Research on spatio-temporal evolution characteristics and influencing factors of extreme precipitation in Hanjiang River Basin from 1961 to 2023

Under the background of global climate change, the suddenness, extremity and abnormality of climate events have become increasingly prominent. Studying the spatio-temporal evolution characteristics of extreme precipitation is of great significance for flood control and drought relief in river basins. Taking the Hanjiang River Basin as the research object, we analyzed the spatio-temporal evolution characteristics of extreme precipitation in the basin from 1961 to 2023 based on extreme precipitation indices, and revealed its influence of elevation and atmospheric circulation on extreme precipitation in the basin. The results showed that from 1961 to 2023, SDII, RX1day, RX5day, R20, CDD, CWD and R95p in the Hanjiang River Basin showed an upward trend, while PRCPTOT, R10 and R99p showed a downward trend. The areas with an upward trend in RX1day were mainly concentrated in the middle of the basin, and the areas with changes in RX5day were basically the same as those of RX1day. Most of the basin showed an upward trend in SDII, with the most obvious increase in the middle of the basin. The CDD in the basin decreased slightly in Wuhan, while other areas increased significantly. R95p, R99p, PRCPTOT showed the same upward and downward areas, with the western and eastern parts of the basin showing a decline, and other areas showing different degrees of increase. The extreme precipitation indices in the Hanjiang River Basin have a close correlation with elevation. In low altitude areas such as Wuhan, Tianmen and Zhongxiang, the extreme precipitation indices showed a lag correlation with the atmospheric circulation indices, with a lag period of one year. In high altitude areas such as Xixia, Fangxian and Ankang, the extreme precipitation indices showed a synchronous correlation with the atmospheric circulation indices. In other areas, extreme precipitation was basically not affected by atmospheric circulation.