Proudman Resonance Research Articles

Meteotsunami Impact in Indonesia Due to the Shockwave of the Hunga Tonga Volcanic Eruption on January 15, 2022

This paper presents the impact of a meteotsunami resulting from the shockwave of the underwater volcanic eruption of Hunga Tonga­–Hunga Ha'apai (HTHH) on January 15, 2022.The tsunami was detected in various locations in Indonesia through a network of water level sensors monitored by the Meteorology, Climatology, and Geophysics Agency (BMKG). The tsunami wave heights varied significantly and exhibited a non-linear relationship with the distance from the volcano. The heights of detected tsunami ranged from 2.8 to 22.6 cm, with the highest recorded at the water level sensor south of Java Island. The heights of waves are believed influenced by Proudman resonance in the Indian Ocean waters beside the local amplification effect. The average period of the tsunami waves was approximately 40 minutes, exceeding five days. The tsunami was triggered by the coupling effect between the shockwave with a velocity of 312 m/s and the sea surface. The air pressure anomalies due to the shockwave ranging from 1.2 to 2.2 hPa. Throughout Indonesian waters, this meteotsunami phenomenon did not have a significant impact.

Resonant effects of long-period ship-induced waves near shallow coasts

This work analyzes the propagation properties of long-period ship-induced waves of vessels in confined waterways that are surrounded by wide and shallow water bodies using numerical simulations. Previous measurements indicated that, in the presence of shallow water surroundings, the drawdown being part of the long-period wave system can travel in the form of depression waves over several ship lengths distance [Parnell et al., “Ship-induced solitary Riemann waves of depression in Venice Lagoon,” Phys. Lett. A 379, 555–559 (2015); Scarpa et al., “The effects of ship wakes in the Venice Lagoon and implications for the sustainability of shipping in coastal waters,” Sci. Rep. 9, 19014 (2019)]. The exact conditions leading to these unexpectedly large propagation distances could to date not be clarified [Parnell et al., “Depression Waves Generated by Large Ships in the Venice Lagoon,” J. Coastal Res. 75, 907–911 (2016)]. In this work, evidence from numerical simulations is presented, indicating that the far-field propagation properties are governed by the wave speed of the shallow water surroundings. In case the ship speed is larger than the surrounding wave speed (supercritical conditions), a free wave is continuously generated traveling over the shallow water with only minimal height decay. In the simulations, depression waves can travel over a distance of three ship-lengths with a height reduction below 10% in the supercritical regime, as compared to 80% height reduction in the sub-critical regime. In a one-dimensional environment, this agreement of free and forced wave speed is known as Proudman resonance.

Mediterranean meteotsunamis of May 2021 and June 2022

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 distribution of general synoptic conditions, have characteristics that support the amplification of long-ocean waves and their propagation toward the bay mouth.

The contribution of a mesoscale cyclone and associated meteotsunami to the exceptional flood in Venice on November 12, 2019

AbstractOn 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 s 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.

Meteotsunamis and other anomalous “tidal surge” events in Western Europe in Summer 2022

We investigate occurrences of anomalous tidal activity in coastal waters of north-west Europe during Summer 2022. Sightings of an anomalous “tidal surge” occurred on 18 June 2022 in Wales, followed by similar observations in Ireland, France, and Spain. Several anomalous long-wave events were also reported in south England and Wales in the morning of 19 July 2022. We analyzed surface and high-altitude air pressure fields, and sea level oscillations for both days. Our detailed analysis reveals that the 18 June events were a series of meteotsunamis, propagating over several countries in Western Europe and triggered by localized pressure perturbations, originating within a low-pressure area over the North Atlantic Ocean. A local analysis of the southern coast of Ireland suggests that Proudman resonance was the determinant mechanism that amplified the meteotsunami traveling eastward in the afternoon of 18 June. A similar analysis of the 19 July events suggests that the tidal surge reported in the UK and anomalous signals recorded in Ireland and France were episodes of seiching triggered by infragravity waves, resonated subharmonically by wind waves. Numerical simulations of the 18 June event were performed with Volna-OP2, which solves the non-linear shallow water equations using a finite volume discretization. The influence of the atmospheric wave velocity on the amplification of the sea surface elevation is analyzed.

