Investigating fire-induced ozone production from local to global scales

Tropospheric ozone (O3 ) production from wildfires is highly uncertain; previous studies have identified both production and loss of O3 in fire-influenced air masses. To capture the total ozone production attributable to a smoke plume, we bridge the gap between near-field fire plume chemistry and aged smoke in the remote troposphere. Using airborne measurements from several major campaigns, we find that fire-ozone production increases with age, with a regime transition from NOx -saturated to NOx -limited conditions, showing that O3 production in well-aged plumes is largely controlled by nitrogen oxides (NOx ). Observations in fresh smoke demonstrate that suppressed photochemistry reduces O3 production by ∼ 70 % in units of ppb Ox (O3 + NO2 ) per ppm CO in the near-field (age < 20 h). We demonstrate that anthropogenic NOx injection into VOC-rich fire plumes drives additional O3 production, sometimes exceeding 50 ppb above background. Using a box model, we explore the evolving sensitivity of O3 production to fire emissions and chemical parameters. We demonstrate the importance of aerosol-induced photochemical suppression over heterogeneous HO2 uptake, validate HONO’s