Search

The wave energy can be a critical solution for growing international renewable energy demand. The present study demonstrates the wave potential of the southern side of the Caspian Sea. In this regard, the mathematical equation of the wave energy was presented. Moreover, the wave energy simulation was performed using the wind data from ECMWF within 2011–2015 by implementing the MIKE software. For this reason, nine nominated stations were presented and the wave height characteristics and the maximum wave potential were evaluated in order to validate the results of the simulation, Amirabad and Neka stations were selected and the results were compared and good agreement was observed. Moreover, a mesh structure was presented to demonstrate the depth variation of the Caspian Sea. The results of the simulation were achieved for nine stations and the wave height and peak wave period was demonstrated. The wave power contours were revealed for every station. The result showed that the May (0.9 kW per meter) and December (3.6 kW per meter) have the lowest and highest wave energy potential for selected stations.

WAM, SWAN and WAVEWATCH III® were implemented to the Finnish archipelago with a 0.1 nmi grid. A comparison with coastal wave buoy observations showed that the models agreed on the significa...

This work investigates the sensitivity of the SWAN model with respect to state-of-the-art wave and wind datasets. The wave model was implemented and validated for the Southern Brazilian nearshore environment and simulated for 2015. Nine combinations of wave and wind datasets have been considered, aiming at establishing the boundary conditions and atmospheric forcing which best reproduce windsea and swell systems. The wave model results have been validated comparing against two buoys deployed in deep water and one buoy in shallow water. Wave parameters such as significant wave height Hs, mean wave direction Dm and peak wave period Tp have been computed and compared. Overall, the performance of the SWAN model satisfactorily reproduce the distinct waves fields for all wind and wave databases. However, the combination of datasets with ERA5 winds and CAWCR wave boundary conditions slightly outperforms the other combinations tested.

Bu çalışmada, Avrupa Orta Vadeli Hava Tahmin Merkezi (ECMWF)’nin yeni yeniden değerlendirme (reanaliz) veri setinin Karadeniz bölgesi dalga tahminine katkı yapıp yapmadığı araştırılmıştır. Bu maksatla, ECMWF’in veri tabanından hem ERA5 hem de mukayese yapmak maksadıyla ERA-Interim veri setlerinin rüzgar verileri indirilmiştir. Performans değerlendirilmesi için dalga tahminlerini gerçekleştirmek maksadı ile bu rüzgar verisini kullanan üçüncü nesil dalga tahmin modeli olan SWAN varsayılan ayarlamalı olarak çalıştırılmıştır. Varsayılan ayarlamalı SWAN simülasyonu sonucunda belirgin dalga yüksekliği (Hm0), ortalama dalga periyodu (Tm02) ve ortalama dalga yönü gibi dalga parametreleri elde edilmiştir. Bu tahminler 1996 yılında NATO TU-WAVES projesi kapsamında Karadeniz’e kurulan şamandıra ölçüm istasyonlarından üçünün (Gelendzhik, Hopa, Sinop) dalga ölçümleri ile kıyaslanarak performansları irdelenmiştir. Performans değerlendirmesi sırasında hata istatistiği parametreleri, zaman serisi grafikleri, saçılım diyagramları, kuantil grafikleri ve dalga gülleri incelenmiştir. Hata istatistiği parametrelerinde örneğin Hopa şamandıra ölçüm verisi ile model veri setleri kıyaslandığında, belirgin dalga yüksekliğinde gözlenen ortalamaların farkı (bias) ERA-Interim veri setinde 0,317 m iken ERA5 veri setinde 0,261 m değerini almıştır. Tüm bu değerlendirme süreci sonucunda ise, Karadeniz özelinde ECMWF tarafından son yıllarda üretilmiş ERA5 model rüzgarlarının dalga modellerine girdi olarak tanımlandığında ERA-Interim rüzgarlarına kıyasla daha doğru dalga tahmini sağladığı sonucuna varılmıştır., This study investigated whether a new re-analysis of ECMWF contributes to wave hindcast performance in the Black Sea. For this purpose, ERA5 and ERA-Interim winds presented by ECMWF were downloaded in order to have an inter-comparison of ECMWF datasets. For performance evaluation of wave hindcasts, third generation wave hindcast model SWAN was run with a default setting. Wave hindcast outputs such as significant wave height (Hm0), mean wave period (Tm02) and mean wave direction were obtained as a result of default setting SWAN run. These hindcasts were compared with wave measurements at three buoys (Gelendzhik, Hopa, Sinop) installed in the Black Sea in 1996 as part of NATO TU-WAVES project. During performance evaluation, error statistics, time series, scatter plots, quantile graphics and wave roses were examined. In error statistics, for example bias observed for Hm0 compared to measurement and model data at Hopa was 0.317 m for ERA-Interim forcing and 0.261 m for ERA5 forcing. As a result of this all evaluation process, it was revealed that in the Black Sea ERA5 produced in the recent years by ECMWF presents a more advanced wind data set in comparison to the ERA-Interim winds because default setting SWAN model performs better in the case of ERA5 winds.

