scholarly journals The Impact of Spume Droplets and Wave Stress Parameterizations on Simulated Near-Surface Maritime Wind and Temperature

2010 ◽  
Vol 40 (6) ◽  
pp. 1373-1389 ◽  
Author(s):  
Valdir Innocentini ◽  
Iury Angelo Gonçalves
Keyword(s):  
Relative Humidity ◽  
Wave Height ◽  
Air Temperature ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
The Other ◽  
Sensible Heat ◽  
Near Surface ◽  
Significant Wave ◽  
The Impact

Abstract The influence of ocean gravity waves on the wind and temperature above the surface is investigated using a one-dimensional boundary layer model. The effect of the wave-induced stress is evaluated using three parameterizations: wave age (WaAg), wave steepness (WaSt), and wind action on the wave spectrum (WiAc). It is found that while the WaAg is more effective in reducing the wind for young waves, in the WaSt approach the maximum reduction is for old waves. On the other hand, the WiAc is very sensitive to the energy present in high frequencies corresponding to periods less than 2 s, which are found in both young and mature spectra. Since observations show that most of the wave stress is due to the small-period wave energy, in this aspect the WaSt parameterization is not recommended; WaAg is not as accurate; and thus WiAc is the best among the three, although its computational cost is the highest. The droplet load contribution to the total surface stress can be neglected for the droplet spectrum produced by 10-m wind speeds up to 15 m s−1, but its importance increases with the speed and its magnitude becomes about ⅕ of the total stress for wind speed ∼30 m s−1. Concerning the latent and sensible heat fluxes accompanying the production of spume droplets by waves, a feasible microphysical formulation for operational use in weather forecasting models is proposed. The droplet spectrum is assumed to be a product of two functions, one depending on the windsea Reynolds number and the other on the droplet radius spectrum. The bulk effect of the latter is analytically evaluated and stored in a table as a function of air temperature Ta, relative humidity R%, and significant wave height Hs. In numerical experiments with initial sea surface temperature 5 K higher than the air surface, latent and sensible heat contributions to the air temperature are computed as a function of the wave spectra. The launched droplet spectrum (which increases the air temperature due to sensible heat) and the relative humidity (which controls the cooling due to the droplet evaporation) define the heat budget and the air temperature evolution. Although in these experiments the sea temperature is much higher than the air temperature, the results show a noticeable dominance of the evaporative cooling in the lower atmosphere mainly for smaller significant wave height. Some air warming is noticeable only from a threshold around Hs ≥ 5 m.

Sea State Estimation Based on Ship Motions Measurements and Data Fusion

2013 ◽  
Author(s):  
Céline Drouet ◽  
Nicolas Cellier ◽  
Jérémie Raymond ◽  
Denis Martigny
Keyword(s):  
Data Fusion ◽  
State Estimation ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Ship Motions ◽  
Sea State ◽  
Significant Wave ◽  
X Band

In-service monitoring can help to increase safety of ships especially regarding the fatigue assessment. For this purpose, it is compulsory to know the environmental conditions encountered: wind, but also the full directional wave spectrum. During the EU TULCS project, a full scale measurements campaign has been conducted onboard the CMA-CGM 13200 TEU container ship Rigoletto. She has been instrumented to measure deformation of the ship as well as the sea state encountered during its trip. This paper will focus on the sea state estimation. Three systems have been installed to estimate the sea state encountered by the Rigoletto: An X-band radar from Ocean Waves with WAMOS® system and two altimetric wave radars from RADAC®. Nevertheless, the measured significant wave height can be disturbed by several external elements like bow waves, sprays, sea surface ripples, etc… Furthermore, ship motions are also measured and can provide another estimation of the significant wave height using a specific algorithm developed by DCNS Research for the TULCS project. As all those estimations are inherently different, it is necessary to make a fusion of those data to provide a single estimation (“best estimate”) of the significant wave height. This paper will present the data fusion process developed for TULCS and show some first validation results.

scholarly journals A Simple Method for Retrieving Significant Wave Height from Dopplerized X-Band Radar

2016 ◽  
Author(s):  
Ruben Carrasco ◽  
Michael Streßer ◽  
Jochen Horstmann
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Doppler Velocity ◽  
Modulation Transfer ◽  
Simple Method ◽  
Backscatter Intensity ◽  
Significant Wave ◽  
X Band ◽  
Variance Spectrum

Abstract. Retrieving spectral wave parameters such as the peak wave direction and wave period from marine radar backscatter intensity is very well developed. However, the retrieval of significant wave height is difficult because the radar image spectrum (a backscatter intensity variance spectrum) has to be transferred to a wave spectrum (a surface elevation variance spectrum) using a modulation transfer function (MTF) which requires extensive calibration for each individual radar setup. In contrast to the backscatter intensity, the Doppler velocity measured by a coherent radar is induced by the radial velocity of the surface scattering and its periodic component is mainly the contribution of surface waves. Therefore, the variance of the Doppler velocity can be utilized to retrieve the significant wave height. Analysing approximately 100 days of Doppler velocity measurements of a coherent on receive radar operating at X-band with vertical polarization in transmit and receive, a simple relation was derived and validated to retrieve significant wave heights. Comparison to wave measurements of a wave rider buoy as well as an acoustic wave and current profiler resulted in a root mean square error of 0.24 m with a bias of 0.08 m. Furthermore, the different sources of error are discussed and investigated.

