Assessment of FY-3E GNOS-II GNSS-R Global Wind Product

Abstract

Two different GNSS-R wind products are to be developed for the GNOS-II payload on the FengYun-3E (FY-3E) satellite: A global wind product optimized for global low-to-medium wind speeds and a cyclone wind product optimized for high wind speeds in the tropical and extratropical cyclones. This paper presents a comprehensive assessment of the GNOS-II global wind product for both Global Positioning System (GPS) and Beidou (BDS) product at wind speeds below 25 m/s using its data of first 6 months. Three datasets including the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis, HY-2B scatterometer and Soil Moisture Active Passive (SMAP) winds are used for the assessment. The assessment of the Level 1 observables shows that the instrument's performance and calibration are generally stable. For the assessment of retrieved winds, the general performances of GPS and BDS products are similar. The overall wind speed root-mean-square error (RMSE) is 1.54 m/s for GPS-R and 1.44 m/s for BDS-R when compared to ECMWF, 1.48 m/s for GPS-R and 1.36 m/s for BDS-R when compared to HY-2B, 2.08 m/s for GPS-R and 2.04 m/s for BDS-R when compared to SMAP. The overall wind speed biases for GPS-R and BDS-R are about zeros when compared to each dataset. The assessment is also made by the dependence on time, signal-to-noise ratio (SNR), observable, GNSS block, wind speed, incidence angle and geography. Overall, the FY-3E GNOS-II global wind product is consistent over time and space with an accuracy meeting the requirement of operational use.