# 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.”

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##### 707. ScottLincoln
 Quoting 706. Xulonn:To believe that both handles belong to the same person would require a high level of incompetence and no ability to think critically. There may be some sockpuppets on the side of science, but they are rare and not at all like like the horde of rabid cockroaches that emerge from the denialist cyberverse to infest the world of AGW/CC blogs....The identity of one commenter at an internet blog isn't going to change the science - nor are multiple denialist sockpuppets at other sites going to change the science... Incompetence? Inability to think critically? Ok, well not necessarily. Without context and previous experience, it would probably jump out to most that a person responded for someone else. Technically, we are all posting behind internet handles to provide some sort of anonymity (although I chose mine back when I had others with a full name), so it's not always straight-forward to prove who is who.I don't agree with Doug on much - it shouldn't come as a surprise - as I think he sometimes comes in here with vague accusations and doesn't get specific. Katrina was directly caused by climate change, anyone?But what I will say is that a situation like this could, at least to some, beg the question. Even though we disagree with him often, I'm not sure that it warrants people piling on the insults. This particular post was probably one of the least-nice ways to convey disagreement. Contrary to many other times, he did actually provide the "proof" he was referring to specifically. How many actually double-checked to see if they were real? I did, and they were right there.I'm not in a place to explain it one way or the other, but maybe we can try to play nicer.
##### 706. Xulonn
 Gee Doug, you're funny - you've made the most asinine series of posts I've ever seen here. It absolutely reeks of desperation and a futile attempt to save face. Nea and John Lonergan are one and the same?? Give me a break!To believe that both handles belong to the same person would require a high level of incompetence and no ability to think critically. There may be some sockpuppets on the side of science, but they are rare and not at all like like the horde of rabid cockroaches that emerge from the denialist cyberverse to infest the world of AGW/CC blogs. Science is science - AGW/CC is based on overwhelming evidence and detailed analysis, and you refuse to accept it. The identity of one commenter at an internet blog isn't going to change the science. - nor are multiple denialist sockpuppets at other sites going to change the science. Besides, your AGW/CC denial is not even of interest to the scientists - there is no debate - they've moved on, and are continuing to study AGW/CC and what it might do to human civilization...leaving you to tilt at windmills.
Member Since: June 11, 2012 Posts: 0 Comments: 1772
##### 705. overwash12
 I say that ice held up pretty good this summer,gonna be one hell of a winter up there!
##### 704. schwankmoe
 Quoting 697. BrownWeather:Big John. Let's not tease Dougie now. Go easy on the big fella.I just realized that all of us are mere figments of dougie's imagination.
Member Since: October 18, 2005 Posts: 0 Comments: 836
##### 703. JohnLonergan
Member Since: June 27, 2012 Posts: 0 Comments: 4319
##### 702. Patrap
 There are so many things that I don't understandThere's a world within me that I cannot explainMany rooms to explore, but the doors look the sameI am lost I can't even remember my name[Hook]I've been, for sometimeLooking for someoneI need to know nowPlease tell me who I am[Verse 2]There are so many thingsThat I don't understandThere's a world within meThat I cannot explainMany rooms to exploreBut the doors look the same(where are the locks to try the key)I am lost I can't even remember my name(and I wonder why)
Member Since: July 3, 2005 Posts: 437 Comments: 134829
 Quoting 694. GiovanniDatoli:You totally got it wrong, Dougie. Take the propaganda like glasses off your face. Remember--science, my friend.Friend....right...
Member Since: July 25, 2006 Posts: 2 Comments: 806
 Quoting 695. BrownWeather:Backpeddling some more there, I see. You're a regular at it.Huh? Are you delusional?
Member Since: July 25, 2006 Posts: 2 Comments: 806
##### 696. JohnLonergan
 Quoting 691. schwankmoe:WHAT DID YOU KNOW AND WHEN DID YOU KNOW IT?EVERYTHING, ALWAYSrAMEN
Member Since: June 27, 2012 Posts: 0 Comments: 4319
 See you fellas later. I know. Don't let the door hit ya ...or some such insult.
Member Since: July 25, 2006 Posts: 2 Comments: 806
##### 691. schwankmoe
 Quoting 686. JohnLonergan:Should I take the fifth or drink it?WHAT DID YOU KNOW AND WHEN DID YOU KNOW IT?
Member Since: October 18, 2005 Posts: 0 Comments: 836
 Quoting 686. JohnLonergan:Should I take the fifth or drink it?Sup Nea?
Member Since: July 25, 2006 Posts: 2 Comments: 806
##### 688. schwankmoe
 Quoting 679. PensacolaDoug:Keep making excuses for your hero..he's so busted.you're a regular james bond.
Member Since: October 18, 2005 Posts: 0 Comments: 836
##### 686. JohnLonergan
 Quoting 683. ScottLincoln:And where were you, Mr. Lonergan, on the morning in question?Should I take the fifth or drink it?
Member Since: June 27, 2012 Posts: 0 Comments: 4319
 Quoting 654. schwankmoe:not over one word in one post, no.Not over one word. That makes no sense.
