Kunnen we nu stellen dat de langdurige effecten van die sterke SSW in februari 2018, waaronder de langdurige blokkades in 2018 en 2019, zo langzamerhand uitgewerkt beginnen te raken? Doordat de huidige westcirculatie wellicht de afwijkingen van de zeewatertemperatueren op het Noordelijk Halfrond terugzet naar normale waardes en t.g.v. de strakke polaire vortex kou in het noordpolgebied gevangen blijft en er daardoor meer ijs kan vormen?Vincent schreef: ↑15-02-2020 18:34En dan te bedenken dat we vorig jaar wél een SSW hadden, maar dat deze ons desondanks op wintergebied helemaal, maar dan ook echt hélemaal niets opleverde! 10 zachte winters op rij lijkt nu ineens een akelig realistisch scenario te zijn dus...In principe zijn de kansen op een SSW volgende winter groter, maar deze winter legt wel een zware hypotheek op de kansen. Het patroon van de huidige winter is dramatisch.
Stratosfeer winter 2019/2020
Re: Stratosfeer winter 2019/2020
Re: Stratosfeer winter 2019/2020
Hier de dagelijkse AO index van deze winter. Het drama begon in de tweede helft van december met de doorsteek van de polar vortex naar Nova Zembla. Hoeft niet altijd dramatisch te zijn: zie bijvoorbeeld de winter van 1962-1963. Het valt deze winter eind december helemaal naar het andere uiterste.
![Afbeelding](https://i.imgur.com/ln09tn8.png)
![Afbeelding](https://i.imgur.com/BcchZfR.png)
![Afbeelding](https://i.imgur.com/vYMRjeJ.png)
![Afbeelding](https://i.imgur.com/ln09tn8.png)
![Afbeelding](https://i.imgur.com/BcchZfR.png)
![Afbeelding](https://i.imgur.com/vYMRjeJ.png)
Re: Stratosfeer winter 2019/2020
Die effecten waren al in de loop van 2018 helemaal uitgewerkt. In januari 2019 hadden we vervolgens wel nog een nieuwe SSW, die ons echter nauwelijks wat opleverde, zeker in vergelijking met één jaar eerder.
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- Berichten: 12295
- Lid geworden op: 31-12-1977
Re: Stratosfeer winter 2019/2020
https://rmets.onlinelibrary.wiley.com/d ... 9065bece99
Analyse SSW winter 2019.
Connection to the troposphere
The dynamic connection between the stratosphere and troposphere can be readily shown by a vertical cross‐section of a time series of polar cap geopotential height anomalies. These are often referred to as ‘dripping paint’ plots as they show the downward propagation of stratospheric anomalies over time. The evolution in 2018–2019 is shown in Figure 8. Prior to the SSW, there is little indication of coupling between the troposphere and stratosphere, although from September to November, there are anomalously high geopotential heights in the troposphere. This indicates a tendency towards blocked and amplified mid‐latitude flow, which may have helped drive the high wave activity during autumn 2018. Following the SSW, the associated anomalies did not propagate downwards below ~200hPa into the troposphere until a brief, weak spell in early February, indicating the SSW did not couple persistently to surface weather patterns. However, it should also be noted that anomalously low geopotential heights were also absent from the Arctic troposphere during this time. Afterwards, the strong vortex event coupled strongly to the troposphere during March, and the final warming in late April also produced a very strong response at the surface that persisted through May (even though the middle‐stratospheric anomalies were not as strong as during the SSW, suggesting the importance of lower‐stratospheric anomalies in stratosphere–troposphere coupling).
Analyse SSW winter 2019.
Connection to the troposphere
The dynamic connection between the stratosphere and troposphere can be readily shown by a vertical cross‐section of a time series of polar cap geopotential height anomalies. These are often referred to as ‘dripping paint’ plots as they show the downward propagation of stratospheric anomalies over time. The evolution in 2018–2019 is shown in Figure 8. Prior to the SSW, there is little indication of coupling between the troposphere and stratosphere, although from September to November, there are anomalously high geopotential heights in the troposphere. This indicates a tendency towards blocked and amplified mid‐latitude flow, which may have helped drive the high wave activity during autumn 2018. Following the SSW, the associated anomalies did not propagate downwards below ~200hPa into the troposphere until a brief, weak spell in early February, indicating the SSW did not couple persistently to surface weather patterns. However, it should also be noted that anomalously low geopotential heights were also absent from the Arctic troposphere during this time. Afterwards, the strong vortex event coupled strongly to the troposphere during March, and the final warming in late April also produced a very strong response at the surface that persisted through May (even though the middle‐stratospheric anomalies were not as strong as during the SSW, suggesting the importance of lower‐stratospheric anomalies in stratosphere–troposphere coupling).
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
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- Berichten: 12295
- Lid geworden op: 31-12-1977
Re: Stratosfeer winter 2019/2020
Vervolg.
