polar front jet stream

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Horizontal divergence and convergence patterns associated with the polar-front jet.

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polar front jet stream

meteorology

Also known as: midlatitude jet stream, polar front jet

Written and fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Jan 23, 2025 • Article History

Also called:: polar front jet or midlatitude jet stream

Related Topics:: polar vortex; jet stream

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polar front jet stream, a belt of powerful upper-level winds that sits atop the polar front. The winds are strongest in the tropopause, which is the upper boundary of the troposphere, and move in a generally westerly direction in midlatitudes. The vertical wind shear which extends below the core of this jet stream is associated with horizontal temperature gradients that extend to the surface. As a consequence, this jet manifests itself as a front that marks the division between colder air over a deep layer and warmer air over a deep layer. The polar front jet can be baroclinically unstable and break up into Rossby waves.

This article was most recently revised and updated by John P. Rafferty.