夏季青藏高原东南部水汽收支气候特征及其影响

Climatological Characteristics of Summertime Moisture Budget over the Southeast Part of Tibetan Plateau with Their Impacts

采用1961—2005年NCEP/NCAR再分析资料,研究了夏季青藏高原东南部水汽收支的气候特征及其影响效应。结果表明:夏季青藏高原东南部总体上是一个水汽汇区,平均总收入为39.9×106kg/s。东亚夏季风的建立、推进对青藏高原东南部的水汽输入有重要影响,而青藏高原东南部的水汽输出则与夏季我国东部雨带的推进过程密切相关。该区对周边地区的水汽收支有重要影响,是向我国西北地区东部、长江中下游地区输送水汽的重要通道,青藏高原东南部的水汽"转运站"效应是长江中下游流域洪涝和北方夏季干旱异常的关键因子之一。青藏高原东南部东、北边界夏季水汽收支均具有准两年周期振荡特征,并分别与长江中下游、西北地区东部夏季降水的准两年振荡特征具有一定的联系。

Climatological characteristics of water vapor budget over the southeast part of Tibetan Plateau and their impacts on ambient areas in summer are investigated based on NCEP/NCAR reanalysis data for the period from 1961 to 2005. The result shows that the southeast part of Tibetan Plateau is a moisture sink, under the seasonal average of summer condition, the water vapor net budget is 39.9 × 10^6 kg/s. The establishment and advance of Asian summer monsoon play an important role in the incoming water vapor of the southeast part of Tibetan Plateau, and the outgoing moisture is closely associated with the advance and retreat of rain belt of East China. The southeast part of Tibetan Plateau, as the moisture transport channel to the east of Northwest China and mid-lower reaches of the Yangtze River, plays a great role in the moisture budget around it. The southeast part of Tibetan Plateau, as a transferring station, is one of the key factors to the flooding anomalies of precipitation in mid-lower reaches of the Yangtze River and the drought anomalies in North China. By power spectrum analysis, it is found that there is quasi-biennial oscillation in the interannual variations of moisture budgets at east/north boundary over the southeast part of Tibetan Plateau and summer precipitation of mid-lower reaches of the Yangtze River/eastern part of Northwest China. An in-phase inter-annual variation are shown by the moisture budgets at east boundary over the southeast part of Tibetan Plateau and the summer precipitation of mid-lower reaches of the Yangtze River, and the same to moisture budgets at north boundary and the summer precipitation of eastern part of Northwest China. It shows that the quasi-biennial oscillation of moisture budgets at east boundary is closely association with that of precipitation in mid-lower reaches of the Yangtze River, and the quasi-biennial oscillation of moisture budgets at north boundary is closely association with that of precipitation of the eastern part of Northwest China.