Study of troposphere–stratosphere coupling through the Northern Annular Mode

Coupling between troposphere and stratosphere through the Northern Annular Mode (NAM) is studied. Cluster analysis of NAM indices at various levels is used in order to reduce the number of the NAM series to two: one tropospheric and one stratospheric. Once the periods when the tropospheric and strat...

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Bibliographic Details
Published in:Journal of atmospheric and solar-terrestrial physics 2006-06, Vol.68 (9), p.989-998
Main Authors: de la Torre, Laura, Gimeno, Luis, Añel, Juan Antonio, Nieto, Raquel
Format: Article
Language:English
Subjects:
Earth, ocean, space
Exact sciences and technology
External geophysics
Northern Annular Mode
Physics of the high neutral atmosphere
Physics of the ionosphere
Physics of the magnetosphere
Stratosphere–troposphere coupling
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Summary:Coupling between troposphere and stratosphere through the Northern Annular Mode (NAM) is studied. Cluster analysis of NAM indices at various levels is used in order to reduce the number of the NAM series to two: one tropospheric and one stratospheric. Once the periods when the tropospheric and stratospheric clusters have similar variability (called “coupled”) are detected, EOF analysis provides the principal modes of variability when the troposphere and the stratosphere are considered coupled and uncoupled. The spatial patterns of variability are very different depending on coupling. The most important difference is found in the spatial pattern in the troposphere (which shows a wave 3 pattern for coupled periods and a NAO-like pattern for uncoupled periods). Then, we distinguish between coupled periods with dominant stratosphere (when the influence of the stratosphere over the troposphere is greater than the influence of the troposphere over the stratosphere) or troposphere (the inverse situation) and analyze the behavior of Eliassen-Palm and Plumb fluxes in each case.
ISSN:1364-6826
1879-1824
DOI:10.1016/j.jastp.2005.12.003