Stratosphere Temperature Watch 2015/2016

[BrickFielder]

  My understanding of the potential vorticity charts at 380k is that they represent low and high pressure areas within the lowest level of the stratosphere. These areas of low and high pressure at this height (low stratosphere) will have a forcing effect on the troposphere through trying to raise or lower the tropopause height (tropopause height varies with low and high pressure weather conditions). This forcing effect must contend with other forcing effects in the troposphere of which Sea Surface Temperatures  (SST's) can modify the signal. This is particularly noticeable over the Atlantic and Pacific Oceans, which means a pinch of salt needs to be used when extrapolating potential tropospheric weather conditions for the UK. Looking at the current 380K potential vorticity charts you might extrapolate that there is a stratospheric forcing to create high pressure towards Scandinavia.

 

If we compare this to the forecast potential vorticity in about a week and a half then it looks very different.

For me this would tend to suggest a forcing to remove high pressure in the near continent. The potential here is for a significant winter storm to cross the UK perhaps leading to some flood conditions for the southern part of the UK. There is always the risk when looking at charts this far out that they will not match up to reality, so its something to look out for rather than any sort of forecast.

Source for charts is at the following link.

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

I am still trying to decide whether current QBO conditions are conducive to stratospheric warmings and am starting to think maybe it is. When considering  whether easterly or westerly QBO conditions prevail then it is not so simple because QBO changes tend to start at the top of the stratosphere and work their way downwards. This means that you can have different conditions at the top of the stratosphere to further down.

Source for this chart is

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

This suggests to me that we have a Westerley phase moving down giving way to easterlies at the topmost level. Assuming that the top most level is the most relevant to stratospheric warmings then we should probably take this as a sign that a stratospheric warming might be more viable. Again it is not so simple because you actually need to combine the ENSO   (El Niño) signal with the QBO state to better understand Stratospheric warming viability. Generally the stratospheric vortex is significantly more disturbed in El Niño years as compared to La Niña years due to increased propagation of ultralong Rossby waves toward high latitudes. However when you combine ENSO signals then SSWs (Sudden Stratospheric Warmings) might be favored by the east phase of the QBO and warm El Niño events or by the west phase of the QBO and La Niña events. There is then a third variable which can affect SSW viability namely the solar cycle. More SSWs occur during QBO east, solar minimum and QBO west,solar maximum conditions.

You can read some of the thinking behind these ideas at the following link.

http://eprints.ucm.es/25520/1/calvofernandez07libre.pdf

Finally I wanted to try to explore whether geomagnetic conditions in the Mesosphere play a part in whether stratospheric warmings occur. The reasoning here may be due to variable propagation and reflectivity of layers above the stratosphere when geomagnetically excited due to changes in ozone. I have struggled to find discussions that really back this up but I did find a workshop summary from 2013 which suggested that not all  SSW periods occur during geomagnetic quiet times. Which kind of suggests a relationship to me. 

https://cedarweb.vsp.ucar.edu/wiki/index.php/2013_Workshop:Stratospheric_Sudden_Warmings

There are some interesting concepts talked about in the summary which has peaked my interest to perhaps examine some other aspects. Selected Quotes below.

SSW signals are present in the EEJ which are stronger during solar maximum than minimum, and correlated with the lunar time.

There is either a direct influence on the stratosphere by production in the stratosphere or an indirect effect by the descent of EPP NOx and HOx from the mesosphere.

Several workshop presentations have identified gravity waves as a significant source of SSW variability in both hemispheres up to the thermosphere, and therefore highlighted its importance.

 

 

 

[Duane S.]

1 hour ago, Interitus said:

Thanks for indirectly highlighting Hannah Attard's site, some great charts there http://www.atmos.albany.edu/student/hattard/realtime.php

With regards to wave heights, this season so far has been below average so recent increases were probably to be expected. With the wave 2 in particular that chart is showing 625 metres at 10mb 60°N and it is 650 metres for the 2 previous days, but to put it into perspective, the record strongest SSW of the January 2009 split vortex was preceded by wave 2 heights of over 2300 metres.

