Adaptability Evaluation of Multi-source Remote Sensing Products to Soil Moisture Retrieval in Loess Hilly and Gully Region

The loess hilly and gully region is the most serious area of soil and water loss on the Loess Plateau.The long-term and accurate monitoring of soil water has important pracitcal significant for the restoration of the ecological environment and high-quality development of agriculture in the region.The paper, takes the measured soil moisture as the reference data, and R, RMSE, Bias, and ubRMSE were used as the evaluation indicators to compare and analyze the specific performance of soil moisture products SMAP, AMSR2 and GLDAS under different topographical conditions in the loess hilly and gully region.According to the research results, the soil moisture products with the highest accuracy were selected to conduct spatio-temporal analysis of soil moisture in the Loess hilly and gully region from 2016 to 2021.The results showed that:(1) SMAP soil moisture products was better than AMSR2 and GLDAS in all evaluation indexes under the three terrain conditions of hilly and sloping farmland, plain and valley, and tidal land, and its applicability was the best.(2) From 2016 to 2021, soil moisture in the loess hilly and gully region showed an increasing trend.From 2016 to 2021, four seasons and multi-year average soil moisture showed a spatial pattern of more soil moisture in the eastern and western areas, and less soil moisture in the central area.