Wave Model Simulating WAves Nearshore Research Articles

NUMERICAL SIMULATION OF GRAVEL NOURISHMENT TO THE SEISHO COASTLINE IN JAPAN

It is feared that as a consequence of the potential future intensification of tropical cyclones due to ongoing climate change the patterns of coastal erosion around the world could change. In this study, the mesoscale meteorological model WRF (Weather Research and Forecasting), the third-generation stand-alone wave model SWAN (Simulating WAves Nearshore), and the coastal deformation model XBeach (eXtreme Beach behavior) are combined to calculate the short-term coastal deformation caused by high waves during the approach of Typhoon No.21 (Paolo) in 2017 to the Seisho Coast and Niigata Coast in Japan (Nishida and Shibayama, 2020). The model is then applied to predict future patterns of coastal erosion. Potential countermeasures to prevent future coastal erosion are then examined. The construction of detached breakwaters, which are currently used as a countermeasure against coastal erosion in many parts of the world, is often opposed by local residents due to the changes they can produce on the fishing environment and landscape. Therefore, it is often desirable to stabilize the beach without constructing structures offshore. Thus, gravel nourishment is proposed as a countermeasure against the short-term erosion that can be caused high waves, and its benefits and impacts were verified through numerical simulations.

A Comparison of Wave Spectra during Pre-Monsoon and Post-Monsoon Tropical Cyclones under an Intense Positive IOD Year 2019

The impact of Indian Ocean Dipole (IOD) events on the generation and intensity of tropical cyclones under the influence of monsoons is explored. The standardized sea surface temperature (SST) anomalies are computed for the pre-monsoon and post-monsoon months for the Bay of Bengal (BOB) and Arabian Sea (AS) from 1971 to 2020 and relationships are analyzed with the frequency of tropical cyclones for the neutral, positive and negative IOD years. Ocean states are sensitive to cyclonic conditions exhibiting a complex spectral distribution of the wave energy. Due to a tropical cyclone, the surface waves remain under high wind forcing conditions for prolonged periods generating a huge amount of energy. The spectral wave model SWAN (Simulating WAves Nearshore) is used to generate the energy density spectra during FANI (26 April–5 May 2019), which was a pre-monsoon extreme severe cyclonic storm, and BULBUL (5–12 November 2019), which was a post-monsoon very severe cyclonic storm in the BOB region. This study aims to estimate the intensity of wave energy during tropical cyclones in the pre- and post-monsoon months for 2019 (an extremely positive IOD year).

The effect of changing sea ice on wave climate trends along Alaska's central Beaufort Sea coast

Abstract. Diminishing sea ice is impacting the wave field across the Arctic region. Recent observation- and model-based studies highlight the spatiotemporal influence of sea ice on offshore wave climatologies, but effects within the nearshore region are still poorly described. This study characterizes the wave climate in the central Beaufort Sea coast from 1979 to 2019 by utilizing a wave hindcast model that uses ERA5 winds, waves, and ice concentrations as input. The spectral wave model SWAN (Simulating Waves Nearshore) is calibrated and validated based on more than 10 000 in situ time point measurements collected over a 13-year time period across the region, with friction variations and empirical coefficients for newly implemented empirical ice formulations for the open-water and shoulder seasons. Model results and trends are analyzed over the 41-year time period using the non-parametric Mann–Kendall test, including an estimate of Sen's slope. The model results show that the reduction in sea ice concentration correlates strongly with increases in average and extreme wave conditions. In particular, the open-water season extended by ∼96 d over the 41-year time period (∼2.4 d yr−1), resulting in a 5-fold increase in the yearly cumulative wave power. Moreover, the open-water season extends later into the year, resulting in relatively more open-water conditions during fall storms with high wind speeds. The later freeze-up results in an increase in the annual offshore median wave heights of 1 % yr−1 and an increase in the average number of rough wave days (defined as days when maximum wave heights exceed 2.5 m) from 1.5 in 1979 to 13.1 d in 2019. Trends in the nearshore areas deviate from the patterns offshore. Model results indicate a saturation limit for high wave heights in the shallow areas of Foggy Island Bay. Similar patterns are found for yearly cumulative wave power.

