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FY-3E/WindRAD双频散射计海面风场反演和验证

Retrieval and Validation of Ocean Surface Wind Field from FY-3E/WindRAD Dual-frequency Scatterometer

  • 摘要: 2021年7月发射的风云三号E星(FY-3E)是世界首颗民用晨昏轨道气象卫星,其搭载的WindRAD双频测风雷达具有全球海面风场探测能力。本文首先基于FY-3E/WindRAD L1级观测资料,研究了雷达海面后向散射和风场之间的非线性关系,分别建立了适用于C和Ku波段VV/HH极化的地球物理模式函数(GMF)。随后,结合最大似然估计法(MLE)对WindRAD散射计探测资料进行风场反演。利用海洋浮标、中法海洋卫星散射计(CSCAT)和美国国家环境预报中心(NCEP)模式风场资料对WindRAD反演风场进行验证。结果显示:WindRAD反演风速与浮标风速偏差约为0.2 m s−1,均方根误差(RMSE)在1.13~1.44 m s−1之间,优于2 m s−1的业务化应用的风速精度要求;两者风向偏差在1.4°~3.0°之间,RMSE在25.3°~30.1°之间。WindRAD和CSCAT风场具有较好的一致性,风速RMSE在1.37~1.6 m s−1之间,风向RMSE在22.9°~25.9°之间。WindRAD和NCEP模式风速RMSE在1.87~2.23 m s−1之间,风向RMSE 在22.4°~27.1°之间。研究表明WindRAD散射计C和Ku波段VV/HH极化反演风场均具有较高的精度,充分显示了WindRAD载荷在全球海面风场探测方面的应用潜力和价值。

     

    Abstract: The FY-3E satellite, launched in July 2021, is the first civilian twilight orbit meteorological satellite in the world. The WindRAD dual-frequency scatterometer it carries can detect global ocean surface wind fields. This study first examined the nonlinear relationship between sea surface backscatter and wind field based on FY-3E/WindRAD L1 level observation data and then established geophysical model functions for C- and Ku-band VV/HH polarization wind field retrievals. Using the maximum likelihood estimation method, ocean surface wind fields were retrieved from the WindRAD scatterometer data. The wind field was validated using ocean buoy data, China France Ocean Satellite Scatterometer data, and National Centers for Environmental Prediction (NCEP) wind field data. The results show that the wind speed bias between the WindRAD and buoy data is approximately 0.2 m s−1, and the root-mean-square error (RMSE) is in the range of 1.20–1.44 m s−1, which is better than the 2 m s−1 required for operational applications. The wind direction bias and RMSE are in the range of 1.4°–3.0° and 25.3°–30.1°, respectively. WindRAD and CSCAT satellite wind fields have good consistency, with the RMSE of wind speed being 1.37–1.6 m s−1 and that of wind direction being 22.9°–25.9°. The RMSE between WindRAD and NCEP wind speeds is 1.87–2.23 m s−1, and that of the wind directions is 22.4°–27.1°. These results indicate that sea surface wind fields retrieved from the WindRAD dual-frequency scatterometer data have high accuracy, demonstrating the application potential and value of the WindRAD payload in global sea surface wind field detection.

     

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