In this study, a data assimilation system is constructed in a third generation ocean surface wave model, MASNUM-WAM, to improve wave simulations. The data assimilation system uses Ensemble Adjustment Kalman Filter (EAKF) method, which is based on dynamic sampling. Difference between 24 h-interval wave parameter fields during the period 7-day before and after assimilation time, is used to construct dynamic ensemble, which is an approximation to background error. Eight experiments are carried out during typhoon Malakas to investigate the impact of different assimilating wave parameters to the simulation errors of significant wave height (SWH). Wave spectrum observations from satellite Sentinel-1 SAR are used for data assimilation. SWH, peak wave period, mean wave direction and wave spectrum are adjusted simultaneously when an observation is available. Results show that the data assimilation system improves the simulation of SWH during typhoon Malakas.

Making use of the fetch- and duration-limited nature of wind-wave growth inside tropical cyclones, an algorithm is developed to estimate the maximum significant wave height and dominant wave period of surface waves generated by tropical cyclone wind fields. The results of the maximum significant wave height and dominant wave period are further approximated by simple power functions of the maximum wind speed. The exponents of the power functions are almost constant, and the proportionality coefficients can be approximated by second-order polynomial functions of the radius of maximum wind speed (RMW). The predicted maximum values agree well with results derived from simultaneous wind and wave measurements obtained during 11 hurricane reconnaissance and research missions in six hurricanes.

The East China Sea, where both the strong Kuroshio Current and powerful low pressures exist, is an inevitable ocean area for various ships sailing between Japan and other Asian and European countries. The safety and economics of such shipping behaviors are often affected by the strong dynamics of the environmental matrix. The wave conditions are usually significant under high ocean winds, leading to interaction between waves and currents. In this study, the third generation wave model SWAN are used to study the wave propagation and wave-current interaction, following by its effects on the ship navigation discussed. Significant interaction between the strong Kuroshio Current and high ocean waves as well as its effects on ship safety have been found by calculations of certain wave parameters, such as significant wave height (SWH), average wave period (AWP), mean wave direction (MWD), wave length (WLEN), frequency and directional spreading.

The 21st century Maritime Silk Road (MSR) proposed by China strongly promotes the maritime industry. In this paper, we use wind and ocean wave datasets from 1979 to 2014 to analyze the spatial and temporal distributions of the wind speed, significant wave height (SWH), mean wave direction (MWD), and mean wave period (MWP) in the MSR. The analysis results indicate that the Luzon Strait and Gulf of Aden have the most obvious seasonal variations and that the central Indian Ocean is relatively stable. We analyzed the distributions of the maximum wind speed and SWH in the MSR over this 36-year period. The results show that the distribution of the monthly average frequency for SWH exceeds 4 m (huge waves) and that of the corresponding wind speed exceeds 13.9 m s−1 (high wind speed). The occurrence frequencies of huge waves and high winds in regions east of the Gulf of Aden are as high as 56% and 80%, respectively. We also assessed the wave and wind energies in different seasons. Based on our analyses, we propose a risk factor (RF) for determining navigation safety levels, based on the wind speed and SWH. We determine the spatial and temporal RF distributions for different seasons and analyze the corresponding impact on four major sea routes. Finally, we determine the spatial distribution of tropical cyclones from 2000 to 2015 and analyze the corresponding impact on the four sea routes. The analysis of the dynamic characteristics of the MSR provides references for ship navigation as well as ocean engineering.

Wave forecasting up to 168 h (one-week) ahead is crucial to the operational management of shipping and construction in the marine work site. The present study proposes a method of areal-time One-week Wave Forecast of Nearshore Waves (OWFNW) at 13 stations on the Japanese coast. For each station, two Group Method of Data Handling (GMDH) based wave prediction models for the wave height and period are developed to transform the global wave data into nearshore waves. For each GMDH-based wave prediction model, four models are trained with four different training data sets using the one-week global wave forecast data released in real-time by the Japan Meteorological Agency (JMA), National Oceanic and Atmospheric Administration (NOAA), and European center for Medium-Range Weather Forecasts (ECMWF). The study conducts a series of training and testing GMDH-based wave prediction models at each station, and examines the accuracy of predictions. The best performing GMDH-based wave prediction model selected among the four models is compared to the best global wave forecast data. It was found that the best performance GMDH-based wave prediction model varies for different locations. On average, the best performing GMDH-based wave height model is able to improve the accuracy of nearshore wave predictions up to 38% compared to that of the best global wave height forecast with 168 h lead time. The best GMDH-based wave period model improves the prediction error up to 65% compared to the 168 h ahead error of the best global wave period forecasts. The present methodology to get OWFNW can be applied to other nearshore seas where global wave forecast data and corresponding observed one are available.

With the increased frequency of shipping activities, navigation safety has become a major concern, especially when economic losses, human casualties and environmental issues are considered. As a contributing factor, sea state conditions play a significant role in shipping safety. However, the types of dangerous sea states that trigger serious shipping accidents are not well understood. To address this issue, we analyzed the sea state characteristics during ship accidents that occurred in poor weather or heavy seas based on a ten-year ship accident dataset. The sea state parameters, including the significant wave height, the mean wave period and the mean wave direction, obtained from numerical wave model data were analyzed for selected ship accidents. The results indicated that complex sea states with the co-occurrence of wind sea and swell conditions represent threats to sailing vessels, especially when these conditions include close wave periods and oblique wave directions.

A 3-D mathematical model of regular wave flume is conducted to investigate the heaving performance of a cylindrical floater. The results show that the transverse velocities near the floater distribute symmetrically at the wave crest and trough times, its symmetry axis is the longitudinal straight line across the floater center, and 4 extreme regions distribute near the floater. With the increase of relative width of wave flume, the trapped wave energy and the relative response amplitude increase firstly. Then, they decreases and appear to be stable for the relative width of wave flume higher than 10. The trapped wave energy and the relative response amplitude increase with the increase of incident wave height, respectively. With the increase of wave period, the trapped wave energy decreases, however, the relative response amplitude increases.

