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This paper provides an overview of the Dragon 4 project dealing with operational monitoring of sea ice and sea surface salinity (SSS) and new product developments for altimetry data. To improve sea ice thickness retrieval, a new method was developed to match the Cryosat-2 radar waveform. Additionally, an automated sea ice drift detection scheme was developed and tested on Sentinel-1 data, and the sea ice drifty capability of Gaofen-4 geostationary optical data was evaluated. A second topic included implementation and validation of a prototype of a Fully-Focussed SAR processor adapted for Sentinel-3 and Sentinel-6 altimeters and evaluation of its performance with Sentinel-3 data over the Yellow Sea; the assessment of sea surface height (SSH), significant wave height (SWH), and wind speed measurements using different altimeters and CFOSAT SWIM; and the fusion of SSH measurements in mapping sea level anomaly (SLA) data to detect mesoscale eddies. Thirdly, the investigations on the retrieval of SSS include simulations to analyse the performances of the Chinese payload configurations of the Interferometric Microwave Radiometer and the Microwave Imager Combined Active and Passive, SSS retrieval under rain conditions, and the combination of active and passive microwave to study extreme winds.

This paper provides an overview of the Dragon 4 project dealing with operational monitoring of sea ice and sea surface salinity (SSS) and new product developments for altimetry data. To improve sea ice thickness retrieval, a new method was developed to match the Cryosat-2 radar waveform. Additionally, an automated sea ice drift detection scheme was developed and tested on Sentinel-1 data, and the sea ice drifty capability of Gaofen-4 geostationary optical data was evaluated. A second topic included implementation and validation of a prototype of a Fully-Focussed SAR processor adapted for Sentinel-3 and Sentinel-6 altimeters and evaluation of its performance with Sentinel-3 data over the Yellow Sea; the assessment of sea surface height (SSH), significant wave height (SWH), and wind speed measurements using different altimeters and CFOSAT SWIM; and the fusion of SSH measurements in mapping sea level anomaly (SLA) data to detect mesoscale eddies. Thirdly, the investigations on the retrieval of SSS include simulations to analyse the performances of the Chinese payload configurations of the Interferometric Microwave Radiometer and the Microwave Imager Combined Active and Passive, SSS retrieval under rain conditions, and the combination of active and passive microwave to study extreme winds.

This paper provides an overview of the Dragon 4 project dealing with operational monitoring of sea ice and sea surface salinity (SSS) and new product developments for altimetry data. To improve sea ice thickness retrieval, a new method was developed to match the Cryosat-2 radar waveform. Additionally, an automated sea ice drift detection scheme was developed and tested on Sentinel-1 data, and the sea ice drifty capability of Gaofen-4 geostationary optical data was evaluated. A second topic included implementation and validation of a prototype of a Fully-Focussed SAR processor adapted for Sentinel-3 and Sentinel-6 altimeters and evaluation of its performance with Sentinel-3 data over the Yellow Sea; the assessment of sea surface height (SSH), significant wave height (SWH), and wind speed measurements using different altimeters and CFOSAT SWIM; and the fusion of SSH measurements in mapping sea level anomaly (SLA) data to detect mesoscale eddies. Thirdly, the investigations on the retrieval of SSS include simulations to analyse the performances of the Chinese payload configurations of the Interferometric Microwave Radiometer and the Microwave Imager Combined Active and Passive, SSS retrieval under rain conditions, and the combination of active and passive microwave to study extreme winds.

Spatial anomalies associated with seamounts and islands have been detected in the South West Indian Ocean using a new surface chlorophyll-a based enrichment index (EI). Calculated from daily L3 4-km MODIS chl-a data from 2003 to 2018, the EI was used to quantify recurrent (seasonal) surface enrichment associated with these features. Most notable were the shallow Walters Shoal (18 m) and nearby deeper WS-2 seamount (480 m), both located on the southern Madagascar Ridge, which showed high EI values of 40% and 15% local enhancement. Tromelin Island, east of Madagascar, exhibited more moderate values of 15% local increase. Other shallower seamounts including La Pérouse (60 m) and MAD-Ridge (240 m) exhibited sporadic or no measurable surface maxima. Regions of strong mesoscale activity such as south of Madagascar where the South East Madagascar Current detaches from the continent also revealed high EI values. A marked seasonality of the EI was observed over the Walters Shoal, with higher values during the oligotrophic season than in the austral winter. The seasonal variability of the MLD in combination with the seamount bathymetry appears to induce the thermal and biological anomalies observed there, possibly favoured by the presence of a Taylor cap at the summit. Ship-collected in situ measurements showed the satellite observed enrichment to be associated with shallowing of the deep chlorophyll maximum, as well as a shift of phytoplankton groups towards diatoms and small flagellates. No net increase of integrated chl-a was measured but a potential doubling in primary productivity is expected. The EI developed in this study, designed to reveal sporadic, small localised chl-a maxima, is likely applicable to other areas in the ocean where there is local enrichments.

This work is part of the MADRidge Project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the South West Indian Ocean: one here named MAD-Ridge (240 m below the surface) plus Walters Shoal (18 m) on the Madagascar Ridge, and La Pérouse (60 m) on the abyssal plain east of Madagascar. The three span latitudes 20°S and 33°S, some 1500 km. The study provides the background oceanography for the once-off, multidisciplinary snapshot cruise studies around the seamounts. As life on seamounts is determined by factors such as summit depth, proximity to the light layers of the ocean, and the ambient circulation, a first description of regional spatial-field climatologies (16–22 years) and monthly along-ridge gradients of surface wind (driving force), water column properties of sea surface temperature, mixed layer depth, chlorophyll-a and eddy kinetic energy, plus ocean currents is provided. Being relevant to many applications in the study domain, these properties in particular reveal contrasting environments along the Madagascar Ridge and between the three seamounts that should drive biological differences. Relative to the other two seamounts, MAD-Ridge is in the more extreme situation, being at the end of the East Madagascar Current, where it experiences sturdy, albeit variable, currents and the frequent passing of mesoscale eddies.

Spatial anomalies associated with seamounts and islands have been detected in the South West Indian Ocean using a new surface chlorophyll-a based enrichment index (EI). Calculated from daily L3 4-km MODIS chl-a data from 2003 to 2018, the EI was used to quantify recurrent (seasonal) surface enrichment associated with these features. Most notable were the shallow Walters Shoal (18 m) and nearby deeper WS-2 seamount (480 m), both located on the southern Madagascar Ridge, which showed high EI values of 40% and 15% local enhancement. Tromelin Island, east of Madagascar, exhibited more moderate values of 15% local increase. Other shallower seamounts including La Pérouse (60 m) and MAD-Ridge (240 m) exhibited sporadic or no measurable surface maxima. Regions of strong mesoscale activity such as south of Madagascar where the South East Madagascar Current detaches from the continent also revealed high EI values. A marked seasonality of the EI was observed over the Walters Shoal, with higher values during the oligotrophic season than in the austral winter. The seasonal variability of the MLD in combination with the seamount bathymetry appears to induce the thermal and biological anomalies observed there, possibly favoured by the presence of a Taylor cap at the summit. Ship-collected in situ measurements showed the satellite observed enrichment to be associated with shallowing of the deep chlorophyll maximum, as well as a shift of phytoplankton groups towards diatoms and small flagellates. No net increase of integrated chl-a was measured but a potential doubling in primary productivity is expected. The EI developed in this study, designed to reveal sporadic, small localised chl-a maxima, is likely applicable to other areas in the ocean where there is local enrichments.

