Rain shadow
A rain shadow is an area of land that lies behind a mountain which gets almost no rainfall. This side of a mountainous area is away from the wind. The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them.
As shown by the diagram to the right, the incoming warm and moist air is drawn by the prevailing winds towards the top of the mountains. As it does so, it cools and condenses, and relief rainfall removes the moisture before it crosses the top. The air, without much moisture left, goes on over the mountains creating a dry side called the "rain shadow".
Rain Shadow Media
Diagram of a rain shadow and its effects.
The Tibetan Plateau (center), perhaps the best example of a rain shadow. Rainfalls from the southern South Asian monsoon do not make it far past the Himalayas (seen by the snow line at the bottom), leading to an arid climate on the leeward (north) side of the mountain range and the desertification of the Tarim Basin (top).
The Atlas mountains' (top) rain shadow effect makes the Sahara even drier.
The mountain ranges on the eastern side of Madagascar provide a rain shadow for the country's western portion.
The eastern regions of the Western Ghats lie in a rain shadow, receiving far less rainfall.
Most of Iran is rain-shadowed by the Alborz mountains in the north (just south of the Caspian sea), hence the country's mostly (semi) arid climate.
Lake Urmia (centre) and surrounds rain-shadowed by the snowy Zagros mountains to the west.
Cantabrian Mountains in the north, which rain-shadow most of Spain.
The Cascade Range to the north and the California Coast Ranges and the Sierra Nevada to the south provide a significant rain-shadow for the inland North American deserts.
The Atherton Tableland rain-shadowing the dry Tablelands Region in Queensland (bottom-right).
