Polar vortex

{{Short description|Persistent cold-core low-pressure area that circles one of the poles}}

{{Multiple image

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| image1 = November2013 polar vortex geopotentialheight mean Large.jpg

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| alt1 = Map of a compact blob over the Arctic

| caption1 = A strong tropospheric polar vortex configuration in November 2013

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| alt2 = Map of a blobs spreading from the Arcitc

| caption2 = A more typical weak tropospheric polar vortex on January 5, 2014

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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. Polar vortices also exist on other rotating, low-obliquity planetary bodies.{{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}} The term polar vortex can be used to describe two distinct phenomena; the stratospheric polar vortex, and the 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, cyclonically rotating winds around 15 km to 50 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 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) 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 km to 15 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.[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. The stratospheric vortex's SSWs were discovered in 1952 with radiosonde observations at altitudes higher than 20 km.{{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}} The tropospheric polar vortex was mentioned frequently in the news and weather media in the 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 extreme frigid temperatures in the central United States, with newspapers linking its effects to climate change.{{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}}

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

Arctic and Antarctic vortices

=Northern Hemisphere=

When the tropospheric vortex of the Arctic is strong, it has a well defined and nearly circular shape. There is a single vortex with a jet stream that is well constrained near the polar front, and the Arctic air is well contained. When this northern tropospheric vortex weakens, it breaks into two or more smaller vortices, the strongest of which are near Baffin Island, Nunavut, and the others over northeast Siberia. When it is very weak, the flow of Arctic air becomes more disorganized, and masses of cold Arctic air can push equatorward, bringing with them a rapid and sharp temperature drop.{{cite web |website=Glossary of Meteorology |date=June 2000 |url=http://glossary.ametsoc.org/wiki/Polar_vortex |title=Polar vortex |publisher=American Meteorological Society |access-date=15 June 2008}}

A deep freeze that gripped much of the United States and Canada in late January 2019 was blamed in some accounts on a "polar vortex". This is not the scientifically correct use of the term polar vortex, but instead is referring to outbreaks of cold Arctic air caused by a weakened polar vortex. The US National Weather Service warned that frostbite is possible within just 10 minutes of being outside in such extreme temperatures, and hundreds of schools, colleges, and universities in the affected areas were closed. Around 21 people died in US due to severe frostbite.{{cite news|title=Casualty|work=BBC News|url=https://www.bbc.com/news/world-us-canada-47088684|date=1 Feb 2019|access-date=12 Feb 2019|language=en}}{{cite web|title=Polar vortex: What is it and how does it happen? |url=https://www.bbc.com/news/av/world-47065461/polar-vortex-what-is-it-and-how-does-it-happen |date=30 Jan 2019|website=BBC video|access-date=31 Jan 2019}} States within the midwest region of the United States had windchills just above -50 °F (-45 °C). The polar vortex is also thought to have had effects in Europe. For example, the 2013–14 United Kingdom winter floods were blamed on the polar vortex bringing severe cold in the United States and Canada.{{Cite web|url=http://climatestate.com/2014/02/09/uk-flooding-and-the-science-of-climate-change/|title=UK Flooding and the Science of Climate Change|date=9 February 2014|access-date=19 April 2019|archive-date=7 June 2019|archive-url=https://web.archive.org/web/20190607235448/http://climatestate.com/2014/02/09/uk-flooding-and-the-science-of-climate-change/|url-status=dead}} Similarly, the severe cold in the United Kingdom in the winters of 2009–10 and 2010–11 were also blamed on the polar vortex.{{Cite web|url=https://www.independent.co.uk/news/uk/home-news/polar-vortex-what-is-coldest-winter-uk-weather-cold-snap-why-arctic-met-office-a7402611.html|title = Britain is about to get very, very cold|website = Independent.co.uk|date = 7 November 2016}}

=Southern Hemisphere=

The Antarctic vortex of the Southern Hemisphere is a single low-pressure zone that is found near the edge of the Ross ice shelf, near 160 west longitude. When the polar vortex is strong, the mid-latitude Westerlies (winds at the surface level between 30° and 60° latitude from the west) increase in strength and are persistent. When the polar vortex is weak, high-pressure zones of the mid-latitudes may push poleward, moving the polar vortex, jet stream, and polar front equatorward. The jet stream is seen to "buckle" and deviate south. This rapidly brings cold dry air into contact with the warm, moist air of the mid-latitudes, resulting in a rapid and dramatic change of weather known as a "cold snap".{{cite press release |title=Stratospheric Polar Vortex Influences Winter Cold, Researchers Say |publisher=American Association for the Advancement of Science |date=December 3, 2001 |url=http://www.eurekalert.org/pub_releases/2001-12/uoia-spv120301.php|access-date=May 23, 2015}}

