# Barriers in the Atmosphere: Arctic Oscillation (3)

By: Dr. Ricky Rood , 12:50 AM GMT on October 03, 2013

Barriers in the Atmosphere: Arctic Oscillation (3)

I want to continue with the Arctic Oscillation / North Atlantic Oscillation. First, however, here is the link to my August presentation. Also here is a link to the GLISAclimate.org project workspace where I collected together the materials I used in the presentation - Arctic Oscillation: Climate variability in the Great Lakes.

Here are the previous entries in the series:
Behavior
Definitions and Some Background

This blog is mostly a setup for the next one. (And yes I did notice that the IPCC AR-5 report was released, but I don’t have anything different to say about it than many of my more able colleagues. I’ll get to it.)

In the talk that I linked to above, I used a couple of diagrams that the audience told me worked very well. I am going to try them out in this blog. In the previous blogs I used the CPC Climate Glossary to give the definition of the Arctic Oscillation. “The Arctic Oscillation is a pattern in which atmospheric pressure at polar and middle latitudes fluctuates between negative and positive phases.” This definition does not really do much for me. It’s one of those definitions that I imagine if I ask 10 atmospheric scientists to tell me what it means, I will get 12 answers. Therefore, I will draw a picture.

Figure 1: Adapted from Jim Hurrell – This picture is a schematic representation of the positive and negative phases of the Arctic Oscillation. In the positive phase the pressure is low at the pole and high at middle latitudes. This is the positive phase because if you calculate the difference between middle and high latitudes it is large. In the negative phase the pressure is not as low at the pole and not as high at middle latitudes. This is the negative phase because if you calculate the difference between middle and high latitudes it is small. The refrigerator suggests that this is like opening and closing the refrigerator door (see Behavior).

This figure helps me with the definition. I want to focus on the low pressure at high latitudes, which in this figure is drawn idealistically at the pole. In reality, it is likely to wander off the pole, a fact that will be important in the next blog. When the pressure is low at the pole, then there is a stronger vortex of air circulating around the pole. When the pressure at the pole is not as low, then there is a weaker vortex. In both cases, strong or weak vortex, the air generally moves from west to east.

For clarity, vorticity is a parameter that describes rotation in a fluid. A vortex is a feature in a fluid dominated by vorticity – that is it is rotationally dominated. Tornadoes and hurricanes are weather features that we often call vortices; there is an obvious circulation of air in these features. In the Earth’s atmosphere at middle and high latitudes rotation is an important characteristic of the flow, due to the rotation of the Earth. The reason air moves in the west to east direction for both the weak and strong vortex cases of Figure 1 is that the rotation of the Earth is important to the flow.

In Figure 2 I have set up an even more idealized figure. I also provide this link to a Powerpoint animation, that I am not smart enough to incorporate into the blog. In the animation I have five slides that clarify the point that I make in Figure 2.

Figure 2: A vortex and a ball. In the center of the figure is low pressure, meant to be an analogue to the vortex over the pole in Figure 1. Parcels of air move around the low pressure system. If it takes the same amount of time for a parcel farther away from the low pressure center to go around the vortex as a parcel nearer the center, then the parcel farther away has to go faster because the distance it has to go is longer. That is why I drew that arrow, saying that air moves “faster” at the outside edge of the vortex.

To set my point a little more, imagine you are on a bridge overlooking a running stream. If you drop a stick in the water near the edge where the water is moving slowly, then if the stick drifts towards the more rapidly flowing water, it is carried downstream at the edge of the fast moving water. It does not cross the core of fast moving water – this jet of water. In fact the jet is something of a barrier that keeps material from crossing the stream. Material is transported downstream.

Back to Figure 2: Imagine that you want to roll a ball into the center of a vortex. As the ball gets to the edge it gets caught up in the flow and pulled around the edge. It does not roll into the center. Look at the this link to a Powerpoint animation to get a better idea of what’s going on.

