Q. With reference to “water vapour”, which of the following statements is/are correct?
- It is a gas, the amount of which decreases with altitude.
- Its percentage is maximum at the poles.
Select the answer using the code given below:
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Answer: (a) 1 only
Notes:
- Water vapour is also a variable gas in the atmosphere, which decreases with altitude. In the warm and wet tropics, it may account for four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air.
- Water vapour also decreases from the equator towards the poles. It also absorbs parts of the insolation from the sun and preserves the earth’s radiated heat. It thus, acts like a blanket allowing the earth neither to become too cold nor too hot. Water vapour also contributes to the stability and instability in the air.
- The cold temperatures at the poles mean that the air can hold very little moisture. In contrast, warm tropical air can hold much more water vapor.