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{{Short description|Study of the topographic relief of mountains}}
{{Use dmy dates|date=April 2017}}
[[File:Map of Eastern Siberia.png|thumbnail|An orographic map of Eastern [[Siberia]] from 1875 by [[Peter Kropotkin]]]]
[[File:Map of Eastern Siberia.png|thumbnail|An orographic map of Eastern [[Siberia]] from 1875 by [[Peter Kropotkin]]]]

'''Orography''' (from the [[Ancient Greek|Greek]] ''όρος'', hill, ''γραφία'', to write) is the study of the [[topographic relief]] of [[mountains]],<ref>[http://www.1911encyclopedia.org/Orography 11th Edition of Encyclopaedia Britannica (1911)]</ref> and can more broadly include hills, and any part of a region's elevated terrain.<ref>[http://amsglossary.allenpress.com/glossary/search?p=1&query=Orography&submit=Search Orography] (from the [[American Meteorological Society]] website)</ref> Orography (also known as ''oreography'', ''orology'' or ''oreology'') falls within the broader discipline of [[geomorphology]].<ref name=WDL1>{{cite web|title=Map of the Southern Half of Eastern Siberia and Parts of Mongolia, Manchuria, and Sakhalin: For a General Sketch of the Orography of Eastern Siberia|url=http://www.wdl.org/en/item/125/|publisher=World Digital Library|accessdate=23 January 2013}}</ref>
'''Orography''' is the study of the [[topographic relief]] of [[mountains]],<ref>{{Cite EB1911|wstitle=Orography|short=x}}</ref> and can more broadly include hills, and any part of a region's elevated terrain.<ref>[http://amsglossary.allenpress.com/glossary/search?p=1&query=Orography&submit=Search Orography] ({{Webarchive|url=https://web.archive.org/web/20070927214627/http://amsglossary.allenpress.com/glossary/search?p=1&query=Orography&submit=Search |date=27 September 2007 }}). [[American Meteorological Society]].</ref> Orography (also known as ''oreography'', ''orology,'' or ''oreology'') falls within the broader discipline of [[geomorphology]].<ref name=WDL1>{{cite web|title=Map of the Southern Half of Eastern Siberia and Parts of Mongolia, Manchuria, and Sakhalin: For a General Sketch of the Orography of Eastern Siberia|url=http://www.wdl.org/en/item/125/|publisher=World Digital Library|access-date=23 January 2013}}</ref> The term orography comes from the [[Ancient Greek|Greek]]: {{lang|grc|όρος}}, hill, {{lang|grc|γράφω}}, to write.


==Uses==
==Uses==
Mountain ranges and elevated land masses have a major impact on global climate. For instance, the elevated areas of East Africa substantially determine the strength of the [[Monsoons#Northern Indian Ocean Monsoon|Indian monsoon]].<ref>Srinivasan, J., Nanjundiah, Ravi S. and Chakraborty, Arindam (2005). [http://hdl.handle.net/2005/76 "Impact of Orography on the Simulation of Monsoon Climate in a General Circulation Model"]. Indian Institute of Science.</ref> In scientific models, such as [[general circulation model]]s, orography defines the lower boundary of the model over land.{{Citation needed|date=January 2009}}


When a river's [[tributaries]] or settlements by the river are listed in 'orographic sequence', they are in order from the highest (nearest the source of the river) to the lowest or [[mainstem (hydrology)|mainstem]] (nearest the mouth).{{Citation needed|date=January 2009}} This method of listing tributaries is similar to the [[Strahler Stream Order]], where the headwater tributaries are listed as category&nbsp;1.
Mountain ranges and elevated land masses have a major impact on global climate, for instance the elevated areas of East Africa substantially determines the strength of the [[Monsoons#Northern_Indian_Ocean_Monsoon|Indian monsoon]].<ref>Srinivasan, J., Nanjundiah, Ravi S. and Chakraborty, Arindam (2005) [http://hdl.handle.net/2005/76 Impact of Orography on the Simulation of Monsoon Climate in a General Circulation Model] ''Indian Institute of Science''</ref> In scientific models, such as [[general circulation model]]s, orography defines the lower boundary of the model over land.{{Citation needed| date=January 2009}}

When a river's [[tributaries]] or settlements by the river are listed in 'orographic sequence', they are in order from the highest (nearest the source of the river) to the lowest or [[mainstem (hydrology)|mainstem]] (nearest the mouth).{{Citation needed| date=January 2009}} This method of listing tributaries is similar to the [[Strahler Stream Order]], where the headwater tributaries are listed as category&nbsp;1.


