Sudden Stratospheric Warmings (SSW's)

By: 24hourprof , 5:09 PM GMT on January 09, 2013

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Jeff Masters forwarded me an e-mail from one of our readers inquiring about sudden stratospheric warming (there's a dramatic SSW ongoing over Asia...see loop of 10-mb temperature anomalies below). As a weather forecaster, most of the sudden warmings that catch my attention are related to tropopause folds (not SSW's). A tropopause fold is a process by which air from the lower stratosphere intrudes into the troposphere. To give you an idea of the spatial scale of tropospheric folds, their horizontal domain is on the order of a few hundred kilometers and the depth is typically a few kilometers.

Tropopause folds are associated with upper-tropospheric frontogenesis, the formation of jet streaks, and tropopause undulations (these processes are all related). By the way, I wrote about tropopause undulations and their role in cyclogenesis in a blog posted on December 29. At any rate, the subsidence and compressional warming associated with tropopause folds promote warming in the lower stratosphere. Moreover, tropopause folds are marked by relatively high concentrations of ozone at altitudes typically reserved for the troposphere. Back in the 1990s, I taught my students that another tracer of stratospheric air associated with folds is the presence of Strontium-90, which was left over from the above-ground testing of atomic bombs in the early 1960s (Strontium-90 obviously has a very long half-life).


Temperature anomalies at 10 mb from December 8, 2012, to January 6, 2013, show a dramatic and sudden warming over Asia.

But I digress. The reader was interested in the spectacular, sudden stratospheric warmings (SSW's...revisit the lollapalooza above). By way of comparison, the life span of an SSW is noticeably longer than a tropopause fold. Specifically, folds tend to have a lifetime of a day or so (perhaps as long as five days), but SSW's can last for weeks. Moreover, SSW's can have long-lasting effects, sometimes keeping the stratosphere warm for the rest of winter.

So why did I broach the idea of tropopause folds? Easy answer. I just didn't want readers to confuse tropopause folds with SSW's. With my worrisome nature appeased, I'll get back on topic now. For starters, spectacular, mid-winter SSW's are marked by a warming of up to 40 degrees Celsius at 50 mb (lower half of the stratosphere) over a period of just a few days. These sudden warmings can impact weather patterns in the troposphere (SSW's can promote a negative NAO and cold weather in the contiguous states, for example), so they are worthy of study.

I usually interject mathematics to help me explain SSW's, so I'll see if I can accomplish the same thing with words. The usual set-up in the Northern Hemisphere's lower stratosphere is a north-south thermal gradient, with a temperature maximum at roughly latitude 45 degrees north and progressively colder air toward the pole (absorption of ultraviolet radiation by ozone fades with increasing latitude as the intensity of solar radiation fades toward the dark high latitudes...keep in mind that it's winter and polar regions are dark).

If you were a student in my class, I'd drill it into your head that any north-south temperature gradient is associated with vertical wind shear. When it's warm to the south and cold to the north (as it is in the normal winter set-up), the vertical wind profile in the stratosphere is characterized by westerly winds whose speeds increase with increasing altitude. Such a relationship between horizontal temperature gradients and vertical wind shear are stipulated by the thermal wind equation. I don't want to get into math, so I'll just use the term, "thermal wind arguments." At any rate, vertical wind shear associated with the normal north-south temperature gradient culminates with a westerly wind maximum (fast winds blowing from the west) near the top of the stratosphere. This wind maximum near the top of the stratosphere is called the stratospheric polar-night jet (this jet is a feature of the stratosphere's general circulation during winter).


A cross section of average temperatures (in Kelvins) from 1979 to 1998 as a function of pressure (right axis) and altitude (left axis). Average isotachs denoting wind speeds in meters per second are represented by thin white contours (solid corresponds to westerly and dashed represents easterly winds). "J" marks the positions and altitudes of jet streams. Courtesy of NASA.

You can see the stratospheric polar-night jet (marked by a big "J" near 10 mb in the Northern Hemisphere) on the cross section of average January temperatures from 1979 to 1998 above. Note the polar vortex at high latitudes, an intense cyclonic vortex that forms over the winter pole. The polar vortex represents one of the most prominent circulation features in the stratosphere during winter. To the south of the polar vortex in the Northern Hemisphere, note the thin, white isotachs (meters per second) that represent the long-term average strength of the polar-night jet. In this cross section, the westerly polar-night jet blows out of the page right at you, with warmer stratospheric air on your left. By the way, dashed white contours indicate easterly winds (blowing from the east).

