Gases such as CFC’s are insoluble in H₂O and comparatively unreactive and are mixed through lower atmosphere from where they rise into the stratosphere. In Antarctic during the winter months i.e. June-August, the region does not receive any sunlight and the temperature falls -80^oC as such that high level ice clouds are formed called Polar stratosphere clouds (PSC’s). These act as an ideal catalytic surface on which chlorine react with ozone. But this reaction requires sunlight and hence occurs during Sept.-Oct. before the PSC’s meet out. The ozone hole disappears again when the Antarctic air warms up enough during late spring and summer. Antarctica is isolated from the rest of the world by natural circulation of wind called polar vortex, which prevents atmospheric mixing of stratospheric ozone, thus leading to depletion of ozone.