High resolution wind fields retrieved from synthetic and real aperture radars

An algorithm designed to retrieve high-resolution ocean surface wind fields from space borne synthetic aperture radar (SAR) data acquired by the European satellites ERS and ENVISAT as well as of the Canadian satellite RADARSAT-1 is introduced. The algorithm extracts wind directions from wind induced streaks that are visible in SAR images at scales above 200 m and that are approximately in line with the mean surface wind direction. Wind speeds are derived from the image intensity and geometry of the SAR images, together with the local SAR-retrieved wind direction. To demonstrate and validate the applicability of the algorithm wind fields were computed from several ERS, ENVISAT and RADARSAT-1 SAR images and compared to atmospheric model results as well as wind measurements of the scatterometer operated aboard ERS-2. The above mentioned algorithms for SAR wind retrieval have been modified to meet the needs of wind retrieval from real aperture radars (RAR) such as nautical radars, which are very cost efficient and available on most ships. To validate the modification, RAR data collected at a tower-based radar station in the North Sea are compared to in situ measurements. Last but not least, some recent applications of radar-retrieved high-resolution wind fields will be presented.