SSW's were discovered over Berlin in the early 1950s (the good old days). Subsequent research indicated that upward-propagating, planetary-scale Rossby waves transported energy and momentum into the stratosphere. Without getting into too much atmospheric physics, upward-propagating Rossby waves produce a meridional transverse circulation in the stratosphere, with sinking air over high latitudes and rising air closer to the equator. The dramatic compressional warming associated with the subsidence over high latitudes is the hallmark of SSW's that I mentioned earlier. As you can imagine, dramatic warming in the region of the polar vortex upsets the circulation in the stratosphere. As the normal north-south temperature gradient breaks down, winds associated with the polar-night jet weaken (thermal wind arguments) and sometimes reverse (become easterly). If stratospheric winds at this level become easterly, further upward transfer of wave energy is blocked, and the deceleration of westerly winds and subsidence warming work its way downward.

SSW's occur almost exclusively in the Northern Hemisphere because of the hemispheric differences in topography. As it turns out, the upward-propagating Rossby waves that incite SSW's are topographically forced (planetary waves are generated by the distribution of land and ocean, mountains, etc.). SSW's usually keep the Northern Hemisphere's stratosphere warmer for relatively long periods so that an ozone hole doesn't develop over the polar region. Indeed, an ozone hole, in the strictest sense of the term, only forms over the Southern Hemisphere.

Lee

Post Script:

SSW's alter the tropospheric circulation through a process called potential vorticity thinking (pretty odd, I know). PVT essentially acts like a thermal wind adjustment. During an SSW, changes to the stratospheric polar vortex in the lower stratosphere cause an imbalance. Generally speaking, when a flow is out of balance, the adjustment process ripples to regions relatively far from the location where the imbalance occurs. In this case, when there is an imbalance in the lower stratosphere, the adjustment extends all the way down to the earth's surface. Indeed, the adjustment "excites" the negative phase of the Northern Annular Mode (also known as the Arctic Oscillation) and the negative phase of the North Atlantic Oscillation. In turn, this "excitation" can pave the way for an outbreak of cold air over the Northeast States.

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33. mitomke
2:31 PM GMT on June 23, 2014
That is a very clear explanation. Suppose an event occurred within the Aleution Low which amplified low pressure, this then led to a jet stream divergence above. Could such an event lead to a SSW?
Member Since: June 10, 2014 Posts: 0 Comments: 0
32. atomant77
12:05 PM GMT on March 31, 2013
Is it possible that the energy that made elnino possible is causing the increase of SSW's? could the accumulated heat in the western Pacific move upwards and northwards instead of east towards south america?
Member Since: March 31, 2013 Posts: 0 Comments: 0
31. WunderAlertBot (Admin)
3:52 PM GMT on January 13, 2013
24hourprof has created a new entry.
30. DelWeather
9:56 PM GMT on January 12, 2013
Quoting georgevandenberghe:
In cases where the surface pressure is less than 1000mb, the thickness is estimated from conditions at the surface and assumptions on how much temperature would have increased as pressure increased down to 1000mb. A similar process is used to estimate "Sea Level Pressure" in elevated regions. When sea level pressure is less than 1000 mb, the 1000-500mb thickness will be larger than the 500mb height.

Man, I never would have guessed that! Thanks for the answer.
Member Since: October 9, 2012 Posts: 0 Comments: 50
29. georgevandenberghe
9:41 PM GMT on January 12, 2013
In cases where the surface pressure is less than 1000mb, the thickness is estimated from conditions at the surface and assumptions on how much temperature would have increased as pressure increased down to 1000mb. A similar process is used to estimate "Sea Level Pressure" in elevated regions. When sea level pressure is less than 1000 mb, the 1000-500mb thickness will be larger than the 500mb height.
Member Since: February 1, 2012 Posts: 19 Comments: 1941
28. DelWeather
2:24 PM GMT on January 12, 2013
Quoting georgevandenberghe:


A better indication of mean layer temperature is the thickness between the 1000mb and the 500mb pressure surface. This is directly proportional to the mean virtual temperature of the layer (the word "virtual" corrects for the small but variable effect water vapor has; thicknesses are a little higher in moist air at a given temperature because water vapor is less dense than either O2 or N2, the dominant components of the air. 1000-500mb thicknesses are displayed on most websites' model output maps. If I had one map to look at I would look at 1000-500mb thickness superimposed on the surface pressure map.




