Fascinating how such an eruption has an effect everywhere.

It was all so subtle that you'd never notice or think twice about it if you did not know to look for it. But it definitely happened. It was exactly like how clouds behave in footage of nuclear explosions when the shockwave passes through them, just slower. It was extremely weird. I'm still kind of stunned by it. I never expected to see such a thing in my life, especially from an eruption so far away.

What a beautiful experience. Those are the things that make life something wonderful. Perceiving your surroundings change due to a cataclysmic event far away and knowing how the chain of events connect each element just to release such a subtle hint, most be an amazing feeling.


It appears that the antipodes of Tonga are located in the south of Algeria (close to Mali):


I don't know if there are any known public seismometers in the region but it would be nice to take a look at them if they exist, since antipodal focusing of seismic waves is a thing worth looking at.

It is fascinating I admit....but I would still favor geoengineering to prevent cataclysmic events that kill people.  This one wasn't so serious but if we could have geoengineered a way to prevent what happened in Dec 2004 in Indonesia I'm 100 pct for that.

You mentioned antipodes, which I find fascinating....is it true there is a direct connection between Yellowstone and a volcano in Indonesia?  So if Yellowstone ever blew so would the other one?  Yet another argument in favor of geoengineering (so are major hurricanes and high end tornadoes.)

This is incredible. If you look closely in satellite imagery you can still see the effect of the pressure wave moving through the atmosphere

A similar image processing now shows the pressure wave concentrating at the antipodes of Tonga (Algeria - Mali border) and the subsequent rebound:
https://i.imgur.com/CgukXBk.mp4

I live 15,600 km away from the eruption.  Still, note the pressure around 18:30 UTC:

x.png

Taking a similar graph for a 1-minute range and for each relevant weather station of the U.S. you can see the pressure wave traveling across the entire country. This is an outstanding visualization.
https://i.imgur.com/kYXoTdu.mp4
Do the Appalachians and Sierra Nevada account for the apparent shadowing effect in some parts of the country?

A similar image processing now shows the pressure wave concentrating at the antipodes of Tonga (Algeria - Mali border) and the subsequent rebound

Indeed.  And I clearly see it in my pressure graph 9 hours later, but the signal appears reversed.  There's a dip in pressure first, then a rebound.

A similar image processing now shows the pressure wave concentrating at the antipodes of Tonga (Algeria - Mali border) and the subsequent rebound:

That's awesome. Great animation. Not surprisingly, although the wave is somewhat intensified, it is quite nonuniform and does not come into a sharp focus at the antipode, thanks to the effects of Earth's oblateness and probably reflections as well. Much like for seismic waves from meteorite impacts simulated in the paper you shared earlier (which was an excellent read.)

Do the Appalachians and Sierra Nevada account for the apparent shadowing effect in some parts of the country?

That does seem to be the case, judging from the animation. I also wondered if shadowing by the Olympic mountains could explain my not being able to hear the eruption sound at my location. They're partially along the line of sight from the volcano. Anchorage and Fairbanks on the other hand are located in a valley between mountain ranges and oriented along the line of sight, which might even have offered a bit of focusing of the sound, or at least not blocking it as much.

A similar image processing now shows the pressure wave concentrating at the antipodes of Tonga (Algeria - Mali border) and the subsequent rebound:

That's awesome. Great animation. Not surprisingly, although the wave is somewhat intensified, it is quite nonuniform and does not come into a sharp focus at the antipode, thanks to the effects of Earth's oblateness and probably reflections as well. Much like for seismic waves from meteorite impacts simulated in the paper you shared earlier (which was an excellent read.)

Do the Appalachians and Sierra Nevada account for the apparent shadowing effect in some parts of the country?

That does seem to be the case, judging from the animation. I also wondered if shadowing by the Olympic mountains could explain my not being able to hear the eruption sound at my location. They're partially along the line of sight from the volcano. Anchorage and Fairbanks on the other hand are located in a valley between mountain ranges and oriented along the line of sight, which might even have offered a bit of focusing of the sound, or at least not blocking it as much.

Sound didn't make it here either.  What would you say was the greatest impact event or greatest volcanic eruption since modern humans have existed on the planet and what kind of an impact did it have on human population at the time?

What would you say was the greatest impact event or greatest volcanic eruption since modern humans have existed on the planet and what kind of an impact did it have on human population at the time?

Check the Toba catastrophe theory on Wikipedia.

Here's my pressure plot from Oslo:

This is exactly why we need geoengineering in the worst way

Tonga volcano: Experts warn Tonga’s future “looks grim” / Twitter

But isn't one of the reasons the Earth's atmosphere is the way it is (habitable) — and has been for such a long time — because of volcanic eruptions?

This is exactly why we need geoengineering in the worst way

How do you geoengineer away volcanic eruptions?

This is exactly why we need geoengineering in the worst way

How do you geoengineer away volcanic eruptions?

No I mean geoengineer the devastating consequences of it like tsunamis.  Sea walls should help with that.  That island nation looks like it's in dire shape.

But isn't one of the reasons the Earth's atmosphere is the way it is (habitable) — and has been for such a long time — because of volcanic eruptions?

Yes but I was referring to their side effects like what happened in Tonga with the tsunami.  There needs to be a way to deal with that, much like the sea walls we've built around our coastal cities here in the US.

