USE OF CORRELATIONS BETWEEN LONG-LIVED ATMOSPHERIC SPECIES IN ASSESSMENT STUDIES

The results of airborne measurement campaigns and two-dimensional (2-D ) model calculations show compact relationships between certain pairs of long-lived species. Such correlations have been used in the present study to reduce the number of transported species used in the Commonw ealth Scientific and Industrial Research Organisation (CSIRO) two-dime nsional chemical transport model (2-D CTM) when calculating ozone chan ges from proposed fleets of supersonic aircraft or changing halocarbon concentrations. Differences to both the composition of the background atmosphere and to the predicted ozone changes are examined. It is sho wn that the use of correlations has only a small effect on the predict ed ozone changes. larger differences are found for the changing haloca rbon scenario than for the supersonic aircraft scenario. These differe nces are due to difficulties associated with correctly accounting for the time variation of the source gas mixing ratios. Further work is re quired to reduce this source of error. The results of these studies sh ould be applicable to 3-D CTMs, where large savings in computational t ime can be achieved through the reduction in the number of transported species.