Stratosphere Temperature Watch 2013/2014

[chionomaniac]

With winter fast approaching it is time for a new thread. It seems that the demand for a new strat thread gets earlier every year and this is the fifth winter that the strat thread will be running!

 

As ever, the first post will become both a reference thread and basic learning thread for those wanting to understand how the stratosphere may affect the winter tropospheric pattern. And then I will have a look at how we may expect the stratosphere to behave this year.

 

The stratosphere is the layer of the atmosphere situated between 10km and 50km above the earth. It is situated directly above the troposphere, the first layer of the atmosphere that is directly responsible for the weather that we receive. The boundary between the stratosphere and the troposphere is known as the tropopause. The air pressure ranges from around 100hPa at the lower levels of the stratosphere to around 1hPa at the upper levels. The middle stratosphere is often considered to be around the 10-30hPa level.

 

 

Every winter the stratosphere cools down dramatically as less solar UV radiation is absorbed by the ozone content in the stratosphere. The difference in the temperature between the North Pole and the latitudes further south creates a strong vortex – the wintertime stratospheric polar vortex. The colder the stratosphere, the stronger this vortex becomes. The stratospheric vortex has a strong relationship with the tropospheric vortex below. The stronger the stratospheric vortex, the stronger the tropospheric vortex becomes.

 

The strength and position of the tropospheric vortex influences the type of weather that we are likely to experience. A strong polar vortex is more likely to herald a positive AO with the resultant jet stream track bringing warmer wet southwesterly winds. A weaker polar vortex can contribute to a negative AO with the resultant mild wet weather tracking further south and a more blocked pattern the result. A negative AO will lead to a greater chance of colder air spreading to latitudes further south such as the UK. So cold lovers will look out for a warmer than average polar stratosphere.

 

 

The stratosphere is a far more stable environment then the troposphere below it. However, there are certain influences that can bring about changes - the stratospheric ozone content, the phase of the solar cycle, the Quasi Biennial Oscillation ( the QBO), wave breaking events from the troposphere and the autumnal Eurasion/Siberian snow cover to name but a few.

 

The ozone content in the polar stratosphere has been shown to be destroyed by CFC's permeating to the stratosphere from the troposphere but there can be other influences as well. Ozone is important because it absorbs UV radiation which creates warming of the stratosphere. The Ozone is formed in the tropical stratosphere and transported to the polar stratosphere by a system known as the Brewer-Dobson -Circulation. The strength of this circulation varies from year to year and can in turn be dictated by other influences.

 

One of these influences is the QBO. This is a tropical stratospheric wind that descends in an easterly then westerly direction over a period of around 28 months. This can have a direct influence on the strength of the polar vortex in itself. The easterly (negative ) phase is though to contribute to a weakening of the stratospheric polar vortex, whilst a westerly (positive) phase is thought to increase the strength of the stratospheric vortex. However, in reality the exact timing and positioning of the QBO is not precise and the timing of the descending wave is critical throughout the winter.

 

The direction of the QBO when combined with the level of solar flux has been shown to influence the BDC. When the QBO is in a west phase during solar maximum there are more warming events (increased strength BDC) in the stratosphere as there is during an easterly phase QBO during solar minimum.( 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)

 

The QBO is measured at 30 hPa and has entered a westerly phase for this winter. 10 out of 11 warming events that have occurred during a wQBO have occurred at a solar maximum. Even though we are seeing a quiet maximum one would expect a slightly increased chance of a warming event this 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 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 can occur by the vortex being displaced off the pole – a displacement SSW, or by the vortex being split in two – a splitting SSW.

 

 

The 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) but we will still need a kick start from the troposphere to feedback into the stratosphere. The kick start often will come from the tropics in the form of pulses of convection interacting with slight 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 can affect this - giving us the underling atmospheric 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 NH 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.

 

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 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 it appears that the reduction in Arctic sea ice may be contributing to this mechanism and this should be factored in to any forecast.

 

So what are we likely to expect this year. Well, so far we know some of the factors. There is a wQBO combined with probable ENSO neutral conditions and even though we are at a possible solar maximum, this is about half the maximum seen in recent times. However, I think that there is still a strong possibility that we will see a SSW - possibly late January or early February this winter. Using similar years analogues we can help predict the likely stratospheric conditions for this year. Unfortunately, there is a shortage of comparable years that meet the above data - but at least we can get an idea. And with another low Arctic sea ice year and early snow gain already then perhaps by the end of the month confidence can increase. Here is the predicted stratospheric height anomaly pattern for this winter at 30 hPa.

