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Thanks for this great blog post, R. Gates!

After reading the whole post, a weird idea for geo-engineering popped up in my head. Since SSW's play a role in the Warm Arctic Cold Continents phenomenon (at least that's what I assume), would it make sense to green the Taklamakan Desert to prevent all that warm air to build up and then get swung upwards against those mountain ranges?

Less SSW's would mean that the polar vortex stays intact and all the cold air stays in the Arctic helping the ice to thicken more. It would also reduce cold outbreaks in Eurasia.

Sorry for the weird thought! :-)

Martin Gisser

Greening the Taklamakan! I just had the same obvious, not weird thought. There's the usual caveat: It might be easier said than done. (Hmm, it might be easier done than Sahara or Australian outback: The Kunlun Shan mountains might be a good source of irrigation water.) Anyhow, afforestation is one of the few serious geoengineering options. This one even with beneficial social side effects (cf. Wangari Maathai).

R. Gates


Thanks for your work in formatting it and the opportunity to guest-post!


I think the apparent "explosion" of that warm blob of air when it reaches the arctic is an artifact of the map projection which is used. You might want to see if you could find a different projection to use, or perhaps one which was oriented differently to avoid significant distortion (e.g., run an "equator" from the desert to the pole).

David vun Kannon

Great post!
So, what occurs one step earlier in the causal chain? If you looked before Dec 21, 2012, for example, would you find a period of low wind over this area? I'm not sure what would allow the desert air to accumulate heat, given that the cloudless air from low humidity usually allows all the heat to escape to space overnight. Does a dust storm act similarly to clouds for trapping heat?

Neven - green and brown plants might absorb more heat than light colored sand. Without knowing what causes the anomalous warming in the first place, it is hard to say what would work.

R. Gates


In regards to what comes earlier in the chain related to winds and the desert accumulating heat, I think the desert in that area would naturally be a source of warm air, but it would be good to get some solid data on what the jet stream was doing around that time as well. There is a pretty tall mountain range also to the north (refer back to the LIDAR image in the post) of the Taklamakan Desert. If jet steam winds were coming down off of this range, they would be compressed and warmed. Then they would scream south across the Taklamakan, before being shot back up into the stratosphere when they hit the Tibetan Plateau. Anyway, that's one possibility, but we need more data which is pretty sparse from that incredibly remote part of the world.

Espen Olsen


Are you looking for a gardening job in Taklamakan Desert?

Susan Anderson

A staggeringly amazing piece of work (but what else does one expect at Neven's). Thanks.

WRT greening the Taklamakan, it is my understanding that it is one of the most desolate and challenging places on earth. I do remember something about planting dry brush to stop the blow, and agree this is a worthwhile thought, if there is some practical way to make it work.

I continue to plug this effort in a much less desolate location, but it is depressingly likely that something so labor-intensive and local, no matter how successful, will be trumped by something large that can be done with machinery. This is mildly OT, with apologies:

This gives a brief overview (in Jordan):

Here's a site that covers a bit more, from the same people:

Don't know if this includes the above; I see one supporter is Virgin's Richard Branson which could be positive if it doesn't overshadow the idea and the work:

Aaron Lewis

In the course of AGW, could this become a normal and stable winter circulation pattern? This would be a mode not considered by Dr. Francis.

It seems to me that in the past, the Arctic was better able to absorb the heat and shut the event down, whereas a "SSW" event with a sea ice free Arctic might form a sustained circulation loop of a nature not considered by the models.

R. Gates


That's a great point. I did notice in my review if the reanalysis data what appeared to be a slight weakening of the vortex in the past 5 years especially-- maybe from declining sea ice? A weaker vortex would be easier to disrupt, even by small or moderate SSW's.

John Hulme

What a tremendous post! Thank you for your hard work.


R. Gates

This was very interesting to read. Thanks. I haven't read as many papers on SSWs as I would like, but from what I am aware of, the common working hypothesis on SSW formation is that mid-latitude Rossby wave-breaking events are responsible for disturbing the polar vortex and creating a SSW event.

This also fits with the observed disparity between SH and NH occurrence of SSWs, because Rossby wave-breaking occurs more often in the northern hemisphere, due to the storm tracks, Rocky Mountains, etc.

This does lead to the somewhat unsatisfying situation that blocking events (where wave-breaking of the flow creates a block in the flow) can be seen both as a precursor to a SSW, and as a consequence of a SSW.

What do you think of the mid-latitude Rossby wave-breaking hypothesis?

SSW events occur roughly one year in two - I would guess that it would be interesting to look at composites of the meteorology in your source region for years with and without a SSW.

It would also be interesting to look at these regions in seasonal forecast models, to see whether differences there are responsible for explaining the difference in predictability of SSW events.

This is a long-winded way of asking for your email address.

Michael Splitt

Thanks for the post, but as a meteorolgist I need to comment on omega:

"A high positive omega over a geographic region would indicate that a large mass of air was rapidly moving upward in that region, and likewise, a negative omega would indicate that a mass of air that was falling or moving downward."

Omega is Dp/Dt in the atmosphere; but is opposite in sign to Dz/Dt (w). Positive omega implies increasing pressure with time and sinking motion (decreasing z), negative omega implies decreasing pressure with time and rising (upward in z) motion. This may require revision of your analysis.

Chris Reynolds

Thanks for a very interesting read.

I agree with David about the term 'explosion' being related to the map projection. But that's a minor issue, the influx is quite obvious, FWIW I've referred to them as 'lift events' in what follows.

I had been anticipating more or less what you've come up with, so it seems I've been paying rather more attention to what you've been posting than I had thought. :)

You mention the Jetstream...

Here's what I'm wondering: Francis suggests that the Eurasian snow advances are pushing the boundary between sub tropical and cold air south, this agrees with Cohen and other researchers. I'm wondering if the reason for these lift events into the upper tropo and thence strato could be due to Jetstream interactions with the region you've correctly identified. i.e. the jetstream is moved into a position where it can interfere with the orography and create a lift event. I'm wondering if the wave activity flux observed by Cohen as the result of snowline advance impacting the atmosphere could be the lift event, with the key factor being jet interaction with the orography.

Jetstream plots are available here:
Or we would use the 5650m* 500mb geopotential height (GPH) in NCEP/NCAR reanalysis as a proxy for the region of the jet. *May need to check up on that figure actually.

Anyway. The lift event of 2012 happened about 25th.

Here's the Jetstream on the 18th,
Then the 25th

Note that the lift event seems to have split the jet into two, a primary southwards branch, and a secondary north branch. This is seen in the NCEP/NCAR mean GPH as a spread in the 5650m (remembered it right, phew!) contour. I've switched to mean GPH (not anom) because those jetstream plots only go to 2009, and I want to look at 2003.