This work is part of the MADRidge Project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the South West Indian Ocean: one here named MAD-Ridge (240 m below the surface) plus Walters Shoal (18 m) on the Madagascar Ridge, and La Pérouse (60 m) on the abyssal plain east of Madagascar. The three span latitudes 20°S and 33°S, some 1500 km. The study provides the background oceanography for the once-off, multidisciplinary snapshot cruise studies around the seamounts. As life on seamounts is determined by factors such as summit depth, proximity to the light layers of the ocean, and the ambient circulation, a first description of regional spatial-field climatologies (16–22 years) and monthly along-ridge gradients of surface wind (driving force), water column properties of sea surface temperature, mixed layer depth, chlorophyll-a and eddy kinetic energy, plus ocean currents is provided. Being relevant to many applications in the study domain, these properties in particular reveal contrasting environments along the Madagascar Ridge and between the three seamounts that should drive biological differences. Relative to the other two seamounts, MAD-Ridge is in the more extreme situation, being at the end of the East Madagascar Current, where it experiences sturdy, albeit variable, currents and the frequent passing of mesoscale eddies.

Spatial anomalies associated with seamounts and islands have been detected in the South West Indian Ocean using a new surface chlorophyll-a based enrichment index (EI). Calculated from daily L3 4-km MODIS chl-a data from 2003 to 2018, the EI was used to quantify recurrent (seasonal) surface enrichment associated with these features. Most notable were the shallow Walters Shoal (18 m) and nearby deeper WS-2 seamount (480 m), both located on the southern Madagascar Ridge, which showed high EI values of 40% and 15% local enhancement. Tromelin Island, east of Madagascar, exhibited more moderate values of 15% local increase. Other shallower seamounts including La Pérouse (60 m) and MAD-Ridge (240 m) exhibited sporadic or no measurable surface maxima. Regions of strong mesoscale activity such as south of Madagascar where the South East Madagascar Current detaches from the continent also revealed high EI values. A marked seasonality of the EI was observed over the Walters Shoal, with higher values during the oligotrophic season than in the austral winter. The seasonal variability of the MLD in combination with the seamount bathymetry appears to induce the thermal and biological anomalies observed there, possibly favoured by the presence of a Taylor cap at the summit. Ship-collected in situ measurements showed the satellite observed enrichment to be associated with shallowing of the deep chlorophyll maximum, as well as a shift of phytoplankton groups towards diatoms and small flagellates. No net increase of integrated chl-a was measured but a potential doubling in primary productivity is expected. The EI developed in this study, designed to reveal sporadic, small localised chl-a maxima, is likely applicable to other areas in the ocean where there is local enrichments.

This work is part of the MADRidge Project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the South West Indian Ocean: one here named MAD-Ridge (240 m below the surface) plus Walters Shoal (18 m) on the Madagascar Ridge, and La Pérouse (60 m) on the abyssal plain east of Madagascar. The three span latitudes 20°S and 33°S, some 1500 km. The study provides the background oceanography for the once-off, multidisciplinary snapshot cruise studies around the seamounts. As life on seamounts is determined by factors such as summit depth, proximity to the light layers of the ocean, and the ambient circulation, a first description of regional spatial-field climatologies (16–22 years) and monthly along-ridge gradients of surface wind (driving force), water column properties of sea surface temperature, mixed layer depth, chlorophyll-a and eddy kinetic energy, plus ocean currents is provided. Being relevant to many applications in the study domain, these properties in particular reveal contrasting environments along the Madagascar Ridge and between the three seamounts that should drive biological differences. Relative to the other two seamounts, MAD-Ridge is in the more extreme situation, being at the end of the East Madagascar Current, where it experiences sturdy, albeit variable, currents and the frequent passing of mesoscale eddies.

With increased geoid resolution provided by the gravity and steady-state ocean circulation explorer (GOCE) mission, the ocean’s mean dynamic topography (MDT) can be now estimated with an accuracy not available prior to using geodetic methods. However, an altimetric-derived MDT still needs filtering in order to remove short wavelength noise unless integrated methods are used in which the three quantities are determined simultaneously using appropriate covariance functions. We studied nonlinear anisotropic diffusive filtering applied to the ocean´s MDT and a new approach based on edge-enhancing diffusion (EED) filtering is presented. EED filters enable controlling the direction and magnitude of the filtering, with subsequent enhancement of computations of the associated surface geostrophic currents (SGCs). Applying this method to a smooth MDT and to a noisy MDT, both for a region in the Northwestern Pacific Ocean, we found that EED filtering provides similar estimation of the current velocities in both cases, whereas a non-linear isotropic filter (the Perona and Malik filter) returns results influenced by local residual noise when a difficult case is tested. We found that EED filtering preserves all the advantages that the Perona and Malik filter have over the standard linear isotropic Gaussian filters. Moreover, EED is shown to be more stable and less influenced by outliers. This suggests that the EED filtering strategy would be preferred given its capabilities in controlling/preserving the SGCs.

With increased geoid resolution provided by the gravity and steady-state ocean circulation explorer (GOCE) mission, the ocean’s mean dynamic topography (MDT) can be now estimated with an accuracy not available prior to using geodetic methods. However, an altimetric-derived MDT still needs filtering in order to remove short wavelength noise unless integrated methods are used in which the three quantities are determined simultaneously using appropriate covariance functions. We studied nonlinear anisotropic diffusive filtering applied to the ocean´s MDT and a new approach based on edge-enhancing diffusion (EED) filtering is presented. EED filters enable controlling the direction and magnitude of the filtering, with subsequent enhancement of computations of the associated surface geostrophic currents (SGCs). Applying this method to a smooth MDT and to a noisy MDT, both for a region in the Northwestern Pacific Ocean, we found that EED filtering provides similar estimation of the current velocities in both cases, whereas a non-linear isotropic filter (the Perona and Malik filter) returns results influenced by local residual noise when a difficult case is tested. We found that EED filtering preserves all the advantages that the Perona and Malik filter have over the standard linear isotropic Gaussian filters. Moreover, EED is shown to be more stable and less influenced by outliers. This suggests that the EED filtering strategy would be preferred given its capabilities in controlling/preserving the SGCs.

