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wind

wind, flow of air relative to the earth's surface. A wind is named according to the point of the compass from which it blows, e.g., a wind blowing from the north is a north wind.

Wind Direction and Velocity

The direction of wind is usually indicated by a thin strip of wood, metal, or plastic (often in the shape of an arrow or a rooster) called a weather vane or weathercock (but more appropriately called a wind vane) that is free to rotate in a horizontal plane. When mounted on an elevated shaft or spire, the vane rotates under the influence of the wind such that its center of pressure rotates to leeward and the vane points into the wind.

Wind velocity is measured by means of an anemometer or radar. The oldest of these is the cup anemometer, an instrument with three or four small hollow metal hemispheres set so that they catch the wind and revolve about a vertical rod; an electrical device records the revolutions of the cups and thus the wind velocity. The pressure tube anemometer, used primarily in Commonwealth nations, is conceptually a Pitot tube mounted on a wind vane. As the wind blows across the tube, a pressure differential is created that can be mathematically related to wind speed. Doppler radar can be used to measure wind speed by shooting pulses of microwaves that are reflected off rain, dust, and other particles in the air, much like the radar guns used by the police to determine the speed of an automobile. Although the U.S. National Weather Service has estimated that tornado winds have reached a velocity of 500 mph (800 kph), the highest wind speeds ever documented, 318 mph (516 kph), were measured using Doppler radar during a tornado in Oklahoma in 1999.

The first successful attempt to standardize the nomenclature of winds of different velocities was the Beaufort scale, devised (c.1805) by Admiral Sir Francis Beaufort of the British navy. An adaptation of Beaufort's scale is used by the U.S. National Weather Service; it employs a scale ranging from 0 for calm to 12 for hurricane, each velocity range being identified by its effects on such things as trees, signs, and houses. Winds may also be classified according to their origin and movement, such as heliotropic winds, which include land and sea breezes, and cyclonic winds, which blow counterclockwise in low-pressure regions of the Northern Hemisphere and clockwise in the Southern Hemisphere.

Prevailing Winds and General Circulation Patterns

Over some zones around the earth, winds blow predominantly in one direction throughout the year and are usually associated with the rotation of the earth; over other areas, the prevailing direction changes with the seasons; winds over most areas also are variable from day to day so that no prevailing direction is evident, such as, for example, the day-to-day changes in local winds associated with storms or clearing skies. Around the equator there is a belt of relatively low pressure known as the doldrums, where the heated air is expanding and rising; at about lat. 30°N and S there are belts of high pressure known as the horse latitudes, regions of descending air; farther poleward, near lat. 60°N and S, are belts of low pressure, where the polar front is located and cyclonic activity is at a maximum; finally there are the polar caps of high pressure.

The prevailing wind systems of the earth blow from the several belts of high pressure toward adjacent low-pressure belts. Because of the earth's rotation (see Coriolis effect), the winds do not blow directly northward or southward to the area of lower pressure, but are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The wind systems comprise the trade winds; the prevailing westerlies, moving outward from the poleward sides of the horse-latitude belts toward the 60° latitude belts of low pressure (from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere); and the polar easterlies, blowing outward from the polar caps of high pressure and toward the 60° latitude belts of low pressure.

This zonal pattern of winds is displaced northward and southward seasonally because of the inclination of the earth on its axis and the consequent migration of the belts of temperature and pressure. In addition, the pattern is considerably modified by the distribution of land and water, especially in the temperate regions, where temperature differences between land and water are greatest. In winter, areas of high pressure tend to build up over cold continental land masses, while low-pressure development takes place over the adjacent, relatively warm oceans. Exactly the opposite conditions occur during summer, although to a lesser degree. These contrasting pressures over land and water areas are the cause of monsoon winds.

Superimposed upon the general circulation of winds are many lesser disturbances, such as the extratropical cyclone (the common storm of the temperate latitudes), the tropical cyclone, or hurricane, the tornado, and the derecho; each of these storms moves generally along a path that follows the direction of the prevailing winds.

See also chinook; climate; roaring forties; sandstorm; sirocco; weather.

