A tropospheric pathway of the stratospheric quasi-biennial oscillation (QBO) impact on the boreal winter polar vortex
A tropospheric pathway of the stratospheric quasi-biennial oscillation (QBO) impact on the boreal winter polar vortex
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DOI：
10.5194/acp-2019-1119
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发表时间：
2019-12
影响因子：
6.3
通讯作者：
K. Yamazaki;Tetsu Nakamura;J. Ukita;K. Hoshi
中科院分区：
文献类型：
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作者：
K. Yamazaki;Tetsu Nakamura;J. Ukita;K. Hoshi
抽象的。准两年期振荡（QBO）是平流层热带纬向风的准周期振荡。当热带低平流层风为东风（西风）时，冬季北半球（NH）平流层极地涡旋趋于弱（强）。这种关系被称为 Holton-Tan 关系。人们已经提出了这种关系的几种机制，特别是通过平流层路径将热带地区与高纬度地区联系起来。尽管 QBO 对对流层的影响已被广泛讨论，但 Holton-Tan 关系的对流层路径此前尚未被探索过。在这里，我们提出了 QBO 影响的对流层路径，这可能部分解释了初冬，特别是 11 月至 12 月期间的 Holton-Tan 关系。该研究基于对观测数据以及简单线性模型和大气环流模型（AGCM）模拟结果的分析。其机制概括为：QBO东位相伴随着热带对流层顶层气温变冷，增强了热带西太平洋上空的对流活动，抑制了印度洋上空的对流活动，从而增强了沃克环流。这种对流异常产生罗斯贝波列，传播到中纬度对流层，对气候驻波，特别是波数1产生相长干扰，导致行星波向上传播增强，极地涡旋减弱。
Abstract. The quasi-biennial oscillation (QBO) is quasi-periodic oscillation of the tropical zonal wind in the stratosphere. When the tropical lower stratospheric wind is easterly (westerly), the winter Northern Hemisphere (NH) stratospheric polar vortex tends to be weak (strong). This relation is known as the Holton–Tan relationship. Several mechanisms for this relationship have been proposed, especially linking the tropics with high latitudes through stratospheric pathway. Although QBO impacts on the troposphere have been extensively discussed, a tropospheric pathway of the Holton–Tan relationship has not been explored previously. Here, we propose a tropospheric pathway of the QBO impact, which may partly account for the Holton–Tan relationship in early winter, especially in the November–December period. The study is based on analyses of observational data and results from a simple linear model and atmospheric general circulation model (AGCM) simulations. The mechanism is summarized as follows: the easterly phase of the QBO is accompanied with colder temperature in the tropical tropopause layer, which enhances convective activity over the tropical western Pacific and suppresses it over the Indian Ocean, thus enhancing the Walker circulation. This convection anomaly generates a Rossby wave train, propagating into the midlatitude troposphere, which constructively interferences with the climatological stationary waves, especially in wavenumber 1, resulting in enhanced upward propagation of the planetary wave and a weakened polar vortex.