Stratosphere Temperature Watch 2014/2015

[mountain shadow]

I remember a time when the two graphs below would have caused great excitement on this thread,with those temperatures shooting up over the pole.

 

pole10_nh.gifpole30_nh.gif

 

 

I also remember a certain Mr Holmes would predict a cold spell about 25 days after a big spike in 30 hpa temperatures....

Is this for real?

 

Surely this is extremely significant?

 

Spike in temps, also showing from this NOAA link..

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/30mb9065.gif

Edited January 7, 2015 by mountain shadow

[Ninman]

Is this for real?

 

Surely this is extremely significant?

 

Spike in temps, also showing from this NOAA link..

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/30mb9065.gif

 

I would have thought it would have some impact, although looking at the charts it doesn't seem to be of any real benefit to the UK in the near term. As mentioned before, the PV tries to get is act back together, but is clearly at a weak state; the GFS has another split of the PV forming in the last week of January.

 

I would think that if the PV had not been forcecast to re-establish itself so quickly then this would have allowed a better evolution of the Trop pattern to emerge and aid HLB.

[bluearmy]

i'm astounded by the reaction to a chart that has been forecast for the past ten days.  some on here really cant be bothered to open the links provided and look at the data.

 

its not a SSW. 

 

i did wonder if JH would be on to make the comment re the 30hpa spike when it verified. three wekks down the line ? could be right !

[johnholmes]

i'm astounded by the reaction to a chart that has been forecast for the past ten days.  some on here really cant be bothered to open the links provided and look at the data.

 

its not a SSW. 

 

i did wonder if JH would be on to make the comment re the 30hpa spike when it verified. three wekks down the line ? could be right !

 

not had a look yet ba, but there is some evidence I found over several years for a time scale of 10-20 days or so and private pm's with GP suggested there seemed to be something in it. Mind you like everything else it does not work all the time. Anyway thanks for commenting and I will take a look if I can find my link whci seems to have gone AWOL at the moment!

[Recretos]

If there are any more significant interactive effects of the trop/strat activities, I will be (or should be) able to track it down in my 3D wider spectrum analysis.

Edited January 7, 2015 by Recretos

[johnholmes]

a quick look back at data I used at times suggests that the NOAA 8-14 IF the 30mb is having any effect should show something approximately between 4th (gone already) and 12-15th=valid for  20th-23rd??

Who knows time wil ltell as I often say!

[Cloud 10]

The temperature rises at 10hpa and 30 hpa have been well advertised from the stratosphere forecasts over the last couple of weeks but have failed to give the "holy grail" official Sudden Stratosphere Warming.

 

10 hpa..  30 hpa..

 

 

Nevertheless,a significant warming has/is taking place which has split the Polar Vortex,if only fairly briefly before it reforms.....

 

http://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-2.93,84.73,512

 

 

Only time will tell whether or not the warming will have further effects on the Troposphere towards the month end and beyond.

 

 

[Interitus]

 

its not a SSW. 

 

 

 

Not a major SSW due to lack of wind reversal but it could be considered a minor SSW - it satisfies the WMO criteria with temperature rise >25 degrees within a week - the MERRA 10mb pole temperature rose from 199.87 to 228.54K in seven days from 26/12/14 to 2/1/15. As can be seen in the Berlin charts at the moment it also satisfies the more general 60-90°N reversed temperature gradient of Andrews et al.

[nick sussex]

Not a major SSW due to lack of wind reversal but it could be considered a minor SSW - it satisfies the WMO criteria with temperature rise >25 degrees within a week - the MERRA 10mb pole temperature rose from 199.87 to 228.54K in seven days from 26/12/14 to 2/1/15. As can be seen in the Berlin charts at the moment it also satisfies the more general 60-90°N reversed temperature gradient of Andrews et al.

Yes its definitely a minor SSW , I think for newer members it would help if this thread would just differentiate between major and minor warmings.

 

This current warming clearly satisfies those conditions for a minor event , regardless of whether it has a big impact it has happened.

