (2000).

Acoustic (153 kHz ADCP and 12 kHz hull-mounted transducers) data and MOCNESS (MOC01 and MOC10) net tow samples collected in the Arabian Sea during the Spring Intermonsoon (April/May) and Southwest Monsoon (August) in 1995 documented substantial diel migrations of fish and zooplankton despite the year-round presence of an oxygen minimum (<0.2 ml l^-1 at 125-150 m). Fish and zooplankton layers were distinguished by comparing 12 kHz sonar and 153 kHz ADCP backscatter data, which indicated that the strongly migrating layers were predominantly composed of fishes. Fish vertical migration speeds were independently estimated from the slopes of the volume scattering layers and from the vertical velocity components of the ADCP, yielding average speeds of 4 and 3 cm s^-1 and maximum speeds of 13 and 10 cm s^-1, respectively. A few migrating zooplankton layers were identified with an average speed of about 2 cm s^-1 and maximum speeds as high as 8 cm s^-1. Migration depths for both zooplankton and fish differed somewhat amongst stations and appeared to be related to local hydrographic conditions (principally the vertical gradients in DO and water temperature). Zooplankton displacement volumes at individual sites suggested that zooplankton biomass during the Southwest Monsoon could be as much as fivefold greater than during the Spring Intermonsoon. This observation was confirmed for the region in general by first deriving a relationship between ADCP backscatter intensity and daytime zooplankton biomass and then comparing the latter between cruises using daytime ADCP data taken along a 1500 km transect that extended from the coast of Somalia to the center of the northern basin.

Mestas-Nuñez, A.M. Orthogonality properties of rotated empirical modes. International Journal of Climatology, 20(12):1509-1516 (2000).

The properties (spatial orthogonality and temporal uncorrelatedness) of orthogonally-rotated empirical modes depend on the normalization of the modes, prior to rotation. It is shown here that these properties also depend on how the empirical modes are formulated. The preferred convention is one that allows us to reconstruct the data from the unrotated or rotated modes. When the empirical modes are normalized so that the spatial eigenvectors are unit length (i.e., EOFs), the rotated modes preserve spatial orthogonality but are no longer temporally uncorrelated. Relaxing the temporal orthogonality in this way does not prejudice conclusions that can be inferred regarding the temporal couplings of the rotated modes.

Mestas-Nuñez, A.M., and D.B. Enfield. El Niño-Southern Oscillation: Canonical and non-canonical aspects. Proceedings, 24th Annual Climate Diagnostics and Prediction Workshop, Tucson, AZ, November 1-5, 1999. National Weather Service, 111-114 (2000).

The main goal of this paper is to investigate and compare the atmospheric signatures associated with the canonical ENSO and residual components of the SST anomaly variability in the eastern tropical Pacific. An expanded version of this paper will appear in the Journal of Climate (Mestas-Nuñez and Enfield, 2001).

Molinari, R.L., and J.F. Festa. Effect of subjective choices on the objective analysis of sea surface temperature data in the tropical Atlantic and Pacific Oceans. Oceanologica Acta, 23(1):3-14 (2000).

Many subjective choices are required to perform an objective interpolation (OI) analysis of environmental variables. Herein, we consider the effects on the statistical analysis of sea surface temperature (SST) using (1) a structure function or covariance analysis, (2) different analytical expressions to represent the statistics of the raw data, and (3) different historical SST data sets. The historical data sets are the well-sampled Comprehensive OceanAtmospheric Data Set (COADS) and the poorly sampled historical expendable bathythermograph (XBT) data set. Results from these analyses are used to generate error maps for a poorly-sampled, two month XBT array and a proposed well-sampled profiling float array. For the relatively data-rich COADS analysis, decorrelation scales are the same using either the structure function or covariance analyses. Results differ for the data-poor XBT analysis. Representative decorrelation scales in the Pacific (Atlantic) are about 11-14 (6-10) degrees in the zonal direction and 4-7 (3-6) degrees in the meridional direction. As COADS SST data are less precise than XBT SST data, error and signal variances are greater for the former. The choice of analytical fit to the raw data (needed to generate error maps) has a dramatic effect on the resulting uncertainty fields. Gaussian fits, because of their parabolic shape near the origin, result in smaller errors than exponential fits for the same observing array. Finally, the proposed float array can achieve the accuracies needed to resolve satisfactory upper layer heat content changes over larger areas than the present XBT network.

Peng, T.-H., and F. Chai. Modeling the carbon cycle in the equatorial Pacific Ocean. Proceedings, Marine Environment: The Past, Present, and Future, Kaohsiung, Taiwan, January 26-28, 1999. Sueichan Press, 240-255 (2000).

An ocean ecosystem model of the equatorial Pacific Ocean has been developed with new and export productivity regulated by Si and Fe to synthesize and to 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. Peilke, Sr. and R. Peikle, Jr. (eds.). Routledge, New York, 196-219 (2000).

No abstract.

Quilfen Y., A. Bentamy, P. Delecluse, K.B. Katsaros, and N. Grima. Prediction of sea level anomalies using ocean circulation model forced by scatterometer wind and validation using TOPEX/Poseidon data. IEEE Transactions on Geoscience and Remote Sensing, 38(4):1871-1884 (2000).

Uncertainties in the surface wind field have long been recognized as a major limitation in the interpretation of results obtained by oceanic circulation models. It is especially true in the tropical oceans, where the response to wind forcing is very strong on short time scales. The purpose of this paper is to show that these uncertainties can be greatly reduced by using spaceborne wind sensors that provide accurate measurements on a global basis. Surface winds over the global oceans have been measured by scatterometry since the launch of the European Remote Sensing Satellite (ERS-1) in August 1991 by the European Space Agency, Noordwijk, The Netherlands, and is currently provided by ERS-2, launched in April 1995. The ground-track wind vectors are processed to compute mean weekly surface winds onto a 1° square grid at the Institut Francais de Recherche pour l'Exploitation de la Mer (IFREMER), Plouzane, France. These winds are validated by comparison with the buoy array in the tropical Pacific Ocean, showing good agreement. In order to further evaluate this wind field, the three-dimensional ocean model OPA7 developed at Laboratoire d'Océanographie Dynamique et de Climatologie, Paris, France, is forced over the tropical oceans by the ERS-derived wind stress fields and by fields from the atmospheric model "Arpege/Climat." Selected ocean parameters are defined in order to validate the ocean model results with measurements of the tropical ocean and global atmosphere (TOGA) buoys in the Pacific Ocean. The ability of the model to describe the short scale (a few weeks to a few years) oceanic variability is greatly enhanced when the satellite-derived surface forcing is used. In this paper, we present further comparison of the ocean model results with the TOPEX-Poseidon altimeter measurements. Simulated and measured sea level variability are described over the three tropical oceans. The annual and semi-annual signals, as well as the interannual variability, partly linked to the El Niño-Southern Oscillation (ENSO) phenomenon, are well simulated by the OPA7 model when the satellite winds are used. Furthermore, it shows that the objective method, kriging technique, used to interpolate the mean ERS wind fields, dramatically reduces the effects of the satellite bandlike sampling. In the last part of this paper, we focus on the relationship between the wind stress anomalies and the sea level anomalies in the case of the 1997-1998 El Niño event. It clearly shows that sea level anomalies in the eastern and western parts of the Pacific are strongly linked to wind stress anomalies in the central Pacific. The forthcoming scatterometers aboard the METOP and ADEOS satellites will provide a much better coverage. It will enable the wind variability spatial and temporal scales to be resolved better, in order that wind uncertainties no longer blur the interpretation of ocean circulation numerical model results.

Reasor, P.D., M.T. Montgomery, F.D. Marks, and J.F. Gamache. Low-wavenumber structure and evolution of the hurricane inner core observed by airborne dual-Doppler radar. Monthly Weather Review, 128(6):1653-1680 (2000).

The asymmetric dynamics of the hurricane inner-core region is examined through a novel analysis of high temporal resolution, three-dimensional wind fields derived from airborne dual-Doppler radar. Seven consecutive composites of Hurricane Olivia's (1994) wind field with 30-min time resolution depict a weakening storm undergoing substantial structural changes. The symmetric and asymmetric mechanisms involved in this transformation are considered separately. To zeroth order the weakening of the primary circulation is consistent with the axisymmetric vortex spindown theory of Eliassen and Lystad for a neutrally-stratified atmosphere. Vertical shear, however, increased dramatically during the observation period, leading to a strong projection of the convection onto an azimuthal wavenumber 1 pattern oriented along the maximum vertical shear vector. Recent theoretical ideas elucidating the dynamics of vortices in vertical shear are used to help explain this asymmetry. The role of asymmetric vorticity dynamics in explaining some of the physics of hurricane intensity change motivates a special focus on Olivia's vorticity structure. It is found that an azimuthal wavenumber 2 feature dominates the asymmetry in relative vorticity below 3-km height. The characteristics of this asymmetry deduced from reflectivity and wind composites during a portion of the observation period show some consistency with a wavenumber 2 discrete vortex Rossby edge wave. Barotropic instability is suggested as a source for the wavenumber 2 asymmetry through a series of barotropic numerical simulations. Trailing bands of vorticity with radial wavelengths of 5-10 km are observed in the inner core approximately 20 km from the storm center, and may be symmetrizing vortex Rossby waves. Elevated reflectivity bands with radial scales comparable to those of the vorticity bands, also near 20-25-km radius, may be associated with these vorticity features.

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, 12 pp. (2000).

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. Surface-based modification of convectively-generated mesovortices and its implications for tropical cyclogenesis. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 151-152 (2000).

Numerical simulations have been performed on a long-lived midlevel mesovortex over the continental United States that was instrumental in initiating and organizing multiple cycles of deep convection. These simulations showed how the cycles of convective redevelopment amplify the mid- to upper-level warm core of the vortex, causing the cyclonic vorticity to strengthen in the midlevels and penetrate down into the lower troposphere, briefly reaching the surface. However, low-level cooling caused by convective and mesoscale downdrafts and adiabatic ascent offsets the impact of the mid- to upper-level warming, limiting the extent to which the cyclonic vorticity penetrates to the surface. In this study the impact of weakening the surface-based cold pool on the structure of the simulated mesovortex is investigated. Methods for weakening the cold pool in the simulations include: eliminating the convective (subgrid-scale) and mesoscale (resolvable-scale) downdrafts and replacing the lower land boundary with a water surface of varying temperatures. The resultant structures of the mesovortex for these different conditions are compared to explain how a mesovortex, with cyclonic vorticity initially confined to the midlevels, can grow downward to the surface, marking a key step in the tropical cyclogenesis process.

Rogers, R.F., J.M. Fritsch, and W.C. Lambert. A simple technique for using radar data in the dynamic initialization of a mesoscale model. Monthly Weather Review, 128(7):2560-2574 (2000).

A simple technique for using radar reflectivity to improve model initialization is presented. Unlike previous techniques, the scheme described here does not infer rain rates and heating profiles from assumed relationships between remotely-sensed variables and precipitation rates. Rather, the radar data are only used to tell the model when and where deep moist convection is occurring. This information is then used to activate the model's convective parameterization scheme in the grid elements where convection is observed. This approach has the advantage that the convective precipitation rates and heating profiles generated by the convective parameterization are compatible with the local (grid element) environment. The premise is that if convection is forced to develop when and where it is observed during a data assimilation period, convectively-forced modifications to the environment will be in the correct locations at the model initial forecast time and the resulting forecast will be more accurate. Three experiments illustrating how the technique is applied in the simulation of deep convection in a warm-season environment are presented: a control run in which no radar data are assimilated, and two additional runs where radar data are assimilated for 12 h in one run and 24 h in the other. The results indicate that assimilating radar data can improve a model's description of the mesoscale environment during the pre-forecast time period, thereby resulting in an improved forecast of precipitation and the mesoscale environment.

Rogers, R.F., S.S. Chen, J.E. Tenerelli, and M. Lonfat. A numerical study of the distribution of precipitation in Hurricane Bonnie (1998). Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 408-409 (2000).

As the damage that accompanied the floods from Hurricanes Georges and Mitch of 1998 and Floyd and Irene of 1999 dramatically highlighted, rainfall is one of the most significant impacts that accompanies a landfalling tropical cyclone. However, quantitative precipitation forecasting (QPF) is one of the most difficult problems in tropical cyclone forecasting. Rainfall measured at a particular location during the landfall of a tropical cyclone depends on many factors, such as the location with respect to the storm's track, the intensity and distribution of rainfall around the storm, the translational speed of the storm, and local effects such as topography and orientation of the coast. Understanding how these and other factors influence the precipitation distribution of landfalling hurricanes is an important step in improving hurricane QPFs. In this study, the distribution of precipitation from Hurricane Bonnie (1998) is explored by performing a numerical simulation using the primitive-equation, nonhydrostatic mesoscale model MM5. A six-day simulation is performed, and precipitation fields from the innermost domain (5-km grid length) are compared against observations. The wealth of observational information that accompanied the third phase of the NASA Convection and Moisture Experiment (CAMEX-3) field program, including the NASA TRMM satellite and various airborne observations from the NOAA P-3's and G-IV and the NASA DC-8 and ER-2, are used to validate the simulation. Statistics related to precipitation distribution, such as radial profiles of rainfall, radial-height profiles of hydrometeors, and probability distributions of various rainfall thresholds, are presented for the simulation and the observations from the TRMM satellite. Validation of these parameters will lend confidence in the skill of the model in capturing the precipitation distribution and enable an investigation of the physical processes governing the distribution to be performed in a later study.

Rogers, R.F., S.D. Aberson, J. Kaplan, S.B. Goldenberg, B. Damiano, R. McNamara, and J. Parrish. Pronounced upper-tropospheric temperature anomalies encountered by the Gulfstream-IV in the vicinity of deep convection. Minutes, 54th Interdepartmental Hurricane Conference, Houston, TX, February 15-18, 2000. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C., 275-279 (2000).

In several instances during the 1999 hurricane season, temperature sensors aboard the NOAA Gulfstream-IV (G-IV) aircraft measured significant temperature increases (some as large as 40°C) while flying between 41,000 and 45,000 feet in the vicinity of deep convection. Similar temperature anomalies have been encountered by commercial aircraft flying at similar altitudes and balloon measurements taken at high temporal frequency in the proximity of deep convection. In this presentation, the observations gathered from the G-IV are summarized and compared to observations taken previously. While it is still not certain whether or not the anomalies measured by the sensors aboard the G-IV last year owed their existence to real meteorological phenomena or to instrument deficiencies, it is important to document this occurrence, since the response of the aircraft's autopilot is to change altitude and airspeed. Suggestions for how to avoid this from happening again are also offered.

Sabine, C.L., R.H. Wanninkhof, R.M. Key, C. Goyet, and F.J. Millero. Seasonal CO₂ fluxes in the tropical and subtropical Indian Ocean. Marine Chemistry, 72(1):33-53 (2000).

Improved estimates of the variability in air-sea CO₂ fluxes on seasonal and interannual time scales are necessary to help constrain the net partitioning of CO₂ between the atmosphere, oceans, and terrestrial biosphere. Few direct measurements of the carbon system have been made in the main Indian Ocean basin. In the mid 1990s, several global carbon measurement programs focused on the Indian Ocean, greatly increasing the existing carbon database for this basin. This study examines the combined surface CO₂ measurements from three major U.S. programs in the Indian Ocean: the global carbon survey cruises, conducted in conjunction with the World Ocean Circulation Experiment (WOCE); the NOAA Ocean-Atmosphere Carbon Exchange Study (OACES) Indian Ocean survey; and the Joint Global Ocean Flux Study (JGOFS) Arabian Sea Process Study. These data are fit with multiparameter linear regressions as a function of commonly-measured hydrographic parameters. These fits are then used with NCEP/NCAR reanalysis and Levitus 94 gridded values to evaluate the seasonal variability of surface seawater CO₂ in the tropical and subtropical Indian Ocean and to estimate the magnitude of the Indian Ocean as a net sink for atmospheric CO₂. The net annual flux for the Indian Ocean (north of 36°S) was -12.4 ± 0.5 × 10¹² mol of carbon (equivalent to -0.15 Pg C) in 1995. The relatively small net flux results from the very different surface water pCO₂ distributions and seasonal variations in the northern and southern Indian Ocean. The equatorial and northern hemisphere regions have values that are generally above atmospheric values. During the southwest monsoon, pCO₂ values in the Arabian Sea coastal upwelling region are among the highest observed in the oceans. The upwelling is seasonal in nature, however, and only affects a relatively small area. The Indian Ocean equatorial region generally has values slightly above atmospheric. Unlike the Pacific and Atlantic Oceans, however, no clear equatorial upwelling signature was observed in 1995. The Southern Hemisphere Indian Ocean, which represents the largest region by area, generally has values below atmospheric. The strongest undersaturations are observed in the austral winter, with summer values reaching near or slightly above atmospheric.

Sabine, C.L., R.A. Feely, R.M. Key, F.J. Millero, R.H. Wanninkhof, T.-H. Peng, A. Kozyr, J.L. Bullister, K. Lee, and M.F. Lamb. Anthropogenic CO₂ distributions in the Pacific. AGU 2000 Fall Meeting, San Francisco, CA, December 15-19, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(48):F692, OS72E-02 (2000).

As a part of the JGOFS synthesis and modeling project, researchers have been working to synthesize the WOCE/JGOFS/NOAA global carbon survey data to better understand carbon cycling in the oceans. Working with international investigators, we have compiled a Pacific Ocean data set with over 36,000 unique sample locations analyzed for at least two carbon parameters. These data are being used to estimate the distribution of anthropogenic CO₂ in the Pacific using the delta-C technique. The physical and geochemical makeup of the Pacific waters, however, poses a particular challenge for the anthropogenic calculations. This measurement-based approach requires a number of assumptions that will be examined with respect to the Pacific. Preliminary estimates of the anthropogenic CO₂ distribution indicate that the largest inventories are in the subtropical South and North Pacific. These distributions will be discussed and compared with three-dimensional global carbon model estimates.

Sabine, C.L., M.F. Lamb, J.L. Bullister, R.A. Feely, G.L. Johnson, R.M. Key, A. Kozyr, K. Lee, F.J. Millero, T.-H. Peng, and R.H. Wanninkhof. U.S. JGOFS team examines Pacific Ocean CO₂ data quality. International WOCE Newsletter, 38:10-14 (2000).

No abstract.

Sainz-Trapaga, S.M., G.J. Goñi, and T. Sugimoto. Identification and variability of the Kuroshio Extension and its northern branch from altimeter and hydrographic data during October 1992-August 1999. AGU 2000 Western Pacific Geophysics Meeting, Tokyo, Japan, June 27-30, 2000. Supplement to EOS, Transactions, American Geophysical Union, 81(22):WP80, OS41A-08 (2000).

The Kuroshio Extension to the east of Japan is an eastward-flowing, meandering jet with current velocities at its core over 100 cm s^-1. This jet presents two quasi-stationary meanders with crests at 144°E and 150°E, and becomes wider and weaker to the east. These and other hydrodynamic modifications along its course can be related to the Shatsky Rise and the Emperor Sea Mounts, the main bathymetric features encountered by the Kuroshio Extension while flowing to the east. The Kuroshio Extension usually bifurcates between 150°E and 165°E, where its northern branch deviates northeastward along the Shatsky Rise approaching the subarctic front. Due to the lack of a long-term and continuous monitoring system, several aspects of the variability at the different regions of the Kuroshio Extension remains unclear. In this work, altimeter-derived sea height anomaly data from November 1992 to August 1999 is combined with climatological hydrographic data within a two-layer reduced gravity ocean model to identify the Kuroshio Extension and its northern branch, to estimate their baroclinic transports, and to study their variabilities, from the Japanese coast to 175°W. Results reveal different patterns of variability to the east and west of 155°E. East of 155°E, the Kuroshio Extension and its northern branch show a clear seasonal cycle. The location of the Kuroshio Extension and its northern branch have both maximum standard deviations from the mean between 150°E and 170°E. This area is characterized by the separation of the northern branch from the Kuroshio Extension. Moreover, the northern branch deviates to the northeast while the main path to the southeast, showing here its lower mean axis position. The location of the Bifurcation Point, partly determined by the bottom topography, correlates also with the Kuroshio Extension axis location and its transport.

Schmid, C., S.L. Garzoli, and R.L. Molinari. The intermediate depth circulation in the tropical Atlantic. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union,80(49):OS44, OS12D-18 (2000).

The intermediate circulation in the interior tropical Atlantic consists, according to the current knowledge, of several narrow zonal currents. Especially south of the equator, many changes of direction have been reported. Due to a lack of data, this flow pattern is only poorly resolved in space and time. Recent observations, both during the mid-1997 Seward Johnson cruise and from PALACE trajectories which extend from mid-1997 to today, allow a more detailed description of the intermediate depth circulation in the tropical Atlantic. The PALACE floats indicate that the intermediate layer flow between the equator and about 4°N consists of two different regimes which are separated by the eastern edge of the Mid-Atlantic Ridge. Velocities in the eastern regime are lower. The zonal flow in the two regimes is going in opposite directions at certain latitudes. We will discuss how the different regimes are related to the water masses and the interbasin exchange. Further south, between 4° and 2°S, westward velocities are clearly dominating the circulation. This latitude range is often occupied by the central South Equatorial Current. The flow between 8° and 4°S is governed by short periods (up to several months) of flow towards the east or west with only weak preferences of either one of the directions. This region is characterized by the (meandering) transition between the central South Equatorial Current and the South Equatorial Countercurrent. It has been proposed earlier that these two currents do not extend beyond about 8°W and that the intermediate water follows a cyclonic path east of 10°W between about 5° and 25°S. This could be seen as an intermediate expression of the Angola Gyre. Such a circulation is not visible in the PALACE trajectories to date.

Schmid, C., G. Siedler, and W. Zenk. Dynamics of intermediate water circulation in the subtropical South Atlantic. Journal of Physical Oceanography, 30(12):3191-3211 (2000).

The circulation of the low-salinity Antarctic Intermediate Water in the South Atlantic and the associated dynamical processes are studied, using recent and historical hydrographic profiles, Lagrangian and Eulerian current measurements as well as wind stress observations. The circulation pattern inferred for the Antarctic Intermediate Water supports the hypothesis of an anticyclonic basin-wide recirculation of the intermediate water in the subtropics. The eastward current of the intermediate anticyclone is fed mainly by water recirculated in the Brazil Current and by the Malvinas Current. An additional source region is the Polar Frontal Zone of the South Atlantic. The transport in the meandering eastward current ranges from 6 Sv to 26 Sv (1 Sv = 10⁶ m³ s^-1). The transport of the comparably uniform westward flow of the gyre varies between 10 Sv and 30 Sv. Both transports vary with longitude. At the western boundary near 28°S, in the Santos Bifurcation, the westward current splits into two branches. About three quarters of the 19 Sv at 40°W go south as an intermediate western boundary current. The remaining quarter flows northward along the western boundary. Simulations with a simple model of the ventilated thermocline reveal that the wind-driven subtropical gyre has a vertical extent of over 1200 m. The transports derived from the simulations suggest that about 90% of the transport in the westward branch of the intermediate gyre and about 50% of the transport in the eastward branch can be attributed to the wind-driven circulation. The structure of the simulated gyre deviates from observations to some extent. The discrepancies between the simulations and the observations are most likely caused by the interoceanic exchange south of Africa, the dynamics of the boundary currents, the nonlinearity, and the seasonal variability of the wind field. A simulation with an inflow/outflow condition for the eastern boundary reduces the transport deviations in the eastward current to about 20%. The results support the hypothesis that the wind field is of major importance for the subtropical circulation of Antarctic Intermediate Water followed by the interoceanic exchange. The simulations suggest that the westward transport in the subtropical gyre undergoes seasonal variations. The transports and the structure of the intermediate subtropical gyre from the Parallel Ocean Climate Model (Semtner/Chervin model) agree better with observations.

Shay, L., G.J. Goñi, and P.G. Black. Effects of a warm oceanic feature on Hurricane Opal. Monthly Weather Review, 128(5):1366-1383 (2000).

On 4 October 1995, Hurricane Opal deepened from 965 to 916 hPa in the Gulf of Mexico over a 14-h period upon encountering a warm core ring (WCR) in the ocean shed by the Loop Current during an upper-level atmospheric trough interaction. Based on historical hydrographic measurements placed within the context of a two-layer model and surface height anomalies (SHA) from the radar altimeter on the TOPEX mission, upper-layer thickness fields indicated the presence of two warm core rings during September and October 1995. As Hurricane Opal passed directly over one of these WCRs, the 1-min surface winds increased from 35 to more than 60 m s^-1, and the radius of maximum wind decreased from 40 to 25 km. Pre-Opal SHAs in the WCR exceeded 30 cm where the estimated depth of the 20°C isotherm was located between 175 and 200 m. Subsequent to Opal's passage, this depth decreased approximately 50 m, which suggests upwelling underneath the storm track due to Ekman divergence. The maximum heat loss of approximately 24 Kcal cm^-2 relative to depth of the 26°C isotherm was a factor of 6 times the threshold value required to sustain a hurricane. Since most of this loss occurred over a period of 14 h, the heat content loss of 24 Kcal cm^-2 equates to approximately 20 kW m^-2. Previous observational findings suggest that about 10%-15% of upper-ocean cooling is due to surface heat fluxes. Estimated surface heat fluxes based upon heat content changes range from 2000 to 3000 W m^-2 in accord with numerically simulated surface heat fluxes during Opal's encounter with the WCR. Composited AVHRR-derived SSTs indicated a 2°-3°C cooling associated with vertical mixing in the along-track direction of Opal except over the WCR where AVHRR-derived and buoy-derived SSTs decreased only by about 0.5°-1°C. Thus, the WCR's effect was to provide a regime of positive feedback to the hurricane rather than negative feedback induced by cooler waters due to upwelling and vertical mixing as observed over the Bay of Campeche and north of the WCR.

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, 26 pp. (2000).

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).

Tenerelli, J.E., S.S. Chen, M. Lonfat, R. Foster, and R.F. Rogers. Surface winds in Hurricane Floyd: A comparison between numerical simulations, aircraft data, and QuikScat satellite data. Preprints, 24th Conference on Hurricanes and Tropical Meteorology, Ft. Lauderdale, FL, May 29-June 2, 2000. American Meteorological Society, Boston, 418-419 (2000).

A principal benefit of numerical simulations of hurricanes is that they provide detailed, high-resolution information on the structure and evolution of the atmosphere that cannot be obtained through current observational techniques. However, simulations can be strongly dependent on the initial and boundary data, as well as on the physical parameterizations in the numerical model, and so it is necessary to compare simulation results with observational data when available. The objectives of this study are to: (1) validate model simulations of Hurricane Floyd with all available observations, including in-situ and remote sensing data sets; and (2) explore the impact of the observations on high-resolution model simulations. One important aspect of the model simulations is the surface wind field. The surface wind has a substantial impact on the fluxes of heat and moisture at the surface, which in turn have a large influence on the storm intensity and structure. Yet, near the surface, the model results are influenced greatly by the parameterization of boundary layer and surface processes. Hurricane Floyd presents an excellent opportunity for model-observation intercomparison of winds near the surface. Several swaths of data from NASA's QuikScat satellite were obtained while Floyd was over water. Additionally, surface winds derived from NOAA/HRD aircraft observations were obtained at several times during the life of the storm. In this study, we conduct a four-day long simulation of Floyd using the PSU/NCAR nonhydrostatic mesoscale model (MM5) with one fixed mesh and two levels of moving nested grid. We compare surface winds derived from QuikScat and aircraft data to the surface winds in our numerical simulation of Floyd. Additionally, we compare vertical profiles of reflectivity and hydrometeors from the simulations with those derived from the TMI and PR instruments on NASA's TRMM satellite. Although the TRMM swaths, the QuikScat swaths, and HRD data are not coincident in time, the MM5 simulations' continuity in time allows a comparison with all observational data sources. The MM5 can be used as a cross-validation platform. This model-observation comparison is the first step towards the goal of assimilating observed surface winds into the MM5.

Wainer, I., P. Gent, and G.J. Goñi. Annual cycle of the Brazil-Malvinas confluence region in the National Center for Atmospheric Research climate system model. Journal of Geophysical Research, 105(C11):26,167-26,177 (2000).

The objective of this study is to compare the mean and seasonal variability of the circulation in the southwest Atlantic with observations. The results used in the comparison are from the last 200 years of a 300-year control integration of the Climate System Model (CSM). The area of study includes the confluence region between the subtropical and subpolar waters represented by the Brazil and Malvinas Currents. The seasonal variation of transport and its relationship to changes in the wind stress forcing and in the sea surface temperature are examined and compared to available oceanographic observations. This study shows that a coarse resolution climate model, such as the CSM, can successfully reproduce major characteristics of the Brazil-Malvinas confluence seasonality, although the mesoscale features involving recirculation and meander dynamics are not resolved. The CSM transport values in the region of 38°S are consistent with hydrographically-derived values. The transport of the CSM Brazil Current is higher during austral summer and smaller during austral winter. Conversely, the Malvinas Current transport is weaker during austral summer and stronger during austral winter. This is also consistent with observations. The CSM seasonal cycle in transport associated with both the Brazil and Malvinas Currents and its meridional displacement is closely linked to the seasonal variations in the local wind stress curl. However, the displacement is much smaller in the model than in observations. The CSM results show that the latitudinal displacement of the 24°C and 17°C at the South American coast between austral summer and winter is 20° and 12°, respectively. This is very similar to the displacement seen in observations.

Wang, C. A unified theory for the El Niño-Southern Oscillation. Proceedings, 10th Conference on Interaction of the Sea and Atmosphere, Ft. Lauderdale, Florida, May 29-June 2, 2000. American Meteorological Society, Boston, J42-J43 (2000).

No abstract.

Wang, C. On the atmospheric responses to tropical Pacific heating during the mature phase of El Niño. Journal of Atmospheric Sciences, 57(22):3767-3781 (2000).

The atmospheric heating and sea surface temperature (SST) anomalies during the mature phase of El Niño are observed to show both eastern and western Pacific anomaly patterns, with positive anomalies in the equatorial eastern/central Pacific and negative anomalies in the off-equatorial western Pacific. The detailed spatial patterns of the heating anomalies differ from the SST anomalies. The heating anomalies are more equatorially confined than the SST anomalies, and maxima of positive and negative heating anomalies are located farther to the west than the SST anomalies. The Gill/Zebiak atmospheric model assumes that the atmospheric initial heating has the same spatial patterns as the SST anomalies. This assumption results in some unrealistic model simulations for El Niño. When the model heating anomaly forcing is modified to resemble the observed heating anomalies during the mature phase of El Niño, the model simulations have been improved to: (1) successfully simulate equatorial easterly wind anomalies in the western Pacific; (2) correctly simulate the position of maximum westerly wind anomalies; and (3) reduce unrealistic easterly wind anomalies in the off-equatorial eastern Pacific. This paper shows that off-equatorial western Pacific negative atmospheric heating (or cold SST) anomalies are important in producing equatorial easterly wind anomalies in the western Pacific. These off-equatorial cold SST anomalies in the western Pacific also contribute to equatorial westerly wind anomalies observed in the central Pacific during the mature phase of El Niño. Although off-equatorial cold SST anomalies in the western Pacific are smaller than equatorial positive SST anomalies in the eastern Pacific, they are enough to produce atmospheric responses of comparable magnitude to the equatorial eastern Pacific. This is because the atmospheric mean state is convergent in the western Pacific and divergent in the equatorial eastern Pacific. By either removing the atmospheric mean convergence or removing off-equatorial cold SST anomalies in the western Pacific, the atmospheric responses show no equatorial easterly wind anomalies in the western Pacific. In the Gill/Zebiak model, the mean wind divergence field is an important background state, whereas the mean SST is secondary.

Wang, C. The El Niño-Southern Oscillation. Proceedings, International Conference on Climate and Environment Variability and Predictability, Shanghai, China, August 7-11, 2000. International Commission on Dynamic Meteorology/International Association of Meteorology and Atmospheric Sciences, 126 (2000).

No abstract.

Wang, C., and R.H. Weisberg. The 1997-1998 El Niño evolution relative to previous Niño events. Journal of Climate, 13(2):488-501 (2000).

The evolution of the 1997-1998 El Niño is described using NCEP sea surface temperature (SST) and outgoing longwave radiation (OLR) data, NCEP-NCAR reanalysis sea level pressure (SLP) fields, and FSU surface wind data. From November 1996 to January 1997, the eastern Pacific is characterized by equatorial cold SST and high SLP anomalies, while the western Pacific is marked by off-equatorial warm SST anomalies and off-equatorial anomalous cyclones. Corresponding to this distribution are high OLR anomalies in the equatorial central Pacific and low OLR anomalies in the off-equatorial far western Pacific. The off-equatorial anomalous cyclones in the western Pacific are associated with a switch in the equatorial wind anomalies over the western Pacific from easterly to westerly. These equatorial westerly anomalies then appear to initiate early SST warmings around the date line in January/February 1997 and around the far eastern Pacific in March 1997. Subsequently, both the westerly wind and warm SST anomalies, along with the low OLR anomalies, grow and progress eastward. The eastward propagating warm SST anomalies merge with the slower westward spreading warm SST anomalies from the far eastern Pacific to form large-scale warming in the equatorial eastern and central Pacific. The anomaly patterns in the eastern and central Pacific continue to develop, reaching their peak values around December 1997. In the western Pacific, the off-equatorial SST anomalies reverse sign from warm to cold. Correspondingly, the off-equatorial SLP anomalies in the western Pacific also switch sign from low to high. These off-equatorial high SLP anomalies initiate equatorial easterly wind anomalies over the far western Pacific. Like the equatorial westerly wind anomalies that initiate the early warming, the equatorial easterly wind anomalies over the far western Pacific appear to have a cooling effect in the east and, hence, help facilitate the 1997-1998 El Niño decay. The paper also compares the 1997-1998 El Niño with previous warm events, and discusses different ENSO mechanisms relevant to the 1997-1998 El Niño.

