What is a Sudden Stratospheric Warming (SSW)?

Posted: October 5, 2018 by tallbloke in solar system dynamics

The Met Office explains the compression-warming of the stratosphere and how it can bring cold snaps to the UK.

Official blog of the Met Office news team

You may have heard talk of the UK possibly seeing some colder weather next week and that ‘things going on’ in the upper atmosphere may be playing a part.

The ‘thing’ happening in the atmosphere is known as Sudden Stratospheric Warming (SSW). When it does happen, it attracts a lot of interest in the UK because it is sometimes linked to the onset of cold weather in winter.

Here we shed a little bit more light on the phenomenon.

What is an SSW?

The term SSW refers to what we observe – rapid warming (up to about 50 ­°C in just a couple of days) in the stratosphere, between 10 km and 50 km up.

You may have heard of the jet stream which helps to steer Atlantic weather systems towards the UK. Well there are other jet streams high up in our atmosphere in both the northern and southern…

View original post 420 more words

  1. oldbrew says:

    In the MetO video they say the stratosphere temperature can rise ‘as much as 50 degrees in a few days’ due to compression.
    – – –
    Downward Wave Reflection as a Mechanism for the Stratosphere–Troposphere Response to the 11-Yr Solar Cycle [2017]
    Hua Lu
    British Antarctic Survey

    The effects of solar activity on the stratospheric waveguides and downward reflection of planetary waves during NH early to midwinter are examined. Under high solar (HS) conditions, enhanced westerly winds in the subtropical upper stratosphere and the associated changes in the zonal wind curvature led to an altered waveguide geometry across the winter period in the upper stratosphere. In particular, the condition for barotropic instability was more frequently met at 1 hPa near the polar-night jet centered at about 55°N. In early winter, the corresponding change in wave forcing was characterized by a vertical dipole pattern of the Eliassen–Palm (E–P) flux divergent anomalies in the high-latitude upper stratosphere accompanied by poleward E–P flux anomalies. These wave forcing anomalies corresponded with negative vertical shear of zonal mean winds and the formation of a vertical reflecting surface. Enhanced downward E–P flux anomalies appeared below the negative shear zone; they coincided with more frequent occurrence of negative daily heat fluxes and were associated with eastward acceleration and downward group velocity. These downward-reflected wave anomalies had a detectable effect on the vertical structure of planetary waves during November–January. The associated changes in tropospheric geopotential height contributed to a more positive phase of the North Atlantic Oscillation in January and February. These results suggest that downward reflection may act as a “top down” pathway by which the effects of solar ultraviolet (UV) radiation in the upper stratosphere can be transmitted to the troposphere. [bold added]

    – – –
    See also: Variability in the stratosphere: The sun and the QBO

  2. JB says:

    Hopefully I have transcribed Adam’s explanation correctly @0:42 “At this point, the air starts to fall into the Arctic, and because it is all falling into the Arctic and getting squashed, it starts to warm, so there’s no heating going on as such, but you are compressing the air, or warming it. And the temperature can rise by as much as 50 degrees in just a few days.”

    He almost starts to make sense. I get the impression when he said “no heating going on as such” he is referring to direct heating by solar flux. Otherwise, his comments seem to fit into the morass of 2013 comments between nuwurld and Britton.

    The cited ametsoc paper is lengthy and takes quite a bit of digestion. But telling are the two plots, figures 12 &13. They are strongly reminiscent of Birkeland currents as documented in Anthony Peratt’s plasma laboratory work. Don Scott has done some work modeling the structure of a Birkeland current with its associative rotational effects, and it strikes me as directly relevant.

    Trying to characterize atmospheric behavior while neglecting the primary force driving it–the UV induced ionization and subsequent current flow within the earth’s magnetic field seems destined to failure.

  3. Ron Clutz says:

    Dr. Judah Cohen of AER sees SSWs as part of the Arctic weather system, and correlated to October snowfalls. His diagram:

    Synopsis of his theory:

    Cohen research article:

  4. ren says:

    The polar light are the best indicator of whether the stream currents will be strong or not. Of course, the tropospheric effect appears with a delay. When the solar wind decreases, the Earth’s magnetic field enters the game.

  5. ren says:

    Magnetic field in the Arctic regions
    Although almost 90% of the observed magnetic field can be approximated by a dipole, the 10% left over, called the non-dipole field cannot be ignored. In places it can be large relative to the dipole field, thus altering noticeably the shape of the observed field. This is especially true in the vicinity of the North Magnetic Pole, with important consequences. In order to appreciate how the non-dipole part of the magnetic field distorts the overall shape of the magnetic field it is important to understand what the dipole field looks like. The three diagrams illustrate the following points.

    The real magnetic field is quite different, as can be seen in the next set of three diagrams.


  6. ren says:

    “There is a strong relationship between polar vortex and polar jet stream.
    When the charge is low the effect of earth’s field on the vortex is weak, the vortex is strong with jet stream more regular mainly restricted to high latitudes.
    With high charge vortex is pulled away by the earth’s MF and eventually splits up into two with jet stream meandering to lower latitudes.”
    image: http://www.vukcevic.co.uk/NH.gif
    movie: https://eoimages.gsfc.nasa.gov/images/imagerecords/36000/36972/npole_gmao_200901-02.mov

  7. ren says:

    The polar vortex is divided into two parts in December 2017.

  8. ren says:

    In October, the polar vortex in the Northern Hemisphere is just being formed.

  9. ren says:

    Galactic radiation is approaching the 2009 level.

  10. ren says:

    ‘This is a 3D animation of the 2009 sudden stratospheric warming event (SSW), where the stratospheric polar vortex was split (classic wave2 split SSW) and almost completely disintegrated. at the bottom is the 150mb geopotential height, and above is the core of the polar vortex in 3D. The data is from ECMWF ERA-Interim reanalysis dataset.
    The animation was produced by our supporter and co-admin Andrej Flis ( https://twitter.com/Recretos )”

  11. oldbrew says:

    Looking at the ‘Complete Oulu data’ chart,1964-2018 (above – October 6, 2018 at 4:55 pm):

    The last three solar cycles started around the time of the peaks, and the next one is due shortly as another peak shows up. IOW lower solar output = higher cosmic rays, as expected.


  12. tom0mason says:

    I have a feeling (not much more) that this year there may well be quite a strong SSW. However winter 2020 may be even bigger.

  13. poly says:

    Ren, thank you for your 3D animation on the SSW. It is worth a thousand words! That thing is awesome!

  14. ren says:

    Poly, see what the SSW looked like in January 2009. You can see that the wave first reached the upper layers of the stratosphere.

  15. oldbrew says:

    Research: Blocking precursors to stratospheric sudden warming events [2009]

    The primary causes for the onset of major, midwinter, stratospheric sudden warming events remain unclear. In this paper, we report that 25 of the 27 events objectively identified in the ERA‐40 dataset for the period 1957–2001 are preceded by blocking patterns in the troposphere. The spatial characteristics of tropospheric blocks prior to sudden warming events are strongly correlated with the type of sudden warming event that follows. Vortex displacement events are nearly always preceded by blocking over the Atlantic basin only, whereas vortex splitting events are preceded by blocking events occurring in the Pacific basin or in both basins contemporaneously.


  16. ren says:

    The stratospheric polar vortex in the middle of winter has nothing to do with global warming. The polar vortex in 2009 was broken into two parts consistent with the arctic magnetic field. You can not pretend to see something else on the animation.
    First, check how the stratospheric polar vortex in the northern hemisphere develops.

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