Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 4 2008 10.5194/acpd-8-16851-2008 http://www.atmos-chem-phys-discuss.net/8/16851/2008/ http://www.atmos-chem-phys-discuss.net/8/16851/2008/acpd-8-16851-2008.html http://www.atmos-chem-phys-discuss.net/8/16851/2008/acpd-8-16851-2008.pdf 16851 16890 2008-09-08 Parameterization of cloud droplet formation for global and regional models: including adsorption activation from insoluble CCN P. Kumar I. N. Sokolik A. Nenes nenes@eas.gatech.edu School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA Dust and black carbon aerosol have long been known to have potentially important and diverse impacts on cloud droplet formation. Most studies to date focus on the soluble fraction of such particles, and ignore interactions of the insoluble fraction with water vapor (even if known to be hydrophilic). To address this gap, we develop a new parameterization framework that considers cloud droplet formation within an ascending air parcel containing insoluble (but wettable) particles mixed with aerosol containing an appreciable soluble fraction. Activation of particles with a soluble fraction is described through well-established Köhler Theory, while the activation of hydrophilic insoluble particles is treated by "adsorption-activation" theory. In the latter, water vapor is adsorbed onto insoluble particles, the activity of which is described by a multilayer Frankel-Halsey-Hill (FHH) adsorption isotherm modified to account for particle curvature. 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