Skip to main content
Select Source:

Wind Shear

Wind shear

Wind shear is a phenomenon describing highly localized variability in wind speed and/or wind direction. Because wind shear can affect the angle of attack on an airfoil (e.g., the wing, or control surfaces of an airplane) wind shear can cause a loss of lift or control. Dangerous to aviation, wind shear is particularly hazardous when encountered during take-off or landing.

Wind shear is the difference in speed or direction between two layers of air in the atmosphere. Wind shear may occur in either a vertical or horizontal orientation. An example of the former situation is the case in which one layer of air in the atmosphere is traveling from the west at a speed of 31 mph (50 km per hour) while a second layer above it is traveling in the same direction at a speed of 6.2 mph (10 km per hour). The friction that occurs at the boundary of these two air currents is a manifestation of wind shear.

An example of horizontal wind shear occurs in the jet stream where one section of air moves more rapidly than other sections on either side of it. In this case, the wind shear line lies at the same altitude as various currents in the jet stream, but at different horizontal distances from the jet stream's center.

Wind shear is a crucial factor in the development of other atmospheric phenomena. For example, as the difference between adjacent wind currents increases, the wind shear also increases. At some point, the boundary between currents may break apart and form eddies that can develop into clear air turbulence or, in more drastic circumstances, tornadoes and other violent storms.

Wind shear has been implicated in a number of disasters resulting in property damage and/or loss of human life. The phenomenon is known as a microburst, a strong localization down draft (down burst) which, when it when reaches the ground, continues as an expanding outflow. For example, it is associated with the movement of two streams of air at high rates of speed in opposite directions. An airplane that attempts to fly through a microburst passes through the wind shear at the boundary of these two air streams. The plane feels, in rapid succession, an additional lift from headwinds and then a sudden loss of lift from tailwinds. In such a case, a pilot may not be able to maintain control of the aircraft in time to prevent a crash.

See also Aerodynamics; Bernoulli's principle; Meteorology; Weather radar; Weather satellite

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Wind Shear." World of Earth Science. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"Wind Shear." World of Earth Science. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/wind-shear

"Wind Shear." World of Earth Science. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/wind-shear

wind shear

wind shear, a sudden, drastic change in wind direction or speed over a comparatively short distance. Most winds travel horizontally, as does most wind shear, but under certain conditions, including thunderstorms and strong frontal systems, wind shear will travel in a vertical direction. Microburst wind shear is an extremely violent downward blast of air that hits the earth and radiates outward. With its sharp shifts in wind direction and relative wind speed, it can cause an aircraft to lose lift and crash, especially during takeoff or landing, when the slower speeds and closeness to the ground make altitude correction more difficult. Since 1996 all U.S. airliners have been required to be equipped with instruments that provide the pilot with advance warning of wind shear. See also weather and wind.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"wind shear." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"wind shear." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/wind-shear

"wind shear." The Columbia Encyclopedia, 6th ed.. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/wind-shear

wind shear

wind shear The gradient of horizontal wind velocity with height, which varies according to the rate of change of temperature with altitude. Vertical wind shear can be a cause of cloud formation in the turbulent mixing taking place in a boundary layer of air moving at different speeds. The shear between the wind at different levels can be expressed as a vector, measuring the difference in speed and direction.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"wind shear." A Dictionary of Earth Sciences. . Encyclopedia.com. 23 Aug. 2017 <http://www.encyclopedia.com>.

"wind shear." A Dictionary of Earth Sciences. . Encyclopedia.com. (August 23, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/wind-shear

"wind shear." A Dictionary of Earth Sciences. . Retrieved August 23, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/wind-shear