IMPACT OF HETEROGENEOUS BRONO2 HYDROLYSIS ON OZONE TRENDS AND TRANSIENT OZONE LOSS DURING VOLCANIC PERIODS

The hydrolysis of BrONO2 on sulphate aerosols has been included in a 2 -D model calculation of ozone changes over the period 1980 - 1995. Inc lusion of this reaction has only a marginal impact on the calculated o zone trends between 1980 and 1990. The effect of the reaction on an at mosphere which has been heavily perturbed by sulphate aerosols for the period June 1991 - 1995 has been examined by using the idealised WMO 1995 scenario. The results show that the addition of this reaction has a major impact on the calculated transient ozone loss under enhanced aerosol conditions and approximately doubles the calculated ozone loss between 60 degrees S and 60 degrees N in 1992 (when maximum loss of o zone occurs). In contrast to the effects of the hydrolysis of N2O5, th e effects of the hydrolysis of BrONO2 are most marked at high latitude s in summer.