青藏高原夏季大气视热源与中国东部降水的关系的年代际变化

Interdecadal Change in the Relation between Atmospheric Apparent Heat Sources over Tibetan Plateau and Precipitation in Eastern China in Summer

基于1979~2017年欧洲中期天气预报中心(ECMWF)提供的ERA-Interim逐日再分析资料和热力学方程,本研究估算了大气视热源,分析研究了青藏高原夏季大气视热源的异常与中国东部降水关系的年代际变化,以及青藏高原大气视热源影响我国东部夏季降水的物理机制。结果表明:(1)高原热源东、西部反相变化模态的重要性发生了年代际转变,表现为由1994年之前方差贡献相对小的第二变异模态变为1994之后方差贡献明显增大而成为第一主导变异模态。(2)青藏高原夏季大气视热源的东、西反相变化模态与中国东部降水的关系存在年代际变化。1993年之前和2008年之后,高原大气视热源的异常分别仅与长江下游降水和长江中游降水异常存在密切的联系;而在1994~2007年,其对长江流域及附近区域和华南地区的夏季降水的影响显著,具体表现为,当高原夏季大气视热源异常表现为东强西弱(东弱西强)时,长江中上游、江淮地区的降水偏多(少),华南地区降水偏少(多)。(3)高原大气视热源显著影响我国东部夏季降水主要是通过经高原上空发展加强的天气系统东移过程影响长江流域及附近地区的降水,以及通过垂直环流影响华南地区的降水。

Based on the ERA-Interim reanalysis data provided by the European Centre for Medium Range Weather Forecasts(ECMWF),in this study,we estimated atmospheric apparent heat sources using a thermal equation.We investigated the interdecadal change in the relation between the atmospheric apparent heat sources over the Tibetan Plateau in summer and the summer precipitation in eastern China,and the mechanism of the impact of these heat sources on the summer precipitation in eastern China.We found the variance in the west-east dipole mode of the atmospheric apparent heat sources over the Tibetan Plateau in summer to exhibit an interdecadal increase,which illustrates the increasing importance of the west-east dipole mode from the second leading mode prior to 1994 to the first mode after 1994.The relationship between the atmospheric apparent heat sources over the Tibetan Plateau and precipitation in eastern China exhibited interdecadal changes around 1994 and 2007.The summer abnormal heat sources over the Tibetan Plateau are closely related only to the precipitation anomalies over the lower reaches of the Yangtze River prior to 1993 and those over the middle Yangtze River after 2008,but are related to the summer precipitation in the Yangtze River Basin and adjacent and southern China regions from 1994-2007.Specifically,the strong(weak)heat sources over the eastern Plateau in summer correspond to abundant(scarce)precipitation over the upper and middle reaches of the Yangtze River and the Huaihe River Basin,with less(more)rainfall in southern China.We found the atmospheric apparent heat sources over the Tibetan Plateau to influence the summer precipitation in the Yangtze River Basin and adjacent regions mainly through the eastward movement of the weather systems that develop as they pass over the Plateau,as well as the precipitation in southern China through anomalous vertical circulation.