Circulation characteristics and formation mechanism of heavy rainfall in summer over the Southeastern Tibetan Plateau

The southeastern Tibetan Plateau (SETP) is the most predominant summer rainfall region in the Tibetan Plateau. However, the atmospheric circulation characteristics associated with regional heavy precipitation over the SETP are still unclear. Based on 35 years of daily precipitation observations in 1980-2014, the types of weather systems causing regional heavy precipitation events over the SETP are objectively classified into two representative patterns, named the Tibetan Plateau vortex type (TPVT) and mid-latitude trough type (MLTT), through hierarchical clustering technique. The classification results show a clear connection between the heavy precipitation and the positive vorticity anomaly, moisture convergence, and southeastward shift of the westerly jet core contributing to anomalous rising motion. It was found that TPVT and MLTT resulting in heavy precipitation events were derived from the eastward development of the Tibetan Plateau vortex related to dry-wet potential vorticity processes and the penetration of deep extratropical trough-ridge circulations, respectively.