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 NO_x-saturated to NO_x-limited conditions, showing that O₃ production in well-aged plumes is largely controlled by nitrogen oxides (NO_x). Observations in fresh smoke demonstrate that suppressed photochemistry reduces O₃ production by ∼ 70 % in units of ppb O_x (O₃ + NO₂) per ppm CO in the near-field (age < 20 h). We demonstrate that anthropogenic NO_x 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 importance as an oxidant precursor, and confirm evolving NO_x sensitivity. We evaluate GEOS-Chem's performance against these observations, finding the model captures fire-induced O₃ enhancements at older ages but overestimates near-field enhancements, fails to capture the magnitude and variability of fire emissions, and does not capture the chemical regime transition. These discrepancies drive biases in normalized ozone production (ΔO₃/ΔCO) across plume lifetime, though the model generally captures observed absolute O₃ enhancements in fire plumes. GEOS-Chem attributes 2.4 % of the global tropospheric ozone burden and 3.1 % of surface ozone concentrations to fire emissions in 2020, with stronger impacts in regions of frequent burning.