Using this site to get omega and GPH

So in 2003 you show events on 22/12/2002 and 10/1/2003, what does the 5650m GPH look like then? There is a broadening around the same place, though not as marked as 2012. By 30/12/2003 the 5650m 500mb GPH is a thin stream of equal thickness to the previous periods I've checked - i.e. no broadening and now suggestion of a split in the jet. I've just checked 20/12/02, a thin 5600m band, before the lift event.

Now to 10/1/03, 5650m 500mb GPH is very broad, but the broadening begins more westerly of the region you specify.

Having been looking at both GPH and jetstream plots; the jetstream is often broken in that region, probably due to the Himalayas. I suspect that the 5650m 500mb GPH is a more useful indicator. e.g. Jan 2009 is interesting, again a broadening of the 5650m GPH at the same as 850mb +ve anomaly of omega in the region you've identified.

I need more information. How have you generated to Hovmoeller type plot of air temp by lat at 100mb? (I only have one criticism of the post, it needs details of where the images/data are sourced from.)

Michael Splitt

Thanks for the posting; as a meteorologist I want to correct a statement regarding omega:

"The vertical rising or falling of air in the atmosphere is known as omega and is measured in Pascals per second (Pascal/s). A high positive omega over a geographic region would indicate that a large mass of air was rapidly moving upward in that region, and likewise, a negative omega would indicate that a mass of air that was falling or moving downward. "

Omega is Dp/Dt in the the atmosphere and is opposite in sign to vertical velocity (Dz/Dt). If omega is positive, movement to higher pressure is implied and infers sinking motion; whereas when omega is negative it implies movement to lower pressure and infers upward motion.


Thank you for this great piece of work! In the omega-december-2012 image, it looks the southern high omega might be south of Himalayas (Bhutan, Nepal)? Is this seen also in the other events you have studied?

Chris Reynolds


How then is the high (+ve) omega at times of apparent uplift to be interpreted?

R. Gates


I am familiar with the Rossby wave breaking hypothesis, and given that these are supposedly vertically directed Rossby, it has a great deal of common dynamics with my Taklamakan-Tibetan Plateau hypothesis.

Here's the thing, you mentioned the Rockies as one source of the mid-latitude Rossby wave breaking, but in my analysis of the 10 hPa warming that always is a precursor to the SSW, I never found a single instance of this occurring over the Rockies. The 10 hPa thermal waves as found in the reanalysis data always occurred over Asia. Would there be a reason that vertically directed Rossby waves should only form over Asia as precursors to SSW's? Also, from a dynamic perspective, I would be curious to know exactly how a vertically directed Rossby wave would be different than the vertically directed mass of warm air as found in high positive Omega areas?

Michael Splitt


I am not sure where the apparent uplift you are referring to is. Note, that the plots have vertically averaged omega and no streamlines. I am wondering if this is simple descent down the sloping terrain from the Himalayas northward (a Chinook effect), or the forced descent from a vertical wave (such as with Colorado wind storms).

R. Gates


Given the prevailing winds in the Taklamakan desert in the winter are from north to south and the positive omega occurs at the south side of the desert, where it rises rapidly to the Tibetan Plateau, I am a bit puzzled by your interpretation. I need to look into this a bit. Any suggestions for resources on omega?

Chris Reynolds


I'm referring to the animated gif in the post showing a warm penetration into the north, and the warming at the stratosphere implying lift.

R Gates,

I can't give a link or my post will be spam filtered (after this thread I'm quitting this site for that reason). But check Wikipedia, it's confirmed in the final paragraph.

I'm really rather puzzled now. Using NCEP/NCAR I've been looking at the evolution of the 25/12/2002 event. There seems to be a pocket travelling up through the atmosphere northwards who's meridional flow is _south_. It got me so puzzled I opened up an ECWMF plot for a few days ago and checked to see if my orientation of +ve and -ve merid flow was correct, it is.

I need to do some thinking. I've been in touch with Dr Cohen and Dr Francis previously and may ask their opinions.

Michael Splitt


Lift usually implies cooling (adiabatic expansion outweighs the advection of warm air upward in the atmosphere -- they exactly counter each other for neutral lapse rates). The warming, then, can be caused by horizontal advection of warm air or by large scale descent, or by diabatic effects (latent heat release, radiative fluxes). My WAG is that we are seeing large scale sinking motion causing the warming -- not uplift.

R. Gates


If the warming is occurring at 10 hPa, at 40N, where is the air sinking from?

Chris Reynolds


"adiabatic expansion outweighs the advection of warm air upward in the atmosphere"

Thanks I wasn't aware of this, I had thought that upward northerly advection would warm the stratosphere with air abnormally warm for the latitude overcoming abiabatic cooling. Given the location and timing, desert/tundra in winter at high altitude, it doesn't seem like latent heat would be a big player.

My meteorology is just what I need to grasp the issue of sea ice, SLP and air temps. So I'll step back for a moment and see how this pans out before deciding to email anyone else.

PS - there is a speculative comment from me about the Jetstream in the spam filter at present.

Michael Splitt

R. Gates:

There is ~10 km vertical separation between 10 mb and 1 mb (where temperature may peak between the stratosphere/mesosphere). Thus, there is still plenty of warmer air (especially if we consider the more relevant potential temperature) above 10 mb that can sink and warm.


Four comments got caught again in the spam filter (sorry!). The comment Chris Reynolds alludes to is a bit further up.

Jai Mitchell

Thanks for the informative post. This reminds me of the "Biotic Pump" theory that has been (to my knowledge) pretty much quashed. Since the charts you are working with are at the 10hPA (10mb) range I was wondering what kind of similarity there is to this mechanism in the 500hPa range?

Thanks for the clarification Michael Splitt re: positive/negative omega vs. high/low pressure anomaly.

link to biotic pump paper: http://www.hydrol-earth-syst-sci.net/13/1299/2009/hess-13-1299-2009.html

Chris Reynolds

Thanks Neven,

Idle musing,

I think I'm getting a bit more of a handle on what's going on. This isn't an issue of warm air moving around.

With regards the animated gif in the post. The issue is that Rossby Waves are radiating from the disturbance in South Central Asia and are breaking into the stratosphere where their dissipation causes the warming (due to adiabatic heating).

This seems to be similar to the mechanism I suspect may be at play in the summer circulation pattern centred on Greenland, where the post 2007 accentuation of the Greenland ridge interacts with zonal flow and causes a ring of low pressure tendency at 3000km distant.

