厄尔尼诺事件对太湖流域降水的影响

为了揭示1951~2016年厄尔尼诺事件影响下太湖流域夏季(6~8月)降水特征,分析了厄尔尼诺事件开始年与结束年的降水状况。结果表明:太湖流域降雨与厄尔尼诺事件存在一定的关系:(1)弱强度厄尔尼诺事件起始年的6月与6~8月、结束年的6月与7月降水均以正常、大旱与极旱为主;中等强度厄尔尼诺事件起始年的6月与6~8月以正常与大涝为主,结束年同时段以正常、偏旱与大旱为主;(超)强厄尔尼诺事件起始年6月以正常或大旱为主,8月以正常或大涝为主,结束年刚好相反。(2)(超)强厄尔尼诺起始年的夏季,西太平洋副热带高压面积偏小,位置偏东,而结束年的夏季,西伸脊点加强西伸,利于太湖流域降雨偏多。(3)(超)强厄尔尼诺起始年的全年编号台风以偏少为主,登陆台风正常略偏少,但事件的起始年夏季6~8月编号台风却以偏多为主,结束年秋季9~11月登陆台风以偏多为主;结束年6月降雨偏多,登陆台风向秋季集中,易造成流域持续洪涝,对防洪产生不利影响。

Influence of El Nino Events on Rainfall in Taihu Basin

In order to reveal summer (from June to August) precipitation characteristics of the Taihu Basin under the influence of El Nino events during 1951-2016, the precipitation differences of the starting and ending years were analyzed. The results show that the El Nino events have some impacts on summer precipitation. (1) For El Nino events with low intensity, the probability of severe and extremely drought is higher in June and June to August of the starting years, as well as June and July of the ending years. For El Nino events with medium intensity, the probability of severe flood is higher in June and June to August of the starting years, while the probability of partial and severe drought is high for the same period of the ending years. For El Nino events with high intensity, the probability of severe drought in June and severe flood in August of the starting years is higher, while the results of that in ending years were inverse. (2) The subtropical high over the western Pacific is smaller, weaker and shifted eastward in summer of the starting years in El Nino events with high intensity, whereas the subtropical high enhanced and stretched westward in summer of the ending years, leading to plentiful precipitation of Taihu Basin. (3) The total number of formatting typhoon and landing typhoon is slightly less in the starting years of El Nino events with high intensity, however, the number of formatting typhoon in summer and landing typhoon in autumn is large. Plenty precipitation in June as well as typhoon concentrated in autumn tends to cause continuous floods over the Taihu Basin.