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Influence of the external mixing state of atmospheric aerosol on derived CCN number concentrations
Author(s) -
Wex H.,
McFiggans G.,
Henning S.,
Stratmann F.
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl043337
Subject(s) - aerosol , cloud condensation nuclei , particle (ecology) , particle number , particle size , chemical composition , atmospheric sciences , mixing ratio , condensation , range (aeronautics) , environmental science , mixing (physics) , meteorology , chemistry , materials science , physics , thermodynamics , geology , volume (thermodynamics) , organic chemistry , quantum mechanics , oceanography , composite material
We derived the range of particle hygroscopicities (κ) that occurs in the atmosphere, based on literature data of measured hygroscopic growth or based on chemical composition. The derived κ‐values show that the atmospheric aerosol often is an external mixture with respect to hygroscopicity. Mean κ were derived for urban, rural, and marine aerosols for the different hygroscopic modes. Using these κ and exemplary particle number size distributions for the different aerosols, the number concentration of cloud condensation nuclei ( N CCN ) was derived for two cases, (1) accounting for the less hygroscopic fraction of particles and (2) assuming all particles to have κ of the more hygroscopic mode. N CCN derived from measured particle hygroscopicity is overestimated for case (2). Overestimation of N CCN is largest for fresh continental aerosol and less pronounced for marine aerosol. With κ derived from bulk aerosol composition data, only the hygroscopicity of more soluble aerosol particles is captured. Bulk or even size‐resolved composition data will be insufficient to predict N CCN under many conditions unless independent information about particle mixing state is available.