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As the foundation of marine infrastructure, pile groups are subjected to extreme wave loads. Existing research primarily focuses on regular waves and wave forces. There is limited research on the pressure distribution of pile bodies under extreme waves. This paper describes a wave flume experiment where waves of a self-proposed extreme wave type were generated. The experiment considers three water depths (25/35/45 cm), three wave-pushing velocities (20/30/40 cm/s), and two clear distances (D, 2D). A total of 216 measuring points equipped with digital pressure sensors captured the vertical and circumferential pressure distribution and wave positive force. The results show that (1) the vertical and circumferential pressure distribution patterns of each component pile and the single pile are similar in various loading scenarios and clear distances. (2) The measuring point pressure, pressure after circumferential integration, and wave positive force are positively correlated with wave-pushing velocity. (3) The wave pressure is positively correlated with the water depth, while the pressure after circumferential integration is negatively correlated with the water depth. (4) When the clear distance is D, the wave positive force coefficient of each component pile is less than 1.0. [ABSTRACT FROM AUTHOR]

The goal of this study is to describe wind wave climate and wave extremes of the Gulf of Gdańsk in the southern Baltic Sea and associated meteorological conditions over the Baltic Sea. We obtain the characteristic features of 34 severe historical storms in the Gulf of Gdańsk during the period 1958–2001 and link them with extreme significant wave heights hindcast for five grid points in this gulf. The long-term statistics of atmospheric pressure systems over central and northern Europe, and the north-eastern Atlantic Ocean are derived from a 44-year REMO reanalysis database. A link between the mean, minimum and variability range of atmospheric pressure has been quantified. In general, the higher the mean pressure the smaller its variability and vice versa. Long-term characteristic features of winds over the Baltic Sea have been estimated from the REMO database. Strong winds directions vary from W, WSW to SW in the southern Baltic to more southerly SSW directions in the northern part of the Baltic Sea. The Empirical Orthogonal Functions (EOF) analysis shows that more than 50% of the variability in the atmospheric pressure in the Baltic Sea can be explained by the first EOF mode. The first four EOF modes can reproduce above 90% variability of the hindcast pressure time series. Statistical properties of the hindcast significant wave height over the Gulf of Gdańsk are computed based on the 44-year HIPOCAS database. All the computed statistics of wave heights reveal a very strong sheltering effect caused by the Hel Peninsula.

This research investigates the behavior and frequency evolution of extreme waves in coastal areas through a combination of physical modeling, spectral analysis, and artificial intelligence (AI) techniques. Laboratory experiments were conducted in a wave flume, deploying various wave spectra, including JONSWAP (γ = 7), JONSWAP (γ = 3.3), and Pierson–Moskowitz, using the dispersive focusing technique, covering a broad range of wave amplitudes. Wave characteristics were monitored using fifty-one gauges at distances between 4 m and 14 m from the wave generator, employing power spectral density (PSD) analysis to investigate wave energy subtleties. A spectral approach of discrete wavelets identified frequency components. The energy of the dominant frequency components, d5 and d4, representing the peak frequency (fp = 0.75 Hz) and its first harmonic (2fp = 1.5 Hz), respectively, exhibited a significant decrease in energy, while others increased, revealing potential correlations with zones of higher energy dissipation. This study underscores the repeatable and precise nature of results, demonstrating the Multilayer Perceptron (MLP) machine learning algorithm's accuracy in predicting the energy of frequency components. The finding emphasizes the importance of a multi-approach analysis for effectively monitoring energy in extreme coastal waves. [ABSTRACT FROM AUTHOR]

Extreme waves pose one of the major threats to marine structures. Furthermore, their non-stationary nature makes proper stochastic analysis of their responses a challenging problem. To address this issue, this paper proposes a method based on a novel linear filter wave model incorporated into the dimension-reduced probability density evolution equation (DR-PDEE). The linear filter system is capable of simulating random background waves conforming with the Joint North Sea Wave Project (JONSWAP) spectrum of any arbitrary sea state by adjusting the parameters of filters directly related to the parameters of the JONSWAP spectrum without reidentification. In particular, by conducting the digital filtering, wave kinematics at different depths below the sea surface can be reproduced conveniently, and therefore only one filter is adequate for the depthwise wave kinematics field. Extreme ocean waves are treated as the superposition of background waves and extreme crests according to the constrained quasi-determinism method, with randomness from both parts. Incorporating the filter into the equation of motion of the offshore structure of interest leads to an augmented high-dimensional stochastic system with multiple random variables. The DR-PDEE then is employed to reduce the dimensions of the equation governing the evolution of probability density of responses of the original complex system to two. Solving the DR-PDEE using the path integral method yields the probability function of the response at each time step. A numerical example involving the response of a National Renewable Energy Laboratory (NREL) 5-MW spar-type floating offshore wind turbine (FOWT) subjected to extreme waves was studied to assess the reliability of the proposed method. The method provides an effective tool for the determination of the stochastic extreme response of offshore structures, and provides a foundation for further dynamic analyses. [ABSTRACT FROM AUTHOR]

As the foundation of marine infrastructure, pile groups are subjected to extreme wave loads. Existing research primarily focuses on regular waves and wave forces. There is limited research on the pressure distribution of pile bodies under extreme waves. This paper describes a wave flume experiment where waves of a self-proposed extreme wave type were generated. The experiment considers three water depths (25/35/45 cm), three wave-pushing velocities (20/30/40 cm/s), and two clear distances (D, 2D). A total of 216 measuring points equipped with digital pressure sensors captured the vertical and circumferential pressure distribution and wave positive force. The results show that (1) the vertical and circumferential pressure distribution patterns of each component pile and the single pile are similar in various loading scenarios and clear distances. (2) The measuring point pressure, pressure after circumferential integration, and wave positive force are positively correlated with wave-pushing velocity. (3) The wave pressure is positively correlated with the water depth, while the pressure after circumferential integration is negatively correlated with the water depth. (4) When the clear distance is D, the wave positive force coefficient of each component pile is less than 1.0.

