10:45 〜 12:15
[SSS04-P09] Air–sea coupled wave at 3.6 mHz excited by the 2022 Hunga Tonga volcanic eruption
キーワード：大気ー海洋カップル波、トンガ噴火、共鳴
Lamb waves and meteotsunamis generated by the Hunga Tonga volcanic eruption in 2022 were observed worldwide. However, the location and duration of the pressure source that excited these waves remains elusive. To investigate the details on the pressure source, we examined spectra of the Lamb waves and meteotsunamis in the records from 150 absolute pressure gauges (APGs) deployed at the bathymetric slope areas from the Japan Trench to the nearshore (S-net: the Seafloor Observation Network for Earthquakes and Tsunamis), 5 barometers deployed at volcanoes in the Japanese Islands (V-net: the volcano observation network), and 10 barometers in the Pacific Ocean (GSN: Global Seismograph Network). The time window is 4000 s, which contains the peaks of the Lamb wave and associated sea level changes. We also calculated the dispersion curves of acoustic and gravity waves in the air-sea coupling system, and synthetic spectra for an upward-moving pressure source.
As a result, we found a distinct spectral peak at approximately 3.6 mHz in the air and seafloor pressures of those waves. Based on the intersection of the dispersion curves, the 3.6 mHz peak in the air pressure represents resonant coupling between Lamb and thermospheric gravity waves. To reproduce the observed spectral structure up to 4 mHz, an upward-moving pressure source with a duration of 1500 s should be placed at an altitude range of 59–71 km. This altitude is slightly higher than the overshooting plume top of 50–57 km derived from the satellite observations, indicating that the observed atmospheric disturbances are primarily excited by the pressure source right above the overshooting plume rather than the umbrella cloud and overshooting plume themselves.
Comparing the spectral amplitudes inside the Japan Trench with those outside, the high-frequency meteotsunamis forced by the coupled wave are further amplified by near-resonance with the tsunami mode upon their passage through the deep Japan Trench. The 3.6 mHz peak can uniquely monitor Pacific-scale air-sea disturbances extending as high as 70 km into the mesosphere and as deep as 8000 m in the trench.
Acknowledgement
We used records of S-net (doi:10.17598/nied.0007), V-net (doi:10.17598/nied.0006) operated by NIED, and barometers from GSN (doi:10.7914/SN/IU).
As a result, we found a distinct spectral peak at approximately 3.6 mHz in the air and seafloor pressures of those waves. Based on the intersection of the dispersion curves, the 3.6 mHz peak in the air pressure represents resonant coupling between Lamb and thermospheric gravity waves. To reproduce the observed spectral structure up to 4 mHz, an upward-moving pressure source with a duration of 1500 s should be placed at an altitude range of 59–71 km. This altitude is slightly higher than the overshooting plume top of 50–57 km derived from the satellite observations, indicating that the observed atmospheric disturbances are primarily excited by the pressure source right above the overshooting plume rather than the umbrella cloud and overshooting plume themselves.
Comparing the spectral amplitudes inside the Japan Trench with those outside, the high-frequency meteotsunamis forced by the coupled wave are further amplified by near-resonance with the tsunami mode upon their passage through the deep Japan Trench. The 3.6 mHz peak can uniquely monitor Pacific-scale air-sea disturbances extending as high as 70 km into the mesosphere and as deep as 8000 m in the trench.
Acknowledgement
We used records of S-net (doi:10.17598/nied.0007), V-net (doi:10.17598/nied.0006) operated by NIED, and barometers from GSN (doi:10.7914/SN/IU).