中法海洋卫星微波散射计青藏高原土壤水分反演研究

Study on CSCAT soil moisture retrieval in the Qinghai-Tibet Plateau

中法海洋卫星(China-France Oceanography SATellite,CFOSAT)搭载国际上首个扇形波束旋转扫描微波散射计(CFOSAT SCATterometer,CSCAT),其丰富的观测几何信息为青藏高原土壤水分遥感监测提供了新的机遇。此研究提出了一种有效的适用于CSCAT的土壤水分变化检测算法,不需要复杂机理模型和查找表的构建,利用后向散射系数的变化差值和植被经验函数构建土壤水分反演算法。将变化检测算法反演结果与地面实测结果比较,发现CFOSAT反演结果与实测结果有很好的一致性,表明本算法的精度较高,能够准确反映土壤水分的变化。同时,对青藏高原地区的土壤水分时空分布特征进行分析,发现青藏高原中北部土壤偏干,西部和东南部偏湿,局部区域存在复杂的空间特征,且具有显著的季节性变化。

The China-France Oceanography SATellite(CFOSAT)carries the first international fan-beam rotary scanning microwave CFOSAT SCATterometer(CSCAT),whose rich observation geometry information provides new opportunities for remote sensing monitoring of soil moisture on the Qinghai-Tibet Plateau.This study proposes an effective method for detecting the changes in soil moisture applicable to the CSCAT,without the need for modeling complex mechanism and constructing look-up table.The soil moisture retrieval algorithm can be constructed by utilizing the changes in the backscattering coefficient difference and the vegetation empirical function.Through comparing the retrieval results of the detection algorithm and the ground measured results,it is found that the CFOSAT retrieval results are in good agreement with the measured results,and it shows that this algorithm has high accuracy and can accurately reflect the changes in soil moisture.Meanwhile,the analysis of the spatial and temporal distribution characteristics of the soil moisture in the Qinghai-Tibet Plateau reveals that the soil is dry in the northern-central part of the plateau and wet in the western and southeastern parts with complex spatial characteristics in localized areas,and the soil moisture is characterized with significant seasonal variations.