Atmos. Chem. Phys. Discuss., 4, 7281-7290, 2004
www.atmos-chem-phys-discuss.net/4/7281/2004/
doi:10.5194/acpd-4-7281-2004
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
On cloud modelling and the mass accommodation coefficient of water
A. Laaksonen1, T. Vesala2, M. Kulmala2, P. M. Winkler3, and P. E. Wagner3
1Department of Applied Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland
2Department of Physical Sciences, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki, Finland
3Institut für Experimentalphysik, Universität Wien, Boltzmanngasse 5, A-1090 Wien, Austria

Abstract. The mass accommodation coefficient of water is a quantity for which different experimental techniques have yielded conflicting values in the range 0.04–1. From the viewpoint of cloud modelling, this is an unfortunate situation, since the value of the mass accommodation coefficient affects the model results, e.g. the number concentration of activated cloud droplets. In this paper we argue that a mass accommodation coefficient of unity should be used in cloud modelling, since this value has been obtained in experimental studies of water droplet growth rates, a quantity which is explicitly described in cloud models. In contrast, mass accommodation coefficient values below unity have been derived from experimental results which are analyzed with different theoretical expressions than those included in cloud models.

Citation: Laaksonen, A., Vesala, T., Kulmala, M., Winkler, P. M., and Wagner, P. E.: On cloud modelling and the mass accommodation coefficient of water, Atmos. Chem. Phys. Discuss., 4, 7281-7290, doi:10.5194/acpd-4-7281-2004, 2004.
 
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