Stratosphere Temperature Watch 2012/2013

[tcc]

I would agree with Nick and John. Normally I can give a good guide at this point as to where the start of December will be heading. But not this year.

Today,it would be something along the lines of becoming increasingly zonal with +ve AO if the zonal mean positive anomalies propagate towards the troposphere or we could see lower stratosphere wave breaking from the troposphere leading to a split vortex and -ve AO and holding the positive mean anomalies in the upper strat.

Take your pick!

pfft...talk about sitting on the fence! Call yourself a forecaster! haha!

[Methuselah]

I would agree with Nick and John. Normally I can give a good guide at this point as to where the start of December will be heading. But not this year.

Today,it would be something along the lines of becoming increasingly zonal with +ve AO if the zonal mean positive anomalies propagate towards the troposphere or we could see lower stratosphere wave breaking from the troposphere leading to a split vortex and -ve AO and holding the positive mean anomalies in the upper strat.

Take your pick!

Thanks entirely to your series of perfectly balanced posts, chio, I had already drawn that conclusion...

[bluearmy]

to take the argument on another stage, to aviod the upper strat flow propogating down to the trop (which we must assume it will evenually do without any resistance from below), we require wave breaking from the trop up into the strat. we know that a greeny and eurasian ridge will both contribute to this but then we need to go back a step and ask what is driving those features? the MJO looks to be in a low amplitude, ENSO is fairly weak. is it simply feedback mechanisms from what we've been seeing through the autumn so far which will continue without any other significant driver intervening ??

[Snowman.]

I'm new to the Stratosphere and stuff like that so don't shout at me! I am slowly learning by looking through your posts and data that you provide I have a question about the polar vortex. What makes the vortex stressed and doesn't settle in particular spot moving around the northern pole and making all weather patterns act weird.

[Eskimo]

I'm new to the Stratosphere and stuff like that so don't shout at me! I am slowly learning by looking through your posts and data that you provide I have a question about the polar vortex. What makes the vortex stressed and doesn't settle in particular spot moving around the northern pole and making all weather patterns act weird.

Don't worry, no one is going to shout at you lol, you'll learn quickly!

[EML Network]

I would agree with Nick and John. Normally I can give a good guide at this point as to where the start of December will be heading. But not this year.

Today,it would be something along the lines of becoming increasingly zonal with +ve AO if the zonal mean positive anomalies propagate towards the troposphere or we could see lower stratosphere wave breaking from the troposphere leading to a split vortex and -ve AO and holding the positive mean anomalies in the upper strat.

Take your pick!

Dr Spock, would answer the logical conclusion lays somewhere in between or a Yo Yo between both (although I'm unsure if that's probable or even possible) ?

[Relativistic]

So I'm guessing we need to see local wave breaking through the troposphere in order for the Strat PV at low levels to stay disorganised. Question for GP: I know you were talking about recently a split in the SIberian High, with ridging across Western Russia/ Eastern Europe, which you described as being the "sweet spot" for poleward wave 2 activity. Should wave breaking occur, Would this activity be of the local kind, and if so, do you think it could be enough for the lower Strat PV to resist forcing from upper levels?

(Sorry if this sounds stupid).

Edited November 5, 2012 by 22nov10blast

[chionomaniac]

I'm new to the Stratosphere and stuff like that so don't shout at me! I am slowly learning by looking through your posts and data that you provide I have a question about the polar vortex. What makes the vortex stressed and doesn't settle in particular spot moving around the northern pole and making all weather patterns act weird.

The stratospheric vortex is usually quite stable and it takes large scale deflected tropospheric planetary waves to create any change to its status.

The tropospheric vortex can be inherently unstable due to the differences of land masses - especially mountain ranges, sea temperatures, and transfer of heat and cold to and from the poles etc. How these all interact together determines how stable the vortex is, but critically a strong stratospheric vortex will potentially override these.

[phil nw.]

This chart shows how slowly the mean zonal winds increase is filtering down from the upper levels.

the trend is very gradually downwards but we can see below 30hPa they are still running at less than 20m/sec but increases here look imminent if that descent continues.

Looking at the GFS pressure forecasts though there still seems some sign of development of those Russian heights towards Scandinavia out at day10-looking at the 100hPa modelling.

so maybe for now the lower levels still resisting the cooling effects from above?

To throw into the equation- are we seeing a hint of Number 2 wavebreaking here?

Could we have a trophospheric led pattern change from the current state of things i wonder?

Any thoughts Ed?

[chionomaniac]

My thoughts Phil?

Sitting high up on the fence and observing.