Now if the Arctic sea ice would just stop doing what it's doing for a few years I'd put understanding planetary waves at the top of my list.

Now I will stop waving my hands around and leave the discussion to those who know more.

Jai Mitchell

Do we have indication of similar patterns in the 500mb level? I am looking more at an increase in the intensity of the Hadley Cell.


R.Gates, an amazing discours… well done and really stimulating.

Like Chris Reynolds, I’ve been noodling a bit with Squall Jet Stream animation and NCEP/NCAR while reading.

Michael Splitt did mingle some doubt in my understanding, I have no immediate knowledge of the behaviour of large air masses (at least, not much more than high school basic physical Gay-Lussac stuff…).

Squall hinted at some interesting interactions between the Subtropical and (very scattered) Polar Jet in the region. NCEP/NCAR showed 1000MB Omega anomalies out there (and over East Greenland BTW).

Further, I’m still in the teleconnection thing… what about the other omega regions on your map: Szechuan and East Nepal? Could they contribute to ‘collision’ of warm tropical air and these Jets? It wouldn’t necessarily have to be warm air lifted in the Takla Makan, which, after all, is a ‘cold’ desert, in December for sure…


I have voiced contrary opinion to Mr Simpson’s finding’s elsewhere, I would only repeat following:
There are strong indications that the north hemisphere's SSW is initiated by volcanic eruptions in Kamchatka peninsula. It is likely that after the volcanic eruption’s dome of warm air punctures the tropopause opening a ‘plug hole’ into the stratosphere, which then may let large volume of the warm Pacific air to pour into the stratosphere.
Mr Simpson cherry picks his animations by choosing 10hPa altitude, by which time SSW origin is lost; however lower altitude e.g. 50hPa clearly show location of the initial burst, as shown by this copy of a NOAA’s animation.
with more details here http://www.vukcevic.talktalk.net/NH.htm
Mr Simpson states:
Small and infrequent SSW's do occur over the south pole, but, as you'll see, there are precise reasons why they are mainly a Northern Hemisphere phenomenon, displaying yet one more reason why the planet is biased toward the advection of energy toward the North Pole versus the South Pole (but more on this later).

Not exactly correct:
Since 1979 or. 33 years of satellite age data, not a single SSW is recorded in the south hemisphere, see max trace at http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/10mb6590.gif
One obvious reason is that Mt Erebus volcano would have to erupt strongly in the Jun-September period, but it has not done so.
Hypothesis is no good if it is valid only 50% of the time.
p.s. past events: http://hal.archives-ouvertes.fr/docs/00/56/34/77/PDF/SSW.pdf

Just Testing

We must at once send a team of our best lepidopterologists to determine the lifecycle of this Taklamakan Desert butterfly.

Kevin O'Neill

vukcevic - "There are strong indications that the north hemisphere's SSW is initiated by volcanic eruptions in Kamchatka peninsula."

No, there isn't. I've read your paper and there's nothing but handwaving. No data showing even correlation, much less causation.

Andy Lee Robinson

Interesting, my out-of-the-box mind just conjured up an image of a planetary-scale lava lamp!
Anyone else?

Kevin O'Neill

Re:vukcevic - I should have added that if Kamchatka was the source of the SSW events then we would expect to see numerous dust and ash signatures in the Greenland icecores from Kamchatka. I have not found any papers that list Kamchatka as a possible source for the dust that has been found in the icecores.

As R. Gates points out, "It has been known for quite some time that Greenland ice cores contain a high level of isotopes that can be traced back specifically to the Taklamakan desert and associated Tarim basin."

This makes the Kamchatka volcanoes as a source of the SSW events extremely dubious.

R. Gates


Respectfully, volcanoes have long ago been discounted as the cause of SSW events. I respect your staunch support of this notion, but the data simply don't support it.

Steve Bloom

Why respect such a thing, Randall?

Neven, the fact that the spam filter seems to have tagged me permanently isn't such a problem since you're pretty on top of releasing caught comments and mine don't tend to be super-timely anyway, but Chris leaving the site over this problem would be a serious loss. The improvement Typepad promised has obviously not been forthcoming.

[Nope, I've asked them about it again today. I hope they solve it soon. I'm getting tired of checking that spam filter.]


Great post and discussion.

My burning question:

Is there any indication that GW is increasing the frequency or intensity of SSW events?

Any light anyone could throw on this question would be most appreciated.


Randall, thank you for all the time and effort you put into this very informative post. Your information along with the comments certainly, once again, demonstrates how the collective intelligence of everyone here is so much greater than any individual.

R. Gates

That's an excellent question wili and I don't think anyone knows the answer. There could be some indication the polar vortex may be a bit weaker, perhaps from diminished sea ice, and that could allow SSW's to exert more influence on winter weather. But that is still very speculative.

Chris Reynolds

Steve Bloom,

I've read your paper and there's nothing but handwaving.

Handwaving from Vukcevic?


Shurely Shome Mishtake!


For those who don't get the sarcasm - I too have dealt with Vukcevic. The impression I got was of a rhetorical windmill.

Steve Bloom

As it happens there's a recent paper on the subject. It will have been in that search link I provided you a few days ago, Randall.

It's here. Title/abstract:

Variability and trends of major stratospheric warmings in simulations under constant and increasing GHG concentrations

Ensemble simulations with a coupled ocean-troposphere-stratosphere model for the pre-industrial era (1860 AD), late twentieth century (1990 AD) greenhouse gas (GHG) concentrations, the SRES scenarios B1, A1B, A2, as well as stabilization experiments up to the Twenty-third century with B1 and A1B scenario GHG concentrations at their values at 2100, have been analyzed with regard to the occurrence of major sudden stratospheric warmings (SSWs). An automated algorithm using 60°N and 10 hPa zonal wind and the temperature gradient between 60°N and the North Pole is used to identify this phenomenon in the large data set. With 1990 CO2 concentrations (352 ppmv), the frequency of simulated SSWs in February and March is comparable to observation, but they are underestimated during November to January. All simulations show an increase in the number of SSWs from the pre-industrial period to the end of the twenty-first century, indicating that the increase of GHG is also reflected in the number of sudden warmings. However, a high variability partially masks the underlying trend. Multi-century averages during the stabilization periods indicate that the increase of SSWs is linear to the applied radiative forcing. A doubling of SSWs occurs when the GHG concentration reaches the level of the A2 scenario at the end of the twenty-first century (836 ppmv). The increase in SSWs in the projections is caused by a combination of increased wave flux from the troposphere and weaker middle atmospheric zonal winds.

Artful Dodger

Hi Randall,

Thank you for this post. You've provided some good, testable hypotheses which is always the hallmark of good science.

