A234-04
Downwind Evolution of FIREX-AQ Wildfire Smoke Reveals Changes in Aerosol Processing Across the Plume Cross-Section

Wednesday, 16 December 2020: 07:12
Virtual
Nicole June1, Anna Lily Hodshire2, Elizabeth Brooke Wiggins3, Richard Moore3, Edward Winstead3, Claire E Robinson3, Kenneth Lee Thornhill II3, Kevin J Sanchez3, Hongyu Guo4, Pedro Campuzano Jost4, Jose L Jimenez5, Sonia M Kreidenweis1, Shantanu Jathar6 and Jeffrey R Pierce7, (1)Colorado State University, Atmospheric Science, Fort Collins, CO, United States, (2)Colorado State University, Chemistry, Fort Collins, CO, United States, (3)NASA Langley Research Center, Hampton, VA, United States, (4)University of Colorado Boulder, Boulder, CO, United States, (5)University of Colorado at Boulder, Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Chemistry, Boulder, CO, United States, (6)Colorado State University, Mechanical Engineering, Fort Collins, CO, United States, (7)Colorado State University, Department of Atmospheric Science, Fort Collins, CO, United States
Recorded Presentation
Abstract:
The evolution of organic aerosols and aerosol size distributions within smoke plumes are uncertain due to differences in the physical and chemical processes that occur in different smoke plumes. We use aircraft data from the western US portion of Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) to evaluate differences in aging between the edge and core of wildfire smoke plumes as well as wide versus narrow plumes. The edge and core of the smoke plume are defined using four ΔCO percentile groups within each plume transect (5-15%, 15-50%, 50-90%, and 90-100%), and we evaluate aging rates of mode aerosol diameter, the total aerosol number, OA enhancement ratios, and ΔO:ΔC ratios. In the 90-100% ΔCO percentile, the mode aerosol diameter increased faster than the 5-15% ΔCO percentile, and the background corrected aerosol number decreased faster, suggesting that coagulation occurs at a faster rate in the thicker portions of the smoke plume. The ΔO:ΔC ratios show that 5-15% ΔCO portions of the plume are more oxidized than the 90-100% ΔCO percentile, indicating faster photochemistry and/or evaporation in the edge of the plume. Since the FIREX-AQ campaign sampled wildfires with a variety of sizes and fuel sources, we are able to make comparisons between wide and narrow smoke plumes. The narrower smoke plumes have a less defined difference between behavior of the edge and core of the plume than those from the larger fires. In these narrower smoke plumes, the mode aerosol diameter increase is slower in comparison to the corresponding ΔCO percentile of the larger smoke plumes, due to a lower total aerosol number in the smaller plumes. The narrow plumes also appear to be more oxidized than the thick plumes due to changes in the photochemistry. Hence, aging in narrow plumes appears to be similar to the aging at the edges of wide plumes. The understanding of the in-plume gradients learned from these observations will be used to develop sub-grid aging parameterizations for regional/global aerosol models.
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