TRAJECTORY MODELING OF EMISSIONS FROM LOWER STRATOSPHERIC AIRCRAFT

A series of isentropic trajectory calculations has been performed for emissions by stratospheric aircraft moving across the northern midlati tude oceanic flight corridors. Emission of exhaust is simulated by the daily initialization of air parcels along a flight path on the 500 K isentropic surface. Parcels are tracked during the first three weeks o f each January from 1980 to 1994 in order to determine the interannual variability in the spatial distribution of the exhaust and the likeli hood of exposure to cold temperatures. Few parcels emitted along these flight paths at this time of year were found to have experienced nitr ic acid trihydrate (NAT) formation temperatures, except for the partic ularly cold Januarys 1986, 1987, and 1992. We also find that large zon al fluctuations in the distribution of the emissions are typical for t his time of year and are strongly dependent on flight path. An extende d 6-month (January-June) run in which parcels were released daily alon g the New York-London route shows that emissions in the flight corrido r increase at a time-averaged rate which is nearly twice the rate at w hich the zonal average increases. In addition, local fluctuations of p ollutant density can be several times higher than the zonal average an d can persist for several weeks. A study of seasonal variability also shows a rapid buildup of emissions during the summer months. These ele vated emission levels must be considered in the interpretation of envi ronmental impact assessments based on two-dimensional transport models .