Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 3 2009 10.5194/acpd-9-14059-2009 http://www.atmos-chem-phys-discuss.net/9/14059/2009/ http://www.atmos-chem-phys-discuss.net/9/14059/2009/acpd-9-14059-2009.html http://www.atmos-chem-phys-discuss.net/9/14059/2009/acpd-9-14059-2009.pdf 14059 14079 2009-06-26 In situ aerosol optics in Reno, NV, USA during and after the summer 2008 California wildfires and the influence of aerosol coatings M. Gyawali gyawalim@unr.nevada.edu W. P. Arnott K. Lewis H. Moosmüller Physics Department, University of Nevada, Reno, Nevada System of Higher Education, 1664 N. Virginia Street, Reno, NV 89557, USA Desert Research Institute, Nevada System of Higher Education, 2215 Raggio Parkway, Reno, NV 89512, USA Hundreds of wildfires in Northern California were sparked by lightning during the summer of 2008, resulting in downwind smoke for the months of June and July. Comparisons are reported for aerosol optics measurements in Reno Nevada made during the very smoky summer month of July and the relatively clean month of August. Photoacoustic instruments equipped with integrating nephelometers were used to measure aerosol light scattering and absorption at wavelengths of 405 nm and 870 nm, revealing a strong variation of the aerosol light absorption with wavelength. Coated sphere calculations were used to show that Ångström exponents of absorption (AEA) as large as 1.6 are possible even with non-absorbing organic coatings on black carbon cores, suggesting care be exercised when diagnosing AEA. Insight on fuels burned is gleaned from comparison of AEA versus single scattering albedo (SSA) of the ambient measurements with laboratory biomass smoke measurements for many fuels. 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