Photochemical production of O3 in biomass burning plumes in the boundary layer over northern Australia

In situ aircraft measurements of ozone (O3) and its precursors were made over northern Australia in August–September 1999 during the Biomass Burning and Lightning Experiment Phase B (BIBLE‐B). A clear positive correlation of O3 with carbon monoxide (CO) was found in biomass burning plumes in the boundary layer (<3 km). The ΔO3/ΔCO ratio (linear regression slope of O3‐CO correlation) is found to be 0.12 ppbv/ppbv, which is comparable to the ratio of 0.15 ppbv/ppbv observed at 0–4 km over the Amazon and Africa in previous studies. The net flux of O3 exported from northern Australia during BIBLE‐B is estimated to be 0.3 Gmol O3/day. In the biomass burning region, large enhancements of O3 were coincident with the locations of biomass burning hot spots, suggesting that major O3 production occurred near fires (horizontal scale <50 km).