Numerical Simulation of Storm Waves during Typhoon Maysak and Haishen in the Korean Peninsula

In this study, we simulated storm waves induced by typhoon Maysak and Haishen in the Korean peninsula by using the third-generation numerical wave model SWAN(Simulating WAves Nearshore). We used the sea-surface wind data of KMA(Korea Meteorological Agency)’s operational meteorological model RDAPS(Regional Data Assimilation Prediction System), and JMA(Japan Meteorological Agency)’s weather forecast model JMA-MSM(Meso-Scale Model) as input forcing of the numerical wave model. In addition, the wind field of the tropical cyclone was established with JTWC(Joint Typhoon Warning Center)’s best track data for the storm wave simulation. We used two different source term options, which consider other physics of energy generation by wind and dissipation by whitecapping. Validation of the simulation result was conducted over statistical analysis with the observation data from KMA and KHOA(Korea Hydrographic and Oceanographic Agency)’s buoys. As a result, the whole scenario tended to overestimate significant wave height. The simulation result by using RDAPS as input forcing outperformed the result by using JMA-MSM. It denoted that the performance of a wave model depends on the accuracy of input forcing wind. The wind field by JTWC’s best track data was not suitable compared with the meteorological numerical model. ST6 simulated the wave height higher than Komen’s source term. However, Komen's source term simulated storm waves better than ST6 in this study, and further researches under various conditions are required to evaluate ST6 for the storm waves simulation. In the simulation of wave period parameters, it was hard to estimate the accuracy of the model, and other approaches are necessary for the evaluation.

Optimization of SWAN Wave Model to Improve the Accuracy of Winter Storm Wave Prediction in the East Sea

In recent years, as human casualties and property damage caused by hazardous waves have increased in the East Sea, precise wave prediction skills have become necessary. In this study, the Simulating WAves Nearshore (SWAN) third-generation numerical wave model was calibrated and optimized to enhance the accuracy of winter storm wave prediction in the East Sea. We used Source Term 6 (ST6) and physical observations from a large-scale experiment conducted in Australia and compared its results to Komen’s formula, a default in SWAN. As input wind data, we used Korean Meteorological Agency's (KMA’s) operational meteorological model called Regional Data Assimilation and Prediction System (RDAPS), the European Centre for Medium Range Weather Forecasts’ newest 5th generation re-analysis data (ERA5), and Japanese Meteorological Agency's (JMA’s) meso-scale forecasting data. We analyzed the accuracy of each model’s results by comparing them to observation data. For quantitative analysis and assessment, the observed wave data for 6 locations from KMA and Korea Hydrographic and Oceanographic Agency (KHOA) were used, and statistical analysis was conducted to assess model accuracy. As a result, ST6 models had a smaller root mean square error and higher correlation coefficient than the default model in significant wave height prediction. However, for peak wave period simulation, the results were incoherent among each model and location. In simulations with different wind data, the simulation using ERA5 for input wind datashowed the most accurate results overall but underestimated the wave height in predicting high wave events compared to the simulation using RDAPS and JMA meso-scale model. In addition, it showed that the spatial resolution of wind plays a more significant role in predicting high wave events. Nevertheless, the numerical model optimized in this study highlighted some limitations in predicting high waves that rise rapidly in time caused by meteorological events. This suggests that further research is necessary to enhance the accuracy of wave prediction in various climate conditions, such as extreme weather.

Generation of unstructured meshes using Delaunay triangles for tidal analysis of the port of Acapulco, Mexico

The main objective of the research is to suggest the use of unstructured meshes in the SWAN wave model because structured meshes require more adjustments in geographically small areas such as rivers, beaches or even bays. Third-party tools and data such as bathymetry, Meteorological Research Forecast (WRF), WaveWatch III (WWIII) and Simulating Waves Nearshore (SWAN) models were used to carry out the research. The aforementioned software and its own developments were used in Acapulco Bay, Guerrero, Mexico for the elaboration of maps that would serve as input in the generation of Delaunay diagrams, which in turn were fundamental parts in the configuration of the experiments and, with this, perform the analysis on the images of the simulations. With the results obtained, it is expected to confirm the validity of the wave data for the bay; therefore, it is considered a useful tool in the process of analysing the natural phenomena present in the port.

