Simulation Analysis of Soil Moisture in the Tibetan Plateau Based on the HRCLDAS/CLM Land Data Assimilation System

China Meteorological Administration High Resolution Land Data Assimilation System (HRCLDAS-V1.0) is used to drive the Community Land Model (CLM) for soil moisture simulation from 1 Jan to 30 Sep 2015 over the Tibetan Plateau region. Results show that the simulated soil moisture with high spatial-temporal resolution (1 km, 1 h) can reflect the spatial distribution characteristics of soil moisture in the Tibetan Plateau, where the soil moisture gradually decreases from the southeast to the northwest. Temporal variability of the soil moisture shows large changes from Jun to Sep, while the changes from Jan to May are more gentle at different depths of soil. Large changes are found in the upper soil layers, while changes are often small in deep soil layers. The correlation coefficient between the observations and simulated soil moisture is above 0.8 of 0-5-cm, 0-10-cm, and 10-40-cm depths, and reaches 0.92 for the layer of 0-5-cm depth. The changes of the root mean square errors for simulated and observed soil moisture are opposite, and the biases of simulated soil moisture are less than 0.04 mm³ mm^-3 in all layers. During the study period, the low value of soil moisture is overestimated, and the simulation ability of the model for soil moisture decreases with the depth of the soil.