Recent research say QBO frequency is emergent property

Gavin Schmidt of NASA tweeted a cite to a recent paper on QBO by a group of 12 scientists

Geller, M. A., Zhou, T., Shindell, D., Ruedy, R., Aleinov, I., Nazarenko, L., Tausnev, N.L., Kelley, M., Sun, S., Cheng, Y., Field, R.D. and Faluvegi, G. (2016), Modeling the QBO – Improvements Resulting from Higher Model Vertical Resolution. J. Adv. Model. Earth Syst.. doi:10.1002/2016MS000699

They claim that the fundamental frequency of QBO relates inversely proportional to the pressure:

"The mean zonal winds from the ERA-Interim reanalysis are shown between 4.5 and 4.5 N between heights of 100 and 1 hPa for the 20 years 1991-2010. Note that ERA-Interim shows that approximately 8 1/2 QBO cycles occurred during this period, implying a QBO period averaging about 28 months. The model results in figure 1b show that no coherent QBO resembling observations exists for the gravity wave momentum flux forcing of 1.5 mPa, which is consistent with the steady jets at low wave forcing demonstrated by Yoden and Holton (1988). It also shows that the QBO-like oscillation for a gravity wave momentum flux forcing of 2.0 mPa has a period of about 8 years, while a forcing of 2.5 mPa gives a period of about 37 months, and a forcing of 3.0 mPa gives a period of about 25 months, and a forcing of 3.5 mPa gives a period of about 21 months. In fact, we find that the best fit to observed QBO periods is for a gravity wave momentum flux forcing of 2.9 mPa, as will be shown in the next section. "

I disagree with this interpretation. I know that this might sound like I am using the argument of personal astonishment, but I can't see how a physical model could operate this way. If anything, pressure may modify the amplitude of the oscillations, i.e. the peak speed, but asserting that the pressure sets the oscillation period is likely the result of a model that no one understands. If it was indeed caused by the pressure, they should be able to come up with a simplified formula, like deriving the resonant frequency of a Rijke tube, instead of suggesting that it is an emergent property of a complicated model. Certainly, pitch can change as a result of say overblowing a woodwind instrument, but even there, the shifts are more than likely harmonics or overtones of the original fundamental frequency, and not a continuous change in frequency.

RHEED oscillations more here

And I realize that the QBO is obviously not an acoustic oscillation yet the physical model for any oscillation does need some sort of mathematically intuitive explanation (see figure to the right), which is greatly lacking in this paper.  To say it emerges from the model is an extremely weak argument.

The 28 month period is ubiquitous in a number of geophysical oscillations. It shows up in (1) the seasonally aliased Draconic lunar cycle, (2) the strongest factor in the model of ENSO, (3) exactly half that period in the Chandler Wobble, (4) its defined as the mean annual flood recurrence interval by the USGS (first reported in 1960), and (5) the fundamental QBO period.

Perhaps no one wants to admit that seeing this number show up in all these measures is most likely a forced response from the nodal lunar cycle factor, as opposed to a natural resonance. The reality is that a forced response is not as "sexy" as finding a natural frequency eigenvalue.

But of course there is no way to verify either way, since a controlled experiment is not available to test a model against.  There is only one earth and it can't be duplicated in the lab. All we have to go on is the empirical data and any model that we can dream up.

A bunch of meteorologists are freaking out that the current QBO data is not meeting up to expectations

I don't understand the rarity of this since the higher altitude QBO aligns more with semiannual seasonal cycles, while the lower altitude QBO aligns more with the nodal lunar cycles. These will constructively add according to a beat frequency and so the alignment will occur occasionally. This summer solstice there is a full moon and that only happens once every 19 years.  I can see this with my QBO model as well, so what is the big deal?

14 thoughts on “Recent research say QBO frequency is emergent property

  1. This is the data I have, and model trained to 2015. The post 2015 model extrapolation is validated against the data.

    I don't understand what their concern is, because I don't understand their qualitative voodoo. All I fit to is the lunar phasing. That will do what it does according to the seasonal aliasing. And because that is not what they are analyzing, of course they will be surprised by the odd QBO excursion.

