Sudden Stratospheric Warming: Causes & Effects

Introduction & Disclosure

My name is Randall Gates Simpson. There is no PhD after my name and I am not a PhD climate scientist. I don't consider myself a traditional "expert" on the subject of SSW's because of my lack of official credentials. I do however think I probably know quite a bit more on the subject than the average person might. I work as a television producer by day, and as a hobby, study climate
and weather on my nights and weekends and have for over 30 years.

In addition to the subject of anthropogenic climate change, I first became interested in SSW's a few years back when it became increasingly apparent to me the extreme effects that SSW's can have on Northern Hemisphere winter weather. It wasn't just their extreme effects that interested me, but rather, the fact that their specific causes were still a bit of a mystery-- and I've always loved a good mystery.  Isn't that what is (or should be) at the heart and soul of any good scientist?

In this post I reveal what I think is an original synthesis that gives the full picture of some of the main causes and effects of Northern Hemisphere Sudden Stratospheric Warming events based on my readings of many other papers along with hours of my own original research. For research material I relied heavily on the use of the amazing amount of satellite derived reanalysis data as well as ground based observations. I am heavily indebted to organizations such as NASA, NCAR and NOAA for the data they have made available at my fingertips through the web.

My research took me "virtually" to the other side of the world from where I live in Colorado, to discover some of the causes of SSW events. My research has also relied on men and women scientists who have physically travelled to extremely remote and desolate locations to gather data that I have relied on to create this synthesis. I hope perhaps one day to travel myself to these remote places to see first hand what I feel are the true birthplaces of Sudden Stratospheric Warming events.

My hope in publishing my findings on the web, is that others who may have some knowledge of or interest in the dynamics I describe here, may find my "theory" interesting, but also might find all the inconsistencies and errors I've made. Self-correction in the search for truth is essential, right? Perhaps, if I'm very lucky, I've actually stumbled on to something that might provide a truly greater understanding of these remarkable natural phenomena.

Lastly, I'd like to thank Neven for allowing me to do this guest post on his amazing Arctic Sea Ice blog. His service in the cause of understanding the dramatic and rapid changes going on in the Arctic is to be highly commended.

Sudden Stratospheric Warming: A Basic Overview & Description

Since their discovery by Richard Scherhag in 1951, Sudden Stratospheric Warming events(SSW's) have drawn considerable attention and research interest due to their sometimes extreme effects on Northern Hemisphere winter weather. Scherhag and others used balloons with radiosondes and rocketsondes for their research, and the rather limited amount of data, especially limited in spatial and temporal coverage, that could be gathered this way led to interesting early theories of the causes of these events-- everything from volcanoes to solar activity.

These early theories were logical based on the limited data available and also based on the amazing essential core discovery related to SSW's-- the upper and middle stratosphere over extreme high latitudes, at elevations ranging from about 25 to 45 km would warm rapidly, in the period of just a few days. What was also of course clear in these early years of research was that the warming was not coming from the troposphere directly under the warming stratosphere, but from some other source. 

This is how the mystery of SSW's began. Then, with the advent of more extensive satellite coverage of the atmosphere in the late 1970's, ever more data was gathered on SSW's and the early theories were modified and abandoned as SSW's were seen to be large scale reorganizations of the winter Northern Hemisphere atmosphere, with effects spanning from the pole to the equator and from the mesosphere to the troposphere.

Here for example, is a comparison of what was happening in the polar stratosphere simultaneously with what was happening over the equator in the stratosphere during the January 2013 SSW:

So as the chart shows us, during the January 2013 SSW, just as air was falling and warming in the North Pole stratosphere, air was rising and cooling over the equator in the stratosphere-- a teleconnected effect covering some 9,000 km! No other atmospheric event of this scope and scale exists on the planet, yet more people are aware of the much smaller hurricane, cyclone, or tornado. And as you'll see, far more people are affected by a large SSW event than a large hurricane, yet the average citizen has scarcely heard of them.  

Basic SSW Characteristics & Classification

Like many atmospheric phenomenons such as hurricanes and tornadoes, SSW events exist on a continuum of size, intensity and effect, even though from the largest to the smallest, they all share a basic set of features, namely:

1) They primarily take place during the Northern Hemisphere winter. 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).

2) They cause a rapid rise in stratospheric temperatures over extreme northern latitudes.