[phil nw.]

Yes I noted the minor warming and based on previous years these usually result in some slow down in zonal wind speeds for a short while.

We usually see some tropospheric response with buckling/ridging of the NH jet so maybe interest for us later in the month which is already being signposted in later gefs.

A major warming I always believed is a much bigger temp.rise so that we see zonal wind reversal at 10hPa around 60N.with consequently a much bigger impact on the vortex ie,shredding,a little later.

We still await the biggy but a few minor warmings at least help to undermine the prospect of endless zonality.

[Recretos]

10 day temperature change. Impressive.

 

Its meant to say 28/12/14, not 15. A typo.

Edited January 7, 2015 by Recretos

[chionomaniac]

I would say that we are seeing a minor stratospheric warming - the confusion on here is exactly why the classification process is being looked at again this year! For me, SSW is wind reversal at 10hPa and 60N which is not occurring and that shouldn't be used to describe this current warming.

[Relativistic]

I hate to interrupt the interesting discussion that's going on here but I am hoping someone can help me.

 

I am currently a first year physics student, and over my Christmas break I was set the task of writing 1500 words about any topic in physics. I used to read these threads a couple of years ago and given how interesting the subject is, as well as how much physics it involves, I thought SSW's would be a perfect subject to write about. Having skimmed through these threads and various scientific papers to regain my (rather basic) understanding, I have now almost finished the assignment, only there is one thing that I need clearing up before I finish it, and I know you probably get sick of this but I was hoping one of the knowledgeable posters on here could help me.

 

In the introduction of this paper (http://www.atmos.washington.edu/~dennis/Limpasuvan_etal_2003.pdf) on the first page (top of second column), it talks about how wave dissipation decelerates the westerly zonal flow, which then bounces back again due to a meridional flow anomaly. Now here is my question: what is it that causes zonal winds to reverse during a SSW, if winds bounce back like this? I thought it could be that the adiabtic heating in the stratosphere after this bounce-back, if big enough to cause a SSW, may actually reverse the temperature gradient between the pole and the equator, which combined with the Coriolis effect causes the zonal winds to reverse direction? Or is it just from really intense wavebreaking that so much westward momentum can be imparted on them that they actually reverse?

 

Sorry for such a long post. I would be extremely grateful if anyone could help me out here.

 

Thanks to everyone who contributes to this thread by the way. This assignment has rekindled my interest in the subject and I'm sure now I'll continue to follow this thread and learn from it  

[JeffC]

and you can see temperature difference here http://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=-24.41,94.29,327

[feb1991blizzard]

Another warming in deep FI on the GFS showing up top, what do the experts make of it?, I know its hard to take seriously given the erratic output lately but is there any reason to believe it could verify? could it end up significant enough to deliver the knockout blow to the vortex? is there anything forecast that teleconnects to it well - ie- mountain torque event etc?, and ultimately could any trop blocking set up favourably to deliver cold to NW Europe?

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015010806&var=HGT&lev=1mb&hour=384

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015010806&var=TMP&lev=1mb&hour=384

 

 

 

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015010806&var=HGT&lev=10mb&hour=384

 

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015010806&var=HGT&lev=30mb&hour=384

[Woollymummy]

Excuse the question please if it is obvious, but do the above charts show that the main vortex is gradually shifting across the NH from the Canadian side to the Russian side, meaning that even if it is not split there will be a significant change in the patterns of weather systems affecting the UK?

Edited January 8, 2015 by Woollymummy

[chionomaniac]

I hate to interrupt the interesting discussion that's going on here but I am hoping someone can help me.

 

I am currently a first year physics student, and over my Christmas break I was set the task of writing 1500 words about any topic in physics. I used to read these threads a couple of years ago and given how interesting the subject is, as well as how much physics it involves, I thought SSW's would be a perfect subject to write about. Having skimmed through these threads and various scientific papers to regain my (rather basic) understanding, I have now almost finished the assignment, only there is one thing that I need clearing up before I finish it, and I know you probably get sick of this but I was hoping one of the knowledgeable posters on here could help me.