Thanks, George. This helps. But since surface pressure is sometimes less than 1000 mb, I'm assuming that 1000-500 mb thickness is basically just the same as the height of the 500 mb line? Anyway, it makes total sense that colder air is comprised of molecules moving more slowly than warmer air, thus they don't "get quite so high" when moving upward, thus bringing down the level for a particular pressure.

All this vertical motion in the troposphere and stratosphere is mind-boggling for me. But confusion is the first step towards understanding!
Member Since: October 9, 2012 Posts: 0 Comments: 50
27. cyclonebuster
11:10 PM GMT on January 11, 2013
Quoting 24hourprof:


I'm not sure there have been studies on this topic. What I can say with some certainty is that the SSW's alter the tropospheric circulation through a process called potential vorticity thinking (pretty odd, I know). PVT essentially is the same as thermal wind adjustment. During an SSW, the changes to the stratospheric polar vortex (in the lower stratosphere) result in an imbalance. When a flow is out of balance, the adjustment process extends to regions far from the location where the imbalance occurs. In this case, when there is an imbalance in the lower stratosphere, the adjustment extends all the way down to the surface. This results in the excitation of the negative phase of the Northern Annular Mode (also known as the Arctic Oscillation) and the negative phase of the North Atlantic Oscillation. This leads to the advection of cold air into the Northeast. If George is onto the forecast, cold weather is in the offing.

Hope this helps.



Thanks for your response. I was wondering if it would help create them or cause them to dissipate??? As of the 6th it looks like the heat is really being poured into the atmosphere up North.....What's it look like between the 6th and the 11th??
Member Since: January 2, 2006 Posts: 127 Comments: 20417
26. 24hourprof
9:47 PM GMT on January 11, 2013
Quoting georgevandenberghe:
I'm not yet ready to buy into an arctic outbreak of 5-10 year
return frequency but suspect that the period days 8-14 will finally
kill off my fall garden with a <-5C nighttime minimum in the DC suburbs.


George,

I'm hoping the teleconnections work in your favor!
Member Since: October 24, 2012 Posts: 91 Comments: 803
25. 24hourprof
9:42 PM GMT on January 11, 2013
Quoting cyclonebuster:


How would it effect the Arctic Dipole?


I'm not sure there have been studies on this topic. What I can say with some certainty is that the SSW's alter the tropospheric circulation through a process called potential vorticity thinking (pretty odd, I know). PVT essentially is the same as thermal wind adjustment. During an SSW, the changes to the stratospheric polar vortex (in the lower stratosphere) result in an imbalance. When a flow is out of balance, the adjustment process extends to regions far from the location where the imbalance occurs. In this case, when there is an imbalance in the lower stratosphere, the adjustment extends all the way down to the surface. This results in the excitation of the negative phase of the Northern Annular Mode (also known as the Arctic Oscillation) and the negative phase of the North Atlantic Oscillation. This leads to the advection of cold air into the Northeast. If George is onto the forecast, cold weather is in the offing.

Hope this helps.

Member Since: October 24, 2012 Posts: 91 Comments: 803
24. georgevandenberghe
8:13 PM GMT on January 11, 2013
Quoting DelWeather:
I'm not sure what "500 mb heights" being low means for the weather. I understand (I think) that we are talking about the altitude where the pressure is 500 mb. Does this pressure being at a lower altitude simply mean that a low pressure system is forecast for the surface at that time?


500mb heights are strongly correlated with temperature for sound physical reasons. The pressure decrease with height is proportional to density so pressure decreases faster with height in a colder atmosphere.
This means at significant altitude there will be a horizontal pressure difference between cold and warm air masses. Low 500mb heights mean mostly colder and high heights mean mostly warmer. There
is a surface pressure reflection in the heights also. You can get fairly high heights over cold air masses in the arctic if they are associated with very intense surface high pressure.

A better indication of mean layer temperature is the thickness between the 1000mb and the 500mb pressure surface. This is directly proportional to the mean virtual temperature of the layer (the word "virtual" corrects for the small but variable effect water vapor has; thicknesses are a little higher in moist air at a given temperature because water vapor is less dense than either O2 or N2, the dominant components of the air. 1000-500mb thicknesses are displayed on most websites' model output maps. If I had one map to look at I would look at 1000-500mb thickness superimposed on the surface pressure map.


