A Method to Implement the Random Signals for Time Varying Offshore Wave Height During Storm Condition in an Intra-Wave Period Wave Model

2006 ◽  
Author(s):  
Yuliang Zhu ◽  
Shunqi Pan ◽  
Premanandan T. Fernando ◽  
Xiaoyan Zhou
Keyword(s):  
Wave Height ◽  
Wave Model ◽  
Peak Frequency ◽  
Wave Period ◽  
Storm Event ◽  
Time Varying ◽  
Wave Heights ◽  
Offshore Wave ◽  
Storm Condition ◽  
Period Wave

In this paper, a method to implement the surface elevation at the offshore boundary during storm conditions is presented in the intra-wave period wave model. At storm condition, the offshore incident significant wave height is time varying. In the case of time varying incident wave height, the JONSWAP energy spectrum can be manipulated as follows: H1/32s(f). s(f) is the energy density function for a unit wave height. During a storm event not only the offshore boundary significant wave heights but also the peak frequency varies. If we choose a mean peak frequency during a storm event, s(f) can be calculated for the mean peak frequency for the storm event. The amplitudes of the component waves for the random signals are calculated from the unit energy density function s(f), and the phase angle of the component wave, So we can numerically generate surface elevation time series for the time varying offshore wave heights. The method was verified in the intra-wave period wave model using field measurements at Sea Palling site Norfolk UK.

Climatology, Variability and Extrema of Ocean Waves: The Web-Based KNMI/ERA-40 Wave Atlas

2006 ◽  
Author(s):  
Andreas Sterl ◽  
Sofia Caires
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Ocean Waves ◽  
Wave Period ◽  
Web Based ◽  
Significant Wave ◽  
Wave Parameters ◽  
Wave Heights ◽  
The Web

The European Centre for Medium Range Weather Forecasts (ECMWF) has recently finished ERA-40, a reanalysis covering the period September 1957 to August 2002. One of the products of ERA-40 consists of 6-hourly global fields of wave parameters like significant wave height and wave period. These data have been generated with the Centre’s WAM wave model. From these results the authors have derived climatologies of important wave parameters, including significant wave height, mean wave period, and extreme significant wave heights. Particular emphasis is on the variability of these parameters, both in space and time. Besides for scientists studying climate change, these results are also important for engineers who have to design maritime constructions. This paper describes the ERA-40 data and gives an overview of the results derived. The results are available on a global 1.5° × 1.5° grid. They are accessible from the web-based KNMI/ERA-40 Wave Atlas at http://www.knmi.nl/waveatlas.

scholarly journals Wave climate in the Arkona Basin, the Baltic Sea

Ocean Science ◽  
2012 ◽  
Vol 8 (2) ◽  
pp. 287-300 ◽  
Author(s):  
T. Soomere ◽  
R. Weisse ◽  
A. Behrens
Keyword(s):  
Baltic Sea ◽  
Wave Height ◽  
Wave Model ◽  
Wave Climate ◽  
Wind Fields ◽  
The Baltic Sea ◽  
Wave Heights ◽  
The Baltic ◽  
Basic Features

Abstract. The basic features of the wave climate in the Southwestern Baltic Sea (such as the average and typical wave conditions, frequency of occurrence of different wave parameters, variations in wave heights from weekly to decadal scales) are established based on waverider measurements at the Darss Sill in 1991–2010. The measured climate is compared with two numerical simulations with the WAM wave model driven by downscaled reanalysis of wind fields for 1958–2002 and by adjusted geostrophic winds for 1970–2007. The wave climate in this region is typical for semi-enclosed basins of the Baltic Sea. The maximum wave heights are about half of those in the Baltic Proper. The maximum recorded significant wave height HS =4.46 m occurred on 3 November 1995. The wave height exhibits no long-term trend but reveals modest interannual (about 12 % of the long-term mean of 0.76 m) and substantial seasonal variation. The wave periods are mostly concentrated in a narrow range of 2.6–4 s. Their distribution is almost constant over decades. The role of remote swell is very small.