 

In the introduction of this paper (http://www.atmos.washington.edu/~dennis/Limpasuvan_etal_2003.pdf) on the first page (top of second column), it talks about how wave dissipation decelerates the westerly zonal flow, which then bounces back again due to a meridional flow anomaly. Now here is my question: what is it that causes zonal winds to reverse during a SSW, if winds bounce back like this? I thought it could be that the adiabtic heating in the stratosphere after this bounce-back, if big enough to cause a SSW, may actually reverse the temperature gradient between the pole and the equator, which combined with the Coriolis effect causes the zonal winds to reverse direction? Or is it just from really intense wavebreaking that so much westward momentum can be imparted on them that they actually reverse?

 

Sorry for such a long post. I would be extremely grateful if anyone could help me out here.

 

Thanks to everyone who contributes to this thread by the way. This assignment has rekindled my interest in the subject and I'm sure now I'll continue to follow this thread and learn from it  

It's a baroclinic collapse from the top down.

[Recretos]

what is it that causes zonal winds to reverse during a SSW, if winds bounce back like this? I thought it could be that the adiabtic heating in the stratosphere after this bounce-back, if big enough to cause a SSW, may actually reverse the temperature gradient between the pole and the equator, which combined with the Coriolis effect causes the zonal winds to reverse direction? Or is it just from really intense wavebreaking that so much westward momentum can be imparted on them that they actually reverse?

Sorry for such a long post. I would be extremely grateful if anyone could help me out here.

Chiono was short and precise. But I will also add my 2 cents.

I am no physician by any means, so I can only try to explain it in layman terms.

I am going to extend this so it also might be a simple crash course in strat wind zonality for others too. It is something I explained before, but oh well, I have a few minutes to spare.

In laymans terms:

The wind reversal simply follows the change in geopotential heights. Basically you have to look at geostrophic wind since the pressure gradient force is being changed due to the warming and geopotential waves which alter geostrophic balance, and you need to look at ageostrophic (wind) flux fields since Coriolis is in play, and ageostrophic flux is also induced by wave-breaking.

In more laymans terms:

When we say reversal of the wind, we do not mean exact 180° reversal from 100% west flow, to 100% east.

In even more laymans terms:

Every wind has momentum components. They are zonal (W-E) and meridional (N-S) component. For example, an exact SW wind has the same zonal and meridional component.

This graphic show it nicely. The v is the meridional component, and u is zonal component. This means that this SW wind basically moves towards east and north at the same time, having a west and north momentum to it. And that movement is in meters per second. Which means that the wind that moves Xm/s towards NE, moves a certain %ofX towards east and a certain %ofX towards north. So the more straight that the wind blows, the stronger the zonal component. Or the more N or south it blows, stronger is the meridional component.

So basically when we are talking about zonal winds in the stratosphere, or the SSW reversal, we are not talking about winds blowing in a straight line from west to east, or east to west. We are talking about zonal momentum component of the wind fields. Or more exact, the zonal average along the 60N lat line (average zonal component).

In even more and more laymans terms:

If we look at this graphic, we can see the zonal wind component at 10mb. I am using a random GFS run and fcst time.

This is the average zonal component (what we look at also on FU Berlin) that corresponds to the map above. It basically shows the average zonal component along the latitude lines.

We can see the reduction of average positive zonal component at 10mb between 30N and 45N. This does not mean the wind there is weaker in general, but if you look at the chart above, you can see there is a blob of negative zonal component (easterly), which affects the average along that longitude.

Now why is there a blob of negative zonal momentum? Well, we can answer that by looking at the geopotential heights and zonal component combined. The answer is a stratospheric high, or more precisely a wave 2 high. We all know in what direction the highs and lows turn.

You can see the zonal component is weaker where the isohypses are turning more N-S and stronger where they are straight. Note that this is not the actual wind speed, but only shows how strong is the zonal (west-east) component of the actual wind speed.

