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Time Evolution of Aerosol Light Scattering Observed in Wildland Fires in BBOP

 
Poster PDF

Authors

Larry Kleinman — Brookhaven National Laboratory
Arthur J Sedlacek — Brookhaven National Laboratory
Timothy B Onasch — Aerodyne Research, Inc.
Kouji Adachi — Meteorological Research Institute
William Patrick Arnott — University of Nevada Reno
Peter R. Buseck — Arizona State University
Duli Chand — Pacific Northwest National Laboratory
Manvendra K. Dubey — Los Alamos National Laboratory
Ed Fortner — Aerodyne Research, Inc.
Andrew Freedman — Aerodyne Research, Inc.
Chongai Kuang — Brookhaven National Laboratory
Fan Mei — Pacific Northwest National Laboratory
Gunnar I. Senum — Brookhaven National Laboratory
John E Shilling — Pacific Northwest National Laboratory
Stephen R. Springston — Brookhaven National Laboratory
Jason Tomlinson — Pacific Northwest National Laboratory
Jian Wang — Washington University in St. Louis
Robert James Yokelson — University of Montana
Rahul Zaveri — Pacific Northwest National Laboratory
Qi Zhang — University of California, Davis

Category

Secondary organic aerosol

Description

The Biomass Burn Operational Project (BBOP) was conducted between the beginning of July, 2013 and the end of October, 2013. This period overlapped the wildland fire season in the Pacific Northwest from July to mid September, and in October, overlapped the season for prescribed agricultural burns in the lower Mississippi River Valley. Here we focus on the time evolution of aerosol particles emitted from wildland fires in the Pacific Northwest. Sampling of fire generated aerosol was done via multiple aircraft transects of a smoke plume, primarily at downwind distances corresponding to transport times of one-half to four hours. Comparisons are made with background aerosol, often an accumulation of smoke from multiple fires that has had a longer, albeit not well-defined, atmospheric residence time. Our primary observation is that the downwind evolution of aerosol mass as measured with an SP-AMS is usually only a couple of tens of percent over a few hours and can be positive or negative. Light scattering in contrast exhibits larger changes, sometimes more than doubling, yielding an increased SSA. Fire generated aerosol which may have an initial SSA low enough to be a net heating agent is rapidly changed into a net cooling agent by its increased scattering. Plume dilution is accounted for by normalizing all quantities to CO, an inert tracer of fire emissions. Increases in light scattering in excess of increases in mass are accomplished by changes in size distribution, whereby aerosol particles become more efficient scatterers. For select cases, scattering data at up to 5 wavelengths (700, 630, 550, 450, 355nm) are compared with direct observations of particle size.