Wobbles in the Barriers: Arctic Oscillation (4)

By: Dr. Ricky Rood , 4:22 PM GMT on October 14, 2013

Wobbles in the Barriers: Arctic Oscillation (4)

This is a continuation of my series on the Arctic Oscillation / North Atlantic Oscillation. Links to background material and previous entries are at the end.

In the last entry I suggested that if you were on a bridge overlooking a swiftly flowing creek then you would notice that twigs floating in the water did not move across the current. They are carried downstream along the edge of the current. The purpose of that comparison was to demonstrate how fast-moving, concentrated flows have the effect of isolating one side of the creek from the other. This is true in the creek, and it is also true about jet streams in the atmosphere.

One way to understand the Arctic Oscillation is to think of it as the variation of an atmospheric jet stream. For the Arctic Oscillation the jet stream of interest is the southern edge of vortex of air that circulates around the North Pole (see previous entry). Air inside the vortex often has characteristics different from air outside it. Intuitively for the Arctic, there is colder air on the side toward the pole. If you look at trace gases, like ozone, they are different across the edge of the vortex. The takeaway idea is that the edge of the vortex is a barrier. It’s not a perfect barrier, but the air on one side is largely separated from the air on the other side. In this blog, I describe the difference between a strong and a weak vortex – which is the same as the difference between the positive and negative phases of the Arctic Oscillation and the North Atlantic Oscillation.

Figure 1: This figure is from the point of view of someone looking down from above at the North Pole (NP). Compare this perspective to Figure 1 in previous blog. This represents a strong, circular vortex centered over the pole, which encloses cold air, represented as blue. The line surrounding the cold air is the jet stream or the edge of the vortex.

Figure 1 shows an idealized schematic of the North Pole as viewed from above. This is the strong vortex case, when there is exceptionally low pressure at the pole. Low pressure is associated with counterclockwise rotation in the Northern Hemisphere. This direction of rotation is called cyclonic. This strong vortex case is the positive phase of the Arctic Oscillation. During this phase, the vortex aligns strongly with the rotation of the Earth, and there are relatively few wobbles of the edge of the vortex – the jet stream. I drew on the figure two points, X and Y. In this case, the point X is hot and the point Y is cold. It is during this phase when it is relatively warm and moist over, for example, the eastern seaboard of the United States.

Figure 2 compares a strong vortex and a weak vortex. In both cases, the circulation around a central point is counterclockwise or cyclonic. However, in the weak vortex case, the vortex does not align as strongly with the rotation of the Earth and there are places where the edge of vortex extends southwards. The vortex appears displaced from the pole; it is not centered over the pole.

Figure 2: Examples of a strong, circular vortex and a weak, more wavy vortex. See text for a more complete description.

Whether the vortex is stronger or weaker is determined by the atmospheric pressure at the pole. In the winter, an important factor that determines the circulation is the cooling that occurs at polar latitudes during the polar night.

What determines the waviness or wobbles at the edge of this vortex? The structure at the edge of vortex is strongly influenced by several factors. These factors include the structure of the high-pressure centers that are over the oceans and continents to the south of jet stream. One could easily imagine a strong high-pressure center over, for example, Iceland, pushing northward at the edge of the vortex. This might push a lobe of air characteristic of the middle latitude Atlantic Ocean northward. Since the edge of the vortex is something of a barrier, this high-pressure system would distort the edge of the vortex and, perhaps, push the vortex off the pole. This would appear as a displacement of the vortex and its cold air over, for example, Russia. If the high grew and faded, then this would appear as wobbles of the vortex.

Other factors that influence the waviness at the edge of the vortex are the mountain ranges and the thermal contrast between the continents and the oceans. The impact of mountains is easy to understand. Returning to the creek comparison used above, the mountains are like a boulder in the stream. The water bulges around and over the boulder; the air in the atmosphere bulges around and over the mountain ranges. The Rocky Mountains in the western half of North America are perfect examples of where there are often wobbles in the atmospheric jet stream.

