Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 10 5 2010 10.5194/acp-10-2467-2010 http://www.atmos-chem-phys.net/10/2467/2010/ http://www.atmos-chem-phys.net/10/2467/2010/acp-10-2467-2010.html http://www.atmos-chem-phys.net/10/2467/2010/acp-10-2467-2010.pdf 2467 2473 2010-03-11 Comprehensively accounting for the effect of giant CCN in cloud activation parameterizations D. Barahona R. E. L. West P. Stier S. Romakkaniemi H. Kokkola A. Nenes athanasios.nenes@gatech.edu School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, USA School of Earth and Atmospheric Sciences, Georgia Institute of Technology, USA Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, UK Department of Physics and Mathematics, University of Eastern Finland, Finland Finnish Meteorological Institute, Kuopio Unit, Finland Large cloud condensation nuclei (CCN) (e.g., aged dust particles and seasalt) cannot attain their equilibrium size during the typical timescale of cloud droplet activation. Cloud activation parameterizations applied to aerosol with a large fraction of large CCN often do not account for this limitation adequately and can give biased predictions of cloud droplet number concentration (CDNC). Here we present a simple approach to address this problem that can easily be incorporated into cloud activation parameterizations. 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