And this is the actual wind and I added wind vectors:

Next in line is ageostrophic wind flux, pretty much induced by wave breaking processes. Notable is the tropical wave breaking / wave dissipation.

Now. Why is all this important? Well, because now we are going to look at an actual SSW and analyse it. And no better example as the 2009 SSW.

The obvious is the zonal components and geopotential height at 10mb. The polar high is established, and there is naturally now the negative zonal momentum around it, since the wind blows clockwise around an anticyclone. And that is pretty much why the winds get reversed.

In zonal average, the north hemisphere was nicely reversed up into the mesosphere.

And that concludes this lesson on zonal wind.

Regards

p.s.: Since you are a future physicist, let me give you an advice on physics as a total amateur / non-physicist:

At least by my experience, physics

(or at least meteo physics) are 80-90% (if not 100%) pure logic. So just try and look at it in a simple way and dont overcomplicate it (like I sometimes do when I try to explain something ). I cant solve equations, but I understand why some things happen the way they do in weather. I am the kind of guy that has a big imagination, and that sees force vectors in a lot of things when doing certain stuff or observing something that involves physics (pretty much anything).

Edited January 8, 2015 by Recretos

[Interitus]

I would say that we are seeing a minor stratospheric warming - the confusion on here is exactly why the classification process is being looked at again this year! For me, SSW is wind reversal at 10hPa and 60N which is not occurring and that shouldn't be used to describe this current warming.

That is fair enough, but until there is an all encompassing classification I don't see what the problem is with a major/minor distinction particularly with regards to possible ensuing effects. To repeat what has been said before (with the hesitation to imply causation) the cold spell of Jan/Feb 2012 followed a minor warming, as did the memorable spell of Feb 1991 and notably Feb 1986 which with the 5th lowest February CET was colder than Dec 2010.

Anyway, to get a further idea of the scale of the recent warming, here are some more analogues based upon MERRA 10mb 60-90°N temperature over the 15-day period to 5/1/15 (point zero on the x-axis) -

Recretos' plot showed the warming focused on the Atlantic side but even averaged over the polar cap the graph shows a marked warming (although unclear it was second warmest at day 0).

The next graph shows what this means in terms of windspeed at 10mb 60°N -

The six analogue years all drop to below 3 m/s at some point in the following fortnight and four record a major SSW, with a minimum mean windspeed of just 0.52 m/s at 14 days. However, though this year did meet another criteria for minor warming with a windspeed between 0 and 20 m/s as used by Sjoberg and Harnik, it was already showing signs of recovery.

Sjoberg and Harnik used the metric in their examination of the amount of forcing required for major SSW and how this might compare for minor warmings, with the conclusion that the duration is more significant than peak wave flux alone -

http://journals.ametsoc.org/doi/full/10.1175/JAS-D-11-0195.1

Looking at a graph of 10mb wave 1 height shows immediately that the forcing in the present warming may have just tailed off too soon -

Edited January 8, 2015 by Interitus

[chionomaniac]

Well done Recretos - I didn't have enough time 

[JeffC]

Chiono was short and precise. But I will also add my 2 cents.

I am no physician by any means, so I can only try to explain it in layman terms.

I am going to extend this so it also might be a simple crash course in strat wind zonality for others too. It is something I explained before, but oh well, I have a few minutes to spare.

In laymans terms:

The wind reversal simply follows the change in geopotential heights. Basically you have to look at geostrophic wind since the pressure gradient force is being changed due to the warming and geopotential waves which alter geostrophic balance, and you need to look at ageostrophic (wind) flux fields since Coriolis is in play, and ageostrophic flux is also induced by wave-breaking.

In more laymans terms:

When we say reversal of the wind, we do not mean exact 180° reversal from 100% west flow, to 100% east.

In even more laymans terms:

Every wind has momentum components. They are zonal (W-E) and meridional (N-S) component. For example, an exact SW wind has the same zonal and meridional component.