Spectral Modeling of Ice-Induced Wave Decay

2020 ◽  
Vol 50 (6) ◽  
pp. 1583-1604 ◽  
Author(s):  
Qingxiang Liu ◽  
W. Erick Rogers ◽  
Alexander Babanin ◽  
Jingkai Li ◽  
Changlong Guan
Keyword(s):  
Wave Height ◽  
Wave Attenuation ◽  
Wave Spectrum ◽  
Wave Model ◽  
Beaufort Sea ◽  
Peak Frequency ◽  
Large Wave ◽  
Wave Decay ◽  
Operational Forecasts ◽  
The Antarctic

AbstractThree dissipative (two viscoelastic and one viscous) ice models are implemented in the spectral wave model WAVEWATCH III to estimate the ice-induced wave attenuation rate. These models are then explored and intercompared through hindcasts of two field cases: one in the autumn Beaufort Sea in 2015 and the other in the Antarctic marginal ice zone (MIZ) in 2012. The capability of these dissipative models, along with their limitations and applicability to operational forecasts, are analyzed and discussed. The sensitivity of the simulated wave height to different source terms—the ice-induced wave decay Sice and other physical processes Sother (e.g., wind input, nonlinear four-wave interactions)—is also investigated. For the Antarctic MIZ experiment, Sother is found to be remarkably less than Sice and thus contributes little to the simulated significant wave height Hs. The saturation of dHs/dx at large wave heights in this case, as reported by a previous study, is well reproduced by the three dissipative ice models with or without the utilization of Sother in the ice-infested seas. A clear downward trend in the peak frequency fp is found as Hs increases. As fp decreases, the dominant wave components of a wave spectrum will experience reduced damping by sea ice, and finally result in the flattening of dHs/dx for Hs > 3 m in this specific case. Nonetheless, Sother should not be disregarded within a more general modeling perspective, as our simulations suggest Sother could be comparable to Sice in the Beaufort Sea case where wave and ice conditions are remarkably different.

Error Estimation of Buoy, Satellite, and Model Wave Height Data

2007 ◽  
Vol 24 (9) ◽  
pp. 1665-1677 ◽  
Author(s):  
Peter A. E. M. Janssen ◽  
Saleh Abdalla ◽  
Hans Hersbach ◽  
Jean-Raymond Bidlot
Keyword(s):  
Collocation Method ◽  
Wave Height ◽  
Wave Model ◽  
Weather Forecasts ◽  
Model Wave ◽  
Analysis Scheme ◽  
Wave Heights ◽  
Forecasting System ◽  
Buoy Data ◽  
Height Data

Abstract Triple collocation is a powerful method to estimate the rms error in each of three collocated datasets, provided the errors are not correlated. Wave height analyses from the operational European Centre for Medium-Range Weather Forecasts (ECMWF) wave forecasting system over a 4-yr period are compared with independent buoy data and dependent European Remote Sensing Satellite-2 (ERS-2) altimeter wave height data, which have been used in the wave analysis. To apply the triple-collocation method, a fourth, independent dataset is obtained from a wave model hindcast without assimilation of altimeter wave observations. The seasonal dependence of the respective errors is discussed and, while in agreement with the properties of the analysis scheme, the wave height analysis is found to have the smallest error. In this comparison the altimeter wave height data have been obtained from an average over N individual observations. By comparing model wave height with the altimeter superobservations for different values of N, alternative estimates of altimeter and model error are obtained. There is only agreement with the estimates from the triple collocation when the correlation between individual altimeter observations is taken into account. The collocation method is also applied to estimate the error in Environmental Satellite (ENVISAT), ERS-2 altimeter, buoy, model first-guess, and analyzed wave heights. It is shown that there is a high correlation between ENVISAT and ERS-2 wave height error, while the quality of ENVISAT altimeter wave height is high.

Wave Height Distribution in Mixed Sea States

2001 ◽  
Vol 124 (1) ◽  
pp. 34-40 ◽  
Author(s):  
German Rodriguez ◽  
C. Guedes Soares ◽  
Mercedes Pacheco ◽  
E. Pe´rez-Martell
Keyword(s):  
Wave Height ◽  
Probabilistic Models ◽  
Simulated Data ◽  
Peak Frequency ◽  
Frequency Separation ◽  
Height Distribution ◽  
Zero Crossing ◽  
Frequency Wave ◽  
Wave Height Distribution ◽  
Wave Heights

The statistical distribution of zero-crossing wave heights in Gaussian mixed sea states is examined by analyzing numerically simulated data. Nine different kinds of bimodal scalar spectra are used to study the effects of the relative energy ratio and the peak frequency separation between the low and high frequency wave fields on the wave height distribution. Observed results are compared with predictions of probabilistic models adopted in practice. Comparisons of the empirical data with relevant probabilistic models reveals that the Rayleigh model systematically overestimates the number of observed wave heights larger than the mean wave height, except for one of the cases analyzed. None of the models used to predict the observed exceedance probabilities is able to characterize adequately all cases of bimodal sea states examined here.

