The impact of aircraft nitrogen oxide emissions on tropospheric ozone studied with a 3D lagrangian model including fully diurnal chemistry

A three-dimensional Lagrangian tropospheric chemistry-transport model is used to investigate the impact of aircraft NOx emissions upon the concentrations of ozone and hydroxyl radicals. The model has a five minute chemistry time-step, and a three-hour advection time step, and hence resolves diurnal variations in chemistry. The model contains a representation of tropospheric inorganic chemistry, as well as that of methane and nine emitted hydrocarbons. Aircraft NOx emissions were found to contribute up to 20–60% towards background upper troposphere NOx levels, and to be responsible for up to 5–10% of upper tropospheric 03, with a maximum contribution in April. The magnitude of the peak ozone change in July is 13 ppb and 8.5 ppb in January, and its location shifts with incident solar radiation. Calculated globally averaged radiative forcing exerted by the extra ozone is 0.05 W m−2, mainly concentrated in the Northern hemisphere.