Editing Polar vortex (section)

{{Not to be confused| Polar low}}
{{Short description|Persistent cold-core low-pressure area that circles one of the poles}}
{{For|[[Shani Mootoo]]'s novel|Polar Vortex}}
{{Multiple image
| header    = The Arctic tropospheric polar vortex
| header_align = center
| caption_align = center
| align     = right
| image1    = November2013 polar vortex geopotentialheight mean Large.jpg
| width1      = 149
| alt1      = Map of a compact blob over the Arctic
| caption1  = A strong [[tropospheric]] polar vortex configuration in November 2013
| image2    = Jan52014 polar vortex geopotentialheight mean Large.jpg
| width2      = 149
| alt2      = Map of a blobs spreading from the Arcitc
| caption2  = A more typical weak tropospheric polar vortex on January 5, 2014
}}

A '''polar vortex''', more formally a '''circumpolar vortex''', is a large region of cold, rotating air; polar vortices encircle both of Earth's [[Polar regions of Earth|polar regions]]. Polar vortices also exist on other rotating, low-[[Axial tilt|obliquity]] [[Planet#Planetary-mass objects |planetary bodies]].<ref>{{cite journal |url=http://doi.org/10.1016/j.pss.2010.04.024 |date=August 2011 |journal=Planetary and Space Science |title=Dynamics and circulation regimes of terrestrial planets |pages=900–914 |first1=P.L. |last1=Read |volume=59 |issue=10 |doi=10.1016/j.pss.2010.04.024 |bibcode=2011P&SS...59..900R|url-access=subscription }}</ref> The term polar vortex can be used to describe two distinct phenomena; the [[stratosphere|stratospheric]] polar vortex, and the [[troposphere|tropospheric]] polar vortex. The stratospheric and tropospheric polar vortices both rotate in the direction of the Earth's spin, but they are distinct phenomena that have different sizes, structures, seasonal cycles, and impacts on weather.

The stratospheric polar vortex is an area of high-speed, [[cyclonic rotation|cyclonically]] rotating winds around 15&nbsp;km to 50&nbsp;km high, poleward of 50°, and is strongest in winter. It forms during autumn when Arctic or Antarctic temperatures cool rapidly as the [[polar night]] begins. The increased temperature difference between the pole and the tropics causes strong winds, and the [[Coriolis effect]] causes the vortex to spin up. The stratospheric polar vortex breaks down during spring as the polar night ends. A [[sudden stratospheric warming]] (SSW) is an event that occurs when the stratospheric vortex breaks down during winter, and can have significant [[Sudden stratospheric warming#Weather effects|impacts on surface weather]]{{Broken anchor|date=2025-04-15|bot=User:Cewbot/log/20201008/configuration|target_link=Sudden stratospheric warming#Weather effects|reason= The anchor (Weather effects) [[Special:Diff/1250438623|has been deleted]].|diff_id=1250438623}}.{{citation needed|date=March 2021}}

The tropospheric polar vortex is often defined as the area poleward of the tropospheric [[jet stream]]. The equatorward edge is around 40° to 50°, and it extends from the surface up to around 10&nbsp;km to 15&nbsp;km. Its yearly cycle differs from the stratospheric vortex because the tropospheric vortex exists all year, but is similar to the stratospheric vortex since it is also strongest in winter when the polar regions are coldest.

The tropospheric polar vortex was first described as early as 1853.<ref>[https://books.google.com/books?id=Df4vAAAAYAAJ&pg=PA430&dq=%22polar+vortex%22 "Air Maps"], ''Littell's Living Age'' No. 495, 12 November 1853, p. 430.</ref> The stratospheric vortex's SSWs were discovered in 1952 with [[radiosonde]] observations at altitudes higher than 20&nbsp;km.<ref>{{cite press release |title=GEOS-5 Analyses and Forecasts of the Major Stratospheric Sudden Warming of January 2013 |publisher=[[Goddard Space Flight Center]] |url=http://gmao.gsfc.nasa.gov/researchhighlights/SSW/ |access-date=January 8, 2014}}</ref> The tropospheric polar vortex was mentioned frequently in the news and weather media in the [[Early 2014 North American cold wave|cold North American winter of 2013–2014]], popularizing the term as an explanation of very cold temperatures. The tropospheric vortex increased in public visibility in 2021 as a result of [[February 2021 North American cold wave|extreme frigid temperatures in the central United States]], with newspapers linking its effects to [[climate change]].<ref>{{Cite web|last=Plumer|first=Brad|date=16 February 2021|title=A Glimpse of America's Future: Climate Change Means Trouble for Power Grids|url=https://www.nytimes.com/2021/02/16/climate/texas-power-grid-failures.html|website=The New York Times}}</ref>

[[Ozone depletion]] occurs most heavily within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring.
[[Category:Snow or ice weather phenomena]]