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chionomaniac

Stratosphere Temperature Watch 2012/2013

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First Class C.

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Thanks C plenty of information for everyone to try and get up to speed and your posts will be eagerly looked for by the coldies on here=most folk.

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Excellent review C and so beautifully explained- even my understanding is increased.

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Good opening post Ed- very informative.

Many of us have looked forward to this thread and i am sure it will be one of the most visited this Winter.

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Always nice to see the new strat thread opened,and a great introductory post by Chio. Posted Image

An interesting post by GP in the old thread (GP copy into this thread?) showing

how the stratosphere might behave this winter by using 1968 as an analogue.

The 30mb zonal wind composite for the winter of 68/69 shows the reduction in

zonal winds at mid-latitudes very nicely...

....along with the sea level pressure anomalies. Posted Image

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Many thanks for that, Ed...After years' of 'ignoring' acronyms, some have finally stuck!

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good to c the strat thread reopening again nice explanation chio.

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Stratospheric analysis and discussion at 1:40am on a Sunday morning...Now that's dedication, or perhaps insomnia Posted Image

Good to see the thread open, here's to the coming weeks and months and lets hope we aren't looking back on this come next March with disappointment. Clearly I am speaking from a person who is also after/favours a more blocked pattern this winter, particularly given the summer we have had. A winter period dominated by zonal, mild, wet and windy muck is not wanted IMO.

Regards to all,

M.

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I hope Matt doesn't mind, but this is hot off the press and I'm sure it is well worth a read. Posted ImageTime for a strong coffee, there is some learning to be done.

http://matthugo.wordpress.com/2012/10/01/stratospheric-conditions-winter-weather-analysis-information/

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I hope Matt doesn't mind, but this is hot off the press and I'm sure it is well worth a read. Posted ImageTime for a strong coffee, there is some learning to be done.

http://matthugo.word...is-information/

Fantastic blog post by Matt Posted Image , i now know alot more than i did 10-15 minutes ago. Thanks for sharing GTLTW.

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I hope Matt doesn't mind, but this is hot off the press and I'm sure it is well worth a read. Posted ImageTime for a strong coffee, there is some learning to be done.

http://matthugo.word...is-information/

It's great to get the word out there in a clear concise way - I've been trying long enough but without Matt's profile.

Technically, last January there wasn't a SSW as defined by Polvani et al (winds reversal at 60ºN and 10hPa), but I can let Matt off as the result in this case is pretty much the same as if there had been!

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Todays update;

The stratosphere is currently cooling rapidly as is expected at this time of year.

Last week we saw a blip where the mean zonal winds went below average for this time of year in the lower stratosphere. These have since recovered and are or about to increase to above average.

Encouragingly, the cooling of the polar stratosphere is not forecast to be straightforward with small projected warmings forecast over the Canadian sector which will put pressure on the strengthening vortex. All of this has been in stratospheric FI but the theme has remained the same, with a lower split even cropping up. Very much a trend that we want to see continue into winter!

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Todays update;

The stratosphere is currently cooling rapidly as is expected at this time of year.

Last week we saw a blip where the mean zonal winds went below average for this time of year in the lower stratosphere. These have since recovered and are or about to increase to above average.

Encouragingly, the cooling of the polar stratosphere is not forecast to be straightforward with small projected warmings forecast over the Canadian sector which will put pressure on the strengthening vortex. All of this has been in stratospheric FI but the theme has remained the same, with a lower split even cropping up. Very much a trend that we want to see continue into winter!

ed, do you think interruptions to the rate of cooling are more important than the actual temp that the strat eventually ends up come november re a strong organised early winter vortex ?

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Nick, I think that the interruptions may help prevent the straightforward cooling of the strat, so are important in both senses. If at the end of November we have a strong vortex in a cold strat then obviously they may not have helped as much as I anticipate!

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Excellent, really looking forward to this thread! It was too technical for me last year but I will have a better grip this year as my knowledge has improved greatly since then. Thanks to Chionomaniac and all those who will contribute to this thread through the Autumn and Winter. It will be brilliant reading!

