Wet removal of black carbon in Asian outflow: Aerosol Radiative Forcing in East Asia (A‐FORCE) aircraft campaign

Abstract

.[1] The Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign was conducted over East Asia in March-April 2009. During the A-FORCE campaign, 120 vertical profiles of black carbon (BC) and carbon monoxide (CO) were obtained in the planetary boundary layer (PBL) and the free troposphere. This study examines the wet removal of BC in Asian outflow using the A-FORCE data. The concentrations of BC and CO were greatly enhanced in air parcels sampled at 3-6 km in altitude over the Yellow Sea on 30 March 2009, associated with upward transport due to a cyclone with modest amounts of precipitation over northern China. In contrast, high CO concentrations without substantial enhancements of BC concentrations were observed in air parcels sampled at 5-6 km over the East China Sea on 23 April 2009, caused by uplifting due to cumulus convection with large amounts of precipitation over central China. The transport efficiency of BC (TE BC , namely the fraction of BC particles not removed during transport) in air parcels sampled above 2 km during the entire A-FORCE period decreased primarily with the increase in the precipitation amount that air parcels experienced during vertical transport, although their correlation was modest (r 2 = 0.43). TE BC also depended on the altitude to which air parcels were transported from the PBL and the latitude where they were uplifted locally over source regions. The median values of TE BC for air parcels originating from northern China (north of 33°N) and sampled at 2-4 km and 4-9 km levels were 86% and 49%, respectively, during the A-FORCE period. These median values were systematically greater than the corresponding median values (69% and 32%, respectively) for air parcels originating from southern China (south of 33°N). Use of the A-FORCE data set will contribute to the reduction of large uncertainties in wet removal process of BC in global-and regional-scale models.

Regional Impact of Biomass Burning in Southeast Asia on Atmospheric Aerosols during the 2013 Seven South-East Asian Studies Project

“…As a result, the southern winds in the peninsula predominantly blew pollutants from the peninsula to the border provinces in China. The horizontal convergence of the mass flux of PM 2.5 in the boundary layer also caused upward transport to the free troposphere (Oshima et al, 2013) (Figs. 5(h)-5(k)).…”

Volatility basis-set approach simulation of organic aerosol formation in East Asia: implications for anthropogenic–biogenic interaction and controllable amounts

“…Many studies have reported impacts of Asian aerosols on regional and hemispherical scales (e.g., Ramanathan et al, 2001;Carmichael et al, 2003;Adhikary et al, 2010;Matsui et al, 2011aMatsui et al, , b, 2013aOshima et al, 2012Oshima et al, , 2013. Several global and regional modeling studies have simulated and evaluated OA over East Asia (e.g., Heald et al, 2005Heald et al, , 2011Han et al, 2008;Matsui et al, 2009a;Utembe et al, 2011;Mahmud and Barsanti, 2013).…”

“…3.2). (Oshima et al, 2012). As described by Takami et al (2005Takami et al ( , 2007, the collection efficiency was assumed to be 0.5 at Fukue and 1.0 at Hedo.…”

Development of a parameterization of black carbon aging for use in general circulation models

“…Note that these initial parameters cover concentrations of chemical species from polluted urban air (e.g., BC = 10.0 µg m −3 and SO 2 = 10.0 parts per billion by volume (ppbv) at the surface in Beijing; Han et al, 2009;Takegawa et al, 2009) to free tropospheric air (e.g., BC = 0.1 µg m −3 and SO 2 = 0.1 ppbv in the free troposphere over the western Pacific; Russo et al, 2003;Oshima et al, 2012). The calculations were conducted using hourly photolysis rates for equinox at midlatitudes, although results obtained in this study can be applied irrespective of latitude and season (see Sects.…”