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The volcano of Hunga Tonga-Hunga Ha'apai in Tonga erupted on 15 January 2022, generating severe disturbances in the atmosphere and the ionosphere. This event provided us with large amount of data of the atmosphere and the ionosphere, and various kinds of observational studies have been made. Recently several simulation studies have also been made to reproduce and understand the atmosphere–ionosphere variations driven by the volcanic eruption. Although the simulation studies have reproduced the global variations of the atmosphere and the ionosphere successfully, phenomena related with acoustic waves have not been fully investigated. We employed an axisymmetric three-dimensional nonhydrostatic atmospheric model and the whole atmosphere–ionosphere coupled model GAIA. We found that the simulation can produce various kinds of atmospheric waves generated by the eruption, such as acoustic waves, gravity waves, Lamb waves, Pekeris waves, and TIDs concentrically propagating from the eruption site, and atmospheric oscillations with a period of a few minutes. In addition, the results indicate that the eruption generates supersonic shock waves in the volcanic region, leading to the extremely large vertical oscillations in the thermosphere and ionosphere above the volcanic eruption region. [ABSTRACT FROM AUTHOR]

The strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga‐Hunga Ha'apai, generating unprecedented atmospheric waves not seen before in observations. We used satellite microwave observations from (a) Advanced Technology Microwave Sounder (ATMS) on board the National Oceanic and Atmospheric Administration (NOAA)‐20 and the Suomi‐National Polar‐orbiting Partnership (SNPP) and (b) Advanced Microwave Sounding Unit (AMSU)‐A on board Meteorological operational satellite (MetOp)‐B/MetOp‐C to study these waves in the stratosphere immediately after the eruption. The NOAA Microwave Integrated Retrieval System (MiRS) was applied to these microwave observations to produce atmospheric temperature profiles. The atmospheric Lamb wave and fast‐traveling gravity waves are clearly revealed in both the brightness temperatures and the MiRS retrieved temperatures, revealing their vertical phase structures. This study is the first attempt to perform a detailed analysis of the stratospheric impact of the Tonga eruption on operational satellite microwave observations and the corresponding MiRS retrievals. Plain Language Summary: The strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga‐Hunga Ha'apai. The microwave instruments onboard the currently operational satellites observed the area in the vicinity of the eruption. The eruption impacts were most obvious at high altitudes (the stratosphere) in the observed microwave brightness temperatures. Additionally, atmospheric temperature profiles have been retrieved using the satellite measured microwave brightness temperatures. The retrieved atmospheric temperature fields also show the impacts of the volcanic eruption in the stratosphere. This study is the first attempt to perform a detailed analysis of the impact of the Tonga volcanic eruption using operational satellite microwave observations and the corresponding retrievals. Key Points: Microwave observations from multiple satellites capture stratospheric waves from the Tonga eruption, including Lamb and gravity wavesMiRS atmospheric temperature retrievals also resolve wave perturbations in the stratosphere after the eruptionThe Lamb wave and the lead gravity wave show no apparent phase change with height, whereas the trailing gravity waves do [ABSTRACT FROM AUTHOR]

The massive eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano in Tonga on 15 January 2022 at 04:15 UTC had a global impact and triggered an atmospheric wave and a tsunami. We first analyzed observation data from meteorological stations and tide gauges at 12 locations. Low-frequency trends in the observation data were removed by using a high-pass filter. Fourier and wavelet spectral analyses were applied to determine the frequency characteristics of the filtered data. Modal analysis was developed and used to investigate natural oscillation periods based on bathymetry. The results showed that the Lamb wave generated by the atmospheric pressure wave arrived ~ 7 and ~ 44 h after the eruption. The tsunami arrived ~ 11 and ~ 45 h after the eruption, which corresponded to the arrival time of the Lamb wave. The dominant periods of the Lamb waves were ~ 7.7 and ~ 7.5 min, and for the tsunamis they were ~ 9.9 and ~ 28.7 min. The periods derived from the spectral analysis matched the natural oscillation of the eigenperiod derived from the modal analysis, in eight out of the twelve stations. This study provides valuable insight and information regarding the nonseismic and far-field effects of tsunamis generated by volcanic eruptions. [ABSTRACT FROM AUTHOR]

