Interdecadal variability and possible drivers of summer extreme precipitation on the low latitude plateau of southwestern China: Interdecadal variability and possible drivers of summer extreme precipitation on the low latitude plateau of southwestern China

We used daily precipitation data from 1961–2022 to study summer extreme precipitation (SEP) in Yunnan Province. To identify the physical mechanisms that could have caused the interdecadal transition of SEP over the low latitude plateau (LLP) region of southwest China, we analyzed water vapor (WV) transport and the dynamic and thermal environment before and after the transition. (1) We found clear regional variations in SEP. In the northwest, elevations are high because of the Hengduan Mountains; here, daily extreme rainfall threshold and extreme rainfall contribution rate were low and the number of extreme rainfall days was high. The extreme rainfall threshold and the number of extreme rainfall days were high and extreme rainfall contribution rate was low in the western Ailao mountain area. In the eastern Yunnan–Guizhou Plateau, summer extreme rainfall threshold was high and the number of extreme rainfall days was low, but extreme rainfall contribution rate was high. (2) We identified change points in the interdecadal SEP trend and found that the SEP trend shifted from negative to positive around 1993. (3) The warming of tropical ocean surfaces and subsequent changes in WV transport were the main causes of abrupt changes in SEP. The activity of cold air in the middle and high latitudes of the Northern Hemisphere was an important dynamic and thermal factor that triggered the interdecadal transition of extreme precipitation in Yunnan.