Abstract

The effect of aircraft emissions on tropospheric ozone was studied using a 2-D zonal model, of longitude versus altitude. An emission inventory for the 1987 civil aircraft fleet was constructed based on fuel usage and civil aviation statistics. For the area covered by the model (30 - 60 degrees N) this resulted in emission rates of 2.0, 0.17, 0.43 and 2.5 Mtonnes/year of NO2, SO2, NMHCs and CO respectively. The addition of 1987 civil aircraft emissions to the modelled standard atmosphere caused increases in concentrations of O3 (12% ; 10ppbv), NOx (40%) ; 20 pptv) and OH (10%) between 8-12 km altitude. A doubling and tripling of the 1987 aircraft emissions corresponding to a present day inclusion of military aircraft emissions and a future scenario respectively caused the increase in 03 concentrations to double (19%) and almost triple (25%). Lightning a source of NOx in the natural atmosphere caused increases in concentrations of O3 (12% ; 10ppbv), NOx (40% ; 20 pptv) and OH (10%) between 8-12 km altitude. A doubling and tripling of the 1987 aircraft emissions and a future scenario respectively caused the increase in O3 concentrations to double (19%) and almost triple (25%). Lightning a source of NOx in the natural atmosphere was found to be an important parameter in this study. When this NOx source was omitted the change in O3 between 8-12 km altitude due to the 1987 civil aircraft was increased to 16%.