Motivated by the potential of oceanic mesoscale eddies to drive intrinsic low-frequency variability, this paper examines geostrophic turbulence in the frequency wavenumber domain. Frequency wavenumber spectra, spectral fluxes, and spectral transfers are computed from an idealized two-layer quasigeostrophic (QG) turbulence model, a realistic high-resolution global ocean general circulation model, and gridded satellite altimeter products. In the idealized QG model, energy in low wavenumbers, arising from nonlinear interactions via the well-known inverse cascade, is associated with energy in low frequencies and vice versa, although not in a simple way. The range of frequencies that are highly energized and engaged in nonlinear transfer is much greater than the range of highly energized and engaged wavenumbers. Lowfrequency, low-wavenumber energy is maintained primarily by nonlinearities in the QG model, with forcing and friction playing important but secondary roles. In the high-resolution ocean model, nonlinearities also generally drive kinetic energy to low frequencies as well as to low wavenumbers. Implications for the maintenance of low-frequency oceanic variability are discussed. The cascade of surface kinetic energy to low frequencies that predominates in idealized and realistic models is seen in some regions of the gridded altimeter product, but not in others. Exercises conducted with the general circulation model suggest that the spatial and temporal filtering inherent in the construction of gridded satellite altimeter maps may contribute to the discrepancies between the direction of the frequency cascade in models versus gridded altimeter maps seen in some regions. Of course, another potential reason for the discrepancy is missing physics in the models utilized here., Pub in Journal of Physical Oceanography, v44 p2050-2069, August 2014.

Ocean tides, and the atmospherically forced oceanic general circulation and its associated mesoscale eddy field, have long been run separately in high-resolution global models. They are now being simulated concurrently in a high-resolution version of the HYbrid Coordinate Ocean Model (HYCOM). The incorporation of horizontally varying stratification with the addition of atmospheric forcing yields internal tides (internal waves of tidal frequency) in high-latitude, low-stratification regions that are qualitatively different from those in earlier global internal tide models, in which atmospheric forcing and horizontally variable stratification were absent. The internal tides in the new concurrent HYCOM simulations compare well with those measured in along-track satellite altimeter data., The original document contains color images. Published in the Journal of Physical Oceanography, v44 p2050-2069, Aug 2014.

Most of the Atlantic bluefin tuna caught by the purse-seine fleet in the Mediterranean Sea are transferred alive into transport cages and towed to coastal facilities where they are fattened. This major fishery is targeting aggregations of reproductive bluefin tuna that continue spawning within the transport cages. Our study is the first attempt to assess the viability of the spawning events within transport cages placed offshore in a priori favourable locations for larval survival. The study was conducted in June 2010 in the Balearic Sea, a main spawning area for bluefin tuna in the Mediterranean. The location of two transport cages, one with wild and one with captive tuna, coincide with the situation of the chlorophyll front using satellite imagery as a proxy for the salinity front between resident surface waters and those of recent Atlantic origin. The results showed that bluefin tuna eggs were spawned almost every day within the two cages but few or no larvae were found. The expected larval densities estimated after applying mortality curves to the daily egg densities observed in the cages were higher than the sampled larval densities. The trajectories of the eggs after hatching estimated from a particle tracking model based on observed geostrophic currents and a drifter deployed adjacent to the cage suggest that larvae were likely to be caught close to the cages within the sampling dates. Spawning events in captive tuna in transport cages may hatch into larvae though they may experience higher mortality rates than expected in natural populations. The causes of the larval mortality are further discussed in the text. Such studies should be repeated in other spawning areas in the Mediterranean if spawning in cages located offshore in areas favourable a priori for larval survival is likely to be considered a management measurement to minimize the impact of purse-seine fishing on tuna.

[EN]Most of the Atlantic bluefin tuna caught by the purse-seine fleet in the Mediterranean Sea are transferred alive into transport cages and towed to coastal facilities where they are fattened. This major fishery is targeting aggregations of reproductive bluefin tuna that continue spawning within the transport cages. Our study is the first attempt to assess the viability of the spawning events within transport cages placed offshore in a priori favourable locations for larval survival. The study was conducted in June 2010 in the Balearic Sea, a main spawning area for bluefin tuna in the Mediterranean. The location of two transport cages, one with wild and one with captive tuna, coincide with the situation of the chlorophyll front using satellite imagery as a proxy for the salinity front between resident surface waters and those of recent Atlantic origin. The results showed that bluefin tuna eggs were spawned almost every day within the two cages but few or no larvae were found. The expected larval densities estimated after applying mortality curves to the daily egg densities observed in the cages were higher than the sampled larval densities. The trajectories of the eggs after hatching estimated from a particle tracking model based on observed geostrophic currents and a drifter deployed adjacent to the cage suggest that larvae were likely to be caught close to the cages within the sampling dates. Spawning events in captive tuna in transport cages may hatch into larvae though they may experience higher mortality rates than expected in natural populations. The causes of the larval mortality are further discussed in the text. Such studies should be repeated in other spawning areas in the Mediterranean if spawning in cages located offshore in areas favourable a priori for larval survival is likely to be considered a management measurement to minimize the impact of purse-seine fishing on tuna.

d region, which is of relevance to Undersea Warfare., http://archive.org/details/alaskstreamcircu109452966, Approved for public release; distribution is unlimited.

Motivated by the ubiquity of time series in oceanic data, the relative lack of studies of geostrophic turbulence in the frequency domain, and the interest in quantifying the contributions of intrinsic nonlinearities to oceanic frequency spectra, this paper examines the spectra and spectral fluxes of surface oceanic geostrophic flows in the frequency domain. Spectra and spectral fluxes are computed from idealized two-layer quasigeostrophic (QG) turbulence models and realistic ocean general circulation models, as well as from gridded satellite altimeter data. The frequency spectra of the variance of streamfunction (akin to sea surface height) and of geostrophic velocity are qualitatively similar in all of these, with substantial variance extending out to low frequencies. The inverse cascade toward larger length scales documented in calculations of the spectral flux flfk) in the wavenumber k domain. Computations of n(u) in the realistic model also display an inverse temporal cascade. In satellite altimeter data, some regions are dominated by an inverse temporal cascade, whereas others exhibit a forward temporal cascade.

Motivated by the ubiquity of time series in oceanic data, the relative lack of studies of geostrophic turbulence in the frequency domain, and the interest in quantifying the contributions of intrinsic nonlinearities to oceanic frequency spectra, this paper examines the spectra and spectral fluxes of surface oceanic geostrophic flows in the frequency domain. Spectra and spectral fluxes are computed from idealized two-layer quasigeostrophic (QG) turbulence models and realistic ocean general circulation models, as well as from gridded satellite altimeter data. The frequency spectra of the variance of stream function (akin to sea surface height) and of geostrophic velocity are qualitatively similar in all of these,with substantial variance extending out to low frequencies. The spectral flux P(v) of kinetic energy in the frequency v domain for the QG model documents a tendency for nonlinearity to drive energy toward longer periods, in like manner to the inverse cascade toward larger length scales documented in calculations of the spectral flux P(k) in the wavenumber k domain. Computations of P(v) in the realistic model also display an inverse temporal cascade. In satellite altimeter data, some regions are dominated by an inverse temporal cascade, whereas others exhibit a forward temporal cascade. However, calculations performed with temporally and/or spatially filtered output from the models demonstrate that P(v) values are highly susceptible to the smoothing inherent in the construction of gridded altimeter products. Therefore, at present it is difficult to say whether the forward temporal cascades seen in some regions in altimeter data represent physics that is missing in the models studied here or merely sampling artifacts., Pub. in Journal of Physical Oceanogprahy, v42 p1577-1600, September 2012.

