Ans. Polar stratospheric clouds (PSCs) play a significant role in the depletion of ozone. These clouds are formed in the polar regions during the winter season when temperatures drop below -78 degrees Celsius. PSCs provide a surface for chemical reactions involving ozone-depleting substances (ODS) such as chlorofluorocarbons (CFCs) and halons. These reactions convert the relatively inactive ODS into highly reactive chlorine and bromine compounds, which then catalytically destroy ozone molecules.