欧空局ERS1/2卫星上的风散射计(WSC),分辨率是50km,4天内能覆盖全球超过80%的范围,并可在多角度下对地物目标进行观测。本文研究利用该散射计数据估算土壤水分的方法。首先,利用基于ERS散射计数据建立的全球C波段雷达后向散射系数数据库,根据传统的几何光学模型(GOM),反演得到与土壤含水量密切相关的法线方向Fresnel反射率,并与两个采样点(安多和那曲)上的实测降雨量及土壤水分相对比,证明了ERS散射计数据与土壤水分的高相关性;第二步,以水云模型为基础,结合AIEM模型,发展了一种简化模型来估算土壤水分绝对值,分别利用气象站实测点数据和同时期的Basist湿度指数(BWI)进行验证,表明反演结果能较好反映土壤水分的空间分布状况。

The ERS-1/2(European Remote-Sensing Satellites-1/2) wind scatterometer(WSC) has a resolution cell of 50 Km,but it covers more than 80% of the Earth surface in four days and can make measurements at multiple incidence angles.In this paper,the method to estimate soil moisture is studied using WSC data.Firstly,based on classical GOM model,the high correlation between WSC data and soil moisture is proved,by comparing in-situ-based precipitation and soil moisture with derived Fresnel reflectivity at normal incidence(which is very closely related to soil moisture) at two points(Amdo and Naqu).This part of work is performed using Database of Global C-Band Radarbackscatter,which is derived from original WSC measurements.Secondly,a simplified algorithm is proposed to estimate soil moisture based on "Water-Cloud" model and AIEM model,the validation is performed using both in-situ-based soil moisture and Basist Wetness Index(BWI),showing that the algorithm can estimate Spatio-temporal soil moisture distribution effectively.