Member Since: July 25, 2006 Posts: 2 Comments: 806
##### 683. ScottLincoln
 Quoting 682. JohnLonergan:They believe in Invisible Pink Unicorns, too.-puts on mock trial hat-And where were you, Mr. Lonergan, on the morning in question?-end mock trial-
##### 682. JohnLonergan
 Quoting 681. Birthmark:Hilarious how yall accept whatever explanation pleases you most, regardless of the lack of evidence. Meanwhile, well-substantiated scientific theories get derided.Weird.They believe in Invisible Pink Unicorns, too.
Member Since: June 27, 2012 Posts: 0 Comments: 4319
##### 680. ScottLincoln
 Quoting 678. schwankmoe:i just copied yours in an attempt to confuse everyone. and i woulda got away with it too, if it weren't for you meddlesome kids.Trying to get the next conspiracy theory to involve me. Just what I need.
 Quoting 662. schwankmoe:A mistype. A poster confused and thinking that they are being referred to and not the other person. A poster who feels like sticking up for someone else.Keep making excuses for your hero..he's so busted.
Member Since: July 25, 2006 Posts: 2 Comments: 806
##### 678. schwankmoe
 Quoting 674. ScottLincoln:Heh. I don't dance.Did you type a comment at the same time, or did it just duplicate mine and give one to your name?i just copied yours in an attempt to confuse everyone. and i woulda got away with it too, if it weren't for you meddlesome kids.
Member Since: October 18, 2005 Posts: 0 Comments: 836
##### 677. ncstorm
 hilarious how yall dance around the evidence..one word that is significant in evidence of multiple handles..earth has cycles..have a good night..LOL!!
Member Since: August 19, 2006 Posts: 13 Comments: 17405
##### 674. ScottLincoln
 Quoting 669. schwankmoe:it's because you're my sockpuppet. I OWN YOU DANCE FOR ME, PUPPETHeh. I don't dance.Did you type a comment at the same time, or did it just duplicate mine and give one to your name?
##### 671. RevElvis
 Verizon, FCC & Net Neutrality: What You Need to Know (PC Mag)Big Deal Big Money (Commoncause.org)(does not directly apply to Climate Change - but definitely could affect the info that is "free" today)
Member Since: September 18, 2005 Posts: 30 Comments: 1085
##### 669. schwankmoe
 Quoting 665. ScottLincoln:??? how did it take my comment and merge it into yours?it's because you're my sockpuppet. I OWN YOU DANCE FOR ME, PUPPET
Member Since: October 18, 2005 Posts: 0 Comments: 836
##### 668. Patrap
 O Noes, # 666 the anti-post'
Member Since: July 3, 2005 Posts: 437 Comments: 134829
##### 665. ScottLincoln
 Quoting 662. schwankmoe:A mistype. A poster confused and thinking that they are being referred to and not the other person. A poster who feels like sticking up for someone else.??? how did it take my comment and merge it into yours?
##### 663. ScottLincoln
 Quoting 640. Birthmark:That is not the only possible explanation. Did you check back in the thread to see what, if any, interactions took place between DealWithIt and John Lonergan? If not, it might be worth a look since you seem interested.A link to the thread might help bolster your position, too.This is everything after about 6AM or so.Time (GMT); Poster; Blog; Post; Page; Comment10/17/2013 09:36 Nea Masters 2556 10 48010/17/2013 11:37 Nea Masters 2556 11 50610/17/2013 11:39 Nea Masters 2556 11 50910/17/2013 11:59 J_L Rood___ 276 4 16810/17/2013 12:43 J_L Rood___ 276 4 16910/17/2013 13:10 J_L Masters 2556 11 53710/17/2013 13:30 J_L Rood___ 276 4 17010/17/2013 14:12 J_L Masters 2556 12 55610/17/2013 14:39 J_L Rood___ 276 4 17210/17/2013 15:39 Nea Masters 2556 12 58010/17/2013 15:56 J_L Rood___ 276 4 17810/17/2013 16:05 Nea Masters 2556 12 58210/17/2013 17:42 Nea Rood___ 276 4 185
##### 662. schwankmoe
 Quoting 636. PensacolaDoug:How would you explain it?A mistype. A poster confused and thinking that they are being referred to and not the other person. A poster who feels like sticking up for someone else.
Member Since: October 18, 2005 Posts: 0 Comments: 836
##### 661. Patrap
 I'm so confused I'm watching The Big Bang Theory on CBS.
Member Since: July 3, 2005 Posts: 437 Comments: 134829
##### 660. schwankmoe
 Quoting 659. BrownWeather:So, we've gone from "proof" to "reasonable people wondering." That's some serious backpedalling in a short period of time. i see what you did there.
Member Since: October 18, 2005 Posts: 0 Comments: 836
##### 658. ScottLincoln
 Quoting 636. PensacolaDoug:How would you explain it?A mistype. A poster confused and thinking that they are being referred to when they aren't. A poster who feels like sticking up for someone else.

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