ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-215-2011 Inferring absorbing organic carbon content from AERONET data Arola A. 1 Schuster G. 2 Myhre G. 3 Kazadzis S. 4 Dey S. 5 Tripathi S. N. 6 7 Finnish Meteorological Institute, P.O. Box 1627, 70211 Kuopio, Finland NASA Langley Research Center Hampton, VA 23681, USA Center for International Climate and Environmental Research–Oslo (CICERO), Blindern, 0318 Oslo, Norway Institute for Environmental Research & Sustainable Development, National Observatory of Athens, 15236 Athens, Greece Department of Atmospheric Sciences, University of Illinois at Urbana Champaign, Urbana, IL, USA NASA Goddard Space Flight Center, Greenbelt, MD 20770, USA Department of Civil Engineering, Indian Institute of Technology, Kanpur-208016, India 11 01 2011 11 1 215 225 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/215/2011/acp-11-215-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/215/2011/acp-11-215-2011.pdf

Black carbon, light-absorbing organic carbon (often called "brown carbon") and mineral dust are the major light-absorbing aerosols. Currently the sources and formation of brown carbon aerosol in particular are not well understood. In this study we estimated the amount of light–absorbing organic carbon and black carbon from AERONET measurements. We find that the columnar absorbing organic carbon (brown carbon) levels in biomass burning regions of South America and Africa are relatively high (about 15–20 mg m<sup>−2</sup> during biomass burning season), while the concentrations are significantly lower in urban areas in US and Europe. However, we estimated significant absorbing organic carbon amounts from the data of megacities of newly industrialized countries, particularly in India and China, showing also clear seasonality with peak values up to 30–35 mg m<sup>−2</sup> during the coldest season, likely caused by the coal and biofuel burning used for heating. We also compared our retrievals with the modeled organic carbon by the global Oslo CTM for several sites. Model values are higher in biomass burning regions than AERONET-based retrievals, while the opposite is true in urban areas in India and China.

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