User:Lacunae/32


 * https://www.esrl.noaa.gov/csd/groups/csd8/sswcompendium/majorevents.html

List of sudden stratospheric warmings '''The discovery of the sudden stratospheric warming is credited to Scherhag [1952], who noted a sudden increase in the radiosonde 10-mbar temperature over Berlin on January 30, 1952. However, the extent of the warming phenomena was unknown until the late 1950's, when a sudden stratospheric warming took place over the American radiosonde network in January 1957. This event allowed Teweles [1958], Craig and Heting [1959], and Lowenthal [1957] to make a partial synoptic analysis of the development of the sudden Warming. Another warming occurred in 1958 during the first IGY, so upper air data from the USSR could be used to complete a synoptic picture.'''

In the most extreme cases, the stratospheric polar vortex can reverse direction completely in an event called a major sudden stratospheric warming (SSW). SSWs in the NH occur roughly six times per decade (Charlton and Polvani, 2007). SSWs can also occur in the Southern Hemisphere (SH), as in a remarkable case in September 2002 (Kruger et al., 2005), but are rare due to smaller planetary wave amplitudes in the SH (van Loon et al., 1973).

Major SSWs occur when the winter polar stratospheric westerlies reverse to easterlies. In minor warmings, the polar temperature gradient reverses but the circulation does not, and in final warmings, the vortex breaks down and remains easterly until the following boreal autumn. No unambiguous standard definition for major, minor, and final warmings yet exists (Butler et al., 2015),

There are two main types of SSW: displacement events in which the stratospheric polar vortex is displaced from the pole and split events in which the vortex splits into two or more vortices. Some SSWs are a combination of both types.

Southern Hemisphere
10.1002/qj.3193 2002, 2019, https://twitter.com/LondonSnowWatch/status/1164957935782547456 only 2 events noted in 40 years of satellite era. SH SSW modelled as a 4% chance annually of occurring.https://twitter.com/clarenasir/status/1172394854824857601

Table
Media reports of a over a possible SSW event beginning in early 2014 and a NOAA climate.gov blog post in early January 2014 originally attributed the breakdown of the polar vortex to a Sudden stratospheric warming event, which did not actually develop. The 2013–14 North American cold wave could not be linked to sudden stratospheric warming as had been the case in other harsh recent winters in the northern hemisphere such as during 2009-10 (Winter of 2009–10 in Europe),

Other
http://vejr.tv2.dk/2018-02-22-specielt-atmosfaerisk-faenomen-sender-isnende-kulde-mod-danmark http://www.knmi.nl/over-het-knmi/nieuws/koude-week-door-verzwakte-poolwervel

Natural hazards in the UK
a Large Icelandic effusive eruption was ranked in the top three hazards to the UK putting it on a par with pandemic influenza and coastal flooding.

National Risk Register Influenza pandemic