金沙江下游某水电站坝区降水特征分析

Analysis of Hourly Precipitation Characteristics of a Hydropower Stations in the Lower Reaches of the Jinsha River

金沙江流域极端小时降水过程局地性强、短时雨量大,了解该区域极端小时降水特征,有助流域水电站应对强降水事件。利用该区域6套自动气象站2011—2022年观测数据集,通过质量控制、特征值提取、分类统计分析等方法,对极端小时降水时空变化特征进行分析。研究发现:①该水电站区域日降水分布的夜雨特征明显,短时强降水在夜间和凌晨出现频率较高;②月际变化方面峰值分别出现在7月和9月,7月降水高发于后半夜,9月的占比高于7月;③选取3个极端小时降水阈值指标,极端小时降水强度由上游向下游、由西北向东南逐渐减小。极端降水事件平均持续时长6.04 h,且前期发展迅速,平均于1.66 h时降水达到峰值;④极端小时降水事件的过程雨量占年平均降水量的24%~33%。将以上结果与近10年实际数据相比对,证明降水特征对蓄水调度和风险管控有一定的应用价值。

Extreme rainfall over the Jinsha River Basin has the characteristics of strong local and heavy short-term rainfall.Analyzing the characteristics of extreme precipitation in this region is helpful for assisting hydropower stations to improve their ability to cope with extreme heavy precipitation events and prevent and mitigate disasters.Using the observation dataset of 6 automatic weather stations in the region from 2011 to 2022,the spatio-temporal variation characterists of extreme hourly precipitation are analyzed by methods as quality control,feature value extraction and classification statistical analysis.The results show that:①The characteristics of night-time precipitation in the distribution of daily precipitation in the hydropower station area are obvious,and the frequency of short-term heavy precipitation is higher at night and early morning.②In terms of monthly and seasonal variation,the peaks occurred in July and September,respectively,and the precipitation in July was higher in the second half of the night,and the proportion in September was higher than in July.③Select the maximum three extreme hourly precipitation threshold indicators were selected to preliminarily analyze the temporal and spatial variation characteristics of extreme hourly precipitation.The intensity of extreme hourly precipitation gradually decreases from upstream to downstream and from northwest to southeast.The extreme precipitation events lasted for an average of 6.04 h,and the precipitation distribution in the processes was asymmetrical,and the precipitations developed rapidly in the early stage of the process,peaking at an average of 1.66 h.④Extreme hourly precipitation events had high intensity and high efficiency,and are more prone to disasters,accounting for 24%to 33%of the average annual precipitation.Through more than ten years of practices,they have shown that the above precipitation characteristics have certain application values for water storage scheduling and risk control.