Wind retrieval from RADARSAT SAR images: Selection of a suitable C-band HH polarization wind retrieval model

A standardized analysis of wind retrieval collocations from a set of ERS (C-band VV polarization) and RADARSAT (C-band HH polarization) synthetic aperture radar (SAR) open ocean images is presented. The field validation opportunities, carried out over the past eight years, provided collocated (in time and space) in situ validation data consisting of wind vector and ocean wave spectrum measurements. In this paper, we present validation results for the SAR-estimated wind direction and speed. The direction estimate is based on the orientation of coherent atmospheric structures in the SAR image. The speed estimate is based on a scatterometer wind retrieval model for C-band VV polarization (specifically, CMOD_IFR2) modified for HH polarization using available polarization ratios. We consider several C-band polarization ratios including empirical and theoretical forms. Use of CMOD_IFR2 and a polarization ratio according to Kirchhoff is recommended for RADARSAT SAR ocean wind retrieval.