Stratosphere Temperature Watch 2015/2016

[joggs]

7 minutes ago, KyleHenry said:

Temperatures, ice sheet,altitude, geographical position. 

Right we're all setting about Greenland with blow torches,hammers and chisels

[ukpaul]

Keep dropping lots of black carbon across Greenland for a start,  this will aid massive ice loss but with the unfortunate side effect of putting millions underwater. I imagine that this tipping point Is of the reasons that some forecasts suggest a window where the UK cools as the rest of the globe warms.  If this leads to movement or slowng down of the gulfstream then that would add to any change.

Edited February 4, 2016 by ukpaul

[Carl46Wrexham]

1 hour ago, joggs said:

Right we're all setting about Greenland with blow torches,hammers and chisels

It was attempted this season...no one however had a hammer and a chisel. This season has proved that using a pencil and a miniature trumpet doesn't work.

[David Morse]

@chionomaniac @phil nw. I see for support of my SSW claim I should have just brought in Judah Cohen:

 

 

Edited February 4, 2016 by David Morse

[phil nw.]

23 minutes ago, David Morse said:

@chionomaniac @phil nw. I see for support of my SSW claim I should have just brought in Judah Cohen:

 

 

Yes David the warming at the top has been quite significant but what we have is a vortex displacement.

 Note the warm area at 90N where the pv has been pushed from,Unfortunately still no split and the cold core is sent over to the Atlantic/Greenland area which gives us a further period of westerlies.So no favours for us from this event if looking for cold.

The warming soon looks to be peaking before declining by day 10.

if you read back through recent posts the w1 warmings and displacement from the pole have been discussed.We are unlucky not to have benefited so far from such a notable warming.  

 

Edited February 4, 2016 by phil nw.
missed word

[chionomaniac]

35 minutes ago, David Morse said:

@chionomaniac @phil nw. I see for support of my SSW claim I should have just brought in Judah Cohen:

 

 

I don't actually understand what Judah is trying to say here? And many have mentioned this as well as Andrej has on twittter.

So let's make this absolutely clear, in old money this can be classified as a minor warming or even a minor SSW at a stretch (though personally I can't stand that term). But this graph does not take into account the mean zonal winds and dynamical shape of the vortex because that would show no mean zonal mean wind reversal at 60N and 10hPa and never has, so no SSW as the majority know and define one. Judah has tried to argue on twitter that this will still lead to a blocked trop profile. But when you look at the dynamical positioning and reforming of the vortex after the warming event then it looks pretty obvious that there is no blocking to be had - certainly not in the Atlantic sector. There is a lot more to strat dynamics than one chart showing the temperature rise at the North Pole, and Judah has yet to demonstrate exactly how the displaced vortex will lead to tropospheric impacts other than what the models show currently and @recretos has so ably demonstrated so far.

[nick sussex]

Chiono I see your irritation at the minor SSW. What is it that you don't like about this term? Personally I don't have a problem with it unless people don't clarify whether its a minor or major one and simply state SSW.

Aren't these technical terms agreed on by the WMO?

[chionomaniac]

10 minutes ago, nick sussex said:

Chiono I see your irritation at the minor SSW. What is it that you don't like about this term? Personally I don't have a problem with it unless people don't clarify whether its a minor or major one and simply state SSW.

Aren't these technical terms agreed on by the WMO?

I think that in this case Judah hasn't stated whether there is a major or minor warming and this has led to a lot of people stating that a SSW is occurring (just like David Morse has done) when in fact a SSW as defined by Polvani et al is known as a major one with wind reversal and isn't occurring. Amy Butler confirmed that this still hasn't been agreed yet and will be further considered when SPARC meet later in the year.

Calling a SSW a minor one is a bit like using the term mini tornado to me. It's either a tornado or it isn't. Likewise SSW.

 

[nick sussex]

34 minutes ago, chionomaniac said:

I think that in this case Judah hasn't stated whether there is a major or minor warming and this has led to a lot of people stating that a SSW is occurring (just like David Morse has done) when in fact a SSW as defined by Polvani et al is known as a major one with wind reversal and isn't occurring. Amy Butler confirmed that this still hasn't been agreed yet and will be further considered when SPARC meet later in the year.

Calling a SSW a minor one is a bit like using the term mini tornado to me. It's either a tornado or it isn't. Likewise SSW.