Indeed. Wave2 looking decent but only in the context of this winter really. Hopefully we will see an uptick in intensity over the coming couple of weeks. 

It would be nice to see charts like this again this winter. From this...

to this in a couple of days...

been a while since we've seen a profile like this on the horizon...

And how about this for a gradual drop off in U winds and high flux activity... !

Interesting that the onset of the January 09 vortex split was relatively sudden and had followed on from a period of strong zonal winds and was in a declining W-QBO. Maybe it is wishful thinking but I do think we have the ingredients for something similar to occur again this winter.

[bluearmy]

well the predicted rate of drop in 1hpa winds looks to be in the right ballpark !

[Recretos]

4 hours ago, BrickFielder said:

  My understanding of the potential vorticity charts at 380k is that they represent low and high pressure areas within the lowest level of the stratosphere. These areas of low and high pressure at this height (low stratosphere) will have a forcing effect on the troposphere through trying to raise or lower the tropopause height (tropopause height varies with low and high pressure weather conditions). This forcing effect must contend with other forcing effects in the troposphere of which Sea Surface Temperatures  (SST's) can modify the signal. This is particularly noticeable over the Atlantic and Pacific Oceans, which means a pinch of salt needs to be used when extrapolating potential tropospheric weather conditions for the UK. Looking at the current 380K potential vorticity charts you might extrapolate that there is a stratospheric forcing to create high pressure towards Scandinavia.

 

If we compare this to the forecast potential vorticity in about a week and a half then it looks very different.

 

For better orientation, the 380K field is roughly on a similar level as the 100mb field. On average around 14-15 km

Edited December 29, 2015 by Recretos

[Interitus]

7 hours ago, BrickFielder said:

  My understanding of the potential vorticity charts at 380k is that they represent low and high pressure areas within the lowest level of the stratosphere. These areas of low and high pressure at this height (low stratosphere) will have a forcing effect on the troposphere through trying to raise or lower the tropopause height (tropopause height varies with low and high pressure weather conditions). This forcing effect must contend with other forcing effects in the troposphere of which Sea Surface Temperatures  (SST's) can modify the signal. This is particularly noticeable over the Atlantic and Pacific Oceans, which means a pinch of salt needs to be used when extrapolating potential tropospheric weather conditions for the UK. Looking at the current 380K potential vorticity charts you might extrapolate that there is a stratospheric forcing to create high pressure towards Scandinavia.

 

If we compare this to the forecast potential vorticity in about a week and a half then it looks very different.

For me this would tend to suggest a forcing to remove high pressure in the near continent. The potential here is for a significant winter storm to cross the UK perhaps leading to some flood conditions for the southern part of the UK. There is always the risk when looking at charts this far out that they will not match up to reality, so its something to look out for rather than any sort of forecast.

 

But by what amount is the lower stratosphere influencing the troposphere and vice versa?

These vorticity charts naturally show a strong relationship to the geopotential heights in the lower stratosphere which in turn reflects the mid-troposphere (eg 500mb) because tropospheric geopotential anomalies propagate upwards via hydrostatic balance. When the trop and strat are well coupled in this way it has been argued that baroclinic development in the troposphere extends well into the strat which is seen in correlated geopotential height changes within just a few days.

At the time of SSW for example it can be seen that geopotential change rapidly from trop to strat and back again within a couple of weeks which is notably shorter than the time required for AO changes by wave processes in the classic Charney-Drazin theory and Baldwin-Dunkerton weak/strong vortex composites. Incidentally this is why some recent suggestions time is running out and that an SSW would only affect things a month later may be wide of the mark. For more on this see Cullen & Ngan http://rsta.royalsocietypublishing.org/content/371/1991/20120180#ref-16

Over longer timescales (month - seasonal) Charlton et al suggest that the lower stratospheric influence on the troposphere is in the region of 5% for the 1000hPa timeseries http://onlinelibrary.wiley.com/doi/10.1256/qj.02.232/abstract

But with regards to individual synoptic systems that you highlight it is very hard to attribute their development to just the stratosphere or troposphere. Probably the best paper I have seen examining specific synoptic developments is by Colucci - http://journals.ametsoc.org/doi/pdf/10.1175/2009JAS3148.1 - this examines geopotential changes via potential vorticity inversion and is well worth looking at but suffice to say in absence of investigation like this it is very hard to say that from the 380k charts that the strat is forcing the changes in the trop rather than mirroring the geopotential heights.