In 2022, the Hunga volcano eruption in Tonga generated atmospheric pressure waves that propagated globally and produced tsunamis in all the world's oceans. The largest pressure wave, with an amplitude of several hundred pascals, is the Lamb wave. Standard Lamb wave models, incorporating the sound‐speed as a function of temperature, satisfactorily explain observations in the near‐field but not in the far‐field. We show that an augmented Lamb wave model that includes the effects of wind and topography accurately reproduces the wavefronts observed by satellites and barometers, including those close to the antipode. Winds, first suggested to explain the travel times of Lamb waves from Krakatau in 1883, are now shown to also play a major role in shaping their waveforms; temperature and topography play smaller, but still detectable, roles. Our augmented model provides a significant advance for the development of early warning and hazard assessments for the meteotsunamis these waves produce. Plain Language Summary: The January 2022 explosive eruption of the Hunga volcano in Tonga produced a pressure wave (of a type known as a Lamb wave) in the atmosphere, which was detected worldwide. This wave circled the Earth more than once, and generated tsunami in unexpected times and places. We have derived a mathematical description that allows us to quickly and accurately model the observations of this atmospheric wave. The description includes the effects of winds, temperature, and topography. The wave modeled using this description reproduces satellite and ground observations much better than simpler models, notably the complex pattern of the wave near the antipode of the eruption. Our model clearly identifies global winds as the crucial influence on global‐scale Lamb‐wave propagation, and provides modeling tools for possible future occurrences of such waves and the global tsunamis created by them. Key Points: A augmented model is proposed to simulate the propagation of planetary scale Lamb waves, incorporating wind, temperature and topographyWinds play a primary role shaping Lamb waves in the far field, especially near the antipode of the sourceThe augmented Lamb wave model will help better assess far‐field volcanic tsunami hazards [ABSTRACT FROM AUTHOR]

At 04:14:45 UT on 2022 January 15, a powerful eruption of the submarine Hunga Tonga–Hunga Ha'apai volcano occurred at about 30 km south of the Ha'apai Islands in the Kingdom of Tonga (at −20.55° N, −175.39° E). This eruption caused atmospheric waves that spread worldwide. In this study, we investigate the the total electron content (TEC) variation over China using the BeiDou Navigation Satellite System. The particularly interesting feature of the data set compared to other ground-based TEC data is the exclusive use of the BeiDou geostationary satellites, which monitor the TEC variations for fixed ionospheric piercing points and can provide more accurate calculations of the travelling speed of the disturbance. For comparison, atmospheric pressure records were examined, which show that the Lamb wave passed by the same stations four times with a constant speed of 310 m s−1. However, the TEC results show that the ionospheric disturbances passing over China four times with different speeds within four days after the eruption, two travelling along the short-path direction and two along the long-path direction. The primary front of the first short-path event travels with a speed of 340 m s−1, which is higher than the Lamb wave. The faster speed suggests that the primary front cannot be fully attributed to the Lamb wave, and further studies need to explore its mechanism. The second short-path and first long-path events travel with speeds of 301 and 310 m s−1, respectively, close to the speed of the Lamb wave, and they may be caused by upward energy leakage during the propagation of the Lamb wave. The second long-path event travels with a speed of 264 m s−1, possibly induced by the gravity waves. [ABSTRACT FROM AUTHOR]

On 15 January 2022, a large eruption of the Hunga Tonga-Hunga Ha'apai volcano in Tonga triggered globally observed tsunami waves. While the first arrival in the observed wave trains is now widely known to be related to the atmospheric Lamb wave generated by the eruption, large later phases, whose amplitudes were comparable to the first ones, were also recorded. In this study, we estimated the source of the later phases based on the Vespa analysis and proposed a new numerical scheme to reproduce them. The Vespa analysis estimates the arrival time and incident angle of each signal by a slant-stack process using its theoretical traveltime. The Vespa analysis revealed that small atmospheric waves excited the large later tsunamis. For the numerical experiments, we used two types of synthetic methods: finite difference method and normal mode theory. We found that both a good atmospheric wave model and bathymetric effect were important to generate the atmospheric-induced tsunamis corresponding to the later phases. A hybrid method calculating tsunamis by the finite difference method with the atmospheric waves by the normal mode theory as the input successfully reproduced the observed records, particularly in amplitude over the entire records. [ABSTRACT FROM AUTHOR]

SUMMARY: The 15 January 2022 eruption of the Hunga–Tunga volcano generated a Lamb pressure wave propagating all over the globe and triggering a tsunami throughout the planet. A first atmospheric wave arrived 16 hr after the eruption on the French Mediterranean coasts and propagated southward. A second one originating from Africa was observed 4 hr later with an attenuated amplitude. The first wave can be roughly defined either by a N wave or a sinusoid signal with a period close to 50 min and an amplitude of 130 Pa. In the Mediterranean Sea, the tsunami was recorded by almost all standard coastal tide gauges or pressure gauges. The French tide gauge stations recorded water waves with amplitudes ranging from a few centimetres to 10 cm and with periods ranging from 10 min to 1 hr. Numerical simulation of the tsunami is performed by the operational code Taitoko for different atmospheric sources. Non-linear shallow water equations are solved by a finite-difference method, using the nested multigrid approach. The tsunami is generated by calculating analytically the atmospheric pressure gradient in the momentum equations. Comparisons of time-series between numerical solutions and records are satisfactory for most tide-gauges along the French Mediterranean coast. Sensitivity analysis on the atmospheric source and on the resolution is performed. For most tide-gauge stations, numerical results show that the wave forms depend first on local resonance phenomena. [ABSTRACT FROM AUTHOR]

