Rain shadow
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fixing genre capitalization mistakes per [[Wikipedia:MUSTARD#Capitalization|WP:MUSTARD]] -> [[Wikipedia:Manual_of_Style_(capital_letters)#Musical_genres|MOS:CAPS]] + cleanup.
''For the Australian television series see [[Rain Shadow (TV series)]].''
''For the [[Australian]] [[Gothic metal]] band, see [[Rainshadow(band)|Rainshadow]].''
[[Image:Rainshadow copy.jpg|right|375px]]
A '''rain shadow''' or '''rainshadow''', or more accurately, '''precipitation shadow''', is a dry region of land that is [[leeward]] of or behind a [[mountain]], with respect to prevailing [[wind]] direction.
==Description==
A rain shadow is usually caused by a [[mountain range]], but can be caused by other things as well, although to a much less degree.{{Clarifyme|date=March 2008}}
A rainshadow is warm and dry because as moist air masses rise to the top of a mountain range or large mountain, the air cools and the [[moisture content]] decreases until it reaches the [[dew point]], the point at which the [[water vapor]] condenses as [[rain]], and then falls either on the [[windward]] side or atop the mountain. This is called ''[[orographic lift]] [[precipitation (meteorology)|precipitation]]''. The effect of this phenomenon is the creation of an [[arid]] region on the leeward side of the mountains. Also, the warm air absorbs moisture from the already dry and warm air (see [[Foehn winds]]). The land gets little precipitation because all the moisture is lost on the mountains. Furthermore, the warm air absorbs moisture from the already dry land.<ref name="Whiteman">{{cite book|author=Whiteman, C. David|title=Mountain Meteorology: Fundamentals and Applications |publisher=Oxford University Press|year=2000|id=ISBN 0-19-513271-8}}</ref>
==Regions of notable rain shadow==
There are regular patterns of [[prevailing winds]] found in bands round the Earth's [[equator]]ial region. The zone designated the [[trade winds]] is the zone between about 30° N. and 30° S., blowing predominantly from the northeast in the [[Northern Hemisphere]] and from the southeast in the [[Southern Hemisphere]]. The [[westerlies]] are the prevailing winds in the [[middle latitudes]] between 30 and 60 degrees [[latitude]], blowing predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. The strongest westerly winds in the middle latitudes can come in the [[Roaring Forties]] between 40 and 50 degrees latitude.{{Fact|date=August 2007}}
Examples of notable rain shadowing include:
===Asia===
{{Prose|date=September 2007}}
* The peaks of the [[Caucasus Mountains]] to the west, the [[Alborz]] mountains to the south and the ranges tied to the [[Himalaya]] to the east rain shadow the [[Karakum]] and [[Kyzyl Kum]] deserts east of the [[Caspian Sea]].
* The [[Dasht-i-Lut]] in Iran is in the rain shadow of the [[Elburz Mountains|Elburz]] and [[Zagros Mountains]] and is one of the most lifeless areas on Earth.
* The Himalaya and connecting ranges also contribute to arid conditions in [[Central Asia]] including [[Mongolia]]'s [[Gobi]] desert and [[China]]'s [[Taklamakan Desert]].
* The [[Ordos Desert]] is rain shadowed by mountain chains including the Kara-naryn-ula, the Sheitenula, and the [[In Shan]] mountains, which link on to the south end of the [[Great Khingan Mountains]].
* The [[Great Indian Desert]] or Thar desert is bounded and rain shadowed by the [[Aravalli]] ranges to the south-east, the Himalaya to the northeast, and the Kirthar and Sulaiman ranges to the west.
*Eastern Side of [[Sahyadri]] ranges on [[Deccan]] Plateau of India.
===South America===
* The [[Atacama Desert]] in [[Chile]] is the driest desert on Earth because it is blocked from moisture on both sides (by the [[Andes mountains]] to the east and high pressure over the [[Pacific Ocean|Pacific]] at a latitude which keeps moisture from coming in from the west).
* [[Patagonia]] is rain shadowed from the prevailing westerly winds by the [[Andes]] range and is arid (e.g., in Santa Cruz few spots are capable of cultivation, the pastures being poor, water insufficient and salt lagoons fairly numerous).
===North America ===
{{Prose|date=September 2007}}
Most rainshadows in the western [[United States]] are due to mountain ranges, notably the [[Sierra Nevada (U.S.)|Sierra Nevada]] and [[Cascade Mountains|Cascades]],<ref>[[USA Today]]. [http://www.usatoday.com/weather/tg/wrnshdw/wrnshdw.htm How mountains influence rainfall patterns.] Retrieved on [[2008-02-29]].</ref> that intercept rain and snowfall that would otherwise reach a valley in the lee of the mid-latitude prevailing westerlies.
* The [[desert]]s of the [[Basin and Range Province]] in the [[United States]] and [[Mexico]], which includes the dry areas east of the [[Cascade Range|Cascade Mountains]] of [[Oregon]] and [[Washington (state)|Washington]] and the [[Great Basin]], which covers almost all of [[Nevada]] and parts of [[Utah]] are rain shadowed.
* The [[Mojave Desert|Mojave]], [[Black Rock Desert|Black Rock]], [[Sonoran Desert|Sonoran]], and [[Chihuahuan Desert|Chihuahuan]] deserts all are in regions which are rain shadowed.
* The aptly-named [[Death Valley]] in the United States is another good example; it is behind both the [[Pacific Coast Ranges]] of [[California]] and the [[Sierra Nevada (U.S.)|Sierra Nevada]] range, and is one of the driest places on the [[planet]].
