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[U09-P02] Tidal oscillations (tsunamis) generated by Tonga volcano eruption
Keywords:tidal oscillation, Proudman resonance, pressure change
A large eruption of Hunga Tonga–Hunga Ha'apai volcano occurred on 15 January 2022, which led to tidal oscillations (tsunamis) observed in the world. It was originally thought that tsunamis generated by the eruption was not so large and there would be little impact in Japan. However, tidal oscillations were observed in the coast of Japan, which was earlier than the estimated arrival time of oceanic shallow water waves, and even the 1-meter level amplitudes were observed at some stations like Amami.
In the almost same time of the tidal oscillations, atmospheric pressure changes were observed in many places, although the changes were not so large. The relation to tidal motion was discussed, and possibility of what we call meteotsunami by Proudman resonance was highlighted.
The basic mechanism of the tidal oscillations was analyzed, considering of atmospheric pressure condition and possibility of Proudman resonance. Many possible moving speeds of atmospheric pressure waves, including sound waves, were suggested, preferable moving speed will be 250-300m/s due to water depths of the Pacific. The occurrence time of tidal oscillations also suggest the possible speeds and limit the range.
Observed surface pressures in the south pacific and Japan indicate that moving speeds were similar to the range, and it is plausible that Proudman resonance generated the tidal oscillations (meteotsunamis). A numerical simulation for the Pacific was conducted with modeled pressure force similar to the first observed pressure changes and motions (Lamb wave), and the tidal oscillations were calculated in the same timing of observations. However, the simulated results could not resolve the maximum amplitudes. Those maximum amplitudes were observed a few hours later and it is unlike that the pressure forcing directly generated the large amplitudes, and thus other factors might have amplified the oscillations.
In the almost same time of the tidal oscillations, atmospheric pressure changes were observed in many places, although the changes were not so large. The relation to tidal motion was discussed, and possibility of what we call meteotsunami by Proudman resonance was highlighted.
The basic mechanism of the tidal oscillations was analyzed, considering of atmospheric pressure condition and possibility of Proudman resonance. Many possible moving speeds of atmospheric pressure waves, including sound waves, were suggested, preferable moving speed will be 250-300m/s due to water depths of the Pacific. The occurrence time of tidal oscillations also suggest the possible speeds and limit the range.
Observed surface pressures in the south pacific and Japan indicate that moving speeds were similar to the range, and it is plausible that Proudman resonance generated the tidal oscillations (meteotsunamis). A numerical simulation for the Pacific was conducted with modeled pressure force similar to the first observed pressure changes and motions (Lamb wave), and the tidal oscillations were calculated in the same timing of observations. However, the simulated results could not resolve the maximum amplitudes. Those maximum amplitudes were observed a few hours later and it is unlike that the pressure forcing directly generated the large amplitudes, and thus other factors might have amplified the oscillations.