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

Autor: Zhao Kai, Jiang Tao, Chen Si, Zheng Xingming, Wan Xiangkun
Rok vydání: 2019
Předmět:
Zdroj: Chinese Geographical Science. 29:283-292
ISSN: 1993-064X
1002-0063
DOI: 10.1007/s11769-019-1028-0
Popis: The parameter bp in the tuo-omega (τ–ω) model is important for retrieving soil moisture data from passive microwave brightness temperatures. Theoretically, bp depends on the observation mode (polarization, frequency, and incidence angle) and vegetation properties and varies with vegetation growth. For simplicity, previous studies have taken bp to be a constant. However, to reduce the uncertainty of soil moisture retrieval further, the present study is of the dynamics of bp 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, bp decreases nonlinearly with vegetation water content (VWC), decreasing critically when VWC becomes less than 2 kg/m2. Second, there is a power law between bp and VWC for both horizontal and vertical polarizations (R2 = 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-bp method based on the HiWATER dataset. Doing so reveals that the dynamic bp method reduces the root-mean-square error of the retrieved soil moisture by approximately 0.06 cm3/cm3, and similar improvement is obtained for the calibrated SMAPVEX12 dataset. Our results indicate that the dynamic bp method is reasonable for different vegetation growth stages and could improve the accuracy of soil moisture retrieval.
Databáze: OpenAIRE
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