Comparison of RADARSAT-1 SAR retrieved wind fields to numerical models

An algorithm is introduced and verified, which is designed to retrieve high-resolution wind fields from C-band synthetic aperture radar (SAR) operating at both vertical and horizontal polarization. SAR wind retrieval is a two-step process: In the first, step wind directions are extracted from wind-induced streaks, which have a typical spacing of 200 to 1600 m and are normally aligned with the mean surface wind direction. In the second step, wind speeds are derived from the normalized radar cross section (NRCS) and image geometry of the calibrated SAR images, together with the local wind direction retrieved in the first step. Several semi empirical C-band models are available, which describe the dependency of the NRCS on wind speed, wind direction and image geometry. To verify the algorithm, wind fields were computed from 84 RADARSAT-1 SAR and ScanSAR scenes of the cast coast of North America and compared to co-located results from the high resolution numerical model NM5.