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Comment by teeray | Hacker News Reader

It was fascinating to watch tweets of people seeing the anomalous barometric pressure spikes pass through as the shockwave circled the earth.

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I’m a private pilot. I was taking off when it happened and the tower radioed me to check my altimeter once more because they weren’t sure if they were having an equipment malfunction. I looked back and it was the exact time of the expected pressure wave picked up by the official readings at the time. So I definitely noticed but figured it was just a general error, it was only after I checked the history did I realize it was probably the volcano !

I counted 6 passes of the wave(s) on my home sensor, and maybe 7, but I have to go check neighboring sensors in the next state over to verify that the bump really is from the eruption.

https://partofthething.com/thoughts/measuring-the-tonga-erup...

I heard that the waves were going to converge at the antipode of the explosion which was supposed to be in Algeria I think. Any interesting data or observations from that incident?

Here is a neat animation based on METEOSAT-11 data: https://twitter.com/weather_models/status/148300643675002880...

Translation: «Antipodes are also animated with METEOSAT-11. The propagation speed seems to be different depending on the route, and the timing of coming to the antipodes is slightly different»

Wonder if this had an impact on altimeters in aircraft, especially older ones that aren't augmented with radar/lidar or GPS.

Airplane altimeters are adjusted according to a radio announced local pressure or a default(29.92 inHg). That make altitudes inaccurate but ensure separation between planes flying directly above and below. So shouldn't matter as long as pressure changes are nonapocalyptic.

Probably only as a transient.

Though it's a reminder that what your instruments report is always only a proxy for the quantity being measured.

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