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Based on the WAVEWATCH III wave model, China's National Marine Environmental Forecasting Center has developed an operational global ocean wave forecasting system that covers the Arctic region. In this study, in situ buoy observations and satellite remote sensing data were used to perform a detailed evaluation of the system's forecasting results for 2022, with a focus on China's offshore and global ocean waters, so as to comprehensively understand the model's forecasting performance. The study results showed the following: In China's coastal waters, the model had a high forecasting accuracy for significant wave heights. The model tended to underestimate the significant wave heights in autumn and winter and overestimate them in spring and summer. In addition, the model slightly underestimated low (below 1 m) wave heights, while overestimating them in other ranges. In terms of spatial distribution, negative deviations and high scatter indexes were observed in the forecasting of significant wave heights in semi-enclosed sea areas such as the Bohai Sea, Yellow Sea, and Beibu Gulf, with the largest negative deviation occurring near Liaodong Bay of the Bohai Sea (−0.18 m). There was a slight positive deviation (0.01 m) in the East China Sea, while the South China Sea exhibited a more significant positive deviation (0.17 m). The model showed a trend of underestimation for the forecasting of the mean wave period in China's coastal waters. In the global oceanic waters, the forecasting results of the model were found to have obvious positive deviations for most regions, with negative deviations mainly occurring on the east coast and in relatively closed basins. There were latitude differences in the forecasting deviations of the model: specifically, the most significant positive deviations occurred in the Southern Ocean, with smaller positive deviations toward the north, while a slight negative deviation was observed in the Arctic waters. Overall, the global wave model has high reliability and can meet the current operational forecasting needs. In the future, the accuracy and performance of ocean wave forecasting can be further improved by adjusting the parameterization scheme, replacing the wind fields with more accurate ones, adopting spherical multiple-cell grids, and data assimilation. [ABSTRACT FROM AUTHOR]

This study focusses on the processes that control the morphodynamics of the seabed in the shoaling wave domain, widely known as the shoreface. Shoreface morphodynamics is not only controlled by the local wave climate but also by associated wave- and wind-driven currents, the grain-size, and antecedent geomorphology. This paper provides basic information on sedimentological action of monochromatic waves at the seabed in the shoaling zone to the non-specialist without him-/herself having to solve the complex equations before arriving at workable solutions. It is emphasized that the traditional oceanographically defined wave base (0.5L0) is not relevant in a geological/sedimentological context and should be replaced by a grain-size dependent effective wave base (EWB). Furthermore, open ocean swell-dominated shorefaces have to be distinguished from those of marginal seas dominated by local wind-generated waves. For convenience, a collection of tables and diagrams are provided in the electronic supplementary material (ESM) attached to this paper. They highlight the depths of effective wave bases for a range of grain sizes, wave heights and wave periods between 2 and 16 s. [ABSTRACT FROM AUTHOR]

The Ba Lang sand beaches, located north of the Nha Trang Bay in Central Vietnam, are famous tourist attractions. However, they are experiencing shoreline and coastal erosion retreat, which is attributed to natural causes (such as tropical depressions, storms, and monsoons) as well as human impacts (such as hydropower generation, sand dredging, and coastal works). According to the forecast of the Vietnam Ministry of Natural Resources and Environment, global climate change will cause the sea level to rise by 74 cm along the coast from the Dai Lanh Cape to the Ke Ga Cape (including the Ba Lang beaches) by the end of this century in the representative concentration pathway (RCP) 8.5 scenario. Sea level rise (SLR) due to global climate change is expected to aggravate the coastal erosion and shoreline retreat problems. In this study, coupled numerical models with the spectral wave module (MIKE 21 SW), hydrodynamic module (MIKE 21 HD), and sand transport module (MIKE 21 ST) in the MIKE 21 package were used to simulate waves, current fields, and sediment dynamics along the Ba Lang beaches considering the impact of SLR. These models were calibrated with the field data measured in December 2016. The results showed that SLR caused the wave height to increase and reduced the current speed and total sediment load in monsoon conditions. The increase in wave height was even intensified under the joint impact of SLR and extreme events.

AbstractCoastal areas are susceptible to coastal processes, such as sea level rise and natural disasters, making them highly dynamic and vulnerable. The study examines factors such as shoreline changes, coastal slope, wave height, tidal range and landforms and shows distinct erosion, accretion and stability patterns across six littoral cells. Coastal slope and sea level rise are crucial for vulnerability assessment, with low slopes and rising sea levels indicating areas of higher risk. The Coastal Vulnerability Index categorizes zones as low, medium and high risk based on physical variables, while the linear regression method calculates an average shoreline change of −2.41 m/year erosion and 2.59 m/year accretion from 1990 to 2015. The results show that 68.14% of the shoreline is classified as low risk, 17.82% as stable and 14.18% as high risk. [ABSTRACT FROM AUTHOR]

In the face of depleting fossil energy and the imperative of sustainable development, there is a compelling drive towards advancing renewable energies. In this context, sustainable and predictable alternatives, like marine energy, gain prominence. Marine energy presents a cleaner option devoid of the adverse effects associated with fossil fuels, playing a crucial role in environmental sustainability by safeguarding coastlines against erosion. This study focuses on Astara Port in the Caspian Sea, exploring the utilization of wave energy converters (WECs). The originality of this study's research lies in exploring WECs' dual role in energy generation and coastal protection. Using MIKE21 software simulations, the impact of number, location, arrangement, and orientation of WECs across various scenarios was investigated, including two WEC number scenarios (11 and 13), three structural placement scenarios (north, front, and south of the port), two structural arrangement scenarios (linear and staggered), two port layout scenarios (original layout and modified layout), and two orientation scenarios for the structures (facing north-east, which is the dominant wave direction, and facing southeast). The results show a remarkable decrease in the significant wave height behind WECs, notably with 13 staggered devices facing dominant waves (from northeast), reducing the significant wave height Hs by 23–25%. This setup also shows the highest wave height reduction, notably 36.26% during a storm event. However, linear WEC setup offers more extensive coastline protection, covering 47.88% of the model boundary during storms. Furthermore, the 11 staggered WECs facing southeast (SE) arrangement had the lowest sediment accumulation at 0.0358 m over one year, showing effective sedimentation mitigation potential. Conversely, the 13 linear WECs facing northeast (NE) had the highest accumulation at 0.1231 m. Finally, the proposed port design redirects high-velocity flow away from the port entrance and removes rotatory flow, reducing sediment accumulation near the harbor entrance. [ABSTRACT FROM AUTHOR]

