Impact of Land Surface Conditions in the Tibetan Plateau on Summer Precipitation in Southeast Asia: Comparing the Roles of Soil Moisture and Soil Temperature

Initialization of land surface conditions, including soil moisture, temperature, and vegetation, plays an important role in seasonal and sub-seasonal prediction in regions where land-atmosphere coupling is strong, and both local and non-local effects can be involved depending on specific regions. Over Asia, past studies suggested that subsurface soil temperature over the Tibetan Plateau in the spring can influence summer precipitation over East Asia. This study evaluates the impact of land surface initialization in Tibetan Plateau on summer precipitation in East Asia using a regional climate model RegCM4.3-CLM4.5, and focuses on the comparison between the role of soil temperature initialization and the role of soil moisture initialization. A long-term simulation driven with boundary conditions from ERA-Interim model produces a well-defined Tibetan Plateau-Southeast Asia relationship and a realistic spatial pattern of climate anomalies for the season of interest (May, June) in the experimental years. Sensitivity experiments featuring different initial soil temperature (Soil_T) over the Tibetan Plateau are used to quantify the impact of soil temperature anomalies alone; similarly, sensitivity experiments featuring different initial soil moisture (Soil_M) are used to quantify the impact of soil moisture anomalies alone; combined experiments with both soil moisture and soil temperature anomalies (Soil_TM) are conducted to examine the potential non-linearity due to the interactions between the two different aspects of land surface conditions. Processes and mechanisms linking the land surface conditions in Tibetan Plateau to precipitation in East Asia at the sub-seasonal and seasonal time scales will be explored.