Geostrophic velocity and vorticity are often estimated by finite difference differentiation of gridded sea surface height fields. Significant differences are obtained in the estimated velocity with the order of the difference operator of stencil width Speed-dependent biases of 10-20% are found for the traditional 3-point centered difference compared to wider, higher-order, stencils Additionally, wider stencils yield estimates of the anisotropy of velocity variance insensitive to the differences in grid spacing between two widely used altimeter products Three-point stencils yield incorrect anisotropies on the 1/4 anisotropic AVISO grid, we recommend the use of 7-point stencils The zonally-averaged, midlatitude eddy kinetic energy field, estimated with wider stencils, is nearly isotropic. Finally, the paper also examines the strengths and limitations of applying noise-suppressing differentiators versus classic centered differences to velocity estimation from altimeter data, Published in Journal of Geophysical Research, v117 p1-18, 2012.

A new mean dynamic topography (MDT) for the Bering Sea is presented. The product is obtained by combining historical oceanographic and atmospheric observations with high-resolution model dynamics in the framework of a variational technique. Eighty percent of the ocean data underlying the MDT were obtained during the last 25 years and include hydrographic profiles, surface drifter trajectories, and in situ velocity observations that were combined with National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) atmospheric climatology. The new MDT quantifies surface geostrophic circulation in the Bering Sea with a formal accuracy of 2 4 cm/s. The corresponding sea surface height (SSH) errors are estimated by inverting the Hessian matrix in the subspace spanned by the leading modes of SSH variability observed from satellites. Comparison with similar products based on in situ observations, satellite gravity, and altimetry shows that the new MDT is in better agreement with independent velocity observations by Argo drifters and moorings. Assimilation of the satellite altimetry data referenced to the new MDT allows better reconstruction of regional circulations in the Bering Sea. Comparisons also indicate that MDT estimates derived from the latest Gravity Recovery and Climate Experiment geoid model have more in common with the presented sea surface topography than with the MDTs based on earlier versions of the geoid. The presented MDT will increase the accuracy of calculations of the satellite altimeter absolute heights and geostrophic surface currents and may also contribute to improving the precision in estimating the geoid in the Bering Sea.

The long-term goal of this research is to develop a physical understanding of the processes that lead to mixing in the ocean with the aim of using this understanding to develop parameterizations of mixing suitable for global and regional models. Of particular focus are the mixing induced by tidal flow over topography and the mixing induced by breaking nonlinear internal waves. The primary scientific objective of this study is to explore internal waves generated by tidal flow through the Luzon Strait in the region close to the sill. A particular scientific focus is nonlinear overturning and breaking within the straits leading to mixing and modification of the wave field. We examine whether transient internal hydraulic jumps are possible in the Luzon Strait, whether these jumps are released to propagate toward the topography as internal bores when the flow relaxes, and whether the bores lead to local mixing. We will explore the details of Luzon Strait topography to identify locations particularly conducive to local overturning processes. The Luzon Strait features two parallel North-South oriented ridges. We will examine how the wave fields of the two ridges interact and affect wave generation and mixing processes. We also will examine the importance of three-dimensional bathymetry in determining the locations of mixing, and the sensitivity of the nonlinear wave response to local stratification near the sill and ambient geostrophic currents. To summarize, our goals are as follows: (1) examine the dependence of nonlinear features and local breaking at the generation site on topographic shape and stratification, (2) evaluate how the interactions between the ridges affect mixing, (3) examine the extent to which the mixing processes are determined by three-dimensional topographic variations, and (4) examine the impact of seasonal variations in stratification and geostrophic currents on the length-scales and amplitude of the internal tides.

A fundamental requirement in realistic ocean simulations and dynamical studies is the optimal estimation of gridded fields from the spatially irregular and multivariate data sets that are collected by varied platforms. In this work, we derive and utilize new schemes for the mapping and dynamical inference of ocean fields in complex multiply-connected domains and study the computational properties of these schemes. Specifically, we extend a multiscale Objective Analysis (OA) approach to complex coastal regions and archipelagos. Bayesian-based OAs using covariances as inputs commonly require an estimate of the distances between data and model points, without going across complex landforms. New OA schemes based on estimating the length of shortest sea paths using the Level Set Method (LSM) and Fast Marching Method (FMM) are thus derived, implemented and utilized in idealized and realistic ocean cases. An FMM-based methodology for the estimation of total velocity under geostrophic balance in complex domains is also presented. Comparisons with other OA approaches are provided, including those using stochastically forced partial differential equations (SPDEs). We find that the FMM-based OA scheme is the most efficient and accurate. We also show that the FMM-based field maps do not require postprocessing (smoothing). Mathematical and computational properties of our new OA schemes are studied in detail using fundamental theorems and illustrations. We find that higher-order FMM's schemes improve accuracy and that a multi-order scheme is efficient. We also provide solutions that ensure the use of positive-definite covariances, even in complex multiply-connected domains., Submitted for publication in Ocean Modelling. Sponsored in part by Office of Naval Research (ONR) grants N00014-07-1-0473 and N00014-08-1-0680.

Seven whale sharks were tracked using satellite-linked tags from Ningaloo Reef, off northern Western Australia, following tagging in April and June 2002 and April–May 2005. We investigated how the movements of those whale shark tracks were influenced by geostrophic surface currents during sequential one-week periods by using a passive diffusion model parameterised with observed starting locations of the sharks and weekly maps of surface current velocity and direction (derived from altimetry). We compared the outputs from the passive diffusion model and maps of chlorophyll-a concentration (SeaWiFs/MODIS) and with the actual tracks of the sharks using GIS and generalized linear mixed-effects models (GLMM). The GLMM indicated very little support for passive diffusion with sea-surface ocean currents influencing whale shark distributions in the north eastern Indian Ocean. Moreover, the sharks' movements correlated only weakly with the spatial distribution of sea-surface chlorophyll-a concentrations. The seven whale sharks had average swimming speeds comparable with those recorded in other satellite tracking studies of this species. Swimming speeds of the seven sharks were similar to those reported in previous studies and up to three times greater than the maximum sea-surface current velocities that the sharks encountered while traversing into lower southerly latitudes (moving northward towards the equator). Our results indicate that whale sharks departing from Ningaloo travel actively and independently of near-surface currents where they spend most of their time despite additional metabolic costs of this behaviour.

A reversal of the mean flow through the Philippines Mindoro Strait occurred in early February 2008. The flow was southward through the strait during late January and northward during most of February. The flow reversal coincided with the period between two intensive observing cruises (IOP08-1 and IOP08-2) sponsored by Office of Naval Research (ONR) as part of the Philippine Straits Experiment (PhilEx). Employing high-resolution models of the ocean and atmosphere along with in situ ocean and air measurements, we detail the regional and local features that influenced this flow reversal. High-resolution air/sea modeling simulations captured the flow reversal and agreed with measured currents from two moorings in the vicinity of Mindoro Strait. A short (24-27 January) easterly monsoon surge and a longer (9-16 February) northerly surge were represented in the model as well as in QuikSCAT and underway wind data taken during IOP08-2. Mesoscale oceanic dipole eddies off Mindoro and Luzon (Pullen et al., 2008) were formed/enhanced and subsequently detached by these wind events. The cyclonic eddy associated with the easterly surge was opportunistically sampled during the IOP08- 1 cruise and the modeled eddy characteristics were verified using in situ shipboard data. The presence of the cyclonic eddy near Mindoro Strait favored a geostrophic flow southward through the strait. This dominant flow was interrupted by a strong and sustained wind-driven (by the northerly surge) flow reversal in early February when the cyclonic eddy was absent. Enhanced upper ocean stratification in winter 2008 due to anomalously high precipitation served to isolate the near-surface circulation in the observations., Published in Oceanography, v24 n1 p28-47, 2010. Sponsored in part by Office of Naval Research (ONR) grant N00014-06-1-0690. Prepared in collaboration with Stevens Institute of Technology, Hoboken, NJ; Columbia University, Palisades, NY; University of California, La Jolla, CA; University of Washington, Seattle, WA; and Computer Science Corporation, Monterey, CA. U.S. Government or Federal Rights License. The original document contains color images.