By the way everyone learns in school that the atmosphere is 21% oxygen and 78% nitrogen (and 1% argon ). This is not true in a warm moist air mass which can be as much as 4% water vapor. The other gases are displaced proportionately yielding 20% oxygen and 75% nitrogen.

Member Since: February 1, 2012 Posts: 19 Comments: 1941
23. DelWeather
7:51 PM GMT on January 11, 2013
I'm not sure what "500 mb heights" being low means for the weather. I understand (I think) that we are talking about the altitude where the pressure is 500 mb. Does this pressure being at a lower altitude simply mean that a low pressure system is forecast for the surface at that time?
Member Since: October 9, 2012 Posts: 0 Comments: 50
22. georgevandenberghe
7:42 PM GMT on January 11, 2013
I'm not yet ready to buy into an arctic outbreak of 5-10 year
return frequency but suspect that the period days 8-14 will finally
kill off my fall garden with a <-5C nighttime minimum in the DC suburbs.
Member Since: February 1, 2012 Posts: 19 Comments: 1941
21. 24hourprof
6:04 PM GMT on January 11, 2013
Quoting georgevandenberghe:
12Z deterministic GFS looks very very cold in the east 288 hours out.
I've often said looking at a single deterministic forecast that far out has the entertainment value of going to a fortuneteller but it is within the envelope of possibility. Haven't seen what the ensembles are doing yet.


Hi George,

The 12Z MREF run on PSU's e-wall has not updated yet, but the 06Z MREF run shows anomalously low 500-mb heights over the East around that time (run your cursor over the forecast times along the top...the left panel is the ensemble mean for 500-mb height anomalies, while the plot on the right shows the spaghetti of the ensemble members for specified 500-mb heights, expressed in dekameters).
Member Since: October 24, 2012 Posts: 91 Comments: 803
20. georgevandenberghe
5:50 PM GMT on January 11, 2013
12Z 1/11/2013 deterministic GFS looks very very cold in the east 288 hours out.
I've often said looking at a single deterministic forecast that far out has the entertainment value of going to a fortuneteller but it is within the envelope of possibility. Haven't seen what the ensembles are doing yet.
Member Since: February 1, 2012 Posts: 19 Comments: 1941
19. 24hourprof
4:32 PM GMT on January 11, 2013
Quoting DelWeather:
I had to come back to this post three times due to time constraints, but I just got about thirty free minutes (ok, to tell the truth, I didn't grade the papers I SHOULD have) and was able to make some headway in understanding the post. And I agree... Google was a friend.

I would love to learn more about Rossby waves. The idea that topographical features on the order of one or two kilometers (mountains), or even just the distribution of land and water, can result in effects as high as 30 or 40 km is just so cool! I knew that stratospheric clouds (which are necessary to provide the catalytic substrate for ozone-chlorofluorocarbon reactions) only formed over the Antarctic because that's the only place the stratosphere gets cold enough, but now I have a little more insight into "why."

Many thanks! I enjoy the high end stuff... makes me work for my dinner.


Many, many thanks.

I did my Masters thesis (not related to Jeff :-) on blocking in the North Atlantic and North Pacific, where the planetary waves (wavenumbers 1, 2 and 3) constructively interfere and amplify via resonance, thereby accounting for the rather high frequency of blocking in these two regions. So, yes, planetary waves are cool. Thanks again.
Member Since: October 24, 2012 Posts: 91 Comments: 803
18. DelWeather
2:52 PM GMT on January 11, 2013
I had to come back to this post three times due to time constraints, but I just got about thirty free minutes (ok, to tell the truth, I didn't grade the papers I SHOULD have) and was able to make some headway in understanding the post. And I agree... Google was a friend.

I would love to learn more about Rossby waves. The idea that topographical features on the order of one or two kilometers (mountains), or even just the distribution of land and water, can result in effects as high as 30 or 40 km is just so cool! I knew that stratospheric clouds (which are necessary to provide the catalytic substrate for ozone-chlorofluorocarbon reactions) only formed over the Antarctic because that's the only place the stratosphere gets cold enough, but now I have a little more insight into "why."

Many thanks! I enjoy the high end stuff... makes me work for my dinner.
Member Since: October 9, 2012 Posts: 0 Comments: 50
16. cyclonebuster
1:13 PM GMT on January 11, 2013
Quoting 24hourprof:


I suspect that SSWs have a "positive" correlation of Arctic Sea Ice extent, but I'm not an expert on this topic.

