Question

2. Why do we find a substantial amount of water vapour in the atmosphere? What is its source​

Answer 1

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Humidity, the amount of water vapour in the air. It is the most variable characteristic of the atmosphere and constitutes a major factor in climate and weather. A brief treatment of humidity follows. For full treatment, see climate: Atmospheric humidity and precipitation

Answer 2

Explanation:

Water vapour is a greenhouse gas even more effective at absorbing thermal radiation from the earth's surface than the carbon dioxide.

The source of water vapour :

The sun heats up the rivers and oceans to turn water in to vapour form . The vapour from water bodies rises in the atmosphere to form clouds