Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 6 9 2006 10.5194/acp-6-2593-2006 http://www.atmos-chem-phys.net/6/2593/2006/ http://www.atmos-chem-phys.net/6/2593/2006/acp-6-2593-2006.html http://www.atmos-chem-phys.net/6/2593/2006/acp-6-2593-2006.pdf 2593 2649 2006-07-05 The effect of physical and chemical aerosol properties on warm cloud droplet activation G. McFiggans g.mcfiggans@manchester.ac.uk P. Artaxo U. Baltensperger H. Coe M. C. Facchini G. Feingold S. Fuzzi M. Gysel A. Laaksonen U. Lohmann T. F. Mentel D. M. Murphy C. D. O'Dowd J. R. Snider E. Weingartner Atmospheric Sciences Group, SEAES, University of Manchester, P.O. Box 88, Manchester, M60 1QD, UK Instituto de Fisica, Universidade de Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900 Sao Paulo, Brazil Paul Scherrer Institut, Labor für Atmosphärenchemie, 5232 Villigen PSI, Switzerland Istituto di Scienze dell'Atmosfera e del Clima, CNR, 40129 Bologna, Italy NOAA Environmental Technology Laboratory, 325 Broadway, Boulder, Colorado 80305, USA Department of Applied Physics, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland Institute for Atmospheric and Climate Science, Schafmattstr. 30, ETH Zurich, 8093 Zurich, Switzerland Forschungszentrum Jülich GmbH, ICG-II: Troposphäre, 52425 Jülich, Germany NOAA Aeronomy Laboratory, 325 Broadway, Boulder, Colorado 80305, USA Department of Physics, National University of Ireland, Galway, Ireland University of Wyoming, Department of Atmospheric Science, Laramie, WY 82071, USA The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. 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