First issue: Winters are cold in the Taklamakan desert, with January average air temperatures around -10°C. This is reasonable given a prevailing North wind. Where does the energy come from to provide the lift to the stratosphere? How is it related to Northerly flow crossing the Himalayas?

Second issue: 10 Hpa is above 100,000 feet pressure altitude. At 100K ft, the atmosphere has 1.4% the density of sea level. What is the maximum amount of heat or momentum that a 10 Hpa air flow can deliver to the surface? What velocities are involved?

Third issue: the Polar Night jet stream altitude occurs around 80,000 feet. Disrupting this flow leads to a breakdown of the Arctic vortex and episodes of cold Arctic outflows at the surface. Is it feasible that SSW are not interacting directly with the surface, but instead disrupting the Polar Night jet stream? Does this chain of events explain observations in Winter 2013?

Thanks again for leading this investigation, Randall!



Here are important points to consider:
- NOAA SSW animation: http://www.vukcevic.talktalk.net/SSW2012-13.gif
- Total absence of SSW in the Antarctica since 1978 : http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/10mb6590.gif
- Volcanic distribution of live volcanoes above 55 degrees of latitude in both hemisphere http://www.volcano.si.edu/world/maps/world.png

In a way of reply to:
Kevin O'Neill
I analysed 6 events in 6 resent years, all show coincidence between Kamchatka eruptions and the SSWs, there were two more since. Presenting 100% correlation on 6-7 events it is not going to give any enhanced credibility to the hypothesis. Btw, it is not a paper as a such, it is a set of observations meant to be a prompt for a further research to those inclined to do so.
Greenland ice deposits (volcanic ash and dust) do not fall down from stratosphere, they are deposited by precipitation from clouds at a much lower altitude

R. Gates:
It is not intention to ‘rain on your parade’, but it appears to me that you have knowledge and scientific skill (that I do not have), which if channelled in a proper direction could make significant contribution to science.
Chris Reynolds:
As you may be well aware ‘windmills’ literal or verbose are currently all the rage. Forgive me, but I can’t recall your name, even less when you ‘dealt with Vukcevic’, but I will take your word for it, unless you are Chris Colose
(Chris Colose evaluated this http://www.vukcevic.talktalk.net/CET1690-1960.htm
as good as counting the cows of Idaho)

Good luck to you all.

Chuck Yokota

R. Gates, thank you for your excellent and thought-provoking post. Your analysis provides a valuable contribution to this blog.


Fantastic post! Just a couple quick comments -- I'm off on vacation in a couple hours:

I'm ok with mercator projection -- it's a common choice for global display and we all learned in school that it distorts things at the poles. Conventionally, Mercator's cylinder makes contact with the earth's surface around the equator but here you are displaying temperature anomalies high in the atmosphere, at 10 HPa, a fixed pressure surface not a fixed height above the earth (ie not a concentric sphere).

Thus there is a second projection from this colored surface down to the conventional cylinder, perpendicular to its axis, that gives the display as overlaid on continental outlines. People outside of meteorology will struggle with this aspect.

Viewers can also walk away with the wrong impression because of the ratio of the frame speed of the animation to actual elapsed time. Here the event happened over 30 days (11 Dec 12 to 09 Jan 13) but is packed into 8 seconds (33 frame animation at 250 ms frame rate). It looks 'explosive' because of this 324,000-fold time compression.

The SSW feature is right-sized already -- increasing map scale is not particularly helpful. Right now, the earth is given 394 x 220 pixels of the 523 x 305 pixel animation rectangle, which cannot then display properly on typepad (maximal width 415), dropping visible animation width down to 313 pixels (= 394 x 415 / 523) which is three-quarters of that attainable by turning the anomaly scale sideways and moving it under the map.

The animation could be supplemented by a more intuitive view, an animated meridional slice through a quarter-earth and its atmosphere. It looks to me however like the event has a natural central track of development (see below) that is more of a rhumb line than a meridian (except for penultimate frames where it bends northwesterly), though some choice of great circle (rhumb lines are not geodesics) would work ok for the quarter-earth plane.

Somewhere in the explanation of this SSW, the direction and speed of central anomaly propagation might be explained, eg is it the same for every event originating in the Taklamakan or influenced by other atmospheric or rotational considerations.

Can the animation be extended to include more of its aftermath, the descent talked about so much in the text? This might be done better separately in polar stereographic projection since it is largely a polar vortex and NH story with the Taklamakan now out of the picture.

Finally, minor point, the title of the animation is rather cryptic. For example, CDAS -- after-the-fact weather reanalysis, Climate Data Assimilation System -- could use an explanatory wikipedia link. Temp Anoms could be spelled out. And 11d rm is a mystery -- the acronym rm has 133 uses already, none applicable here (http://acronyms.thefreedictionary.com/Registered+Midwife).

 photo SSWtrack_zpscd06098c.png


Re animation:
A-Team : It looks 'explosive' because of this 324,000-fold time compression……
It looks to me however like the event has a natural central track of development (see below) that is more of a rhumb line than a meridian (except for penultimate frames where it bends northwesterly)….

Good points
SSW coincides with Tolbachik, Kamchatka’s volcano eruption during December 2012


I'm wondering if Jason Box's croudsourced trip to Greenland will recover dust with Taklamakan's signature from the large SSW event you are describing, rather than (or in addition to) soot from the nearby Lapland fire that they are looking for. Here I recall they are melting down this year's snow column from some five sites along a southern Greenland east-west transect to concentrate particulate matter and its chemical constituents.

At the much higher latitude core sites, such as NEEM, they've also melted out recent snowfall as a sideline to main drilling location. Unless the station had people over-wintering again, this winter's SSW would not have been studied. However it is no big deal to go out from Thule on a snowmobile.

In discussing dust, every published study makes a fuss over particle size -- the bigger ones are harder to get high enough in the atmosphere long enough to be transported any distance but are easier to count and analyze. I'm recalling that they get just about straight Taklamakan dust at higher latitudes at the larger particle sizes. On the other hand, if you collect dust of all sizes out of Qaqortoq in extreme southern Greenland, with ordinary westerlies overhead, don't expect every mote will originate from Taklamakan.

On the isotopic signature, this depends on geologists having sufficiently sampled potential source sites all over the world. Basically, they do a scatter plot of isotopic ratios and draw tight circles about all the samples from a given desert (or a sphere if a 3D plot). Over the last 15 years, as far as I know, the northern Greenland dust has always landed unambiguously within the Taklamakan circle, specifically the Takim sub-circle.