Satellite altimeters are the most common source of wave measurement in phenomenal sea states, with significant wave heights exceeding 14 m. Unfortunately their data is still considered with skepticism, because there is usually no other data to verify the accuracy of the largest values. Here we investigate the self‐consistency of the measurement, and their small scale variability, in order to define an estimate of satellite altimeter precision. Using numerical simulations of ocean surfaces and the processing involved in satellite retracking, we find that wave groups are responsible for a variance in estimated altimeter wave heights that is proportional to the square of the spectral peakedness parameter and the significant wave height. Additional variance induced by speckle noise is proportional to the wave height. The effect of wave groups generally dominates in the most severe storms. This variability requires a relatively large scale smoothing or filtering to yield accurate wave height estimates. For example, the largest ever reported 1 s average significant wave height from altimeters sampled by Jason‐2 in the North Atlantic in 2011, at H‾s=20.1 ${\overline{H}}_{s}=20.1$m, is now interpreted to correspond to a true wave height Hs = 18.5 ± 0.3 m. The difference between 20.1 and 18.5 m is mostly due to wave group contributions to the raw measurement. We argue that wave group effects should not be included in the definition of the significant wave height, just like the maximum wave height differs from the significant wave height. Plain Language Summary: Over most of the past 30 years, satellite altimeters have been the only means to measure wave properties in the most severe ocean storms. How do we know that these data are trustworthy, and how can we define uncertainties? Here we show that as a satellite flies along its orbit, it reports wave height that fluctuate because of the random nature of the wavefield that can be organized in groups at the scale of a few kilometers. We are able to simulate the precision of the measurements, as a function of the wave height and the degree of organization of the wavefield, measured by a "spectral peakedness" parameter. This novel understanding can be used to define the precision of the measurements. For example, as far as we know, the largest reported value for a 1 s averaged satellite measurement of the significant wave height was H‾s=20.1 ${\overline{H}}_{s}=20.1$m in a 2011 North Atlantic Storm, with no precision given. We can now re‐interpret this data as evidence of a true significant wave height Hs = 18.5 ± 0.3 m. The local fluctuations up to 20 m are caused by wave groups and should not be counted in the significant wave height. Key Points: Retracking of altimeter waveforms yields fluctuations in wave height and sea level, correlated at the scale of the effective footprintA good approximation for the effective footprint diameter is the square root of the product of wave height and satellite altitudeEstimating phenomenal wave heights precise to better than 2% requires filtering over wave groups, typically over a distance of 20–50 km [ABSTRACT FROM AUTHOR]

Doppler mis-registrations in azimuth can lead to ocean waves shorter than a specific wavelength being undetectable by SAR. In order to evaluate the actual ocean wave observation ability, the accuracy of Sentinel-1 SAR ocean wave spectra from January 2016 to December 2021 is evaluated by comparisons to NDBC buoys, ERA5 wave height, and CMEMS buoys. The results compared with NDBC show that the spectral shape of Sentinel-1 SAR ocean wave spectra is accurate, while the spectral values need to be improved. The wave spectra of Sentinel-1 have the best observations in season autumn. The comparison results of total wave height show the RMSE and bias are 0.91 m and −0.52 m for the comparisons to NDBC buoy wave spectra data, 0.93 m and −0.68 m for the comparison to ERA5 wave height data, and 0.9 m and −0.35 m for the comparisons to CMEMS buoy data. The comparison results of wave height in different wind speeds and areas shows that the accuracy of Sentinel-1 wave mode data is relatively good in the open ocean located in middle and low latitude area under the medium wind speed, while those are relatively poor in high latitude areas or the areas with excessively high or low wind speed. [ABSTRACT FROM AUTHOR]

The ICESat-2 photon-counting lidar can simultaneously observe high-resolution radiometric and geometric characteristics of ocean waves. In this study, combining the wave radiometric and geometric characteristics, ICESat-2 can provide robust and accurate wind speeds over oceans that cannot be achieved by using a single characteristic. Specifically, with an along-track segment of 700 m, the sea surface photons and surface profile are detected and generated from ICESat-2 ATL03 geolocated photons by which the received energy and wave height are obtained. The unknown atmospheric transmittance and swell wave height have significant impacts on deriving the water surface reflectance (radiometric characteristic) and the wind-driven water height (geometric characteristic), respectively. We use all available ICESat-2 data in 2018 and 2019 to determine the unknown parameters and further separately estimate wind speeds. The radiation-based method performs better at low wind speeds, while the geometry-based method performs better at high wind speeds, and we combine each specific advantage to obtain more reliable wind speeds. In the Pacific Ocean, Atlantic Ocean, and Indian Ocean, thousands of ICESat-2 ground tracks from 2020 are used to estimate wind speeds, and the performance is validated against a trustworthy data source of ERA5 with a root-mean-square error (RMSE) of ∼0.3 m for wave heights and an RMSE of ∼1.5 m/s for wind speeds. ICESat-2 has shown great ability to provide independent wind speeds over oceans with high accuracy and resolution, which may fill the gap of wind speeds on a small scale as the large-scale results are well observed by spaceborne microwave devices.

