Search

The high‐frequency sea level oscillations (SLO) associated with meteotsunamis can have hazardous consequences for coastal populations. They are triggered by high‐frequency atmospheric disturbances generating an oceanic response that is amplified mainly by Proudman and harbor resonance. So far, the lack of high‐resolution data had prevented a comprehensive characterization of these atmospheric disturbances, even in an extensively studied "hot spot" as Ciutadella (Balearic Islands). Here, we analyze atmospheric disturbances triggering meteotsunamis in Ciutadella during 2021 using data from an ultra‐dense meteorological network (BalearsMeteo). Atmospheric pressure time series with a sampling rate ≤1 min are used to estimate propagation speed and direction, spectral energy content, and the spatial homogeneity of atmospheric disturbances linked to meteotsunami events. We find that the spatial structure of the disturbances are rather heterogeneous, but the inferred propagation velocities are consistent with the occurrence of Proudman resonance on the continental shelves located upstream of Ciutadella (speeds between 24 and 36 m/s and directions from 210° to 260°). Although during meteotsunami events these velocity estimates undergo some changes both in time and in space, they show two key characteristics: (a) the atmospheric pressure disturbances are mostly non‐dispersive; and (b) the largest SLO are observed when the speed and direction of propagation velocities are more homogeneous in space and time. Nevertheless, an empirical relationship between the analyzed atmospheric features and the SLO amplitudes could not be established. That is, the prediction of meteotsunami amplitudes remains challenging due to the intricate interplay of atmospheric and oceanic processes. Plain Language Summary: Meteotsunamis are extreme sea level oscillations that can cause rapid sea level changes of several meters in just a few minutes. The flooding and currents associated with this rapid sea level change are dangerous for coastal infrastructure and even to human lives. Meteotsunamis are generated by rapid changes in the atmospheric pressure that generate a sea wave. Since the atmospheric perturbations are not strong enough to generate large sea waves, it is necessary that a chain of amplification mechanism acts on the generated sea wave to amplify it before reaching the coast. In this process the characteristics of the atmospheric disturbances is a key parameter that conditions the amplification process. In the present work, we use the atmospheric pressure data collected in the Balearic Islands by an ultra‐dense meteorological network to analyze in detail the atmospheric disturbances that generate meteotsunamis in Ciutadella harbor. This new set of data allows us to study with an unprecedented level of detail the spatial structure of the atmospheric disturbances and to estimate for first time the time evolution of their propagation velocity in different locations. Therefore, these results provide evidence of the complexity of the atmospheric disturbances that generate the meteotsunamis. Key Points: We characterize the atmospheric disturbances generating meteotsunamis in the Balearic Islands using an ultra‐dense observational networkThe atmospheric disturbances generating meteotsunamis have a significant spatial and temporal variabilityNo clear relationship is found between any of the analyzed characteristics of the perturbations and the meteotsunami magnitude [ABSTRACT FROM AUTHOR]

In recent years, there has been an increase in awareness and research on meteotsunamis (MT) caused by atmospheric disturbances (AD), such as widespread and long-lived cold fronts, squalls, and storms. In this work, an AD model that was developed previously has been used along with depth-integrated Navier Stokes equations to conduct 34,560 numerical experiments in the Gulf of Mexico using High-Performance Computing. The data generated is visualized with a newly developed characterization tool—the meteotsunami rose chart, described in detail. For a given location, MT rose charts provide a detailed relationship between the expected maximum MT amplitude and the AD's path, direction, and forward speed. Another new tool, the severe MT rose charts, complements these by summarizing the case scenarios with an amplitude of more than 0.3 m. An interactive online implementation has also been introduced. A sensitivity study conducted on the various constant parameters associated with it gives an idea of the factors to account for when using MT rose charts. The newly developed visualization tools are used to study the meteotsunami hazard for Clearwater Beach, FL; some critical scenarios were identified, and observations were made. These tools were then applied to 7 other places along the Gulf of Mexico to draw some broad conclusions on how the bathymetry of the region relates to severe MT hazard scenarios. It was observed that relatively slower-moving ADs produce the most severe MTs along coasts with broad continental shelves. In comparison, narrower continental shelves cause the most severe MTs for fast-moving ADs. [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]

Abstract 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.

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]

On November 12, 2019, an exceptional flood event took place in Venice, second only to the one that occurred on November 4, 1966. The sea level reached a peak value of 1.89 m above the local datum determining the flooding of almost 90% of the pedestrian surface of the historical city. Several processes concurred to raise the water level in Venice and the northern Adriatic Sea on November 12, 2019. Among these, a fast‐moving mesoscale cyclone travelled at about 12 m ·$$ \cdotp $$ s−1$$ {}^{-1} $$ in the northwestward direction over the northern Adriatic Sea, raising the sea levels at the shore in front of the Lagoon of Venice. High‐resolution numerical simulations indicated that atmosphere–ocean resonance occurred on November 12, 2019, generating a meteotsunami‐like wave that contributed significantly to the extreme sea level in Venice. The relative contributions of the wind and air pressure to the peak sea level were also estimated. Additional numerical experiments were performed to prove the occurrence of Proudman resonance and to determine a transfer function of such high‐frequency sea‐level perturbations for the Lagoon of Venice. [ABSTRACT FROM AUTHOR]

We study, for the first time, the physical coupling and detectability of meteotsunamis in the earth's atmosphere. We study the June 13, 2013 event off the US East Coast using Global Navigation Satellite System (GNSS) radio occultation (RO) measurements, Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures, and ground-based GNSS ionospheric total electron content (TEC) observations. Hypothesizing that meteotsunamis also generate gravity waves (GWs), similar to tsunamigenic earthquakes, we use linear GW theory to trace their dynamic coupling in the atmosphere by comparing theory with observations. We find that RO data exhibit distinct stratospheric GW activity at near-field that is captured by SABER data in the mesosphere with increased vertical wavelength. Ground-based GNSS-TEC data also detect a far-field ionospheric response 9 h later, as expected by GW theory. We conclude that RO measurements could increase understanding of meteotsunamis and how they couple with the earth's atmosphere, augmenting ground-based GNSS TEC observations. [ABSTRACT FROM AUTHOR]

The 2022 Hunga Tonga-Hunga Ha'apai eruption generated tsunamis that propagated across the Pacific Ocean. Along the coast of Japan, nearshore amplification led to amplitudes of nearly 1 m at some locations, with varying peak tsunami occurrence times. The leading tsunami wave can generally be reproduced by Lamb waves, which are a type of air-pressure wave generated by an eruption. However, subsequent tsunamis that occurred several hours after the leading wave tended to be larger for unknown reasons. This study performs multi-scale numerical simulations to investigate subsequent tsunami waves in the vicinity of Japan induced by air pressure waves caused by the eruption. The atmospheric pressure field was created using a dispersion relation of atmospheric gravity wave and tuned by physical parameters based on observational records. The tsunami simulations used the adaptive mesh refinement method, incorporating detailed bathymetry and topography to solve the tsunami at various spatial scales. The simulations effectively reproduced the tsunami waveforms observed at numerous coastal locations, and results indicate that the factors contributing to the maximum tsunami amplitude differ by region. In particular, bay resonance plays a major role in determining the maximum amplitude at many sites along the east coast of Japan. However, large tsunami amplification at some west coast locations was not replicated, probably because it was caused by amplification during oceanic wave propagation rather than meteorological factors. These findings enhance our understanding of meteotsunami complexity and help distinguish tsunami amplification factors. [ABSTRACT FROM AUTHOR]

Abstract 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.