3) They cause a rapid rise in stratosphere pressure over the extreme northern latitudes.

4) They cause some level of wind pattern disturbance over the pole, with the larger ones displacing, disrupting, or outright destroying the polar vortex.

Here are some examples of 3 general levels of SSW's: Small, Medium or Intermediate, and Large. First, a series of rather small SSW's between January and the end of March in 1996:

Here's a moderate SSW that occurred at the beginning of February 2001:

And finally, here's a very large SSW that took place in January 2006:

Major Winter Weather Disruptions at Lower Latitudes

If all SSW's did, was affect the upper or middle stratosphere over the pole or even the equator (as shown in the chart above), they would remain an interesting atmospheric curiosity or mystery much as Scherhag found them in 1951. What we've learned in the past few decades however, is that they have enormous and profound effects (especially the larger ones) on the entire weather patterns of the Northern Hemisphere winter. These effects begin with the descending air and increasing pressure that comes with the sinking air over the pole.  Here is the pressure anomaly chart of the January 2013 SSW:

Along with this sinking air, we see the corresponding disruption of the Arctic polar vortex as shown in the zonal wind anomaly chart from winter 2013:

During a large SSW, the breakdown of the polar vortex reverses the normal westerlies in high latitudes (westerlies partially driven by the counter clockwise flow of wind around the polar vortex). When the vortex breaks down or is disrupted, the winds shift rapidly (as shown in the chart above) and come from the east. In places like northern Europe, when the winds come from the east of course that brings cold air from Siberia, stormier weather and much colder temperatures. This large scale shift of NH winds from westerly to easterly affects hundreds of millions of people from the associated extreme cold, snow, and general misery.

Though certainly declines in Arctic sea ice may be changing the patterns of NH weather, the research on these effects is ongoing. In terms of the winter of 2013, we can trace the change in England's weather this winter almost to the day of the onset of the large SSW event over the pole. If you look at the chart above for the SSW that peaked around the 6th of January, and then take a look at the Central England Temperature record for the winter, you'll see this:

 

SSW's and the Arctic Oscillation Index (AO)

The misery that SSW's can bring to lower latitudes due to their wind and pressure effects can be measured quite readily in the useful Arctic Oscillation Index (AO). Rather than go into a detailed explanation of the AO Index, for the purposes of this paper it suffices to say that generally high pressure over the pole relative to lower latitudes leads to a negative AO Index and lower pressure over the pole relative to lower latitudes leads to a positive AO Index. Generally speaking, when the AO Index is high, we can expect generally better and warmer weather over lower latitudes during that period in the winter, and when the AO Index goes negative or even very negative, we can expect generally nastier and colder weather over lower latitudes.

When a large SSW event occurs such as we had in 2013, warm and descending air over the pole compresses even more, warms even more, disrupts the vortex (as shown above) and turns the AO Index negative. What needs to be clear however is that the AO Index is of course a tropospheric reading, and the SSW begins in the stratosphere and the pressure effects can work their way down into the troposphere and last over a period of many weeks. 

Here's a most revealing chart showing a direct chronologically aligned comparison of the timing of the early January 2013 SSW seen in the normalized zonal GPH anomaly (top) aligned with the AO Index (center), and the Central England Temperature (bottom) from January 1, 2013 through April 1, 2013:

The correlation between the three is remarkable and directly related to the initial event-- the SSW that began in early January when England's weather turned cold and a prevailing wind began to blow from the east as the vortex was shattered and the AO Index turned to the negative.

Now this mention of the association between SSW's, the disruption of the Arctic vortex, and a negative AO index is not to suggest that SSW's are the only thing that affects the AO index, just like it would be wrong to suggest that all low pressure and rain over the Gulf of Mexico is related to hurricanes. What it does show, is that when a large SSW event occurs (which is every few years on average) it will tend to dominate the Arctic weather and lower latitudes during that time period.

So now that we've taken a look at some of the effects of SSW's on the NH winter weather, as interesting and far-reaching as they can be, let's get to what I consider the even more interesting part-- the causes of SSW's.

Following the Warm Air Back to Asia

There are a few clues that one can use to trace the origin of the descending warm air over the pole, but before looking at that, let's talk about that descending air in general. Of course the rapid descent of air in the stratosphere compresses and warms, but a key clue comes from knowing that it was already anomalously warm before it began to be compressed. What warmed it and where?