 

November

 

 

Here we see a strong central vortex beginning to build that is well established by Dec

 

December

 

 

However the height anomaly at latitudes south of the vortex suggest to me that there is some wave propagation from the troposphere - and this builds through January

 

January

 

 

before overwhelming the vortex and weakening it during February ( remember that the anomaly's are for the whole month and the vortex will have recovered somewhat from any warming episode)

 

February

 

 - Split type SSW?

 

The suggested pattern of warming at 30 hPa for January and February are as follows:

 

January

 

 

Feb

 

 

 

So, during the coming months we will need to keep an eye on all the stratospheric data.

 

Here are the links:

 

Forecasts:

 

ECM http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

 

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

 

and here: http://www.netweather.tv/index.cgi?action=stratosphere;sess=75784a98eafe97c5977e66aa65ae7d28

 

http://www.instantweathermaps.com/GFS-php/strat.php

 

Analysis here: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html

and here: http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/

 

Many papers for further reading found here: http://forum.netweather.tv/topic/73911-technical-teleconnective-papers/

 

Fingers crossed for another exciting and productive stratospheric watch this winter.

 

c

 

 

 

[simshady]

Looking forward to the thoughts of all contributors immensely! Great learning thread!

[bluearmy]

Here's to the best thread on meteorological forums. Shame we will miss stewart's input and insight but there are plenty of informed posters to make up for this.

quite a bold opening post ed and you've made a solid 'prediction' of where you think we may be headed. My attention is drawn to the canadian sector at this early stage of the season.

[chionomaniac]

Here's to the best thread on meteorological forums. Shame we will miss stewart's input and insight but there are plenty of informed posters to make up for this.quite a bold opening post ed and you've made a solid 'prediction' of where you think we may be headed. My attention is drawn to the canadian sector at this early stage of the season.

Agree with that - Stewart will be missed greatly.

 

I think that by the end of November we will see where that prediction is heading. I think that if the strat cools down less quickly than anticipated then we may even be able to bring the feedback schedule through a bit quicker. The low sea ice years 500 hpa anomaly give us a massive tropospheric headstart.

 

[phil nw.]

Great to see this seasons thread up and running Ed.

I am sure many members have been eagerly waiting for this and i am sure this will become more popular than ever thanks to your efforts over the last few years.

[Ian Brown]

Thanks for that Ed, I would just advise members not to get too obsessed the Strat or see it as a refuge to come to for future hope when we see that barrelling zonality setup.

There have been many instances of the Greenland PV refusing to yield to supposed tropospheric developments and the colder spells of last winter and spring were not necessarily what 'should' have happened, though of course we are talking about positioning of blocking and how that impacts on small mid latitude islands .

[Strider]

Thanks - this thread is very informative for all - will you update the forecasts in the OP peridocially?

 

What happened to GP?

[lorenzo]

Here's to another great season (with no Polar Vortex remnants trailing about in the Atlantic again !).

 

What looked like a month or two ago for a SSW to be a statistical improbability, and thinking that we are due a cold and vortexy Winter, things this season have echoes of last year and the SAI and Siberian High potential have ramped things up somewhat.  

 

Hopefully another season of the vortex finding setting up home problematic and providing us all with some great model watching.  The best thing about this thread is that it is one of the best learning threads on any weather forum around, so much new material and 5 months to watch it all play out.

[feb1991blizzard]

Thanks - this thread is very informative for all - will you update the forecasts in the OP peridocially?

 

What happened to GP?

 

He's left Netweather and his new job prohibits him from doing forecasts available to the public.

Here's to another great season (with no Polar Vortex remnants trailing about in the Atlantic again !).

 

What looked like a month or two ago for a SSW to be a statistical improbability, and thinking that we are due a cold and vortexy Winter, things this season have echoes of last year and the SAI and Siberian High potential have ramped things up somewhat.  

 

Hopefully another season of the vortex finding setting up home problematic and providing us all with some great model watching.  The best thing about this thread is that it is one of the best learning threads on any weather forum around, so much new material and 5 months to watch it all play out.

