Spatial and temporal variations of the surface soil moisture in the source region of the Yellow River from 2003 to 2010 based on AMSR-E

Abstract

BackgroundHydrological processes in the source region of the Yellow River (SRYR) are increasingly attracting local concern, particularly when coupled with a changing climate. Nonetheless, large-scale spatial and temporal variations in soil moisture have received minimal research attention compared to other hydrological variables in the area. MethodsBased on a two-channel retrieval method with a Qp model through monthly regression analysis and Advanced Microwave Scanning Radiometer-EOS (AMSR-E) soil moisture data, we investigate the spatial and temporal variations of the surface soil moisture and its influencing factors in the SRYR and through five natural zonings in the SRYR during 2003-2010. ResultsThrough successive corrections with the dual-channel retrieval algorithm with the Qp model and the monthly regression analysis, the AMSR-E soil moisture shows strong agreement with in situ data in the SRYR. The average annual surface soil moisture in the SRYR is 0.140-0.380 cm3/cm3. There is a decreasing trend in the moisture content in the entire SRYR over the study period (2003-2010). Generally, a decreasing trend occures in the areas with higher initial soil moisture values from 2003 to 2010, while increasing trend in the areas with lower initial soil moisture concentrations over the same period. The soil moisture is highly positively correlated with precipitation (r = 0.80, P < 0.01) and the NDVI (r = 0.79, P < 0.01) over the entire year. The soil moisture is also negatively correlated with air temperature in months with high temperatures (from April to September) and positively correlated with air temperature in months with low temperatures (from January to March and from October to December). ConclusionsThis paper illustrates that the surface soil moisture of the SRYR has the tendency of drying, and precipitation and vegetation account for the decrease of soil moisture. Results of this paper provide an effective way for AMSR-E official soil moisture products application, would help to understand the hydrological process and its response to climate change, and have a scientific significance for ecological environment construction in Plateau.