Thanks to satellite reanalysis data, we can in fact see exactly where the warm air came from before reaching the polar latitudes. As this animation so excellently displays, a wave of warm air moved up from South Central Asia in the weeks prior to the SSW event that occurred in early January 2013. This wave in fact seems to almost "explode" up into the stratosphere, almost like the warming you'd get from a volcanic eruption (again, hence the reason for early theories on SSW's looking for a volcanic connection).

Again, this bubble of warm air rises up to become a thermal wave over South Central Asia on about December 21, 2012 and seems to nearly explode to the north and to the east. The rapidity with which this wave forms, indicates that some very strong dynamical event was forcing warm air up into the stratosphere from the troposphere. It then moves north and east at 10 hPa stratospheric levels and higher. Here's different view of the same thermal wave on December 28, 2013:

Here's yet another perspective on this wave that shows both its lower latitude origin, as well as it's progress toward the north. Remember, this is occurring at the 10 hPa mid-stratosphere level:

I consider the chart above to be what I call the "standard fingerprint" of the thermal waves that I investigated as far back as reliable reanalysis data is available. Up until now I've been using the latest 2012-2013 winter as an example of the thermal wave that originates over South Central Asia, but, before continuing to explore in much greater detail the formation of this wave, I want to show you a view of a similar wave, or "standard fingerprint", that occurred during a SSW event in the winter of 2002-2003:

Again, a similar development in the thermal wave as it develops at lower latitudes and moves north.  This 10 hPa anomaly chart has been constrained at over Asia from 0E to 80E. Again, I found similar waves are seen in the weeks before every SSW event, minor or major, over the NH that I was able to find reliable data on. Using reanalysis data back to 1948, I found no example of the thermal wave forming anywhere else other than over Asia prior to NH SSW events. Now, once the wave forms and moves north it can actually rotate to the east around the pole (and even migrate back west), before penetrating the vortex at some point and descending, but in my research, the initial formation of the thermal wave was found to always be over Asia. Here's one developing before the big SSW event of January 2009:

In considering the development of these thermal waves at mid-stratospheric levels over Asia, there are several factors that must be considered. First, such a rapid build-up of rising warm air can obviously not come from evaporation as normal adiabatic cooling would occur and we would see the exact opposite condition such as we find associated with the normal convective processes in thunderstorms or on a larger scale in Hadley Cells.

The second consideration is the rapidity necessary to bring such a large mass of warm air upward into the stratosphere. Some process must essentially "launch" this warm air, as we see it seems to "explode" into the stratosphere. Finally, the air must be relatively warm to begin with (anomalously warm relatively to normal stratospheric temperatures at 10 hPa), for no matter how rapidly it is launched or how warm it was, it will expand and cool by some amount, no matter what. So in our search for the source of the thermal wave, we are looking for a source of warm air and a mechanism by which that air is launched rapidly upward into the stratosphere.

Again, It was this basic realization that led a few early researchers to consider volcanoes as a possible cause of SSW's. Other factors however did not support the volcanic theory, not the least of which was the lack of other normal signs associated with volcanoes such as elevated levels of volcanic aerosols.

Looking for High Positive 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. 

Obviously, in the formation of a thermal wave in the stratosphere over South Central Asia we would be looking for a region in the troposphere in the same proximate region with unusually high positive omega. It would have to be an area that displayed what would be much like vertical jet stream or plume of warm air moving rapidly upward in the troposphere, through the tropopause, to form the bubble or thermal wave in the stratosphere.

In looking at the omega reanalysis data for the period around the formation of the thermal wave that formed over Asia in December 2012, we find the following very interesting data that displays the average omega across the entire troposphere from 1000 hPa up to 100 hPa. This chart was further constrained to show the region of interest, namely South Central Asia from 60E to 110E longitude and 0 to 70N latitude:

In looking at this reanalysis chart we see three regions of high positive omega. These regions represent areas where air was moving rapidly upward across the entire troposphere averaged over the month. Each region is worthy of special consideration in their own right, and should be the subject of future research, but for the sake of simplicity, I chose to narrow my analysis down to the area of highest positive omega of the three, which was the one furthest north and west near 85E and 37.5N.  Here's a closer view of the omega in that region during December 2012:

Again, for a clearer understanding of omega, in looking at the preceding diagram, one can imagine a stream of air moving right out of the center of the red and orange area, outward from the screen or page. This stream would be flowing up through the entire depth of the troposphere, centered at 85E and 37.5N during the month of December 2012. For the sake of comparison, here's the omega for the exact same region during the month of July 2012:

In comparing the two, we see that the high omega over this region in December 2012 truly is at least a monthly anomaly and not a year-round feature of this region. So we at least now have a potential area for a vertical stream of air moving into the stratosphere to form our thermal wave in December 2012. Let's take a closer look at this region near 85E and 37.5N.