While there is always some lack of finality -- maybe not all source deserts are represented, or those represented have unsampled sub-regions with different composition, it is rather late in the day for this type of objection -- geologists have been over the ground quite thoroughly by now.

In terms of Holocene frequency of large SSW events, taken as Taklamakan fall-out layers in northern Greenland ice cores, that's already available from the published scan line record.

The very first things done with a new core are from non-destructive sampling, here just optical scattering off the bubbles and larger dust (which are readily distinguished). Only the larger depositions provide enough material to source them isotopically and not every one that could be sourced would be sourced.

So -- before looking at this data of putative frequency of large SSW Holocene events -- you might write up what your mechanism predicts here, are there specific periods of the Holocene during which SSWs would be more or less frequent?


"Less SSW's would mean that the polar vortex stays intact and all the cold air stays in the Arctic helping the ice to thicken more."

Correct! If you look at my latest work, http://eh2r.blogspot.ca/, 2011 had sea ice which started to melt consistently on the underside the latest. Look for the multiple collage of sea ice horizons. Unlike 2010,2012 and 2013 which had consistent underside melts starting at March 14,12 and 18 , 2011 had an underside melt which was steady from April 15 onwards. Not a bad educated guess as usual Neven .

Thank You Mr Gates for effort well done. Although SSW's are more complex than presented, the physics of the Arctic Polar Stratospheric Vortex is very much complicated, has something to do with Ozone formation or destruction, huge wind layer laminas which collapse by their own unstable size and more as you presented. Although There are some points raised deserving further reflection.


Released another set of non-spam comments. Getting really annoyed now. Can't a blogger sleep?

Not a bad educated guess as usual Neven .

Thanks, Wayne. I have a big ass to pull those from. ;-)


I looked for the ultimate basin map, an oblique shaded relief map of the Taklamakan and surrounding mtns with exaggerated vertical scale, no luck on that.

Here are a couple of on-topic papers from 2006. Pasting the titles in google scholar gives 39 newer articles citing the first and the 116 citing the second. Sounds like the dust plume from the 2013 event might be traceable from the satellite record ... spare us that trip to Greenland.

Late Quaternary environmental changes in the Taklamakan Desert, western China, inferred from OSL-dated lacustrine and aeolian deposits

Sediment records from the Tarim Basin of western China are of great importance for understanding Late Quaternary climatic variability in Central Asia. A chronology of aeolian and lacustrine deposits from the centre and southern margin of the Taklamakan Desert, central Tarim Basin, has been established using optical dating methods. Distinct variations in humidity during the last 40,000 a in this extremely arid inland basin have been identified. Lacustrine sediments were deposited in the centre of the Taklamakan during two periods of wetter than present day conditions at around 2000 and 30,000 years ago.... Sedimentological evidence for a late Holocene humid period are consistent with records in ancient Chinese literature. Wetter environmental conditions in the past within the Taklamakan, as indicated by the presence of lacustrine deposits, are also supported by data from adjacent regions. It is assumed that changes of global westerlies and of the mobile polar high triggered the fluctuations of precipitation in the study area. However, variations in temperature in the Taklamakan Desert are presumed to be mainly controlled by the intensity of the winter monsoon.


A review on East Asian dust storm climate, modelling and monitoring

In arid and semi-arid area of Asia, dust storms occur frequently. Asian dust storms have a major impact on the air quality of the densely populated areas of China, Korea and Japan, and are important to the global dust cycle... Much progress has been made in the development of integrated dust storm monitoring and modeling systems by making use of advanced numerical models, satellite remote sensing and GIS data. In this paper, we summarize the recent achievements in Asian dust storm research with an emphasis on dust climatology, modeling and satellite monitoring. The concept of integrated dust storm monitoring and modeling system is described and a summary of the developments in key research areas is given, including new dust models and techniques in satellite remote sensing and system integration...


David Madsen

I have been a lurker here for some years, but do not post because the Arctic is not my area of expertise. I follow things here because my interests are in paleoenvironmental change on the Tibetan Plateau (sometimes called the “third pole”), and much of what is presented here is relevant there (particularly the graphics….thank you all!). Now, however, R.Gates has hit on something I do know a bit about as I have actually collected sediment samples from northern Chinese deserts for use in analyzing dust found in Greenland ice cores.
There are multiple sources of dust in the cores. The primary source is, indeed, the Taklamakan Desert in the Tarim Basin. Dust from this source is produced primarily in the spring and transported across the Pacific to North America and Greenland by the prevailing Westerlies. Secondary sources are other Chinese deserts, such as the Badain Jaran, the Tengger, and the Ordos, which supply dust to Greenland during the summer through winter months. In other words, December is not when dust from the Taklamakan usually gets transported to Greenland. That is not to say that some unusual event could not trigger such a winter dust storm, but that is not the norm.
In short, I am not sure what the dust in Greenland ice cores has to do with your SSWs. That does not necessarily mean your basic thesis is wrong, but, rather, it simply means I would not recommend you use the provenience of ice core dust to support your argument.
As an aside, I follow modern climate syntheses for the region rather closely in order to acquire comparative analogues for the paleoenvironmental records I study. I have not seen the kind of event you discuss….a plume of warm air heated above the Taklamakan in the winter and driven south by Mongolian cyclones into the Kunluns and up into the higher atmosphere….mentioned in that literature. Again, that is not to say such events do not occur or that I may simply have missed reference to them. However, I would think that if they were common enough to a major explanation for dust in Greenland ice cores, then I would have probably run across some discussion of them.
It is an interesting idea, but you might want to dig a little more deeply into work from the region before pursuing it.

Susan Anderson

OT (great discussion, will be reading and rereading later) but I agree the loss of Chris Reynolds would be serious, and I have another friend who has trouble posting here.* My largely irrelevant early comment with three links in it appears to have gone straight through. I mostly lurk.

*The problem might be Facebook. I use google (via Typepad) which is probably not optimal, but is not troublesome. You would lose your icon, but that's no big deal. Would this help? I don't know what other problems that might create, not being very tech-savvy.

This note should probably be deleted once anyone to whom it might be of use has seen it.

Chris Reynolds

David Madsen,

My understanding is that this isn't a rise of warm air at all but a planetary scale wave causing warming in the stratosphere.

The Wikipedia article on SSWs confirms it's the 'breaking' of waves in the stratosphere that causes the warming, and I think that Michael Splitt's helpful interjections really put a hole in the idea of warm influxes into the stratosphere.

This is just another occasion when the importance of waves in the atmosphere has been made clear to me.