Cultural heritage (CH) sites are frequently exposed to natural elements, and their exposure becomes particularly precarious with the onset of climate change. This increased vulnerability places these sites at risk of deterioration or complete destruction. Risks such as land deformation, floods, acid rain, and erosion significantly threaten historic monuments, while water-related hazards, significantly influenced by both climate change and human activities, present a particularly grave risk to these invaluable sites. Considerable research efforts have focused on safeguarding CH sites. However, there remains a deficiency in systemic approaches towards identifying and mitigating risks for CH sites. The TRIQUETRA project proposes a technological toolbox and a methodological framework for tackling climate change risks and natural hazards threatening CH in the most efficient way possible. It aims at creating an evidence-based assessment platform allowing precise risk stratification as well as a database of available mitigation measures and strategies, acting as a Decision Support System (DSS) towards efficient risk mitigation and site remediation. TRIQUETRA is a European project that brings together a diverse group of researchers with varied expertise, encompassing university research groups, research institutes, public entities, as well as small and medium-sized enterprises. In this article, TRIQUETRAs overall methodology is presented, and preliminary results concerning risk identification, TRIQUETRAs knowledge base, as well as novel sensors and coatings, are discussed. [ABSTRACT FROM AUTHOR]

The Mediterranean Sea is a primary source of food, ecosystem services and economic activities and one of the most active cydogenetic regions in the world, where the influence of orographic and morphological features of the relatively small basin plays an important role. Together with the explosive cyclogenesis, tropical-like cyclones (also called Mediterranean Hurricanes or Medicanes) are among the strongest types of storms that can be found in the Mediterranean basin, occurring predominantly in the Ionian, Balearic and Tyrrhenian sub-basins. Similarly to tropical cyclones (Hurricanes or Typhoons), these cyclonic structures are characterized by strong rotating and translating wind fields, which often lead to a combination of remotely generated swell waves and locally generated wind waves, often referred to as crossing sea states. Despite the well-known potential of Medicanes to cause significant damage near islands and coastal zones, which is predicted to intensify as a result of climate change, to date the characterization of maximum individual waves generated during these events is still lacking. In this study, we carry out the first analysis of the large-scale geographical distribution of wave maxima within the wave fields generated during three recent Medicane events using the WAVEWATCH III® spectral wave model forced by ERA5 reanalysis winds, also investigating the influence of crossing sea states on the maximum wave amplitudes with novel statistical formulations developed for such conditions. Our results show that, as in the case of tropical cyclones, several regions of the cyclone field are characterized by crossing sea states, whose role in the formation of the maximum individual waves occurring near the eye of the storm was found to be confined. Furthermore, extreme wave predictions accounting for the local crossing conditions yield differences up to 5% compared to standard statistical distributions. [ABSTRACT FROM AUTHOR]

In the present study, a fully nonlinear Boussinesq equation model, FUNWAVE 2.0, is employed to simulate the propagation of multidirectional irregular waves over a sloping bottom. The influences of both the principal wave direction and the directional spreading of the wave energy on the statistics of extreme waves are examined. Comparisons of the skewness, the kurtosis, and the probability density function of the surface elevation analyzed based on the measurements of wave fields with various principal wave directions and different directional spreading parameters are conducted. The results show that both the principal wave direction and the directional spreading of the wave field have significant influences on the statistical parameters associated with extreme waves at different relative water depths. It is consequently essential to include the effects of the two directional factors in the context of extreme waves to have an accurate estimation of their probability of occurrence in the nearshore region. Furthermore, the effect of the wave nonlinearity of multidirectional wave fields is also revealed by comparing the simulated results with the theoretical predictions based on the linear and seconder-order nonlinear wave theories. [ABSTRACT FROM AUTHOR]

The Mediterranean Sea is a primary source of food, ecosystem services and economic activities and one of the most active cyclogenetic regions in the world, where the influence of orographic and morphological features of the relatively small basin plays an important role. Together with the explosive cyclogenesis, tropical-like cyclones (also called Mediterranean Hurricanes or Medicanes) are among the strongest types of storms that can be found in the Mediterranean basin, occurring predominantly in the Ionian, Balearic and Tyrrhenian sub-basins. Similarly to tropical cyclones (Hurricanes or Typhoons), these cyclonic structures are characterized by strong rotating and translating wind fields, which often lead to a combination of remotely generated swell waves and locally generated wind waves, often referred to as crossing sea states. Despite the well-known potential of Medicanes to cause significant damage near islands and coastal zones, which is predicted to intensify as a result of climate change, to date the characterization of maximum individual waves generated during these events is still lacking. In this study, we carry out the first analysis of the large-scale geographical distribution of wave maxima within the wave fields generated during three recent Medicane events using the WAVEWATCH III® spectral wave model forced by ERA5 reanalysis winds, also investigating the influence of crossing sea states on the maximum wave amplitudes with novel statistical formulations developed for such conditions. Our results show that, as in the case of tropical cyclones, several regions of the cyclone field are characterized by crossing sea states, whose role in the formation of the maximum individual waves occurring near the eye of the storm was found to be confined. Furthermore, extreme wave predictions accounting for the local crossing conditions yield differences up to 5% compared to standard statistical distributions.

