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 ✓ UPSC's answer
(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

Why the answer is (a)

• The troposphere is about 16–18 km thick at the equator but only about 8 km at the poles — Statement-I is correct.

• At the equator intense surface heating drives strong convectional currents that carry heat and moisture to great heights, pushing the tropopause upward; at the cold poles convection is weak and the layer is shallow — Statement-II is correct.

• The Earth's rotation also flings the atmosphere outward at the equator, but convection is the main reason for the difference, so Statement-II explains Statement-I.

• The tropopause is therefore higher and colder over the equator than over the poles.

• Hence option (a).

Why the other options are wrong

(b) Both Statement-I and Statement-II are correct, but Statement-II does not explain…: Statement-II is the main cause of the thicker equatorial troposphere, so it does explain Statement-I.
(c) Statement-I is correct, but Statement-II is incorrect: Statement-II is also correct: equatorial convection is strong.
(d) Statement-I is incorrect, but Statement-II is correct: Statement-I is correct: the troposphere is thickest at the equator.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2024, held on 16 June 2024. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.