With reference to "water vapour", which of the following statements is/are correct?

Select the answer using the code given below:

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Correct Answer: (a) 1 only

Statement 1: Water vapour is a gas, the amount of which decreases with altitude.
- This statement is correct. The quantity of water vapour in the air depends on the rate of evaporation and the temperature of the air, which determines its holding capacity. Both temperature and evaporation decrease with altitude, resulting in a rapid decrease in water vapour with altitude .
Statement 2: Its percentage is maximum at the poles.
- This statement is incorrect. Water vapour is present in varying amounts in the atmosphere, but its concentration is generally lower in arid or very cold locations, such as polar regions. The amount of water vapour is higher in warmer regions and decreases from the equator towards the poles .

Water Vapour:
- Definition: Water vapour is the gaseous phase of water, produced from the evaporation or boiling of liquid water or from the sublimation of ice .
- Properties: It is transparent and less dense than most other constituents of air. It plays a crucial role in the hydrologic cycle and atmospheric processes.
- Role in Climate: Water vapour is a significant greenhouse gas, contributing more to the greenhouse effect than non-condensable gases like carbon dioxide and methane. It acts as a feedback mechanism, amplifying the effects of initial warming forces .
- Distribution: The concentration of water vapour in the atmosphere varies, typically making up 2-3% of the atmosphere on average, but can be as high as 4% in some regions. It is lower in colder and arid regions .
- Altitude Effect: The amount of water vapour decreases with altitude due to lower temperatures and reduced evaporation rates at higher altitudes .
- Hydrologic Cycle: Water vapour is a key component of the hydrologic cycle, contributing to cloud formation, precipitation, and the overall distribution of water on Earth .
- Climate Impact: As a greenhouse gas, water vapour creates a positive feedback loop for global warming. Increased temperatures lead to higher evaporation rates, which in turn increase the amount of water vapour in the atmosphere, further enhancing warming .