The nonlinear dynamic response of an aquaculture cage array caused by wave-frequency and low-frequency excitations coupled with the nonlinearity of the mooring and the netting system is a complicated problem. So far, this problem still has not been completely understood. To address this issue, we consider the nonlinear interaction of an extreme wave with an aquaculture cage array containing 16 net cages in a 2 × 8 configuration. This paper aims to provide insight into understanding the nonlinear dynamics of an aquaculture cage array via time–frequency analysis. Time-domain analysis shows that the cage array exhibits weak nonlinearity in the surge and heave motions. On the contrary, there is strong nonlinearity in the sway motion under 45 ° and 90 ° wave attacks. Aside from this, the frequency-domain analysis indicates that nonlinearities exist in all three of these different responses (surge/sway/heave). Particularly, the low-frequency component has a predominant effect on the nonlinearity of the sway motion under 45 ° and 90 ° wave attacks. With this understanding, future aquaculture fish farms that contain multiple cages (i.e., cage array) can be potentially designed to withstand severe conditions in the open ocean. [ABSTRACT FROM AUTHOR]

Efforts towards the numerical simulation of the Baltic Sea wave properties, started in the 1950s, have reached maturity by the implementation of contemporary third generation spectral wave models, such as WAM and SWAN. The purpose of this paper is to give an overview of the relevant efforts since the beginning of numerical wave simulations. The Sverdrup-Munk-Bretschneider (SMB) type models are still valuable tools for rapid estimates of some properties of wave climate in single locations. The spatial resolution of spectral wave models for the entire sea has increased from about 20 km to 1 km, and to 100–200 m in specific areas. The number of directional bins has increased from 10–15 to 24–36 and the number of spectral frequency bins from about 15 to 35–42. The models replicate all main features of the wave climate of the Baltic Sea, such as an overall mild but intermittent wave climate, the predominance of short windseas and the scarcity of long swell, east-west asymmetry, the strong impact of seasonal ice, and the specific properties of wave growth in some areas. The wave climate changes involve variations in regional wave intensity, core properties of wave-driven sediment transport and wave set-up. Reconstruction of wave properties in the nearshore, archipelago areas, and in narrow subbasins remains a challenge. These areas require finer spatial resolution and possibly advancement of wave physics to account for changes in the spectral composition of wave fields and specific features of wave growth in narrow basins. Progress in these fields is a pillar for a number of applications, from the quantification of sediment transport to proper input into management issues of the coastal zone.

The South China Sea spans the tropics and subtropics. Tropical cyclones in the area are extremely active, due to the features of its marine environment, such as wide water-depth profile, complex topography and hydrology. The maximum wave heights along the coast of China are normally generated by typhoons. Especially in the context of global warming, extreme weather events have significantly increased in the recent years, leading to more frequent strong and super typhoons. With the development of resources and energy in China expanding into the deep sea, extreme waves have caused serious damage to sea projects, endangering people's lives and properties. Selecting the accurate typhoon gradient model to calculate various extreme waves, including the probable maximum tropical cyclone (PMTC) wave, is of significance for the safety of marine engineering construction and disaster prevention and mitigation. In this paper, we first proposed a wind field fusion model suitable for the South China Sea by superimposing an empirical typhoon model with the background wind field, and further verified it using the measured typhoon data. Secondly, the fused wind field was used as the input wind field of the SWAN (Simulating Waves Nearshore) model, and the wave fields of typhoons "Usagi" and "Mangosteen" were used to verify the model. The relevant parameters of PMTC were calculated using the Pearson Type III frequency fitting method, while the verified SWAN model was used to calculate the probable maximum typhoon wave, and P-III frequency analysis was carried out by direction of the extrapolated result of typhoon waves to obtain the design wave elements of each return period. Finally, a model for calculating the probable maximum typhoon wave suitable for this sea area was proposed to derive the characteristic parameters and time-histories of the probable maximum typhoon wave and the wave heights and their corresponding frequencies of various extreme waves. [ABSTRACT FROM AUTHOR]

In the previous companion study, satellite data were used to describe peculiar characteristics of ocean surface wave fields, generated by two extra-tropical cyclones (ETCs) rapidly propagating in the North Atlantic. Based on a 2D parametric wave model, further details are now provided to analyse and interpret the spatio-temporal evolution of very intense ETC-generated waves. Significant wave height and wavelength values are shown to reach extreme values, 18 m and 500 m, respectively. Resulting energetic swell systems waves then radiate in the whole eastern part of the North Atlantic, and more particularly in the Norwegian sea region. Moving to higher latitudes, wind forcing characteristics of ETCs evolve, with the shape of the wind field changing from quasi-cyclonic to "air jets/Icelandic lows". In this paper, the resulting swell generation and propagation, after the deformation of an individual ETC, were studied, as well. Confirmed with comparisons with multi-satellite observations, the application of the parametric-2D wave-ray model was demonstrated to provide robust and highly detailed information on wave generation under very complex wind regime changes. [ABSTRACT FROM AUTHOR]

