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

In situ aircraft measurements of ozone (O 3 ) 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 O 3 with carbon monoxide (CO) was found in biomass burning plumes in the boundary layer (<3 km). The ΔO 3 /ΔCO ratio (linear regression slope of O 3 ‐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 O 3 exported from northern Australia during BIBLE‐B is estimated to be 0.3 Gmol O 3 /day. In the biomass burning region, large enhancements of O 3 were coincident with the locations of biomass burning hot spots, suggesting that major O 3 production occurred near fires (horizontal scale <50 km).