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The Hunga‐Tonga volcano eruption on 15 January 2022 generated tsunami waves that impacted both the Pacific and Atlantic coasts of the Americas. A unique feature of this event was the dual tsunami generation mechanism, which led to motions with long (several days) ringing and slow energy decay. The first ocean waves to reach the coast were "atmospheric tsunamis" generated by atmospheric Lamb waves that propagated with the speed of sound (∼314 m/s) and circled the globe in both directions several times before being fully attenuated. The second type of ocean waves were classical "oceanic tsunami" waves forced directly by the volcanic eruption and which propagated across the Pacific at roughly 2/3 the speed of the atmospheric waves. This study focuses on time series of the Hunga‐Tonga event recorded by tide gauges, microbarographs and Deep‐ocean Assessment and Reporting of Tsunamis on and off the Pacific coasts of North and Central America and in the Gulf of Mexico. Atmospheric tsunami waves only were recorded in the Gulf of Mexico, where the sea level response to the second, westward (shoreward) propagating atmospheric wave was stronger than to the first, eastward (seaward) propagating wave. Along the Pacific coast, the atmospheric tsunami waves were approximately 3–4 times smaller than the oceanic tsunami waves, which at several Mexican stations exceeded 2 m in height. The broad frequency range of 0.2–0.25 to 30 cph spanned by the oceanic tsunami in the Pacific indicates that the "effective" source area for the oceanic waves was more extensive than initially proposed. Plain Language Summary: The eruption of the Hunga‐Tonga volcano in January 2022 generated two types of tsunami waves: ordinary "oceanic" tsunami waves forced by the eruption itself and "atmospheric" tsunami waves forced by propagating pressure waves in the atmosphere. The oceanic tsunamis radiated outward into the Pacific while the atmospheric waves propagated around the globe several times in both the eastward and westward directions. Measurements by tide gauges, microbarographs and open‐ocean Deep‐ocean Assessment and Reporting of Tsunamis stations on and off the Pacific coasts of North and Central America and the Gulf of Mexico show that both types of waves were recorded on the Pacific coast but that only the atmospherically generated waves were recorded in the Atlantic Ocean and adjoining Gulf of Mexico. The atmospheric tsunamis were 3–4 times smaller than the oceanic tsunamis, which at Port San Luis and several Mexican locations, including Manzanillo and Ensenada, were higher than 2 m. The broad frequency content of the oceanic waves indicates that their source region had an "effective" area that greatly exceeded that directly spanned by the volcanic eruption. Key Points: The Tonga volcanic event generated two types of tsunami waves: "oceanic" by the eruption and "atmospheric" by atmospheric Lamb wavesThe open‐ocean and coastal records enabled us to separate the two types of tsunami waves and determine their physical propertiesThe waves span a wide frequency range, indicating that the "effective" source region greatly exceeded that covered by the eruption [ABSTRACT FROM AUTHOR]

The dual frequency Global Navigation Satellite System (GNSS) observations could determine the total electron content (TEC) in the ionosphere. In this study, GNSS TEC was applied to detect traveling ionospheric disturbances (TIDs) after the eruption of Hunga Tonga–Hunga Ha'apai (HTHH) on 15 January 2022. The eruption caused two types of tsunamis, first is tsunami generated by atmospheric wave (meteo‐tsunami) and second is caused by eruption induces water displacement or tsunami classic. At the same time with former tsunami, the atmospheric wave (shock and lamb waves) also caused TIDs at a speed of approximately ∼0.3 km/s. We found moderate correlation between this TIDs amplitude and the tsunami wave height model from tide gauge stations in New Zealand (0.64) and Australia (0.65). Further we attempted to reveal 3D structure of the TIDs in New Zealand, South Australia, and Philippines using 3D tomography. The tomography was set up > 1,170 blocks, as large as 1.0° (east–west) × 1.0° (north–south) × 100 km (vertical), up to 600 km altitude over selected regions. Tomogram shows beautiful concentric directivity of the first TIDs generated by atmospheric wave (AW). Key Points: 3D ionospheric disturbances during the 2022 Tonga eruption was investigated with spatial and temporal directionThe highest concentration of the electron disturbances was observed at an altitude of 200–300 km, which decreased at 500–600 kmA correlation between ionospheric disturbances and the height of tsunami associated with eruption was observed [ABSTRACT FROM AUTHOR]

This study presents the observation and evaluation of a meteotsunami in the Indian Ocean triggered by the Hunga‐Tonga volcanic eruption. The event was detected through tide gauges and bottom‐pressure recordings across the Indian Ocean, with an amplitude of 10–15 cm, lasting for a few days. A numerical model was used to understand the ocean's response to meteotsunami and evaluate the dynamics behind it. The model results show that the sea‐level oscillations result from the ocean waves generated by a propagating Lamb wave. In addition to interaction with bathymetry, refracted and reflected waves also determine the sea‐level variability. Our analysis shows that bathymetric slope plays a vital role in near‐shore processes. The spectral and spatial characteristics of the meteotsunami were reminiscent of seismic tsunamis. Our research on this rare event elucidates the unresolved issues and eventually leads to designing a blueprint for future observation and modeling of meteotsunamis and seismic tsunamis. Plain Language Summary: This study evaluates the observation of a rare meteotsunami event that occurred in the Indian Ocean. An atmospheric pressure wave generated by the eruption of the Hunga‐Tonga volcano in the Pacific Ocean caused the meteotsunami. The signatures of this event were captured by tide gauges installed along the coast and pressure recorders moored at the ocean floor. We demonstrate using a numerical model that fast‐moving atmospheric pressure waves, Lamb waves, caused the sea‐level oscillations. Interactions with bathymetry further influenced sea‐level variability in the basin, reflected waves, and refracted waves. The vulnerable areas showed a striking resemblance to the area impacted by the tsunami that hit the Indian Ocean in 2004. This research eventually helps to identify and incorporate observational and modeling issues associated with seismic tsunamis and meteotsunami. Key Points: We present the first comprehensive evaluation of meteotsunami in the Indian Ocean using observation and modelingA forced wave to free wave transformation happens on the continental slope, and the bathymetry slope is crucial to near‐shore processesThe meteotsunami exhibits a spectral and spatial similarity to seismic tsunamis that previously occurred in the Indian Ocean [ABSTRACT FROM AUTHOR]