白鹤滩水电站坝区小时极端降水特征OA

The Baihetan hydropower station,located in the lower reaches of the Jinsha River,is a key power supply hub of China's"West-to-East Electricity Transmission"project.Its safe and stable operation is directly related to China's energy security and regional socioeconomic development.However,the dam area is characterized by complex topography and fragile geological conditions,where extreme precipitation not only threatens power generation stability but also significantly increases the risk of secondary hazards such as landslides and debris flows.Therefore,a thorough studying of the spatiotemporal characteristics of short-duration extreme rainfall in this area is essential for improving flood control scheduling and disaster prevention. This study aimed to fill this gap by long-term hourly precipitation observations to reveal the extreme characteristics of hourly precipitation in the Baihetan dam area.It utilized hourly precipitation records from eleven meteorological stations in the Baihetan dam area during 2011 to 2023.Twelve extreme precipitation indices were selected to comprehensively characterize rainfall intensity,frequency,and persistence,including annual total precipitation(PTOT),maximum 1-hour precipitation(Rx1h),maximum 12-hour precipitation(Rx12h),hours of light precipitation(HLP),hours of heavy precipitation(HHP15 mm),hours of very heavy precipitation(HHP20 mm),total precipitation hours(R1 h),simple hourly intensity index(ISDⅡ),annual heavy precipitation amount(R95),annual very heavy precipitation amount(R99),heavy precipitation threshold(P95),and very heavy precipitation threshold(P99).Linear regression analysis was employed to examine temporal trends,and P-value significance testing were conducted at three different temporal scales(interannual,monthly,and diurnal)and the spatial dimension of elevation,thereby depicting the spatiotemporal characteristics of short-duration extreme precipitation in the Baihetan dam area. The results reveal pronounced spatiotemporal heterogeneity of short-duration extreme precipitation in the Baihetan dam area.Interannually,none of the indices exhibited statistically significant trends at individual stations,but substantial spatial differences were observed among stations.Heavy precipitation(R95)and very heavy precipitation(R99)contributed more than one-third and one-eighth of the annual total precipitation(PTOT),respectively,highlighting the dominant role of extreme events in shaping annual rainfall totals.In contrast,light-precipitation hours(HLP)accounted for approximately 80%of total precipitation hours(R1 h),indicating that low-intensity rainfall occurs frequently and persistently.Seasonally,extreme precipitation indices were strongly concentrated during June and September,with July to August contributing the largest fraction to annual precipitation.At the diurnal scale,both precipitation amount and frequency exhibited a clear nocturnal maximum,with peak values occurring mainly between 00:00 and 08:00,especially around 03:00-04:00,forming a distinct"more rainfall at night and less during daytime"pattern.Regarding elevation effects,the thresholds of heavy and very heavy precipitation(P95 and P99)showed a slight decreasing tendency with increasing elevation,whereas HLP and R1 h were significantly and positively correlated with elevation,suggesting that high-altitude areas are more prone to persistent but low-intensity rainfall. This study demonstrates that short-duration extreme precipitation in the Baihetan dam area exhibits strong seasonal concentration,pronounced nocturnal dominance,and marked spatial heterogeneity driven by topographic effects.Extreme rainfall events play a disproportionate role in annual precipitation totals.The significant positive relationship between precipitation duration and elevation implies that high-altitude regions are more susceptible to prolonged low-intensity rainfall.These findings provide scientific support for optimizing flood control scheduling,improving disaster early-warning systems,and enhancing the operational safety of large hydropower stations in mountainous terrain.