ENSO与长江流域中游地区雨季极端降水的关系

The Relationship between ENSO and the the Precipitation Extremes along the Middle Reaches of Yangtze River during the Monsoon Season

湖北、湖南和江西沿长江地区的极端降水在长江中游的洪水灾害中发挥着重要的作用。选取可以表征极端降水的7种指数进行降水趋势分析,发现除连续最大降水日数外,1951—2009年间的5—9月>25 mm和>50mm降水日数、>95%与>90%降水量百分位数值的日数以及1 d最大降水量、连续5 d最大降水量都没有明显的变化趋势。相关分析显示雨季的各种极端降水指数与前年9月至当年2月Nino3区海温有较好的正相关关系。

As a flood suffered region,the precipitation extremes of Hubei,Hunan and Jiangxi Province along the middle and low reaches of Yangtze River play significant roles in flood formation.Choosing 7 indices to represent the precipitation extremes during May to September of every year and by the trend analysis,we found that such the indices,number of days during may to September with rainfall more than 25,50 mm and 95th and 90th percentiles precipitation,one-day and five-day maximum precipitation,all show no obvious trend since 1951,however,the maximum continuous wet days（CWD） shows a significant decrease trend.Correlation analysis shows there are good relationship between these indices and the Nino 3 sea level temperature（SST） during former May to Much next year,almost all the correlation coefficients pass the 5% significant test.During former September to next February,except the number of days with rainfall more than 25 mm,the relationship between other extremes and the former the Nino 3 SST are much better,and pass 0.01 significant tests.The relationship of one-day maximum precipitation is better than that of five-day maximum precipitation with Nino 3 SST,and the relationship of the number of days with rainfall more than 50 mm and 95th is better than that of 25 mm and 90th percentiles suggest that Very heavy rainfall events posses very strong relationship with Nino 3 SST.Based on these strong relationships,the Nino 3 SST can be used as a＂predictor＂of monsoon precipitation extremes of the middle reaches of Yangtze River.