Happy 4th everyone. I want to apologize for the thread yesterday. Lets just say it wasnt written w/ a good head on my shoulders. I went back and read it and noticed there are plenty of grammatical errors and the structure is loony! Sorry to all who had to try and decipher! Anyway, for an Independence Day treat, I thought I would post about the Brewer-Dobson Circulation, since I discuss it frequently. This is a relatively simple concept and, as you guessed from the name, has to do with Ozone. The significance of this circulation (with regards to long range forecasting) will be explained here.

Here is a graphic of how it works-->


Equatorial convection, when above average, will essentially help raise the average tropopause height. The oxygen molecules will go through photolysis because of the strong sun and form into ozone. The acquired ozone will "upwell" into the lower and middle stratosphere over the tropics and then downwell into the hemispheric poles. This circulation is very slow and on average takes 3-5 months to transport from the tropics to the poles. When acquired ozone is above normal and adds to the ozone layer, it can make the circulation stronger than normal. The stronger the upwelling, the stronger the downwelling. The stronger the downwelling, the more ozone at the poles. It's significance is HUGE with regards to major global players that control our wx/climate.

Interesting facts:
1) The BDC helps explain why there is actually more ozone at the poles or as one increases in latitude.
2) The BDC explains why there is the most total ozone during the spring hemisphere and least during the autumn hemisphere. The common misconception is that it's winter and summer.
3) The BDC's strength is determined by stratospheric "regulators" like the QBO and solar flux.
4) The BDC is currently the only known stratospheric-tropospheric interaction of significance. The other interactions have to do with upwelling/downwelling gravity/planetary waves.

The stronger the BDC, the higher amount of ozone in the poles and greater baroclinicity in the winter hemisphere, especially the northern hemisphere where there are more mountains/topography differences. This creates stronger planetary waves, which help disturb the polar vortex and help make the westerlies more meridional.

If you guys have any questions about the circulation that an internet search or research paper cannot answer, feel free to send me it. I will be most helpful on the forecasting aspect of it.

enjoy the holiday

Another picture showing the circulation

Great discussion to post HM. This is a weather board and things like this are important to talk about even if it doesn't get the fanfare it deserves. I will try and chime in later when I have more time. Or questions.

Thanks. Very very interesting, cannot get enough of stuff like this.

Very good discussion, HM. Although, I am confused about the talk on the stratospheric- tropospheric interactions. I will read it again though!

Happy 4th everyone. Stay Safe.

Hey HM, will read your stuff a little later, but I found this pretty good paper on ozone and the winter PV and circulations at CPC.

http://www.cpc.ncep.noaa.gov/products/stra...etins/nh_05-06/

This thread has the potential to go places. ( Where I have not seen in this forum )To bad it's July 4th and everyone's busy. Glad it was pinned though.

A great discussion (lesson) that even I can wrap my head around. You provide a link between everyday short range forcasting and long term climate change with these types of posts..At least for me.

It would seem.... that understanding different seasonal patterns is key to understanding longer term climate issues......Keep up the good work...even as I struggle to keep up!

HM,

I think you need to consider what the PET Cycle possibly does to the BDC. I briefly touched base on this with Brian tonight in my PET Cycle discussion.

I know you have a keen understanding of how things work so it shouldn't be to hard for you to understand where I am coming from here. Example...Just think about what I wrote about in reference to the time frame around the western QBO peak. Especially this current PET Cycle.

The Western QBO peak is currently bad for the cycle..Why? BDC weaker.

Yes it takes 3-6 months to show up in ozone levels but there is obviosly some other interrelated forcing going on that inhibits the preferred state of the negative POL this cycle and changes in the the BDC are most likely related to this.

I agree... until the solar flux becomes strong and nearing the/or at the max, the westerly QBO is usually a bad sign if you like disturbed PVs.

By raising the average tropopause height over the equator and literally creating ozone, its forced upward into the stratosphere b/c of its identity and velocity. Once the Ozone collects it then slowly migrates poleward, which is essentially the "circulation' cycle.