 

I understand your point however we're talking about different levels of the stratosphere. Those different levels are still part of the strat so what could you call a sudden warming of the strat at the level not sufficient to cause the zonal reversal at 60N, 10 Hpa.

It has to be called something? Or some other name should be given to the major one to distinguish it.  Judah Cohen however should have clearly stated it was a minor SSW  because it seems to have led to some confusion.

Isn't this a case of over complicating something? The minor or major term surely makes it clear that one has a bigger impact than the other. Personally I really don't see the problem as long as people differentiate between the two when mentioning a SSW.

 

Edited February 4, 2016 by nick sussex

[phil nw.]

Hi Nick,

My twopennyworth.

What has caused some confusion here is that Cohen in his tweet talks about the temperatures at 10hPa at 90N with reference to the warming.

As i understand things a full blown SSW is measured at 60N and 10hPa and the temperature rise there is much less and so consequently is the reduction in mean zonal wind speeds.

The MO seem to support measurement of a SSW at 60N/10hPa and they look at a temperature rise of around 50C .This sudden rise has been achieved over the pole as mentioned by Cohen but not at 60N so he seems to be using the term in a general sense.

"What is an SSW?

The term SSW refers to what we observe – rapid warming (up to about 50 ­°C in just a couple of days) in the stratosphere, between 10 km and 50 km up."

 link.http://blog.metoffice.gov.uk/tag/sudden-stratospheric-warming/

I would simply say we have had a partial warming with a vortex displacement rather than a complete SSW based on the criteria i have highlighted.

Edited February 4, 2016 by phil nw.

[chionomaniac]

7 minutes ago, phil nw. said:

Hi Nick,

My twopennyworth.

What has caused some confusion here is that Cohen in his tweet talks about the temperatures at 10hPa at 90N with reference to the warming.

As i understand things a full blown SSW is measured at 60N and 10hPa and the temperature rise there is much less and so consequently is the reduction in mean zonal wind speeds.

The MO seem to support measurement of a SSW at 60N/10hPa and they look at a temperature rise of around 50C .This sudden rise has been achieved over the pole as mentioned by Cohen but not at 60N so he seems to be using the term in a general sense.

"What is an SSW?

The term SSW refers to what we observe – rapid warming (up to about 50 ­°C in just a couple of days) in the stratosphere, between 10 km and 50 km up."

 link.http://blog.metoffice.gov.uk/tag/sudden-stratospheric-warming/

I would simply say we have had a partial warming with a vortex displacement rather than a complete SSW based on the criteria i have highlighted.

Well that's a dumbed down definition of a SSW if ever I saw one. Well done MO for confusing a definition even more. At what point do scientists ever use the word 'about' in definitions!?

[phil nw.]

1 minute ago, chionomaniac said:

Well that's a dumbed down definition of a SSW if ever I saw one. Well done MO for confusing a definition even more. At what point do scientists ever use the word 'about' in definitions!?

lol yes for general consumption i guess Ed.Still Strat. wind reversals are mentioned further down in the piece which i guess is the main measurement.

 

[knocker]

10 hours ago, chionomaniac said:

I think that in this case Judah hasn't stated whether there is a major or minor warming and this has led to a lot of people stating that a SSW is occurring (just like David Morse has done) when in fact a SSW as defined by Polvani et al is known as a major one with wind reversal and isn't occurring. Amy Butler confirmed that this still hasn't been agreed yet and will be further considered when SPARC meet later in the year.

Calling a SSW a minor one is a bit like using the term mini tornado to me. It's either a tornado or it isn't. Likewise SSW.

Sticking with the tornado analogy perhaps a scale along the lines of the EF scale just to denote strength of warming. etc. It could be known as the ChioRec scale.

[Interitus]

 

Well if we go by the original definition of SSW when first observed by Scherhag in the 1950s as "explosive warmings in the stratosphere" then this is absolutely a SSW befitting the acronym, that it doesn't fulfil one metric used by Charlton and Polvani (commonly referred to as CP07) for their particular study of reanalysis data is neither here nor there. I linked the Defining Sudden Stratospheric Warmings paper by Amy Butler et al previously and urge everyone interested to read it - http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-13-00173.1 and the supplement paper http://journals.ametsoc.org/doi/suppl/10.1175/BAMS-D-13-00173.1/suppl_file/10.1175_bams-d-13-00173.2.pdf