Edited December 29, 2015 by Interitus

[bluearmy]

Very different end to the 06z op re 10hpa temps. anomoly or start of the beginning of the end? 

[fergieweather]

Just now, bluearmy said:

Very different end to the 06z op re 10hpa temps. anomoly or start of the beginning of the end? 

Yes, interesting indeed...

[Glacier Point]

I make that four out of the last six GFS op runs in the extended period, 12th-14th January, which have exhibited significant distress signals for the vortex - of the sort that signals something terminal: stretching across a displaced axis and rapid transfers of energy through the lobes.

[feb1991blizzard]

I wonder if Ian would be kind enough to let us know as and when anything significant happens towards early Feb on the GLOSEA5 please?

Edited December 30, 2015 by feb1991blizzard

[MPG]

23 minutes ago, fergieweather said:

Yes, interesting indeed...

 

5 minutes ago, Glacier Point said:

I make that four out of the last six GFS op runs in the extended period, 12th-14th January, which have exhibited significant distress signals for the vortex - of the sort that signals something terminal: stretching across a displaced axis and rapid transfers of energy through the lobes.

Gents, can we have a little laymans please, so I could understand what this may mean for the UK. I can see on the output the amount of blocking, but the UK seems to miss the cold air. Maybe another 7 days before the icandy charts start to show? Thanks.

[bluearmy]

4 minutes ago, MPG said:

 

Gents, can we have a little laymans please, so I could understand what this may mean for the UK. I can see on the output the amount of blocking, but the UK seems to miss the cold air. Maybe another 7 days before the icandy charts start to show? Thanks.

I'm afraid it's way too early to speculate what might transpire for nw Europe as a result of a weakening strat vortex or indeed a SSW. We wouldn't even be sure if we would be looking at a displacement or split at this stage. 

Assume that Glosea-5 will have its own ideas on what may be around the corner re the strat but translating that to the trop is full of pitfalls. 

[Paul_1978]

39 minutes ago, bluearmy said:

 Very different end to the 06z op re 10hpa temps. anomoly or start of the beginning of the end? 

Beginning of the end of what? The vortex?

[fergieweather]

2 minutes ago, feb1991blizzard said:

I wonder if Ian would be kind enough to let us know as and when anything significant happens towards early Feb on the GLOSEA5 please?

I'm back into the office today so will have a discussion on this. However, very latest thinking (on non-stratospheric output) is thus for mid to end of Jan:

- EC Monthly shows statistically insignificant deviation from climatology for both PPN and screen temperature

- GloSea5, meanwhile, leans tentatively towards milder than average, taking the period overall. It also has a W-E split in ppn anomaly (drier in east)

- Signs in both models of MSLP building at times towards S and SW (thus frost/fog more likely); with colder, showery phases especially to NW between passing frontal systems

- This all superimposed on overall zonal pattern; no strong indicators currently exist in either suite for blocked or prolonged colder weather through the period to end of Jan

[KyleHenry]

Signal picked up by GFS 06z at outer limits for a big wave event. 

Is this the knockout blow?

