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Stratosphere Temperature Watch 2015/2016


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Posted
  • Location: The Netherlands
  • Location: The Netherlands

    What I am so far struggeling to see in relation to this SSW (sudden stratospheric warming) event is what the effects are on the weather in the lower stratosphere (in terms of pressure patterns). Comparing the 100 and 10 hPa plots of the ECMWF run from  yesterday, valid for yesterday and 9 days out does not give any kind of clear relationship.

    A clear warming event aloft

    ECMWF10A12.thumb.gif.bc3ab5f878324e03d82

    10 hPa yesterday 12 UTC

    ECMWF10F240.thumb.gif.935e173946160c96fb

    10 hPa 9 days out from now

    The first image (at 10 hPa, far into the stratosphere) shows a classic wave 1 sudden stratospheric warming (correct me if I am wrong?), with the polar vortex being pushed towards the Eurasian side (wave 1 because a single 'high pressure cell' is pushing the vortex away). 10 days later, the high pressure area has caused a split in the polar vortex with one piece residing over Siberia and the other over the US.

    But what happens at the lowest part of the stratosphere?

     

    ECMWF100A100.thumb.gif.ef2738b40818a0e1d

    100 hPa (lower stratosphere) yesterday 12 UTC

    ecmwf100f240.thumb.gif.0299c7c3c61d488d9

    100 hPa 9 days from now.

    Initially the 'lower stratospheric polar vortex' seems to be mainly located over the Eurasian continent with its main center over Siberia. Yet there does not seem to be a clear sign of the 'high pressure' that pushes the vortex away to the Eurasian continent.

    10 days later, the pressure field at 100 hPa does still not agree at all with the pressure field at 10 hPa. There seems to be little in the way of ridging over the pole; only some weak ridging is present near California and near Western Europe.

    Little downwelling or own interpretation

    This all leaves me with a question - am I thinking too simply about the downwelling of the SSW (or in other words: are the pressure patterns in the stratosphere not connected in such a way), or is there really a kind of 'disconnect' between the upper and lower stratosphere? I'm curious on your thoughts about this subject matter.

     

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    Posted
  • Location: Slovenia, Central Europe 1050m ASL
  • Location: Slovenia, Central Europe 1050m ASL

    Simply put, there is a disconnection, or weak coupling, together with possible stronger trop-forcing which can override the signal. The temperature has downwelled, but the heights have not responded. Pretty much what I am trying to emphasise the whole season, and which was the "theme" of this winter. The troposphere is kinda playing a game of its own, with partial coupling, but at this point in time the trop and strat are generally slowly starting to de-couple anyway. 

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    Posted
  • Location: The Netherlands
  • Location: The Netherlands
    14 minutes ago, Recretos said:

    Simply put, there is a disconnection, or weak coupling, together with possible stronger trop-forcing which can override the signal. The temperature has downwelled, but the heights have not responded. Pretty much what I am trying to emphasise the whole season, and which was the "theme" of this winter. The troposphere is kinda playing a game of its own, with partial coupling, but at this point in time the trop and strat are generally slowly starting to de-couple anyway. 

    You are right - upon a closer look the temperature profiles on the 100 and 10 hPa do seem to match nicely. The warming to the northeast of the pole yesterday is both evident at 10 and 100 hPa, with the same being valid for the warming in 9 days to the immediate south of the pole.

    Probably the overarching question resulting from your point (which I have heard being valid on quite a few occasions at least this winter), is: what mechanisms have caused this decoupling between the troposphere and stratosphere? If this question is to be answered, it might well explain a lot - and bring our knowledge one step higher for next winter!

    Thanks for the answer to my initial reasoning btw!

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    13 hours ago, Recretos said:

    Still too much emphasis on the temperature and too little on the other energies involved. Were all this really worthy of hype in terms of super effects, I would be among the first to jump the train. But since its not, that is the reason for my lack of activity in here.

    Edit:
    I really do hope that this season was a very good lesson for us all, how each SSW is a unique feature and we cannot handle SSWs  with "Wikipedia-ish" approach. One thing that Mr. Judah Cohen also needs to learn, with all due respect. Regardless of the impressive temperature numbers, SSWs, are simply not just temperature-only features, and much more things are involved in the whole process that can make or break a winter period. 

    Regards. :)

    No, the temperatures are critical as I posted previously https://forum.netweather.tv/topic/84231-stratosphere-temperature-watch-20152016/?page=42#comment-3354558

    The two key points are that it is the meridional temperature gradient which is important (which is why it is used as one method for identifying SSW) and temperature at the 10mb level is not the best indicator of 10mb zonal wind.