==Orographic precipitation==
==Orographic precipitation==
{{See also|Orographic lift}}
{{refimprove section|date=January 2009}}
{{Split|Orographic precipitation|date=November 2020|discuss=Talk:Orography#Splitting proposal|section=y}}
{{see also|Orographic lift}}
[[Image:Steigungsregen.jpg|thumb|right|Orographic precipitation occurs when moist air is forced upwards by terrain.]]
Orographic [[precipitation (meteorology)|precipitation]], also known as [[relief precipitation]], is precipitation generated by a forced upward movement of air upon encountering a physiographic upland (see [[anabatic wind]]). This lifting can be caused by two mechanisms:
Orographic precipitation, also known as relief precipitation, is [[precipitation (meteorology)|precipitation]] generated by a forced upward movement of air upon encountering a physiographic upland (see [[anabatic wind]]). This lifting can be caused by:


# The upward deflection of large scale horizontal flow by the orography.
# Upward deflection of large-scale horizontal flow by the orography.
# The anabatic or upward vertical propagation of moist air up an orographic slope caused by daytime heating of the mountain barrier surface.
# Anabatic or upward vertical propagation of moist air up an orographic slope, caused by daytime heating of the mountain barrier surface.


Upon ascent, the air that is being lifted will expand and cool. This [[adiabatic]] cooling of a rising moist air parcel may lower its temperature to its [[dew point]], thus allowing for condensation of the water vapor contained within it, and hence the formation of a [[cloud]]. If enough water vapor condenses into cloud droplets, these droplets may become large enough to fall to the ground as precipitation. In parts of the world subjected to relatively consistent [[wind]]s (for example the [[trade winds]]), a wetter climate prevails on the windward side of a mountain than on the leeward (downwind) side as moisture is removed by orographic precipitation. Drier air (see [[katabatic wind]]) is left on the descending, generally warming, leeward side where a [[rain shadow]] is formed.
Upon ascent, the air that is being lifted expands and cools adiabatically. This [[Adiabatic lapse rate|adiabatic cooling]] of a rising moist air parcel may lower its temperature to its [[dew point]], thus allowing for condensation of the water vapor contained within it, and hence the formation of a [[cloud]]. If enough water vapor condenses into cloud droplets, these droplets may become large enough to fall to the ground as precipitation.


[[Terrain|Terrain-induced]] precipitation is a major factor for [[meteorologists]] as they forecast the local weather. Orography can play a major role in the type, amount, intensity and duration of precipitation events. Researchers have discovered that barrier width, slope steepness and [[updraft]] speed are major contributors for the optimal amount and intensity of orographic precipitation. [[Computer model]] simulations for these factors showed that narrow barriers and steeper slopes produced stronger updraft speeds which, in turn, enhanced orographic precipitation.
[[Terrain|Terrain-induced]] precipitation is a major factor for [[meteorologists]] to consider when they forecast the local weather. Orography can play a major role in determining the type, amount, intensity, and duration of precipitation events. Researchers have discovered that barrier width, slope steepness, and [[updraft]] speed are major contributors when it comes to achieving the optimal amount and intensity of orographic precipitation. [[Computer model]]s simulating these factors have shown that narrow barriers and steeper slopes produce stronger updraft speeds, which in turn increase orographic precipitation.


Orographic precipitation is well known on oceanic [[island]]s, such as the [[Hawaiian Islands]] or [[New Zealand]], where much of the rainfall received on an island is on the windward side, and the [[leeward]] side tends to be quite dry, almost [[desert]]-like, by comparison. This phenomenon results in substantial local gradients of average rainfall, with coastal areas receiving on the order of {{convert|20|to|30|in|mm}} per year, and interior uplands receiving over {{convert|100|in|mm}} per year. Leeward coastal areas are especially dry&mdash;less than {{convert|20|in|mm|abbr=on}} per year at [[Waikiki]]&mdash;and the tops of moderately high uplands are especially wet&mdash;about {{convert|475|in|mm|abbr=on}} per year at [[Wai'ale'ale]] on [[Kaua'i]].
Orographic precipitation is known to occur on oceanic [[island]]s, such as the [[Hawaiian Islands]] and [[New Zealand]]; much of the rainfall received on such islands is on the windward side, and the [[leeward]] side tends to be quite dry, almost [[desert]]-like. This phenomenon results in substantial local gradients in the amount of average rainfall, with coastal areas receiving on the order of {{convert|20|to|30|in|mm}} per year, and interior uplands receiving over {{convert|100|in|mm}} per year. Leeward coastal areas are especially dry&mdash;less than {{convert|20|in|mm|abbr=on}} per year at [[Waikiki]]&mdash;and the tops of moderately high uplands are especially wet&mdash;about {{convert|475|in|mm|abbr=on}} per year at [[Wai'ale'ale]] on [[Kaua'i]].


Another well known area for orographic precipitation is the [[Pennines]] in the north of England where the west side of the Pennines receives more rain than the east because the clouds (generally arriving from the west) are forced up and over the hills and cause the rain to fall preferentially on the western slopes. This is particularly noticeable between [[Manchester]] (West) and [[Leeds]] (East) where Leeds receives less rain due to a rain shadow of 12 miles from the Pennines.
Another area in which orographic precipitation is known to occur is the [[Pennines]] in the north of [[England]]: the west side of the Pennines receives more rain than the east because the clouds are forced up and over the hills and cause the rain to tend to fall on the western slopes. This is particularly noticeable between [[Manchester]] (to the west) and [[Leeds]] (to the east); Leeds receives less rain due to a rain shadow of {{convert|12|mi}} from the Pennines.