Wang, Z.; Wu, K.; Gao, S., and Li, Q., 2017. Nearshore wave forecast for Xiamen, China. In: Zhi, Y. and Guido Aldana, P.A. (eds.), Sustainability of Water Resources and the Development of Coastal Environments: Select Proceedings from the 2016 International Conference on Water Resource and Environment (WRE2016). Journal of Coastal Research, Special Issue No. 80, pp. 48–54. Coconut Creek (Florida), ISSN 0749-0208. The paper aimed to develop a wave forecasting system for the nearshore areas of Xiamen, with practical implications in operational wave forecasting. The SWAN model, a state-of-art third-generation wave model used for the simulation of nearshore waves, was powered by the WRF (weather research and forecasting) model with spatial resolution up to 180 m. The SWAN model output was comprised of significant wave height, mean wave period, and mean wave direction in forecast modes of 24 h, 48 h, and 72 h. Extensive validation exercises were performed to evaluate the model's performance under diffe...

The accuracy of the operational ocean state forecast system at ESSO-INCOIS during extreme events as well as calm conditions for a lead time of 24, 72 and 144 h is evaluated in this paper. Forecasted wave parameters (significant wave height, mean wave period and mean wave direction) are compared with in situ data for three cyclones (Sidr, Khai Muk and Nisha) that occurred in the Bay of Bengal (BoB). Forecasts obtained for 24 and 72 h showed good agreement with in situ data. Error statistics obtained during extreme events (SI .75) suggests the good quality of the wave forecasts, which could be used for issuing high wave alerts. The two-dimensional energy spectra from the wave model during the Sidr cyclone period showed the capability of the model to simulate wind seas and swells even under cyclonic conditions. During winter monsoon, the error statistics obtained in the BoB suggests, good quality of 24- and 72-h wave forecasts. Thus the wave model is good at simulatin...

In this study, the wave energy potential in the coastal region of Romania was analyzed. For this purpose, a reanalysis data set downloaded from ECMWF (European Centre for Medium-Range Weather Forecasts) was used. The reanalysis data contains information for various models. In this analysis the significant height of combined wind waves and swell, the mean wave direction and the mean wave period were analyzed in order to determine the potential of extracting clean energy from waves. The aim of this research is to analyze some performances factors (capacity factor, rated capacity, operating capacity, annul electricity production) of some of the most used wave energy convertors.

This paper presents a thirty year (1976-2005) assessment of wave energy resource within the South China Sea (SCS) by simulation. Significant wave height (SWH) between simulation and observation shows good agreement. This shows the reliability of an along-side simulated wave period in estimating wave energy in the SCS. Results show that estimates of wave power density are more reliable in the north-central SCS and most sufficient during winter. The annual mean wave power density peaked at 12.7kW/m and 12.9kW/m during years 1986 and 1999 respectively while the highest seasonal mean of 29kW/m occurred in year 1999 during winter. The wave power density is most stable in winter and is generally more stable in offshore regions of SCS. Wave power density is most stable in years 1976, 1997 and 2004 with stability values of 1.96, 1.98 and 1.9 respectively. The stability value of 0.9 in year 1980 is the greatest in the winter of all years. Relative-rich energy regions occupy the largest area during winter. The relatively richest energy is generally concentrated in the central and north-central SCS. No area is identified as a relative-rich energy region during spring. Winter 1999 has the highest relative-rich energy with value of 37kW/m.

The modified versions of the linear theoretical model of Longuet-Higgins (1983) are derived in this work and also compared with the laboratory experiments carried out in MARINTEK. The main feature of modifications is to replace the mean frequency in the formulation with the peak frequency of the wave spectrum. These two alternative forms of joint distributions are checked in three typical random sea states characterized by the initial wave steepness. In order to further explore the properties of these models, the associated marginal distributions of wave heights and wave periods are also researched with the observed statistics and some encouraging results are obtained.

The assimilated coastal wave data are useful for wave climate study, coastal engineering, and design for marine disaster protection. However, the assimilated coastal wave data are few. Here, wave analysis data produced by the JMA (Japan Meteorological Agency) and ERA5 wave data were compared with GPS (Global Positioning System) buoy-measured wave data. In addition, the accuracy of ERA5 wave data for various conditions was investigated. The accuracy of JMA analysis wave height was better than that of ERA5 wave height. The ERA5 wave height was underestimated as the wave height increased. The accuracy of the ERA5 wave height was significantly different in fetch-unlimited and fetch-limited conditions. The difference of the skill metrics between fetch-unlimited and fetch-limited conditions was due to the overestimation of the fetch in the ERA5 grid. This result also applied to the wave period.