Inter-comparison of long-term wave power potential in the Black Sea based on the SWAN wave model forced with two different wind fields

In this study, a long-term comparative assessment of the potential of wave power in the Black Sea was conducted using the calibrated and validated SWAN (Simulating WAves Nearshore) model forced by two well-known wind fields. The European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) wind fields were used, covering data from 1979 to 2018. In general, the wave power potential based on the results of the CFSR wind field was found to be slightly higher than that obtained with the ERA-Interim wind field. The greatest discrepancy between the results of the ERA-Interim and CFSR wind fields was observed in the northeastern Black Sea. The spatial distributions of the wave power were also evaluated on a seasonal scale using wave parameters obtained from the calibrated SWAN model. The wave climate obtained from both long-term and seasonal assessments indicates that the western Black Sea, especially the southwestern Black Sea, is characterized by higher wave power potential and lower variability, while the eastern Black Sea has lower wave power potential and higher variability. Stable and powerful long-term wave conditions in the southwestern Black Sea can indicate that this region is a suitable location for wave farms. In contrast, the effect of the long-term variability on wave power is greatest in the eastern Black Sea owing to the highly variable wave conditions in this region.

Application of SWAN model for storm generated wave simulation in the Canadian Beaufort Sea

The wave model SWAN (Simulating WAves Nearshore) is implemented for the Canadian Beaufort Sea and storm generated waves are investigated through comparisons between in situ buoy observations and numerical simulations. Simulations are performed for four storms using the SWAN wave model. We specifically use SWAN's non-stationary and two-dimensional modes in a fine resolution nested domain within a coarse resolution domain. Two established whitecapping formulations in SWAN are examined; one is dependent on mean spectral wave steepness and the other is on local spectral steepness. Model simulations in the shallow fine resolution domain also consider the effects of bottom friction and nonlinear triad interactions. For the Beaufort Sea study area, wave simulations in which the white capping formulation is dependent on local spectral steepness are better than those where the dependency is on mean spectral steepness; however implementation of bottom friction term and triad mechanisms in the present study does not lead to any notable enhancement in the simulations.

Characteristics of global waves based on the third-generation wave model SWAN

Long-term wave data at a global scale are crucial for the studying characteristics of global waves, such as spatial distributions and extreme waves. These characteristics play significant roles in the design, construction, installation and operation activities of marine structures. Because of the limited resolution and coverage of instrumental measurements, the global wave hindcast is widely used. To develop this hindcast, the Simulating WAves Nearshore (SWAN) model is forced with the ERA-Interim wind database from 1979 to 2017 with a resolution of 0.25° in both longitude and latitude. The hourly wave parameters, such as the significant wave height and the mean period, are validated against buoy measurements over the Northwest Pacific Ocean, the Northeast Pacific Ocean and the Northwest Atlantic Ocean. Based on the 39-year simulated results, the spatial distributions of mean and maximal significant wave heights are analysed for all 39 years, every decade, 4 seasons, 12 months and special years; extreme waves are studied at the global scale and at every computational point.

Influence of Wave State and Sea Spray on the Roughness Length: Feedback on Medicanes

Occasionally, storms that share many features with tropical cyclones, including the presence of a quasi-circular “eye” a warm core and strong winds, are observed in the Mediterranean. Generally, they are known as Medicanes, or tropical-like cyclones (TLC). Due to the intense wind forcings and the consequent development of high wind waves, a large number of sea spray droplets—both from bubble bursting and spume tearing processes—are likely to be produced at the sea surface. In order to take into account this process, we implemented an additional Sea Spray Source Function (SSSF) in WRF-Chem, model version 3.6.1, using the GOCART (Goddard Chemistry Aerosol Radiation and Transport) aerosol sectional module. Traditionally, air-sea momentum fluxes are computed through the classical Charnock relation that does not consider the wave-state and sea spray effects on the sea surface roughness explicitly. In order to take into account these forcing, we implemented a more recent parameterization of the sea surface aerodynamic roughness within the WRF surface layer model, which may be applicable to both moderate and high wind conditions. The implemented SSSF and sea surface roughness parameterization have been tested using an operative model sequence based on COAWST (Coupled Ocean Atmosphere Wave Sediment Transport) and WRF-Chem. The third-generation wave model SWAN (Simulating Waves Nearshore), two-way coupled with the WRF atmospheric model in the COAWST framework, provided wave field parameters. Numerical simulations have been integrated with the WRF-Chem chemistry package, with the aim of calculating the sea spray generated by the waves and to include its effect in the Charnock roughness parametrization together with the sea state effect. A single case study is performed, considering the Medicane that affected south-eastern Italy on 26 September 2006. Since this Medicane is one of the most deeply analysed in literature, its investigation can easily shed some light on the feedbacks between sea spray and drag coefficients.

