ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-14059-2009 In situ aerosol optics in Reno, NV, USA during and after the summer 2008 California wildfires and the influence of aerosol coatings Gyawali M. 1 Arnott W. P. 1 Lewis K. 1 Moosmüller H. 2 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 26 06 2009 9 3 14059 14079 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-discuss.net/9/14059/2009/acpd-9-14059-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/14059/2009/acpd-9-14059-2009.pdf

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. Measurements during the month of August, which were largely unaffected by fire smoke, exhibit surprisingly low AEA for aerosol light absorption when the SSA is highest, again likely as a consequence of the underappreciated wavelength dependence of aerosol light absorption by particles coated with non absorbing organic and inorganic matter.

 References Abel, S. J., Haywood, J. M., Highwood, E. J., Li, J., and Buseck, P. R.: Evolution of biomass burning aerosol properties from an agricultural fire in southern Africa, Geophys. Res. Lett., 30, 1783, doi:10.1029/2003GL017342, 2003. Andreae, M. O. and Gelencsér, A.: Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols, Atmos. Chem. Phys., 6, 3131–3148, 2006. Arnott, W. P., Moosmüller, H., Rogers, C. F., Jin, T., and Bruch, R.: Photoacoustic spectrometer for measuring light absorption by aerosols: Instrument description, Atmos. Env., 33, 2845–2852, 1999. Bergstrom, R. W., Pilewskie, P., Russell, P. B., Redemann, J., Bond, T. C., Quinn, P. K., and Sierau, B.: Spectral absorption properties of atmospheric aerosols, Atmos. Chem. Phys., 7, 5937–5943, 2007. Chen, L.-W. A., Moosmüller, H., Arnott, W. P., Chow, J. C., Watson, J. G., Susott, R. A., Babbitt, R. E., Wold, C. E., Lincoln, E. N., and Hao, W. M.: Emissions from laboratory combustion of wildland fuels: Emission Factors and Source Profiles, Environ. Sci. Technol., 41, 4317–4325, 2007. Chen, L.-W. A., Moosmüller, H., Arnott, W. P., Chow, J. C., Watson, J. G., Susott, R. A., Babbitt, R. E., Wold, C. E., Lincoln, E. N., and Hao, W. M.: Particle emissions from laboratory combustion of wildland fuels: In situ optical and mass meausurements, Geophys. Res. Lett., 33, L04803, doi:10.1029/2005GL024838, 2006. Clarke, A., McNaughton, C., Kapustin, V., Shinozuka, Y., Howell, S., Dibb, J., Zhou, J., Anderson, B., Brekhovskikh, V., Turner, H., and Pinkerton, M.: Biomass burning and pollution aerosol over North America: Organic components and their influence on spectral optical properties and humidification response, J. Geophys. Res., 112, D12S18, doi:10.1029/2006JD007777, 2007. Hoff, R. M., Palm, S. P., Engel-Cox, J. A., and Spinhirne, J.: GLAS long-range transport observation of the 2003 California forest fire plumes to the northeastern US, Geophys. Res. Lett., 32, L22S08, doi:10.1029/2005GL023723, 2005. Hudson, P. K., Murphy, D. M., Cziczo, D. J., Thomson, D. S., de Gouw, J. A., Warneke, C., Holloway, J., Jost, H.-J., and Hübler, G.: Biomass-burning particle measurements: Characteristic composition and chemical processing, J. Geophys. Res., 109, D23S27, doi:10.1029/2003JD004398, 2004. Ito, A. and Penner, J. E.: Global estimates of biomass burning emissions based on satellite imagery for the year 2000, J. Geophys. Res., 109, D14S05, doi:10.1029/2003JD004423, 2004. Johnson, B. T., Osborne, S. R., Haywood, J. M., and Harrison, M. A. J.: Aircraft measurements of biomass burning aerosol over West Africa during DABEX, J. Geophys. Res., 113, D00C06, doi:10.1029/2007JD009451, 2008. Kirchstetter, T. W., Novakov, T., and Hobbs, P. V.: Evidence that the spectral dependence of light absorption by aerosols is affected by organic carbon, J. Geophys. Res., 109, D21208, doi:10.1029/2004JD004999, 2004. Lack, D. A., Cappa, C. D., Covert, D. S., Baynard, T., Massoli, P., Sierau, B., Bates, T. S., Quinn, P. K., Lovejoy, E. R., and Ravishankara, A. R.: Bias in Filter-Based Aerosol Light Absorption Measurements Due to Organic Aerosol Loading: Evidence from Ambient Measurements, Aer. Sci. Tech., 42, 1033–1041, doi:10.1080/02786820802389277, 2008. Lewis, K., Arnott, W. P., Moosmüller, H., and Wold, C. E.: Strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual wavelength photoacoustic instrument, J. Geophys. Res., 113, D16203, doi:10.1029/2007JD009699, 2008. Moosmüller, H., Chakrabarty, R. K., and Arnott, W. P.: Aerosol Light Absorption and its Mea surement: A Review, J. Quant. Spectrosc. Radiat. Transfer, 110, 844–878 ,doi:10.1016/j.jqsrt.2009.02.035, 2009. Mulholland, G. W. and Bryner, N. P.: Radiometric model of the transmission cell-reciprocal nephelometer, Atmos. Env., 28, 873–887, 1994. Naik, V., Mauzerall, D. L., Horowitz, L. W., Schwarzkopf, M. D., Ramaswamy, V., and Oppenheimer, M.: On the sensitivity of radiative forcing from biomass burning aerosols and ozone to emission location, Geophys. Res. Lett., 34, L03818, doi:10.1029/2006GL028149, 2007. Pfister, G. G., Wiedinmyer, C., and Emmons, L. K.: Impacts of the fall 2007 California wildfires on surface ozone: Integrating local observations with global model simulations, Geophys. Res. Lett., 35, L19814, doi:10.1029/2008GL034747, 2008. Rahmah, A. A., Arnott, W. P., and Moosmüller, H.: Integrating nephelometer with a low truncation angle and an extended calibration scheme, Meas. Sci. Technol., 17, 1723–1732, 2006. Roden, C. A., Bond, T. C., Conway, S., and Pinel, A. B. O.: Emission Factors and Real-Time Optical Properties of Particles from Traditional Wood Burning Cookstoves, Environ. Sci. Tech., 40, 6750–6757, 2006. Subramanian, R., Roden, C. A., Boparai, P., and Bond, T. C.: Yellow beads and missing particles: Trouble ahead for filter-based absorption measurements, Aerosol Sci. Tech., 41, 630–637, 2007. Toon, O. B. and Ackerman, T. P.: Algorithms for the calculation of scattering by stratified spheres, Appl. Opt., 20, 3657–3660, 1981. Westerling, A. L., Hidalgo, H. G., Cayan, D. R., and Swetnam, T. W.: Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity, Science, 313, 940–943, 2006. Yang, M., Howell, S. G., Zhuang, J., and Huebert, B. J.: Attribution of aerosol light absorption to black carbon, brown carbon, and dust in China – interpretations of atmospheric measurements during EAST-AIRE, Atmos. Chem. Phys., 9, 2035–2050, 2009.