An intelligent single radar image de-raining method based on unsupervised self-attention generative adversarial networks is proposed to improve the accuracy of wave height parameter inversion results. The method builds a trainable end-to-end de-raining model with an unsupervised cycle-consistent adversarial network as an AI framework, which does not require pairs of rain-contaminated and corresponding ground-truth rain-free images for training. The model is trained by feeding rain-contaminated and clean radar images in an unpaired manner, and the atmospheric scattering model parameters are not required as a prior condition. Additionally, a self-attention mechanism is introduced into the model, allowing it to focus on rain clutter when processing radar images. This combines global and local rain clutter context information to output more accurate and clear de-raining radar images. The proposed method is validated by applying it to actual field test data, which shows that compared with the wave height derived from the original rain-contaminated data, the root-mean-square error is reduced by 0.11 m and the correlation coefficient of the wave height is increased by 14% using the de-raining method. These results demonstrate that the method effectively reduces the impact of rain on the accuracy of wave height parameter estimation from marine X-band radar images.

Based on the WAVEWATCH III wave model, China’s National Marine Environmental Forecasting Center has developed an operational global ocean wave forecasting system that covers the Arctic region. In this study, in situ buoy observations and satellite remote sensing data were used to perform a detailed evaluation of the system’s forecasting results for 2022, with a focus on China’s offshore and global ocean waters, so as to comprehensively understand the model’s forecasting performance. The study results showed the following: In China’s coastal waters, the model had a high forecasting accuracy for significant wave heights. The model tended to underestimate the significant wave heights in autumn and winter and overestimate them in spring and summer. In addition, the model slightly underestimated low (below 1 m) wave heights, while overestimating them in other ranges. In terms of spatial distribution, negative deviations and high scatter indexes were observed in the forecasting of significant wave heights in semi-enclosed sea areas such as the Bohai Sea, Yellow Sea, and Beibu Gulf, with the largest negative deviation occurring near Liaodong Bay of the Bohai Sea (−0.18 m). There was a slight positive deviation (0.01 m) in the East China Sea, while the South China Sea exhibited a more significant positive deviation (0.17 m). The model showed a trend of underestimation for the forecasting of the mean wave period in China’s coastal waters. In the global oceanic waters, the forecasting results of the model were found to have obvious positive deviations for most regions, with negative deviations mainly occurring on the east coast and in relatively closed basins. There were latitude differences in the forecasting deviations of the model: specifically, the most significant positive deviations occurred in the Southern Ocean, with smaller positive deviations toward the north, while a slight negative deviation was observed in the Arctic waters. Overall, the global wave model has high reliability and can meet the current operational forecasting needs. In the future, the accuracy and performance of ocean wave forecasting can be further improved by adjusting the parameterization scheme, replacing the wind fields with more accurate ones, adopting spherical multiple-cell grids, and data assimilation.

In order to study the impact of landslides at different locations and volumes in the narrow reservoir on wave height and project safety, the physical models of H1 and 1# landslides of Yangqu Hydropower Station, China, at a scale of 1:200 were established. Wave heights generated by landslides with 1 million, 2 million and 5 million m³ are studied. The influence of wave on the stability of bridge and dam is analyzed. The results show that the wave type is linear wave, and the wave height is proportional to the landslide volume at the landslide site and dam site. The damage of the landslide location to the project is not necessarily inversely proportional to the distance, but also related to the water conditions where the landslide is located. The wave generated by H1 or 1# landslide has no impact on the bridge. However, when the H1 landslide volume is greater than 2 million m³ or 1# landslide volume is greater than 5 million m³, the dam overflow by the generated waves occurs. The results can provide a reference for the prevention of landslide wave disasters in Yangqu reservoir, China. [ABSTRACT FROM AUTHOR]

Accurate prediction of water waves generated by landslides is of significant importance in the early warning and risk assessment of landslide disasters. And previous studies shown that landslide-induced waves are of various types, which indicates that there are different generation regimes for landslide-induced waves. In the present study, the generation of water waves by a rigid landslide is studied numerically and theoretically. According to the motion characteristics of a landslide, three types of landslide motions, including piston-like, plunger-like, and transition landslide motions, are detected. The performed analyses demonstrate that the solitary-like wave and dissipative transient bore are generated by piston-like landslides. Moreover, nonlinear oscillatory and transition waves are generated by plunger-like and transition landslides, respectively. It is also found that the wave height generated by piston-like landslide depends on the effective velocity of fluid translated by the landslide. For piston-like landslide motion, the correlation between the wave height, wavelength, and the effective velocity of a rigid landslide is established theoretically, and then, it is verified using numerical results. The present study is expected to provide a reference to investigate early warning of landslide-induced waves. [ABSTRACT FROM AUTHOR]

The escalating global demand for fish protein necessitates the expansion of aquaculture from land to sea, facilitated by floating sea cages. In this study, the National Institute of Ocean Technology (NIOT), Chennai, Tamil nadu conducted a pilot-scale culture of hatchery-reared cobia seeds (Rachycentron canadum) in HDPE collar floating cages (9 m diameter with a cultivable volume of 320 m³). These cages were strategically deployed at Olaikuda (Gulf of Mannar, Tamil Nadu) and Thuplipalem (Andhra Pradesh), representing semi-protected (SP) and open sea (OS) environments respectively. The evaluation focused on growth performance, with cobia seeds stocked in cages at an initial biomass of 150 g/m³ (SP) and 154 g/m³ (OS), featuring an initial average weight of 32.49 ± 1.77 g and a total length of 15.6 ± 0.91 cm during stocking. In SP site, cobia exhibited significant growth, reaching an average weight of 3830 g in 270 days, with a specific growth rate (SGR) of 1.76% with a survival rate of 77%. In contrast, despite the longer culture period of 322 days at the OS site, lower average weight of 2550 g with an SGR of 1.35% with survival rate 62% at SP. Physicochemical and biological parameters at both sites remained within optimal ranges. Notably, the OS site experienced higher wave heights (ranging from 0.56 to 2.28 m); potentially impacting feeding patterns, high energy expenditure due to the exposed weather conditions resulted into reduced growth rate compared to the sheltered bay. This study aims to elucidate the comparative suitability of environmental settings and its economic feasibility for open sea cage farming. [ABSTRACT FROM AUTHOR]