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]

Meteorological tsunamis (i.e., tsunami-like waves of atmospheric origin) are regularly observed in the Mediterranean Sea. During a single event, destructive flooding usually occurs in one location or limited area. However, in May 2021 and June 2022, strong meteotsunamis hit several Mediterranean locations up to 500 km apart. In the morning hours of the 24th of May 2021, a meteotsunami hit Bonifacio on the island of Corsica (western Mediterranean, France) and in the afternoon hours of the same day, another meteotsunami hit Široka Bay on the island of Ist (Adriatic Sea, Croatia), 500 km away. About 13 months later, on the 26th of June 2022, a meteotsunami hit Ciutadella on the island of Menorca (Spain) and two days later Bonifacio, 400 km away. Sea-level and atmospheric pressure data and satellite imagery, as well as synoptic conditions, associated with both events were analysed in detail. It has been confirmed that in the Mediterranean, meteotsunamis occur when meteotsunamigenic synoptic conditions prevail over the area, with a strong southwesterly jet stream embedded in dynamically or convectively unstable atmospheric layers standing out as the most important condition. The meteotsunamigenic potential of each of the three bays (Ciutadella, Bonifacio, Široka Bay) was investigated by considering: (1) the potential for Proudman resonance on the shelves offshore of the bays, (2) the orientation of the mouth of the bay and (3) the frequency of meteotsunamigenic synoptic conditions over the area. The strongest and most frequent meteotsunamis occur at locations where the shelf characteristics (width, depth, orientation), bay mouth orientation and climatology of 500-hPa winds and atmospheric stability have characteristics that support the amplification of long-ocean waves and their propagation toward the bay mouth. [ABSTRACT FROM AUTHOR]

Abstract 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. Graphical Abstract

Abstract Meteotsunamis (forced waves) triggered by atmospheric disturbances of Lamb waves due to the 2022 Hunga–Tonga volcanic eruption have been observed in coastal areas surrounding the Pacific Ocean. However, the spatiotemporal evolution of the wavefield of meteotsunamis and meteotsunami-induced free waves remains elusive. Here, we show the detailed spatial distribution of the propagation velocities and directions of these waves in the bathymetric slope area between the Japan Trench and nearshore, using a dense array of 150 absolute pressure gauges deployed at water depths of 100–8000 m. Records show that free wave components (i.e., tsunamis) were generated when the forced wave was propagating over the slope area. Amplitudes of the generated free waves are large in the southern half of the slope area, where the equi-arrival time contour lines are densely paralleled. Such amplifications occur due to the relationship between the incoming direction of Lamb waves and the gradient of the bathymetric slope. This indicates that, if meteotsunamis excited by Lamb waves due to future volcanic eruptions come from different directions to this region, a different spatial pattern of free wave amplification on a regional scale is obtained in the bathymetric slope areas. Graphical Abstract

Employing a linear shallow water equation (LSWE) model in the spherical coordinates, this paper investigates the tsunami waves generated by the atmospheric pressure shock waves due to the explosion of the submarine volcano Hunga Tonga–Hunga Ha'apai on 15 January 2022. Using the selected 59 atmospheric pressure records in the Pacific Ocean, an empirical atmospheric pressure model is first constructed. Applying the atmospheric pressure model and realistic bathymetric data in the LSWE model, tsunami generation and propagation are simulated in the Pacific Ocean. The numerical results show clearly the co‐existence of the leading locked waves, propagating with the speed of the atmospheric pressure waves (∼1,100 km/hr), and the trailing free waves, propagating with long gravity ocean wave celerity (∼750 km/hr). During the event, tsunamis were reported by 41 Deep‐ocean Assessment and Reporting of Tsunamis (DART) buoys in the Pacific Ocean, which require corrections because of the occurrence of atmospheric pressure waves. The numerically simulated tsunami arrival time and the amplitudes of the wave crest and trough of the leading locked waves compare reasonably well with the corrected DART measurements. The comparisons for the trailing waves are less satisfactory, since free waves could also have been generated by other tsunami generation mechanisms, which have not been considered in the present model, and by the scattering of locked waves over changing bathymetry. In this regard, the numerical results show clearly that the deep Tonga trench (∼10 km) amplifies the trailing waves in the Southeast part of the Pacific Ocean via the Proudman resonance condition. Plain Language Summary: On 15 January 2022, the eruption of the submarine volcano Hunga Tonga–Hunga Ha'apai, the largest volcano eruption in recent centuries, produced worldwide atmospheric pressure fluctuations and tsunami waves. In this paper we produced a simple model for atmospheric pressure in the Pacific Ocean based on selected pressure recordings. Based on this pressure model and realistic ocean depth data, we simulate the tsunami generation and propagation in the Pacific Ocean. We found that the explosion shock wave induced by the volcanic eruption is the main mechanism for tsunami generation. Two separate tsunami waves, traveling at different speeds, can be distinguished. Additional tsunami waves are also generated when the pressure wave travels over steep deep ocean features such as the Tonga Trench, leading to significantly larger waves in the Southeast part of the Pacific Ocean. Key Points: Using the measured data, an N‐wave shaped atmospheric pressure model is constructed for the 2022 Tonga eventThe atmospheric pressures generate both locked waves, propagating at the speed of pressure, and trailing free waves with a long wave speedThe trailing free tsunami waves can be as significant as the leading locked tsunami waves, which are amplified by the Proudman resonance [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]

On 15 January 2022, the Tonga-Hunga submarine volcano erupted in the southwest Pacific Ocean and created strong tsunami waves that had a dual generation mechanism: "direct" (caused by the explosion) and "atmospheric" (induced by propagating atmospheric Lamb waves). Trans-oceanic waves spread across the ocean and were clearly recorded in marginal seas of the northwestern Pacific, including the Sea of Japan. The two distinct types of incoming waves produced a variety of effects in the sea as determined by the wave origin, propagation features and local topographic properties. Statistical and spectral properties of the tsunami waves recorded in the Sea of Japan and vicinity, including the adjacent part of the northwestern Pacific, are the main subject of the present study. The Sea of Japan is a semi-isolated basin connected to the Pacific Ocean through several straits. The features of these straits (widths, depths, and geometry) significantly affected the arriving waves, strongly modifying their statistical characteristics and spectral content. As discussed in detail in this paper, the two types of incoming tsunami waves are consequently transformed in substantially different ways. [ABSTRACT FROM AUTHOR]

Low-tidal coastal regions, such as the Baltic Sea, are known to be particularly vulnerable to exceptional high-frequency sea level oscillations such as meteotsunamis. Possibilities of studying sub-hourly sea level variations have recently improved, owing to advancement in temporal resolution of tide gauge observations. In this work, we study high-frequency (period

