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What are Jet Streams? Definition, Development, Purpose, and Importance

written by: R. Elizabeth C. Kitchen•edited by: Laurie Patsalides•updated: 7/8/2011

Jet streams are important, especially for aviation. Understanding a jet stream, its purpose, and its cause is very important in helping to understand other processes, such as future power generation.

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    What are Jet Streams?

    Jet streams are narrow, fast-flowing air currents found in the atmospheres on certain planets. The main jet streams are located close to the tropopause. Earth's major jet streams are westerly winds. The path of the winds tends to have a meandering shape. Jet streams can split into two parts or more, stop, start, flow in various directions, or combine into one stream. Polar jets are the strongest jet streams.

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    Size and Speed of Jet Streams

    Jet streams are most often a few hundred miles wide. They tend to be less than three miles in vertical thickness. Discontinuities are common, however, most are continuous over long distances. Temperature gradient affects the wind speeds which typically exceed 92 kilometers per hour. However, they have been known to exceed 398 kilometers per hour in some instances.

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    What Causes a Jet Stream?

    What are Jet Streams Jet streams occur when air masses meet where the winds are the strongest, just under the tropopause. When two different masses of air with different densities come together, winds increase due to the different densities creating pressure. As these winds try to flow down to the cooler area from the warm area, the Coriolis effect deflects the the wind and flows along the two air masses' boundaries, but does not directly flow from the hot area to the cold area. This then results in the subtropical and polar jet streams that form throughout the world.

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    How Jet Streams Develop

    The pressure difference that is caused by a density difference that occurs when two air masses of different densities and temperatures meet causes wind and jet streams. These winds will highest in the transition zone.

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    Purpose and Importance of Jet Streams

    Jet stream location is used by meteorologists to help them in weather forecasting. Jet streams are responsible for pushing weather all over the world. Meteorologist look at the strength and position of a jet stream when predicting future weather patterns. Air travel also heavily relies on jet streams because flight time can be greatly impacted by flying either against a jet stream or with a jet stream. A potential hazard to an aircraft, clear-air turbulence, is most often found within the vicinity of a jet stream. Airborne wind turbines are a potential future benefit of jet streams.

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    University of Oregon. (2011). Jet Streams. Retrieved on April 20, 2011 from the University of Oregon:

    NOVA Online. (2001). Inside the Jet Stream. Retrieved on April 20, 2011 from NOVA Online:

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    Image Credits

    Jet Stream: Wikimedia Commons - United States Federal Government