Coastal protection of the Romanian nearshore throughout hybrid wave and offshore wind farms

The objective of the present work is to estimate the influence of several hybrid wind and wave farm configurations on the wave conditions reported in the vicinity of the Saint George coastal area, in the Romanian nearshore of the Black Sea. Based on the wave data coming from a climatological database (ERA20C) and also on in situ measurements, it was possible to identify the most relevant wave patterns, which will be further considered for assessment. The numerical simulations were carried out with the SWAN (Simulating Waves Nearshore) wave model, which may provide a comprehensive picture of the wave transformation in the presence of the marine farms. Although the impact of the wind farm is not visible from the spatial maps, from the analysis of the values corresponding to the reference points, it was noticed that a maximum variation of 2% may occur for several wave parameters.

Coastal protection of the Romanian nearshore throughout hybrid wave and offshore wind farms

The objective of the present work is to estimate the influence of several hybrid wind and wave farm configurations on the wave conditions reported in the vicinity of the Saint George coastal area, in the Romanian nearshore of the Black Sea. Based on the wave data coming from a climatological database (ERA20C) and also on in situ measurements, it was possible to identify the most relevant wave patterns, which will be further considered for assessment. The numerical simulations were carried out with the SWAN (Simulating Waves Nearshore) wave model, which may provide a comprehensive picture of the wave transformation in the presence of the marine farms. Although the impact of the wind farm is not visible from the spatial maps, from the analysis of the values corresponding to the reference points, it was noticed that a maximum variation of 2% may occur for several wave parameters.

Uncertainty quantification and sensitivity analysis applied to the wind wave model SWAN

We report on measuring uncertainty in the computational results of the wind wave model SWAN (Simulating WAves Nearshore) on an unstructured mesh and exploring the sources of this uncertainty. We considered an area in the vicinity of the Saint Petersburg Flood Prevention Facility Complex and treat the results as risks on using the model results for the Facility gate operation.We found that model response uncertainty is significant for small waves (Hs<0.3m), and the results variability is moderate (≈10%) for the extreme values of the model prediction. Thus the risk on the use of model results to predict flood threats is low together with visible uncertainty about the prediction of flood start time.Uncertainty in wind velocity has a substantial influence on the model response. In addition, uncertainty in the bathymetry, water level, and breaker index affects model output. Therefore, result uncertainty can be decreased obtaining more certain values of these model inputs.

The effects of tropical cyclone characteristics on the surface wave fields in Australia's North West region

The numerical wave model SWAN (Simulating WAves Nearshore) and historical wave buoy observations were used to investigate the response of surface wave fields to tropical cyclone (TC) wind forcing on the Australian North West Shelf (NWS). Analysis of historical wave data during TC events at a key location on the NWS showed that an average of 1.7 large TCs impacted the region each year, albeit with high variability in TC track, intensity and size, and also in the surface wave field response. An accurately modeled TC wind field resulted in a good prediction of the observed extreme wave conditions by SWAN. Results showed that the presence of strong background winds during a TC and a long TC lifetime (with large variations in translation speed) can provide additional energy input. This potentially enhances the generated swell waves and increases the spatial extent of the TC generated surface wave fields. For the TC translation speeds in this study, a positive relationship between TC translation speed and the resulting maximum significant wave height and wave field asymmetry was observed. Bottom friction across the wide NWS limited the amount of wave energy reaching the coastal region; consistently reducing wave energy in depths below 50m, and in the case of the most extreme conditions, in depths up to 100m that comprise much of the shelf. Nevertheless, whitecapping was still the dominant dissipation mechanism on the broader shelf region. Shelf-scale refraction had little effect on the amount of wave energy reaching the nearshore zone; however, refraction locally enhanced or reduced wave energy depending on the orientation of the isobaths with respect to the dominant wave direction during the TC.