(At least for a few days)

[snowking]

This chart shows how slowly the mean zonal winds increase is filtering down from the upper levels.

the trend is very gradually downwards but we can see below 30hPa they are still running at less than 20m/sec but increases here look imminent if that descent continues.

Looking at the GFS pressure forecasts though there still seems some sign of development of those Russian heights towards Scandinavia out at day10-looking at the 100hPa modelling.

so maybe for now the lower levels still resisting the cooling effects from above?

To throw into the equation- are we seeing a hint of Number 2 wavebreaking here?

Could we have a trophospheric led pattern change from the current state of things i wonder?

Any thoughts Ed?

Those wave number 2 forecasts have shown pretty similar things out at day 9/10 for 3 out of the last 4 days incidentally - the trouble at the moment is its staying at day 9/10 . But there's certainly a fairly strong hint at some tropospheric upwelling later this month

SK

[phil nw.]

My thoughts Phil?

Sitting high up on the fence and observing.

(At least for a few days)

Fair enough Ed.I did read your earlier post indicating your, shall i say, neutral stance?

Thought i would try and prod you off the fence

I guess we are learning as we go along-new situation re.vortex cooling so far this year i guess.

Those wave number 2 forecasts have shown pretty similar things out at day 9/10 for 3 out of the last 4 days incidentally - the trouble at the moment is its staying at day 9/10 . But there's certainly a fairly strong hint at some tropospheric upwelling later this month

SK

Hi SK,

I must admit i havent viewed those since last week .Still we keep watching and see if they start to creep into a nearer timeframe.

Edited November 5, 2012 by phil n.warks.

[syed2878]

hi guys i don't know if this article been posted on here, if it has then mod's plz remove thx. i think this would be useful to some of new peeps on here.

The simplified artist's conception shows how changes in polar vortex winds high in the stratosphere can influence the North Atlantic to cause changes in the global conveyor belt of ocean circulation; Credit: © Thomas Reichler, University of Utah.

Changes in the winds high in the stratosphere affect the seas and climate, according to a new study. The research from the University of Utah study suggests changes in winds from 15-30 miles up hit at a vulnerable "Achilles heel" in the North Atlantic and alter mile-deep sea circulation patterns that change the weather. The findings have been published in the online journal Nature Geoscience.

Senior author Thomas Reichler says, "We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate."

It was already realised that changes in the stratosphere, between 6-30 miles above Earth, affect what happens in the troposphere, which stretches from Earth's surface up to six miles or about 32,800 feet up and where weather occurs.

It was also known that global circulation patterns in the seas, caused mainly by changes in water temperature and saltiness, influence global climate.

Associate professor of atmospheric sciences at the university, Thomas Reichler, says, "It is not new that the stratosphere impacts the troposphere. It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean."

Thomas Reichler carried out the research with University of Utah atmospheric sciences doctoral student Junsu Kim, atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, from the Max Planck Institute for Meteorology based in Hamburg, Germany. The study was financed by the University of Utah.

The team used weather observation data supercomputer simulations of 4,000 years of weather to reveal a surprising association between decade-scale, alterations in stratospheric wind patterns called the polar vortex, and rhythmic differences in deep-sea circulation patterns.

There are two main changes:

• Stratospheric sudden warming that happen when temperatures increase and 80-mph polar vortex Artic winds weaken or alter direction. These changes last for up to 60 days, which provides time for the effects to filter through the atmosphere to the ocean.

• Alterations in the speed of the Atlantic circulation pattern, called the Atlantic Meridional Overturning Circulation, which affects seas around the world as it acts in a similar way to a conveyor belt, transporting water around the earth.

These can happen several years running or miss a decade, so adding this decade-scale effect into climate modelling is important in forecasting decade-to-decade climate changes that are difference from global warming, says Thomas Reichler.

"If we as humans modify the stratosphere, it may - through the chain of events we demonstrate in this study - also impact the ocean circulation.

"Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate," he explains.

"The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide. In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough - and thus dense enough - so the water starts sinking."

The area is the most important region of seawater downwelling on Earth. The sinking of cold, salty water "drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans."

"This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them," he says.

Due to that sensitivity, Thomas Reichler has named the sea south of Greenland "the Achilles heel of the North Atlantic."

During the winter months the stratospheric Arctic polar vortex turns counterclockwise around the North Pole, which means powerful 80-mph winds are around 60 degrees north latitude. They are even stronger than jet stream winds that travel at less than 70 mph in the troposphere. But every few years the stratospheric air is suddenly and dramatically altered and the vortex becomes warmer and weaker and can even go clockwise.

"These are catastrophic rearrangements of circulation in the stratosphere," and the weaker or reversed polar vortex persists up to two months. Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface," Thomas Reichler says.