Wilson, W.D., and K.D. Leaman. The NOPP Year of the Ocean drifter program: A new Lagrangian perspective on IAS circulation. AGU 2000 Ocean Sciences Meeting, San Antonio, TX, January 24-28, 2000. Supplement to EOS, Transactions, American Geophysical Union, 80(49):OS234, OS41E-24 (2000).

Since March of 1998, 130 "WOCE-type" drifting buoys, drogued at 15 m, have been launched in the Gulf of Mexico and the Caribbean Sea and its approaches, providing in excess of 15,000 "drifter days" of data to date. Buoys were provided by the U.S. National Ocean Partnership Program (NOPP); launch coordination was provided by scientists at NOAA/AOML and UM/RSMAS; and logistical and data processing support was provided by the NOAA/AOML Global Drifter and Data Assembly Centers. Buoys were launched with the cooperation of commercial ships, the Colombian Navy, the U.S. Coast Guard, and research vessels working in the region. Drifter track figures and data have been made available in real time via the World-Wide Web at www.IASlinks.org and www.drifters.doe.gov. Repeated launches were concentrated in three areas: The Panama-Colombia gyre in the southwest Caribbean; the island passages in the eastern Caribbean; and in the North Brazil Current rings, a primary source of mesoscale variability upstream of the Caribbean. This strategy was designed to maintain maximum coverage within the IAS, as well as study propagation of variability through the region, the formation and intensification of the Caribbean Current, and the structure and permanence of the circulation within the Panama-Colombia gyre. Individual drifter tracks are shown which illustrate pathways and time scales of connectivity within the region. There is also sufficient data coverage to estimate fields of mean velocity, velocity variability, and several different indicators of dispersal. Drifter-derived fields are compared to existing estimates of mean velocity (ship drift, climatological, geostrophic, and Ekman estimates) and variability (ship drift, altimetry). Discussion will focus on the usefulness of Lagrangian measurements for larval and other transport studies, and diagnostics of the large-scale IAS circulation field. A companion presentation by Leaman and Wilson will focus on drifters in the Panama-Colombia Gyre and comparison with the high-resolution MICOM model. The merits of a cooperative plan for maintaining long-term drifter coverage of the IAS will be considered.

Wilson, W.D., and K.D. Leaman. Transport pathways through the Caribbean: The tropical origins of the Gulf Stream. Current, 16(1):14-18 (2000).

No abstract.

Yvon-Lewis, S.A. Methyl bromide in the atmosphere and ocean. IGACtivities Newsletter, 19:9-12 (2000).

No abstract.

Zhang, J.-Z. Shipboard automated determination of trace concentrations of nitrite and nitrate in oligotrophic water by gas-segmented continuous flow analysis with a liquid waveguide capillary flow cell. Deep-Sea Research, Part I, 47(6):1157-1171 (2000).

Incorporation of a liquid waveguide capillary flow cell to a gas-segmented continuous flow auto-analyzer significantly enhances the sensitivity of automated colorimetric analysis. Nanomolar concentrations of nitrite and nitrate in oligotrophic surface seawater can be accurately determined. The advantages of this technique are low detection limit, high precision, and automation for rapid analysis of a large number of samples. This technique has been successfully used on shipboard measurements of about 1000 seawater samples during a one-month cruise in North Atlantic.

Zhang, J.-Z. The use of pH and buffer intensity to quantify the carbon cycle in the ocean. Marine Chemistry, 70(1-3):121-131 (2000).

The pH of seawater is governed by the content of total carbon dioxide and ionic equilibra between hydrogen ions and various inorganic carbon species in seawater. Buffer intensity is defined as a measure of the ability of seawater to accommodate the addition of acid or base without appreciable pH change. It can be calculated from pH and total carbon dioxide of seawater. pH data in conjunction with buffer intensity can be used to quantify the carbon cycle in the ocean. The total amount of acid that has been released or consumed by any biogeochemical processes can be calculated from the change in pH multiplied by buffer intensity of seawater, dC_H = d(beta-pH). This approach has been used to quantify the remineralization process in the Antarctic Intermediate Water in the South Pacific. Based on the observational data (pH, total carbon dioxide, O₂, and nutrient measurements on P18 cruise), calculated elemental remineralization ratios are 173, 107, and 14.3 for O/P, C/P and N/P, respectively. The dissolution of calcium carbonate accounts for 21.5% of carbon increased from the remineralization in the Antarctic Intermediate Water.

Zhang, J.-Z., and C.R. Kelble. Gas-segmented continuous flow analysis of iron in water with a long liquid waveguide capillary flow cell. Proceedings, 8th International Conference on Flow Analysis, Warsaw, Poland, June 25-29, 2000. International Union of Pure and Applied Chemistry, 107 (2000).

A long liquid waveguide capillary flow cell has been successfully adapted into a gas-segmented continuous flow auto-analyzer for trace analysis of iron. The flow cell was made of a new material, Teflon AF-2400, that has a refractive index (1.29) lower than water (1.33). Total reflection of light can be achieved when the light beams intersect the water/AF-2400 Teflon tubing interfaces at greater than critical angle. Teflon AF-2400 is superior to currently used materials in both refractivity and mechanical stability. This allows the construction of a long liquid waveguide capillary flow cell in helical, rather than linear shape, with compact dimension. Small sample volumes are required since the internal volume of a 2 m-long liquid waveguide capillary flow cell with 550 µm ID is only approximately 0.5 cm³. According to the Lambert-Beer law, the absorbance of a sample in spectrophotometry is proportional to the light path length in the flow cell. Utilization of this long flow cell significantly enhances the sensitivity of automated colorimetric analysis of iron by the ferrozine method. Nanomolar concentrations of iron in natural water can be accurately determined. The advantages of this technique are low detection limit, small sample volume, high precision, and automation for rapid analysis of a large number of samples. This technique has potential application in many spectrophotometric detections to augment the capability of gas-segmented continuous flow analysis and flow injection analysis.

Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Comparison of open tubular cadmium reactors and packed cadmium columns in automated gas-segmented continuous flow nitrate analysis. International Journal of Environmental Analytical Chemistry, 76(2):99-113 (2000).

Detailed procedures are provided for preparing packed cadmium columns to reduce nitrate to nitrite. Experiments demonstrated the importance of conditioning both open tubular cadmium reactor (OTCR) and packed copper-coated cadmium columns to achieve 100% reduction efficiency. The effects of segmentation bubbles in the OTCR upon reduction efficiency and baseline noise in nitrate analysis are investigated using an auto-analyzer. Metal particles derived from segmentation bubbles in OTCR result in i nterference with continuous flow analyses. Therefore, packed columns are recommended for determination of low level nitrate in natural waters.

Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. New production in oligotrophic waters: Estimation based on diel cycle of nitrate. Proceedings, Joint Global Ocean Flux Study (JGOFS) Open Science Conference, Bergen, Norway, April 13-17, 2000. JGOFS International Project Office, 76-77 (2000).

New production can be estimated from accurate measurements of inventory change in nitrate at nM levels in the photic zone. A strong diel cycle was observed in nitrate concentrations in response to photosynthesis in the eastern North Atlantic during the GASEX-98 cruise. During a diel study, nitrate concentration was 92 nM in the morning and decreased to 12 nM by 6 p.m. It increased after dark, presumably due to the diffusive flux from the nitracline. Oxygen showed a similar diel cycle with a change in concentration of about 2 µM. The vertical eddy diffusivity was derived from temporal changes in concentrations of a deliberate tracer, SF6, below the mixed layer. Together with vertical nitrate distributions, the nitrate flux from nitracline throughout the nighttime can account for a nitrate concentration of 102 nM by morning, which is in good agreement with measured nitrate of 92 nM at 6 a.m. The new production estimated from changes of nitrate inventory in the photic zone during the day was 28 mmole C/m² d. Increases in the mixed layer nitrate were observed during storm events that deepened the mixed layer and brought the nitrate to the surface. The storm-induced nitrate disappeared within two days, indicating a rapid uptake by phytoplankton. The relative importance of sporadic storm events versus daily diffusive flux in supply nitrate to new production can be estimated based on nitrate inventory changes in the photic zone.

Zhang, J.-Z., C.W. Mordy, L.I. Gordon, A. Ross, and H.E. Garcia. Temporal trends in deep ocean Redfield ratios. Science, 289:1839 (2000).

No abstract. **1999**

Aberson, S.D. Ensemble-based products to improve tropical cyclone forecasting. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 843-844 (1999).

No abstract.

Aberson, S.D. Targeting and sampling strategies to improve hurricane forecasts. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 105-107 (1999).

No abstract.

Aberson, S.D., and J.L. Franklin. Impact on hurricane track and intensity forecasts of GPS dropwindsonde observations from the first-season flights of the NOAA Gulfstream-IV jet aircraft. Bulletin of the American Meteorological Society, 80(3):421-428 (1999).

In 1997, the Tropical Prediction Center (TPC) began operational Gulfstream-IV jet aircraft missions to improve the numerical guidance for hurricanes threatening the continental United States, Puerto Rico, and the Virgin Islands. During these missions, the new generation of Global Positioning System dropwindsondes were released from the aircraft at 150-200-km intervals along the flight track in the environment of the tropical cyclone to obtain profiles of wind, temperature, and humidity from flight level to the surface. The observations were ingested into the global model at the National Centers for Environmental Prediction, which subsequently served as initial and boundary conditions to other numerical tropical cyclone models. Because of a lack of tropical cyclone activity in the Atlantic basin, only five such missions were conducted during the inaugural 1997 hurricane season. Due to logistical constraints, sampling in all quadrants of the storm environment was accomplished in only one of the five cases during 1997. Nonetheless, the dropwindsonde observations improved mean track forecasts from the Geophysical Fluid Dynamics Laboratory hurricane model by as much as 32%, and the intensity forecasts by as much as 20% during the hurricane watch period (within 48 h of projected landfall). Forecasts from another dynamical tropical cyclone model (VICBAR) also showed modest improvements with the dropwindsonde observations. These improvements, if confirmed by a larger sample, represent a large step toward the forecast accuracy goals of TPC. The forecast track improvements are as large as those accumulated over the past 20-25 years, and those for forecast intensity provide further evidence that better synoptic-scale data can lead to more skillful dynamical tropical cyclone intensity forecasts.

Albrecht, B., T. Faber, A. Savtchenko, D. Churchill, F.D. Marks, and P.G. Black. Surface-based remote sensing of a landfalling tropical storm. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 489-492 (1999).

No abstract.

Alvarez-Zarikian, C., P.L. Blackwelder, T. Hood, T.A. Nelsen, and C.M. Featherstone. A century of hydrological variability in the lower Everglades National Park as interpreted from stable isotopes on ostracods and foraminifers. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 198 (1999).

Stable isotopic analysis of selected ostracods and foraminifers were carried out from high-resolution sediment cores collected from Oyster and Florida Bays. The core localities provide distinctive environmental conditions in which the effects of freshwater runoff, rainfall, and, consequently, salinity, can be assessed. Oyster Bay lies at the end of the Shark River Slough and is an area that experiences extreme salinity fluctuations due to the interaction between freshwater runoff and marine water input from the Gulf of Mexico due to tidal flow. A second core, collected near Jimmy Key, in the center of Florida Bay, provides a contrasting salinity history in which salinity has remained close to marine during this century. Stable isotope (¹³C, ¹⁸O) trends of ostracods and foraminifers at Oyster Bay and Jimmy Key suggest a general transition to more saline conditions over this time period. Relative abundance of salinity-sensitive species confirmed this observations. Moreover, stable isotopes indicate an increase in salinity variability over time, which is represented in the microfaunal assemblage by survivor-mode dominance by highly-tolerant species, both in foraminifers and ostracods, that occurred during a period of drought or highly evaporative conditions during the mid to late 1980s that also lead to reduced flow from Shark River Slough. Fluctuations on stable isotope values appeared to be more a direct response to regional rainfall than freshwater runoff; however, distinct patterns can be temporally correlated to freshwater management strategies by the South Florida Water Management District.

Alvarez-Zarikian, C., T. Hood, P. Blackwelder, T.A. Nelsen, P. Swart, H. Wanless, J. Trefry, and W.-J. Kang. Paleoecological significance of temporal fluctuations in assemblages and isotopic composition of ostracoda and foraminifera from Florida Bay. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. EOS, Transactions, American Geophysical Union, 80(17):S178, OS31A-17 (1999).

Microfaunal populations and stable isotopic analysis of selected ostracods and benthic foraminifers were examined from high-resolution sediment cores in the lower Everglades/Florida Bay ecosystem. Microfaunal characteristics and population fluctuations can be temporarily related to forces of natural (hurricanes, precipitation) and anthropogenic (historic practices from the South Florida Water Management District [SFWMD]) origin since the turn of the century. Dramatic shifts in community structure are observed in both microfaunal groups and are represented by major swings in species diversity and dominance, and total loss of numerous species. Before the 1960s, significant crashes in the community structure of both groups were temporally correlated with major hurricanes, but fairly rapid recoveries indicate a relatively resilient community. Community changes during the 1970s were most systematic, and temporally correlate with changes in SFWMD policy. In Oyster Bay, the 1970s Monthly Water Allocation Plan corresponds to a boom period for ostracods and benthic foraminfers possibly due to a more efficient water flow and exchange. This is followed by a dramatic crash in both groups corresponding to the start of the SFWMD's Rainfall Plan and the closing of the Buttonwood Canal in the early 1980s, from which neither community has recovered. Sediment cores from Oyster Bay and near Jimmy Key in Florida Bay show a reduction in the number of species and a pronounced dominance of survivor-type species since that time. delta-180 data from ostracods and foraminifers shift to heavier values during this period, indicating drought conditions. Microfaunal and isotopic data from this study complemented with an analysis of historical rainfall, gauged freshwater flow, and limited near-shore salinity data show a significant increase in the magnitude and range of seasonal salinity variability due to fluctuations in regional rainfall and the current water management plan, resulting in significantly drier conditions in the lower portion of Shark River Slough.

Amat, L.R., M.D. Powell, and S.H. Houston. A real-time, Internet-based application for the archival, quality control, and analysis of hurricane surface wind observations. Preprints, 15 International Conference on Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 573-576 (1999).

No abstract.

Ataktürk, S.S., and K.B. Katsaros. Wind stress and surface waves observed on Lake Washington. Journal of Physical Oceanography, 29(4):633-650 (1999).

New results from turbulent flux measurements made over Lake Washington include the following:

(1) The only direct measure of the vertical transport of the horizontal momentum, heat, and matter in the surface boundary layer is the so-called eddy correlation method. However, even if the measurement errors are negligible, the results obtained from point observations may show large scatter due to lack of stationarity and horizontal homogeneity in the turbulent field and to the sampling variability. Scatter may be greatly reduced by spatial averaging. In this study, such an effect is achieved by determining the surface roughness length; hence, the neutral drag coefficient from the measured wave height spectrum, which reflects the atmospheric input integrated over the fetch. Applicability and usefulness of the approach for general field measurements and remote sensing is discussed.

(2) The evolution of the wave field observed on Lake Washington agrees in peak frequency and the slope of the equilibrium range parameter as a function of "wind forcing" with other observations, while the magnitude is significantly smaller (by a factor of 2.1) than the values obtained from larger bodies of water. Based on the results obtained from a wave model, we attribute this observed difference to the narrower width of the water body on Lake Washington. These findings indicate that the state-of-the-art spectral parameterization of surface waves has limitations in describing the observations from a natural but small body of water.

Baringer, M.O., and R.L. Molinari. Atlantic Ocean baroclinic heat flux at 24-26°N. Geophysical Research Letters, 26(3):353-356 (1999).

The spatially varying, interior geostrophic baroclinic heat flux component of the total meridional oceanic heat flux near 24°N in the Atlantic Ocean is examined using four transatlantic hydrographic sections including the October 1957 Discovery II IGY section, the September 1981 Atlantis section, the August 1992 Hesperides section, t he February 1998 Ronald H. Brown section and the 1982 Levitus and the Lozier, Owens, Curry climatologies. The 1992 section is complemented by shorter western boundary sections obtained concurrently during the Trident cruise. We find an average southward baroclinic heat flux of 0.9 0.3 PW with an annual cycle amplitude of 0.3 PW. More than 90% of the annual cycle is captured within 30° of the western boundary.

Baringer, M.O., and J.F. Price. A review of the physical oceanography of the Mediterranean Outflow. Marine Geology, 155(1-2):63-82 (1999).

The physical oceanography of the Mediterranean Sea is reviewed with particular emphasis on the Mediterranean outflow in the Gulf of Cadiz. In this region the dense Mediterranean water forms a high velocity bottom current that interacts strongly with the sea floor. The major energy source for the plume comes from the release of potential energy as the plume descends the continental slope, and the major energy sink is work against bottom stress, which is as large as 4 Pa where the plume begins to descend the continental slope. In this region the current makes a nearly inertial turn that would otherwise appear to be steered by the underlying topography. The Mediterranean plume entrains the overlying North Atlantic Central Water and thereby loses much of its density anomaly. The mixed Mediterranean water becomes neutrally buoyant in the lower portion of the North Atlantic thermocline near Cape St. Vincent. There are then two preferred transport modes having somewhat different temperature and salinity whose distinct characteristics can be found far into the open North Atlantic. The temperature, salinity and volume of the Mediterranean water in the Strait of Gibraltar and in the Gulf of Cadiz appear to be roughly constant since modern measurements have been made. The estimated westward transport of Mediterranean water has gone down considerably as direct measurement techniques have been applied. A recent estimate is that the westward transport of pure Mediterranean water is only about a half a Sv (1 Sv = 10⁶ m³/s); the transport of mixed Mediterranean water in the western Gulf of Cadiz is larger by about a factor of three or four because of the entrainment of North Atlantic water.

Bentamy, A.P., P. Queffeulou, Y. Quilfen, and K.B. Katsaros. Ocean surface wind fields estimated from satellite active and passive microwave instruments. IEEE Transactions on Geoscience and Remote Sensing, 37(5):2469-2486 (1999).

This study examines the consistency of surface wind speeds estimated from the European Remote Sensing Satellite (ERS-1) scatterometer, ERS-1 altimeter, and the special sensor microwave/imager (SSM/I). The goal is to combine these wind estimates to produce surface wind fields. With this in mind, a comparison with buoy wind measurements and comparison among the three sensors is performed. According to the in-situ data, the rms errors of the three wind estimates are all within 2 m/s. The differences between the remotely-sensed and buoy wind speeds are studied according to atmospheric and oceanic variables, and their impact is shown. A large data base is obtained from the comparisons among the three sensor winds. The rms values of the differences between the scatterometer and the altimeter and between the scatterometer and the SSM/I are 1.67 and 1.45 m/s, respectively. There is no global bias between the scatterometer and the SSM/I, but between the scatterometer and the altimeter wind speeds, the bias is about 0.3 m/s. Furthermore, it is shown that the difference between the scatterometer and the altimeter wind estimates is dependent on the significant wave height, while the difference between the scatterometer and the SSM/I winds is dependent on the integrated water vapor content. The comparison enables some corrections to be made for consistency and combining products. The use of combining scatterometer, altimeter, and SSM/I wind estimates is illustrated by two examples.

Berberian, G.A., and A.Y. Cantillo. Oceanographic conditions in the Gulf of Mexico and Straits of Florida: Fall 1976. NOAA Data Report, OAR AOML-36 (PB2000-106209), 64 pp. (1999).

NOAA conducted an investigation in the Gulf of Mexico and the Straits of Florida of oceanographic conditions and nutrients and trace metal levels in seawater during September and October 1976 aboard the NOAA Ship Researcher. This report lists the chemical data obtained from 118 stations. Collection and analyses methodologies, as well as results, are described.

Bishop, C.H., S. Majumdar, I. Szunyogh, Z. Toth, and S.D. Aberson. Using ensembles to simulate the impact of targeted observations. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 117-118 (1999).

No abstract.

Black, M.L. Recent observations of the hurricane eyewall: Unusual and complex structure. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 313-316 (1999). No abstract.

Black, M.L., and J.L. Franklin. Recent observations of the convective structure associated with low-level wind maxima in the hurricane eyewall. Preprints, 29th International Conference on Radar Meteorology, Montreal, Quebec, Canada, July 12-16, 1999. American Meteorological Society, Boston, 370-373 (1999).

No abstract.

Black, R.A., and J. Hallett. Electrification of the hurricane. Journal of the Atmospheric Sciences, 56(12):2004-2028 (1999).

A survey of reports of electrical activity in hurricanes and typhoons from flight notes and personal experience (18 years, >230 eyewall penetrations for R. A. Black; ~20 years for J. Hallett, plus that of others at the Hurricane Research Division), and perusal of flight notes dating from 1980, show that lightning in and within 100 km or so of the eyewall is usually sparse. However, occasionally, significant electrical activity (>one flash per minute) occurs in or near the eyewall. National Oceanic and Atmospheric Administration WP-3D aircraft penetrations through a number of storms relate the lightning occurrence to strong vertical velocity (>10 m s^-1) and the presence of supercooled liquid cloud droplets extending to temperatures below 20°C. Specific measurements of cloud properties during eyewall penetrations show that the supercooled cloud water content increases with upward velocities > ~5.0 m s^-1, as does the presence of large (>2 mm) supercooled drops. Measurements at temperatures >-13°C show that the transition of supercooled cloud water to ice along an outward radial in all systems is associated with local electric fields (occasionally >20 kV m^-1) and negative charge above positive charge. In systems with stronger vertical velocity there is a larger region of supercooled cloud extending to lower temperatures where charge separation may occur, as judged by the presence of regions containing graupel, small ice, and cloud droplets. The ratio of ice to supercooled water increases radially outward from the eyewall and depends upon altitude (temperature). The spatial distribution of charge is further influenced by the relation of vertical velocity to the radial flow, with the upper charge regions tending to be advected outward. In symmetrical, mature hurricanes, supercooled water usually occurs only in regions at temperatures above about -5°C. The upward transport of supercooled cloud water is limited by a balance between water condensed in the eyewall updraft and its erosion by ice in downdrafts descending in the outward regions of the eyewall. This ice originates from both primary and secondary ice nucleation in the updraft. This is consistent with an exponential increase in ice concentration, as the rate at which the ice particle concentrations increase depends on the production of secondary particles by preexisting graupel, some of which ultimately grow into new graupel, and its outward transport in the anvil flow aloft. Penetrations at temperatures as low as -15°C show the presence of electric fields consistent with specific laboratory-derived criteria for charge separated during ice-graupel collisions, given that a liquid water-dependent sign reversal temperature may occur. Such a reversal may result from either a changing temperature in the vertical, a changing cloud liquid water content in the horizontal, or a combination of the two. Since cloud-to-ground (CG) lightning can be observed with remote detection networks that provide the polarity and frequency of CG lightning, there is potential that hurricane evolution may be detected remotely and that lightning may be usable as an indicator of a change in the storm intensity and/or track.

Blackwelder, P.L., T. Hood, C. Alvarez-Zarikian, P. Swart, C.M. Featherstone, and T.A. Nelsen. Historical salinity effects on microfauna in the lower Everglades and Florida Bay. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 181 (1999).

A multi-faceted approach examines the relationship between microfauna (ostracods and foraminifers) and salinity in Florida Bay and its environs. Several "levels" of microfaunal population variability were examined, which range from overall population characteristics to species- and individual-specific isotopic composition and morphological differences. These levels include documentation of changes in population abundance and diversity over time with variability in salinity and individual species-specific responses, which produce decipherable salinity-related records. Isotopic composition of stained individuals living in the surface sediment in each environment, as well as documentation of salinity related ostracod valve morphological change are studied. Attention is focused on those species capable of withstanding the greatest salinity fluctuations. Core and surface microfaunal populations at Oyster Bay, Jimmy Key, and First National Bank are compared and contrasted. These three sites comprise distinct environmental regimes with well-documented salinity records. Oyster Bay has experienced the greatest salinity variability of the three sites, as well as freshest overall conditions over the last 100 years. The Jimmy Key site, in the center of the Bay, has experienced higher average salinity with less variability over this period. Taphonomic microfaunal studies routinely utilize population characteristics as a tool for paleoenvironmental reconstruction. This study extends population work to include species and individual-specific characteristics, which may record salinity variability. In addition to the field and core collections, we are culturing ostracods to examine isotopic and morphological relationships under controlled conditions. This multi-faceted approach extends our population characterization work to include documentation of physiological response of individuals within the microfaunal populations to documented changes in salinity. This data will extend the use of microfauna as indicators of modern and paleo-salinity change.

Boebel, O., C. Schmid, and W. Zenk. Kinematic elements of Antarctic Intermediate Water in the western South Atlantic. Deep Sea Research, Part II, 46(1-2):355-392 (1999).

The northward flowing Antarctic Intermediate Water (AAIW) is a major contributor to the large-scale meridional circulation of water masses in the Atlantic. Together with bottom and thermocline water, AAIW replaces North Atlantic Deep Water that penetrates into the South Atlantic from the north. On the northbound propagation of AAIW from its formation area in the southwestern region of the Argentine Basin, the AAIW progresses through a complex spreading pattern at the base of the main thermocline. This paper presents trajectories of 75 subsurface floats, seeded at AAIW depth. The floats were acoustically tracked, covering a period from December 1992 to October 1996. Discussions of selected trajectories focus on mesoscale kinematic elements that contribute to the spreading of AAIW. In the equatorial region, intermittent westward and eastward currents were observed, suggesting a seasonal cycle of the AAIW flow direction. At tropical latitudes, just offshore the intermediate western boundary current, the southward advection of an anticyclonic eddy was observed between 5°S and 11°S. Farther offshore, the flow lacks an advective pattern and is governed by eddy diffusion. The westward subtropical gyre return current at about 28°S shows considerable stability with the mean kinetic energy to eddy kinetic energy ratio being around one. Farther south, the eastward deeper South Atlantic Current is dominated by large-scale meanders with particle velocities in excess of 60 cm s^-1. At the Brazil-Falkland Current Confluence Zone, a cyclonic eddy near 40°S, 50°W seems to act as injector of freshly mixed AAIW into the subtropical gyre. In general, much of the mixing of the various blends of AAIW is due to the activity of mesoscale eddies, which frequently reoccupy similar positions.

Boebel O., C. Schmid, G. Podestá, and W. Zenk. Intermediate water in the Brazil-Malvinas Confluence Zone: A Lagrangian view. Journal of Geophysical Research, 104(C9):21,063-21,082 (1999).

The subsurface flow within the subantarctic and subtropical regions around the Brazil-Malvinas Confluence Zone is studied, using daily hydrographic and kinematic data from four subsurface floats and a hydrographic section parallel to the South American shelf. The trajectories are mapped against sea-surface flow patterns as visible in concurrent satellite sea-surface temperature images, with focus on the November 1994 and October/November periods. The unprecedented employment of Lagrangian-S diagrams enables us to trace the advection of patches of fresh Antarctic Intermediate Water (AAIW) from the Confluence Zone into the subtropical region. The fresh AAIW consists of a mixture of subtropical AAIW and Malvinas Current core water. Within the subtropical gyre, these patches are discernible for extended periods and drift over long distances, reaching north to 34.26°S and east to 40.26°W. The cross-frontal migration of quasi-isobaric floats across the Confluence Zone from the subtropical to the subantarctic environment is observed on three occasions. The reverse process, float migration from a subpolar to a subtropical environment was observed once. These events were located near 40.26°S, 50.26°W, the site of a reoccurring cold core feature. Subsurface float and SST data comparison reveals similarities with analogous observations made in the Gulf Stream (Rossby, 1996) where cross-frontal processes were observed close to meander crests. The limited number of floats of this study and the complex structure of the Brazil-Malvinas Confluence Zone, however, restricts the analysis to a description of two events.

Boebel, O., R.E. Davis, M. Ollitrault, R.G. Peterson, P.L. Richardson, C. Schmid, and W. Zenk. Direct observations of the western South Atlantic intermediate depth circulation. Geophysical Research Letters, 26(21):3329-3332 (1999).

The subsurface oceanic circulation is an important part of the Earth climate system. Subsurface currents traditionally are inferred indirectly from distributions of temperature and dissolved substances, occasionally supplemented by current meter measurements. Neutrally-buoyant floats, however, now enable us to obtain for the first time directly measured intermediate depth velocity fields over large areas such as the western South Atlantic. Here, our combined data set provides unprecedented observations and quantification of key flow patterns, such as the Subtropical Gyre return flow (12 Sv; 1 Sverdrup = 10⁶ m³ s^-1), its bifurcation near the Santos Plateau and the resulting continuous narrow and swift northward intermediate western boundary current (4 Sv). This northward flowing water passes through complex equatorial flows and finally enters into the North Atlantic.

Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black. Environmental influences on the rapid intensification of Hurricane Opal (1995) over the Gulf of Mexico. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 983-984 (1999).

No abstract.

Bourles, B., R.L. Molinari, E. Johns, W.D. Wilson, and K.D. Leaman. Upper layer currents in the western tropical North Atlantic (1989-1991). Journal of Geophysical Research, 104(C1):1361-1376 (1999).

Shipboard Acoustic Doppler Current Profiler (ADCP) measurements and hydrographic observations of temperature, salinity, and dissolved oxygen are used to examine the upper water column flow field in the North Brazil Current (NBC) retroflection region of the western tropical Atlantic Ocean. Observations are presented from six cruises, one conducted in August 1989 and the other five conducted during the Western Tropical Atlantic Experiment (WESTRAX) between January 1990 and September 1991. The upper water column is divided into two layers, an upper thermocline layer located between the surface and the 24.5 sigma theta isopycnal surface, and a lower subthermocline layer located between the 24.5 and 26.75 isopycnals. In the upper layer the NBC retroflects north of the equator to form the eastward flowing North Equatorial Counter Current (NECC). During the six cruises the retroflection appeared complete. However, data coverage did not extend shoreward of the 200 m isobath, so the possibility of a continuous flow over the shelf still remains. There were also indications of several NBC rings which had apparently separated from the NBC retroflection and drifted to the northwest towards the eastern Caribbean Sea. North of the NBC retroflection and the NECC, the North Equatorial Current (NEC) flows west as the southern limb of the subtropical gyre. Part of the NEC is observed to retroflect cyclonically to join the eastward NECC flow. In the lower layer, beneath the NBC, the North Brazil Undercurrent (NBUC) retroflects to feed the eastward North Equatorial Undercurrent (NEUC). To the north, a deeper component of the NEC recurves to also contribute to the NEUC.

Boutin, J., J. Etcheto, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, H.Y. Inoue, M. Ishii, R.D. Ling, P.D. Nightingale, N. Metzl, and R.H. Wanninkhof. Satellite sea surface temperature: A powerful tool for interpreting in-situ pCO₂ measurements in the equatorial Pacific Ocean. Tellus B, 51(2):490-508 (1999).

In order to determine the seasonal and interannual variability of the CO₂ released to the atmosphere from the equatorial Pacific, we have developed pCO₂-temperature relationships based upon shipboard oceanic CO₂ partial pressure measurements, pCO₂, and satellite sea surface temperature, SST, measurements. We interpret the spatial variability in pCO₂ with the help of the SST imagery. In the eastern equatorial Pacific, at 5°S, pCO₂ variations of up to 100 µatm are caused by undulations in the southern boundary of the equatorial upwelled waters. These undulations appear to be periodic with a phase and a wavelength comparable to tropical instability waves, TIW, observed at the northern boundary of the equatorial upwelling. Once the pCO₂ signature of the TIW is removed from the Alize II cruise measurements in January 1991, the equatorial pCO₂ data exhibit a diel cycle of about 10 µatm with maximum values occurring at night. In the western equatorial Pacific, the variability in pCO₂ is primarily governed by the displacement of the boundary between warm pool waters, where air-sea CO₂ fluxes are weak, and equatorial upwelled waters which release high CO₂ fluxes to the atmosphere. We detect this boundary using satellite SST maps. East of the warm pool, DELTA-P is related to SST and SST anomalies. The 1985-1997 CO₂ flux is computed in a 5° wide latitudinal band as a combination of DELTA-P and CO₂ exchange coefficient, K, deduced from satellite wind speed, U. It exhibits up to a factor 2 seasonal variation caused by K-seasonal variation and a large interannual variability, a factor 5 variation between 1987 and 1988. The interannual variability is primarily driven by displacements of the warm pool that makes the surface area of the outgassing region variable. The contribution of DELTA-P to the flux variability is about half of the contribution of K. The mean CO₂ flux computed using either the Liss and Merlivat (1986) or the Wanninkhof (1992) K-U parameterization amounts to 0.11 GtC yr^-1 or to 0.18 GtC yr^-1, respectively. The error in the integrated flux, without taking into account the uncertainly on the K-U parameterization, is less than 31%.

