Wind: Difference between revisions
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Obama Bin Laden!!! |
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{{otheruses}}<br> |
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{{Cleanup|date=May 2007}} |
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{{Refimprove|date=April 2007}} |
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[[Image:33-vento orientale,Taccuino Sanitatis, Casanatense 4182..jpg|thumb|250px|Wind, [[tacuinum sanitatis]] casanatensis (14th century)]] |
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'''Wind''' is the [[Flux|flow]] of [[air]] or other [[gas]]es that compose an [[atmosphere]] (including, but not limited to, the [[Earth|Earth's]]).<ref>{{cite web |url=http://www2.jpl.nasa.gov/galileo/status970813.html |title=Jupiter's Hurricane-Force Winds Increase In Depths of the Planet's Atmosphere |accessdate=2007-09-05 |work= |publisher=[[NASA]] [[JPL]] }}</ref> It occurs as air is heated by the Sun and thus rises. Cool air then rushes to occupy the area from which the hot air has just moved. It could be loosely classed as a convection current. |
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Winds are commonly classified by their spatial scale, their speed, the types of forces that cause them<!-- (according to the atmospheric [[equations of motion]]) -->, the geographic regions in which they occur, and their effect. While wind is often a standalone [[weather]] phenomenon, it can also occur as part of a [[storm|storm system]], most notably in a [[cyclone]]. |
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Winds can shape landforms, via a variety of [[aeolian processes]]. |
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<!-- Wind occurs on a range of scales, from local breezes generated by heating of land surfaces and lasting tens of minutes, to [[global]] winds resulting from the difference in absorption of [[solar energy]] between the [[climate zone]]s on [[Earth]]. The two major driving factors of large scale [[atmospheric circulation]] are the differential heating between the equator and the poles, and the rotation of the planet ([[Coriolis effect]]). --> |
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<!-- Wind is caused by Na's cleverness spatially varying [[Atmospheric_pressure|atmospheric pressure]]. On Earth such pressure variations are primarily produced by uneven heating of the [[Earth]]'s surface from [[sunlight]].--> |
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In [[human]] [[civilization]], wind has inspired [[mythology]], changed the course of [[history]], expanded the range of [[transport]] and [[warfare]], and provided a [[power source]] for [[mechanical work]], [[electricity]], and [[recreation]].<!-- Needs much expansion --> |
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==Forces== |
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{{Expand-section|date=April 2008}} |
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Forces which drive wind or affect it are the [[pressure gradient force]], the [[Coriolis force]], [[buoyancy]] forces, and [[friction]] forces. When a difference in [[pressure]] exists between two adjacent air masses, the air tends to flow from the region of [[high pressure area|high pressure]] to the region of [[low pressure area|low pressure]]. On a rotating planet, flows will be acted upon by the [[Coriolis force]], in regions sufficiently far from the equator and sufficiently high above the surface. |
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The two major driving factors of large scale global winds <!-- atmospheric circulation --> are the differential heating between the equator and the poles (difference in absorption of [[solar energy]] between these [[climate zone]]s), and the rotation of the planet. |
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===Components of wind=== |
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Winds defined by an equilibrium of physical forces are used in the decomposition and analysis of wind profiles. They are useful for simplifying the atmospheric [[equations of motion]] and for making qualitative arguments about the horizontal and vertical distribution of winds. Examples are: |
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* [[Geostrophic wind]] (wind that is a result of the balance between [[Coriolis force]] and pressure gradient force; flows parallel to [[isobar]]s and approximates the flow above the [[atmospheric boundary layer]] in the midlatitudes if [[friction]]al effects are low) |
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* [[Thermal wind]] (not actually a wind but a wind ''difference'' between two levels; only exists in an atmosphere with horizontal [[temperature gradient]]s, i.e. [[baroclinicity]]) |
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* [[Ageostropic wind]] (difference between actual and geostrophic wind; the wind component which is responsible for air "filling up" [[cyclone]]s over time) |
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* [[Gradient wind]] (like geostrophic wind but also including [[centrifugal force]]) |
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==Classification== |
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There are global winds, such as the wind belts which exist between the atmospheric circulation cells. There are upper-level winds which typically include narrow belts of concentrated flow called [[jet stream]]s. There are [[Synoptic scale meteorology|synoptic scale]] winds that result from pressure differences in surface air masses in the middle latitudes, and there are winds that come about as a consequence of [[geography|geographic]] features, such as the [[sea breeze]]s on coastlines or canyon breezes near mountains. [[Scale (spatial)|Mesoscale]] winds are those which act on a local scale, such as [[Gusts|gust]] fronts. At the smallest scale are the microscale winds, which blow on a scale of only tens to hundreds of meters and are essentially unpredictable, such as [[dust devils]] and [[microburst]]s. |
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===Wind terms=== |
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''''Gusts'''' are inconstant [[wind]]s. Unlike relatively constant winds, such as the [[Chinook wind]], gusting winds are characterized by the apparent rapid change in the force and/or direction of the wind. The wind appears, to those who experience it, to come in ''blasts'' of varying strength with brief lulls between. Such a blast is known as a ''gust''. |
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A [[squall]] is a sudden, sharp increase in wind speed which usually is associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to an increase in the non-sustained winds over an extended time interval, as there may be lower gusts during a squall event. |
