Calibration and validation of the HY-2 scatterometer backscatter measurements over ocean

The Normalized Radar Cross-Sections (NRCS,σ0) measured by spaceborne scatterometer are used to determine the near-surface wind field using the geophysical model functions (GMF). The accuracy of the retrieved wind field is a sensitive function of the radiometric accuracy of the σ0 measurements. Therefore, in-orbit calibration is essential for the retrieval of optimum quality geophysical products. In this paper, the scatterometer onboard HY-2A satellite (HY-2 SCAT) is calibrated using Numerical Ocean Calibration (NOC) and its winds retrieval after calibration are validated by winds from global buoys and from the European Centre for Medium-Range Weather Foresting (ECMWF) Numerical Weather Prediction model (NWP). The standard deviations for wind speed and wind direction against buoy winds are better than 1.3 m/s and 15°, indicating that the HY-2 SCAT calibration has been successful and that HY-2 SCAT wind products after NOC are of high quality.