Impact of the heterogeneous hydrolysis of BrONO2 on calculated ozone changes due to HSCT aircraft and increased sulphate aerosol levels

The heterogeneous hydrolysis of BrONO2 via sulphate aerosols has been included in 2-D model calculations of the impact of projected fleets of supersonic aircraft on atmospheric ozone. Calculations have been performed 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 saturation in regions where the night length is short. At 4x the lower limit of aerosols, the additional calculated change in aircraft impact due to the inclusion of BrONO2 hydrolysis is of the same order as the impact 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.