Investigating Effects of Biomass Burning Cross Plume Gradients and Plume Concentration on Photochemistry, Secondary Aerosol Formation, and Coagulation

NICOLE JUNE, Archana Dayalu, Marikate Mountain, Matthew Alvarado, Jeffrey R. Pierce, Colorado State University

     Abstract Number: 37
     Working Group: Aerosol Chemistry

Abstract
The evolution of organic aerosols, aerosol size distributions, and ozone within smoke plumes are uncertain due to the variability across different smoke plumes and potentially in different locations of a single plume. We use the SAM-ASP large eddy simulation coupled with the TUV radiation model to examine evolution of ozone, organic aerosols, and size distributions within smoke plumes during the first several hours of aging. We configure the model to run for a case study on a fire sampled during the FIREX-AQ field campaign. We find that the model is able to reasonably capture the evolution of this smoke plume, representing evolution in both the transect averages and along in-plume gradients. We then run additional simulations to examine the impacts of variability in smoke concentrations on the plume evolution both in terms of a transect average and in plume gradients. We find evidence of faster photochemistry along the plume edges than in the plume core. Ozone formation is initially suppressed in-plume prior to the first transect of measurements, and increases in ozone start on the plume top and plume edges. Due to faster coagulation, the particle diameter grows faster in the center of the plume than on the edge. However, mixing between the edge and core allows for faster growth of particles in the edge than if there was no mixing. We find faster growth in plumes with a higher smoke concentration, and faster photochemistry in plumes of a lower smoke concentration. Our results may be beneficial to understanding how these processes may need to be parameterized in coarse-grid regional and global models.