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Looking forwards to your posts Chiono. A great introductory post. Can you explain a little more about the phenomenon of "wave-breaking" as in this quote "One noticeable aspect of the recent previous winters is how the stratosphere has been susceptible to wave breaking from the troposphere through the lower reaches of the polar stratosphere - not over the top as seen in the SSWs"

What is the cause of "wave breaking"? What are the outside influences on sudden stratospheric "warming" events? Are we talking about sun activity? Does this depend on sun activity cycles / sunspots?

Always wanting to learn more :) - thanks for the insights.

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Looking forwards to your posts Chiono. A great introductory post. Can you explain a little more about the phenomenon of "wave-breaking" as in this quote "One noticeable aspect of the recent previous winters is how the stratosphere has been susceptible to wave breaking from the troposphere through the lower reaches of the polar stratosphere - not over the top as seen in the SSWs"

What is the cause of "wave breaking"? What are the outside influences on sudden stratospheric "warming" events? Are we talking about sun activity? Does this depend on sun activity cycles / sunspots?

Always wanting to learn more Posted Image - thanks for the insights.

Hi kumquat.

Lots of questions and ones that took me a lot of time to get my head around.

The tropospheric atmosphere consists of large scale planetary waves that flow from west to east normally. These waves are known as Rossby waves and there can be a number of these flowing around the NH at any one time. As with any wave there is a peak and a trough between . I have demonstrated the troughs in the following NH H500 ECM chart (typically not an easy day to demonstrate!)

post-4523-0-95024500-1349288532_thumb.gi

The height of the atmosphere varies between the peaks and the troughs of these waves and as a wave comes in from the sea and break as it nears land the same phenomenem can occur with Rossby waves. However, these waves need to be a certain amplitude before this occurs and need to hit a large planetary object such as a mountain range before this occurs.

So when a large Rossby wave hits a mountain range (like a ripple from a pebble) we can see this wave break upwards into the stratosphere (as well as be deflected sideways into the troposphere and lose energy to the earth in the form of a mountain torque). The effect of a wave breaking into the stratosphere will depend upon the size of the wave - the bigger the wave, the greater the deflection. Once a wave is big enough it can create a disturbance which travels around the boundary of the stratospheric polar vortex - known as the 'surf zone' - and penetrate into the polar vortex at the top of the stratosphere. It can then rebound back towards the troposphere and if it is great enough completely disrupt the polar vortex causing it to warm as it does so. Hence a Sudden Stratospheric Warming (SSW).

These type of wave breaks occur regularly but are of insufficient strength to create SSW's most of the time. If one wave breaks into the stratosphere at any one time we have a wavenumber 1 type break, if two occur simultaneously then we have a wavenumber 2 type and so on.

One other thing to note is that I have witnessed similar type breaks into the stratosphere in recent years that have occurred with planetary waves breaking around Greenland. Rather than travelling up around the surf zone to the top of the stratosphere these wave break 'internally' - almost through the core of the vortex. It is these types of break that do not create full SSWs but have led to very potent cold outbreaks here in recent years.

If in the following link you click ' ongoing observations' and then 'Rossby waves shed by greenland' it is easier to visualise how these interactions occur.

http://www.pa.op.dlr...ctic/index.html

Ps if any one can embed this into a post I would be grateful!

c

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Thanks for that Ed-i wondered what the difference between Wavenumber 1 and 2 actually meant.

From your explanation that a Wavenumber 2 event is a double event am i correct in assuming that this would give a better chance of an effective SSW.?

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Thanks for that Ed-i wondered what the difference between Wavenumber 1 and 2 actually meant.

From your explanation that a Wavenumber 2 event is a double event am i correct in assuming that this would give a better chance of an effective SSW.?

It's a certain wavelength pattern breaking into the stratosphere commonly with Atlantic and Pacific wave breaks. Wavenumber 2 breaks are more likely to cause split SSWs rather than wavenumber 1 breaks which are the cause of displacement SSWs.

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I should also point out that from the stronger the mountain torque observed, we can forecast that the wave break into the stratosphere will be stronger. So that this is a useful guide as to what occurs down the line.

