Co-Cross-Polarization Coherence Over the Sea Surface From Sentinel-1 SAR Data: Perspectives for Mission Calibration and Wind Field Retrieval

Spaceborne synthetic aperture radar (SAR) has been used for years to estimate high-resolution surface wind field from the ocean surface backscattered signal. Current SAR platforms have one single fixed antenna, and traditional inversion/retrieval schemes rely on one copolarized channel, leading to an unconstrained optimization problem for providing independent estimates of wind speed and direction. For routine application, this is generally solved with a priori information from the numerical weather prediction (NWP) model, inducing severe limitations for rapidly evolving meteorological systems where discrepancies can be significant between model and measurements. In this study, we investigate the benefit of having two simultaneous acquisitions with phase-preserving information in copolarization and cross polarization provided by Sentinel-1 (S-1). A comprehensive analysis of the co-cross-polarization coherence (CCPC) is performed to adequately estimate and calibrate CCPC values from S-1 interferometric wide (IW) mode images acquired over the ocean. A new polarimetric calibration (PolCAL) methodology based on least-squares (LS) criterion and direct matrix inversion is proposed yielding crosstalk estimates. We document CCPC odd symmetry with respect to relative wind direction for light to medium wind speeds (up to 14 m/s) and incidence angle from 30x00B0; to 45x00B0;. The azimuthal modulation is found to increase with both wind speed and incidence angle. An analytical model C-band polarimetric geophysical model function (CPGMF) is provided. The synergy of the CCPC with other radar parameters, such as backscattering coefficients or Doppler, to further constrain the inversion scheme is assessed, opening new perspectives for SAR-based wind field retrieval independent of any NWP model information.

Keyword(s)

Wind, Synthetic aperture radar, Sea measurements, Spaceborne radar, Sea surface, Radar, Wind speed, Dual-polarization, polarimetric calibration (PolCAL), Sentinel-1 (S-1), single look complex (SLC), synthetic aperture radar (SAR), wind field retrieval

Full Text

FilePagesSizeAccess
Publisher's official version
166 Mo
Author's final draft
187 Mo
How to cite
Longepe Nicolas, Mouche Alexis, Ferro-Famil Laurent, Husson Romain (2022). Co-Cross-Polarization Coherence Over the Sea Surface From Sentinel-1 SAR Data: Perspectives for Mission Calibration and Wind Field Retrieval. Ieee Transactions On Geoscience And Remote Sensing. 60. 4200816 (16p.). https://doi.org/10.1109/TGRS.2021.3055979, https://archimer.ifremer.fr/doc/00742/85382/

Copy this text