    Further to the reference in the previous post, to quote J R Holton (of the Holton-Tan relationship between QBO and vortex strength) describing SSW -

    Quote

    in a major sudden warming the pole-to-equator temperature gradient reversal may occur over a sufficiently deep layer so that the polar westerly jet is replaced by an easterly mean zonal flow over much of the depth of the polar stratosphere

    Here is a more recent description by Kornich -

    Quote

    Increased planetary wave activity flux (Eliassen-Palm flux) propagates from the troposphere upwards. After precondition the polar vortex the breaking of the waves takes place in high latitudes of the stratosphere. The induced wave drag gives rise to a stronger residual circulation accompanied with a strong polar warming. The change in the meridional temperature gradient creates stratospheric easterlies.

    It doesn't matter if temperature is viewed as cause or effect because it is 'chicken and egg' depending on the frame of reference used to describe the processes. Looking at various equations  eg - hypsometric for geopotential thickness, potential vorticity, EP-flux - they all have temperature related terms and it plays a role in any atmospheric kinetic energy, apart from some basic barotropic simplification. More than 98% of atmospheric motion is driven by horizontal heating gradients, the remainder by convection ie vertical heating gradients (http://www.atmos.washington.edu/2010Q2/545/545_Ch_1.pdf) so I'm curious which other energies you refer to.

    The Kornich reference is actually topical with the potential for downwelling - Predictability of the coupled troposphere-stratosphere system

    http://www.ecmwf.int/sites/default/files/elibrary/2012/10604-predictability-coupled-troposphere-stratosphere-system.pdf

     

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    Posted
  • Location: Slovenia, Central Europe 1050m ASL
  • Location: Slovenia, Central Europe 1050m ASL

    All is fine and good. Of course temperature has a major role in all physical dynamics. 

    But my point was of quite a different nature. I was talking to the "general population" about monitoring the stratosphere, where there is this bias towards temperature, which is especially notable when NWP starts drawing potential strat warmings. Be it minor or not. 

    Mostly people naturally expect every strat warming to produce cold shots and severe winter down the line. And that was my point that more parameters need emphasis when *monitoring* the strat. 

    But you are right when it comes to *calculating* the strat dynamics. But that is usually done for us by NWPs. And this year they were doing a good job, with the prediction of the warming and the potential effects. 

    One could say that the strat warming or warm strat temperature, as important in each aspect as it might be, failed us this year, which is just as normal as when it rewards us. 

    Thats just the complexity of the world we live in. 

    Kind regards. 

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    What puzzles me is how a split-vortex SSW, which has been observed to propagate through the tropopause, can be halted by some other barrier in the lower-strat. It must be quite the feature - driven by EPS I gather? 

    I am thinking back to Lorenzo's post on 15th Jan this year:

    This thing may be a primary factor behind the turmoil  experienced with respect to many of the seasonal forecasts made for the winter just gone. The ultimate excuse for our shortfalls? :rolleyes::D

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    3 hours ago, Nouska said:

    The subject of a session at the EGU General Assembly.

    http://meetingorganizer.copernicus.org/EGU2016/orals/20710

    Interesting stuff, this one - A study of the properties of the Grand Solar Minima throughout the past 13,000 years and the implications for Space Weather - might not be popular here

    Quote

    In conclusion, we speculate that the sun may now be entering one of its extended periods of high activity which will persist for ∼1000 y

     

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    Posted
  • Location: Surrey and SW France.
  • Location: Surrey and SW France.
    2 hours ago, Interitus said:

    Interesting stuff, this one - A study of the properties of the Grand Solar Minima throughout the past 13,000 years and the implications for Space Weather - might not be popular here

     

    I think the Julius Bartels* Medal lecture would be interesting too

    http://meetingorganizer.copernicus.org/EGU2016/EGU2016-1463.pdf

    With all these complicated processes meandering through the various layers of atmosphere, how can we hope to arrive at any type of prediction or forecast for one specific layer?

    * http://www.egu.eu/egs/bartels.htm

     

     

     

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    From one of the records Nouska has provided a link to ("Energetic particle influences in Earth’s atmosphere":

    "Energetic particles, whether solar or galactic in origin, may influence the troposphere and stratosphere through a range of different mechanisms, each probably contributing a small amount. Some of the suggested processes potentially acting over a wide spatial area in the troposphere include enhanced scavenging of charged aerosol particles, modification of droplet or droplet-droplet behavior by charging, and the direct absorption of infra-red radiation by the bending and stretching of hydrogen bonds inside atmospheric cluster-ions ."

