夏季青藏高原大气热源与西南地区东部旱涝的关系

Contemporaneous Relationships between Summer Atmospheric Heat Source over the Tibetan Plateau and Drought/Flood in Eastern Southwest China

利用1959～2006年西南地区东部20个测站逐日降水量资料和NCEP/NCAR再分析月平均资料,分析了夏季青藏高原大气热源特征,指出了影响西南地区东部夏季旱涝的热源关键区域,并就关键区大气热源对该区域夏季旱涝的影响进行了诊断,得出了以下主要结论:西南地区东部夏季降水与高原主体东南部的热源变化关系密切,当该区域(该区域的平均大气热源值定义为热源指数)大气热源偏强时,西南地区东部夏季降水偏多的可能性大。当夏季青藏高原关键区大气热源值偏强(偏弱)时,西太平洋副高和南亚高压脊线位置偏南(偏北),东亚夏季风偏弱(偏强),出现有利于西南地区东部夏季降水偏多(偏少)的环流形势;同时西南地区东部夏季水汽输送增强(减弱),水汽辐合上升运动也增强(减弱),因此,该地区夏季降水容易偏多(偏少),出现洪涝(干旱)的可能性大。

Based on the NCEP/NCAR reanalysis monthly data and daily precipitation data at 20 stations in eastern Southwest China from 1959 to 2006,the features of atmospheric heat source over the Tibetan Plateau and the key area associated with the drought/flood in summer over eastern Southwest China have been analyzed.Results show that there is a close relationship between the flood/drought over eastern Southwest China and the intensity of the atmospheric heat source over southeastern Tibetan Plateau（key area）,i.e.,the rainfall is more than normal while the heat source is stronger.It is propitious to appearance of circulation making for the summer rainfall in eastern Southwest China;furthermore,the vapor transport and convergent upward velocity are strengthened,the East Asian summer monsoon is weaker,and the ridge positions of the western Pacific subtropical high and South Asia high lean to south when the intensity of the atmospheric heat source over eastern Tibetan Plateau（key area） is stronger than normal,vice versa.