# 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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##### 907. auburn (Mod)
 Please keep personal disputes out of Dr. Ricky Roods blog. Thanks All.
##### 903. Patrap
 They will suck every last BBL out the ground for profit over People.The Forces involved care not for Humanity.Govt's come and go, but Oil is King, of All.
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##### 901. RevElvis
 James Hansen: How We Can Stop Big Oil in its Tracks and Keep Dirty Energy in the GroundHere's a way to stop the global reach of Big Oil, hasten the transition to clean energy, and keep coal and tar sands deposits where they belong – in the ground.I could not help thinking of David versus Goliath earlier this week as I was working on a letter to Jose Manuel Barroso, President of the European Commission. I was writing about the tax that Europe applies to unconventional fossil fuels in its Fuel Quality Directive: Will it account for all the emissions during the mining and processing of such fuels or will they pretend that energy from tar sands and oil shale is the same as conventional oil? It matters – a lot. If total emissions are counted, the fees tacked to oil from tar sands or tar shale will make that carbon-intensive fuel less competitive in the market. Add a rising fee on carbon, and these dirtiest of fuels will be the first to be eliminated and replaced by clean energy and energy efficiency. Tar sands production today is moderate, but there are plans to quintuple the rate of extraction over the next decade. Tar sands operations today are ugly enough, but if that expansion happens and infrastructure is put in place to carry the products to market, we surely will see a monstrous pillage of the land. Massive carbon loadFrom the climate standpoint, we cannot accept the massive carbon load associated with unconventional fossil fuels without guaranteeing climate disasters. Conventional oil and gas should be the transition fuel to a clean energy future, and they could be that, if we put a rising fee on carbon,...Alternet.orgPeople are shocked that drug users would inject themselves with a cheap version of Krokodil that makes their skin die off, but say nothing when the millions of people who are addicted to oil would inject the planet with nasty chemicals and kill off large swaths of land and ocean. - Alternet Poster
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##### 899. Patrap
 when the Atlantic flips to cold, the Arctic sea ice will recover to normal. Really ?Go Phish JB.
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##### 898. JohnLonergan
 I missed this in my last post, all you need to know about James Taylor's climate credibility:Background James Taylor is a Senior Fellow with the Heartland Institute and managing editor of the Heartland publication Environment & Climate News.
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##### 895. JohnLonergan
 Quoting 894. Neapolitan:Still going on about that, are they? Wilson--"implicated" in the thoroughly manufactured and debunked "climategate 2.0" "scandal" has previously spoken out against denialists misconstruing his comments. And Mann certainly didn't "lash out" at Wilson; he merely questioned Wilson's own dendroclimatological methods, a subject with which Mann is intimately familiar. That's what scientists do...Question, if Wilson is not in the skeptic camp, why did he make his claim on uber denialist Andrew Montford's blog, Bishop Hill? If you lie down with dogs, you wake up with fleas. Just saying
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##### 894. Neapolitan
 Quoting 888. iceagecoming:Mann Attacks Fellow Warmist for Questioning Hockey StickOctober 22, 2013James M. Taylor, J.D.James M. Taylor is managing editor of Environment & Climate News, a national monthly... (read full bio)EMAIL PrintPrint EmailEmailProminent global warming alarmist Michael Mann venomously attacked fellow warmist Rob Wilson after Wilson pointed out flaws in Mann’s “hockey stick” reconstruction of historic temperatures.Wilson, a paleoclimatologist who is a post-doctoral research fellow at Scotland’s prestigious University of Edinburgh and an adjunct research fellow at Columbia University in the United States, delivered a two-hour lecture on climatology last week at Scotland’s University of St. Andrews. While discussing historical climate, Wilson documented several major procedural and substantive flaws in Mann’s hockey stick. Taking care to reassure people he is not part of the “skeptic” camp, Wilson nevertheless emphasized the importance of sound, unbiased science. Wilson concluded Mann’s hockey stick was “ultimately a flawed study.”LinkI sense a lawsuit brewing, Dr. Mann will be right, no matter how wrong.Time for a political distraction in VA, Oh! that already happened.Still going on about that, are they? Wilson--"implicated" in the thoroughly manufactured and debunked "climategate 2.0" "scandal" has previously spoken out against denialists misconstruing his comments. And Mann certainly didn't "lash out" at Wilson; he merely questioned Wilson's own dendroclimatological methods, a subject with which Mann is intimately familiar. That's what scientists do...
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##### 893. MisterPerfect
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##### 890. iceagecoming
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##### 889. RevElvis
 "Think about it this way: We're killing people in foreign lands in order to extract 200 million-year-old sunlight. We frack our own backyards and pollute our rivers, or we blow up our mountaintops... for an hour of electricity, when we could just take what's falling free from the sky."- Danny Kennedy, former Greepeace activist & founder of Sungevity
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##### 888. iceagecoming
 Mann Attacks Fellow Warmist for Questioning Hockey StickOctober 22, 2013James M. Taylor, J.D.James M. Taylor is managing editor of Environment & Climate News, a national monthly... (read full bio)EMAIL PrintPrint EmailEmailProminent global warming alarmist Michael Mann venomously attacked fellow warmist Rob Wilson after Wilson pointed out flaws in Mann’s “hockey stick” reconstruction of historic temperatures.Wilson, a paleoclimatologist who is a post-doctoral research fellow at Scotland’s prestigious University of Edinburgh and an adjunct research fellow at Columbia University in the United States, delivered a two-hour lecture on climatology last week at Scotland’s University of St. Andrews. While discussing historical climate, Wilson documented several major procedural and substantive flaws in Mann’s hockey stick. Taking care to reassure people he is not part of the “skeptic” camp, Wilson nevertheless emphasized the importance of sound, unbiased science. Wilson concluded Mann’s hockey stick was “ultimately a flawed study.”LinkI sense a lawsuit brewing, Dr. Mann will be right, no matter how wrong.Time for a political distraction in VA, Oh! that already happened.
