宜昌小时极端降水长期变化特征分析

Analysis of Long Term Variation Characteristics of Hourly Extreme Precipitation in Yichang

利用宜昌1956—2020年4—10月逐分钟降水资料分析了宜昌小时极端降水的长期变化特征,对极端降水分布较为集中的6月下旬—8月下旬极端降水强度进行主分量分析。结果表明:宜昌极端降水频次及强度均呈弱增加趋势,在1975年前后出现了1次由强到弱的突变,在1985年前后出现了1次由弱到强的突变,此外还呈现出接近3 a的周期性变化特征。极端降水频次旬变化呈单峰型分布,主要集中在6月下旬—8月下旬,峰值出现在7月下旬。其日变化呈“V字型”分布,主要集中在17时—次日03时之间,峰值出现在22—23时之间。极端降水持续时间多集中在2~4 h之间,其中以2 h居多,数学期望值是2.4 h。旬降水强度在6月下旬—8月下旬表现出3种主要特征:①各旬极端降水强度呈现整体一致特性,即同时增大或同时减小;②极端降水强度在7月下旬和其他各旬呈反向分布;③极端降水强度在7月下旬—8月上旬与其他各旬呈反向分布。

Based on the minute precipitation data from April to October in Yichang from 1956 to 2020,the long-term variation characteristics of extreme hourly precipitation in Yichang hour were analyzed,and the intensity of extreme precipitation from late June to late August was analyzed by principal component analysis.The results show that the frequency and intensity of extreme precipitation in Yichang show a weak increasing trend,with a sudden change from strong to weak around 1975 and a sudden change from weak to strong around 1985.In addition,it also shows a periodic change of nearly three years.The ten day variation of extreme precipitation frequency in Yichang presents a single peak distribution,mainly from late June to late August,and the peak appears in late July.The diurnal variation is a"V-shaped"distribution,mainly between 17∶00 and 03∶00 the next day,with the peak value between 22∶00 and 23∶00.The duration of extreme precipitation in Yichang is mostly between 2~4 hours,most of which are 2 hours,and the mathematical expectation is 2.4 hours.During the precipitation concentration period from late June to late August,the intensity of precipitation in each ten day period shows three main characteristics:①The intensity of extreme precipitation in each ten day period is consistent,that is,it increases or decreases at the same time;②The intensity of extreme precipitation is inversely distributed in late July and other ten days;③The intensity of extreme precipitation is inversely distributed with other ten days from late July to early August.