ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-4-3669-2004 A new convective cloud field model based on principles of self-organisation Nober F. J. 1 Graf H. F. 1 Department of Geography, University of Cambridge, United Kingdom 01 07 2004 4 4 3669 3698 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/4/3669/2004/acpd-4-3669-2004.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/4/3669/2004/acpd-4-3669-2004.pdf

A new cumulus convection parameterisation is presented in this paper. The parameterisation uses an explicit spectral approach and determines, unlike other convection schemes, for each convection event a new cloud distribution function regarding to the given vertical temperature and humidity profiles. This is done by using a one-dimensional cloud model to create a spectrum of different clouds. The interaction between all non convective physical processes in the AGCM and all different clouds is taken into account to calculate a self consistent cloud spectrum. The model has been implemented in the ECHAM5 AGCM and tested against a large eddy simulation model. The representation of a shallow cumulus cloud field by the AGCM could be much improved. Diurnal cycle, cloud cover, liquid water path and the vertical structure of the mass flux, determined by the new convection scheme are close to the large eddy simulation, whereas the standard convection scheme failed in simulating this convection episode.