Thanks, I'll still be over at the Forum, and will still read. But having posts appear post dated out of the flow of the conversation is just too frustrating. The problem is whenever I use links. And I find it hard to say things without reference to evidence. You'll probably find my making 'drive by' comments but not getting into discussion. As always if you need to get my attention there's my blog.


I am not Chris Colose, for the record I have the greatest respect for him and his opinion. The discussion was years ago, likely at Realclimate, I may have posted as Chris R back then. I can't recally what your claim was but I ended up suggesting I'd consider it further when you had it published in a peer reviewed journal. Which is my way of saying 'I'm bored and this is not a valuable use of my time'. Which is my attitude when arguments don't impress me.


Mr. Reynolds
We are all entitled to our opinions, expressed privately or publicly. As far as peer review publishing is concerned, I have no such ambitions, or even illusions. My aim is to make others aware of minor but real ‘points of contention’, that may conflict with whatever happens to be ‘applauded’ at the time.

Chris Reynolds


Thanks for the suggestion. I use Typepad as a separate ID for this blog only. Otherwise Blogger uses Google ID. I have no presence on, or interest in, things like Facebook or Twitter.

Chris Reynolds

PS. This post has been mentioned in Stewart Stanniford's 'Early Warning' blog.

Martin Gisser

Re Chris Reynold's posting problems: Like Susan I have no spam filter problem, can post links and get posted immediately when authentifying via google accounts. Only my wordpress icon gets lost. E.g. the 2nd comment here. Said link was entered as an HTML tag: <a href="[fill in URL]">blah</a>. Once again as plain URL: http://neven1.typepad.com/blog/2013/04/sudden-stratospheric-warmings-causes-effects.html?cid=6a0133f03a1e37970b017eea7920f9970d#comment-6a0133f03a1e37970b017eea7920f9970d

You might simply get a goole mail account and the problems could be gone. (You might possibly get thrown out when the session gets inconsistent, i.e. other comments got posted while you were typing: As always, copy your text (CTRL-A CTRL-C) before any other clicking, so just in case you can paste (CTRL-V) it into a freshly reloaded page.)

Re Chris Reynold's posting problems: Like Susan I have no spam filter problem,

Sorry to say, but I retrieved this one as well from spam hell. I was quick to see it there though (only 11 minutes).

I'm in contact with TypePad about this. We've waited long enough.

Andy Lee Robinson

If I can get hold of high res mercator projection maps, I'll gladly map them onto a sphere and do another animation. :)

Ac A

Folks, no worries!

"The emerging view is that the Arctic will lose essentially all of its summer sea ice cover by the end of this century, perhaps as early as 2030-2040." says Mark Serreze

...well, I am with A-team on this!



Thank you, Randall, for this post and the great effort you put into it. I found it a fascinating read. Unfortunately, I do not have sufficient knowledge to add much constructive to what you've done here. The only thing I wondered, and it's probably wrong, is whether air from the Tibetan Plateau might spill into the Taklamakan Desert and get adiabatically warmed though I think it would still need a helping hand from winds to launch it into the stratosphere.

R. Gates

David Madsen,

What do you think of my idea to take air samples inside one of the 10 hPa thermal wave events that are precursors to SSW's. Would a high percentage of Taklamakan desert and/or Tarim Basin isotope readings in the dust of this thermal wave tell us anything useful?

R. Gates

Also, for anyone who has knowledge of such things, I would like someone to address the fact that during a big SSW the stratospheric air over the equator is lifted (and of course cooled) just as air is descending rapidly over the north pole. It would seem that the air over the equatorial stratosphere is simply acting to fill in void left by the rapidly falling air over the pole. This would mean that that entire stratosphere is tele-connnected across 9,000km, and during an SSW, a very rapid acceleration in the Brewer-Dobson circulation takes place. Does this seem possible? What else would explain the tele-connection?

R. Gates

This article by NASA talks specifically about the formation of planetary waves and the Himlayas:


And this is a more in depth article about planetary waves:


Account Deleted

"It would seem that the air over the equatorial stratosphere is simply acting to fill in void left by the rapidly falling air over the pole." (R. Gates)

This process you describe seems conservation of total mass of the stratosphere. In a compressible gas, the flow to balance mass displacements propagates at the speed of sound, which is fairly constant in stratosphere (~1000 km/h). To fully blow an upward flow in equator caused by downward flow in polar regions would take order of 10 hours. This is a fairly small timescale compared to the 5-day timescale of the phenomenon you describe. So does this seem possible? Absolutely. What amuses me is the strength of the SSW event to displace such an amount of air mass.

R. Gates


Thanks for that. This process seems to be integral to the Brewer-Dobson circulation. I didn't realize that the speed for mass balance would be that high, but given the close correlation between two events, it makes sense. I plan to do a Part II of this post, and will include this fact in there. I think few people could imagine a large teleconnected effect like this spanning over 9000km on this planet, but that indeed seems to be the case, with the effect traveling from pole to equator in just over 9 hours! Truly, as you say "amusing" but I would add--amazing!

Account Deleted

Just clarification, that I don't mean the air will move at 1000 kmh... only that the effect of the downward flow over the arctic will be felt 1 hour later 1000 km away, 2 hour later 2000 km away and so... 9 hour later one will observe upward flow in equator (but the flow itself is much slower than sound...)



interesting read. One question, if these northerly winds are the climatological normal at that location, how does it come that some years have and some have no SSW's?

dominik lenné

Concerning the map: my favorite is the Goode approach, an equal area projection minimizing the distortions at the price of cutting the map up.

R. Gates


Of course. Air moving that fast would create some very interesting effects though. This teleconnection between the pole and the equator in the would be a wave-- much like pulling one end of a string and the other end moves, with the speed of response based partially on the density and elasticity of the medium through which the wave travels

Timothy Chase

ulisescervantes wrote, "Just clarification, that I don't mean the air will move at 1000 kmh... only that the effect of the downward flow over the arctic will be felt 1 hour later 1000 km away, 2 hour later 2000 km away and so... 9 hour later one will observe upward flow in equator (but the flow itself is much slower than sound...)"

Reminds me of electricity. The individual electrons travel at under 1 cm/s, but the speed of electricity is a significant fraction of the speed of light. Or for something similar...


... the balls swing only at something on the order of a meter per second, but the collision between balls that are in contact with one-another gets transmitted at the speed of sound in a metal.

Kevin McKinney

Fascinating post. Thanks.

R. Gates

Wouterlefebvrete asked, " One question, if these northerly winds are the climatological normal at that location, how does it come that some years have and some have no SSW's?"
What's more critical is the status of the tropopause that is so much lower in the NH winter meaning more momentum and energy can therefore be carried across it into the stratosphere to become planetary waves. Also of course, the overall NH jet steams are configured differently in winter, and finally Brewer-Dobson circulation is different in winter.

