Editorial Type:
Article
Article Type:
Research Article

Simple Solutions to Steady-State Cumulus Regimes in the Convective Boundary Layer

Jerôme Schalkwijk Delft University of Technology, Delft, Netherlands

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Harmen J. J. Jonker Delft University of Technology, Delft, Netherlands

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A. Pier Siebesma Delft University of Technology, Delft, and Royal Netherlands Meteorological Institute, De Bilt, Netherlands

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Print Publication:
01 Nov 2013
DOI:
https://doi.org/10.1175/JAS-D-12-0312.1
Page(s):
3656–3672
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Abstract

A modeling framework is developed that extends the mixed-layer model to steady-state cumulus convection. The aim is to consider the simplest model that retains the essential behavior of cumulus-capped layers. The presented framework allows for the evaluation of stationary states dependent on external parameters. These states are completely independent of the initial conditions, and therefore represent an asymptote that might help deepen understanding of the dependence of the cloudy boundary layer on external forcings. Formulating separate equations for the lifting condensation level and the mixed-layer height, the dry and wet energetics can be distinguished. Regimes that can support steady-state cumulus clouds and regimes that cannot are identified by comparison of the dry and wet buoyancy effects. The dominant mechanisms that govern the creation and eventual depth of the cloud layer are identified. Model predictions are tested by comparison with a large number of independent large-eddy simulations for varying surface and large-scale conditions and are found to be in good agreement.

Corresponding author address: Jerôme Schalkwijk, Delft University of Technology, Stevinweg 1, 2628 CN Delft, Netherlands. E-mail: j.schalkwijk@tudelft.nl

Abstract

A modeling framework is developed that extends the mixed-layer model to steady-state cumulus convection. The aim is to consider the simplest model that retains the essential behavior of cumulus-capped layers. The presented framework allows for the evaluation of stationary states dependent on external parameters. These states are completely independent of the initial conditions, and therefore represent an asymptote that might help deepen understanding of the dependence of the cloudy boundary layer on external forcings. Formulating separate equations for the lifting condensation level and the mixed-layer height, the dry and wet energetics can be distinguished. Regimes that can support steady-state cumulus clouds and regimes that cannot are identified by comparison of the dry and wet buoyancy effects. The dominant mechanisms that govern the creation and eventual depth of the cloud layer are identified. Model predictions are tested by comparison with a large number of independent large-eddy simulations for varying surface and large-scale conditions and are found to be in good agreement.

Corresponding author address: Jerôme Schalkwijk, Delft University of Technology, Stevinweg 1, 2628 CN Delft, Netherlands. E-mail: j.schalkwijk@tudelft.nl
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