Analysis of the Detailed Characteristics of Different Short duration Extreme Precipitation Events in the Shaying River Basin

Using hourly precipitation data from 35 national stations and 886 regional stations in the Shaying River basin from May to September during 2013—2022, a detailed comparison is conducted of the characteristics of extreme precipitation for three short durations (1 h, 3 h and 6 h), including their extremes, thresholds, average precipitation intensities and frequencies. The results are as follows: (1) The spatial distribution of extreme values of short-duration precipitation in the Shaying River Basin shows the characteristics of smaller values in the western part and larger values in the northern, northeastern and southern parts. The longer the duration, the stronger the regional distribution of extreme values becomes. (2) Taking the 99.5th percentile of precipitation as the threshold for short-duration extreme precipitation, the spatial distribution of extreme precipitation thresholds for different durations exhibits a pattern of "lower in the west and higher in the east". This characteristic becomes more pronounced as the duration increases. (3) The spatial distributions of short duration extreme precipitation intensity and frequency exhibit pronounced regional heterogeneity across the basin. High-intensity zones are concentrated in transition areas between Songshan Mountain and the plain in the northern part of the Shaying River Basin, and the plain areas in the southern and northeastern parts of the Shaying River Basin, while high-frequency zones dominate the western mountainous areas of the Shaying River Basin. Notably, spatial inhomogeneity of both intensity and frequency distributions becomes more pronounced with increasing precipitation duration. (4) On the monthly scale, the average intensity of short duration extreme precipitation transitions from a monomodal pattern (peaking in July for 1 h and 3 h durations) to a bimodal pattern (dual peaks in July and September for 6 h duration) with increasing duration, while the frequency consistently exhibits a monomodal concentration in July. Diurnal variation is shown, both intensity and frequency display bimodal variations, characterized by a primary peak (afternoon to evening) and a secondary peak (early morning). The intensity shows a temporal phase shift toward later hours for the primary peak and earlier hours for the secondary peak with prolonged duration, resulting in peak concentration gradually concentrated during nighttime. In contrast, the 6 h precipitation frequency exhibits a reverse pattern in peak phase compared to shorter durations (1 h, 3 h) and shorter durations (notably 1 h) demonstrate more pronounced diurnal variability in frequency, with higher amplitude and stronger day-night contrast. This study significantly enhances the understanding of local short-duration extreme precipitation processes and improves early warning capabilities. Furthermore, it establishes a critical data foundation for subsequent probabilistic forecasting and nowcasting of short-duration extreme precipitation events.