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Rain shadow
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{{Short description|Leeward side of a mountain range}} {{For|the Australian television series|Rain Shadow (TV series)}} [[File:Rain shadow effect.jpg|thumb|upright=1.7|Effect of a rain shadow]] [[File:Himalaya composite.jpg|right|thumb|upright=1.6|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).]] A '''rain shadow''' is an area of significantly reduced [[rain]]fall behind a [[mountain]]ous region, on the side facing away from [[prevailing winds]], known as its [[leeward]] side. Evaporated [[moisture]] from [[body of water|bodies of water]] (such as [[ocean]]s and large [[lake]]s) is carried by the prevailing [[sea breeze|onshore breezes]] towards the drier and hotter inland areas. When encountering elevated [[landform]]s, the moist air is [[orographic lift|driven upslope]] towards the [[summit|peak]], where it expands, cools, and its moisture [[condense]]s and starts to [[Precipitation|precipitate]]. If the landforms are tall and wide enough, most of the [[humidity]] will be lost to precipitation over the [[windward]] side (also known as the ''rainward'' side) before ever making it past the top. As the air descends the leeward side of the landforms, it is compressed and heated, producing [[Foehn wind]]s that ''absorb'' moisture downslope and cast a broad "shadow" of [[arid|dry climate]] region behind the [[ridge|mountain crests]]. This climate typically takes the form of [[shrub–steppe]], [[xeric shrublands]], or [[desert]]s. The condition exists because warm moist air rises by [[orographic lifting]] to the top of a mountain range. As atmospheric pressure decreases with increasing altitude, the air has expanded and [[Adiabatic process#Adiabatic heating and cooling|adiabatically cooled]] to the point that the air reaches its adiabatic [[dew point]] (which is not the same as its [[isobaric process|constant pressure]] dew point commonly reported in weather forecasts). At the adiabatic dew point, moisture condenses onto the mountain and it precipitates on the top and [[windward]] sides of the mountain. The air descends on the leeward side, but due to the precipitation it has lost much of its moisture. Typically, descending air also gets warmer because of [[adiabatic compression]] (as with foehn winds) down the leeward side of the mountain, which increases the amount of moisture that it can absorb and creates an [[arid]] region.<ref name="Whiteman">{{cite book|last=Whiteman|first= C. David|title=Mountain Meteorology: Fundamentals and Applications |publisher=Oxford University Press|year=2000|isbn=0-19-513271-8}}</ref>
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