近30年青藏高原东部夏季降水异常特征及成因

The Characteristics and Genetic of Summer Precipitation Anomaly over the Eastern Qinghai-Xizang Plateau during the Last 30 Years

摘要: 文章利用青藏高原东部地区近30年的逐日夏季平均降水量及NCEP/NCAR逐月平均再分析风场、位势高度场资料，对青藏高原东部近30年夏季平均降水量的气候态、方差和趋势分布特征进行了分析，通过EOF分析了青藏高原东部夏季降水异常的3种主要分布类型，又利用回归分析方法，分析了与3种典型模态匹配的风场异常特征，以明确青藏高原东部夏季降水异常的环流特征。结果表明：1) 近30年青藏高原东部的夏季降水量存在一个东南向西北递减的分布特征，而且在东南部降水比较偏多，降水大值区年际变化也大，降水趋势变化不明显。2) 夏季降水异常空间分布为3种类型，即南北反相型、中间多南部少型以及东西反相型。3) 当青藏高原东部夏季降水南多北少时，印度季风槽偏弱，西太平洋副高位置偏南，高原东部的南侧为气旋性距平环流，南亚高压偏南，西风急流减弱；当青藏高原东部降水呈中间多南部少型时，印度季风增强，西太平洋副高位置偏北偏西，南亚高压位置偏北偏东，且青藏高原东北侧西风急流增强；当青藏高原东部降水呈东西反相型时，西太平洋副热带高压位置偏西，而高原东部地区西侧以偏西风距平为主，同时高层南亚高压位置偏东。

Abstract: In this paper, based on the daily average rainfall in summer and the NCEP/NCAR monthly mean reanalysis wind field, geopotential height field data in eastern Qinghai-Xizang Plateau in nearly 30 years, climatology, variance and trend distribution characteristics of average rainfall in summer in eastern Qinghai-Xizang Plateau in nearly 30 years were analyzed. Three main distribution types of summer precipitation anomaly in eastern Qinghai-Xizang Plateau were analyzed by EOF, and the wind field anomaly characteristics matching the three typical modes were analyzed by using re-gression analysis method, so as to make clear of the circulation characteristics of the summer precipitation anomaly in eastern Qinghai-Xizang Plateau. The results show that: 1) In nearly 30 years, summer rainfall in eastern Qinghai-Xizang Plateau is a southeast-to-northwest of diminishing distribution characteristics, and there is more precipitation in the southeast, and the precipitation inter-annual variability of greater value is also big, and precipitation change trend is not obvious. 2) Spatial distribution of summer rainfall anomaly is divided into three types, namely the North-South inverting type, more middle and less southern type and eastwest inverting type. 3) When eastern Qinghai-Tibet Plateau in summer of less precipitation from south to the north, the Indian monsoon trough is weak, West Pacific subtropical high southward, in the eastern part of the plateau, is located to the south of the cyclonic anomaly circulation, South Asia high southerly and westerly jet weaken; when the precipitation in the eastern Qinghai-Xizang Plateau is more over middle, enhance the Indian monsoon, location of Western Pacific subtropical high northerly and westerly, position of South Asia high north easterly and westerly jet over the northeast side of the Qinghai-Tibet Plateau enhanced; when the precipitation in the eastern Qinghai-Xizang Plateau is eastwest inverting type, West Pacific subtropical high extends westward, and in the eastern part of the plateau area on the west side to westerly anomaly, also top South Asian anticyclone eastward.