Comparison of derived wind speed from synthetic aperture radar and scatterometer during the ERS tandem phase

A validation of wind retrieval from synthetic aperture radar (SAR) images has been performed by comparing wind speed estimated from European Remote Sensing Satellite (ERS)-2 SAR with ERS-1 wind scatterometer (WSC) measurements, both using the CMOD-IFR2 algorithm. This was made possible by using data from the open ocean and north of 63/spl deg/ of latitude during the tandem phase of the ERS satellites. Here, the WSC and SAR coverage overlapped with a time difference in the data acquisition of only 30 min. The SAR-derived wind speed values from subimages centred around the WSC wind vectors, agreed to within /spl plusmn/2 m/s but underestimated the WSC wind speed values by approximately 0.4 m/s. Studying the spatial variability of the high resolution wind speed values leads the authors to conclude that the SAR wind field seems useful at least down to a spatial resolution of 500 m, provided that external information on the wind direction is available.