Development of an unstructured-grid wave-current coupled model and its application

An unstructured grid wave-current coupled model was developed by coupling the SWAN (Simulating Waves Nearshore) wave model and ADCIRC (Advanced Circulation model) ocean model through the Model Coupling Toolkit (MCT). The developed coupled model has high spatial resolution in the coastal area and is efficient for computation. The efficiency of the newly developed SWAN+ADCIRC model was compared with that of the widely-used SWAN+ADCIRC coupled model, in which SWAN and ADCIRC are coupled directly rather than through the MCT. Results show that the directly-coupled model is more efficient when the total number of computational cores is small, but the MCT-coupled model begin to run faster than the directly-coupled model when more computational cores are used. The MCT-coupled model maintains the scalability longer and can increase the simulation efficiency more than 35% by comparing the minimum wall clock time of one day simulation in the test runs.The MCT-coupled SWAN+ADCIRC model was used to simulate the storm surge and waves during the typhoon Usagi which formed in the western Pacific on September 17, 2013 and landed at Shanwei, China. Three numerical experiments were performed to investigate the effect of wave-current interaction on the storm surge and waves. The results show that the coupled model can better simulate the storm surge and waves when considering the wave-induced radiation stress, the wave effect on the wind stress drag coefficient and the modulation of current and water level on waves. During the typhoon Usagi, the effect of wave radiation stress could result in a maximum of 0.75m increase in the extreme storm surge, and the wave induced wind stress could cause a −0.82∼0.48m change of the extreme storm surge near the coastal area. Besides, the radiation stress forced currents cannot be ignored either in the study of mass transport at coastal zones. Results of this study are useful for understanding the wave-current interaction processes and the development of the operational prediction technique for storm surge and waves.

Variability of Benthic Communities in Relation to Hydrodynamic Conditions in the North-Eastern Baltic Sea

ABSTRACT Herkul, K.; Torn, K.; Suursaar, U.; Alari, V., and Peterson, A., 2016. Variability of benthic communities in relation to hydrodynamic conditions in the north-eastern Baltic Sea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 867–871. Coconut Creek (Florida), ISSN 0749-0208. Wave forcing is an important hydrodynamic variable that influences spatial patterns and temporal dynamics of marine benthos. In this study, we used three principally different wave models – simplified wave model (SWM), spectral wave model SWAN (simulating waves nearshore), and locally calibrated point model (LCPM) – to assess the effects of wave forcing on the distribution and temporal dynamics of macrobenthos in the north-eastern Baltic Sea. Other important environmental variables like depth, salinity, turbidity etc., were also included into analyses of benthos distr...

The impact of surface currents and sea level on the wave field evolution during St. Jude storm in the eastern Baltic Sea

Summary A third generation numerical wave model SWAN (Simulating WAves Nearshore) was applied to study the spatio-temporal effect of surface currents and sea level height on significant wave height; and to describe the mechanisms responsible for wave–current interaction in the eastern Baltic Sea. Simulation results were validated by comparison with in situ wave measurements in deep and shallow water, carried out using the directional wave buoy and RDCP respectively, and with TerraSAR-X imagery. A hindcast period from 23 to 31 October 2013 included both a period of calm to moderate weather conditions and a severe North-European windstorm called St. Jude. The prevailing wind directions were southerly to westerly. Four simulations with SWAN were made: a control run with dynamical forcing by wind only; and simulations with additional inputs of surface currents and sea level, both separately and combined. A clear effect of surface currents and sea level on the wave field evolution was found. It manifested itself as an increase or decrease of significant wave height of up to 20%. The strength of the interaction was influenced by the propagation directions of waves and surface currents and the severity of weather conditions. An increase in the wave height was mostly seen in shallower waters and in areas where waves and surface currents were propagating in opposite directions. In deeper parts of the eastern Baltic Sea and in case of waves and surface currents propagating in the same direction a decrease occurred.