They point out the benefits and simplicity of CP07, but also some misconceptions and drawbacks, in short (tl;dr) -

Quote

Among the definitions surveyed here, the CP07 definition provides a strong basis for a definition of major SSWs because of its simplicity and relevance. However, it lacks robustness. Using a latitudinal average of zonal winds rather than one particular latitude, or using 65°N instead of 60°N, may decrease sensitivity to changes in the vortex edge

Their fuller appraisal -

Quote

One of the most commonly used SSW definitions (pertaining to major midwinter SSWs) in the recent literature is based on the diagnostic of zonal-mean zonal wind at 60° latitude and 10 hPa and is described in detail by CP07. The CP07 definition is likely popular because of its simplicity (one variable at one latitude and pressure level) and because it includes detailed implementation guidelines pertaining to a) the separation of closely timed events (i.e., if the zonal-mean zonal wind reverses twice within a short period of time, are those events considered separate and independent?), b) exclusion of final warmings, and c) identification of split-type events. In recent years, this definition has commonly (but mistakenly) been cited as “the WMO definition.” However, it lacks the meridional temperature gradient reversal requirement and the consideration of zonal winds poleward of 60° latitude in the McInturff (1978) definition. Moreover, the CP07 definition clearly distinguishes between late midwinter and final warmings, requiring zonal-mean zonal winds to return to westerly for at least 10 days prior to 30 April to be classified as a major midwinter event. As demonstrated in the next section, these distinctions matter.

Quote

some studies (e.g., Charlton and Polvani 2007, hereafter CP07) classify Canadian warmings as major warmings if a circulation reversal occurs, while Labitzke (1977) argues against this based on differences in synoptic development

Quote

Some definitions show noticeably more decadal variability than others. For example, the definitions based on zonal-mean zonal winds at 60°N yield no major warmings during most of the 1990s, when other definitions, including one based on zonal mean zonal wind reversal at 65°N [eg Hannah Attard's charts], show two to five major SSWs during that decade . Why do these differences—among the definitions and over time—exist? One contributing factor may be changes in the observations assimilated into reanalyses. Definitions based on one latitude or region may be more sensitive to this than definitions based on larger domains. This explanation appears possible in light of changes in the Northern Hemisphere radiosonde network (Fig. 3). The number of regularly reporting radiosonde stations in the region 50°–90°N increased from the 1960s to the 1980s, but then it dramatically decreased in the 1990s in association with the collapse of the Union of Soviet Socialist Republics (USSR; ~45°–135°E) and parts of its meteorological networks. The timing of the largest reduction in radiosonde observations from 55° to 65°N (which is especially noteworthy in the region of the former USSR; not shown) roughly coincides with the period when few major SSWs are detected using the zonal mean zonal wind reversal at 60°N. We find it worth noting that the definition most dependent on this particular latitude detects the fewest major SSWs during a decade that experienced the greatest loss of measurements there. Arguably, assimilation of satellite data into the reanalysis products used to calculate SSW events here should somewhat mitigate the sampling inhomogeneities in radiosonde observations. Moreover, major SSW events are still detected in the early 2000s despite reduced numbers of radiosonde stations. The mid-1990s are known to have been particularly cold years in the Arctic stratosphere (e.g., Pawson and Naujokat 1999), which argues against invoking sampling issues to explain the lack of detected SSWs in the 1990s. On the other hand, the fact that the zonal-mean zonal wind diagnostic at 65°N rather than 60°N does detect major SSWs in the 1990s suggests sensitivity to this particular latitude. This begs the question: Is 60° latitude a reasonable choice for defining SSWs, particularly now that near-global satellite measurements are available? Does this latitude represent some key physical feature of stratospheric circulation? Or does it make sense to choose a more poleward latitude, average over a larger latitude region, or (more stringently) require a reversal of the zonal winds everywhere poleward of a particular latitude? Figure 4a shows the dependence of major SSW frequency on the latitude of circulation reversal. When major SSWs are diagnosed using the reversal of the zonal-mean zonal winds at one latitude only (local reversal, blue line), the number of major SSWs (1979–2012) minimizes if that latitude is between 50° and 60°N. To understand this result, we also consider the number of major SSWs that occur if instead the zonal winds everywhere poleward of a particular latitude must also reverse direction (coherent reversals, red line). Poleward of 60°N, the local and coherent reversal requirements yield nearly identical numbers of SSWs; anywhere in this region, if the wind reverses from westerly to easterly at one latitude, it is also almost certain that the wind is reversing everywhere poleward of that latitude. Equatorward of 60°N, however, the number of coherent reversals continues to decrease while the number of local reversals increases. This bifurcation can be explained by noting that these latitudes mark the surf zone (McIntyre and Palmer 1984), where breaking waves can drive local reversals in the stratospheric circulation, which is not associated with coherent polar vortex dynamics. Thus, 60°N is near the average edge of the coherent polar vortex.