Localized Influences on Wind Patterns

The diurnal, or daily, heating and cooling of land near a lake or ocean of fairly constant temperature causes air to blow toward the relatively warmer land during the day (sea breeze) and toward the relatively warmer water at night (land breeze). These breezes are shallow and seldom penetrate far inland or attain high velocity. Similar diurnal changes occur on mountain slopes, the air in the valley becoming heated and expanding so that it moves up the slope in the daytime, the cold air settling into the valley at night. Friction with the earth's surface, eddies caused by surface irregularities, and inequalities of heating with consequent convection currents tend to reduce wind velocity near the earth's surface and cause winds to blow in gusts.

Bibliography

See A. Watts, Instant Wind Forecasting (1988); P. Gipe, Wind Energy Comes of Age (1995); J. DeBlieu, Wind: How the Flow of Air Has Shaped Life, Myth, and the Land (1999).

The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Wind

 

the movement of air in the atmosphere almost parallel to the earth’s surface. Wind is usually understood to mean the horizontal component of that movement; sometimes the vertical component, which is hundreds of times less than the horizontal, is also meant. The vertical component of wind attains significant magnitude only in special cases: in clouds when there is strongly developed convection, or in the mountains when air descends along a slope.

Wind arises as a result of uneven horizontal distribution of pressure, which in turn is caused by the inequality of temperature in the atmosphere. Under the influence of pressure drops, the air experiences acceleration directed from high pressure to low. However, along with the initiation of movement, other forces begin to act upon the air: the deflecting force of the earth’s rotation (Coriolis force), friction, and in curved trajectories, centrifugal force. The influence of friction is substantial only in the lower hundreds of meters (in the friction layer). With altitude the effect of friction gradually diminishes, and wind velocity increases. In free atmosphere, above the friction layer, the wind is almost a geostrophic wind.

In the lower layer of the atmosphere, which is a few hundred meters thick and in which friction is substantial, the wind is deflected from the isobars in the direction of low pressure. The magnitude of the angle formed by the wind and the isobar changes according to the character of the underlying surface, the altitude, and also time. Over the sea this angle is 10°-20°; over dry land, 40°-50°. The angle gradually diminishes to zero with increasing altitude.

Wind is characterized by velocity and direction. The wind velocity at the earth’s surface is measured with an anemometer and is expressed in m/sec, km/hr, or knots. Wind velocity may also be approximately estimated visually by the action of the wind on objects; in such cases it is expressed in arbitrary units (the Beaufort scale). Wind direction is determined by a wind vane, streamer, wind sock, and so on and is indicated by the azimuth of the point from which it is blowing. Wind direction is expressed either in degrees or in rhumbs according to a 16-rhumb system (N, NNE, NE, ENE, E, ESE, and so on). In the free atmosphere, the velocity and direction of the wind are measured by theodolitic and radiotheodolitic observations of free-flying pilot balloons.

Wind velocity and direction always fluctuate to a greater or lesser degree. These fluctuations are called gustiness and are associated with atmospheric turbulence. In making observations, the mean values of wind velocity and direction are usually given. Wind velocities of 5-8 m/sec are considered moderate; over 14 m/sec, strong; on the order of 20-25 m/sec, a gale; and over 30 m/sec, a hurricane. An abrupt short-term increase in wind up to 20 m/sec is called a squall. In tropical cyclones, individual gusts may reach 100 m/sec. The complete absence of wind (calm) is sometimes observed at the earth’s surface. In the troposphere, wind velocity increases with altitude, reaching a maximum at an altitude of 8-10 km. So-called jet streams, with velocities exceeding 60-70 m/sec, are often observed here.

Wind velocity and direction have a clearly expressed daily cycle. At night, the wind velocity at the earth’s surface reaches a minimum, and in the afternoon hours it reaches a maximum. The daily cycle of wind is especially well expressed in the summer on clear days over steppe or desert regions; no daily wind cycle is observed over the sea.

The annual cycle of wind velocity depends substantially on the characteristics of the total atmospheric circulation and also on local conditions. Over the greater part of the European USSR, wind velocity reaches its maximum in the winter and its minimum in the summer. However, in Eastern Siberia, for example, minimum wind velocity is observed in the winter, and the wind becomes stronger in the summer.

Local winds, which are usually associated with features of local circulation, local topography, and so on, are observed in a number of places on the globe.

REFERENCES

Matveev, L. T. Osnovy obshchei meteorologii. Leningrad, 1965.
Khromov, S. P. Meteorologiia i klimatologiia dlia geografieheskikhfakul’tetov, 2nd ed. Leningrad, 1968.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

What does it mean when you dream about wind?

