High Resolution Wind Field Retrieval from Synthetic Aperture Radar: North Sea Examples

Abstract

A methodology for retrieving high resolution ocean surface wind fields from satellite borne Synthetic Aperture Radar (SAR) data is introduced and validated. The algorithm is applicable to SAR data acquired at C-band at moderate incidence angles. Wind directions are extracted from wind induced streaks that are visible in SAR images and that are very well aligned with the mean surface wind direction. To extract the orientation of these streaks an algorithm based on the derivation of local gradients is utilized. Ocean surface wind speeds are derived from the Normalized Radar Cross Section (NRCS) using a geophysical model function that describes the dependency of the NRCS on the wind and imaging geometry. To validate the algorithm and demonstrate its applicability, SAR retrieved wind fields of the North Sea are compared to numerical atmospheric model results of the German Weather Service.