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Tonga Eruption

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HansR
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Re: Tonga Eruption

Post by HansR »

RayProudfoot wrote: Sun 16 Jan 2022 9:36 am Same anomaly here at the same time. What caused that? Secondary shockwave but unlike the first one pressure dropped before rising.
I assume you mean by 'Same anomaly' the second shockwave (as the first is obviously directly from the volcano).

My interpretation would be as follows:
As Tonga for us would be really almost at the opposite side of the earth (our antipodes?), the shockwave from its starting point would travel around the world and meet each other in the real antipode of the volcano. There it would start to interfere with each other and echo back (possibly reversing the amplitude depending on the interference point) the so called interference waves. (to simulate this, fill the bath at home and start dipping your index fingers 1 meter apart (once, at the same time). Observe what happens if the waves touch. Waves in air behave similar to waves in water. While interfering and travelling the wave looses energy so the amplitude is much lower.
Hope this helps.
Last edited by HansR on Sun 16 Jan 2022 10:44 am, edited 1 time in total.
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Re: Tonga Eruption

Post by RayProudfoot »

@HansR, thanks, makes sense. The second shockwave would be from the one that went in the opposite direction.

As Tonga is at 175°W and the UK is between 0-3°W the one to hit us first would have come from the West. The one from the East arrived some time later having further to travel.
Cheers,
Ray, Cheshire.

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Re: Tonga Eruption

Post by forestedge »

Just to join in :D
Screenshot 2022-01-16 at 07-42-13 Recent Graphs – New Forest Weather.png
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Re: Tonga Eruption

Post by mcrossley »

I just updated my first post to include the secondary event.

If I had the time it would be interesting to do a time plot of the primary and secondary events on a globe or world map. Something like WUnderground would be a good source of global data.
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HansR
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Re: Tonga Eruption

Post by HansR »

mcrossley wrote: Sun 16 Jan 2022 1:26 pm I just updated my first post to include the secondary event.

If I had the time it would be interesting to do a time plot of the primary and secondary events on a globe or world map. Something like WUnderground would be a good source of global data.
Indeed great exercise. Be selective with stations though :)
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Re: Tonga Eruption

Post by sutne »

Also detected up in th high north:
1C85C308-AB43-48CF-A729-573AFCF0EEF2.jpeg
Since the general pressure is dropping fast, it does not look much, but it is rising to 1015.8 and dropping to 1013.0, almost 3 hPa.

And a second drop at 03:30.
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HansR
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Re: Tonga Eruption

Post by HansR »

sutne wrote: Sun 16 Jan 2022 2:29 pm Also detected up in th high north:
1C85C308-AB43-48CF-A729-573AFCF0EEF2.jpeg

Since the general pressure is dropping fast, it does not look much, but it is rising to 1015.8 and dropping to 1013.0, almost 3 hPa.

And a second drop at 03:30.
That is nice btw: your first wave is 19h30 (half an hour before here in NL) but the second event is roughly 3h30 i.e. half an hour later than in NL. So I would say the interference point should be somewhere in the North Sea between Manchester, Bergen and Groningen
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Re: Tonga Eruption

Post by HansR »

Somebody over here has calculated the speed of the shockwave to be roughly 900 km/hr. Could we calculate the interference point of the waves from that and the the points we know so far?
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Re: Tonga Eruption

Post by Mapantz »

The antipode has been calculated at roughly Tamanrasset in southern Algeria. If you go by the times it hit the UK, the pressure wave was travelling at the speed of sound, possibly higher, at 800mph.
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Re: Tonga Eruption

Post by HansR »

Mapantz wrote: Sun 16 Jan 2022 2:50 pm The antipode has been calculated at roughly Tamanrasset in southern Algeria. If you go by the times it hit the UK, the pressure wave was travelling at the speed of sound, possibly higher, at 800mph.
The antipod is correct (I did not expect it there btw), the speed not sure.