This is one of the pioneer and preliminary attempt to study the influence of wave energy trends on the absorbed power of wave energy converters. For that purpose, the reanalysis of the past century ERA20 has been calibrated via quantile-matching against the reanalysis ERA-Interim in their intersection period (1979–2010). The validation against four buoys in the Bay of Biscay is presented in this paper, showing a better agreement of ERA-Interim-WAM model when compared to the original ERA20. In addition, calibrated ERA20 shows a significant error reduction compared to the original ERA20. Hence, calibrated ERA20 presents an increment of the wave energy resource, more than 1 kW/m per decade, in the area of study and a general increment of the wave height and wave period throughout the analyzed decades. Finally, using the calibrated series at a given gridpoint in the bay, power absorption of a generic wave energy converter (WEC) is examined, combining the power matrix of the WEC and the two-variable (wave height and period) probability density functions (PDF) of the five do-decades of the past century. Results show important variations of the PDF, which results in significant differences, up to a 15% increase between two do-decades, in the annual mean power production.

As a part of our calibration/validation activities five months of SARAL/AltiKa wave data have been analyzed in this study. A robust quality control procedure using threshold values on signal and retrieved wave heights was implemented before the assimilation. Assimilation runs in the wave model Meteo-France (MFWAM) were performed for a long period. The validation of the model outputs was performed with independent wave observations from altimeter and buoy data. The results indicate good performance in terms of bias and scatter index for the significant wave height and the peak wave period. Statistical analyses were performed for different ocean basins (high and intermediate latitudes and tropics). The use of SARAL/AltiKa and Jason-2 wave data combined was also investigated. This leads to further improvements for the analysis and forecast periods. In other respects, the impact of the assimilation of SARAL/AltiKa wave data is discussed for waves under strong wind conditions such as typhoons Fitow and Danas w...

This paper develops the temporal-spatial distribution of wave energy at the Beibu Gulf at a monthly, seasonal, and annual base using the Simulated WAves Nearshore (SWAN) model, which is called third generation wave prediction model. The model is forced with the ECMWF ERA Interim wind field data covering 34 years at a time interval of 6 h. Wave parameters, including significant wave height (Hs), peak wave period (Tp), and wave direction (θ) are simulated by SWAN model. Simulated data are validated against the altimeter data using Bias, MSE, and R, and the validation results show that the simulated data can effectively be used to calculate the wave energy in Beibu Gulf. This paper highlights the temporal-spatial distributions of monthly, seasonal, and annual of wave energy. The results reveal that (1) the wave energy propagations in inner waters are dominantly along northeast and west-northwest; (2) the high-energy areas are located at the middle and the southern Beibu Gulf; (3) the biggest monthly wave energy is from January through March with approximately 2.5 kW/m, and the biggest seasonal wave energy is from winter through spring with approximately 1.7 kW/m, and the biggest annual wave energy is about 1.5 kW/m. Additionally, the quantitative analysis, in which the total storage of wave energy vs. the percentage of wave energy greater than 2 kW/m is mapped at a 0.5° × 0.5° grid, identifies those grids used for wave energy convertor deployment. Finally some suggestions are drawn up for decision-makers of the local government.

The significant wave height and average wave period form an essential input for operational activities in ocean and coastal areas. Such information is important in issuing appropriate warnings to people planning any construction or instillation works in the oceanic environment. Many countries over the world routinely collect wave and wind data through a network of wave rider buoys. The data collecting agencies transmit the resulting information online to their registered users through an internet or a web-based system. Operational wave forecasts in addition to the measured data are also made and supplied online to the users. This paper discusses operational wave forecasting in real time mode at locations where wind rather than wave data are continuously recorded. It is based on the time series modeling and incorporates an artificial intelligence technique of genetic programming. The significant wave height and average wave period values are forecasted over a period of 96 hr in future from the observations of wind speed and directions extending to a similar time scale in the past. Wind measurements made by floating buoys at eight different locations around India over a period varying from 1.5 yr to 9.0 yr were considered. The platform of Matlab and C++ was used to develop a graphical user interface that will extend an internet based user-friendly access of the forecasts to any registered user of the data dissemination authority.

Choi, J.; Lim, C.H., and Yoon, S.B., 2014. A rip current warning system based on real-time observations for Haeundae Beach, Korea. A real-time rip current warning system was studied to help mitigate against rip current accidents at Haeundae Beach. The system produces a real time sequence of index representing the risk and the likelihood of rip current based on the real time observations such as waves, currents, and tide. The index is estimated by using the rip current likelihoods derived from the results of various numerical simulations with various sea conditions, the parameters of which correspond to the observation quantities. The rip current warning system is operated by taking into account the effect of wave height, wave period, wave direction, wave spectrum (i.e., frequency-directional spreading), longshore currents, and tidal elevation on the rip current likelihood. The real-time wave and tidal observations at the Haeundae coast in 2012 were applied to the rip current warning system, and i...

Wave attenuation from two field experiments in the ice‐covered Southern Ocean is examined. Instead of monotonically increasing with shorter waves, the measured apparent attenuation rate peaks at an intermediate wave period. This “rollover” phenomenon has been postulated as the result of wind input and nonlinear energy transfer between wave frequencies. Using WAVEWATCH III®, we first validate the model results with available buoy data, then use the model data to analyze the apparent wave attenuation. With the choice of source parameterizations used in this study, it is shown that rollover of the apparent attenuation exists when wind input and nonlinear transfer are present, independent of the different wave attenuation models used. The period of rollover increases with increasing distance between buoys. Furthermore, the apparent attenuation for shorter waves drops with increasing separation between buoys or increasing wind input. These phenomena are direct consequences of the wind input and nonlinear energy transfer, which offset the damping caused by the intervening ice. MOE (Min. of Education, S’pore) Published version

The SWAN (Simulating WAves Nearshore) model was applied to study the characteristics of water waves in the Bohai Sea. The model was calibrated against both short-term and long-term field measured data from six different stations in the Bohai Sea and the computational results are in good agreement with the measured data. Then the wave process during 1999 to 2009 in the Bohai Sea was simulated using the calibrated model. The wave characteristics such as significant wave height, average period, dominant wave direction and their seasonal variations were analyzed based on the simulated results. The distributions of wave height and wave period are similar to those of the previous studies, but the wave height is slightly smaller than that given by other researchers.

