The reasons why the Antarctic ozone hole is due to the formation of a unique cloud in occurs the lower stratosphere w temperatures drop well below -70°C for several months in the winter (a similar thing happens in the Arctic, but to much lesser extent). In the absence of sunlight in a the winter, this cloud persists as a rapidly whirling vortex. It is composed largely of ice crystals a and supercooled ternary mixtures of HNO3, HNo, 3HLO, H2so4, and Ho. Also present is some l generated when CFCs undergo photochemical dissociation and abstract H from stratospheric CH4. This HCI and chlorine nitrate produced by the following reaction are unreactive ozone in destruction: