Improved sea surface wind retrievals from dual-frequency backscatter measurements of the FY-3E WindRAD scatterometer

WindRAD, onboard the FY-3E satellite, is the first operational scatterometer capable of providing synchronous C- and Ku-band backscatter measurements. This study evaluates the in-orbit performance of sea surface wind products retrieved from the dual-frequency observations. Relative to other rotating scatterometers, the WindRAD dual-frequency observational geometry effectively mitigates the near-nadir region retrieval deficiency of single-frequency scatterometers by leveraging complementary incident angles, enhancing wind performances in the sub-satellite track area. Compared with winds retrieved from WindRAD single-frequency measurements, dual-frequency results benefit from the complementary characteristics of Ku- and C-band measurements, as well as the doubled number of observations, improving overall wind retrieval accuracy. The impacts of rain are further examined. Results show that dual-frequency retrieval reduces environmental sensitivities and offers additional potential for rain characterization. Overall, this work leverages the first operational dual-frequency scatterometer to provide first quantitative validation of dual-frequency improvements using real in-orbit data. The findings highlight the capability and limitations of WindRAD dual-frequency measurements and underscore the need for improved GMFs (geophysical model functions) and joint retrieval methods to enhance cross-frequency consistency. FY-3E卫星搭载的WindRAD是首个可同步提供C波段和Ku波段后向散射测量的业务散射计.本文利用其在轨观测数据, 系统评估双频观测反演海面风产品的性能.与单频散射计相比, WindRAD双频观测几何通过互补入射角缓解星下点区域反演缺陷, 结合两波段互补特性及观测数量翻倍的优势, 提升了整体反演精度.研究还分析了降雨的影响, 发现双频反演可降低环境敏感性, 具备降雨表征潜力.本研究首次利用业务化双频散射计在轨实测数据, 定量验证了双频反演的改进效果, 明确了其能力与局限, 强调需改进地球物理模型函数及联合反演方法以提升跨频一致性.