Madden–Julian Oscillation impacts on South American summer monsoon season: precipitation anomalies, extreme events, teleconnections, and role in the MJO cycle
Madden–Julian Oscillation impacts on South American summer monsoon season: precipitation anomalies, extreme events, teleconnections, and role in the MJO cycle
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DOI：
10.1007/s00382-019-04622-6
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发表时间：
2019-01
期刊：
影响因子：
4.6
通讯作者：
A. Grimm
中科院分区：
文献类型：
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作者：
A. Grimm
在对流和环流传播异常的全球背景下，分析了麦登朱利安涛动（MJO）对南美季风季节的影响。在整个周期中，揭示了MJO频带的大陆尺度日降水异常和极端降雨事件频率的变化等未被探索的方面。在其他影响中，MJO使平均日降水量增加了气候学值的30%以上，并使南美洲中东部（SA），包括南大西洋辐合带（SACZ）的极端事件频率增加了一倍。大多数强降水异常的演变取决于热带-热带和热带-温带遥相关的相互作用，而南亚中东部的地形似乎对低层辐合起着增强作用。最大异常是由热带-温带波列产生的。它不仅有利于南亚南区和副热带南风的降水异常，而且在系统向东北传播过程中增强了热带南风的降水异常。对与MJO异常对流相关的高空异常辐散不同分量响应的影响函数分析和模拟表明，导致南亚主要降水异常的异常环流的可能来源。它是由次级异常对流触发的，而主要的热带异常环流是由最强的赤道对流异常产生的。有迹象表明，南太平洋MJO相关的异常有助于对其他区域的影响，并有助于印度洋MJO的开始。
The impacts of the Madden Julian Oscillation (MJO) on the South American monsoon season are analyzed in the global context of the MJO propagating anomalies of convection and circulation. Unexplored aspects, such as the continental-scale daily precipitation anomalies in the MJO frequency band and changes in the frequency of extreme rainfall events, are disclosed throughout its cycle. Among other effects, the MJO increases the average daily precipitation by more than 30% of the climatological value and doubles the frequency of extreme events over central-east South America (SA), including the South Atlantic Convergence Zone (SACZ). The evolution of the most intense precipitation anomalies depends on the interplay between tropics–tropics and tropics–extratropics teleconnections, and the topography over central-east SA seems to play a role in enhancing low-level convergence. The maximum anomalies are produced by a tropics-extratropics wave train. It not only favors precipitation anomalies over the SACZ and subtropical SA, but also strengthens the anomalies over tropical SA when the system propagates northeastward. Influence function analysis and simulations of the responses to different components of upper-level anomalous divergence associated with the MJO anomalous convection indicate the probable origin of the anomalous circulation leading to the main precipitation anomalies over SA. It is triggered by secondary anomalous convection, while the main tropical anomalous circulation is produced by the strongest equatorial convection anomalies. There are indications that MJO-related anomalies over SA contribute to the impacts on other regions and to the initiation of the MJO in the Indian Ocean.