This paper indicates a positive correlation between SSW's and increased "anticyclonic activity" over the Beaufort Sea. To the extent that anticyclones promote cold nights, there might be a positive correlation. I haven't read the paper thoroughly, but it's on my to-do list.

Hope this helps.


How would it effect the Arctic Dipole?
Member Since: January 2, 2006 Posts: 127 Comments: 20417
15. 24hourprof
12:58 PM GMT on January 11, 2013
Quoting cyclonebuster:
Looks like it is headed over the North Arctic.. Is that good for Northern polar ice extent/mass?


I suspect that there's a "positive" correlation between SSW's and Arctic sea ice, but I'm not an expert on this topic.

This paper indicates a positive correlation between SSW's and increased "anticyclonic activity" over the Beaufort Sea. To the extent that anticyclones promote clear, cold nights, which are pretty long during winter (if there's any daylight at all...depends on latitude, of course), it makes sense to me that such a positive correlation exists. I haven't read the paper thoroughly, but it's on my to-do list.

Hope this helps.
Member Since: October 24, 2012 Posts: 91 Comments: 803
14. 24hourprof
12:57 PM GMT on January 11, 2013
Quoting islandraider:
Hi Lee & thanks for the great blog post on SSW! (I was not able to respond to your email: out of the office at meetings yesterday & home today with a cold.)

I would be interested about implications for arctic sea ice, as well. Lots of heat in the stratosphere... how does that translate for all the new ice forming?

Also, from your blog name "From the Lee Side", I thought maybe you need a blog song:

Link

Thanks again!
Brian.


Thanks Brian.

I suspect that there's a "positive" correlation between SSW's and Arctic sea ice, but I'm not an expert on this topic.

This paper indicates a positive correlation between SSW's and increased "anticyclonic activity" over the Beaufort Sea. To the extent that anticyclones promote clear, cold nights, which are pretty long during winter (if there's any daylight at all...depends on latitude, of course), it makes sense to me that such a positive correlation exists. I haven't read the paper thoroughly, but it's on my to-do list.

In the 1950s, there was a popular song called "Mr. Lee." Perhaps that should be my theme song. On the other hand, I'm a huge fan of Eddie from Ohio and my favorite EFO song is "Number Six Driver."
Member Since: October 24, 2012 Posts: 91 Comments: 803
13. cyclonebuster
8:57 PM GMT on January 10, 2013
Looks like it is headed over the North Arctic.. Is that good for Northern polar ice extent/mass?
Member Since: January 2, 2006 Posts: 127 Comments: 20417
12. islandraider
6:47 PM GMT on January 10, 2013
Hi Lee & thanks for the great blog post on SSW! (I was not able to respond to your email: out of the office at meetings yesterday & home today with a cold.)

I would be interested about implications for arctic sea ice, as well. Lots of heat in the stratosphere... how does that translate for all the new ice forming?

Also, from your blog name "From the Lee Side", I thought maybe you need a blog song:

Link

Thanks again!
Brian.
Member Since: January 10, 2013 Posts: 0 Comments: 0
11. 24hourprof
12:25 PM GMT on January 10, 2013
Quoting NEWxSFC:
Maybe there's still hope for this winter...

"Pronounced weakenings of the NH wintertime
stratospheric polar vortex tend to be followed by episodes of anomalously low surface air temperatures and increased frequency of occurrence of extreme cold events throughout densely populated regions such as eastern North America,northern Europe, and eastern Asia that persist for ~2 months."

http://www.nwra.com/resumes/baldwin/pubs/Thompson etal_2002.pdf


That's great. Thanks. Let's see what happens. Thanks again.
Member Since: October 24, 2012 Posts: 91 Comments: 803
10. NEWxSFC
12:10 AM GMT on January 10, 2013
Maybe there's still hope for this winter...

"Pronounced weakenings of the NH wintertime
stratospheric polar vortex tend to be followed by episodes of anomalously low surface air temperatures and increased frequency of occurrence of extreme cold events throughout densely populated regions such as eastern North America,northern Europe, and eastern Asia that persist for ~2 months."

http://www.nwra.com/resumes/baldwin/pubs/Thompson etal_2002.pdf
Member Since: January 5, 2013 Posts: 0 Comments: 3
9. 24hourprof
10:15 PM GMT on January 09, 2013
Quoting NEWxSFC:
JMA has a good suite of observational data depicting wind and temp at 30 mb and 10 mb useful for monitoring the current event...