With the increase of available global observations at a minute resolution, emerging studies of high-frequency sea-level oscillations have already produced climatologies and explored the atmospheric processes driving the related flooding events, in a qualitative manner and/or at a very local scale. In the presented work, however, the global connections between nonseismic sea-level oscillations at tsunami timescales (NSLOTTs) and synoptic patterns are quantified for 307 tide gauge sites around the world. A global index, constructed for each site over the whole data interval as the linear combination of a prescribed set of synoptic variables extracted from the ERA5 atmospheric reanalysis, is correlated with hourly-averaged NSLOTTs. The correlation between this index and the NSLOTT ranges varies between sites but is generally higher at mid-latitudes and particularly in the Mediterranean Sea where correlations reach 0.8. Mid-troposphere wind speed is found to be the best correlated synoptic variable at roughly one third of all sites together with the mid-troposphere relative humidity. Consequently, wave-ducting is believed to be the dominant mechanism for the NSLOTT propagation and longevity. For such conditions, extreme NSLOTT events are accompanied, on average, by a very specific synoptic pattern including mid-troposphere jet streams, low-troposphere thermal fronts and poleward surface cyclones, independently of the hemisphere or the site and despite some differences in intensity. Following this study, in regions with high correlations, various applications of the index - from climate studies to operational forecasts - could lead to a broader understanding of the NSLOTT events around the world.

This paper examined the occurrence and seasonality of meteotsunami in the United Kingdom (UK) to present a revised and updated catalogue of events occurring since 1750. Previous case studies have alluded to a summer prevalence and rarity of this hazard in the UK. We have verified and classified 95 events using a developed set of identification criteria. The results have revealed a prominent seasonal pattern of winter events which are related to mid latitude depressions with precipitating convective weather systems. A geographical pattern has also emerged, highlighting three 'hotspot' areas at the highest risk from meteotsunami. The evidence reviewed, and new data presented here shows that the hazard posed by meteotsunami has been underestimated in the UK. [ABSTRACT FROM AUTHOR]

Meteotsunamis (forced waves) triggered by atmospheric disturbances of Lamb waves due to the 2022 Hunga–Tonga volcanic eruption have been observed in coastal areas surrounding the Pacific Ocean. However, the spatiotemporal evolution of the wavefield of meteotsunamis and meteotsunami-induced free waves remains elusive. Here, we show the detailed spatial distribution of the propagation velocities and directions of these waves in the bathymetric slope area between the Japan Trench and nearshore, using a dense array of 150 absolute pressure gauges deployed at water depths of 100–8000 m. Records show that free wave components (i.e., tsunamis) were generated when the forced wave was propagating over the slope area. Amplitudes of the generated free waves are large in the southern half of the slope area, where the equi-arrival time contour lines are densely paralleled. Such amplifications occur due to the relationship between the incoming direction of Lamb waves and the gradient of the bathymetric slope. This indicates that, if meteotsunamis excited by Lamb waves due to future volcanic eruptions come from different directions to this region, a different spatial pattern of free wave amplification on a regional scale is obtained in the bathymetric slope areas. [ABSTRACT FROM AUTHOR]

Meteotsunamis are both a well‐known and poorly understood phenomenon. In particular, the influence of and disturbance by meteotsunamis on isolated coastal wetlands is largely unknown. This paper documents a case illustrating how water levels in an incipient foredune/swale complex in northern Lake Michigan responded to a meteotsunami event. We identified potential meteotsunami influence on wetland water levels through slope‐break and wavelet analysis, verified the presence of meteotsunami waves at surrounding lake water level gauge stations with wavelet analysis, analyzed both regional and small‐scale meteorological data to establish what source of atmospheric forcing resulted in meteotsunami formation, and used a hydrodynamic model to simulate lake surface response and meteotsunami generation. On 20 July 2019, an atmospheric bore wave propagating away from a convective storm formed a meteotsunami event in Lake Michigan that struck Sand Bay, Beaver Island and generated a 36 cm increase in subsurface wetland water levels over the course of a 1‐hr period. The potential for multiple sources of meteorological forcing and secondary wave refraction highlights several challenges with predicting generation of and effects from meteotsunami events. Additionally, while irregular, the effects of these events on isolated wetland systems have the potential to alter hydrologic and sediment budgets, vegetation growth, and dune stability; yet meteotsunami influence on isolated wetlands is an understudied phenomenon. The event presented in this study make a strong case for focused research on coastal wetland response to meteotsunamis (and meteotsunami‐like events) to address this understudied impact given its implications for coastal processes and resiliency. Plain Language Summary: While scientists are learning more about meteorological tsunamis ("meteotsunamis") so we can predict what causes them and where they might strike, we know less about how meteotsunamis affect wetlands, especially wetlands that aren't directly connected to a body of water ("isolated wetlands"). This is important because wetlands often act as the first line of defense, helping to protect coastlines from wave damage. We looked at how water levels in an isolated wetland on an island in Lake Michigan changed when a meteotsunami impacted the lake and bay near the wetland. We found that weather events that happen offshore can produce meteotsunamis big enough to change wetland water levels. But we still don't fully understand how much water these events bring to the wetland (or how long it stays) which is important to how we manage these wetlands and their ability to protect our coast. Future research needs to move beyond only deadly or destructive meteotsunamis so that we can effectively predict potential causes and hazards of these events and make informed decisions about how to manage coastal wetlands. Key Points: We documented and described hydrologic response to a meteotsunami event in an isolated wetlandAtmospheric bores may lead to meteotsunamis that are remote of the convective forcingThe observed response to meteotsunami influence highlights the need for further research into this previously undocumented phenomenon [ABSTRACT FROM AUTHOR]

A traveling air pressure disturbance of several hPa over a short period (5–10 min) can generate tsunami-like waves in coastal areas owing to a multi-resonant mechanism. In recent years, pressure-forced meteotsunamis have been regularly reported over the Korean Peninsula. However, the Korean meteotsunami early warning system does not always provide sufficient lead time. The early warning system comprises two-segmented zones for tracking the intensity and propagation of air pressure disturbances via 89 meteorological stations in the precaution (offshore islands) and warning zones (coastline and inland areas). To address the lead time problem in the current observation-based monitoring system, we used an atmospheric model with a horizontal resolution of 1.5 km, the Korea Meteorological Administration's local data assimilation and prediction system (LDAPS). The ability of the LDAPS to detect air pressure disturbances was tested for a widespread and destructive meteotsunami event that occurred on March 4, 2018. The detection capability of significant air pressure disturbances (>1.5 hPa/10 min) was 67% in the precaution zone, and the propagation pattern (direction, speed, and spatial scale) was reasonably consistent with the monitoring results. Based on LDAPS prediction and the established observation-based monitoring system, monitoring operators can determine the potential meteotsunami risk from the open Yellow Sea beyond the observation system with sufficient lead time. This case study contributes to developing observation- and atmospheric model-based early warning systems for meteotsunami mitigation. An early warning of tsunamigenic disturbances in the Korean Peninsula is expected to be provided with the LDAPS-based modeling system using a high-resolution atmosphere-ocean coupled model shortly.