Gerrit Vanniekerk

I've been reading a bit about SSW's, and the prevailing theory, namely that a slowed-down Rossby wave rises into the Stratosphere, blocking flow and thereby causing warming, just doesn't add up: If moving air is to slow down, it has to encounter a positive pressure gradient. This increase in pressure compresses the air, causing the temperature to rise. If it would come to a complete standstill, either by massive Rossby wave, turbulence, breaking waves, or whatever, it will reach stagnation temperature. It can't become warmer than that by dynamic effects. Now, to cause a 30K increase at 240K, an initial wind speed of .625M would be needed (that is average wind speed of 600km/h)... nope.
Also, a rising stream of bone dry desert air is cooling at about 1K per 100m. Assuming it could manage to reach the Stratosphere by some mechanism, it would be at least 100K colder up there than down on the surface, and would rather have a cooling effect.
The only plausible mechanism by which such a massive volume of air can heat up rapidly, is for it to decent, causing it to compress. The 30K warming will need a 50% pressure increase, meaning the air volume will have to drop by about 3000m. It is massive, but I can't see that it isn't possible, and it is also consistent with the notion of a lot of Arctic air spilling out. And it is consistent with the time of year - a rapidly cooling Arctic air mass, got to become more dense and start sinking.
The question is just why all of a sudden, and not gradually as the Arctic starts cooling down in Autumn? There must be some meta-stable mechanism keeping it up, and maybe conditions above the Taklamakan sets this tipping process in motion, as Michael noted strongly descending air, as if plucking the first card from the card house, and then the rest of the house starts collapsing.
Well, just a few more considerations to work into the theory. Hopefully those still reading aren't bored to death :)


...that was also my first thinking reading the text (@ Gerrit). No way to increase stratospheric temperature by RISING air, and particularly not if it ogirin is from the cooler tropopause.
But those mountains, deserts may play a role. higher mountains to the south, cold wintery deserts to the north, higher to the north the icy arctic. Behind the mountains, the pretty warm subtropical and tropical regions are shielded from sibirian cold air.

But as this cold air moves south on other pathways, particularly in higher elevations (see the 500hPa pressure height) the pressure drops over the complete northern part of the northern hemisphere. What if you get once a disturbance riding into the Himalayan region? Suddently the polar front, the jet stream will bend, and the way is free for higher tropopause air masses to stream north, filling up the low pressure aloft. As this air mass is pushed now over the mountains it drops, warms (also in the Troposphere), exactly what happened several times this year. Than a warm layer is coating the very cold bottom arctic air mass, stabilizing the usual wind systems(increasing pressure, pushing out cold air on the bottom).

But what happens in stratosphere, with that kind of massive falling winds in the troposphere, causing huge,and some of them standing, gravity waves?

In some places that will cause the air to drop for thousands of merters, generating high tenperatures.

Another effect is simply, that warmer, southern stratospheric air, pushed to the north by stratospheric lows and heights, will genrerate a HUGE temperature deviation, when replacing, the cold statospheric air in arctic winter...

The only contra is the coriolis force, usually southern, warm stratospheric air cannot reach the pole. But with disturbances breaking those stratospheric jets, all of a sudden those muves are possible. And than air with 0°C moves into egions where normally you find -60°C... That is a huge deviation, and that will have influence downstream in the troposphere...


about 130 days until the minimum (if we don't hit 0 sooner). Is there going to be a poll this year on what we think the minimum area/extent/volumes might be?

Or phrase differently - Neven, can we please have a poll on each of the above?

For my part, I'd like to put in the following guesses:
Area goes to 1.9-2.0 million km^2
Extent goes to 2.8-2.9 million km^2
Volume goes to 3000-3100 km^3


Actually dust storms in the Taklamakan, though peaking in April, can occur at any time of year -- attached is a notable 02 Nov 12 event as caught by Modis. Since we can flip easily through the rapid response imagery, the Greenland dust event putatively associated with the Dec-Jan SSW is accessible -- its plume track, if any, is can be followed with satellite CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) and/or numerical simulation.

On the Greenland side, it's important not to conflate snow pits with ice cores. The former represent melt down of some 150 kg of snow per horizion and only sample a decade or so back in time, attaining a time resolution of only two months; most studies have saved only the fines. Cores can go back 125,000 years but an annual layer at depth has a millionth the starting mass to work from -- a whole decade may need be melted to get the milligrams of dust required for strontium 87/86 and neodynium 143/144 analysis -- there's no seasonal resolution at all.

Back at the Taklamakan, because the peaks surrounding the basin run to 5,000 meters, raised dust often stays within the basin. But if not, the dust launched higher in the atmosphere implies a higher energy weather event. This dust has to move north and stay high to deposit at 3,000 m core sites in northern Greenland.

Since everyone agrees dust in northern Greenland comes mostly from the Taklamakan, the question is how much of it, particularly the larger particles harder to get aloft, is associated with SSW events. That is going to depend very much on the definition of SSW and whether they, as proposed, originate from the influence of the unique topography of the Talim Basin on weather patterns.

If we now start to slowly dial back the definition of SSW, what are we left with? Is there in fact a distinction between the mildest admissible SSW and a conventional weather pattern strong enough to lift dust out of the Takim Basin to an upper troposphere atmospheric elevation? 

I would suggest not -- the mechanisms under discussion here for strong events may moderate down to long-known Chinese weather features giving rise to weak to moderate out-of-basin dust storms, described in a large literature. (Ironically China itself is minimally affected, as dust from these events largely fails to descend onto their network of 146 surrounding long-term meteorlogical stations.)

About a dozen out-of-basin Taklamakan dust storms occur per year, a far higher frequency frequent than SSWs, depending on how narrowly these are defined, eg if rapid warming the top of the troposphere is not deemed good enough and disruption of the Polar Vortex is required. Meanwhile, an upper troposphere plume originating from the Talim Basin in 2009 took 13 days to circle the globe, which it then did a second time .