Bove, M.C., J.B. Elsner, C.W. Landsea, X. Niu, and J.J. O'Brien. Effect of El Niño on U.S. landfalling hurricanes, revisited. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 278-281 (1999).

No abstract.

Broecker, W.S., S. Sutherland, and T.-H. Peng. A possible 20th-century slowdown of Southern Ocean deep water formation. Science, 286(5442):1132-1135 (1999).

Chlorofluorocarbon-11 inventories for the deep Southern Ocean appear to confirm physical oceanographic and geochemical studies in the Southern Ocean, which suggests that no more than 5 × 10⁶ cubic meters per second of ventilated deep water is currently being produced. This result conflicts with conclusions based on the distributions of the carbon-14/carbon ratio and a quasi-conservative property, PO₄, in the deep sea, which seem to require an average of about 15 × 10⁶ cubic meters per second of Southern Ocean deep ventilation over about the past 800 years. A major reduction in Southern Ocean deep water production during the 20th century (from high rates during the Little Ice Age) may explain this apparent discordance. If this is true, a seesawing of deep water production between the northern Atlantic and Southern Oceans may lie at the heart of the 1500-year ice-rafting cycle.

Broecker, W.S., E. Clark, D.C. McCorkle, T.-H. Peng, I. Hajdas, and G. Bonani. Evidence for a reduction in the carbonate ion content of the deep sea during the course of the Holocene. Paleoceanography, 14(6):744-752 (1999).

The paleo carbonate ion proxy proposed by Broecker et al. (1999) is applied in a search for trends in the Holocene acidity of waters in the transition zone between North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). A clear signal emerges that the carbonate ion content of waters in this zone declined during the last 8000 years. In order to determine whether this decline represents a strengthening of the northward penetrating tongue of low CO₃ content AABW or a global reduction of CO₃ ion, measurements were made on a core from the Ontong Java Plateau in the western equatorial Pacific. Evidence for a similar decline in CO₃ ion over the course of the Holocene was obtained, lending support of the latter explanation. Such a drop is consistent with the recent finding by Indermuhle et al. (1999) that the CO₂ content of the atmosphere (as recorded in the Taylor Dome Antarctica ice core) rose by 20 to 25 ppm during the last 8000 years.

Butler, J.H., D.B. King, and S.A. Yvon-Lewis. Computation of the air-sea exchange coefficient from halocarbon disequilibria. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S46, A31C-10 (1999).

Studies conducted by NOAA during the past decade show that it is possible to use measurements of halocarbon saturation anomalies to calculate air-sea gas transfer velocities. These methods provide independent, averaged measures of air-sea transfer in the open ocean and are based upon the exchange of halocarbon across the air-sea interface on a broad scale; the source and sink are both ubiquitous. Computations can be made for conservative halocarbons, such as CFC-11 or CFC-12, for a hydrolyzable halocarbon such as CH₃CCl₃, or even for a chemically and biologically reactive compound such as CH₃Br, if accompanied by measures of production and degradation. During GasEx-98, we acquired data on a number of trace halocarbons from which we can estimate air-sea exchange. The method that appears to be most useful with respect to this data set involves computations from disequilibria of conservative gases (e.g., CFCs) during heating of a water mass. Unfortunately, the waters during much of the cruise were not sufficiently warm for hydrolysis of CH₃CCl₃ to be the dominant loss mechanism. Nevertheless, disequilibrium computations for this gas did require consideration of hydrolysis. We also attempted to obtain air profiles of halocarbons, but most gases were not sufficiently supersaturated for this to be reliable. Exceptions were CH₃I and isoprene (a hydrocarbon), both of which were highly supersaturated and which, under limited sampling conditions, yielded reasonable profiles in the air.

Butler, J.H., D.B. King, S.A. Yvon-Lewis, J.M. Lobert, S.A. Montzka, and J.W. Elkins. Seasonal and temporal variability in the distribution of methyl bromide in the surface ocean. International Union of Geodesy and Geophysics, XXII General Assembly, Birmingham, England, July 18-30, July 1999. IUGG99 Abstracts, A110 (1999).

The ocean is both the largest source and the second largest sink for methyl bromide (CH₃Br) in the atmosphere, yet we still don't fully understand how the ocean regulates the atmospheric burden of this gas, nor can we predict accurately how the oceanic fluxes of methyl bromide will respond to global change. From first-order calculations, it is clear that the steady-state, net flux of this gas from the ocean will act in opposition to changes in the atmospheric burden. However, the distribution of the oceanic sources and sinks of CH₃Br appears to be patchy on both small and large scales. The open oceans are typically undersaturated in CH₃Br, with coastal waters typically supersaturated. Warm waters tend to be undersaturated; cooler waters can be super- or undersaturated. However, there are significant exceptions to any generalities. Although the chemical degradation of dissolved CH₃Br is predominantly a function of sea-surface temperature, production appears to be mainly biological and there is strong evidence for biological degradation as well. Here, we examine the distribution of methyl bromide from recent studies of its saturation in the Pacific, Atlantic, and Southern Oceans to examine spatial and temporal dependencies upon its net flux and, consequently, its production and degradation.

Cantillo, A.Y., L. Pikula, and K. Hale. Preliminary data and document rescue of material relevant to the south Florida ecosystem. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 246 (1999).

There are significant amounts of unpublished documents and data on the marine and estuarine environment of Florida that are so far unavailable to the scientific community, academia, and the general public. These data and documents are important because they represent the Florida coastal ecosystems in times past, and are the basis for comparing past with current conditions. Currently, an innovative prototype data and document rescue effort is underway that combines the expertise of a senior scientist with that of librarians. Its main purpose is to inventory unpublished documents and data, perform a quality-assurance review of the scientific content, convert the material to electronic and printed form, and make it available through printed and online resources. If the data and documents are not rescued, they will be lost as printed material physically deteriorates, personnel retire, and corporate memory disappears. Examples of rescued documents relevant to the south Florida ecosystem are presented and the data and document rescue approach discussed.

Cantillo, A.Y., K. Hale, R. Caballero, E. Collins, and L. Pikula. Environmental history of Biscayne Bay. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 218 (1999).

Biscayne Bay is surrounded on the north by the growing urban areas of Dade County, which includes Miami and Miami Beach, and on the south by the sparsely inhabited Homestead area and the northern Florida Keys. Its environmental history is closely related to the development of the Greater Miami area. Urban development of the northern part of the Bay during the 1920s began the decline that remained largely unchecked until the early 1970s. Recently, environmental degradation of the Bay has reversed. This work describes the major events impacting the Bay's ecosystem and how it has changed over time.

Carsey, T.P. Shipboard measurements of active nitrogen gases during INDOEX. AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(46):F162, A22A-01 (1999).

A suite of active nitrogen gases (NO, NO₂, and NO_y) were measured on board the NOAA ship Ronald H. Brown during the INDOEX experiment during February-March 1999. The cruise track included crossing of the Indian Ocean ITCZ, as well as several air mass types in that region including clean marine and heavily anthropogenically influenced air masses. The results will be presented and discussed in the context of related meteorological and chemical data.

Checkley, D.M., P.B. Ortner, F.E. Werner, L.R. Settle, and S.R. Cummings. Spawning habitat of the Atlantic menhaden in Onslow Bay, North Carolina. Fisheries Oceanography, 8:22-36 (1999).

The Continuous, Underway Fish Egg Sampler (CUFES) was used to sample pelagic eggs of the Atlantic menhaden (Brevoortia tyrannus) from a 3-m depth off North Carolina in winter 1993-1994 and 1994-1995. Simultaneous measurements were made of temperature, salinity, and the concentration of chlorophyll a. The maximal concentration of eggs was 346 eggs m^-3. Eggs were highly aggregated in patches which occurred between the Gulf Stream and mid-shelf fronts (17-23°C, 36.0-36.4 ppm). Unexpectedly, eggs were found almost exclusively in water of 20-60 m (mode 20 m) bottom depth. Thus, spawning appears related to bathymetry as well as hydrography. Variograms for egg concentration indicated a mean (± SE) patch scale of 3.6 ± 1.7 km and a high degree of spatial variance explained by CUFES sampling. Lagrangian modeling of particles moving in response to tides, winds, and a prescribed flow from the north indicated that the region of observed, maximal occurrence of eggs is favorable for the retention of eggs and larvae on the shelf adjacent to inlets used to enter nursery areas.

Dickerson, R.R., K.P. Rhoads, T.P. Carsey, S.J. Oltmans, J.P. Burrows, and P.J. Crutzen. Ozone in the remote marine boundary layer: A possible role for halogens. Journal of Geophysical Research, 104(D17):21,385-21,395 (1999).

On the spring 1995 cruise of the National Oceanic and Atmospheric Administration research vessel Malcolm Baldrige, we measured very large diurnal variations in ozone concentrations in the marine boundary layer. Average diurnal variations of about 32% of the mean were observed over the tropical Indian Ocean. We simulated these observations with the Model of Chemistry in Clouds and Aerosols, a photochemical box model with detailed aerosol chemistry. The model was constrained with photolysis rates, humidity, aerosol concentrations, NO, CO, and O₃ specified by shipboard observations and ozonesondes. Conventional homogeneous chemistry, where ozone photolysis to O(¹D) and HO_x 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.

Cione, J.J., P.G. Black, and S.H. Houston. Cooling and drying within the hurricane near-surface environment? Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1027-1030 (1999).

No abstract.

Cook, S.K. Vertical thermal structure of midshelf waters: Water temperatures and climatological conditions south of New England, 1974-1983. NOAA Technical Report, NMFS-134, 43 pp. (1999).

No abstract.

DeMaria, M., and J. Kaplan. An updated Statistical Hurricane Intensity Prediction Scheme (SHIPS) for the Atlantic and eastern North Pacific basins. Weather and Forecasting, 14(3):326-337 (1999).

Updates to the Statistical Hurricane Intensity Prediction Scheme (SHIPS) for the Atlantic basin are described. SHIPS combines climatological, persistence, and synoptic predictors to forecast intensity changes using a multiple regression technique. The original version of the model was developed for the Atlantic basin and was run in near-real time at the Hurricane Research Division beginning in 1993. In 1996, the model was incorporated into the National Hurricane Center operational forecast cycle, and a version was developed for the eastern North Pacific basin. Analysis of the forecast errors for the period 1993-1996 shows that SHIPS had little skill relative to forecasts based upon climatology and persistence. However, SHIPS had significant skill in both the Atlantic and east Pacific basins during the 1997 hurricane season. The regression coefficients for SHIPS were rederived after each hurricane season since 1993 so that the previous season's forecast cases were included in the sample. Modifications to the model itself were also made after each season. Prior to the 1997 season, the synoptic predictors were determined only from an analysis at the beginning of the forecast period. Thus, SHIPS could be considered a "statistical-synoptic" model. For the 1997 season, methods were developed to remove the tropical cyclone circulation from the global model analyses and to include synoptic predictors from forecast fields, so the current version of SHIPS is a "statistical-dynamical" model. It was only after the modifications for 1997 that the model showed significant intensity forecast skill.

Doddridge, B.G., W.T. Luke, C.A. Piety, R.R. Dickerson, A.M. Thompson, J.C. Witte, J.E. Johnson, T.S. Bates, P.K. Quinn, and T.P. Carsey. Trace gas and aerosols over the Atlantic Ocean during the ACE-Aerorsols cruise. AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(46):F163, A22A-09 (1999).

The ACE-Aerosols cruise was conducted on board the NOAA R/V Ronald H. Brown (R-104) on January 14-February 20, 1999. This paper focuses on measurements conducted during a North-South Atlantic Ocean transect from Norfolk, Virginia to Cape Town, South Africa, January 14-February 8, 1999. Hourly-averaged marine boundary layer (MBL) carbon monoxide data ranged from 105 to 200 ppbv and 45 to 75 ppbv in the northern and southern hemisphere (SH), respectively. Aerosol optical depth showed significant variability along the same transect, with elevated values dominated by upper level transport from Africa. Hourly MBL ozone data ranged from 6 to 40 ppbv, showing a diurnal cycle superimposed upon a strong hemispheric gradient, and were strongly influenced by several pollution episodes, corroborated by bulk aerosol chemistry data. Using these tracers, along with computed air parcel trajectories, cruise data indicate substantial influence of Saharan, equatorial, and SH subtropical regions of Africa on the remote Atlantic Ocean MBL.

Dodge, P.P., R.W. Burpee, and F.D. Marks. The kinematic structure of a hurricane with sea-level pressure less than 900 mb. Monthly Weather Review, 127(6):987-1004 (1999).

A National Oceanic and Atmospheric Administration aircraft recorded the first Doppler radar data in a tropical cyclone with a minimum sea level pressure (MSLP) <900 mb during a reconnaissance mission in Hurricane Gilbert on 14 September 1988, when its MSLP was ~895 mb. A previous mission had found an MSLP of 888 mb, making Gilbert the most intense tropical cyclone yet observed in the Atlantic basin. Radar reflectivity identified the hurricane eye, inner and outer eyewalls, a stratiform region between the eyewalls, and an area outside the outer eyewall that contained a few rainbands but that had mostly stratiform rain. Pseudo-dual Doppler analyses depict the three-dimensional kinematic structure of the inner eyewall and a portion of the outer eyewall. The vertical profiles of tangential wind and reflectivity maxima in the inner eyewall are more erect than in weaker storms, and winds >50 m s^-1 extended to 12 km, higher than has been reported in previous hurricanes. The inner eyewall contained weak inflow throughout most of its depth. In contrast, the portion of the outer eyewall described here had shallow inflow and a broad region of outflow. The stratiform region between the two eyewalls had lower reflectivities and was the only region where the vertically incident Doppler radar data seemed to show downward motion below the freezing level. Gilbert's structure is compared with other intense Atlantic and eastern North Pacific hurricanes with MSLP >900 mb. Storms with lower MSLP have higher wind speeds in both inner and outer eyewalls, and wind speeds >50 m s^-1 extend higher in storms with lower MSLP. Hurricanes Gilbert and Gloria (1985), the strongest Atlantic hurricanes yet analyzed by the Hurricane Research Division, had different outer eyewall structures. Gloria's outer eyewall had a deep region of inflow, while Gilbert's inflow layer was shallow. This may explain differences in the subsequent evolution of the two storms.

Dodge, P.P., S.H. Houston, W.-C. Lee, J.F. Gamache, and F.D. Marks. Windfields in Hurricane Danny (1997) at landfall from combined WSR-88D and airborne Doppler radar data. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 61-62 (1999). No abstract.

Donnelly, W.J., J.R. Carswell, R.E. McIntosh, P.S. Chang, J.C. Wilkerson, F.D. Marks, and P.G. Black. Revised ocean backscatter models at C and Ku-bands under high wind conditions. Journal of Geophysical Research, 104(C5):11,485-11,498 (1999).

A series of airborne scatterometer experiments designed to collect C and Ku-band ocean backscatter data in regions of high ocean surface winds has recently been completed. Over 100 hours of data were collected using the University of Massachusetts C and Ku-band scatterometers, CSCAT and KUSCAT. These instruments measure the full azimuthal normalized radar cross section (NRCS) of a common surface area of the ocean simultaneously at four incidence angles. Our results demonstrate limitations of the current empirical models, CMOD4, SASSII and NSCAT1, that relate ocean backscatter to the near surface wind at high wind speeds. The discussion focuses on winds in excess of 15 m/sec in clear atmospheric conditions. The scatterometer data is collocated with measurements from ocean data buoys and GPS dropsondes, and a Fourier analysis is performed as a function of wind regime. A three-term Fourier series is fit to the backscatter data, and a revised set of coefficients is tabulated. These revised models, CMOD4HW and KUSCAT1, are the basis for a discussion of the NRCS at high wind speeds. Our scatterometer data show a clear over prediction of the derived NRCS response to high winds based on the CMOD4, SASSII and NSCAT1 models. Furthermore, saturation of the NRCS response begins to occur above 15 m/sec. Sensitivity of the upwind and crosswind response is discussed with implications towards high wind speed retrieval. wind speed retrieval.

Ellsberry, R.L., and F.D. Marks. The Hurricane Landfall Workshop summary. Bulletin of the American Meteorological Society, 80(4):683-685 (1999).

No abstract.

Enfield, D.B., and E.J. Alfaro. The dependence of Caribbean rainfall on the interaction of tropical Atlantic and Pacific Oceans. Journal of Climate, 12(7):2093-2103 (1999).

Seasonally-stratified analyses of rainfall anomalies over the Intra-Americas Sea and surrounding land areas and of onset and end dates of the Central American rainy season show that the variability of the tropical Atlantic sea surface temperature anomaly (SSTA) is more strongly associated with rainfall over the Caribbean and Central America than is tropical eastern Pacific SSTA. Seasonal differences include the importance of antisymmetric configurations of tropical Atlantic SSTA in the dry season but not in the rainy season. Both oceans are related to rainfall, but the strength of the rainfall response appears to depend on how SSTA in the tropical Atlantic and eastern Pacific combine. The strongest response occurs when the tropical Atlantic is in the configuration of a meridional dipole (antisymmetric across the ITCZ) and configuration of a meridional dipole (antisymmetric across the ITCZ) and the eastern tropical Pacific is of opposite sign to the tropical North Atlantic. When the tropical North Atlantic and tropical Pacific are of the same sign, the rainfall response is weaker. The rainy season in lower Central America tends to start early and end late in years that begin with warm SSTs in the tropical North Atlantic, and the end dates are also delayed when the eastern equatorial Pacific is cool. This enhancement of date departures for zonally antisymmetric configurations of SSTA between the North Atlantic and Pacific is qualitatively consistent with the results for rainfall anomalies.

Enfield, D.B., and A.M. Mestas-Nuñez. Contrary tropospheric direct circulations associated with Pacific decadal variability and canonical ENSO oscillations. AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(46):F180, A31D-07 (1999).

Our analysis shows that the intensity of the 1982-1983 and 1997-1998 El Niño events, occurring only 15 years apart, are among the three or four warmest in 130 years of trans-Pacific sampling. However, when the 130 year record of global sea surface temperatures (SST) is subjected to a complex empirical orthogonal function (CEOF) analysis, the leading mode has all the known characteristics (amplitude and phase) of the El Niño-Southern Oscillation (ENSO), yet the associated canonical variation of SST in the equatorial Pacific does not include the spectacular amplitudes of the 1980s and 1990s, seen in the unanalyzed SST data. When the equatorial reconstruction of the global ENSO mode is subtracted from the SST data, the residual equatorial variability (NINO3 region) is seen to have a pronounced decadal variability, with many of the characteristics that others have identified with the Pacific Decadal Oscillation (PDO). As much as 50% of the total amplitudes of the NINO3 SST anomalies in 1982-1983 and 1997-1998 are explained by this residual, which was unusually high after 1978. In this paper, we describe and compare the surface oceanic (SST) and atmospheric (pressure, winds) characteristics associated with these two components of the NINO3 variability (ENSO and residual). We also examine the anomalous direct circulation (Walker and Hadley circulations) of the global troposphere associated with each component. The tropospheric analysis, of greatest interest to this session, yields a startling result: the anomalous direct circulation associated with the canonical ENSO warmings in the NINO3 series is in most ways opposite to that associated with the residual (decadal) warmings. The contrary behavior of the two components extends to convection near the dateline, over the Amazon basin and over the Indian Ocean, while the Hadley circulations in the Pacific and Atlantic sectors are also affected in opposite ways. A unique feature of the decadal component is the occurrence of a stronger winter monsoon over India and northeast Africa, in association with warm background SSTs in the eastern equatorial Pacific.

Enfield, D.B., and A.M. Mestas-Nuñez. Multiscale variabilities in global sea surface temperatures and their relationships with tropospheric climate patterns. Journal of Climate, 12(9):2719-2733 (1999).

El Niño-Southern Oscillation (ENSO) is a global phenomenon with significant phase propagation within and between basins. We capture and describe this in the first mode of a complex empirical orthogonal function (CEOF) analysis of sea surface temperature anomaly (SSTA) from the mid-19th century through 1991. We subsequently remove the global ENSO from the SSTA data, plus a linear trend everywhere, in order to consider other global modes of variability uncontaminated by the intra- and inter-basin effects of ENSO. An ordinary EOF analysis of the SSTA residuals reveals three non-ENSO modes of low-frequency variability that are related to slow oceanic and climate signals described in the literature. The first two modes have decadal-to-multidecadal time scales with high loadings in the Pacific. They bear some spatial similarities to the ENSO pattern but are broader, more intense at high latitudes, and differ in the time domain. A CEOF analysis confirms that they are not merely the phase-related components of a single mode and that all three modes are without significant phase propagation. The third mode is a multidecadal signal with maximal realization in the extratropical North Atlantic southeast of Greenland. It is consistent with studies that have documented connections between North Atlantic SSTA and the tropospheric North Atlantic Oscillation (NAO). All three SSTA modes have mid-tropospheric associations related to previously classified Northern Hemisphere teleconnection patterns. The relationships between SSTA modes and tropospheric patterns are consistent with the ocean-atmosphere interactions discussed in previous studies to explain low-frequency climate oscillations in the North Pacific and North Atlantic sectors. The first three leading modes of non-ENSO SSTA are most related, respectively, to the tropospheric patterns of the Pacific North American (PNA), the North Pacific (NP) and the Arctic Oscillations (AO), respectively. The 500 hPa pattern associated with the third SSTA mode also bears similarities to the NAO in its Atlantic sector. This North Atlantic mode has a region of high, positive SSTA loadings in the Gulf of Alaska, which appear to be connected to the North Atlantic SSTA by a tropospheric bridge effect in the AO.

Enfield, D.B., A.M. Mestas-Nuñez, D.A. Mayer, and L. Cid-Serrano. How ubiquitous is the dipole relationship in tropical Atlantic sea surface temperatures? Journal of Geophysical Research, 104(C4):7841-7848 (1999).

Several kinds of analysis are applied to the departures of sea surface temperatures from climatology (SSTA, 1856-1991) to determine the degree to which SSTA of opposite sign in the tropical North and South Atlantic occur. Antisymmetric ("dipole") configurations of SSTA on basin scales are not ubiquitous in the tropical Atlantic. Unless the data are stratified by both season and frequency, inherent dipole behavior cannot be demonstrated. Upon removing the global ENSO signal in SSTA (which is symmetric between the North and South Atlantic) from the data, the regions north or south of the intertropical convergence zone have qualitatively different temporal variabilities and are poorly correlated. Dipole configurations do occur infrequently (12-15% of the time), but no more so than expected by chance for stochastically-independent variables. Non-dipole configurations that imply significant meridional SSTA gradients occur much more frequently, nearly half of the time. Cross-spectral analysis of seasonally averaged SSTA indices for the North and South Atlantic show marginally significant coherence with antisymmetric phase in two period bands: 8-12 years for the boreal winter-spring, and 2.3 years for the boreal summer-fall. Antisymmetric coherence is optimal for a small sub-region west of Angola in the South Atlantic, with respect to SSTA of basin scale in the tropical North Atlantic. Dipole variability, even where optimal, explains only a small fraction of the total variance in tropical Atlantic SSTA (<7%).

Enfield, D.B., A.M. Mestas-Nuñez, D.A. Mayer, and L. Cid-Serrano. The dipole in tropical Atlantic SST: Common? Random? Intrinsic? Proceedings, 23rd Annual Climate Diagnostics and Prediction Workshop, Miami, Florida, October 26-30, 1998. National Weather Service, 223-226 (1999).

In this paper we clarify the confusing and apparently contradictory views regarding tropical Atlantic dipole variability. The issue is revisited by using a recently reconstructed 136-year SST anomaly (SSTA) analysis for the globe (Kaplan et al., 1998; henceforth, K98). An expanded analysis will appear in the Journal of Geophysical Research-Oceans (Enfield et al., 1999).

Esenkov, O.E., and B. Cushman-Roisin. Modeling of two-layer eddies and coastal flows with a particle method. Journal of Geophysical Research, 104(C5):10,959-10,980 (1999).

An existing particle-in-cell (PIC) numerical code is applied to lens-like anticyclonic vortices and buoyant coastal currents. A first series of experiments with initially elongated eddies reveals that motions induced in the lower layer act to increase the rate of rotation of the structure; eccentricity reduction, if any, produces a final vortex of aspect ratio between 1.8 and 1.9, in accordance with a theoretical prediction. A second series of experiments determines the maximal separation distance that can exist between two identical and circular vortices before they spontaneously merge; this distance is a function of the vortex size and ambient stratification. In a third series of experiments, vortex interactions across layers are considered; results similar to those obtained with two-layer point vortices (hetons) are obtained. Finally, the PIC method is generalized to simulate the finite-amplitude instability of a buoyant geostrophic current flowing a long 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).

Etcheto, J., J. Boutin, D.C.E. Bakker, Y. Dandonneau, R.A. Feely, H.Y. Inoue, M. Ishii, R.D. Ling, L. Merlivat, P.D. Nightingale, N.Metzl, and R.H. Wanninkhof. pCO₂ in the equatorial Pacific and Atlantic Oceans: Determination of air-sea CO₂ flux using satellite-borne instruments. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 119-125 (1999).

No abstract.

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 pCO_2OC 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 pCO_2OC 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%.

Feely, R.A., M.F. Lamb, D.J. Greeley, and R.H. Wanninkhof. Comparison of the carbon system parameters at the global CO₂ survey crossover locations in the North and South Pacific Ocean between 1990-1996. Technical Report, ORNL/CDIAC-115, Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, 73 pp. (1999).

As a collaborative program to measure global ocean carbon inventories and provide estimates of the anthropogenic carbon dioxide (CO₂) uptake by the oceans, the National Oceanic and Atmospheric Administration and the U.S. Department of Energy have sponsored the collection of ocean carbon measurements as part of the World Ocean Circulation Experiment and Ocean-Atmosphere Carbon Exchange Study cruises. The cruises discussed here occurred in the North and South Pacific from 1990 through 1996. The carbon parameters from these 30 crossover locations have been compared to ensure a consistent global data set emerges from the survey cruises. The results indicate that for dissolved inorganic carbon, fugacity of CO₂, and pH, the agreement at most crossover locations are well within the design specifications for the global CO₂ survey, whereas in the case of total alkalinity, the agreement between crossover locations is not as close.

Feely, R.A., C.L. Sabine, R.M. Key, and T.-H. Peng. CO₂ survey synthesis results: Estimating the anthropogenic carbon dioxide sink in the Pacific Ocean. U.S. JGOFS News, 9(4):1-4 (1999).

Our results to date suggest that the cumulative amount of anthropogenic CO₂ in the global ocean is somewhere between 105 and 118 PgC through the year 1996. These results can be utilized as a constraint on other global carbon model simulations, similar to Princeton/Geophysical Fluid Dynamics Laboratory Ocean Biogeochemical Model and National Center for Atmospheric Research model simulations. As we refined and complete the estimates of the oceanic uptake of anthropogenic CO₂, the results will be compared to CO₂ uptake estimates for the atmosphere and terrestrial biosphere.

Feely, R.A., R.H. Wanninkhof, T. Takahashi, and P. Tans. Influence of El Niño on the equatorial Pacific contribution to atmospheric CO₂ accumulation. Nature, 398:597-601 (1999).

The equatorial ocean is an important CO₂ source to the atmosphere, contributing annually 0.7-1.5 Pg of carbon as CO₂, as much as 80% of which is attributed to the equatorial Pacific. This source is known to change significantly by ENSO events. To better understand the regional and interannual variability of CO₂ fluxes from the equatorial Pacific, field measurements of the partial pressure of CO₂ (pCO₂) have been made in the equatorial Pacific region since 1992. Here, we report that during the 1991-1994 ENSO period the net annual sea-to-air flux of CO₂ was 0.3 PgC from the fall of 1991 to the fall of 1992, 0.6 PgC in 1993, and 0.7 PgC in 1994. These fluxes are 30%-80% of the 0.9 PgC observed during the non-El Niño year of 1996. The total reduction of the sea-to-air CO₂ flux during the 1991-1994 El Niño is estimated to be 0.8-1.2 PgC, which accounts for 16-36% of the atmospheric anomaly (the difference between the annual atmospheric CO₂ increase in PgC yr^-1 and the long-term average increase of 3.18 PgC yr^-1) observed over the same period.

Feely, R.A., C.L. Sabine, R.M. Key, T.-H. Peng, and R.H. Wanninkhof. The U.S. global CO₂ survey in the North and South Pacific Ocean. Preliminary synthesis results. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 193-198 (1999).

As a collaborative program to measure global ocean carbon inventories and provide estimates of the anthropogenic CO₂ uptake in the oceans, the National Oceanic and Atmospheric Administration, the U.S. Department of Energy, and the National Science Foundation have co-sponsored the collection of ocean carbon measurements as part of the World Ocean Circulation Experiment (WOCE) and Ocean-Atmospheric Carbon Exchange Study (OACES). The cruises discussed here occurred in the North and South Pacific from 1990 through 1996. The new estimates for anthropogenic CO₂, employing the DELTA-C* method of Gruber et al. (1996), indicate that the largest buildup of anthropogenic CO₂ occurs in subtropical waters. Along 155°W, anthropogenic CO₂ penetrates to a maximum depth of 900 m at about 37°N in the North Pacific and 1300 m at about 48°S in the South Pacific. Strong shoaling of anthropogenic CO₂ occurs southward of 50°S and northward of 48°N. The anthropogenic CO₂ inventories from the observations are smaller than the Princeton Ocean Biogeochemical Model (POBM) model estimates, primarily because the Princeton model produces too much deep convective mixing of anthropogenic CO₂ in the Southern Ocean. The NCAR Climate System Ocean model, which has very different physics and biological parameterizations, appears to do a better job of reproducing the general patterns in the data-based section.

Feely, R.A., R.H. Wanninkhof, D. Hansell, M.F. Lamb, K. Lee, and R.D. Castle. Water column CO₂ measurements during the GasEx 98 cruise. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S46, A31C-11 (1999).

During the recent GasEx 98 cruise in the North Atlantic aboard the NOAA Ship Ronald H. Brown, carbon measurements were performed in the area of 46°N, 20.5°W. This process study followed a warm core ring tagged with the deliberately-introduced tracer, SF6. Continuous surface water measurements were combined with vertical profiles sampled twice daily to depths up to 1000 m for carbon mass balance studies. Dissolved inorganic carbon (DIC) and fCO₂ measurements were conducted onboard in both underway and discrete analysis modes. During the 25-day experiment in the tagged patch, surface water fCO₂ values averaged 275 ± 9 µatm, providing a constant condition of undersaturation and flux of CO₂ into the ocean. Using the Wanninkhof (1992) exchange coefficient, the estimated CO₂ flux ranged from 2-10 moles m^-2 yr^-1. The largest CO₂ flux occurred during a large storm beginning on June 6. After the storm, DIC and fCO₂ values decreased for a few days as a result of increased productivity associated with the strong mixing event. The DIC were combined with the DOC, oxygen, and nutrient data to provide a mass balance for carbon within the patch. The mass balance of CO₂ can be reconciled with the gas transfer velocities determined during the cruise.

Franklin, J.F., M.L. Black, and S.E. Feuer. Wind profiles in hurricanes determined by GPS dropwindsondes. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 167-168 (1999).

No abstract.

Fratantoni, D.M., P.L. Richardson, W.E. Johns, C.I. Fleurant, R.H. Smith, S.L. Garzoli, W.D. Wilson, and G.J. Goñi. The North Brazil Current Rings Experiment. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S179, OS31B-10 (1999).

North Brazil Current rings are large (400 km diameter) anticyclonic vortices shed from the retroflecting North Brazil Current (NBC) in the low-latitude western Atlantic Ocean. NBC rings carry a large volume of South Atlantic water northwestward along the coast of South America towards the islands of the southeastern Caribbean. These rings are thought to be one of several processes responsible for the northward transport of upper-ocean water across the equatorial-tropical gyre boundary and into the North Atlantic subtropical gyre. Such transport is required to close the Atlantic meridional overturning cell (MOC) forced by the high-latitude production and southward export of North Atlantic Deep Water. The objective of this multi-institutional study is to obtain, for the first time, comprehensive observations of the NBC retroflection, the NBC ring formation process, and the physical structure and evolution of NBC rings as they translate along the low-latitude western boundary. We seek to understand the process of NBC ring generation and to quantify the role of NBC rings as a component of the Atlantic MOC. To accomplish our objectives we used several complementary measurement techniques including detailed shipboard CTD/ADCP/XBT surveys, surface drifter and subsurface RAFOS float observations, moored velocity and temperature-salinity measurements, and a moored array of inverted echo sounders. We will present results obtained during the first two NBC rings cruises in November-December 1998 and February-March 1999. A total of three rings were surveyed in detail, each differing substantially from the others in intensity and vertical structure. Maximum azimuthal surface velocities were typically of order 150 cm/s at a radius of 120-150 km from the ring center. In one ring, coherent swirl velocities of 20 cm/s were observed to extend as deep as 2000 m. Two of the three rings exhibited subsurface velocity maxima near 100 m depth. We will present a summary of our shipboard and surface drifter observations and share some initial conclusions regarding the physical structure and watermass composition of NBC rings.

Gamache, J.F. Airborne Doppler observations of intensity change in eastern Pacific Hurricane Guillermo. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 325-328 (1999).

No abstract.

Garzoli, S.L., and R.L. Molinari. Ageostrophic currents in the tropical Atlantic. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S179, OS31B-09 (1999).