To analyze the macroscopic distribution characteristics of different exceedance probability wave heights in global waves, based on the five-year FHDI-GNWM global wave data from 2011 to 2015, the spatial macroscopic distribution patterns of different exceedance probabilities significant wave heights Hs worldwide were studied. The research shows that Hs with different exceedance probabilities exhibit obvious strong extremes and weak middles globally. For the Northwest Pacific, North Atlantic, and South Atlantic, Hs with different exceedance probabilities show a "first increase then decrease" trend with increasing latitude. For the Eastern Pacific, Hs with different exceedance probabilities exhibit a distinct pattern of being strong in the south and weak in the north, forming a distinct high-value zone near 55毅S. For the Indian Ocean, a distinct high-value zone is formed near 50毅S, and then decreases northward along the latitude zone. [ABSTRACT FROM AUTHOR]

The feasibility of using millimeter-wave radars for wave observations was investigated in this study. The radars used in this study operate at a center frequency of 77.572 GHz. To investigate the feasibility of wave observations and extract one-dimensional and two-dimensional wave spectra, arrays consisting of multiple radar units were deployed for observations in both laboratory and field environments. Based on the data measured with the millimeter-wave radars, one-dimensional wave spectra and two-dimensional wave directional spectra were evaluated using the periodogram method and the Bayesian directional spectrum estimation method (BDM), respectively. Meanwhile, wave parameters such as the significant wave height, wave period, and wave direction were also calculated. Via comparative experiments with a capacitive wave height meter in a wave tank and RADAC's WG5-HT-CP radar in an offshore field, the viability of using millimeter-wave radars to observe water waves was validated. The results indicate that the one-dimensional wave spectra measured with the millimeter-wave radars were consistent with those measured with the mature commercial capacitive wave height meter and the WG5-HT-CP wave radar. Via wave direction measurement experiments conducted in a wave tank and offshore environment, it is evident that the wave directions retrieved with the millimeter-wave radars were in good alignment with the actual wave directions. [ABSTRACT FROM AUTHOR]

Wave energy is still insufficiently explored and exploited as a future energy source. Climate change is an additional force that affects energy potential changes. Therefore, this study aims to evaluate the wave energy under climate change and to project it for the near (2025–2044) and far (2081–2100) future by applying the wave energy flux (WEF) approach and statistical relations between wind speeds and wave heights. The study was concentrated on the Baltic Sea nearshore at the Lithuanian territorial water. The analysis of existing relations between wind speeds and wave heights was found based on historical observations of the reference period (1995–2014), and the projections of WEF were created using the downscaled output of best-fit global climate models (GCMs) according to four scenarios of Shared Socioeconomic Pathways (SSP). The results indicated strong relations between wind speed and wave height, especially for the west-origin winds. Depending on the selected scenarios, the projected WEF may increase up to 10% (SSP5-8.5) and 11% (SSP1-2.6) in the near and far future respectively. The absence of large differences between the periods may be caused by the rough resolution of grid cells of GCMs. The comparison with the results based on regional climate models output could be a future perspective in order to reach a better representation of regional forces and to introduce more clarity to the obtained results. The results of this study may be advantageous for the primary planning of renewable energy sources (RES) development, especially in the face of climate change.

The reason fishermen lose control is wave height and wind speed. The impact is also felt by all users of the marine sector. This research uses the Long Short Term Memory (LSTM) method because this method has accurate values in the forecasting process with a lot of historical data and uses the Prophet method to detect outliers with Newton interpolation to replace the detected outlier data. The total number of data was 2074 obtained from BMKG Perak Surabaya from January 2020 to November 2022 at four research points, namely north, northeast, east and south points. The test results provide varying error values with MAPE as the model evaluation value. The error value for sea wave height at the north, northeast, east and south points is 13.32 respectively; 13.32; 9.32 and 8.85 with data without interpolation. Meanwhile, the error value in the wind speed data is 14.74; 14.85; 15.14 and 14.52 with a 3rd order Newton interpolation process at the northeast and east points. MAPE values below 20% prove that the LSTM model is good for predicting wave height and wind speed data at four points in Sumenep Regency. The system implementation is made into a web-based application.

The joint design criteria of significant wave heights and wind speeds are quite important for the structural reliability of fixed offshore platforms. However, the design method that regards different ocean environmental variables as independent is conservative. In the present study, we introduce a bivariate sample consisting of the maximum wave heights and concomitant wind speeds of the threshold by using the peak-over-threshold and declustering methods. After selecting the appropriate bivariate copulas and univariate distributions and blocking the sample into years, the bivariate compound distribution of annual extreme wave heights and concomitant wind speeds is constructed. Two joint design criteria, namely, the joint probability density method and the conditional probability method, are applied to obtain the joint return values of significant wave heights and wind speeds. Results show that (28.5±0.5)ms−1 is the frequently obtained wind speed based on the Atlantic dataset, and these joint design values are more appropriate than those calculated by univariate analysis in the fatigue design. [ABSTRACT FROM AUTHOR]

