青藏高原夏季降水的区域特征及其与周边地区水汽条件的配置

Regional Characteristics of Summer Precipitation on Tibetan Plateau and It′s Water Vapor Feature in Neighboring Areas

使用青藏高原地区97个测站1961-2005年6--8月降水总量及同期NCEP／NCAR月平均u，v风、比湿和300hPa位势高度等再分析资料．首先使用旋转经验正交函数分解方法得到青藏高原夏季降水的4种主要分布类型，之后利用相关分析方法，分析了与4种降水类型匹配的水汽输送以及相应的环流背景，最后使用合成分析对高原异常旱涝年的水汽输送和环流形势的差异进行了分析。结果表明，青藏高原夏季降水的主要气候特征是南部与北部降水异常呈现相反分布的特征，其水汽输送和环流形势配置差异显著。如果孟加拉湾海区向北的水汽输送和东部海洋向西的水汽输送加强，同时乌拉尔山阻高强盛，东亚从低纬至高纬呈现“＋-＋”位势高度环流形势时，有利于西南水汽输送并与来自东部海洋的水汽形成辐合，造成高原夏季降水偏多，反之降水则偏少。

Regional characteristics of summer precipitation of 97 weather stations in Tibetan Plateau are analyzed by using a rotated empirical orthogonal function, based on summer total precipitation （June- August） from 1961 to 2005. And then the relationships between the first four regional characteristics corresponding to other factors such as water vapor transport and the circulation feature in neighboring areas are explored by using NCEP/NCAR monthly mean reanalysis data in summer from 1961 to 2006. At last, the differences of water vapor transport and the circulation feature between flood and drought years are investigated. The results show that the summer precipitation in the southern part of Tibetan Plateau is oppo- site to the northern part, and there is a remarkable difference between them in water vapor transport and circulation feature. If the moisture from Indian Ocean and Bay of Bengal transporting to the north and the moisture from the West Pacific Ocean transporting to the east are strengthened, also the Ural blocking high is strong and the circulation pattern is ＂＋ -＋＂ from low to high latitudes in East Asia, water vapor will converging in Tibetan Plateau, so the rain in summer will be more than normal. And, contrariwise, the precipitation will be less than normal.