==See also==
==See also==
* [[Coverage (telecommunication)]]
* [[Coverage (telecommunication)]]
* [[Orographic lift]]
* [[Orographic lift]]
* [[Rain shadow]]


== References ==
== Citations ==
{{Reflist}}
{{Reflist}}

== General and cited references ==
* {{Cite book |last=Stull |first=Roland |date=2017 |title=Practical Meteorology: An Algebra-based Survey of Atmospheric Science |url=https://www.eoas.ubc.ca/books/Practical_Meteorology/ |publisher=University of British Columbia |isbn=978-0-88865-283-6}}
* {{Cite book |last=Whiteman |first=C. David |year=2000 |title=Mountain Meteorology: Fundamentals and Applications |publisher=Oxford University Press |isbn=0-19-513271-8}}


==External links==
==External links==
* [http://www.euratlas.net/geography/europe/mountains/index.html Map of the Orography of Europe] from [[Euratlas.com]]
* [http://www.euratlas.net/geography/europe/mountains/index.html Map of the Orography of Europe] from [[Euratlas.com]]


{{Authority control}}
[[Category:Climate forcing agents]]

[[Category:Geomorphology]]
[[Category:Geomorphology]]
[[Category:World Digital Library related]]

Latest revision as of 17:28, 17 November 2024

An orographic map of Eastern Siberia from 1875 by Peter Kropotkin

Orography is the study of the topographic relief of mountains,[1] and can more broadly include hills, and any part of a region's elevated terrain.[2] Orography (also known as oreography, orology, or oreology) falls within the broader discipline of geomorphology.[3] The term orography comes from the Greek: όρος, hill, γράφω, to write.

Uses

[edit]

Mountain ranges and elevated land masses have a major impact on global climate. For instance, the elevated areas of East Africa substantially determine the strength of the Indian monsoon.[4] In scientific models, such as general circulation models, orography defines the lower boundary of the model over land.[citation needed]

When a river's tributaries or settlements by the river are listed in 'orographic sequence', they are in order from the highest (nearest the source of the river) to the lowest or mainstem (nearest the mouth).[citation needed] This method of listing tributaries is similar to the Strahler Stream Order, where the headwater tributaries are listed as category 1.

Orographic precipitation

[edit]
Orographic precipitation occurs when moist air is forced upwards by terrain.

Orographic precipitation, also known as relief precipitation, is precipitation generated by a forced upward movement of air upon encountering a physiographic upland (see anabatic wind). This lifting can be caused by:

  1. Upward deflection of large-scale horizontal flow by the orography.
  2. Anabatic or upward vertical propagation of moist air up an orographic slope, caused by daytime heating of the mountain barrier surface.

Upon ascent, the air that is being lifted expands and cools adiabatically. This adiabatic cooling of a rising moist air parcel may lower its temperature to its dew point, thus allowing for condensation of the water vapor contained within it, and hence the formation of a cloud. If enough water vapor condenses into cloud droplets, these droplets may become large enough to fall to the ground as precipitation.

Terrain-induced precipitation is a major factor for meteorologists to consider when they forecast the local weather. Orography can play a major role in determining the type, amount, intensity, and duration of precipitation events. Researchers have discovered that barrier width, slope steepness, and updraft speed are major contributors when it comes to achieving the optimal amount and intensity of orographic precipitation. Computer models simulating these factors have shown that narrow barriers and steeper slopes produce stronger updraft speeds, which in turn increase orographic precipitation.

Orographic precipitation is known to occur on oceanic islands, such as the Hawaiian Islands and New Zealand; much of the rainfall received on such islands is on the windward side, and the leeward side tends to be quite dry, almost desert-like. This phenomenon results in substantial local gradients in the amount of average rainfall, with coastal areas receiving on the order of 20 to 30 inches (510 to 760 mm) per year, and interior uplands receiving over 100 inches (2,500 mm) per year. Leeward coastal areas are especially dry—less than 20 in (510 mm) per year at Waikiki—and the tops of moderately high uplands are especially wet—about 475 in (12,100 mm) per year at Wai'ale'ale on Kaua'i.

Another area in which orographic precipitation is known to occur is the Pennines in the north of England: the west side of the Pennines receives more rain than the east because the clouds are forced up and over the hills and cause the rain to tend to fall on the western slopes. This is particularly noticeable between Manchester (to the west) and Leeds (to the east); Leeds receives less rain due to a rain shadow of 12 miles (19 km) from the Pennines.

See also

[edit]

Citations

[edit]
  1. ^ "Orography" . Encyclopædia Britannica (11th ed.). 1911.
  2. ^ Orography (Archived 27 September 2007 at the Wayback Machine). American Meteorological Society.
  3. ^ "Map of the Southern Half of Eastern Siberia and Parts of Mongolia, Manchuria, and Sakhalin: For a General Sketch of the Orography of Eastern Siberia". World Digital Library. Retrieved 23 January 2013.
  4. ^ Srinivasan, J., Nanjundiah, Ravi S. and Chakraborty, Arindam (2005). "Impact of Orography on the Simulation of Monsoon Climate in a General Circulation Model". Indian Institute of Science.

General and cited references

[edit]
[edit]