The response of the troposphere to SPV variability is traditionally discerned in terms of the behaviour of the hemispheric AO pattern and the more regionalised NAO pattern. The sign of these, on average, is negative following major SSWs and positive following strong SPV events. For example, following the February 2018 SSW, a strong and persistent negative AO/NAO pattern developed, indicating anomalously weak tropospheric westerlies. For deep and persistent cold in Europe, a negative NAO is usually required. The evolution of the two indices in 2018–2019 is shown in Figure 9. Neither index transitioned into a strongly negative state following the SSW. However, during January 2019, the AO was persistently more negative than the NAO. This indicates that, whilst anomalously high pressure developed over higher latitudes, this did not project onto the NAO pattern. The opposite followed during February into early March, when the strongly positive AO was not reflected in a strongly positive NAO; however, it is unlikely that, during this time, the AO was responding to the strong vortex at 10hPa as lower stratospheric winds remained weak (cf. positive height anomalies during this time in Figure 8), possibly indicating other tropospheric drivers. During both periods, the NAO remained persistently neutral or weakly positive. Indeed, the distribution of the daily NAO index during February was unusual in the historical record; no other February since 1950 exhibited the combination of both a weakly positive mean state and weak variance about the monthly mean. Following mid‐March, the AO and NAO began to be more in‐phase as the strong vortex event propagated downwards and evolved similarly through April into May. A negative NAO/AO pattern then developed following the final warming. The NAO was more negative following the final warming than following the SSW or at any other point in the extended winter period (the mean NAO index for May 2019 was −2.62σ, the lowest for the month of May in the CPC record stretching back to 1950), giving an unusual example of late‐season stratosphere–troposphere coupling. May 2019 was also the first month for the United Kingdom with a mean temperature below the 1981–2010 average since September 2018 and had the largest negative anomaly of any month since March 2018 (Met Office, 2019) (during which the ‘Beast from the East’ coldwave occurred)
The response of the troposphere to SPV variability is traditionally discerned in terms of the behaviour of the hemispheric AO pattern and the more regionalised NAO pattern. The sign of these, on average, is negative following major SSWs and positive following strong SPV events. For example, following the February 2018 SSW, a strong and persistent negative AO/NAO pattern developed, indicating anomalously weak tropospheric westerlies. For deep and persistent cold in Europe, a negative NAO is usually required. The evolution of the two indices in 2018–2019 is shown in Figure 9. Neither index transitioned into a strongly negative state following the SSW. However, during January 2019, the AO was persistently more negative than the NAO. This indicates that, whilst anomalously high pressure developed over higher latitudes, this did not project onto the NAO pattern. The opposite followed during February into early March, when the strongly positive AO was not reflected in a strongly positive NAO; however, it is unlikely that, during this time, the AO was responding to the strong vortex at 10hPa as lower stratospheric winds remained weak (cf. positive height anomalies during this time in Figure 8), possibly indicating other tropospheric drivers. During both periods, the NAO remained persistently neutral or weakly positive. Indeed, the distribution of the daily NAO index during February was unusual in the historical record; no other February since 1950 exhibited the combination of both a weakly positive mean state and weak variance about the monthly mean. Following mid‐March, the AO and NAO began to be more in‐phase as the strong vortex event propagated downwards and evolved similarly through April into May. A negative NAO/AO pattern then developed following the final warming. The NAO was more negative following the final warming than following the SSW or at any other point in the extended winter period (the mean NAO index for May 2019 was −2.62σ, the lowest for the month of May in the CPC record stretching back to 1950), giving an unusual example of late‐season stratosphere–troposphere coupling. May 2019 was also the first month for the United Kingdom with a mean temperature below the 1981–2010 average since September 2018 and had the largest negative anomaly of any month since March 2018 (Met Office, 2019) (during which the ‘Beast from the East’ coldwave occurred)
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
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- Berichten: 12295
- Lid geworden op: 31-12-1977
Re: Stratosfeer winter 2019/2020
Interessante studie over blokkades in de toekomst.
https://link.springer.com/article/10.10 ... 018-0108-z
Conclusie. Interne variabiliteit blijft waarschijnlijk de komende decennia de overhand houden. Daarna een afname?
https://link.springer.com/article/10.10 ... 018-0108-z
Conclusie. Interne variabiliteit blijft waarschijnlijk de komende decennia de overhand houden. Daarna een afname?
Re: Stratosfeer winter 2019/2020
Was ook mijn indruk: Quote uit de intro van dit topic. Pas na de Final Warming, de opwarming van de stratosfeer door de toenemende zonnekracht, werd de stroming in de troposfeer weer geblokkeerd. Een residu van de SSW in de troposfeer heeft hierbij waarschijnlijk mede bijgedragen aan de blokkades van mei tot juli, die het zomerweer van 2019 zoveel kleur hebben gegeven.Sebastiaan schreef: ↑18-02-2020 19:25https://rmets.onlinelibrary.wiley.com/d ... 9065bece99
Analyse SSW winter 2019.
