湖南省汛期极端强降水事件的时空分布特征OA

Hunan Province,located in the core region of the East Asian monsoon and characterized by complex topography,is highly vulnerable to extreme heavy rainfall events(EHREs).Previous studies have primarily relied on daily precipitation data or instantaneous rainfall measurements,which limits the ability to capture the detailed evolution characteristics of EHREs with different durations.Using hourly precipitation data from the National Me-teorological Information Center of the China Meteorological Administration and ERA5 reanalysis data,this study investigates the multiscale temporal and spatial characteristics and formation mechanisms of EHRE with different durations during the flood season(April-September)from 2016 to 2024 in Hunan Province.The results provide a scientific basis for forecasting,early warning,and disaster prevention and mitigation.The results show that:1)High-frequency EHREs are mainly distributed in the Wuling Mountains,the eastern foothills of the Xuefeng Mountains,and the Nanling Mountains.The occurrence probability of EHREs initially increases and then decreases with increasing precipitation amount,intensity,and maximum hourly precipitation,while decreasing monotonically with increasing duration.2)The onset,development,and termination of EHREs exhibit a bimodal intraseasonal distribution,with a primary peak in late June and a secondary peak in early August.Diurnal variations differ sig-nificantly among durations:short-duration events(2 h)occur mainly from afternoon to evening;medium-duration events(7-8 h)tend to initiate and develop at night and end the following morning;and long-duration events(～14 h)typically persist from nighttime into the following afternoon.3)Short-duration EHREs are associated with an eastward-and northward-shifted subtropical high,significant negative geopotential height anomalies on its southwestern flank,and frequent activity of mid-latitude short-wave troughs and tropical low-pressure systems.In contrast,medium-and long-duration EHREs are closely related to large-scale adjustments in the mid-high latitudes and the sustained interactions between the subtropical high and westerly troughs.4)Short-duration EHREs domi-nate during the flood season,while long-duration events occur less frequently.The probability of high-accumulation events(≥250 mm)increases with duration,whereas the probability of high-intensity events(≥30 mm·h-1)decreases with duration.5)Extreme rainfall intensity is mainly concentrated in the Wuling Mountains and northern Xuefeng Mountains,while a low-value center is observed in the basin extending from the eastern flank of the southern Xuefeng Mountains to the northern Yuecheng Mountains.Rainfall intensity extremes associ-ated with different EHRE durations show exhibit clear subseasonal dependence and asymmetric diurnal character-istics.