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/ STRAT/#monit_nh

This one is quite dramatic...
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/ STRAT/html_e/pole10_n.html


Nice.

Thanks.

Lee
Member Since: October 24, 2012 Posts: 91 Comments: 803
8. 24hourprof
10:12 PM GMT on January 09, 2013
Quoting Some1Has2BtheRookie:
Lee,

I suggest that you keep it high end for those that can benefit more from the discussion. Should I have a question, I will raise my hand and ask if you can dumb it down a bit. ...... Well, dumb it down a lot! "Google" is my friend. :-)


Understood. And thanks.
Member Since: October 24, 2012 Posts: 91 Comments: 803
7. NEWxSFC
10:06 PM GMT on January 09, 2013
JMA has a good suite of observational data depicting wind and temp at 30 mb and 10 mb useful for monitoring the current event...

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/ STRAT/#monit_nh

This one is quite dramatic...
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/ STRAT/html_e/pole10_n.html
Member Since: January 5, 2013 Posts: 0 Comments: 3
6. Some1Has2BtheRookie
9:56 PM GMT on January 09, 2013
Lee,

I suggest that you keep it high end for those that can benefit more from the discussion. Should I have a question, I will raise my hand and ask if you can dumb it down a bit. ...... Well, dumb it down a lot! "Google" is my friend. :-)
Member Since: August 24, 2010 Posts: 0 Comments: 4758
5. 24hourprof
9:12 PM GMT on January 09, 2013
Folks,

I realize that this blog is on the "high end" of science. Just so you're not scared away, these kinds of "high-end" blogs won't happen very often. I just didn't want to let this event slip by without mention.

So please don't feel overwhelmed...it's tough material, no two ways about it. If anything, it should show you just how complex the atmosphere really is.
Member Since: October 24, 2012 Posts: 91 Comments: 803
4. 24hourprof
9:06 PM GMT on January 09, 2013
Quoting georgevandenberghe:
Thanks for response. I also looked at this in graduate school in 1985 but
have lost my notes for that period and the treatment there was not rigorous enough to answer the energetics questions. It's very rewarding to communicate with someone with both deep knowledge and good pedagogy.


George,

Funny you should say that. That's EXACTLY what I did...rooted through my old notes from graduate school stored in the basement (dead spiders, etc.). To be perfectly honest, I hadn't thought about SSW's in at least 25 years, but to let this event go by without mention would have been disappointing. Thank you for being so kind.
Member Since: October 24, 2012 Posts: 91 Comments: 803
3. georgevandenberghe
7:18 PM GMT on January 09, 2013
Thanks for response. I also looked at this in graduate school in 1985 but
have lost my notes for that period and the treatment there was not rigorous enough to answer the energetics questions. It's very rewarding to communicate with someone with both deep knowledge and good pedagogy.
Member Since: February 1, 2012 Posts: 19 Comments: 1941
2. 24hourprof
6:00 PM GMT on January 09, 2013
Quoting georgevandenberghe:
A few energetics questions. What happens to the kinetic energy of the stratospheric polar night jet during a warming? Is the warming reducing Available Potential Energy in the NH atmosphere?. Where does the energy to drive the thermally indirect circulation driving the sinking
and warming come from?

And of course the bottom line, not directly inferable from answers to the above. Will this FINALLY generate a cold outbreak in the Middle Atlantic region? :-)



George...the energy comes from the upward-propagating Rossby waves that dump energy and momentum into the stratosphere.

I have to admit that this one was a real challenge for me. I don't think I've thought about SSW's since graduate school...a long, long time ago.
Member Since: October 24, 2012 Posts: 91 Comments: 803
1. georgevandenberghe
5:49 PM GMT on January 09, 2013
A few energetics questions. What happens to the kinetic energy of the stratospheric polar night jet during a warming? Is the warming reducing Available Potential Energy in the NH atmosphere?. Where does the energy to drive the thermally indirect circulation driving the sinking
and warming come from?

And of course the bottom line, not directly inferable from answers to the above. Will this FINALLY generate a cold outbreak in the Middle Atlantic region? :-)

Member Since: February 1, 2012 Posts: 19 Comments: 1941

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Retired senior lecturer in the Department of Meteorology at Penn State, where he was lead faculty for PSU's online certificate in forecasting.

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