Retrieval and Validation of Ocean Surface Wind Field from FY-3E/WindRAD Dual-frequency Scatterometer

The FY-3E satellite, launched in July 2021, is the first civilian twilight orbit meteorological satellite in the world. The WindRAD dual-frequency scatterometer it carries can detect global ocean surface wind fields. This study first examined the nonlinear relationship between sea surface backscatter and wind field based on FY-3E/WindRAD L1 level observation data and then established geophysical model functions for C- and Ku-band VV/HH polarization wind field retrievals. Using the maximum likelihood estimation method, ocean surface wind fields were retrieved from the WindRAD scatterometer data. The wind field was validated using ocean buoy data, China France Ocean Satellite Scatterometer data, and National Centers for Environmental Prediction (NCEP) wind field data. The results show that the wind speed bias between the WindRAD and buoy data is approximately 0.2 m s−1, and the root-mean-square error (RMSE) is in the range of 1.20–1.44 m s−1, which is better than the 2 m s−1 required for operational applications. The wind direction bias and RMSE are in the range of 1.4°–3.0° and 25.3°–30.1°, respectively. WindRAD and CSCAT satellite wind fields have good consistency, with the RMSE of wind speed being 1.37–1.6 m s−1 and that of wind direction being 22.9°–25.9°. The RMSE between WindRAD and NCEP wind speeds is 1.87–2.23 m s−1, and that of the wind directions is 22.4°–27.1°. These results indicate that sea surface wind fields retrieved from the WindRAD dual-frequency scatterometer data have high accuracy, demonstrating the application potential and value of the WindRAD payload in global sea surface wind field detection.