Evaluation of Remotely Sensed Winds from the UK TechDemoSat-1 Mission in the Northwest Pacific

The emergence of Global Satellite Navigation System reflectometry (GNSS-R) has provided a new possibility for sensing ocean wind speed. GNSS-R can be used as an important supplement to traditional remote sensing methods. The UK TechDemoSat-1 (TDS-1) is the first satellite to demonstrate the capability of GNSS-R to measure ocean winds. A systematic evaluation study of the UK TDS-1 remotely sensed winds is presented in this study. The L2 calibrated bistatic radar equation algorithm version 1.0 (L2 CBRE v1.0) wind product is collected from April 2015 to December 2018. The European Centre for Medium-Range Weather Forecasts (ECMWF)/Copernicus Climate Change Service (C3S) ERA5 (ECMWF Reanalysis 5th Generation) wind fields are taken as the reference. Matchups between the UK TDS-1 and the ECMWF ERA5 products are processed during three years of the UK TDS-1 mission. Overall performance of the UK TDS-1 wind product evaluated by the bias and the root-mean-square error (RMSE) in the Northwest Pacific. Comparison between the UK TDS-1 L2 CBRE v1.0 wind speeds and the ECMWF/C3S ERA5 values was investigated and shown that the bias is-0.09mathrm{m} /mathrm{s} and the RMSE is 2.10m/s. The results show that the TDS-1 winds generally agreed with the ECMWF ERA5 ones. Furthermore, we systematically compared the UK TDS-1 and the ECMWF ERA5 winds on spatial and temporal scales. The spatial characteristics of errors are discussed in the Northwest Pacific, and temporal variability of the UK TDS-1 is analyzed. Finally, the applicability of TDS-1 wind product in the Northwest Pacific is concluded and discussed across the entire lifespan of the TDS-1 mission.