Which type of rainfall occurs when two air masses of different temperature and other physical properties meet?

Step 1: Analyze the question The question asks for the rainfall type that forms when two air masses with different temperatures and physical properties (such as humidity and density) meet.

Step 2: Review the types of rainfall

• Orographic (Relief) rainfall: Moist air is forced to rise over a mountain or highland, cools, condenses and falls as rain on the windward side. Orographic and relief are the same thing, so A and B cannot both be correct.
• Convectional rainfall: The sun heats the ground strongly, the air warms and rises, then cools and condenses into cumulonimbus clouds. This is common in the tropics, often in the afternoon.
• Cyclonic (frontal) rainfall: A warm, light air mass meets a cold, dense air mass. The warm air is forced to rise over the cold air along a front, cools, condenses and gives rain.

Step 3: Match to the question "Two air masses of different temperature and other physical properties meet" describes a front, so this is cyclonic (frontal) rainfall. In Nigeria, a good example is where the moist tropical maritime (mT) air from the Atlantic meets the dry tropical continental (cT) air from the Sahara at the Inter-Tropical Discontinuity (ITD), which brings rain.

Step 4: Answer The answer is **C.

Exam tip: Link each rainfall type to its keyword:

• Relief/Orographic = mountain
• Convectional = heating and rising
• Cyclonic/Frontal = meeting of air masses

If A and B look like the same thing in an exam, neither is likely to be the answer.