In the second generation intact stability criteria formulated by IMO, parametric rolling is one of the five failure modes. In this paper, a method of equivalent roll damping is used to study the parametric rolling of the KCS container ship. This method converts the nonlinear roll damping calculated by CFD into linear roll damping. Then the parametric rolling of the KCS container ship in regular waves is predicted based on the Rankine panel method. To compare the effectiveness of this method, the improved Ikeda's empirical formula is used to calculate the roll damping and predict the parametric rolling, and the results of the two methods are compared with the test results of the KCS container ship. Finally, the influence of initial roll angles, the ratio of the encounter frequency ω e to the rolling natural frequency ω roll and the wave height on parametric rolling are studied. The results show that the calculation results of the equivalent roll damping method are in good agreement with the experimental results, and the parameter rolling can be predicted with high accuracy. The initial roll angle will not affect the roll angle when the stable situation is acquired, but it will affect the time to reach the steady state. The range of ω e / ω roll can be quite wide when parametric rolling occurs. The wave height will affect the range of ω e / ω roll when the parametric rolling occurs. [ABSTRACT FROM AUTHOR]

In the face of depleting fossil energy and the imperative of sustainable development, there is a compelling drive towards advancing renewable energies. In this context, sustainable and predictable alternatives, like marine energy, gain prominence. Marine energy presents a cleaner option devoid of the adverse effects associated with fossil fuels, playing a crucial role in environmental sustainability by safeguarding coastlines against erosion. This study focuses on Astara Port in the Caspian Sea, exploring the utilization of wave energy converters (WECs). The originality of this study’s research lies in exploring WECs’ dual role in energy generation and coastal protection. Using MIKE21 software simulations, the impact of number, location, arrangement, and orientation of WECs across various scenarios was investigated, including two WEC number scenarios (11 and 13), three structural placement scenarios (north, front, and south of the port), two structural arrangement scenarios (linear and staggered), two port layout scenarios (original layout and modified layout), and two orientation scenarios for the structures (facing north-east, which is the dominant wave direction, and facing southeast). The results show a remarkable decrease in the significant wave height behind WECs, notably with 13 staggered devices facing dominant waves (from northeast), reducing the significant wave height Hs by 23–25%. This setup also shows the highest wave height reduction, notably 36.26% during a storm event. However, linear WEC setup offers more extensive coastline protection, covering 47.88% of the model boundary during storms. Furthermore, the 11 staggered WECs facing southeast (SE) arrangement had the lowest sediment accumulation at 0.0358 m over one year, showing effective sedimentation mitigation potential. Conversely, the 13 linear WECs facing northeast (NE) had the highest accumulation at 0.1231 m. Finally, the proposed port design redirects high-velocity flow away from the port entrance and removes rotatory flow, reducing sediment accumulation near the harbor entrance.

Doppler mis-registrations in azimuth can lead to ocean waves shorter than a specific wavelength being undetectable by SAR. In order to evaluate the actual ocean wave observation ability, the accuracy of Sentinel-1 SAR ocean wave spectra from January 2016 to December 2021 is evaluated by comparisons to NDBC buoys, ERA5 wave height, and CMEMS buoys. The results compared with NDBC show that the spectral shape of Sentinel-1 SAR ocean wave spectra is accurate, while the spectral values need to be improved. The wave spectra of Sentinel-1 have the best observations in season autumn. The comparison results of total wave height show the RMSE and bias are 0.91 m and −0.52 m for the comparisons to NDBC buoy wave spectra data, 0.93 m and −0.68 m for the comparison to ERA5 wave height data, and 0.9 m and −0.35 m for the comparisons to CMEMS buoy data. The comparison results of wave height in different wind speeds and areas shows that the accuracy of Sentinel-1 wave mode data is relatively good in the open ocean located in middle and low latitude area under the medium wind speed, while those are relatively poor in high latitude areas or the areas with excessively high or low wind speed.

Featured Application: With the continuous development of marine engineering, super-large-diameter piles have been designed and constructed in deep water with complex and severe waves and currents. It is an important challenge in engineering design to determine wave and current loads of the super-large-diameter pile reasonably and accurately. However, the hydrodynamic coefficient given in the current design specifications are determined based on the model tests of small-diameter piles, which will no longer be applicable to the calculation of wave and current loads of super-large-diameter pile. In this article, taking one of the 6.3-m super-large-diameter piles of the main pier foundation of the Xihoumen Rail-cum-Road Bridge as the research object, we focused on the wave and current load characteristics and development laws of the super-large-diameter pile, and proposed the hydrodynamic coefficients of the super-large-diameter pile suitable for deep water, strong wave and current conditions. It can provide important reference for the engineering design of super-large-diameter pile for the foundation projects of cross-sea bridges, offshore platforms and offshore wind turbines in the future. Recently, the diameters and construction water depths of the pile foundations of planned and newly built sea-crossing bridges have been increasing greatly. Hydrodynamic loads are the key control factors in the design of super-large-diameter piles. However, most of the previous studies focused on the inline force on the pile with a small diameter, and there were few cases to consider the impact of the transverse force on the hydrodynamic load of the pile under wave-current actions. In this study, to understand the hydrodynamic loads on such deep-water super-large-diameter piles, the prototype was one of the 6.3-m piles used in the Xihoumen Rail-cum-Road Bridge, and 1:60-scale model tests were carried out in an experimental tank, with the actions of regular waves and waves combined with currents used as loads. The influence of the current velocity and static wave height on the inline and transverse forces on the pile was measured and analyzed. The experimental results indicate that with increasing current velocity, the fluctuation characteristics of the wave-current-induced inline and transverse forces change significantly, and their peak values increase obviously compared to those induced by only waves. In particular, the peak transverse force increases tens of times and can become equivalent to the inline force. The modified Morison formula and Kutta–Joukowski formula are used to derive the correlations between the drag coefficient CD, inertia coefficient CM, lift coefficient CL, and redefined Keulegan–Carpenter number KC*. Under wave-current action, the transverse force contributes quite significantly to the hydrodynamic load on a super-large-diameter pile, making it easier to trigger extreme structural loads. The results presented herein are an important reference for the engineering designs of such super-large-diameter piles. [ABSTRACT FROM AUTHOR]

