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?

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?

Accepted Answer

Both Statement-I and Statement-II are correct and Statement-II explains Statement-I Quick Verdict: The troposphere is thickest at the equator precisely because intense solar heating generates powerful convection currents that push the warm air and the upper boundary of the troposphere (the tropopause) higher into the atmosphere. Therefore, Option (a) is the correct choice. Thematic Discussion: The Thickness of the Troposphere  The troposphere is the lowermost layer of the atmosphere, containing almost all of its water vapour and dust particles. While its average height is roughly 13 km, its thickness varies dramatically by latitude. At the Poles: The air is cold, dense, and tends to subside (sink). Consequently, the troposphere is only about 8 km thick. At the Equator: The troposphere bulges outward, reaching a maximum thickness of approximately 18 km. Why does this massive latitudinal variation exist? The primary driver is the differential heating of the Earth. The equatorial region receives direct and intense solar radiation year-round. This intensely heats the Earth's surface, which in turn violently heats the overlying air. Because warm air is lighter and less dense, it expands and rises rapidly in the form of strong convectional currents. These powerful vertical updrafts transport heat to great heights, literally pushing the "lid" of the troposphere (the tropopause) further outward. While thermal convection (Statement II) is the primary reason for the increased thickness, an additional contributing factor is the Earth's rotation. The rotational velocity of the Earth is highest at the equator, which generates a stronger centrifugal force. Just as this force causes the solid Earth to bulge at the equator, it also flings the atmospheric gases outward, further contributing to a thicker troposphere at the lower latitudes compared to the poles. (Reference: Chapter 8, “Composition and Structure of Atmosphere” in the Class 11 NCERT book “Fundamentals of Physical Geography”).