星载GNSS-R海面风速反演方法研究

Ocean Surface Wind Speed Retrieval Using Spaceborne GNSS-R

星载GNSS-R因其时延-多普勒相关功率(DDM)波形对风速的敏感性较低,采用理论与实测波形匹配的方法所得风速精度较差。针对这一问题,该文采用一种直接建立相关功率值与风速之间联系的方法获取风速信息。基于相关功率模型对散射功率进行了归一化修正及其简化处理,利用UK TDS-1卫星试验数据和散射计(ASCAT)同比观测风速分别建立归一化散射功率及其简化式与海面风速之间的经验模型。与ASCAT观测风速对比结果表明:在0~20 m/s的风速范围内,采用归一化散射功率反演风速的均方根误差为2.11 m/s;两种方法的反演精度相近,简化修正方式避免了复杂的积分运算更适用于实时处理。

For spaceborne GNSS-R, Delay-Doppler Map （DDM） shape is less sensitive to wind speed, resulting in poor retrieval accuracy measured by fitting theoretical DDM to the measured one. To solve this problem, a method directly linking the individual DDM power measurement to wind speed is developed to obtain wind speed. Scattered power is normalized by correction factor and its simplified form based on Zavorotny-Voronovich （Z-V） model, respectively. Empirical geophysical model functions linking both normalized scattered power and its simplified form to ocean surface wind speed are derived using spaceborne data on UK TechDemoSat-1 （TDS-1） together with in-situ Advanced Scatterometer （ASCAT） wind measurements. The Root-Mean-Square Error （RMSE） of wind speeds retrieved utilizing normalized scattered power is 2.11 m/s at 0-20 m/s. Simplified normalized scattered power by which wind speed accuracy retrieved is the same level with normalized scattered power is more suitable for real-time processing on-board.