A number of observations and theoretical researches have proved that fast moving atmospheric pressure disturbances can excite large tsunami-like water waves in the coastal regions. The oscillation can become more intense inside harbors or bays due to multi-resonant mechanisms. This study mainly focuses on the impact of the disturbance heading direction on water oscillations inside a harbor. A series of cases have been numerically investigated to reveal the significance of the heading direction and the influence of other characteristic parameters. Results show that the harbor oscillation is very sensitive to the disturbance heading direction. The water response is rather intense when the disturbance moves along the coastline. In this situation, notable edge wave trains are excited nearshore and may induce significant resonance if the edge wave frequency is close to one of the eigen frequencies of the harbor. Generally, the response intensity drops with the increase in the angle between the disturbance trajectory and coastline. Meanwhile, the disturbances moving landward usually generate larger water oscillations than the seaward situations. It should be noticed that the most threatening water elevation appears when the disturbance skims over the harbor with a small angle to the coastline landward. [ABSTRACT FROM AUTHOR]

Numerical simulations were generated using a nonlinear shallow-water model of velocity potential to study the fundamental processes of tsunami generation and amplification by atmospheric pressure waves. When an atmospheric pressure wave catches up with an existing tsunami that is propagating as a free wave over an abrupt change in water depth, the amplified tsunami propagates in the shallower water. An existing tsunami propagating as a free wave over a sloping seabed is also amplified by being passed by atmospheric pressure waves. When atmospheric pressure waves travel over an abrupt change in water depth, the water surface profile of tsunamis in the shallower water depends on both the interval of the atmospheric pressure waves and the phase of the tsunami-generation process over the change in water depth. Moreover, when atmospheric pressure waves travel over an abrupt change in water depth, the tsunami amplitude in the shallower water increases, as the water depth of the shallower area is decreased and the Proudman resonance is further reduced. When an atmospheric pressure wave train with positive pressure travels over a sloping seabed, the amplification of tsunami crests propagating as free waves is controlled by leaving the forced water waves following the atmospheric pressure waves. Conversely, the amplitudes of tsunami troughs propagating as free waves increase. [ABSTRACT FROM AUTHOR]

In the frame of the Interreg Italy-Croatia program, the EU has funded the PMO-GATE project, focusing on the prevention and mitigation of the socioeconomic impact of natural hazards in the Adriatic region. The Database of Adriatic Tsunamis and Meteotsunamis (DAMT) is one of the deliverables of this project. DAMT is a collection of data documenting both meteotsunami and tsunami effects along the Eastern and Western Adriatic coasts, and it was realized by starting from the available database and catalogues, with the inclusion of new data gained from recent studies, newspapers and websites. For each tsunami and meteotsunami, the database provides an overview of the event and a detailed description of the effects observed at each affected location and gives a picture of the geographical distribution of the effects. The database can be accessed through a GIS WebApp, which allows the user to visualize the georeferenced information on a map. The DAMT WebApp includes three layers: (1) Adriatic Tsunami Sources, (2) Adriatic Tsunami Observation Points and (3) Adriatic Meteotsunamis Observation Points. The database contains 57 observations of tsunami effects related to 27 tsunamis along the Italian, Croatian, Montenegrin and Albanian coasts and 102 observations of meteotsunami effects related to 33 meteotsunamis. [ABSTRACT FROM AUTHOR]

• Analyzed atmospheric and tide gauge data of hurricane leslie to study the combined effects of storm surge and meteotsunami. • Proposed a new numerical scheme combining storm surge and meteotsunami. • Identified the origin of the tsunami-like waves near leixões (north of Portugal) through numerical simulations. In recent years, Portugal's coastal regions have experienced an increase in the frequency and intensity of severe weather events, including tropical cyclones and extratropical storms. This paper presents an analysis of Hurricane Leslie(2018)'s impact on Portugal, with a specific focus on the complex and often underestimated meteotsunami phenomena accompanying the storm system. Our analysis examines data collected from multiple sources, and employs advanced numerical simulations, integrated within the GeoClaw framework. These simulations encompass both storm surge and meteotsunami effects. One of the findings is the significant role played by meteotsunamis in amplifying coastal sea levels during extreme weather events. The observed sea-level fluctuations closely align with the combined surge-meteotsunami simulations, emphasizing the importance of considering these high-frequency phenomena in coastal hazard assessments. [ABSTRACT FROM AUTHOR]

From 18 January 2013 (175.16 m a.s.l.) to 8 September 2020 (177.82 m a.s.l.), Lake Michigan experienced its fastest and highest rise (2.67 m) since 1860, when instrumental measurements began. Extensive foredunes developed since the last high lake levels began eroding in 1997 at fast rates. This study focuses on coastal morphodynamics along the 800 m coast within the central Indiana Dunes State Park on Lake Michigan's southern shores during this time. Severe foredune erosion, in terms of total horizontal dune loss and total volume of eroded sand, occurred unevenly over the three-year period, both temporally, during a single storm, a season, a year, or three years, and spatially, in the eastern, central, and western study areas. Late autumn storms accounted for most foredune erosion in 2018 and 2019, when foredune scarps retreated up to 4 and 9 m, respectively. Erosion was highest in the updrift eastern study area, where about 8 m3/m of sand was removed in 2018 and about 19 m3/m of sand was removed in 2019. The lack of shelf ice along the shore, rising lake levels, and convective storms that triggered meteotsunamis changed the foredune erosion pattern in 2020. Erosion became most vigorous in the downdrift central (13 m scarp retreat) and western (11 m scarp retreat) study areas. The average volume of eroded sand (21.5 m3/m) was more than double that of 2019 (8 m3/m), and almost quadruple the 2018 volume (5.5 m3/m). After foredune erosion events, the beach rapidly recovered and maintained its width as the shoreline migrated landward. On many occasions following these severe erosion events the dry portion of the beach aggraded and absorbed significant sand amounts removed from the foredunes. The remaining sand was transferred to the surf zone, where it changed the sand bar morphology and led to their coalescence and flattening. [ABSTRACT FROM AUTHOR]

This study aims to use a fully realistic high-resolution mesoscale atmospheric and wave model to reproduce met-ocean conditions during a meteotsunami in the Persian Gulf. The atmospheric simulations were performed with the Weather and Research Forecasting (WRF) model by varying planetary boundary layer, microphysics, cumulus, and radiations parameterizations. The atmospheric results were compared to the meteorological observations (e.g., air pressure and wind speed) from the coastal and island synoptic and buoy stations of the nearest area to the meteotsunami event. The results show that using Mellor-Yamada-Nakanishi-Niino (MYNN) scheme for planetary boundary and surface layer had the best performance for stations over the water, whereas applying Mellor-Yamada-Janjic scheme for planetary boundary and Eta similarity surface layer had the best performance for stations over the land. For wave simulations, the WAVEWATCH-III model was employed with the well-known WAM-Cycle4 formulation and a more recent ST6 package. Six WRF experiments and ERA5 wind data were used to force the wave models. The new error parameter was introduced to identify the optimum wind data for wave simulation. EXP4 configuration which uses the MYNN scheme for planetary boundary and surface layer was led to minimum error, while ERA5 severely underestimated Hs and Tp parameters. For the first time, the Gaussian Quadrature Method (GQM) was implemented in the WAVEWATCH-III model and combined with a depth scale to be used in the Persian Gulf. This method is more accurate for non-linear wave-wave interaction than the default Discrete Interaction Approximation (DIA) method. Lower coefficients for dissipation term were required for GQM and the resulted bulk wave parameters were improved compared to the DIA method. The calibrated ST6 formulation with GQM resulted in a more realistic prediction of wave spectrum than the default settings of the WAVEWATCH-III.

