Abstract. Total number concentrations of particles having a diameter larger than 10 nm (N_CN), cloud condensation nuclei at several supersaturation (S) values (N_CCN) and number size distributions of particles with 10–414 nm diameter were measured in Seoul between 2004 and 2010. Overall average values of N_CN and geometric mean diameter were 17 811 ± 5581 cm⁻³ and 48 ± 6 nm. Average N_CCN at 0.4, 0.6 and 0.8% S were 4145 ± 2016, 5323 ± 2453 and 6067 ± 2780 cm⁻³ and corresponding N_CCN / N_CN were 0.26 ± 0.11, 0.33 ± 0.11 and 0.37 ± 0.12. There is a clear seasonal variation in aerosol concentration, which seems to be due to the monsoon. N_CN and N_CCN are also found to depend on the volume of traffic and the height of the planetary boundary layer, respectively.

During aircraft campaigns in 2009 and 2011, N_CN and N_CCN at 0.6% S (N_0.6%) were measured in and around the Korean Peninsula. During the 2011 campaign, the aerosol scattering coefficient was also measured. N_CN and N_0.6% in the lower altitudes were generally higher than at higher altitudes, except for cases when particle formation and growth events were thought to occur at higher altitudes. N_CN and N_0.6% generally show a positive correlation with aerosol scattering coefficients but this correspondence tends to vary with altitude. Occasional instances of low (< 0.3) N_0.6% / N_CN in the boundary layer are demonstrated to be associated with particle formation and growth events. With the support of ground measurements, it is confirmed that a particle formation and growth event did indeed occur over the Yellow Sea on a flight day, and the areal extent of this event is estimated to be greater than 100 km × 450 km.

With the combination of the current and several relevant previous studies, a composite map of N_CN and N_CCN in and around the Korean Peninsula is produced. Overall, the exhibited concentrations are typical of values measured over polluted regions elsewhere on the globe. Moreover, there is a generally decreasing trend from west to east over the region, implying that the region is constantly under the dominant influence of continental outflow.