Spatiotemporal Characteristics and Associated Synoptic Patterns of Regional Extremely Persistent Heavy Precipitation in estern Yunnan-Guizhou Plateau, China

The Yunnan-Guizhou Plateau (YGP) represents the steepest and most sophisticated terrain in China, as well as being highly susceptible to extreme meteorological disasters. The eastern YGP has a high incidence of regional extremely persistent heavy precipitation (REPHP). Hourly gridded precipitation data from May to July during 2019-2023 were used to define and study REPHP in eastern YGP. It was found that the REPHP events in the eastern YGP were mainly concentrated near the southern boundary and western mountainous areas. Two distinct high-incidence areas (HIAs) of REPHP were identified: the Plain-Hills HIA, situated on the southeastern windward slopes near the Nanling Mountains, and the Plateau-Mountain HIA, located on the western windward slopes near the Laowang Mountains. They mainly occurred from May to July, but especially in June. Influenced by local characteristics, the peaking time of diurnal variations differed between HIAs. ERA5 reanalysis data were used to investigate the synoptic patterns and their impacts in HIAs. The synoptic patterns in both HIAs were accompanied by the Western Pacific Subtropical High (WPSH). When the WPSH was located near 112°E, 16°N and there were southwest low-level jets (LLJs), shear line at 850 hPa and upslope wind would lead to REPHP over the Plain-Hills HIA. If WPSH extended to Beibu Gulf, the Plateau-Mountain HIA was controlled by the updraft generated by South Asia high (SAH), the trough at 500 hPa, shear line at 700 hPa and southerly LLJs. The Plain-Hills HIA features a more favorable convective environment than the Plateau-Mountain HIA, with higher most unstable convective available potential energy MUCAPE, stronger 0–3 km vertical wind shear, and higher precipitable water. Consequently, REPHP events in the Plain-Hills HIA typically exhibit a longer duration, stronger intensity and larger spatial extent.