西南地区夏季降水的变化特征分析

Analysis on the Change Characteristics of Summer Precipitation in Southwest China

摘要: 本文利用中国气象中心整编的全国636站1961年1月~2014年12月的月平均降水数据和NCEP/NCAR逐月再分析资料，采用了经验正交函数分析方法、Lanczos滤波等方法对西南地区54年四季的年降水分布特征、夏季降水的空间分布以及夏季降水的年际/年代际特征进行来分析，结果表明：西南地区54年来夏季的降水量最多，春季和秋季的降水量次之，冬季的降水量最少，由于夏季降水量明显多于其他季节，所以，对夏季降水的年际/年代际特征以及时空分布特征针对性分析，夏季降水存在明显的年际变化特征，且存在2~3年以及6~8年的显著性周期，同时也存在明显的年代际变化特征，显著性周期为15年左右，在1998年，西南地区夏季降水存在一个异常年的波峰。西南地区年降水第一、第二、第三载荷向量分别反映西南地区夏季降水三种类型，即东北西南型、南北对称型和非对称三极型。西南地区夏季降水的水汽来源主要是来自于孟加拉湾和印度洋，由于副高东退，且西南地区位于短波槽中，水汽源源不断汇入西南地区，同时，来自于贝加尔湖以及蒙古地区的干冷气流与来自孟加拉湾和印度洋的暖湿气流在西南地区交汇，配合着低层和中层的气旋性环流，水汽辐合上升到达高层之后，在反气旋性环流的控制下，水汽辐散下沉，从而形成降水。

Abstract: This paper by using the country’s 636 BGF China meteorological center station in January 1961- December 2014, the average monthly precipitation data and NCEP/NCAR monthly reanalysis data, using the empirical orthogonal function (EOF) analysis method, such as Lanczos filtering method for 54 years in southwest four seasons of year rainfall distribution and spatial distribution of summer precipitation and summer precipitation interannual decadal characteristics of analysis, the results showed that: 54 years of summer precipitation in southwest China, most of the spring and autumn rainfall times, winter precipitation at least, because the summer precipitation obviously more than other seasons, so the summer precipitation interannual/decadal characteristics and time-space distribution characteristics of targeted analysis of characteristics of interannual variability of summer precipitation exists obviously, and there are 2 to 3 years of significant cycle, at the same time also has obvious interdecadal variation characteristics, significant period of 15 years or so, in 1998, the summer precipitation in southwest China is an exception in the wave. The first, second and third load vectors of annual precipitation in southwest China respectively reflect three types of summer precipitation in southwest China, namely, northeast southwest type, north-south symmetric type and asymmetric tripole type. Summer precipitations in the southwest of the water vapor sources are mainly from the bay of Bengal and the Indian Ocean, due to the subtropical high back east, and the southwest region is located in the short-wave trough, the water vapor flowing into the southwest, at the same time, from Lake Baikal and Mongolia region air dry and cold and warm moist air flows from the bay of Bengal and the Indian Ocean in southwest region, with the lower and middle cyclonic circulation, the water vapor convergence rises, after arriving in top under the anticyclonic circulation of the control, water vapor divergence subsidence, thus forming precipitation.