Now go back to Figure 1. The vortex in Figure 1 is also a barrier. The southern edge of vortex is a jet stream. Air on the two sides of the vortex often has different characteristics. Intuitively, there is colder air on the poleward side. 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 air on one side is largely separated from the air on the other side. In the next blog, I will describe the difference between the strong and the weak case and its relevance to weather, climate and, perhaps, climate change.

r

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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##### 369. RevElvis
 Dan Dennett: Dangerous MemesInteresting ideas - especially considering everything that is going on right now
Member Since: December 31, 1969 Posts: Comments:
##### 367. JohnLonergan
 Quoting 366. Naga5000:Oh, I was just wondering why you chose to quote me and post here and then not discuss the climate. I see there are many questions abound this evening.I think the monsoon rains and flooding have driven the trolls out from under their bridges.
Member Since: December 31, 1969 Posts: Comments:
##### 366. Naga5000
 Quoting 365. tramp96:No just wondering if you want to control this blog since your not the administrator.Oh, I was just wondering why you chose to quote me and post here and then not discuss the climate. I see there are many questions abound this evening.
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##### 364. Naga5000
 Quoting 363. tramp96:Whatever I choose to do. Problem?Internet tough guy. Rock on, bud.
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##### 362. Naga5000
 Quoting 361. tramp96:What do you have something against people predicting weather way into the future.Hi, welcome to the blog! Do you have any climate science to discuss, or did you just drop by to throw a few one liners?If they don't have any evidence to base their predictions on, it's not so much a prediction, but more of a random guess.
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##### 360. FLwolverine
 Quoting 348. yoboi:I am still waiting for the 16 yr long elnino.....they hype all the time.....Do you have any idea how ridiculous it sounds when you mention this for the umpteenth time and it gets debunked again? Or are you hoping to reach some lurker who doesn't know that it was said in an interview and only intended as a figure of speech?Man, yoboi, I had higher hopes for you than this!
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##### 358. Naga5000
 Quoting 356. yoboi: Read the IPPC report.....I know there are parts you would like to skip in it.....it is what it is....You made the claim...obviously it isn't there. I have read it. Sorry buddy. Nice try.
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##### 357. ScottLincoln
 Quoting 339. Naga5000:North Carolina has been warming about .37 degrees F per decade. You can look it up here: LinkTemperatures have not leveled off.One year does not make climate. You've been here for awhile, surely you know that.Once the government is appropriated money to function again, you can use the NCDC timeseries site that is more up-to-date.
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##### 354. Naga5000
 Quoting 353. yoboi:If you can't explain the pause.....how is it you can explain the cause????????Did you make that up yourself? Still waiting for any evidence...
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##### 352. Naga5000
 Quoting 350. yoboi:Here is one justoday trying to scare people that the whole globe is going to ice over and what's really funny 7 people plussed the comment.......285. schwankmoe 2:04 PM GMT on October 13, 2013 +7 at this rate the whole earth will be covered in ice in 20 years! run for your lives! Your sarcasm detector broke.
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##### 351. overwash12
 Quoting 348. yoboi:I am still waiting for the 16 yr long elnino.....they hype all the time..... CAN'T predict the future no matter what. They still try though,don't they?
##### 349. Naga5000
 Quoting 345. yoboi:The IPPC said you are WRONG!!!!!!!!Yeah, where? You couldn't the first time, you still can't now. :EdBegleyJr:
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##### 347. overwash12
 I get your point,it seems to me that a lot of the doomsday scenarios are over hyped. Then when it does not materialize they change their tune. I wish we could come up with better sources of energy.
##### 346. Astrometeor
 Quoting 345. yoboi:The IPPC said you are WRONG!!!!!!!!It did? Where?
##### 344. Naga5000
 Quoting 343. overwash12: Where did that false report that said no global warming the past 2 decades come from?Probably some conspiracy pseudo science website I'm sure. If you haven't noticed, we've been very busy debunking crazy. Link
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##### 343. overwash12
