Stratosphere Temperature Watch 2014/2015

[chionomaniac]

Thanks skin. Funny enough, I registered and was accepted yesterday to belong to the discussion group. Will be good to get the SSW ambiguity sorted once and for all.

[karyo]

The top - middle  strat looks like it will be cooling now so the best we can hope for between now and the first third of Feb in my opinion is that some sort of 2 wave trop pattern can at least stave of any downwelling of the re strengthening vortex up top and buy us some more time and have another go later on, Glory A of course would be a load of sliders followed by the end of GFS(p) FI and we get the scandi high first time around (outsider of course).

 

EDIT : first day for ages today that I never even looked at the Berlin charts, I as nothing posted here then I guess they didn't take your breath away!

The most noticeable thing for me currently is the warming in the European sector which lasts for a few days before easing and the vortex restrengthens.

[bluearmy]

Thanks skin. Funny enough, I registered and was accepted yesterday to belong to the discussion group. Will be good to get the SSW ambiguity sorted once and for all.

 

we await the photo of you and dr cohen having lunch  !

[Recretos]

As far as major SSW goes, anything less then a mean reversal of the zonal wind component is not accepted by me.

Chio, where have you registered? I would like to try too.

[chionomaniac]

As far as major SSW goes, anything less then a mean reversal of the zonal wind component is not accepted by me.

Chio, where have you registered? I would like to try too.

PMed you

[Lacking Geopotential]

I asked ed with whether the qbo would be changing to a westerley phase by the end of the year to one of the members and they seemed to reckon it would, now I checked the site which deals with the qbo data and it went more negative over December. Was wondering whether the qbo change is still on?

 

http://www.geo.fu-berlin.de/met/ag/strat/produkte/qbo/qbo_wind.jpg

 

I'm not 100% certain of the full definition of a westerly qbo, but the above (found here: http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/qbo/) would indicate that a westerly phase has already started at the top of the strat.

[karyo]

I guess next winter we will have a westerly QBO like last year...

[summer blizzard]

I asked ed with whether the qbo would be changing to a westerley phase by the end of the year to one of the members and they seemed to reckon it would, now I checked the site which deals with the qbo data and it went more negative over December. Was wondering whether the qbo change is still on?

QBO is still easterly where we need it to be and will change in summer probably as the westerly QBO downwells (could be good for summer if EL Nino hangs around).

[feb1991blizzard]

Another warming underway again.

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015011218&var=TMP&lev=1mb&hour=384.

 

 

A few runs lately have shown a shift of the vortex way to the East, not a million miles away from a reversal surely.

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015011218&var=HGT&lev=1mb&hour=384

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015011218&var=HGT&lev=10mb&hour=384

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2015011218&var=HGT&lev=30mb&hour=384

 

The question is can we maintain this on the next few runs.

 

 

[feb1991blizzard]

That displacement event still showing on the 0z.

 

 

EDIT : and it looks like its there on the parallel as well.

Edited January 13, 2015 by feb1991blizzard

[karyo]

QBO is still easterly where we need it to be and will change in summer probably as the westerly QBO downwells (could be good for summer if EL Nino hangs around).

And a poor winter 2015/6

That displacement event still showing on the 0z.

 

 

EDIT : and it looks like its there on the parallel as well.

I wonder how that can translate in the troposphere if it verifies.

[Recretos]

This is not the point.

 

I am still left with the question whether the geopotential height pattern in the troposphere affects the height of the geo's in the stratosphere

 

Well of course it does. It is all connected, tho the reflection is not 100% as you may know. 

 

But first, just to clarify that temperature question a bit more. Yes, generally and globally the temperature and temperature gradients do run the weather more or less, but in the strat where the changes are relatively fast and "localized" different rules apply. Besides, The pressure gradient force drives the wind in the first place. The warming could not reduce the wind when the pressure pattern doesn't favour it. If you would understand what me and Chiono replied to 22nov, regarding his question on wind reversal, you would not be questioning why the zonal mean was not reversed in the first place.

 

As far as you second question on the trop pattern preventing an SSW. I made an animation of December 2014. 150mb level on the bottom, 30mb above, and the -40C isosurface. 

