Validation of Special Sensor Microwave Imager monthly-mean wind speed from July 1987 to December 1989

Since July 1987, wind speed has been routinely computed from first principles, using Special Sensor Microwave Imager (SSM/I) measurements of the intensity of microwave radiation emitted at the ocean surface. The accuracy of monthly-mean SSM/I wind speeds is determined by comparisons with moored-buoy wind measurements. All results for 1988 were virtually identical with 1989. The range of monthly mean moored-buoy wind speeds was 2-10 ms^-1. During 1987, the equatorial matchups were not equivalent with 1988 and 1989, and the cause remains unknown. The root-mean-square (rms) difference of 697 monthly-mean matchups of the composite 1988 and 1989 data set was 1.2 ms ^-1. The rms differences were smaller in the equatorial zone and higher in middle latitudes. At middle latitudes the time series of rms differences displayed an annual cycle. In the equatorial zone the agreement between SSM/I and in situ data was better in regions with a lesser amount of clouds, and vice versa