Effect of Uni- and Bi-Directional Coupling of Ocean-Met Interaction on Significant Wave Height and Local Wind

2017 ◽  
Author(s):  
Adil Rasheed ◽  
Jakob Kristoffer Süld ◽  
Mandar Tabib
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Surface Wind ◽  
Wave Model ◽  
Ocean Surface ◽  
Observation Data ◽  
Local Wind ◽  
Near Surface ◽  
Significant Wave ◽  
Bidirectional Coupling

Accurate prediction of near surface wind and wave height are important for many offshore activities like fishing, boating, surfing, installation and maintenance of marine structures. The current work investigates the use of different methodologies to make accurate predictions of significant wave height and local wind. The methodology consists of coupling an atmospheric code HARMONIE and a wave model WAM. Two different kinds of coupling methodologies: unidirectional and bidirectional coupling are tested. While in Unidirectional coupling only the effects of atmosphere on ocean surface are taken into account, in bidirectional coupling the effects of ocean surface on the atmosphere are also accounted for. The predicted values of wave height and local wind at 10m above the ocean surface using both the methodologies are compared against observation data. The results show that during windy conditions, a bidirectional coupling methodology has better prediction capability.

scholarly journals Wave spectral shapes in the coastal waters based on measured data off Karwar, west coast of India

2017 ◽  
Author(s):  
M. Anjali Nair ◽  
V. Sanil Kumar
Keyword(s):  
Wave Height ◽  
Coastal Waters ◽  
High Frequency ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Temporal Variations ◽  
Wave Spectra ◽  
Monsoon Period ◽  
Significant Wave ◽  
Spectral Shapes

Abstract. Understanding of the wave spectral shapes is of primary importance for the design of marine facilities. In this paper, the wave spectra collected from January 2011 to December 2015 in the coastal waters are examined to know the temporal variations in the wave spectral shape. For 31.15 % of the time, peak frequency is between 0.08 and 0.10 Hz and the significant wave height is also relatively high (~ 1.55 m) for waves in this class. The slope of the high-frequency tail of the monthly average wave spectra is high during the Indian summer monsoon period (June–September) compared to other months and it increases with increase in significant wave height. There is no much interannual variation in slope for swell dominated spectra during the monsoon, while in the non-monsoon period when wind-seas have much influence, the slope varies significantly. Since the high-frequency slope of the wave spectrum is within the range 3–4 during the monsoon period, Donelan spectrum shows better fit for the wave spectra in monsoon months compared to other months.

Gap-Filling and Predicting Wave Parameters Using Support Vector Regression Method

2011 ◽  
Author(s):  
Maziar Golestani ◽  
Mostafa Zeinoddini
Keyword(s):  
Support Vector Regression ◽  
Wave Height ◽  
Significant Wave Height ◽  
Rational Design ◽  
Wave Spectrum ◽  
Support Vector ◽  
Wave Spectra ◽  
Significant Wave ◽  
Wave Parameters ◽  
Data Gaps

Knowledge of relevant oceanographic parameters is of utmost importance in the rational design of coastal structures and ports. Therefore, an accurate prediction of wave parameters is especially important for safety and economic reasons. Recently, statistical learning methods, such as Support Vector Regression (SVR) have been successfully employed by researchers in problems such as lake water level predictions, and significant wave height prediction. The current study reports potential application of a SVR approach to predict the wave spectra and significant wave height. Also the capability of the model to fill data gaps was tested using different approaches. Concurrent wind and wave records (standard meteorological and spectral density data) from 4 stations in 2003, 2007, 2008 and 2009 were used both for the training the SVR system and its verification. The choice of these four locations facilitated the comparison of model performances in different geographical areas. The SVR model was then used to obtain predictions for the wave spectra and also time series of wave parameters (separately for each station) such as its Hs and Tp from spectra and wind records. New approach was used to predict wave spectra comparing to similar studies. Reasonably well correlation was found between the predicted and measured wave parameters. The SVR model was first trained and tested using various methods for selecting training data. Also different values for SVM parameters (e.g. tolerance of termination criterion, cost, and gamma in kernel function) were tested. The best possible results were obtained using a Unix shell script (in Linux) which automatically implements different values for different input parameters and finds the best regression by calculating statistical scores like correlation of coefficient, RMSE, bias and scatter index. Finally for a better understanding of the results, Quantile-Quantile plots were produced. The results show that SVR can be successfully used for prediction of Hs and wave spectrum out of a series of wind and spectral wave parameters inputs. Also it was noticed that SVR is an efficient tool to be used when data gaps are present in the data.

