Modeling and Assessment of Vegetation Water Content on Soil Moisture Retrieval via the Synergistic Use of Sentinel‐1 and Sentinel‐2

Abstract

As one of the important parameters of the fifty "basic climate variables", soil moisture plays an important role in ecology, hydrology, climatology, and meteorology (Attarzadeh et al., 2018;Laachrate et al., 2020). From an ecological point of view, soil moisture is an important water element absorbed by plant roots, which directly affects plant growth, soil respiration, and plant function (Blyth et al., 2011). For the hydrology, soil moisture controls surface infiltration and redistribution of surface runoff and is an important part of the global water cycle (Kornelsen & Coulibaly, 2013). From a climatological perspective, soil moisture regulates the distribution and circulation of water and energy on the land surface, which in turn affects the global climate pattern (Seneviratne et al., 2010).Studies on carbon and water cycles, climate change, and energy balance with large-scale and spatial-temporal characteristics often require the participation of global soil moisture products such as Soil Moisture Active and Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), etc (Carrera et al., 2017;Jones et al., 2017). However, these products with low spatial resolution cannot be used for research studies on crop yield evaluation, drought monitoring, and agricultural irrigation management (Carrao et al., 2016;Rivers et al., 2015). Ground measurements based on this point is often expensive and laborious. Therefore, it is extremely necessary and important to achieve high spatial and temporal resolutions of soil moisture retrieval. Optical and thermal infrared remote sensing are susceptible to surface coverings and severely affected by weather clouds and fog, and the accuracy of soil moisture retrieval is greatly reduced. High-resolution Synthetic Aperture Radar (SAR) data with microwave bands of band C, band X, and band L (e.g., COSMO-SkyMed, Sentinel-1, and ALOS), which have the advantage of being unaffected by weather, low frequency band, and being sensitive to soil moisture, and thus