In Australia, the polar vortex, known there as a "polar blast" or "polar plunge", is a cold front that drags air from Antarctica which brings rain showers, snow (typically inland, with blizzards occurring in the highlands), gusty icy winds, and hail in the south-eastern parts of the country, such as in Victoria, Tasmania, the southeast coast of South Australia and the southern half of New South Wales (but only on the windward side of the Great Dividing Range, whereas the leeward side will be affected by foehn winds).{{cite web|title=Polar Blast Set To Hit Australia This Weekend, First in 15 Years |url=https://www.sciencetimes.com/articles/26982/20200821/polar-blast-australia-weekend-first-15-years.htm |date=21 Aug 2020|website=Science Times|access-date=25 September 2020}}{{cite news|title='Twin peaks': Sydney prepares for double burst of polar chill |url=https://www.smh.com.au/environment/weather/twin-peaks-sydney-prepares-for-double-burst-of-polar-chill-20180509-p4ze7g.html |date=9 May 2018 |website=Sydney Morning Herald|access-date=25 September 2020}}

Identification

The bases of the two polar vortices are located in the middle and upper troposphere and extend into the stratosphere. Beneath that lies a large mass of cold, dense Arctic air. The interface between the cold dry air mass of the pole and the warm moist air mass farther south defines the location of the polar front. The polar front is centered roughly at 60° latitude. A polar vortex strengthens in the winter and weakens in the summer because of its dependence on the temperature difference between the equator and the poles.Halldór Björnsson. {{cite web |url=http://andvari.vedur.is/~halldor/HB/Met210old/GlobCirc.html |archive-url=https://web.archive.org/web/20100324184958/http://andvari.vedur.is/~halldor/HB/Met210old/GlobCirc.html |archive-date=March 24, 2010 |title=Global circulation |url-status=dead |access-date=September 2, 2016 }}. Veðurstofa Íslands. Retrieved on 2008-06-15.{{self-published inline|date=January 2014}}

Polar cyclones are low-pressure zones embedded within the polar air masses, and exist year-round. The stratospheric polar vortex develops at latitudes above the subtropical jet stream.{{cite journal |last1=Hartmann |first1=D |last2=Schoeberl |first2=M |year=1991 |title=Mixing of polar vortex air into middle latitudes as revealed by tracer-tracer scatterplots |doi=10.1029/96JD03715 |bibcode = 1997JGR...10213119W |volume=102 |issue=D11 |journal=Journal of Geophysical Research |pages=13119|doi-access=free }} Horizontally, most polar vortices have a radius of less than {{convert|1000|km|mi}}. Since polar vortices exist from the stratosphere downward into the mid-troposphere, a variety of heights/pressure levels are used to mark its position. The 50 hPa pressure surface is most often used to identify its stratospheric location.{{cite journal|url=https://www.academia.edu/223963|date=April 2010|journal=Quarterly Journal of the Royal Meteorological Society|title=The association between stratospheric weak polar vortex events and cold air outbreaks in the Northern Hemisphere|page=887|first1=Erik W.|last1=Kolstad|first2=Tarjei|last2=Breiteig|first3=Adam A.|last3=Scaife|volume=136|issue=649|bibcode=2010EGUGA..12.5739K|doi=10.1002/qj.620|arxiv=0906.0027|s2cid=119249497|access-date=2017-12-02|archive-date=2020-02-24|archive-url=https://web.archive.org/web/20200224132726/https://www.academia.edu/223963|url-status=dead}} At the level of the tropopause, the extent of closed contours of potential temperature can be used to determine its strength. Others have used levels down to the 500 hPa pressure level (about {{convert|5460|m|ft}} above sea level during the winter) to identify the polar vortex.{{cite journal|url=http://www.ccsenet.org/journal/index.php/jgg/article/viewFile/28960/18761|journal=Journal of Geology and Geography|date=2013-11-22|author=Abdolreza Kashki & Javad Khoshhal|title=Investigation of the Role of Polar Vortex in Iranian First and Last Snowfalls|issn=1916-9779|volume=5|number=4|access-date=2014-01-30|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304065215/http://www.ccsenet.org/journal/index.php/jgg/article/viewFile/28960/18761|url-status=dead}}

