Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 19 2008 10.5194/acp-8-5869-2008 http://www.atmos-chem-phys.net/8/5869/2008/ http://www.atmos-chem-phys.net/8/5869/2008/acp-8-5869-2008.html http://www.atmos-chem-phys.net/8/5869/2008/acp-8-5869-2008.pdf 5869 5887 2008-10-13 The effect of organic compounds on the growth rate of cloud droplets in marine and forest settings N. C. Shantz nicole.shantz@ec.gc.ca W. R. Leaitch L. Phinney M. Mozurkewich D. Toom-Sauntry Department of Chemistry, University of Toronto, Toronto, Ontario, Canada Climate Research Division, Environment Canada, Toronto, Ontario, Canada Air Quality Sciences, Meteorological Service of Canada, Dartmouth, Nova Scotia, Canada Department of Chemistry and Centre for Atmospheric Chemistry, York University, Toronto, Ontario, Canada Organic matter represents an important fraction of the fine particle aerosol, yet our knowledge of the roles of organics in the activation of aerosol particles into cloud droplets is poor. A cloud condensation nucleus (CCN) counter is used to examine the relative growth rates of cloud droplets for case studies from field measurements on the North Pacific Ocean and in a coniferous forest. A model of the condensational growth of water droplets, on particles dissolving according to their solubility in water, is used to simulate the initial scattering of the droplets as they grow in the CCN counter. 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