On Tsunami Waves Induced by Atmospheric Pressure Shock Waves After the 2022 Hunga Tonga‐Hunga Ha'apai Volcano Eruption

AbstractEmploying 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.

Destructive Potential of Planetary Meteotsunami Waves beyond the Hunga Tonga–Hunga Ha‘apai Volcano Eruption

Abstract Worldwide tsunamis driven by atmospheric waves—or planetary meteotsunami waves—are extremely rare events. They mostly occur during supervolcano explosions or asteroid impacts capable to generate atmospheric acoustic-gravity waves including the Lamb waves that can circle the globe multiple times. Recently, such ocean waves have been globally recorded after the Hunga Tonga–Hunga Ha‘apai volcano eruption on 15 January 2022, but did not pose any serious danger to the coastal communities. However, this study highlights that the mostly ignored destructive potential of planetary meteotsunami waves can be compared to the well-studied tsunami hazards. In practice, several process-oriented numerical experiments are designed to force a global ocean model with the realistic atmospheric response to the Hunga Tonga–Hunga Ha‘apai event rescaled in speed and amplitude. These simulations demonstrate that the meteotsunami surges can be higher than 1 m (and up to 10 m) along more than 7% of the world coastlines. Planetary meteotsunami waves thus have the potential to cause serious coastal damages and even human casualties during volcanic explosions or asteroid impacts either releasing intense acoustic energy or producing internal atmospheric gravity waves triggering the deep-ocean Proudman resonance at a speed of ∼212 m s−1. Based on records of catastrophic events in Earth’s history, both scenarios are found to be realistic, and consequently, the global meteotsunami hazards should now be properly assessed to prepare for the next big volcanic eruption or asteroid impact even occurring inland.

Tsunami waves induced by the atmospheric pressure disturbance originating from the 2022 volcanic eruption in Tonga

On January 15, 2022, a violent eruption of Tonga volcano formed an explosion-like atmospheric shock wave, and subsequently many parts of the Pacific coast were hit by tsunami waves. This study focuses on the leading tsunami wave tightly linked with the widespread atmospheric pressure disturbance, and attempts to reveal whether the notable tsunami waves along the coast of Japan are attribute to the mechanism of Proudman resonance. It can be clearly shown that a pressure disturbance radiating from the volcanic eruption spread rapidly over the Pacific Ocean with an average speed of 309 m/s, while a group of tsunami waves appeared closely following the atmospheric disturbance. In most area of the Pacific Basin, the pressure disturbance moved too fast to excite the Proudman resonance, which is proved by the DART data in the deep ocean. The leading tsunami wave associating with the pressure disturbance was several centimeters high in deep ocean, but could be more than 20 cm along the coast of Japan. Based on the analysis of observation data and numerical simulation, it is revealed that the nearshore amplification instead of the Proudman resonance plays the dominant role in producing the threatening nearshore tsunamis, which may not be easily detected and aware by deep water buoys.

Observation and simulation of atmospheric gravity waves exciting subsequent tsunami along the coastline of Japan after Tonga explosion event

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.