The Taklamakan Desert, Kunlun Shan & Altun Mountains

The area of high positive omega over South Central Asia in December 2012 is centered on the Kunlun Shan mountains and the southwestern part of the Altun Mountain range. These mountain ranges collectively form the southern border of the Tarim Basin and Taklamakan Desert and mark the northern edge of the Tibetan Plateau.

 

Of course, it is not surprising at all to get a high omega for this area as the Kunlun Sham and Altun mountains rise rapidly from their close proximity to the Taklaman Desert and offer the potentially ideal combination of topographic features to produce strong topographically induced lift to air. Here's a roughly placed overlapping map of the high positive omega in the region during December 2012, in the weeks prior to the SSW of early January:

Note that in the previous image we clearly see the area of high omega to be the southern side of Taklamakan Desert. In the red and orange areas in this region - since this omega is averaged over the month and across the entire troposphere - a large mass of air is streaming at a high rate through topographic forcing, through the tropopause and up into the stratosphere. The prevailing winds on the ground during the winter over the Taklamakan Desert tend to be from the northwest, north, and northeast as you move west to east respectively across the region, as illustrated here (Yoshino, 1991, 1992):

The north to south direction of these prevailing winter winds across the Taklamakan Desert would possibly be a key part of the energy that serves to launch the warmer desert air off the Kunlun Shan and Altun Mountains with the right overall conditions. It is also possible, and much further research would need to occur for verification, that given the general lowering of the winter tropopause and the elevations involved in the region, that jet stream winds could dip lower in the area and be integrally involved in providing some of the energy for the topographic lift.

Topographic Profiles of the Region of High Positive Omega

We've identified the boundary between the Taklamakan Desert and the Kunlun Shan and Altun Mountains as the general region of high positive omega during the month of December 2012. It's now time to look at the region in more detail. Generally, of course, the relatively flat Tarim Basin and Taklaman Desert give way to the Tibetan Plateau as you move south. The Taklamakan Desert is typical for deserts around the planet, with tens of thousands of square kilometers of dunes that look like this:

But as you travel south, those dunes rapidly give way to the Tibetan Plateau. Here's what the transiton zone between the two regions looks like:

And to get an even better feel, here's a Calipso LIDAR image showing the dramatic rise at the boundary between the Taklamakan Desert and the Tibetan Plateau (image courtesy of NASA/LARC):

In the LIDAR image above, we see that the transition between the Taklamakan Desert and the Tibetan Plateau is, relatively speaking, very rapid-- occurring in just few tens of kilometers.  The peaks along the boundary soar to well over 6,000 meters high, and represent ideal topographically induced  "launch points" to send tropospheric air rapidly into the stratosphere with the proper wind conditions coming off of the Taklamakan Desert.

Here's a few topographic profiles (with the Taklamakan Desert to the right) of some the typical peaks in the region, all of them in the Kunlun Shan or Altun Mountains:

The Full Picture

SSW's are marked by rapidly descending air over the polar region.  This air warms as it descends but we've seen that it was warmer than normal to begin with. Through reanalysis, we have seen that the air traveled to the high latitudes as a stratospheric thermal wave at 10 hPa. In looking at the origins of this thermal wave we find high omega areas just south of the Taklamakan Desert in the Kunlun Shan and Altun Mountains.

When prevailing north to south winter winds blowing across the Taklamakan desert (and including possible energy from jet stream winds) are directed toward the Tibetan Plateau under the right conditions, the perfect topological lifting conditions occur, allowing the warmer air from the desert to ascend rapidly into the stratosphere where it builds into a thermal planetary wave of warmer air that is carried north by prevailing upper level winds.

Upon reaching the higher latitudes of the Arctic, the warmer air begins to descend rapidly, warming even more but also carrying enough momentum during the descent to drag mesospheric air down into the stratosphere as well. This intrusion of mesospheric air during SSW events has been well documented, but is outside the scope of my research. Suffice to say it has been measured by many researchers and can be identified through its unique chemical signature. One excellent recent source for more information on this is Kvissel et al., 2012. 

