scholarly journals Coupling of wave and circulation models in coastal-ocean predicting systems: a case study for the German Bight

2015 ◽  
Vol 12 (6) ◽  
pp. 3169-3197
Author(s):  
J. Staneva ◽  
K. Wahle ◽  
H. Günther ◽  
E. Stanev
Keyword(s):  
Extreme Events ◽  
German Bight ◽  
Wind Wave ◽  
Wind Waves ◽  
Ocean Waves ◽  
Coastal Ocean ◽  
Prediction Errors ◽  
State Variables ◽  
Nonlinear Feedback ◽  
The Impact

Abstract. This study addresses the impact of coupling between wind wave and circulation models on the quality of coastal ocean predicting systems. This is exemplified for the German Bight and its coastal area known as the Wadden Sea. The latter is the area between the barrier islands and the coast. This topic reflects the increased interest in operational oceanography to reduce prediction errors of state estimates at coastal scales, which in many cases are due to unresolved nonlinear feedback between strong tidal currents and wind-waves. In this study we present analysis of wave and hydrographic observations, as well as results of numerical simulations. A nested-grid modelling system is used to producing reliable nowcasts and short-term forecasts of ocean state variables, including wind waves and hydrodynamics. The data base includes ADCP observations and continuous measurements from data stations. The individual and collective role of wind, waves and tidal forcing are quantified. The performance of the forecast system is illustrated for the cases of several extreme events. Effects of ocean waves on coastal circulation and sea level are investigated by considering the wave-dependent stress and wave breaking parameterization. Also the effects which the circulation exerts on the wind waves are tested for the coastal areas using different parameterizations. The improved skill of the coupled forecasts compared to the non-coupled ones, in particular during extreme events, justifies the further enhancements of coastal operational systems by including wind wave models.

scholarly journals Coupling of wave and circulation models in coastal–ocean predicting systems: a case study for the German Bight

Ocean Science ◽  
2016 ◽  
Vol 12 (3) ◽  
pp. 797-806 ◽  
Author(s):  
Joanna Staneva ◽  
Kathrin Wahle ◽  
Heinz Günther ◽  
Emil Stanev
Keyword(s):  
Extreme Events ◽  
German Bight ◽  
Wind Waves ◽  
Coastal Ocean ◽  
Linear Feedback ◽  
Prediction Errors ◽  
State Variables ◽  
Wave Effects ◽  
The Individual ◽  
The Impact

Abstract. This study addresses the impact of coupling between wave and circulation models on the quality of coastal ocean predicting systems. This is exemplified for the German Bight and its coastal area known as the Wadden Sea. The latter is the area between the barrier islands and the coast. This topic reflects the increased interest in operational oceanography to reduce prediction errors of state estimates at coastal scales, which in many cases are due to unresolved non-linear feedback between strong currents and wind waves. In this study we present analysis of wave and hydrographic observations, as well as results of numerical simulations. A nested-grid modelling system is used to produce reliable nowcasts and short-term forecasts of ocean state variables, including waves and hydrodynamics. The database includes ADCP observations and continuous measurements from data stations. The individual and combined effects of wind, waves and tidal forcing are quantified. The performance of the forecast system is illustrated for the cases of several extreme events. The combined role of wave effects on coastal circulation and sea level are investigated by considering the wave-dependent stress and wave breaking parameterization. Also the response, which the circulation exerts on the waves, is tested for the coastal areas. The improved skill of the coupled forecasts compared to the non-coupled ones, in particular during extreme events, justifies the further enhancements of coastal operational systems by including wave effects in circulation models.

scholarly journals Ocean forecasting for the German Bight: from regional to coastal scales

Ocean Science ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1105-1136 ◽  
Author(s):  
Emil V. Stanev ◽  
Johannes Schulz-Stellenfleth ◽  
Joanna Staneva ◽  
Sebastian Grayek ◽  
Sebastian Grashorn ◽  
...  
Keyword(s):  
German Bight ◽  
Unstructured Grid ◽  
Wind Waves ◽  
Radar Data ◽  
Coastal Ocean ◽  
Hf Radar ◽  
Regional Models ◽  
Arctic Seas ◽  
The North ◽  
Ocean Forecasting

