UPSC CSE Prelims
Question 70
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:
View correct answer and explanation
Correct answer: C
Correct Option: C
Explanation: Tropospheric air is heated largely from below and cools with altitude as pressure and density decrease.
Statement/Item-wise Analysis:
1: Correct - Solar-heated land and ocean surfaces transfer heat to near-surface tropospheric air.
2: Incorrect - The atmosphere does not generally become moister with altitude; upper air is often drier.
3: Correct - Lower pressure/density aloft allows rising air to expand and cool adiabatically.
Option-wise Analysis:
A: Incorrect - omits correct item 3.
B: Incorrect - includes incorrect item 2; omits correct item 1.
C: Correct - includes exactly the valid statements/items and excludes the invalid ones.
D: Incorrect - includes incorrect item 2.
Review Note: “Heated upwards only from Earth’s surface” simplifies real radiative and latent-heating processes; it is the textbook intent.