* The [[Colorado Front Range]] is limited to the rainfall that makes it over the [[continental divide]]. While many places west of the divide receive as much as {{convert|40|in|mm}} of precipitation throughout the year, some places on the east side, notably [[Evergreen, Colorado]] and [[Denver, Colorado]] only receive about 17-19 inches. Thus, the [[continental divide]] acts as a barrier for the precipitation. This effect only applies to west to east storms. When low pressure areas skirt the [[Rocky Mountains]] to the south, they can give high precipitation to the east side and none to the west side. This only happens on somewhat rare occasions.
* The east slopes of the Coast Ranges in central and southern California also cut off the southern [[San Joaquin Valley]] from enough precipitation to ensure desert-like conditions in areas around [[Bakersfield, California|Bakersfield]].
* The eastern side of the [[Coast Mountains]] and the [[Cascade Range]] in the province of [[British Columbia]], [[Canada]] is a rain shadow. The [[Okanagan Valley]] which sits in this rain shadow is home to [[Osoyoos]], Canada's only hot desert.
* The Dungeness Valley around [[Sequim]], [[Washington]] lies in the rain shadow of the [[Olympic Mountains]]. The area averages 10-15 inches of rain per year, less than half of the amount received in nearby [[Port Angeles]] and approximately 10% of that which falls in [[Forks, Washington|Forks]] on the western side of the mountains.
* The effect appears even in the eastern United States. Although much more humid than any obvious deserts or steppes, the [[Shenandoah Valley]] mostly in western [[Virginia]], lying between the [[Blue Ridge Mountains|Blue Ridge]] and the [[Appalachian Mountains]], is drier than areas to the east and west because the modest mountains reduce rainfall within the valley. The lesser rainfall than that of surrounding areas makes this long valley paradoxically a richer agricultural area than rainier areas nearby. [ftp://ftp.ftw.nrcs.usda.gov/pub/prism/maps/va.pdf][http://www.ocs.orst.edu/pub/maps/Precipitation/Total/States/WV/wv.gif]
=== Europe ===
* The [[Cantabrian Mountains]] make a sharp divide between "[[Green Spain]]" to the north and the dry central plateau. The northern-facing slopes receive heavy rainfall from the [[Bay of Biscay]], but the southern slopes are in rain shadow. The most evident effect on the Iberian Peninsula occurs in the [[Almería (province)|Almería]], [[Region of Murcia|Murcia]] and [[Alicante (province)|Alicante]] areas, each with an average rainfall of 300 mm. and the dryest spot in Europe (see [[Cabo de Gata]]) mostly due to the mountainous range running through their western side which blocks the westerlies.
* Some valleys in the inner [[Alps]] are also strongly rainshadowed by the high surrounding mountains.
* [[Athens]] is shielded strongly by mountains from the strong moisture-bearing winds of the [[Adriatic Sea]] and receives only a quarter the rainfall of most of [[Albania]].
* [[Skjåk]], a [[municipalities of Norway|municipality]] in [[Norway]], lies in a deep valley and is rain shadowed such that it sees less annual precipitation than the [[Sahara]] desert.
===Africa===
* 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 formation of the [[Atlas Mountains]] has been deemed at least partially responsible for the climatic change which eventually created the [[Sahara]]. There is a strong rain shadow effect to the south side of the mountains.
===Oceania===
* [[New Caledonia]] lies astride the [[Tropic of Capricorn]], between 19° and 23° south latitude. The climate of the islands is [[tropical]], and rainfall is brought by trade winds from the east. The western side of the Grande Terre lies in the rain shadow of the central mountains, and rainfall averages are significantly lower.
* [[Hawaii]] also has rain shadows, with some areas of the islands being desert, much to the surprise of many [[tourist]]s. Orographic lifting produces the world's highest annual percipitation record, 12.7 meters (500 inches), on the island of [[Kauai]]; the leeward side is understandably rain shadowed<ref name="Whiteman">{{cite book|author=Whiteman, C. David|title=Mountain Meteorology: Fundamentals and Applications |publisher=Oxford University Press|year=2000|id=ISBN 0-19-513271-8}}</ref>. The entire island of [[Kahoolawe]] lies in the rain shadow of Maui's East Maui Volcano.
* [[New Zealand]] boasts one of the most remarkable rain shadows anywhere on Earth. On the South Island, the Southern Alps intercept moisture coming off the Tasman Sea. The mountain range is home to significant glaciers and 250 to {{convert|350|in|mm}} liquid water equivalent per year. To the east and down slope of the Southern Alps, scarcely {{convert|30|mi|km}} from the snowy peaks, yearly rainfall drops to less than {{convert|30|in|mm}} and some areas less than 15.
* In [[Tasmania]], one of the states of [[Australia]], the central Midlands region is in a strong rain shadow and receives only about a fifth as much rainfall as the highlands to the west.
* In [[New South Wales]] and [[Victoria (Australia)|Victoria]] (both states of [[Australia]]), the [[Monaro, New South Wales|Monaro]] is shielded by both the Snowy Mountains to the northwest and coastal ranges to the southeast. Consequently, parts of it are as dry as the wheat-growing lands of those states.
== See also ==
*[[Foehn wind]]
==References==
{{reflist}}
==External links==
:*[http://www.usatoday.com/weather/tg/wrnshdw/wrnshdw.htm USA Today on rain shadows]
:*[http://www.weatherpages.com/rainshadow/ Weather pages on rain shadows]
[[Category:Mountain meteorology]]
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