Duration and strength

File:Polarvortexwinter.jpg

Polar vortices are weakest during summer and strongest during winter. Extratropical cyclones that migrate into higher latitudes when the polar vortex is weak can disrupt the single vortex creating smaller vortices (cold-core lows) within the polar air mass.{{cite book|url=https://books.google.com/books?id=-tBa1DWYoDIC&pg=PA167|page=174|title=Polar lows: mesoscale weather systems in the polar regions|author=Erik A. Rasmussen and John Turner|year=2003|publisher=Cambridge University Press|isbn=978-0-521-62430-5}} Those individual vortices can persist for more than a month.

Volcanic eruptions in the tropics can lead to a stronger polar vortex during winter for as long as two years afterwards.{{cite journal |bibcode=2000RvGeo..38..191R |title=Volcanic eruptions and climate |last1=Robock |first1=Alan |volume=38 |year=2000 |pages=191–219 |journal=Reviews of Geophysics |doi=10.1029/1998RG000054 |issue=2|s2cid=1299888 |url=https://pdfs.semanticscholar.org/ce8e/392a97dbd25c7f20855547ec8be444416c4e.pdf |archive-url=https://web.archive.org/web/20200219140441/https://pdfs.semanticscholar.org/ce8e/392a97dbd25c7f20855547ec8be444416c4e.pdf |url-status=dead |archive-date=2020-02-19 }} The strength and position of the polar vortex shapes the flow pattern in a broad area about it. An index which is used in the northern hemisphere to gauge its magnitude is the Arctic oscillation.Todd Mitchell (2004). [http://jisao.washington.edu/ao/ Arctic Oscillation (AO) time series, 1899 – June 2002] {{Webarchive|url=https://web.archive.org/web/20031212174712/http://jisao.washington.edu/ao/ |date=2003-12-12 }}. University of Washington. Retrieved on 2009-03-02.

When the Arctic vortex is at its strongest, there is a single vortex, but normally, the Arctic vortex is elongated in shape, with two cyclone centers, one over Baffin Island in Canada and the other over northeast Siberia. When the Arctic pattern is at its weakest, subtropic air masses can intrude poleward causing the Arctic air masses to move equatorward, as during the Winter 1985 Arctic outbreak.Kevin Myatt (2005-01-17). [http://www.roanoke.com/weather/wb/16914 Cold enough for snow, and more's on the way] {{webarchive|url=https://archive.today/20130201105159/http://www.roanoke.com/weather/wb/16914 |date=2013-02-01 }}. Roanoke Times. Retrieved on 2012-02-24. The Antarctic polar vortex is more pronounced and persistent than the Arctic one. In the Arctic the distribution of land masses at high latitudes in the Northern Hemisphere gives rise to Rossby waves which contribute to the breakdown of the polar vortex, whereas in the Southern Hemisphere the vortex is less disturbed. The breakdown of the polar vortex is an extreme event known as a sudden stratospheric warming, here the vortex completely breaks down and an associated warming of 30–50 °C (54–90 °F){{clarify|date=February 2019}} over a few days can occur.

The waxing and waning of the polar vortex is driven by the movement of mass and the transfer of heat in the polar region. In the autumn, the circumpolar winds increase in speed and the polar vortex rises into the stratosphere. The result is that the polar air forms a coherent rotating air mass: the polar vortex. As winter approaches, the vortex core cools, the winds decrease, and the vortex energy declines. Once late winter and early spring approach the vortex is at its weakest. As a result, during late winter, large fragments of the vortex air can be diverted into lower latitudes by stronger weather systems intruding from those latitudes. In the lowest level of the stratosphere, strong potential vorticity gradients remain, and the majority of that air remains confined within the polar air mass into December in the Southern Hemisphere and April in the Northern Hemisphere, well after the breakup of the vortex in the mid-stratosphere.{{cite journal |last1=Nash |first1=E |last2=Newman |first2=P |last3=Rosenfield |first3=J |last4=Schoeberl |first4=M |year=2012 |title=An objective determination of the polar vortex using Ertel's potential vorticity |journal=Journal of Geophysical Research |volume=101 |issue=D5 |pages=9471–9478 |doi=10.1029/96JD00066 |bibcode = 1996JGR...101.9471N |url=https://zenodo.org/record/1231378 }}

