近50a三峡库区汛期极端降水事件的时空变化

利用三峡库区35个台站1961-2010年汛期(5-9月)的逐日降水量资料,首先定义不同台站的极端降水量阈值,统计各站近50 a逐年汛期极端降水事件的发生频次,进而分析其时空变化特征.结果表明:三峡库区汛期极端降水事件发生频次的最主要空间模态是主体一致性,同时存在东西和南北相反变化的差异.三峡库区汛期极端降水事件发生频次具有较大的空间差异,可分为具有不同变化特点的5个主要异常区.滑动t检验表明,三峡库区西南部区代表站巴南的极端降水事件在1974年后发生了一次由偏多转为偏少的突变,北部区代表站北碚在1981年后和1993年后分别发生了由偏少转为偏多和由偏多到偏少的突变,中部区代表站武隆在1984年后发生了一次由偏多转为偏少的突变.结合最大熵谱和功率谱分析表明,近50 a来各分区汛期极端降水事件发生频次的周期振荡不太一致,三峡库区东北部区代表站宜昌、北部区代表站北碚和中部区代表站武隆分别存在5、2.4和8.3 a的显著周期.

Temporal and spatial variation of extreme precipitation events in flood season over Three Gorges Reservoir area in recent 50 a

Based on the daily precipitation data in flood season(from May to September) in 1961-2010 from 35 stations over Three Gorges Reservoir area,the extreme precipitation threshold value for all stations are determined firstly,then the frequency of extreme precipitation event in the flood season are counted and their temporal and spatial characteristics are analyzed.Consistent anomaly distribution is the main spatial model of extreme precipitation event frequency in flood season over Three Gorges Reservoir area.The spatial distribution of extreme precipitation event frequency is complex with anomaly difference between in the south and west,and in the east and west of Three Gorges Reservoir area,which can be divided into five main regions.The moving t-test analysis shows that there are abrupt changes of Banan in 1974,Beibei in 1981 and 1993,and Wulong in 1984 for the extreme precipitation event frequency.The Maximum Entropy Spectral and Estimation Power Spectral analysis shows that the periodic oscillations of these regions are not consistent in recent 50 a.The distinct periodic oscillation of the extreme precipitation event frequency of Yichang,Beibei and Wulong is 5,2.4 and 8.3 a,respectively.