Also, in todays forecasts there is a strong 10 day trend to displace the polar vortex towards Baffin bay/ N Canada region. So will we see some kind of height rises in the Scandi region around this time tropospherically - not programmed as of yet!

(Edit - of course these height rises could be Eurasion placed)

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I should also point out that from the stronger the mountain torque observed, we can forecast that the wave break into the stratosphere will be stronger. So that this is a useful guide as to what occurs down the line.

Also, in todays forecasts there is a strong 10 day trend to displace the polar vortex towards Baffin bay/ N Canada region. So will we see some kind of height rises in the Scandi region around this time tropospherically - not programmed as of yet!

Some suggestion of this on 12z ECM/GFS means at T240hrs. Ed

post-2026-0-00939400-1349297421_thumb.pnpost-2026-0-99067400-1349297432_thumb.pn

Not sure how much the height rises across Scandi.would be but a definite modelling of the core of low heights towards Canada.

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Some suggestion of this on 12z ECM/GFS means at T240hrs. Ed

post-2026-0-00939400-1349297421_thumb.pnpost-2026-0-99067400-1349297432_thumb.pn

Not sure how much the height rises across Scandi.would be but a definite modelling of the core of low heights towards Canada.

One to watch and see how it develops, Phil.

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There are a couple of pages from a BDC paper I found that put waves into diagrams, always helps me, perhaps Ed can add further explanation to the below.

post-7292-0-45028500-1349299316_thumb.pn post-7292-0-40410800-1349299335_thumb.pn

The last diagram helped me picture the surf zone well.

post-7292-0-77124000-1349299552_thumb.pn

The paper is unfortunately too big to attach here, Dylan Jones, Dept of Physics, Toronto. 2005

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There are a couple of pages from a BDC paper I found that put waves into diagrams, always helps me, perhaps Ed can add further explanation to the below.

post-7292-0-45028500-1349299316_thumb.pn post-7292-0-40410800-1349299335_thumb.pn

The first I think is self explanatory.

The second diagram shows that large scale thunderstorms in troughs contained in the Rossby waves, act as a trigger mechanism helping propagate the feedback.

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    • By chionomaniac
      Welcome to the latest stratospheric temperature watch thread.
       
      A bit later this year with a new thread – but better late than never! It is now the 7th winter stratospheric temperature watch thread on netweather, and how much have we learnt in the past years!
       
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       AO chart
       

       
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      Ozone Content in the stratosphere
       
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      http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/index.shtml
       
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      Diagram of the descending phases of the QBO: (with thanks from http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/qbo/index.html )
       

       
       
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      http://www.atmos-chem-phys.net/13/4563/2013/acp-13-4563-2013.pdf
       
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      http://strat-www.met.fu-berlin.de/labitzke/moreqbo/MZ-Labitzke-et-al-2006.pdf
      http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50424/abstract  
      http://onlinelibrary.wiley.com/doi/10.1002/2013JD021352/abstract
       
       
      The QBO is measured at 30 hPa and has entered a westerly phase for this winter. As mentioned warming events are more likely during solar maximum when in this westerly phase – with the solar flux below 110 units. Currently, we have just experienced a weak solar maximum and the solar flux heading into winter is still around this mark. This doesn’t rule out warming events, but they will not be as likely – perhaps if the solar flux surges then the chance will increase.
       
      Latest solar flux F10.7cm:
       

       
      http://www.swpc.noaa.gov/products/solar-cycle-progression
       
       
      Sudden Stratospheric Warmings:
       
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      Any SSW will be triggered by the preceding tropospheric pattern - in fact the preceding troposheric pattern is important in disturbing the stratospheric vortex even without creating a SSW.  Consider a tropospheric pattern where the flow is very zonal - rather like the positive AO phase in the diagram above. There has to be a mechanism to achieve a more negative AO or meridional pattern from this scenario and there is but it is not straightforward.  It just doesn't occur without some type of driving mechanism. Yes, we need to look at the stratosphere - but if the stratosphere is already cold and a strong polar vortex established, then we need to look back into the troposphere. In some years the stratosphere will be more receptive to tropospheric interactions than others but we will still need a kickstart from the troposphere to feedback into the stratosphere. This kickstart will often come from the tropics in the form of pulses and patterns of convection. These can help determine the position and amplitude of the long wave undulations – Rossby waves - that are formed at the barrier between the tropospheric polar and Ferrel cells. The exact positioning of the Rossby waves will be influenced by (amongst other things) the pulses of tropical convection – such as the phase of the Madden Jullian Oscillation and the background ENSO state and that is why we monitor that so closely. These waves will interact with land masses and mountain ranges which can absorb or deflect the Rossby waves disrupting the wave pattern further - and this interaction and feedback between the tropical and polar systems is the basis of how the Global Wind Oscillation influences the global patterns.
       