Another interesting factor is stratospheric temperatures. Since the stratosphere is essentially our lower atmospheric lid, the temperature differences can impact the troposphere. For example, there is an inverse relationship that exists where if the stratosphere is colder than normal, the troposphere tends to be warmer than normal in the upper portion to "make up" for the inversion temp differences. Can be tricky to imagine though b/c you might ask, why does it have to balance out? I would imagine it has to do with keeping a stable equilibrium of our atmosphere.

However--- sometimes a very COLD stratosphere isnt a bad thing in the winter IF its VERY cold. IF you draw a height map in a X/Y graph in a linear fashion, you can essentially draw out this idea. IF you lower the heights significantly enough between 50-10mb, you will have to draw your lines in the upper troposphere "trough-like" to compensate for the stratospheres HUGE anomaly. But this usually occurs where the PV is. And it is USUALLY a BAD thing for the mid latitudes b/c the polar night jets velocity increases significantly and also the zonal component.

I knew you would agree with this part but do you have any idea as to why the western QBO would reverse or inhibit the preferred cyclical state of the POL? Or any QBO peak for that matter.

We know the POL and stratosphere have a relationship or at least the POL values are indicative of the state of the PV.
The BDC will be weaker with the western QBO and last winter's wintertime Solar-QBO formula said that the Polar stratosphere was to be cooler-less ozone. This happened somewhat but it was not extreme and one could argue about neutral depending upon the anomalies used or definition.

So we know that last summer definitely had a better chance of going against the grain since the time frame of 3-6 months is needed with the BDC. And this lined up perfectly with the POL changes.

What any stratospheric regulator does is control ozone amounts and distribution which can affect the latitude baroclinicity of any season---especially the northern hemisphere winter. In the case of westerly QBOs, they tend to squash planetary wave propagation because of the 30-50mb wind/momentum transfer. With a strong west to east wind shift in the tropical stratosphere, waves arent free to expand and disturb the flow when they encounter topographical elements. In an easterly QBO, the flow is easterly throughout the latitudes and the planetary waves are free to expand. They can then disturb the polar vortex and create more interesting weather. But this is one piece to the puzzle, b/c the PV could be displaced in Asia, america, europe ... and those details cannot be inferred from the QBO in and of itself.

Ozone distribution and atmospheric baroclinicity in the y-direction, however, can determine how meridional the flow will be. And ozone distribution can be inferred from prior seasons stratospheric behavior. The one good thing about the stratosphere is the timing---- things last months--- and in long range forecasting, thats a good thing!

Interesting stuff. What I gather is westerly QBO keeps planetary waves from expanding poleward and influencing the PV. However, isn't it true that a strong easterly QBO slows down the waves so that they can't progress enough into the Pacific? If my understanding is correct, this also means that El Ninos are better off forming in westerly QBO. I wonder if La Nina has an opposite preference.

Another idea I was thinking about earlier...weak solar flux means less UV radiation. Less UV radiation means less ozone production in the tropics and thus less ozone to be transported to the poles and thus a cooler stratosphere. So how exactly does low solar flux cause a disturbed PV? I'm not doubting it does, just curious as to why...perhaps my reasoning is too simplistic. There may be a QBO-solar flux relationship I'm missing.

And this can also tell you alot about the upcoming QBO.

stratospheric waves feel the effects of topography?

In the context of the sentenced highlighted, the "waves" are that of tropospheric planetary waves. Basically, im saying that when the QBO is westerly (especially when the solar flux is low), the tropospheric planetary waves are usually less amplified and the PV remains undisturbed. The northern hemisphere has one key difference vs the southern hemisphere and that is of course (like you thought) .... more topographical differences/mountains etc... so therefore our waves are easily manipulated and enhanced. Things cannot stay as zonal in the northern hemisphere as they can in the southern hemisphere. As a result, we can get frequent stratospheric warming events.

These puppies are especially interesting and tend to happen more frequently in easterly QBOs and especially easterly QBOs during lower solar flux.

