Limited by the scarcity of in situ vertical observation data, the influences of biomass burning in Southeast Asia on major atmospheric carbonaceous compositions in downwind regions have not been thoroughly studied. In this study, aircraft observations were performed to obtain high time-resolved in situ vertical distributions of black carbon (BC) as well as carbon monoxide (CO) and carbon dioxide (CO2). Four types of profiles were revealed: Mode I (from 2000 to 3000 m, the BC, CO and CO2 concentrations were enhanced), Mode II (with increasing altitude, the BC, CO and CO2 concentrations almost decreased), Mode III (inhomogeneous vertical BC, CO and CO2 profiles with BC peaks were observed from 2500 to 3000 m) and Mode IV (the BC, CO and CO2 concentrations increased above 1500 m). Furthermore, simulations were conducted to calculate radiative forcing (RF) caused by BC and study the heating rate (HR) of BC in combination with the vertical BC profiles. A larger BC distribution in the atmosphere re-sulted in a sharp RF change from negative to positive values, imposing a nonnegligible influence on the atmospheric temperature profile, with maximum HR values ranging from 0.4 to 5.8 K/day. The values of the absorption Angstrom exponent (AAE) were 1.46 +/- 0.11 and 1.48 +/- 0.17 at altitudes from 1000 to 2000 and 2000-3000 m, respectively. The average BC light absorption coefficient at the 370 nm wavelength (alpha BC (370)) accounted for 50.3 %-76.8 % of the alpha (370), while the brown carbon (BrC) light absorption coefficient at the 370 nm wavelength (alpha BrC (370)) contrib-uted 23.2 %-49.7 % to the alpha (370) at altitudes of 1000-2000 m. At altitudes of 2000-3000 m, alpha BC (370) and alpha BrC (370) contributed 43.8 %-88.2 % and 11.8 %-56.2 % to the alpha (370), respectively. These findings show that calculations that consider the surface BC concentration but ignore the vertical BC distribution could result in massive uncertainties in estimating the RF and HR caused by BC. This study helped achieve a deeper understanding of the influences of biomass burning over the region of Southeast Asia on the profiles of atmospheric carbonaceous compositions and atmospheric BC absorption and its warming effect.

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 (18013nm) than BC attributed to South Korea (15225nm), and BC associated with long-range transport was less thickly coated (604nm) than that sourced from South Korea (7516nm). The column BC direct radiative effect at the top of the atmosphere was estimated to be 1.0-0.5+0.9W/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.