       
      If the deflection of the Rossby Wave then a wave breaking event occurs – similar to a wave breaking on a beach – except this time the break is of atmospheric air masses. Rossby wave breaks that are directed poleward can have a greater influence on the stratosphere. The Rossby wave breaks in the troposphere can be demonstrated by this diagram below –
       
      RWB diagram:
       

       
      https://www.jstage.jst.go.jp/article/jmsj/86/5/86_5_613/_pdf
       
       
       
       This occurs a number of times during a typical winter and is more pronounced in the Northern Hemisphere due to the greater land mass area. Most wave deflections into the stratosphere do change the stratospheric vortex flow pattern - this will be greater if the stratosphere is more receptive to these wave breaks (and if they are substantial enough, then a SSW can occur). The change in the stratospheric flow pattern can then start to feedback into the troposphere - changing the zonal flow pattern into something with more undulations and perhaps ultimately to a very meridional flow pattern especially if a SSW occurs - but not always. If the wave breaking occurs in one place then we see a wave 1 type displacement of the stratospheric vortex, and if the wave breaking occurs in two places at once then we will see a wave 2 type disturbance of the vortex which could ultimately squeeze the vortex on half and split it – and if these are strong enough then we would see a displacement SSW and split SSW respectively. The SSW is defined by a reversal of mean zonal mean winds from westerly to easterly at 60ºN and 10hPa. This definition is under review as there have been suggestions that other warmings of the stratosphere that cause severe disruption to the vortex could and should be included. http://birner.atmos.colostate.edu/papers/Butleretal_BAMS2014_submit.pdf
       
      A demonstration of the late January 2009 SSW that was witnessed in the first strat thread has been brilliantly formulated by Andrej (recretos) and can be seen below:
       

       
       
      The effects of a SSW can be transmitted into the troposphere as the downward propagation of the SSW occurs and this can have a number of consequences. There is a higher incidence of northern blocking after SSW’s but we are all aware that not every SSW leads to northern blocking. Any northern blocking can lead to cold air from the tropospheric Arctic flooding south and colder conditions to latitudes further south can ensue. There is often thought to be a time lag between a SSW and northern blocking from any downward propagation of negative mean zonal winds from the stratosphere. This has been quoted as up to 6 weeks though it can be a lot quicker if the polar vortex is ripped in two following a split SSW. A recent paper has shown how the modelling of SSW and strong vortex conditions have been modelled over a 4 week period. This has shown that there is an increase in accuracy following weak or strong vortex events – though the one area that the ECM overestimates blocking events following an SSW at week 4 is over Northwestern Eurasia.
       
      http://iopscience.iop.org/article/10.1088/1748-9326/10/10/104007
       
      One noticeable aspect of the recent previous winters is how the stratosphere has been susceptible to wave breaking from the troposphere through the lower reaches of the polar stratosphere - not over the top as seen in the SSWs. This has led to periods of sustained tropospheric high latitude blocking and repeated lower disruption of the stratospheric polar vortex. This has coincided with a warmer stratosphere where the mean zonal winds have been reduced and has led to some of the most potent winter spells witnessed in recent years.
       
      We have also seen in recent years following Cohen's work the importance of the rate of Eurasian snow gain and coverage during October at latitudes below 60ºN. If this is above average then there is enhanced feedback from the troposphere into the stratosphere through the Rossby wave breaking pattern described above and diagrammatically below.
       