Not much to say, except how the troposphere seemingly drove the 30mb plane or the low-mid strat, like I was saying the whole time. The feedback from the strat was the reorganisation of the strat vortex which connected downward with the trop around the 12th. Around the 18th-20th you can see in the background how the pacific ridge intensifies, and with some lag the pacific wave 1 at 30mb starts intensifying. The troposphere went later with the help of this ridge creating an Atlantic ridge into a stretched mode by the emergence of the Atlantic ridge, around 27.12, which with some lag resulted in a wave 2 response at 30mb. Which is the Atlantic wave2 i was expecting for so long to do the ugly work for us, but the vortex was too sneaky. Now this is only for December and only shows the 30mb strat plane. 

 

http://youtu.be/r4keByIvhLs

 

And next is a multi layer geopotential height analysis, which also tends to show how the mid strat was more in run by the trop., while the top strat has its own fun. The layers top down are 3mb, 10mb, 30mb and 150mb.

 

http://youtu.be/53TkfxeWuD8

 

Regards.

[Catacol]

And a poor winter 2015/6

 

 

There is no substance to that statement. Plenty of cold months have occurred under a wQBO - including the much quoted Dec 10.

 

I note that the eQBO this year is a significantly strong one. I wonder what the significance of that may be? Something I need to read into.

[Interitus]

 

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?

 

 

That section of the paper doesn't describe a 'bounce-back' of zonal flow as measured at a constant latitude eg 60°N.

It describes wave-breaking and to understand it take a look at geostrophic or gradient flow. As the zonal wind is decelerated the flow becomes unbalanced allowing the pressure force to cause meridional flow towards the pole. As it moves northwards the flow is accelerated by the Coriolis force, becomes more westerly again and the zonal flow is re-established at a higher latitude (assisted also by temperature changes). This is the balancing of geostrophic flow and to imagine it more simply it is the anticyclonic flow like round the northern side (northern hemisphere) of an area of high pressure.

Then they describe the meridional flow towards the pole causing sinking and adiabatic warming of air and in very basic terms this is what causes the sudden warming. What is important to remember is that the Eulerian zonal and meridional coordinates only consider two dimensions. Whilst there are these components of the wind following geopotential height contours for example, stratospheric flow over short time-scales is adiabatic and has a vertical component as it follows heights of equal potential temperature up and down. This is isentropic flow, brief description - http://www.cpc.ncep.noaa.gov/products/stratosphere/theta/theta_info.shtml

More detailed - http://vortex.nsstc.uah.edu/data/tmurphy/Teaching/ATS452_SynopticMeteorology/Lecture/04152013_Isentropic_3.pdf

 

Although the second link uses an example from the troposphere it stresses the following -

 

Important point:

 

Air DOES NOT follow the pressure surfaces (constant height charts we normally use)

 

Can not say what happened will just move on to another point on that same map

 

The air at that point will not be at that pressure surface for any length of time… instead traveling up and down isentropes to different pressure surfaces

 

This consideration is implicit to a Lagrangian approach compared to the fixed coordinate Eulerian view.

 

This is not the point.

 

I am still left with the question whether the geopotential height pattern in the troposphere affects the height of the geo's in the stratosphere. It sometimes does, so it seems to me. If (purely hypothetically) over a large area there would be created a vacuum, the pressure would drop. The geo's above this area would be pulled down, as is in a minor way for instance the case with a tropical cyclone or tornado.

Analoguely in the 8 januari case the cold reservoir above northern Canada and Greenland and the associated vast tropospheric low pressure area may have hindered the rising of the stratospheric geo's, thus the forming of a SSW.  In some cases, the tropospheric pressure pattern, might hinder the emergence of a ssw , if not prevent it completely. That's my thesis.

 

The geopotential height pattern in the troposphere 100% affects heights in the stratosphere because the geopotential height at any particular pressure level or layer is proportional to the mean virtual temperature in that layer. So the absolute geopotential height is proportional to temperatures all the way down to the surface. This can be seen when vortex splits occur because troposphere vortex is split.