Analysis of the Effect of a Marine Energy Farm to Protect a Biosphere Reserve

Sacalin Peninsula in the Black Sea is a new land located south of the Saint George branch of the Danube. Since 1938 this area became a biosphere reserve since many rare species of animals and plants are to be found there. The generation of this new peninsula is due to the sedimentary process induced by the Danube River outflow and it was started more than 150 years ago. In the winter of 2013 this environment was seriously affected by some very strong storms putting in real danger this ecosystem. From this perspective, the objective of the present work is to evaluate the protection that might be offered to this area by a marine energy farm that would be deployed in front of the peninsula. In order to assess the coastal protection offered by the proposed solution, simulations with the SWAN (Simulating Waves Nearshore) wave model have been performed for the most relevant storm patterns. The results show that a marine energy farm can provide a real sheltering effect to the ecological reserve. Such approach seems to be also economically viable since this coastal environment represents a real hot spot in the Black Sea from the point of view of marine energy resources.

Wave Simulation for Submarine Cable Route of Southwest Sea Offshore Wind Farm Using the SWAN Model

Submarine cable installation is essentials for grid connection between existing power grid and newly produced electricity which will be from offshore wind farm in Southwest sea area of Korea. Especially, submarine cable route and protection method is designed in order to ensure the economical efficiency, workability and stability of submarine cable installation. On this paper, we will give the basic information about the submarine cable route and protection method of offshore wind farm which will be built in Southwest sea area of Korea. For this, we have a numerical simulation at high and low tide based on the third-generation wave model SWAN(Simulating WAves Nearshore) using the long term wave data from Korea Institute of Ocean Science and Technology(KIOST). The results of the study, year mean Hs is 1.03m, Tz is 4.47s and dominant wave direction is NW and SSW When the incident wave direction is NW(Hs: 7.0 m, Tp: 11.76s), the distribution of shallow water design wave height Hs was calculated about 4.0~5.0m at high tide and 2.0~3.0m at low tide. When the incident wave direction is SSW(Hs: 5.84 m, Tp: 11.15s), the distribution of shallow water design wave height Hs was calculated about 3.5~4.5m at high tide and 1.5~2.5m at low tide. The wave direction on a dominant influence in the section of longitude UTM 249749~251349(about 1.6 km) and UTM 251549~267749(about 16.2 km) in the submarine cable route are each NW and SSW. Prominently, wave focusing phenomenon appears between Wi-do and Hawangdeung-do, in this sea area is showing a relatively high wave hight than the surrounding sea areas.

Sea state observation in island-sheltered nearshore zone based on in situ intermediate-water wave measurements and NCEP/CFSR wind data

In this study, wind-seas, swells, and the coastal wind pattern are examined to interpret the temporal diversity of the sea state in the island-sheltered nearshore zone off Karwar on the west coast of India. The sea state is analyzed based on the sea swell energy ratio (SSER) criteria and inverse wave age (IWA) criteria. The SSER is estimated following a one dimensional spectral split of in situ intermediate-water waves measured by deploying a directional waverider buoy. The IWA is estimated based on the measured waves and the National Centres for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) wind data followed by validation with the autonomous weather station (AWS) wind data. Additionally, wave transformation in and around offshore islands is examined using the wind wave model SWAN (Simulating WAves Nearshore). The NCEP/CFSR wind data exhibited sea breezes as well as land breezes, and also revealed good correlation to the AWS wind data during sea breeze events. Observation revealed that the SSER criteria is more practical than the IWA criteria for interpreting the sea state in the nearshore zone, where the diversity of the sea states depend significantly on the variation of coexisting wind-seas and swell proportions. The SWAN model revealed that wave propagation and transformation in the island-sheltered nearshore zone is influenced considerably by the direction of the offshore waves to the associated island(s), where the simulated wave characteristics in the SWAN model are found more reliable based on the parametric boundary condition. Further, the study revealed that modeling is a necessary task apart from a single point observation to understand surface wave propagation and transformation in an island-sheltered nearshore zone.