Although relatively rare, meteotsunamis are capable of causing coastal infrastructure damage and casualties. Analyses of water level and meteorological data in the U.S. show that meteotsunamis occur more frequently than expected, and therefore, it is important to include meteotsunami assessment in coastal hazard mitigation efforts. In this study, we conducted numerical experiments to investigate the generation and propagation of meteotsunami waves and assessed hazards on a broad scale in the northeastern Gulf of Mexico (GOM). The numerical experiments used a simple 2D depth-averaged hydrostatic shallow water model forced by an idealized atmospheric pressure disturbance on a set of trajectories and directions (1260 runs) covering the whole Florida GOM shelf. Results show that bathymetry pattern has control over the direction of major meteotsunami waves and that forward speed has more influence on maximum water level than the trajectory location. Maximum water level anomaly tracking and Proudman length analysis both demonstrate that Florida's wide and long straight continental shelf in the northeastern GOM is favorable for producing large meteotsunamis. Statistical analysis indicates that pressure disturbances coming from southwest–west direction result in higher water level near south Florida region, while east direction in the Florida panhandle region. The forward speed distribution shows that 20–25 m/s have the most potential. These results can help identify vulnerable coastal regions and pressure disturbance scenarios that most likely generate higher meteotsunami waves. [ABSTRACT FROM AUTHOR]

Meteotsunamis pose a unique threat to coastal communities and often lead to damage of coastal infrastructure, deluge of nearby property, and loss of life and injury. The Great Lakes are a known hot-spot of meteotsunami activity and serve as an important region for investigation of essential hydrodynamic processes and model forecast requirements in meteotsunami-induced coastal flooding. For this work, we developed an advanced hydrodynamic model and evaluate key model attributes and dynamic processes, including: (1) coastal model grid resolution and wetting and drying process in low-lying zones, (2) coastal infrastructure, including breakwaters and associated submerging and overtopping processes, (3) annual/seasonal (ambient) water level change, and (4) wind wave-current coupling. Numerical experiments are designed to evaluate the importance of these attributes to meteotsunami modeling, including a "representative storm" scenario in the context of regional climate change in which a meteotsunami wave is generated under high ambient lake-level conditions with a preferable wind direction and speed for wind-wave growth. Results demonstrate that accurate representation of coastal topography and fully resolving associated hydrodynamic processes are critical to forecasting the realistic hazards associated with meteotsunami events. As most of existing coastal forecast systems generally do not resolve many of these features due to insufficient model grid resolution or lack of essential model attributes, this work shows that calibrating or assessing existing forecast models against coastal water level gauges alone may result in underestimating the meteotsunami hazard, particularly when gauging stations are sparse and located behind harbor breakwaters or inside estuaries, which represent dampened or otherwise unrepresentative pictures of meteotsunami intensity. This work is the first hydrodynamic modeling of meteotsunami-induced coastal flooding for the Great Lakes, and serves as a template to guide where resources may be most beneficial in forecast system development and implementation. [ABSTRACT FROM AUTHOR]

Due to a lack of suitable coupled atmosphere‐ocean modeling tools, the atmospheric source mechanisms that trigger the potentially destructive meteotsunami waves – which occur with periods ranging from a few minutes to a few hours – have remained partially unexplored until recently. In this process‐oriented numerical work we therefore investigate and quantify the impacts of orography and extreme climate changes on the generation and propagation of the atmospheric pressure disturbances that occurred during six different historical meteotsunami events in the Adriatic Sea. In addition, the impact of bathymetry, and hence Proudman resonance, on the propagation of the meteotsunami waves is investigated for the same ensemble of events. Our main findings can be summarized as follows: (a) Removing the mountains does not have a strong effect on either the generation or propagation of the meteotsunamigenic disturbances but may slightly increase their intensity, especially over land; (b) Extreme climate warming has the potential to increase the intensity of both atmospheric disturbances and meteotsunami waves near sensitive coastal areas; while (c) Flattening the bathymetry of the deepest Adriatic Sea tends to deflect the meteotsunami waves away from sensitive harbor locations. Such sensitivity studies, if generalized to other geographic locations with a higher number of events, may provide new insights into the still unknown physics of meteotsunami generation. Plain Language Summary: Among extreme sea‐level hazards, meteotsunami waves – which occur at periods from a few minutes to a few hours – remain the least studied due to a lack of suitable high‐resolution coupled atmosphere‐ocean modeling tools. Consequently, neither the impact of orography and bathymetry on meteotsunamigenic disturbances and meteotsunami waves nor their characteristics in a projected future climate have been properly quantified. In this process‐oriented numerical work we analyze these impacts using sensitivity experiments for six different meteotsunami events in the Adriatic Sea. We found that meteotsunamigenic disturbances are not strongly modulated by the orography which can reinforced their intensity, but could be significantly increased under extreme climate warming. In addition, flattening the bathymetry of the deepest ocean parts tends to deflect the meteotsunami waves away from the sensitive harbor locations. Because meteotsunami events have the potential to cause substantial human and structural damage worldwide, this type of studies may be critical to better understand their key physical processes. Key Points: Sensitivity of meteotsunami generation and propagation to some environmental conditions is quantified in the Adriatic SeaRemoving mountains has little impact on meteotsunamis while flattening the bathymetry diverts them from the coastsExtreme climate warming could increase the meteotsunami wave intensities along the most sensitive Adriatic coastal areas [ABSTRACT FROM AUTHOR]

This study reports an ocean‐bottom pressure gauge (OBP) network, S‐net, which captured meteotsunamis with amplitudes as small as a few cm, and investigates its validity and limitation for meteotsunami research studies through data analyses and numerical simulations. On July 1, 2020, S‐net recorded tsunami‐like signals, although no earthquake was reported. These waves, propagating northward with a velocity of ∼110 m/s, were explained by an atmospheric low pressure with a maximum amplitude of −0.5 ± 0.1 hPa moving northeastward at a speed of 45–50 m/s. The maximum amplitudes of the sea‐surface height during the low‐pressure passing were up to twice larger than those directly converted from the ocean‐bottom pressure without considering the effect of the atmospheric pressure. Our results suggest that the S‐net with numerical simulations can detect the generation and propagation of meteotsunamis, which could not be achieved in the past when dense OBP networks were not available. Plain Language Summary: Recent developments in deep‐ocean tsunami observation networks using ocean‐bottom pressure gauge sensors have been remarkable, which have an advantage of continuously monitoring the ocean. On July 1, 2020, a deep‐ocean observation network off eastern Japan, S‐net, recorded small tsunami‐like ocean waves. Although tsunamis are often excited by earthquakes, no earthquake was reported at that time. We investigated the observed feature of these waves, which suggests that the waves were meteorological tsunamis, or meteotsunamis, originating from an atmospheric pressure disturbance. To investigate the behavior of these waves in detail, we conducted numerical meteotsunami simulations. The maximum amplitudes of the sea‐surface height during the atmospheric low‐pressure passing were up to twice larger than those expected from the observed seafloor pressure change without considering the contribution of the atmospheric pressure disturbance. We demonstrated that analyzing the data from the wide and dense array of S‐net made it possible to understand the behavior of the meteotsunamis in detail, which could not be achieved in the past when only a few pressure gauges were available. The S‐net's continuous monitoring of the seafloor pressure in the deep ocean will contribute to deepening our understanding of oceanography and meteorology. Key Points: Deep‐ocean pressure gauge array observation off NE Japan detected nonseismic tsunami‐like pressure signals with amplitudes of several hPaA numerical simulation revealed that the signals were meteotsunamis related to a northeastward‐moving atmospheric low pressureIt is necessary to consider the effects of the atmospheric pressure to appropriately estimate sea‐surface height from seafloor pressure gauge [ABSTRACT FROM AUTHOR]

