Stratosfeer winter 2020/2021
Re: Stratosfeer winter 2020/2021
Meer stratosfeerinvloed bij een SSW als er meer frictie is in de troposfeer.
https://wcd.copernicus.org/articles/2/111/2021/
A pronounced signature of stratosphere–troposphere coupling is a robust negative anomaly in the surface northern annular mode (NAM) following sudden stratospheric warming (SSW) events, consistent with an equatorward shift in the tropospheric jet. It has previously been pointed out that tropospheric synoptic-scale eddy feedbacks, mainly induced by anomalies in the lowermost extratropical stratosphere, play an important role in creating this surface NAM signal. Here, we use the basic set-up of idealised baroclinic life cycles to investigate the influence of stratospheric conditions on the behaviour of tropospheric synoptic-scale eddies. Particular attention is given to the enhancement of the tropospheric eddy response by surface friction and the sensitivity to wind anomalies in the lower stratosphere. We find systems that include a tropospheric jet only (modelling post-SSW conditions) to be characterised by an equatorward shift in the tropospheric jet in the final state of the life cycle, relative to systems that include a representation of the polar vortex (mimicking more undisturbed stratospheric wintertime conditions), consistent with the observed NAM response after SSWs. The corresponding relative surface NAM signal is increased if the system includes surface friction, presumably due to a direct coupling of the eddy field at tropopause level to the surface winds. We further show that the jet shift signal observed in our experiments is mainly caused by changes in the zonal wind structure of the lowermost stratosphere, while changes in the wind structure of the middle and upper stratosphere have almost no influence.
https://wcd.copernicus.org/articles/2/111/2021/
A pronounced signature of stratosphere–troposphere coupling is a robust negative anomaly in the surface northern annular mode (NAM) following sudden stratospheric warming (SSW) events, consistent with an equatorward shift in the tropospheric jet. It has previously been pointed out that tropospheric synoptic-scale eddy feedbacks, mainly induced by anomalies in the lowermost extratropical stratosphere, play an important role in creating this surface NAM signal. Here, we use the basic set-up of idealised baroclinic life cycles to investigate the influence of stratospheric conditions on the behaviour of tropospheric synoptic-scale eddies. Particular attention is given to the enhancement of the tropospheric eddy response by surface friction and the sensitivity to wind anomalies in the lower stratosphere. We find systems that include a tropospheric jet only (modelling post-SSW conditions) to be characterised by an equatorward shift in the tropospheric jet in the final state of the life cycle, relative to systems that include a representation of the polar vortex (mimicking more undisturbed stratospheric wintertime conditions), consistent with the observed NAM response after SSWs. The corresponding relative surface NAM signal is increased if the system includes surface friction, presumably due to a direct coupling of the eddy field at tropopause level to the surface winds. We further show that the jet shift signal observed in our experiments is mainly caused by changes in the zonal wind structure of the lowermost stratosphere, while changes in the wind structure of the middle and upper stratosphere have almost no influence.
Re: Stratosfeer winter 2020/2021
Uitkomst van de winter: typisch SSW met warme Noordpool en koud Siberië.
https://www.aer.com/science-research/cl ... cillation/
https://www.aer.com/science-research/cl ... cillation/
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
-
- Berichten: 12294
- Lid geworden op: 31-12-1977
Re: Stratosfeer winter 2020/2021
Dat zijn flinke afwijkingen in het noorden van Siberië.
Re: Stratosfeer winter 2020/2021
Ja, de hele herfst al, later doorzettend in de winter. Tijdens de SSW zien we de opbouw van kou boven Siberië, later ook Noord-Amerika.
Het verhaal van Reinout dat je voor kou in West-Europa een koude Noordpool nodig hebt zie ik niet bevestigd. Weinig zee-ijs in later zomer en in de herfst bleken gunstig voor ontwikkeling van de SSW.
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
-
- Berichten: 12294
- Lid geworden op: 31-12-1977
Re: Stratosfeer winter 2020/2021
IJsbedekking Noordpool deed denken aan de winter van 2013.
Re: Stratosfeer winter 2020/2021
Speculatief, maar interessant om te volgen:
The plot of the Wave Activity Flux (WAFz and is proportional to poleward heat transport) forecast is showing currently normal to below normal WAFz especially in the stratosphere over the next week (Figure 12). However, starting next week, the WAFz is predicted to become much more active. It looks to me that this new pulse has the potential to result in a dynamic Final Warming (where the stratospheric PV disappears until the fall). A dynamic Final Warming can have a similar influence on the weather analogous to PV disruptions or weakenings (though usually on a smaller scale) that results in cooler weather across the mid-latitudes.
https://www.aer.com/science-research/cl ... cillation/
The plot of the Wave Activity Flux (WAFz and is proportional to poleward heat transport) forecast is showing currently normal to below normal WAFz especially in the stratosphere over the next week (Figure 12). However, starting next week, the WAFz is predicted to become much more active. It looks to me that this new pulse has the potential to result in a dynamic Final Warming (where the stratospheric PV disappears until the fall). A dynamic Final Warming can have a similar influence on the weather analogous to PV disruptions or weakenings (though usually on a smaller scale) that results in cooler weather across the mid-latitudes.
https://www.aer.com/science-research/cl ... cillation/
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
Re: Stratosfeer winter 2020/2021
Is de huidige aprilkoude t.g.v. een hardnekkig hogedrukgebied boven de Britse Eilanden nog een gevolg van de SSW van afgelopen januari?
Re: Stratosfeer winter 2020/2021
Mijn gevoel zegt van wel, vergelijkbaar met 2013 toen twee maanden later de echte kou kwam.
Omdat het effect van de SSW halverwege februari zo snel uit de atmosfeer verdween kun je nu een residu-reactie verwachten. Kijkende naar de anomalie van de GPH (geopententiale hoogte) van het noordelijke halfrond zie ik inderdaad een verband.
https://www.cpc.ncep.noaa.gov/products/ ... trat-trop/
Dit is hoe het uitwerkt de laatste twee weken:
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
Re: Stratosfeer winter 2020/2021
De anomaliën van de afgelopen jaren. Interessant, de verschillende reacties van de atmosfeer op de SSW (2018/2019) of niet-SSW (2020). Je ziet ook goed de invloed van de final warming. In 2018 was die invloed het kleinst.
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.
-
- Berichten: 12294
- Lid geworden op: 31-12-1977