Wind Speed Inversion Based on Azimuth Cutoff of Sentinel-1 Wave Mode Products With Small Incidence Angles

Synthetic aperture radar (SAR) imaging with small incidence angles shows that the azimuth cutoff, caused by ocean wave motion along the radar radial direction, is primarily driven by the vertical orbital velocity component, while the horizontal component plays a minor role. Furthermore, the orbital velocity of wind waves—the dominant factor inducing azimuth cutoff effect in SAR imagery—exhibits a strong correlation with wind speed. On the basis of this, we proposed a new wind speed inversion model by integrating the azimuth cutoff from Sentinel-1 wave mode with an incidence angle of 23.8°±0.7° (S-1 WV1) products and the Elfouhaily spectrum, which can be applied to retrieve sea surface wind speeds. Based on the new model, sea surface wind speeds were retrieved using the azimuth cutoff from S-1 WV1 products in 2020, and the accuracy was evaluated using wind speeds provided by European Centre for Medium-Range Weather Forecasts (ECMWF) and National Data Buoy Center (NDBC). The evaluation results show that the correlation coefficients between the wind speeds retrieved utilizing the new model and those provided by ECMWF and NDBC are 0.82 and 0.78, respectively, and the RMSE are 1.44 and 1.42 m/s, respectively, which indicate that the new model has a high accuracy in wind speed inversion. In addition, for this model, the study found that errors in the significant orbital velocity of wind waves and azimuth cutoff are the primary error sources in the wind speed inversion model, and they have an approximately linear influence on the accuracy of wind speed inversion.