The breakup of the northern polar vortex occurs between mid March to mid May. This event signifies the transition from winter to spring, and has impacts on the hydrological cycle, growing seasons of vegetation, and overall ecosystem productivity. The timing of the transition also influences changes in sea ice, ozone, air temperature, and cloudiness. Early and late polar breakup episodes have occurred, due to variations in the stratospheric flow structure and upward spreading of planetary waves from the troposphere.{{clarify|date=April 2016}} As a result of increased waves into the vortex, the vortex experiences more rapid warming than normal, resulting in an earlier breakup and spring. When the breakup comes early, it is characterized by{{Clarify|reason = by what?|date=November 2018}} with persistent of remnants of the vortex. When the breakup is late, the remnants dissipate rapidly. When the breakup is early, there is one warming period from late February to middle March. When the breakup is late, there are two warming periods, one January, and one in March. Zonal mean temperature, wind, and geopotential height exert varying deviations from their normal values before and after early breakups, while the deviations remain constant before and after late breakups. Scientists are connecting a delay in the Arctic vortex breakup with a reduction of planetary wave activities, few stratospheric sudden warming events, and depletion of ozone.{{cite journal |last1=Li |first1=L |last2=Li |first2=C |last3=Pan |first3=Y |date=2012 |title=On the differences and climate impacts of early and late stratospheric polar vortex breakup |journal=Advances in Atmospheric Sciences |volume=29 |issue=5 |pages=1119–1128 |doi=10.1007/s00376-012-1012-4|bibcode = 2012AdAtS..29.1119L |s2cid=123846176 }}{{cite journal |last1=Wei |first1=K |last2=Chen |first2=W |last3=Huang |first3=R |date=2007 |title=Dynamical diagnosis of the breakup of the stratospheric polar vortex in the northern hemisphere| journal=Science in China Series D: Earth Sciences |volume=50 |issue=9 |pages=1369–1379 |doi=10.1007/s11430-007-0100-2 |bibcode=2007ScChD..50.1369W |s2cid=195309667 }}{{clarify|date=April 2016}}

File:Polarvortexjan211985.jpg, Maine, and New Brunswick, part of the northern polar vortex weakening, on the record-setting cold morning of January 21, 1985]]

