Aircraft measurements of ozone, NOx, CO, and aerosol concentrations in biomass burning smoke over Indonesia and Australia in October 1997: Depleted ozone layer at low altitude over Indonesia

Abstract

The 1997 El Niño unfolded as one of the most sever El Niño Southern Oscillation (ENSO) events in this century and it coincided with massive biomass burning in the equatorial western Pacific region. To assess the influence on the atmosphere, aircraft observations of trace gases and aerosol were conducted over Kalimantan in Indonesia and Australia. Over Kalimantan in Indonesia, high concentrations of O 3 , NOx, CO, and aerosols were observed during the flight. Although the aerosol and NOx decreased with altitude, the O 3 had the maximum concentration (80.5 ppbv) in the middle layer of the smoke haze and recorded very low concentrations (∼20 ppbv) in the lower smoke layer. This feature was not observed in the Australian smoke. We proposed several hypotheses for the low O 3 concentration at low levels over Kalimantan. The most likely are lack of solar radiation and losses at the surface of aerosol particles.