Abstract. This paper describes recent developments based on advances in coastal ocean forecasting in the fields of numerical modeling, data assimilation, and observational array design, exemplified by the Coastal Observing System for the North and Arctic Seas (COSYNA). The region of interest is the North and Baltic seas, and most of the coastal examples are for the German Bight. Several pre-operational applications are presented to demonstrate the outcome of using the best available science in coastal ocean predictions. The applications address the nonlinear behavior of the coastal ocean, which for the studied region is manifested by the tidal distortion and generation of shallow-water tides. Led by the motivation to maximize the benefits of the observations, this study focuses on the integration of observations and modeling using advanced statistical methods. Coastal and regional ocean forecasting systems do not operate in isolation but are linked, either weakly by using forcing data or interactively using two-way nesting or unstructured-grid models. Therefore, the problems of downscaling and upscaling are addressed, along with a discussion of the potential influence of the information from coastal observatories or coastal forecasting systems on the regional models. One example of coupling coarse-resolution regional models with a fine-resolution model interface in the area of straits connecting the North and Baltic seas using a two-way nesting method is presented. Illustrations from the assimilation of remote sensing, in situ and high-frequency (HF) radar data, the prediction of wind waves and storm surges, and possible applications to search and rescue operations are also presented. Concepts for seamless approaches to link coastal and regional forecasting systems are exemplified by the application of an unstructured-grid model for the Ems Estuary.

scholarly journals An atmosphere–wave regional coupled model: improving predictions of wave heights and surface winds in the southern North Sea

Ocean Science ◽  
2017 ◽  
Vol 13 (2) ◽  
pp. 289-301 ◽  
Author(s):  
Kathrin Wahle ◽  
Joanna Staneva ◽  
Wolfgang Koch ◽  
Luciana Fenoglio-Marc ◽  
Ha T. M. Ho-Hagemann ◽  
...  
Keyword(s):  
North Sea ◽  
German Bight ◽  
Wind Wave ◽  
Surface Wind ◽  
Wave Model ◽  
Atmospheric Model ◽  
Induced Drag ◽  
Wave Heights ◽  
Wave Induced ◽  
The Impact

Abstract. The coupling of models is a commonly used approach when addressing the complex interactions between different components of earth systems. We demonstrate that this approach can result in a reduction of errors in wave forecasting, especially in dynamically complicated coastal ocean areas, such as the southern part of the North Sea – the German Bight. Here, we study the effects of coupling of an atmospheric model (COSMO) and a wind wave model (WAM), which is enabled by implementing wave-induced drag in the atmospheric model. The numerical simulations use a regional North Sea coupled wave–atmosphere model as well as a nested-grid high-resolution German Bight wave model. Using one atmospheric and two wind wave models simultaneously allows for study of the individual and combined effects of two-way coupling and grid resolution. This approach proved to be particularly important under severe storm conditions as the German Bight is a very shallow and dynamically complex coastal area exposed to storm floods. The two-way coupling leads to a reduction of both surface wind speeds and simulated wave heights. In this study, the sensitivity of atmospheric parameters, such as wind speed and atmospheric pressure, to the wave-induced drag, in particular under storm conditions, and the impact of two-way coupling on the wave model performance, is quantified. Comparisons between data from in situ and satellite altimeter observations indicate that two-way coupling improves the simulation of wind and wave parameters of the model and justify its implementation for both operational and climate simulations.

EFFECTS OF AN OIL SLICK ON WIND WAVES1

1979 ◽  
Vol 1979 (1) ◽  
pp. 665-674 ◽  
Author(s):  
Hsien-Ta Liu ◽  
Jung-Tai Lin
Keyword(s):  
Wave Breaking ◽  
Wind Wave ◽  
Wind Waves ◽  
Ocean Waves ◽  
Diesel Oil ◽  
Wave Tank ◽  
Oil Slick ◽  
Wave Profiles ◽  
The Waves ◽  
Integrated Program

ABSTRACT Laboratory experiments were performed to investigate the effects of an oil slick on ocean waves. This is part of an integrated program aimed at understanding the vertical dispersion of oil in the upper ocean. The experiments were conducted in a wind-wave tank which measured 9.1 m long, 1.2 m wide, and 1.8 m deep. Both wind waves and mechanically-generated waves with wind were considered. No. 2 Diesel oil was fed at a rate of 0.35 liters/sec onto the water surface from the upstream end of the wave tank. To measure the wave profiles, an optical sensor-photodiode wave gauge was developed and is described herein. The effects of an oil slick on wind waves were examined in terms of wave profiles and rms wave amplitudes. For wind waves, the presence of the oil slick damps the waves significantly. The amount of damping increases with the wind speed in the range from U∞ = 4 m/sec to 10 m/sec. At U∞ = 10 m/sec, the oil slick breaks into small lenses. The rms amplitudes of the wind-generated waves increase with the fetch without the oil slick, but they do not change appreciably in the presence of the oil slick. For mechanically-generated waves with wind, wave damping by the oil slick becomes insignificant when the waves are sufficiently steep and wave breaking occurs. Prior to wave breaking, however, steepening of the wave crests due to the presence of the oil slick has been observed occasionally as a result of the reduction in the surface tension by the oil film.

