Spatiotemporal changes and trends in surface soil moisture in Mongolia using SMAP datasets

This study investigates the spatial and temporal dynamics of soil moisture across Mongolia using satellite data from NASA's SMAP mission over the past eight years. Given Mongolia's highly seasonal and extreme continental climate, soil moisture is strongly associated with precipitation and temperature. Between April and October, soil moisture ranges from 0.01 to 0.35 m³/m³, with the lowest values observed in May due to minimal rainfall following snowmelt. From June to August, increased rainfall raises soil moisture levels, peaking in August. Although precipitation declines from September onward, cooler temperatures help retain soil moisture. Using the Theil–Sen slope method, trend analysis reveals that 32.7% of the territory experienced a decline in soil moisture, while 38.9% showed an increasing trend. The analysis employed both active and passive satellite sensing, assessing soil moisture every 10 days to capture detailed seasonal patterns. These datasets highlight climate–soil interactions and provide a basis for understanding moisture variability under changing climatic conditions.