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

Analyze the question: It asks for the type of rainfall caused by the meeting of two air masses with different temperatures and physical properties (e.g., a warm, moist air mass and a cold, dry one).

Explain the concept: Rainfall is classified by how the air is forced to rise and cool:

• Convectional rainfall: Intense heating of the ground makes warm air rise, cool, and condense. It is common in the equatorial regions, usually in the afternoon, and is often accompanied by thunder.
• Orographic (relief) rainfall: Moist air is forced to rise over mountains or highlands. The windward side gets the rain, and the leeward side is a dry "rain shadow". Options A and B are the same thing under two names.
• Cyclonic (frontal) rainfall: A warm air mass meets a cold air mass. The warmer, lighter air is forced to rise over the colder, denser air along a "front", then cools and condenses to give rain. It is also called frontal rainfall.

Solution:

1. The question says "two air masses of different temperatures" meet, so this is a front.
2. Orographic and relief rainfall depend on highlands, not on air masses meeting, so A and B are out.
3. Convectional rainfall depends on surface heating, not on air masses meeting, so D is out.
4. Frontal or cyclonic rainfall is the one that results from the meeting of contrasting air masses.

Answer: C. Cyclonic rainfall

Exam tip: Match the keyword to the rainfall type:

• Heating / rising warm air → Convectional
• Mountains / highlands → Orographic (relief)
• Meeting of air masses / fronts → Cyclonic (frontal)

Also remember that A and B mean the same thing, so they cannot both be correct. This can help you eliminate options quickly.