Between 23 June 1997 and 12 August 1997, the R/V Seward Johnson completed two basin-wide transects in the Atlantic along 6°N and 6°S and a partial transect along the equator. During this time, the vessel occupied 81 oceanographic stations at which hydrographic, CTD, and lowered acoustic Doppler current profiler (LADCP) measurements were acquired. Hull-mounted ADCP data were collected continuously along the transects. In this paper, the data collected along 6°N and 6°S are analyzed and discussed. Direct measurement of the ageostrophic transport are obtained and compared with estimates of the Ekman transports derived from wind measurements. Estimates of divergence are compared with other results in terms of upwelling. From the present analysis it may be concluded that in the tropical Atlantic, the Ekman drift plays an important role in the upper layer (<300 m) transports but does not account totally for the ageostrophic ones. At 6°N, instability waves and inertial currents are dominant. At 6°S, most of the ageostrophic transport can be attributed to Ekman with the difference explained by inertial waves.

Garzoli, S.L., P.L. Richardson, C.M. Dumcombe Rae, D.M. Fratantoni, G.J. Goñi, and A.J. Roubicek. Three Agulhas rings observed during the Benguela Current Experiment. Journal of Geophysical Research, 104(C9):20,971-20,986 (1999).

A field program to study the circulation of the Benguela Current and its extension into the southeastern Atlantic Ocean has completed the survey and instrument deployment phase. We report here new observations of three Agulhas rings north and west of Cape Town, South Africa. Three mesoscale anticyclonic rings initially identified by means of TOPEX/POSEIDON altimetry were surveyed with expendable bathythermographs (XBTs), conductivity-temperature-depth-oxygen (CTDO) profiles, direct current measurements from a lowered acoustic Doppler current profiler (LADCP), a hull-mounted acoustic Doppler current profiler (ADCP), and satellite-tracked surface drifters. Characteristics of the rings are presented and their origins are discussed. Two are typical Agulhas rings surveyed at different times after their generation; the third Agulhas ring has an anomalous watermass structure whose most likely origin is the Subtropical Front.

Godin, O.A., D. Yu. Mikhin, and D.R. Palmer. Ocean current monitoring in the coastal zone. Oceanologia, 13:174 (1999).

A new technique has recently been put forward for real-time monitoring of ocean currents in the coastal zone. The acoustic technique, called matched non-reciprocity tomography (MNT), is being developed to extend traditional ocean acoustic tomography to the coastal zone. It should provide maps of the current field extending out tens of kilometers in range and throughout the water column. These maps will have applications to several important scientific problems such as measuring ocean circulation and upwelling and monitoring global climate change. Alternative approaches for monitoring currents in the coastal zone are surveyed and their limitations when compared with the MNT approach are discussed. Non-reciprocity tomography is based on recent progress in the theory of acoustic propagation in moving media and in the use of matched-field processing to solve tomographic inverse problems. The MNT technique can be viewed as an application of matched-field processing to a judiciously selected acoustic observable that is sensitive to flow velocity, but insensitive to sound speed and bathymetric variations, and leads to robust inversions for the depth-dependence of the velocity. The development of non-reciprocity tomography is reviewed in this article in the context of extended opportunities the technique offers in monitoring ocean dynamics in the coastal zone by acoustic means. Applications of the MNT technique to problems not directly related to coastal current monitoring are also noted.

Goldenberg, S.B., and C.W. Landsea. Relationships between decadal-scale fluctuations in vertical shear from NCEP/NCAR reanalysis data and Atlantic basin tropical cyclone activity. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1089-1091 (1999).

No abstract.

Goñi, G.J. Transport estimates of the Kuroshio Current from satellite altimeter data. In Ecosystem Dynamics of the Kuroshio Oyashio Transition Region, M. Terazaki, K. Ohtani, T. Sugimoto, and Y. Watanabe (eds.). Japan Marine Science Foundation, Tokyo, 1-8 (1999).

The Kuroshio, together with the Gulf Stream, its counterpart in the North Atlantic, are the two major western boundary currents in the northern hemisphere. These currents have been viewed as the principal channel of water exchange between the equatorial regions, where heat is added to the oceans to be later removed in the polar regions. The transport of the Kursohio current remains one of the largest uncertainties in the meridional heat flux estimate across the North Pacific subtropical gyre. Estimates of the Kuroshio mean transports vary from 21 Sv to 33 Sv (1 S v =10⁶ m³ s^-1). Some characteristics of the dynamics of this current and its variability will be also briefly addressed in this work. One very important issue in ocean dynamics is to constantly monitor the subsurface thermal structure and transport of a western boundary current. This work presents a methodology that uses a combination of satellite altimetry-derived sea height anomaly and inverted echosounder-derived hydrographic data to estimate the thickness of the ocean upper layer and baroclinic transport. The estimates reveal that during the end of 1996 and beginning of 1997 the Kuroshio Current presents an anomalous behavior.

Goñi, G.J., and W.E. Johns. Synoptic study of North Brazil Current rings from altimeter data. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S179, OS31B-12 (1999).

TOPEX/POSEIDON-derived sea height anomaly fields from 1993 to 1998 are used to study the mesoscale variability off northeastern South America between 0 to 15°N and 40 to 65°W. The North Brazil Current (NBC) and the anticyclonic rings generated at this current's retroflection are the major sources of mesoscale variability in the region. Space-time diagrams show a very pronounced annual cycle of the sea height anomaly field. Once this annual cycle is removed, the sea height residuals clearly show the northwest translation of the North Brazil Current rings generated at the retroflection. Using a two-layer model, the sea height anomaly field is converted into an upper layer thickness field using parameters derived from historical hydrographic data, where the base of the upper layer is defined by the 20° isotherm. The maps of the upper layer thickness are used to find the trajectory of each ring, their velocities, length scales, and mass transport. These maps also show that 5 to 8 rings are formed every year, with the greatest frequency of formation being in boreal spring. The rings translation velocities range between 7 and 18 km/day. These rings seem to have preferred trajectories which are closely related to changes in bathymetry. Estimates of the baroclinic transport of the North Brazil Current from a T/P groundtrack across the upstream part of the retroflection show that peaks in the transport are usually followed by the formation of rings.

Goñi, G.J., M.M. Huber, and L.K. Shay. TOPEX/POSEIDON-derived Atlantic Ocean hurricane heat content estimates. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, American Meteorological Society 79th Annual Meeting, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1037-1042 (1999).

No abstract.

Goodwin, K.D., R.A. Varner, P.M. Crill, and R.S. Oremland. Uptake of near-ambient levels of methyl bromide by strain IMB-1, a facultative methylotrophic bacterium. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S64, A42C-06 (1999).

A bacterium isolated from agricultural soils, Strain IMB-1, is a facultative methylotroph able to grow on high levels (500 µM) of the agricultural fumigant, methyl bromide (CH₃Br). Agricultural and structural fumigation can release 20 to 80% of the gas that is applied, creating a potential source of stratospheric-ozone-destroying Br radicals. Investigation of Strain IMB-1 has focused on harnessing its ability to consume high levels of CH₃Br (ppmv) in order to decrease the amounts of CH₃Br released during the soil fumigation process. However, agricultural soils have also been determined to irreversibly break down ambient levels of CH₃Br (pptv). Strain IMB-1 was thus tested for its ability to consume near-ambient levels of CH3Br with the use of a permeation tube/dynamic dilution system during dynamic flow-through incubations. Strain IMB-1 grown in the presence of 0.3% CH₃Br was able to consume CH₃Br supplied at 12 parts per trillion by volume (pptv). The presence of glucose or methylamine did not inhibit CH₃Br consumption. Glucose-grown cells were induced to uptake 12 pptv CH₃Br by exposure to 0.3% CH₃Br during either exponential or stationary phases of growth. Glucose-grown cells were induced to uptake 12 pptv by exposure to 100 pptv CH₃Br only during exponential growth. The uptake rate of CH₃Br by IMB-1 grown on glucose was linearly related to concentration in the range from 12 to 19,430 pptv.

Graber, H.C., M.A. Donelan, S. Ataktürk, W.M. Drennan, and K.B. Katsaros. Marine flux-profile relations from an air-sea interaction spar buoy. Proceedings, Symposium on the Wind-Driven, Air-Sea Interface, Sydney, Australia, January 10-15, 1999, M. Banner (ed.). The University of New South Wales, 317-324 (1999).

The Air-Sea Interaction Spar (ASIS) is a new autonomous spar buoy designed to permit long-term measurements of processes at the air-sea interface. During a two-month deployment in the Gulf of Mexico in April/May 1997, the buoy recorded waves as high as 3.5 m and wind speeds up to 20 m/s. The ASIS buoy was instrumented to measure high resolution wave directional properties, wind stress, and four level profiles of wind speed, temperature, and humidity. These data are used to examine marine flux-profile relations and to explore the effect of a thick wave boundary layer on the validity of Monin-Obukhov similarity theory.

Grima, N., A. Bentamy, K.B. Katsaros, Y. Quilfen, P. Delecluse, and C. Levy. Sensitivity of an oceanic general circulation model forced by satellite wind stress fields. Journal of Geophysical Research, 104(C4):7967-7989 (1999).

Satellite wind and wind stress fields at the sea surface, derived from the scatterometers on European Remote Sensing satellites 1 and 2 (ERS-1 and ERS-2) are used to drive the ocean general circulation model (OGCM) "OPA" in the tropical oceans. The results of the impact of ERS winds are discussed in terms of the resulting thermocline, current structures, and sea level anomalies. Their adequacy is evaluated on the one hand by comparison with simulations forced by the Arpege-Climat model and on the other hand by comparison with measurements of the Tropical Atmosphere-Ocean (TAO) buoy network and of the TOPEX/Poseidon altimeter. Regarding annual mean values, the thermal and current responses of the OGCM forced by ERS winds are in good agreement with the TAO buoy observations, especially in the central and eastern Pacific Ocean. In these regions the South Equatorial Current, the Equatorial Undercurrent, and the thermocline features simulated by the OGCM forced by scatterometer wind fields are described. The impact of the ERS-1 winds is particularly significant to the description of the main oceanic variability. Compared to the TAO buoy observations, the high-frequency (a few weeks) and the low-frequency of the thermocline and zonal current variations are described. The correlation coefficients between the time series of the thermocline simulated by ERS winds and that observed by the TAO buoy network are highly significant; their mean value is 0.73, over the whole basin width, while it is 0.58 between Arpege model simulation and buoy observations. At the equator the time series of the zonal current simulated by the ERS winds, at three locations (110°W, 140°W, and 165°E) and at two depths, are compared to the TAO current meter and acoustic Doppler current profiler (ADCP) measurements. The mean value of the significant correlation coefficients computed with the in-situ measurements in 0.72 for ERS, while it is 0.51 for the Arpege-Climat model. Thus, ERS wind fields through the OGCM generate more realistic current variations than those obtained with Arpege climate winds, and they are particularly efficient in capturing abrupt changes ("wind bursts") which may be important regarding ocean dynamics.

Hansen, D.V., and W.C. Thacker. Estimation of salinity profiles in the upper ocean. Journal of Geophysical Research, 104(C4):7921-7934 (1999).

A new algorithm is presented for estimating salinity profiles in the upper ocean from measurements of temperature profiles and surface salinity. In application to the eastern tropical Pacific the method replicates a large fraction of the variability of salinity in the upper few tens of meters and provides modest to substantial improvement at nearly all levels. Estimated salinity profiles are able to characterize barrier layers, regions formed by a halocline within the thermal mixed layer. The rms error of geopotential-height calculations based on estimated salinity profiles is reduced more than 50 percent by this method relative to methods not using surface salinity. Even without the surface salinity measurement some reduction of error in geopotential heights can be obtained relative to previous methods.

Hendee, J.C. An environmental information synthesizer for expert systems. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 217 (1999).

As an enhancement to the SEAKEYS environmental monitoring network, software called the Environmental Information Synthesizer for Expert Systems (EISES) has been constructed which synthesizes knowledge from near real-time acquired meteorological and oceanographic data. This knowledge is acquired in the form of facts which can be used by expert systems designed to monitor and match environmental parameters as they meet criteria generally thought to be conducive to certain biological events. The initial expert system constructed to use the facts from EISES, which we have dubbed the Coral Reef Early Warning System (CREWS), represents a first step in the construction of a larger coral reef specific expert system. When environmental conditions are conducive to coral bleaching, according to different bleaching theories or models, CREWS produces alerts which are automatically posted to the Web and emailed to researchers so they can verify and study bleaching events as they might happen. The models are refined using feedback from field data on bleaching recorded after alerts from the expert system. CREWS has now been implemented not only for the Florida Keys National Marine Sanctuary, but also for the Great Barrier Reef Marine Park Authority, and will hopefully be developed in the future for other coral reef sanctuaries or parks throughout the world. In addition to CREWS, expert systems for Florida Bay are being developed with collaborators to model juvenile pink shrimp and fish spawning migrations (with UM/RSMAS and NOAA/NMFS) and conditions conducive to harmful algal blooms (with NOAA/NESDIS). Some other example events that might be monitored or predicted from EISES expert systems include good diving and/or fishing conditions (e.g., clear water, low winds), at remote locations, phytoplankton blooms, hypo- or hypersaline influxes from Florida Bay, and excessive dissolved nutrient encroachment (inferred from high fluorometry values).

Hood, M., R.H. Wanninkhof, and L. Merlivat. The effects of wind-induced mixing on short timescale surface variability of fCO₂ and fluorescence: Results from the GasEx-98 CARIOCA buoy data. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S47, A31C-12 (1999).

During the Lagrangian deliberate tracer study in the North Atlantic, GasEx-98, hourly measurements of wind speed, sea surface temperature, fCO₂, and fluorescence were made from two CARIOCA drifting buoys near 46°N and 21.5°W over a period of approximately 20 days. Shipboard measurements of fCO₂ were used to calibrate the buoy data, and the hourly time series of the two buoys and the ship were in good agreement. Using these data, we investigated the air-sea flux of CO₂, the importance of short-term wind-induced mixing events for longer-term estimates of flux, and the physical versus biological processes controlling surface variability of fluorescence. The air-sea flux estimate for the ~20 day experiment using the Wanninkhof (1992) gas transfer velocity formulation was -0.012 mol m^-2 d^-1, and using the Liss and Merlivat (1986) formulation was -0.007 mol m^-2 d^-1. A storm with wind speeds reaching as high as 16-17 m s^-1 led to a sharp decrease in sea surface temperature and an increase in fCO₂ of approximately 30 µatm. The magnitude of this sudden change in fCO₂ is equal to approximately half of the annual range of fCO₂ in this area and accounted for approximately 38% of the flux over the 20-day period. Approximately 16 hours after the onset of the storm, there was an increase in surface fluorescence coincident with the initial increase in fCO₂. Nitrate measurements made from the ship show a sharp peak in surface concentrations about 24 hours after the increase in winds and approximately 6-8 hours after the increase in surface fluorescence. This increase in surface fluorescence that occurs in tandem with the increase in fCO₂ and decrease in SST and before the arrival of nutrients to the surface suggests an upwelling of a relatively shallow chlorophyll maximum in this area. Phaeopigment to chlorophyll ratios are consistent with this mechanism. After the upwelling of the NO₃, the fluorescence increases more sharply while the fCO₂ decreases, consistent with biological productivity.

Houston, S.H., and M.D. Powell. Hurricanes and tropical storms in Florida Bay. Florida Sea Grant College Program, FLSGP-G-99-016, 2 pp. (1999).

No abstract.

Houston, S.H., W.A. Shaffer, M.D. Powell, and J. Chen. Comparisons of HRD and SLOSH surface wind fields in hurricanes: Implications for storm surge modeling. Weather and Forecasting, 14(5):671-686 (1999).

Surface wind observations analyzed by the Hurricane Research Division (HRD) were compared to those computed by the parametric wind model used in the National Weather Service Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model's storm surge computations for seven cases in five recent hurricanes. In six cases, the differences between the SLOSH and HRD surface peak wind speeds were 6% or less, but in one case (Hurricane Emily of 1993) the SLOSH computed peak wind speeds were 15% less than the HRD. In all seven cases, statistics for the modeled and analyzed wind fields showed that for the region of strongest winds, the mean SLOSH wind speed was 14% greater than that of the HRD and the mean inflow angle for SLOSH was 19° less than that of the HRD. The radii beyond the region of strongest winds in the seven cases had mean wind speed and inflow angle differences that were very small. The SLOSH computed peak storm surges usually compared closely to the observed values of storm surge in the region of the maximum wind speeds, except Hurricane Emily where SLOSH underestimated the peak surge. HRD's observation-based wind fields were input to SLOSH for storm surge hindcasts of Hurricanes Emily and Opal (1995). In Opal, the HRD input produced nearly the same computed storm surges as those computed from the SLOSH parametric wind model, and the calculated surge was insensitive to perturbations in the HRD wind field. For Emily, observation-based winds produced a computed storm surge that was closer to the peak observed surge, confirming that the computed surge in Pamlico Sound was sensitive to atmospheric forcing. Using real-time, observation-based winds in SLOSH would likely improve storm surge computations in landfalling hurricanes affected by synoptic and mesoscale factors that are not accounted for in parametric models (e.g., a strongly sheared environment, convective asymmetries, and stably stratified boundary layers). An accurate diagnosis of storm surge flooding, based on the actual track and wind fields, could be supplied to emergency management agencies, government officials, and utilities to help with damage assessment and recovery efforts.

Houston, S.H., G. Forbes, A. Chiu, W.-C. Lee, and P.P. Dodge. Super Typhoon Paka's (1997) surface winds. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1032-1033 (1999).

No abstract.

Huang, H., R.E. Fergen, J.J. Tsai, and J.R. Proni. Evaluation of mixing zone models: CORMIX, PLUMES, and OMZA with field data from two Florida ocean outfalls. Proceedings, Second International Symposium on Environmental Hydraulics, Hong Kong, China, December 16-18, 1998. Environmental Hydraulics, pp. 249-254 (1999).

This paper presents an evaluation of three mixing zone models: CORMIX, PLUMES, and OMZA using field data from two Florida ocean outfalls: Hollywood and Miami-Central outfalls. The hollywood outfall has a single port outlet and the Miami-Central outfall has a multiport diffuser. Both outfalls discharge secondary effluent. For the nearfield, all of the three models predict realistic initial dilutions for the tests at the outfall except three cases in CORMIX predictions and two cases in PLUMES predictions (out of 20 cases). For the nearfield and farfield combined, CORMIX significantly overestimates dye concentrations for the tests at the Hollywood outfall but underestimates dye concentrations within the 300 m to 400 m range for the tests at the Miami-Central outfall. PLUMES predictions agree reasonably well with the filed data for the range from 300 m to 800 m but do not agree well within the 300 m range for the tests at both outfalls. OMZA predictions agree well with the field data within the 800 m range for the test at both outfalls.

Huber, M.M., L.K. Shay, and G.J. Goñi. The Atlantic Ocean's role on intensity change. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, American Meteorological Society 79th Annual Meeting, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 36-39 (1999).

No abstract.

Humphrey, J.C., S.L. Vargo, J.C. Ogden, and J.C. Hendee. SEAKEYS 1999: Florida Keys monitoring initiative. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Program and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 240-241 (1999).

The Sustained Ecological Research Related to the Management of the Florida Keys Seascape (SEAKEYS) program was organized in 1991 by the Florida Institute of Oceanography (FIO) with initial funding from the John D. and Catherine T. MacArthur Foundation, and continuing funding from the South Florida Ecosystem Restoration, Prediction and Monitoring (SFERPM) program, administered by the National Oceanic and Atmospheric Administration (NOAA). The SEAKEYS environmental monitoring program, which is basically an oceanographic extension to the meteorologically-oriented Coastal-Marine Automated Network of NOAA, has accumulated an unparalleled long-term database of meteorological and oceanographic data from the Florida Straits and Florida Bay. During 1998, the SEAKEYS network was upgraded with more precise oceanographic sensors, and selected stations were augmented with fluorometers, transmissometers, and water-level sensing equipment. A seventh monitoring station, a cooperative effort between FIO and the University of South Florida's Department of Marine Science (USF/DMS), was completed in Northwest Florida Bay at 25°05'00"N, 81°05'30"W during summer, 1998. This station also contains a full suite of meteorological and oceanographic instrumentation and also transmits its data hourly via a NOAA GOES satellite. The Northwest Florida Bay station is the northwestern most station in the SEAKEYS network, as well as the southernmost link in the West Florida Coastal Ocean Monitoring and Prediction System of USF/DMS. Turbulent weather was prominent during 1998 in the Florida Keys. Severe conditions reported by the SEAKEYS stations included the Ground Hog Day Storm, Hurricane Georges, and Tropical Storm Mitch. In most cases the SEAKEYS stations contained the only instruments to measure the meteorological and oceanographic measurements accompanying these events in the Florida Keys. The Long Key station measured the highest winds (119 mph) in South Florida during the Ground Hog Day Storm of February 2, 1998. On September 25, 1998 the eye of Hurricane Georges passed over Key West at 1150 EDT as wind speeds dropped from 85.2 mph to 9.6 mph. The eye moved across the Dry Tortugas station at 1610 EDT with barometric pressures dropping to 974.4 mb. Winds gusted to hurricane force only after the eye passed at 2100 EDT. Georges' most severe winds in the Florida Keys gusted to 113 mph at Sombrero Reef, with a sustained wind speed of 94 mph. Long Key, Molasses Reef, and Fowey Rocks received gusts of tropical storm force. The tide station at Sombrero Reef reported a storm water level of 2.87 feet above mean lower low water. This contrasted with below normal levels reported at a station on Florida Bay. Hurricane Mitch passed northwest of the Florida Keys on the evening of November 4, 1998, bringing peak winds of 62.4 mph at Molasses Reef and sustained gale force winds until the following afternoon. Numerous localized tornadoes spawned by this storm caused extensive damage in the Upper Keys. Daily near real-time SEAKEYS data are available to researchers via NOAA's Coral Health and Monitoring Program (CHAMP) Web site at http://www.coral.noaa.gov, while historical data are available at http://www.neptune.noaa.gov. The Coral Reef Early Warning System (CREWS), which utilizes the near real-time data from six SEAKEYS stations, is an online expert system which monitors environmental conditions on the reef that are theoretically conducive to coral bleaching. If these conditions occur, alerts are sent via email to researchers and posted to the Web at http://www.coral.noaa.gov/sferpm/seakeys/es.

Johns, E., W.D. Wilson, and T.N. Lee. Surface salinity variability of Florida Bay and southwest Florida coastal waters. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 169-171 (1999).

No abstract.

Johns, E., W.D. Wilson, and R.L. Molinari. Direct observations of velocity and transport in the passages between the Intra-Americas Sea and the Atlantic Ocean, 1984-1996. Journal of Geophysical Research, 104(C11):25,805-25,820 (1999).

Shipboard acoustic Doppler current profiler observations of the velocity in the upper 200 m of the water column collected during 1984-1996 using the National Oceanic and Atmospheric Administration R/V Malcolm Baldrige are used to examine the velocity structure and transport in the passages between the Atlantic Ocean and the Intra-Americas Sea (IAS). Data were colected during 23 cruises along the following sections: across the Straits of Florida, in the Northwest Providence Channel (NWPC), across the northern passages into the Caribbean Sea (Windward, Mona, and Anegada), across the eastern Caribbean along 63°30'W, thereby forming a closed quadrangle, and in the Grenada Passage. The Florida Current, the eastern Caribbean, and the Grenada Passage share a similar mean velocity structure characterized by high-velocity, surface intensified flows with strong vertical and horizontal shears. The northern Caribbean passages (NWPC, Windward, Mona, and Anegada) share a different common mean velocity structure, with subsurface velocity maxima directed into the IAS, and surface-intensified counterflows along one side of each paassage. On average, there is a transport balance in the upper 200 m between waters entering and exiting the IAS, with the 16.5 ± 2.4 Sv (1 Sv = 10⁶ m³ s^-1) transport of the Florida Current at 27°N comprised of 0.4 ± 0.8 Sv from the NWPC, 2.2 ± 1.5 Sv from the Windward Passage, 2.8 ± 2.1 and 2.4 ± 2.8 Sv from the Mona and Anegada passages, respectively, and 9.5 ± 4.7 Sv across the eastern Caribbean, for a total of 17.3 Sv. The four passages north of 17°N (from NWPC to Anegada Passage) have a combined transport of 7.8 Sv, nearly half of the transport of the Florida Current in the upper 200 m. Of the 9.5 Sv flowing through the eastern Caribbean between 11°N and 17°N, 4.9 ± 2.6 Sv, or more than half, come from the Grenada Passage. This is significant to the subject of cross-equatorial exchange of mass, heat, and salt, as the Grenada Passage is where the highest transport of waters originating in the southern hemisphere is thought to enter the Caribbean.

Jones, R.W., and M. DeMaria. Further studies of the optimization of a hurricane track prediction model using the adjoint equations. Monthly Weather Review, 127(7):1586-1598 (1999).

The method of model fitting, or adjoint method, is applied to a barotropic hurricane track forecast model described by DeMaria and Jones using a large sample of forecast cases. The sample includes all Atlantic tropical cyclones that reached hurricane intensity during the 1989-1993 hurricane seasons (141 72-h forecasts of 17 storms). The cases considered by DeMaria and Jones are a subset of the present sample. Model-fitting calculations using strong, weak, strong followed by weak, or weak followed by strong model constraints are discussed for data assimilation periods varying from 6 to 72 h. Generally, the best track forecasts occur for shorter assimilation periods and for weak constraints, although only the 12-h assimilation with the weak constraint has less track error than the control forecast without assimilation, and only for the 12-h forecast. The principle reason for this lack of improvement is that the fit of the model to the observed track is good at the middle of the assimilation period, but not very good at the end where the forecast begins. When a future track position at 6 h is included in the assimilation, in order to improve the track fit at the synoptic data time, the resulting track errors average about 10% smaller than the control forecast. The control forecast may also be improved in the same way. In that case, the best assimilation forecasts have 2.5% smaller track errors than the modified control forecasts.

Jones, R.W., and H.E. Willoughby. Results of generalizing a semispectral shallow-water barotropic hurricane tracking model into a two-layer baroclinic model. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 747-750 (1999).

No abstract.

Kaplan, J., and M. DeMaria. Climatological and synoptic characteristics of rapidly intensifying tropical cyclones in the North Atlantic basin. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 592-595 (1999).

No abstract.

Kelly, P.S., K.M. Lwiza, R.K. Cowen, and G.J. Goñi. Low-salinity lenses at Barbados, West Indies: Their origin, frequency, and variability. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S185, OS42C-01 (1999).

A vertical array of conductivity-temperature sensors moored west of Barbados, West Indies, from May 1996 to November 1997 revealed a heterogeneous and variable salinity pattern punctuated by six intrusions of low-salinity water (less than 34.5 psu). A typical intrusion extended to 30 m depth and lasted ~25 days, although one intrusion extended to 47 m and lasted 94 days. Water samples taken during an intrusion in May 1997 have Radium 228/226 activity ratios of approximately 1, consistent with previous measurements in Barbados of water that originated in the Amazon River mixing zone. The Amazon water likely was translated to Barbados in rings spawned from the North Brazil Current (NBC). Analysis of sea height anomaly derived from the TOPEX/Poseidon satellite altimeter supports this conclusion and reveals that, contrary to previous studies, rings are shed throughout the year, mostly during spring. The intrusions of low-salinity water and their associated velocities dramatically changed the already variable flow in our study area. The complex salinity and flow we observed represented the effects of NBC rings passing the island, perhaps disrupted by the relatively shallow Tobago-Barbados ridge. The complex velocity and water structure are interesting in their own right as evidence of the Barbados region as a mixing zone and for their influence on recruitment of larval fishes to the reef along the island's west coast.

Landsea, C.W., and J.F. Knaff. How much "skill" did the various forecasting methods available have for the 1997-1998 El Niño event? Preprints, Second Hayes Symposium on Seasonal to Interannual Climate Variability--The 1997/1998 ENSO Cycle, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 73 (1999).

No abstract.

Landsea, C.W., R.A. Pielke, A.M. Mestas-Nuñez, and J.A. Knaff. Atlantic basin hurricanes: Indices of climatic changes. Climatic Change, 42:89-129 (1999).

Accurate records of basin-wide Atlantic and U.S. landfalling hurricanes extend back to the mid 1940s and the turn of the century, respectively, as a result of aircraft reconnaissance and instrumented weather stations along the U.S. coasts. Such long-term records are not exceeded elsewhere in the tropics. The Atlantic hurricanes, U.S. landfalling hurricanes, and U.S. normalized damage time series are examined for interannual trends and multidecadal variability. It is found that only weak linear trends can be ascribed to the hurricane activity and that multidecadal variability is more characteristic of the region. Various environmental factors including Caribbean sea level pressures and 200 mb zonal winds, the stratospheric Quasi-Biennial Oscillation, the El Niño-Southern Oscillation, African West Sahel rainfall, and Atlantic sea surface temperatures, are analyzed for interannual links to the Atlantic hurricane activity. All show significant, concurrent relationships to the frequency, intensity, and duration of Atlantic hurricanes. Additionally, variations in the El Niño-Southern Oscillation are significantly linked to changes in U.S. tropical cyclone-caused damages. Finally, much of the multidecadal hurricane activity can be linked to the Atlantic Multidecadal Mode, an empirical orthogonal function pattern derived from a global sea surface temperature record. Such linkages may allow for prediction of Atlantic hurricane activity on a multidecadal basis. These results are placed into the context of climate change and natural hazards policy.

Landsea, C.W., C.A. Anderson, G. Clark, J. Fernandez-Partagas, P. Hungerford, C. Neumann, and M. Zimmer. The Atlantic hurricane database re-analysis project. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 394-397 (1999).

No abstract.

Lapitan, R.L., R.H. Wanninkhof, and A.R. Mosier. Methods for stable gas flux determination in aquatic and terrestrial systems. In Approaches to Scaling of Trace Gas Fluxes in Ecosystems, A.F. Bouwman (ed.), Elsevier, Amsterdam, 27-66 (1999).

A general description of the current approaches for measuring trace gas fluxes in aquatic and terrestrial systems is presented in this paper. Our aim is to provide an overview of the current methodologies employed in trace gas flux measurements and the most recent advancements made; with emphasis on the uncertainties observed and potential areas for future developments required to further minimize these uncertainties brought about by spatial and temporal variabilities of fluxes in the field. The increase in sensitivity and improved response time of analytical devices for measuring trace gases within the last five years, such as advancements in laser spectroscopy, have significantly improved the effectiveness of the current methods of measuring these gases in aquatic and terrestrial systems. Systematic errors in trace gas flux estimates have also been reduced with the refinements in estimates of the gas transfer velocity,k, through the use of tracers in the two systems. Footprint corrections of micrometeorological flux measurements in terrestrial systems have provided a better means of identifying the spatial sources of trace gases, and thus, have increased the scope of inference from trace gas flux measurements. Despite these improvements, however, flux measurement errors still remain high. Experimental and sampling designs that can efficiently and effectively deal with the spatial and temporal variabilities in trace gas flux measurements to the minimum are of utmost priority. The same can be said of the modeling procedures; that is, there is a need for an effective method that can reduce instead of propagate potential errors in scaling from field plot to regional or global scales.

Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global distribution of total inorganic carbon in surface water. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 493-496 (1999).

No abstract.

Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely. Interannual variations in oceanic uptake of anthropogenic carbon dioxide for the period of 1982-1995. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 31-34 (1999).

No abstract.

Lee, T.N., E. Williams, E. Johns, and W.D. Wilson. First year results from enhanced observations of circulation and exchange processes in western Florida Bay and connecting coastal waters, including effects of El Niño and Hurricane Georges. 1999 Florida Bay and Adjacent Marine System Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 145-147 (1999).

No abstract.

Majumdar, S.J., S.D. Aberson, C.H. Bishop, and Z. Toth. Real time hurricane track targeting using a VICBAR ensemble. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 755-756 (1999).

No abstract.

Marks, F.D., and H.A. Friedman. 1999 Hurricane Field Program Plan. U.S. Department of Commerce, NOAA/Atlantic Oceanographic and Meteorological Laboratory, Miami Florida (published for limited distribution), 142 pp. (1999).

No abstract.

Marks, F.D., P.P. Dodge, and C. Sandin. WSR-88D observations of hurricane atmospheric boundary layer structure at landfall. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 1051-1054 (1999).

No abstract.

McGillis, W., J. Edson, and R.H. Wanninkhof. Direct air-sea flux measurements of carbon dioxide over the North Atlantic Ocean and the comparison to indirect methods. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22,1999. Center for Global Environmental Research (CGER-I037-99), 367-377 (1999).