The Naval Oceanographic Office uses the Navy Coupled Ocean Data Assimilation (NCODA) system to perform data assimilation for ocean modeling. Currently the system uses a 3D multivariate optimum interpolation (3D MVOI) algorithm to produce outputs of temperature, salinity, geopotential, and u/v velocity. NCODA is run in a stand-alone mode to support automated ocean data quality control (NCODA OcnQC) and to test software updates. NCODA is also coupled with the Regional/Global Navy Coastal Ocean Model (RNCOM/GNCOM). The RNCOM/NCODA system is being used as part of an Adaptive Sampling and Prediction (ASAP) pre-operational project that makes use of the Ensemble Transform (ET) and Ensemble Transform Kalman Filter (ET KF) applied to ensemble runs of the RNCOM. The ET KF is used to predict the posterior error covariances resulting from possible profile measurements. These results aid in predicting the impact of ocean observations on the future analysis, and thus allow the direction of limited assets to areas that will have the maximum gain (for applications such as ocean acoustics). A review of these systems will be given as well as examples of the metrics used for the RNCOM/NCODA system, ensemble modeling, and ASAP., See also ADM202806. Proceedings of the Oceans 2009 MTS/IEEE Conference held in Biloxi, Mississippi on 26-29 October 2009. Copyright belongs to the Marine Technology Society. The original document contains color images.

Salt advection in the top 5 m layer of the monsoon-influenced Indian Ocean has been studied with high resolution HYbrid Coordinate Ocean Model (HYCOM) simulated sea surface salinity (SSS) during 2003-06. The effect of monsoon reversals and roles of Ekman drift and geostrophic currents are emphasized. The Ekman drift component is found to be more important than the geostrophic component in exchange of salt in the basins; an indication of the influence of winds and the associated surface currents. The strongest differences in the salt advection terms occurred in the Bay of Bengal (BoB), an indication of the significant role of advection for the distribution of freshwater and the Ekman processes. The Inter-Tropical Convergence Zone (ITCZ) is seen to influence advection patterns via Ekman drift along the equatorial region. This results in the creation of two salt advection bands whose positions vary seasonally. This study will help to interpret data from the recently launched Soil Moisture Ocean Salinity (SMOS) and future Aquarius salinity missions for the Indian Ocean., Work unit no. 73-5732-10-5 Published in Geophysical Research Letters, v37 p1-6, 2010. Supported in part by NASA project NNX08AO33G.

Ocean bottom boundary layers are regions adjacent to topography where turbulence mixes heat, momentum and biogeochemical tracers. These regions serve as a dynamical control on the circulation by dissipating energy and shape the local characteristics of the marine environment by redistributing tracers. Tracers, such as sediment and nutrients, are transported by the lateral circulation near the bottom as well as the vertical circulation into and out of these layers. In order to quantify these momentum and tracer fluxes, an understanding of the strength and structure of this circulation is needed. Friction plays an important role in driving this lateral and vertical circulation. The boundary exerts a frictional stress on the flow that reduces the near bottom velocity within a frictional boundary layer, the Ekman layer. This frictional force induces an ageostrophic Ekman flow down the pressure gradient through a subinertial balance between the frictional force, the Coriolis acceleration, and the horizontal pressure gradient. The vertically-integrated Ekman flow, the Ekman transport, is directed to the right (left) of the frictional force in the Northern (Southern) Hemisphere. Convergences and divergences in the Ekman transport eject fluid out of, Ekman pumping, or inject fluid into, Ekman suction, the boundary layer. This process drives an ageostrophic secondary circulation that can accelerate or decelerate the geostrophic flow in the interior.

The annual mean heat budget of the upper ocean beneath the stratocumulus/stratus cloud deck in the southeast Pacific is estimated using Simple Ocean Data Assimilation (SODA) and an eddy-resolving Hybrid Coordinate Ocean Model (HYCOM). Both are compared with estimates based on Woods Hole Oceanographic Institution (WHOI) Improved Meteorological (IMET) buoy observations at 208S, 858W. Net surface heat fluxes are positive (warming) over most of the area under the stratus cloud deck. Upper-ocean processes responsible for balancing the surface heat flux are examined by estimating each term in the heat equation. In contrast to surface heat fluxes, geostrophic transport in the upper 50 meters causes net cooling in most of the stratus cloud deck region. Ekman transport provides net warming north of the IMET site and net cooling south of the IMET site. Although the eddy heat flux divergence term can be comparable to other terms at a particular location, such as the IMET mooring site, it is negligible for the entire stratus region when area averaged because it is not spatially coherent in the open ocean. Although cold-core eddies are often generated near the coast in the eddy-resolving model, they do not significantly impact the heat budget in the open ocean in the southeast Pacific., Published in the Journal of Physical Oceanography, v40 p103-120, January 2010. Sponsored in part by the National Oceanic and Atmospheric Administration (NOAA) under Grant NA06AR4310146; and National Science Foundation (NSF) Grants NSF-ATM-0745872 and NSF-OCE-0351802.

The annual mean heat budget of the upper ocean beneath the stratocumulus/stratus cloud deck in the southeast Pacific is estimated using Simple Ocean Data Assimilation (SODA) and an eddy-resolving Hybrid Coordinate Ocean Model (HYCOM). Both are compared with estimates based on Woods Hole Oceanographic Institution (WHOI) Improved Meteorological (IMET) buoy observations at 20 deg S, 85 deg W. Net surface heat fluxes are positive (warming) over most of the area under the stratus cloud deck. Upper-ocean processes responsible for balancing the surface heat flux are examined by estimating each term in the heat equation. In contrast to surface heat fluxes, geostrophic transport in the upper 50 m causes net cooling in most of the stratus cloud deck region. Ekman transport provides net warming north of the IMET site and net cooling south of the IMET site. Although the eddy heat flux divergence term can be comparable to other terms at a particular location, such as the IMET mooring site, it is negligible for the entire stratus region when area averaged because it is not spatially coherent in the open ocean. Although cold-core eddies are often generated near the coast in the eddy-resolving model, they do not significantly impact the heat budget in the open ocean in the southeast Pacific., The original document contains color images. All DTIC reproductions will be in black and white. Pub. in Journal of Physical Oceanography, v40 p103-120, January 2010. Supported in part by National Science of Foundation.

