祁连山近45a5～9月日降水气候特征

Climatic Characteristics of Daily Precipitation from May to September in Recent 45 Years in Qilian Mountains

应用祁连山地区17个测站1960～2004年5～9月逐日降水资料,统计逐年5～9月不同量级的雨日数及对应的降水量,进而得到各站小雨和中雨以上日降水雨强,用区域平均值来代表祁连山地区整体的不同降水量级雨日数和雨强,用线性趋势系数及5阶主值函数分析不同量级降水日数和雨强的变化趋势。用墨西哥帽状连续小波变换方法分析其周期变化情况。结果表明:祁连山地区5～9月降水量与不同量级的雨日数的气候平均分布具有地理分布上的相似性,无论年降水量还是不同量级的雨日数,同纬度地区西侧明显多于东侧,祁连山东段多于西段,等值线呈西北—东南走向。近45a,祁连山地区小雨日数呈下降趋势,中雨以上降水日数则呈上升趋势,而小雨雨强与中雨以上降水的雨强均呈增强态势,不同量级降水日数与雨强的共同作用使得5～9月降水量与总雨日数呈相反变化趋势,即5～9月降水量呈上升趋势,而总雨日数呈微弱下降趋势。小波分析发现,祁连山地区小雨日数有5a左右的变化周期,而中雨以上降水日数的周期变化较小雨日数周期变化明显复杂。

The different level rainy days and its homologous precipitation quantity are obtained by using the daily precipitation data from May to September （1960-2004） of 17 stations in the Qilian Mountain area,thus,we know the daily precipitation intensity of light rainfall and moderate rainfall（and more） at each station.Based on regional mean value of the different level rainy days and rainfall intensity in Qilian Mountain area,the tendency of the different level rainy days and rainfall intensity was analyzed using linear trend coefficient and 5 levels main value function.The results show that both precipitation and different level rainy days from May to September in Qilian Mountain area presented more in the west side and less in the east side in the same latitude area,and more in the east and less in the west part of Qilian Mountain.In recent 45 years,the light rainfall days was descending,but the moderate rainfall days was ascending.The precipitation intensity of light rainfall and moderate rainfall （and more） presented ascending trend too from May to September in Qilian Mountain area.The morlet wave analysis show that the light rainfall days had a period of five years,but the period of the moderate rainfall （and more） days was more complex.