scholarly journals THE CHARACTERISTICS OF WIND-WAVES GENERATED IN THE LABORATORY

1968 ◽  
Vol 1 (11) ◽  
pp. 4
Author(s):  
Theodore E. Lee
Keyword(s):  
Wind Wave ◽  
Wind Waves ◽  
Ocean Waves ◽  
Coastal Engineering ◽  
Wave Period ◽  
Zero Crossing ◽  
Wave Data ◽  
Wave Characteristics ◽  
Significant Correction ◽  
Wave Heights

Wind-wave characteristics were recorded in the laboratory for the primary purposes of (a) analysis of the probability distribution of wave height and wave period with wind speed, water depth, and fetch length as major parameters, and (b) comparison of the test results with existing theory and empirical formulae. An important aspect of this study was to test the validity of the Tucker and Draper method (Draper, 1966) for the presentation of ocean wave data as applicable to wave-data analysis for simulated wind waves. It was interesting to note that some corrections were necessary when the method proposed by Draper at the 10th Coastal Engineering Conference was used for analyzing waves generated in the laboratory. Approximately a positive 20% correction was necessary for this study in which the wave spectra distribution is of very narrow range, the wave width parametere = V1-(T /T ) varles from 0.25 to 0.50, where Tc and T2 represent crest wave period ana zero-crossing wave period, respectively. However, only a negative 5% correction was necessary when the method was used to analyze sea waves (e = 0 73 to 0 76) measured off the shoreline near Look Laboratory Therefore, it was concluded that the Tucker and Draper Method is quite feasible for engineering purposes in analyzing wind-waves having a spectral width parameter of 0.60 to 0.75 The experimental data were compared with those wave heights predicted by the Darbyshire formulas (Francis, 1959) developed for ocean waves. A significant correction factor was necessary for laboratory waves produced by low-speed wi nds. The "fetch graph" was prepared and compared with those developed theoretically by Hino (1966) and empirically by Ijima and Tang (1966) at the 10th Conference on Coastal Engineering, Tokyo, Japan Comparison was also made with the previous empirical formulae by Bretschneider (1951, 1957), Sverdrup and Munk (1947), and Wilson (1961,1962). The experimental results compared well with the Hino theory for both wave heights and wave periods, and fairly well with Bretschneider's fetch graph for wave heights The difference in the comparison of wave data with other investigators is illustrated in this paper. It is recommended that further study be made with emphasis on (a) theoretical and experimental studies of wind-wave characteristics on pre-existing waves, particularly moving storms, (b) wave-energy spectra involving stochastic characteristics and extreme values of wind waves

scholarly journals Influence of Storm Tidal Current Field and Sea Bottom Slope on Coastal Ocean Waves during Typhoon Malakas

2021 ◽  
Vol 13 (22) ◽  
pp. 4722
Author(s):  
Meng Sun ◽  
Yongzeng Yang ◽  
Yutao Chi ◽  
Tianqi Sun ◽  
Yongfang Shi ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Ocean Waves ◽  
Coastal Ocean ◽  
Ocean Current ◽  
Analytic Model ◽  
Bottom Slope ◽  
Sea Bottom ◽  
Current Interaction ◽  
Wave Models ◽  
The Impact

Wave–current interaction in coastal regions is significant and complicated. Most wave models consider the influence of ocean current and water depth on waves, while the influence of the gradient of the sea bottom slope is not taken into account in most research. This study aimed to analyze and quantify the contribution of storm tidal currents to coastal ocean waves in a case where sea bottom slope was not ignored. Fourier analysis was applied to solve the governing equation and boundary conditions, and an analytic model for the calculation of the variation of amplitude of wave orbital motion was proposed. Ocean currents affect ocean waves through resonance. In this paper, an implemented instance of this analytic model was given, using the Shengsi area during Typhoon Malakas as an example. The results suggest that vertical variation in the amplitude of wave orbital motion is remarkable. The impact of wave–current interaction is noticeable where the gradient of the sea bottom slope is relatively large.