Hunga Tonga-Hunga Ha'apai climactic eruption on January 15, 2022, released enormous energy that affected the ionosphere over the Pacific Rim. We analyzed ionospheric disturbance following volcanic eruptions using near-field (<1000km), regional (1000–5000 km), and far-field (5000–12000 km) global positioning system (GPS) observations. The results indicate that the near-field ionospheric perturbation that occurred 8–15 min after the cataclysmic eruption was mainly derived from the shock wave (~1000 m/s) generated by the blast, while the low-frequency branch with long-distance propagation characteristics over the regional and the far-field was mainly associated with atmospheric Lamb waves (~330 m/s). Moreover, the amplitude of disturbance and background total electron content (TEC) are related proportionally. The intensity of the volcanic eruption and the background ionospheric conditions determine the magnitude of ionospheric responses. TEC perturbations were invisible on the reference days. Furthermore, the source location and onset time were calculated using the ray tracing technique, which confirms that the Tonga event triggered the ionospheric anomaly beyond the crater. Finally, the change in the frequency of the perturbations coincided with the arrival of the initial tsunami, implying the generation of a meteotsunami. [ABSTRACT FROM AUTHOR]

Abstract—The possibility of remote studying the electromagnetic and ionospheric effects of the eruption of the Tonga volcano on January 15, 2022 is demonstrated. At distances up to 15000 km from the source, geomagnetic variations associated with Schuman resonance (SR) perturbations, propagation of Lamb wave and acoustic-gravity waves were detected. It is shown that the formation of a high-power source of thunderstorm activity caused by the eruption resulted in a significant (more than threefold) increase in the amplitude of geomagnetic disturbances at SR frequencies, which correlates with the number of lightning events. The effect of the eruption on the frequency characteristics of the SR was not detected. [ABSTRACT FROM AUTHOR]

We simulate the gravity waves (GWs) and traveling ionospheric disturbances (TIDs) created by the Hunga Tonga‐Hunga Ha'apai (hereafter "Tonga") volcanic eruption on 15 January 2022 at ∼04:15 UT. We calculate the primary GWs and forces/heatings generated where they dissipate with MESORAC, the secondary GWs with HIAMCM, and the TIDs with SAMI3. We find that medium and large‐scale TIDs (MSTIDs and LSTIDs) are induced by the secondary GWs, with horizontal phase speeds cH ≃ 100–750 m/s, horizontal wavelengths λH ≃ 600–6,000 km, and ground‐based periods τr ≃ 30 min to 3 hr. The LSTID amplitudes over New Zealand are ≃2–3 TECU, but decrease sharply ≃ 5,000 km from Tonga. The LSTID amplitudes are extremely small over Australia and South Africa because body forces create highly asymmetric GW fields and the GWs propagate perpendicular to the magnetic field there. We analyze the TIDs from SAMI3 and find that a 30 min detrend window eliminates the fastest far‐field LSTIDs. We analyze the GPS/TEC via detrending with 2–3 hr windows, and find that the fastest LSTIDs reach the US and South America at ∼8:30–9:00 UT with cH ≃ 680 m/s, λH ≃ 3,400 km, and τr ≃ 83 min, in good agreement with model results. We find good agreement between modeled and observed TIDs over New Zealand, Australia, Hawaii, Japan and Norway. The observed F‐peak height, hmF2, drops by ≃ 110–140 km over the western US with a 2.8 hr periodicity from 8:00 to 13:00 UT. We show that the Lamb waves (LWs) observed by AIRS with λH = 380 km have amplitudes that are ≃ 2.3% that of the primary GWs at z ≃ 110 km. We conclude that the observed TIDs can be fully explained by secondary GWs rather than by "leaked" LWs. Plain Language Summary: Gravity waves (GWs) are created by various processes, such as volcanic eruptions. A breaking GW imparts momentum and energy to the atmosphere, which creates secondary GWs. Traveling ionospheric disturbances (TIDs) are created by GWs through collisions between neutral and ion molecules. We simulate the GWs and TIDs created by the Tonga eruption on 15 January 2022. We find that medium and large‐scale TIDs (MSTIDs and LSTIDs) are induced by the secondary GWs. These TIDs propagate globally, and have speeds of 100–750 m/s and horizontal scales of hundreds to thousands of km. The fastest TIDs reach the United States and South America at ∼8:30–9:00 UT; these TIDs have large scales and large periods, in agreement with observations. These LSTIDs can only be seen if they are not "detrended out" when processing the ionospheric data. Previous studies eliminated these LSTIDs by restricting their detrend windows, and then incorrectly suggested that Lamb waves were responsible for the TIDs they observed. Using longer detrend windows, we find good agreement between the modeled and observed TIDs. We find that the observed TIDs can be fully explained by secondary GWs, rather than by the leakage of Lamb waves into GWs. Key Points: Globally‐propagating concentric TIDs are induced by secondary GWs from the Tonga eruption with cH = 100−750 m/s and τr = 30 min to 3 hrThe fastest LSTIDs from Tonga in the far field are eliminated when detrending SAMI3 and GPS/TEC data with a 30 min windowThe fastest modeled LSTIDs from Tonga reach the US and South America at 8:30‐9:00 UT with cH = 600 m/s, in good agreement with data [ABSTRACT FROM AUTHOR]