To date, large uncertainties in the extent of the CO₂ flux between the atmosphere and ocean have prevented us from accurately quantifying how the increasing atmospheric CO₂ burden partitions between the ocean and the terrestrial biosphere. This limits our ability to accurately predict future atmospheric CO₂ levels. We have recently designed a direct CO₂ flux measurement system that considerably improves our estimates of air-sea gas exchange. The system measures the direct air-sea flux of CO₂ in the atmospheric boundary layer using eddy correlation (direct covariance). It was successfully deployed during the large scale experiment to study air-sea gas fixes, GASES98, which was conducted in the CO₂ sink region of the North Atlantic during May/June of 1998. The seasonal algal bloom caused air-sea pCO₂ differences of between -80 to ~100 µatm. This large concentration gradient generated large signals for accurate measurement of the CO₂ flux using a close path CO₂ sensor. In addition to the CO₂ gas flux, the comprehensive atmospheric flux measurement suite included momentum, heat, and moisture fluxes. Atmospheric flux and air-sea gas concentration measurements were performed for over 500 hours, providing more than 1000 observations. Wind speeds between 1 and 16 m/s were experienced over the range of these observations. Preliminary flux estimates from our system compare extremely well with previous estimates of the gas transfer velocity for wind speeds below 7 m/s. At higher wind speeds, the transfer velocities obtained from our system are as much as 20-50% higher than those estimated by empirical relationships. Based on accurate air-sea CO₂ coefficients obtained by our investigation and atmospheric and surface ocean pCO₂ data obtained to date, estimates of the global ocean CO₂ sink are now feasible. Our findings will also provide better predictions of the seasonal and interannual variability of sea-air CO₂ flux observed in various global regions.

McTaggart, K.E., G.C. Johnson, C.I. Fleurant, and M.O. Baringer. CTD/O₂ measurements collected on a Climate and Global Change cruise along 24°N in the Atlantic Ocean (WOCE section A6) during January-February 1998. NOAA Data Report, ERL PMEL-68 (PB99-155194), 368 pp. (1999).

Summaries of CTD/O₂ measurements and hydrographic data acquired on a Climate and Global Change cruise during the winter of 1998 aboard the NOAA ship Ronald H. Brown are presented. The majority of these data were collected along 24.5°N from 23.5°W to 69°W. Completing the transatlantic section are data collected along a northeast-southwest dogleg off the coast of Africa, and along a second, short, zonal section along 26.5°N off the coast of Abaco Island from 69°W to 77°W, jogging north along 27°N in the Straits of Florida to 80°W. Data acquisition and processing systems are described and calibration procedures are documented. Station location, meteorological conditions, CTD/O₂ summary data listings, profiles, and potential temperature-salinity diagrams are included for each cast. Section plots of oceanographic variables and hydrographic data listings are also given.

Mestas-Nuñez, A.M., and D.B. Enfield. Rotated global modes of non-ENSO sea surface temperature variability. Journal of Climate, 12(9):2734-2746 (1999).

A varimax rotation was applied to the EOF modes of global SST derived by Enfield and Mestas-Nuñez (1999). The SST anomaly record is more than a century long, with a global complex EOF representation of ENSO and a linear trend removed at every grid point. The rotated EOF modes capture localized centers of variability that contribute to the larger scale spatial patterns of the unrotated modes. The first rotated EOF represents a multidecadal signal with larger response in the North Atlantic. The second rotated EOF represents an interdecadal uctuation with larger response in the eastern North Pacific and out of phase fluctuations of smaller amplitude in the central North Pacific. The third rotated EOF captures interdecadal fluctuations in the eastern tropical Pacific with a dominant peak that coincides with the 1982-83 ENSO. The fourth rotated EOF has an interdecadal to multidecadal nature with larger response in the central equatorial Pacific and quasi-symmetric out of phase response in the western North and South Pacific. The fifth mode represents multidecadal fluctuations with large response at about 40°N in the North Pacific. The sixth mode has interannual to interdecadal time scales with largest response confined to the South Atlantic. Our rotated modes are dominated by intra- rather than interocean uctuations supporting the hypothesis that the non-ENSO variability is more regional than global in nature. Analyses of sea level pressure and surface wind stress show that in general the non-ENSO rotated EOFs are consistent with an ocean response to local atmospheric forcing. An exception is the eastern tropical Pacific mode which is more consistent with an atmospheric response to changes in the ocean SST.

Mestas-Nuñez, A.M., and D.B. Enfield. Rotated global modes of non-ENSO sea surface temperature. Proceedings, 23rd Annual Climate Diagnostics and Prediction Workshop, Miami, Florida, October 26-30, 1998. National Weather Service, 162-165 (1999).

No abstract.

Molinari, R.L. Lessons learned from operating global ocean observing networks. Bulletin of the American Meteorological Society, 80(7):1413-1420 (1999).

The Global Ocean Observing System Center (GOOSC) at the National Oceanic and Atmospheric Administration's (NOAA) Atlantic Oceanographic and Meteorological Laboratory operates two global observing networks, a drifting buoy array, and a Voluntary Observing Ship network. The arrays provide in real time surface atmospheric and subsurface oceanographic data needed by NOAA weather and climate forecasters. The data are used in delayed mode to verify model simulations of the ocean and atmosphere, to provide in situ calibration/validation data for remote sensing observations, and to increase understanding of the dynamics of the ocean and atmosphere. The operational and research lessons learned in the operation of the GOOSC are reviewed. Operationally, it was learned that, because of costs, international participation is required to maintain global networks; data management methodology is a critical component of operations; and integrated observing systems using multiple platforms provide more accurate products. Scientifically, it was learned, for example, that accurate characterizations of the salinity field must be available in model simulations. As more data become available it is found that scales of important phenomena such as equatorial upwelling are smaller, and high-frequency signals can impact on the mean structure of the upper ocean. These findings must be considered when designing effective sampling strategies.

Molinari, R.L., S.L. Garzoli, and R.W. Schmitt. Equatorial currents at 1000 m in the Atlantic Ocean. Geophysical Research Letters, 26(3):361-364 (1999).

Twenty-seven Profiling ALACE (PALACE) floats were deployed in the equatorial Atlantic during July-August 1997. The floats were ballasted to drift at 1000 m for 10 to 14 days, return to the surface while obtaining a temperature profile, transmit data via satellite, and then after one day return to 1000 m. One-year float paths are now available. Floats deployed on the equator were launched into a deep westward jet. The jet extends some 1-2° north of the equator, with eastward motion observed in floats to the north of 2°N. The equatorial current reverses in the central basin to the east in mid-October and then back to the west in mid-February. Flow to the north also reverses. The short space and time scales contrast with earlier work based on fewer floats that inferred space scales of some 5 -10 in latitude and time scales greater than one year. The new results are consistent with models that indicate that equatorial Rossby waves are the cause of the reversing currents.

Murillo, S.T., and J.J. O'Brien. The influence of ENSO on eastern Pacific tropical cyclones. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 437-438 (1999).

No abstract.

Murillo, S.T., W.-C. Lee, K. Hondl, P.P. Dodge, C. McAdie, and F.D. Marks. Implementation of the GBVTD technique in nowcasting hurricane wind fields using the WSR-88D. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 311-312 (1999). No abstract.

Nelsen, T.A., and J.R. Proni. Detecting, mapping, sampling, and analyzing oceanic suspended particulate matter: Methods complementary to acoustic detection of environmentally sensitive ocean outfall and dumped materials. Joint Meeting, 137th Regular Meeting of the Acoustical Society of America and 2nd Convention of the European Acoustics Association: Forum Acousticum 99, Berlin, Germany, March 15-19, 1999. Journal of the Acoustical Society of America, 105(2):1322 (1999).

Natural systems such as lakes, rivers, and oceans can be described by dissolved and particulate components. Particulate sources in coastal oceanic environments include natural materials from seaward riverine and estuarine flows and anthropogenic sources such as ocean dumping and outfalls. Plumes of suspended particulate matter (SPM) can be natural (lithogenic and biogenic), anthropogenic, and any mixture of these. Because SPM can range from environmentally neutral (i.e.,lithogenic and biogenic) to hazardous (heavy metals, bacteria), detecting, tracking, sampling, and sourcing SPM plumes can be beneficial for the environment and human health. Acoustic methods have proven successful in detecting and mapping oceanic SPM over large spatial areas but are limited in resolving internal fine structure, estimating relative contributions of merged plumes from various sources (e.g., river outflow vs. dumping), and differentiating between introduced and in-situ SPM. To complement acoustics, CTD/optical/water survey tools have been employed for guided sampling of plumes. Water samples for total suspended matter (TSM) and particle size distributions have proven useful to both calibrate acoustic measurements and provide insight into signatures provided by particle size distributions. Signatures, determined by factor and component analyses, allows mapping of SPM components, as well as estimating their dilution and long-termed budgets.

Nelsen, T.A., and J.R. Proni. Distribution and movement of discharged dredged material at the San Juan Ocean Disposal site. Final Report to the U.S. Army Corps of Engineers, MIPR No. W32CS580843181, 57 pp. (1999).

No abstract.

Nelsen, T.A., and J.R. Proni. Signatures contained in suspended particulate matter with application to coastal-ocean environmental studies. In Coastal Engineering and Marine Developments, C. Brebbia and P Anagnostopoulos (eds.). WIT Press, Southampton, 328-346 (1999).

Suspended particulate matter (SPM) samples from the New York Bight Apex collected during a sewage-dump experiment were analyzed for chemical as well as physical parameters such as particle-size distributions. The latter provided a signature of the SPMs' sewage component that allowed differentiation from other components. These results were applied to a series of eight Water Column Characterization (WCC) cruises in this area. Co-analysis of WCC and sewage dump particle-size distributions by factor analysis and Distribution Component Analysis revealed patterns that allowed differentiation of sewage-derived components for all WCC samples. From this, a long-termed budget of SPM components, including sewage-derived materials, was constructed. Given this, we conclude that useful tools are available for developing signatures of anthropogenic components of SPM plumes which are independent of study sites or subject materials. These signatures can be applied to understand the sources, pathways, and sinks of such materials in the coastal ocean, as well as constructing long-termed budgets thereof. Ultimately such estimates can be critical to waste management strategies and decisions in an ever more anthropogenically-impacted coastal ocean.

Nelsen, T.A., G. Garte, C.M. Featherstone, P.L. Blackwelder, T. Hood, C. Alvarez-Zarikian, P. Swart, H.R. Wanless, L. Tedesco, C. Souch, J. Pachut, and J. Arthur. Understanding long-term rainfall, freshwater flow, and salinity patterns with concomitant responses of benthic microfauna, stable isotopes, and pollen in Oyster and Florida Bays. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 189-190 (1999).

Salinity records exhibited variability from the decadal scale to the monthly scale that can be accounted for by changing patterns in regional rainfall. Changes in salinity, both near the outflow of the Shart River Slough at Oyster Bay, and in central Florida Bay near Jimmy Key, show a direct response to regional rainfall on these time scales. Moreover, regional rainfall, represented by the 80+ year record at Homestead, Florida, proved representative of the study area and indicated high correlation with flow into Shark River Slough prior to major watershed construction instigated in the early 1960s. During subsequent periods of water management strategies, enacted from the mid-1960s to present, results indicate essentially no correlation between regional ranfall and flow during the Monthly Allocation Plan. In contrast, correlations most closely paralleled pre-construction, apparently more natural condtions, during the Rainfall Plan. Investigated characteristics for the benthic microfaunal community (foraminifers and ostracods) such as stable isotopes, abundance, and community diversity, exhibited changes and trends that apparently more closely paralleled natural rather than anthropogenic influences over the whole period of record. At both Jimmy Key and Oyster Bay, foraminifer and ostracod data indicate direct correlation to rainfall patterns for temporal scales ranging from decadal down to the limit-of-resolution of our geochronology. An exception to this natural influence was observed from the late-1940s to mid-1950s during which time a dual transition occurred in the sediments adjacent to the Shark River Slough in Oyster Bay. Organic carbon content permanently declined from above- to below-average with concurrent onset of major increases in foraminifer and ostracod abundances. These events temporally conicided with the construction of the Everglades Agricultural Area, which impounded 700,000 acres of organic-rich swampland. These effects were not observed for sediments representing the same time period at Jimmy Key. Stable isotope (delta ¹⁸O, delta ¹³O) trends alone for ostracods and foraminifers at Oyster Bay and Jimmy Key showed mixed signals, with most data suggesting upcore trends to less fresh, more marine conditions. However, when long-term trends for relative abundance of salinity-sensitive species were examined, for the same time periods and locations, they confirmed a statistically valid upcore trend toward less fresh, more marine conditions at both Oyster and Florida Bay study sites. This trend was coincident with a weak decline in regional rainfall over the same time span. Changes in the stable isotopic values of these microfauna indicated, to the limits of our geochronology, direct responses to regional rainfall. Such responses more closely paralleled rainfall than freshwater runoff, even adjacent to the outflow of the Shark River Slough. At Oyster Bay, istracod stable isotope (delta¹⁸O) trends correlated better with variabions in regional rainfall than with freshwater outflow from the adjacent Shark River Slough. Crashes in microfaunal abundances at Oyster Bay and more gradual declines at Jimmy Key were salinity related. This abundance drop was concurrent with an equally dramatic drop in community diversity. The latter was characterized by survivor-mode dominance by two microfaunal species and occurred over a period of drought at both sites and the related reduced flow from Shart River Slough. A non-traditional use of pollen allowed evaluation of the degree of paleo-flushing from Shark River Slough that not only correlated well with existing flow and rainfall records but suggests validity as a flushing proxy for pre-record eras. Analysis of regional pollen indicated taxa associations that allowed discrimination of pollen zonations from coastal mangrove to upland slough environments. This, in turn, allowed reconstruction in the sediment record of historical periods of major to minor flushing from Shark River Slough.

Ooyama, K.V. Boundary-layer parameterization in a cloud-resolving model using the radical thermodynamic formulation. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 150-152 (1999).

No abstract.

Ortner, P.B., L.B. Crowder, and D.E. Hoss. The South Atlantic Bight Recruitment Experiment: Introduction and overview. Fisheries Oceanography, 8:1-6 (1999).

The South Atlantic Bight Recruitment Experiment (SABRE) brought together an interdisciplinary team of scientists to conduct research to enhance our understanding of the relationship between variation in environmental factors and the variable recruitment of "estuarine dependent" fishes within the South Atlantic Bight. The project sought to develop a new fusion of government and academic scientists, each possessing unique skills, to address the difficult problem of recruitment variability in fishes. This fusion required the development of appropriate and, at that time, novel management and administrative strategies. SABRE initially focused on recruitment dynamics of Atlantic menhaden, Brevoortia tyrannus, in the South Atlantic Bight, but expanded over time to include several estuarine-dependent species and much of the Middle Atlantic Bight as well. The project was conducted from 1991 to 1997 and resulted in a substantial improvement in our understanding of the life history and ecology of Atlantic menhaden and the potential constraints upon its recruitment. SABRE also contributed to our understanding of the physical oceanography of the western North Atlantic shelf and adjacent coastal inlets and the implications of physical dynamics upon the potential pathways for larval transport.

Ortner, P.B., M.J. Dagg, G.S. Kleppel, and C.R. Tomas. Grazing by zooplankton in Florida Bay waters. Florida Sea Grant College Program, FLSGP-G-99-012, 2 pp. (1999).

No abstract. Palmer, D.R. Parabolic approximations for global acoustic propagation modeling. NOAA Technical Memorandum, ERL AOML-94 (PB99-171571), 54 pp. (1999).

Motivated by the difficulty in using the splitting matrix method to obtain parabolic approximations to complicated wave equations, we have developed an alternative method. It is three-dimensional, does not a priori assume a preferred direction or path of propagation in the horizontal, determines spreading factors, and results in equations that are energy conserving. It is an extension of previous work by several authors relating parabolic equations to the horizontal ray acoustics approximation. Unlike previous work, it applies the horizontal ray acoustics approximation to the propagator rather than to the Green's function or the homogenous field. The propagator is related to the Green's function by an integral over the famous "fifth parameter" of Fock and Feynman. Methods for evaluating this integral are equivalent to narrow-angle approximations and their wide-angle improvements. When this new method is applied to simple problems, it gives the standard results. In this paper, it is described by applying it to a problem of current interest: the development of a parabolic approximation for modeling global underwater and atmospheric acoustic propagation. The oceanic or atmospheric waveguide is on an Earth (or other heavenly body) that is modeled as an arbitrary convex solid of revolution. The method results in a parabolic equation that is energy conserving and has a spreading factor that describes field intensification for antipodal propagation. Significantly, it does not have the singularities in its range-sliced version possessed by many parabolic equations developed for global propagation. The work is generalized to allow for refracted geodetics and the possibility that the depth dependence of the pressure field can be described by adiabatic normal modes.

Peng, T.-H., and F. Chai. Modeling the carbon cycle in the equatorial Pacific Ocean. Proceedings, Second International Symposium on CO₂ in the Ocean, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 183-189 (1999).

As part of the U.S. JGOFS SMP program, we have developed an ocean ecosystem model of the equatorial Pacific Ocean with new and export productivity regulated by Si and Fe to synthesize and to analyze data collected during the process-study-oriented survey cruises in 1992. The circulation model is based on the Modular Ocean Model of the NOAA/GFDL ocean general circulation model. The ecosystem model consists of nine components describing two size phytoplankton, two size zooplankton, two detritus pool, and three dissolved nutrients: silicate, nitrate, and ammonium. The carbonate chemistry is parameterized in the model to evaluate the variations of pCO₂, and hence the CO₂ flux across the air-sea interface. At this initial stage, a test case by using a 1D model is performed to simulate low-silicate, high-nitrate, and low-chlorophyll conditions in the equatorial Pacific, and to investigate how the carbon system behaves in this ecosystem structure. The model includes the vertical upwelling and diffusion processes. The upwelling rate and vertical diffusivity were initially averaged for the region 5°S to 5°N, 180°W to 90°W, the "cold tongue" of the equatorial Pacific from the parameter values of 3D model simulations. Temperature is used to calibrate model upwelling and vertical diffusion rates. Comparison of model results with the observations made during the NOAA/OACES EqPac 1992 expeditions indicates that the vertical profiles of DIC, NO₃ and Si(OH)₄ are consistent with the measurements made in the fall season when the ocean was in a normal non-El Niño condition. A tight fit of profiles between model and observation is not possible because of spatial variations of the observed values. A 3D simulation is required, which is in progress. The 1D model CO₂ evasion rate is estimated to be 2.9 mol/m²/yr, which is within the range of estimates from measurements made during non-El Niño conditions.

Peng, T.-H., and R.H. Wanninkhof. Re-evaluation of historical carbon data based on recent high-quality measurements. AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(46):F579, OS51E-15 (1999).

In the Indian Ocean, crossover stations between GEOSECS and recent NOAA/DOE CO₂ survey sampling cruises are selected. Measurements of temperature, salinity, oxygen, TCO₂, and alkalinity for samples taken below 2000 m depth at these crossover stations are compared. Because water masses below this depth are relatively stable with respect to anthropogenic disturbances, the carbon chemistry and hydrographic properties should remain unchanged in the last three decades. Hence, comparison of deep water properties between new and old data will provide information regarding the need for correction or adjustment in the older data sets. Systematic differences between the two data sets reflect the need for such correction. We apply "Linear Least-Squares Multiple Regression" of TCO₂ against salinity, potential temperature, oxygen, and alkalinity of deep waters in new data sets. Using this relationship, TCO₂ is predicted from these parameters measured during GEOSECS at the crossover station. The difference between the predicted TCO2 and the GEOSECS observed TCO₂ is the adjustment needed for this historical data. The overall average is 21.6 ± 4.1 mol/kg, which is the mean adjustment needs to be made to all GEOSECS TCO2 measurements in the Indian Ocean.

Peng, T.-H., J.-J. Hung, R.H. Wanninkhof, and F.J. Millero. Carbon budget in the East China Sea in spring. Tellus B, 51(2):531-540 (1999).

Results of total dissolved inorganic carbon (DIC) and total alkalinity (TA) measurements made in the East China Sea (ECS) during a geochemical expedition of KEEP (Kuroshio Edge Exchange Processes) program in May of 1996 show that ECS is a CO₂ sink during the spring season. The mean difference of fCO₂ (fugacity of CO₂) between the atmosphere and surface water is calculated to be 28 µatm, and the resulting net CO₂ invasion flux is 2.1 mol/m²/yr, which gives about 0.03 GtC/yr of CO₂ uptake in this continental shelf in spring. This study supports the notion that shelf regions can be a significant CO₂ sink. The riverine alkalinity, which discharges into ECS, is estimated to be 1,743 µmol/kg on the basis of a linear relationship between TA and salinity. The observed salinity-normalized alkalinity in ECS is higher than that in the open sea, and this excess alkalinity is estimated to be 42 µmol/kg. With the known rate of the Changjiang discharge, this excess TA gives a mean residence time of 1.2 years for the continental shelf water in the ECS. The DIC in the ECS is also found to be higher than that in the open sea. This excess DIC is estimated to be about 76 ± 70 µmol/kg, which is equal to a net carbon input to ECS of 3.9 ± 3.6 mol/m²/yr. Based on the riverine alkalinity input, the equivalent riverine carbon flux from Changjiang discharge is estimated to be about 1.8 mol/m²/yr. With net CO₂ invasion flux of 2.1 ± 2.8 mol/m²/yr, the remaining 0 ± 4.6 mol/m²/yr could come from remineralization of organic matter derived from biological pump in the shelf or terrestrial sources. Although this preliminary carbon budget implies that gas exchange and riverine input are the main sources of excess carbon in ECS, the contribution of biological carbon flux can not be ruled out because of the large uncertainty associated with these estimates.

Pielke, R.A., and C.W. Landsea. La Niña, El Niño, and Atlantic hurricane damages in the United States. Bulletin of the American Meteorological Society, 80(10):2027-2034 (1999).

Hurricanes result in considerable damage in the United States. Previous work has shown that Atlantic hurricane landfalls in the United States have a strong relationship with the El Niño-Southern Oscillation phenomena. This paper compares the historical record of La Niña and El Niño events defined by eastern Pacific sea surface temperature with a data set of hurricane losses normalized to 1997 values. A significant relationship is found between the ENSO cycle and U.S. hurricane losses, with La Niña years exhibiting much more damage. Used appropriately, this relationship is of potential value to decision makers who are able to manage risk based on probabilistic information.

Powell, M.D. Hurricanes at landfall. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 107-108 (1999).

No abstract.

Powell, M.D., and S.H. Houston. Comments on "A multiscale numerical study of Hurricane Andrew (1992). Part I: Explicit simulation and verification." Monthly Weather Review, 127(7):1706-1710 (1999).

No abstract.

Powell, M.D., P.G. Black, S.H. Houston, and T.A. Reinhold. GPS sonde insights on boundary layer structure in hurricanes. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 881-884 (1999).

No abstract.

Proni, J.R., and T.A. Nelsen. Integrated measurements of sewage effluent and dredged material discharges. In Coastal Engineering and Marine Developments, C. Brebbia and P Anagnostopoulos (eds.). WIT Press, Southampton, 368-379 (1999).

A series of measurements to characterize sewage effluent discharge plumes and dredged material discharge plumes were carried out in coastal ocean waters off the coast of Puerto Rico in April 1998. A multiple sensor suite including an acoustic backscatter profiler, a towed optical backscatter containing CTD device, a vertical cast CTD having an optical transmissometer and oxygen sensors, and an acoustic Doppler current profiler (ADCP) was utilized to determine the subsurface plume spatial distribution and dilution. The sewage effluent plumes resulted from discharges at several diffusers located approximately one or more miles from the coastline. Using the multiple sensor systems listed above, it was possible to relate measurements made at water locations distant from the diffuser to plumes emanating from various parts of the diffuser under study. That is, a "connectivity" was established so that quantities inherent in the effluent discharge could be used for dilution calculations. Typical "initial" dilutions observed were on the order of 60:1. Using inherent tracers, such as plume salinity, effluent plume distributions were determined out to several hundred meters from the diffuser. "Macro" scale comparisons of multiple sensor outputs were carried out with good general agreement on plume distributions. Comparisons between in-situ "contact" sensors, e.g., temperature and salinity probes, and in-situ remote sensor probes, e.g., optical and acoustic backscatter, optical transmissivity (transmissometry), were made with good agreement resulting.

Proni, J.R., and T.A. Nelsen. Puerto Rico outfall/dredged material disposal studies: April 13-26, 1998. Contract EPA/IAG DW13937869-01-04 (Final report). U.S. Environmental Protection Agency, 74 pp. (1999).

No abstract.

Proni, J.R., and T.A. Nelsen. Recent advances in coastal ocean pollution research and monitoring. Joint Meeting, 137th Regular Meeting of the Acoustical Society of America and 2nd Convention of the European Acoustics Association: Forum Acousticum 99, Berlin, Germany, March 15-19, 1999. Journal of the Acoustic Society of America, 105(2):1323 (1999).

Design of both real-time studies of oceanic discharges of potential pollutants such as sewage effluent, and long-term monitoring of same, are complicated by a number of factors. These factors include lack of knowledge of the space and time distribution of the discharge plume, proper placement sites for sample gathering, and lack of knowledge of the space-time distribution of "interfering" plumes (plumes from sources other than the discharge plume under study). Progress has been made in the development of "integrated sensor suites" which produce data with substantial synergistic benefits. Ocean acoustics plays a key role in integrated sensor suite data unification. In a recent study in the coastal waters off San Juan, Puerto Rico, the ability of acoustics systems to view essentially the complete oceanic water enabled a connection to be made between salinity, temperature, and turbidity measurements gathered in the upper 5 m in the water column to a specific port of a sewage effluent diffuser. Having established the "connectivity" of the distal field measurement to a specific port, a dilution value at the distal point could confidently be calculated. This example is but one of many of the synergies available from utilization of multiple sensor suites unified through acoustics.

Quilfen, Y., A. Bentamy, K.B. Katsaros, and G. Lorand. Estimation of ocean-atmosphere turbulent fluxes from satellite measurements. Proceedings, 1999 International Geoscience and Remote Sensing Symposium (IGARSS '99), Hamburg, Germany, June 28-July 2, 1999. Institute of Electrical and Electronic Engineers, 2 pp. (1999).

No abstract.

Reasor, P.D., M.T. Montgomery, and F.D. Marks. The asymmetric structure of Hurricane Olivia's inner core. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 301-304 (1999).

No abstract.

Rodbell, D.T., G.O. Seltzer, D.M. Anderson, M.B. Abbott, D.B. Enfield, and J.H. Newman. A high-resolution ~15,000 year record of El Niño driven alluviation in southwestern Ecuador. Science, 283:516-520 (1999).

Debris flows have deposited inorganic laminae in an alpine lake 75 kilometers east of the Pacific Ocean, in Ecuador. These storm-induced events are dated by radiocarbon, and the age of laminae that are less than 200 years old matches the historic record of El Niño events. From about 15,000 to about 7,000 calendar years before the present, the periodicity of clastic deposition is greater than or equal to 15 years; thereafter, there is a progressive increase in frequency to periodicities of 2-8.5 years. This is the modern El Niño periodicity, which was established about 5,000 calendar years before present. This may reflect the onset of a steeper zonal sea surface temperature gradient, which was driven by enhanced trade winds.

Rogers, R.F. Amplification of warm-core vortices by convective redevelopment: A key component of tropical cyclogenesis. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 929-932 (1999).

No abstract.

Rogers, R.F., and J.M. Fritsch. Amplification of warm-core vortices by convective redevelopment: A key component of tropical cyclogenesis. Preprints, Eighth Conference on Mesoscale Processes, Boulder, CO, June 28-July 1, 1999. American Meteorological Society, Boston, 55-60 (1999).

Theories explaining the transition of a relatively disorganized area of convection into a coherent, self-sustaining system (i.e., tropical cyclogenesis) have traditionally relied upon the presence of a vortex before genesis can occur. Observations have confirmed the need for these vortices, often detecting them in radar and satellite imagery several days prior to the formation of a tropical depression. However, observational, theoretical, and numerical studies of similar systems over land have found that the initial vortices are often confined to the mid-troposphere. Therefore, an important question to address is how these vortices grow down to the surface in maritime tropical environments, for it is not until the vortex is reflected at the surface that intensification can begin, provided the large-scale environment is not unfavorable. This study investigates how midlevel vorticity within mesoscale convective vortices (MCVs) can amplify and grow downward to the surface by the redevelopment of deep convection. It is shown that the diabatic heating within the convection can increase the magnitude of the balanced warm core of the vortex, further lowering heights beneath the warm core and causing a cyclonic circulation closer to the surface. This cyclonic vorticity can develop in the lower troposphere even in the presence of the anomalously cold air of the low-level cold pool, given a sufficiently strong warm core aloft. The factors that play a key role in governing the downward penetration of vorticity to the surface are 1) onset of deep moist convection; 2) local reduction of the Rossby radius of deformation; and 3) weakening of the surface-based cold pool. These concepts are explored by performing a 48-hour numerical simulation of an observed MCV that underwent multiple cycles of convective redevelopment, amplifying after each cycle. The model was successful in reproducing the creation and evolution of the MCV. The amplitude of the midlevel vortex increased considerably after each convective cycle, as cyclonic vorticity reached the surface during the third cycle. Conditions prior to the third cycle showed a strong southwesterly low-level jet that was transporting warm, moist air over an outflow boundary left from the previous convective cycle and underneath the existing MCV. Deep convection developed within the existing cyclonic circulation and intense latent heat release amplified the warm core. As a result of this warming, lower-tropospheric geopotential heights lowered, creating low-level convergence which increased cyclonic vorticity under the amplifying vortex. This convergence led to an intense vortex in the lower troposphere during the strongest periods of the convective cycle, despite the fact that the lower troposphere was anomalously cold during the entire period. A conceptual model incorporating these ideas is presented.

Schmid, C. On the circulation in the tropical Atlantic. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S179, OS31B-08 (1999).

The circulation in the tropical Atlantic is studied using recent and historical Lagrangian observations. The measurements of the Lagrangian velocities were performed at two levels: near the surface and at intermediate depth. The surface measurements were collected with surface drifters whose drogues were centered at 15 m depth. The intermediate layer measurements derive from an array of 17 PALACE floats deployed in the tropical Atlantic during the summer of 1997. They cycle between about 1000 m and the surface to take a temperature profile every 11 days. Between the two profiles, the PALACE floats drift at depth for 10 days. The presentation will focus on the description of the velocity field and the analysis of the seasonal variability. The available surface drifter data allow the estimation of the mean monthly circulation patterns over large parts of the tropical Atlantic. The resulting fields show the seasonal reversal of the North Equatorial Countercurrent with predominantly westward velocities in the first half of the year and eastward velocities during the second half of the year. The PALACE floats also indicate the existence of a seasonal variability at about 1000 m.

Smith, R.H. IASlinks.org: Online management and distribution of oceanographic and meteorological data for the Gulf of Mexico and Caribbean Sea. Proceedings, First Biennial Intra-Americas Sea Initiative (IASI) Science Meeting, Panama City, Panama, November 9-11, 1999. University of Miami (1999).

There is a growing recognition of the connectivity among oceanic processes within the Gulf of Mexico and Caribbean Sea region (Intra-Americas Sea). Recent technological breakthroughs in communication, specifically the Internet, provide a common denominator for scientific collaboration and data exchange among the region's institutions and government agencies that collect data and utilize data products. The growing need for regional scale models requires that interaction between research endeavors take place, enabling the creation of larger, regional data sets and a more unified approach to understanding the oceanography, climate, and ecology of the Intra-Americas Sea. The Internet web site, http://IASlinks.org, hosted by NOAA/AOML in Miami, Florida, has been developed to facilitate the sharing of resources, results, and data sets relevant to research conducted throughout the Intra-Americas Sea region. The site is presently designed with indices describing the different types of research and the different institutions, agencies, and personnel involved, with regular highlights of specific regional research topics; it is our hope that the site will continue to expand, becoming a more complete representation of observational programs presently underway in and around the Gulf of Mexico and Caribbean Sea. The usefulness of a venue such as IASlinks.org will continue to be realized as scientists and operational observing systems throughout the Intra-Americas Sea make more of their data available over the Internet. In particular, the Internet as a medium for data exchange will play a pivotal role in the forthcoming IOCARIBE-GOOS regional observing system. IASlinks will complement the IASI web site, which will emphasize research programs, education, and training. This collaborative atmosphere, where scientific information and resources are shared with one another, will provide investigators working in the region the ability to tackle larger questions regarding climate, circulation, the propagation of species, and the connectivity of regional marine environments.

Swenson, M.S., and D.V. Hansen. Tropical Pacific Ocean mixed-layer budget: The Pacific cold tongue. Journal of Physical Oceanography, 29(1):69-82 (1999).

Data from satellite-tracked drifting buoys and VOS/XBT profiles for the years 1979-1995 were used to evaluate the seasonal cycle of how major oceanic processes redistribute heat in the cold tongue region of the tropical Pacific. The most active processes for the annual cycle are local heat storage and heat export by entrainment of upwelling and by mean meridional advection. Heat export by zonal advection, however, is not negligible, and meridional eddy heat fluxes associated with tropical instability waves effect a negative feedback that offsets a considerable fraction of that produced by the mean meridional advection. All of these processes mimic the essentially one cycle per year of the surface wind stress, as do those of the depths of both the bottom of the surface mixed layer and the thermocline. Because it is associated with poleward Ekman transports, upwelling, and baroclinic adjustment near the equator, the zonal wind stress component appears to be the more important. The meridional wind stress, while weaker in the annual mean, has a larger annual variation and, therefore, has equal influence on the annual variation of the scalar stress and perhaps the mixed layer thickness. The Monin-Obukov length is found to underestimate the mixed layer thickness very considerably. Finally, we produce the first estimates of the seasonal cycle of eddy heat flux convergence, which plays a significant role in the evolution of the cold tongue, and show that the eddy heat flux convergence can be quantitatively modeled as eddy diffusion with a diffusivity derived from single-particle buoy statistics.

