Changes in Moisture Flux over the Tibetan Plateau during 1979-2011 and Possible Mechanisms
Changes in Moisture Flux over the Tibetan Plateau during 1979-2011 and Possible Mechanisms
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DOI：
10.1175/jcli-d-13-00321.1
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发表时间：
2014-03-01
影响因子：
4.9
通讯作者：
Zhang, Yongxin
中科院分区：
文献类型：
--
作者：
Gao, Yanhong;Cuo, Lan;Zhang, Yongxin
利用全球陆地资料同化系统（GLDAS）集合平均径流和再分析资料，分析了1979-2011年青藏高原地区降水-蒸散（P - E）的变化特征及其可能原因。结果表明，TP总体上变湿，但空间变化较大。气候湿润的东南部TP变得越来越干燥，而广大的干旱和半干旱的西北部TP变得越来越湿润。Clausius-Clapeyron关系式不能解释TP上P-E的变化，通过将P-E的变化分解为动力、热力和瞬态涡动三个主要分量，发现动力分量在TP上P-E的变化中起着关键作用。热力分量对TP南部和中部有正贡献，而瞬变涡动分量对TP南部和北方部分地区（TP中部）的动力分量有加强（抵消）的趋势，在季节上，动力分量对湿季P-E变化贡献较大，热力和瞬变涡动分量贡献较小.进一步的分析揭示了东亚西风急流的极移0.7度和极向水汽输送以及由于全球变暖而加强的夏季风环流，这些都是造成TP普遍增湿趋势的原因。它进一步表明，由于TP及其周围环境的差异加热发生的局部环流的变化是负责在TP的水分的空间变化的变化。
Changes in moisture as represented by P - E (precipitation - evapotranspiration) and the possible causes over the Tibetan Plateau (TP) during 1979-2011 are examined based on the Global Land Data Assimilation Systems (GLDAS) ensemble mean runoff and reanalyses. It is found that the TP is getting wetter as a whole but with large spatial variations. The climatologically humid southeastern TP is getting drier while the vast arid and semiarid northwestern TP is getting wetter. The Clausius-Clapeyron relation cannot be used to explain the changes in P - E over the TP.Through decomposing the changes in P - E into three major components-dynamic, thermodynamic, and transient eddy components-it is noted that the dynamic component plays a key role in the changes of P - E over the TP. The thermodynamic component contributes positively over the southern and central TP whereas the transient eddy component tends to reinforce (offset) the dynamic component over the southern and parts of the northern TP (central TP).Seasonally, the dynamic component contributes substantially to changes in P - E during the wet season, with small contributions from the thermodynamic and transient eddy components. Further analyses reveal the poleward shift of the East Asian westerly jet stream by 0.7 degrees and poleward moisture transport as well as the intensification of the summer monsoon circulation due to global warming, which are shown to be responsible for the general wetting trend over the TP. It is further demonstrated that changes in local circulations that occur due to the differential heating of the TP and its surroundings are responsible for the spatially varying changes in moisture over the TP.