High-frequency (HF) surface-wave (SW) radar systems have demonstrated their capability to capture the signals from seismic and non-seismic tsunami events using the estimation of surface current changes. Several ocean radar systems, operating in the upper HF band, were already optimized for tsunami alerting and installed for real-time tsunami monitoring at the coast. If the shelf extends tens of kilometers off the coast then the first appearance of tsunami waves can be monitored at the shelf quite early. On May 25, 2018, an HF SW phased-array radar system, operating in the lower HF band (6.9 MHz), detected strong changes in measured radial currents at distances up to 60 km off the coast. The system tracked the tsunami-like current pattern in the Bight of Benin. The wave propagation coincided with an atmospheric cold front passage. No earthquake occurred at that time but a strong atmospheric disturbance was present and it is the most likely reason for the detected disturbance. This localized event could be classified as a meteorological tsunami (meteotsunami). It is important to note that this is the very first detection of meteotsunami in the whole West African region. This detection showed the capability of the radar to measure unusual surface current velocities induced by tsunami waves using the lower part of the HF band. The detection of this tsunami-like event has shown good applicability of HF phased-array radar technology for offshore tsunami monitoring and providing safe navigation, in real-time. At the same time, it has been shown that a single HF SW radar system, originally optimized for vessel tracking at very long ranges using a proper output power, transmitter's noise optimization and integration time, can also be utilized as a component of Tsunami early warning systems (TEWS).

Although most tsunamis are generated by the sea‐bottom deformation caused by earthquakes, some tsunamis are excited by sea‐surface pressure changes. This study theoretically investigated tsunamis generated by sea‐surface pressure changes and derived the solutions in three‐dimensional (3‐D) space, whereas most past studies employed two‐dimensional equations. Using the solutions, we simulated and visualized tsunami generation by a growing pressure change. Negative pressure change made the sea surface uplifted inside the source region and negative leading waves were radiated from the source region. We also simulated the tsunami generation when the pressure change at the sea surface moves at almost the same speed as the tsunami propagation speed. The tsunami height increased with increasing travel distance, including the dispersion effects. The 3‐D solutions in this study, including vertical velocity distribution, indicate that both tsunami height and sea‐surface pressure changes contribute to ocean‐bottom pressure changes, suggesting the difficulty in measuring tsunami height with ocean‐bottom pressure observations. When the pressure change source was characterized by short‐wavelength components, the dispersion sometimes possibly increased the tsunami height more extensively than the nondispersive tsunamis. The 3‐D solutions are necessary for describing tsunami generation where the long‐wave approximations are not applicable in open oceans. Plain Language Summary: Although most tsunamis are generated by giant earthquakes, some tsunamis are excited by meteorological phenomena such as storms and moving convective system. These are known as meteorological tsunamis or meteotsunamis. Most studies employ two‐dimensional equations for modeling meteorological tsunamis. This is mainly because past studies used coastal records that cannot directly observe tsunami generation. However, recent tsunami sensors have enabled us to capture the tsunamis in open oceans and we expect that they can help us directly observe their generation. In order to fully investigate the generation process including vertical water flow, the theory needs to be formulated in three‐dimensional (3‐D) space. This study theoretically formulates meteorological tsunamis in 3‐D space. We derive new solutions that can theoretically visualize tsunami generation and growth processes. The solutions also predict the pressure changes at the sea bottom during the generation process, which are observable by recent tsunami observation networks. Key Points: Three‐dimensional solutions describing tsunami generation due to sea‐surface pressure change are derivedThe solutions can simulate ocean‐bottom pressure changes during the generation that are detectable by recent open‐ocean array observationsShort‐wavelength dispersive tsunamis can be enlarged more by a moving pressure change source, compared with long‐wavelength tsunamis [ABSTRACT FROM AUTHOR]

This study documents the atmospheric system driving the observed meteotsunami waves that hit the northern Persian Gulf on 19 March 2017 during high tide. This destructive meteotsunami event resulted in coastal inundations that reached several hundred metres inland along the 100-km coastline between the cities of Dayyer and Asaluyeh and caused the death or injury of 27 persons. Based on previously published research, eyewitness reports, oceanic and atmospheric observations, including synoptic station and weather radar data, and available reanalysis ERA5 products, this study provides new insights into destructive events, particularly mesoscale atmospheric systems conjoined with observed meteotsunami waves. Precipitation intensity, maximum reflectivity and echo top height images provided by the weather radar covering the affected area and the area over which the meteotsunamigenic disturbance travelled revealed that a strong convective system that encompassed the mid- and upper troposphere entered the northern Persian Gulf approximately 4 h before the event and moved eastward. Two hours before reaching the affected coastline, this convective system was reshaped to an elongated and narrow squall line varying between 70 and 130 km in length with a width of less than 10 km and travelled at an average speed of approximately 24 m/s over the sea. The peak maximum reflectivity of the squall line always surpassed 40 dBZ, while it increased to 60 dBZ near the Dayyer area. As such, intense atmospheric disturbances are known to be associated with sharp air pressure increases, and these disturbances were found to resonantly pump energy to the ocean through Proudman resonance for over 12 or more disturbance wavelengths (i.e. up to 120 km in this study). A half-metre meteotsunami wave was presumably created in the open sea and then amplified while travelling towards the shore where it broke as a meteotsunami bore and inundated the coastal areas. Further research on the physical mechanisms driving the interactions between meteotsunamigenic disturbances and ocean responses, the recurrence of such events and meteotsunami hazard assessments along the affected coastline is envisaged. [ABSTRACT FROM AUTHOR]