Takahashi, T., R.H. Wanninkhof, R.A. Feely, R.F. Weiss, D.W. Chipman, N. Bates, J. Olafsson, C.Sabine, and S.C. Sutherland. Net sea-air CO₂ flux over the global oceans: An improved estimate based on the sea-air pCO₂ difference. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 9-15 (1999).

No abstract.

Tedesco, L.P., C. Souch, J. Pachut, J.A. Arthur, H.R. Wanless, P.L. Blackwelder, T. Hood, C. Alvarez-Zarikian, J. Trefry, W.J. Kang, S. Metz, and T.A. Nelsen. The signature of hurricane sedimentation in the lower Everglades/Florida Bay ecosystem: Recognition of sedimentologic, geochemical, and microfaunal indicators. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 194-195 (1999).

Winter storm and hurricane resuspension and transport processes are responsible for building the bulk of the sediment sequence in the accreting bank flanks in both northwest Oyster Bay (Whitewater Bay) and Florida Bay. Repetitive resuspension by winter storms provides fine silt-sized carbonate, siliceous and organic laminae as thin event laminae, mostly a millimeter or less in thickness. As these repetitive winter storms produce similar wind and transport sequences in an area, the constituent composition and mineralogy of the laminae are similar. Vertical profiles of excess ²¹⁰Pb activity in sediments from northwest Oyster Bay, Jimmy Key, and First National Bank showed that sedimentation at these sites has been in steady state during the last 40 years. However, two to three discontinuities of short duration (<2 years) in the decay profiles of excess ²¹⁰Pb activities were observed in the sedimentary records from northwest Oyster Bay, Jimmy Key, and First National Bank. Based on excess 210Pb-based ages, the discontinuities occurred at about 1960, 1948, and 1935, dates coincident with major hurricanes passing through Florida Bay: Donna in September 1960 (category 4); an unnamed hurricane in September 1948 (category 3); and the Great Labor Day Hurricane in September 1935 (category 5). Hurricane layers from 1935, 1948, 1960 (Donna), and 1992 (Andrew) in Oyster Bay are identified by a sharp surface on which sand-sized shell, carbonate peloids, and organic detritus are concentrated and overlain by a white, fine sand to silt layer, 0.5-2 cm in thickness. Sedimentologic and geochemical data on discontinuity surfaces show that the base of each hurricane layer is an erosional surface from which several centimeters of sediment was eroded. This is expected as the upper 3-10 cm of the sediment in these accreting flanks is a very soft zone with as much as 80% water content that could easily be removed. Discontinuities of ²¹⁰Pb profiles and, therefore, erosion were more pronounced in open water sites such as Jimmy Key and First National Bank (3-20 cm thick) relative to the more protected, mangrove coastline surrounded environment of northwest Oyster Bay (~2 cm thick). Major hurricanes (categories 4 and 5) are devastating to the red and black mangrove communities, causing destruction to 50-100% of the forest in the eye wall of the storm. This loss is reflected in the organic detritus content of sediments in cores from northwest Oyster Bay and other areas surrounded by extensive mangrove coastlines. Prior to a major hurricane, the macro-organic detritus is mainly partly decayed fragments of mangrove leaves released from the adjacent forests. Defoliation, uprooting, and death of the forest during and following the storm result in a change in the amount and composition of organic detritus in sediments. Organic detritus is composed of fine root hairs for a period of 5-10 years following the event. This reflects an extended period of erosion and release of root-hair detritus from the disrupted and decaying mangrove peat substrate. Organic detritus gradually decreases and becomes dominated by leaf detritus as the forest recovers. Hurricane-related signals in the microfaunal assemblage data (benthic ostracods and foraminifers) are both site- and event-specific. The two hurricanes that significantly modified the microfaunal assemblages from Jimmy Key and northwest Oyster Bay are the Labor Day Hurricane of 1935 and Hurricane Donna (1960). Hurricane Donna resulted in peaks in relative abundance of atypical benthic foraminifer species at both sites. At Jimmy Key, the species comprising this peak were derived from elsewhere within Florida Bay. In contrast, in northwest Oyster Bay, species were comprised of continental shelf species transported from the Gulf of Mexico by Donna's last winds. An example of hurricane-specific effects can be seen in the differing signals recorded by the 1935 and 1960 hurricanes at Jimmy Key. The 1960 hurricane left a distinct lag-type deposit, whereas the 1935 hurricane sediments were essentially barren of microfauna. High organic carbon influx and subsequent oxygen depletion associated with these hurricane events appear to be recorded in the microfaunal assemblages as well.

Thacker, W.C. Principal predictors. International Journal of Climatology, 19:821-834 (1999).

Principal predictors are linear combinations of variables from one set that efficiently describe the collective variability of those from a second set. Their defining eigenproblem is similar to that of canonical-correlation analysis, and when the two sets are taken to be the same, principal predictors reduce to principal components. Within the context of a forecast model for the circulation in the Gulf of St. Lawrence, they are shown to be capable of providing a low-dimensional characterization of high-resolution model dynamics.

Uhlhorn, E.W., P.G. Black, and A.F. Hasler. Evolution of mesoscale flow in a mature tropical cyclone as determined from satellite imagery. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 200-203 (1999).

No abstract.

Vachon, P.W., and K.B. Katsaros. Atmospheric cyclones from spaceborne SAR. Backscatter, 10(4):14-19 (1999).

No abstract.

Vachon, P.W., K.B. Katsaros, P.G. Black, and P.P. Dodge. RADARSAT synthetic aperture radar measurements of some 1998 hurricanes. Proceedings, 1999 International Geoscience and Remote Sensing Symposium (IGARSS '99), Hamburg, Germany, June 28-July 2, 1999. Institute of Electrical and Electronic Engineers, 1631-1633 (1999).

The RADARSAT synthetic aperture radar (SAR) acquired C-band and HH polarization images over four 1998 hurricanes: Bonnie, Danielle, Georges, and Mitch. We present the SAR images and discuss their quantitative use in understanding hurricane morphology. The SAR provides a complementary "view from below" that is most beneficial when considered in the context of more conventional hurricane observations.

Wang, C., R.H. Weisberg, and J.I. Virmani. Western Pacific interannual variability associated with the El Niño-Southern Oscillation. Journal of Geophysical Research, 104(C3):5131-5149 (1999).

Observations of sea surface temperature (SST), sea level pressure (SLP), surface wind, and outgoing longwave radiation (OLR) show that the El Niño-Southern Oscillation (ENSO) displays western Pacific anomaly patterns in addition to eastern Pacific anomaly patterns. During the warm phase of ENSO, warm SST and low SLP anomalies in the equatorial eastern Pacific and low OLR anomalies in the equatorial central Pacific are accompanied by cold SST and high SLP anomalies in the off-equatorial western Pacific and high OLR anomalies in the off-equatorial far western Pacific. Also, while the zonal wind anomalies over the equatorial central Pacific are westerly, those over the equatorial far western Pacific are easterly. The nearly out-of-phase behavior between the eastern and western tropical Pacific is also observed during the cold phase of ENSO, but with anomalies of opposite sign. These western Pacific interannual anomaly patterns are robust features of ENSO, independent of data sets. It is argued that equatorial easterly (westerly) wind anomalies over the far western Pacific during the warm (cold) phase of ENSO are initiated by off-equatorial western Pacific cold (warm) SST anomalies, and that these winds are important for the evolution of ENSO. An atmosphere model is employed to demonstrate that small off-equatorial western Pacific cold (warm) SST anomalies (compared to those in the east) are sufficient to produce equatorial easterly (westerly) wind anomalies as observed over the far western Pacific. The coupled ocean-atmosphere model of Zebiak and Cane is then modified to investigate the evolution of the western Pacific interannual anomaly patterns in a coupled ocean-atmosphere system, by including a meridional structure to the subsurface temperature parameterization in the western Pacific. The modified model produces both western and eastern Pacific interannual anomaly patterns.

Wang, C., R.H. Weisberg, and H. Yang. Effects of the wind speed-evaporation-SST feedback on the El Niño-Southern Oscillation. Journal of the Atmospheric Sciences, 56(10):1391-1403 (1999).

The thermodynamical process of latent heat flux is added to an analogical delayed oscillator model of the El Niño-Southern Oscillation (ENSO) that mainly considers equatorial ocean dynamics and produces regular, non-phase-locked oscillations. Latent heat flux affects the model sea surface temperature (SST) variations by a positive feedback between the surface wind speed and SST operating through evaporation which is called the wind speed-evaporation-SST feedback. The wind speed-evaporation-SST feedback in which the atmosphere interacts thermodynamically with the ocean through surface heat flux differs from the conventional zonal wind stress-SST feedback in which the atmosphere interacts dynamically with the ocean through momentum flux. The combination of equatorial ocean dynamics and thermodynamics produces relatively more realistic model oscillations. When the annual cycle amplitude of the zonal wind in the wind speed-evaporation-SST feedback is gradually increased, the model solution undergoes a transition from periodic to chaotic and then to periodic oscillations for some ranges of the parameters, whereas for other ranges of the parameters the transition goes from periodic to quasi-periodic and then to periodic oscillations. The route to chaos is the intermittency route. Along with such irregularity, the nonlinear interactions between the annual and interannual cycles operating through the wind speed-evaporation-SST feedback also produce a phase-locking of ENSO to the seasonal cycle. The model ENSO onset and peak occur in the boreal winter and spring, respectively, consistent with the observed phase-locking of ENSO in the far eastern Pacific. It is shown that ENSO decadal or interdecadal variability may result from the nonlinear interactions between the annual and interannual cycles in the tropics.

Wanninkhof, R.H. An overview of GAS EX-98. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S49, A32A-01 (1999).

The gas experiment in the North Atlantic (GAS EX-98) had as its main objective to improve our knowledge of air-sea CO₂ fluxes. Understanding of the physics controlling the gas transfer in the field necessitates measuring gas transfer on the time scales of the environmental forcing (sub-hour). Conventional waterside mass balance methods have a response time of at least a day such that we must rely on micrometeorological measurements, or proxies of CO₂ such as heat, along with assumption of similarities. Since micrometeorological measurements have yielded too high fluxes compared to mass balance approaches in the past, the first step was to reconcile the measurements. Micrometeorological CO₂ flux estimates were obtained from gradients of CO₂ and dimethyl sulfide in the (air) marine boundary layer, and by CO₂ co-variance measurements. Gas transfer velocities were measured using the dual-deliberate tracer technique with 3He and SF6 in the water column. Changes of CO₂ in the water column were used as overall constraints for the gas fluxes after accounting for changes of CO₂ concentrations due to biology. The selection of study location was based on the site being a constrained watermass in an eddy in a large CO₂ sink region. The anticyclonic (warm core) eddy inhibited dispersion of the deliberate tracers, thereby extending the duration of the experiment, and SF6 concentrations were measurable for the duration of the 24-day process study. The large CO₂ sink, averaging -85 µatm during the study, improved the signal to noise for the direct flux measurements. The post-bloom environment was thought to minimize the biological signal compared to the change due to CO₂ invasion in the water column mass balance. However, despite the near absence of major nutrients, several lines of evidence suggest rapid biological cycling. The independent estimates of gas transfer velocities agreed well with each other. This is the first time that such concordance is observed between the micrometeorological-based measurements and the water column mass balance based observations. The results from the co-variance data of McGillis and Edson (see abstract in this session) can be fit with a cubic dependence with wind speed. Such a relationship can be reconciled with global flux constraints based on bomb ¹⁴C. If such a relationship holds universally over the ocean, the net global CO₂ uptake would increase by a half based on the monthly pCO2 climatology of Takahashi (1997).

Wanninkhof, R.H. Recent advances in determining air-sea CO₂ fluxes. Proceedings, Second International Symposium on CO₂ in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 101-104 (1999).

Uncertainties in inverse calculations to determine regional carbon fluxes between the atmospheric, oceanic, and terrestrial reservoirs (Fan et al., 1998) have clearly indicated the need to improve our oceanic carbon flux estimate. There have been significant advances in several aspects of air-sea flux determinations to address this question, including direct estimates of fluxes by co-variance and gradient measurements in the air-boundary layer, extrapolation routines using remote sensing products, and a rapidly increasing observational database of air-sea partial pressure differences. The gas fluxes are commonly expressed as F = k s DELTA-pCO₂ where F is the air-sea flux CO₂ (mol m^-2 day^-1), k is the gas transfer velocity (m day^-1), s is the solubility (mol m³ µatm^-1) and DELTA-pCO₂ is the air-water partial pressure difference (µatm). This overview discusses recent research aimed at improving estimates of F, k, and DELTA-pCO₂.

Wanninkhof, R.H., and W.M. McGillis. A cubic relationship between air-sea CO₂ and wind speed. Geophysical Research Letters, 26(13):1889-1892 (1999).

Using recent laboratory and field results we explore the possibility of a cubic relationship between gas exchange and instantaneous (or short-term) wind speed, and its impact on global air-sea fluxes. The theoretical foundation for such a dependency is based on retardation of gas transfer at low to intermediate winds by surfactants, which are ubiquitous in the world's oceans, and bubble-enhanced transfer at higher winds. The proposed cubic relationship shows a weaker dependence of gas transfer at low wind speed and a significantly stronger dependence at high wind speed than previous relationships. A long-term relationship derived from such a dependence, combined with the monthly CO₂ climatology of Takahashi (1997), leads to an increase in the global annual oceanic CO₂ uptake from 1.4 Gigaton C yr^-1 to 2.2 Gigaton C yr^-1. Although a cubic relationship fits within global bomb-¹⁴C oceanic uptake constraints, additional checks are warranted, particularly at high wind speeds where the enhancement is most pronounced.

Wanninkhof, R.H., E. Lewis, R.A. Feely, and F.J. Millero. The optimal carbonate dissociation constants for determining pCO₂ from alkalinity and total inorganic carbon. Marine Chemistry, 65(3-4):291-301 (1999).

In many numerical ocean chemistry models total dissolved inorganic carbon (DIC) and total alkalinity (TA) are transported between subsurface boxes, and partial pressure pCO₂ is calculated from TA and DIC in the surface box in order to account for air-sea exchange of carbon dioxide. The conversion is commonly performed by solving the thermodynamic relationships for equilibria between carbonate, bicarbonate, and aqueous CO₂ using apparent carbonate dissociation constants. Four independent determinations of the constants have been performed for seawater in the past 50 years. These results have been corrected, refit, and combined by others, creating a virtual cottage industry of laboratory and field verification and cross checks. Here we show that, based on extensive field observations in three major ocean basins, the calculated surface pCO₂ from TA and DIC corresponds best with the measured pCO₂ of the constants proposed by Mehrbach et al.

Wanninkhof, R.H., S. Doney, T.-H. Peng, J.L. Bullister, K. Lee, and R.A. Feely. Comparison of methods to determine the anthropogenic CO₂ invasion into the Atlantic Ocean. Tellus B, 51(2):511-530 (1999).

A comparison of different methods of estimating anthropogenic CO₂ into the Atlantic Ocean through the center of the basin between 62°N and 42°S is performed using referenced high quality total dissolved inorganic carbon (DIC) data. The specific anthropogenic input is determined utilizing analytical procedures as described in Gruber et al. (1996), and Chen and Millero (1979) to correct for remineralization and to estimate preanthropogenic endmembers. These estimates are compared with results of the Princeton ocean biogeochemical model (OBM). The results show the specific inventories of anthropogenic carbon agreeing to within 20% but with different uptake patterns. The differences are largely caused by differing assumptions about mixing and winter outcrop endmembers. The same photosynthetic quotients (Redfield ratios) were used each methods. Varying these constants within the range of literature values causes changes in specific inventories of similar magnitude as the different methodologies. Comparison of anthropogenic CO₂ uptake and chlorofluorocarbon ages, and preanthropogenic photosynthetic quotients utilizing the analytical methods suggest that anthropogenic CO₂ penetration is too shallow following the procedure according to Gruber et al. (1996), and too deep using those of Chen and Millero (1979) in the North Atlantic. The results support previous observations that the uptake of CO₂ in the North Atlantic is disproportionate to its surface area. This is caused by a combination of deep water formation and deep winter mixed layers.

Whung, P.-Y., C.J. Fischer, and T. Meyers. Atmospheric deposition of nitrogen and phosphorous to the South Florida Bay ecosystems. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 87 (1999).

The monitoring nutrient deposition to South Florida Bay is now underway. A 10-m meteorological tower was installed at the Keys Marine Laboratory at Long Key in April 1998. Air samples, both dry and wet deposition such as gaseous ammonia (NH₃), particulate ammonium (NH₄⁺), particulate nitrate (NO₃^-), organic phosphorous (org-PO₄), and total phosphorous (PO₄), are measured. Meteorological parameters such as wind speed, wind direction, air temperature, relative humidity, and solar radiation are also collected at the sampling site. Atmosphere nitrogen, which include NH₃, NH₄⁺, and NO₃^-, were sampled using treated filter packs. The preliminary results for the gaseous nitrogen species during the period of April 1998 and March 1999 showed that the NH₃ concentrations varied greatly (between 0.034 and 0.76 ug/m³), with relatively higher concentrations in the summer season. The averaged particulate NH₄⁺ and NO₃^- concentrations were 1.20 ug/m³ and 2.17 ug/m³, respectively. The observed atmospheric NH₃ concentrations in South Florida Bay were similar to the averaged NH₃ concentrations in other coastal regions (such as Tampa Bay and Chesapeake Bay). Since late October of 1998, aerosol monitoring of phosphorous and wet deposition of nitrogen has been underway. The sampling protocol, sample analysis, and shipping logistics have been worked out in collaboration with the laboratory at the Illinois State Water Survey who conducted the analysis for the National Atmospheric Deposition Program (NADP). Samples collected through mid-February have been analyzed. For this period, the average dry deposition rate of ammonium aerosol was estimated to be about 0.18 mg/m²/wk, compared to an average wet deposition rate of 0.1 mg/m²/wk. The averaged weekly wet deposition rate of nitrate was on the order of 0.7 mg/m²/wk. For phosphorous, there has only been one week in which the wet deposition data were above the detectable limit. However, measurable air concentrations have been obtained each week in order to obtain a dry deposition rate. At this time, the averaged weekly PO₄^- deposition rate was estimated to be about 0.1 mg/m²/wk. The analysis for organic contributions (that do not show up as PO₄) (which includes the organic fraction) have been 30% higher than the inorganic fractions. Further analyses of elemental ratios will be used to determine the possible origin of this organic fraction.

Wilkerson, J.C., J.R. McCollum, and J.R. Proni. A methodology for validating satellite estimates of rainfall over the ocean using underwater acoustic techniques. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S99, H21A-05 (1999).

Current methods for validating satellite estimates of precipitation over the open ocean use rain gauge or radar data. The rain gauge data come from low-lying islands and atolls or from moored buoys. The intercomparison of satellite and rain gauge estimates leads to uncertainties in the satellite error estimates due largely to the differences in spatial coverage. Satellite rainfall estimates cover tens to hundreds of km² while the representative area measured by a rain gauge is only several cm². In addition to sampling uncertainties, most of these gauges are in the tropical Pacific, while satellite estimation errors depend upon location on the globe. Radar rainfall estimates have sufficient spatial resolution for comparisons with satellite estimates, but the amount of radar data from coastal sites or ships is scarce. In addition, satellite rainfall estimation techniques based on passive microwave emission cannot be applied to grid boxes containing coast, which further limits the amount of comparison data. Due to the current difficulties in validation of oceanic rainfall estimates, we have examined the possibility of utilizing underwater acoustics for oceanic rainfall estimation. It has subsequently been shown that underwater sound can, in fact, be used to detect and classify rainfall in coastal ocean regions and that rainfall estimation to useful accuracy appears feasible. The acoustic technique is now being tested in the deep ocean at the U.S. Navy Atlantic Undersea Test and Evaluation Center located in the Tongue of the Ocean, Bahamas. A 12-hydrophone array tethered to the ocean floor at a depth of 1.5 km has been made available to NOAA for investigation. Acoustic data from the array, covering a 500 km² area of the ocean surface, is sampled continuously once every 12 seconds giving temporal and spatial data coverage comparable to that of satellite rainfall estimates. This paper presents results of an initial comparison of four satellite rainfall products for the acoustic site with concurrent estimates of rainfall from the underwater array made at comparable time and space scales. These data are supported by independent measurements of rainfall over the array from a WR 74C weather radar located at Nassau, 60 km distant. Products from the Geostationary Operational Environmental Satellite (GOES) include estimates from the Global Precipitation Index (GPI), the GOES Multi-Spectral Rainfall Algorithm (GMSRA), and the Auto Estimator. Rainfall observations from the Special Sensor Microwave Imager (SSM/I) on the Defense Meteorological Satellite Program (DMSP) polar orbiting satellites are also examined.

Willis, P.T. An evaluation of NEXRAD (WSR88D) data as a measure of fresh water flux into the Florida Bay/Everglades system. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 153 (1999).

The radar measurement of rain provides excellent spatial and temporal resolution over a large area. This is true even over water areas, where a dense gauge network may be impossible or prohibitively expensive. But, since the radar does not measure rainfall rate directly, but measures the sixth moment of the raindrop size distribution (dsd), the measurement requires a definitive relation between rainfall rate and the shape of the drop size distribution. The shape of the dsd is not uniquely related to the rainfall rate. This is a source of error, and scatter, in the radar rainfall rate measurements. A major thrust of the project has been to characterize the shape of raindrop size distributions in south Florida. The project described herein involves the measurement of dsd's at a site at the ENP Research Center, and a comparison of the radar rain measurements to the gauge measurements from the extensive gauge network associated with the Florida Bay/Everglades Restoration project. The raw radar data has a spatial scale of approximately 1 x 1 km and a time resolution of 5-6 min. The NEXRAD hydrologic product (dpa) has been smoothed to a spatial scale of 4 x 4 km and a time resolution of 1 hr. This can be easily averaged to larger scales, and longer times to provide desired products. The radar data are empirically related to the gauge data using a probability matching methodology (PMM) which forces the overall match of the radar mean rainfall rate and the mean gauge rainfall and also forces an empirical match in data bin intervals. From extensive data comparisons between the dpa and 1-hr gauge data it is found that the radar significantly underestimates the higher rainfall rates, and overestimates the lower rainfall rates. This is true even from a smaller sample of the full resolution radar data, and high-resolution gauge and disdrometer data. The match provided by the PMM is virtually the same as that from the 4 km/1 hr data. The stability of this relation is being checked with an additional year of radar and gauge data, and the result will be reported. A single gauge/radar rainfall product that retains the best features of each data type is being developed using a cokriging methodology. Sample one-month mean radar data, and combined products using the empirical calibrations, are presented. Planned improvements and future work are also presented.

Willis, P.T. The WSR-88D tropical Z-R relationship in south Florida. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 237-240 (1999).

No abstract.

Willoughby, H.E. Hurricane heat engines. Nature, 401:649-650 (1999).

No abstract.

Willoughby, H.E. Vortex tracking semispectral hurricane models. Preprints, 23rd Conference on Hurricanes and Tropical Meteorology, Dallas, TX, January 10-15, 1999. American Meteorological Society, Boston, 662-665 (1999).

No abstract.

Wilson, W.D. Atlantic western boundary currents. Proceedings, South Florida Measurement Center Workshop: Establishment of a Center for Innovative Oceanography in the 21st Century, Dania, FL, February 24-26, 1999. National Science Foundation, 131-140 (1999).

No abstract.

Wilson, W.D., E. Johns, R.H. Smith, T.N. Lee, and E. Williams. Interaction of freshwater riverine discharges from the Everglades with the Gulf of Mexico and Florida Bay: Preliminary results from a moored array and shipboard surveys. 1999 Florida Bay and Adjacent Marine Systems Science Conference, Programs and Abstracts, Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 175-177 (1999).

No abstract.

Wilson, W.D., S.L. Garzoli, G.J. Goñi, W.E. Johns, R.H. Smith, C.I. Fleurant, P.L. Richardson, and D.M. Fratantoni. The North Brazil Current Retroflection: Two recent surveys. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union,80(17):S179, OS31B-11 (1999).

The North Brazil Current is the low-latitude western boundary current that flows northward across the equator in the western Atlantic along the coast of Brazil. The NBC is the main source of inter-hemispheric warm water transport in the Atlantic. Its retroflection supplies water to equatorial zonal currents at various latitudes and depths, and rings separate from the retroflection at irregular intervals and propagate into the western tropical Atlantic. Because of its broad spatial extent, and non-linear and rapidly changing nature, synoptic surveys that adequately describe the NBC are difficult to perform. Two such surveys, by far the most complete to date, were conducted as part of the North Brazil Current Rings Experiment in November/December 1998 and February/March 1999. Surveys contain data from XBT, CTD, and shipboard and lowered ADCP data sources, providing water properties and current velocities to 2000 m. Continuity between cruises is provided by satellite altimetry. In November/December, 1998, the near-surface currents of the retroflection reached to nearly 9°N, 52°W, and a closed recirculation center was evident, which separated shortly thereafter to form an NBC ring. At sub-thermocline level, only the closed circulation of the ring was seen, with the subsurface retroflection completely turning eastward near 4° to 5°N, east of 48°W. During the February/March 1999 survey, the retroflection was found further to the south, its northernmost tip extending to only 7°N, 51°W, with a newly formed NBC ring found just northwest of the retroflection.

Yvon-Lewis, S.A., J.H. Butler, D.B. King, S.A. Montzka, J. Rodriguez, J.M. Lobert, and M. Ko. The oceanic contribution to organic bromine in the atmosphere. International Union of Geodesy and Geophysics, XXII General Assembly, Birmingham, England, July 18-30, July 1999. IUGG99 Abstracts, A110 (1999).

The ocean delivers considerable organic bromine into the troposphere. Although many of the oceanic, bromine-containing compounds are short-lived in the troposphere, they can be convected periodically into the stratosphere, where they contribute to the destruction of stratospheric ozone. Methyl bromide (CH₃Br) and the halons are recognized as being the primary carriers of bromine into the stratosphere, but contributions from other compounds may be significant. Some of these other trace gases include CH₂Br₂, CHBr₃, CH₂BrCl, CHBr₂Cl, and CHBrCl₂. All of these gases are produced to some extent in the ocean and their collective sea-air flux is of the same order as the total flux of CH₃Br from all sources. We have been measuring CH₃Br, CH₂Br₂, CHBr₃, and other bromine-containing compounds in air and surface seawater samples on research cruises in the Pacific, Atlantic, and Southern Oceans since 1994. Results show CH₃Br undersaturations throughout much of the ocean, suggesting that the ocean is a net sink for this brominated trace gas. However, results for CH₂Br₂, CHBr₃, and the other bromine-containing compounds show these trace gases to be supersaturated throughout much of the ocean, often with higher degrees of saturation in the tropics and subtropics. These data are presented here and will be used in conjunction with a two-dimensional model to examine the role that the oceans play in the cycling of atmospheric organic bromine.

Zhang, J.-Z. Ship determination of nM nitrite and nitrate by gas-segmented continuous flow analysis with a liquid waveguide capillary flow cell. AGU 1999 Fall Meeting, San Francisco, CA, December 13-17, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(46):F46, B12B-09 (1999).

Incorporation of a 2-m long liquid waveguide capillary flow cell to a gas-segmented continuous flow auto-analyzer significantly enhances the sensitivity of automated colorimetric analysis. Nanomolar concentrations of nitrite and nitrate in oligotrophic surface seawater can be accurately determined. Using this technique the diel cycle of nitrate at nM level in oligotrophic water was observed. The advantages of this technique are low detection limit, high precision, and automation for rapid analysis of a large numbers of samples. This technique has been successfully used on shipboard measurements of about 1000 seawater samples during a one-month cruise in North Atlantic.

Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Laboratory glassware as a contaminant in silicate analysis of natural water samples. Water Research, 33(12):2879-2883 (1999).

When glassware is used for the storage of water samples, reagents, and standard solutions, dissolution of silicate from the glass containers can contaminate the samples. Experimental results demonstrate that dissolution from glassware can introduce micromolar silicate within a few hours. The extent of dissolution depends upon contact time, salinity, and pH of the solution, and the size and shape of the containers.

Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Optimization of performance and minimization of silicate interference in continuous flow phosphate analysis. Talanta, 49(2):293-304 (1999).

Specific reaction conditions for automated continuous flow analysis of phosphate are optimized in regard to minimizing coating and silicate interference, while maintaining high sensitivity. Use of Sb in the reagent increases sensitivity and yields absorbances with little temperature dependence. Coating can be minimized by using a final solution at a pH >0.5. At final pH of 0.78, there is maximum interference from silicate in the sample. We recommend, therefore, as an optimal reaction condition with minimal silicate interference, the use of Sb, a final solution pH of 1.00, room temperature for the reaction, and a [H+]/Mo ratio of 70. An equation is provided to correct silicate interference in high precision phosphate determination.

Zhang, J-Z., R.H. Wanninkhof, and K. Lee. New production estimated from diel cycle of nutrient and oxygen in the mixed layer. AGU 1999 Spring Meeting, Boston, MA, June 1-4, 1999. Supplement to EOS, Transactions, American Geophysical Union, 80(17):S50, A32A-03 (1999).

New production can be estimated from accurate measurement of inventory change in nutrient at nM level in the mixed layer. A strong diel cycle was observed in nutrient concentration in response to photosynthesis in an anticyclonic eddy in North Atlantic during the GASEX-98 cruise. During a diel study, nitrate concentration was about 92 nM in the morning and decreased to 12 nM at 6 p.m. Nitrate concentration increased after dark, presumably due to the diffusive flux from the nitracline. Oxygen data in the mixed layer also showed a similar diel cycle. The oxygen production during the day caused concentrations to increase by about 2 uM. Under steady state conditions, eddy diffusion is a dominant process for transportation of nutrient to the euphotic zone to sustain the new production. The vertical eddy diffusion coefficients were derived from temporal changes in concentrations of a deliberate tracer, SF6, in the upper thermocline. Together with vertical nitrate distributions, the nitrate flux from nitracline could be estimated. Such a diffusive flux throughout the night can account for a nitrate concentration of 102 nM by morning, which is in good agreement with measured nitrate of 92 nM at 6 a.m. The new production estimated from changes of nitrate inventory in the mixed layer during the day was 28 mmole C/m², which is in good agreement with 31 mmole C/m² estimated from the oxygen inventory change. Increases in mixed layer nutrients were observed during a storm event that deepened the mixed layer and brought the nutrient to the surface (1.2 uM nitrate). A good correlation between wind speed and the concentrations of nitrate and nitrite is observed. Addition of nitrate to the mixed layer by the storm disappeared within two days, indicating a rapid nutrient cycle by marine organisms. The relative importance of sporadic storm events versus daily diffusive flux in supply nutrient to new production can be estimated from accurate measurement of inventory change of nutrient and oxygen in the mixed layer.

Zhang, J.-Z., C.J. Fischer, C.R. Kelble, and F.J. Millero. Phosphate distribution coefficients for suspended sediments in Florida Bay. 1999 Florida Bay and Adjacent Marine System Science Conference, Programs and Abstracts Key Largo, FL, November 1-5, 1999. University of Florida Sea Grant Program, 77 (1999).

The distribution coefficient K_d (K_d = C_s/C_w,where C_s is concentration of phosphorus on particle surface and C_w in seawater) is a key parameter that governs phosphorus partitioning between seawater and particle surface. To estimate the distribution coefficient for phosphorus partitioning between suspended sediments and seawater, surface sediments were collected from Florida Bay at various locations with different environmental conditions. The sediments were equilibrated with low nutrient seawater for 24 hours at constant temperature. The particles were then separated from seawater by filtration. The phosphate concentrations in equilibrated seawater were determined by spectrophotometric method using an autoanalyzer. The sediments were then equilibrated with a 1 M MgCl₂ solution at pH of 8 for 4 hours. The sorbed and desorbable phosphorus was then extracted into the solution by a complexing reaction with MgCl₂. The extracted phosphate was determined after separation from the suspended sediments. The results showed a linear correlation between phosphate concentrations in seawater and exchangeable phosphate on the sediments surface. Preliminary estimated K_d is of 100 L/kg. Further experiments are underway to study the effect of salinity and temperature on the K_d. A fitted equation of K_d as a function of salinity and temperature can be used in a water quality model to predict the fate of input phosphorus in Florida Bay. **1998**

Aberson, S.D. Five-day tropical cyclone track forecasts in the North Atlantic basin. Weather and Forecasting, 13(4):1005-1015 (1998).

Statistical analyses of the most recent 40 years of hurricane tracks (1956-1995) are presented, leading to a version of the North Atlantic climatology and persistence (CLIPER) model that exhibits much smaller forecast biases but similar forecast errors compared to the previously used version. Changes to the model involve the inclusion of more accurate historical tropical cyclone track data and a simpler derivation of the regression equations. Nonlinear systems analysis shows that the predictability timescale in which the average errors increase by a factor e is approximately 2.5 days in the Atlantic basin, which is larger than that found by similar methods near Australia. This suggests that five-day tropical cyclone track forecasts may have some benefit, and, therefore, a version of CLIPER extended to five days to be used as a baseline to measure this skill is needed.

Aberson, S.D. Impact of the Gulfstream-IV jet aircraft on hurricane forecasts. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C. (paper was mistakenly omitted from the Minutes) (1998).

No abstract.

