Previous Year Question
Normally, the temperature decreases with the increase in height from the Earth’s surface, because
the atmosphere can be heated upwards only from the Earth’s surface.
there is more moisture in the upper atmosphere.
the air is less dense in the upper atmosphere.
Select the correct answer using the codes given below.
Correct Answer: C
Detailed Solution
This normal pattern is mainly observed in the troposphere, where temperature decreases by approximately 6.5°C for every 1,000 metres of ascent. This is called the normal lapse rate.
Statement 1 is correct: The atmosphere is heated only to a limited extent directly by the Sun. The Earth’s surface absorbs solar radiation, becomes warm and emits long-wave terrestrial radiation. This terrestrial radiation heats the atmosphere from below. Consequently, air closer to the surface is generally warmer.
Statement 2 is incorrect: Most atmospheric water vapour and moisture are concentrated in the lower part of the troposphere. Air pressure, density and generally the amount of water vapour decrease with altitude.
Statement 3 is correct: Both air pressure and density decrease with altitude. As air rises into a region of lower pressure, it expands. In doing work during expansion without receiving external heat, the air cools—a process known as adiabatic cooling.