Third-generation Ocean Wave Model Research Articles

A high-resolution wave energy assessment of south-east Australia based on a 40-year hindcast

In this study, a third-generation ocean wave model (WAVEWATCH III; WW3) implemented on a high-resolution unstructured grid was developed to investigate wave energy in the south-east of Australia over the 40-year period from 1981 to 2020. The simulated wave power shows good agreement with values estimated from multiplatform satellite data. Thus, the modeled data were used to study statistics (mean conditions, seasonality, extremes, and long-term trends) of wave power in the domain, which show impacts of Southern Ocean swell and protection provided by the land mass of Tasmania. The results indicate increasing wave power trends, with the largest values in the southeastern part of the domain over the 40-year period. These positive trends are mainly a result of an increase in significant wave height rather than peak wave period. By utilizing the simulated wave properties, we estimated regional annual electric power at 14 coastal locations using 9 typical wave energy converters (WECs). To do so, we conducted a comprehensive analysis (seasonal variations, wave power roses, probability distributions, and bivariate probability distributions) at these locations. The results demonstrate that the western and southwestern coasts of the domain are promising generation sites but with large seasonal variability. The central and eastern coasts are protected by Tasmania, and exhibit more stable conditions but are far less energetic for electricity production. This study has critical implications for the region, which provides a benchmark for coastal WEC deployment.

Effect of Tide Level Change on Typhoon Waves in the Taiwan Strait and Its Adjacent Waters

In recent years, most research on typhoons in the Taiwan Strait and its adjacent waters has focused on simulating typhoon waves under the influence of wind fields. In order to study the influence of tidal level changes on typhoon waves, a numerical model was established in the Taiwan Strait based on the third-generation ocean wave model SWAN. The simulation results of the tide level during the corresponding typhoon landing time were incorporated into the model to optimize its performance. Subsequently, the wave height of the typhoon landing at the lowest tide level was compared with that at the highest tide level. This comparison serves as a reference and warning for ocean engineering, highlighting the hazards of the typhoon landing at high tide. The simulation results were verified and analyzed using the measured data of significant wave heights and wind speeds when typhoons Mekkhala (2006) and Maria (0607) approached. The results show that after optimization, the relative error of the significant wave peak is reduced. Furthermore, there has been a decrease in the maximum wind speed, bringing it closer to the measured value. These improvements signify enhanced model accuracy. The tide level has a great influence on the typhoon wave, and the tide level height at the time of the typhoon landing is positively correlated with the significant wave height of the waves generated by the typhoon. When the typhoon’s landing time coincides with the high tide level, the resulting waves are significantly higher, reaching up to 0.71 m. This has a substantial impact on the safety of marine structures, particularly breakwaters.

NUMERICAL DISTRIBUTION SIMULATION OF TYPHOONS’ WAVE ENERGY IN THE TAIWAN STRAIT AND ITS ADJACENT WATERS

As new energy technologies boom in recent years, marine renewable energy, especially wave power is one potential trend. However, few relevant studies focus on extreme sea conditions. In this paper, a numerical model of typhoon waves in the Taiwan Strait is established based on the third-generation ocean wave model SWAN and then calculated by the wave energy empirical equation. Typhoon No. 200808 Fung-wong, strong typhoon No. 200815 Jangmi and strong typhoon No. 201808 Maria are used for verification and analysis. Finally, the results show that most concentrated wave energy values are more than 300 kW/m for typhoon and more than 900 kW/m for strong typhoons, over 60 times and 180 times the annual average (5 kW/m) in the Chinese sea area, respectively. In terms of other locations, corresponding values are more than 50 kW/m and over 100 kW/m. Therefore, typhoons’ wave energy is certainly a huge asset if fully utilized.

Impacts of climate changes on ocean surface gravity waves over the eastern Canadian shelf

A numerical study is conducted to investigate the impact of climate changes on ocean surface gravity waves over the eastern Canadian shelf (ECS). The “business-as-usual” climate scenario known as Representative Concentration Pathway RCP8.5 is considered in this study. Changes in the ocean surface gravity waves over the study region for the period 1979–2100 are examined based on 3 hourly ocean waves simulated by the third-generation ocean wave model known as WAVEWATCHIII. The wave model is driven by surface winds and ice conditions produced by the Canadian Regional Climate Model (CanRCM4). The whole study period is divided into the present (1979–2008), near future (2021–2050) and far future (2071–2100) periods to quantify possible future changes of ocean waves over the ECS. In comparison with the present ocean wave conditions, the time-mean significant wave heights (H s ) are expected to increase over most of the ECS in the near future and decrease over this region in the far future period. The time-means of the annual 5% largest H s are projected to increase over the ECS in both near and far future periods due mainly to the changes in surface winds. The future changes in the time-means of the annual 5% largest H s and 10-m wind speeds are projected to be twice as strong as the changes in annual means. An analysis of inverse wave ages suggests that the occurrence of wind seas is projected to increase over the southern Labrador and central Newfoundland Shelves in the near future period, and occurrence of swells is projected to increase over other areas of the ECS in both the near and far future periods.

