Wind field retrieval using satellite based synthetic aperture radars

The high spatial resolution and large coverage of satellite-based synthetic aperture radars (SAR) offer an unique opportunity to derive mesoscale wind fields over the ocean surface especially in coastal areas. For this purpose an algorithm was developed and tested using the C-band SAR images from the European remote sensing satellite ERS-2 and from the Canadian satellite RADARSAT-1. Wind speeds are derived from the normalized radar cross sections (NRCS) using a semi empirical model. The model was originally developed for a C-band scatterometer with vertical polarization and therefore has to be modified for horizontal polarization of the RADARSAT-1 SAR. Several C-band polarization ratios were considered including theoretical and empirical forms. To improve and verify the algorithm, wind speeds were computed from several RADARSAT-1 ScanSAR images and compared to results of the Danish high resolution limited area model (HIRLAM). Furthermore the main error sources in SAR wind field extraction are studied with respect to both polarizations