Optical closure experiments for biomass smoke aerosols
1Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
2Desert Research Institute, Nevada System of Higher Education, Reno, NV, USA
3Department of Physics, University of Nevada, Reno, NV, USA
4US Forest Service, RMRS Fire Sciences Laboratory, Missoula, MT, USA
5Air Resources Division, US National Park Service, Fort Collins, CO, USA
*now at: Centre for Atmospheric Science, University of Manchester, Manchester, UK
Abstract. A series of laboratory experiments at the Fire Laboratory at Missoula (FLAME) investigated chemical, physical, and optical properties of fresh smoke samples from combustion of wildland fuels that are burned annually in the western and southeastern US The burns were conducted in the combustion chamber of the US Forest Service Fire Sciences Laboratory in Missoula, Montana. Here we discuss retrieval of optical properties for a variety of fuels burned in FLAME 2, using nephelometer-measured scattering coefficients, photoacoustically-measured aerosol absorption coefficients, and size distribution measurements. Uncertainties are estimated from various instrument characteristics and instrument calibration studies. Our estimates of single scattering albedo for different dry smoke samples varied from 0.428 to 0.990, indicative of observed wide variations in smoke aerosol chemical composition. In selected case studies, we retrieved the complex refractive index from measurements but show that these are highly sensitive to uncertainties in measured size distributions.