Some time ago formation of polar stratospheri clouds reported over Antarctica. Why were these formed ? What happens when such clouds break up by warmth of sunlight ?

Explanation

In summer season, nitrogen dioxide and methane react with chlorine monoxide and chlorine atoms forming chlorine sinks, perventing much ozone depletion. Whearas in winter, special tupe of clouds calld polar stratospheric clouds are formed over Anaractica.
`ClO^(•)(g)+NO(g)rarrunderset("Chlorine nitrate")(ClONO_(2)(g))`
`Cl^(•)(g)+CH_(4)(g)rarr.^(•)CH_(3)(g)+HCl(g)`
`ClONO_(2)(g)+H_(2)O(g)overset("Hydrolysis")rarrHOCl(g)+HNO_(3)(g)`
`ClONO_(2)(g)+HCl(g)rarrCl_(2)(g)+HNO_(3)(g)`
When sunlight returns to the Antaractica in the spring, the sun's warmth breaks up the clouds and `HOCl, Cl_(2)` are photolysed by sunlight.
`HOCl(g) overset(hv)rarrO^(•)H(g)+Cl^(•)(g)`
`Cl_(2)(g)overset(hc)rarr2Cl^(•)(g)`
The chlorine radicals thus formed, initiate the chain reaction for ozone depletion.