One of the most remarkable renewable energy applications is the floating photovoltaic (FPV) power plants in recent years. Although it reduces evaporation and increases solar energy production with the thermal cooling effect, determining the location for the installation of the facilities is a significant problem. There is a lack of a common methodology of evaluating the optimum deployment locations for FPV systems for micrositing of water reservoirs in anywhere in the world. Firstly, solar irradiance should be evaluated over the entire reservoir area because of the shading effects. There are also some dynamical constraints through the formation of extreme winds and water waves over the reservoir surface. Consideration of these restrictions provides a geographically suitable site location for FPV installation. In the present study, three essential natural constraints, namely solar irradiance, wind speed, and wave height, were analyzed over the reservoir of a dam located in the southwest of Turkey. The places where the insolation is high, and the wind speed and the wave height are both low in the entire reservoir area are spatially determined with this approachment, which is named as the FPV Convenient Reservoir Surface (FPV-CRS). The goal of this research is to offer a new methodology including essential guideline for micrositing of the FPV facilities. [ABSTRACT FROM AUTHOR]

Several coastal barriers experienced significant erosion and change in shape throughout the Mediterranean coasts over the past decades, and the issue has become of increasing concern for scientists and policymakers. With reference to a case study and by meteorological and geomorphological investigations, this note aims to define the wind–wave conditions, infer the net longshore transport, and detect the geomorphological processes that shape the landforms of the Cesine Lagoon barrier (South Italy). Despite the importance of the site in coastal defense and environmental conservation, there are still no specific studies. A challenge for this research was to obtain significant results from publicly available sources and simple and inexpensive methods. Geomorphological changes, such as the retreat of dune toes, accretion of washover fans, and formation of gravel beaches, are related to the analyzed wind–wave conditions. The net longshore transport is found in accordance with the direction of the more intense winds. The role of extreme events in the shaping of coastal landforms is yet to be established, even if they greatly increase the vulnerability to flooding of the study area. The results achieved so far are starting points for further data collection and analysis in the perspective of assessing the impact of climate changes and the threatening hazards on the lagoon barrier. [ABSTRACT FROM AUTHOR]

Abstract Coastal bridges are susceptible to severe damage when subjected to successive earthquake-tsunami events. Previous studies mainly consider the tsunami loadings as hydrodynamic forces, whereas other hydrodynamic forces such as uplift and slamming forces, are not fully investigated. Moreover, there are limited studies on the dynamic performance of simply supported girder bridges under the earthquake-tsunami sequences. To this end, this paper aims to conduct an in-depth investigation on dynamic performance of simply supported bridges subjected to sequential earthquake and tsunami hazards by means of a high-fidelity wave force simulation approach. More specifically, a typical, already constructed simply supported girder bridge is taken as the example bridge, and the numerical model of this bridge is built using the analytical platform OpenSees. The applied time series of tsunami wave force with five wave heights are generated based on a refined computational fluid dynamics (CFD) model, and are separately combined with the time histories of 21 pairs of far-field earthquake records to generate the sequential earthquake and tsunami loadings. Subsequently, nonlinear time history analyses (NTHAs) are carried out to obtain the structural dynamic responses, and the effects of preceding earthquakes and wave heights on the performance are investigated. Results indicate that the bearings are susceptible to the damage in the longitudinal direction of the bridge under the sequential earthquake and tsunami loadings, while the piers sustain more damage in the transverse direction. The preceding earthquakes have a significant effect on the bridge performance, and the effect becomes more pronounced with the increase of the ground motion intensity. The contribution of the tsunami loadings to the bridge response increases as the wave height rises. In particular, the transverse pier drift is dominated by the tsunami loadings when the wave height is higher than 7 m. The outcome of this study could aid the design and management of coastal bridge subjected to successive earthquake-tsunami events.

Integrating existing liquid storage and supply tanks in buildings with tuned liquid dampers (TLDs) are significant for reducing the effective cost of TLDs. However, existing water supplement devices for fire-suppression liquid tanks may overfill with water, which leads to TLD mistuning. To overcome this problem, a passive liquid control system named TLD with a stable replenishment sub-tank system (TLD-SRS) is proposed. The system, which consists of an additional sub-tank connected to the main tank and a floating ball, replenishes liquid in the TLD automatically. The system can avoid vibration interference and maintain the normal operation of the passive replenishment system under usual wind loads. According to the studies of tuned liquid column dampers (TLCD), the proposed TLD with a stable replenishment sub-tank system (TLD-SRS) uses simple devices to ensure that the liquid level in the TLD is steady at the target liquid level with a floating ball. The TLD-SRS is verified on a large-scale TLD shaking table experiment. The overshoot, which is the percentage of liquid that exceeds the target volume of TLD is calculated during sloshing with wind loads. Compared with TLD installed with a regular liquid replenishment device, the proposed TLD-SRS significantly reduces the overshoot of liquid and acceleration on the roof of the building. [ABSTRACT FROM AUTHOR]

In this paper, we present some wave height estimates for the two-dimensional steady periodic water waves subject to the effect of vorticity. The lower bounds of wave heights for the case of positive vorticity and negative vorticity are derived, respectively. These results are associated with the pressure data at the flat bed and velocity data on trough line, and to the pressure data at the flat bed and velocity data on crest line, respectively. Furthermore, we provide some upper bounds of wave heights, which rely on velocity and pressure data at an arbitrary intermediate depth. In addition, we show some applications of the present model.