His research investigated whether changes in stratospheric polar vortex winds make the sea warmer or colder and how the sea is affected.

Scientists knew that the wind changes affected the North Atlantic Oscillation, low pressure centred on Greenland and high pressure over the Azores to the south. The pattern can reverse or fluctuate.

As the changing pressure patterns are over the sea downwelling area near Greenland, it remains to be confirmed if the pattern affects the downwelling and the global oceanic circulation conveyor belt.

The computer simulations reveal a decadal on-off pattern of correlated alternations in the polar vortex, atmospheric pressure changes above the North Atlantic and differences in sea circulation over one mile under the waves. Observations are consistent with the pattern revealed in computer simulations.

In the 1980s and 2000s, several stratospheric sudden warming events made polar vortex winds weaker. In the 1990s, the polar vortex remained strong.

Thomas Reichler and his team used global ocean observations from various studies to reconstruct the way the conveyor belt ocean circulation behaved during the same 30-years.

"The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic," Thomas Reichler says.

To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years of atmosphere and ocean circulation.

"The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events," he explains.

To further back up the findings, the researchers combined 18 atmosphere and ocean models into one giant simulation and saw similar outcomes.

The researchers say the study suggests there is "a significant stratospheric impact on the ocean."

"Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system."

http://www.earthtimes.org/climate/stratosphere-wind-affect-seas-climate-study-shows/2193/

[sebastiaan1973]

There are two important regions; north pacific and eastern Europe

http://www.atmos.was...&Sassi_2009.pdf -> Lorenzo posted it.

Regional extratropical tropospheric variability affects the wave driving of the Northern Hemisphere wintertime stratospheric polar vortex. Simple reasoning is used to understand the nature of the regional variability that reinforces extratropical planetary waves, and thus vertical EP flux leaving the troposphere. In the European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis record and in WACCM (Whole Atmosphere Community Climate Model), one regional pathway for enhanced planetary wave driving is a deeper low over the North Pacific, and a second pathway is an enhanced high over Eastern Europe.

Perturbations in the vortex induced by the two pathways add linearly. These two pathways begin to weaken the upper stratospheric vortex nearly immediately, with a peak influence after a lag of some twenty days. The influence then propagates downwards in time, as expected from wave-mean flow interaction theory. These patterns are influenced by the El-Nino Southern Oscillation (ENSO) and October Eurasian snow cover. These two patterns and the Quasi-Biennial Oscillation (QBO) explain 40% of polar vortex variability during winter.

Edited November 6, 2012 by sebastiaan1973

[sebastiaan1973]

http://web.mit.edu/~...netal_GRL10.pdf

So we have a positive SAI. Be do we have 'observed sea level pressure anomaly'? And 100hpa WAFz?

In Figure 1a we present the polar cap diagnostic from October 1, 2009 through March 31, 2010 (red shading represents

above normal heights around the polar cap; all atmospheric data is taken from NCEP/NCAR Reanalysis

[Kalnay et al., 1996]). In Figure 1c we plot the daily polar cap index at 1000 hPa as a proxy for the daily AO for the same

period where two distinct and strong negative surface AO events are seen, one in December and a second in February

(labeled “6†in Figure 1). But as argued by Cohen et al. [2002], not only can the negative AO events be traced back

in time up into the stratosphere (labeled “4†and “5â€) as demonstrated by Baldwin and Dunkerton [2001], they can be

traced even further back in time to two distinctive upward WAF events (labeled “3†and Figure S3). Furthermore, the

stratospheric warming and the upward WAF events were preceded still by strong tropospheric events associated with

positive geopotential heights (labeled “2â€). Note that the polar cap diagnostic clearly shows that two major events of

high heights originated or commenced in the troposphere and not in the stratosphere. As will shortly be demonstrated, both

strong negative AO events can be shown to originate as regional perturbations across Northern Eurasia. The first

tropospheric precursor that initiated the midâ€November minor stratospheric warming we estimate existed from the

second half of October until midâ€November. The second tropospheric precursor that initiated a major stratospheric

warming existed at the end of January. Cohen et al. [2002] argued that tropospheric precursors preceded both the

stratospheric warming that oftenâ€lead strong surface AO events, which was more easily highlighted in the polar cap

diagnostic. These tropospheric precursors force anomalous WAF that drives stratospheric variability.

[11] Snow cover extent was well below normal across Eurasia the first week of October 2009. But during the last

three weeks of October the SCE rapidly advanced by over 15 × 106 km2 to 18 × 106 km2 (SCE was derived from

NOAA’s satelliteâ€sensed observations [Robinson et al., 1993]). So even though SCE was well below normal after

the first week of October, by the end of the month Eurasian SCE was the greatest since 1976. Furthermore, monthly

Eurasian SCE remained in the top quartile for the months October–February (winter 2009–2010 Eurasian SCE was the

second greatest on record for DJF).

