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Around this time of year I often search out new papers to assist in winter forecasting. However, quite often I lose the links to these papers by the time winter arrives.

So, I think it makes sense to have a drop off zone for these type of papers that I and others come across. Please post in here any abstracts or PDF links that you may find of interest.

A brief description of the paper would be most welcome.

( No climate change papers please)

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And to start off here is an abstract on a paper to be verified soon.

This suggests that Vortex splitting events in the stratosphere are more likely to give colder outbreaks over NA and Eurasia than displacement events.

A strong link exists between stratospheric variability and anomalous weather patterns at the Earth's surface. Specifically, during extreme variability of the Arctic polar vortex termed a "weak vortex event", anomalies can descend from the upper stratosphere to the surface on timescales of weeks. Subsequently the outbreak of cold-air events have been noted in high Northern Latitudes, as well as a quadrapole pattern in surface temperature over the Atlantic and western European sectors. It is currently not understood why certain events descend to the surface while others do not, although this may be associated with the scale of vertically propagating Rossby waves which cause the initial vortex perturbation. In this study we demonstrate that the subdivision of weak vortex events into vortex displacements and vortex splits has important implications for tropospheric weather patterns on weekly-monthly timescales. Using reanalysis data we find that vortex splitting events play a highly significant role on surface weather with positive temperature anomalies over eastern North-America of more than 1.5K, and negative anomalies over Eurasia of up to -3K. Associated with this is an increase in tropospheric blocking over the Pacific basin and a decrease over the Atlantic/European sector. The corresponding signals are far weaker during displacement events, although ultimately they prove to be the cause of cold-air outbreaks over North America. Owing to the predictability and importance of stratosphere-troposphere coupling for medium-range weather forecasts, our findings suggest the need for such forecasting systems to correctly identify the type of stratospheric variability, otherwise surface responses cannot be accurately reproduced.

(Bolded by me)


Edited by chionomaniac
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This next paper suggests that SSW's are more likely in ENSO event years rather than ENSO neutral years. Interestingly, this is true of both El Nino events and La Nina events.

I have extracted interesting info below about El Nino years

. During an El Niño winter, it is wellâ€

established that (1) temperatures are colder than normal in

the tropical stratosphere and warmer than normal in the

polar stratosphere; (2) ozone concentrations are anomalously low in the tropics and anomalously high at the pole,

reflecting an enhanced Brewerâ€Dobson circulation [Randel

et al., 2009; Cagnazzo et al., 2009]; and (3) the planetary

wave flux into the stratosphere is enhanced resulting in a

weakerâ€thanâ€normal stratospheric polar vortex [van Loon

and Labitzke, 1987; Garcíaâ€Herrera et al., 2006; Garfinkel

and Hartmann, 2008].


And the follow up paper suggests why El Nino and La nIna events may be matched


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A paper on the positioning of blocking highs and their relationship to the upward propagation of planetary waves.


Previous studies have suggested the importance of blocking high (BH)

development for the occurrence of stratospheric sudden warming (SSW),

while there is a recent study that failed to identify their statistical

linkage. Through composite analysis applied to high-amplitude

anticyclonic anomaly events observed around every grid point over the

extratropical Northern Hemisphere, the present study reveals distinct

geographical de- pendence of BH influence on upward propagation of

planetary waves (PWs) into the stratosphere. Tropospheric BHs that

develop over the Euro-Atlantic sector tend to en- hance upward PW

propagation, leading to the warming in the polar stratosphere and, in

some occasions, to major SSW events. In contrast, the upward PW

propagation tends to be suppressed by BHs developing over the western

Pacific and the Far East, resulting in the polar stratospheric cooling.

This dependence is found to arise mainly from the sensi- tivity of the

interference between the climatological PWs and upward-propagating

Rossby wave packets emanating from BHs to their geographical locations.

This study also reveals that whether a BH over the eastern Pacific and

Alaska can enhance or re- duce the upward PW propagation is

case-dependent. It is suggested that BHs that induce the stratospheric

cooling can weaken statistical relationship between BHs and SSWs

A video here from a workshop on SSWs from Kyoto, Japan.


I can edit out the video link if you want to keep this strictly papers though?

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I can edit out the video link if you want to keep this strictly papers though?

No all contributions like this are welcome thanks.

I haven't had a chance to go through all the Kyoto papers yet!