Lee, J.Y. Jun, K. C., Lee, S. C and Lee, J.L. Haeundae beach draws one million visitors every summer season, and more than 100 people are rescued from rip currents every year. Beachgoers are unexpectedly carried away seawards, as far as 50 ~ 100 meters from shore, where swimming is restricted for safety reasons. Rescuers have strengthened lookout measures at several spots where dangerous rip currents have occurred. The determination of a predictive index for rip currents is vitally important for the protection of human life. Such an index allows governmental agencies to issue rip current warnings directly to the public, and allows for the establishment of preventative measures according to the magnitude of the rip current threat. We apply a modified rip current predictive index suitable for Haeundae - using wave height, wave period, and incident wave angle from the north. Compared with wave data acquired for the summer of 2011, the result of NERiPS-H (NEarshore Rip current Predictive System at Ha...

An autonomous vessel, the Offshore Sensing Sailbuoy, was used for wave measurements near the Ekofisk oil platform complex in the North Sea (56.5o N, 3.2o E, operated by ConocoPhillips) from 6 to 20 November 2015. Being 100 % wind propelled, the Sailbuoy has two-way communication via the Iridium network and has the capability for missions of 6 months or more. It has previously been deployed in the Arctic, Norwegian Sea and the Gulf of Mexico, but the present study was the first test for wave measurements. During the campaign the Sailbuoy held position about 20 km northeast of Ekofisk (on the lee side) during rough conditions. Mean wind speed measured at Ekofisk during the campaign was 9.8 m/s, with a maximum of 20.4 m/s, with wind mostly from south and southwest. A Datawell MOSE G1000 GPS-based 2 Hz wave sensor was mounted on the Sailbuoy. Mean significant wave height (H s 1 min) measured was 3 m, whereas maximum H s was 6 m. Mean wave period was 7.7 s, while maximum wave height, H max, was 12.6 m. These measurements have been compared with non-directional Waverider observations at the Ekofisk complex. The agreement between the two data sets was very good, with a mean percent absolute error of 7 % and a linear correlation coefficient of 0.97. The wave frequency spectra measured by the two instruments compared very well, except for low H s (∼1 m), where the motion of the vessel seemed to influence the measurements. Nevertheless, the Sailbuoy performed well during this campaign, and results suggest that it is a suitable platform for wave measurements in a broad range of sea conditions.

Temporal and spatial evolution of Atmospheric Gravity Waves(AGW) in the troposphere have been analyzed in vertical wind at Koto Tabang (0.20°S, 100.32°E) on 7 – 8 Dec 2005 during Coupling Processes in Equatorial Atmosphere (CPEA)-II campaign. AGWs with vertical wavelength of 2 – 3.5 km, horizontal wavelength of ~ 20-25 km and wave period of ~ 55 – 65 min were observed in the troposphere (3-10 km heights) during convection events. Observed variation in vertical wavelength with time during convection and after its termination suggests the characteristic features of convective sources and gravity waves, respectively in a convective environment.

The performance of two well accepted formulations for white capping and wind input of third generation wave models, viz., WAM-3 and WAM-4, were investigated using parallel unstructured SWAN (PunSWAN). Several alternative formulations were also considered to evaluate the effects of higher order steepness and wave number terms in white capping formulations. Distinct model configurations were calibrated and validated against available in situ measurements from the Gulf of Mexico. The results showed that some of the in situ calibrated models outperform the saturation level calibrated models in reproducing the idealized wave growth curves. The simulation results also revealed that increasing the power of the steepness term can enhance the accuracy of significant wave height ( H s ) , at the expense of a higher bias for large waves. It also has negative effects on mean wave period ( T a ) and peak wave period ( T p ) . It is also demonstrated that the use of the quadratic wave number term in the WAM-3 formulation, instead of the existing linear term, ameliorates the T a underestimation; however, it results in the model being unable to reach any saturation level. In addition, unlike H s and T p , it has been shown that T a is sensitive to the use of the higher order WAM-4 formulation, and the bias is decreased over a wide range of wave periods. However, it also increases the scatter index (SI) of simulated T a . It is concluded that the use of the WAM-4 wind input formulation in conjunction with the WAM-3 dissipation form, is the most successful case in reproducing idealized wave growth curves while avoiding T a underestimation of WAM-3 and a potential spurious bimodal spectrum of WAM-4; consequently, this designates another perspective to improve the overall performance of third generation wave models.