Meteotsunamis in the northern Baltic Sea and their relation to synoptic patterns

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 <6 h) sea level oscillations – strongest of which we consider to be meteotsunamis – on the coast of Finland, in the northern Baltic Sea, using quality-checked 1-min observations collected between 2004 and 2015 at 13 tide gauge stations. The intensity of the oscillations varies substantially between stations due to local coastal morphologies. The most intense oscillations predominantly occur in late summer and autumn, although the seasonality may differ between sub-regions. Measured atmospheric data and reanalysis products related to the strongest events reveal two distinct types of atmospheric processes and governing synoptic patterns that are mostly associated with warmer and colder period of year. Consequently, meteotsunamis are classified as summer-type or winter-type events. Most of the summer-type events are caused by surface atmospheric pressure jumps associated with mesoscale convective systems, which are advancing northward over the sea and are embedded into a mid-troposphere jet overtopping an inflow of warm low-troposphere air. At the surface, weak air pressure gradients due to a high-pressure area to the east and a low-pressure area to the west of the Baltic are usually found during summer-type events. The winter-type events, on the contrary, are mostly related to cold fronts and strong northerly-northwesterly-westerly winds at the surface layer. Contrary to summer-type events, surface atmospheric pressure jumps are not necessarily detected during the strongest winter-type events. Deep lows and extratropical cyclones are commonly centered to the north of the Baltic Sea and, at the mid-troposphere level, there is a pronounced westerly jet stream. A hypothesis about the generation mechanism of intense high-frequency sea level oscillations is given: Proudman resonance appears to be the main driver of summer-type events, whereas the main driver of winter-type events is less clear.

Tsunamis Generated and Amplified by Atmospheric Pressure Waves Due to an Eruption over Seabed Topography

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.

Meteotsunamis in Orography‐Free, Flat Bathymetry and Warming Climate Conditions

AbstractDue 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.

Propagation of a Meteotsunami from the Yellow Sea to the Korea Strait in April 2019

A meteotsunami with a wave height of 0.1–0.9 m and a period of 60 min was observed at tide gauges along the Korea Strait on 7 April 2019, while a train of two to four atmospheric pressure disturbances with disturbance heights of 1.5–3.9 hPa moved eastward from the Yellow Sea to the Korea Strait. Analysis of observational data indicated that isobar lines of the atmospheric pressure disturbances had angles of 75–83° counterclockwise due east and propagated with a velocity of 26.5–31.0 m/s. The generation and propagation process of the meteotsunami was investigated using the Regional Ocean Modeling System. The long ocean waves were amplified due to Proudman resonance in the southwestern Yellow Sea, where the water is deeper than 75 m; here, the long ocean waves were refracted toward the coast on the shallow coastal region of the northern Korea Strait. Refraction and reflection by offshore islands significantly affect the wave heights at the coast. To investigate the effects of an eastward-moving velocity and angle of atmospheric pressure disturbance on the height of a long ocean wave, sensitivity simulations were performed. This result will be useful for the real-time prediction system of meteotsunamis in the Korea Strait.

Propagation and amplification of meteotsunamis in multiple harbors along the eastern Yellow Sea coast

This study investigates the propagation and principal resonance characteristics of meteorological tsunamis (i.e., meteotsunamis) along the eastern Yellow Sea coast, which were anomalously strong in multiple harbors on April 25–26, 2008. Meteorological and sea level data were used to examine the link between atmospheric disturbances and meteotsunamis, and meteorological images were collected to estimate the propagation of atmospheric disturbances. Significant tsunami-like sea level oscillations were sequentially detected at the harbor tide gauges with increased spectral energy within broad period bands of less than 30 min, containing the fundamental period of each harbor. Meteorological parameters indicating the passage of a squall line, such as air pressure disturbances, wind disturbances, high rain rates, and lightning strikes, were also observed. The long ocean waves forced by the propagating squall line generated internal resonances, causing local amplification in multiple harbors. It appears that meteotsunami-induced harbor seiches were generated. Our results demonstrated that the pressure-forced meteotsunamis propagated toward the entrance of the harbors located on the propagation path, resulting in additional amplification by harbor resonance after the Proudman resonance amplifying the long waves in the open sea. The resonance characteristics favorable to additional amplification are the propagation of intense air pressure disturbances, harbors with large quality factors, and dominant period bands of the incoming long waves. The proposed resonance characteristics of specific sites can help in improving the accuracy of the current meteotsunami monitoring system in the Yellow Sea.

