Aerosols impact the radiative balance of the earth directly by scattering and absorbing sunlight and semi-directly by altering the vertical temperature profile of the atmosphere and modifying cloud properties. The magnitudes of these effects are highly uncertain thereby limiting our understanding of and ability to predict earth's climate. Absorption of sunlight by black carbon (BC) aerosols is thought to be the largest positive radiative forcing after carbon dioxide and biomass burning accounts for greater than half of BC in the atmosphere. A key parameter in describing aerosol radiative properties is the single scattering albedo (SSA), which is difficult to reliably quantify from space, thus, making in-situ measurements essential. A suite of instruments will be deployed to the Fire Sciences Laboratory in Missoula, Montana for a 4-week investigation (entitled FLAME-IV (the 4th Fire Lab At Missoula Experiment)) of biomass-burning emissions from globally important fuel types. Emissions will be characterized with a photoacoustic absorption spectrometer (PAS), a cavity attenuated phase shift spectrometer (CAPS), a thermal denuder, and the aerosol scattering to extinction ratio (ASTER) instrument. Aerosol absorption, enhanced absorption caused by semi-volatile coatings, brown carbon, the SSA of the bulk aerosol and the SSA of single particles will be quantified. The single-particle SSA distribution for biomass burning emissions will provide new information regarding the size, character, and mixing state of particles responsible for absorption. These detailed optical properties will inform satellite retrievals and climate models.
Project data will be archived in easily accessible formats and available publicly for use by modelers and others. Result will facilitate informed public policy decisions regarding the climatic implications of biomass burning emissions. The project will support 2 full-time graduate students and provide opportunities for undergraduate research. This study will foster collaboration among the Atmospheric Science Department at the University of Wyoming (an EPSCOR University), the Fire Sciences Lab, and other groups participating in Flame IV. Results will be reported at national conferences and in the peer-reviewed literature. Results will also be incorporated into courses offered in the principal investigator's department, presentations to community groups, and workshops for both high school students and K-12 teachers.