Edited December 30, 2015 by KyleHenry

[feb1991blizzard]

4 minutes ago, fergieweather said:

I'm back into the office today so will have a discussion on this. However, very latest thinking (on non-stratospheric output) is thus for mid to end of Jan:

- EC Monthly shows statistically insignificant deviation from climatology for both PPN and screen temperature

- GloSea5, meanwhile, leans tentatively towards milder than average, taking the period overall. It also has a W-E split in ppn anomaly (drier in east)

- Signs in both models of MSLP building at times towards S and SW (thus frost/fog more likely); with colder, showery phases especially to NW between passing frontal systems

- This all superimposed on overall zonal pattern; no strong indicators currently exist in either suite for blocked or prolonged colder weather through the period to end of Jan

Thanks Ian.

[snowking]

I realise there have been upgrades in the interim but one slight note of caution - from following the Jan 2013 warming episode, the 6z GFS was often the most aggressive in terms of the forecast warming. 

This was the peak of the warming itself:

Here were a couple of the 6z predictions in the run up to it:

Not a catastrophic amount of difference but it was always something that stuck in my mind and I've remained a little wary about it's suggestions ever since.

SK

 

[blizzard81]

Any news on the possible canadian warming?

[karyo]

25 minutes ago, snowking said:

I realise there have been upgrades in the interim but one slight note of caution - from following the Jan 2013 warming episode, the 6z GFS was often the most aggressive in terms of the forecast warming. 

This was the peak of the warming itself:

Here were a couple of the 6z predictions in the run up to it:

Not a catastrophic amount of difference but it was always something that stuck in my mind and I've remained a little wary about it's suggestions ever since.

SK

 

The same also happened with last January's warming. The 6z was often showing it as more intense than the rest of the runs.

[Gael_Force]

12 minutes ago, karyo said:

The same also happened with last January's warming. The 6z was often showing it as more intense than the rest of the runs.

I remember that being talked about at the time but was that the old GFS or was the current one live by that time? The new parallel run is only intermittantly loading but does not look to be showing much in far FI.

[Recretos]

GEFS does end the last intensification period, with no further zonal intensification in sight.

  

[chionomaniac]

No SSW in there though, @Recretos

[feb1991blizzard]

6 minutes ago, chionomaniac said:

No SSW in there though, @Recretos

And not even close to one, some of those ensembles though do back the 6z op temperature wise at the end of the run, lets just hope its the start.

[Recretos]

I cant see where I even mentioned one? :) I am just saying that the seasonal peak of the vortex strength is coming into fruition, and after that there is no further intensification in sight on the current runs.

[chionomaniac]

2 minutes ago, Recretos said:

I cant see where I even mentioned one? I am just saying that the seasonal peak of the vortex strength is coming into fruition, and after that there is no further intensification in sight on the current runs.

I didn't say you did!!! ; ) Just frustratingly so to see there isn't! Glad that VI is coming to an end and you demonstrate this well.

[BrickFielder]

19 hours ago, Interitus said:

But by what amount is the lower stratosphere influencing the troposphere and vice versa?

These vorticity charts naturally show a strong relationship to the geopotential heights in the lower stratosphere which in turn reflects the mid-troposphere (eg 500mb) because tropospheric geopotential anomalies propagate upwards via hydrostatic balance. When the trop and strat are well coupled in this way it has been argued that baroclinic development in the troposphere extends well into the strat which is seen in correlated geopotential height changes within just a few days.

At the time of SSW for example it can be seen that geopotential change rapidly from trop to strat and back again within a couple of weeks which is notably shorter than the time required for AO changes by wave processes in the classic Charney-Drazin theory and Baldwin-Dunkerton weak/strong vortex composites. Incidentally this is why some recent suggestions time is running out and that an SSW would only affect things a month later may be wide of the mark. For more on this see Cullen & Ngan http://rsta.royalsocietypublishing.org/content/371/1991/20120180#ref-16

Over longer timescales (month - seasonal) Charlton et al suggest that the lower stratospheric influence on the troposphere is in the region of 5% for the 1000hPa timeseries http://onlinelibrary.wiley.com/doi/10.1256/qj.02.232/abstract

But with regards to individual synoptic systems that you highlight it is very hard to attribute their development to just the stratosphere or troposphere. Probably the best paper I have seen examining specific synoptic developments is by Colucci - http://journals.ametsoc.org/doi/pdf/10.1175/2009JAS3148.1 - this examines geopotential changes via potential vorticity inversion and is well worth looking at but suffice to say in absence of investigation like this it is very hard to say that from the 380k charts that the strat is forcing the changes in the trop rather than mirroring the geopotential heights.