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===Named winds=== |
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In modern usage, many [[List of local winds|local wind systems]] have their own names. <!-- would be nice to talk about why people name winds and the history of naming winds --> |
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===Local winds=== |
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{{seealso|List of local winds}} |
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Some local winds blow only under certain circumstances, i.e. they require a certain temperature distribution. |
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''Differential heating'' is the motive force behind '''[[land breeze]]s''' and '''[[sea breeze]]s''' (or, in the case of larger lakes, lake breezes), also known as on- or off-shore winds. Land absorbs and radiates heat faster than water, but water releases heat over a longer period of time. The result is that, in locations where sea and land meet, heat absorbed over the day will be radiated more quickly by the land at night, cooling the air. Over the sea, heat is still being released into the air at night, which rises. This convective motion draws the cool land air in to replace the rising air, resulting in a land breeze in the late night and early morning. During the day, the roles are reversed. Warm air over the land rises, pulling cool air in from the sea to replace it, giving a sea breeze during the afternoon and evening. |
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'''[[Mountain breezes]]''' and '''[[valley breezes]]''' are due to a combination of differential heating and geometry. When the sun rises, it is the tops of the mountain peaks which receive first light, and as the day progresses, the mountain slopes take on a greater heat load than the valleys. This results in a temperature inequity between the two, and as warm air rises off the slopes, cool air moves up out of the valleys to replace it. This upslope wind is called a ''valley breeze''. The opposite effect takes place in the afternoon, as the valley radiates heat. The peaks, long since |
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cooled{{Vague|say why|date=March 2008}}, |
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transport air into the valley in a process that is partly gravitational and partly convective and is called a ''mountain breeze''. |
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Forested areas are less windy than plains and cities because the trees disrupt wind patterns. Trees are defined to have a dampening effect on wind speeds in that they reduce the partial derivative of pressure differences across non-infinitively occupying plain. Further effects of trees wind reducing capabilities is in the fact that trees bend in the wind. Considering the mass of a tree in comparison to air particles it is highly predicable that much of the total energy of the wind is lost in kinetic energy to the trees. |
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Mountain breezes are one example of what is known more generally as a [[katabatic wind]]. These are winds driven by cold air flowing down a slope, and occur on the largest scale in [[Greenland]] and [[Antarctica]]. Most often, this term refers to winds which form when air which has cooled over a high, cold plateau is set in motion and descends under the influence of gravity. Winds of this type are common in regions of [[Mongolia]] and in glaciated locations. |
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Because ''katabatic'' refers specifically to the vertical motion of the wind, this group also includes winds which form on the lee side of mountains, and heat as a consequence of compression. Such winds may undergo a temperature increase of 20 [[°C]] (68 [[°F]]) or more, and many of the world's "named" winds (see [[#Named Winds]] above) belong to this group. Among the most well-known of these winds are the [[Chinook wind|chinook]] of Western Canada and the American Northwest, the Swiss [[Foehn wind|foehn]], California's infamous [[Santa Ana wind]], and the French [[Mistral (wind)|Mistral]]. |
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The opposite of a katabatic wind is an [[anabatic wind]], or an upward-moving wind. The above-described ''valley breeze'' is an anabatic wind. |
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A widely-used term, though one not formally recognised by meteorologists, is ''[[orographic]] wind''. This refers to air which undergoes orographic lifting. Most often, this is in the context of winds such as the chinook or the föhn, which undergo lifting by mountain ranges before descending and warming on the lee side. |
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==In civilization== |
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{{Expand|date=May 2008}} |
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===Mythology=== |
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{{see|Wind god}} |
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As a natural force, the wind was often personified as one or more [[wind god]]s or as an expression of the [[supernatural]] in many cultures. |
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In ancient [[Greek mythology]], the four winds were personified as gods, called the [[Anemoi]] - ''Boreas'', ''Notos'', ''Euros'' and ''Zephyros''. [[Aeolus]], in varying interpretations the ruler or keeper of the four winds, has also been described as [[Astraeus]], the god of dusk who fathered the four winds with [[Eos]], goddess of dawn. |
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The [[Ancient Greeks]] also observed the seasonal change of the winds, as evidenced by the [[Tower of the Winds]] in [[Athens]]. |
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The winds are discussed in the [[Bible]]: |
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{{Quote|'''Winds''' - blowing from the four quarters of heaven (Jer. 49:36; Ezek. |
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37:9; Dan. 8:8; Zech. 2:6). The east wind was parching (Ezek. |
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17:10; 19:12), and is sometimes mentioned as simply denoting a |
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strong wind (Job 27:21; Isa. 27:8). This wind prevails in |
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[[Palestine]] from February to June, as the west wind ([[Gospel of Luke|Luke]] 12:54) |
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does from November to February. The south was a hot wind (Job |
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37:17; [[Gospel of Luke|Luke]] 12:55). It swept over the Arabian peninsula. The |
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rush of invaders is figuratively spoken of as a whirlwind (Isa. |
