Ka-Band Dual Copolarized Empirical Model for the Sea Surface Radar Cross Section

Type Article
Date 2017-03
Language English
Author(s) Yurovsky Yury YuORCID1, Kudryavtsev Vladimir N.1, 2, Grodsky Semyon A.3, Chapron Bertrand4
Affiliation(s) 1 : RAS, Fed State Budget Sci Inst, Inst Marine Hydrophys, Sevastopol 299011, Ukraine.
2 : Russian State Hydrometeorol Univ, Satellite Oceanog Lab, St Petersburg 195196, Russia.
3 : Univ Maryland, Dept Atmospher & Ocean Sci, College Pk, MD 20742 USA.
4 : Inst Francais Rech Exploitat Mer, F-29280 Plouzane, France.
Source Ieee Transactions On Geoscience And Remote Sensing (0196-2892) (Ieee-inst Electrical Electronics Engineers Inc), 2017-03 , Vol. 55 , N. 3 , P. 1629-1647
DOI 10.1109/TGRS.2016.2628640
WOS© Times Cited 27
Keyword(s) Capillary waves, cross section, radar backscattering, sea surface, wave breaking
Abstract This paper presents dual copolarized (PP) (VV and HH) Ka-band sea surface backscattering measurements taken from the Black Sea research platform at incidence angles ranging from 25 degrees to 65 degrees and in the wind speed range from 3 to 18 m/s. These measurements are corrected for radar antenna pattern and geometry of observations. The resulting normalized radar cross section (NRCS) is parameterized in a form of truncated azimuthal Fourier series with coefficients dependent on the incidence angle and wind speed. This dual PP empirical model (KaDPMod) is consistent with the Ku-band NSCAT-4 model. However, some remarkable differences are revealed. They are apparent when analyzed using a decomposition of VV and HH measurements into polarized Bragg backscattering (polarization difference, PD = VV-HH) and nonpolarized (NP) backscattering from breaking waves. The polarization difference (PD) has strong azimuth and wind dependencies, with the wind exponent ranging from 2.5 to 3. The saturation wave spectra derived from multifrequency PD (based on KaDPMod and Ku- and C-band empirical models) have a notable peak in the capillary-gravity range. The relative contribution of NP radar return to the Ka-band NRCS is significant. In the upwind direction, it reaches up to 60%-80% and 25%-50% for HH and VV, respectively. It is found that the NP wind exponent is lower than that for Bragg backscattering. Therefore, the relative contribution of the NP to Ka-band NRCS decreases with increasing wind speed at both polarizations. Such a behavior is the opposite of that observed in the Ku-band.
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