IMPACT OF THE HETEROGENEOUS HYDROLYSIS OF BRONO2 ON CALCULATED OZONE CHANGES DUE TO HSCT AIRCRAFT AND INCREASED SULFATE AEROSOL LEVELS

The heterogeneous hydrolysis of BrONO2 via sulphate aerosols has been included in 2-D model calculations of the impact of projected fleets o f supersonic aircraft on atmospheric ozone. Calculations have been per formed for aerosol levels ranging from zero to 16x the lower limit in WMO [1992]. The results show that the addition of this reaction has a major effect when the heterogeneous hydrolysis of N2O5 has reached sat uration in regions where the night length is short. At 4x the lower li mit of aerosols, the additional calculated change in aircraft impact d ue to the inclusion of BrONO2 hydrolysis is of the same order as the i mpact calculated when this reaction is not included. Calculations for background atmospheres at high aerosol levels show that the inclusion of this reaction significantly increases the predicted ozone depletion resulting from volcanically-enhanced aerosol levels.