Simulation and Analysis of Ocean Wave in the Northwest Pacific Ocean

In order to obtain more accurate results than the traditional method of wave statistics，the third-generation ocean wave model WAVEWATCH III (WW3) is applied to simulate the sea wave field of the Northwest Pacific. The model is driven by the QSCAT/NCEP blended winds. Then wave parameters are analyzed by statistical analysis method. The comparison of the significant wave heights between the simulation results and observation data indicates that the correlation coefficient is greater than 0.9. Furthermore, a post-processor system which integrates data analysis and graphic display is established. A comprehensive evaluation is presented after analyzing the time and spatial distribution of computational wave heights. During the winter there is a big wave area in the Japan Sea. In the East China Sea, there is a period of relatively big wave in summer. Throughout the year, the average wave height is the maximum in the South China Sea.

Impact of Wave-Ocean Interaction on Typhoon Hai-Tang in 2005

We investigated the impact of wave-ocean interaction on numerical predictions for Typhoon Hai-Tang in 2005 using a nonhydrostatic atmosphere model coupled with a third-generation ocean wave model and a mixed-layer ocean model. Here we address the effect of breaking surface waves on entrainment induced at the mixed-layer base, assuming that the turbulent transport due to breaking surface waves is expressed as a function of both wave-induced and surface wind stresses. The introduction of breaking surface waves into the coupled model enables us to reproduce the evolution of Hai-Tang's central pressure and sea-surface temperature (SST) distribution more realistically. SST decreases significantly (rarely) along Hai-Tang's track where the mixed-layer depth is relatively shallow (deep). Hai-Tang tends to intensify where the initial mixed layer is relatively deep along Hai-Tang's track. Introducing the wave-ocean interaction may lead to more precise tropical cyclone intensity prediction through more realistic reproduction of the SST distribution.

Reanalysis of Storm Surges and High Waves along the Sanin Coasts (North Yamaguchi) by Means of Atmosphere-Ocean Coupled Model

Reanalysis of storm surges and high waves along the Sanin Coasts (North Yamaguchi) was conducted for 15 major meteorological disturbances of 12 typhoons and 3 extra-tropical depressions. The atmosphere-ocean coupled model which consists of meso-scale meteorological model, quasi-three dimensional ocean model, and third-generation ocean wave model, was employed to simulate the reliable wind and atmospheric pressure fields that determines storm surges and ocean waves. The study revealed the most dangerous typhoon track and the past maximum for tide level, surge anomaly, wave height and period.

Dynamic Coupling of Wave and Surge Models by Eulerian-Lagrangian Method

An Eulerian-Lagrangian method is employed in a third-generation ocean wave model and a two­ dimensional storm surge model that are dynamically coupled. The stability, accuracy, and consistency of the synchronously coupled models are first verified using an idealized case of waves on a Gulf Stream Ring by comparing the computed results with that by others. Application of the coupled models to two hindcastings of storms occurred in the northern South China Sea under different forcing conditions, taking into account the mutual influences of waves and currents, gives satisfactory results in comparison with observations. Calculations show that the surface wave-dependent drag has significant effects on the surges, but the wave radiation stress has only slight effects. For prediction of wave heights, the inclusion of both the wave-dependent drag and the wave radiation stress in the storm surge model has a very small effect on the computed results. The coupled models can be easily applied to prediction or hindcasting of ocean waves and storm surges without the need for further treatment. ABSTRACT: An Eulerian-Lagrangian method is employed in a third-generation ocean wave model and a two­ dimensional storm surge model that are dynamically coupled. The stability, accuracy, and consistency of the synchronously coupled models are first verified using an idealized case of waves on a Gulf Stream Ring by comparing the computed results with that by others. Application of the coupled models to two hindcastings of storms occurred in the northern South China Sea under different forcing conditions, taking into account the mutual influences of waves and currents, gives satisfactory results in comparison with observations. Calculations show that the surface wave-dependent drag has significant effects on the surges, but the wave radiation stress has only slight effects. For prediction of wave heights, the inclusion of both the wave-dependent drag and the wave radiation stress in the storm surge model has a very small effect on the computed results. The coupled models can be easily applied to prediction or hindcasting of ocean waves and storm surges without the need for further treatment. numerically been proved useful and successful by many au­ thors, but physically, a process usually needs to be split into several steps, and thus noninherently conservative errors are raised (Leonard et al. 1995). Compared with the piecewise ray method, the full ray method requires the computation to be conducted separately and independently at each position, and, hence, is less advantageous for the evaluation of horizontal distribution of wave characteristics (Yamaguchi and Hatada 1990). Casulli (1990) developed a semiimplicit finite difference scheme for the solution of the two-dimensional shallow water equations with a Eulerian-Lagrangian method for the approx­ imation of the convective terms, which was proved to be sta­ ble, accurate, and conservative. The Eulerian-Lagrangian method has advantages over other commonly used numerical methods, such as upwind method, ADI method, time-splitting or operator-splitting techniques, and the mode-splitting tech­ nique. The scheme was subsequently extended to three di­

Modification of the Physics and Numerics in a Third-Generation Ocean Wave Model

Abstract The ocean wave model WAM was recently upgraded to improve the coupling between the sea state and the air flow and, in particular, enhance the growth of young wind sea over that of old wind sea. Prior to this change, numerous validations of the original wind input physics by the wave modeling community had shown a consistent underprediction of wave heights in the Southern Hemisphere. Preliminary tests of the upgraded version indicated that the change in physics improved wave height predictions but did not completely eliminate the bias. To specifically test the upgraded version, a one-month hindcast study for the Australian region was conducted using both the improved and the original physics. The hindcast significant wave heights were compared against observations from three locations wound the Australian coast and were found to he overpredicted by the upgraded physics and underpredicted by the original physics. A series of experiments were then made that indicated the upgraded physics were sensit...