This graphic show it nicely. The v is the meridional component, and u is zonal component. This means that this SW wind basically moves towards east and north at the same time, having a west and north momentum to it. And that movement is in meters per second. Which means that the wind that moves Xm/s towards NE, moves a certain %ofX towards east and a certain %ofX towards north. So the more straight that the wind blows, the stronger the zonal component. Or the more N or south it blows, stronger is the meridional component.

So basically when we are talking about zonal winds in the stratosphere, or the SSW reversal, we are not talking about winds blowing in a straight line from west to east, or east to west. We are talking about zonal momentum component of the wind fields. Or more exact, the zonal average along the 60N lat line (average zonal component).

In even more and more laymans terms:

If we look at this graphic, we can see the zonal wind component at 10mb. I am using a random GFS run and fcst time.

This is the average zonal component (what we look at also on FU Berlin) that corresponds to the map above. It basically shows the average zonal component along the latitude lines.

We can see the reduction of average positive zonal component at 10mb between 30N and 45N. This does not mean the wind there is weaker in general, but if you look at the chart above, you can see there is a blob of negative zonal component (easterly), which affects the average along that longitude.

Now why is there a blob of negative zonal momentum? Well, we can answer that by looking at the geopotential heights and zonal component combined. The answer is a stratospheric high, or more precisely a wave 2 high. We all know in what direction the highs and lows turn.

You can see the zonal component is weaker where the isohypses are turning more N-S and stronger where they are straight. Note that this is not the actual wind speed, but only shows how strong is the zonal (west-east) component of the actual wind speed.

And this is the actual wind and I added wind vectors:

Next in line is ageostrophic wind flux, pretty much induced by wave breaking processes. Notable is the tropical wave breaking / wave dissipation.

Now. Why is all this important? Well, because now we are going to look at an actual SSW and analyse it. And no better example as the 2009 SSW.

The obvious is the zonal components and geopotential height at 10mb. The polar high is established, and there is naturally now the negative zonal momentum around it, since the wind blows clockwise around an anticyclone. And that is pretty much why the winds get reversed.

In zonal average, the north hemisphere was nicely reversed up into the mesosphere.

And that concludes this lesson on zonal wind.

Regards

p.s.: Since you are a future physicist, let me give you an advice on physics as a total amateur / non-physicist:

At least by my experience, physics

(or at least meteo physics) are 80-90% (if not 100%) pure logic. So just try and look at it in a simple way and dont overcomplicate it (like I sometimes do when I try to explain something ). I cant solve equations, but I understand why some things happen the way they do in weather. I am the kind of guy that has a big imagination, and that sees force vectors in a lot of things when doing certain stuff or observing something that involves physics (pretty much anything).

I think I need a paracetamol now...my brain aches

[johnholmes]

this link may be relevant for in here?

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf

[feb1991blizzard]

Judah Cohen's page on Aer.com has updated. Not sure if he means the cold could get this far west though?

 

 

The longer-term prospects for the AO are complex for a few reasons. Typically following a SSW, the AO turns more negative in the lower stratosphere and eventually throughout the troposphere within 2 weeks. However, given that this warming was a minor SSW and that the vortex will be slow to recover, the transition to a tropospheric negative AO likely will be delayed, potentially until week 4. In terms of tropospheric forcing influencing the AO this period, current tropical convection across the Maritime Continent is anticipated to move into the western Pacific but then possibly weaken. The current convection pattern promotes a warm signal for much of North America and a positive NAO for Europe into weeks 2 and 3 (there is a 8-14 day lag in the signal based on the literature). Thereafter, if the convection does indeed weaken, the impact of the tropics on the polar jet stream will weaken and thus allow the AO to shift to more neutral conditions. Thus, we foresee that the AO should average near neutral or slightly positive for week 3 and part of week 4 before turning more negative with the downward influence of the SSW.

