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Cloud-resolving model simulations with one and two-way couplings via the weak-temperature gradient approximation

Daleu, C. L., Woolnough, S. and Plant, R. S. (2012) Cloud-resolving model simulations with one and two-way couplings via the weak-temperature gradient approximation. Journal of the Atmospheric Sciences, 69 (12). pp. 3683-3699. ISSN 1520-0469

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To link to this article DOI: 10.1175/JAS-D-12-058.1

Abstract/Summary

A Cloud-Resolving Model is modified to implement the weak temperature gradient approximation in order to simulate the interactions between tropical convection and the large-scale tropical circulation. The instantaneous domain-mean potential temperature is relaxed toward a reference profile obtained from a radiative-convective equilibrium simulation of the Cloud-Resolving Model. For homogeneous surface conditions, the model state at equilibrium is a large-scale circulation with its descending branch in the simulated column. This is similiar to the equilibrium state found in some other studies, but not all. For this model, the development of such a circulation is insensitive to the relaxation time scale and the initial conditions. Two columns of the Cloud-Resolving Model are fully coupled by relaxing the instantaneous domain-mean potential temperature in both columns towards each other. This configuration is energetically closed in contrast to the reference column configuration. No mean large-scale circulation develops over homogeneous surface conditions, regardless of the relative area of the two columns. The sensitivity to non-uniform surface conditions is similar to that obtained in the reference column configuration if the two simulated columns have very different areas, but is markedly weaker for columns of comparable area. The weaker sensitivity can be understood as being a consequence of a formulation for which the energy budget is closed. The reference-column configuration has been used to study the convection in a local region under the influence of a large-scale circulation. The extension to a two-column configuration is proposed as a methodology for studying the influence on local convection of changes in remote convection.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical and Physical Sciences > NCAS
Faculty of Science > School of Mathematical and Physical Sciences > Department of Meteorology
ID Code:28698
Publisher:American Meteorological Society

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