scholarly journals Wave Height and Wave Period Derived from a Shipboard Coherent S-Band Wave Radar in the South China Sea

2019 ◽  
Vol 11 (23) ◽  
pp. 2812 ◽  
Author(s):  
Chen ◽  
Chen ◽  
Zhao ◽  
Wang
Keyword(s):  
South China Sea ◽  
Wave Height ◽  
South China ◽  
Doppler Shift ◽  
Wave Period ◽  
Ocean Wave ◽  
Significant Wave ◽  
Wave Radar ◽  
Wave Heights ◽  
Wavenumber Spectrum

To expand the scope of ocean wave observations, a shipboard coherent S-band wave radar system was developed recently. The radar directly measures the wave orbital velocity from the Doppler shift of the received radar signal. The sources of this Doppler shift are analyzed. After removing the Doppler shifts caused by the ocean current and platform, the radial velocities of water particles of the surface gravity waves are retrieved. Subsequently, the wavenumber spectrum can be obtained based on linear wave theory. Later, the significant wave height and wave periods (including mean wave period and peak wave period) can be calculated from the wavenumber spectrum. This radar provides a calibration-free way to measure wave parameters and is a novel underway coherent microwave wave radar. From 9 September to 11 September, 2018, an experiment involving radar-derived and buoy-measured wave measurements was conducted in the South China Sea. The Doppler spectra obtained when the ship was in the state of navigation or mooring indicated that the quality of the radar echo was fairly good. The significant wave heights and wave periods measured using the radar are compared with those obtained from the wave buoy. The correlation coefficients of wave heights and mean wave periods between these two instruments both exceed 0.9 while the root mean square differences are respectively less than 0.15 m and 0.25 s, regardless of the state of motion of the ship. These results indicate that this radar has the capability to accurately measure ocean wave heights and wave periods.

Wave Probabilities Consistent with Official Tropical Cyclone Forecasts

2016 ◽  
Vol 31 (6) ◽  
pp. 2035-2045 ◽  
Author(s):  
Charles R. Sampson ◽  
James A. Hansen ◽  
Paul A. Wittmann ◽  
John A. Knaff ◽  
Andrea Schumacher
Keyword(s):  
Surface Wave ◽  
Wind Speed ◽  
Tropical Cyclone ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Ocean Surface Wave

Abstract Development of a 12-ft-seas significant wave height ensemble consistent with the official tropical cyclone intensity, track, and wind structure forecasts and their errors from the operational U.S. tropical cyclone forecast centers is described. To generate the significant wave height ensemble, a Monte Carlo wind speed probability algorithm that produces forecast ensemble members is used. These forecast ensemble members, each created from the official forecast and randomly sampled errors from historical official forecast errors, are then created immediately after the official forecast is completed. Of 1000 forecast ensemble members produced by the wind speed algorithm, 128 of them are selected and processed to produce wind input for an ocean surface wave model. The wave model is then run once per realization to produce 128 possible forecasts of significant wave height. Probabilities of significant wave height at critical thresholds can then be computed from the ocean surface wave model–generated significant wave heights. Evaluations of the ensemble are provided in terms of maximum significant wave height and radius of 12-ft significant wave height—two parameters of interest to both U.S. Navy meteorologists and U.S. Navy operators. Ensemble mean errors and biases of maximum significant wave height and radius of 12-ft significant wave height are found to be similar to those of a deterministic version of the same algorithm. Ensemble spreads capture most verifying maximum and radii of 12-ft significant wave heights.

scholarly journals Comparison of Envisat ASAR Ocean Wave Spectra with Buoy and Altimeter Data via a Wave Model

2009 ◽  
Vol 26 (3) ◽  
pp. 593-614 ◽  
Author(s):  
Jian-Guo Li ◽  
Martin Holt
Keyword(s):  
Wave Height ◽  
Spectral Characteristics ◽  
Wave Model ◽  
Ocean Wave ◽  
Global Ocean ◽  
Altimeter Data ◽  
Wave Spectra ◽  
Envisat Asar ◽  
Comparison Results ◽  
Wave Heights

