An extreme rainfall event (ERE) with a record-breaking daily rainfall of 428.2 mm occurred in the Eastern Periphery of the Tibetan Plateau (EPTP) on August 10, 2020. However, the mesoscale dynamic and cloud microphysical processes behind such ERE in complex terrain regions remain unclear. Based on multi-source observations and convective-permitting model, this study examines the dominant synoptic systems and key cloud microphysical processes associated with this ERE. The results reveal that the ERE was primarily driven by the synergistic interaction between the Tibetan Plateau Vortex (TPV) to the northwest of the EPTP region and the Low-Level Jet (LLJ) to the southeast. This interaction enhanced local vorticity, strengthened vertical upward motion, and intensified the rainstorm. Diagnostic analysis indicates that the increase in vorticity in the EPTP region above 500 hPa was mainly caused by positive vorticity advection from the eastward-moving TPV, while the inhomogeneous diabatic heating induced by the LLJ played a key role in low-level vorticity growth. Latent heat budget analysis shows that diabatic heating in the upper levels is primarily driven by the deposition of water vapor into snow, while in the mid-to-lower atmosphere, it is mainly due to the condensation of water vapor into cloud water. The growth of rainwater particles was largely attributed to the collection of cloud water, the melting of snow, and a small contribution from graupel melting. Such weather systems and cloud microphysical characteristics provide new insights into the physical mechanisms of rainstorms in the EPTP region.

 

Eextreme rainfall,Eastern Periphery of the Tibetan Plateau,synoptic systems,cloud microphysical processes