Retrieval of the Near-Surface Wind Velocity and Direction: Scat-3 Orbit-Borne Scatterometer

Abstract

The new concept proposed during the development of the first Russian orbit-borne scatterometer SCAT-3 requires an additional study for estimating its efficiency and comparison with the current scatterometer concepts. Using the fan antenna pattern (with angular dimensions 1◦ × 6◦), we have reduced the antenna rotation speed by about a factor of three compared with the prototype (the “SeaWinds” scatterometer) and measured the backscattering cross section for each wind cell at the horizontal and vertical polarizations. The numerical model of the scatterometer was developed with allowance for the technical characteristics of the radar, orbital parameters, and observation scheme. The scatterometer operation is simulated with the subsequent swath formation and partitioning into the wind cells. It is shown that using the fan pattern in the scatterometer, one can improve the accuracy of the wind-direction r5etrieval in a wind cell due to employing the radiometric resolution in the processing algorithm. The main error in determining the wind direction is related to the ambiguity ±180◦, which is caused by the type of the azimuthal dependence of the backscattering cross section. With the help of the two-dimensional median filtering, we can significantly reduce the wind-direction retrieval error. This error can probably be smaller than that for the current scatterometers.