On C-Band Quad-Polarized Synthetic Aperture Radar Properties of Ocean Surface Currents

Type Article
Date 2019-10
Language English
Author(s) Fan Shengren1, Kudryavtsev Vladimir2, 3, Zhang Biao1, 4, Perrie William5, Chapron Bertrand2, 6, Mouche AlexisORCID6
Affiliation(s) 1 : School of Marine Sciences, Nanjing University of Information Science & Technology, Nanjing 210044, China
2 : Russian State Hydrometerorological University, St. Petersburg 195196, Russia
3 : Marine Hydrophysical Institute, Sebastopol 299011, Russia
4 : Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, China
5 : Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS B2Y 4A2, Canada
6 : Laboratoire d’Océanographie Physique Spatiale, Ifremer, Brest 29200, France
Source Remote Sensing (2072-4292) (MDPI AG), 2019-10 , Vol. 11 , N. 19 , P. 2321 (17p.)
DOI 10.3390/rs11192321
WOS© Times Cited 1
Note This article belongs to the Special Issue Synthetic Aperture Radar Observations of Marine Coastal Environments
Keyword(s) quad-polarized SAR, ocean surface current, polarization decomposition, Bragg scattering, breaking waves
Abstract

We present new results for ocean surface current signatures in dual co- and cross-polarized synthetic aperture radar (SAR) images. C-band RADARSAT-2 quad-polarized SAR ocean scenes are decomposed into resonant Bragg scattering from regular (non-breaking) surface waves and scattering from breaking waves. Surface current signatures in dual co- and cross-polarized SAR images are confirmed to be governed by the modulations due to wave breaking. Due to their small relaxation scale, short Bragg waves are almost insensitive to surface currents. Remarkably, the contrast in sensitivity of the non-polarized contribution to dual co-polarized signals is found to largely exceed, by a factor of about 3, the contrast in sensitivity of the corresponding cross-polarized signals. A possible reason for this result is the co- and cross-polarized distinct scattering mechanisms from breaking waves: for the former, quasi-specular radar returns are dominant, whereas for the latter, quasi-resonant scattering from the rough breaking crests governs the backscatter intensity. Thus, the differing sensitivity can be related to distinct spectral intervals of breaking waves contributing to co- and cross-polarized scattering in the presence of surface currents. Accordingly, routinely observed current signatures in quad-polarized SAR images essentially originate from wave breaking modulations, and polarized contrasts can therefore help quantitatively retrieve the strength of surface current gradients

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