The validation and assessment of Envisat advanced synthetic aperture radar (ASAR) ocean wave spectra products are important to their application in ocean wave numerical predictions. Six-year ASAR wave spectra data are compared with one-dimensional (1D) wave spectra of 55 co-located moored buoy observations in the northern Pacific Ocean. The ASAR wave spectra data are firstly quality control filtered and spatio-temporal matched with buoy data. The comparisons are then performed in terms of 1D wave spectra, significant wave height (SWH) and mean wave period (MWP) in different spatio-temporal offsets respectively. SWH comparison results show the evident dependence of SWH biases on wind speed and the ASAR SWH saturation effect. The ASAR wave spectra tend to underestimate SWH at high wind speeds and overestimate SWH at low wind speeds. MWP comparison results show that MWP has a systematic bias and therefore it should be bias-modified before used. The comparisons of 1D wave spectra show that both wave spectra agree better at low frequencies than at high frequencies, which indicates the ASAR data cannot resolve the high frequency waves.

Natuna Sea is one economy strategic outer area, which connected into archipelagic international sea lanes (ALKI I). The research area is in that area using two specifics observation Naval base stations: (South) Dabo Singkep and (North) Ranai. Wave characteristics are needed to be conducting a secure the naval operation cruises. The statistical analysis is carried out using 2016 ECMWF 6 hourly datasets with 14 km grid spatial resolution. The variable of significant wave height (SWH), period and wave direction has been analyzed by monthly-yearly averages. Maximum SWH during rough wave period is range of 5.1 m (January) and 2.3 m (February). The minimum SWH is range of 0.2 m (April) and 0.1 m (July). The predominantly wave direction at Dabo Singkep is coming from southeast (135°; mostly in July), and at Ranai is coming from the northeast (45°; mostly in January). During the rough wave period, it is highly recommended using the KRI warship with length > 82 m and high hull > 2.3 m for surveillance cruise in the southern part of Natuna Sea. While in the northern part, would be needed KRI with a length > 146 m, and the high hull > 4.8 m.

Temperature change has been shown to affect daily mortality even though different analytical methods produce different results. The effect of air pollution on the relationship between the temperature and the mortality is not large, although differences exist between temperature models. The aim of this study was to examine how the temperature change affected the daily mortality in Seoul by comparing the results from the temperature model using two study periods: one from 1994 to 2007 and the other from 1997 to 2007. Generally mean temperature, minimum temperature and Q10 temperature was derived as an optimal model, even though there are differences between age and cause of death. The analysis of threshold using total mortalities in all ages from 1994 to 2007 and from 1997 to 2007 showed that the number of the deaths increased 7.02% (95% CI: 6.06~7.98) and 2.51% (95% CI: 1.83~3.19), respectively as the mean temperature increased 1℃ from a threshold temperature of 27.5℃ and 25.7℃ respectively. These results indicated that the temperature has less effect on the number of death than does an extreme heat wave period.

The spectral characteristics of shallow water waves with significant wave height more than 2 m based on the data collected along the Indian coast is examined. It was found that the value of Joint North Sea Wave Project (JONSWAP) parameters ( α and γ ) increases with significant wave height and mean wave period and decreases with spectral peak period. The estimated average value (0.0027 and 1.63) of the JONSWAP parameters, α and γ were less than the generally recommended values of 0.0081 and 3.3, respectively. By carrying out a multi-regression analysis, an empirical equation is arrived relating the JONSWAP parameters with significant wave height, peak wave period and mean wave period. It was found that the Scott spectra underestimate the maximum spectral energy of high waves. The study shows that the measured wave spectra can be represented by JONSWAP spectra with the JONSWAP parameters estimated based on the equation proposed in this paper.

Wave growth in slanting fetch (with wind blowing obliquely off a coast) is investigated with 7 years worth of routine wave measurements in Lake IJssel in The Netherlands and with the SWAN wave model. Two aspects are considered in particular for this case: the validity of the concept of effective fetch and the role of the non-linear four-wave interactions. For slanting and parallel fetch conditions, we found some significant deviations from the effective fetch assumption, leading to 20–35% mismatch in either the peak period T p or the significant wave height H m0 respectively. However, the effect of discrepancies between various widely accepted wave growth formulas turned out to be even more important. The wave directions during slanting fetch are significantly ‘steered’ by the coastline, especially in the first kilometre(s) off the coast. The role of the non-linear four-wave interactions is investigated by running the SWAN (version 40.41) wave model with three different quadruplet formulations. Exact quadruplet methods (Xnl) yielded relatively strong wave steering, despite the four-wave interactions being relatively weak. Application of Xnl did not lead to better overall agreement with measurements — improvements for the mean wave period T m01 were offset by some deterioration for the wave height H m0 .

With the aim of assessing the merits of the new source function proposed earlier in Polnikov (2005), it was tested and validated by means of the modification of the well known model WAVEWATCH-III. Assessment was done on the basis of comparing the wave simulation results found from both models against the buoy data obtained in three oceanic regions: eastern and western parts of the North Atlantic, and the Barenz Sea. First of all, incorporation of the new source function into the numerical codes of WAVEWATCH was done, and this modified version of WAVEWATCH was fitted and tested by standard tests. On the basis of these results some physical conclusions were drawn. Then, sophisticated fitting of the modified model was carried out, using the observation data of 19 buoys obtained in two regions of the North Atlantic for a period of 30 days at 1-hour time intervals. After this, the standard validation of both models was continued on the basis of the 8-month historical data, corresponding to 12 buoys located in the western part of the North Atlantic. Finally, comparative validation of the models was done against the wave observations obtained at one buoy in the Barenz Sea for a period of 3 years at 6-hour time intervals. Estimations of simulation accuracy were carried out for the three parameters of wind waves: significant wave height, Hs , peak wave period, Tp , and mean wave period, Tm. Comparative analysis of these estimations was carried out for the original and modified model WAVEWATCH. The advantage of the modified model was revealed, with an increase of simulation accuracy for Hs by 20 to 50% for more than 70% of the buoys considered. Additionally, it was found that the speed of calculation was increased by 15%.

