AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Black Carbon Aging from Biomass Burning
ALLISON AIKEN, Manvendra Dubey, Kyle Gorkowski, Claudio Mazzoleni, Swarup China, Shang Liu, Caleb Arata, Team FLAME-IV, Los Alamos National Lab
Abstract Number: 494 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Black carbon (BC) is now considered the second most important global warming factor behind CO2 and is underestimated by a factor of two in most global models (Bond et al., 2013). ~50% of BC is from biomass burning (BB), estimated to contribute up to ~0.6 W/m2 warming of the atmosphere. Organic carbon (OC) from fires condenses and/or mixes, lowering the forcing from BB to 0.03 ± 0.12 Wm-2. The reduction depends strongly on the composition and mixing state of OC and BC. Models and laboratory measurements indicate that a BC core coated with a non-absorbing layer can enhance absorption by 2, although it has not been observed to this degree in ambient data (Cappa et al., 2012). Direct on-line measurements of BC are made with the single particle soot photometer (SP2) from "fresh" and "aged" BB. We investigate BC in concentrated BB plumes from the two largest wildfires in New Mexico’s history with different ages and compare them to BC from indoor generation from single-source fuels, e.g. ponderosa pine, sampled during Fire Lab At Missoula Experiments IV (FLAME-IV). FLAME-IV includes direct emissions, well-mixed samples, and aging studies. Las Conchas Fire (July-August, 2011) BC was sampled after only a few hours of aging and exhibits mostly core-shell structure. Whitewater Baldy Fire (May-June, 2012) BC was sampled after an aging period of 10-20 hours and includes partially coated BC in addition to thickly coated core-shell BC. Partially coated BC is not expected to enhance absorption as much as core-shell BC, therefore, determining the morphology of the BC is important to constraining the extent warming due BC on climate. Ambient BC physical and optical properties from the photoacoustic soot spectrometer are compared with direct laboratory emissions to understand BC aging in order to improve model treatment of BC absorption in global climate models.