But the height reduction due to the troposphere may be countered by increased geopotential thicknesses in the stratosphere because changes in virtual temperature there. Also tropospheric troughing imprinted on the stratosphere affects the isentropic flow which leads to warming when the vortex is perturbed and not aligned directly over the trough.

[Catacol]

Follow up question on QBO. NOAA archive has the QBO negative throughout 1948, 1949, 1950 and on into the first few months of 1951. At no other point in the record is the cycle broken like this. In 1951 it turned positive again for 2 months before returning to anther fairly extended spell of  negative values. Can anyone explain this?

Edited January 13, 2015 by Catacol_Highlander

[Recretos]

Follow up question on QBO. NOAA archive has the QBO negative throughout 1948, 1949, 1950 and on into the first few months of 1951. At no other point in the record is the cycle broken like this. In 1952 it turned positive again for 2 months before returning to anther fairly extended spell of negative values. Can anyone explain this?

Could be an error by first estimate. I will check ECMWF datasets to see if its the same.

[Interitus]

Follow up question on QBO. NOAA archive has the QBO negative throughout 1948, 1949, 1950 and on into the first few months of 1951. At no other point in the record is the cycle broken like this. In 1951 it turned positive again for 2 months before returning to anther fairly extended spell of  negative values. Can anyone explain this?

 

Many researchers discard the early data. As described in this paper (where u_eq is equatorial zonal mean zonal wind) - http://www.aos.wisc.edu/~mag/NCEP.pdf

 

During the first decade, observations were insufficient to adequately capture the QBO, but by 1958 the QBO in u_eq was fairly uniform

[Recretos]

After almost liquefying my RAM, here is a new animation, showing strat dynamics of November and December. Top down levels are 1mb, 3mb, 10mb, 30mb, 150mb.

 

Edited January 13, 2015 by Paul
Getting the video to embed for you

[Tyfelin]

I think we should have whip-round to buy Recretos some extra RAM. Spectacular!

[Woollymummy]

That is beautiful. And so much easier to understand in 3D. Thankyou!

[Trom]

Hat's off to that - that makes it easier to see the top down effect than anything I've seen.  

[John Badrick]

A quick question for the knowledgeable-If the cold charts we are seeinging tropospherically in recent days are a result of the warming/split we saw earlier this month, would we be seeing even colder charts for a longer period if we had a full SSW event? If so when the PV reorganises will we see a more zonal/milder outlook for the uk going into February?

[chionomaniac]

Who knows John. Statistically speaking the AO is lower in the period after an SSW especially in an EN year. It would be very difficult to say whether this would be the case just because we have had the 1/2 SSW. I know that the metoffice are saying that the cold outlook is all MJO driven, but the downwelling pattern from the strat is there to see - and it is no surprise to see the Atlantic jet stream become more disrupted soon after the Greenland daughter polar vortex was blown away by the warming. ( A first in the last 6 years of monitoring).

 

Furthermore, tthe position and amount of tropical convection that is demonstrated by the MJO does feedback stratospherically and there is a lot more that we need to study long term regarding these relationships.

[Paul123]

 

The geopotential height pattern in the troposphere 100% affects heights in the stratosphere because the geopotential height at any particular pressure level or layer is proportional to the mean virtual temperature in that layer. So the absolute geopotential height is proportional to temperatures all the way down to the surface. This can be seen when vortex splits occur because troposphere vortex is split.

But the height reduction due to the troposphere may be countered by increased geopotential thicknesses in the stratosphere because changes in virtual temperature there. Also tropospheric troughing imprinted on the stratosphere affects the isentropic flow which leads to warming when the vortex is perturbed and not aligned directly over the trough.

 

Thank you for your affirmation of my trop-strat premise. 

 

Amazing, that a strat split can be caused by a trop split. 

 

Well of course it does. It is all connected, tho the reflection is not 100% as you may know. 

 

 

Thank you for your explanation. I learn a lot from your animations. Can't wait for the Januari update.

 

Would you please explain what the upper level of http://youtu.be/r4keByIvhLs is portraying? I remember some time ago you explaining it, but wasn't paying enough attention then and can't trace your posting back now. 

Edited January 14, 2015 by Paul123

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