Surface waves generated by Extra-Tropical Cyclones (ETCs) can significantly affect shipping, fishing, offshore oil and gas production, and other marine activities. This paper presents the results of a satellite data-based investigation of wind waves generated by two North Atlantic ETCs. These ETCs were fast-moving systems, inhibiting resonance (synchronism) between the group velocity of the generated waves and the ETC translation velocity. In these cases, wave generation begins when the front boundary of the storm appears at a given ocean location point. Since developing waves are slow, they move backward relative to the storm, grow in time, and then leave the ETC stormy area through the rear sector. Multi-satellite observations confirm such a paradigm, revealing that the storm regions are filled with young developing wind waves, the most developed in the rear-right sector. As observed, the energy of these waves grew in time during the ETC life span. It is demonstrated that the extended-fetch concept (inherent for Tropical Cyclones) does not apply to ETC. Instead, by analogy, the concept of extended-duration wave growth is more relevant. Satellite observations confirmed the validity of duration-laws for waves generated by ETCs, and demonstrated that extended-fetch solutioncan be valid at time scales exceeding the lifespan of considered ETCs. [ABSTRACT FROM AUTHOR]

The sudden generation of wave disturbances in the ocean is associated with a change in the pressure field in the liquid layer. Consequently, compression-type of waves, known as acoustic-gravity waves, form and radiate at the speed of sound, carrying information on the event source, namely its magnitude and location. This information can be recorded by hydrophones hundreds of kilometres away from the event, and if analyzed at near-real time using an inverse model it could allow for an early warning system. The near-real time analysis requires an explicit form of the pressure field induced by the acoustic-gravity waves. In this work, we derive an explicit solution for the bottom pressure field using stationary phase approximation. Then, to demonstrate the effectiveness of the warning system, we apply an inverse model to calculate the generation time and location of the event. [ABSTRACT FROM AUTHOR]

An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra. Relationships between statistical parameters indicative of the occurrence of large-amplitude waves are discussed in the context of the initial steepness of the waves combined with the effect of spectral peakedness. The spatial evolution of the relevant statistical and spectral parameters and features is also considered. It is demonstrated that over the distance the spectra exhibit features typical for developing nonlinear instabilities, such as spectral broadening and downshift of the peak, along with lowering of the high-frequency tail and decrease of the peak magnitude. The wave fields clearly show an increase of third-order nonlinearity with the distance, which can be significant, depending on the input wave environment. The steeper initial conditions, however, while favouring the occurrence of extremely large waves, also increase the chances of wave breaking and loss of energy due to dissipation, which results in lower extreme crests and wave heights. The applied Miche-Stokes-type criteria do confirm that some of the wave extremes exceed the limiting individual steepness. Eventually, this result agrees with the observation that the largest number of abnormal waves is recorded in sea states with moderate steepness. [ABSTRACT FROM AUTHOR]

Three typhoons, Meranti, Malakas, and Megi, occurred successively in eastern Taiwanese waters in September 2016, causing extreme waves (significant wave height > 10.0 m), and these events were selected to investigate the effect of model grid resolution and wave–wave interaction on simulating typhoon-driven waves. The WAVEWATCH III (WW3) model, with 0.50 deg, 0.25 deg, 0.20 deg, 0.10 deg, and 0.05 deg grid resolutions, and two reanalysis wind fields were adopted to simulate ocean waves during these three typhoons. The results indicated that the exertion of the Climate Forecast System version 2 (CFSv2) winds over the WW3 model with 0.10 deg grid resolution yielded optimum simulations of typhoon waves in a compromise between accuracy and elapsed time. In the present study, the WW3 model modeled nonlinear wave–wave interactions using discrete interaction approximation (DIA). The numerical experiments revealed that the underestimations of typhoon waves were significant when the WW3 model excluded nonlinear wave–wave interactions, especially when employing a higher grid resolution. This study also found that the WW3 model is superior to the Wind Wave Model III (WWM-III) using the CFSv2 winds because the WWM-III tended to overestimate the extreme waves in all three of these eastern Taiwan typhoon events that occurred in September 2016. [ABSTRACT FROM AUTHOR]

Blocks transported or moved by the energy of large waves have been the subject of research in different geographical areas of the planet, including some areas of the Caribbean. In Cuba, other authors have identified coastal sectors with the presence of these accumulations; however, a project included in the National Program "Integral Characterization of the Geology of Cuba" allowed for an update of these deposits in coastal areas. This work is aim to develop a new national map with the spatial distribution of coastal boulders. The importance of this result lies in the connection with the extreme wave events that have affected the shores of the Cuban island, both in the past and in the present, a topic that, at the same time, is closely related to Life Task program, especially with the Prevention of Disaster Risks on the coastal zones of Cuba. [ABSTRACT FROM AUTHOR]

