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The tropopause and the thermal stratification in the extratropics of a dry atmosphere

Schneider, Tapio (2004) The tropopause and the thermal stratification in the extratropics of a dry atmosphere. Journal of the Atmospheric Sciences, 61 (12). pp. 1317-1340. ISSN 0022-4928. http://resolver.caltech.edu/CaltechAUTHORS:SCHNjas04

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Abstract

A dynamical constraint on the extratropical tropopause height and thermal stratification is derived by considerations of entropy fluxes, or isentropic mass fluxes, and their different magnitudes in the troposphere and stratosphere. The dynamical constraint is based on a relation between isentropic mass fluxes and eddy fluxes of potential vorticity and surface potential temperature and on diffusive eddy flux closures. It takes baroclinic eddy fluxes as central for determining the extratropical tropopause height and thermal stratification and relates the tropopause potential temperature approximately linearly to the surface potential temperature and its gradient. Simulations with an idealized GCM point to the possibility of an extratropical climate in which baroclinic eddy fluxes maintain a statically stable thermal stratification and, in interaction with large-scale diabatic processes, lead to the formation of a sharp tropopause. The simulations show that the extratropical tropopause height and thermal stratification are set locally by extratropical processes and do not depend on tropical processes and that, across a wide range of atmospheric circulations, the dynamical constraint describes the relation between tropopause and surface potential temperatures well. An analysis of observational data shows that the dynamical constraint, derived for an idealized dry atmosphere, can account for interannual variations of the tropopause height and thermal stratification in the extratropics of the earth's atmosphere. The dynamical constraint implies that if baroclinic eddies determine the tropopause height and thermal stratification, an atmosphere organizes itself into a state in which nonlinear interactions among eddies are inhibited. The inhibition of nonlinear eddy–eddy interactions offers an explanation for the historic successes of linear and weakly nonlinear models of large-scale extratropical dynamics.


Item Type:Article
Additional Information:© 2004 American Meteorological Society. Manuscript received 8 October 2002, in final form 5 December 2003. My thanks go to Isaac Held for advice on the research on which this paper is based and on constructing the idealized GCM, and for many discussions over several years that helped to clarify, among other things, the commonalities and differences between the theoretical developments of this paper and quasigeostrophic theory. The simulations described in section 4c were prompted by discussions with Kerry Emanuel, Richard Lindzen, and Alan Plumb. I also thank Vladimir Gryanik, Peter Haynes, Paul Kushner, Shafer Smith, Ka-Kit Tung, and a reviewer for helpful discussions and comments on the paper, and Heidi Swanson for editing the manuscript. Parts of the research on which this paper is based were carried out while I was with the Courant Institute of Mathematical Sciences at New York University (supported partially by NSF Grant DMS-9972865 and ONR Grant N00014-96-1-0043) and with the Atmospheric and Oceanic Sciences Program at Princeton University (supported by a NASA Earth System Science Fellowship).
Subject Keywords:ZONALLY AVERAGED CIRCULATION; BAROCLINIC ADJUSTMENT; STATIC STABILITY; BETA-PLANE; NONGEOSTROPHIC THEORY; GENERAL-CIRCULATION; LOWER STRATOSPHERE; HEAT-TRANSPORT; MEAN FLOWS; TROPOSPHERE
Record Number:CaltechAUTHORS:SCHNjas04
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SCHNjas04
Alternative URL:http://dx.doi.org/10.1175/1520-0469(2004)061<1317:TTATTS>2.0.CO;2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7146
Collection:CaltechAUTHORS
Deposited By: Lindsay Cleary
Deposited On:10 Jan 2007
Last Modified:26 Dec 2012 09:29

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