Cloud condensation nuclei activity at Jeju Island, Korea in spring 2005

M. Kuwata (1) , Y. Kondo (1) , Y. Miyazaki (1) , Y. Komazaki (1) , J. H. Kim (2) , S. S. Yum (2) , H. Tanimoto (3) , H. Matsueda (4)

1 RCAST - Research Center for Advanced Science and Technology [Tokyo]
2 Department of Atmospheric Sciences [Seoul]
3 NIES - National Institute for Environmental Studies
4 Geochemical Research Department

We measured the number concentrations of cloud condensation nuclei (CCN) and the size distributions of CCN/CN (CN: condensation nuclei) ratios at supersaturations (SSs) of 0.097, 0.27, 0.58, and 0.97% at Jeju-Island, Korea during March-April 2005. Measurements of aerosol inorganic ions, water-soluble organic carbon (WSOC), organic carbon (OC), and elemental carbon (EC) in PM_2.5 were simultaneously made. The CCN/CN ratios increased with increasing particle diameter, and the diameter at CCN/CN=0.5 was defined as D₅₀. D₅₀ represents the activation dry diameter of atmospheric particles. The average D₅₀ at SS=0.097% and 0.97% was 136 nm and 31 nm, respectively. The temporal variation of D₅₀ at SS=0.097% was correlated with the mass fraction of water-soluble components (inorganic ions + WSOC), indicating that the temporal variation of CCN activity was mainly controlled by changes in the water-soluble components fraction. The critical dry diameter (D_crit), which is the threshold dry diameter for CCN activation, was calculated from the observed aerosol chemical compositions by Köhler theory for comparison with D₅₀. The D₅₀ at SS=0.097% was correlated (r²=0.48) with calculated D_crit, although D_crit were larger than D₅₀ by 20?29% on average. The systematic difference between D₅₀ and D_crit could be caused by the size dependence of the aerosol chemical compositions or surface tension lowering caused by the mixing of water-soluble organic compounds. This difference corresponds to a 27±14% uncertainty in the CCN number concentration estimated from the observed particle number size distribution.

Domaines: Océan, Atmosphère

M. Kuwata, Y. Kondo, Y. Miyazaki, Y. Komazaki, J. H. Kim, et al.. Cloud condensation nuclei activity at Jeju Island, Korea in spring 2005. Atmospheric Chemistry and Physics Discussions, 2007, 7 (6), pp.15805-15851. ⟨hal-00303170⟩