The royal Society publishing document on the relationship between stratospheric structure and tropospheric blocking patterns is interesting. I would agree that it makes sense that tropospheric conditions would affect the lower stratosphere. Where conditions in both the stratosphere and troposphere are acting to raise or lower the tropopause then they are likely to affect each other. What I think is not really explained well in the report is the concept of decoupling between the stratosphere and the troposphere and the importance of the scale of disturbances. Lets look at two current charts. Firstly the 380K Potential Vorticity Chart which I think has some correlation to tropospheric conditions (Not exactly but could be used for an element of prediction). Here I assume (always dangerous) that tropospheric influence on the stratosphere has been taken into account in the modelling.

Secondly the 475K Potentail Vorticity Chart which correlates much better with the upper stratospheric vortex conditions rather than the lower stratosphere or troposphere.

What I think is happening is that the lower stratosphere and upper troposphere tend to be reasonably well coupled, but when you get a major disturbance in the upper stratosphere you get some weak coupling between the upper stratosphere and the very lower stratosphere. Depending on the size of the upper stratosphere disturbance (like a vortex split) you get an element of decoupling somewhere in the mid to lower stratosphere initially (I think some of the graphs in the paper show this). Over time the stratosphere will slowly begin to strengthen the coupling to all levels of the stratosphere (barring another disturbance due to upward effects) having effects on the troposphere (blocking). Equally when the upper stratosphere disturbance goes away you get a similar weakening of coupling somewhere in the mid to lower stratosphere initially. In the absence of a significant stratospheric vortex or change in that vortex then it seems reasonable that tropospheric conditions would tend to drive stratospheric conditions (Ignoring mesosphere and ionosphere conditions which is unwise). When it comes to the question of time between an upper level stratospheric disturbance affecting the troposphere then I think the answer is complicated. It may have no effect, or if conditions in the troposphere are conducive to a change it may be relatively quick. Either way you are quite right to point out that the lower stratosphere is not a major driver of winter weather conditions and ice cover along with sea surface temperatures amongst others have a big influence (even reaching up into the stratosphere). The paper does sort of imply the stratosphere is important though. Here is a quick quote from the paper  (It is out of context so reading the full paper is advised).

An accurate representation of the stratospheric vortex structure (and thus the vertical wind shear in the lower stratosphere) is necessary for accurate predictions of blocking.

On the Charlton et al paper then I think the key here is  that they are looking at seasonal timescales. They do imply the statistically the effect of the stratosphere is limited on the troposphere . A later paper suggests that a stratospheric vortex displacement and stratospheric vortex split  affects on the troposphere are statistically more significant than 5 percent (Slightly different to arguing that the lower stratosphere influences the troposphere I agree)

http://centaur.reading.ac.uk/34207/1/mitchell.pdf

A quick quote from this paper  (out of context ).

 It is further found that the stratospheric contribution to tropospheric development can be larger in magnitude than the tropospheric contribution and can even overwhelm an opposing tropospheric effect.   

Following on from the Colucci paper.

http://www.see.leeds.ac.uk/misc/ejournal/Issue%209%20articles/9;%2064-121.pdf

Quote

Most layers of the stratosphere and indeed possibly even the mesosphere can have a direct and immediate impact  on  the   whole  column  of  atmosphere  below  through  thickness  changes  altering  the  surface pressure of possible mid latitude cyclones below.

I think my head hurts now from reading all this stuff. Essentially I think we are agreeing that both the stratosphere and troposphere affect each other, that significant stratospheric disturbances can affect weather, 380K potential vorticity forecast charts can be useful as a hint to possibilities.