The spatial response function of SeaWinds backscatter measurements

Abstract

Designed to retrieve near-surface winds over the ocean, the SeaWinds scatterometer makes 13.4 GHz Ku-band measurements of the normalized radar backscatter of the Earth's surface. SeaWinds backscatter measurements are being used in a wide variety of studies, including ocean wind retrieval, sea-ice mapping and classification, iceberg tracking, vegetation, soil moisture, and snow accumulation. Two SeaWinds instruments are currently flying in orbit. Due to the high spatial sampling density, SeaWinds data is ideally suited for the application of reconstruction and resolution enhancement algorithms. Such algorithms require accurate knowledge of the spatial response function of the individual measurements, "slices" and "eggs." Standard SeaWinds data products from JPL include the locations of the measurements, but not the response functions. In this paper we derive the spatial response function for both egg and slices. The response functions vary with antenna azimuth and orbit location. Because computation of the response function is laborious, methods of tabularizing and interpolating the response function have been developed. These are described in this paper. We provide code and the tables to enable computation the response function using information from standard JPL data products. We hope these will further the development of resolution-enhanced SeaWinds data. Examples of resulting enhanced resolution images are included.