Abstract:

Based on daily precipitation data from 337 meteorological monitoring stations in Qinling Mountains and surrounding areas during 1980—2021, the spatiotemporal characteristics of extreme precipitation were analyzed. The generalized extreme value distribution and climate statistics methods were used to compare the differences in extreme precipitation years and seasons (spring, summer, and autumn) between two phases: the first phase (1980—2000) and the second phase (2001—2021). The results are as follows: (1) Extreme precipitation in Qinling and surrounding areas mainly concentrated from April to November, with July registering the highest number of extreme precipitation days. Over the past 40 years, extreme precipitation has shown an overall increasing trend. Spatially, the southeast exhibits higher values for the extreme daily precipitation threshold and daily maximum precipitation than the northwest. Additionally, a clear boundary along the north-south direction, aligning with the Qinling, highlights more occurrences in the southern region than in the northern region. (2) On an annual scale, there is a discernible rise in both the number and intensity of extreme precipitation events during 2001—2021 compared with 1980—2000. The spatial changes in the extreme daily precipitation threshold, the number of extreme precipitation days, and daily maximum precipitation also show an overall increasing trend, with more meteorological stations exhibiting an increasing trend. (3) Considerable seasonal differences in extreme precipitation exist, particularly between spring and summer/autumn. The probability and frequency of extreme precipitation were generally higher in spring during 1980—2000, whereas in 2001—2021, extreme precipitation peaks in summer and autumn. Spatial distribution differences are also evident. In spring, the extreme daily precipitation threshold and the number of extreme precipitation days generally show an increasing trend in the western region, contrasting with a decreasing trend in the eastern region, transitioning from positive to negative values. A greater number of stations display a decreasing trend than an increasing trend. In contrast, in summer and autumn, the number of stations demonstrating an increase in the extreme daily precipitation threshold and the number of extreme precipitation days exceeds those witnessing decreasing trends, particularly in autumn, where the proportion of stations with increasing trends is higher.

Key words: extreme daily precipitation threshold, daily maximum precipitation, the number of extreme precipitation days, temporal change