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Fluctuations in an Equilibrium Convective Ensemble. Part I: Theoretical Formulation

Craig, George C. and Cohen, Brenda G. (2006) Fluctuations in an Equilibrium Convective Ensemble. Part I: Theoretical Formulation. Journal of the Atmospheric Sciences, 63, pp. 1996-2004. DOI: 10.1175/JAS3709.1.

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To provide a theoretical basis for stochastic parameterization of cumulus convection, the equilibrium fluctuations of a field of cumulus clouds under homogeneous large-scale forcing are derived statistically, using the Gibbs canonical ensemble from statistical mechanics. In the limit of noninteracting convective cells, the statistics of these convective fluctuations can be written in terms of the large-scale, externally constrained properties of the system. Using this framework, the probability density function of individual cloud mass fluxes is shown to be exponential. An analytical expression for the distribution function of total mass flux over a region of given size is also derived, and the variance of this distribution is found to be inversely related to the mean number of clouds in the ensemble. In a companion paper, these theoretical predictions are tested against cloud resolving model data.

Document Type:Article
Title:Fluctuations in an Equilibrium Convective Ensemble. Part I: Theoretical Formulation
AuthorsInstitution or Email of Authors
Cohen, Brenda G.Univ. of Reading, Reading, UK
Journal or Publication Title:Journal of the Atmospheric Sciences
Page Range:pp. 1996-2004
Keywords:convective ensemble, equilibrium fluctuation
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Cloud Physics and Traffic Meteorology
Deposited By: Jana Freund
Deposited On:24 Jul 2007
Last Modified:12 Dec 2013 20:21

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