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chionomaniac

Stratosphere Temperature Watch 2012/2013

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Thanks C plenty of information for everyone to try and get up to speed and your posts will be eagerly looked for by the coldies on here=most folk.

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Excellent review C and so beautifully explained- even my understanding is increased.

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Good opening post Ed- very informative.

Many of us have looked forward to this thread and i am sure it will be one of the most visited this Winter.

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Always nice to see the new strat thread opened,and a great introductory post by Chio. Posted Image

An interesting post by GP in the old thread (GP copy into this thread?) showing

how the stratosphere might behave this winter by using 1968 as an analogue.

The 30mb zonal wind composite for the winter of 68/69 shows the reduction in

zonal winds at mid-latitudes very nicely...

....along with the sea level pressure anomalies. Posted Image

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Many thanks for that, Ed...After years' of 'ignoring' acronyms, some have finally stuck!

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good to c the strat thread reopening again nice explanation chio.

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Stratospheric analysis and discussion at 1:40am on a Sunday morning...Now that's dedication, or perhaps insomnia Posted Image

Good to see the thread open, here's to the coming weeks and months and lets hope we aren't looking back on this come next March with disappointment. Clearly I am speaking from a person who is also after/favours a more blocked pattern this winter, particularly given the summer we have had. A winter period dominated by zonal, mild, wet and windy muck is not wanted IMO.

Regards to all,

M.

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I hope Matt doesn't mind, but this is hot off the press and I'm sure it is well worth a read. Posted ImageTime for a strong coffee, there is some learning to be done.

http://matthugo.word...is-information/

Fantastic blog post by Matt Posted Image , i now know alot more than i did 10-15 minutes ago. Thanks for sharing GTLTW.

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I hope Matt doesn't mind, but this is hot off the press and I'm sure it is well worth a read. Posted ImageTime for a strong coffee, there is some learning to be done.

http://matthugo.word...is-information/

It's great to get the word out there in a clear concise way - I've been trying long enough but without Matt's profile.

Technically, last January there wasn't a SSW as defined by Polvani et al (winds reversal at 60ºN and 10hPa), but I can let Matt off as the result in this case is pretty much the same as if there had been!

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Todays update;

The stratosphere is currently cooling rapidly as is expected at this time of year.

Last week we saw a blip where the mean zonal winds went below average for this time of year in the lower stratosphere. These have since recovered and are or about to increase to above average.

Encouragingly, the cooling of the polar stratosphere is not forecast to be straightforward with small projected warmings forecast over the Canadian sector which will put pressure on the strengthening vortex. All of this has been in stratospheric FI but the theme has remained the same, with a lower split even cropping up. Very much a trend that we want to see continue into winter!

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Todays update;

The stratosphere is currently cooling rapidly as is expected at this time of year.

Last week we saw a blip where the mean zonal winds went below average for this time of year in the lower stratosphere. These have since recovered and are or about to increase to above average.

Encouragingly, the cooling of the polar stratosphere is not forecast to be straightforward with small projected warmings forecast over the Canadian sector which will put pressure on the strengthening vortex. All of this has been in stratospheric FI but the theme has remained the same, with a lower split even cropping up. Very much a trend that we want to see continue into winter!

ed, do you think interruptions to the rate of cooling are more important than the actual temp that the strat eventually ends up come november re a strong organised early winter vortex ?

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Nick, I think that the interruptions may help prevent the straightforward cooling of the strat, so are important in both senses. If at the end of November we have a strong vortex in a cold strat then obviously they may not have helped as much as I anticipate!

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Excellent, really looking forward to this thread! It was too technical for me last year but I will have a better grip this year as my knowledge has improved greatly since then. Thanks to Chionomaniac and all those who will contribute to this thread through the Autumn and Winter. It will be brilliant reading!

Edited by 22nov10blast

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Looking forwards to your posts Chiono. A great introductory post. Can you explain a little more about the phenomenon of "wave-breaking" as in this quote "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"

What is the cause of "wave breaking"? What are the outside influences on sudden stratospheric "warming" events? Are we talking about sun activity? Does this depend on sun activity cycles / sunspots?

Always wanting to learn more :) - thanks for the insights.

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Looking forwards to your posts Chiono. A great introductory post. Can you explain a little more about the phenomenon of "wave-breaking" as in this quote "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"

What is the cause of "wave breaking"? What are the outside influences on sudden stratospheric "warming" events? Are we talking about sun activity? Does this depend on sun activity cycles / sunspots?

Always wanting to learn more Posted Image - thanks for the insights.

Hi kumquat.

Lots of questions and ones that took me a lot of time to get my head around.