 Quoting 342. Naga5000:I'm not saying you are. I'm simply showing you A) it is still warming in your state. B) It is still warming around the world and C) One year does not make climate Where did that false report that said no global warming the past 2 decades come from?
##### 342. Naga5000
 Quoting 340. overwash12: Been here for 33 years now. been thru alot of Hurricanes,blizzards,heat waves,cold outbreaks. Even witnessed the all time record low of -5 F. So,I can say this summer was cooler than most,I ain't making it up.I'm not saying you are. I'm simply showing you A) it is still warming in your state. B) It is still warming around the world and C) One year does not make climate
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##### 341. overwash12
 Quoting 338. BaltimoreBrian:Is there a Knotts landing there? They gossip worse around here,BIGTIME!
##### 340. overwash12
 Quoting 339. Naga5000:North Carolina has been warming about .37 degrees F per decade. You can look it up here: LinkTemperatures have not leveled off.One year does not make climate. You've been here for awhile, surely you know that. Been here for 33 years now. been thru alot of Hurricanes,blizzards,heat waves,cold outbreaks. Even witnessed the all time record low of -5 F. So,I can say this summer was cooler than most,I ain't making it up.
##### 339. Naga5000
 Quoting 337. overwash12: Knotts island,N.C. and the world I am apart of. Just seems that we are headed for cooler times ahead and that my friend is what makes average temps.Have they leveled off?North Carolina has been warming about .37 degrees F per decade. You can look it up here: LinkTemperatures have not leveled off.One year does not make climate. You've been here for awhile, surely you know that.
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##### 338. BaltimoreBrian
Member Since: December 31, 1969 Posts: Comments:
##### 337. overwash12
 Quoting 336. Naga5000:Your house still isn't the world. Where are you again? Knotts island,N.C. and the world I am a part of. Just seems that we are headed for cooler times ahead and that my friend is what makes average temps.Have they leveled off?
##### 336. Naga5000
 Quoting 335. overwash12: Where's the warming? Seawater temp's at my beach never got very warm this summer and we only had a handful or days above 90.Usually we have several days in a row above 90.Very comfy summer.Your house still isn't the world. Where are you again?
Member Since: December 31, 1969 Posts: Comments:
##### 335. overwash12
 Quoting 334. Naga5000:So the warming is mysteriously going to stop? Sounds like you've been reading the Farmer's Almanac. Where's the warming? Seawater temp's at my beach never got very warm this summer and we only had a handful or days above 90.Usually we have several days in a row above 90.Very comfy summer.
##### 334. Naga5000
 Quoting 331. overwash12: AGW who!So the warming is mysteriously going to stop? Sounds like you've been reading the Farmer's Almanac.
Member Since: December 31, 1969 Posts: Comments:
##### 333. overwash12
 Quoting 332. BaltimoreBrian:Ewe!A little chuckle,Ha Ha! Baaawhaaa!
##### 332. BaltimoreBrian
 Quoting 331. overwash12: AGW who!Ewe!
Member Since: December 31, 1969 Posts: Comments:
##### 331. overwash12
 Quoting 330. Astrometeor:Your point is? AGW who!
##### 330. Astrometeor
 Quoting 329. overwash12: You don't study history of weather patterns ,do you? While it might not get as cold as 1977,it very well may rival it. We shall see,let's talk in January!Your point is?
##### 329. overwash12
 Quoting 328. Astrometeor:He's going to need a leaf bigger than that to smother the above ignorance. You don't study history of weather patterns ,do you? While it might not get as cold as 1977,it very well may rival it. We shall see,let's talk in January!
##### 328. Astrometeor
 Quoting 327. Naga5000:Please. Ed Begley Jr, get him!He's going to need a leaf bigger than that to smother the above ignorance.
##### 327. Naga5000
 Quoting 326. overwash12:It's coming iceagecoming,it's a comming!The signs are all around,just don't believe a bunch of scientists with an agenda or getting paid to perpetuate the falsehood.Please. Ed Begley Jr, get him!
Member Since: December 31, 1969 Posts: Comments:
##### 326. overwash12
 It's coming iceagecoming,it's a comming!The signs are all around,just don't believe a bunch of scientists with an agenda or getting paid to perpetuate the falsehood.
##### 325. overwash12
 Quoting 319. JohnLonergan: Interesting cartoon. The truth is there are alot of Wooly Mammoths found frozen in the ice all the time.HMMM... makes you wonder what really happened long time ago.
##### 324. Xulonn
 I can't handle any more denier crap today...see y'all tomorrow.And 'ya know, Nea, I think that cat's too smart to chase yarn.
##### 323. JohnLonergan
 Liars gotta lie, deniers gotta deny.
Member Since: December 31, 1969 Posts: Comments:
##### 322. JohnLonergan
 Figure 1: Easterbrook's global temperature projections (Source)http://www.skepticalscience.com/graphics/Easterbr ook_Projection_500.jpg">
Member Since: December 31, 1969 Posts: Comments:

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