論文

査読有り
2020年4月

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
出版者・発行元
COPERNICUS GESELLSCHAFT MBH

The quasi-biennial oscillation (QBO) is quasiperiodic 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.


リンク情報
DOI
https://doi.org/10.5194/acp-20-5111-2020
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000531565400002&DestApp=WOS_CPL

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