西南地区近60年夏季降水的区域特征

Regional Characteristics of Summer Precipitation in Southwest China in Recent 60 Years

为对西南地区近60年夏季降水的空间分布特征以及时间变化特征进行研究,利用西南地区75个气象站点1961年1月1日-2017年12月31日的逐日降水资料,采用旋转经验正交函数分解方法、线性趋势估计法、Morlet小波分析以及Mann-Kendall突变检验等分析方法。结果表明:西南地区近60 a的夏季降水总体呈下降趋势,年代际变率为-2.893 mm/10 a,其夏季降水在空间分布上表现出明显的地域性。据此对西南地区夏季降水进行REOF分区,可分为4个区域:Ⅰ区为贵州以及重庆南部地区;Ⅱ区为四川中东部地区以及重庆北部地区;Ⅲ区为川西高原地区以及四川南部地区;Ⅳ区主要是云南地区。4个区域中Ⅰ区以及Ⅲ区夏季降水呈上升趋势,Ⅱ区和Ⅳ区夏季降水有下降趋势。4个区域的夏季降水突变集中在20世纪70年代。西南地区的降水周期特征为大周期中包含小周期,并且该4个区域夏季降水以25~30 a、准15 a以及5~10 a周期最为普遍。

Based on the daily precipitation data of 75 meteorological stations in the southwestern region from January 1,1961 to December 31,2017,the spatial distribution characteristics and temporal variation characteristics of summer precipitation in the southwestern China in the past 60 years were analyzed by using the rotational empirical orthogonal function decomposition method,linear trend estimation method,wavelet Analysis and Mann-Kendall mutation analysis.The analysis results show that the summer rainfall in the entire southwestern region in the past 60 years has shown a general downward trend,with an interdecadal variability of-2.893 mm/10 a,and its summer precipitation shows obvious regional distribution in space.Based on this,the REOF zoning of summer precipitation in the southwestern region can be divided into 4 regions:RegionⅠis Guizhou and southern Chongqing;RegionⅡis central and eastern Sichuan and northern Chongqing;RegionⅢis the western Sichuan plateau and southern Sichuan;AreaⅣis mainly Yunnan.Among the four regions,summer precipitation in areasⅠandⅢshowed an upward trend,and summer precipitation in areasⅡandⅣshowed a downward trend.The abrupt changes in summer precipitation in the four regions were concentrated in the 1970 s.The characteristics of the precipitation cycle in the southwestern region are that large cycles include small cycles,and summer precipitation in these four regions is most common at periods of 25 to 30 a,quasi 15 a and 5 to 10 a.