Equatorial plasma bubbles are a phenomenon of plasma density depletion with small-scale density irregularities, normally observed in the equatorial ionosphere. This phenomenon, which impacts satellite-based communications, was observed in the Asia-Pacific region after the largest-on-record January 15, 2022 eruption of the Tonga volcano. We used satellite and ground-based ionospheric observations to demonstrate that an air pressure wave triggered by the Tonga volcanic eruption could cause the emergence of an equatorial plasma bubble. The most prominent observation result shows a sudden increase of electron density and height of the ionosphere several ten minutes to hours before the initial arrival of the air pressure wave in the lower atmosphere. The propagation speed of ionospheric electron density variations was ~ 480–540 m/s, whose speed was higher than that of a Lamb wave (~315 m/s) in the troposphere. The electron density variations started larger in the Northern Hemisphere than in the Southern Hemisphere. The fast response of the ionosphere could be caused by an instantaneous transmission of the electric field to the magnetic conjugate ionosphere along the magnetic field lines. After the ionospheric perturbations, electron density depletion appeared in the equatorial and low-latitude ionosphere and extended at least up to ±25° in geomagnetic latitude. [ABSTRACT FROM AUTHOR]

The Hunga Tonga‐Hunga Ha'apai (hereafter HTHH) submarine volcano erupted at 04:14:45 UT on 15 January 2022, causing ionospheric disturbances. This paper uses carrier phase observations from GNSS tracking stations in New Zealand and Australia to calculate the vertical total electron content. At 06:10, the ground‐based GNSS tracking station in New Zealand observes a maximum amplitude of 2.26 TECU anomaly caused by a mesoscale traveling ionospheric disturbance (MSTID) with a wavelength of 200–250 km, a period of 6–13 min, and a maximum propagation velocity of 330 m/s. The anomaly developed with time along the north‐south island direction toward the south island and lasted for about three and a half hours, with the ionosphere returning to pre‐eruption levels after 09:50, indicating a correlation between ionospheric activity and volcanic eruption. An ionospheric anomaly caused by an MSTID was also observed off the east coast of Australia around 08:11, with a maximum amplitude of 3.17 TECU and a maximum propagation velocity of 356 m/s. The ionospheric anomaly in Australia spreads out in a plane. In the process of propagation, it continuously impacts the area it passes through, and the entire anomaly process lasts for more than 7 hr. Still, the anomalous propagation velocities are more significant than in New Zealand, indicating that the Lamb waves excited by the eruption of the HTHH submarine volcano are directional in propagation speed; westward travels faster than southward. This finding will provide more references for scholars to study the mechanism and characteristics of anomaly propagation. Plain Language Summary: This paper reports on the Hunga Tonga‐Hunga Ha'apai submarine volcanic eruption event at Tonga on 15 January 2022, which caused air pressure waves in the form of Lamb waves to propagate to ionospheric heights and caused traveling ionospheric disturbances. Analysis of the filtered total electron content in the ionosphere using dense GNSS tracking stations in Australia and New Zealand revealed large‐scale, intense ionospheric disturbances. The propagation of the anomaly is also directional, with the New Zealand ionospheric anomaly initially propagating from north to south in a ripple pattern with a maximum mesoscale traveling ionospheric disturbance (MSTID) propagation velocity of ∼330 m/s. The impact of Lamb waves on the ionosphere in Australia is more pronounced, with the disturbance unfolding in a faceted pattern from east to west for up to 7 hr, during which the maximum MSTID propagation velocity is ∼356 m/s. In addition, the anomaly is affected by small‐amplitude gravity waves and excites multiple ionospheric disturbance phenomena during its propagation in both locations. This result confirms the natural phenomenon of ionospheric disturbances induced by extreme natural hazards and shows that severe explosive events can have a lasting and far‐reaching impact on the ionosphere. Key Points: Evidence of widespread traveling ionospheric disturbances caused by volcanic eruptionsThe propagation of the anomaly is directional, propagating westward at a greater rate than southwardSmall‐scale gravity waves have caused multiple transient ionospheric disturbances in both New Zealand and Australia [ABSTRACT FROM AUTHOR]

The Hunga Tonga-Hunga Ha'apai volcano eruption resulted in propagation of tsunamis globally. Atmospheric pressure disturbances and tsunamis were recorded in Lingding Bay, China, situated more than 9000 km from the volcano. We studied the features of tsunamis in Lingding Bay and its surrounding areas by using records from tide gauges and meteorological stations. Lamb waves were observed in the bay approximately 8, 44 and 80 hr after the volcanic eruption. The first and second tsunami waves arrived approximately 11 and 45–47 hr following the eruption, respectively, indicating consistency with the arrival time of Lamb waves. In addition, wavelet and Fourier analyses were applied to the sea level records to investigate the frequency characteristics. The ratio of the tsunami spectra to the background spectra for two tsunami waves was calculated as the source spectra. The source spectra of two tsunami waves were mostly of the same shape, with dominant periods of ∼17 and ∼46 min. Our results provide information for theoretical investigation of the Tonga tsunami event. More efforts should be devoted to relevant research on the generating mechanism and early warning of tsunamis from non-seismic origins. [ABSTRACT FROM AUTHOR]