The feasibility of using millimeter-wave radars for wave observations was investigated in this study. The radars used in this study operate at a center frequency of 77.572 GHz. To investigate the feasibility of wave observations and extract one-dimensional and two-dimensional wave spectra, arrays consisting of multiple radar units were deployed for observations in both laboratory and field environments. Based on the data measured with the millimeter-wave radars, one-dimensional wave spectra and two-dimensional wave directional spectra were evaluated using the periodogram method and the Bayesian directional spectrum estimation method (BDM), respectively. Meanwhile, wave parameters such as the significant wave height, wave period, and wave direction were also calculated. Via comparative experiments with a capacitive wave height meter in a wave tank and RADAC’s WG5-HT-CP radar in an offshore field, the viability of using millimeter-wave radars to observe water waves was validated. The results indicate that the one-dimensional wave spectra measured with the millimeter-wave radars were consistent with those measured with the mature commercial capacitive wave height meter and the WG5-HT-CP wave radar. Via wave direction measurement experiments conducted in a wave tank and offshore environment, it is evident that the wave directions retrieved with the millimeter-wave radars were in good alignment with the actual wave directions.

An intelligent single radar image de-raining method based on unsupervised self-attention generative adversarial networks is proposed to improve the accuracy of wave height parameter inversion results. The method builds a trainable end-to-end de-raining model with an unsupervised cycle-consistent adversarial network as an AI framework, which does not require pairs of rain-contaminated and corresponding ground-truth rain-free images for training. The model is trained by feeding rain-contaminated and clean radar images in an unpaired manner, and the atmospheric scattering model parameters are not required as a prior condition. Additionally, a self-attention mechanism is introduced into the model, allowing it to focus on rain clutter when processing radar images. This combines global and local rain clutter context information to output more accurate and clear de-raining radar images. The proposed method is validated by applying it to actual field test data, which shows that compared with the wave height derived from the original rain-contaminated data, the root-mean-square error is reduced by 0.11 m and the correlation coefficient of the wave height is increased by 14% using the de-raining method. These results demonstrate that the method effectively reduces the impact of rain on the accuracy of wave height parameter estimation from marine X-band radar images. [ABSTRACT FROM AUTHOR]

Facing the exhaustion of fossil energy and in the context of sustainable development, strong incentives are pushing for the development of renewable energies. Nuclear energy and fossil fuels like petroleum, coal, and natural gas provide most of the energy produced today. As a result, greenhouse gases are released and climate change becomes irreversible. Furthermore, radioactive waste disposal causes severe radiation pollution in nuclear power. Alternatives such as marine energy are more sustainable and predictable. It has none of the detrimental effects of fossil and nuclear energies and is significant in terms of environmental sustainability by defending the coastline from erosion. Here, we study the Palm Beach-Azur region near Algiers on the Mediterranean Sea. The study aims to use wave energy converters (WEC) to generate clean energy and reduce coastline erosion. The results of this study show that in the presence of wave energy converters, the wave height decreased by 0.3 m, and sediment deposition increased by 0.8 m. Thus, sand deposit prediction demonstrates that the presence of WEC decreases marine erosion and contributes to an accumulation of sediments on the coast. Moreover, this confirms that WECs can serve a dual role of extracting marine energy by converting it into electrical energy and as a defence against marine erosion. Therefore, WECs justify their efficiency both in energy production and economic and environmental profitability due to coastal protection. [ABSTRACT FROM AUTHOR]

The effects of wave height and forward speed on the seakeeping performance of a small fishing vessel in irregular waves are evaluated using computational fluid dynamics (CFD). The wave height effect changed linearly for a forward speed in the head sea and beam sea. In the stationary state, the heave and roll motions attributed to the wave height appear nonlinearly. The effect of the speed showed a non-linear shape wherein the heave motion became larger with an increase in the forward speed in beam sea. The seakeeping performance of pitch motion is greatly improved at forward speed rather than in a stationary state. The seakeeping performance of the roll motion is more dangerous than the pitch motion, regardless of wave height and vessel speed. The mean roll period in irregular waves is obtained through this study, and it is longer than the natural roll period in still water. It is necessary to be careful as the probability of exceeding the limit is high and GM is decreased in transverse waves. [ABSTRACT FROM AUTHOR]

The constraint conditions have a great influence on the geometry of reservoir landslides during mass movement and are one of the most important parameters for predicting landslide-generated waves. To explore the effects of constraint conditions on the characteristics of landslide-generated waves (such as wave height, amplitude and period), 54 sets of landslide-generated wave physical model experiments based on the orthogonal experimental design method were conducted in this paper. Furthermore, the wave characteristics under constrained and semiconstrained conditions were analysed using statistical methods. The results indicate that the wave period is basically unaffected by the constraint conditions, while the wave height and amplitude of the semiconstrained model are smaller than those of the constrained model, the initial wave height of the semiconstrained model is approximately 0.95 times higher than that of the constrained model, and the maximum amplitude of the semiconstrained model is approximately 0.9 times that of the constrained model. Therefore, it is safer to predict the initial wave height and maximum amplitude by using the geometric parameters before failure, although the geometry of the landslide has been greatly changed from its original state.This study can provide a theoretical basis for landslide-tsunamis prediction.

The demand for liquid carriers, such as liquefied natural gas (LNG), has increased in recent years. One of the most common types of LNG carriers is the membrane type, which is often built by a shipyard with a prismatic tank shape. This carrier is commonly known for its effective ways to mitigate sloshing using a baffle. Therefore, this study was performed to evaluate sloshing in a prismatic tank using vertical and T-shape baffles. The sloshing was conducted with 25% and 50% filling ratios because it deals with the nonlinear free-surface flow. Furthermore, the smoothed particle hydrodynamics (SPH) was used to overcome sloshing with ratio of a baffle and water depth is 0.9. A comparison was made for the dynamic pressure with the experiment. The results show that SPH has an acceptable accuracy for dynamic and hydrostatic pressures. Baffle installation significantly decreases the wave height, dynamic pressure and hydrodynamic force.

