Previous Year Question
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?
Both Statement I and Statement II are correct and Statement II explains Statement I
Both Statement I and Statement II are correct, but Statement II does not explain Statement I
Statement I is correct, but Statement II is incorrect
Statement I is incorrect, but Statement II is correct
Correct Answer: A
Detailed Solution
Statement I is correct. The troposphere is the lowest layer of the atmosphere. Its upper boundary is known as the tropopause. The troposphere extends to approximately 18-20 km over the equator, about 9 km over the middle latitudes and nearly 6 km over the poles.
The equatorial region receives comparatively greater solar energy throughout the year. Consequently, the Earth’s surface and the air in contact with it become warmer.
Statement II is correct. Warm air becomes less dense and rises. This produces strong convectional currents in the equatorial region, which transport heat and water vapour to greater heights in the troposphere.
Thermal expansion of warm air and intense vertical convection raise the tropopause to a greater height. In contrast, the extremely cold and dense polar air experiences weak vertical convection, making the troposphere thinner over the poles.
Therefore, Statement II is not only correct but also correctly explains the greater thickness of the troposphere at the equator stated in Statement I.