Why Are Deserts Found on the Leeward Side of Mountain Ranges?

Deserts on the leeward (downwind) side of mountains are classic rain shadow deserts. The mechanism:

1. Moist Air Ascends Windward Slopes: Prevailing winds force humid air up the mountain.
2. Adiabatic Cooling & Condensation: Rising air expands and cools (~1°C/100 m). Water vapor condenses → clouds → heavy precipitation on windward side (orographic lift).
3. Air Descends Leeward: Having lost moisture, air descends the leeward slopes.
4. Adiabatic Warming: Descending air compresses and warms (~1°C/100 m). Relative humidity plummets; clouds evaporate.
5. Rain Shadow: Warm, dry air creates arid conditions—high evaporation, low precipitation, sparse vegetation.

Famous Examples

• Sierra Nevada / Death Valley (USA)
• Andes / Atacama Desert (Chile)
• Southern Alps / Canterbury Plains (New Zealand)
• Himalayas / Tibetan Plateau & Gobi (Asia)
• Cascades / Eastern Washington & Oregon (USA)

Modulating Factors

• Distance from moisture source
• Mountain height & width
• Prevailing wind consistency
• Latitudinal climate zone

The rain shadow effect is a fundamental driver of global desert distribution.