What's all the fuss with Polar Stratospheric Clouds?

Why is the ozone hole above Antarctica when it is the developed countries in the Northern Hemisphere which use the highest concentration of CFCs? The answer is Polar Stratospheric Clouds!!

Without Polar Stratospheric Clouds

Incoming UV radiation breaks down chloroflurocarbons. This results in either ClO (Chlorine Monoxide) which has reacted with ozone or as Chlorine atoms (Cl). Subsequently, naturally occurring gasses such as Nitrogen dioxide and methane react with ClO and Cl to form chemically inactive molecules (CIONO2 & HCI) Shown in Figure 1. The reaction then ends, therefore ozone depletion is minimal.

Comparing reactions in the presence of polar stratospheric clouds and their absence.

With Polar Stratospheric Clouds

Contrary to the above conditions where there are no polar stratospheric clouds(PSCs) present, when they are, the reactions occurring are very different. PSCs initiate reactions between the two reservoirs which withdraws Cl from its reservoirs in the form of Cl2. Sunlight will then break up molecular Chlorine (Cl2) into separate Chlorine atoms which are highly reactive with ozone. This reaction then forms ClO & O2, which rapidly react with each other giving off producing Cl2O2 which in the presence of visible light will break down into Cl atoms and Oxygen molecules. 

Reservoirs are not reformed because of the precipitation of Nitric acid which prevents them from occurring.