Figure 3: This figure is from the point of view of someone looking down from above at the North Pole (NP). This represents a weak, wavy, wobbly vortex displaced from the pole. The vortex encloses cold air, represented as blue. The line surrounding the cold air is the jet stream or the edge of the vortex. (definition of vortex)

Figure 3 shows an idealized schematic of the North Pole as viewed from above. This is the weak vortex case, when the low pressure at the pole is not as low as average and the pressure is much higher than the strong vortex case of Figure 1. This weak vortex case is the negative phase of the Arctic Oscillation. During this phase, the alignment of the vortex with the rotation of the Earth is less prominent, and there are wobbles of the edge of the vortex – the jet stream. In this case, the point X is cold and the point Y is hot. It is during this phase where it is relatively cool and dry (but potentially snowy) over, for example, the eastern part of the United States.

These figures help to explain the prominent signal of the Arctic Oscillation discussed in the earlier entries (specifically, this blog). That is, when the vortex is weak and wobbly, then there are excursions of colder air to the south and warmer air to the north. This appears as waviness and is an important pattern of variability - warm, cold, warm, cold.

The impact of the changes in the structure of edge of the vortex does not end with these persistent periods of regional warm and cold spells. The edge of the vortex or the jet stream is also important for steering storms. Minimally, therefore, these changes in the edge of the vortex are expected to change the characteristics of how storms move. Simply, if the edge of the vortex has large northward and southward extensions, then storms take a longer time to move, for example, across the United States from the Pacific to the Atlantic Oceans. In the positive phase of the Arctic Oscillation they just whip across. In the negative phase, the storms wander around a bit. A more complete discussion of this aspect of the role of the Arctic Oscillation will be in the next entry. (Note use of dramatic tension and the cliffhanger strategy of the serial.)

r

Previous entries:

Barriers in the Atmosphere
Behavior
Definitions and Some Background

August Arctic Oscillation presentation

CPC Climate Glossary “The Arctic Oscillation is a pattern in which atmospheric pressure at polar and middle latitudes fluctuates between negative and positive phases.”

