Estimating Source Region Influences on Black Carbon Abundance, Microphysics, and Radiative Effect Observed Over South Korea

Abstract

East Asia is the strongest global source region for anthropogenic black carbon (BC), the most important light-absorbing aerosol contributing to direct radiative climate forcing. To provide extended observational constraints on regional BC distributions and impacts, in situ measurements of BC were obtained with a single particle soot photometer during the May/June 2016 Korean-United States Air Quality aircraft campaign (KORUS-AQ) in South Korea. Unique chemical tracer relationships were associated with BC sourced from different regions. The extent and variability in vertical BC mass burden for 48 profiles over a single site near Seoul were investigated using back trajectory and chemical tracer analysis. Meteorologically driven changes in transport influenced the relative importance of different source regions, impacting observed BC loadings at all altitudes. Internal mixing and size distributions of BC further demonstrated dependence on source region: BC attributed to China had a larger mass median diameter (180 ± 13 nm) than BC attributed to South Korea (152 ± 25 nm), and BC associated with long-range transport was less thickly coated (60 ± 4 nm) than that sourced from South Korea (75 ± 16 nm). The column BC direct radiative effect at the top of the atmosphere was estimated to be 1:0 þ0:9 À0:5 W/m 2 , with average values for different meteorological periods varying by a factor of 2 due to changes in the BC vertical profile. During the campaign, BC sourced from South Korea (≤ 31%), China (22%), and Russia (14%) were the most significant single-region contributors to the column direct radiative effect.

Enhanced heating rate of black carbon above the planetary boundary layer over megacities in summertime

“…Summer mountain valley breezes in Beijing can lift surface pollutants above the PBL (Chen et al 2009). A recent study conducted over Korea (Lamb et al 2018) also indicated some enhanced coating thickness for BC above the PBL (in figure 4(b) at about 800 hPa compared to 100 hPa), whereas the mixing state of BC at higher altitude was more influenced by synoptic conditions. The enhanced coating of BC above the boundary layer therefore tends to be a general phenomenon for sites where intensive solar radiation is received above the PBL.…”

Meteorology influencing springtime air quality, pollution transport, and visibility in Korea

“…These processes ultimately lofted dust particles over a broad range of altitudes, facilitating transport to Korea. However, as each storm system passed over the industrialized regions of northern China, the same lifting mechanisms enabled other forms of pollution to reach similar altitudes (e.g, Shin et al, 2015;Lamb et al, 2018), facilitating heterogeneous chemical reactions (e.g., Ren et al, 2019;Wu et al, 2019). Complex layering of aerosol particles was a frequent occurrence during the early dynamic period of KORUS-AQ, especially between 04 and 07 May.…”

Secondary organic aerosol production from local emissions dominates the organic aerosol budget over Seoul, South Korea, during KORUS-AQ

“…The potential aerosol mass (PAM) OFR measures the aerosol mass that can be formed from the precursors that are present in ambient or laboratory air (Kang et al, 2007;Lambe et al, 2011). The OFR has been successfully deployed in multiple urban and forested locations to quantify potential SOA Kang et al, 2018).…”