Climatology: UPSC Previous Year Questions (Geography)

Explanation

Insolation, or the solar radiation received by the Earth, plays a crucial role in driving atmospheric circulation by heating the surface unevenly. This creates temperature and pressure differences, which, in turn, influence atmospheric thickness and convection patterns. Assertion (A) is true: Thickness of the atmosphere is maximum over the Equator. The Equator experiences greater atmospheric thickness due to intense heating, causing air to expand and rise to higher altitudes, increasing the vertical extent of the atmosphere. Reason (R) is true: The Equator receives high levels of insolation year-round due to its position, with the Sun being directly overhead during the equinoxes and nearly overhead at other times, contributing to sustained heating. This results in strong convection currents that lift air to higher altitudes, contributing to the greater atmospheric thickness. Reason(R) explains Assertion(A): Because the strong insolation and convection over the Equator lead to the expansion and lifting of air, directly causing the atmosphere to be thicker in this region compared to higher latitudes.