The pioneering work done in late 1970s and early 1980s on research into rissaga events or meteotsunamis in the Balearic Islands is briefly reviewed in this paper and contrasted with the present state of the art on the phenomenon. The early research phase used existing observational evidence to construct a doctrine for the initial comprehension and forecasting of the phenomenon. By the beginning of the 1980s, it had already been established that the rissaga is a marine response to quick atmospheric pressure oscillations in resonance conditions, initially attributed exclusively to internal atmospheric gravity waves and later to convective pressure jumps too. Forty years later, new observational methods have provided a much richer database, with theoretical research and the use of forecasts using numerical models underpinning a much more solid perspective. With regard to predictability, quick atmospheric pressure oscillations were associated with a three-layer atmospheric vertical structure from the beginning: a thermodynamically neutral lower layer of Mediterranean air, a thermal inversion layer (Saharan air lying above and Mediterranean air below) and a deep upper layer with conditional instability in at least some strata. This structure is compatible with a high-level trough or cut-off low over the Iberian Peninsula; strong south-westerly flow over the Western Mediterranean area; jet stream speed being reached at the highest tropospheric levels, and forced Saharan air advection at the low/medium levels. A weak low-pressure area is usually present at low levels in the Mediterranean. The identification of the meteorological framework favourable to a rissaga event soon led to a probabilistic and purely meteorological forecasting method for the rissaga phenomenon. This method is still used today, albeit in combination with objective methods, some of which are based on the use of coupled atmospheric and oceanic forecasting models. [ABSTRACT FROM AUTHOR]

In June 2014, a number of meteotsunamis were detected in the Mediterranean and Black Sea area. These meteotsunamis were initiated by a unique high-altitude dynamical system which was initially originated above Spain and traveled across the Mediterranean Sea towards Black Sea and Turkey. Meteotsunamis unlike tsunamis driven by strong earthquakes are local events, and their formation has different mechanism. Atmospheric internal gravity waves (IGWs) are one of the main known sources of meteotsunamis (e.g. Vilibić et al. in Pure Appl Geophys 165:2169–2195, 2008). The synoptic system produced short-lived and small-scale atmospheric pressure perturbations which drifted with the jet stream-like bubbles and generated tsunami-like waves in the open waters. The bubbles with typical dimensions 15–60 km continuously form and collapse in the atmosphere at altitudes of 3–6 km. Such a "boiled" atmosphere generated IGWs propagating both downward, where they produced meteotsunamis (presumably under Proudman resonance condition) and upward into the ionosphere, with following dissipation and excitation of plasma density perturbations. One of the few experimental techniques, which can monitor perturbations of the ionization within the lower ionosphere, uses long-wave probing by very low and low frequency (VLF/LF) radio signals. To study the ionospheric disturbances observed during the chain of meteotsunamis affecting the Mediterranean Sea, we used VLF/LF data collected in South Europe by "The International Network for Frontier Research on Earthquake Precursors". By applying the spectral analysis method to the anomalous VLF/LF signals, it was found that revealed periods of the signal variations were from 10 to 40–70 min in different stations, which are in the range of the atmospheric pressure oscillations and the meteotsunami events. These periods also correspond to the periods of IGWs. [ABSTRACT FROM AUTHOR]

Meteotsunamis are long waves generated by displacement of a water body due to atmospheric pressure disturbances that have similar spatial and temporal characteristics to landslide tsunamis. NAMI DANCE that solves the nonlinear shallow water equations is a widely used numerical model to simulate tsunami waves generated by seismic origin. Several validation studies showed that it is highly capable of representing the generation, propagation and nearshore amplification processes of tsunami waves, including inundation at complex topography and basin resonance. The new module of NAMI DANCE that uses the atmospheric pressure and wind forcing as the other inputs to simulate meteotsunami events is developed. In this paper, the analytical solution for the generation of ocean waves due to the propagating atmospheric pressure disturbance is obtained. The new version of the code called NAMI DANCE SUITE is validated by comparing its results with those from analytical solutions on the flat bathymetry. It is also shown that the governing equations for long wave generation by atmospheric pressure disturbances in narrow bays and channels can be written similar to the 1D case studied for tsunami generation and how it is integrated into the numerical model. The analytical solution of the linear shallow water model is defined, and results are compared with numerical solutions. A rectangular shaped flat bathymetry is used as the test domain to model the generation and propagation of ocean waves and the development of Proudman resonance due to moving atmospheric pressure disturbances. The simulation results with different ratios of pressure speed to ocean wave speed (Froude numbers) considering sub-critical, critical and super-critical conditions are presented. Fairly well agreements between analytical solutions and numerical solutions are obtained. Additionally, basins with triangular (lateral) and stepwise shelf (longitudinal) cross sections on different slopes are tested. The amplitudes of generated waves at different time steps in each simulation are presented with discussions considering the channel characteristics. These simulations present the capability of NAMI DANCE SUITE to model the effects of bathymetric conditions such as shelf slope and local bathymetry on wave amplification due to moving atmospheric pressure disturbances. [ABSTRACT FROM AUTHOR]

Meteotsunamis are created by transitory weather disturbances moving over water, have a long history of impacting the United States (U.S.) and have resulted in loss of life and property. Many of these events have been historically mischaracterized as seiches, anomalous weather-related waves, or ignored altogether. In this paper, we review meteotsunami generation mechanisms common in the U.S. and highlight several classic historical cases of U.S. meteotsunami formation and impact. We then describe recent advances in sensing and understanding that led to the establishment of initial, rudimentary alerting capabilities for the U.S. Great Lakes and U.S. East Coast. Finally, we describe the major challenges and gaps that must be overcome to move the U.S. toward a comprehensive meteotsunami forecast and warning capability. We also discuss how we envision the various relevant offices of the national oceanic and atmospheric administration (NOAA) working together to achieve this vision. These offices include the NOAA research laboratories, national weather service (NWS) Weather Forecast Offices and National Centers, National Ocean Service Center for Operational Oceanographic Products and Services and NWS Tsunami Warning Centers. [ABSTRACT FROM AUTHOR]

Two hazardous typhoons, Lionrock (August 2016) and Jebi (September 2018), destructively affected the coast of Japan and produced extreme sea level variations. The results of field surveys in the impacted regions showed that multiple deaths and extensive floods were caused by the combined effect of low-frequency sea level raise (storm surges) and intensive high-frequency (HF) tsunami-like waves (meteotsunamis). The data from ten tide gauges for the 2016 event and eight gauges for the 2018 event were used to examine the properties of the observed sea levels, to estimate the relative contribution of the two sea level components and to evaluate their statistical characteristics (maximum wave heights, amplitudes and periods of individual components, etc.). For the 2016 event, we found that the surge heights were from 12 to 35 cm and that the mean contribution of surges into the total observed sea level heights was ~ 39%; the meteotsunami amplitudes were from 22 to 92 cm, and they contributed 61% of the total height. For the 2018 event, storm surges were significantly stronger, from 46 to 170 cm, while HF amplitudes were from 38 to 130 cm; their relative inputs were 67% and 33%, respectively. Combined, they formed total flood heights of up to 120 cm (2016 event) and 288 cm (2018 event). Previously, the contribution of storm seiches (meteotsunamis) in coastal floods had been underestimated, but results of the present study demonstrate that they can play the principal role. What is even more important, they produce devastating currents: according to our estimates, current speeds were up to 3 knots (1.5 m/s) during the Lionrock event and more than 5 knots (2.6 m/s) during Jebi; these strong currents appear to be the main reason for the resulting damage of coastal infrastructure. The most important characteristic of the recorded meteotsunamis is their trough-to-crest maximum height. During the 2016 event, these heights at three stations were > 1 m: 171 cm at Erimo, 109 cm at Hachijojima and 102 cm at Ayukawa. The 2018 event was stronger; maximum meteotsunami wave heights were 257 cm at Gobo, 138 cm at Kushimoto, 137 cm at Kumano and 128 cm at Murotomisaki. The 2018 Gobo height of 257 cm is much larger than historical non-seismic seiche maxima for the Pacific coast of Japan (140–169 cm) estimated by Nakano and Unoki (1962) for the period of 1930–1956. [ABSTRACT FROM AUTHOR]

