Editing Sudden stratospheric warming (section)

== Classification and description ==
[[File:SuddenStratosphericWarming.png|thumb|This MERRA-2 Reanalysis Plot shows how Sudden Stratospheric Warming (SSW) can affect polar vortexes.]]
SSW events are categorized by a sudden and abrupt increase in stratospheric temperatures over a short period of time, usually within a few days. SSW events occur in the winter, when winds in the stratosphere are normally westerly. SSW events disrupt the normal westerly wind flow of the upper troposphere, and, depending on severity, can sometimes reverse it entirely. As a result, some of the warmed air can intrude into the troposphere, which often disrupts the Polar Vortex. SSW events usually affect polar areas only, although the strongest SSW events can come down to 60 degrees north.<ref name=":6" /> Almost all SSW events take place in the northern hemisphere, which normally sees one SSW every 2-3 years.<ref>{{Cite web |title=GMAO - Global Modeling and Assimilation Office Research Site |url=https://gmao.gsfc.nasa.gov/research/science_snapshots/2024/SSW_Jan2024/SSW_Jan2024.php |access-date=2025-04-11 |website=gmao.gsfc.nasa.gov |language=en}}</ref> There was one major SSW event in the southern hemisphere in 2002, but no other major SSW events have been detected in the southern hemisphere since then.

Because SSW of come in all magnitudes and sizes, leading meteorologists to classify SSW events in two main categories: major and minor, based on how much they change temperature patterns and disrupt the polar vortex circulation.<ref>{{Cite journal |last=Gogoi |first=Jinee |last2=Bhuyan |first2=Kalyan |last3=Sharma |first3=Som Kumar |last4=Kalita |first4=Bitap Raj |last5=Vaishnav |first5=Rajesh |date=2023-04-15 |title=A comprehensive investigation of Sudden Stratospheric Warming (SSW) events and upper atmospheric signatures associated with them |url=https://linkinghub.elsevier.com/retrieve/pii/S027311772201095X |journal=Advances in Space Research |volume=71 |issue=8 |pages=3357–3372 |doi=10.1016/j.asr.2022.12.003 |issn=0273-1177}}</ref> Sometimes, if an SSW event permanently reverses stratospheric winds to the east, which is the typical stratospheric wind flow for the summer, it is called a final warming.<ref name="Compendium">{{cite journal |last1=Butler |first1=Amy H. |last2=Sjoberg |first2=Jeremiah P. |last3=Seidel |first3=Dian J. |last4=Rosenlof |first4=Karen H. |date=9 February 2017 |title=A sudden stratospheric warming compendium |journal=Earth System Science Data |volume=9 |issue=1 |pages=63–76 |bibcode=2017ESSD....9...63B |doi=10.5194/essd-9-63-2017 |doi-access=free}}</ref>

=== Major ===
A major SSW event is the strongest type of SSW event. These events are usually strong enough to entirely reverse the westerly flow that is common in the stratosphere during winter. These events influence temperatures as far south as 60 degrees north and are usually strong enough to completely disrupt the [[polar vortex]], often splitting it into smaller vortices or displacing it entirely from its normal location.<ref name="McInturff">{{cite report |url=https://ntrs.nasa.gov/api/citations/19780010687/downloads/19780010687.pdf |title=Stratospheric warmings: Synoptic, dynamic and general-circulation aspects |date=1978 |publisher=NASA Scientific and Technical Information Office |issue=1017, ''NASA Reference Publication'' |access-date=3 July 2024 |editor-first=Raymond M. |editor-last=McInturff}}</ref> In order to qualify as a major SSW event, the event must completely reverse the westerly flow and come down to 60 degrees north.

=== Minor ===
A minor SSW event is the weaker type of SSW event. These events are usually not strong enough to entirely reverse the westerly flow that is common in the stratosphere during winter, but instead add a noticeable easterly component to the westerly flow. Minor SSW events are usually not strong enough to break down the polar vortex and affect temperatures as far south as 60 degrees N.<ref name="McInturff" />

=== Final ===
A final SSW event is any SSW event that permanently reverses the stratospheric wind flow from westerly to easterly for the summer. Normally, stratospheric winds are westerly in the winter and easterly in the summer, so any late-winter SSW event that permanently causes this is called a final warming. Final warmings are usually major SSW events.<ref name=":1">{{cite journal |last1=Hio |first1=Yasuko |last2=Yoden |first2=Shigeo |date=1 March 2005 |title=Interannual Variations of the Seasonal March in the Southern Hemisphere Stratosphere for 1979–2002 and Characterization of the Unprecedented Year 2002 |journal=Journal of the Atmospheric Sciences |volume=62 |issue=3 |pages=567–580 |bibcode=2005JAtS...62..567H |doi=10.1175/JAS-3333.1 |doi-access=free}}</ref><ref>{{cite journal |last1=Shiotani |first1=Masato |last2=Shimoda |first2=Naoki |last3=Hirota |first3=Isamu |title=Interannual variability of the stratospheric circulation in the southern hemisphere |journal=Quarterly Journal of the Royal Meteorological Society |date=April 1993 |volume=119 |issue=511 |pages=531–546 |doi=10.1002/qj.49711951110|bibcode=1993QJRMS.119..531S }}</ref><ref name=":4">{{cite journal |last1=Byrne |first1=Nicholas J. |last2=Shepherd |first2=Theodore G. |title=Seasonal Persistence of Circulation Anomalies in the Southern Hemisphere Stratosphere and Its Implications for the Troposphere |journal=Journal of Climate |date=May 2018 |volume=31 |issue=9 |pages=3467–3483 |doi=10.1175/JCLI-D-17-0557.1|bibcode=2018JCli...31.3467B }}</ref>