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21:1); a commotion among the nations of the world as a striving |
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of the four winds (Dan. 7:2). The winds are subject to the |
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divine power (Ps. 18:10; 135:7). |
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<ref>from the public domain [[Easton's Bible Dictionary]], originally published in 1897.</ref>}} |
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===History=== |
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[[Kamikaze (typhoon)|Kamikaze]] (神風) is a Japanese word, usually translated as divine wind, believed to be a gift from the gods. The term is first known to have been used as the name of a pair or series of typhoons that are said to have saved Japan from two Mongol fleets under Kublai Khan that attacked Japan in 1274 and again in 1281. |
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[[Protestant Wind]] is a name for the storm that deterred the [[Spanish Armada]] from an invasion of [[England]] in 1588 or the favourable winds that enabled [[William of Orange]] to invade England in 1688. |
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===Transportation=== |
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[[Image:Exeter-20may44.jpg|thumb|An aerial view of [[Exeter International Airport|RAF Exeter]] airfield on 20 May 1944, showing the [[Triangle|triangular]] layout of the [[runway]]s allowing aircraft to always take off and land into the wind]] |
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* [[Sailing ship]] |
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* While [[aircraft]] usually travel under an internal power source, [[tail wind]]s affect airspeed, and in the case of [[hot-air balloons]] and other lighter-than-air vehicles, wind may play a significant role in their propulsion. In addition, the direction of wind plays a role in the takeoff and landing of [[fixed-wing aircraft]] and [[airfield]] runways are usually aligned to take the direction of wind into account. |
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===Wind power=== |
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{{see|Wind power}} |
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===Culture=== |
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{{see|Cultural significance of tornadoes}} |
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Wind has featured in human cultural works, including [[art]], [[poetry]], [[music]], [[theatre]], [[novel]]s, [[film]]s, and television. |
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{{quote|'Westron wynde, when wilt thou blow, |
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The small raine down can raine. |
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Cryst, if my love were in my armes |
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And I in my bedde again!'|An anonymous poem [[The Western Wynde]] dating from before the 16th century}} |
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===Recreation=== |
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Wind figures prominently in several popular sports, including recreational [[sailing]], [[windsurfing]], and [[kiteboarding]]. Finally, wind enables the simple pleasure of flying a [[kite]]. |
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==Role in the natural world== |
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Wind has a very important role in aiding plants and other immobile organisms in dispersal of seeds, spores, pollen, etc. Although wind is not the primary form of seed dispersal in plants, it provides dispersal for a large percentage of the biomass of land plants. |
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* [[Biological dispersal]] |
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==The study of wind== |
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The [[Beaufort scale|Beaufort wind force scale]] is an empirical measure for describing wind speed based mainly on observed sea conditions. |
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===Meteorological instruments to measure wind speed and/or direction=== |
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Wind direction is reported by the direction from which it originates. For example, a ''northerly'' wind blows from the north to the south. |
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Local sensing techniques: |
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* [[Anemometer]] (measures [[wind speed]], either directly, e.g. with rotating cups, or indirectly, e.g. via pressure differences or the propagation speed of [[ultrasound]] signals) |
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* [[Rawinsonde]] ([[GPS]]-based wind measurement is performed by the probe) |
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* [[Weather balloon]] (passive measurement, [[balloon]] position is tracked from the ground visually or via [[radar]]; wind profile is computed from drift rate and the theoretical speed of ascent) |
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* [[Weather vane]] (used to indicate wind direction) |
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* [[Windsock]] (primarily used to indicate wind direction, may also be used to estimate wind speed by its angle) |
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* [[Pitot tube]]s |
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[[Remote sensing]] techniques: |
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* [[SODAR]] |
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* [[Doppler effect|Doppler]] [[LIDAR]]s and [[RADAR]]s can measure the [[Doppler shift]] of [[electromagnetic radiation]] scattered or reflected off suspended [[aerosol]]s or [[molecule]]s. This measurement can be directly related to wind velocity. |
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* [[Radiometer]]s and radars can be used to measure the surface roughness of the ocean from space or airplanes. This measurement can be used to estimate wind velocity close to the sea surface over oceans. |
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==See also== |
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*[[Climatology]] |
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*[[High Wind Warning]] |
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*[[Wind Advisory]] |
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*[[Atmospheric circulation]] |
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{{Meteorological variables}} |
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==Sources== |
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<!-- must have sources --> |
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==References== |