As illustrated earlier, the rapidly descending air in the stratosphere over the Arctic has effects or teleconnections that reach some 9,000 km away to the equator. Here we see that the momentum of the polar descending air pulls the air in the stratosphere up at the equator, such that this air cools and expands and creates a temporary temperature and pressure anomaly.

Again, here's another example of this from the large SSW event that occurred around January 21, 2009 where, in this equatorial stratosphere profile of temperature, you can readily see the effect of air being drawn upward into the stratosphere: 

Other Causal Elements of SSW's: The Winter Tropopause

I have only briefly mentioned the tropopause thus far, but it should of course not be left out in a discussion of the full dynamics of SSW's. Certainly, the intrusion of a rapidly ascending stream of warm air into the stratosphere from the troposphere means that this stream must penetrate through the tropopause as it ascends.

We've talked about the unique topological circumstances with location of the Taklamakan desert next to the Tibetan Plateau. The desert provides the ideal source of warm air to be "launched" upward and the rapid and steep mountain Kunlun Shan and Altun Mountains are the perfect launch pads. With the winter winds prevailing from the desert toward the mountains is this region, it only takes the right set of circumstances to initiate the precursor events to an SSW. 

We must however add the additional factors of the lower winter tropospheric height and the fact that the Kunlun Shan and Altun Mountains are at an ideal position for penetrating the tropopause with warm air from below as the tropopause drops down rapidly between 30 and 40 degrees, as seen in this simple illustration (B. Geerts and E. Linacre, 1997):     

Thus, not only does the tropopause lower in the winter, it also drops down dramatically just at the point where the Kunlun Shan and Altun Mountains ranges are located and ready to provide the necessary launch platform for warm air from the Taklamakan desert. It is quite possible that had these mountain ranges been located five hundred hundred kilometers further south where the tropopause is higher, that the character of NH SSW's and NH winters might be completely different.

This is not to say that the Kunlun Shan and Altun Mountains are the only places in the region that offer a suitable high omega area, for we know there are others, and they need to be investigated and researched as well. 

Other Potential Corroborating Evidence

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. It was only very recently however that I became aware of this fact. Considering that the high omega topographically induced "launch sites" for warm air into the stratosphere exist just south of these regions, and that the air that the Kunlun Shan and Altun Mountains ranges launch upward, would be coming directly from the Taklamakan desert, then it stands to reason that the air would contain traces of the dust of the isotopes from these regions. 

Furthermore, it stands to reason that as this air forms the thermal wave that travels north toward the Arctic to descend as a SSW event, then some of that air would naturally make its way into the Greenland glacial ice. There are of course other paths that dust and trace isotopes could take to Greenland, i.e. more westerly across the Pacific and North America, and certainly some of it does take this path, but the existence in high quantities in the Greenland ice raises an interesting potential future avenue of research whereby samples of air could be taken over high latitudes of Asia and Siberia just prior to  SSW event, before 10 hPa thermal wave reaches the pole. If these samples contain isotopes from the Taklamakan desert, it would provide some confirmation of the correctness of my overall SSW model.

Summary & Conclusion

My investigation into numerous SSW events using reanalysis data has shown that in every event that I could find reliable data on, the initial locus of the warm air has come from South Central Asia. I investigated one potential source of this warm air among several-- namely at the point where the Taklamakan Desert meets the Tibetan Plateau in the Kunlun Shan and Altun Mountain ranges. 

This combination provides an ideal topographically forced "launching pad" for warm air to be lifted up through the lowered winter tropopause into the stratosphere. This air is then advected as a thermal wave toward the northern latitudes where it eventually descends, warms further, and creates an SSW event. This diagram illustrates the overall dynamics of this entire process:

In addition to the extensive reanalysis data, there appears to be tangential corroborating evidence in support of this overall dynamic, such as the high level of dust in Greenland ice cores that has an origin point in the Taklamakan desert and Tarim Basin. This dust could be part of the thermal wave that descends over the Arctic during the SSW and is eventually deposited in Greenland ice.

