QBO/Solar Influences on the Tropical Madden‐Julian Oscillation: A Mechanism Based on Extratropical Wave Forcing in Late Fall and Early Winter
QBO/Solar Influences on the Tropical Madden‐Julian Oscillation: A Mechanism Based on Extratropical Wave Forcing in Late Fall and Early Winter
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DOI：
10.1029/2022jd037824
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发表时间：
2023-03
期刊：
影响因子：
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通讯作者：
L. Hood;Natasha E. Trencham;Thomas J. Galarneau
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文献类型：
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作者：
L. Hood;Natasha E. Trencham;Thomas J. Galarneau
利用41年的再分析资料和存档的气候模式资料，研究了平流层准两年振荡（QBO）和11年太阳周期对热带Madden-Julian振荡（MJO）调制的可能来源。在秋末和初冬，QBO的东风阶段比西风阶段观测到更大的对流层外行星尺度波的向上通量，在某些情况下导致平流层突然变暖（SSW）（“霍尔顿-谭效应”）。平均而言，在太阳极小期相对于太阳极大期出现类似但较小的增加。除了高纬度地区的变暖外，热带外波强迫事件还导致热带平流层下部的冷却和静力稳定度降低。在这里，发现如果SSW发生在初冬（1月中旬之前），平均而言，静态稳定性降低会产生统计上显著的MJO滞后加强。因此，这代表了一种可能的机制，用于生产，或至少增强，所观察到的QBO和太阳调制的MJO在北方冬季。存档的气候模式数据的初步分析表明，至少有一个模型版本与现实的QBO和太阳强迫和4 × $\次$CO2强迫部分模拟这两个特点（QBO/太阳调制初冬波强迫和滞后加强的MJO以下初冬SSW）。然而，建模的MJO对QBO引起的静态稳定性降低不够敏感，排除了QBO-MJO连接的模拟。
Possible sources of the observed modulation of the tropical Madden‐Julian oscillation (MJO) by the stratospheric quasi‐biennial oscillation (QBO) and the 11‐year solar cycle are investigated using 41 years of reanalysis data and archived climate model data. Larger upward fluxes of extratropical planetary‐scale waves, leading in some cases to sudden stratospheric warmings (SSWs), are observed in late fall and early winter during the easterly phase of the QBO than during the westerly phase (the “Holton‐Tan effect”). A similar but smaller increase occurs, on average, during solar minima relative to solar maxima. In addition to the warming at high latitudes, extratropical wave forcing events produce cooling and reduced static stability in the tropical lower stratosphere. Here, it is found that if SSWs occur in early winter (before ∼mid‐January), the reduced static stability produces, on average, a statistically significant, lagged strengthening of the MJO. This therefore represents a possible mechanism for producing, or at least enhancing, the observed QBO and solar modulations of the MJO in boreal winter. An initial analysis of archived climate model data shows that at least one model version with realistic QBO and solar forcing and with 4 × $\times $ CO2 forcings partly simulates both of these characteristics (QBO/solar modulation of early winter wave forcing and lagged strengthening of the MJO following early winter SSWs). However, the modeled MJO is insufficiently sensitive to QBO‐induced static stability reductions, precluding simulation of the QBO‐MJO connection.