A modeling study has been conducted to simulate the June 13, 2013 U.S. East Coast meteotsunami event as a test of the model forecast concept. A numerical simulation based on the MOST (Method of Splitting Tsunami) model was employed for the meteotsunami propagation forecast, while the weather radar reflection imagery was used to simulate real-time input data for the atmospheric pressure-induced tsunami generation. The model tsunami was generated by a moving pressure field during 2.87 h of forcing, and the resultant tsunami was then simulated for additional 5.68 h of propagation without any forcing for a total of 8.55 h of meteotsunami evolution from generation to coastal impact. Simulated time series were compared with the measurements from sea-level coastal gages and the Deep-ocean Assessment and Reporting for Tsunami (DART) data. The model is able to reproduce in general the recorded sea-level changes in the deep ocean and at the coast in terms of arrival times and amplitudes. The model was able to predict coastal tsunami impacts that occurred from one to two hours after the model data assimilation phase ended. Therefore, this approach shows promise for developing meteotsunami model forecast capability based on measurements and data assimilation in real time, at least for meteotsunamis generated by fast-moving weather systems visible on radar reflection imagery. All the data used in this study are already available in real time, the MOST model is already implemented as a seismically generated tsunami forecast model at the Tsunami Warning Centers (TWCs), which makes transition of potential meteotsunami forecast capability to warning operations straightforward. [ABSTRACT FROM AUTHOR]

On 6 and 7 July 2010, uncommon sea waves were observed along the coast of Portugal. The Portuguese tide gauge network recorded the sea-level signals showing tsunami-like waves of heights varying from 0.14 to 0.6 m (crest-to-trough) and of periods in the range of 30 to 60 min. Analysis of both oceanic and atmospheric data revealed the occurrence of a meteotsunami in the night of July 6th that propagated from Lagos, south, up to Viana, north. Here, we present the first investigation of the 2010 meteotsunami that struck the coast of Portugal. We use the atmospheric pressure data to force the sea surface and numerically generate the 2010 meteotsunami. We then simulate the 2010 meteotsunami propagation over high-resolution bathymetric models using a validated nonlinear shallow water code. The comparison of the simulated waveforms with the records shows satisfactory agreement of wave heights and periods in most stations. Taking the 2010 event as a reference of meteotsunamis along the Portuguese coast, we further provide an insight into the meteotsunami hazard posed by events propagating from south to north of the country. This is done by considering a 2D Gaussian-shape pressure disturbance that propagates along the shelf under varying conditions of speed and incident angle. This allows identifying "hot spots" on the coast of Portugal where the focus of meteotsunami energy is favourable. Our results suggest that meteotsunamis present a real threat on the highly occupied Portuguese coast and therefore should be considered in tsunami hazard and forecasting strategies of the NE Atlantic countries. [ABSTRACT FROM AUTHOR]

Meteotsunamis (localized ocean waves with periods similar to those of tsunamis but caused by meteorological phenomena) have been observed around the globe and are frequently observed in the Adriatic Sea. Numerous studies have focused on numerical modeling of meteotsunamis, but only a few have modeled flooding and drying of the coastal areas that play an important role in risk assessment. In this study, we model four historic meteotsunami events (Vela Luka Bay, June 21, 1978; Široka Bay, August 22, 2007; Mali Lošinj Bay August 15, 2008; Stari Grad Bay February 19, 2010) that occurred in the Adriatic Sea, using ADICRC, a flooding and drying capable ocean numerical model. Comparison of those results with similar simulations that do not use the flooding and drying algorithm was made to determine differences in modeled wave height. Three of the modeled events (Vela Luka, Široka and Mali Lošinj) are more accurately depicted if including the flooding and drying algorithm, suggesting that extreme events can be more realistically modeled than with the more commonly used cut-off depth (i.e., specifying minimum depth larger than expected maximum wave height). Modeling results for the fourth event (Stari Grad) confirm a previous assumption that flooding occurred due to the superposition of a storm surge and a meteotsunami, rather than a meteotsunami alone. [ABSTRACT FROM AUTHOR]

We examine the physical processes that led to the meteotsunami observed along the English Channel and North Sea coasts on 29 May 2017. It was most notably reported along the Dutch coast, but also observed on tide gauges from the Channel Islands to the coast of Germany, and also those in eastern England. From an assessment of multiple observations, including rain radar, LIDAR, satellite, surface observations and radiosonde reports we conclude that the event was driven by a rear flank downdraft in association with a mesoscale convective system (MCS). This downdraft, from a medium level or elevated MCS, led to a hydrostatically forced internal or ducted gravity wave below the MCS. The gravity wave was manifested by a marked rise and fall in pressure, a meso-high, which then interacted with the sea surface through Proudman resonance causing a measured wave of close to 0.9 m in amplitude, and an estimated wave run-up on Dutch beaches of 2 m. Through examination of existing research, we show that the basic assumptions here relating to the formation of the Dutch meteotsunami are consistent with previously described physical processes, and confirm the correlation between the speed of the ocean wave and medium level steering winds. This raises the possibility that high-resolution, coupled, weather-ocean numerical weather prediction (NWP) models can be utilised to predict future events. However, deterministic high-resolution NWP models still struggle with modelling convective systems with sufficient precision because of the chaotic nature of the atmosphere and incomplete observations. A way forward is proposed here to improve forecasting through post-processing of NWP model output by overlaying medium level wind fields with ocean bathymetry. [ABSTRACT FROM AUTHOR]

The paper presents sea level and air pressure observations acquired during the 2007 experiment carried out along the southwestern coast of Sicily. The experiment aimed to quantify the atmospheric and oceanic conditions related with the phenomenon of marrobbio, a kind of meteotsunami that is frequently observed in the Strait of Sicily. Sea level data measured at surrounding tide gauges, radio-sounding atmospheric profiles and ERA5 reanalysis data conjoined the analysis. Rapid air pressure and sea level oscillations were measured simultaneously during marrobbio events, while the atmospheric disturbances were estimated to propagate mostly towards east-northeast with a predominant speed of 19–24 m/s. The observed propagation direction and speed were found conducive for generation of long ocean waves through Proudman resonance over a wide outer shelf, although a complex bathymetry in front of affected area may strongly modify the generation. The atmospheric patterns were favourable for wave ducting mechanism during most of the observed marrobbio events. A need for establishing long-term high-frequency observations at marrobbio hot spots, as well to apply high-resolution atmospheric and oceanic models for proper quantification of meteotsunamis, is emphasized. [ABSTRACT FROM AUTHOR]