     

     

    On the first term in bold, I have found this:

    http://www.sciencedirect.com/science/article/pii/S0169809502000200

    From the abstract: "For the charge levels expected naturally on supercooled water drops and aerosol active as contact nuclei, the charge-enhanced collection efficiency leads to an increased capture of ice nuclei (IN), causing the freezing probability by contact nucleation to be increased over neutral collisions."

    I believe this amounts to a faster generation of ice crystals as supercooled (sub-zero) water droplets freeze having found a nuclei (freezing can only occur when there is something 'rough' onto which the first frozen molecules can attach). I can see how this affects tropospheric weather, but stratospheric - not much as far as I can imagine, apart from polar stratospheric clouds perhaps.

     

    On the second, there is this:

    http://iopscience.iop.org/article/10.1088/1748-9326/8/1/015026

    The gist from what I gather is that such charged particles absorb infra-red radiation in a way that non-charged particles do not. However, it is noted in the abstract that, "The average change in longwave radiation in this absorption band due to molecular cluster ions is 7 mWm−2. The integrated atmospheric energy density for each event is 2 Jm-2, representing an amplification factor of 1012 compared to the estimated energy density of a typical air shower. This absorption is expected to occur continuously and globally, but calculations suggest that it has only a small effect on climate"

     

    So at this point I am still left wondering in what way this may drive a disconnect in the lower stratosphere - especially one that still allows a flux from the troposphere to impact the stratosphere right up to 1 hPa.

     

     

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    Posted
  • Location: Surrey and SW France.
  • Location: Surrey and SW France.

    You'll see in the media info I did a screen capture of, they are referring to chemical changes in the atmosphere - I don't fully understand it but a couple of reference articles for you to look at, James.

    http://www.atmos-chem-phys.net/14/8009/2014/acp-14-8009-2014.pdf

    http://solarisheppa.geomar.de/heppa2

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    3 hours ago, Nouska said:

    You'll see in the media info I did a screen capture of, they are referring to chemical changes in the atmosphere - I don't fully understand it but a couple of reference articles for you to look at, James.

    http://www.atmos-chem-phys.net/14/8009/2014/acp-14-8009-2014.pdf

    http://solarisheppa.geomar.de/heppa2

    Thanks for those Nouska, I will take a look early next week, tomorrow I am out and about :D (Have a good Sunday everyone!)

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    Tentatively, using the GEOS/MERRA data the SSW was marginally the strongest recorded at 10mb 60°N on 11/03/16 at -31.43 m/s just stronger than the -31.08 m/s from 2009 - tentatively because this is from the GEOS-FP assimilation, not yet from the MERRA reanalysis. The Berlin ECMWF analysis had it at -31. and both have today at about the same or a tad stronger before it begins to weaken.

    The GEOS forecast downwelling as measured by change in wind shear was initially quite strong - here the forecast from the 6th the day after onset shows the easterly wind shear predicted to propagate down from the 10mb level to the others one by one -

    layers1.thumb.gif.434477a1d0b4e3e6877995

    and the forecast from the next day was quite dramatic with an actual wind reversal forecast all the way down to 150mb 60°N for today 15th -

    layers2.thumb.gif.e8b9a66796ac59958d0f75

    However the following day (8th) the wind propagation was minimal, and though subsequent forecasts have not been as weak a reversal has only been forecast as low as 70mb -

    layers3.thumb.gif.9ad084096fa85fce2eea37

    This initial week from onset is when we would expect to see a rapid response if the atmosphere is well coupled but the CPC time series anomaly charts show polar stratosphere positive geopotential height anomalies propagating down due to increased thicknesses from the warming while most of the lower polar troposphere has a negative height anomaly reflecting a cold and fairly vigorous vortex -

    time_pres_HGT_ANOM_JFM_NH_2016.thumb.png

    The wind anomalies tell a similar tale with weaker than normal flow gradually permeating throughout the strat so far but slightly stronger flow than normal below 500mb say (or the bottom half of the atmosphere by mass) -

     time_pres_UGRD_ANOM_JFM_NH_2016.thumb.pn

    This situation looks likely to change with gradual downwelling continuing over the next few days with a rise in pressure and heights over the Arctic and a splitting of the troposphere vortex mirroring the stratosphere which has really only just started in the past couple of days. The differences we're seeing between a fairly benign and temporary northerly shot from the GFS and something perhaps more wintry and unseasonal from the ECM could be due to handling of the stratosphere. If we look at the 10mb 240 hour charts from yesterday lunchtime they are in generally broad agreement but the ECM has the vortices further west, with the European vortex remnant in particular closer and with lower heights more influential for the UK -

      NH_HGT_10mb_240.thumb.gif.46e1ecd8af7dd1ecmwf10f240.thumb.gif.4b299195826ac1b32e

    charts courtesy Instantweathermaps & FU Berlin

    I get the impression that Recretos is slightly unimpressed and disillusioned with this SSW, but his animations might be quite illuminating right now!

