New publication on photochemical environment over Southeast Asia primed for hazardous ozone levels with influx of nitrogen oxides from seasonal biomass burning published in Atmospheric Chemistry and Physic Discussion.

Marvin, M. R., Palmer, P. I., Latter, B. G., Siddans, R., Kerridge, B. J., Latif, M. T., and Khan, M. F. (2020). Photochemical environment over Southeast Asia primed for hazardous ozone levels with influx of nitrogen oxides from seasonal biomass burning. Atmos. Chem. Phys. Discuss. 2020, 1-33.

In this study we use the nested GEOS-Chem atmospheric chemistry transport model (horizontal resolution of 0.25° × 0.3125°), in combination with satellite observations from the Ozone Monitoring Instrument (OMI) and ground-based observations from Malaysia, to investigate ozone photochemistry over Southeast Asia in 2014. Seasonal cycles of tropospheric ozone columns from OMI and GEOS-Chem peak with biomass burning emissions. Compared to OMI, the model has a mean annual bias of −11 % but tends to overestimate tropospheric ozone near areas of seasonal fire activity. We find that outside of these burning areas, the underlying photochemical environment is generally NOx-limited, dominated by anthropogenic NOx and biogenic non-methane VOC emissions. Pyrogenic emissions of NOx play a key role in photochemistry, shifting towards more VOC-limited ozone production and contributing about 30 % of the regional ozone formation potential during both biomass burning seasons. Using the GEOS-Chem model, we find that biomass burning activity coincides with widespread ozone exposure at levels that exceed world public health guidelines, resulting in 272 premature deaths on mainland Southeast Asia in March of 2014 and another 273 deaths across Indonesia in September. Despite a positive model bias, hazardous ozone levels are confirmed by surface observations during both burning seasons.