 

That comment deserves a +10.

[syed2878]

nice to c this thread back up an running chio. Gp's input will be mist how ever chio, lorenzo and 1-2 others will get most of us thru this up coming rolacoster ride. To lot of the new comers take a look at the links to websites and papers on the opening post by chio.

[John (Netherlands)]

Chio,

 

I've been reading your posts all those years with great interest. Will be exciting tot see how this thread and the strat will develop over the coming months. Keep up the good work!

 

John

[lorenzo]

Typhoon Wipha does a recurve as explained in some great detail here .

 

Net result is that over the course of the 10 day period North Pacific Ridge of some strength is reinforced, looks similar to the Kamchatka Peninsula feature from last year, and the troughing in the Aleutians develops. 

Potentially more wave activity to follow then and more disruption to the vortex as it starts it's winter engines.

[Suburban Streamer]

Great to see the thread back. Fingers crossed for a winter heatwave in the stratosphere.

Edited October 15, 2013 by Suburban Streamer

[Recretos]

A great new topic, and so much material to work with. And the awesome intro post by chionomaniac. 

 

I think that by the end of November we will see where that prediction is heading. I think that if the strat cools down less quickly than anticipated then we may even be able to bring the feedback schedule through a bit quicker. The low sea ice years 500 hpa anomaly give us a massive tropospheric headstart.

 

Low sea Ice Jan- March.png

 

That composite speaks for itself, but you have to keep in mind that there is much more to those years than just the low sea ice, like the oceans. So if I could rephrase that sentence, I would say "The current AMO/PDO combination 500 hpa anomaly give us a massive tropospheric headstart".  Of course among many other things, but keeping the main players in mind. Also realizing that the PDO and AMO are the "gatekeepers" to the Arctic. Too bad the sea ice data goes only back to 1980, because it would be interesting to see a correlation of these two cycles and the sea ice, for at least 100 years back.  

 

For example: Comparison of the last 3 great ocean cycle swings. 

50-75= Cold PDO / Warm AMO

80-98= Warm PDO / Cold AMO

99-12= Cold PDO / Warm AMO (as 50-75)

 

That would be all for now.

 

Best regards.

Edited October 15, 2013 by Recretos

[chionomaniac]

A great new topic, and so much material to work with. And the awesome intro post by chionomaniac. 

 

 

That composite speaks for itself, but you have to keep in mind that there is much more to those years than just the low sea ice, like the oceans. So if I could rephrase that sentence, I would say "The current AMO/PDO combination 500 hpa anomaly give us a massive tropospheric headstart".  Of course among many other things, but keeping the main players in mind. Also realizing that the PDO and AMO are the "gatekeepers" to the Arctic. Too bad the sea ice data goes only back to 1980, because it would be interesting to see a correlation of these two cycles and the sea ice, for at least 100 years back.

 

For example: Comparison of the last 3 great ocean cycle swings. 

50-75= Cold PDO / Warm AMO

80-98= Warm PDO / Cold AMO

99-12= Cold PDO / Warm AMO (as 50-75)

 

That would be all for now.

 

Best regards.

Interesting that the last cycle shows no negative anomaly areas though Recretos - so one would think that there is more at play here - hence the difference being the low sea ice link?

 

Oh and to edit - love the phrase the 'gatekeepers'.

Edited October 15, 2013 by chionomaniac

[Gael_Force]

Interesting that the last cycle shows no negative anomaly areas though Recretos - so one would think that there is more at play here - hence the difference being the low sea ice link?

 

Oh and to edit - love the phrase the 'gatekeepers'.

 

Would that not be because the base period for climate is the most recent and the warmest; 1950 - 1975 would probably not have the same negative anomalies when referenced to the appropriate base.

 

Thanks for the great opening post - my favourite topic on here.

Edited October 15, 2013 by Gael_Force

[chionomaniac]

Would that not be because the base period for climate is the most recent and the warmest; 1950 - 1975 would probably not have the same negative anomalies when referenced to the appropriate base.

 

Thanks for the great opening post - my favourite topic on here.

Yes and no. I was in particular referring to the the last phase which was from 1999-2012 against the climatological mean of 1981 -2010. I would expect over the whole NH to have areas of positive anomalies and negative anomalies similar to 1950-1975, even allowing for the change in base state. With the composite building site still out of bounds I can't have a play around to demonstrate this. If the climatology comparison was using the years 1950-2010 I don't think the composites would look too different - though I could be wrong without checking.

