I just saw the Periodic Video Ozone on Bondi Beach - Periodic Table of Videos where the impact of Chlorine from CFCs on Ozone is discussed. At around
04:00 or so, the adsorption of chlorine on to very small atmospheric ice crystals above the poles, especially the south pole is described. The chlorine is "stored" until hemispheric spring, when the sun releases the chlorine from the ice, so its impact on ozone spikes.
My main question is about the ice crystals. What keeps them suspended in the atmosphere for months? Why don't they fall, or participate in precipitation? Are they "hovering" over the pole for the whole winter? How?
Note: The video then goes on to discuss a "recent paper" (as of 2011) where the UV light reaching nearer the surface enabled by the ozone "hole" goes on to affect rainfall patterns over Australia. Is this now believed to be significant?