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. The FLAME experiments were a series of laboratory studies of the chemical, physical, and optical properties of fresh smokes from the combustion of wildland fuels that are burned annually in the western and southeastern US. The burns were conducted in the combustion chamber of the USFS Fire Sciences Laboratory in Missoula, Montana. Here we discuss the 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 the various instrument characteristics and from instrument calibration studies. Our estimates of single scattering albedo for different dry smokes varied from 0.43–0.99, indicative of the wide variations in smoke aerosol chemical composition that were observed. In selected case studies, we retrieved the complex refractive index from the measurements, but show that these are highly sensitive to the uncertainties in measured size distributions.