The ozone hole - The role of polar stratospheric cloud particles

The role of polar stratospheric clouds in the formation of the Antarctic ozone hole is considered. Several researchers have suggested that the decrease in ozone over Antarctica is related to the polar stratospheric clouds (PSCs) which had been observed in the antarctic winter stratosphere. Some of the pertinent characteristics of polar stratospheric clouds are discussed, and it is shown how these clouds may participate in the ozone destruction process. The satellite data for PSCs is analyzed, and statistical information regarding the number and maximum extinctions of these clouds is presented. Evidence that the polar stratospheric clouds are composed of frozen nitric acid is considered. It is suggested that the evaporation of the clouds, in late August and September, will release HOCl and HNO3 to the environment. This could be followed by the photodissociation of HOCl to OH and Cl, which would very effectively destroy ozone. However, the ozone destruction mechanism could be halted when enough of the evaporated nitric acid is photolized.