Inversion Of Soil Water Content Based On Sentinel-1A And Landsat-8 OLI Images-Beiluhe Of Northern Tibet

Soil water content is closely related to vegetation growth,and especially in arid and semi-arid regions,vegetation is more susceptible to changes in soil water content,as well vegetation changes will have a strong feedback effect on regional ecological environment,climate and human production and life,Therefore,The inversion of soil water content and its dynamic analysis have been the focus of research at home and abroad.In this paper,the Beiluhe of northern Tibet as a typical research area,weakening the contribution of vegetation layer to soil backscattering coefficient by the “water-cloud” model,inverting the surface soil moisture by using the Sentinel-1A SAR and Landsat-8 OLI data,and proposing an idea of combining empirical models that combined by existing experience and semi-empirical models to eliminate the dependence of soil permittivity and soil roughness,as well,directly establish the relationship both soil backscattering coefficient and soil water content.The parameter of the combined model is modified by using the measured soil water content data in the study area,and which minimizes the difference between the soil water content inversion data and the measured data is found by loop iteration,then the soil water content data of Beiluhe of northern Tibet in July 2018 was obtained,and analyzed the distribution characteristics of soil water content in the study area and its influencing factors,finally the article uses the combined model to invert the soil water content data of the study area in July 2017,and analyzes the annual variation of soil volumetric water content in the study area.The conclusions of this article are as follows:(1)The soil water content distribution map in this paper shows that the soil moisture content in the western part of the whole study area is higher than that in the eastern part,and in the central part of the whole study area,the soil moisture content in southern and northern is slightly higher than that in the middle part.(2)The distribution of soil water content in the study area is affected by many factors,such as topography,vegetation,river and soil distribution,which will affect the soil moisture content of the area.(3)Comparing the distribution of soil volumetric water content and the distribution of humidity components in the study area in 2018,the numerical values of the two maps are basically the same,which verifies the reliability of the inversion results of the soil water content data in the whole study area;Comparing the distribution of soil volumetric water content and the distribution of humidity components in the study area in 2017,the numerical values of the two maps are basically the same,It is verified that the combined empirical model has certain stability for calculating the time series image data of the study area.(4)For the change of soil water content in the whole study area,the soil water content in 2018 is higher than that in 2017.