page_title: Rain shadow
section_title: Africa
hierarchical_section_title: Rain shadow / Regions of notable rain shadow / Africa
caption_attribution_description: English: Tenerife Island (Canary Islands, Spain) from LANDSAT7 satellite of NASA. Coordinates: -16.52792W 28.29799N Español: Isla de Tenerife (Islas Canarias, España) desde el satélite LANDSAT7 de la NASA. Coordenadas: -16.52792W_28.29799N
context_page_description: A rain shadow is a dry area on the leeward side of a mountainous area. The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them. Wind and moist air are drawn by the prevailing winds towards the top of the mountains, where it condenses and precipitates before it crosses the top. The air, without much moisture left, advances across the mountains creating a drier side called the "rain shadow".
context_section_description: The windward side of the island of Madagascar, which sees easterly on-shore winds, is wet tropical, while the western and southern sides of the island lie in the rain shadow of the central highlands and are home to thorn forests and deserts. The same is true for the island of Réunion. On Tristan da Cunha, Sandy Point on the east coast is warmer and drier than the rainy, windswept settlement of Edinburgh in the west.
  In Western Cape Province, the Breede River Valley and the Karoo lie in the rain shadow of the Cape Fold Mountains and are arid; whereas the wettest parts of the Cape Mountains can receive 1,500 millimetres (59 in), Worcester receives only around 200 millimetres (8 in) and is useful only for grazing.
  The Sahara Desert is made even drier because of two strong rain shadow effects caused by some major mountain ranges (whose highest points can culminate to more than 4,000 meters high). To the northwest, the Atlas Mountains, covering the Mediterranean coast for Morocco, Algeria and Tunisia as well as to the southeast with the Ethiopian Highlands, located in Ethiopia around the Horn of Africa. On the windward side of the Atlas Mountains, the warm, moist winds blowing from the northwest off the Atlantic Ocean which contain a lot of water vapor are forced to rise, lift up and expand over the mountain range. This causes them to cool down, which causes an excess of moisture to condense into high clouds and results in heavy precipitation over the mountain range. This is known as orographic rainfall and after this process, the air is dry because it has lost most of its moisture over the Atlas Mountains. On the leeward side, the cold, dry air starts to descend and to sink and compress, making the winds warm up. This warming causes the moisture to evaporate, making clouds disappear. This prevents rainfall formation and creates desert conditions in the Sahara. The same phenomenon occurs in the Ethiopian Highlands, but this rain shadow effect is even more pronounced because this mountain range is larger, with the tropical Monsoon of South Asia coming from the Indian Ocean and from the Arabian Sea. These produce clouds and rainfall on the windward side of the mountains, but the leeward side stays rain shadowed and extremely dry. This second extreme rain shadow effect partially explains the extreme aridity of the eastern Sahara Desert, which is the driest and the sunniest place on the planet. Similar levels of aridity and dryness are only seen in the Atacama Desert, located in Chile and Peru.
  Desert regions in the Horn of Africa (Ethiopia, Eritrea, Somalia and Djibouti) such as the Danakil Desert are all influenced by the air heating and drying produced by rain shadow effect of the Ethiopian Highlands, too.
caption: Tenerife, Madeira and other Macaronesian islands have a laurisilva forest where the rain shadow effect is not present.
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