The realization of accurate extreme wave height occurrence prediction is essential for offshore and onshore structures. In this paper, a new hybrid Natural Outlier Factor-Extreme Learning Machine (NOF-ELM) method is proposed to predict the extreme wave height occurrence based on the meteorological data. Four major hurricanes in the Gulf of Mexico are used to evaluate the performance of the proposed model. Moreover, the effect of metrological parameters on the occurrence of extreme wave height is investigated. The results of the ELM classifier are then compared with traditional classification techniques, including Logistic Regression, C4.5 Decision Trees, Discriminant Analysis, k-Nearest Neighbours, classic Multi-Layer Perceptron neural networks, and Support Vector Machines. The results show that the proposed method performs well in extreme wave height detection based on metrological parameters by mean accuracy higher than 99%. Furthermore, the results indicate that radial basis ELM has the best performance in extreme wave detection. [ABSTRACT FROM AUTHOR]

Extreme waves induced by extreme tropical cyclones (TCs) with a very strong intensity threaten marine production and transportation. In this paper, six tropical cyclones with a typical track and extremely strong intensity were synthesized to study the extreme waves. The data on TC tracks were extracted from the China Meteorological Administration. The historic TCs from 1949 to 2018 were classified into six groups according to their tracks, and a representative track was synthesized for each group of TCs. We applied an extremely strong intensity to the tracks for studying the extreme wave field. The synthesized track of typical track cyclones (TTCs) was based on the maximum probability of the translation distance and direction of the TC center according to historical data. The central pressure (Pc) was used to represent the TC intensity and was studied at the recurrence periods of 100, 1,000, and 10,000 years. The synthetic TC with a representative track and extremely strong intensity was called a typical tropical cyclone (TTC). The extreme wave fields driven by TTCs were simulated by Simulating Waves Nearshore (SWAN). The wind field driving the waves was calculated using the Holland parametric wind model and was well-verified with observations. This paper calculated the extreme Hs and Tp values of the return periods of 100, 1,000, and 10,000 years for six types of TTCs. It was found that the extreme Hs values were very different for each TTC. The highest Hs could reach 31.3 m in the recurrence period of 10,000 years. Followed by TTC-I with 18 m, TTC-VI was the weakest with less than 10 m. The TC track position frequency and its spatial variation of extreme intensity were discussed. The synthetic tracks were representative, and the intensity could be influenced by spatial variation. In the end, four historical typhoons with great intensity, wide impact, and serious disaster-causing effects were selected to compare with TTC. This paper can provide guidance for maritime planners.

The study of extreme ocean waves has gained considerable interest in recent years, due to their importance for offshore design and navigation safety, and several theoretical approaches have been developed for their statistical description. However, in the case of crossing seas, where two or more wave systems of different characteristics are present, a full understanding of the main physical mechanisms responsible for the occurrence of very high individual waves is still lacking. As a consequence, the prediction of extremes in such conditions currently relies on integrated parameters of the total sea state, such as the spectral wave steepness. In this study, to gain further insight into the role of the crossing wind sea and swell wave systems in producing extreme individual waves, we investigate realistic sea states during typhoon Kong-rey (2018) using an ensemble of numerical simulations obtained from a phase-resolving wave model based on the High-Order Spectral (HOS) method. The reliability of the numerical fields is assessed for the first time with stereo wave measurements of the sea surface elevation field collected from an offshore platform in the area of interest. We show that, in specific conditions, space-time extreme crest heights in crossing seas can be larger than in unimodal seas due to second-order bound wave interactions between the wind sea and the swell. To improve existing prediction capabilities, we propose a novel formulation for the wave steepness in crossing seas, which includes nonlinear effects up to the second order and accounts for the spectral parameters of the interacting wave systems.

The nonlinear dynamic response of an aquaculture cage array caused by wave-frequency and low-frequency excitations coupled with the nonlinearity of the mooring and the netting system is a complicated problem. So far, this problem still has not been completely understood. To address this issue, we consider the nonlinear interaction of an extreme wave with an aquaculture cage array containing 16 net cages in a 2 × 8 configuration. This paper aims to provide insight into understanding the nonlinear dynamics of an aquaculture cage array via time–frequency analysis. Time-domain analysis shows that the cage array exhibits weak nonlinearity in the surge and heave motions. On the contrary, there is strong nonlinearity in the sway motion under 45° and 90° wave attacks. Aside from this, the frequency-domain analysis indicates that nonlinearities exist in all three of these different responses (surge/sway/heave). Particularly, the low-frequency component has a predominant effect on the nonlinearity of the sway motion under 45° and 90° wave attacks. With this understanding, future aquaculture fish farms that contain multiple cages (i.e., cage array) can be potentially designed to withstand severe conditions in the open ocean.

There is growing evidence that many large coastal boulder deposits found on the exposed rocky ocean shores were deposited by extreme storm waves rather than by catastrophic tsunamis, as previously thought. In addition, before the first discovery in the northern Adriatic a few years ago, such deposits were not expected in relatively shallow semi-enclosed inland basins. Here we report on a large coastal coarse-clast deposit on the central Adriatic island of Mana, which also contains numerous large storm boulders that weigh up to several tons. Large solitary boulders are also located outside of the deposit, closer to the partly submerged sea cliff and the wave impact. The erosion of the cliff top and displacement of the carbonate bedrock fragments began when the extreme waves inundated the lowermost part of the cliff edge, probably during the late Holocene sea-level rise. The UAS photogrammetry-based fragmentation analysis of the storm deposit and the calculated fractal dimension value indicate that the material was fragmented by multiple high-energy events. A comparison of the available photographs indicates that displacements of the most exposed solitary boulders probably occurred during Vaia, the last extreme storm that hit the Adriatic on the 29th of October 2018. However, the modeled maximum wave height south of Mana during the peak of the storm would be insufficient to move these boulders. Yet local geomorphology probably further influenced the increase in wave height that, in combination with specific geological features, caused displacements of the boulders. There is a shorter fetch affecting Mana Island with respect to the northern Adriatic boulder field in southern Istria. Thus, such an active local erosion of the generally stable eastern Adriatic karstic coast depends on the extreme storms that have a weaker impact in the central than in the northern Adriatic. [ABSTRACT FROM AUTHOR]

