Guest Post by Willis Eschenbach
I stumbled across an interesting journal study the other day titled “The solar force of the semiannual variation in the length of – of – daysIt issues the following sequence of statements:
• Sunspot-related variations somehow affect the speed of “geographical” winds. These are the components of the wind that blows parallel to the Equator. The study asserts that whether variations affect “meridian” winds, the composition of winds perpendicular to the equator, do not.
• The variations in the geotropical winds indicate that then affect, not the length of day (LOD), but according to the study, “A-range of the semiannual year-to-year variation in the length of – of – days”.
This chain of effects seems more correct… mmm… let me call it “fragile” to me, so I decided to take a look. Let me start with overall duration of day (LOD) data.
Figure 1. Unusual length of the day
As you can see, the length of the date varies on several time scales. Base on the research:
The length – of – days (lod) experiences a wide range of fluctuations.
The decaying oscillations (10 to 30 years) are mainly due to the exchange of angular momentum between the core and the mantle of the planet. [e.g., Lambeck, 1980; Jault and Le Mouël, 1991; Gross, 2007].
The seasonal changes, including semiannual, annual, and biennial components, are almost entirely due to variations in the atmospheric wind circulation (in addition to the important tidal component). The amplitude of the seasonal variation is not fixed between years and different hypotheses have been put forward to explain this variation.
Of interest to their study are the semi-annual variations. Below is an overlay of each annual outlier by the length of the day, with the magnitude of anomaly taken around the mean of each year. I have repeated every year so we can look at the overall cycle.
Figure 2. Unusual length of the day
As the authors discussed, there is indeed a drastic half-year variation in the length of the day. It is usually longest around April 15 with a second peak in November and lowest in July with a second bottom in January.
Now, I’m a simple person, I realize that if you care about “amplitude A of the semi-annual variation in length – of – days ”, you know, measure from top to bottom every year. Isn’t that what “amplitude” means?
But not these good people. Here is their process:
Figure 3. Authors’ amplitude calculation method
I could only shake my head in disgust. They are using 4-year central Fourier analysis to get the amplitude of the 6-month period… to me it seems like they are claiming that sunspot-related variations could influence the future.
Also, there’s one big problem with their method – there’s no actual six-month cycle. The distance from the November peak to the April peak is five months, not six… and as a result we can get a stronger Fourier six month result both because of the variation in amplitude and variation in time. of the vertices.
But I was born yesterday, what do I know?
In any case, I do not wish to enter into such a procedure without considering the individual years. Here is a said number of years, with LOW smoothness (black/yellow line) and signs of semiannual change (black/red line).
Figure 4. Authors’ amplitude calculation method
I highly doubt that a Fourier analysis of that kind of variation will tell us anything. It’s not even clear what we can call it “A-range of the semiannual year-to-year variation in the length of – of – days”
So I put that whole question aside to consider the question of geotropical winds. Unfortunately, the only long-term information on this is the result of a reanalyzed computer model… but “A must have when the devil drives”, so that’s what I used. Here are the average local winds:
Figure 5. Moderate geotropical winds, views of the central Atlantic and Pacific Oceans.
Hmm… the strong winds are causing in the Southern Ocean, the latitude that sailors like me call the “Roaring Fifties”, and the “Screaming Fifties”.
Note that the mean wind value is negative, which means the average winter wind. And the direction of the earth’s rotation means stronger Easters will tend to slow the rotation, and therefore increase the length of the day.
So what does the annual cycle of geotropical winds look like? I took the monthly average of both the tropics and the LOD. Here is the comparison.
Figure 6. Monthly mean geotropical wind and monthly LOD.
As you can see, the geotropical winds obviously speed up and slow down the Earth’s rotation every year.
So… is there any correlation between sunspots and geotropical wind speeds? To test that, I used CEEMD . Analysis breaks the fundamental frequency of the two signals. Below is a comparison of the periodic graphs of the CEEMD analysis of two data sets, geotropical winds and sunspots.
Figure 7. Periodic chart of sunspots and tropical winds, from 1948 to present
Now the first thing you have to understand about spectral analysis is that old Joe Fourier proved hundreds of years ago that ANY time series can be broken down into individual signals that, when added together, will recreate the original time series. So the presence of such individual signals does not necessarily mean that they are externally controlled.
Looking at the different signals in Figure 7 above, you can see that the sunspots have a clear 11-year signal in Experimental Modes C6 and C7, with a smaller signal of 14 years. On the other hand, the tropical wind (red) has a signal at about 12 years, with a smaller signal at 9 years.
What this means when we plot the two empirically experienced mode 7 signals, shown as “C7” in the figure above.
Figure 7. Periodic chart of sunspots and tropical winds, from 1948 to present
As you can see, both signals show a ~11 year component… but since they don’t have the same period, they start in phase and end completely out of phase.
In other words, although the annual variation in the geotropical winds is clearly responsible for part of the annual variation in the LOD, I have not found any evidence that the variations are related. to the sunspot in the sun that is driving the tropics.
Finally, my excursions into geotropical and meridian winds led me to think about the overall global average wind speed. The actual wind speed is the square root of the sum of the squares of the geotropical and meridian winds. Here’s a global look at long-term average wind speeds.
Figure 8. Average wind speed, from 1948 to present, views focus on Atlantic and Pacific
The wind speed over the ocean is greater than the speed over land, and the wind speed over the tropics is greater than the wind speed over the ocean. And this is the change in wind speed over time.
Figure 9. Average monthly wind speed, from 1948 to present
And why is a small increase in wind speed of a few percent important?
Essentially, evaporation varies linearly with wind speed. And globally, evaporation cools the surface by something on the order of 80 watts per square meter (W/m2) each year. So a 4.7% increase in wind speed would translate to an additional surface cooling of about 3.7 W/m2 … suffice it to say, there’s a lot going on in this massive heat engine that doesn’t work. we call “climate” for nothing. What to do with CO2.
Here on our northern California hillside on Gifting Day, we had rain… lucky rain, life-giving rain. I had a wonderful Christmas with the people I live with in the ramshackle house I built myself – my beautiful fiancee, my daughter and her husband, two-year-old niece and two-year-old grandson our month old. . (The walls are not steep, it is from the camera lens.)
I, I am the luckiest guy on the planet…
Wishing your life to be filled with joy, just enough sunshine and rain,
w.
PS — This is “Letter from Mexico to my future fiancée“.
PPS — When you comment, please cite the exact words you’re referring to, so we can all be clear on the exact topic you’re discussing.
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