(a) Name the three types of rainfall (b) With the aid of relevant diagrams describe the formation and characteristics of any two types named in (a) above

Answer Details

(a) The three types of rainfall

1. Convectional rainfall
2. Orographic (relief) rainfall
3. Cyclonic (frontal) rainfall

(b) Formation and characteristics of any two

Convectional rainfall

• Formation: intense heating of the ground makes the air in contact with it warm, expand and rise as strong convection currents. As the air rises it cools, condenses around the dew point and forms towering cumulonimbus clouds, releasing heavy rain.
• Characteristics: occurs in the hot afternoons, is heavy and of short duration, and is usually accompanied by thunder and lightning. It is typical of equatorial regions and of the wet season in the tropics.

Orographic (relief) rainfall

• Formation: moist winds from the sea are forced to rise over a mountain or highland barrier. The rising air cools, condenses and drops its moisture as rain on the windward slope. On the far (leeward) side the descending air is dry and warm, giving a rain shadow.
• Characteristics: heavy and prolonged rain on the windward slope, marked contrast with the dry leeward side, and it occurs wherever moist winds meet highlands.

Cyclonic (frontal) rainfall (alternative)

• Formation: where a mass of warm, light air meets a mass of cold, dense air, the warm air is forced to rise gently over the cold air along a front. It cools, condenses and produces rain.
• Characteristics: steady, moderate rainfall over a wide area lasting several hours or days, common in temperate latitudes.