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From Sparc newsletter Jan 2012


Extract 1:

Within the same theme, A. Scaife addressed challenges and progress in prediction for regional spatial scales on a

wide range of timescales. The importance

of prediction for monthly to decadal timescales in conjunction with understanding

the effects of climate changes is underlined

by the incidence of large impact events

(e.g., floods, droughts, cold periods) that

are associated with seasonal to decadal

scale variability that accompanies the

more slowly varying climate signal. Predictions for months to years must rely on

both accurate measures of the initial state

and its uncertainty as well as on accurate

estimates of changes in climate forcing

mechanisms (“boundary values†such as

changes in the radiatively active components of atmospheric composition). In recent years considerable progress has been

made in understanding key processes that

influence monthly and seasonal predictability. These include improved understanding and modelling of the coupling

between tropical and extratropical intraseasonal oscillations such as the MaddenJulian Oscillation (MJO) and the North

Atlantic Oscillation (NAO), the lagged

coupling between stratospheric sudden

warmings (SSWs) and tropospheric circulation anomalies, and predictability of

El Niño Southern Oscillation (ENSO)

events and their effect on weather patterns

(rainfall) both in the tropics and the extratropics. There is now evidence that more

accurate initialisation improves longrange predictions, particularly in the tropics. However long range predictability

of extratropical weather events is generally poor. Some improvements have been

achieved in making skilful prediction of

the occurrence of high-impact weather

events such as the numbers of hurricanes

and the frequency of hot days. Further improvements in extended range forecasting

are expected to emerge from the results of

international activities such as the CMIP5

decadal hindcast activity

Extract 2:

B. Dong’s work was motivated by a

change in interannual NAO variability in

the late 1970s, which was characterised

by an eastward shift of the NAO centre

of action. His analysis showed a downstream extension of climate anomalies

associated with the NAO. Using Hadley

Centre model experiments, he showed

that both SST and CO2

changes independently force an eastward shift in interannual NAO variability, and found that

the effects of SST changes could be understood in terms of mean changes in the

troposphere while those due to CO2


not. The implication is that stratospheric

changes may play an important role in

the observed eastward shift in interannual NAO variability and related climate


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Have you subscribed to strat_list Chio?

I signed up for it about 2-3 years ago with the intention of improving my stratospheric knowledge, but having gotten so caught up in all the polar and sea ice stuff I just haven't been able to give it as much time as I'd like.

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Have you subscribed to strat_list Chio?

I signed up for it about 2-3 years ago with the intention of improving my stratospheric knowledge, but having gotten so caught up in all the polar and sea ice stuff I just haven't been able to give it as much time as I'd like.

I have now thanks!

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That is a good find.. Cat among the Pigeons then...

Here is the link to the Met Office's new toy GloSea4 http://iopscience.iop.org/1748-9326/7/3/034031/

What do you make of the enhanced profiling from 50km to 80km Chiono? A small step or a stage for them to factor in things talked about readily on the SSW thread, Zonal wind reversal, EP Flux?

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That is a good find.. Cat among the Pigeons then...

Here is the link to the Met Office's new toy GloSea4 http://iopscience.io...326/7/3/034031/

What do you make of the enhanced profiling from 50km to 80km Chiono? A small step or a stage for them to factor in things talked about readily on the SSW thread, Zonal wind reversal, EP Flux?

I think that it is a small but important step. Modelling the tropospheric impact of stratospheric changes is a welcome step forward and todays news regarding this is important. To hear Steve Wright on radio 2 talking about SSW's today was very surreal.
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Atmospheric Blocking and Atlantic Multidecadal Ocean Variability

Going to add this one in here, cannot access the full paper sadly. Abstract is here.


A good write up from NASA here.


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This may be a vintage paper but it's a goodie..


I am sad enough to have the links to the whole amount of a lot of these papers, l!


I have to say that this one is very comprehensive regarding stratospheric polar vortices:


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Waugh & Polvani got me onto EP Flux.. a good work out for the brain ..estimated time frame to decipher... 2018.. !

Thanks for the link to the original above :)

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Waugh & Polvani got me onto EP Flux.. a good work out for the brain ..estimated time frame to decipher... 2018.. !

Thanks for the link to the original above Posted Image

After last year with the EP flux being very unfavourable I think I have come on leaps and bounds in that respect!

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Found last Winter archive of randomness...

Limpasuvan_etal_JClim_04 The Life Cycle of the Northern Hemisphere Sudden Stratospheric Warmings


El Niño, La Niña, and stratospheric sudden warmings:A re-evaluation in light of the observational record


Blocking precursors to stratospheric sudden warming events


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Found last Winter archive of randomness...

Limpasuvan_etal_JClim_04 The Life Cycle of the Northern Hemisphere Sudden Stratospheric Warmings


El Niño, La Niña, and stratospheric sudden warmings:A re-evaluation in light of the observational record


Blocking precursors to stratospheric sudden warming events


I'll cough on the second paper.

(if you look above you'll see why -[already posted])

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Think its worthwhile to add a bookmark for the paper linked by SM and MH over the last 24 hours.

Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation.


Relationship of ENSO to stratospheric sudden warmings - slide with useful statistics


EP Flux Re-analysis Tool -http://www.esrl.noaa.gov/psd/data/epflux/ ( new toy to mess around with !)

