Model study of polar stratospheric clouds and their effect on stratospheric ozone .2. Model results

We use detailed microphysical/chemical/dynamical two-dimensional model described in part I [De Rudder et al., this issue] to study the effect of heterogeneous reactions occurring on the surface of polar stratospheric clouds (PSCs) on stratospheric ozone. The calculations show that the heterogeneous reactions occurring on the surface of PSCs are the likely causes of the ozone decrease observed from 1980 to 1990 in both Antarctica and the Arctic. The calculation shows that the dense sulfate aerosol cloud produced by the eruption of Mount Pinatubo (in the Phillipines, 1991) has enhanced the formation rate of type I PSCs in the Arctic and the Antarctic. In the calculation, the concentration and surface area of type I PSCs are enhanced. The effect on the ozone depletion in the Antarctic is, however, limited due to fact that the conversion from ClONO2 to ClO on PSCs is almost ''saturated'' under no-volcanic conditions. For the potential ozone depletion, the enlargement in the area covered by PSCs may therefore be more important than the increase in PSC density. The calculation also shows that in the future, the density of PSCs in the Arctic could be enhanced owing to the potential emission of water vapor and nitrogen species by high altitude aircraft. The increase in PSC density could lead to a maximum of ozone depletion of 10% at the northern high latitudes in winter.