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Geosci. Model Dev. Discuss., 5, 1743-1780, 2012
www.geosci-model-dev-discuss.net/5/1743/2012/ doi:10.5194/gmdd-5-1743-2012 © Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. |
Unified parameterization of the planetary boundary layer and shallow convection with a higher-order turbulence closure in the community atmosphere model: single column experiments
1National Center for Atmospheric Research, Boulder, Colorado, USA
2University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA
Abstract. This paper describes the coupling of the Community Atmosphere Model (CAM) version 5 with a unified multi-variate probability density function (PDF) parameterization, Cloud Layers Unified by Binormals (CLUBB). CLUBB replaces the planetary boundary layer (PBL), shallow convection, and cloud macrophysics schemes in CAM5 with a higher-order turbulence closure based on an assumed PDF. Comparisons of single-column versions of CAM5 and CAM-CLUBB are provided in this paper for several boundary layer regimes. As compared to Large Eddy Simulations (LES), CAM-CLUBB and CAM5 simulate marine stratocumulus regimes with similar accuracy. For shallow convective regimes, CAM-CLUBB improves the representation of cloud cover and liquid water path (LWP). In addition, for shallow convection CAM-CLUBB offers better fidelity for sub-grid scale vertical velocity, which is an important input for aerosol activation. Finally, CAM-CLUBB results are more robust to changes in vertical and temporal resolution when compared to CAM5.
Citation: Bogenschutz, P. A., Gettelman, A., Morrison, H., Larson, V. E., Schanen, D. P., Meyer, N. R., and Craig, C.: Unified parameterization of the planetary boundary layer and shallow convection with a higher-order turbulence closure in the community atmosphere model: single column experiments, Geosci. Model Dev. Discuss., 5, 1743-1780, doi:10.5194/gmdd-5-1743-2012, 2012.