Impact of Thermally Forced Circulations on the Diurnal Cycle of Summer Precipitation Over the Southeastern Tibetan Plateau

The summer precipitation over the southeastern Tibetan Plateau (SETP) exhibits significant diurnal variability, with a notable peak before midnight. This study investigates how thermally forced circulations regulate the diurnal precipitation over the SETP, using surface rain-gauge observations and high-resolution reanalysis data from June to August during 2015-2019. Water vapor supply and precipitation onset in the afternoon are associated with the upslope winds and upward motions of the mountain-plains solenoid (MPS) between the SETP and nearby lowlands (the Sichuan Basin and Yunnan-Guizhou Plateau). After sunset, the sustained easterly and stronger southerly winds below 500 hPa transport abundant moisture from the rainy lowlands to the SETP. The findings suggest that these winds are mainly due to the larger zonal continental-scale thermally forced circulation combined with the meridional large-scale MPS before midnight and the meridional small-scale MPS after midnight.