The last quote shows that classification of SSW is highly sensitive to the chosen metric, both for historical data and future climate forecasting. Butler et al compared 7 SSW definitions with reanalysis data from 1958-2014 and found that -

Quote

The average number of major SSWs per winter for this 57-yr period range from 0.46 to 0.81 per winter among the seven definitions, and the dates of major SSWs for each definition differ substantially (see also Table ES2). In fact, of the 26–46 SSWs identified in each definition, only 13 SSWs are identified by all seven definitions using NCEP–NCAR reanalysis data. Using different reanalyses (or six-hourly winds rather than dailyaveraged winds, or data on a coarser horizontal grid) produces slightly different results

A final indirect criticism of CP07 and other definitions comes from the vortex moments work of Mitchell et al 2011 and is particularly pertinent regarding the major/minor debate -

Quote

One of the major conclusions drawn from this study is that traditional definitions of SSW events often miss extreme behavior of the vortex. The analysis of the distributions of each of the moment diagnostics has shown that so-called minor SSW events often have a larger influence on the geometry of the vortex than major SSW events. Likewise, the subdivision of splitting and displacement events is not always as well defined as the names suggest. Often a vortex displacing event will split into two daughter vortices before the vortex returns to its stable state, and vice versa. It is therefore not only the use of such traditional diagnostics that often leads to poor characterization of the vortex, but the very binary definition of SSW events that is used in the mainstream literature

 

[Interitus]

12 hours ago, phil nw. said:

Hi Nick,

My twopennyworth.

What has caused some confusion here is that Cohen in his tweet talks about the temperatures at 10hPa at 90N with reference to the warming.

As i understand things a full blown SSW is measured at 60N and 10hPa and the temperature rise there is much less and so consequently is the reduction in mean zonal wind speeds.

The MO seem to support measurement of a SSW at 60N/10hPa and they look at a temperature rise of around 50C .This sudden rise has been achieved over the pole as mentioned by Cohen but not at 60N so he seems to be using the term in a general sense.

"What is an SSW?

The term SSW refers to what we observe – rapid warming (up to about 50 ­°C in just a couple of days) in the stratosphere, between 10 km and 50 km up."

 link.http://blog.metoffice.gov.uk/tag/sudden-stratospheric-warming/

I would simply say we have had a partial warming with a vortex displacement rather than a complete SSW based on the criteria i have highlighted.

 

From the MERRA data, for SSW in January & February, the peak in average 60-90°N 10mb polar cap temperature is 235.08 K (-37.92°C) occurring on day of reversal.

The most recent available GEOS 60-90°N 10mb forecast for 08/02 is 241.79 K (-31.21°C), warmer than 12 of 17 SSW and 7th warmest Jan/Feb period behind (max dates)

23/01/09 - 251.83 K - SSW (as per 60°N 10mb wind)

29/02/80 - 247.42 K - SSW

27/02/99 - 243.41 K - SSW

05/02/81 - 243.16 K - NO SSW (+0.6 m/s)

02/01/85 - 242.92 K - SSW

30/01/95 - 242.83 K - SSW (-0.02 m/s!)

[lorenzo]

Last conversation I had with Amy Butler

For now we are not re-classifying beyond the WMO definition of 10 hPa 60N reversal but more work will be done on that soon...

Hope that helps- yes I agree definitely scope for more categories / definitions. Each year the study of the stratosphere takes on new layers, over summer I think it will evolve up a notch again.

Great warming going on - and probably the best example of the two extremes - warming and brutal vortex equalling no guarantees...

[Paul123]

On 5-2-2016 at 10:04 PM, lorenzo said:

Last conversation I had with Amy Butler

For now we are not re-classifying beyond the WMO definition of 10 hPa 60N reversal but more work will be done on that soon...

Hope that helps- yes I agree definitely scope for more categories / definitions. Each year the study of the stratosphere takes on new layers, over summer I think it will evolve up a notch again.

