Dynamic and Thermodynamic Aspects of the Parameterization of Cumulus Convection: Part II

Klaus Fraedrich Meteorologisches Institut der Universität Bonn, Bonn, West Germany

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Abstract

A parameterization scheme for cumulus convection is derived by averaging the conservative quantities, total energy and Ertel’s Wirbelinvariante, separately over the cloud and cloud-free areas and the lifetime of the convective elements. This leads 1) to one-dimensional models of a cloud ensemble where the mass fluxes within the convective elements and their life cycle (storage) are considered; and 2) to synoptic-scale equations including the related sources of heat, moisture and vorticity which are determined by the mechanisms of compensating subsidence and lateral mixing due to the convective activity. The simplified version of the interaction model is tested by mesoscale data of a cumulonimbus element and applied to the cloud cluster of a synoptic disturbance. Realistic results are obtained for the temperature, moisture and voracity distributions, the condensation rate and the convergence and storage of moisture (temperature) within the cloud ensemble, and for the large-scale sources of heat, moisture and vorticity.

Abstract

A parameterization scheme for cumulus convection is derived by averaging the conservative quantities, total energy and Ertel’s Wirbelinvariante, separately over the cloud and cloud-free areas and the lifetime of the convective elements. This leads 1) to one-dimensional models of a cloud ensemble where the mass fluxes within the convective elements and their life cycle (storage) are considered; and 2) to synoptic-scale equations including the related sources of heat, moisture and vorticity which are determined by the mechanisms of compensating subsidence and lateral mixing due to the convective activity. The simplified version of the interaction model is tested by mesoscale data of a cumulonimbus element and applied to the cloud cluster of a synoptic disturbance. Realistic results are obtained for the temperature, moisture and voracity distributions, the condensation rate and the convergence and storage of moisture (temperature) within the cloud ensemble, and for the large-scale sources of heat, moisture and vorticity.

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