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Climate change can give rise to significant changes in the intensity and frequency of extreme events. In the present study, extreme wave events off the central-eastern coast of the Red Sea, near the city of Jeddah, were investigated using a 39-year wave hindcast generated using WaveWatch III configured at a 3.3 km resolution forced with ERA5 reanalysis winds. The validated model outputs were used to derive the annual and seasonal climatology for the region at a few selected locations off the Jeddah coast. The study revealed robust temporal and spatial variability in the region, considering the influence of both northern and southern Red Sea waves that meet at the convergent zone. Generalized Pareto Distribution (GPD) and Generalized Extreme Value (GEV) were two models used for the estimation of extreme wave analysis in the study region. The extreme significant wave heights were estimated for 10, 25, 50, and 100-year return periods. For offshore locations, the estimated return periods using the GPD method were 3.27, 3.44, and 3.38 m, respectively. GPD with the POT method was the more suitable approach, as it produced reduced bias and RMSE. At all locations, linear trends show an increase during the summer, winter, and pre-summer periods. No significant increase in the Hs trend was observed at the selected locations near and off the coast. However, the decrease in trend observed at all locations during the pre-winter period was noticeable for the 99th percentile Hs. [ABSTRACT FROM AUTHOR]

Abstract This work addresses the problem of weakly non linear ocean waves propagation in intermediate waters. We have shown that the propagation of waves similar to hole solitons, as well as progressive waves of high intensity multipeaks are likely to occur in this non linear regime. In addition, we note that along intermediate waters, these particular non-linear waves satisfy a wave equation model similar to Korteweg de Vries equation, and their propagation features strongly depend on the initial conditions adopted to the present problem.

Three typhoons, Meranti, Malakas, and Megi, occurred successively in eastern Taiwanese waters in September 2016, causing extreme waves (significant wave height > 10.0 m), and these events were selected to investigate the effect of model grid resolution and wave–wave interaction on simulating typhoon-driven waves. The WAVEWATCH III (WW3) model, with 0.50 deg, 0.25 deg, 0.20 deg, 0.10 deg, and 0.05 deg grid resolutions, and two reanalysis wind fields were adopted to simulate ocean waves during these three typhoons. The results indicated that the exertion of the Climate Forecast System version 2 (CFSv2) winds over the WW3 model with 0.10 deg grid resolution yielded optimum simulations of typhoon waves in a compromise between accuracy and elapsed time. In the present study, the WW3 model modeled nonlinear wave–wave interactions using discrete interaction approximation (DIA). The numerical experiments revealed that the underestimations of typhoon waves were significant when the WW3 model excluded nonlinear wave–wave interactions, especially when employing a higher grid resolution. This study also found that the WW3 model is superior to the Wind Wave Model III (WWM-III) using the CFSv2 winds because the WWM-III tended to overestimate the extreme waves in all three of these eastern Taiwan typhoon events that occurred in September 2016.

Ortiz Royero, J.C.; Henriquez Cera, S., and Gomes, H., 2022. Coastal meteo-marine parameters of Hurricane Matthew along the Colombian Caribbean coast: Establishing a baseline of knowledge. Journal of Coastal Research, 38(1), 66–76. Coconut Creek (Florida), ISSN 0749-0208. The hurricanes on the Colombian continental coast have been lower in intensity and number than in other areas of the Caribbean Sea. Thus, given the lack of knowledge about the hurricane parameters in this area, the protocols to deal with a hurricane emergency on the Columbian continental coast are not clear. This work analyzes the meteo-marine parameters caused in Colombia by the passage of Hurricane Matthew to establish a baseline of knowledge. Further progress in understanding the effects the hurricane may have had on several coastal areas, particularly in the areas of hydrology, morphological changes, storm surge, and flood, is expected in future work. The results show that the most significant meteo-marine parameter was the swell generated by the hurricane; although it followed a NW trajectory toward the coast, the swell reached up to 4.5 m of significant wave height and a peak period of 14 seconds. Also, the accumulated rainfall in only 3 days significantly exceeded the average monthly values of October (the rainiest month of the year). This effect is of particular interest given that recent modeling studies established an increase in precipitation rates associated with tropical hurricanes. The wind was not significant with respect to typical values in the zone. [ABSTRACT FROM AUTHOR]

This study inspects the global changes in seasonal extreme ocean wave heights under different levels of global warming (1.5 °C, 2 °C, and 3 °C) based on statistical wave projections derived from CMIP5 multi-model simulations. The results show robust increases in wave extremes up to 15% (∼1 m) over Southern Hemisphere high latitudes and tropical Pacific, particularly at 3 °C warming. Strong seasonality is observed, especially for the North Pacific. Under higher warming, stronger increases are identified in both amplitude and area of extreme wave heights. The change in magnitude translates into shorter return intervals of extreme wave events in a warmer world, particularly at 3 °C warming. Differences between 1.5 °C and 2 °C worlds reveal potential benefits of limiting global warming over large regions of global ocean. Strong inter-model relationships indicate that wave height increases are associated with intensified climate mode variability, particularly the Southern Annular Mode and El Niño–Southern Oscillation, in a warmer world. An important implication is the potential impact of increased wave extremes on West Antarctic ice shelves with respect to calving and associated loss of buttressing, which would facilitate sea level rise in a warmer world.

