The Experts below are selected from a list of 67275 Experts worldwide ranked by ideXlab platform
Erwan Hascoet - One of the best experts on this subject based on the ideXlab platform.
-
Diagnosis of high-resolution upper Ocean Dynamics from noisy sea surface temperatures
Journal of Geophysical Research: Oceans, 2014Co-Authors: J. Isern-fontanet, Erwan HascoetAbstract:[1] The noise present in infrared satellite measurements of sea surface temperature (SST) hampers the use of surface quasi-geostrophic (SQG) equations to diagnose Ocean Dynamics at high resolutions. Here we propose a methodology to reduce the contribution of noise when diagnosing surface vorticity, divergence, and vertical velocity from SST able to retain the Dynamics at scales of a few kilometers. It is based on the use of denoising techniques with curvelets as basis functions and the application of a selective low-pass filters to improve the reconstruction of surface upwelling/downwelling patterns. First, it is tested using direct numerical simulations of SQG turbulence and then applied to diagnose low-frequency vertical velocity patterns from real MODIS (Moderate Resolution Imaging Spectroradiometer) images. The methodology here presented, which is not tied to the validity of SQG equations nor to the use of SST, is quite general and can be applied to a wide range of measurements and dynamical frameworks.
Menghua Wang - One of the best experts on this subject based on the ideXlab platform.
-
Ocean Dynamics Observed by VIIRS Day/Night Band Satellite Observations
Remote Sensing, 2018Co-Authors: Wei Shi, Menghua WangAbstract:Three cases of Day/Night Band (DNB) observations of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) are explored for applications to assess the Ocean environment and monitor Ocean Dynamics. An approach to use the ratio between the target radiance and the reference radiance was developed in order to better assess the Ocean diurnal and short-term environmental changes with VIIRS DNB observations. In the La Plata River Estuary, the sediment fronts showed 20–25 km diurnal inshore-offshore movements on 13 March 2017. In the waters off the coast of Argentina in the South Atlantic, VIIRS DNB measurements provided both daytime and nighttime observations and monitoring of the algal bloom development and migration between 24 and 26 March 2016. This algal bloom generally kept the same spatial patterns, but moved nearly 20 km eastward in the three-day period. In the Yangtze River Estuary and Hangzhou Bay region along China’s east coast, VIIRS DNB observations also revealed complicated coastal dynamic changes between 12 and 14 April 2017. Even though there are still some challenges and limitations for monitoring the Ocean environment with VIIRS DNB observations, this study shows that satellite DNB observations can provide additional data sources for Ocean observations, especially observations during the nighttime.
-
Ocean Dynamics Observed by the VIIRS Day-Night Band Measurements
2017Co-Authors: Wei Shi, Menghua WangAbstract:Three cases of Day-Night Band (DNB) observations of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) are explored for applications to assess the Ocean environment and monitor Ocean Dynamics. An approach to use the DNB radiance ratio was developed in order to better continuously assess the Ocean diurnal and short-term environmental changes with VIIRS DNB observations. In the La Plata River Estuary, the sediment fronts showed 20–25 km diurnal inshore-offshore movements on March 13, 2017. In the waters off the Argentina coast in the South Atlantic, VIIRS DNB measurements provided continuous observations and monitoring of the algae bloom development and migration between 24–26 March 2016. This algae bloom generally kept the same spatial patterns, but moved nearly 20 km eastward in the three-day period. In the Yangtze River Estuary and Hangzhou Bay region in China’s east coast, VIIRS DNB observations also revealed the complicated coastal dynamic changes between 12–14 April 2017. Even though there are still some challenges and limitations for monitoring the Ocean environment with VIIRS DNB observations, this study shows that satellite DNB observations can provide additional data sources for Ocean observations, especially observations during the nighttime.
Denise Fernandez - One of the best experts on this subject based on the ideXlab platform.