Sudden stratospheric warming events are associated with weaker polar vortices. This warming of stratospheric air can reverse the circulation in the Arctic Polar Vortex from counter-clockwise to clockwise.{{cite journal |last1=Reichler| first=Tom| last2=Kim| first2=J |last3=Manzini |first3=E |last4=Kroger |first4=J|year=2012 |title=A stratospheric connection to Atlantic climate variability |journal=Nature Geoscience |volume=5 | issue=11|pages=783–787 |doi= 10.1038/ngeo1586|bibcode = 2012NatGe...5..783R }} These changes aloft force changes in the troposphere below.{{cite journal |last=Ripesi |first=Patrizio |year=2012 |title=The February 2010 Artcic Oscillation Index and its stratospheric connection|journal=Quarterly Journal of the Royal Meteorological Society|volume=138|issue=669 |pages=1961–1969|url=http://clima.meteoam.it/Articoli/Art14.pdf |doi=10.1002/qj.1935|bibcode = 2012QJRMS.138.1961R |s2cid=122729063 |display-authors=etal}} An example of an effect on the troposphere is the change in speed of the Atlantic Ocean circulation pattern. A soft spot just south of Greenland is where the initial step of downwelling occurs, nicknamed the "Achilles Heel of the North Atlantic". Small amounts of heating or cooling traveling from the polar vortex can trigger or delay downwelling, altering the Gulf Stream Current of the Atlantic, and the speed of other ocean currents. Since all other oceans depend on the Atlantic Ocean's movement of heat energy, climates across the planet can be dramatically affected. The weakening or strengthening of the polar vortex can alter the sea circulation more than a mile beneath the waves.{{cite journal |last1=Reichler |first1=Tom |last2=Kim |first2=J |last3=Manzini |first3=E |last4=Kroger |first4=J |year=2012 |title=A stratospheric connection to Atlantic climate variability |journal=Nature Geoscience |volume=5 |issue=11 |pages=783–787 |doi=10.1038/ngeo1586 |bibcode = 2012NatGe...5..783R }} Strengthening storm systems within the troposphere that cool the poles, intensify the polar vortex. La Niña–related climate anomalies significantly strengthen the polar vortex.{{cite journal |last1=Limpasuvan |first1=Varavut |last2=Hartmann |first2=Dennis L. |last3=Thompson |first3=David W.J. |last4=Jeev |first4=Kumar |last5=Yung |first5=Yuk L. |year=2005 |title=Stratosphere-troposphere evolution during polar vortex intensification |journal=Journal of Geophysical Research |volume=110 |issue=D24 |page=27 |doi=10.1029/2005JD006302 |url=http://yly-mac.gps.caltech.edu/ReprintsYLY/n173limpasuvan_2005.pdf |bibcode=2005JGRD..11024101L |citeseerx=10.1.1.526.9159 |access-date=2014-01-06 |archive-date=2017-08-12 |archive-url=https://web.archive.org/web/20170812193924/http://yly-mac.gps.caltech.edu/ReprintsYLY/n173limpasuvan_2005.pdf |url-status=dead }} Intensification of the polar vortex produces changes in relative humidity as downward intrusions of dry, stratospheric air enter the vortex core. With a strengthening of the vortex comes a longwave cooling due to a decrease in water vapor concentration near the vortex. The decreased water content is a result of a lower tropopause within the vortex, which places dry stratospheric air above moist tropospheric air.{{cite journal |last1=Cavallo |first1=S |last2=Hakim |first2=G.J. |year=2013 |title=Physical mechanisms of tropopause polar vortex intensity change |journal=Journal of the Atmospheric Sciences |volume=70 |issue=11 |pages=3359–3373 |doi=10.1175/JAS-D-13-088.1 |bibcode=2013JAtS...70.3359C |doi-access=free }} Instability is caused when the vortex tube, the line of concentrated vorticity, is displaced. When this occurs, the vortex rings become more unstable and prone to shifting by planetary waves. The planetary wave activity in both hemispheres varies year-to-year, producing a corresponding response in the strength and temperature of the polar vortex.{{cite journal |last1=Hartmann |first1=D |last2=Schoeberl |first2=M |year=1991 |title=The dynamics of the stratospheric polar vortex and its relation to springtime ozone depletions |journal=Science |volume=251 |issue=4989 |pages=46–52 | doi = 10.1126/science.251.4989.46 |pmid=17778602|bibcode = 1991Sci...251...46S |s2cid=24664477 |url=http://pdfs.semanticscholar.org/b06e/6b492b632e72ea08f30a681500e8859bb4c7.pdf |archive-url=https://web.archive.org/web/20190302053349/http://pdfs.semanticscholar.org/b06e/6b492b632e72ea08f30a681500e8859bb4c7.pdf |url-status=dead |archive-date=2019-03-02 }} The number of waves around the perimeter of the vortex are related to the core size; as the vortex core decreases, the number of waves increase.{{cite journal |last1=Widnall |first1=S |last2=Sullivan |first2=J |year=1973 |title=On the stability of vortex rings |journal=Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences |volume=332 |issue=1590 |pages=335–353 |doi=10.1098/rspa.1973.0029 |bibcode = 1973RSPSA.332..335W |s2cid=119959924 }}

The degree of the mixing of polar and mid-latitude air depends on the evolution and position of the polar night jet. In general, the mixing is less inside the vortex than outside. Mixing occurs with unstable planetary waves that are characteristic of the middle and upper stratosphere in winter. Prior to vortex breakdown, there is little transport of air out of the Arctic Polar Vortex due to strong barriers above 420 km (261 miles). The polar night jet which exists below this, is weak in the early winter. As a result, it does not deviate any descending polar air, which then mixes with air in the mid-latitudes. In the late winter, air parcels do not descend as much, reducing mixing.{{cite journal |last1=Manney |first1=G |last2=Zurek |first2=R |last3=O'Neill |first3=A |last4=Swinbank |first4=R |year=1994 |title=On the motion of air through the stratospheric polar vortex |journal=Journal of the Atmospheric Sciences |doi=10.1175/1520-0469(1994)051<2973:otmoat>2.0.co;2 |volume = 51 |issue =20 | pages= 2973–2994 |bibcode = 1994JAtS...51.2973M |doi-access=free }} After the vortex is broken up, the ex-vortex air is dispersed into the middle latitudes within a month.