The ultrafinestrip (UFS) of the Gaofen-3 (GF-3) satellite provides extensive ocean wave details due to the high spatial resolution of 3 m. In this article, a new empirical model is developed to estimate wave height from GF-3 UFS mode data in South China Sea (SCS). Traditional methods either have more input parameters or complex forms or complex transformations, and most of them depend on the visible wave pattern. The model has the advantages of fewer input parameters and unnecessary visual wave patterns. The wave height estimation model is developed based on the collated data pairs between GF-3 UFS data in horizontal-horizontal polarization and the ERA5 reanalysis dataset from 2018 to 2021. The datasets are randomly divided into two groups. One group (about 80%) is used to develop the empirical relation; the other group (about 20%) and some altimeter data are used for significant wave height (SWH) verification. The comparison of the model data with the remaining ERA5 (ECMWF Reanalysis v5) data and the altimeter shows that the root-mean-square error is 0.41 and 0.47 m, the scatter index is 29.24% and 29.79%, and the correlation coefficient is 0.90 and 0.82, respectively. These statistical indices suggest that the developed model is suitable for SWH retrievals. So, the study results indicate that the GF-3 UFS mode data provide valuable information about wave conditions in the SCS.

Coastal flooding compound events can be caused by climate-driven extremes of storm surges and waves. To assess the risk associated with these events in the context of climate variability, the bivariate extremes of skew surge (S) and significant wave height (HS) are modeled in a nonstationary framework using physical atmospheric/oceanic parameters as covariates (atmospheric pressure, wind speed and sea surface temperature). This bivariate nonstationary distribution is modeled using a threshold-based approach for the margins of S and HS and a dynamic copula for their dependence structure. Among the covariates considered, atmospheric pressure and related wind speed are primary forcings for the margins of S and HS, but temperature is the main positive forcing of their dependence. This latter relation implies an increasing risk of compound events of S and HS for the studied site in the context of increasing global temperature. [ABSTRACT FROM AUTHOR]

Due to climate change, hydroclimatic extremes are becoming more frequent and intense and their characterization and analysis is essential for climate modelling. One of the regions that will be most affected by these extremes is the Mediterranean coast of Spain. Therefore, this paper analyses the significant wave height (Hs), peak wave period (Tp) and sea level (SL) extremes and their correlation along the Spanish Mediterranean coast. After conducting this analysis, it is finally concluded that and adjustment of the extreme long-term distribution of Tp is urgently needed to create accurate models and projections, which must be considered in combination with the intense extremes happening in the Levantine basin when modelling this area and designing new projects. [ABSTRACT FROM AUTHOR]

Coastal dynamic forces, such as waves and tides, altogether drive groundwater circulation and salt transport in the intertidal zone. However, few numerical studies have ever considered the combined effects of waves and tides. In this study, the fluctuations of wave height are integrated with tidal level together using an iterative least squares fitting method, in which the wave height can be acquired from measured sea level in the surf zone, and this fitted wave height is further verified by wind speed. Groundwater flow and salt transport were then simulated using the MARUN code to evaluate the impacts after considering wave effect. The simulated equivalent freshwater head and salinity of the model with wave effect presented less difference with the measured data compared with the simulated results of the model without wave effect. After incorporating the wave effect in a model, submarine groundwater discharge (SGD) was increased, among which recirculated SGD grew more rapidly than the fresh, leading to the proportion of the fresh SGD accounting for a small proportion (1.1%). The water influx and efflux rates increased greatly especially during the period of high wave height. Most of the influx occurred in the intertidal zone, while a considerable amount of efflux occurred in the subtidal zone. The iterative algorithm to separate the wave height from the mixed field data can be employed to identify and quantify the respective effects of tides and the combined effects of waves and tides on the density‐dependent beach groundwater flow. Key Points: A new iterative algorithm was proposed to quantify tidal level and wave height using hourly measured surf zone sea level dataBeach groundwater flow and salinity distribution were numerically reproduced using wave height and setup as boundary conditionsWaves may significantly change groundwater flow and salinity distribution in a beach aquifer [ABSTRACT FROM AUTHOR]

Coastal bridges are susceptible to severe damage when subjected to successive earthquake-tsunami events. Previous studies mainly consider the tsunami loadings as hydrodynamic forces, whereas other hydrodynamic forces such as uplift and slamming forces, are not fully investigated. Moreover, there are limited studies on the dynamic performance of simply supported girder bridges under the earthquake-tsunami sequences. To this end, this paper aims to conduct an in-depth investigation on dynamic performance of simply supported bridges subjected to sequential earthquake and tsunami hazards by means of a high-fidelity wave force simulation approach. More specifically, a typical, already constructed simply supported girder bridge is taken as the example bridge, and the numerical model of this bridge is built using the analytical platform OpenSees. The applied time series of tsunami wave force with five wave heights are generated based on a refined computational fluid dynamics (CFD) model, and are separately combined with the time histories of 21 pairs of far-field earthquake records to generate the sequential earthquake and tsunami loadings. Subsequently, nonlinear time history analyses (NTHAs) are carried out to obtain the structural dynamic responses, and the effects of preceding earthquakes and wave heights on the performance are investigated. Results indicate that the bearings are susceptible to the damage in the longitudinal direction of the bridge under the sequential earthquake and tsunami loadings, while the piers sustain more damage in the transverse direction. The preceding earthquakes have a significant effect on the bridge performance, and the effect becomes more pronounced with the increase of the ground motion intensity. The contribution of the tsunami loadings to the bridge response increases as the wave height rises. In particular, the transverse pier drift is dominated by the tsunami loadings when the wave height is higher than 7 m. The outcome of this study could aid the design and management of coastal bridge subjected to successive earthquake-tsunami events. [ABSTRACT FROM AUTHOR]