Submicron aerosol size distributions and cloud condensation nuclei concentrations measured at Gosan, Korea, during the Atmospheric Brown Clouds–East Asian Regional Experiment 2005

Abstract

Submicron aerosol size distributions, CN and CCN concentrations at a constant supersaturation of 0.6% were measured at a relatively remote coastal site at Gosan in Jeju Island, Korea, during the ABC‐EAREX from 11 March to 8 April 2005. The average CN concentrations were 6088 ± 3988, 5231 ± 2454 and 3513 ± 1790 cm−3, respectively, for the three major air mass types classified by their origins. The corresponding CCN concentrations were 2393 ± 1156, 2897 ± 1226 and 1843 ± 585 cm−3. The type III air mass was the closest to maritime origins, but these lowest concentrations at Gosan were an order of magnitude higher than those of clean marine boundary layer, indicating that regardless of air mass designation springtime submicron aerosols at Gosan were under steady continental influences. Distinct new particle formation and growth events occurred on 6 d, when clear sky weather conditions prevailed that brought air from northern China, Mongolia or Russia by anticyclonic circulations. Simultaneous occurrence of these events at a western coastal site in the Korean Peninsula 350 km north of Gosan suggests that these events were not local but at least regional‐scale events. CCN concentrations were predicted with the aerosol size distributions and the assumption of particles being composed of (NH4)2SO4. The predicted to measured CCN concentration ratio was 1.27 ± 0.29 and the r2 was 0.77 for the whole measurement period. The type I air mass that has the most continental influences showed a slight tendency to overpredict CCN concentrations but the good agreement overall suggests that springtime Gosan aerosols act almost like ammonium sulfate as far as CCN activity is concerned, almost regardless of air mass origin.