MJO Initiation Triggered by Amplification of Upper-tropospheric Dry Mixed Rossby-gravity Waves
MJO Initiation Triggered by Amplification of Upper-tropospheric Dry Mixed Rossby-gravity Waves
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对流层上层干混合罗斯贝重力波放大引发的 MJO 引发
DOI：
10.1002/essoar.10507006.1
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Suematsu Tamaki
中科院分区：
文献类型：
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作者：
Takasuka Daisuke;Kohyama Tsubasa;Miura Hiroaki;Suematsu Tamaki
提出了马登-朱利安振荡（MJO）对流引发的一个可能重要的动力学过程。 “CINDY2011”现场活动期间的MJO事件是由向东移动的对流层低层混合罗斯贝重力（MRG）波包触发的，其主要前兆是印度洋（IO）对流层上层MRG的主导地位。简单的三维模型实验表明，由于沃克环流平均东风带的上层辐合，IO 中的上层对流层 MRG 通过向西的平流和波浪积累而被放大，特别是在西 IO (WIO) 中。该模型还预测了放大的对流层上层 MRG 的向下扩散以及由此产生的对流层下层 MRG 波包的形成。这种 MRG 演化一致地解释了 CINDY2011 期间 MJO 的启动过程，并通过 MRG 的射线追踪进一步验证了这一过程。上层对流层环航开尔文波通过增强纬向辐合和减弱东风（增强东风）促进西风（东风）阶段的 MRG 波积累（平流），从而协助所提出的机制。
A possibly important dynamical process for the Madden–Julian oscillation (MJO) convective initiation is proposed. An MJO event during the “CINDY2011” field campaign is triggered by eastward‐moving lower‐tropospheric mixed Rossby‐gravity (MRG) wave packets, and its leading precursor is predominance of upper‐tropospheric MRGs in the Indian Ocean (IO). Simple three‐dimensional model experiments reveal that the upper‐tropospheric MRGs in the IO are amplified particularly in the western IO (WIO) by their westward advection and wave accumulation due to the upper‐level convergence in mean easterlies of the Walker circulation. The model also predicts downward dispersion of the amplified upper‐tropospheric MRGs and resultant lower‐tropospheric MRG wave packet formation. This MRG evolution consistently explains the MJO initiation process during CINDY2011, which is further verified by ray tracing for MRGs. Upper‐tropospheric circumnavigating Kelvin waves assist the proposed mechanism by promoting MRG‐wave accumulation (advection) in their westerly (easterly) phases via enhanced zonal convergence and weakened easterlies (enhanced easterlies).