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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57. georgevandenberghe
 Just chatting with a fellow gardener who hailed from Western Montana. He asserts things have changed significantly for the warmer in the past ten years and whereas before no one grew vine ripened tomatoes in his region, in the past ten years it has become possible. Just one datapoint.
55. Neapolitan
 Quoting 53. Cochise111:So, if the MWP was much warmer than today's climate, and it was a world-wide event, just how can CO2 be responsible for warmth when CO2 levels were over 100 ppm lower in the MWP? Another inconvenient fact for the warmists to explain.LinkSo if Hockey Shtick and Goddard's site and Watts' sites went down permanently, you'd have absolutely nothing to do, would you?Anyway:--The MWP wasn't global.--A "paper" from the fossil fuel-funded SPPI and CO2 Science isn't a paper as in "peer-reviewed" or "refereed" or "credible"; it's a one-sided opinion piece. And putting one's faith into anything that "paper" has to say is akin to reading a "paper" from the local biker gang that details how healthy smoking crystal meth is, then picking up the pipe...Sorry, Koch-ise; you've been fooled yet again. Doesn't that ever get old?
Member Since: December 31, 1969 Posts: Comments:
54. JohnLonergan
 Sea level in the 5th IPCC reportWhat is happening to sea levels? That was perhaps the most controversial issue in the 4th IPCC report of 2007. The new report of the Intergovernmental Panel on Climate Change is out now, and here I will discuss what IPCC has to say about sea-level rise (as I did here after the 4th report).Let us jump straight in with the following graph which nicely sums up the key findings about past and future sea-level rise: (1) global sea level is rising, (2) this rise has accelerated since pre-industrial times and (3) it will accelerate further in this century. The projections for the future are much higher and more credible than those in the 4th report but possibly still a bit conservative, as we will discuss in more detail below. For high emissions IPCC now predicts a global rise by 52-98 cm by the year 2100, which would threaten the survival of coastal cities and entire island nations. But even with aggressive emissions reductions, a rise by 28-61 cm is predicted. Even under this highly optimistic scenario we might see over half a meter of sea-level rise, with serious impacts on many coastal areas, including coastal erosion and a greatly increased risk of flooding.Fig. 1. Past and future sea-level rise. For the past, proxy data are shown in light purple and tide gauge data in blue. For the future, the IPCC projections for very high emissions (red, RCP8.5 scenario) and very low emissions (blue, RCP2.6 scenario) are shown. Source: IPCC AR5 Fig. 13.27.More »
Member Since: December 31, 1969 Posts: Comments:
51. ScottLincoln
 Quoting 48. Neapolitan:"Trillions of tons per day"?Say what?Well that's rather high...
50. ScottLincoln
 Quoting 34. BaltimoreBrian:After all that it just cited 2 science papers. One supporting global warming, and one global cooling SkulDouggery said he had a page full of science papers from the 1970s predicting global cooling and there was just one.ONEWow.Not surprising. We've had literature reviews done before that have shown the vast majority of papers have predicted warming, not cooling, even back in the 1970s.It's a zombie myth that, at best, came from a handful of poor media articles misinterpreted by people with less-than-stellar critical thinking skills.
48. Neapolitan
 Quoting 45. EllenPettit:Ehem. I think it is pretty clear that the current drought conditions in TX--along with New Mexico anD Colorado--and the neighboring states are among the worst in history.And it will only get worse, much worse. As long as trillions of tons of C02 is being pumped into the Earth's atmosphere per day, it is very hard to say whether or not things will ever get back to normal. I don't think I'd necessarily say GW is over. But you could dream, right? ;-)"Trillions of tons per day"?Say what?You've been repeatedly corrected in the past on this sort of inane statement, yet here you are again talking the same worthless nonsense. I guess it's true what they say: some people never learn...
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46. JohnLonergan
 From Rabett Run:"Al Gore has taken a lot of abuse for prematurely being against climate change over the years. One of the sillier ones was for a bit of artwork that appeared on the cover of his latest book %u201COur Choice: A Plan to Solve the Climate Crisis%u201D with Gore's commentWhen you unfold the cover, the image you see if the earth as we know it today with its deep blue oceans, rich soil, and green forests. This side of the cover reveals an artist%u2019s rendering of an earth where unchecked global warming has wreaked havoc. We are at a crossroads. We must choose which earth will be home to future generations.He would, perhaps have done better to run the image past Kerry Emanuel first, but of course, the jackals pounced.Well, these days there are three pretty big storms out there, on the other side of the earth, Cyclone Phailin which set a new record for Indian Ocean cyclones, has struck India, Typhoon Nari worked over the Philippeans and another is building up behind it and Typhoon Whipha is out there, strengthening and forcast to sideswipe Tokyo. Of course, Typhoon Usagi which worked over the Chinese coast between Hong Kong and Shanghai, a few days ago, was early to the party. Now some, not Eli to be sure, tell us nevermind that because no hurricanes have hit the US in a while (Sandy, having weakened before landing does not count). Others will note that there have been three tropical cyclones going at the same time before, so never mind. Ah, never mind. Perhaps the artist and Al were not so far off."Yes, I know that the artist got the cyclonic rotation backwards.