CONCLUSIONS: Geostrophic transport in the upper 50m causes net cooling in most of the stratus cloud region. Ekman transport provides net warming north of the IMET site and net cooling south of the IMET site. The eddy heat flux divergence term can be comparable to other terms at a particular location such as the IMET site, but it is negligible for the entire stratus region when area averaged since it is not spatially coherent in the open ocean. Surface buoy observations in locations both north and south of the IMET site would be useful., Presented at the Layered Ocean Model Workshop (LOM 2009), Miami, FL. Prepared in cooperation with University of Colorado; NOAA-ESRL/PSD; Ohio State University; and Texas A&M University. Document includes briefing charts only. The original document contains color images.

A version of the reduced control space four-dimensional variational method (R4DVAR) of data assimilation into numerical models is proposed. In contrast to the conventional 4DVAR schemes, the method does not require development of the tangent linear and adjoint codes for implementation. The proposed R4DVAR technique is based on minimization of the cost function in a sequence of low-dimensional subspaces of the control space. Performance of the method is demonstrated in a series of twin-data assimilation experiments into a nonlinear quasigeostrophic model utilized as a strong constraint. When the adjoint code is stable, R4DVAR's convergence rate is comparable to that of the standard 4DVAR algorithm. In the presence of strong instabilities in the direct model, R4DVAR works better than 4DVAR whose performance is deteriorated because of the breakdown of the tangent linear approximation. Comparison of the 4DVAR and R4DVAR also shows that R4DVAR becomes advantageous when observations are sparse and noisy., Performed in collaboration with University of New Orleans, New Orleans, LA: University of Southern Mississippi, Stennis Space Center, MS; and University of Alaska, Fairbanks, AK. Published in Monthly Weather Review, v137 p2966-2978, 2009.

The long-term goals of this research are to gain an understanding of the dynamical processes that govern small-scale lateral dispersion in the ocean on scales of 10m-10km, and to use this knowledge to develop and implement parameterizations for regional-scale ocean models. This project represents one of several numerical modeling efforts by ONR that is focused on submesoscale lateral dispersion. The primary objective of the project is to understand the impact of small-scale vortices produced by geostrophic adjustment following wave breaking events. Several aspects of this problem are being considered, including the influence of larger scale vortices on the submesoscale vortices, the role of mean shears, and of near-inertial waves. Process numerical simulations in idealized deep ocean environments (away from boundaries or topography) are performed with a three-dimensional pseudo-spectral code. The model is run at high resolutions on parallel platforms including a Linux cluster and DoD supercomputers. Funding for this project only became available in mid-June. Consequently, the work discussed in this report is very much work in progress. Focus has been on understanding the characteristics of turbulent fields produced by ensembles of wave breaking events. In particular, we would like to understand if and how this type of turbulence differs from turbulence that is generated by different mechanisms. The goal is to obtain quantitative estimates of spectral fluxes that can be compared to the spectral fluxes that result from other submesoscale energy sources such as frontal and geostrophic instabilities. The spectral energy fluxes that we obtain will ultimately be compared to the fluxes estimated by the other participants in the Lateral Mixing DRI and will help us assess the relative contribution of adjustment-driven turbulence to lateral mixing rates on scales of 0.1-10km in the ocean.

The long term goal of the "Scalable Lateral Mixing and Coherent Turbulence" DRI, under which the PIs are funded, is to understand the processes that stir and mix tracers in the ocean on lateral scales of 100 kilometers to 10 meters, the so-called submesoscales. The specific long term goals of the PIs are to understand the influence of mesoscale strain in driving stirring and mixing at the submesoscale, and to develop a robust theoretical framework through which to interpret the observations. The objective of the DRI group is to devise and execute field experiments, supported by numerical simulations, that will distinguish between potential mechanisms of submesoscale stirring and mixing. The many interacting processes occurring at the submesoscales present a serious challenge to this effort. In order to focus the team work, potential mechanisms were distilled into three core hypotheses: (H1) Isopycnal mixing at scales of 10 m -10 km in the stratified ocean is the result of stirring by coherent vortices generated by mixing events associated with gravity wave breaking (the so-called vortical modes); (H2) Isopycnal mixing at the submesoscale is effected by motions resulting from a cascade of tracer and potential vorticity (PV) variance from the deformation scale (where baroclinic instability generates mesoscale eddies) to smaller scales; (H3) Both diapycnal and isopycnal mixing in the upper ocean are enhanced by ageostrophic instabilities along lateral density fronts generated at the submesoscale., Performed in cooperation with New York University, New York, NY.

Observations and inverse models suggest that small-scale turbulent mixing is enhanced in the Southern Ocean in regions above rough topography. The enhancement extends 1 km above the topography suggesting that mixing is supported by breaking of gravity waves radiated from the ocean bottom. In other regions, gravity wave radiation by bottom topography has been primarily associated with the barotropic tide. In this study, we explore the alternative hypothesis that the enhanced mixing in the Southern Ocean is sustained by internal waves generated by geostrophic motions flowing over bottom topography. Weakly-nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow. A major finding is that the waves generated at the ocean bottom at finite inverse Froude numbers drive vigorous inertial oscillations. The wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations and differs substantially from the classical lee wave problem. The theoretical predictions are tested versus two-dimensional and three-dimensional high resolution numerical simulations with parameters representative of the Drake Passage region. Theory and fully nonlinear numerical simulations are used to estimate internal wave radiation from LADCP, CTD and topography data from two regions in the Southern Ocean: Drake Passage and the Southeast Pacific. The results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation measured in the region., The original document contains color images.

The main components of large-scale circulation of the eastern tropical Pacific were identified in the mid 20th century, but the details of the circulation at length scales of 102 km or less, the mesoscale field, are less well known particularly during summer. The winter circulation is characterized by large mesoscale eddies generated by intense cross-shore wind pulses. These eddies propagate offshore to provide an important source of mesoscale variability for the eastern tropical Pacific. The summer circulation has not commanded similar attention, the main reason being that the frequent generation of hurricanes in the area renders in situ observations difficult. Before the experiment presented here, the large-scale summer circulation of the Gulf of Tehuantepec was thought to be dominated by a poleward flow along the coast. A drifter-deployment experiment carried out in June 2000, supported by satellite altimetry and wind data, was designed to characterize this hypothesized Costa Rica Coastal Current. We present a detailed comparison between altimetry-estimated geostrophic and in situ currents estimated from drifters. Contrary to expectation, no evidence of a coherent poleward coastal flow across the gulf was found. During the 10-week period of observations, we documented a recurrent pattern of circulation within 500 km of shore, forced by a combination of local winds and the regional-scale flow. Instead of the Costa Rica Coastal Current, we found a summer eddy field capable of influencing large areas of the eastern tropical Pacific. Even in summer, the cross-isthmus wind jet is capable of inducing eddy formation.

