Stratospheric Aerosols and Clouds

The existence of aerosol surfaces in the stratosphere has been known for many decades, but it was not until the discovery of the Antarctic ozone hole that their role in surface chemistry was recognized. Here the stratospheric sulfate layer and polar stratospheric clouds will be 

Sulfur dioxide is relatively stable and is thus present in fairly large abundance in the stratosphere. It can be photodissociated by radiation in the 200-230 nm region, where its absorption cross section is of the order of 10-18 to 10-17cm2. 

The HSO3 intermediate is probably destroyed by O2 (Calvert and Stockwell, 1983 McKeen et al., 1984)  

Sulfur trioxide can combine with water vapor to form sulfuric acid  

It should be noted that the reaction sequences which convert S02 to sulfate do not modify the HOx budget (McKeen et al., 1984). The intrusion of large amounts of S02 in the stratosphere during volcanic eruptions could enhance the short-term amount of ozone in the middle atmosphere by direct chemical effects (Crutzen and Schmailzl, 1983 Bekki et al., 1993) through the following mechanism  

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