1961—2017年尉犁县极端降水和极端气温日数变化趋势分析

Trend analysis of days of extreme precipitation and temperature in Yuli County during 1961-2017

基于尉犁县东南、西北2个气象站1961-2017年逐日平均气温和降水资料,通过集合经验模态分解(EEMD)分析尉犁县极端气温、极端降水和连续干旱日数的变化特征,采用Morlet小波和重标极差分析法得到其周期特征和未来变化趋势。结果表明:(1)近57 a尉犁县东南部和西北部极端降水日数增加,连续干旱日数东南部比西北部减少更多,西北部极端高温日数减少而东南部极端高温日数增加,西北和东南部极端低温日数减少幅度接近。即过去57 a尉犁县西北部极端气候趋于冷湿,尉犁县东南部极端气候趋于暖湿;(2)未来尉犁县西北部极端高温和极端低温日数可能减少,极端降水和连续干旱日数可能增加,尉犁县东南部连续干旱和极端低温日数可能减少,极端降水和极端高温日数可能增加;(3)尉犁县西北部极端降水和连续干旱日数的主周期分别为28 a和8 a,极端高温和极端低温日数的主要周期均为28 a;尉犁县东南部极端降水和连续干旱日数的主周期分别为13 a和28 a,极端高温和极端低温日数主要周期均为28 a。

By using EEMD,the characteristics of extreme temperature days,extreme precipitation days and continuous drought days were analyzed based on long-term(1961-2017)daily average temperature and daily precipitation data of two weather stations in the south east and northwest of Yuli County.Meanwhile,based on Morlet wavelet analysis method and R/S analysis method,the periodic characteristics and long memory property were analyzed.It is found that(1)the number of extreme precipitation days in Yuli County was increased,continuous drought days in the southeast was much shorter than in the northwest,the number of extreme high temperature days in the northwest was decreased,but the southeast was increased in past 57 years.In addition,the extreme low temperature days in the northwest and southeast both decreased,and the magnitude of the reduction was closed.In the past 57 years,the trend of extreme weather events in the northwest part of Yuli County tends to be cold and wet;in the southeast part of Yuli County tends to be warm and humid.(2)In the future,extreme high temperature days and low temperature days in northwestern Yuli County may decrease,extreme precipitation days and extended drought days may increase.Continuous drought days and extreme low temperature days in southeastern Yuli County may decrease,and extreme precipitation days and extreme high temperature days may increase.(3)The main periods of extreme precipitation and continuous drought days in the northwest part of Yuli County were 28 and 8 years respectively,and the periods of extreme high temperature and extreme low temperature days were 28 years;the main periods of extreme precipitation days and continuous drought days in the southeast part of Yuli County were 13 and 28 years respectively.The periods of extreme high temperature days and extreme low temperature days were 28 years.