A Reanalysis of the October 2016 “Meteotsunami” in British Columbia With Help of High-Frequency Radars and Autoregressive Modeling

On October 14, 2016, the coastal high-frequency radar system in Tofino (British Columbia, Canada) triggered an automatic tsunami warning based on the identification of abnormal surface current patterns. This occurred in the absence of any reported seismic event but coincided with a strong atmospheric perturbation, which qualified the event as meteotsunami. We reanalyze this case in the light of a new radar signal processing method, which was designed recently for inverting fast-varying sea surface currents from the complex voltage time series received on the antennas. This method, based on autoregressive modeling combined with a maximum entropy method, yields a dramatic improvement in both the signal-to-noise ratio and the quality of the surface current estimation for very short integration time. This makes it possible to evidence the propagation of a sharp wavefront of surface current during the event and to map its magnitude and arrival time over the radar coverage. We show that the amplitude and speed of the inferred residual current do not comply with a Proudman resonance mechanism but are consistent with the propagation of a low-pressure atmospheric front. This supports the hypothesis of a storm surge rather than a true meteotsunami to explain this event. Beyond this specific case, another outcome of the analysis is the promising use of HF radars as proxy’s for the characterization of atmospheric fronts.

An 8-yr Meteotsunami Climatology across Northwest Europe: 2010–17

AbstractMeteotsunamis are shallow-water waves that, despite often being small (~0.3 m), can cause damage, injuries, and fatalities due to relatively strong currents (&gt;1 m s−1). Previous case studies, modeling, and localized climatologies have indicated that dangerous meteotsunamis can occur across northwest Europe. Using 71 tide gauges across northwest Europe between 2010 and 2017, a regional climatology was made to understand the typical sizes, times, and atmospheric systems that generate meteotsunamis. A total of 349 meteotsunamis (54.0 meteotsunamis per year) were identified with 0.27–0.40-m median wave heights. The largest waves (~1 m high) were measured in France and the Republic of Ireland. Most meteotsunamis were identified in winter (43%–59%), and the fewest identified meteotsunamis occurred in either spring or summer (0%–15%). There was a weak diurnal signal, with most meteotsunami identifications between 1200 and 1859 UTC (30%) and the fewest between 0000 and 0659 UTC (23%). Radar-derived precipitation was used to identify and classify the morphologies of mesoscale precipitating weather systems occurring within 6 h of each meteotsunami. Most mesoscale atmospheric systems were quasi-linear systems (46%) or open-cellular convection (33%), with some nonlinear clusters (17%) and a few isolated cells (4%). These systems occurred under westerly geostrophic flow, with Proudman resonance possible in 43 out of 45 selected meteotsunamis. Because most meteotsunamis occur on cold winter days, with precipitation, and in large tides, wintertime meteotsunamis may be missed by eyewitnesses, helping to explain why previous observationally based case studies of meteotsunamis are documented predominantly in summer.

Long wave generation and coastal amplification due to propagating atmospheric pressure disturbances

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.

Convective rear-flank downdraft as driver for meteotsunami along English Channel and North Sea coasts 28–29 May 2017

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.

Atmospherically induced large amplitude sea-level oscillations on October 29, 2019 at Santa Catarina, Brazil

Several strong sea-level oscillations in the southern region of Brazil with periods in the range of tsunamis, but attributed to atmospheric disturbances, have been publicized in the media or in scientific articles in recent years. However, only a few were registered by instruments. On October 29, 2019, a squall line, linked to an atmospheric storm and a positive jump in atmospheric pressure, spread from south to north along the coast of Santa Catarina. The atmospheric disturbance generated, through Proudman's resonance mechanism, at least two tsunami-like waves with heights greater than 0.70 m and periods around 15 min. These waves were recorded by a network of tide gauges, allowing to monitor their evolution and transformations for more than 200 km. Although there were no reported fatalities, there were significant material losses linked to this occurrence. The objective of the present work is to analyze and connect atmospheric conditions and wave signals in order to further understand the circumstances leading to the formation of this type of event in the southern coast of Brazil.

Observing meteotsunamis (“Marrobbio”) on the southwestern coast of Sicily

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.