Aberson, S.D. Targeted observations to improve tropical cyclone forecasts. Scientific Programme, XXIII General Assembly, European Geophysical Society, Nice, France, April 20-24, 1998. European Geophysical Society, 256 (1998).

No abstract.

Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of tropical cyclone intensity. Preprints, Symposium on Tropical Cyclone Intensity Change, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 150-153 (1998).

No abstract.

Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of tropical cyclone tracks. Preprints, 12th Conference on Numerical Weather Prediction, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 290-292 (1998).

No abstract.

Aberson, S.D., M.A. Bender, and R.E. Tuleya. Ensemble forecasting of tropical cyclone tracks and intensity. Scientific Programme, XXIII General Assembly, European Geophysical Society, Nice, France, April 20-24, 1998. European Geophysical Society, 255 (1998).

No abstract.

Aberson, S.D., R.E. Tuleya, and M.A. Bender. Ensemble forecasting of hurricane track and intensity using the GFDL model during 1997. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C.,143-145 (1998).

Tropical cyclone track predictions have shown considerable skill past three days, and intensity predictions are beginning to show some skill. While most forecasts are good, great variability in the utility of individual forecasts occurs. Ensemble forecasting provides a mechanism by which the inherent uncertainty in model forecasts can be assessed. During the 1996 and 1997 hurricane seasons, more than 100 sets of ensemble forecasts using a two-mesh version of the Geophysical Fluid Dynamics Laboratory (GFDL) hurricane model have been run, based upon the bred growing modes produced operationally at the National Centers for Environmental Prediction (NCEP). Results of these track and intensity forecasts will be presented, including information as to how well the models conform to the "perfect model" scenario, whether the forecasts envelope the evolution of the atmosphere, and whether information on the utility of individual model forecasts can be obtained from the ensembles. Plans to continue ensemble forecasting runs during the 1998 hurricane season will be presented.

Aberson, S.D., R.E. Tuleya, and J. Heming. Five-day forecasts of tropical cyclone tracks in the Atlantic basin. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C. (paper was mistakenly omitted from the Minutes) (1998).

Tropical cyclone track predictions have improved so that skill, as assessed by the improvement of forecasts over a forecast provided by a simple statistical model based upon climatology and persistence, averages more than 30% at 72 h, the current standard length of forecasts. Because of the possibility of such skill levels at longer forecast times during the 1997 Atlantic hurricane season, four tropical cyclone track models produced quasi-operational 120 h forecasts. The models were a new version of CLIPER, with which to assess skill, and extensions of the currently run VICBAR, GFDL, and UKMO models. Individual track forecasts and skill assessments for the various models will be shown, and recommendations for future work in this area, both operationally and for research, will be made.

Alfaro, E., L. Cid, and D.B. Enfield. Relationships between the start and end date of the rainy season in Central America and the tropical Atlantic and Pacific Oceans. Investigaciones Marinas, 26:59-69 (1998).

In recent years, several studies have shown that anomalies in the sea surface temperature of the tropical Atlantic and Pacific Oceans are related to variations in the intensity and timing of the rainy season in Central America. In order to study anomalous behavior of the rainy season over Central America, tropical Atlantic and Pacific Oceans indices are used to produce correlation series with the starting and ending date (IELL and TELL) of the rainy season. The North Atlantic (ATN) and SOI-Niño3 indices show the main correlations with the IELL and the TELL respectively.

Amat, L.R., M.D. Powell, and S.H. Houston. WANDA: HRD's real-time tropical cyclone "Wind Analysis Distributed Application." Preprints, 16th Conference on Weather Analysis and Forecasting, Symposium on the Research Foci of the U.S. Weather Research Program, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, J29-J31 (1998).

No abstract.

Asher, W.E., and R.H. Wanninkhof. The effect of bubble-mediated gas transfer on purposeful dual gaseous-tracer experiments. Journal of Geophysical Research, 103(C5):10,555-10,560 (1998).

For air-water gas exchange across unbroken surfaces, the only gas-dependent parameter affecting the transfer velocity is the molecular diffusivity of the transferring species. In contrast, bubble-mediated transfer processes can cause the transfer velocity to depend on both molecular diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual-gaseous tracer gas transfer experiments. Bubble effects also complicate the estimation of transfer velocities for other gases from the transfer velocity calculated using the dual-tracer data. Herein, a method for incorporating the effects of bubble-mediated gas transfer processes on the transfer velocity is presented. This new procedure is used to analyze the data from two recent dual-tracer gas transfer experiments. Transfer velocities that include the effect of bubbles are calculated using the data from two previous oceanic dual-gaseous tracer experiments. Comparing these transfer velocities with transfer velocities calculated by neglecting the effect of bubbles shows that bubble-mediated transfer increased the transfer velocity of helium 3 by 5% at a wind speed of 10.6 m s^-1. However, when using the transfer velocities form helium 3 to calculate transfer velocities for carbon dioxide under the same conditions, including the effect of bubbles, decreases the transfer velocity of carbon dioxide by 18%. This shows that bubble-mediated transfer does not have a large effect on the analysis of dual-tracer data, but it is important in relating transfer velocities determined using helium 3 and sulfur hexafluoride to transfer velocities of more soluble gases at wind speeds above 10 m s^-1.

Asher, W.E., and R.H. Wanninkhof. Transient tracers and air-sea gas transfer. Journal of Geophysical Research, 103(C8):15,9393-15,958 (1998).

This paper provides a review of the physics and chemistry associated with air-sea gas transfer of transient atmospheric trace gases and the available laboratory and field measurement techniques used to study air-water gas transfer. The mechanistic principals and their relation to the measurement techniques are used to show that the error associated with estimating air-sea transfer velocities of transient tracers from transfer velocities measured using proxy tracers can be significant if an incorrect dependence of the transfer velocity on molecular diffusivity is assumed. Bubble-mediated transfer processes are also demonstrated to have a significant effect on the parameterization of the transfer velocity.

Ataktürk, S.S., and K.B. Katsaros. Estimates of surface humidity and wind speed obtained from satellite data in the stratocumulus regime in the Azores region. In Remote Sensing of the Pacific Ocean by Satellites, R.A. Brown (ed.). Southwood Press, Marrickville, Australia, 16-22 (1998).

No abstract.

Bauer, S., M.S. Swenson, A. Griffa, A.J. Mariano, and K. Owens. Eddy-mean flow decomposition and eddy-diffusivity estimates in the equatorial Pacific. Journal of Geophysical Research, 103(C13):30,855-30,872 (1998).

The ocean-atmospheric dynamics of the tropical Pacific Ocean create longitudinally coherent zonal flow () with strong meridional shear () in the large-scale mean and energetic mesoscale (O(100 km)) component. Parameterization of the effects of the mesoscale field depends on the separation of the large-scale mean and mesoscale eddy components in order to compute meaningful eddy diffusivity estimates in flow regimes that demonstrate strong currents and strong shear. Large gradients in the large-scale mean have precluded diffusivity estimation by traditional binning techniques. In this first of two publications, a method is developed for using Lagrangian data to estimate the diffusivity addressing the inhomogeneity of the mean flow. The spatially dependent estimate of the mean field is computed with a least squares bicubic smoothing spline interpolation scheme with an optimized roughness parameter which guarantees minimum energy in the fluctuation field at low frequencies. Numerical simulations based on a stochastic model of a turbulent shear flow are used to validate our approach in a conceptually simple but realistic scenario. The technique is applied to near-surface drifter observations obtained from 1979-1996 from two dynamically distinct time-space regions of the tropical Pacific Ocean. The first region, in the SEC, is characterized by a linear zonal shear mean flow and an approximately exponential autocovariance structure in the residuals. The residual velocity variance is s² ~ 130 cm² s^-2 for both components and horizontal diffusivities are 7 × 10⁷ cm² s^-1, and 3 × 10 cm² s^-1. The second region, in the NECC and the NEC, has a mean flow with a strong zonal shear and a weak northward velocity. The autocovariance is approximately exponential for the zonal component while the meridional component has a negative lobe at about 10 days probably due to the presence of instability waves. The variance is approximately tripled compared to the SEC region estimate while the meridional diffusivity estmate is nearly the same magnitude. The zonal diffusivity is estimated to be 15 × 10⁷ cm² s^-1.

Black, M.L., S.H. Houston, and G. Carter. AFRES-NOAA flight-level data comparisons. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C. (paper was mistakenly omitted from the Minutes) (1998).

A coordinated flight between an Air Force Reserve (AFRES) C-130 aircraft and both National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft was conducted on 12 July 1997. This mission was the third in recent years and resulted from a recommendation made at the 49th Interdepartmental Hurricane Conference. The AFRES and NOAA aircraft each recorded, at 1-sec intervals, the standard suite of flight-level meteorological data (winds, temperature, dew point, pressure) and navigational information (e.g., position, true air speed, heading, etc.). The data were collected during clear and moderate-wind conditions along the Florida west coast, about 100 miles north of Tampa. The NOAA and AFRES aircraft conducted "fly-bys" adjacent to an Air Force Aerostat balloon which was carrying a NOAA calibrated instrument package. The balloon approaches were at altitudes ranging from 1,000 to 10,000 feet and provide the basis for the intercomparisons. A GPS dropwindsonde was released along the coast to supply another set of independent measurements. Comparisons between the flight-level data collected from the balloon, the dropsonde, and the NOAA and AFRES aircraft will be presented. Recommendations, if any, will be made to improve the data collection, processing, and strategies for future intercomparison flights. Additionally, the calibration information gained from this flight will be used to investigate the data quality from concurrent flights into tropical cyclones by both the NOAA and AFRES aircraft this past hurricane season.

Black, P.G., and L.K. Shay. Observations of tropical cyclone intensity change due to air-sea interaction processes. Preprints, Symposium on Tropical Cyclone Intensity Change, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 161-168 (1998).

No abstract.

Black, P.G., F.D. Marks, P. Dodge, I. Popstefanija and R. Pauwl. First observations from the vertically scanning Doppler radar (VSDR): A key to G-IV reconnaissance operations. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C., A236-A256 (1998).

No abstract.

Boebel, O., C. Duncombe Rae, S.L. Garzoli, J. Lutjeharms, P. Richardson, T. Rossby, C. Schmid, and W. Zenk. Float experiment studies interocean exchanges at the tip of Africa. EOS, Transactions, American Geophysical Union, 79(1):7-8 (1998).

No abstract.

Bosart, L.F., W.E. Bracken, J. Molinari, C.S. Velden, and P.G. Black. Environmental influences on the rapid intensification stage of Hurricane Opal (1995) over the Gulf of Mexico. Preprints, Symposium on Tropical Cyclone Intensity Change, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 105-112 (1998).

No abstract.

Bove, M.C., J.J. O'Brien, J.B. Eisner, C.W. Landsea, and X. Niu. Effect of El Niño on U.S. landfalling hurricanes, revisited. Bulletin of the American Meteorological Society, 79(11):2477-2482 (1998).

Changes in the frequency of U.S. landfalling hurricanes with respect to the El Niño-Southern Oscillation (ENSO) cycle are assessed. Ninety-eight years (1900-1997) of U.S. landfalling hurricanes are classified, using sea surface temperature anomaly data from the equatorial Pacific Ocean, as occurring during an El Niño (anomalously warm tropical Pacific waters), La Niña (anomalously cold tropical Pacific waters), or neither (neutral). The mean and variance of U.S. landfalling hurricanes are determined for each ENSO phase. Each grouping is then tested for Poisson distribution using a chi-squared test. Resampling using a "bootstrap" technique is then used to determine the 5% and 95% confidence limits of the results. Last, the frequency of major U.S. landfalling hurricanes (sustained winds of 96 kt or more) with respect to ENSO phase is assessed empirically. The results indicated that El Niño events show a reduction in the probability of a U.S. landfalling hurricane, while La 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, Part I, Keeling's World: Is CO₂ Greening the Earth? Eldigio Press, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, 111 pp. (1998).

This section's hero is Charles David Keeling. In the late 1950s, he had the wisdom to establish two stations for the continuous precise measurement of atmospheric carbon dioxide, one high on Hawaii's extinct volcano Mauna Loa and the other at the South Pole. The records from these stations provide the foundation upon which all studies of man's perturbation of the Earth's carbon cycle rest. Not only did Keeling have the foresight to establish these stations but also the tenacity to make sure that year in and year out they produced accurate results. Keeling took on this task as part of a career-long effort to understand the flux of CO₂ gas through the atmosphere, into the ocean and into and out of the terrestrial biosphere. He was the first to realize the wealth of information contained in the spatial and seasonal texture of the atmosphere's CO₂ content. In addition to his direct scientific contribution, he fostered a secondary one. Son, Ralph, is doing for atmospheric O₂ all the kinds of things papa did for atmospheric CO₂.

Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles, Part II, Martin's World: CO₂'s Glacial Hideout? Eldigio Press, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, 73 pp. (1998).

The selection of the hero of this section has proven difficult. Under consideration were those who first measured the low CO₂ contents of air trapped in glacial age ice, those who used carbon isotope ratios and cadmium contents in foraminifera to set constraints on scenarios designed to explain this drop, and those who demonstrated that the high latitude outcrops of the deep sea dictated the CO₂ content of the entire surface ocean and, in turn, that of the atmosphere. But in the end, we initially selected a dark horse, David Archer, who at the time this book was being written, put his finger on what appeared to be the mechanism responsible for the atmosphere's glacial to interglacial CO₂ cycle. He obtained microelectrode O₂ and pH data from the upper few centimeters of deep sea sediments which clearly demonstrated the importance of bacterial respiration as a driver of calcite dissolution. Encouraged by preliminary boron-isotope-based paleo pH measurements which suggested large deep sea CO⁼₃ concentrations during glacial time, Archer showed that an increase in the rain rate of organic matter could generate the required CO⁼₃ ion change with little or no change in lysocline depth. But alas, now five years later, Archer's hypothesis has like its predecessors fallen on hard times. Danny Sigman, while a graduate student at Woods Hole, demonstrated that the requisite large separation between the saturation horizon and the lysocline could not be sustained. So in this second edition, we replace David Archer with the late John Martin who pioneered the concept that the availability of iron limits plant productivity in many parts of the oceans. He also pointed out that the large excess of iron carried to the sea during glacial time by the several-fold higher dust rain may have been responsible for the CO₂ drawdown.

Broecker, W.S., and T.-H. Peng. Greenhouse Puzzles, Part III, Walker's World: CO₂ , Chemical Traffic Controller? Eldigio Press, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, 93 pp. (1998).

This section's hero is James C.G. Walker, a space physicist at the University of Michigan. In 1981, together with his colleagues P.B. Hays and J.F. Kasting, he published a paper which lays out in beautiful simplicity the role of atmospheric CO₂ as the chemical policeman controlling the flow of continental weathering products to the sea, and thereby maintaining a balance between the rate of outgassing of CO₂ gas from our planet's interior and the rate of CO₂ removal to sea floor sediments as calcite. The important consequence of this police action is its influence on Earth climate. Walker and his colleagues pointed out that early in the Earth's history the tendency toward cooler temperatures related to the faintness of the young Sun was mostly likely compensated by higher atmospheric CO₂ contents. In an attempt to explain the cooling of the Earth over the last 100 million years, the role of Walker's mechanism was subsequently expanded by Berner, Lasaga and Garrels, who postulated that the cooling was driven by a decrease in the planetary outgassing rate related to a progressive slowing of plate motions. This suggestion was met with wide interest and became known as the BLAG hypothesis in honor of its creators. In the enthusiasm to explore all the aspects of BLAG, the earlier contribution of Walker tended to be forgotten. Hopefully, in naming this section, we will help to return the credit for the CO₂ policing concept to its originator, James C.G. Walker.

Broecker, W.S., S.L. Peacock, S. Walker. R. Weiss, E. Fahrbach, M. Schroeder, U. Mikolajewicz, C. Heinze, R. Key, T.-H. Peng, and S. Rubin. How much deep water is formed in the Southern Ocean? Journal of Geophysical Research, 103(C8):15,833-15,843 (1998).

Three tracers are used to place constraints on the production rate of ventilated deep water in the Southern Ocean. The distribution of the water mass tracer PO₄* ("phosphate star") in the deep sea suggests that the amount of ventilated deep water produced in the Southern Ocean is equal to or greater than the outflow of North Atlantic Deep Water from the Atlantic. Radiocarbon distributions yield an export flux of water from the North Atlantic which has averaged about 15 Sv over the last several hundred years. CFC inventories are used as a direct indicator of the current production rate of ventilated deep water in the Southern Ocean. Although coverage is as yet sparse, it appears that the CFC inventory is not inconsistent with the deep water production rate required by the distributions of PO₄* and radiocarbon. It has been widely accepted that the major part of the deep water production in the Southern Ocean takes place in the Weddell Sea. However, our estimate of the Southern Ocean ventilated deep water flux is in conflict with previous estimates of the flux of ventilated deep water from the Weddell Sea, which lie in the range 1-5 Sv. Possible reasons for this difference are discussed.

Bryan, G.H., R.F. Rogers, and J.M. Fritsch. Cloud-scale resolution simulations in moist absolutely unstable layers. Preprints, Eighth Pennsylvania State University/National Center for Atmospheric Research's Mesoscale Model Users Workshop, Boulder, CO. National Center for Atmospheric Research, 59-62 (1998).

No abstract.

Butler, J.H., J.W. Elkins, S.A. Montzka, T.M. Thompson, T.H. Swanson, A.D. Clarke, F.L. Moore, D.F. Hurst, P.A. Romashkin, S.A. Yvon-Lewis, J.M. Lobert, M. Dicorleto, G.S. Dutton, L.T. Lock, D.B. King, R.E. Dunn, E.A Ray, M. Pender, P.R. Wamsley, and C. M. Volk. Nitrous oxide and halocompounds. In Climate Monitoring and Diagnostics Laboratory Summary Report No. 24, D.J. Hofmann, J.T. Peterson, and R.M. Rosson (eds.). National Technical Information Services, Springfield, VA, 91-121 (1998).

No abstract.

Castle, R.D., R.H. Wanninkhof, J.L. Bullister, S.C. Doney, R.A. Feely, B.E. Huss, E. Johns, F.J. Millero, K. Lee, D. Frazel, D. Wisegarver, D. Greeley, F. Menzia, M. Lamb, G. Berberian, and L.D. Moore. Chemical and hydrographic profiles and underway measurements from the eastern North Atlantic during July and August of 1993. NOAA Data Report, ERL AOML-32 (PB98-131865), 82 pp. (1998).

From July 4-August 30, 1993, the National Oceanic and Atmospheric Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES) and Radiatively Important Trace Species (RITS) programs participated in an oceanographic research cruise aboard the NOAA ship Malcolm Baldrige. The objectives of the OACES component were to determine the source and sink regions of CO₂ in the equatorial and North Atlantic during the summer and to establish a baseline of total carbon inventory in the region. Data were collected from 5°S to Iceland along a nominal longitude of 20°W. This report presents only the OACES-related data from legs 1, 2A, and 2B, including hydrography, nutrients, carbon species, dissolved oxygen, total inorganic carbon, chlorofluorocarbons, total alkalinity, pH, and salinity. Included are contour plots of the various parameters and descriptions of the sampling techniques and analytical methods used in data collection.

Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark. A new look at the diurnal variation of global oceanic precipitation from the ocean TOPography EXperiment (TOPEX) and the TOPEX Microwave Radiometer (TMR). International Journal of Remote Sensing, 19(1):171-180 (1998).

New results on the diurnal variation of global oceanic precipitation are obtained by using one year's TOPEX (ocean TOPography EXperiment) and TMR (TOPEX Microwave Radiometer) data, derived from the dual-frequency (Ku and C band) capacity of the altimeter and the non-Sun-synchronous orbit of the satellite. The diurnal variation is characterized by a three-maximum structure which peaks at 00:00, 08:00, and 16:00 local time. The midnight-morning-afternoon maxima and dawn-noon-evening minima pattern seems to correlate with the results of most previous studies and to offer a unified picture of the diurnal variation of oceanic rainfall. A slight daytime (06:00-18:00) preference of oceanic precipitation appears to be significant in all seasons with the day/night ratio varying from 1.032 to 1.141 and the annual mean being 1.082. Examination of the geographical distribution of the timing of diurnal variation shows that the majority of the world oceans favor an afternoon maximum and an evening minimum. Moreover, the northern hemisphere is more coherent in reaching its maximum, while the southern hemisphere in reaching its minimum. In addition, the mechanisms responsible for the diurnal variations are discussed.

Chen, G., B. Chapron, J. Tournadre, K.B. Katsaros, and D. Vandemark. Identification of possible wave damping by rain using TOPEX and TMR data. Remote Sensing of Environment, 63(1):40-48 (1998).

A global picture of wave damping by rain (WDBR), a phenomenon familiar to seafarers for centuries, has been so far unavailable owing to the fact that neither rules nor tools exist for its systematic measurement. The situation has changed following the launch of the first dual-frequency (5.3 GHz and 13.6 GHz) radar altimeter TOPEX, along with the three-frequency (18 GHz, 21 GHz, and 37 GHz) radiometer TMR (TOPEX Microwave Radiometer). In this study, a scheme for detecting possible WDBR using TOPEX/TMR data is proposed. The geographical distribution of identified WDBR is consistent with the simultaneous presence of high sea state and intensive rainfall. Frequent occurrences of WDBR are observed in the midlatitude of the two hemispheres, particularly in the Pacific Ocean. In contrast, WDBR rarely occurs in the majority of the tropical and subtropical oceans. The global seasonality of WDBR is found to be weak as a result of the hemispheric phase opposition of sea state and rainfall in their annual variations. Knowledge of spatial distribution and temporal variation of WDBR is useful in dealing with potential systematic biases in satellite wind and wave measurements due to rain/sea interaction. It would have been interesting to compare the WDBR with coincident estimates of global rainfall from the SSM/I (Special Sensor Microwave/Imager).

Cione, J.J., and P.G. Black. Surface thermodynamic observations within the tropical cyclone inner core. Preprints, Symposium on Tropical Cyclone Intensity Change, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 141-145 (1998).

No abstract.

Cione, J.J., S. Raman, L.J. Pietrafesa, R.A. Neuherz, K. Keeter, and X. Li. The use of pre-storm low-level baroclinicity in determining and implementing the Atlantic surface cyclone intensification index. Boundary Layer Meteorology, 89:211-224 (1998).

The lateral motion of the Gulf Stream off the eastern seaboard of the United States during the winter season can act to dramatically enhance the low level baroclinicity within the coastal zone during periods of offshore cold advection. The relative close proximity of the Gulf Stream current off the mid-Atlantic coast can result in the rapid and intense destabilization of the marine atmospheric boundary layer directly above and shoreward of the Gulf Stream within this region. This airmass modification period oftentimes precedes either wintertime coastal cyclogenesis or the cyclonic re-development of existing mid-latitude cyclones. A climatological study investigating the relationship between the severity of the pre-storm, cold advective period, and subsequent cyclogenic intensification was undertaken by Cione et al. in 1993. Findings from this study illustrate that the thermal structure of the continental airmass, as well as the position of the Gulf Stream front relative to land during the pre-storm period (i.e., 24-48 h prior to the initial cyclonic intensification), are linked to the observed rate of surface cyclonic deepening for storms that either advected into or initially developed within the Carolina-southeast Virginia offshore coastal zone. It is a major objective of this research to test the potential operational utility of this pre-storm low level baroclinic linkage to subsequent cyclogenesis in an actual National Weather Service (NWS) coastal winter storm forecast setting. The ability to produce coastal surface cyclone intensity forecasts recently became available to North Carolina State University researchers and NWS forecasters. This statistical forecast guidance utilizes regression relationships derived from a nine-season (January 1982- April 1990), 116-storm study conducted by Cione et al. (1993). During the period between February 1994 and February 1996, the Atlantic Surface Cyclone Intensification Index (ASCII) was successfully implemented in an operational setting by the NWS at the Raleigh-Durham forecast office for 10 winter storms. Analysis of these ASCII forecasts will be presented.

Crane, M.L. Project ACCESS: Community coastal monitoring for year 2007. Earth System Monitor, 8(4):12-16 (1998).

No abstract.

Donelan, M.A., H.C. Graber, S. Ataktürk, W.M. Drennan,, E.A. Terray, and K.B. Katsaros. Marine flux-profile relations from an air-sea interaction spar buoy. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(1):OS99, OS31J-09 (1998).

During the Spring of 1997, the Air Sea Interaction Spar (ASIS) buoy was deployed in the northeastern Gulf of Mexico. Continuous data on profiles of wind speed, temperature, and humidity were obtained with concurrent wind stress, heat flux, and wave directional properties. This paper examines the flux-profile relations and the effect of non-local or non-equilibrium wave fields on them.

Doney, S.C., J.L. Bullister, and R.H. Wanninkhof. Climatic variability in upper ocean ventilation rates diagnosed using chlorofluorocarbons. Geophysical Research Letters, 25(9):1399-1402 (1998).

The chlorofluorocarbon CFC-12 (CCl₂-F₂) distributions from two occupations of a meridional hydrographic section in the eastern North Atlantic are used to describe the oceanic penetration of CFCs and change in the integrated ventilation patterns over the five years from 1988 to 1993. The CFC-12 water-column inventories increased by 30-40%, despite a slowing atmospheric growth rate (14%), because of continuing uptake by undersaturated subsurface water masses whose response is lagged by the ventilation time-scales. After removing the long-term CFC temporal trend using a tracer age based normalization technique, we observe a distinct dipole pattern in upper ocean ventilation, with reduced convection in the subpolar gyre and enhanced production of saline subtropical underwater in 1993. These differences are discussed in relation to interannual variability in atmospheric surface forcing, upper ocean anomalies, and convection patterns associated with the North Atlantic Oscillation.

Duncombe Rae, C., S.L. Garzoli, P. Richardson, and D. Fratantoni. Hydrography of some rings in the southeast Atlantic. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(1):OS131, OS41D-02 (1998).

Mesoscale rings and eddies in the southeast Atlantic Ocean have three potential sources: the Brazil-Malvinas Current Confluence, the Agulhas Current Retroflection, and the South Atlantic Subtropical Front. Previous hydrographic surveys have identified Agulhas rings and Brazil eddies in the region of the Cape Basin. During a component cruise of KAPEX (Cape of Good Hope Experiment), an experiment to track the flow of intermediate water around the southern tip of Africa and through the Benguela Current, three large eddies were encountered in the Cape Basin and east of the Mid-Atlantic Ridge during September 1997. The eddies were detected in satellite altimetry before the cruise and surveyed with XBT, CTD and LADCP profiles. One of the rings, closest to the Agulhas retroflection, appeared a typical Agulhas ring in its first year after shedding, with a single surface isothermal stad of 16.1°C down to 280 m. The ring furthest from the supposed shedding point exhibited two lenses, 130-210 m and 320-420 m depth, at 15.27°C and 14.45°C, respectively, in addition to the surface mixed layer, 17.6°C, suggesting an Agulhas ring which had experienced two winter mixing periods since leaving the retroflection. The middle ring had a stad of 12.22°C between 440 and 600 m and showed little evidence of convective overturning events above that level, apart from a surface mixed layer (160 m, 16.7-16.8°C) which was evident also in the background water column. The origin, structure, and temperature-salinity characteristics of these three eddies are examined. It is surmised that these eddies were shed from the Agulhas retroflection and subsequently modified by atmospheric cooling, convective overturning during winter, and possibly interaction with the Subtropical Front.

Dunion, J., S.H. Houston, C. Velden, M.D. Powell, and P.G. Black. Use of GOES high-density low-level VIS winds to improve the estimation of tropical cyclone outer wind radii. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C., A72-A87 (1998).

UW-CIMSS recently began providing real-time GOES low-level VIS winds in the vicinity of tropical cyclones on a demonstrational basis to NOAA's Hurricane Research Division (HRD). These data were included in many of HRD's real-time tropical cyclone surface wind analyses which were sent to NHC forecasters on an experimental basis during 1997. These wind analyses are used as guidance in their tropical cyclone advisories and warnings. The satellite observations provide essential coverage in the periphery of hurricanes where conventional in-situ observations (e.g., ships, buoys, etc.) are often widely spaced or non-existent and reconnaissance aircraft do not normally fly. The GOES VIS winds were adjusted to the surface using a PBL model. These adjusted data were used in real-time surface wind analyses for Hurricanes Danny and Erika of 1997 and were available for post-storm analyses in 1996 Hurricanes Edouard, Fran, Hortense, and Lili. The satellite observations improved the estimation of the 34 kt wind radii in many cases and also helped place the 50 kt wind radii for some cases. Examples of the impact of these data on hurricane surface wind analyses will be shown. Statistics on comparisons (>100 cases) of the adjusted and unadjusted GOES VIS winds with in-situ surface measurements will be presented. Also, in some cases GPS-sonde profiles were available in the vicinity of the GOES VIS winds. Comparisons of these highly detailed soundings with the satellite winds and their height assignments will be shown. The potential for further improvement of outer wind radii estimation through joint use of GOES VIS winds and satellite-based scatterometer surface winds will be discussed.

Durand, P., H. Dupuis, D. Lambert, B. Bénech, A. Druilhet, K.B. Katsaros, P.K. Taylor, and A. Weill. Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments. Journal of Geophysical Research, 103(C11):25,125-25,136 (1998).

Two major campaigns (Surface of the Oceans, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphére, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were conducted in 1992 and 1993, respectively, in the Azores region. Among the various platforms deployed, instrumented aircraft and ship allowed the measurement of the turbulent flux of sensible heat, latent heat, and momentum. From coordinated missions we can evaluate the sea surface fluxes from (1) bulk relations and mean measurements performed aboard the ship in the atmosphere surface layer and (2) turbulence measurements aboard aircraft, which allowed the flux profiles to be estimated through the whole atmospheric boundary layer and therefore to be extrapolated toward the sea surface level. Continuous ship fluxes were calculated with bulk coefficients deduced from inertial-dissipation measurements in the same experiments, whereas aircraft fluxes were calculated with eddy-correlation technique. We present a comparison between these two estimations. Although momentum flux agrees quite well, aircraft estimations of sensible and latent heat flux are lower than those of the ship. This result is surprising, since aircraft momentum flux estimates are often considered as much less accurate than scalar flux estimates. The various sources of errors on the aircraft and ship flux estimates are discussed. For sensible and latent heat flux, random errors on aircraft estimates, as well as variability of ship flux estimates, are lower than the discrepancy between the two platforms, whereas the momentum flux estimates cannot be considered as significantly different. Furthermore, the consequence of the high-pass filtering of the aircraft signals on the flux values is analyzed; it is weak at the lowest altitudes flown and cannot therefore explain the discrepancies between the two platforms but becomes considerable at upper levels in the boundary layer. From arguments linked to the imbalance of the surface energy budget, established during previous campaigns performed over land surfaces with aircraft, we conclude that aircraft heat fluxes are probably also underestimated over the sea.

Eads, L.J., H.A. Friedman, and D.J. Garcia. From humble beginnings as the Inner City Marine Project to selection as a National School of Excellence. Preprints, Seventh Symposium on Education, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 162-165 (1998).

The evolution of the MAST Academy (Maritime and Science Technology High School), a Dade County Magnet School of Choice, from its predecessor, the Inner City Marine Project (ICMP), is described. ICMP originated after Dade County experienced civil unrest in the Black community in 1984. At that time, Dr. Linda J. Eads, currently MAST Academy's principal, was assigned to design a program in maritime education which emphasized career exploration for minorities. The ICMP operated from the District Office of the Dade County Public Schools and targeted elementary and middle schools in the inner city with high minority populations. When the MAST Academy opened its doors in 1991, the ICMP became the MAST Academy Outreach Department which continued to provide programs for the targeted schools. The MAST Academy presently carries on the tradition of the ICMP by providing high school students with specialized marine-theme science and technology courses. In 1996, the MAST Academy was selected as a U.S. Department of Education National Blue Ribbon School of Excellence.

Ellis, G., P. Swart, M. Lutz, C. Alvarez-Zarikian, P. Blackwelder, T.A. Nelsen, H. Wanless, and J. Trefry. The stable isotope composition of foraminifera, ostracods, and organic material in a dated core from Whitewater Bay. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 2 pp. (1998).

No abstract.

Ellsberry, R.L., and F.D. Marks. U.S. Weather Research Program Hurricane Landfall Workshop Report. Technical Note, NCAR/TN-442, 40 pp. (1998).

No abstract.

Feely, R.A., R.H. Wanninkhof, C.D. Cosca, and K. Lee. The impact of the 1997-1998 El Niño on the air-sea exchange flux of CO₂ in the oceans. AGU 1998 Fall Meeting, San Francisco, CA, December 6-10, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(45):F507, OS41H-08 (1998).

