Chemical Drivers of Ozone Production in Smoke Transport: Characterization by Model Diagnostics and Measurements During FIREX-AQ

Biomass burning releases substantial amounts of ozone precursors that affect ozone production, air quality, and climate change. The complexity of the emissions and the coupled chemical and physical processes presents a challenge to quantify ozone production from fires. In this work, we study the dominant drivers behind ozone evolution in smoke transport using the regional chemical transport model WRF-Chem diagnostic tools together with the aircraft and ground-based observations during FIREX-AQ (the Fire Influence on Regional and Global Environments and Air Quality) 2019 field campaign. The WRF-Chem Integrated Reaction Rate (IRR) and process tendency diagnostics are applied along WRF online trajectories to investigate ozone evolution during smoke transport. In particular, we examine the roles of different volatile organic compounds (VOCs) and NOx in ozone production. To evaluate the model performance nearby and downstream of fires, we compare model results with FIREX-AQ airborne measurements and with TOLNet (Tropospheric Ozone Lidar Network) observations. Preliminary results for the Williams Flats Fire in 6-8 August 2019 show that acetaldehyde, formaldehyde, isoprene, glycolaldehyde, and cresol are the key VOCs species driving the active photochemical ozone production during the first 4-5 hours of smoke transport in the free troposphere. This study will reveal the chemical evolution behind ozone production from fire emissions.