It seems I was not the only one who thought you were talking about somehow preventing volcanic eruptions, lol. :) I think the more accurate term here is hazard mitigation (reducing the impacts caused by natural processes) rather than geoengineering (changing those processes directly). 

Easier to build protection from a tsunami than to prevent one from happening, but it still is not cheap. Other options are to try to reduce the amount of people or infrastructure in high risk areas, or have a good warning system and fast way to safety.

That's awesome. Great animation. Not surprisingly, although the wave is somewhat intensified, it is quite nonuniform and does not come into a sharp focus at the antipode, thanks to the effects of Earth's oblateness and probably reflections as well.

True that.
There's now a beautiful visualization about this, made by Angel Amores:

https://youtu.be/oXa-QsSYpfg

[Source: https://twitter.com/an_amores/status/1484516695087759363]

You can see a simulated atmospheric pressure wave traveling across the globe from Tonga.
A few things to comment here:

1) The antipodal focusing is not perfectly symmetric and thus the model might have some interesting level of detail. I'm guessing that he has considered the departure from the ideal perfect sphericity of Earth (as Watsisname has commented), the damping and deceleration of the wave when crossing important topographic features (the Himalayas perhaps?) and possibly the Coriolis effect due to the differential motion of the atmosphere at different latitudes due to Earth's rotation (but my guess is that this might be extremely weak since other random winds might have a larger effect on the wave).

2) Another consideration here is the fact that the pressure wave gets a 90º phase shift when reflected against itself in the antipodes, as midtskogen noted with his weather station when he recorded the antipodal rebound as a decrease in pressure followed by an increase (instead of the increase followed by a decrease as in the first wave transit). This can be clearly seen in the simulation as the incoming wave has a blue-yellow color palette that gets inverted in order after the rebound.

3) One awesome thing of this video is that you can see the expected data retrieved from the theoretical simulation overlayed on top of the actual data registered by a few barometers around the world. You can see there that the timing of the wave and its rebounds is precisely predicted as well as the general intensity of each signal. This in my opinion shows how well we actually know the shape of the Earth, the wave propagation properties of our atmosphere and the energy involved in the eruption. I hope that almost all the fluctuations seen in the data come from local pressure variations unrelated to the Tonga event. But in any case we will see more detailed models in the next months.


This is also an awesome visualization of the barometric data gathered in Switzerland:

[Source: https://twitter.com/myweather_ch/status/1484150854236135428]

The S1 mark shows the first wave passing over Switzerland, followed some hours later by the rebound (N1). Then the wave rebounded once again at Tonga and came back (S2) and rebound at the antipodes for a second time (N2). You can clearly see the barometric signal of even the fourth rebound after 5 days of traveling across the globe several times.

Another thing I liked about this data is the way it is visualized. The actual barometric signal is the bottom graph. You can see the wave decaying as expected after each passage. You can see that the peaks in pressure are noticeable but if we wish to make them stand more strongly above the noise (other pressure fluctuations registered that have nothing to do with the shock wave from Tonga), then we must increase the contrast between low values and large values. We could mathematically do that by multiplying the signal by some number (for example by ten), which would enlarge the differences between peaks and valleys in the signal. But this is problematic because the peaks in the noise will also be enlarged and we will end up noticing more noise than before. A nice technique is to perform the first derivative of the signal below. This is a neat trick. By doing that mathematically you are looking for changes in pressure and not the pressure itself. You can perform a second derivative over the signal to get knowledge about the curvature of the signal as we approach a drastic peak. That's exactly what they do in the first and second graph. You can clearly see the peaks as prominent lines on those graphs.

I'm using this data as an excuse to show the technique, which I think is quite neat, and because now we can understand how satellite data can be processed to show the wave traveling around the world quite clearly.

By performing a first derivative with respect to time on the IR images (apparently infrared shows changes in pressure more clearly than optical images) taken GOES-West Satellite (which is geostationary) we can clearly see the wave as if the atmosphere was a giant pond:

https://i.imgur.com/lvxhFUX.mp4
[Source: https://twitter.com/MathewABarlow/status/1484907406182301697]

The same thing can be done with IR images from EUMETSAT (another geostationary satellite) to reveal the wave as it converges in the antipodes as clearly as possible:
https://i.imgur.com/e7bJhud.mp4
[Source: https://github.com/mathewbarlow/animations]

It seems I was not the only one who thought you were talking about somehow preventing volcanic eruptions, lol. :) I think the more accurate term here is hazard mitigation (reducing the impacts caused by natural processes) rather than geoengineering (changing those processes directly). 

Easier to build protection from a tsunami than to prevent one from happening, but it still is not cheap. Other options are to try to reduce the amount of people or infrastructure in high risk areas, or have a good warning system and fast way to safety.

Hazard mitigation!  That's a better term for it, I guess I call it geoengineering because of this trillion dollar project of building a huge seawall around the southern parts of NYC seems costly enough to be a geoengineering project lol.  By the time it's finished it should be able to protect us from sea level rise for decades and buy us some time until we finally start reducing the CO2 levels in the atmosphere.
Reducing the amount of people in high risk areas would be ideal, but using NY as an example, we have a lot of lower income people living in places like Howard Beach (as an example of a particularly vulnerable area), and it's difficult to relocate people who really have no where else to go.