Observations of Black Carbon characteristics and radiative forcing over a Global Atmosphere Watch supersite in Korea

Abstract

This paper provides an account of observed variations in Black carbon (BC) mass concentrations and BC induced radiative forcing for the first time over a background Global Atmosphere Watch (GAW) site, Anmyeon in South Korea. BC concentrations were continuously measured over the site during January 2003–December 2004 periods using an Aethalometer. BC showed higher concentrations during 2003 in majority of the months (except in January, August and October). BC found to be showing higher concentrations in September 2003, with values reaching up to 3μgm−3 over the site. It also showed higher peaks in May and December in 2003. BC values were found to be comparatively less during wet season (July–August; especially august), which could be associated with the rainout and washout associated with the Changma season (summer monsoon). Optical Properties of Aerosols and Clouds (OPAC) model in combination with a radiative transfer model (SBDART) were used to estimate aerosol radiative forcing separately for composite aerosols (total aerosols) and solely for BC aerosols using chemical composition data sets of Total Suspended Particulates (TSP) and BC. The atmospheric forcing for composite aerosols found to be +14.9 to +25.9Wm−2 during spring, +13.4 to +20.4Wm−2 in summer, +12.9 to +19.1Wm−2 in autumn and +16 to +18.2Wm−2 during winter,respectively. The respective BC atmospheric forcings were +8.1 to +11.8Wm−2, +8.4 to +11.1Wm−2, +8.7 to +11.4Wm−2 and +8.8 to +11.7Wm−2 during spring, summer, autumn and winter. The study suggests that BC induced atmospheric forcing can contribute up to 88% of total aerosol induced atmospheric warming.