As part of the NOAA Ocean Atmosphere Carbon Exchange Study (OACES), measurements of CO₂ partial pressure were made in the atmosphere and in the surface waters of the central and eastern equatorial Pacific from 1992 to 1998. Surface water pCO₂ data indicate significant diurnal, seasonal, and interannual variations. The largest variations were associated with the 1997-98 ENSO event, which reached maximum intensity in the winter of 1997-1998. The lower surface pCO₂ values during the 1997-98 ENSO period were the result of the combined effects of both remotely and locally forced physical processes: (1) development of a low-salinity surface cap as part of the formation of the warm pool in the western and central equatorial Pacific; and (2) deepening of the thermocline by propagating Kelvin waves in the eastern Pacific. Both these processes serve to reduce pCO₂ values towards near equilibrium values at the height of the warm phase of ENSO. These changes resulted in a lower-than-normal CO₂ flux to the atmosphere. The annual average fluxes indicate that strong ENSOs exchange about 0.3-0.4 GtC/yr to the atmosphere; whereas, during non-El Niño years the equatorial Pacific exchanges about 0.9-1.0 GtC/yr to the atmosphere. This difference is enough to account for approximately one-third of the atmospheric anomaly during an El Niño. Our models suggest that this effect occurs in temperate and polar regions as well. Thus, the ENSO process is the major controlling factor of the interannual variability of the air-sea exchange of CO₂ in the oceans. During decades dominated by strong ENSO events, such as this one, as much as 2-3 Gt more C are retained by the oceans compared with normal decades. Clearly, the equatorial Pacific is a very important region for studying climate feedbacks of greenhouse warming.

Feely, R.A., R.H. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P. Murphy. A new automated underway system for making high precision pCO₂ measurements onboard ships of opportunity. Analytica Chimica Acta, 377:185-191 (1998).

We have developed a new temperature-controlled, automated underway system for making atmospheric and surface ocean pCO₂ measurements onboard research vessels equipped with an uncontaminated seawater intake system. Uncontaminated seawater is supplied to a showerhead plexiglass equilibrator at the rate of approximately 50 liters/minute. After about 3 minutes, the air trapped in the equilibrator is equilibrated with seawater. This air is sampled six times per hour. In addition, atmospheric air is sampled three times per hour from the intake on the bow flagstaff through 3/8" Dekabon^TM tubing to the underway system. The CO₂ measurements are made with a differential, non-dispersive, infrared analyzer LiCor^TM (model 6252). The underway system operates on an hourly cycle with the first quarter of each hour devoted to calibration with three CO₂ standards, each measured for 5 minutes. A second order polynomial calibration curve is calculated from the voltage values of the standards. The remaining time in each hour is used to measure equilibrator air (15 min), bow air (15 min), and equilibrator air once again (15 min). To date, we have successfully used the underway pCO₂ system on 12 cruises of the NOAA Ship Ka'imimoana in the equatorial Pacific. The analytical precision of the system is approximately 0.3-0.4 ppm for seawater and for air.

Ffield, A., C.I. Fleurant, R.L. Molinari, and W.D. Wilson. NOAA Ship Malcolm Baldrige 1995 cruises: MB95-02, MB95-04, and MB95-07 hydrographic data. LDEO-98-1, Technical Report, 310 pp. (1998).

No abstract.

Fleurant, C.I., and R.L. Molinari. Comparison of bottle salinity and bottle oxygen values from WHP repeat lines I7N, I1W, I8N, and I8S. International WOCE Newsletter, 33:27-29 (1998).

No abstract.

Franklin, J.L., and M.L. Black. GPS dropwindsonde data in hurricanes. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C., A111-A142 (1998).

The 1997 hurricane season was the first with both NOAA WP-3D aircraft equipped with the new NCAR GPS dropwindsonde system. The GPS sonde replaces the old Omega-based ODW, in use since the early 80's on the P-3s. During the season, the first successful dropwindsonde releases (of any kind) were made in a hurricane eyewall (Guillermo). These were followed by additional eyewall releases in Hurricane Erika. The wind profiles show that surface winds in the eyewall may be much higher than what is typically inferred from flight-level reconnaissance data. Very strong jets resolved by the GPS dropsondes in and just above the boundary layer may be indicative of peak surface gusts.

Fratantoni, D.M., P.L. Richardson, C.M. Duncombe Rae, and S.L. Garzoli. Three warm-core rings in the eastern south Atlantic. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(1):OS131, OS41D-04 (1998).

During the September 1997 Benguela Current Experiment, three large (300 km) anticyclonic rings were identified and surveyed near 30°S in the eastern South Atlantic. Preliminary analysis suggests that these rings were formed from the retroflecting Agulhas Current south of Africa. Two of the rings were observed west of the Walvis Ridge and appear to have been freely translating for nearly two years. The transport of intermediate water (approximate depth range 400-1000 m) within Agulhas rings is thought to be an important interbasin transport pathway associated with the global-scale thermohaline circulation. Employing an array of Lagrangian floats and drifters, this experiment and others associated with the U.S., German, and South African KAPEX (Cape of Good Hope Experiment) program constitute the first direct examination of this pathway. In-situ hydrographic and direct velocity measurements were performed aboard the R/V Seward Johnson. Nominal ring positions were estimated prior to departure using satellite altimetry. During the cruise intensive shipboard XBT and ADCP surveys revealed the three-dimensional structure of temperature and velocity associated with each ring and facilitated a determination of the ring center. Multiple acoustically-tracked subsurface RAFOS floats (at 700 m depth) and satellite-tracked surface drifters were then launched near the center of each ring to measure ring translation and the evolution of core properties over a two-year period. Additional floats and drifters were deployed along 30°S and 7°W to characterize the background flow of surface and intermediate water in the Benguela Current and the eastern South Atlantic subtropical gyre. In this poster we describe the horizontal structure of these large (300 km diameter) and energetic (40 cm/s) warm-core rings using both in-situ and Lagrangian measurements. We present synoptic plan-view depictions of thermocline depth, upper-ocean velocity, and integrated heat content for each ring. The scale and intensity of each ring is discussed in the context of a translation history compiled from archived TOPEX/Poseidon altimetry. Finally, surface drifter trajectories are used to assess ring translation and to describe the temporal evolution of azimuthal velocity structure and intensity.

Friedman, H.A., and D.J. Garcia. Tropical cyclone public awareness programmes: Preparing for the twenty-first century. Preprints, Seventh Symposium on Education, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 166-168 (1998).

During the period from 1969 to 1993, a total of 1551 tropical cyclones, typhoons, and hurricanes occurred worldwide. Literally millions of lives are affected each year, and billions of dollars are lost as a result of these storms. At present, we can do little, if anything, to lessen the occurrence, frequency, or intensity of tropical cyclones, or to influence their paths. But over the past three decades, significant advances have been made in mankind's capability to prepare for and mitigate their damaging effects. Concerted international scientific efforts have resulted in better understanding the phenomenon of tropical cyclones, their formation, characteristics, path of movement, and effects. Technical advances in weather monitoring equipment satellites, computers, improved radar systems, and other space age meteorological tools enable scientists today to vigilantly monitor cyclones as they form, track them as they move, and predict with some accuracy where they are likely to impact on land and people. Correspondingly, meteorological services in many countries have been substantially improved in recent years. Cyclone monitoring equipment has been installed in most cyclone-prone regions of the world. National systems have been linked to regional and international networks through which meteorological data is shared and warnings of approaching cyclones conveyed. In many localities, local communication systems and administrative procedures have been strengthened to ensure that information about approaching cyclones is passed to communities most at risk. While great strides have been made in our ability to understand and live with cyclones, still more must be done. We must strive to further expand our basic knowledge about tropical cyclones, upgrade tools needed for weather monitoring and prediction, improve the warning and communications network, and strengthen meteorological services. It is a useful reminder that the primary objectives of these varied activities is to prevent the loss of lives and prevent or minimize property damage from cyclones. The need for continued effort is reconfirmed by the deaths and destruction left in the wake of each tropical cyclone that affects populated areas today; a problem that is likely to continue and increase in seriousness as coastal populations enlarge. The goal of preventing loss of life and reducing property damage from tropical cyclones, however, can not be achieved simply through improved technical and meteorological services. Accurate prediction and timely notice are critically important, but loss of life and property can only be minimized if officials and the general public are knowledgeable of the hazards faced, understand the warnings provided, and take the proper actions to protect life and property before, during, and after a cyclone. The process required to achieve a public state of readiness is commonly referred to as an awareness program. A resource guide, designed to provide a framework for the development and implementation of local tropical cyclone awareness programs, will be discussed. The Internet was used extensively to obtain up-to-date information on worldwide issues concerning tropical cyclones. The guide's design encourages interactive use by disaster preparedness officials and educators at the local level. Questionnaires and community-specific checklists are provided to elicit local participation in the process of creating tropical cyclone awareness.

Garcia, D.J., H.A. Friedman, and L.J. Eads. MAST Academy outreach: Serving the community with marine theme programs. Preprints, Seventh Symposium on Education, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 169-171 (1998).

The MAST Academy's Outreach Department provides marine theme enrichment programs which emphasize career opportunities for targeted schools with high minority enrollments. Enrichment programs include the Land SHARC (Science Hands-on and Related Careers) and WOW (Weather On Wheels) mobile laboratories, environmental field trips, internships, and the MAST Mariners Program, a middle school summer course focused on, but not exclusively for, minority students. The role of NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML) and other outside agencies in providing school year and summer internships for MAST Academy students is discussed. Meteorologists from AOML's Hurricane Research Division serve as advisory board members for the WOW; their contributions to the program are presented.

Garzoli, S.L., C. Duncombe Rae, D. Fratantoni, G.J. Goñi, J. Mantel, A. Roubicek, P. Fratantoni, and C. Whittle. Benguela Current Experiment. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(1):OS131, OS41D-01 (1998).

Although intermediate water is an important component of the northward-flowing meridional circulation cell in the Atlantic, the pathways, velocity, and variability of this water are poorly known. In order to study the northward flow of intermediate water in the Benguela Current and its extension, a program was initiated by scientists of WHOI, NOAA/AOML, and Sea Fisheries (South Africa). The main objective was to obtain the first subsurface Lagrangian float measurements of the northward flow of intermediate water in t he eastern South Atlantic and to measure the characteristics of this water. This program is a component of KAPEX (Cape of Good Hope Experiment), a joint U.S., Germany, and South Africa effort. During September 1997, we participated in a cruise aboard the RV Seward Johnson from Cape Town to Recife. The main objectives of this cruise were: to launch an array of RAFOS floats and surface drifters; to perform an intensive survey to determine the characteristics of the flow; and to search for and study Agulhas rings in the area. Agulhas rings are considered to be one of the main carriers of Indian Ocean waters into the Atlantic. Hydrographic casts (CTD-O₂) and direct measurements of currents (ADCP/LADCP) were performed along 30°S (between 14°E and 7°W) and along 7°W (between 33°S and 18°S) to study the characteristics and paths of the intermediate water flow at the time of deployments. Three anticyclonic rings were identified through intensive XBT surveys guided by satellite images of sea surface height. CTD/LADCP stations were performed and RAFOS floats and drifters launched in a radial from the center of the rings. The eddies are tentatively identified as being Agulhas rings, although a deep (600 m), cold (12.2°C), mixed layer in one ring raises questions about its origin. Thirty-two RAFOS floats and 11 surface drifters were launched along the sections and in the rings. This poster will provide an overview of the Benguela Current Experiment and the preliminary results from the September 1997 cruise.

Goñi, G.J., and S.L. Garzoli. Origin and evolution of the Benguela Current Experiment rings by altimetry. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(1):OS131, OS41D-03 (1998).

Historical hydrographic data is used to compute the mean upper layer thickness and reduced gravity in the southeastern Atlantic. These parameters, along with the altimeter-derived sea surface height anomaly, are used to derive the upper layer thickness of the ocean. This product proved to be an efficient means to identify and track anticyclonic rings. In September 1997, as part of the Benguela Current Experiment, a cruise on the R/V Seward Johnson guided by the TOPEX/POSEIDON product identified and surveyed three rings. The water mass characteristics of these rings indicate that at least two of them could have their origin in the Agulhas retroflection. The third ring has hydrographic characteristics that raise questions about its origin. This poster shows the results of a study of these rings based on altimetry. Synoptic maps of the upper layer thickness are analyzed to determine the trajectories of the rings in the region for a period of two years previous to the Benguela Current Experiment. The origins and evolution of the three rings observed during the September 1997 cruise are established and discussed. The translation velocity, available potential energy, and heat content are calculated from the altimeter data. A comparison between the shipboard and altimeter-derived values of the upper layer thickness is also presented.

Graber, H.C., M.A. Donelan, S. Ataktürk, W.M. Drennan, and K.B. Katsaros. Evaluation of NSCAT scatterometer winds with wind stress measurements in the Gulf of Mexico. AGU 1998 Fall Meeting, San Francisco, CA, December 6-10, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(45):F417, OS72G-03 (1998).

Wind vectors and radar backscatter observed by the NASA scatterometer (NSCAT) are compared with wind and wind stress measurements from an air-sea interaction spar (ASIS) buoy and wind measurements from a nearby NDBC discus buoy. ASIS is a new autonomous spar buoy designed to permit long-term measurements of interfacial processes. During a two-month deployment in the Gulf of Mexico in April 1997, the buoy experienced several fronts associated with rapid changes in wind speed and direction. The ASIS buoy was equipped for motion-corrected measurements of the wind stress vector, as well as high resolution wave directional properties. These are used to explore wind and backscatter measurements of scatterometers. Time difference and spatial separation between NSCAT and buoy observations were limited to less than 30 minutes and 25 km, respectively.

Gray, W.M., C.W. Landsea, J.A. Knaff, P.W. Mielke, and K.J. Berry. Verification of the 1997 seasonal hurricane forecasts and a prediction for 1998. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C., A331-A338 (1998).

No abstract.

Hacker, E., E. Firing, W.D. Wilson, and J.C. Kindle. Evidence for a North Equatorial Countercurrent in the eastern Indian Ocean during the northeast monsoon. AGU 1998 Ocean Sciences Meeting, San Diego, CA, February 9-13, 1998. Supplement to EOS, Transactions, American Geophysical Union, 79(1):OS75, OS21J-02 (1998).

Data collected during February and March 1995 as part of the WOCE Hydrographic Program Expedition in the Indian Ocean provide evidence for an eastward-flowing countercurrent, a possible North Equatorial Countercurrent (NECC), extending from 80°E south of Sri Lanka to about 92°E. The current is associated with a local surface salinity maximum (34.5 psu) representing its probable northwest Indian Ocean source. At 80°E, the combination of shipboard and lowered acoustic Doppler current profiler (ADCP) data shows weak flow to the east between 2°N and 2.8°N near the surface, with flow to the east extending from 1.5°N to 4°N at a depth of 100 m. The eastward flow is imbedded in a westward flow of lower salinity water extending from 3°S to 6°N. The westward flow represents a combination of the outflow of fresher, surface Bay of Bengal water and westward return flow of the eastward-flowing South Equatorial Countercurrent water. At 92°E, the NECC is part of an intense circulation feature with eastward flow extending from 3°N to 6°N and peak speed of 0.8 m/s. NOAA data from the repeat hydrographic line along 80°E during late October 1995, during the monsoon transition period, show evidence of a weak eastward flow in the upper 100 m between 4°N to 5°N imbedded in a broader westward flow between 1°N and 6°N. The observations are compared to model circulation features from the NRL high-resolution, three-layer, non-linear, model forced by ECMWF winds. Although the NRL model does not show an NECC south of Sri Lanka, it does show a weak countercurrent trough further to the east between 4°N and 7°N. The temporal and spatial smoothing of historical data products may be the reason that the NECC has not been reported previously.

Hansen, D.V., and M.S. Swenson. Application of oceanic heat budgets to evaluation of surface heat flux climatologies. Proceedings, First International Conference on Reanalyses, Washington, D.C., October 27-31, 1997. World Climate Research Programme, 40 (1998).

We are using the extensive WOCE/TOGA data sets from drifting buoys and VOS/XBT measurements for quantification of climatological heat budget processes in the equatorial cold tongue and NECC regions of the eastern tropical Pacific Ocean. One interesting application of the results is in their implication for the net surface heat flux. Early results suggest that the heat flux climatology generated from the NCEP/NCAR Reanalysis Project is superior to other popular climatologies. A major factor in the improvement appears to be the annual cycle of downward shortwave radiation.

Hasler, A.F., K. Palaniappan, C. Kambhammetu, P.G. Black, E.W. Uhlhorn, and D. Chesters. High-resolution wind fields within the inner core and eye of a mature tropical cyclone from GOES 1-min images. Bulletin of the American Meteorological Society, 79(11):2483-2496 (1998).

Mesoscale wind fields have been determined for a mature hurricane with high spatial and temporal resolution, continuity, and coherency. These wind fields, near the tropopause in the inner core and at low levels inside the eye, allow the evolution of mesoscale storm features to be observed. Previously, satellite-derived winds near hurricanes have been determined only at some distance from the eye over a typical time period of 1V2 h. Hurricane reconnaissance aircraft take 30 min to 1 h to complete an inner-core pattern. With the long observation periods of these previous methods, steady-state conditions must be assumed to give a complete description of the observed region. With the advent of 1-min interval imagery, and fourfold improvement of image dynamic range from NOAA's current generation of GOES satellites, there is a new capability to measure inner-core tropical cyclone wind fields near the tropopause and within the eye, enabling mesoscale dynamical processes to be inferred. These measurements give insights into the general magnitude and structure of the hurricane vortex, along with very detailed measurements of the cloud-top wind's variations in response to convective outbursts. This paper describes the new techniques used to take advantage of the GOES satellite improvements that, in turn, allowed the above innovations to occur. The source of data for this study is a nearly continuous 12-h sequence of 1-min visible images from NOAA GOES-9 on 6 September 1995. These images are centered on Hurricane Luis with maximum winds of 120 kt (CAT4) when it was 250 km northeast of Puerto Rico. A uniform distribution of long-lived cirrus debris with detailed structure is observed in the central dense overcast (CDO), which has been tracked using the 1-min images. The derived wind field near the tropopause at approximately 15 km in the CDO region has a strong closed circulation with speeds up to 25 m s^-1, which pulses in response to the convective outbursts in the eyewall. Cloud displacements are computed at every pixel in every image, resulting in a quarter-million uVv winds in each of 488 hurricane images observed at 1- to 4-min intervals over 12 h. For analysis and presentation, these ultradense wind fields are reduced to 8- or 16-km grids using a 7-min time base by smoothing displacement vectors in space and time. Cloud structures were tracked automatically on a massively parallel processing computer, but with manual spot-checking. Manual tracking has been used to follow CDO structure over long time periods, up to 90 min for a small test sample. Cloud tracking for the wind fields presented here is accomplished using a Massively Parallel Semi-Fluid Motion Analysis (MPSMA) automatic technique. This robust deformable surface-matching algorithm has been implemented on the massively parallel Maspar supercomputer. MPSMA automatic tracking typically follows a feature for 7 min. For this time base the error of these winds is estimated to be 1.5 m s^-1. However, systematic navigation and height assignment errors in the moderately sheared hurricane environment must still be considered. Spatial and temporal smoothing of the wind field have been performed to reduce systematic navigation errors and small-scale turbulent noise. The synthesis used here to compute the wind fields gives an order of magnitude reduction in the amount of data presented compared to the amount of data processed. Longer tracking could give higher accuracy but would smooth out the smaller-scale spatial and temporal features that appear dynamically significant. The authors believe that the techniques described in this paper have great potential for further research on tropical cyclones and severe weather as well as in operational use for nowcasting and forecasting. United States and foreign policymakers are urged to augment the GOES, GMS, FY2, and Meteosat geostationary satellite systems with dual imaging systems such that 1-min observations are routinely taken.

Hendee, J.C. An expert system for marine environmental monitoring in the Florida Keys National Marine Sanctuary and Florida Bay. Proceedings, 2nd International Conference on the Coastal Environment, Cancun, Mexico, September 8-10, 1998. Computational Mechanics Publications/WIT Press, Southampton, 57-66 (1998).

The National Oceanic and Atmospheric Administration's (NOAA, U.S. Department of Commerce) Atlantic Oceanographic and Meteorological Laboratory (AOML) works cooperatively with the Florida Institute of Oceanography (FIO) in the implementation of the SEAKEYS (Sustained Ecological Research Related to Management of the Florida Keys Seascape) network, which is situated along 220 miles of coral reef tract within the Florida Keys National Marine Sanctuary (FKNMS). This network is itself actually an enhanced framework of seven Coastal-Marine Automated Network (C-MAN) stations for long-term monitoring of meteorological parameters (wind speed, wind gusts, air temperature, barometric pressure, relative humidity). To the C-MAN network, SEAKEYS adds oceanographic parameters (sea temperature, photosynthetically active radiation, salinity, fluorometry, optical density) to the stations. As a recent enhancement to the SEAKEYS network, an expert system shell is being employed to provide daily interpretations of near real-time acquired data for the benefit of scientists, fishermen, and skin divers. These interpretations are designed to be automatically emailed to Sanctuary managers and to the FIO maintainers of the network. The first set of interpretations include those dealing with environmental conditions conducive to coral bleaching. Other marine environmental interpretations are slated to follow.

Hendee, J.C., C. Humphrey, and T. Moore. A data-driven expert system for producing coral bleaching alerts. Proceedings, 7th International Conference on the Development and Application of Computer Techniques to Environmental Studies, Las Vegas, Nevada, November 10-12, 1998. Computational Mechanics Publications/WIT Press, Southampton, 139-147 (1998).

As a recent enhancement to the SEAKEYS (Sustained Ecological Research Related to Management of the Florida Keys Seascape) environmental monitoring network, an expert system shell was employed to provide daily interpretations of near real-time acquired combinations of meteorological and oceanographic parameters as they meet criteria generally thought to be conducive to coral bleaching. These interpretations were automatically posted to the World-Wide Web and emailed to Florida Keys National Marine Sanctuary managers and scientists so they could witness and study bleaching events as they might happen, and so that a model could be developed with greater precision in identifying physical factors conducive to coral bleaching. The expert system, as a model, was successful in showing that certain assumptions by experts regarding coral bleaching apparently do not hold at Sombrero Reef.

Henderson-Sellers, A., H. Zhang, G. Berz, K. Emanuel, W. Gray, C.W. Landsea, G. Holland, J. Lighthill, S.-L. Shieh, P. Webster, and K. McGuffie. Tropical cyclones and global climate change: A post-IPCC assessment. Bulletin of the American Meteorological Society, 79(1):19-38 (1998).

The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but there is no clear evidence of long-term trends. Efforts have been initiated to use geological and geomorphological records and analysis of oxygen isotope ratios in rainfall recorded in cave stalactites to establish a paleoclimate of tropical cyclones, but these have not yet produced definitive results. Recent thermodynamical estimation of the maximum potential intensities (MPI) of tropical cyclones shows good agreement with observations. Although there are some uncertainties in these MPI approaches, such as their sensitivity to variations in parameters and failure to include some potentially important interactions such as ocean spray feedbacks, the response of upper-oceanic thermal structure and eye and eyewall dynamics do appear to be an objective tool with which to predict present and future maxima of tropical cyclone intensity. Recent studies indicate the MPI of cyclones will remain the same or undergo a modest increase of up to 10%-20%. These predicted changes are small compared with the observed natural variations and fall within the uncertainty range in current studies. Furthermore, the known omissions (ocean spray, momentum restriction, and possibly also surface to 300-hPa lapse rate changes) could all operate to mitigate the predicted intensification. A strong caveat must be placed on analysis of results from current GCM simulations of the "tropical-cyclone-like" vortices. Their realism, and hence prediction skills (and also that of "embedded" mesoscale models), is greatly limited by the coarse resolution of current GCMs and the failure to capture environmental factors that govern cyclone intensity. Little, therefore, can be said about the potential changes of the distribution of intensities as opposed to maximum achievable intensity. Current knowledge and available techniques are too rudimentary for quantitative indications of potential changes in tropical cyclone frequency. The broad geographic regions of cyclogenesis and, therefore, also the regions affected by tropical cyclones are not expected to change significantly. It is emphasized that the popular belief that the region of cyclogenesis will expand with the 26 C SST isotherm is a fallacy. The very modest available evidence points to an expectation of little or no change in global frequency. Regional and local frequencies could change substantially in either direction, because of the dependence of cyclone genesis and track on other phenomena (e.g., ENSO) that are not yet predictable. Greatly improved skills from coupled global ocean-atmosphere models are required before improved predictions are possible.

Hitchcock, G.L., C. Wiebinga, and P.B. Ortner. CTD hydrographic data from the Global Ocean Ecosystem Dynamics (GLOBEC) Indian Ocean cruises. University of Miami Technical Report, 97-006, 69 pp. (1998).

No abstract.

Hitchcock, G., G.A. Vargo, T. Lee, E. Johns, E. Williams, and J. Jurado. The influence of circulation on nutrient distributions in western Florida Bay. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 98-99 (1998).

No abstract.

Hood, T., C. Alvarez-Zarikian, P. Blackwelder, P. Swart, T.A. Nelsen, H.R. Wanless, J.H. Trefry, and L. Tedesco. The sediment record as a monitor of natural and anthropogenic changes in the lower Everglades/Florida Bay ecosystem. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 33-34 (1998).

No abstract.

Houston, S.H., and M.D. Powell. Reconstruction of surface wind fields for hurricanes affecting Florida Bay. Preprints, Second Conference on Coastal Atmospheric and Oceanic Prediction and Processes, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 241-244 (1998).

Hurricanes constitute episodic events which affect the physical and oceanographic processes within Florida Bay. These effects are manifested by significant changes in water-levels, waves, currents, and sediment transport processes. In addition, these storms impact plant and animal life in the Bay and the surrounding areas. Hurricane wind fields are now being made available to researchers, such as oceanographers and biologists, on a Hurricane Research Division World Wide Web site (http://www.aoml.noaa.gov/hrd). Researchers can use the wind fields to estimate the potential impacts of future tropical cyclones on the south Florida ecosystem and especially on Florida Bay. The hurricanes used in this study were the Labor Day Hurricane of 1935, Donna of 1960, Betsy of 1965, Felix of 1987, and Andrew of 1992. These tropical cyclones represented vastly different scenarios for the type of event that might be expected over extreme south Florida. The 1935 hurricane was a category 5 storm and is the most intense hurricane known to have struck the USA. This hurricane had a relatively small, concentrated wind field when it crossed the Florida Keys and Florida Bay. Hurricane Donna (1960) was a category 4 hurricane with a much broader wind field that crossed the Keys and Bay on a similar track to the 1935 Hurricane. Hurricane Andrew was a fast moving category 4 hurricane when it struck south Florida recently. However, its strongest winds covered only a very small area, especially to the south of the storm track. The direct impact of Andrew on Florida Bay appears to have been minimal, but decomposing organic storm debris in the Everglades likely contributed to water quality problems in the Bay.

Houston, S.H., and M.D. Powell. Surface wind field in Florida Bay hurricanes. Proceedings, 1998 Florida Bay Science Conference, Miami, Florida, May 12-14, 1998. Florida Sea Grant College Program, 35 (1998).

No abstract.

Houston, S.H., and M.D. Powell. Surface wind fields in hurricanes. Proceedings, Third International Symposium, Waves '97, Virginia Beach, VA, November 3-7, 1997. American Society of Civil Engineers (ASCE), 1391-1399 (1998).

No abstract.

Houston, S.H., and M. D. Powell. The potential impact of GPS sondes in real-time surface wind analyses for hurricanes. Minutes, 52nd Interdepartmental Hurricane Conference, Clearwater, FL, January 26-30, 1998. Office of the Federal Coordinator for Meteorological Services and Supporting Research, Washington, D.C., A-110 (1998).

During the 1996 and 1997 hurricane seasons, GPS sondes were dropped within the inner core of some tropical cyclones (i.e., Josephine of 1996; Danny, Erika, Guillermo, and Linda of 1997). The data from these sondes provided some highly detailed boundary layer profiles and surface measurements of each tropical cyclone's wind and thermodynamic properties after the fact. During the upcoming 1998 hurricane season, two potential developments may make the GPS sonde data useful for defining the hurricane's surface wind structure in real-time: (1) The GPS sonde "temp drop message" sent from AFRES and NOAA missions in and near hurricanes (including drops from the NOAA G-IV) may include additional essential information that will likely enhance the real-time use of these sondes. For example, the splash location and time are two additional parameters that may be available in the drop messages. (2) When it is deemed necessary by NHC for the issuance of warnings and (or) other critical factors, GPS sondes may be dropped along the flight-track of tasked reconnaissance flights. These drops have the potential to provide estimates of the peak surface winds and may help define some of the wind radii (i.e., 34, 50, and/or 64 kt wind radii) in those quadrants where the drops are made. This study examines the potential impacts additional wind and thermodynamic observations from sondes might have on surface wind analyses in hurricanes, which are currently provided to NHC's forecasters in real-time by HRD on an experimental basis. Some examples of post-storm analyses in 1997 hurricanes utilizing these new data in addition to conventional data sources will be presented and the potential impacts will be assessed. In addition, some preliminary comparisons of the boundary layer measurements from GPS sondes with reliable in-situ surface observations (e.g., buoys, C-MAN's, etc.) of wind, temperature, and pressure in the vicinity of tropical cyclones will be shown.

Houston, S.H., M. Lawrence, S. Spisak, and S.T. Murillo. A verification of National Hurricane Center forecasts of surface wind speed radii in hurricanes. Preprints, Symposium on Tropical Cyclone Intensity Change, American Meteorological Society 78th Annual Meeting, Phoenix, AZ, January 11-16, 1998. American Meteorological Society, Boston, 139-140 (1998).

The National Hurricane Center (NHC) issues a position and intensity forecast every six hours on all tropical cyclones in the Atlantic and eastern Pacific basins. This forecast is contained in the forecast/advisory product and includes a forecast of the horizontal distribution of the surface wind field. This distribution is given as radii in four quadrants from the center of the tropical cyclone to three wind speed values: 17.5, 25.7, and 32.9 m s^-1 (i.e., 34, 50, and 64 kt, respectively). A set of opportunistic marine observations w ere collected to determine the wind speed radii from the center of each tropical cyclone to the observation site. This can be done when a tropical cyclone's wind field affects a measurement platform with the required wind speeds. The wind speed radii based on the marine platform data were used to verify the official NHC radii forecasts described above. The preliminary results are for 17.5 m s^-1 wind speeds and are based on only 25 cases. Statistics will be presented showing that the mean absolute error of the 25 cases of verification is about 83 km (45 nm) at the initial (i.e., 0 h) forecast period and decreases about 25% by the 36 h forecast. There is a positive bias (the forecasts were larger than observed) of about 37 km (20 nm) for these cases, which also appears to decrease with longer forecast periods. The small number of cases limits our analysis to simple averages. This is the first time that such a data set has been prepared and that forecasts of tropical cyclone intensity in terms of wind speed radii have been verified. Details on the method of verification will be given along with the final statistics of the study, including 17.5 and 25.7 m s^-1 radii verification.

Huang, H., R.E. Fergen, J.R. Proni, and J.J. Tsai. Initial dilution equations for buoyancy-dominated jets in currents. Journal of Hydraulic Engineering, 124:105-108 (1998).

Initial dilution of submerged, single, round, buoyancy-dominated jets in a current is considered. Two simple semi-empirical equations, one for centerline dilution and the other for minimum surface dilution, are presented. These equations are derived based on the continuity equation for the buoyant jet flow with a hypothesis that shear entrainment and forced entrainment can be added. Available laboratory and field data are used to determine the constants in the equations. Unlike asymptotic equations which apply for the limiting flow regimes, the proposed equations span all flow regimes, from the buoyancy-dominated near field (BDNF), to the transition, and to the buoyancy-dominated far field (BDFF), providing continuous predictions for dilutions.

Jameson, A.R., A.B. Kostinski, and R.A. Black. The texture of clouds. Journal of Geophysical Research-Atmospheres, 103(D6):6211-6220 (1998).

Using a precise definition of clustering, it is shown that in two tropical cumulus clouds, droplets appear to be bunched over distances ranging from at least a kilometer or more down to several centimeters. A statistical framework is proposed for quantifying clustering in terms of a Poisson probability mixture. While these observations require further substantiation in many different clouds, droplet clustering may play a role in diverse phenomena from the coalescence growth of raindrops to the scattering of radiation by clouds.

Johns, E., and W.D. Wilson. Direct observations of velocity structure in the passages between the Intra-Americas Sea and the Atlantic Ocean, 1984-1996. Proceedings, Conference on the Transports and Linkages of the Intra-Americas Sea (IAS), Cozumel, Mexico, November 1-5, 1997. IOC/IOCARIBE/MMS, 36 (1998).

Shipboard acoustic Doppler current profiler (ADCP) velocity data collected between 1984 and 1996 in connection with several NOAA research programs have been used to examine the mean and variability of the velocity structure within the Straits of Florida, the Northwest Providence Channel, a northern approach to the Windward Passage, the Mona and Anegada Passages, and across the eastern Caribbean Sea. Historically, direct velocity data collection in these important passages between the Gulf of Mexico, the Caribbean Sea, and the Atlantic Ocean has been very sparse. Herein, we examine the transport and velocity structure in the passages using a more complete data set than previously available. This newer data set allows computation of statistically significant mean and standard deviations of the transport and velocity fields, and examination of the temporal (seasonal to interannual) variability of these fields. Comparison will be made of the mean and varying flow fields with the results of previous studies and with available time series of regional forcing functions such as the COADS wind stress data set. Most importantly, the mean transports should prove useful to numerical modelers of the Intra-Americas Sea for calibration and refinement of model boundary conditions.

Johns, E., W.D. Wilson, and T.N. Lee. Interaction of Florida Bay waters with the Gulf of Mexico and the Atlantic Ocean. Proceedings, 1998 Meeting of the Oceanography Society and the Intergovernmental Oceanographic Co