Abstract The Advanced Synthetic Aperture Radar (ASAR) on board the Envisat satellite is an important resource for observation of global ocean surface wave spectra. However, assessment of this valuable dataset is not straightforward as a result of a lack of other independent ocean wave spectral observations. The radar altimeter (RA-2) on board the same satellite measures ocean wave height at the same time as the ASAR but at a location about 200 km distant. A small number of moored buoys produce one-dimensional (1D) ocean wave spectra but few ASAR spectra fall on the buoy positions in a given period. Indirect comparison of the Envisat ASAR 2D wave spectra with the RA-2 wave heights and 1D spectra of three selected buoys from July 2004 to February 2006 is facilitated by a wave model, which provides coherent spatial and temporal links between these observations. In addition to the conventional significant wave height (SWH), four spectral subrange wave heights (SRWHs) are used to illustrate the spectral characteristics of these observations. A comparison of three Envisat ASAR 2D spectra with the closest model and buoy spectra is also attempted to illustrate the qualities of these different observations and to demonstrate the restrictions to their direct comparison. Results indicate that these three independent observations are in good agreement in terms of SWH, though the Envisat ASAR shows the largest variance. Comparison of SRWHs indicates that the ASAR spectra agree well with buoy and model in moderately long waves, but the ASAR instrument does not resolve high-frequency waves, especially along the satellite track.

scholarly journals CHARACTERISTIC WAVE PERIOD

1976 ◽  
Vol 1 (15) ◽  
pp. 15 ◽  
Author(s):  
M. Manohar ◽  
I.E. Mobarek ◽  
N.A. El Sharaky
Keyword(s):  
Wave Height ◽  
Energy Flux ◽  
Spectral Width ◽  
Wave Period ◽  
Distribution Analysis ◽  
Density Spectrum ◽  
Total Energy Flux ◽  
Wave Heights ◽  
Definition Of ◽  
Height Use

The wave period estimates obtained from different procedures are not consistent unlike statistical distribution analysis of wave heights. Thus not one definition of wave period is satisfactory for engineering analysis of coastal processes. There are at least 10 different measures of wave periods including the zero up-crossing period, the average wave period, significant height period and peak of the energy density spectrum period. For Lhe analysis of periods, 20 min. records were obtained from offshore pressure recorders. Summer and winter records were analysed separately. In the analysis, zero up-crossing period and average period were taken as reference periods. There were significant differences between the wave periods and they were found to depend also on the spectral width parameter. Finally comparison was made between the energy flux obtained under the spectral diagrams and energy flux obtained using various wave periods and heights. Study shows that if the total energy flux is desired, then the most appropriate values to be used are the root mean square wave height and period corresponding to that wave height. Use of significant wave height, along with zero up-crossing period gives higher values.

scholarly journals Extreme Gravity Waves In The Arabian Gulf

2009 ◽  
Vol 6 (1) ◽  
pp. 21 ◽  
Author(s):  
S. Neelamani ◽  
K. Al-Salem ◽  
K. Rakha
Keyword(s):  
Wave Height ◽  
Arabian Gulf ◽  
Wave Period ◽  
Return Periods ◽  
Threshold Method ◽  
Total Period ◽  
Significant Wave ◽  
Wave Heights ◽  
Mean Wave Period ◽  
Significant Wave Heights

The extreme significant wave heights and the corresponding mean wave periods were predicted for return periods of 12, 25, 50, 100 and 200 years for 38 different locations in the territorial and offshore locations of countries surrounding the Arabian Gulf. The input wave data for the study is hindcast waves obtained using a WAM model for a total period of 12 years, (1993 to 2004). The peak over threshold method (with 1.0 m as threshold value), is used for selecting the data for the extreme wave analysis. In general, a Weibull distribution is found to fit the data well compared to the Gumbel distribution for all these locations. From the joint probability of wave height and wave period, a simple polynomial relationship (Tmean = C3 (Hs)C4) is used to obtain the relationship between the significant wave height and mean wave period for all the 38 locations. The value of C3 is found to vary from 3.8 to 4.8 and the value of C4 is found to vary from 0.19 to 0.32. The mean wave period was found to be more sensitive to change in locations within the Gulf and it is less sensitive to change in return periods from 12 years to 200 years. The significant wave heights for 100 year return period varied from 3.0 to 4.5 for water depths of 9 to 16 m, whereas in the offshore sites (depths from 30 to 60 m) it varied from 5.0 to 7.0 m. A large number of coastal projects are in progress in the Arabian Gulf and many new projects are being planned in this region for the future. The results of the present study will be highly useful for optimal design of the ocean structures for these projects. 

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