The relationship between radar cross section and surface wind in two oceanic regions: ERS-1 scatterometer and buoy measurements

A wind vector retrieval algorithm is developed and validated using the ERS-1 scatterometer and collocated buoy measurements in two oceanic regions during 1992 and 1993. This algorithm, denoted RBT, and the ESA delivered winds are compared. The wind speed is retrieved from near 0.1 m/s to 18 m/s overestimating the lowest winds by about 0.4 m/s using the RBT algorithm; whereas the ESA algorithm is restricted to U>2 m/s. Existing algorithms consistently retrieve 180° ambiguities in wind direction about as often as the true directions. These ambiguities are caused by a small and variable upwind/downwind modulation inherent in the C-band vertically polarized backscatter. The wind speed and direction variability are similar for both algorithms; a rms deviation near 1.2 m/s and 25° provided the directional ambiguities are removed