    • If those two graphs overlay, do they show any periods where all the peaks occur at once? (I find it difficult to compare well vertically).

      • I don't think it's that vital a comparison, as it is just a single point in time. I would rather focus on the collective agreement over long spans of time.

        • OK. Just that a cursory examination seems to support your argument of a phase relationship which is sometimes additive and other times not (at least as I understand it), which would in turn seem to argue against there being an internal causal relationship directly between those two elements and more for them both being affected by some external force which has slightly different timings for both.

          I have spent quite a bit of time recently reading through this blog from the beginning (not the earlier sites) and it all seems quite coherent and cogent to me.

  2. I think the reason that these weather guys say "All QBO layers between 50mb-10mb peaked at the same time in September 2015. That should not happen, but it did." is because they think that all those layers interact in some way whereby one layer leads another, largely due to some form of vertical transport. If they all align, then the implication is that the vertical transport is instantaneous, which of course they should be incredulous about ... if their premise was correct.

    Yet, with a lunar forcing model, each layer can respond independently, as the differing densities have different transfer function responses to the various lunisolar forcing frequencies. The fact that they may align is just a consequence of the phases happening to align at that period of time. Not a big deal in this case.

    Also, I commented on the above tweets and got into a discussion with what appeared to be a couple of undergrad meteorology students. Apparently I got one of them so riled up that he ended up blocking me.

  3. "If anything, pressure may modify the amplitude of the oscillations, i.e. the peak speed, but asserting that the pressure sets the oscillation period is likely the result of a model that no one understands."

    Isn't it more likely it's a model *you* don't understand -- rather than the authors?

    Actually the authors state: ".. we find that the best fit to observed QBO periods is for a gravity wave momentum flux forcing of 2.9 mPa"

    I think the key terms here are 'momentum flux' -- the momentum of the gravity wave is changing. This can cause an oscillation. Isn't this change in gravity wave momentum the actual physical cause of oceanic and atmospheric tides?

    • I did admit that I didn't understand it and that I was personally astonished that a pressure would change a frequency instead of simply changing the magnitude of the effect.

      It sounds as if they have never heard of sanity checks. No matter what their simulation tells them, they should be able to recover the salient relationships from at least a dimensional analysis. For example, it might be reciprocal square root of pressure and they can go from there.

      Or consider that pressure is related to force. Now one situation where force will clearly change the period is in determining an orbital cycle. The period of a pendulum is a similar mechanism. They may want to check that out.

      They have 12 people writing the paper! Couldn't they assign one of them to attempt a sanity check?

      In any case, the much more plausible effect is that the QBO period is a forced response from the lunar period. As I have stated many times before, it was Lindzen - the "expert" on QBO - who said that finding a lunar periodicity in the results will by all accounts establish that as the root cause. As I have found that relationship it is up to them to contradict it. The simple sanity check on this one is to derive an atmospheric tide from the lunar forcing. No problem.


      I am ignoring your comment on the change in gravity wave momentum because I don't see the units of a change - that would be change in pressure per time, and that is not in their units.

  4. "I don't see the units of a change - that would be change in pressure per time, and that is not in their units."

    I'm confused by this statement. The wave has a period. It has an amplitude. That is a change over time, isn't it?

    • The analogy is the voltage or current on an outlet. Saying it is 120 volts and 10 amps won't give the frequency. Nor will giving the rate of change of voltage or current. But if you had both 120 volts and a maximum rate of change, you can infer the frequency.

      I use that instead of a hydraulics or pnuematics analogy because those aren't normally oscillating. But if they were, the same would apply. See hydraulic_analogy on wikipedia.

      They still have to explain why the QBO frequency follows the seasonally aliased nodal lunar cycle so closely. Devising more and more complex models for QBO won't make that fact disappear. Geez, if I detected a 60 Herz signal coming out of my speakers, I wouldn't claim that it was an internal resonance in a circuit. I would immediately blame the line voltage leaking through somehow. Yet, that would seem to go over the heads of Lindzen and his followers, who prefer to find an emergent property instead of being pragmatic and admitting that the lunar cycle needs to be ruled out first.

      And the weird thing is that Lindzen advocated the possibility in the first place.

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