The effects of future supersonic aircraft on stratospheric chemistry modeled with varying meteorology

The potential impact of a future fleet of high-speed civil transports (HSCT s) on the year 2015 atmosphere is examined using the three-dimensional stra tospheric chemical transport model, SLIMCAT. The model scenarios performed are identical to those used by the recent Intergovernmental Panel on Climat e Change [1999] aircraft assessment. The importance of the background meteo rological conditions in determining the potential impact of HSCTs is assess ed by forcing the model with U.K. Meteorological Office analyses for the ye ars 1992-1998. The use of annually varying meteorological analyses leads to an interannual variability ill the modeled transport of air-craft-emitted NOx and H2O from the North Atlantic flight corridor. The resulting calculat ed O-3 perturbation exhibits an interannual variability of similar to 50 pp bv in the middle stratosphere, which is of a magnitude similar to the diffe rences between the O-3 perturbations calculated by models within Intergover nmental Panel on Climate Changes [1999]. This result highlights both the im portance of the chosen background meteorological conditions in aircraft ass essments and the extent to which differences in meteorology contribute to d ifferences between model calculations.