Two major modes of variability of the East Asian summer monsoon
Two major modes of variability of the East Asian summer monsoon
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东亚夏季风的两种主要变化模式
DOI：
10.1002/qj.635
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发表时间：
2010-04-01
影响因子：
8.9
通讯作者：
Latif, Mojib
中科院分区：
文献类型：
--
作者：
Sun, Xuguang;Greatbatch, Richard J.;Latif, Mojib
我们研究了与东亚夏季风相关的两种主要的变率模态，这两种模态是使用多变量经验正交函数（ERF）分析确定的。第二种模态与100 hPa南亚高压强度的变化有关，而与以前的工作一致，第一种模态与季风区850 hPa纬向风切变涡度指数有关。我们发现，一个线性的，干的动力学模型，当驱动的非绝热加热异常与每个模式，可以重现许多异常的环流特征，特别是第一次对流层和低层。模式结果表明热带印度洋上空非绝热加热异常在两种模态动力学中的重要性，特别是在1991 - 1992年的1991 - 1991年的1991 - 1992年的1992 - 19993年的19991 - 19993年的19992 - 19993年的1999运行交叉相关分析表明，第二次厄尔尼诺与整个研究期间（1958-2001年）厄尔尼诺/南方涛动（ENSO）事件的衰减和开始阶段始终相关。我们属性的连接，在发病阶段的纬向风异常沿着赤道在西太平洋与此模式。另一方面，只有在1979年之后才发现第一次厄尔尼诺现象和ENSO之间的联系。我们还注意到热带印度洋海表温度异常在2001年动力学中的作用，以及与2002年印度夏季风变化的联系。皇家气象学会
We study the two primary modes of variability associated with the East Asian summer monsoon, as identified using a multivariate Empirical Orthogonal Function (EOF) analysis. The second mode is shown to be related to changes in intensity of the South Asian High at 100 hPa while, consistent with previous work, the first mode is associated with an index for the shear vorticity of the 850 hPa zonal wind over the monsoon region. We show that a linear, dry dynamical model, when driven by the diabatic heating anomalies associated with each mode, can reproduce many of the anomalous circulation features, especially for the first EOF and in the lower troposphere. The model results indicate the importance of diabatic heating anomalies over the tropical Indian Ocean in the dynamics of both modes, especially EOF‐1, and illustrate the role of local diabatic feedback for intensifying the circulation anomalies; in particular, the subtropical anticyclonic anomalies that are found in the positive phase of both modes, and the circulation anomaly associated with the Meiyu/Changma/Baiu rain band. A running cross‐correlation analysis shows that the second EOF is consistently linked to both the decaying and the onset phase of El Niño/Southern Oscillation (ENSO) events throughout the study period (1958–2001). We attribute the connection in the onset phase to zonal wind anomalies along the Equator in the west Pacific associated with this mode. On the other hand, a link between the first EOF and ENSO is found only in the post‐1979 period. We note also the role of sea‐surface temperature anomalies in the tropical Indian Ocean in the dynamics of EOF‐1, and a link to the variability of the Indian summer monsoon in the case of EOF‐2. Copyright © 2010 Royal Meteorological Society