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##### 887. Patrap
 The IPCC explains... Reliability of Climate Projection ModelsIPCC FAQ 8.1How Reliable Are the Models Used to Make Projections of Future Climate Change? "...models are unanimous in their prediction of substantial climate warming under greenhouse gas increases, and this warming is of a magnitude consistent with independent estimates derived from other sources, such as from observed climate changes and past climate reconstructions."There is considerable confidence that climate models provide credible quantitative estimates of future climate change, particularly at continental scales and above. This confidence comes from the foundation of the models in accepted physical principles and from their ability to reproduce observed features of current climate and past climate changes. Confidence in model estimates is higher for some climate variables (e.g., temperature) than for others (e.g., precipitation). Over several decades of development, models have consistently provided a robust and unambiguous picture of significant climate warming in response to increasing greenhouse gases.Climate models are mathematical representations of the climate system, expressed as computer codes and run on powerful computers. One source of confidence in models comes from the fact that model fundamentals are based on established physical laws, such as conservation of mass, energy and momentum, along with a wealth of observations.
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##### 886. Patrap
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##### 879. JohnLonergan
 Quoting 877. Birthmark:The last link in your post doesn't work.. This is what the denialists argue when they claim that there's been no warming, though they probably haven't thought about it up to now.(I will also post this on my blog for those that want to discuss this or correct me without the trolls.)http://ourchangingclimate.wordpress.com/2013/09/2 7/bbc-interview-global-warming-pause-climate-scept ics-long-timescales/Try this, works for me.
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##### 878. JohnLonergan
 Climate debate must stick to the science: professorThe author of a report that lays bare the connection between climate change and extreme bushfires has expressed his ''frustration'' with Prime Minister Tony Abbott and Environment Minister Greg Hunt for their refusal to accept scientific consensus on climate change.Professor Will Steffen, who co-authored the soon-to-be-released bushfire report by the Climate Council, was responding to Mr Abbott's assertion in a newspaper interview with leading climate sceptic Andrew Bolt that drawing a link between the savage fires now plaguing NSW and climate change was ''complete hogwash''.We never go to secondary sources like that. The Climate Council report, a summary of which was revealed by Fairfax Media on Friday, found a clear link between rising temperatures and a longer, more dangerous bushfire season in south-eastern Australia."We never go to secondary sources like that.": Professor Will Steffen."We never go to secondary sources like that.": Professor Will Steffen. Photo: Alex Ellinghausen''We would certainly prefer that this debate be elevated to the real scientific facts as are reported in the scientific literature and as are assessed very competently by the IPCC, the CSIRO and the Bureau [of Meteorology] and the scientists we rely on,'' Professor Steffen said.Read more >>
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##### 876. Daisyworld
 Quoting 875. schwankmoe:why do you ask a question to which you already know the answer?You're right, of course. I guess I just wanted to read the answer from the source directly, hoping for a reasonable reply and for cooler heads to prevail. Maybe I'm naive in that respect.
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##### 875. schwankmoe
 Quoting 874. Daisyworld:So then, what purpose does it serve for you to be manufacturing an unrelated controversy in the comments of a blog devoted to climate change communication and understanding of climate science?why do you ask a question to which you already know the answer?
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##### 873. Patrap
 Lordy, all this "fluff" sure has ZERO impact as to the continued warming of the Earth via Fossil Fuel burning increasing the CO2 ppm score.Seems the naysayers have actually gone off da rails and into the Science surge.
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##### 862. schwankmoe
 I know, lol about "hate speech". dude's pretty sensitive about being constantly debunked and starts flailing after awhile. pretty juvenile.
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##### 860. Xulonn
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##### 857. goosegirl1
 Quoting 852. Doxienan:We installed a heat pump water heater. Initially, we wanted to install a solar hot water system, but the solar installer explained that the cost of solar PV is so low that solar thermal doesn't make sense. We added another 2KW of solar panels to provide hot water. There is more than enough for the two of us and lots of company on weekends. And I think we got a rebate from the electric company for it.Our house is south-facing and unobstructed. We live in New Hampshire at a high elevation. Lots of sun, but lots of winter. The PV system supples more than enough for our household electric, the water heater, and our plug-in car. We also added a lot of insulation (spray-on and rigid foam) and new windows. So far, an efficient woodstove is all we need to heat the house, with the original oil furnace as backup if we ever have to go away. If you're building a new house, I would investigate the German 'passive house'. Although our house is more than 200 years old, with careful planning, we have insulated it to withstand even the coldest NH winters.I like the passive house concept. I didn't know it at the time, but we incorporated a few of the design elements. The HVAC is a high efficiency reversable heat pump, with a 95% efficient propane furnace as back-up when the temps are too cold for the heat pump. The house is heavily insulated and well sealed. I'm hoping the heat pump water heater saves a lot of energy, along with energy star appliances. It only makes sense to us- it's responsible, and it saves money. We are also adding solar outside lighting.
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