Seasonal cycles of monthly means of ground truth wind speed of METAR station GVAC and of area-averaged TMI wind speed at 37 GHz for the Cape Verde Island Sal

In the present paper ground truth and remotely sensed datasets were used for the investigation and quantification of the impact of Saharan dust on microwave propagation, the verification of theoretical results, and the validation of wind speeds determined by satellite microwave sensors. The influence of atmospheric dust was verified in two different study areas by investigations of single dust storms, wind statistics, wind speed scatter plots divided by the strength of Saharan dust storms, and wind speed differences in dependence of microwave frequencies and dust component of aerosol optical depth. An increase of the deviations of satellite wind speeds to ground truth wind speeds with higher microwave frequencies, with stronger dust storms, and with higher amount of coarse dust aerosols in coastal regions was obtained. Strong Saharan dust storms in coastal areas caused mean relative errors in the determination of wind speed by satellite microwave sensors of 16.3% at 10.7 GHz and of 20.3% at 37 GHz. The mean relative errors were smaller in the open sea area with 3.7% at 10.7 GHz and with 11.9% at 37 GHz.

本研究采用地面实测（ground truth）与遥感数据集，开展撒哈拉沙尘对微波传播影响的探究与量化、理论结果验证，以及对卫星微波传感器反演风速的精度校验工作。本研究通过对单次沙尘事件、风速统计数据、按撒哈拉沙尘强度分级的风速散点图，以及基于微波频率和气溶胶光学厚度沙尘组分的风速差异分析，在两个不同研究区域验证了大气沙尘的影响效应。研究结果表明，沿海区域内卫星反演风速与地面实测风速的偏差，随微波频率升高、沙尘风暴强度增强以及粗沙尘气溶胶含量增加而显著增大。沿海区域的强撒哈拉沙尘风暴会导致卫星微波传感器反演风速的平均相对误差分别为10.7 GHz频段下16.3%、37 GHz频段下20.3%。远海区域的平均相对误差则更低：10.7 GHz频段为3.7%，37 GHz频段为11.9%。