UPSC Prelims 2024 Q2: Geography – Atmosphere & Climatology
Consider the following statements :
Statement - I :
Thickness of the troposphere at the equator is much greater as compared to poles.
Statement - II :
At the equator, heat is transported to great heights by strong convectional currents.
Which one of the following is correct in respect of the above statements ?
- (a) Both Statement - I and Statement - II are correct and Statement - II explains Statement - I
- (b) Both Statement - I and Statement - II are correct, but Statement - II does not explain Statement - I
- (c) Statement - I is correct, but Statement - II is incorrect
- (d) Statement - I is incorrect, but Statement - II is correct
Answer: (a) Both Statement - I and Statement - II are correct and Statement - II explains Statement - I
Explanation
Thickness of the troposphere
| Location | Height of troposphere | Why |
|---|---|---|
| Equator | About 18 km | Intense heating creates strong convection currents that carry heat high up |
| Poles | About 8 km | Weak heating; little convection |
| Average | About 13 km | Varies with season and latitude |
Statement I — correct. The troposphere is more than twice as thick at the Equator.
Statement II — correct, and it is the reason. Strong convectional currents at the Equator lift heat and air to great heights, pushing the tropopause upward.
Troposphere basics:
| Feature | Fact |
|---|---|
| Weather | Almost all weather happens here |
| Temperature | Falls about 6.5°C per km of height |
| Upper limit | Tropopause — about −80°C over the Equator, −45°C over the poles |
Answer: (a) Both Statement - I and Statement - II are correct and Statement - II explains Statement - I.
Why each option is right or wrong
- (a) CORRECT. The troposphere is about 18 km at the Equator because convection carries heat to great heights.
- (b) Incorrect. Statement II is not a side fact; convection is the direct reason for the greater thickness.
- (c) Incorrect. Statement II is true; strong equatorial convection is a core NCERT fact.
- (d) Incorrect. Statement I is true; the troposphere is about 18 km at the Equator and 8 km at the poles.
Key point
Troposphere: about 18 km at the Equator, 8 km at the poles — thicker where convection is stronger.
Remember
The troposphere is about 18 km thick at the Equator and 8 km at the poles.
Common mistakes
- Assuming the atmosphere is evenly thick everywhere; the tropopause is much higher over the Equator.
- Expecting the coldest tropopause over the poles; it is coldest over the Equator because it is highest there.
- Not linking thickness to convection, which is the explanation asked for in Statement II.
Exam tip
Hot air rises higher → thicker troposphere. Equator 18 km, poles 8 km.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, Ch 8 (Structure of Atmosphere)
- Savindra Singh — Climatology (Prayag Pustak Bhawan)