"The dust ball was formed when a wind storm ripped across the desert, kicking up the dust, and trapping it against the mountains of the Tibetan plateau. The scientists said [in Nature Geoscience] the 800,000 tons of dust was forced higher and higher into the air, until it reached an altitude of around 16,250ft. A warm convection flow then lofted it further to between 26,000 ft and 32,500 ft. The dust was then trapped in the polar jetstream, a fast-flowing air current that lies just under the stratosphere, and began its journey around the world." [news clip]
"All dust storms in China are associated with cold air outbreaks, which result in the occurence of frontal systems and the Mongolian cyclonic depressions. The routes of cold air can be divided into north, northwest and west ...The dust storms in the Taklimakin Desert are associated mainly with the western route of cold air outbreaks.... Only the strong upwards wind created by highly unstable synoptic systems during the spring may provide favorable conditions for the dust to easily escape the basin."
"As the cold air from the northwest broke into the Taklamakan Desert from its northeastern entrance, it provided strong motion to mobilize the dust. The northeasterly wind was presumed to lift the dust in the Taklamakan Low toward the southwest, but because of high mountains, the air masses were elevated to around 5 km agl and merged into the conveyer belt between the Taklamakan Low and the Tibetan High, which is clearly indicated by the back trajectories and the NAAPS model. [ref 3]
"Indeed, dust from the TM is entrained to elevations >5000 m and often takes a northern route before being transported in the westerlies... Dust is first transported to the north, reaching 50°N, before moving eastward over Lake Baikal and northeastern China which makes it more plausible for the Taklamakan dust to be transported towards higher latitudes, eventually reaching Greenland." [[Sun et a 2001 and ref 4]


 photo taklimakanNovDust2_zps3384d2fa.jpg


Or phrase differently - Neven, can we please have a poll on each of the above?

There are (and will be more) polls on the Forum, NLPatents. :-)

R. Gates

Lots of great comments here and some very useful input. Based on some of that input I have been looking further into several different areas and hope to have a Part II of this post in the next few weeks, involving a closer look at the specific (rather than general) configuration of the troposphere and stratosphere over the region of 50E to 100E and equator to about 50N during the time frame of Dec. 18 to Dec. 26 2012. Additionally, the status of the Brewer-Dobson Circulation, the MJO and QBO during this time frame interest me greatly. The Brewer-Dobson circulation in particular interests me as it forms that direct connection between the equatorial stratospheric air and polar stratosphere.

Rob Dekker

For starters, thank you very much for a great post, and really cool scientific detective work.

I know very little about SSW events, so please correct me, but after looking around a bit I have the feeling that you may have attached a bit more relevance to the Taklamakan than is granted, at least for this (late 2012/early 2013) event.

For example, looking at your first animation, it almost looks like the source of the 10mb anomaly starts at the Arabian Peninsula, or possibly even the Sahara desert. It then very quickly spreads over the entire Himalaya area, with also Northern India involved.

Of course, that is just one animation, from the 10mb anomaly only, so I looked around a bit more, and was very surprised that there are entire communities looking at Stratospheric warming events.

Couple of example forums that covered this event in excruciating detail :
which is 'late', but has an interesting 50 mb animation...

Thousands of comments, starting in Sept. 2012, which note SSW over Russia as early as end of November 2012.

Really cool thread with commenters posting lots of graphics.
These guys also note SSW over Russia in November 2012, strengthening in Dec 2012, and finally causing the break up of the Polar Vortex in early Jan.

Much of this stuff is way over my head, but in all these forums, I don't see that Taklamakan played a significant factor in this SSW event.

Rob Dekker

One of the most convincing posts I found was this one from early December 2012 :

which post the origin of SSW event in central Siberia.

Incidentally, didn't Cohen have a theory about Siberian high in winter, caused by excessive snow deposits due to reduced Arctic sea ice ?


Rob, you are absolutely right, although I’m not sure he got all the details right.

This long winter can actually be summarized into a fairly short storyline:

Last autumn, the absence of sea ice and lingering positive SST anomalies in the Barents and Kara seas led to an early snow cover in Scandinavia and Northwestern Russia. Nocturnal radiative cooling led to a massive high pressure build up, which forced the Polar Vortex to the south. As seen in this 30 hPa animation:


this ridging led to the strong SSW event over Asia. Forcing humid subtropical air over the Himalayas – and cooling this air mass from below over the Taklamakan Desert basin, must have released the latent energy needed to lift this air mass into the stratosphere. Sinking air over the Arctic built up the high pressure over the Beaufort Sea, temperatures dropped and cracks developed.

The rest is history.

R. Gates


Thanks for that link. You realize that was a model run in early December, projecting what the 10 hPa would be like later that month, right?

In general though I agree that putting to much weight on specifically the Taklamakin is not prudent as there are many areas in the entire Tibetan and Himalayas that can force strong topographic induced planetary waves. I do plan a Part II of this post, incorporating some of what I've learned since my original post. In the meantime, I would disagree with the contention that there was an SSW event in Nov. 2012:

The basic data seem not to show it:


If anything, there is a slight cooling of the stratosphere during this period.


The full video Chasing Ice is now available on YouTube (73 minutes) --

National Geographic: Chasing Ice 720p

Rob Dekker

Randell, yes, you are right. That was a forecast.
I checked where I got the SSW warning over Siberia from in November, and it seems that they were all forecasts for December.
Here is one from Nov 30, ECMWF forecast for December 10 :

Now, what I am wondering about is not so much if the forecasts came true, but what the actual development was over entire Asia during the entire month of December, at many different pressure levels.

I think that if we had such a complete 4D (3 space, one time) overview, it should be much easier to see where this SSW event started, and when, and how it developed, and why.

Rob Dekker

Randell, one silly question from a newbie like me on stratospheric weather.
The graph you provide in your link has the Y-axis labeled as BOTH 'pressure' and 'height' (altitude), which are fixed against each other.

I've seen these graphs before, and always wondered why there is a hard link between pressure and height.

Doesn't 'height' of a particular 'pressure' level depend on the temperature of the entire air column below it ?

Rob Dekker

Sorry, but I find this stratospheric weather quite fascinating, so one more post :

I realize that the very early Dec 2012 forecast I posted (which shows stratospheric warming over central Siberia) is at 1 hpa. Now, it seems that this is almost up in the mesosphere, so now I'm wondering is SSW events originate from below (by heat funneled up from the troposphere) or from above (by the mesosphere 'falling' down and heating by 'crashing' onto the statosphere.

Also, on the stratosphere blogs, I often see references to the "wave-1" and "wave-2" in the stratosphere. In your follow-up post, could you please explain a bit to us newbie's what these waves are and what they mean ?

Thanks again for you awesome work on this still poorly understood SSW phenomenon.

R. Gates

Here' s an older NASA Story that is related to SSW events, but from a diifferent angle:


Pekka Pirilä

Very interesting discussion that gives many starting points for further learning. Right now I would only propose a different way of saying, what a couple of comments already have said.

It seem clear that the only way to get rapidly warm air to some location is to move there air that had the same high potential temperature before being moved there. And where do we have high potential temperatures. Obviously high enough in the stratosphere.

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