Short-duration extreme precipitation over mountainous areas will increase under global warming

A new study led by Prof. CUI Xiaopeng from the Institute of Atmospheric Physics of the Chinese Academy of Sciences, in collaboration with experts from the National Meteorological Center of China, has uncovered a trend of increased short-duration extreme precipitation over mountainous regions under global warming in Southwest China.

The findings were published in Journal of Applied Meteorology and Climatology on Nov. 8.

While total global precipitation increases, the intensification of short-duration extreme precipitation outpaces the overall rise. This phenomenon is especially pronounced in the complex topography of Southwest China, encompassing Sichuan, Chongqing, Yunnan, and Guizhou, where multiple climatic systems converge.

"In warm seasons, heavy precipitation frequently plagues Southwest China, resulting in severe hydrological and geological disasters," said Prof. CUI. "Our study has uncovered a concerning trend of extreme hourly precipitation increasing in the region, a pattern that is more susceptible to global warming."

The study, spanning from 1981 to 2020, delved into the spatiotemporal variations of extreme hourly precipitation events (EHPs) during warm seasons and the underlying mechanisms. Results showed that EHPs exhibited a stronger increase than total precipitation, predominantly in areas with terrain heights above 500 meters. Furthermore, EHPs primarily occurred between June and August, demonstrating a bimodal structure in diurnal variation.

The researchers found that EHPs often occurred accompanied by anomalous changes in circulation, including positive anomalies of pseudo-equivalent potential temperature, humidity, geopotential height, and anomalous cyclonic circulation in the low-level wind field. The westward and northward extension of the western North Pacific subtropical high as well as pseudo-equivalent potential temperature rise were believed to be a primary driver of the surge of EHPs.

The consequences of this increase are far-reaching, as short-duration extreme precipitation events can lead to flash floods and landslides, endangering lives and ecosystems, particularly in mountainous areas. "The characteristics, changes, mechanisms, and predictions of short-duration extreme precipitation in mountainous areas require high attention," said Prof. CUI.