Sulphate particles from subsonic aviation: impact on upper tropospheric and lower stratospheric ozone

An assessment study is presented here on the impact of sulphate particles emitted by subsonic aircraft. The strategy has been design a tracer fuel experiment to deduce a first approximation of the surface area density change of sulphate aerosols produced by subsonic aviation. Five three-dimensional chemical-transport models (CTM) have run this tracer experiment. Effects on upper tropospheric-lower stratospheric (UTLS) chemistry runs performed by three CTMs. The partecipating models are from: University of L'Aquila, the University of Utrecht, University of Cambridge, University of Oslo, Deutsches Zentrum fur Luft- und Raumfahrt, Meteo- France. The calculated average aerosol perturbation maximum of 0.8 x l0-8 cm-1 at an altitude of 11 km and poleward of 50°N and shows some upward transport into the lowermost stratosphere from the upper troposphere: physical and possible numerical reasons for this behaviour are discussed in the paper. This effect has implications on the chemical budged of the UTLS region, making heterogeneous chemical reactions faster. The magnitude of ozone changes is found to be comparable but smaller (up to 60% globally) than that produced by NOx emissions from subsonic aircraft, and of the opposite sign. Sulphate particle formation from subsonic aircraft would then have the overall effect of lowering the upper tropospheric ozone increase produced by the additional NOx from the aircraft.