Difference between revisions of "AY Honors/Weather/Answer Key"

Revision as of 03:34, 9 March 2006

This wave cloud pattern formed off of the Île Amsterdam in the far southern Indian Ocean, due to orthographic lift of an airmass with alternating bands of high and low humidity over the island.

Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it expands and cools adiabatically. This cooler air cannot hold the moisture as well as warm air and this effectively raises the relative humidity to 100%, creating clouds and frequently precipitation.

Orographic lift is demonstrated in many places in the world, but few examples are as clear as those in the Northwestern United States. In the states of Washington and Oregon, places on the sea-facing side of coastal mountains see over 100 inches (over 2.5 m) of precipitation per year. These locales are on the side of the mountains which are in the path of storm systems, and therefore receive the moisture which is effectively squeezed from the clouds. However, on the other side of the mountains, sometimes as little as 15 miles (25 km) away, annual precipitation can be as low as 8 inches (200 mm) per year.

Also it happens on the Hawaiian island of Kauai.

Orthographic lift can create lenticular clouds and wave clouds on the leeward side of mountains.

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-A '''convection cell''' is a phenomenon of [[fluid dynamics]] which occurs in situations where there are [[temperature]] differences within a body of [[liquid]] or [[gas]].
+{{mergefrom|Rain shadow}}
-Fluids are materials which exhibit the property of [[flow]]. Both gases and liquids have fluid properties, and, in sufficient quantity, even particulate solids such as salt, grain, or gravel show some fluid properties. When a volume of fluid is heated, it expands and becomes less dense, and thus more buoyant than the surrounding fluid. The colder, more dense fluid settles underneath the warmer, less dense fluid and forces it to rise. Such a mother fuckin movement is called [[convection]], and the moving body of liquid is referred to as a ''convection cell''.
+[[Image:Wave cloud.jpg|thumb|320 px|This wave cloud pattern formed off of the [[Île Amsterdam]] in the far southern [[Indian Ocean]], due to orthographic lift of an airmass with alternating bands of high and low humidity over the island.]]
-A rising body of fluid typically loses heat because it encounters a cold surface, because it exchanges heat with colder liquid through direct exchange, or in the example of the earth's [[earth's atmosphere|atmosphere]], because it radiates heat. At some point the fluid becomes more dense than the fluid underneath it, which is still rising. Since it cannot descend through the rising fluid, it moves to one side. At some distance its downward force overcomes the rising force beneath it and the fluid begins to descend. As it descends, it warms again through surface contact, conductivity, or compression, and the cycle repeats itself. (The heating through compression of descending air is what is responsible for such welcome winter phenomena as what is known in Western North America as a [[chinook]] or in the Alps as a [[Wind#Special_winds|foehn]].)
+'''Orographic lift''' occurs when an [[air mass]] is forced from a low [[elevation]] to a higher elevation as it moves over rising terrain.  As the air mass gains [[altitude]] it expands and cools [[Adiabatic cooling|adiabatically]]. This cooler air cannot hold the moisture as well as warm air and this effectively raises the [[relative humidity]] to 100%, creating [[cloud]]s and frequently [[precipitation (meteorology)|precipitation]].
-[[image:altocumulus.jpg|right|thumb|Altocumulus cloud as seen from the space shuttle. Altocumulus is formed through convective activity.]]
+Orographic lift is demonstrated in many places in the world, but few examples are as clear as those in the [[Northwestern United States]]. In the states of [[Washington]] and [[Oregon]], places on the sea-facing side of coastal mountains see over 100 inches (over 2.5 m) of [[precipitation (meteorology)|precipitation]] per year. These locales are on the side of the [[mountain]]s which are in the path of [[storm]] systems, and therefore receive the moisture which is effectively squeezed from the clouds. However, on the other side of the [[mountain]]s, sometimes as little as 15 miles (25 km) away, annual [[precipitation (meteorology)|precipitation]] can be as low as 8 inches (200 mm) per year.
-Convection cells can form in any fluid, including the Earth's atmosphere, boiling water or soup (where the cells can be identified by particles they transport, such as grains of rice), the ocean, the surface of the sun, or even a farmer's field, where large rocks have been seen to be forced to the surface over time in a process either analogous to or directly related to convection (the connection is not yet clear).
+Also it happens on the [[Hawaii]]an [[island]] of [[Kauai]].
-The size of convection cells are largely determined by the fluid's properties, and they can even occur when the heating of a fluid is uniform.
+Orthographic lift can create [[lenticular cloud]]s and [[wave cloud]]s on the leeward side of mountains.
-[[image:granules2.jpg|right|thumb|Convection cells on the Sun with North America superimposed]]
+==See also==
+* [[Orography]]
+* [[Rain shadow]]
-The [[Sun]]'s [[photosphere]] is composed of convection cells called ''[[Granule (solar physics)|granule]]s'', rising columns of superheated (5800 &deg;C) [[Plasma (physics)|plasma]] averaging about 1000 kilometres in diameter. The plasma cools as it rises and descends in the narrow spaces between the granules.
+[[Category:Climate forcing]]
+[[fr:Onde orographique]]
-==External links==
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-* [http://www.solarviews.com/eng/edu/convect.htm Jet Propulsion Lab description of convection cells]
-* [http://www.mountainnature.com/Climate/Chinook.htm Mountainnature.com - Chinook]
-[[Category:Severe weather and convection]]
-[[Category:Fluid dynamics]]