Relative Roles of Preconditioning Moistening and Global Circumnavigating Mode on the MJO Convective Initiation During DYNAMO
Relative Roles of Preconditioning Moistening and Global Circumnavigating Mode on the MJO Convective Initiation During DYNAMO
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DOI：
10.1029/2018gl080987
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发表时间：
2019-01-28
影响因子：
5.2
通讯作者：
Zhang, Fuqing
中科院分区：
文献类型：
--
作者：
Chen, Xingchao;Zhang, Fuqing
使用一系列对流允许的区域模式模拟研究了预处理增湿和全球环绕模式在2011年10月Madden-Julian振荡（MJO）事件的对流启动中的相对重要性，该事件是在Madden-Julian振荡（MJO）场活动的动力学期间观察到的。结果表明，在季节内尺度上，MJO对流的形成主要受全球环流模式的控制。与这种向东传播模式密切相关的快速增湿在MJO活跃期前几天是深对流和降水增强的关键。然而，这种增湿过程不能被“排放-补给”假说准确地描述，该假说推测了在大约2周的时间内逐渐积累水分导致活跃的MJO阶段到来的重要性。简单的语言总结Madden-Julian振荡（MJO）是热带地区季节内（20-100天）变化的主要模式。MJO的对流开始对应于热带海洋上空从主要的浅云到广泛的深对流的过渡。有关MJO对流启动的物理机制仍有争议。本研究使用了一系列的对流允许区域模型模拟表明，逐渐建立的润湿所描述的“放电-再充电”的假设不能准确地描述对流开始的10月MJO事件观察期间的动态的马登-朱利安振荡场运动。对流层中层的快速增湿对MJO对流的形成有重要作用。在季节内时间尺度上，全球向东传播的绕航模式主要是负责中层预处理增湿和最终的对流启动和增强降水的活跃MJO阶段。
The relative importance of preconditioning moistening and global circumnavigating mode in the convective initiation of the October 2011 Madden-Julian Oscillation (MJO) event observed during the Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign is investigated using a series of convection-permitting regional model simulations. It is demonstrated that the MJO convective initiation is largely controlled by the global circumnavigating mode at the intraseasonal scales. Rapid moistening closely related to this eastward propagating mode a few days prior to the MJO active phase is crucial to the initiation of deep convection and enhanced rainfall. This moistening process nevertheless cannot be accurately described by the "discharge-recharge" hypothesis, which speculates the importance a gradual moisture buildup over an approximately 2-week period leading to the arrival of the active MJO phase.Plain Language summary The Madden-Julian Oscillation (MJO) is a dominant mode of intraseasonal (20-100 days) variability over the tropics. The convective initiation of the MJO corresponds to a transition from predominate shallow clouds to widespread deep convection over tropical oceans. The physical mechanisms related to the MJO convective initiation are still debated. This study uses a series of convection-permitting regional model simulations to show that the gradual buildup of moistening described by the "discharge-recharge" hypothesis cannot accurately describe the convective initiation of the October MJO event observed during the Dynamics of the Madden-Julian Oscillation field campaign. Rapid moistening in the middle troposphere a few days before the MJO active phase is important to the MJO convective initiation. A global eastward propagating circumnavigating mode at the intraseasonal time scales is primarily responsible for the middle-level preconditioning moistening and the eventual convective initiation and enhanced rainfall during the active MJO phase.