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[U09-01] The tide level changes due to the volcanic eruption at the Hunga Tonga-Hunga Ha’apai -The correspondence of JMA-
Keywords:tide level change, atmospheric pressure waves
The large-scale eruption occurred at the Hunga Tonga-Hunga Ha’apai around 13:00(JST) on January 15, 2022. Volcanic plume generated by the eruption reached an altitude of about 16,000 m, furthermore, the atmospheric pressure waves accompanying the eruption spread were confirmed by observations of the meteorologic satellite Himawari. Because of the observations of slight tide level changes at observation points on the propagation path to Japan, JMA announced distance earthquake information and a tsunami forecast (slight sea level changes along the coast of Japan). However, clear tide level changes began to be observed in the Pacific coast. These tide level changes began about two and a half hours earlier than the expected arrival time. Before these tide level changes, atmospheric pressure changes of about 2 hPa were also observed over a wide area of Japan. We considered that these tide level changes were not normal tsunami phenomena because they did not match the theoretical estimated tsunami arrival time and were larger than the tide level changes observed at the observation points on the propagation path to Japan. Although it was unclear to what extent these tide level changes would cause disasters, JMA thought that it was necessary to call for warning and advisory as the tide level changes became even larger. We considered that it was the best way to call for disaster prevention actions by utilizing the announcement mechanism of tsunami warnings and we issued tsunami warnings and advisories to the Pacific coast of Japan.
It took time to announce the tsunami warning for this phenomenon, and the information dissemination between the eruption occurrence and the announcement of the tsunami warning was insufficient. As a response to such a phenomenon for the time being, when a large-scale volcanic eruption is observed, JMA will utilize “distance earthquake information” to inform that there is a possibility that tide level changes due to volcanic eruptions will be observed in Japan as well. In the event of a large-scale eruption of Manam volcano in Papua New Guinea on March 8, 2022, information could be immediately announced based on this emergent response policy.
In addition, JMA held a “Study Meeting on Tsunami Prediction technology” once in February and once in March by experts in various research fields such as volcanoes, atmospheric oceans, and tsunamis to understand a basic mechanism of this phenomenon. From these study meetings, there were reports such as,
・Atmospheric pressure waves were generated and propagated by the eruption, causing tide level changes.
・The tide level change due to the atmospheric boundary wave (Lamb wave, velocity about 300 m/s) captured and propagated at the sea surface and the atmospheric boundary arrived earlier than estimated time of arrival of the tsunami due to a normal earthquake.
・The tide level change can be large due to the Proudman resonance of the atmospheric pressure wave, but further investigation is required for the amplification effect in this case.
・It is difficult to quantitatively predict the tide level change along the coast of Japan from easy-to- observe phenomena such as smoke altitude and the amount of pressure change and tide level change observed overseas.
・On the other hand, it is possible to judge that a tide level change may occur and to roughly predict the start time of the tide level change.
In the future, JMA plans to discuss how to disseminate information when a similar phenomenon occurs, together with experts such as disaster information.
Regarding the same phenomenon as this time, it is expected that further detailed elucidation and examination of the possibility of prediction will proceed in the research field. JMA will incorporate these results into its operation as needed and disseminate appropriate information.
In this presentation, we will report on the response of JMA to these tidal changes on the day and the status of examinations for understanding the phenomenon.
It took time to announce the tsunami warning for this phenomenon, and the information dissemination between the eruption occurrence and the announcement of the tsunami warning was insufficient. As a response to such a phenomenon for the time being, when a large-scale volcanic eruption is observed, JMA will utilize “distance earthquake information” to inform that there is a possibility that tide level changes due to volcanic eruptions will be observed in Japan as well. In the event of a large-scale eruption of Manam volcano in Papua New Guinea on March 8, 2022, information could be immediately announced based on this emergent response policy.
In addition, JMA held a “Study Meeting on Tsunami Prediction technology” once in February and once in March by experts in various research fields such as volcanoes, atmospheric oceans, and tsunamis to understand a basic mechanism of this phenomenon. From these study meetings, there were reports such as,
・Atmospheric pressure waves were generated and propagated by the eruption, causing tide level changes.
・The tide level change due to the atmospheric boundary wave (Lamb wave, velocity about 300 m/s) captured and propagated at the sea surface and the atmospheric boundary arrived earlier than estimated time of arrival of the tsunami due to a normal earthquake.
・The tide level change can be large due to the Proudman resonance of the atmospheric pressure wave, but further investigation is required for the amplification effect in this case.
・It is difficult to quantitatively predict the tide level change along the coast of Japan from easy-to- observe phenomena such as smoke altitude and the amount of pressure change and tide level change observed overseas.
・On the other hand, it is possible to judge that a tide level change may occur and to roughly predict the start time of the tide level change.
In the future, JMA plans to discuss how to disseminate information when a similar phenomenon occurs, together with experts such as disaster information.
Regarding the same phenomenon as this time, it is expected that further detailed elucidation and examination of the possibility of prediction will proceed in the research field. JMA will incorporate these results into its operation as needed and disseminate appropriate information.
In this presentation, we will report on the response of JMA to these tidal changes on the day and the status of examinations for understanding the phenomenon.