# 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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##### 1157. FLwolverine
 Quoting 1153. cyclonebuster:She doesn't want solutions so she banned me..May I copy the info over there?
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1156. FLwolverine
 Quoting 1149. Cochise111:Totally cherry picked and out of context. The program - with three scientists and a coastal management guy from Florida - is actually pretty good, and it's clear from Dr Long's statement that she means the IPCC is underestimating the effects of climate change - that no one can predict any longer whether we can actually keep temperature increases under 2% by cutting emissions.Here is the link to the whole program: LinkI think the Florida guy is just blowing smoke when he says Miami won't have to be abandoned.Added: here's the link to the New York Times sea level site shown in the video - Link
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1148. FLwolverine
 #1146 - CB - your post would be very appropriate over on Angela Fritz's blog too.Good article; terrible news.
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1145. barbamz
 Climate migration 'a complex problem'Deutsche Welle English, October 29, 2013Climate change is forcing people to flee their homes. But when does someone become a climate migrant, and what does the status mean? Dina Ionesco from the International Organization for Migration, explains.
##### 1144. FLwolverine
 Thanks, Pat.To the lurking Grothar, if one there be - many good wishes to you.
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1143. georgevandenberghe
 Quoting 1110. overwash12:That nail was put in the coffin for me this summer when the heat just wasn't there!DC summer was overall warmer than normal but much cooler than thelast three. August was cooler than the long term mean but notextreme. First year in several (I don't closely track) that July 25 planted sweetcorn did not quite mature but it's been a real long time (2006) since we had a cooler than normal August.
Member Since: February 1, 2012 Posts: 19 Comments: 5252
##### 1142. Patrap
 I'm sure he is a lurking from time to time.
Member Since: July 3, 2005 Posts: 452 Comments: 144116
##### 1141. FLwolverine
 Hi, Pat. Do you have any news of Grothar that you can share with us?
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1140. Patrap
Member Since: July 3, 2005 Posts: 452 Comments: 144116
##### 1139. georgevandenberghe
 Quoting 1102. Xulonn:"A study from Fairleigh Dickinson University is making news today after one of its findings seemingly indicated that Fox News has the least-informed national audience, while NPR has the best-informed.""The study even determined that many people who watch no news at all are more informed than those who watch Fox News, and, of course, people who watch the Daily Show are more informed than both of the above." I remember the quote from the 1960s Rowan and Martin's Laugh InTV show."You think we're stupid. You're watching"OOPS.. Modification. I lost the Fox sign. I meant to take a deserved poke at Fox. By the way in the wild, foxes are rabies carriers.. they tolerate it longer than many species and can function for a while while spreading it. Parallels intended! GWV
Member Since: February 1, 2012 Posts: 19 Comments: 5252
##### 1137. schwankmoe
 Quoting 1128. PensacolaDoug:So SP's would be a breeze.nea's also a member of the illuminati, so he has plenty of help too.
##### 1136. ScottLincoln
 Quoting 1129. JohnLonergan:GISS September anomaly data is out, record equaling .74 http://data.giss.nasa.gov/gistemp/tabledata_v3/GL B.Ts dSST.txtBut wasn%u2019t the arctic the coldest in a century?Looks like 0.74C ties the previous record from 2005.Using my crude attempt to approximate temperature contributions from various natural factors and the background anthropogenic warming rate, I forecasted 0.66C anomaly, assuming neutral ENSO. The 95% uncertainty bars on that forecast would probably be approximately 0.1C either way. To be within the range, we would need roughly 0.5C average for the rest of the year. To be spot on, we'd need roughly 0.87C average for the rest of the year (seems unlikely). Once the year is done and more data comes in for each of the natural factors (ENSO/Volcanic aerosols/Solar), I should be able to do a "corrected hindcast," which will basically say what the forecast should have been, if we had a perfect forecast for the natural forcings.
##### 1135. ScottLincoln
 Quoting 1125. Birthmark:Yeah, you probably want to think a bit about what you read, if you read.(If you look at and think about the numbers involved...well, it doesn't really say anything that you'd like. lol)If you look at the numbers involved and how they calculated them, you can see how bad the critiquers are at arithmetic. It was a very bad attempt to critique a paper done by people far more experienced in that field, and it shows.
##### 1134. Patrap
 Come on in, its Hump Day.The warming continue's, unabated
Member Since: July 3, 2005 Posts: 452 Comments: 144116
##### 1133. Patrap
 No, your link says it all, as the wu prompt tells us its not worthy.Anything else?