Great warming going on - and probably the best example of the two extremes - warming and brutal vortex equalling no guarantees...

Measuring (determining) a warming in (by) meter per second is asking for trouble. Sooner or later someone will come up with a more plausible alternative, resulting in even more confusion.

To use one line in space also is far from elegant, when defining a warming for the whole of the polar stratosphere. 

Everwhere on forums, and when talking to people, I notice incomprehension concerning the used method of classification.

This definition should be adjusted sooner or later, I think.

Edited February 7, 2016 by Paul123

[Recretos]

Measuring (determining) a warming in (by) meter per second is asking for trouble.

But thats exactly what it is. Everybody make the same mistake of looking and emphasising the temperature, like its THE alpha and the omega of the strat. All we always hear about is the temperature. But like this year when the warming has a negative effect, people cant seem to understand how and why that is possible "if like the strat warming is like the most certain thing to like make two months of cold shots and like a big greenland block". 

Those meters per second have a lot more meaning than people give it credit for. Even proffesionals like Judah Cohen Phd. 

I remember back in my strat beginings 4 years ago I was already emphasizing the importance of the heights when everybody was looking at temperature. Unless it was a split forecasted. Then it gets some attention.  

[Paul123]

3 hours ago, Recretos said:

But thats exactly what it is. Everybody make the same mistake of looking and emphasising the temperature, like its THE alpha and the omega of the strat. All we always hear about is the temperature. But like this year when the warming has a negative effect, people cant seem to understand how and why that is possible "if like the strat warming is like the most certain thing to like make two months of cold shots and like a big greenland block". 

Those meters per second have a lot more meaning than people give it credit for. Even proffesionals like Judah Cohen Phd. 

I remember back in my strat beginings 4 years ago I was already emphasizing the importance of the heights when everybody was looking at temperature. Unless it was a split forecasted. Then it gets some attention.  

I fully agree. Last four years for example each had strong warming events, but only the winter of 2013 delivered a wind reversal and a really cold continuation of the tropospheric winter combined with a prolonged negative AO.

Classifying stratospheric events by its wind reversal always is preferrable , but then call it what it is: a wind reversal. For instance a Winter Stratospheric Wind Reversal (WSWR). 

 

Edited February 7, 2016 by Paul123

[Recretos]

Well yes, but I am not talking about definitions. I will leave that to people with Phd's. 

I am talking about actual dynamics. As far as the definitions go, I support multi definitions, or multi category classification. 

[Singularity]

http://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-61.47,87.69,315/loc=148.900,84.514

You can see how little the vortex cares about the powerful wave-1 warming taking place. You can even see the acceleration relating to the 'anti-vortex' that Recretos has talked about.

[KyleHenry]

Time wise it is all a formality.

Second forecasted +MT event in outer range of GFS, will be a swift end to the vortex.

Let it be said that if it verifies, it won't be classed as a final warming event as it is too early. 

Cold Spring early Summer anyone?

[SnowManClan]

Forecasts seem to have a much larger than normal penetration of lows from north to southern Europe. Is this in any way connected to the shifted polar vortex? Thanks in advance for any input : )

[feb1991blizzard]

4 hours ago, KyleHenry said:

Time wise it is all a formality.

Second forecasted +MT event in outer range of GFS, will be a swift end to the vortex.

Let it be said that if it verifies, it won't be classed as a final warming event as it is too early. 

Cold Spring early Summer anyone?

It might do although maybe unlikely, if the mean zonal wind speed at 60N up at 10mb never recovers to above zero for the rest of the stratospheric season, then it would by definition be a final warming.

[bryan629]

This is Cohens latest blog..... 

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

What i would like to know is this paragraph good news or bad news for the uk 

30–day

I remain confident that a T-S-T coupling event is ongoing and about to enter its final stage.   The strong negative AO state that dominated January (Figure 1) was a tropospheric precursor that initiated a strong burst of vertical energy transfer (and is predicted to be record breaking) from the troposphere into the stratosphere that will peak over the next few days as seen in the vertical wave activity flux (WAFz) plot (Figure 8). Model runs continue to predict that this energy burst will result in record warm temperatures for the polar stratosphere and force an impressive SSW.  As we discussed above, this will result in an almost immediate tropospheric response resulting in Arctic outbreaks for East Asia and especially the Eastern United States.