The aim of this study is to evaluate the impact of the bandlike sampling of spaceborne scatterometers on the ability of scatterometer winds to successfully force the mean flow and seasonal cycle of an ocean model in the context of equatorial and tropical dynamics. The equatorial ocean is simulated with a four-layer, primitive equation, reduced gravity model of the Indian Ocean. The variable wind stress used in this study is derived from one year (1988) of 6-hour analyses of the 10-m wind vector over the Indian Ocean performed at the Euorpean Centre for Medium-Range Weather Forecasts (ECMWF). It is applied as a forcing at every grid point of the model to drive a referece circulation. Scatterometer winds are simulated from ECMWF winds, using the nominal configurations and orbital parameters of the Euorpeon Remote Sensing 1 (ERS-1) and NASA Scatterometer (NSCAT) missions.

The model is forced in real time under swaths with the raw scatterometer winds of ERS-1 and NSCAT, with a persistance condition (i.e., wind is kept constant until the next passage of the satellite provides a new value). The circulation obtained for each of the scatterometer experiments is compared with the referce circulation. The seasonal circulation of the Indian Ocean with NSCAT winds is very similar to the reference. The perturbations introduced by the bandlike sampling and the persistance condition have an impact similar to that of a small uncorrelated noise added to the reference forcing. The persistence condition for ERS-1 does not give results which are as good as those obtained for NSCAT. ¿ American Geophysical Union 1994