What is an example of orographic rainfall and its mechanism?

• A. West coast of Scotland; moist air forced over mountains cools and condenses, causing rain on windward slopes and drier on leeward side.
• B. The Amazon rainforest experiences rainfall due to high humidity.
• C. The central plains experience rainfall due to frontal passages.
• D. The Sahara Desert receives rainfall from desert heat.

Answer: (A)

Orographic rainfall happens when moist air is forced to rise over mountains. As the air climbs, it expands and cools, so its water vapour condenses into clouds and heavy rain forms on the windward (upwind) slopes. When the air descends on the leeward side, it warms and becomes drier, creating a rain shadow.

The West coast of Scotland is a classic example: moist air from the Atlantic moves in from the west and is pushed up the Highlands and other mountains. This uplift causes rapid cooling and condensation, producing rain on the western facing slopes, while the eastern side remains comparatively drier due to the rain shadow.

Other options describe different rainfall processes: rainfall in the Amazon is driven by high humidity and convection, not mountain uplift; central plains rainfall typically comes from frontal systems; Sahara rainfall is rare and not caused by mountains.