Measurements of ocean surface stress using airborne and spaceborne microwave scatterometers

Results have been obtained that permit comparisons between estimates of the sea surface friction velocity from both the K_u -band Scatterometer and from in-situ, large area estimates of surface wind stress and direction, acquired during the SWADE 1991 experiment. These results address the accuracy of the K_u-band model function for estimating the magnitude of the friction velocity, and the ability of the azimuthal variation of the scatterometer data to estimate the wind direction. They demonstrate an excellent accuracy for estimating friction velocity magnitude. But they show the potential for frequent errors in estimating wind direction because of small upwind/downwind differences in the radar cross section at the lower incidence angles; however accuracy improves at the higher incidence angles. These results provide useful information in the development of NSCAT/ADEOS algorithms