The Action of Irregular Waves on Ships Moored on Terminals

1982 ◽  
Vol 104 (4) ◽  
pp. 363-368
Author(s):  
Yu-Cheng Li
Keyword(s):  
Transfer Function ◽  
Impact Energy ◽  
Dynamic Characteristics ◽  
Significant Relationship ◽  
Wind Waves ◽  
Ocean Waves ◽  
Irregular Waves ◽  
Directional Spectrum ◽  
The Impact

For the analysis of the dynamic characteristics of ships moored at the offshore terminals under the action of wind waves, the moored ship system may be simplified to be linear. Introducing the transfer function Ye(ω), the impact energy of a moored ship on the terminal resulting from a random sea may be obtained from the spectrum of the ocean waves. Furthermore, by using the directional function of impact Y2(α), the directional spectrum of the impact by ships can also be estimated. The results show that there is a significant relationship between the spectrum of the ocean waves and the impact energy of the ship.

Modelling the Impact of Squall on Wind Waves with the Generalized Kinetic Equation

2015 ◽  
Vol 45 (3) ◽  
pp. 807-812 ◽  
Author(s):  
Sergei Annenkov ◽  
Victor Shrira
Keyword(s):  
Kinetic Equation ◽  
Wave Field ◽  
Wind Wave ◽  
Wind Waves ◽  
Qualitative Difference ◽  
Time Interval ◽  
Short Time Interval ◽  
Spectral Evolution ◽  
Generalized Kinetic Equation ◽  
The Impact

AbstractThis is a first study of short-lived transient sea states, arising from fast variations of wind fields. This study considers the response of a wind-wave field to a sharp increase of wind over a short time interval (a squall). Conventional wind-wave models based on the Hasselmann equation assume quasi stationarity of a random wave field and are a priori inapplicable for such transient states. To describe fast spectral changes, the authors use the generalized kinetic equation (GKE) derived without the quasi-stationarity assumption. A novel efficient highly parallelized algorithm for the numerical simulation of the GKE is presented. Simulations with the GKE and the Hasselmann equation are examined and compared. While under steady wind, the spectral evolution in both cases is shown to be practically identical, but after the squall the qualitative difference emerges: the GKE predicts formation of a transient sea state with a considerably narrower peak.

scholarly journals HORIZONTAL AND VERTICAL WATER PARTICLE VELOCITIES INDUCED El WAVES

1972 ◽  
Vol 1 (13) ◽  
pp. 27
Author(s):  
Yoshito Tsuchiya ◽  
Masataka Yamaguchi
Keyword(s):  
Particle Velocity ◽  
Wind Wave ◽  
Wind Waves ◽  
Power Spectra ◽  
Surface Displacement ◽  
Ocean Waves ◽  
Regular Waves ◽  
Water Particle ◽  
Cross Correlations ◽  
Particle Velocities

Measurements of horizontal and vertical water particle velocities induced by regular waves, wind waves generated by a wind wave tank and ocean waves in shallow water were made using a Doppler-type sonic current meter. For regular waves, the validity of wave theories such as Stokes and cnoidal waves is investigated by comparison between theoretical curves and the experimental results. For wind waves and ocean waves, power spectra of water particle velocities and cross-correlations between surface displacement and water particle velocity are considered, especially in the latter case, directional spectra calculated from both the records are compared each other.

Impacts of separate rejection water treatment on the overall plant performance

2003 ◽  
Vol 48 (4) ◽  
pp. 139-146 ◽  
Author(s):  
B. Wett ◽  
J. Alex
Keyword(s):  
Water Treatment ◽  
Treatment Plant ◽  
Operating Experience ◽  
Plant Performance ◽  
High Tech ◽  
State Variables ◽  
Total N ◽  
Unit Process ◽  
Innovative Tool ◽  
The Impact

A separate rejection water treatment appears as a high-tech unit process which might be recommendable only for specific cases of an upgrading of an existing wastewater treatment plant. It is not the issue of this paper to consider a specific separate treatment process itself but to investigate the influence of such a process on the overall plant performance. A plant-wide model has been applied as an innovative tool to evaluate effects of the implemented sidestream strategy on the mainstream treatment. The model has been developed in the SIMBA environment and combines acknowledged mathematical descriptions of the activated sludge process (ASM1) and the anaerobic mesophilic digestion (Siegrist model). The model's calibration and validation was based on data from 5 years of operating experience of a full-scale rejection water treatment. The impact on the total N-elimination efficiency is demonstrated by detailed nitrogen mass flow schemes including the interactions between the wastewater and the sludge lane. Additionally limiting conditions due to dynamic N-return loads are displayed by the model's state variables.

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