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.

在全球气候变化的背景下，气候事件的突发性、极端性与异常性日益凸显。研究极端降水的时空演变特征，对于流域防汛抗旱具有重要意义。本研究以汉江流域为研究对象，基于极端降水指数，分析了1961年至2023年该流域极端降水的时空演变特征，并阐明了海拔高度与大气环流对流域极端降水的影响作用。研究结果显示，1961-2023年间汉江流域的SDII、RX1day、RX5day、R20、CDD、CWD及R95p均呈上升趋势，而PRCPTOT、R10与R99p则呈下降趋势。RX1day呈上升趋势的区域主要集中于流域中部，RX5day的变化区域与RX1day基本一致。流域大部分区域的SDII呈上升趋势，其中以中部地区的增幅最为显著。流域内CDD在武汉地区呈小幅下降趋势，其余区域则显著上升。R95p、R99p与PRCPTOT的升降区域分布一致，流域西部与东部呈下降趋势，其余区域则呈现不同程度的上升。汉江流域的极端降水指数与海拔高度存在显著相关性。在武汉、天门、钟祥等低海拔区域，极端降水指数与大气环流指数存在滞后相关性，滞后时长为1年；在西峡、房县、安康等高海拔区域，极端降水指数与大气环流指数则呈同步相关性；其余区域的极端降水基本不受大气环流影响。