Dynamic b_p in the L Band and Its Role in Improving the Accuracy of Soil Moisture Retrieval  

作　　者：JIANG Tao ZHAO Kai ZHENG Xingming CHEN Si WAN Xiangkun 

机构地区：[1]Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences [2]University of Chinese Academy of Sciences [3]Changchun Jingyuetan Remote Sensing Test Site, Chinese Academy of Sciences

出　　处：《Chinese Geographical Science》2019年第2期283-292,共10页中国地理科学（英文版）

基　　金：Under the auspices of the Outstanding Young Talent Foundation Project of the Jilin Science and Technology Development Plan(No.20170520078JH);the Science and Technology Basic Work of Science and Technology(No.2014FY210800-4)

摘　　要：The parameter b_p in the tuo-omega(τ–ω)model is important for retrieving soil moisture data from passive microwave brightness temperatures.Theoretically,b_p depends on the observation mode(polarization,frequency,and incidence angle)and vegetation properties and varies with vegetation growth.For simplicity,previous studies have taken b_p to be a constant.However,to reduce the uncertainty of soil moisture retrieval further,the present study is of the dynamics of b_p based on the SMAPVEX12 experimental dataset by combining a genetic algorithm and the L-MEB microwave radiative transfer model of vegetated soil.The results show the following.First,b_p decreases nonlinearly with vegetation water content(VWC),decreasing critically when VWC becomes less than 2 kg/m^2.Second,there is a power law between b_p and VWC for both horizontal and vertical polarizations(R^2=0.919 and 0.872,respectively).Third,the effectiveness of this relationship is verified by comparing its soil-moisture inversion accuracy with the previous constant-b_p method based on the HiWATER dataset.Doing so reveals that the dynamic b_p method reduces the root-mean-square error of the retrieved soil moisture by approximately 0.06 cm^3/cm^3,and similar improvement is obtained for the calibrated SMAPVEX12 dataset.Our results indicate that the dynamic b_p method is reasonable for different vegetation growth stages and could improve the accuracy of soil moisture retrieval.The parameter b_p in the tuo-omega(τ–ω)model is important for retrieving soil moisture data from passive microwave brightness temperatures.Theoretically,b_p depends on the observation mode(polarization,frequency,and incidence angle)and vegetation properties and varies with vegetation growth.For simplicity,previous studies have taken b_p to be a constant.However,to reduce the uncertainty of soil moisture retrieval further,the present study is of the dynamics of b_p based on the SMAPVEX12 experimental dataset by combining a genetic algorithm and the L-MEB microwave radiative transfer model of vegetated soil.The results show the following.First,b_p decreases nonlinearly with vegetation water content(VWC),decreasing critically when VWC becomes less than 2 kg/m^2.Second,there is a power law between b_p and VWC for both horizontal and vertical polarizations(R^2=0.919 and 0.872,respectively).Third,the effectiveness of this relationship is verified by comparing its soil-moisture inversion accuracy with the previous constant-b_p method based on the HiWATER dataset.Doing so reveals that the dynamic b_p method reduces the root-mean-square error of the retrieved soil moisture by approximately 0.06 cm^3/cm^3,and similar improvement is obtained for the calibrated SMAPVEX12 dataset.Our results indicate that the dynamic b_p method is reasonable for different vegetation growth stages and could improve the accuracy of soil moisture retrieval.

关 键 词：soil VEGETATION microwave RADIOMETRY TRANSMISSIVITY 

分 类 号：S152.7[农业科学—土壤学]