The constant-Q Gabor atom is developed for spectral power, information, and uncertainty quantification from time–frequency representations. Stable multiresolution spectral entropy algorithms are constructed with continuous wavelet and Stockwell transforms. The recommended processing and scaling method will depend on the signature of interest, the desired information, and the acceptable levels of uncertainty of signal and noise features. Selected Lamb wave signatures and information spectra from the 2022 Tonga eruption are presented as representative case studies. Resilient transformations from physical to information metrics are provided for sensor-agnostic signal processing, pattern recognition, and machine learning applications. [ABSTRACT FROM AUTHOR]

The 2022 eruption of the Hunga Tonga-Hunga Ha'apai volcano excited an atmospheric Lamb wave, which induced a fast-traveling tsunami. This tsunami was driven by the pressure-forced wave traveling at the speed of the Lamb wave and, thus, was much faster than conventional tsunamis. This was the first case in which ocean bottom monitoring systems widely observed an air pressure-induced tsunami. We found that the pressure-forced waves split and generated ocean gravity waves after passing the Japan Trench based on the S-net data. Our simulations show that changes in water depth can amplify or decrease the pressure-forced wave. Simultaneously, an ocean gravity wave is generated due to the conservation of water volume. Because the ocean gravity wave was slower than the pressure-forced wave near Japan, it was separated from, and traveled behind, the pressure-forced wave. We explained the wave separation phenomenon and reproduced the waveforms of different splitting stages observed by the stations near the Japan Trench. [ABSTRACT FROM AUTHOR]

This paper investigates concentric traveling ionospheric disturbances (CTIDs) associated with the Tonga volcanic eruption. Results show that: (a) two types of CTIDs (CTID #1 and CTID #2) were identified that traveled radially from Tonga at the speed of 610–880 m/s (acoustic‐mode) and 300–380 m/s (Lamb‐mode), respectively. CTID #1 reached 3,800 and 5,000 km away from the eruption location toward the directions of New Zealand and Australia, respectively. CTID #2 propagated persistently for ∼9 hr over New Zealand and Australia. (b) The CTID #2 wavefront changed after 08:35 UT over New Zealand, possibly due to a combination of factors including the anisotropic propagation of CTID #2, the regional geomagnetic declination, and westward‐moving Lamb waves. (c) Topside total electron content (TEC) enhancement with a magnitude over two TECu was observed from COSMIC‐2 measurements. The enhancement agrees with CTID #1 peak from nearby ground‐based TEC observations and could be related to the upward propagation of the F layer's CTID #1 signatures. Plain Language Summary: The Tonga volcanic eruption on 15 January triggered various atmospheric waves that propagate from the Earth's surface and throughout the atmosphere and ionosphere. In this study, we discuss two types of concentric traveling ionospheric disturbances (CTIDs, #1 and #2) propagating outward from the Tonga site based on measurements collected by ∼1,000 ground‐based global navigation satellite system receivers. Our analysis based on the CTID propagation speed showed that CTIDs #1 and #2 traveled at acoustic and Lamb wave modes, respectively. We also analyzed COSMIC‐2 satellite radio occultation observations and showed that CTID #1‐related enhancement signatures were observed at the topside ionosphere near the eruption site. Moreover, it is interesting to note that CTID #2 wavefront changed over New Zealand after 08:35 UT on 15 January likely followed the regional geomagnetic declination and westward‐moving Lamb waves. Key Points: Two distinctive types of concentric traveling ionospheric disturbances (CTIDs #1 and #2) were identified, and they propagated radially outward from Tonga at the speed of 610–880 m/s (acoustic‐mode) and 300–380 m/s (Lamb‐mode), respectivelyThe wavefront of the long‐lasting CTID #2 changed after 08:35 UT over New Zealand, possibly due to the regional geomagnetic declination and westward‐moving Lamb wavesDistinctive total electron content (TEC) enhancement of over 2 TECu magnitude observed above 530 km near the eruption site could be associated with the upward propagation of the acoustic‐mode CTID #1 signatures in the F layer [ABSTRACT FROM AUTHOR]

Tsunamis are commonly generated by earthquakes beneath the ocean floor, volcanic eruptions, and landslides. The tsunami following the Tonga eruption of 2022 is believed to have been excited by atmospheric pressure fluctuations generated by the explosion of the volcano. The first, fast-traveling tsunami was excited by Lamb waves; however, it has not been clarified observationally or theoretically which type of atmospheric fluctuations excited more prominent tsunami which followd. In this study, we investigate atmospheric gravity waves that possibly excited the aforementioned subsequent tsunami based on observations and atmosphere-ocean coupling simulations. The atmospheric fluctuations are classified as Lamb waves, acoustic waves, or gravity waves. The arrival time of the gravity wave and the simulation shows that the gravity wave propagated at a phase speed of 215 m/s, coinciding with the tsunami velocity in the Pacific Ocean, and suggesting that the gravity wave resonantly excited the tsunami (Proudman resonance). These observations and theoretical calculations provide an essential basis for investigations of volcano-induced meteotsunamis, including the Tonga event. [ABSTRACT FROM AUTHOR]

