Normally, the temperature decreases with the increase in height from the Earth’s surface, because:

1. The atmosphere can be heated upwards only from the Earth’s surface.
2. There is more moisture in the upper atmosphere.
3. The air is less dense in the upper atmosphere.

Select the correct answer using the code given below:

1. 1 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3

Explanation

Statement 1 is correct

• The atmosphere is primarily heated from below, i.e., from the Earth’s surface. The surface absorbs solar radiation and then transfers heat to the lower layers of the atmosphere through conduction, convection, and terrestrial radiation. As altitude increases, this heating effect decreases, leading to a fall in temperature.

Statement 2 is incorrect

• The upper atmosphere generally contains less moisture, not more. Most water vapour is concentrated in the lower troposphere near the Earth’s surface. Therefore, this statement is incorrect.

Statement 3 is correct

• As altitude increases, air becomes less dense and pressure decreases. The expansion of rising air leads to adiabatic cooling, which contributes to the decrease in temperature with height.

Answer: (c) 1 and 3 only; Difficulty Level: Easy