10:00 AM - 10:15 AM
[MIS23-05] A global numerical simulation of the pressure waves excited by the Hunga Tonga-Hunga Haʻapai volcano eruption on January 15, 2022
Keywords:Lamb wave, Pekeris wave , Nonhydrostatic global model
Around 13 UTC on January 15, 2022. The eruption of Hunga Tonga-Hunga Haʻapai volcano in Tonga caused sea-level pressure fluctuations of about 2 hPa around Japan and tidal fluctuations caused by a meteo-tsunami. To accurately predict meteo-tsunamis and understand their mechanisms, it is necessary to understand the spatio-temporal propagation of the atmospheric pressure fluctuations generated by the eruption. In this study, we attempt to reproduce the pressure fluctuations using NICAM, a global nonhydrostatic model with a 3.5 km grid.
The 14-km mesh NICAM model was initialized by using MERRA2 at 00 UTC on January 15 and integrated to 04 UTC. Then, we performed two experiments with a 3.5-km mesh NICAM, one with a warm bubble representing a volcanic plume and the other without the warm bubble, and analyzed the difference between the two as an eruption signal. The warm bubble with a temperature deviation of 100 K and a specific humidity deviation of 50 g/kg was placed from the surface to 500 hPa at the nearest four grid points on a 0.14-degree latitude-longitude grid to the volcano.
As eruption signals of the sea level pressure, Lamb waves propagating horizontally at about 305 m/s and Pekeris waves propagating slower at 240 m/s were observed with relatively large amplitudes.
Since the tidal fluctuations were observed a little later than the arrival of the pressure fluctuations associated with the Lamb waves, we focus on the Lamb waves in our analysis. Since the Lamb waves are not dispersive, the energy propagation can be discussed if the phase velocity field is obtained. We assume that the Lamb wave arrives between the arrival times of waves propagating at 280 m/s and 330 m/s from the volcano. The arrival time of the Lamb wave is when the sea level pressure reaches its maximum value in that time period. The phase velocity vector at each grid point was analyzed from the spatial distribution of arrival times. The results showed that the phase velocity of the Lamb wave is not constant, for example, it is slower than 300 m/s near Japan, The Lamb wave amplitude did not decay with propagation distance, but was locally large. The area with a large amplitude corresponded well with the convergence of the Lamb wave phase velocity (and thus the group velocity). In this presentation, we will also compare the results with the phase velocity distribution of Lamb waves analyzed by the geostationary meteorological satellite "Himawari".
The 14-km mesh NICAM model was initialized by using MERRA2 at 00 UTC on January 15 and integrated to 04 UTC. Then, we performed two experiments with a 3.5-km mesh NICAM, one with a warm bubble representing a volcanic plume and the other without the warm bubble, and analyzed the difference between the two as an eruption signal. The warm bubble with a temperature deviation of 100 K and a specific humidity deviation of 50 g/kg was placed from the surface to 500 hPa at the nearest four grid points on a 0.14-degree latitude-longitude grid to the volcano.
As eruption signals of the sea level pressure, Lamb waves propagating horizontally at about 305 m/s and Pekeris waves propagating slower at 240 m/s were observed with relatively large amplitudes.
Since the tidal fluctuations were observed a little later than the arrival of the pressure fluctuations associated with the Lamb waves, we focus on the Lamb waves in our analysis. Since the Lamb waves are not dispersive, the energy propagation can be discussed if the phase velocity field is obtained. We assume that the Lamb wave arrives between the arrival times of waves propagating at 280 m/s and 330 m/s from the volcano. The arrival time of the Lamb wave is when the sea level pressure reaches its maximum value in that time period. The phase velocity vector at each grid point was analyzed from the spatial distribution of arrival times. The results showed that the phase velocity of the Lamb wave is not constant, for example, it is slower than 300 m/s near Japan, The Lamb wave amplitude did not decay with propagation distance, but was locally large. The area with a large amplitude corresponded well with the convergence of the Lamb wave phase velocity (and thus the group velocity). In this presentation, we will also compare the results with the phase velocity distribution of Lamb waves analyzed by the geostationary meteorological satellite "Himawari".