Question

The amount of water vapour in the air decreases with altitude. Give a reason.

Answer 1

The amount of water vapour in the air decreases with altitude because:

• As altitude increases, the temperature of the air decreases.
• Cooler air can hold less water vapour compared to warm air.
• Also, at higher altitudes, air pressure is lower, and air becomes thinner (less dense), which means fewer water vapour molecules are present.
• Thus, with increasing height, both temperature and air pressure drop, reducing the capacity of air to hold water vapour, so the amount of water vapour decreases.