scholarly journals Atmospheric Cold Front-Generated Waves in the Coastal Louisiana

2020 ◽  
Vol 8 (11) ◽  
pp. 900
Author(s):  
Yuhan Cao ◽  
Chunyan Li ◽  
Changming Dong
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Cold Front ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Wave Direction ◽  
Significant Wave ◽  
Cold Fronts ◽  
Directional Wave ◽  
Coastal Louisiana

Atmospheric cold front-generated waves play an important role in the air–sea interaction and coastal water and sediment transports. In-situ observations from two offshore stations are used to investigate variations of directional waves in the coastal Louisiana. Hourly time series of significant wave height and peak wave period are examined for data from 2004, except for the summer time between May and August, when cold fronts are infrequent and weak. The intra-seasonal scale variations in the wavefield are significantly affected by the atmospheric cold frontal events. The wave fields and directional wave spectra induced by four selected cold front passages over the coastal Louisiana are discussed. It is found that significant wave height generated by cold fronts coming from the west change more quickly than that by other passing cold fronts. The peak wave direction rotates clockwise during the cold front events. The variability of the directional wave spectrum shows that the largest spectral density is distributed at low frequency in the postfrontal phase associated with migrating cyclones (MC storms) and arctic surges (AS storms).

scholarly journals The Influence of Air–Sea Roughness, Sea Spray, and Storm Translation Speed on Waves in North Atlantic Storms

2008 ◽  
Vol 38 (4) ◽  
pp. 817-839 ◽  
Author(s):  
Weiqing Zhang ◽  
William Perrie
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Storm Track ◽  
Wave Drag ◽  
Sea Spray ◽  
Wave Spectra ◽  
Translation Speed ◽  
Significant Wave ◽  
Directional Wave ◽  
The Impact

Abstract A coupled atmosphere–wave–sea spray model system is used to evaluate the impact of sea spray and wave drag on storm-generated waves, their height variations, and directional wave spectra in relation to the storm location and translation speed. Results suggest that the decrease or increase of significant wave height due to spray and wave drag is most significant in high-wind regions to the right of the storm track. These processes are modulations on the maximum-wave region and tend to occur several hours after the peak wind events, depending on the storm translation velocity. The translation speed of the storm is important. The directional variation between local winds and wind-generated waves within rapidly moving storms that outrun the waves is notably different from that of trapped waves, when the dominant waves’ group velocity approximates the storm translation speed. While wave drag and spray can increase or reduce the magnitudes of wind and significant wave height, their nondirectional formulations allow them to have little apparent effect on the directional wave spectra.

Physical and Numerical Investigations on Wave Run-Up and Dissipation under Breakwater with Fence Revetment

2021 ◽  
Vol 9 (12) ◽  
pp. 1355
Author(s):  
Enjin Zhao ◽  
Lin Mu ◽  
Zhaoyang Hu ◽  
Xinqiang Wang ◽  
Junkai Sun ◽  
...  
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Significant Wave Height ◽  
Irregular Waves ◽  
Structure Stability ◽  
Wave Impact ◽  
Significant Wave ◽  
Tide Level ◽  
Run Up ◽  
The Impact

Revetment elements and protective facilities on a breakwater can effectively weaken the impact of waves. In order to resist storm surges, there is a plan to build a breakwater on the northern shore of Meizhou Bay in Putian City, China. To better design it, considering different environmental conditions, physical and numerical experiments were carried out to accurately study the effects of the breakwater and its auxiliary structures on wave propagation. In the experiments, the influence of the wave type, initial water depth, and the structure of the fence plate are considered. The wave run-up and dissipation, the wave overtopping volume, and the structure stability are analyzed. The results indicate that the breakwater can effectively resist the wave impact, reduce the wave run-up and overtopping, and protect the rear buildings. In addition, under the same still water depth and significant wave height, the amount of overtopped water under regular waves is larger than that under irregular waves. With the increase of the still water depth and significant wave height, the overtopped water increases, which means that when the storm surge occurs, damage on the breakwater under the high tide level is greater than that under the low tide level. Besides, the fence plate can effectively dissipate energy and reduce the overtopping volume by generating eddy current in the cavity. Considering the stability and the energy dissipation capacity of the fence plate, it is suggested that a gap ratio of 50% is reasonable.

