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Intraseasonal Variability of the Zonal-Mean Extratropical Tropopause: The Role of Changes in Polar Vortex Strength and Upper-Troposphere Wave Breaking.

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Barroso Pellico, Jesús Ángel and Zurita Gotor, Pablo (2016) Intraseasonal Variability of the Zonal-Mean Extratropical Tropopause: The Role of Changes in Polar Vortex Strength and Upper-Troposphere Wave Breaking. Journal of the atmospheric sciences, 73 (3). pp. 1383-1399. ISSN 0022-4928

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Official URL: http://dx.doi.org/10.1175/JAS-D-15-0177.1


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Abstract

A principal component analysis of the Northern Hemisphere extratropical zonal-mean tropopause variability at intraseasonal time scales is presented in this work. Wavy deformations of the tropopause dominate this variability and explain significantly more variance than changes in the extratropical-mean tropopause height. The first mode is well correlated with the zonal index. Analysis of the dynamical evolution of the modes shows that tropopause deformations are caused by anomalous wave breaking at the tropopause level occurring in a preexisting anomalous stratospheric polar vortex. Specifically, an intense (weak) polar vortex is associated with a rising (sinking) of the polar tropopause, while anomalous wave breaking in the midlatitudes produces a dipolar tropopause change that is consistent with the anomalous meridional eddy flux of quasigeostrophic potential vorticity. These two forcings operate on different time scales and can be separated when the data are filtered at high or low frequency. Baroclinic equilibration seems to play a small role in the extratropical internal tropopause variability and the impact of tropospheric and stratospheric dynamics is quantitatively similar. A similar analysis for the Southern Hemisphere extratropics displays the same qualitative behavior.


Item Type:Article
Additional Information:

© 2015 American Meteorological Society.
This work was supported by the COMETH project (Grant CGL2013-30641) of the Ministerio de Economía y Competitividad of Spain. We are grateful to two anonymous reviewers for their constructive comments.

Uncontrolled Keywords:Tropopause; Atm/Ocean Structure/ Phenomena; Planetary waves; Circulation/ Dynamics; Wave breaking; Stratosphere-troposphere coupling; Potential vorticity.
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
Sciences > Physics > Geophysics
ID Code:37190
Deposited On:18 Apr 2016 15:22
Last Modified:01 Oct 2016 23:01

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