Using brightness temperature Tb measurements from L-band airborne microwave radiometers, with independent sea surface temperature (SST) observations, sea surface salinity (SSS) can be remotely determined with errors of about 1 psu in temperate regions. Nonlinearities in the relationship between $Tb$, SSS, and SST produce variations in the sensitivity of salinity S to variations in Tb and SST. Despite significant efforts devoted to SSS remote sensing retrieval algorithms, little consideration has been given to deriving density D from remotely sensed SSS and SST. Density is related to S and T through the equation of state. It affects the ocean's static stability and its dynamical response to forcings. By chaining together two empirical relationships (flat-sea emissivity and equation of state) to form an inversion algorithm for sea surface density (SSD) in terms of Tb and SST, we develop a simple L-band SSD retrieval algorithm. We use this to investigate the sensitivity of SSD retrievals to observed $Tb$ and SST and infer errors in D for typical sampling configurations of the airborne Salinity, Temperature, And Roughness Remote Scanner (STARRS) and satellite-borne Soil Moisture and Ocean Salinity (SMOS) and Aquarius radiometers. We then derive D from observations of river plumes obtained using STARRS and demonstrate several oceanographic applications: the observations are used to study variations in T and S effects on D in the Mississippi plume, and the across-shelf density gradient is used to infer surface geostrophic shear and subsurface geostrophic current in the Plata plume. Future basin-scale applications of SSD retrievals from satellite-borne microwave radiometers such as SMOS and Aquarius are anticipated., The original document contains color images. All DTIC reproductions will be in black and white.

Using brightness temperature Tb measurements from L-band airborne microwave radiometers, with independent sea surface temperature (SST) observations, sea surface salinity (SSS) can be remotely determined with errors of about 1 psu in temperate regions Nonlinearities in the relationship between Tb, SSS and SST produce variations in the sensitivity of salinity S to variations in Tb and SST. Despite significant efforts devoted to SSS remote sensing retrieval algorithms, little consideration has been given to deriving density D from remotely sensed SSS and SST. Density is related to S and T through the equation of state. It affects the ocean's static stability and its dynamical response to forcings. By chaining together two empirical relationships (flat-sea emissivity and equation of state) to form an inversion algorithm for sea surface density (SSD) in terms of Tb and SST, we develop a simple L-band SSD retrieval algorithm. We use this to investigate the sensitivity of SSD retrievals to observed Tb and SST and infer errors in D for typical sampling configurations of the airborne Salinity, Temperature, And Roughness Remote Scanner (STARRS) and satellite-borne Soil Moisture and Ocean Salinity (SMOS) and Aquarius radiometers. We then derive D from observations of river plumes obtained using STARRS and demonstrate several oceanographic applications: the observations are used to study variations in T and S effects on D in the Mississippi plume, and the across-shelf density gradient is used to infer surface geostrophic shear and subsurface geostrophic current in the Plata plume. Future basin-scale applications of SSD retrievals from satellite-borne microwave radiometers such as SMOS and Aquarius are anticipated., The original document contains color images. All DTIC reproductions will be in black and white. Pub. in Jnl. of IEEE Transactions on Geoscience and Remote Sensing, v46 n3 p765-785, March 2008.

A field data collection program in Boston Harbor, MA, was conducted for the U.S. Army Engineer District, New England, during the late fall and winter of 2004/2005. The purpose of the program was to obtain data needed to validate a numerical hydrodynamic model (ADvanced CIRCulation (ADCIRC) model) of Boston Harbor and adjacent areas. The currents calculated by the verified model were input to a ship simulator used to assess the design of the Boston Harbor navigation improvement project. A total of four water-level recorders and two acoustic profiling current meters were deployed on 10 November 2004. The water-level recorders were located adjacent to a bridge between Chelsea and East Boston in Boston s inner harbor, at the seaward end of Boston North Channel, at Gallops Island, and at the Hull Yacht Club in Allerton Harbor. The current meters were located at the seaward end of Boston North Channel and near the location where Boston's main navigation channel enters the inner harbor. Data from these instruments were supplemented by tide data from a National Oceanic and Atmospheric Administration (NOAA) tide gage in the inner harbor, and NOAA wind measurements at Logan Airport. In addition, daylight current transect surveys using a downward looking acoustic profiling current meter attached to a survey vessel were conducted on 11 November 2004 and 8 February 2005. Five transect survey lines across the main navigation channel were surveyed. All instrumentation was recovered on 7 and 8 February 2005. Maximum-measured ebb tidal currents in the harbor were 0.9 to 3.84 ft/sec. Maximum-measured flood currents were 0.77 to 3.61 ft/sec. In general, the ebb currents were stronger than the flood currents. The data from the current meter deployed at the seaward end of Boston North Channel were analyzed to evaluate the importance of the winddriven and tide-induced residual currents., The original document contains color images.

This study investigates synoptic scale regimes in the forcing of 25 knot winds at Hickam and Andersen AFB. Ten years of data from January 1996 through December 2005, as well as case studies from June, July and August of 2006 were considered for this study. Days were grouped together to isolate the events of trade wind flow only and to alleviate days where trade wind flow was interrupted by synoptic scale weather events or local weather phenomena. Of the approximately 3,650 days of observations, Hickam AFB had 258 days in which the winds gusted to or above 25 knots and 1,077 days in which the winds remained between 15 and 24 knots. Similarly, Andersen AFB had 99 days where the winds gusted to or above 25 knots and 448 days where the winds remained between 15 and 25 knots. These days were then combined in their respective lists and were compiled to create composite sea level pressure surface analyses, winds, temperature, dew point, and geopotential height for each list of days. Upon examination of the compiled charts, identifiable climatological regimes became evident for days in which the winds gust to or above 25 knots and when the winds remained between 15 and 24 knots. The climatological average for Hickam AFB for winds gusting to or above 25 knots consisted of the subtropical high located 894 miles almost due north of Hawaii and the strength of the high at 1024 mb. The subsequent gradient across Hawaii produced an average geostrophic flow of 15 m s-1 across. North to South cross sections of potential temperature and winds across Hawaii indicated low static stability and analyzed winds of 7-9 m s-1. The climatological average when the winds remained between 15 and 24 knots consisted of the subtropical high located much further east and with a strength of 1022 mb. This reduced the gradient across Hawaii and produced an average geostrophic flow of 11 m s-1. North to South cross sections indicated stronger static stability and analyzed winds of 5-7 m s-1.

Presented at at the HYCOM NOPP GODAE Meeting held in Miami, FL on 6-8 Dec 2005.

Advanced DA Technique Based on Optimal Estimation Theory. Oceanographic version of MVOI method used in NWP systems Lorenc (1981), Daley (1991). Simultaneous analysis of five ocean variables: temperature, salinity, geopotential, and u-v velocity components (T, S, phi, u, v). Developed as part of the ONR sponsored coupled modeling projects at NRL MRY (COAMPS/NCOM and NOGAPS/POP) Flexible System. Supports variety of map projections. Performs multi-scale analyses on nested, successively higher resolution grids. Initialize/update ocean forecast model or run stand-alone. 2D analyses of sea ice and SST (NWP boundary conditions). 3D temperature and salinity analysis (geostrophic currents). 3D MVOI sequential incremental update cycle., Presented at the HYCOM NOPP GODAE Meeting RSMAS, October 2004.