Now if you want to get into upwelling planetary waves (the troposphere to stratosphere connection), then let me know. That is a whole different beast. We can talk about wave guides, wave flux and "critical lines" (aka the QBO) and how they are affected by the QBO. Its these waves, that travel equatorward and help shape PV behavior and modulate planetary waves.

HM, I took it upon myself to do some monthly composites to test the "disturbed" PV theory with easterly (negative) QBOs. I took winter months with a QBO of -10 or lower. Pretty strong correlation with 200mb anomalies, for Dec, Jan, Feb
Dec -QBO (-10 or lower) 200mb Height anomalies
Click to view attachment
Jan
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Feb
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And now to test the opposite, I took Winter months with a positive QBO of 8 or higher
Dec +QBO (+8 or higher) 200mb Height anomalies
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Jan +QBO (+8 or higher) 200mb Height anomalies
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Feb +QBO (+8 or higher) 200mb Height anomalies
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NOtice the higher height anomalies in the polar regions during the strong -QBO winters, and the negative anomalies near the pole in the strong +QBO winters. This backs up your statements about the "disturbed" PV during the strong -QBO winter months. This means, that "blocking" and a negative AO phase is much more likely in negative QBO winter months as opposed to +QBO winter months. Now obviously as you mentioned, we could have a situation like in winter 05-06 where EUrope and Asia got all the weather, and we still baked.

Hey Raleighwx, good post and thanks for the maps. The dataset is small, so the correlations merit comes down somewhat. However, at the same time, the correlation is strong. Baldwin_et_al in their 2001 QBO paper also did a similar correlation and got similar results. They found that the QBO in the easterly phase also tends to produce more stratospheric warming events...especially in the solar min. The westerly QBO is not always a done deal either, for if it occurs during the solar maximum, there would be more radiation/ozone in the poles, and it would help keep the stratospheric temperatures from being too cold. The thing that did last winter in as far as the strong +AO is that the stratosphere lacked a decent amount of Ozone and was fairly cold. The stratospheric PV, on average (especially first half) was consolidated and cold.

The data base is small of course but this is where the PET Cycle seems to come into play. Nov & Dec CW's in 59-60 ,78-79, 80-81, but 57-58 was a no show. EL Nino though. The western QBO -high solar flux- startospheric warmings was not as strong during the 90's with the positive PET Cycle. Nor was the time frame around Solar Cycle 20 peak, another positive PET Cycle time frame. But that solar cycle was weaker.

Well Jim how do we stand for the 2007-08 winter as far as the PET cycle and space wx? Its becoming clear that our stratosphere will have an easterly QBO will a relatively low solar flux. Perhaps reduced aerosols but enhanced ozone from the strong BDC.

Things appear to be setting up for frequent stratospheric warmings and disturbed PVs.

The Pet Cycle points toward higher ozone / weaker PV this upcoming winter and this preffered state should continue until the start of the next cycle. Which should be at least another two years away or more depending upon how the next cycle behaves - starts. This cycle's preference , along with the upcoming low solar flux- eastern QBO for this winter , only enhance the chances for a disturbed stratosphere in my opinion.

Just look what happened the last time around two winters ago. I think the further we get away from Pinatubo the better. I am not talking about aerosols per say, but I agree with your aerosol comments. I am referring more to what it did to our climate system. I believe the climate system is correcting itself and it''s possible use of the positive AMO is just one example.

Just to clear things up. I have read much about the western QBO - low solar flux and I agree with this on the most part in regards to what you mentioned earlier. My only concern lies with the possible differences between the -/+ PET Cycles and what this possibly means within the whole scheme of things. The usual dampening of planetary waves seems to be slightly weaker in my opinion during the negative PET Cycle. At least early on within the November-December time frame. But I guess something else could be happening with momentum transfer somehow. Either way the relationship seems to be slightly weaker but the data base is small.

I forgot to get back to you about this because you definitely caught my attention here. I have wondered about this in reference to certain climate patterns and it makes some sense. Do you any examples (time frames) of this showing up - occurring? I know about some individual cooler monthly extremes but not the whole winter.