AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Ice Nuclei Produced from Prescribed Fires in Southeastern United States
CHRISTINA S. MCCLUSKEY, Paul DeMott, Anthony J. Prenni, Amy P. Sullivan, Gavin McMeeking, Yury Desyaterik, Gary D. Franc, Thomas C. Hill, Sonia Kreidenweis, Colorado State University
Abstract Number: 601 Working Group: Aerosols, Clouds, and Climate
Abstract The role of various aerosol particle types acting as ice nuclei (IN) in affecting cold cloud microphysics, and how the concentrations of IN active under certain cloud conditions depend on major aerosol sources and chemical characteristics remain poorly understood. Such understanding is needed to explain the impact of IN on cloud phase and precipitation processes, as well as their indirect influence on climate. Previous chemical analyses of captured IN have shown that carbonaceous aerosols can serve as IN, and laboratory studies confirm that biomass combustion of some fuel types may represent a large source of IN to the atmosphere.
In this study, we aim to provide a better understanding of the contribution of biomass burning as an IN source. IN number concentration at various temperatures was measured with a continuous flow diffusion chamber operated in the condensation/immersion freezing nucleation mode during one background day and four large prescribed burns in southwest Georgia. Measurements were located within close range of fires using a mobile laboratory. IN were captured as activated ice crystals for offline measurement of residual aerosol elemental composition (via TEM). Also measured for relation to IN measurements were bulk aerosol composition, mass concentrations and size distribution. The fires were fueled by four different materials typically burned in the southeast United States during springtime; wiregrass, pine needles, small shrubs, and longleaf pine trees. Fire flame phase, fuel mass consumed, meteorological conditions, and soil types were also categorized.
Temporal dependence of IN concentrations at various activation temperatures, how these varied with smoke concentrations, the relation of IN activity and variability to bulk aerosol characteristics, and the varied compositions of IN found will be presented. Results demonstrate the clear potential contribution of burning as a source of IN of different types while the regional impact on clouds remains to be explored.