Edited October 15, 2013 by chionomaniac

[snowking]

I know this blog has been referred to a number of times already:

 

http://torontowxcenter.blogspot.co.uk

 

Of particular interest (http://torontowxcenter.blogspot.co.uk/2013/10/late-winter-stratospheric-warming-likely.html):

 

 

Confidence continues to stay high with regards to a warm DEC in the east with a wet and cool pattern in the west. Analogs and modelling continue to stay in decent agreement. In sharp contrast, JAN-March looks increasingly interesting across the eastern CONUS. Looking back at +QBO, Low Solar and neutral ENSO years (85-86,90-91, 80-81 and 01-02) I found that in all cases their have been at least one late winter stratospheric warming event. With the expected warming ENSO state things could get very interesting in late winter and early spring if warmth can work its way down to 500mb. With an overall state of low solar continuing, this winter should be no different then the analog years with late winter EAMT events helping disrupt the upper stratospheric vortex. 

 

 

Tends to back up the general thoughts from many on here so far. 

 

And if we take a look at the composite years chosen there:

 

 

The general idea is of a late January/Early February potential SSW, with 85/86 being the odd one out (and a little bit of a curveball generally I feel).

 

If we take a look at two of our other discussed analog years, 08/09 and 78/79:

 

 

(The data doesn't quite go back to 1978/79, but as you can see by the time we get to February 1979, an SSW has already taken place)

 

So this is where the general idea of a potential SSW during the second half of this winter comes from, and it may well be a case of having to be rather patient until then without a few surprises.

 

SK

[phil nw.]

Taken from the Tokyo centre shows the cooling vortex at 30hPa

 

 

 

cooling around the average for this point in Autumn.

Latest models reflecting this with a more influencial 500hPa vortex developing Atlantic mobility.

 

 

[feb1991blizzard]

Taken from the Tokyo centre shows the cooling vortex at 30hPa

 

tlat_t30_nh.gif  pole30_nh.gif

 

cooling around the average for this point in Autumn.

Latest models reflecting this with a more influencial 500hPa vortex developing Atlantic mobility.

 

There is just the minutest of spikes on that North pole chart, lets hope that becomes a massive spike in the coming days.

[Snowy L]

I was feeling optimistic about an SSW this winter with us being at solar maximum with a west QBO (SSWs are more common under these conditions than in an east based QBO during solar minimum). However, the solar cycle has been very weak this year and it's gone against predictions of a maximum this year. 2011 is now considered to be the maximum and in fact we've seen a sharp drop in sun spot counts to levels last seen in the mid 2000s in the last few weeks.

 

Snow is advancing nicely below 60 degrees and we've already seen a few wobbles in the temperature profile in the stratosphere. I'm hoping we will see a minor warming or 2 to give us a shot at a cold spell in late November/December. Wave-1 activity is set to increase in the next few days, but while it will give a warming it doesn't look like anything too strong and I doubt it will disrupt the vortex too much,

Edited October 15, 2013 by Snowy L

[Yarmy]

I was feeling optimistic about an SSW this winter with us being at solar maximum with a west QBO (SSWs are more common under these conditions than in an east based QBO during solar minimum). However, the solar cycle has been very weak this year and it's gone against predictions of a maximum this year. 2011 is now considered to be the maximum and in fact we've seen a sharp drop in sun spot counts to levels last seen in the mid 2000s in the last few weeks.

 

Snow is advancing nicely below 60 degrees and we've already seen a few wobbles in the temperature profile in the stratosphere. I'm hoping we will see a minor warming or 2 to give us a shot at a cold spell in late November/December. Wave-1 activity is set to increase in the next few days, but while it will give a warming it doesn't look like anything too strong and I doubt it will disrupt the vortex too much,

 

Solar max is a somewhat nebulous arithmetic concept anyway: where's the max here?

 

 

Rest assured we are in the current year(s) of peak activity. The poles have flipped recently as we can see here:

 

 

I'm pretty dubious about solar-climate connections to be honest, especially at the short range.

[Recretos]

Interesting that the last cycle shows no negative anomaly areas though Recretos - so one would think that there is more at play here - hence the difference being the low sea ice link?

