AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Rapid Transformations of Biomass Burning Particulate Emissions in the Near Field
ARTHUR J. SEDLACEK, Timothy Onasch, Kouji Adachi, W. Patrick Arnott, Peter Buseck, Qi Zhang, John Shilling, Mikhail Pekour, Sonya Collier, Shan Zhou, Andrew Freedman, Lawrence Kleinman, Brookhaven National Lab
Abstract Number: 570 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Aerosols from biomass burning are recognized to perturb Earth’s climate through the direct effect, the semi- direct effect, and indirect effects. Whether wildfires are determined to heat or cool the atmosphere depends on the abundance and refractive index of emitted primary particles and secondary aerosol species. Currently inputs for model calculations are often based upon measurements of fresh (nascent) aerosols. However, a growing body of experimental evidence is beginning to indicate that aerosols generated in biomass burning (BB) events undergo rapid changes in their chemical, microphysical, and optical properties. Such rapid change suggests caution in the use of near-field aerosol properties in far field radiative forcing calculations.
During the summer and fall of 2013, the Department of Energy’s Atmospheric Radiation Measurement (ARM) program sponsored a coordinated field campaign that combined aircraft-based measurements with mountain top observations to investigate the near-field (< 5 hrs) as well as regional evolution of biomass-burning (BB) aerosol particles. This field campaign, known as BBOP (Biomass Burning Observation Project), represents the first time that the near-field evolution of BB aerosol particles has been exclusively targeted with research aircraft. For the wildfire flights (17 fires sampled, ~175 plumes), a Lagrangian sampling protocol was employed in which flight transects orthogonal to the plume direction were conducted at selected distances downwind of the source. The plume age was calculated using prevailing wind speed/direction and the assumption of a constant emission source during the sampling period.
We will present recent findings on the formation and evolution of tar balls, near field changes in aerosol chemical, microphysical, and optical properties, and on measurements from the Mt. Bachelor Observatory (MBO, ~ 2700k) in Central Oregon which provide complementary information on regional characteristics of wildfire plumes to the BBOP flight results.