Depth distribution of expected longshore bedload transport was shown by easy function of beach slope and wave parameter at the wave breaking point. It was calculated from the bedload transport based on physical calculation of regular wave and flow, by the probability operation using the occurrence rate of wave height and tide level. Moreover, the variances of the depth distribution of longshore bedload transport by tidal range, mean wave height, wave period and wave direction were shown. For use of actual prediction, it is necessary to use the depth distribution after consideration of the seasonal or monthly occurrence rate of wave height and wave direction.

Due to the high density of ocean traffic and the influence of marine weather on the route planning of vessels, as well as berth allocation in harbors, it is important to be able to predict arrival times as precise as possible. This paper shows the influence of marine weather on ship speed by analyzing publicly available ship traffic and weather data from different sources. A linear regression model is created to explain recorded ship speed in terms of certain ship properties and marine weather. The model has an adjusted R2 value of 83.98% with a significant correlation of many weather related data such as wind direction (0.211), significant wave height (0.195), peak wave period (0.133), as well as ship-related data including ship type, dead weight tonnage, and gross register tonnage. Given the variables in the model the speed of the ship could be estimated fairly well. These variables along with other factors are tested regarding their usefulness for the prediction of arrival times.

Altimeter wave period data obtained from continental shelf seas are analyzed in this paper. Empirical models are introduced for zero up-crossing and peak wave period calculation with TOPEX/POSEIDON data. Their performances are assessed using independent validation dataset in four sites in the open ocean of China. To provide more accurate wave period estimation, new coefficients are applied to reliablein situ data. Comparison of our estimated the wave periods with new linear calibrations based on independent data of Seapac 2100 deployed in the East China Sea and South China Sea showed that the accuracy was improved over estimates determined from earlier empirical models. Regional analysis indicated that the wave period model works better under wind sea condition.

For validating the results of retrieved mean wave period, four empirical algorithms established previously are introduced. Based on the data of over five years derived from TOPEX satellite altimeter for the entire East China Sea, ocean wave periods were calculated and statistical comparison among them was performed. The retrieved mean wave period obtained with our new distribution parameters showed better agreement with the wave periodT B measured by buoy than that calculated by other three algorithms. The difference between the mean values of and that ofT B is 0.16 s and the RMSE (root mean square error) of is the lowest value (0.48).

Wind and wave characteristics in Lake Erie, the Great Lakes are investigated based on the analysis of measurement data at 3 buoy stations over one month from October 22 to November 22, 2000. Relation between dimensionless wave height and wave period data is approximated by Toba's 3/2 power law with a slightly smaller coefficient. Wave hindcast using BRTM (Backward Ray Tracing Model) is conducted under the same bathymetry and wind input conditions as those used by Lalbeharry et al. Intercomparison among BRTM-based wave data, WAM-based wave height data and measurement wave data shows that BRTM yields as close an agreement with measurement data as does WAM and that error statistics may suggest a slightly higher estimating ability of BRTM over WAM.

The statistical distribution of zero up-crossing wave periods in Gaussian mixed sea-states is examined by using numerically simulated data. Nine different kinds of bimodal spectra are used to analyze the effects of the relative energy ratio and the peak frequency separation between the low- and high-frequency wave fields on the wave period distribution. Observed results are compared with predictions given by probabilistic models suitable for practical applications. Numerical results reveal a different behavior for low- and high-period bands. Furthermore, comparisons of the empirical data with some probabilistic models often used in practice shows that none of these models is able to characterize adequately all the cases of combined sea-states examined. In fact, they might be used only in the case of wind-sea dominated sea-states with small separation between spectral frequency peaks. However, a model recently proposed by Myrhaug and Slaattelid [1] represents adequately the observed distributions of wave period.

Relationships between the mean wavelength and mean wave-period of wind waves are derived for fetch-limited and fully developed seas. The derivations start from the Rice solution of zero-crossing problem and use the JONSWAP and Pierson–Moscowitz spectra, respectively. The spectral moments of order 4 involved in the derivations are estimated through a time-averaging technique. Experiments were conducted in a wind-wave channel. Comparisons between the relationships and the experimental results show a favorable agreement.

By an international research consortium between Japan, Indonesia and Australia, we have been operating a meteor wind radar (MWR) near Jakarta (6.4°S, 106.7°E) since November 1992, and a medium frequency (MF) radar in Pontianak (0.03°N, 109.3°E), west Kalimantan, from November 1995, respectively. We also conducted campaign observations with a balloon-borne radiosonde in LAPAN observatories in Watukosek (7.6°S, 112.7°E), Bandung (6.9°S, 107.6°E) and Pontianak since February 1990. In this paper, radar observations of wind fields in the mesosphere and lower thermosphere (MLT) region are used to study equatorial atmosphere dynamics. We first describe the long-term behavior of zonal wind at 70–100 km using the Jakarta MWR data during November 1992 and October 1997. The mesospheric semiannual oscillation (MSAO) is dominant in the equatorial MLT region, whose westward winds were much larger in March–April than in September–October. Moreover, the maximum amplitudes of MSAO showed a clear biennial periodicity. We also discuss characteristics of ultra-fast Kelvin (UFK) waves, having wave period of 3–4 days. A correlative study between the Jakarta MWR and MF radars at Pontianak and Christmas Island (2°N, 158°W) has indicated that the UFK wave propagates eastward at a zonal wavenumber one. We have further analyzed the long-term behavior of the UFK waves in Jakarta, and have found that the wave activity is characterized by strong enhancements twice a year, having a large value in the westward winds of MSAO.