Future research could focus on gathering mid-stratosphere air samples at 10 hPa during one of the thermal wave episodes, just prior to the SSW event. A high level of dust inside that thermal wave that could be identified through isotopic analysis as coming from the Taklamakan Desert and Tarim Basin would be strong evidence of the origin of the warm air. Other avenues of research should include the analysis of other regions of South Central Asia that also show high positive omega values in the days leading up to the formation of the 10 hPa thermal wave. It is quite possible that several high positive omega areas could be involved simultaneously or each during different SSW events. 

Finally, a close analysis of the regions involved in high positive omega events should be conducted to see what meteorological conditions exist to create the wind field energy necessary for topographic lifting. In addition to pressure zones and prevailing winds, energy from the lowering of the tropopause and the jet stream during winter could be an important source of energy for high positive omega events and the precursors to SSW's.

Update #1:  I came across the following chart from this site:  http://arise-project.eu/atmospheric-dynamics.php

Both the chart and the Arise website are right on target with what we've been talking about related to the causes of some of the various types of waves we can find in the stratosphere and mesosphere (though their mountains are better than in my simple drawing!). In short, there are multiple sources (thunderstorms, cyclones, and yes, topography) that can send waves into the stratosphere. 

It should be also be noted that vertically forced Rossby Waves have been discussed quite a bit by some posters related to SSW's, and that indeed, topological factors (i.e. the Tibetan Plateau and other high mountain ranges) can play a big role in these types of waves.  Here's a quote from a paper on these types of waves that is worth reading (some rather heavy math edited out):

"Rossby waves are often forced by topography...Rossby waves cannot propagate vertically if the mean zonal winds are easterly, or if they are westerly and exceed a certain speed.This has important implications for the dynamics of the middle atmosphere (defined as the stratosphere and mesosphere). In the summertime the zonal winds in the middle atmosphere are easterly, and so energy from topographically forced Rossby waves cannot reach the middle atmosphere. In the wintertime, however, the zonal winds in the middle atmosphere are westerly, allowing Rossby waves to reach the middle atmosphere and deposit energy. This explains the sudden stratospheric warming episodes (as much as 40-50 K within a few days) observed in the Northern Hemisphere wintertime. This phenomenon is not as pronounced in the Southern Hemisphere because there are not as many topographical features in that hemisphere to generate topographically forced Rossby waves."

The full paper for this quote (with the maths) can be found here: http://snowball.millersville.edu/~adecaria/ESCI343/esci343_lesson11_rossby_waves.pdf

Comments

[Neven]

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]

Neven,

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

[Dr2chase.wordpress.com]

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]

David,

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]

Neven;

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):
http://www.youtube.com/watch?v=sohI6vnWZmk

Here's a site that covers a bit more, from the same people:
http://permaculturenews.org/2007/03/01/greening-the-desert-now-on-youtube/

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:
http://www.greeningthedesert.com/

[Aaron Lewis]

Randall,
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]

Aaron,

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.

[Misfratz.wordpress.com]

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:
http://squall.sfsu.edu/crws/archive/jet_nh_arch.html
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,
http://virga.sfsu.edu/pub/jetstream/jetstream_norhem/1212/12121818_jetstream_norhem.gif
Then the 25th
http://virga.sfsu.edu/pub/jetstream/jetstream_norhem/1212/12122500_jetstream_norhem.gif

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.

[Erimaassa.blogspot.com]

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]

Michael,

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

[R. Gates]

Misfratz,

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]

Chris,

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]

Michael,

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]

Michael,

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]

Chris,

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]

Michael,

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

[Chris Reynolds]

Michael,

"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.

[Neven]

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.

[Werther]

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…

[vukcevic]

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.
http://www.vukcevic.talktalk.net/SSW2012-13.gif
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]

Vukcevic,

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.]

[wili]

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.

[VaughnA]

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?

No!

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!

Cheers,
Lodger

[vukcevic]

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
http://images.intellicast.com/WxImages/SatelliteLoop/hinpole_None_anim.gif

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)
http://www.realclimate.org/index.php/archives/2012/04/unforced-variations-april-2012/

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.

[A-Team]

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).

[vukcevic]

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

[A-Team]

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?

[wayne]

"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.

[Neven]

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. ;-)

[A-Team]

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.

http://www.sciencedirect.com/science/article/pii/S0277379105001976

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...

http://www.sciencedirect.com/science/article/pii/S0921818106000324

[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.

Steve,

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.

Vukcevic,

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.

[vukcevic]

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]

Susan,

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.)

