Responses of June Precipitation in Eastern China to Late Spring Soil Temperature Anomaly over the Qinghai–Xizang Plateau: Results from a Regional Climate Model

Spring land surface temperature/subsurface soil temperature over the Qinghai–Xizang Plateau (QXP) substantially impacts downstream precipitation on subseasonal timescales. However, how well can climate models reproduce this impact and its assoicated interannual variation remains unclear. This study utilized the Regional Climate Model (RegCM) Version 4.7 coupled with the Community Land Model (CLM) Version 4.5 (RegCM4.7-CLM4.5) to investigate the impact of May QXP soil temperature anomalies on June precipitation in eastern China. Causes for different precipitation responses to land surface/subsurface conditions and atmospheric background states in four years were analyzed. The results indicate that warm surface and soil temperature anomalies over the QXP in May led to increased precipitation in the southern Yangtze River basin (SYRB) in June. Due to soil temperature memory, the QXP warming persisted into June, sustaining a negative geopotential height anomaly at 500 hPa above the QXP. Concurrently, negative and positive height anomalies developed over northern China and the Sea of Japan. The corresponding cyclonic anomaly in the mid-to-lower troposphere over QXP enhanced monsoonal moisture transport in May, and the persistent soil temperature anomaly over QXP sustained moisture convergence over southern China in June, resulting in increased precipitation there. Of the four years examined, both the precipitation response in the SYRB and the intensity of the associated wave train pattern are the strongest in 1998. The combined effect of land surface conditions in May and the atmospheric circulation background in June influenced the precipitation responses. Thermal conditions affected snow cover variations and consequently the radiative balance in the western QXP, causing stronger low-level atmospheric responses in 1998 compared to other years. Additionally, the position of the westerly jet influenced the propagation of atmospheric anomalies, contributing to the different responses in the mid-to-high troposphere. The above findings underscore the role of spring soil temperature anomalies over the QXP as a source of predictability for precipitation in eastern China at the subseasonal timescale.