The tropospheric atmosphere consists of large scale planetary waves that flow from west to east normally. These waves are known as Rossby waves and there can be a number of these flowing around the NH at any one time. As with any wave there is a peak and a trough between . I have demonstrated the troughs in the following NH H500 ECM chart (typically not an easy day to demonstrate!)

post-4523-0-95024500-1349288532_thumb.gi

The height of the atmosphere varies between the peaks and the troughs of these waves and as a wave comes in from the sea and break as it nears land the same phenomenem can occur with Rossby waves. However, these waves need to be a certain amplitude before this occurs and need to hit a large planetary object such as a mountain range before this occurs.

So when a large Rossby wave hits a mountain range (like a ripple from a pebble) we can see this wave break upwards into the stratosphere (as well as be deflected sideways into the troposphere and lose energy to the earth in the form of a mountain torque). The effect of a wave breaking into the stratosphere will depend upon the size of the wave - the bigger the wave, the greater the deflection. Once a wave is big enough it can create a disturbance which travels around the boundary of the stratospheric polar vortex - known as the 'surf zone' - and penetrate into the polar vortex at the top of the stratosphere. It can then rebound back towards the troposphere and if it is great enough completely disrupt the polar vortex causing it to warm as it does so. Hence a Sudden Stratospheric Warming (SSW).

These type of wave breaks occur regularly but are of insufficient strength to create SSW's most of the time. If one wave breaks into the stratosphere at any one time we have a wavenumber 1 type break, if two occur simultaneously then we have a wavenumber 2 type and so on.

One other thing to note is that I have witnessed similar type breaks into the stratosphere in recent years that have occurred with planetary waves breaking around Greenland. Rather than travelling up around the surf zone to the top of the stratosphere these wave break 'internally' - almost through the core of the vortex. It is these types of break that do not create full SSWs but have led to very potent cold outbreaks here in recent years.

If in the following link you click ' ongoing observations' and then 'Rossby waves shed by greenland' it is easier to visualise how these interactions occur.

http://www.pa.op.dlr...ctic/index.html

Ps if any one can embed this into a post I would be grateful!

c

Edited by chionomaniac
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Thanks for that Ed-i wondered what the difference between Wavenumber 1 and 2 actually meant.

From your explanation that a Wavenumber 2 event is a double event am i correct in assuming that this would give a better chance of an effective SSW.?

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Thanks for that Ed-i wondered what the difference between Wavenumber 1 and 2 actually meant.

From your explanation that a Wavenumber 2 event is a double event am i correct in assuming that this would give a better chance of an effective SSW.?

It's a certain wavelength pattern breaking into the stratosphere commonly with Atlantic and Pacific wave breaks. Wavenumber 2 breaks are more likely to cause split SSWs rather than wavenumber 1 breaks which are the cause of displacement SSWs.

Edited by chionomaniac
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I should also point out that from the stronger the mountain torque observed, we can forecast that the wave break into the stratosphere will be stronger. So that this is a useful guide as to what occurs down the line.

Also, in todays forecasts there is a strong 10 day trend to displace the polar vortex towards Baffin bay/ N Canada region. So will we see some kind of height rises in the Scandi region around this time tropospherically - not programmed as of yet!

(Edit - of course these height rises could be Eurasion placed)

Edited by chionomaniac

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I should also point out that from the stronger the mountain torque observed, we can forecast that the wave break into the stratosphere will be stronger. So that this is a useful guide as to what occurs down the line.

Also, in todays forecasts there is a strong 10 day trend to displace the polar vortex towards Baffin bay/ N Canada region. So will we see some kind of height rises in the Scandi region around this time tropospherically - not programmed as of yet!

Some suggestion of this on 12z ECM/GFS means at T240hrs. Ed

post-2026-0-00939400-1349297421_thumb.pnpost-2026-0-99067400-1349297432_thumb.pn

Not sure how much the height rises across Scandi.would be but a definite modelling of the core of low heights towards Canada.

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Some suggestion of this on 12z ECM/GFS means at T240hrs. Ed

post-2026-0-00939400-1349297421_thumb.pnpost-2026-0-99067400-1349297432_thumb.pn

Not sure how much the height rises across Scandi.would be but a definite modelling of the core of low heights towards Canada.

One to watch and see how it develops, Phil.

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There are a couple of pages from a BDC paper I found that put waves into diagrams, always helps me, perhaps Ed can add further explanation to the below.

post-7292-0-45028500-1349299316_thumb.pn post-7292-0-40410800-1349299335_thumb.pn

The last diagram helped me picture the surf zone well.

post-7292-0-77124000-1349299552_thumb.pn

The paper is unfortunately too big to attach here, Dylan Jones, Dept of Physics, Toronto. 2005

Edited by lorenzo
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There are a couple of pages from a BDC paper I found that put waves into diagrams, always helps me, perhaps Ed can add further explanation to the below.

post-7292-0-45028500-1349299316_thumb.pn post-7292-0-40410800-1349299335_thumb.pn

The first I think is self explanatory.

The second diagram shows that large scale thunderstorms in troughs contained in the Rossby waves, act as a trigger mechanism helping propagate the feedback.

Edited by chionomaniac

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