[Neven]

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!

Alex

[Syddbridges]

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:

http://science.nasa.gov/science-news/science-at-nasa/2001/ast11oct_1/

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

http://www.nwra.com/news/planetary_waves.pdf

[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]

ulisescervantes,

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...)

[Wouterlefebvre]

Randall,

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.
http://en.wikipedia.org/wiki/Goode_homolosine_projection

[R. Gates]

ulisescervantes,

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...

http://www.youtube.com/watch?v=mDsqpeiTqg8

... 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 :)

[Herfried]

...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...

[NLPatents]

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

[A-Team]

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]

http://onlinelibrary.wiley.com.oca.ucsc.edu/doi/10.1029/2000JD900665/pdf
https://www.jstage.jst.go.jp/article/sola/8/0/8_2012-025/_pdf
http://onlinelibrary.wiley.com/doi/10.1029/2002GL016446/pdf
http://www.atmos-chem-phys.net/10/2615/2010/acp-10-2615-2010.pdf

[Neven]

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]

Randell,
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 :
http://www.democraticunderground.com/10022207929
which is 'late', but has an interesting 50 mb animation...

http://forum.netweather.tv/topic/74587-stratosphere-temperature-watch-20122013/
Thousands of comments, starting in Sept. 2012, which note SSW over Russia as early as end of November 2012.

http://www.boards.ie/vbulletin/showthread.php?t=2056803618
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 :
http://www.boards.ie/vbulletin/showpost.php?p=82220060&postcount=27

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 ?

[P-maker]

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:

http://img21.imageshack.us/img21/7107/15decto13jantempanom30m.gif

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]

Rob,

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:

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2012.gif

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

[Donald]

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

National Geographic: Chasing Ice 720p
http://www.youtube.com/watch?feature=player_embedded&v=ajFoSPgCtpw

[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 :
http://forum.netweather.tv/topic/74587-stratosphere-temperature-watch-20122013/page-44#entry2422108

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:

http://science.nasa.gov/science-news/science-at-nasa/2001/ast11oct_1/

[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.

[D]

Hello
I am an anthropologist, with little background in atmospheric science. While I believe your logic is correct, I believe you may have missed a tiny but critical component. If you very slowly process through the GIF, you will notice at 03:08 to 03:20 that the "trigger" of the event was not in the Taklamakan (China) desert, but in Dasht-i-Lut (eastern Iran), where much hotter temperatures, plus prevailing winds lofted over northern Pakistan by the Himalayan range (and northerly flows at that location), produce the required rapidly ascending air mass into which the massive heat, from the already elevated desert of China, then joins in a "full conflagration" event. Just a thought.

[Eric Apel]

I find this post fascinating, and as a meteorologist my first thought was, "How can I predict the trigger?"

I have not looked at historical or reanalysis data yet, but I just had a look at the GFS model 06Z 12/11/2014 data. If you look at the 200 hPa winds over Asia you see that the GFS model predicts the Jet Stream will strengthen over the Taklamakan Desert around the 18th of December. Going further from there and then looking at 10 hPa temperatures we do see a sudden increase in temperatures originating in that same place then moving up toward Mongolia and further NE.

Immediately following that there is an even stronger warming event that takes place but the origin is norther Iran near Tehran over the Elburz Mountains (only half the elevation of the Tibetan Plateau). However there seems to be a very weak Jet preceding that event, and in fact there is a split flow over that region during that time. I'm not yet sure what that might mean, as I'm investigating it further, but I would be interested to hear people's thoughts.

[Susan Anderson]

I am hoping those more qualified than I will think about this SSW business. I noticed something else about it a couple of weeks back and a meteorologist friend responded with this in a personal note. My fellows in the US may remember how intense that was, though it is also my understanding that SSW events don't always knock on in a predictable way.

I have no idea how a potential stratospheric warming would interact with the very warm Ocean Basins throughout the northern Hemisphere, though it would make sense that long wave troughs associated with a double shift in the main polar vortex circulation splitting over both Canada and Siberia would be a good bet since those are the two places where the colder air would be concentrated with the warmer oceans, especially the ridiculously high ocean temperatures in the high latitudes. The latest longer range models are trending for colder than usual over east Asia and warmer over North America through the rest of the month. But that could quickly change if the stratospheric warming becomes significant. It should be a good learning experience to see if, when, and how it develops.