Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 7 2008 10.5194/acp-8-1985-2008 http://www.atmos-chem-phys.net/8/1985/2008/ http://www.atmos-chem-phys.net/8/1985/2008/acp-8-1985-2008.html http://www.atmos-chem-phys.net/8/1985/2008/acp-8-1985-2008.pdf 1985 1988 2008-04-08 Technical note: Analytical formulae for the critical supersaturations and droplet diameters of CCN containing insoluble material H. Kokkola M. Vesterinen T. Anttila A. Laaksonen K. E. J. Lehtinen Finnish Meteorological Institute, Kuopio Unit, P.O.Box 1627, FI-70211 Kuopio, Finland Finnish Meteorological Institute, P.O.Box 503, FI-00101 Helsinki, Finland Department of Physics, University of Kuopio, P.O.Box 1672, FI-70211 Kuopio, Finland In this paper, we consider the cloud drop activation of aerosol particles consisting of water soluble material and an insoluble core. Based on the Köhler theory, we derive analytical equations for the critical diameters and supersaturations of such particles. We demonstrate the use of the equations by comparing the critical supersaturations of particles composed of ammonium sulfate and insoluble substances with those of model organic particles with varying molecular sizes. Abdul-Razzak, H. and Ghan, S J.: Parameterization of the influence of organic surfactants on aerosol activation, J. Geophys. Res., 109, D03205, doi:10.1029/2003JD004043., 2004. Hänel, G.: The properties of atmospheric aerosol particles as functions of relative humidity at thermodynamic equilibrium with the surrounding moist air, 19, 73–188, 1976. Khvorostyanov, V. I. and Curry, J. A.: Refinements to the Kohler's theory of aerosol equilibrium radii, size spectra, and droplet activation: Effects of humidity and insoluble fraction, J. Geophys. Res, 112, D05206, doi:10.1029/2006JD007672, 2007. Köhler, H.: The nucleus in the growth of hygroscopic droplets, Trans. Faraday Soc., 32, 1152–1161, 1936. Laaksonen, A., Korhonen, P., Kulmala, M., and Charlson, R J.: Modification of the Köhler equation to include soluble trace gases and slightly soluble substances., J. Atmos. Sci., 55, 853–862, 1998. Lehmann, K., Massling, A., Tilgner, A., Mertes, S., Galgon, D., Wiedensohler A.: Size-resolved soluble volume fractions of submicrometer particles in air masses of different character, Atmos. Environ., 39, 4257–4266, 2005. Nenes, A. and Seinfeld, J H.: Parameterization of cloud droplet formation in global climate models, J. Geophys. Res., 108(D14), 4415, doi:10.1029/2002JD002911, 2003. Padró, L. T., Asa-Awuku, A., Morrison, R., and Nenes, A.: Inferring thermodynamic properties from CCN activation experiments: a) single-component and binary aerosols, Atmos. Chem. Phys. Discuss., 7, 3805–3836, 2007. Seinfeld, J H. and Pandis, S N.: Atmospheric Chemistry and Physics, John Wiley & Sons inc., 1998. Shulman, M L., Jacobson, M C., Charlson, R J., Synovec, R E., and Young, T E.: Dissolution behavior and surface tension effects of organic compounds in nucleating cloud droplets, Geophys. Res. Lett., 23, 277, 1996. Sorjamaa, R., Svenningsson, B., Raatikainen, T., Henning, S., Bilde, M., and Laaksonen, A.: The role of surfactants in Köhler theory reconsidered, Atmos. Chem. Phys., 4, 2107–2117, 2004. Sorjamaa, R. and Laaksonen, A.: The effect of H₂O adsorption on cloud drop activation of insoluble particles: a theoretical framework, Atmos. Chem. Phys., 7, 6175–6180, 2007. Twomey, S.: The nuclei of natural cloud formation part II: The supersaturation in natural clouds and the variation of cloud droplet concentration, Geofis. Pura Appl., 43, 243–249, 1959.