Sensible weather impacts for the long term will be a progressive flow pattern across the hemisphere and overall variable temperature regimes. Models continue to show mild to potentially warm conditions across North America and much of Eurasia for week 3. Colder air should begin to seep into northern Europe and Asia during the end of week 3 and into week 4. This change is typical of AO regime changes to a negative phase – i.e., the cold air typically enters Eurasia first with a dip in the jet and then changes in the jet stream occur downstream

 

 

 

http://www.aer.com/science-research/climate-weather/arctic-oscillation

Edited January 8, 2015 by feb1991blizzard

[Recretos]

Interitus mentioned 3 examples above. 2012, 1986 and 1991. 

 

Lets have a look, shall we.

 

1986;
A quick overview: The strat warming was there, but the real effect was nothing more than a North America ridge, to be exact. Tho that ridge had its role down the line, the real kicker in this animation comes from the E Europe ridge that is tropospherically driven, and that kicks up really strongly and even almost instantly leaves a good wave bumb at 30mb, and a bit later even at 10mb (not shown on this animation, but I did check it out). So via the feedback from this wave, the mid strat vortex bounces and aides in creating the cold spell down in the trop, where the vortex core moved more over Scandinavia via the help of the N pacific ridge. Near the end of the animation you can also see the trop vortex splitting via the new Atlantic/Azore ridge, and with some delay the 30mb level goes into wave 2 mode. All in all, this was a period of more tropospheric dominance rather than stratospheric.

 

http://youtu.be/5O_rB99toYM

 

 

1991: 

Well. A big mess, to put it simply.

On a quick glance again, the warming was again on the outskirts of the vortex, on the Asian side into Pacific, aiding a ridge formation over NA/Alaska. Meanwhile you can see a small ridge bumb being created at 30mb over Atlantic on 17. and 24.01, created by the Atlantic ridges a few days earlier.

The Atlantic ridge persisted as the natural wave response, ultimately splitting trop vortex and soon at 30mb via wave2 attack. The Atlantic side of the strat vortex, free from the wave bounds quickly re-intensified, sending the response down to the trop, creating a strong cyclonic area, and via wave response helping to further intensify a menacing Atlantic/Azore ridge which bumped up and completely splited the trop vortex and up into the strat and the game continued. The rest is history.

 

Of note is how the vortex "stabbed" itself in the beginning of February with that Azore ridge.

 

http://youtu.be/XKeb00iUDoo

 

 

2012:

Boy is this one an even bigger mess. To note before start, the vortex both in the strat in trop is more organised, and in at 30mb a bit less prone to effects from tropospheric Atl. ridging like the two examples above, which were constantly affecting it with every cycle almost.

Starting out notable is the warming combined with strong pacific strat high, creating a ridge over NA, and via wave response an Atlantic/Azore ridge. The game continued with re-intensified strat Pacific highs pressuring the vortex and in the process pressuring and elongating the trop vortex aswell, and creating NA ridging, and down the line more Atlantic/Azores ridges.

With the aid of further warming and this ridging game, the trop vortex broke into a wave 3 pattern, partially "disconnecting" from the strat vortex, but also soon reflected in the strat with a wave 3 pattern, which gave a feedback down again when the core in the strat resettled and briefly intensified and reconnected with the trop core, also in the process stabbed itself with an emergent Azore ridge created in the troposphere that went fast back up into strat, and also bringing the frigid temps into central Europe. After this, the vortex was driven by the trop processes.

 

http://youtu.be/NZhGq9WGHwA

 

 

summa summarum

Pretty much a game of back and forward, like it always is, between the trop and the strat. These animations just simply show it more nicely.

 

I created a brand new color table for the last video, to better show ridging. 

 

So please give me some feedback, which color table looks better. The one on the top two videos or the last one.

 

Data is from the ECMWF ERA-Interim dataset.

 

Regards.

 

Edit: Added zonal height means to each year, which show, like the animations, that 2012 was the only year with a stronger strat involvement.

Edited January 8, 2015 by Recretos

[Cleeve Hill]

For those that follow Michael Ventrice on Twitter he has recently commented on the strat warming in the Atlantic. He refers to it as off the scale. Sigma 3 model at at 1900hrs 8th jan. Of interest guys ?