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Published November 2008 | Published
Journal Article Open

Moist Convection and the Thermal Stratification of the Extratropical Troposphere

Abstract

Simulations with an aquaplanet general circulation model show that sensible and latent heat transport by large-scale eddies influences the extratropical thermal stratification over a wide range of climates, even in relatively warm climates with small meridional surface temperature gradients. Variations of the lapse rate toward which the parameterized moist convection in the model relaxes atmospheric temperature profiles demonstrate that the convective lapse rate only marginally affects the extratropical thermal stratification in Earth-like and colder climates. In warmer climates, the convective lapse rate does affect the extratropical thermal stratification, but the effect is still smaller than would be expected if moist convection alone controlled the thermal stratification. A theory for how large-scale eddies modify the thermal stratification of dry atmospheres is consistent with the simulation results for colder climates. For warmer and moister climates, however, theories and heuristics that have been proposed to account for the extratropical thermal stratification are not consistent with the simulation results. Theories for the extratropical thermal stratification will generally have to take transport of sensible and latent heat by large-scale eddies into account, but moist convection may only need to be taken into account regionally and in sufficiently warm climates.

Additional Information

© 2008 American Meteorological Society. (Manuscript received 16 October 2007, in final form 11 April 2008) We are grateful for support by the National Science Foundation (Grant ATM-0450059) and by a David and Lucile Packard Fellowship. The simulations were performed on Caltech's Division of Geological and Planetary Sciences Dell cluster. Both the program code for the simulations, based on the Flexible Modeling System of the Geophysical Fluid Dynamics Laboratory, and the simulation results themselves are available from the authors upon request.

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Created:
August 22, 2023
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October 17, 2023