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

Explanation

### Step-by-Step Solution

1. **Understanding Polar Stratospheric Clouds (PSCs)**:
- Polar stratospheric clouds form in the stratosphere over Antarctica during the winter months. These clouds are composed of ice crystals and play a significant role in ozone depletion.

2. **Formation of PSCs**:
- During winter, the conditions in the stratosphere become very cold, allowing for the formation of PSCs. The presence of chlorine compounds is crucial in this process.
- In the winter, chlorine free radicals (Cl•) can react with compounds such as methane (CH4) and nitrogen oxides (NOx), leading to the formation of chlorine-containing compounds like ClO and ClONO2.
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