Sometimes, a mass of the polar vortex breaks off before the end of the final warming period. If large enough, the piece can move into Canada and the Midwestern, Central, Southern, and Northeastern United States. This diversion of the polar vortex can occur due to the displacement of the polar jet stream; for example, the significant northwestward direction of the polar jet stream in the western part of the United States during the winters of 2013–2014, and 2014–2015. This caused warm, dry conditions in the west, and cold, snowy conditions in the north-central and northeast.{{cite web|url=http://climatenexus.org/learn/planetary-systems/warm-west-cool-east-us-temperature-divide |title=The Warm West, Cool East U.S. Temperature Divide | Climate Nexus |access-date=2015-11-26 |url-status=dead |archive-url=https://web.archive.org/web/20151207233627/http://climatenexus.org/learn/planetary-systems/warm-west-cool-east-us-temperature-divide |archive-date=2015-12-07 }} Occasionally, the high-pressure air mass, called the Greenland Block, can cause the polar vortex to divert to the south, rather than follow its normal path over the North Atlantic.{{cite web| last=Erdman |first=Jon |date=2014 |title=What's a Polar Vortex?: The Science Behind Arctic Outbreaks |website=wunderground |url=http://www.wunderground.com/news/polar-vortex-plunge-science-behind-arctic-cold-outbreaks-20140106 |

access-date= 25 February 2014}}

Extreme weather

A study in 2001 found that stratospheric circulation can have anomalous effects on weather regimes. In the same year, researchers found a statistical correlation between weak polar vortex and outbreaks of severe cold in the Northern Hemisphere.{{cite web|title=Stratospheric Polar Vortex Influences Winter Cold|author=NASA|url=http://earthobservatory.nasa.gov/Newsroom/view.php?id=22082|archive-url=https://web.archive.org/web/20100316223817/http://earthobservatory.nasa.gov/Newsroom/view.php?id=22082|url-status=dead|archive-date=March 16, 2010|access-date=January 7, 2014|publisher=Earth Observatory|date=December 21, 2001}} In later years, scientists identified interactions with Arctic sea ice decline, reduced snow cover, evapotranspiration patterns, NAO anomalies or weather anomalies which are linked to the polar vortex and jet stream configuration.{{cite journal |doi=10.1126/science.1063315 |title=Stratospheric Harbingers of Anomalous Weather Regimes |year=2001 |last1=Baldwin |first1=M.P. |journal=Science |volume=294 |issue=5542 |pages=581–584 |pmid=11641495 |last2=Dunkerton |first2=TJ|bibcode = 2001Sci...294..581B |s2cid=34595603 }}{{cite journal |doi=10.1175/1520-0469(2004)061<1711:DMFSIO>2.0.CO;2 |year=2004 |volume=61 |pages=1711–1725 |title=Dynamical Mechanisms for Stratospheric Influences on the Troposphere |last1=Song |first1=Yucheng |last2=Robinson |first2=Walter A. |journal=Journal of the Atmospheric Sciences |issue=14|bibcode = 2004JAtS...61.1711S |doi-access=free }}

=Climate change=

{{excerpt|Jet stream#Longer-term climatic changes|paragraphs=1-8|file=yes}}

Ozone depletion

File:Srnhemozoneconcentration.gif

The chemistry of the Antarctic polar vortex has created severe ozone depletion, although the effect has been weakening since the 2000s. It is expected to return to 1980 levels in about 2075. {{cite web |url=https://svs.gsfc.nasa.gov/30602 |title=The Antarctic Ozone Hole Will Recover|date=June 4, 2015|publisher=NASA |access-date=2017-08-05 }} The nitric acid in polar stratospheric clouds reacts with chlorofluorocarbons to form chlorine, which catalyzes the photochemical destruction of ozone.{{cite book|pages=42–44|title=The Arctic and environmental change|author=J.A. Pyle|date=1997|publisher=CRC Press|isbn=978-90-5699-020-6|url=https://books.google.com/books?id=CSH2CU3eqNUC&pg=PA41}} Chlorine concentrations build up during the polar winter, and the consequent ozone destruction is greatest when the sunlight returns in spring.{{cite book|url=https://books.google.com/books?id=hXH-LO4iTZAC&pg=PA49|page=47|year=2010|title=Tracer-tracer Relations as a Tool for Research on Polar Ozone Loss|author=Rolf Müller|publisher=Forschungszentrum Jülich|isbn=978-3-89336-614-9}} These clouds can only form at temperatures below about {{Convert|-80|C|F}}.

