論文

査読有り
2020年4月30日

A tropospheric pathway of the stratospheric quasi-biennial oscillation (QBO) impact on the boreal winter polar vortex

Atmospheric Chemistry and Physics
  • Koji Yamazaki
  • ,
  • Tetsu Nakamura
  • ,
  • Jinro Ukita
  • ,
  • Kazuhira Hoshi

20
8
開始ページ
5111
終了ページ
5127
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.5194/acp-20-5111-2020

<jats:p>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.
</jats:p>

リンク情報
DOI
https://doi.org/10.5194/acp-20-5111-2020

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