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 (LST/SUBT) over the Qinghai-Xizang Plateau (QXP) substantially impacts downstream precipitation patterns on subseasonal timescales. This study utilized the RegCM4.7-CLM4.5, focusing on four specific years to investigate the impact of May QXP soil temperature anomalies on June precipitation in eastern China, and further explored the causes of differences in precipitation responses across the four years by analyzing land surface conditions and atmospheric background states. The results indicate that warm anomalies over the QXP in May lead to increased precipitation in the southern Yangtze River basin (YRB) in June. The results show that the QXP warming anomaly persists into June due to soil temperature memory, sustaining a negative geopotential height anomaly at 500 hPa above the QXP. Concurrently, negative and positive geopotential height anomalies develop over northern China and the Sea of Japan, respectively. The corresponding cyclonic anomaly in the mid-to-lower troposphere over QXP enhances monsoon moisture transport in May, and the persistent soil temperature anomaly over QXP sustains moisture convergence over southern China in June, thereby leading to increased precipitation. Of the four years examined, both the precipitation response in the southern YRB 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 state in June influence the precipitation responses. The thermal conditions affect snow cover variations and, consequently, the radiative balances in the western QXP, leading to stronger low-level atmospheric responses in 1998 compared to other years. Additionally, the position of the westerly jet stream influences the propagation of atmospheric anomalies, contributing to the different responses in the middle-to-high atmosphere. This study underscores the role of spring temperature anomalies over the QXP as a source of predictability for precipitation in eastern China at the subseasonal timescale.