Low-to-Moderate Wind Speed Retrieval from Sentenel-L Dual-Polarized Sar Images

Abstract

It's difficult to retrieve low to moderate wind speeds from Synthetic aperture radar (SAR) data at cross-polarization because of low signal to noise ratio. In this paper, we proposed a new approach for retrieving sea surface low to moderate wind speeds utilizing C-band dual-polarized SAR observations from the Sentinel-I. Dual-polarized SAR images and in situ buoy winds were collected and used to analyze the relations of the normalized radar cross section (NRCS) with the sea surface wind speed and incidence angle. The cross-polarized NRCS is hardly dependent on wind speed under 5m/s but is strongly dependent on incidence. Finally, a new cost function which combines co- and cross-polarized geophysical model functions was proposed. The resulting bias of −0.9 m/s and correlation coefficient of 0.846 demonstrate the effectiveness of the proposed cost function for wind speed under 20m/s. Furthermore, comparisons show that low wind speed retrieval from cross-polarized SAR data is hard, but it can contribute to that from co-polarized SAR data.