Absolute geostrophic velocities were calculated along TOPEX/Poseidon (T/P) ground tracks located in the Ulleung Basin of the southwestern Japan/East Sea (JES) from a combined analysis of nearly a decade of T/P data and two years of pressure-gauge-equipped inverted echo sounder (PIES) data obtained during the United States Office of Naval Research's JES Program. Geostrophic velocities were calculated daily for the Ulleung Basin from June 1999 to July 2001 from a three-dimensional mapping of temperature and salinity produced by PIES data interpreted via the Gravest Empirical Mode (GEM) technique combined with the Navy's Modular Ocean Data Assimilation System (MODAS). These velocities were then used to convert T/P velocity anomalies to absolute velocities for the T/P time period of 1993 to 2002. Current intensities and variabilities associated with the East Korean Warm Current, Ulleung Warm Eddy, and Offshore Branch were examined. Results showed that spatial and temporal variations of the sea surface circulation are strong; intensification of the currents generally occurred during the fall season; and the flow pattern in individual years differed greatly from year to year, and differed from climatology in important qualitative ways., Published in the Journal of Oceanography, v60, p1023-1033, 2004. Sponsored through program number VSF-73-7507-03-5.

Advanced DA Technique Based on Optimal Estimation Theory. Oceanographic version of MVOI method used in NWP systems Lorenc (1981), Daley (1991). Simultaneous analysis of five ocean variables: temperature, salinity, geopotential, and u-v velocity components (T, S, omega, u, v). Developed as part of the coupled modeling projects at NRL MRY (COAMPS and NOGAPS/POP) Flexible System. Supports variety of map projections performs multi-scale analyses on nested, successively higher resolution grids. Initialize/update ocean forecast model or run stand-alone. 2D analyses of sea ice and SST (NWP boundary conditions), 3D temperature and salinity analysis (geostrophic currents), 3D MVOI sequential incremental update cycle., Presented at the HYCOM Ocean Model Workshop NCEP August 2003. Contains briefing charts only.

Weekly upwelling was estimated at 25 sites off the North and South American west coasts from August 1999 to December 2001 using geostrophically derived winds, model-derived winds from the U.S. Navy's global atmospheric (NOGAPS) model, and QuikSCAT satellite-measure winds. Satellite-measured winds, verified with 15 U.S. west coast buoys, were within 1.3 m s-1 and 26 RMS. Upwelling estimates derived from geostrophic winds using the Pacific Fisheries Environmental Laboratory (PFEL) technique were compared to those derived from both satellite-measured winds and model- derived winds. Upwelling estimates from model-derived winds agreed with satellite-based estimates at all 14 North American sites and 9 of 11 South American sites. Estimates from geostrophic winds agreed with satellite-based estimates at 12 of 14 North American sites and 7 of 11 South American sites. These comparisons showed that upwelling estimates based on the Navy's global model winds were accurate in more regions than those based on geostrophic winds. A fine-scale upwelling investigation using the Navy's high-resolution atmospheric model (COAMPS) revealed narrow near-shore bands of strong wind-stress and wind-stress-curl missed in the above upwelling estimates. Improvements in the depiction of coastal upwelling will require wind data and upwelling estimates with at least a 10 km resolution., The original document contains color images.

In this study, we used the Navy's Generalized Digital Environmental Model (GDEM) climatological temperature and salinity data on a 0.5 deg x 0.5 deg grid to investigate the seasonal variabilities of the southwest Philippines Sea (0.5 deg - 9 deg N, 123.5 deg - 136.5 deg) thermohaline structure and circulation. The GDEM for the area was built up on historical (1930 - 1997) temperature and salinity profiles. A three dimensional estimate of the absolute geostrophic velocity field on isopycnal surface was obtained from the GDEM temperature and salinity fields using the P-vector method. The seasonal variabilities of the thermohaline structure and currents (obtained from the inverse method) such as the Mindanao Current, Mindanao Undercurrent, North Equatorial Counter Current, New Guinea Coastal Undercurrent, and dual-eddies (cyclonic Mindanao Eddy and anticyclonic Halmahera Eddy) are identified., Pub. in Chinese Jnl. of Oceanology and Limnology, v21 n3 p193-213, 2003.

A characteristic property of geostrophic turbulence is that energy undergoes an inverse cascade to large spatial scales, whereas potential enstrophy cascades directly to small spatial scales. In the presence of weak dissipation, such as in the ocean, energy is therefore quasi-conserved whereas potential enstrophy is always dissipated. As a consequence geostrophic eddies only partially mix potential vorticity along isopycnals, with the amount of mixing being dependent on the energy available in the initial state. To illustrate these ideas, two oceanographic applications are considered: the generation of abyssal recirculations around topographic features and the formation of inertial zonal jets. A new eddy parameterization is developed that dissipates potential enstrophy subject to the constraint of conserving energy. Results obtained using the parameterization are compared with those from an eddy-resolving calculation. Possible extensions of these ideas are discussed, including the possibility of incorporating additional constraints such as conservation of angular momentum., Original contains color plates: All DTIC reproductions will be in black and white. Presented at the 'Aha Huliko'a Hawaiian Winter Workshop (12th) held in Honolulu, HI on 16-19 Jan 2001, p9-15. This article is from ADA412459 From Stirring to Mixing in a Stratified Ocean. Proceedings Hawaiian Winter Workshop (12th) Held in the University of Hawaii at Manoa on January 16-19, 2001

The development of the Global Ocean Data Assimilation Experiment (GODAE), its relationship to the Array for Real-time Geostrophic Oceanography (ARGO) project, and Fleet Numerical Meteorology and Oceanography Center's role in GODAE are discussed in this thesis. The drifting buoys used for data collection are described and the data available is outlined. This thesis analyses GODAE data available from the North Atlantic Ocean, collected in near-real-time from September 1, 2000 through March 8, 2001, in order to evaluate the relative success of the experiment to date and to identify the scope of possibilities for utilizing this data both at present, and once GODAE and ARGO are fully operational. The GODAE project endeavors to be a single database, serving as a collection point for worldwide oceanographic data to be utilized in ocean climate prediction. GODAE does not offer a mechanism for visualization of the data available. This thesis analyzes the data presently available through graphic representation. Visualization products include: float trajectories, temperature (T) and salinity (S) profiles, T-S diagrams, mixed layer depths and observed temperature compared to temperature climatology., Original contains color plates: All DTIC reproductions will be in black and white.

The Global Ocean Data Assimilation Experiment (GODAE) is an endeavor that will likely change the path of oceanography for many years. This attempt to assimilate, organize and provide massive quantities of widely varied oceanographic and meteorological data to the world could be a catalyst for new and innovative research opportunities. One of the data sources important to GODAE and of great possible value, the Array for Real-time Geostrophic Oceanography (ARGO), is another innovation that may lead to significant improvements in oceanographic modeling and research. The concept of thousands of autonomous floats, reporting ocean conditions to a database that can assimilate and provide this data in real or near-real time, affords countless opportunities for new methods of ocean prediction. The true test of GODAE is to assess the utility of the data available in a real world setting, and ascertain the relative usefulness as it relates to research opportunities and operational data needs. This thesis will assess the utility of the USGODAE data server by retrieving, processing, visualizing and employing the data to observe conditions in and near the Kuroshio Current. By attempting to use the data server in a method similar to future research and operational use, an understanding of its true potential may be reached., Original contains color plates: All DTIC reproductions will be in black and white.