Using simplified linear and nonlinear models to assess ENSO-modulated MJO teleconnections
Using simplified linear and nonlinear models to assess ENSO-modulated MJO teleconnections
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DOI：
10.1007/s00382-023-06864-x
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发表时间：
2023-06
期刊：
影响因子：
4.6
通讯作者：
Marybeth Arcodia;B. Kirtman
中科院分区：
文献类型：
--
作者：
Marybeth Arcodia;B. Kirtman
简单的动力学模型是用来了解如何ENSO调制亚季节遥相关的MJO的热带印记剥离复杂的现象的基本过程。利用一个干线性斜压模式和一个干非线性斜压模式，（1）评估了在特定的ENSO位相中，线性和非线性动力学能捕捉到多少MJO遥相关型;（2）分析了ENSO调制的MJO强迫和基态在再现遥相关型中的作用。模拟实验表明，线性动力学是足够的，在捕捉与厄尔尼诺和拉尼娜现象的MJO在北方半球遥相关之间的差异。非线性动力学适度捕获更多的北方半球MJO遥相关模式，特别是在北美，这表明北美的遥相关响应更为复杂。遥相关型对ENSO背景状态和月MJO相关强迫域的变化都很敏感。应用Rossby波源诊断来进一步理解潜在的机制。此外，一系列的实验交换MJO强迫在厄尔尼诺事件与拉尼娜事件与ENSO中性的基本状态，反之亦然，表明MJO强迫有一个更大的遥相关模式比基本状态的影响。因此，ENSO对MJO对流的调制主导了北方半球遥相关型的ENSO相位相关变化。这些模拟实验强调，MJO遥相关必须考虑在正在进行的ENSO事件的背景下。
Simple dynamical models are used to understand fundamental processes of how ENSO modulates subseasonal teleconnections associated with tropical imprints of the MJO by stripping away complex phenomena. Both a dry linear baroclinic model and a dry nonlinear baroclinic model are employed to (1) assess how much of the MJO teleconnection pattern in a particular ENSO phase can be captured by linear and nonlinear dynamics and (2) analyze the role of the ENSO-modulated MJO forcing and base state in reproducing the teleconnection patterns. The modeling experiments reveal that linear dynamics are sufficient in capturing differences between the Northern Hemisphere teleconnections associated with the MJO during El Niño and La Niña. Nonlinear dynamics modestly capture more of the Northern Hemisphere MJO teleconnection pattern, particularly over North America, suggesting the teleconnection response over North America is more complex. The teleconnection patterns are sensitive to changes in both the ENSO background state and the domain of the monthly MJO-associated forcing. A Rossby wave source diagnosis is applied to further understand the underlying mechanisms. Further, a series of experiments swapping MJO forcings during El Niño events versus La Niña events with an ENSO-neutral base state and vice versa show that the MJO forcing has a larger influence over the teleconnection pattern than the base state. Therefore, the modulation of the MJO convection by ENSO dominates the ENSO-phase-dependent changes to the Northern Hemisphere teleconnection pattern. These modeling experiments highlight that MJO teleconnections must be considered in the context of the ongoing ENSO event.