WAEC Geography 2022 Theory — Question 23

Model answer

(a) The troposphere's gases absorb very little incoming solar radiation directly; air is instead heated by radiation/conduction from the earth's surface, so air closer to the surface is warmer; higher atmospheric pressure occurs near the surface due to gravitational pull, decreasing with altitude; high altitudes contain less dust and water vapour, allowing heat to escape and the air to remain cold. (b) See diagram in the Diagram column. Orographic rainfall occurs when moisture-laden air is forced to rise over a mountain barrier (usually on the windward slope). As the air rises, it expands and cools, relative humidity increases until the air becomes saturated, water vapour condenses into cloud, and rain falls on the windward slope, while descending (drier) air occurs on the leeward side.