Application and extension of a quasioperational approach to wind speed measurement from spaceborne synthetic aperture radar

Over the past several years, a consensus has been firmly established that it is possible to make high-resolution (sub-kilometer) marine wind speed measurements from space using synthetic aperture radars (SARs) [F.M. Monaldo, et al., 2003). Conventionally, the wind field is measured from space using active microwave scatterometry or passive microwave measurements. For example, the SeaWinds scatterometer on the QuikSCAT satellite uses microwave backscatter to measure ocean surface wind vectors. The special sensor microwave/imager aboard the defense meteorological satellite program satellites makes passive microwave measurements of wind speed. These instruments are best suited for global measurements, so their 25-km resolution misses important high-spatial-frequency phenomena, particularly in coastal areas. Since 1999, we have operated a near-real time processing scheme that converts quick-look processed RADARSAT-1 SAR imagery into high-resolution estimates of wind speed. This software and processing protocols have matured and evolved into the APL/NOAA SAR wind speed retrieval system (ANSWRS). ANSWRS has been upgraded recently to process ENVISAT SAR imagery as well. This paper is a brief description of this system.