Measuring Global Ocean Wave Skewness by Retracking RA-2 Envisat Waveforms

2007 ◽  
Vol 24 (6) ◽  
pp. 1102-1116 ◽  
Author(s):  
J. Gómez-Enri ◽  
C. P. Gommenginger ◽  
M. A. Srokosz ◽  
P. G. Challenor ◽  
J. Benveniste
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Likelihood Estimation ◽  
Ocean Waves ◽  
Ocean Wave ◽  
Global Ocean ◽  
Radar Altimeter ◽  
Significant Wave ◽  
Linear And Nonlinear ◽  
The Impact

For early satellite altimeters, the retrieval of geophysical information (e.g., range, significant wave height) from altimeter ocean waveforms was performed on board the satellite, but this was restricted by computational constraints that limited how much processing could be performed. Today, ground-based retracking of averaged waveforms transmitted to the earth is less restrictive, especially with respect to assumptions about the statistics of ocean waves. In this paper, a theoretical maximum likelihood estimation (MLE) ocean waveform retracker is applied tothe Envisat Radar Altimeter system (RA-2) 18-Hz averaged waveforms under both linear (Gaussian) and nonlinear ocean wave statistics assumptions, to determine whether ocean wave skewness can be sensibly retrieved from Envisat RA-2 waveforms. Results from the MLE retracker used in nonlinear mode provide the first estimates of global ocean wave skewness based on RA-2 Envisat averaged waveforms. These results show for the first time geographically coherent skewness fields and confirm the notion that large values of skewness occur primarily in regions of large significant wave height. Results from the MLE retracker run in linear and nonlinear modes are compared with each other and with the RA-2 Level 2 Sensor Geophysical Data Records (SGDR) products to evaluate the impact of retrieving skewness on other geophysical parameters. Good agreement is obtained between the linear and nonlinear MLE results for both significant wave height and epoch (range), except in areas of high-wave-height conditions.

Analysis of the Geometric Constraints Employed in Constructal Design for Oscillating Water Column Devices Submitted to the Wave Spectrum through a Numerical Approach

2019 ◽  
Vol 390 ◽  
pp. 193-210
Author(s):  
Mateus das Neves Gomes ◽  
Matheus José de Deus ◽  
Elizaldo Domingues dos Santos ◽  
Liércio André Isoldi
Keyword(s):  
Water Column ◽  
Wave Height ◽  
Significant Wave Height ◽  
Fluid Dynamic ◽  
Wave Spectrum ◽  
Geometric Constraints ◽  
Oscillating Water Column ◽  
Incident Wavelength ◽  
Significant Wave ◽  
Constructal Design

This paper aims a numerical investigation about the fluid dynamic behavior of an oscillating water column (OWC) wave energy converter (WEC) into electrical energy. Constructal design is employed to perform a geometric evaluation of an OWC WEC submitted a Pierson-Moskowitz wave spectrum. The objective function is to maximize the energy conversion. The hydropneumatic chamber volume (VHC) and the total OWC volume (VT) are adopted as geometric constraints. In the first stage, the values are constant during the maximization process. However, in a second stage they are changed according to the constraint variation (CV). One of the goals is to analyze the influence of the choice of this geometric constraints value on the OWC performance in relation to the wave spectrum. For this purpose, are considered three different scenarios: 1)VHydis equal to the minimum incident wavelength (λmin), that is relative to the maximum frequency of the wave spectrum times the significant wave height (HS); 2)VHydis equal to the peak incident wavelength (λpeak), that is relative to peak frequency of the wave spectrum times the significant wave height (HS); and 3)VHydis equal to the maximum incident wavelength (λmax), that is relative to minimum frequency of the wave spectrum times the significant wave height (HS). To do so, constructal design is employed varying the degree of freedom (DOF)H1/L(ratio between the height and length of OWC chamber), while the others DOF’sH2/l(ratio between height and length of chimney) andH3(lip submergence), are kept fixed. It is employed a Pierson-Moskowitz wave spectrum with significant period (TS) equal to 7.5 s and significant wave height (HS) equal to 1.5 m. For the numerical solution it is used the computational fluid dynamic (CFD) code, based on the finite volume method (FVM). The multiphase volume of fluid (VOF) model is applied to tackle with the water-air interaction. The computational domain is represented by the OWC WEC coupled with the wave tank. The results showed that whenCV= 2.25 forλmaxand (H1/L)O= 0.2152 the highest average for power was obtained, nearly 18,000 W. While forλminand (H1/L)O= 0.2193 it was smaller than 1,000 W. Besides, it was obtained a theoretical recommendation about the geometric constraints employed for the constructal design application, aiming the maximization of the OWC energy conversion from the incident wave spectrum.

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