      Six stage Cohen Process:
       

       
       
      The effect of warming of the Arctic ocean leading to colder continents with anomalous wave activity penetrating the stratosphere has also been postulated
       
      http://www.tos.org/oceanography/archive/26-4_cohen.pdf
       
       
      Last year we saw a large snow gain but unfortunately tropospheric atmospheric patterns prevented the full potential of these being unleashed on the stratosphere – hence no SSW, but this winter could be different, but we will have to wait until the end of October.
       
       
       ENSO Influences
       
      One of the main influences in the global atmospheric state this winter will be the upcoming El Nino, and that is forecast to be the strongest since 1997. Studies have shown that SSW’s are more likely during strong ENSO events ( http://www.columbia.edu/~lmp/paps/butler+polvani-GRL-2011.pdf) 
       but also that there is a particular pattern of upward propagating waves. During El Nino events wave formation is suppressed over the Indian Ocean Basin whilst it is enhanced over the Pacific Ocean
       
      http://link.springer.com/article/10.1007%2Fs00382-015-2797-5
       
      The ENSO pathway taken may be all critical this year as can be demonstrated by this paper  http://www.columbia.edu/~lmp/paps/butler+polvani+deser-ERL-2014.pdf
       
      This can lead us to suggest that a rather distinctive wave 1 pattern is likely this winter with the trigger zone likely to be over the north Pacific in the form of a quasi stationary enhanced wave 1 – a traditional Aleutian low SSW trigger pattern is suggested by Garfinkel et al ( http://www.columbia.edu/~lmp/paps/garfinkel+etal-JGR-2012.pdf ) and this should be expected at some point this winter.
       
       
       

       
       
       
      The reported incidence of SSW in EL Nino years is roughly around 60%  - which is more than ENSO neutral years.  A big question remains however, whether the ENSO wave 1 pattern will override the negative HT effect that the wQBO with the reducing solar ouput link brings. And even if it does, and we do achieve a displacement SSW, the next question is how will this affect the Atlantic sector of the Northern Hemisphere? My suspicion is that even if we do achieve a SSW this winter it will be in the second half, and also any subsequent blocking may not be quite right for the UK and, that if we were to achieve a –ve NAO, any block will be nearer Canada than Iceland, leaving the Atlantic door ajar.  It is still too early this winter to be making any definitive forecasts – the next 6 weeks are very important stratospherically, determining in what vein winter will start. Already we are seeing a forecast of weak wave activity disrupting the growing vortex and it will be interesting to see if this is repeated during November.
       
      And it will be especially interesting to see what occurs in November and what is forecast for December before winter starts because typical strong El nino wQBO stratospheric composite analogues tell an opposite story. They suggest that the stratospheric vortex will be disrupted and weaker early in the winter before gaining in strength by February.
       
      December:
       

       
      January
       

       
      February
       

       
      The mean zonal winds are already forecast to be below average so perhaps an early disrupted vortex is more likely this year!
       

       
      As ever, I will supply links to various stratospheric websites were forecasts and data can be retrieved and hope for another fascinating year of monitoring the stratosphere.
       
       
       
      GFS: http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/
       
      ECM/Berlin Site: http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html  
       
      Netweather: http://www.netweather.tv/index.cgi?action=stratosphere;sess=75784a98eafe97c5977e66aa65ae7d28
       
      Instant weather maps: http://www.instantweathermaps.com/GFS-php/strat.php
       
       NASA Merra site: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
       
       
      Previous stratosphere monitoring threads:
       
      2014/2015 https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/
       
      2013/2014 https://forum.netweather.tv/topic/78161-stratosphere-temperature-watch-20132014/
       
      2012/2013 https://forum.netweather.tv/topic/74587-stratosphere-temperature-watch-20122013/
       
      2011/2012 https://forum.netweather.tv/topic/71340-stratosphere-temperature-watch-20112012/
       
      2010/2012 https://forum.netweather.tv/topic/64621-stratosphere-temperature-watch/?hl=%20stratosphere%20%20temperature%20%20watch
       
      2009/2010 https://forum.netweather.tv/topic/57364-stratosphere-temperature-watch/
       
      2008/2009 https://forum.netweather.tv/topic/50299-stratosphere-temperature-watch/
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