ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-7-5937-2007 Spectral absorption properties of atmospheric aerosols Bergstrom R. W. 1 Pilewskie P. 2 Russell P. B. 3 Redemann J. 4 Bond T. C. 5 Quinn P. K. 6 Sierau B. 7 Bay Area Environmental Research Institute, Sonoma, CA, USA Laboratory for Atmospheric and Space Physics, Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO, USA NASA Ames Research Center. Moffett Field, CA, USA Bay Area Environmental Research Institute, Ventura, CA, USA University of Illinois, Champaign-Urbana, IL, USA Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, Washington, USA Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland 04 12 2007 7 23 5937 5943 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/7/5937/2007/acp-7-5937-2007.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/7/5937/2007/acp-7-5937-2007.pdf

We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We combined airborne measurements of the solar net radiant flux density and the aerosol optical depth with a detailed radiative transfer model for all but one of the cases. The field programs (SAFARI 2000, ACE Asia, PRIDE, TARFOX, INTEX-A) contained aerosols representing the major absorbing aerosol types: pollution, biomass burning, desert dust and mixtures. In all cases the spectral absorption optical depth decreases with wavelength and can be approximated with a power-law wavelength dependence (Absorption Angstrom Exponent or AAE). We compare our results with other recent spectral absorption measurements and attempt to briefly summarize the state of knowledge of aerosol absorption spectra in the atmosphere. We discuss the limitations in using the AAE for calculating the solar absorption. We also discuss the resulting spectral single scattering albedo for these cases.

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