The Hunga-Tonga volcanic eruption occurred on 15 January 2022 generated different modes of atmospheric and ionospheric waves. Using the Geostationary Operational Environment Satellite-17 (GOES-17), Aqua and Global Positioning System (GPS) satellite observations, an atmospheric and ionospheric multi-layer study of the Tonga volcano induced signatures over the New Zealand region is performed. The visible and infrared channel data of GOES-17 and Atmospheric Infrared Sounder (AIRS) data from NASA Aqua satellite confirm the presence of a highly convective zone and occurrence of concentric Lamb and gravity waves at lower atmospheric altitudes. The Total Electron Content (TEC) derived from 175 GPS stations covering the entire New Zealand region brings out two dominant modes of Travelling Ionospheric Disturbances (TIDs) having periodicity between 30 and 50 min. These two different modes having the phase speeds of 542 m/s and 354 m/s are allied to atmospheric gravity waves and Lamb wave triggered gravity waves respectively and are observed to propagate towards the south-west direction over the New Zealand region. [ABSTRACT FROM AUTHOR]

On 15 January 2022, Tonga's Hunga Tonga‐Hunga Ha'apai (HTHH) volcano violently erupted, generating a tsunami that killed three people. Acoustic‐gravity waves propagated by the eruption and tsunami caused global complex ionospheric disturbances. In this paper, we study the nature of these perturbations from Global Navigation Satellite System observables over the southwestern Pacific. After processing data from 818 ground stations, we detect supersonic acoustic waves, Lamb waves, and tsunamis, with filtered magnitudes between 1 and 7 Total Electron Content units. Phase arrivals appear superpositioned up to ∼1,000 km from HTHH and are distinct by ∼2,200 km. Within ∼2,200 km, signals have an initial low‐frequency pulse that transitions to higher frequencies. We note the presence of a faster perturbation generated 1 hr post‐eruption which crosses the tsunami disturbance ∼3,000 km from HTHH, potentially contributing to premature land arrivals. Lastly, the arrival of tsunami‐generated disturbances coincides with deep‐ocean observations. Plain Language Summary: The 15 January 2022 volcanic eruption of Hunga Tonga‐Hunga Ha'apai and subsequent tsunamis sent powerful energy waves into the ionosphere (a layer of Earth's atmosphere that is deformed by energy emitted from events like volcanic eruptions, tsunamis, earthquakes, tornadoes, hurricanes, and large man‐made explosions). These waves can provide valuable information about different phases of the event, such as the powerful explosion, sound wave, and tsunami. Using Global Positioning Systems data, we measure these ionospheric signals over the southwestern Pacific Ocean to examine which phases of the event contributed to each ionospheric disturbance. We successfully detect all three event phases in the ionosphere and determine the distance at which these signals separate from one another. Furthermore, we validate our data by comparing tsunami signals in the ionosphere against direct ocean‐based observations of tsunami activity. Of particular note is our observation of a faster ionospheric signal that forms an hour after the eruption and catches up to the tsunami's disturbance. Our work supports the hypothesis that others have proposed in which high‐energy waves from the eruption escalated tsunami speeds and wave heights. This, in turn, supports the observation of early tsunami arrivals that were reported along many Pacific coastlines. Key Points: We see distinct phase arrivals in the ionosphere for a supersonic wave, Lamb wave, and tsunami (the latter is validated by ocean sensors)Phase arrivals begin to separate at ∼1,000 km from Tonga and are fully separated by ∼2,200 kmWe highlight a faster disturbance that propagates 1 hr post‐eruption and meets the tsunami perturbation ∼3,000 km from the volcano [ABSTRACT FROM AUTHOR]

The Tonga volcano erupted on 15 January 2022, at 04:15:45 UTC, which significantly influenced the atmosphere and space environment, at the same time, an unprecedented opportunity to monitor ionospheric anomalies is provided by its powerful eruption. In current studies of traveling ionospheric disturbance (TID) triggered by the 2022 Tonga volcanic eruption, the particular phenomenon of ionospheric disturbances in various parts of the world has not been reasonably explained, and the vertical ionospheric disturbances are still not effectively detected. In this paper, we calculate the high-precision slant total electron content (STEC) from more than 3000 ground-based GPS stations distributed around the world, then we obtain the radio occultation (RO) data from near-field COSMIC-2 profiles and investigate the horizontal TID and the vertical ionospheric disturbances by the singular spectrum analysis (SSA). Horizontal TID propagation captured by GPS STEC results indicates that acoustic-gravity waves dominate the energy input at the beginning of the ionospheric disturbance with an approximate speed of 1050 m/s initially. With the dissipation of the shock energy, lamb waves become a dominant mode of ionospheric disturbances, moving at a more stable speed of about 326 m/s to a range of 16,000 km beyond the far-field. Local characteristics are evident during the disturbance, such as the ionospheric conjugation in Australia and the rapid decay of TID in Europe. The shock-Lamb-tsunami waves' multi-fluctuation coupling is recorded successively from the COSMIC-2 RO observation data. The shock and Lamb waves can perturb the whole ionospheric altitude. In contrast, the disturbance caused by tsunami waves is much smaller than that of acoustic-gravity waves and Lamb waves. In addition, influenced by the magnetic field, the propagation speed of TID induced by Lamb waves is higher towards the northern hemisphere than towards the southern hemisphere. [ABSTRACT FROM AUTHOR]