 

Oh and to edit - love the phrase the 'gatekeepers'.

 

Oh snap. Cant believe that I forgot to address that. 

Of course that also got my attention, as soon as I made those composites a year and a half ago. After some research, I got down to a few points that I think are worth considering:

 

1.- Pre satellite era - data.

The data in that period might be somewhat less reliable than after 1980 when the satellite era began. All the surface data gathered from land observation is accurate, so we can get quite accurate ideas about the patterns above or near the landmasses (proportional to the data available), especially when reconstructing patterns that correspond to to the classical configuration, like NAO, PNA, EPO, WPO, AO, negative and positive phases. So I have no doubt at all in the accuracy of the basic patterns.

The problem are areas out in the middle of nowhere and tropics. There are ship and some buoy data, but it is slightly harder to accurately reconstruct the patterns without some specific configurations. And the areas that are unaffected or less affected by NAO, PNA for example. And of course because there are more drivers than just the PDO and AMO, there are other possible influences for the negative anomalies. Tho I still don't believe that such widespread deep negative anomalies would exist near or at the tropical belt. Which leads me to my second point.

As you can see on the composites, with 1980 on, there are no more widespread negative or positive anomalies anomalies. The overall picture is much less noisy. 

 

2.- Dataset errors.

I remember when I was doing some reanalysis for the march pattern. I came across a few days in the 60' ( I think 65 and 62), that had dataset errors. Large widespread negative anomalies, going below -2000, with normal positive anomalies. If there is one or two days like this, it doesn't mean much, but when you have around 10 or 15, the anomalies can have significant influence on the overall picture. 

I also made a few composites with the ECMWF ERA reanalysis dataset, and surprisingly enough, there are some negative anomalies, but not like in the NCEP dataset. 

Climatology doesn't really have any effect. Anomalies are just departure of the mean from the norm. So regardless how you change the norm, the mean values are always the same. So the only thing you can change with the climatology, is the distribution of the blue and red colours.

 

These are two main points to consider before even starting to look at linkage with other factors. I hope I answered your question.

You did gave me something to think about, and I will look into it again, as soon as the USA federal sites get back online. These composites were originally made in march 2012 I think. There were some changes to the dataset since then.

----------------------------------------------------------------------------------------------------------------------------------------------------

 

To get back on topic. Good post by SK.

Again, I really wish that the NOAA sites get back up a.s.a.p., and we can dig into reanalysis and data search again.

 

When looking at those temperature charts, the idea seems to be there. So I am going to add the corresponding vertical mean cross-sections. 

 

 

And this year so far:

 

So far, the 01/02 situation seems "close" to what we have now, but to be realistic, that warming event was basically useless, and not even a downweller (like the classic 81 and 91 events), which serves as a reality check in the great world of the stratosphere and cold shots.

 

About the current situation. A powerful rossby wave (successively through the typhoon re-curve, as it was nicely pointed out just before) emerging in the troposphere, and having its implications all the way to the lower-mid stratosphere. And of course the corresponding wave1 activity we can see on the ECM charts. The issue I have with this, is that it leaves the main vortex slightly off, but it is still mainly intact and free to cool down and deepen. We are in the time of the year where the vortex get stronger by the day. This rossby wave will probably drop off soon after, giving the vortex some more free time to get its act together. Maybe some Eurasic shots after that?  

 

 

 

 

I'm pretty dubious about solar-climate connections to be honest, especially at the short range.

 

 

Well, in an interactive system like the BDC (refer to the great intro post by chionomaniac for more details), you better believe in its influence. Not to mention the solar role in the whole energy budget.  And of course keeping in mind that short range on a climate level is not really the same as the short range on the "local weather" level.

 

Best regards.

[Don]

 

So far, the 01/02 situation seems "close" to what we have now, but to be realistic, that warming event was basically useless, and not even a downweller (like the classic 81 and 91 events), which serves as a reality check in the great world of the stratosphere and cold shots.

 

 

Well if we get a Winter similar to 2001/02 there will certainly be very little to cheer about from a coldie's perspective!

[bobbydog]

Well if we get a Winter similar to 2001/02 there will certainly be very little to cheer about from a coldie's perspective!

 

he is only referring to one particular warming though. a singular event. remember that no two winters are the same