Just spotted some EP papers, brain gave up.. !


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Worth a browse, ECMWF recently had an annual seminar, papers from which are all listed on this page.

Who says weather geeks are boring they even kick things off with a Monday night cocktail party !!


This one is excellent.


Edited by lorenzo
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Couple more from same archive, good to find them in presentation form versus having to grind through a proper academic paper..

ENSO and Europe (2010)

Scaife - Enso(1).pdf

MJO Impact on European Weather (2010) http://www.ecmwf.int...ions/Vitart.pdf

ENSO and ENSO Teleconnections (2012) http://www.ecmwf.int...tations/Kim.pdf

Model Layers and Resolution (2012) http://www.ecmwf.int...ions/Takaya.pdf

Edited by lorenzo

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    • By chionomaniac
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      The QBO is measured at 30 hPa and has entered an easterly phase for this winter. As mentioned warming events are more likely during solar minimum – solar flux below 110 units. Currently, we have just experienced a weak solar maximum and the solar flux heading into winter is slightly above 110 units. This doesn’t rule out warming events, but they will not be as likely unless the solar flux continues to drop prior to winter.

      One warming event that can occur in the stratospheric winter is a Sudden Stratospheric Warming (SSW) or also known as a Major Midwinter Warming (MMW). This as the name suggests is a rather dramatic event. Normally the polar night jet at the boundary of the polar vortex demarcates the boundary between warmer tropical and cooler polar stratospheric air (and ozone levels) and is very difficult to penetrate. SSWs can be caused by large-scale planetary waves being deflected up into the stratosphere and towards the North Pole, often after a strong mountain torque event. These waves can introduce warmer temperatures into the polar stratosphere and can seriously disrupt the stratospheric vortex, leading to a slowing or even reversal of the vortex. This year if the solar flux drops below 110 units then the chances of a SSW increase - as can be seen by the following chart.

      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 (such as the eQBO this year) 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 of convection interacting with long wave undulations in the polar vortex which influence the positions of the sub tropical jet stream and polar jet streams respectively. The exact positioning of the large scale undulations (or Rossby waves) will be influenced by (amongst other things) the pulses of tropical convection (aka the phase of the MJO) 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. The ENSO state will influence the GWO base state
      If the deflection of the Rossby Wave is great enough then the wave can be deflected into the stratosphere. 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 place then we will see a wave 2 type disturbance of the vortex which could ultimately squeeze the vortex on half and split it – a split vortex SSW. The SSW is defined by a reversal of mean zonal 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
      The effects of a SSW can be transmitted into the troposphere as the 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.
      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.

      And it appears that the reduction in Arctic sea ice may be contributing to this mechanism and this should be factored in to any forecast.  http://web.mit.edu/jlcohen/www/papers/Cohenetal_NGeo14.pdf
      So that leaves us to the try and forecast what will happen in the stratosphere this year. Out of the many variables what we do know at the moment is that the QBO is descending easterly and that we are probably entering El Nino conditions – although weak presently. And as mentioned earlier, the level of solar flux is slightly above conditions that are favourable for SSW’s. Despite this, conditions are favourable enough to suggest that we will see a warmer than average stratosphere this year. Evidence of this may already be suggested by an enhanced BDC in the Southern Hemisphere leading to a possible early final warming.
       If we look at 500hPa analogue composites for comparable easterly QBO/ El Nino 'lite' years (holding off on solar flux analogues just yet) then we see that the suggestions are that the polar vortex will have positive anomalies in December and January, before the vortex gains strength later in the winter. I would put the likelihood of an SSW at around 80% with the peak time for this to occur around early January. http://www.columbia.edu/~lmp/paps/butler+polvani+deser-ERL-2014.pdf



      It’s a little too early to suggest how exactly this will effect the troposphere until we see other data - including the updated solar flux and ENSO as well as the SAI, SCE values. But all in all, if the stratosphere behaves as we expect at this point, then tropospheric northern blocking would be favoured during the winter leading to a negative AO index and mid latitude polar episodes being experienced.
      But after last year, when the stratosphere cooled dramatically, it is best that we remain cautious and wait to see how cold the stratosphere becomes over the next 6 weeks prior to winter, and how this may subsequently affect the strength of the polar vortex.
      As ever the best sites to monitor the stratosphere and forecasts are listed below:
      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
      Analysis can be found here: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
      Previous NW stratosphere monitoring threads:
      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/
      2010/2011 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/
      Here's hoping for another exciting and intriguing season.
      PS I look forward to all the contributers on this thread. It has grown from strength to strength over the years which has helped increase our knowledge of this fascinating and important subject - and there have been a core of extremely knowledgeable contributers from both national and international quarters and I thank them all and ask them to keep the discussion coming!
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