Reliable long-term wave data are significant for understanding changes and variability of ocean waves, which has important implications for coastal engineering, land erosion, and coastal flooding. This study develops a regression-guided weather-type statistical method for modelling regional or global significant wave height H s. The model classifies the atmospheric circulation patterns (predictor) through the regression-guided clustering approach, linking the atmospheric circulation with clustered regional H s (predictand). It is applied in the Chinese marginal seas and also the global ocean. A comprehensive skill assessment shows robust skill and computationally efficiency of the model in capturing climatology and variability of both mean and extreme H s in the Chinese marginal seas and global oceans. Furthermore, the reconstructed global H s data show similar seasonal trends as the ERA5 data, with a gradual decrease in H s observed during boreal summer in the central Pacific and western North Atlantic regions at lower latitudes. This method proves to be robust for both regional and global H s reconstruction, and also applicable for H s climate prediction and projections. • A weather-type wave statistical downscaling is developed based on wave clustering. • Adding wave clustering to the model improves the generalizability of weather types. • The model is robust in capturing mean, extreme, and trends of wave statistics. • The model is computing efficient and applicable for large ensemble simulations. [ABSTRACT FROM AUTHOR]

Natural hazards such as extreme wind, rainfall and ocean waves can have severe impacts on built and natural environments, contributing to the occurrence of disastrous events in some cases. These hazards are often caused by weather systems such as cyclones, fronts and thunderstorms. Previous studies typically examine one type of hazard and/or one type of weather system, with some studies in recent years starting to focus on compound hazards. Here we systematically examine compound hazards (extreme precipitation, extreme wind gusts, and extreme waves) from a weather system typology perspective. Cyclones and fronts are identified automatically from ERA-Interim reanalysis data, and thunderstorm events are based on lightning observations from 2005 to 2015, defining the study period. Relationships are examined over this period between the different compound hazard types and the weather system types, globally for different seasons. Most of the individual and compound hazards are most likely to be associated with the front-only or cyclone and front weather system types, while in the tropics, most hazards are strongly associated with the thunderstorm-only type. Despite being less frequent than the double weather system types, the triple weather system type shows comparable importance for many of the hazards, and especially the triple hazard. Individual case studies are examined using this compound event framework. It is intended that a greater understanding of compound hazards and the weather systems that cause them in regions throughout the world will help lead to improved preparedness and disaster risk reduction, given the importance of this for our rapidly changing world.

The sinking of the cargo ship SS El Faro is investigated by providing a comprehensive analysis of the wind, wave and ocean currents associated with Hurricane Joaquin. Using state-of-the-art reanalyses the event is assessed in high resolution and from a long-term climate perspective. The last known location of the SS El Faro was in the north-west eye-wall of Hurricane Joaquin when it was a category four major Hurricane. The maximum individual wave height in this region was over 10 m and the Benjamin-Feir index was 0.69 indicating a high likelihood of rogue waves. As the vessel tried to outrun the hurricane it was continually impacted by strong wind and waves on its port side. This was compounded with flooding that caused a starboard list which likely eventually caused the vessel to sink. [ABSTRACT FROM AUTHOR]

The frequency of extreme wave events is increasing with climate change. The temporal and spatial variations of extreme wave height affect both human livelihood and the usage of ocean resources. The South China Sea and northern Indian Ocean both support coastal communities of high population density, with varied terrain structures and extreme wind and wave systems. This study focuses on the temporal and spatial variations of the extreme significant wave height in the South China Sea and northern Indian Ocean. Using nonstationary generalized extreme value analysis, trends for a 100-year return period of significant wave height were obtained for both. The most rapid increase in the 100-year return was found to be 0.015 m yr-1 in the northern South China Sea and in the Arabian Sea; however, the 100-year return significant wave height fell in the mouth of the Bay of Bengal. After analyzing the possible causes and influence factors, we found that the increase in significant wave height in the northern South China Sea was dominated by local wind-waves and similarly, the Arabian Sea was affected by swell. The NINO3.4 index shows good correlation with the significant wave height in the northern South China Sea because typhoons are related to NINO3.4 in this area. The trends of the extreme wave height in the Arabian Sea and southern Bay of Bengal have good correlations with the South Asian summer monsoon index. [ABSTRACT FROM AUTHOR]

