Abstract
In the earth ecosystem, surface soil moisture is an important factor in the process of energy exchange between land and atmosphere, which has a strong control effect on land surface evapotranspiration, water migration, and carbon cycle. Soil moisture is particularly important in an oasis region because of its fragile ecological environment. Accordingly, a soil moisture retrieval model was conducted based on Dubois model and ratio model. Based on the Dubois model, the in situ soil roughness was used to simulate the backscattering coefficient of bare soil, and the empirical relationship was established with the measured soil moisture. The ratio model was used to eliminate the backscattering contribution of vegetation, in which three vegetation indices were used to characterize vegetation growth. The results were as follows: (1) the Dubois model was used to calibrate the unknown parameters of the ratio model and verified the feasibility of the ratio model to simulate the backscattering coefficient. (2) All three vegetation indices (Normalized Difference Vegetation Index (NDVI), Vegetation Water Content (VWC), and Enhanced Vegetation Index (EVI)) can represent the scattering characteristics of vegetation in an oasis region, but the VWC vegetation index is more suitable than the others. (3) Based on the Dubois model and ratio model, the soil moisture retrieval model was conducted, and the in situ soil moisture was used to analyze the accuracy of the simulated soil moisture, which found that the soil moisture retrieval accuracy is the highest under VWC vegetation index, and the coefficient of determination is 0.76. The results show that the soil moisture retrieval model conducted on the Dubois model and ratio model is feasible.
Highlights
Oases are important parts of the ecosystem that constitute arid and semi-arid regions; they are the “source of life” throughout the arid and semi-arid regions
(3) Based on the Dubois model and ratio model, the soil moisture retrieval model was conducted, and the in situ soil moisture was used to analyze the accuracy of the simulated soil moisture, which found that the soil moisture retrieval accuracy is the highest under VWC vegetation index, and the coefficient of determination is 0.76
The ratio model was used to eliminate the backscatter contribution of vegetation, in which the growth of vegetation is characterized by three vegetation indices of VWC, NDVI, and EVI, and the three vegetation indices were derived by optical data
Summary
Oases are important parts of the ecosystem that constitute arid and semi-arid regions; they are the “source of life” throughout the arid and semi-arid regions. Accurate detection of surface soil moisture is important and can be applied in a variety of hydrological and climate models (e.g., rainfall mapping, drought monitoring, vegetation water requirement analysis, etc.). Soil moisture is an important indicator for monitoring land degradation and drought [3], an indispensable key factor in the land water cycle [4,5,6], and the basic guarantee for vegetation growth and development. It has guiding significance in estimating crop yield and drought monitoring [7,8]
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