The present work is the first attempt to methodologically assess the wave power prospects off the coast of Lebanon. Working around 1.5 years of buoy data, measurements for the significant wave height and wave period were inputted to establish a joint frequency table that was related to power matrixes of three selected wave energy converters. The spatial and temporal representability of the analysis was extended through assessing altimeter data of Hs over 20 years and for three points off the coast of Lebanon; southern Lebanon, buoy location off the coast of Beirut, and northern Lebanon. The altimeter data indicated that Hs values as measured through the buoy is within 1 standard deviation of the offshore regional mean, however adopting the regional mean value of Hs would more than double the potential power from waves from 4.6 kW/m to 9.8 kW/m. This puts the wave resources in the lower end of what is ‘technically viable’ and therefore it can be concluded that, given the current state of technology, wave power cannot contribute to the 12% target of renewable energy in the Lebanese energy mix by 2020. A re-evaluation of the wave power prospects post-2020, based on an actual and more robust data collection system, is recommended.

The sea state of South China is influenced by typhoon obviously. It is important to carry out the long-term prediction of typhoon wind, wave height and wave period for the coastal and offshore engineering. In this paper the measured wind and wave data during typhoon processes from 1964-1989 are used to predict the extreme sea states by using Grey Markov Chain Model. The calculated results show the reasonableness of the proposed method. key words—Typhoon, Extreme sea states, Long term prediction, Grey Markov Chain Model.

In this study, numerical simulations for winds and waves were carried out using WRF and WW3 and the predicted wind speed, wave height and wave period were validated with measurement. Annual average values of absolute monthly error of wind speed, wave height and wave period were 4.30%, 12.3% and 7.8%. The prediction accuracy were improved by bias modification in the region of low wave height and short wave period. Predicted seasonal frequency distributions showed good agreement with measurements. The criteria of experienced construction methods were investigated at Choshi and Kitakyushu wind farm and the sensitivity of environmental conditions on weather downtime were clarified. At Choshi, the weather downtime was predicted by using wind and wave simulations and showed good agreement with the actual weather downtime.

A comparative study of joint distributions of wave height and period, as well as wave height and steepness, is presented. The analysis includes two theoretical joint distributions of wave height and wave period. These two distributions are transformed into joint distributions of wave height and wave steepness. The theoretical distributions are compared with measured data, as well as parametric models which are obtained by fitting to the data. The data used for comparison are relatively broad-banded and are obtained from measurements in deep waters on the Norwegian continental shelf. It is found that the theoretical distributions are inadequate to describe the joint distributions of the primary wave characteristics of these broad-band data, and thus it is suggested to use parametric models to describe such data. Finally, the engineering relevance of the joint distribution of wave height and wave steepness is discussed.

[1] The global visual wave observations are reanalyzed within the theoretical concept of self-similar wind-driven seas. The core of the analysis is one-parametric dependencies of wave height on wave period. Theoretically, wind-driven seas are governed by power-like laws with exponents close to Toba's one 3/2 while the corresponding swell exponent (−1/2) has an opposite signature. This simple criterion was used and appeared to be adequate to the problem of swell and wind-driven waves discrimination. This theoretically based discrimination does not follow exactly the Voluntary Observing Ship (VOS) data. This important issue is considered both in the context of methodology of obtaining VOS data and within the physics of wind waves. The results are detailed for global estimates and for analysis of particular areas of the Pacific Ocean. Prospects of further studies are discussed. In particular, satellite data are seen to be promising for tracking ocean swell and for studies of physical mechanisms of its evolution.

The author discusses how knowledge of wave-induced loads is essential in both the design and operation of offshore structures. In hostile areas like the North Sea, the significant wave height (mean of the highest one third of the waves present in a sea) can be larger than 2 m 60% of the time. The most probable largest wave height in 100 years can be more than 30 m. The mean wave period can be from 15 to 20 s in extreme weather situations, and it is seldom below 4 s. Environmental load due to current and wind are also important, and in some cases the interactive effect between waves and current is significant. Current velocities of 1-2 m s{sup {minus} 1} and extreme wind velocities of 40-45 m s{sup {minus}1} must be used in designing offshore structures in the North Sea.

Yuk, J.-H.; Kim, K.O.; Jung, K.T., and Choi, B.H., 2016. Swell prediction for the Korean coast. The accurate prediction of abnormally high waves occurring in the East Sea during winter is important in terms of the prevention of coastal disasters along the east Korean coast. This study attempts to hindcast the abnormally high swell wave events that occurred in October 2006 and February 2008 using the unstructured grid wave model UnSWAN with high-resolution reanalysis data from the European Centre for Medium-Range Weather Forecasts as meteorological inputs. The model used in this study incorporates an additional weighting factor for the relative wave-number in dissipation source term to improve swell propagation and wave period. Wave heights and periods are well reproduced compared with the observational data. Examination of the meteorological data and model results shows that the abnormally high waves in October 2006 were induced by the overlap of a swell wave and a wind-generated wave with nearly...