Contribution of the phase transition of Pacific Decadal Oscillation to the late 1990s' shift in East China summer rainfall
Contribution of the phase transition of Pacific Decadal Oscillation to the late 1990s' shift in East China summer rainfall
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DOI：
10.1002/2015jd023545
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发表时间：
2015-09
期刊：
影响因子：
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通讯作者：
Yali Zhu;Huijun Wang;Jiehua Ma;Tao Wang;Jianqi Sun
中科院分区：
文献类型：
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作者：
Yali Zhu;Huijun Wang;Jiehua Ma;Tao Wang;Jianqi Sun
本文在前人研究的基础上，进一步探讨了90年代末中国东部夏季降水的年代际变化。局地上升运动的增加是黄淮下游降水增加的主导因素。使用社区大气模式第4版的观测和数值试验都表明，负太平洋年代际涛动(PDO)模式可以导致异常上升，从而导致低层大气环流的降水增加。东亚西风急流(EAWJS)是连接太平洋海温异常与东亚夏季降水的桥梁。模式结果表明，负的PDO模可以导致东亚地区显著的东风异常。其结果是，东亚夏季风减弱并向极地移动，这与1990年代末以后观测到的东亚夏季风的变化相吻合。此外，减弱和极移的EAWJS可以通过调制与急流有关的次级经向垂直环流而导致其南侧(LHR)的异常上升运动。因此，1990年代后期以后，LHR的降雨量增加。此外，正大西洋经向涛动只能引起东亚上空不显著的变化，部分抵消了东亚地区的负PDO效应。
Based on our previous study, the interdecadal changes in summer rainfall over East China in the late 1990s are further explored here. The increased local rising motion is implicated as the dominant factor of increased rainfall in the lower Huang‐Huai River valley (LHR). Both the observation and numerical experiments using Community Atmosphere Model, version 4 suggest that the negative Pacific Decadal Oscillation (PDO) mode can result in rising anomalies and thus more rainfall in the LHR. The East Asian westerly jet stream (EAWJS) is suggested as a bridge to link the Pacific sea surface temperature anomalies and East Asian summer rainfall. Model results reveal that the negative PDO mode can lead to significant easterly anomalies over East Asia. As a result, the EAWJS is weakened and shifts poleward, which coincides with observed changes in EAWJS after the late 1990s. In addition, weakened and poleward shifted EAWJS can result in an anomalous ascending motion to its south (in the LHR) by modulating the jet‐related secondary meridional‐vertical circulation. Consequently, rainfall increased in the LHR after the late 1990s. Besides, the positive Atlantic Meridional Oscillation can only induce insignificant changes over East Asia and partly counteract the negative PDO effect there.