Changes of event-based extreme hourly precipitation in Pearl River Basin

Under the background of global warming, extreme precipitation events are becoming more and more frequent, posing severe challenges to the ecological environment and human society. It is of great significance to deeply understand their changing characteristics for flood prevention and disaster reduction. This paper uses the hourly precipitation dataset fused by multi-source data and the Event-based Extreme Hourly Precipitation (EEHP) analysis framework to explore the spatiotemporal variation characteristics of EEHP in the Pearl River Basin from 2000 to 2023, mainly focusing on the analysis of the dominant temporal distribution pattern, diastolic-intensity combination mode and its spatial distribution pattern. The results showed that: ① The total frequency of EEHP showed an upward trend, but the average precipitation and duration generally showed a downward trend. The high incidence period during the year was concentrated in May and June, and the main-peak of EEHP events during the day was mostly in the morning (7:00—8:00) and afternoon (16:00). ② The indicators of EEHP have a similar spatial distribution pattern, generally characterized by "low in the west and high in the east". ③ The pre-peak temporal distribution model (TDP1) was the dominant type of EEHP in the Pearl River Basin (accounting for 87.4%), with most active in spring and summer. It was mainly distributed in Yunnan-Guizhou-Guangxi in the west of the basin, Guangdong-Fujian in the east, and the coastal areas of Guangdong-Guangxi. ④ The long-duration-low-intensity EEHP is the type with the highest proportion of events in the Pearl River Basin. The spatial distribution of low-intensity events shows a pattern of "low in the northwest and high in the southeast", while the spatial distribution of high-intensity events is relatively uniform. The average intensity and duration of EEHP events across different types exhibit a pronounced inverse relationship, with the duration decreasing significantly as the intensity increases.