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    1 hour ago, Interitus said:

    A tad premature - it may end up being the case, but the net radiative balance still slightly favours cooling and westerlies resume at the top of the stratosphere in the next few days.

    So is there a feedback process that could see the vortex regain strength even after the radiative balance turns? I am curious as to how well the vortex can hold on in the face of the warming brought about as a result of UV absorption by ozone. Which reminds me, has anyone got a link for stratospheric ozone concentrations? Thanks in advance :hi:

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    18 hours ago, Woollymummy said:

    Thanks :good:

    Surprisingly, I can't seem to find anomaly maps. Seems I'll have to familiarise myself more with what the typical concentration distributions are. 

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    Posted
  • Location: Surrey and SW France.
  • Location: Surrey and SW France.
    13 minutes ago, Singularity said:

    Thanks :good:

    Surprisingly, I can't seem to find anomaly maps. Seems I'll have to familiarise myself more with what the typical concentration distributions are. 

    Environment Canada have 'normal' ozone concentration maps for each month. It is a short sample period so maybe not of much use in the greater scheme of things. Current observations and forecast in left side bar.

    http://exp-studies.tor.ec.gc.ca/e/ozone/normalozone.htm

    Stratospheric ozone forecast for different layers.

    http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/#emcoz

     

     

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    2 hours ago, Nouska said:

    Environment Canada have 'normal' ozone concentration maps for each month. It is a short sample period so maybe not of much use in the greater scheme of things. Current observations and forecast in left side bar.

    http://exp-studies.tor.ec.gc.ca/e/ozone/normalozone.htm

    Stratospheric ozone forecast for different layers.

    http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/#emcoz

     

     

    Thanks Nouska :good: There seems to be a fair old deficit over East Asia at the moment, more than 50 DU in places, otherwise just a little below normal (20-30 DU). 

    That's just at a glance, mind. As usual, lots of other things going on for me...

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    Posted
  • Location: @scotlandwx
  • Weather Preferences: Crystal Clear High Pressure & Blue Skies
  • Location: @scotlandwx

    Really looking forward to getting back into reanalysis in general of this season, had to vanish for a bit due to changes at work meaning the last 6-8 weeks have left strictly zero time for close monitoring of conditions. Forgive me if not up to speed, great thing is that these threads whilst busy in the 'live' environment of things unfolding dynamically - also serve as historical bookmarks to both evolution of the atmosphere and understanding.

    i.e where was OPI originally or where is EPF now... as two variables to call out.

    Thankfully still get twitter alerts so not entirely blind, so caught the phenomenal vortex eventually moving beyond the event horizon into destabilization,

    ecmwf10f144.thumb.gif.0a754bec0397cbddab

    The EP Flux chart for me is the one of interest, so few are the poleward vectors within the seasonal wave activity, even when considering the MERRA extreme noted by u reversal.

    Also for the El Nino Background, I recall another March where the prevalence of a UK block led to a very, very mild week and similar pattern, but cannot put place on the year - no direct correlation just a thought to now.

    compday.0132dlH420.thumb.gif.631f213d5db

    Apologies for nothing more constructive at present, and great to see the debate still firing ahead. Each year we peel back another layer of understanding and this has been no different.

    Capture.JPG

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    http://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-9.19,57.60,315

    A beautiful wave-3 pattern... except that it's at 10 hPa so not in the usual sense!

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    • 1 month later...
    • 3 months later...
    Posted
  • Location: Exile from Argyll
  • Location: Exile from Argyll
    On 03/08/2016 at 19:56, sebastiaan1973 said:

    Winter 2017. LIkely a weak La Nina, Solar activity in the declining phase. Which resembles a positive NAO phase and QBO in it's easterly phase (right now it is still westerly -> http://www.esrl.noaa.gov/psd/data/correlation/qbo.data)

    What's your thoughts on the twitter conversations around the QBO behaving erratically?

     

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