Preliminary accuracy evaluation and improvement of Sentinel-1C SAR sea surface wind speed products

CHEN Yihong; WANG He; ZHU Jianhua; HUANG Xiaoqi

doi:10.19513/j.cnki.hyqxxb.20251017001

Abstract：This paper conducts an accuracy evaluation and improvement study on the synthetic aperture radar(SAR)sea surface wind speed products from the Sentinel-1C satellite under IW mode.Using the buoy observation data from the National Data Buoy Center(NDBC)as the ground truth,the accuracy of the official Sentinel-1C SAR Level-2 OCN wind speed products from April to June 2025 is evaluated.It is found that the root mean square error(RMSE)is 1.31 m·s-1,which meets the requirements of routine applications,but there is still room for improvement.To enhance the product accuracy,three improvement schemes are designed to systematically explore the influence of background wind field types,the adaptability of the geophysical model function and the correction of deviations in the normalized radar cross section(NRCS).The results are shown below.(1)Replacing the ECMWF(European Centre for Medium-Range Weather Forecasts)background wind field with higher-resolution CMEMS(Copernicus Marine Environment Monitoring Service)data can reduce the RMSE to 1.28 m·s-1.The retrieval effect of CMOD5.n model performs better than that of C-SARMOD2 due to its adaptation to conventional wind conditions and medium incidence angles.The NRCS re-calibration model constructed based on CMEMS and CMOD5.n can effectively correct the incidence angle-related residuals of the original NRCS.(2)The optimal improvement scheme significantly improves the product accuracy:the deviation drops to-0.35 m·s-1,the RMSE reduces to 1.21 m·s-1,and the correlation coefficient increases to 0.88.The research results can provide technical support for the operational improvement of SAR sea surface wind speed products from the Sentinel-1C satellite and offer reference for the accuracy improvement of similar C-band SAR wind speed products.