Soon after the rapid advance in SCE began, temperatures responded by reversing from above normal to below

normal. For the period from late October and the first half of November the only meaningful region with below normal

surface temperatures (Ts) across the entire extratropical NH was Siberia (Figure S4). The cold dense air also helped

to build high pressure in the region. The largest positive SLP anomalies in the extratropical NH are centered across

Northern Eurasia to the northwest of the climatological center of the Siberian high (Figure 2a). The SLP and Ts anomalies

across Northern Eurasia are similar in location and orientation as the tropospheric precursor to stratospheric warming and

Figure 1. (a) The daily geopotential height normalized anomaly area averaged around the polar cap poleward of

60°N from 1000 to 10 hPa, (http://forum.nwstatic.co.uk//public/style_emoticons/<#EMO_DIR#>/cool.png the daily wave activity flux (WAF) area averaged between 40–80°N latitude and 30–

180°E longitude from the 1000 to 10 hPa, © the daily polar cap index at 1000 hPa. Plots are all October 2009–March

2010. Numbers 2–6 in Figures 1a–1c correspond to the six steps of the conceptual model described in the text.

The tropospheric precursor forces an increase in upward WAF (Figure 2b) focused across

Northern Eurasia in general and Siberia in particular, which is then absorbed in the stratosphere leading to warming

over the pole (Figure 2c). Finally, the hemispheric circulation anomalies propagate from the stratosphere down through the

troposphere (as seen in Figure 1a) culminating in a negative AO. The negative AO is characterized by positive SLP

anomalies across the Arctic, negative SLP anomalies in the midâ€latitude ocean basins (Figure 2d) and an expansion of

cold Ts into Europe and North America (Figure S4).

[sebastiaan1973]

Different EC32? Temperaturewise it looks different, in week 2-3 i'ts too warm in Europe. It seems there is high pressure in the East of Europe. Perhaps Matt can tell us more?

Edited November 6, 2012 by sebastiaan1973

[lorenzo]

Maybe no news is good news... !

[BLAST FROM THE PAST]

Different EC32? Temperaturewise it looks different, in week 2-3 i'ts too warm in Europe. It seems there is high pressure in the East of Europe. Perhaps Matt can tell us more?

Bringing exceptionally mild weather towards us?

BFTP

[geoffw]

fred we need chio''s and gp's comments

[chionomaniac]

Maybe no news is good news... !

Every day that passes with no news is a day with an edge closer to zonal.......

[BLAST FROM THE PAST]

fred we need chio''s and gp's comments

On the EC32? Why? Anyone who has access to it may comment, what about Matt? If C or GP comment fine but I want to know more from anyone who has acces out of interest...so I need anyone's comments who has access.

BFTP

[bluearmy]

Every day that passes with no news is a day with an edge closer to zonal.......

i concur with this Ed though NAEFS anomolys at the end of the run arent too bad, retaining the kamchatkan ridge, returning the newfoundland/greenland heights and developing a gentle rise across n greenland to join the eurasian anomoly. one would assume without these anomolys driving ridges into the high arctic, we may be struggling for trop impact on the strat as discussed yesterday

[lorenzo]

Every day that passes with no news is a day with an edge closer to zonal.......

Yep.. not a lot to inspire us at the moment, was trying some reverse psychology.. iirc - Think Matt said the ECM 32 final long term out look was due on the 8th. Reminds me of a post from the AmWx thread.

What's the Strat Doing?.... it's all cold and Vortexy.

[Skyraker]

Just out of interest.... (I've highlighted the bits)

[MattH]

The latest ECM 32 day model is similar to the previous runs which keeps low pressure dominant across the UK or to the NW for the foreseeable future. The primary difference is it is signalling a more pronounced area of higher pressure across E Europe which as a result allows for the potential development of milder S or SW'lies at times with temperatures around the middle of the month potentially slightly above average.

However and importantly, the final block which now takes us into the opening week of December maintains a trend for pressure to become lower to the south of the UK, whilst pressure becomes higher to the north, essentially creating a -NAO pattern and a signal for temperatures to become below average into early December. That is the reason why if you read the 15 to 30 day update on the UKMO site, they highlight potentially colder conditions long term and it is just to that signal within the ECM 32 day which has been there now consistently, so it'll be interesting to see what happens.

The ECM seasonal update will be out on the 8th, I'll comment accordingly, but I wouldn't expect much luck from that model if you are after a blocked, colder pattern as up to present it hasn't signaled it.

Cheers, Matt.