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44. pcola57
 Quoting 41. greentortuloni:Hi all,I was just wondering what your opinions on the problems in Washington are from a climate standpoint?Personally I've been worried about it.. and then it occurred to me that while the politicians are turned and screaming at each other, this might be the break we've all been looking for: the economy shuts down and there is a slight respite from pollution.Or is this a foolish hope and all that will happen is vital research is halted?I keep making arguments back and forth with no clear ideas.(sorry if this has already been discussed)Morning greentortuloni.. :)My personal opinion is until we go "full on" with efforts akin to WWII concerning planet responsibility and using all available Green technology "NOW",as in right now,, we shall have enjoyed the best mankind has to offer and will now experience our decline into to relative obscurity in the blip of time in which we occupy..Edit: I do have a basic internal belief that we will snap out of this "throw away the world" mentality..
43. pcola57
 Quoting 9. RickyRood:This is David Archer's U of Chicago course which is very good. I hope to start putting my course lectures on line in the near future. I have a different focus of climate change and its intersection with all things, but I do cover the basics of the science of climate change as well. Plus if you haven't figured it out, some of my blogs fit into the course.rThank you Dr. Rood for your sharing of info in this blog..Keeping it real and simple really helps me..I don't have a great attention span but am able to fully absorb the jist of what you convey..I for one want to send out a hearty thank you for allowing the discussions here to work themselves out..The community does work well when allowed..When and if you start posting online please share the Address and pertinent info..Thanks again..
41. greentortuloni
 Hi all,I was just wondering what your opinions on the problems in Washington are from a climate standpoint?Personally I've been worried about it.. and then it occurred to me that while the politicians are turned and screaming at each other, this might be the break we've all been looking for: the economy shuts down and there is a slight respite from pollution.Or is this a foolish hope and all that will happen is vital research is halted?I keep making arguments back and forth with no clear ideas.(sorry if this has already been discussed)
40. Naga5000
 Quoting 39. Daisyworld:I've suspected you may be using this blog as an in-course case study for climate communication over the past few years, as that's probably what I would be doing were I teaching a course on climate change. I applaud your efforts in providing your students a method to engage in the discussion outside of the classroom!I always hoped some of my wittier replies were discussion starters. ;)
39. Daisyworld
 Quoting 9. RickyRood:This is David Archer's U of Chicago course which is very good. I hope to start putting my course lectures on line in the near future. I have a different focus of climate change and its intersection with all things, but I do cover the basics of the science of climate change as well. Plus if you haven't figured it out, some of my blogs fit into the course.rI've suspected you may be using this blog as an in-course case study for climate communication over the past few years, as that's probably what I would be doing were I teaching a course on climate change. I applaud your efforts in providing your students a method to engage in the discussion outside of the classroom!
38. BaltimoreBrian
 I posted that article back on October 10, RevElvis. I even gave it three stars :) But it's an important finding so I'm glad you posted posted it again.
37. RevElvis
 Increased human life expectancy correlates to increase in species extinctionAs GDP per capita increases, so does the percentage of invasive species.A study published by a team of biologists suggests that as a nation's population life expectancy increases, so does its percentage of invasive and endangered birds and mammals. It suggests that rather than population density alone being the largest threat to wildlife, it's the quality of life that matters most.The very presence of humans is often blamed for the increasing numbers of extinct species on the planet. But a team of biologists from the University of California-Davis examined 15 economic, ecological, and social variables to judge which factors of that human presence are the biggest contributors to the downfall of species.Expanding the survey to include the number of invasive species in a country revealed even more interesting results. Introducing a non-indigenous species to any given ecosystem can have devastating effects. Controlling the number of invasive species was identified as the greatest challenge threatening the Galapagos when the World Heritage Committee placed it on its danger list, for