Bimodal spectrum wave conditions, known as crossing seas, can produce extreme waves which are hostile to humans during oceanic activities. This study reports some new findings of the probability of extreme waves in deep crossing random seas in response to the variation of spectral bandwidth through fully non-linear numerical simulations. Two issues are addressed, namely (i) the impacts of the spectral bandwidth on the changes of extreme wave statistics, i.e., the kurtosis and crest exceedance probability, and (ii) the suitability of theoretical distribution models for accurately describing the wave crest height exceedance probability in crossing seas. The numerical results obtained by simulating a large number of crossing sea conditions on large spatial-temporal scale with a variety of spectral bandwidth indicate that the kurtosis and crest height exceedance probability will be enhanced when the bandwidth of each wave train becomes narrower, suggesting a higher probability of encountering extreme waves in narrowband crossing seas. Meanwhile, a novel empirical formula is suggested to predict the kurtosis in crossing seas provided the bandwidth is known in advance. In addition, the Rayleigh and second-order Tayfun distribution underestimate the crest height exceedance probability, while the third-order Tayfun distribution only yields satisfactory predictions for cases with relatively broader bandwidth regarding the wave conditions considered in this study. For crossing seas with narrower bandwidth, all the theoretical distribution models failed to accurately describe the crest height exceedance probability of extreme waves.

This article considers additional phenomena that complement the earlier topics addressed by Ibrahim [(Liquid Sloshing Dynamics: Theory and Applications. Cambridge University Press, Cambridge, 2005), (ASME J Fluids Eng 137(9):090801, 2015)]. The first phenomenon is the localized Faraday waves known as oscillons, which were observed in granular materials and liquid layers subjected to parametric excitation. Extreme waves, known as rogue, generated in the Faraday surface ripples, are related to the increase in the horizontal mobility of oscillating solitons (oscillons), and their horizontal motion is random over a limited range of excitation acceleration amplitude. Parametric excitation of water in a Hele–Shaw cell and the associated localized standing surface waves of large amplitude will be discussed. The surface wave pattern exhibited a certain similarity with the three-dimensional axisymmetric oscillon. Faraday waves in superfluid Fermi–Bose mixtures and their wave function will be addressed in terms of position and time as described by the Schrödinger equation with time-dependent parabolic potential. The phenomenon of walking fluid droplets on Faraday waves constitutes the majority portion of this article. Different regimes of droplet motion in terms of droplet physical properties, the fluid bath excitation acceleration amplitude and frequency will be discussed. The droplet trajectory diffraction, when passes through a slit, shares the same random features of electron diffraction. The duality of the droplet-wave field together with the path-memory-driven nonlocality and other related topics will be assessed. This article is complemented with the fascinating phenomenon of the stone and bombs skipping/ricochet over water surface. [ABSTRACT FROM AUTHOR]

In this note we discuss some recent results on extreme steady waves under gravity. They include the existence and regularity theorems for highest waves on finite depth with and without vorticity. Furthermore, we state new results concerning the asymptotic behavior of surface profiles near stagnation points. In particular, we find that the wave profile of an extreme wave is concave near each crest, provided that the vorticity is negative near the surface. [ABSTRACT FROM AUTHOR]

Climate change can give rise to significant changes in the intensity and frequency of extreme events. In the present study, extreme wave events off the central-eastern coast of the Red Sea, near the city of Jeddah, were investigated using a 39-year wave hindcast generated using WaveWatch III configured at a 3.3 km resolution forced with ERA5 reanalysis winds. The validated model outputs were used to derive the annual and seasonal climatology for the region at a few selected locations off the Jeddah coast. The study revealed robust temporal and spatial variability in the region, considering the influence of both northern and southern Red Sea waves that meet at the convergent zone. Generalized Pareto Distribution (GPD) and Generalized Extreme Value (GEV) were two models used for the estimation of extreme wave analysis in the study region. The extreme significant wave heights were estimated for 10, 25, 50, and 100-year return periods. For offshore locations, the estimated return periods using the GPD method were 3.27, 3.44, and 3.38 m, respectively. GPD with the POT method was the more suitable approach, as it produced reduced bias and RMSE. At all locations, linear trends show an increase during the summer, winter, and pre-summer periods. No significant increase in the Hs trend was observed at the selected locations near and off the coast. However, the decrease in trend observed at all locations during the pre-winter period was noticeable for the 99th percentile Hs.

This numerical work aims to better understand the behavior of extreme Adriatic Sea wave storms under projected climate change. In this spirit, 36 characteristic events—22 bora and 14 sirocco storms occurring between 1979 and 2019, were selected and ran in evaluation mode in order to estimate the skill of the kilometer-scale Adriatic Sea and Coast (AdriSC) modelling suite used in this study and to provide baseline conditions for the climate change impact. The pseudo-global warming (PGW) methodology—which imposes an additional climatological change to the forcing used in the evaluation simulations, was implemented, for the very first time, for a coupled ocean–wave–atmosphere model and used to assess the behavior of the selected storms under Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 greenhouse gas projections. The findings of this experiment are that, on the one hand, the AdriSC model is found capable of reproducing both the Adriatic waves associated with the 36 storms and the northern Adriatic surges occurring during the sirocco events and, on the other hand, the significant wave heights and peak periods are likely to decrease during all future extreme events but most particularly during bora storms. The northern Adriatic storm surges are in consequence also likely to decrease during sirocco events. As it was previously demonstrated that the Adriatic extreme wind-wave events are likely to be less intense in a future warmer climate, this study also proved the validity of applying the PGW methodology to coupled ocean–wave–atmosphere models at the coastal and nearshore scales. [ABSTRACT FROM AUTHOR]