Abstract
Abstract. Total number concentrations of particles having a diameter larger than 10 nm (NCN), cloud condensation nuclei at several supersaturation (S) values (NCCN) and number size distributions of particles with 10–414 nm diameter were measured in Seoul between 2004 and 2010. Overall average values of NCN and geometric mean diameter were 17 811 ± 5581 cm−3 and 48 ± 6 nm. Average NCCN at 0.4, 0.6 and 0.8% S were 4145 ± 2016, 5323 ± 2453 and 6067 ± 2780 cm−3 and corresponding NCCN / NCN 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. NCN and NCCN 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, NCN and NCCN at 0.6% S (N0.6%) were measured in and around the Korean Peninsula. During the 2011 campaign, the aerosol scattering coefficient was also measured. NCN and N0.6% 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. NCN and N0.6% generally show a positive correlation with aerosol scattering coefficients but this correspondence tends to vary with altitude. Occasional instances of low (< 0.3) N0.6% / NCN 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 NCN and NCCN 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.
Highlights
With increasing attention to climate change, interest in cloud condensation nuclei (CCN) has not been limited to the cloud physics community due to CCN effects on various cloud properties, including cloud albedo and lifetime
N0.6% shows a similar trend but with smaller vertical gradients, implying that the influence of the surface sources is less pronounced for CCN
It is worth noting that when the layer with enhanced particle concentration is not considered, NCN and N0.6% measured near or above 3000 m altitude were comparable to those measured during ACE-1 in 1995 over the Southern Ocean when the air mass originated from the Australian continent (Hudson et al, 1998)
Summary
With increasing attention to climate change, interest in cloud condensation nuclei (CCN) has not been limited to the cloud physics community due to CCN effects on various cloud properties, including cloud albedo and lifetime (i.e., aerosol indirect effects, AIE). AIE has attracted many researchers because its magnitude is estimated to be large enough to compensate for a significant portion of the greenhouse gas effect and because of its large uncertainty (IPCC, 2007), especially for determining climate sensitivity (Kiehl, 2007; Schwartz et al, 2010). One reason for such large uncertainty is that aerosol properties exhibit high geographical heterogeneity due to short atmospheric lifetime (days) compared to greenhouse gases (years) (IPCC, 2007).
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