Global Applicability Analysis of GNSS-R Sea Surface Wind Speed Retrieval Based on TM-1

Global Navigation Satellite System Reflectometry (GNSS-R) technology demonstrates significant potential in sea surface wind speed retrieval due to its advantages of low cost, strong signal penetration, and all-weather observation capabilities. However, current spaceborne GNSS-R research primarily focuses on low-latitude regions owing to the limited coverage of CYGNSS satellites, lacking systematic validation of GNSS-R wind speed retrieval' s global applicability. Therefore, this study systematically evaluates the global applicability of GNSS-R wind speed retrieval from three dimensions—wind speed range, GNSS signal sources, and geographical regions—using the Tianmu-1 meteorological constellation (TM-1) L2 sea surface wind speed product combined with ERA5, the fifth-generation global reanalysis data from the European Centre for Medium-Range Weather Forecasts. Statistical results indicate that TM-1 wind speed products exhibit global inversion capability with an overall root mean square error (RMSE) of 2. 22m/s, and the inversion accuracy shows a significant dependence on wind speed. The inversion accuracy is higher in the low wind speed range below 10m/s, but the inversion accuracy gradually decreases with increasing wind speed, particularly demonstrating limitations in sensing sea surface roughness variations under high wind speeds. Furthermore, wind speed retrieval accuracy varies among different GNSS signal sources, with Galileo signals showing optimal performance and Glonass signals the poorest. Geographically, inversion accuracy decreases with increasing latitude, displaying distinct latitudinal gradient characteristics. This phenomenon suggests GNSS-R maintains good applicability in low-latitude regions, while experiencing significantly increased inversion errors in high-latitude polar areas due to sea ice coverage and enhanced wind-wave interactions. This research provides quantitative assessment of GNSS-R' s global applicability for wind speed retrieval and establishes a foundation for optimizing GNSS-R applications in mid-high latitude regions and high wind speed conditions.