Since there is greater air exchange between the Arctic and the mid-latitudes, ozone depletion at the north pole is much less severe than at the south.{{cite book|url=https://books.google.com/books?id=B93SSQrcAh4C&pg=PA34|page=34|title=Stratosphere troposphere interactions: an introduction|author=K. Mohanakuma|isbn=978-1-4020-8216-0|publisher=Springer|year=2008}} Accordingly, the seasonal reduction of ozone levels over the Arctic is usually characterized as an "ozone dent", whereas the more severe ozone depletion over the Antarctic is considered an "ozone hole". That said, chemical ozone destruction in the 2011 Arctic polar vortex attained, for the first time, a level clearly identifiable as an Arctic "ozone hole".{{cite news|title=Arctic ozone loss at record level|url=https://www.bbc.co.uk/news/science-environment-15105747|publisher=BBC News Online|access-date=October 3, 2011|archive-url=https://web.archive.org/web/20111003182807/http://www.bbc.co.uk/news/science-environment-15105747|archive-date=October 3, 2011|url-status=live|date=October 2, 2011}}

Outside Earth

File:Mars cyclone.jpg view of the colossal polar cloud on Mars]]

Other astronomical bodies are also known to have polar vortices, including Venus (double vortex – that is, two polar vortices at a pole),{{Cite news|url=http://www.esa.int/Our_Activities/Space_Science/Venus_Express/Double_vortex_at_Venus_South_Pole_unveiled|title=Double vortex at Venus South Pole unveiled!|work=European Space Agency|access-date=2018-09-11|language=en-GB}} Mars, Jupiter, Saturn, and Saturn's moon Titan.

Saturn's south pole is the only known hot polar vortex in the Solar System.{{cite web|url = http://www.nasa.gov/vision/universe/solarsystem/saturn-020305.html|title = Saturn's Bull's-Eye Marks Its Hot Spot|year = 2005|publisher = NASA|access-date = January 8, 2014|archive-date = November 25, 2013|archive-url = https://web.archive.org/web/20131125121735/http://www.nasa.gov/vision/universe/solarsystem/saturn-020305.html|url-status = dead}}

References

{{Reflist|30em|refs=

{{cite journal |last1=Waugh |first1=D |last2=Plumb |first2=R |last3=Elkins |first3=J |last4=Fahey |first4=D

| title=Mixing of polar vortex air into middle latitudes as revealed by tracer-tracer scatterplots

| journal=Journal of Geophysical Research: Atmospheres |volume=102 |issue=D11 |pages=13119–13134

| doi=10.1029/96JD03715 |bibcode = 1997JGR...10213119W |doi-access=free }}

{{cite journal | title=Potential Vorticity Diagnosis of a Tropopause Polar Cyclone

| author1=Cavallo, Steven M. | author2= Hakim, Gregory J. |date=April 2009|journal=Monthly Weather Review

| volume=137|pages= 1358–1371|issue=4|doi=10.1175/2008MWR2670.1|bibcode = 2009MWRv..137.1358C | s2cid=16226331 |doi-access=free}}

}}

External links

{{cite web |title=Current map of arctic winds and temperatures at the 10 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=00.000,90.000/loc=00.000,90.000}}
{{cite web |title=Current map of arctic winds and temperatures at the 70 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/70hPa/overlay=temp/orthographic=00.000,90.000/loc=00.000,90.000}}
{{cite web |title=Current map of arctic winds and temperatures at the 250 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/250hPa/overlay=temp/orthographic=00.000,90.000/loc=00.000,90.000}}
{{cite web |title=Current map of arctic winds and temperatures at the 500 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/500hPa/overlay=temp/orthographic=00.000,90.000/loc=00.000,90.000}}
{{cite web |title=Current map of antarctic winds and temperatures at the 10 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=180.000,-89.999/loc=180.000,-89.999}}
{{cite web |title=Current map of antarctic winds and temperatures at the 70 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/70hPa/overlay=temp/orthographic=180.000,-89.999/loc=180.000,-89.999}}
{{cite web |title=Current map of antarctic winds and temperatures at the 250 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/250hPa/overlay=temp/orthographic=180.000,-89.999/loc=180.000,-89.999}}
{{cite web |title=Current map of antarctic winds and temperatures at the 500 hPa level|url=https://earth.nullschool.net/#current/wind/isobaric/500hPa/overlay=temp/orthographic=180.000,-89.999/loc=180.000,-89.999}}

Category:Atmospheric dynamics

Category:Regional climate effects

Category:Polar regions of the Earth

Category:Vortices