The eruption was 4h14 UTC
Britain and NL were hit by the shockwave at roughly 19h UTC, NO half an hour earlier, the wave came from the north, the second event came from the south.
The return wave came at 2 UTC after midnight so the roundtrip was 7 hrs (UK and NL) so that is 3.5 hrs for NL and UK, 4 hrs for NO.
That means the interference point (the antipod) was hit around 22h so it took 18 hrs to travel 20.000 km
With some rounding: that is 1127 km/hr (== 313 m/s)
The speed of sound is 343 m/s (20 deg C) so it was slower (it's cold on the pole).

The distance between my station and Sutne's is roughly 750 km so it would take 39 minutes between our stations
Could well be. (and 800 mph = 358 m/s or 1287 km/h)

This is all just for understanding what happened and where, sure it can be refined of course but afaiac it is all correct within error margin ;)
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Re: Tonga Eruption

Post by PaulMy »

I've been trying to join the fun...
Found some pressure change in charts in CMX here but couldn't quite relate to the correct time. Data logs was not very helpful. Then used my Weatherlink.com which saves data at 5 min interval but also shows high/low for the interval. The capture images don't clearly show the high and lows but it is better in WL.com.

From Hans' post - The eruption was 2022/01/15 4h14 UTC
That would make it 2022/01/14 23:14 EST (UTC -5)

My WL.com does have a pressure drop about that time but that appears to be a normal fluctuation (image 20220116a)
WL.com has a significant drop at 2022/01/15 10:20am EST - about 11 hours later (image 20220116b)
But the biggest dip in WL.com is 2022/01/16 00:35 EST - about 25 hours after the event (image 20220116c). Does that seem reasonable?

Enjoy,
Paul
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Re: Tonga Eruption

Post by AndyKF650 »

Its fascinating how a network of like minded citizen scientists can remotely analyse a global atmospheric event.

My main comment to Hans is how does CUtils graph pressure. The axis on my graph is very large 960hPa to 1040hPa so whilst I can see the anomaly it is quite small. I finer axis would help greatly.
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Re: Tonga Eruption

Post by HansR »

AndyKF650 wrote: Sun 16 Jan 2022 5:13 pm The axis on my graph is very large 960hPa to 1040hPa so whilst I can see the anomaly it is quite small. I finer axis would help greatly.
The scale of the pressure axis does not auto scale but is fixed to the max and min values of the station to mimic the effect of a classic barometer and better show the variation to low, middle, high values. For analysis like I use the interface. If you want to do this in CUtils you have to make a pressure chart with a free axis (and set the text in the language file) to use the autoscale feature of Highcharts.
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Re: Tonga Eruption

Post by AndyKF650 »

Hi Hans

Thanks for the suggestion, Well that works for me as well, I will think about the updated pressure chart in CUtils
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Re: Tonga Eruption

Post by HansR »

PaulMy wrote: Sun 16 Jan 2022 4:48 pm I've been trying to join the fun...
Found some pressure change in charts in CMX here but couldn't quite relate to the correct time. Data logs was not very helpful. Then used my Weatherlink.com which saves data at 5 min interval but also shows high/low for the interval. The capture images don't clearly show the high and lows but it is better in WL.com.

From Hans' post - The eruption was 2022/01/15 4h14 UTC
That would make it 2022/01/14 23:14 EST (UTC -5)

My WL.com does have a pressure drop about that time but that appears to be a normal fluctuation (image 20220116a)
Anything around eruption time would have nothing to do with the eruption itself: it would still have to propagate (you're too far away)
PaulMy wrote: Sun 16 Jan 2022 4:48 pm WL.com has a significant drop at 2022/01/15 10:20am EST - about 11 hours later (image 20220116b)
This must be the shockwave and is consistent with this timelapse animation of the shockwave passing the US.
PaulMy wrote: Sun 16 Jan 2022 4:48 pm But the biggest dip in WL.com is 2022/01/16 00:35 EST - about 25 hours after the event (image 20220116c). Does that seem reasonable?
That must be the second event but apparently it coincides with a natural decrease of pressure which may cause confusion.

Looks all good to me.
Last edited by HansR on Sun 16 Jan 2022 6:25 pm, edited 1 time in total.
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