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GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L03818, doi:10.1029/2007GL031075, 2008

Cloud forming potential of secondary organic aerosol under near atmospheric conditions

J. Duplissy

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


M. Gysel

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


M. R. Alfarra

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


J. Dommen

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


A. Metzger

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


A. S. H. Prevot

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


E. Weingartner

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


A. Laaksonen

Department of Physics, University of Kuopio, Kuopio, Finland


T. Raatikainen

Finnish Meteorological Institute, Helsinki, Finland


N. Good

Centre for Atmospheric Sciences, University of Manchester, Manchester, UK


S. F. Turner

Centre for Atmospheric Sciences, University of Manchester, Manchester, UK


G. McFiggans

Centre for Atmospheric Sciences, University of Manchester, Manchester, UK


U. Baltensperger

Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland


Abstract

Cloud droplets form by nucleation on atmospheric aerosol particles. Populations of such particles invariably contain organic material, a major source of which is thought to be condensation of photo-oxidation products of biogenic volatile organic compounds (VOCs). We demonstrate that smog chamber studies of the formation of such biogenic secondary organic aerosol (SOA) formed during photo-oxidation must be conducted at near atmospheric concentrations to yield atmospherically representative particle composition, hygroscopicity and cloud-forming potential. Under these conditions, the hygroscopicity measured at 95% relative humidity can be used reliably to predict the CCN activity of the SOA particles by assuming droplet surface tension of pure water. We also show that the supersaturation required to activate a given size of particle decreases with age.

Received 21 June 2007; accepted 5 December 2007; published 15 February 2008.

Keywords: hygroscopicity; secondary organic aerosol; cloud condensation nuclei.

Index Terms: 3311 Atmospheric Processes: Clouds and aerosols; 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906).

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Citation: Duplissy, J., et al. (2008), Cloud forming potential of secondary organic aerosol under near atmospheric conditions, Geophys. Res. Lett., 35, L03818, doi:10.1029/2007GL031075.