The eruption of Hunga-Tonga Volcano on January 15, 2022 has stimulated a wide spectrum of atmospheric waves globally. To probe the surface deformation pattern, Sentinel-1 Synthetic Aperture Radar (SAR) data has been analyzed. It has been approximated that an overall area of about 2.47 square kilometres experienced deformation in conjunction with this event. To characterize the atmospheric wave propagation, barometric pressure data from 1814 stations distributed all around the globe have been examined. This study encompassed with the propagation characteristics of the waves over four zones including Indian and Polar regions for the first time using barometric data. Time-series observations indicate that the waves propagated globally multiple times. Within the Indian region, three minor arc passages and one major arc passage were identified. In Japan, two minor arc passages and one major arc were present. Conversely, in North America, both minor and major arc passages were detected, occurring a minimum of three times. Moreover, the attributes of these waves, such as their propagation speed and periodicity, were compared across these four regions. The estimated phase speed and periodicity fall within the ranges of approximately 291–314 m/s and 10–180 min, respectively including Polar Regions. These speed and periodicity measurements of the observed waves suggest that the dominant mode of wave propagation generated during the Tonga volcanic eruption is that of Lamb waves. In addition, a slower propagation phase speed of about 226.6 m/s was identified in Japan which corresponds to Pekeris mode of waves. • Hunga-Tonga volcanic eruption triggered atmospheric waves that travelled globally in all direction multiple times. • Analysis of barometric data from India, Japan, North America and Polar Regions reveal the multi-wave characteristics of atmospheric waves. • The comparison of phase speed and periodicities are in the range ∼291–314 m/s and 45–50 min respectively. [ABSTRACT FROM AUTHOR]

The January 15, 2022, Tonga eruption provides a rare opportunity to understand global tsunami impacts of explosive volcanism, including "air-shock" tsunamis induced by Lamb waves travelling in the atmosphere, and to evaluate future hazards. The propagation of the air-shock and oceanic tsunami components were analyzed using globally distributed 1-min measurements of air pressure and water level (tide gauges and deep-water buoys). Oceanic tsunamis (up to 1.7m) propagated primarily throughout the Pacific, but air-shock tsunamis arrived first and traveled globally, producing water-level perturbations in the Indian Ocean, the Mediterranean, and the Caribbean. The air-shock induced water level response of most Pacific Rim gauges was amplified, likely related to bathymetric processes. The air-shock wave repeatedly boosted tsunami wave energy as it circled the planet several times. In some locations, the air-shock was amplified as much as 35X relative to inverse barometer by Proudman resonance and topographic effects. Thus, a large volcanic air-shock (10-30mb) could cause a 3.5-10m near-field tsunami that would occur in advance of (usually) larger oceanic tsunami waves, posing an additional hazard to local populations. Present tsunami warning systems do not consider this threat. [ABSTRACT FROM AUTHOR]

The 2022 volcanic eruption in Tonga caused an unusually large tsunami around the Pacific. It travels with a faster apparent velocity and has larger amplitudes at long distances than what would be expected from a conventional tsunami from the volcanic source. This tsunami was generated by the moving atmospheric Lamb wave and traveled at the speed of the Lamb wave (0.31 km/s). Japanese data showed the amplitude of this first tsunami becomes small when approaching the coast, due to the weaker air‐sea coupling at the shallow depth. This wave split when passing the continental slope, and traveled at the speed of the ocean gravity wave. Therefore, the tsunami observed at the coast is delayed by thousands of seconds from the passage of the Lamb wave. Tsunamis generated by this atmospheric mechanism have not been previously observed by modern digital recording systems and should be considered in the tsunami warning systems. Plain Language Summary: A tsunami is usually generated by the sudden changes of the water heights, and caused by offshore earthquakes, coastal landslides, and submarine volcanic eruptions. The generated vertical displacement of the water propagates as a very long wave, and the tsunami waves become compressed with increased heights as they approach the coast. The 2022 volcanic eruption in Tonga caused an unusually large tsunami, which cannot be explained by conventional sources. The speed and amplitude are very different from theoretical values: the speed is about 0.31 km/s, whereas the average tsunami speed in the Pacific is 0.2 km/s. These data suggest that the tsunami from the Tonga eruption was excited by a pulse of atmospheric pressure as it traveled from the volcano. This source of the tsunami in the atmosphere needs to be considered for the tsunami warning system in the future. Key Points: Lamb wave produced by the volcanic eruption excites the sea surface as it travels across the Pacific and generates a tsunami pulseThe effect of the air‐sea coupling becomes weaker as the Lamb wave approaches the coastThe tsunami wave splits when passing the continental slope of Japan causing more complex waves [ABSTRACT FROM AUTHOR]

