Three different downstream fates of the boreal-summer MJOs on their passages over the Maritime Continent
Three different downstream fates of the boreal-summer MJOs on their passages over the Maritime Continent
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DOI：
10.1007/s00382-017-3985-2
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发表时间：
2018-09
期刊：
影响因子：
4.6
通讯作者：
Joshua X. Fu;Wanqiu Wang;H. Ren;Xiaolong Jia;T. Shinoda
中科院分区：
文献类型：
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作者：
Joshua X. Fu;Wanqiu Wang;H. Ren;Xiaolong Jia;T. Shinoda
北半球夏季MJO在其通过海洋大陆（MC）时表现出三种不同的下游演变：（i）从印度洋（IO）平稳过渡到西太平洋（I型）;（ii）在MC上迅速衰减（II型）;（iii）在MC上显著增强（III型）。在I型和III型MJO的生命周期中，流域范围的翻转环流连接了北太平洋西部和东部之间的对流偶极子。对于II型MJO，区域翻转环流连接IO和西北太平洋（WNP）之间的对流偶极子。对于I型和III型MJO，IO东部上空的相关对流能够在MC和西太平洋上空产生强烈的Kevin波响应和显著的正SST异常。另一方面，对于IO中的II型MJO，WNP周围存在持续的对流。它加强了西风季风流，从而阻止了在IO MJO对流之前产生相干的正SST异常。它还通过延迟干相向东北方向的迁移，阻止了在MC和西太平洋形成一个强大的开尔文波响应。I型和III型MJO在IO东部的对流能够产生正的边界层水汽异常沿着与正的柱积分水汽趋势在MC和西太平洋，从而使他们顺利地向东传播。另一方面，II型MJO对流在IO东部是与一个非常干燥的对流层和负的柱集成的水汽趋势在西太平洋，这导致在MC对流的快速衰减。这些结果强调了强大的开尔文波响应和积极的SST异常的北半球夏季MJO在MC通过湿润对流层前向东传播的重要作用。
The boreal-summer MJOs exhibit three distinctive downstream evolutions on their passages over the Maritime Continent (MC): (i) smoothly transitioning from Indian Ocean (IO) to western Pacific (type-I); (ii) rapidly decayed over the MC (type-II); and (iii) significantly intensified over the MC (type-III). During the life cycles of type-I and -III MJOs, basin-wide overturning circulations connect the convective dipoles between western and eastern north Pacific. For type-II MJO, regional overturning circulations connect the convective dipoles between the IO and Western North Pacific (WNP). For type-I and -III MJOs, the associated convection over eastern IO is able to generate strong Kevin-wave responses and significant positive SST anomalies over the MC and western Pacific. On the other hand, for type-II MJO in the IO, a persistent convection lingers around the WNP. It intensifies westerly monsoon flows, thus preventing the generation of coherent positive SST anomalies ahead of the IO MJO convection. It also blocks the formation of a robust Kelvin-wave response over the MC and western Pacific by delaying the northeastward migrations of the dry phase. The convection of type-I and -III MJOs at eastern IO is able to generate positive boundary-layer moisture anomalies along with positive column-integrated moisture tendencies over the MC and western Pacific, thus allowing them to propagate eastward smoothly. On the other hand, the type-II MJO convection in eastern IO is associated with a very dry troposphere and negative column-integrated moisture tendency over western Pacific, which result in the rapid decay of convection over the MC. These results emphasize the important roles of robust Kelvin-wave responses and positive SST anomalies on the eastward propagation of boreal-summer MJOs over the MC through moistening the troposphere ahead of the convection.