THE IMPACT OF AIRCRAFT NITROGEN-OXIDE EMISSIONS ON TROPOSPHERIC OZONESTUDIED 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 c oncentrations of ozone and hydroxyl radicals. The model has a five min ute chemistry time-step, and a three-hour advection time step, and hen ce resolves diurnal variations in chemistry,The model contains a repre sentation of tropospheric inorganic chemistry, as well as that of meth ane and nine emitted hydrocarbons. Aircraft NOx emissions were found t o contribute up to 20-60% towards background upper troposphere NOx lev els, and to be responsible for up to 5-10% of upper tropospheric O-3, 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 shif ts with incident solar radiation. Calculated globally averaged radiati ve forcing exerted by the extra ozone is 0.05 W m(-2), mainly concentr ated in the Northern hemisphere. (C) 1997 Elsevier Science Ltd.