The eruption of the Hunga Tonga‐Hunga Ha'apai volcano on 15 January 2022 triggered atmospheric waves at all altitudes. The National Aeronautics and Space Administration Ionospheric Connection Explorer (ICON) and European Space Agency Swarm satellites were well placed to observe its impact on the ionospheric wind dynamo. After the Lamb wave entered the dayside, Swarm A observed an eastward and then westward equatorial electrojet (EEJ) on two consecutive orbits, each with magnitudes exceeding the 99.9th percentile of typically observed values. ICON simultaneously observed the neutral wind (90–300 km altitude) at approximately the same distance from Tonga. The observed neutral winds were also extreme (>99.9th percentile at some altitudes). The covariation of EEJ and winds is consistent with recent theoretical and observational results, indicating that the westward electrojet is driven by strong westward winds in the Pedersen region (∼120–150 km). These observations imply that the dynamo is a key mechanism in the ionospheric response to the Tonga disturbance. Plain Language Summary: The January 2022 Tonga volcanic eruption caused atmospheric impacts around the world. As a natural experiment, it can be used to test our understanding of how the lower atmosphere affects space weather. Researchers are only beginning to document the chain of events post‐eruption, and this paper focuses on its impact on the generator that drives electric fields in near‐Earth space, a key part of space weather. This generator is driven by the atmosphere pushing charged particles across Earth's magnetic field. This usually creates a strong eastward current above the equator. When the Swarm A satellite coincided with the wave from Tonga, it observed that this current strengthened dramatically, then reversed. Although reversals are not unusual, this was the strongest reversal observed by Swarm since its 2013 launch, except for one large geomagnetic storm in 2015. Another satellite, the Ionospheric Connection Explorer, was luckily at the right time and place to observe related motions of the upper atmosphere, which were similarly extreme. These observations are shown to be consistent with our theoretical understanding of the generator. This study is important because it represents a critical test of atmosphere‐space interactions and implies that the Tonga eruption caused a major space weather event. Key Points: Extreme thermospheric winds and ionospheric currents were observed in coordinated space/ground‐based measurements, 10 hours post‐eruptionThe westward electrojet current when the Lamb wave reaches the dayside is consistent with recent studies of the wind‐driven electrojetObservations of linked dynamo processes provide direct evidence of the space‐weather impacts of acute lower atmospheric forcing [ABSTRACT FROM AUTHOR]

The major eruption of volcano Hunga Tonga‐Hunga Ha'apai in Tonga on 15 January 2022 generated atmospheric Lamb waves that propagated over the world. This seemed the first volcanic Lamb wave event that was clearly captured by the state‐of‐the‐art geostationary meteorological satellites. This paper provides visualization of the waves using thermal infrared images from geostationary satellite Himawari‐8. The second time derivatives of 10‐min interval images clearly illustrated the waves propagating at about 310 m s−1. The waves could be tracked for more than a week while they propagated five times round the earth. Automated wavefront identification illustrated nonuniform propagation speed. The signals in the satellite images well matched the surface pressure observations in Japan. Plain Language Summary: The major eruption of volcano Hunga Tonga‐Hunga Ha'apai in Tonga on 15 January 2022 generated atmospheric pressure pulses that propagated over the world. This seemed the first event that was clearly captured by the state‐of‐the‐art geostationary meteorological satellites, such as Himawari‐8. Taking the time difference of Himawari‐8's 10‐min interval images twice, the waves that propagated at about 310 m s−1 could be tracked for more than a week while they propagated five times round the earth. This was not possible with the previous‐generation geostationary meteorological satellites. Visualized waves also illustrated how the propagation speed changes in space and time. The signals in the satellite images well matched the surface pressure observations in Japan. Key Points: Lamb waves from an eruption were clearly visualized by the second time derivative of satellite infrared images every 10 minThe waves could be tracked for more than a week while they propagated at least five times round the earth at a speed of about 310 m s−1The signals in the satellite images matched the surface pressure changes quantitatively [ABSTRACT FROM AUTHOR]

Tide gauge data indicated that ocean waves were generated by the eruption of the Hunga Tonga-Hunga Ha'apai volcano on January 15, 2022. These high-amplitude waves reached the Japanese coast earlier than expected for free ocean waves. These fluctuations in sea level were reasonably reproduced by an ocean model, with realistic bottom topography forced by sea-level pressure perturbations well reproduced by atmospheric general circulation models. While early arrival times are associated with atmospheric Lamb waves, the amplitude of the sea level changes cannot be fully explained by the resonance mechanism associated with sea-level pressure fluctuations of Lamb and Pekeris waves alone. Rather, resonance due to atmospheric waves in conjunction with the amplification effects caused by a steep continental slope is required in order to reproduce sea level fluctuations along the Japanese coast. In particular, the deep Northwest Pacific Basin to the east of Japan is important for strengthening the amplitude of the meteorological tsunami. • Sea level fluctuations due to the 2022 volcanic eruption in Tonga was reproduced. • Meteorological tsunamis were generated by Lamb and Pekeris waves. • Meteorological tsunamis by Pekeris waves are amplified due to Proudman resonance. • Meteorological tsunamis are amplified by entering the sharp continental slope. [ABSTRACT FROM AUTHOR]