-
Interannual Variability of Sea Surface Temperature in the Southwest Pacific and the Role of Ocean Dynamics
Journal of Climate, 2017Co-Authors: Melissa Bowen, Jordan Markham, Philip Sutton, Xuebin Zhang, Nick T. Shears, Denise FernandezAbstract:AbstractThis paper investigates the mechanisms causing interannual variability of upper Ocean heat content and sea surface temperature (SST) in the southwest Pacific. Using the ECCOv4 Ocean reanalysis it is shown that air–sea heat flux and Ocean heat transport convergence due to Ocean Dynamics both contribute to the variability of upper Ocean temperatures around New Zealand. The Ocean Dynamics responsible for the Ocean heat transport convergence are investigated. It is shown that SSTs are significantly correlated with the arrival of barotropic Rossby waves estimated from the South Pacific wind stress over the latitudes of New Zealand. Both Argo observations and the ECCOv4 reanalysis show deep isotherms fluctuate coherently around the country. The authors suggest that the depth of the thermocline around New Zealand adjusts to changes in the South Pacific winds, modifies the vertical advection of heat into the upper Ocean, and contributes to the interannual variability of SST in the region.
Vladimir Kudryavtsev - One of the best experts on this subject based on the ideXlab platform.
-
imaging mesoscale upper Ocean Dynamics using synthetic aperture radar and optical data
Journal of Geophysical Research, 2012Co-Authors: Vladimir Kudryavtsev, Alexander Myasoedov, Bertrand Chapron, J A Johannessen, Fabrice CollardAbstract:A synergetic approach for quantitative analysis of high-resolution Ocean synthetic aperture radar (SAR) and imaging spectrometer data, including the infrared (IR) channels, is suggested. This approach first clearly demonstrates that sea surface roughness anomalies derived from Sun glitter imagery compare very well to SAR roughness anomalies. As further revealed using these fine-resolution (similar to 1 km) observations, the derived roughness anomaly fields are spatially correlated with sharp gradients of the sea surface temperature (SST) field. To quantitatively interpret SAR and optical (in visible and IR ranges) images, equations are derived to relate the surface roughness signatures to the upper Ocean flow characteristics. As developed, a direct link between surface observations and divergence of the sea surface current field is anticipated. From these satellite observations, intense cross-frontal Dynamics and vertical motions are then found to occur near sharp horizontal gradients of the SST field. As a plausible mechanism, it is suggested that interactions of the wind-driven upper layer with the quasi-geostrophic current field (via Ekman advective and mixing mechanisms) result in the generation of secondary ageostrophic circulation, producing convergence and divergence of the surface currents. The proposed synergetic approach combining SST, Sun glitter brightness, and radar backscatter anomalies, possibly augmented by other satellite data (e.g., altimetry, scatterometry, Ocean color), can thus provide consistent and quantitative determination of the location and intensity of the surface current convergence/divergence (upwelling/downwelling). This, in turn, establishes an important step toward advances in the quantitative interpretation of the upper Ocean Dynamics from their two-dimensional satellite surface expressions.
J. Isern-fontanet - One of the best experts on this subject based on the ideXlab platform.
-
Diagnosis of high-resolution upper Ocean Dynamics from noisy sea surface temperatures
Journal of Geophysical Research: Oceans, 2014Co-Authors: J. Isern-fontanet, Erwan HascoetAbstract:[1] The noise present in infrared satellite measurements of sea surface temperature (SST) hampers the use of surface quasi-geostrophic (SQG) equations to diagnose Ocean Dynamics at high resolutions. Here we propose a methodology to reduce the contribution of noise when diagnosing surface vorticity, divergence, and vertical velocity from SST able to retain the Dynamics at scales of a few kilometers. It is based on the use of denoising techniques with curvelets as basis functions and the application of a selective low-pass filters to improve the reconstruction of surface upwelling/downwelling patterns. First, it is tested using direct numerical simulations of SQG turbulence and then applied to diagnose low-frequency vertical velocity patterns from real MODIS (Moderate Resolution Imaging Spectroradiometer) images. The methodology here presented, which is not tied to the validity of SQG equations nor to the use of SST, is quite general and can be applied to a wide range of measurements and dynamical frameworks.