Co-Polarized SAR Imaging of Ocean Current Features
Kudryavtsev, Vladimir1; Chapron, Bertrand2; Kozlov, Igor1; Collard, Fabrice2; Johannessen, Johnny3
1SOLab, RSHU, RUSSIAN FEDERATION; 2IFREMER, FRANCE; 3NERSC, NORWAY
An approach recently suggested by Kudryavtsev et al. (2013) for analysis of co-polarized (VV and HH) SAR images is extensively employed to interpret imaging mechanisms of surface current features. Following this approach, co-pol SAR images are simply transformed into two other images, one whose intensity is dominated by polarized resonant scattering (PD) and the second whose intensity is dominated by non-polarized returns from breaking waves (NP). A number of quad-pol Radarsat-2 SAR images acquired over the White Sea in July 2012 and supported by in situ ship measurements are presented and analyzed. These SAR images exhibit signatures of numerous upper ocean phenomena (internal waves, meso-scale current features and temperature fronts), as well as near surface wind field peculiarities. Distinctly different quantitative manifestations are derived in PD and NP images being strongly dependent on radar-look-direction relative to the wind direction, wind speed, and scale of the ocean features. Generally, the current features are well detected in NP-images and almost invisible in PD images suggesting that the modulation of wave breaking plays the dominant role in the formation of surface signatures, while impact of Bragg waves modulations is negligibly small. The Radar Imaging Model is invoked to support the interpretation of these observations.
Core support of this research was provided by Russian Government via Mega-Grant No. 11.G34.31.0078.