Member Since: July 3, 2005 Posts: 452 Comments: 144116
##### 1131. barbamz
 The Guardian is focussing on the strange political situation in Australia with its new government concerning CC:Climate change chairman attacks policy 'flip-flopping' and lack of consensusKatharine Murphy deputy political editortheguardian.com, Wednesday 30 October 2013 05.19 GMT Bernie Fraser criticises Abbott's 'extreme' position and says policy reversals create uncertainty for investorsMissing logic of Australian prime minister's denial of climate change link to bushfiresPosted by Graham Readfearn, Tuesday 29 October 2013 02.32 GMT theguardian.com The popular climate sceptic debating trick used by Tony Abbott fails the logic test
##### 1130. JohnLonergan
 Guess what?Climate change is happening, it has always happened, and it is happening faster then it should because of we humans, and our burning fossil fuels. ......Please enjoy this video from Hank as he dismisses 10 common climate denier memes.
Member Since: June 27, 2012 Posts: 0 Comments: 4603
##### 1129. JohnLonergan
 GISS September anomaly data is out, record equaling .74 http://data.giss.nasa.gov/gistemp/tabledata_v3/GL B.Ts dSST.txtBut wasn%u2019t the arctic the coldest in a century?
Member Since: June 27, 2012 Posts: 0 Comments: 4603
 Quoting 1053. Neapolitan:Well, I develop sophisticated web apps for a living; let me have a look...So SP's would be a breeze.
##### 1126. RevElvis
 Hurricane Sandy's Path Could Become More Frequent For Other StormsHuffingtonPost.com (Video Interview / Columbia Earth Institute)
##### 1123. Astrometeor
 Quoting 1122. cyclonebuster:Doesn't seem to accessible when you you have to use a barge to get to the water when all you have to do is insulate it and pipe it onshore...That would work, but California is so heavily developed where Google is located, it would be mightily hard for them to build a piping infrastructure there. A barge isn't hard to make, plus it's capable of being moved if one needs it to be.
##### 1121. Astrometeor
 Quoting 1116. StallworthSwing:Haha. Very funny. A boatload of Nea's sockpuppets just got banned within the last two days. What does that tell you?I was hoping you would say drawer full of sockpuppets...
##### 1120. FLwolverine
 Quoting 1116. StallworthSwing:Haha. Very funny. A boatload of Nea's sockpuppets just got banned within the last two days. What does that tell you?That you like to spout nonsense?
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1119. Astrometeor
 Quoting 1117. cyclonebuster:Nah you can do that with well water...Well, yes, but for a large-scale system like a data center you would want a good, easily accessible amount of water on-hand.
##### 1118. overwash12
 Quoting 1114. FLwolverine:Neither you nor anyone else has proven it isn't bad. Would it be more truthful for you to say: "AGW isn't the same because I believe the science that says smoking is harmful but I refuse to read the science that says AGW s harmful." I'll smoke a cig and cut firewood for the upcoming winter!We still have that choice!
Member Since: June 24, 2007 Posts: 0 Comments: 1499
##### 1115. FLwolverine
 Hey, I just responded to Overwash who was conversing with Nea! Does that mean I'm a sock puppet?
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1114. FLwolverine
 Quoting 1112. overwash12: No,I say it's not the same. Bad analogy. Smoking has been proven to be bad. AGW is not the same.Neither you nor anyone else has proven it isn't bad. Would it be more truthful for you to say: "AGW isn't the same because I believe the science that says smoking is harmful but I refuse to read the science that says AGW s harmful."
Member Since: January 6, 2013 Posts: 3 Comments: 2773
##### 1113. overwash12
 Is Dr. Rood having difficulties posting a new entry? I keep clicking on New Entry when it pops up and it takes me back to this one.
Member Since: June 24, 2007 Posts: 0 Comments: 1499
##### 1112. overwash12
 Quoting 1111. Neapolitan:That makes sense. It's like a heavy smoker claiming that because he hasn't yet contracted cancer, cigarettes are perfectly good for you... No,I say it's not the same. Bad analogy. Smoking has been proven to be bad. AGW is not the same.
Member Since: June 24, 2007 Posts: 0 Comments: 1499
##### 1111. Neapolitan
 Quoting 1110. overwash12:That nail was put in the coffin for me this summer when the heat just wasn't there!That makes sense. It's like a heavy smoker claiming that because he hasn't yet contracted cancer, cigarettes are perfectly good for you...
Member Since: November 8, 2009 Posts: 4 Comments: 15213
##### 1110. overwash12
 That nail was put in the coffin for me this summer when the heat just wasn't there!
Member Since: June 24, 2007 Posts: 0 Comments: 1499
##### 1108. Astrometeor
 Quoting 1106. cyclonebuster:Is Google building some Tunnels? Link...I heard one rumor that it could be a data center. Lots of computers put together in one spot need a way to cool off, and apparently one of the best ways is to use water, a barge, and some piping and do a transfer of heat similar to what nuke plants do.
##### 1107. TropicalAnalystwx13

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