Impact of aircraft NOx emissions.: Part 1:: Interactively coupled climate-chemistry simulations and sensitivities to climate-chemistry feedback, lightning and model resolution

Simulations with the fully coupled climate-chemistry model E39/C suggest that the 1990 aircraft NOx emissions contributed substantially to the Northern Hemisphere NOx (30-40%) and ozone (3-4%) tropospheric burdens. Ozone production rates are increased by air traffic NOx emissions in the mid- and upper troposphere, whereas ozone loss rates are increased in the lower troposphere but decreased at cruise altitudes. The latter reduction results from increased tropospheric NO and NO2 concentrations and a change in the OH:HO2 ratio at cruise altitudes. Sensitivity studies showed that feedback processes between chemical species and dynamics are not altered significantly by air traffic. However, the results are sensitive to the lightning NOx emission patterns, the vertical resolution of the model at tropopause altitudes, model domain, and maximum flight level.