对近50a云南降水量的时空变化特征分析

利用云南省124个国家气象站1961-2010年的月降水量资料,运用倾向率分析和EOF分析方法,研究了云南最近50a来降水量变化的基本特征。通过倾向率变化分析表明:云南冬季降水量倾向率呈东部和北部为正,西南部为负的分布趋势,变化幅度在4个季节中最小;春季大部地区降水量呈增加的趋势,增加的幅度西部地区大于中东部地区;夏季全省大部倾向率均为负;但倾向率数值各地差异较大;秋季云南西北部降水量有增加而东南部降水量减少的趋势。EOF分析表明:第1主分量序列可表征云南年降水量变化趋势,1999和2001年是近50a云南降水量最多年份,2009年是最少的年份。近50a来第1主分量波动下降,表明云南年降水量呈减少趋势;第2特征向量在云南西北部为负,东南部为正,对应的第2主分量也呈波动下降的趋势变化,表明近50a来云南西北部降水增加、东南部降水量减少,这与云南秋季降水量的变化特征相符。

Analysis on Spatial and Temporal Variation Characteristic of Rainfall in Yunnan of Latest 50 Years

Based on the monthly rainfall date from 1961 to 2010 in 124 national weather stations of Yunnan province,the rainfall variation characteristic of Yunnan in latest 50 years is studied by using inclination rate analysis and EOF analysis method.The inclination rate analysis result shows that the distribution tendency of inclination rate of winter rainfall is positive in eastern and northern region and negative in western and southern region,and is the smallest in the four seasons;the rainfall shows increasing tendency in spring in a majority of regions and the increasing degree of the western region is larger than that of the middle and eastern region;the rainfall all shows decreasing tendency in summer;the inclination rate values have great difference in different regions;in autumn,the rainfall shows increasing tendency in northwest region while decreasing tendency in southeast region.The EOF analysis result shows that the 1st principal component serial can express the rainfall variation tendency of Yunnan;in the latest 50 years,the largest rainfall is in 1999 and 2001 year and the least rainfall is in 2009 year,the 1st principal component serial is fluctuating decreased,which indicates the decreasing tendency of annual rainfall;the 2nd characteristic vector is negative in northwest region and positive in southeast region,the corresponding 2nd principal component serial is fluctuating decreased,too,which indicates the decreasing tendency of rainfall in northwest region and increasing tendency of rainfall in southeast region.This is consistent with the rainfall variation characteristic in autumn.