instance, and in the UK the introduction of the eastern gray squirrel from North America is blamed for devastating the red squirrel population, now down to under 200,000. What the report found, however, is that a combination of economic and social factors is responsible for this devastation—just as, in reality, deforestation and other factors have contributed to the fall of the red squirrel.Taking in data from 100 countries, representing 87 percent of the world's total population and 43 percent of global GDP, the study focused on the following: GDP, export-import ratio, tourism, undernourishment, energy efficiency, agricultural intensity, rainfall, water stress, wilderness protection, biodiversity, life expectancy, adult literacy, pesticide regulation, political stability, and female participation in national government. It is a comprehensive look at the human impact on the landscape, but it became clear that life expectancy was the greatest correlating factor responsible for the damage."It's not a random pattern," says lead author Aaron Lotz, a postdoctoral scholar in the Department of Wildlife, Fish, and Conservation Biology at the time of the study. "Out of all this data, that one factor—human life expectancy—was the determining factor for endangered and invasive birds and mammals."ARSTechnica.com
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36. BaltimoreBrian
 Oh, I know birthmark. I use this article for rebuttal when denier trolls start saying/lying "but scientists were predicting global cooling in the 1970s!"
34. BaltimoreBrian
 I went through skuldouggery's page and its links. 34 links total3 links are dead3 are to other climate depot pages1 USA TODAY6 New York Times3 Time magazine2 Washington Times2 Dennis Dutton blog (philosophy professor died in 2010)2 John Daly blog entries (died in 2004, not a scientist)1 Newsweek1 zombietime.com/zomblog1 icecap.us, denier blog entry1 algorelied.com1 anonymous blog on blogspot1 capitalismmagazine.com1 amazon book page1 peopleofglobalwarming.com1 Wisconsin Energy Cooperative webpage1 Business and media Institute1 paper supporting global warming1 paper from 1971 supporting global cooling (due to aerosol pollution)After all that it just cited 2 science papers. One supporting global warming, and one global cooling SkulDouggery said he had a page full of science papers from the 1970s predicting global cooling and there was just one.ONEWow.
33. BaltimoreBrian
 a fair answer tramp96. Incomplete but fair.
30. JohnLonergan
 No basis to deny global warmingWhen I was a first-year graduate student at Caltech, my Ph.D. adviser published a paper called “Impact-induced energy partitioning.” He asked how an asteroid’s energy would change form if it collided with the Earth. He used computer models to estimate what fraction would go into lofting debris, heating, melting, vaporizing rocks, and so on.This subject was not settled science then, and is still not. One thing is for sure, however. The laws of physics dictate that energy is conserved. If an asteroid is hurtling toward your city, you might not be concerned that scientists are not 100 percent certain about how its energy will be “partitioned.”Global warming is no different. Another one of my professors was Richard Feynman. In his famous “Feynman Lectures” he had a chapter called “Conservation of Energy” in which he says:“There is a fact, or if you wish, a law, governing all natural phenomena that are known to date. There is no exception to this law – it is exact so far as we know. The law is called conservation of energy.”......Uncertainty in exactly how something happens does not translate into uncertainty that it is happening. There is no rational basis for denial of the reality, or the risks, of global warming.And there is no excuse for ignoring it.
Member Since: December 31, 1969 Posts: Comments:
29. BaltimoreBrian
 Oh dear. You are banned from the blog for 5 minutes Revelvis! ;)
28. RevElvis
 17 - +'d the wrong post!
Member Since: December 31, 1969 Posts: Comments:
27. BaltimoreBrian
 tramp96, you didn't say whether people who agreed with the comments or stories I quoted and linked to are crazy. Do you agree with any of them?
25. JohnLonergan
 Quoting 9. RickyRood:This is David Archer's U of Chicago course which is very good. I hope to start putting my course lectures on line in the near future. I have a different focus of climate change and its intersection with all things, but I do cover the basics of the science of climate change as well. Plus if you haven't figured it out, some of my blogs fit into the course.rThanks, Dr. Rood, Id be interested in seeing your lectures if you put them on online.
Member Since: December 31, 1969 Posts: Comments:
24. Xulonn
 Quoting 17. Cochise111:Climate models versus reality:wattsupwiththat silly graph.I think that was 50 runs with different parameters of one model, not runs of many models. So your use of the plural "models" is wrong and makes your post laughable. If you had said that temperature data the barely falls within the bounds of the model runs, you would have appeared to be a bit more intelligent. You may have heard of a website called "WeatherUnderground" that was started by Jeff Masters, a Ph.D. Meteorologist. He's also an expert on AGW/CC, and probably a lot smarter, better educated, and wiser than you. You might consider reading his blog post from earlier this year for some factual reality regarding AGW/CC with respect to warming in the biosphere, and where the excess heat from the earth's current ongoing energy imbalance is going.There is still surplus global heat every year, and there are other factors that can affect surface and lower troposphere temperatures. Your simple minded, cherry picked graph is one anomaly in a veritable flood of evidence that global warming is still with us in a big way.I feel sorry for you, because it appears that you have been seriously fooled by the fossil-fuel funded denial-o-sphere via the Anthony Watts disinformation center, and are not able to see the big picture and comprehend complex issues. You might want to work on your critical thinking skills as well, which appear to be severely limited. As Mark Twain said:
Member Since: December 31, 1969 Posts: Comments:
21. BaltimoreBrian
 That anyone (comment 3) would have a problem with introductory science courses not requiring their students to have a previous science background is crazy.It's the stupidest comment I've seen in weeks.
19. indianrivguy
 Norway's Investments in Renewable Energy "Could Change the World."Interesting article about shifting the BIG dollars to something renewable.. as the World Banks are now refusing to underwrite coal plants.. things are looking better for us. The world would throw away oil in a heartbeat if there was a way to make the same profits doing something clean.
18. Patrap
 http://wattsupwiththat.files.wordpress.com/2013/10/ cmip5-90-models-global-tsfc-vs-obs1.jpgReally ?Go Fish.
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16. Xulonn
Member Since: December 31, 1969 Posts: Comments:
15. RevElvis
 Why Small-Scale Biomass Energy Projects Aren't a Solution To Climate Change"Roberto Bissio has an excellent piece in a roundtable on biomass energy, pointing out that small scale biomass energy projects designed for people in poor countries aren't really a solution to climate change. After pointing out that patent protections could impede wide-spread adoption, Bissio adds that the people in these countries aren't really contributing to climate change in the first place: 'Why? Because poor people, whose carbon emissions these technologies would reduce, produce very little carbon in the first place. As I mentioned in Round One, the planet's poorest 1 billion people are responsible for only 3 percent of global carbon emissions. The 1.26 billion people whose countries belong to the Organization for Economic Co-operation and Development account for 42 percent of emissions. The rich, if they reduced their emissions by just 8 percent, could achieve more climate mitigation than the poor could achieve by reducing their emissions to zero. The rich could manage this 8 percent reduction by altering their lifestyles in barely noticeable ways. For the poor, a reduction of 100 percent would imply permanent misery.'"Slashdot.orgBulletin of the Atomic Scientists
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14. BaltimoreBrian
 For tramp96, comment 392 in previous entry. tramp96: "Why do you feel the Tea Party members are crazy? Just a question don't read anything into it please."Because of this, and a thousand other incidents like this at tea party rallies.Rallier tells Obama to 'put the Quran down'The speaker is Larry Klayman, the founder and former chairman of Judicial Watch, and now a leader in Freedom Watch, a major tea party organization.'Truckers for the Constitution' Plan to Slow D.C. Beltway, Arrest CongressmenDr. Ben Carson Making Waves Again: Obamacare 'Worst Thing Since Slavery' Really? Worse than segregation laws and Pearl Harbor?"I think, personally, it would bring stability to the world markets." on what happens if the debt limit isn't raised.Rep. Ted Yoho (R-Fla.)And all the "Obama is a Muslim" and "Obama is a Kenyan" crap.These are a few from the last week. I could go on but I think I made my point. People who believe this crap are crazies.
13. ScottLincoln
 Quoting 7. JohnLonergan:More on the Coursera offering at RealClimate:Sample video(8:13)I'm interested in the course, anyone else?I'm interested, but almost wondering if it would be worth my time or just a rehashing of concepts I already know. I've thought about taking it before as sort of a "continuing education" sort of thing. We are asked by office management to do additional training every 6 months.
12. ScottLincoln
 Quoting 8. Naga5000:Yoboi, you also may be appalled to know this, but AGW is even taught in college level Intro to Meteorology courses. You know scientists teach science, correct?Next thing you know, scientists at colleges will be requiring their students to think critically!!!
9. RickyRood
 This is David Archer's U of Chicago course which is very good. I hope to start putting my course lectures on line in the near future. I have a different focus of climate change and its intersection with all things, but I do cover the basics of the science of climate change as well. Plus if you haven't figured it out, some of my blogs fit into the course.rQuoting 7. JohnLonergan:More on the Coursera offering at RealClimate:Sample video(8:13)I'm interested in the course, anyone else?
8. Naga5000
 Yoboi, you also may be appalled to know this, but AGW is even taught in college level Intro to Meteorology courses. You know scientists teach science, correct?
7. JohnLonergan
 More on the Coursera offering at RealClimate:Sample video(8:13)I'm interested in the course, anyone else?
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