Connection to the troposphere
The dynamic connection between the stratosphere and troposphere can be readily shown by a vertical cross‐section of a time series of polar cap geopotential height anomalies. These are often referred to as ‘dripping paint’ plots as they show the downward propagation of stratospheric anomalies over time. The evolution in 2018–2019 is shown in Figure 8. Prior to the SSW, there is little indication of coupling between the troposphere and stratosphere, although from September to November, there are anomalously high geopotential heights in the troposphere. This indicates a tendency towards blocked and amplified mid‐latitude flow, which may have helped drive the high wave activity during autumn 2018. Following the SSW, the associated anomalies did not propagate downwards below ~200hPa into the troposphere until a brief, weak spell in early February, indicating the SSW did not couple persistently to surface weather patterns. However, it should also be noted that anomalously low geopotential heights were also absent from the Arctic troposphere during this time. Afterwards, the strong vortex event coupled strongly to the troposphere during March, and the final warming in late April also produced a very strong response at the surface that persisted through May (even though the middle‐stratospheric anomalies were not as strong as during the SSW, suggesting the importance of lower‐stratospheric anomalies in stratosphere–troposphere coupling).
Uitstekende beschrijving verder, alleen krijg ik geen antwoord waarom precies de koppeling zo zwak was in januari. Wel zoekt hij naar antwoorden als hij de NAO bij zijn uitleg betrekt. Er is een studie die het verband legt met de positionering van het hoog bij Ierland, de eerste twee weken vanaf de start van de SSW. We hebben de verontrustende uitkomsten van dat onderzoek destijds besproken in de eerdere editie van dit topic. De positieve NAO in januari heeft achteraf gezien de koppeling genekt. Ook de hieraan verbonden connectie met ongelukkige positionering van het restant van de polar vortex is een issue.
De zwakke respons van de troposfeer in februari tot april kan gelinkt worden aan de versterkte SPV na de SSW, die pas verdween bij de Final Warming.
Re: Stratosfeer winter 2019/2020
@Karel Dank je voor je grafiek. Historische hoge AO.
Rondje kansloosheid voor wat betreft verstoring van de SPV.
Bijna geen verstoringen.
Geen enkel teken van verandering.
Idem. De neergaande tak van de SPV helpt richting verkoeling, later in de week.
Rondje kansloosheid voor wat betreft verstoring van de SPV.
Bijna geen verstoringen.
Geen enkel teken van verandering.
Idem. De neergaande tak van de SPV helpt richting verkoeling, later in de week.
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
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- Berichten: 12295
- Lid geworden op: 31-12-1977
Re: Stratosfeer winter 2019/2020
Strat. Polar Vortex draait op volle toeren.
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
Re: Stratosfeer winter 2019/2020
Dit wordt een heel late final warming.
Lange continuering van het huidige weer, lijkt me.
Heel interessant is een bijdrage over de sprinkhanenplaag op CNN vanavond. Dit werd toegeschreven aan de positieve fase van de IOD de laatste jaren. Ik heb dit nog eens nagezocht, inderdaad hadden we vorige winter ook te lijden onder dit fenomeen.
Ook een aantal cyclonen in de regio Oost-Afrika en Arabisch Schiereiland zijn hierop terug te voeren. Veel neerslag en aanwas van vegetatie en daarna groei van de populatie van de sprinkhanen, in vijfmaandelijkse cycli als ik het goed begrepen heb. Tegelijk droogte in Australië.
In ieder geval is dit ook een verheldering over het waarom van de zwakke uitwerking van de SSW van vorige winter. Het patroon in de Indische Oceaan moet echt anders, volgend jaar, anders wordt het weer niks met het winterweer.
Lange continuering van het huidige weer, lijkt me.
Heel interessant is een bijdrage over de sprinkhanenplaag op CNN vanavond. Dit werd toegeschreven aan de positieve fase van de IOD de laatste jaren. Ik heb dit nog eens nagezocht, inderdaad hadden we vorige winter ook te lijden onder dit fenomeen.
Ook een aantal cyclonen in de regio Oost-Afrika en Arabisch Schiereiland zijn hierop terug te voeren. Veel neerslag en aanwas van vegetatie en daarna groei van de populatie van de sprinkhanen, in vijfmaandelijkse cycli als ik het goed begrepen heb. Tegelijk droogte in Australië.
In ieder geval is dit ook een verheldering over het waarom van de zwakke uitwerking van de SSW van vorige winter. Het patroon in de Indische Oceaan moet echt anders, volgend jaar, anders wordt het weer niks met het winterweer.
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.