Abstract. A detailed geophysical evaluation of the initial NASA scatterometer (NSCAT) wind data sets was performed in order to determine the error characteristics of these data and their applicability to ocean surface analysis and numerical prediction. The first component of this evaluation consisted of collocations of NSCAT data to ship and buoy wind reports, special sensor microwave imager wind observations, and National Centers for Environmental Prediction and Goddard Earth Observing System (GEOS) model wind analyses. This was followed by data assimilation experiments to determine the impact of NSCAT data on analysis and forecasting. The collocation comparisons showed the NSCAT wind velocity data to be of higher accuracy than operational ERS 2 wind data. The impact experiments showed that NSCAT has the ability to correct major errors in analyses over the oceans and also to improve numerical weather prediction. NSCAT data typically show the precise locations of both synoptic-scale and smaller-scale cyclones and fronts over the oceans. This often results in significant improvements to analyses. Forecast experiments using the GEOS model show approximately a 1-day extension of useful forecast skill in the southern hemisphere, in good agreement with the results of Observing System Simulation Experiments conducted prior to launch.
IntroductionOcean surface winds are the most important factor coupling the ocean and atmosphere. Surface winds control the fluxes of momentum, heat, and moisture at the atmosphere-ocean interface. They are key to the scientific understanding of climate and to operational forecasting at the long range (1 month to 1 year). Surface wind data are also needed for nowcasting conditions at sea, for wave forecasting, for providing boundary conditions for ocean general circulation models, and for refining the analyses of ocean surface wind which are part of the initial conditions for numerical weather prediction (NWP).The ocean is vast; ships and buoys are few and irregularly located. Satellite microwave remote sensing of the ocean surface now provides a complete and accurate depiction of the surface wind over the ocean. The focus of this paper is the validation of the wind vectors observed by the NASA scatterometer (