第31回 ESCセミナー
Solar Influence on Stratosphere-Troposphere Dynamical Coupling
- 日時
- 2007年11月12日(月) 11:00-12:00
- 場所
- 横浜研究所 シミュレータ研究棟1階 大会議室
- 講演者
- Mike Blackburn(1)
Joanna D. Haigh(2)
Isla Simpson(2)
Sarah Sparrow (1,2)
(1) Department of Meteorology, University of Reading
(2) Department of Physics, Imperial College London - 使用言語
- 英語
要旨
The observed tropospheric response to the 11-year solar cycle involves a weakening and poleward shift of the mid-latitude jets at solar Maximum compared to solar minimum. This extra-tropical response is obtained in atmospheric GCMs when the stratospheric response to increased UV absorption by stratospheric ozone at solar maximum is imposed. An idealised atmospheric GCM has been used to investigate the mechanisms which determine the tropospheric response to imposed distributions of heating in the lower stratosphere. The equilibrated response in the troposphere is shown to be dynamical and to involve transient eddy feedbacks on the zonal mean flow. Ensemble spin-up experiments show that initial changes at the tropopause associated with stratospheric heating alter the propagation of wave activity and that this initiates a feedback which displaces the jet and storm-track.
The tropospheric response projects strongly onto the natural annular variability of the idealised GCM. The dynamics of this variability are investigated, revealing quite different behaviour on short and long timescales. The low frequency variability comprises periods of poleward migration of the jet driven by transient eddy momentum flux anomalies,closely resembling the equilibrium response to forcing.
This study is relevant to other research on the tropospheric response to stratospheric forcing, which has focused more on the downward influence of changes in the stratospheric polar vortex, and to the extra-tropical response to global warming, where models predict poleward migration of the jets and storm-tracks.
問い合わせ先
地球シミュレータセンター大気・海洋シミュレーション研究グループ
大淵 済
Phone : 045-778-5765
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