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<!-- this 'empty' section displays references defined elsewhere --> |
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{{reflist}} |
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==External links== |
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*[http://www.animalu.com/pics/dd1.htm Dancing with the Devils] - A short movie showing dust devils in action on a dry lakebed |
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*[http://www.winddata.com Database of Wind Characteristics] - Wind data for wind (turbine) design and wind resource assessment and siting |
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*[http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/home.rxml Meteorology Guides: Forces and Winds] - Instructional module from the University of Illinois |
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*[http://ggweather.com/winds.html Names of Winds] - A list from Golden Gate Weather Services |
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*[http://www.windatlas.dk Wind Atlases of the World] - Lists of wind atlases and wind surveys from all over the world |
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*[http://www.lpi.usra.edu/publications/slidesets/winds.html Winds of Mars: Aeolian Activity and Landforms] - Paper with slides that illustrate the wind activity on the planet [[Mars (planet)|Mars]] |
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*[http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/wind_speeds.html&edu=high Classification of Wind Speeds] |
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*[http://www.magenn.com/winddata.php Wind-speed chart] |
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*[http://www.cambridgenetwork.co.uk/news/article/default.aspx?objid=46042 Wind Simulation Equipment] |
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*[http://www.lbk.ars.usda.gov/wewc/biblio/bar.htm The Bibliography of Aeolian Research] |
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[[Category:Winds| ]] |
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[[af:Wind]] |
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[[ar:رياح]] |
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[[ast:Vientu]] |
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[[gn:Yvytu]] |
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[[zh-min-nan:Hong]] |
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[[be-x-old:Вецер]] |
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[[bs:Vjetar]] |
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[[br:Avel]] |
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[[bg:Вятър]] |
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[[ca:Vent (meteorologia)]] |
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[[cs:Vítr]] |
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[[da:Vind]] |
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[[de:Wind]] |
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[[et:Tuul]] |
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[[el:Άνεμος]] |
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[[es:Viento]] |
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[[eo:Vento]] |
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[[eu:Haize]] |
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[[fa:باد]] |
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[[fr:Vent]] |
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[[gd:Gaoth]] |
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[[gl:Vento]] |
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[[ko:바람]] |
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[[hi:पवन]] |
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[[hr:Vjetar]] |
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[[io:Vento]] |
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[[id:Angin]] |
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[[is:Vindur]] |
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[[it:Vento]] |
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[[he:רוח]] |
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[[sw:Upepo]] |
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[[la:Ventus]] |
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[[lv:Vējš]] |
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[[lt:Vėjas]] |
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[[hu:Szél]] |
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[[mk:Ветер]] |
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[[ml:കാറ്റ്]] |
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[[ms:Angin]] |
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[[nl:Wind (meteorologie)]] |
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[[nds-nl:Wiend]] |
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[[new:फे]] |
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[[ja:風]] |
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[[no:Vind]] |
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[[nn:Vind]] |
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[[nrm:Vent]] |
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[[pl:Wiatr]] |
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[[pt:Vento]] |
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[[ro:Vânt]] |
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[[qu:Wayra]] |
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[[ru:Ветер]] |
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[[sq:Era]] |
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[[scn:Ventu]] |
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[[simple:Wind]] |
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[[sk:Vietor]] |
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[[sl:Veter]] |
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[[sr:Ветар]] |
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[[sh:Vetar]] |
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[[fi:Tuuli]] |
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[[sv:Vind]] |
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[[tl:Hangin]] |
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[[th:ลม]] |
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[[vi:Gió]] |
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[[tr:Rüzgâr]] |
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[[uk:Вітер]] |
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[[wa:Vint]] |
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[[yi:ווינט]] |
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[[zh-yue:風]] |
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[[bat-smg:Vies]] |
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[[zh:風]] |
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Revision as of 21:29, 22 July 2008
Obama Bin Laden!!!