Wind in a dream may represent turmoil in the dreamer’s emotions. It can also indicate the energy available for launching in new directions in life.

The Dream Encyclopedia, Second Edition © 2009 Visible Ink Press®. All rights reserved.

wind

[wind]
(electronics)
The manner in which magnetic tape is wound onto a reel; in an A wind, the coated surface faces the hub; in a B wind, the coated surface faces away from the hub.
(meteorology)
The motion of air relative to the earth's surface; usually means horizontal air motion, as distinguished from vertical motion, and air motion averaged over the response period of the particular anemometer.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

wind

1. British term for twist.
2. A once-used synonym for warped or wined.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

Wind

Aeolian harp
musical instrument activated by winds. [Gk. Myth.: Jobes, 40]
Aeolus
steward of winds; gives bag of winds to Odysseus. [Gk. Myth: Kravitz, 10; Gk. Lit.: Odyssey]
Afer (Africus)
southwest wind. [Gk. Myth.: Kravitz, 11]
Apeliotes (Lips)
east or southeast wind. [Gk. Myth.: Kravitz, 27]
Aquilo
equivalent of Boreas, the Greek north wind. [Rom. Myth.: Kravitz, 30]
Argestes
name of the east wind. [Gk. Myth.: Kravitz, 32]
Aura
goddess of breezes. [Gk. Myth.: Kravitz, 42]
Auster
the southwest wind. [Rom. Myth.: Kravitz, 42]
Boreas
god of the north wind. [Gk. Myth.: Parrinder, 49]
Caicas
the northeast wind. [Gk. Myth.: Kravitz, 50]
Corns
god of the north or northwest wind. [Rom. Myth.: Jobes, 374]
Eurus (Volturnus)
the southeast wind. [Gk. Myth.: Kravitz, 97, 238]
Favonius
ancient Roman personification of west wind. [Rom. Myth.: Howe, 103]
Gentle Annis
weather spirit; controls gales on Firth of Cromarty. [Scot. Folklore: Briggs, 185]
gregale (Euroclydon)
cold, northeast wind over the central Mediterranean. [Meteorology: EB, IV: 724; N.T.: Acts 27:14]
Keewaydin
the Northwest Wind, to whose regions Hiawatha ultimately departed. [Am. Lit.: Longfellow The Song of Hiawatha in Magill I, 905]
Mudjekeewis
Indian chief; held dominion over all winds. [Am. Lit.: “Hiawatha” in Benét, 466]
Njord
god of the north wind. [Norse Myth.: Wheeler, 260]
Ruach
isle of winds. [Fr. Lit.: Pantagruel]
Sleipnir
Odin’s eight-legged horse; symbolizes the wind that blows from eight points. [Norse Myth.: Benét, 937]
Zephyrus
the west wind. [Gk. Myth.: Kravitz, 38, 242]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.

wind

1. a current of air, sometimes of considerable force, moving generally horizontally from areas of high pressure to areas of low pressure
2. Chiefly poetic the direction from which a wind blows, usually a cardinal point of the compass
3. air artificially moved, as by a fan, pump, etc.
4. (often used in sports) the power to breathe normally
5. Music
a. a wind instrument or wind instruments considered collectively
b. the musicians who play wind instruments in an orchestra
c. of, relating to, or composed of wind instruments
6. an informal name for flatus
7. the air on which the scent of an animal is carried to hounds or on which the scent of a hunter is carried to his quarry
8. between wind and water the part of a vessel's hull below the water line that is exposed by rolling or by wave action
9. have in the wind to be in the act of following (quarry) by scent
10. off the wind Nautical away from the direction from which the wind is blowing
11. on the wind Nautical as near as possible to the direction from which the wind is blowing
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

Wind

(dreams)
The wind in your dream could be symbolic of your own spirit or the life force. The wind may represent changes in your life; the greater the force of the wind, the grater the change. A very gusty wind could represent stress and turmoil but also the energy that you need or have to make changes. The sound of the wind and the movement of objects around you are probably what alert you to the wind in the dream, rather than a sensation of wind on your skin (most people don’t have tactile experiences in their dreams). The sound of the wind is considered by some to be special because it is a sound of nature and has spiritual significance.
Bedside Dream Dictionary by Silvana Amar Copyright © 2007 by Skyhorse Publishing, Inc.
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