Proceedings of the International medcoast Conference on Wind and Wave Climate of  the Mediterranean and the Black Sea, MEDCOAST 99, March 30-April 2, 1999; Antalya, Turkey, S. Abdalla-E.Özhan (Editors)

WIND & WAVE CLIMATE 99

TABLE OF CONTENTS

1. Wind and Wave Climatology of the Turkish Coast and the Black Sea: An Overview of the NATO TU-WAVES Project.

Erdal Özhan and Saleh Abdalla 1

2. Wind-Wave Studies in the North-Western Part of the Black Sea.

V. V. Efimov 21

3. An Introduction to the Operational Data Buoy System in Taiwan.

Chia Chuen Kao, Laurence Z. Chuang, Yen-pin Lin and Beng-chun Lee 33

4. Altimeter Wind and Wave Measurements in Fetch- Limited Conditions.

Pierre Queffeulou 41

5. Integral Wind Wave Parameters for Fetch Limited Conditions in The Black Sea

M.V. Shokurov and V.V. Efimov 49

6. Short-term wave statistics by the measurements of the buoy near the Russian coast of the Black Sea.

A. Boukhanovsky, B. Divinsky, R. Kos'yan, L. Lopatoukhin, Saleh Abdalla and Erdal Özhan 59

7. Wind Wave in the Coastal Zone as a Nonlinear Probability Process.

Zhivelina Cherneva 71

8. Some New Result of Non-Linear Energy Transfer in the Wind Wave Spectrum.

I.V. Lavrenov 81

9. Climatic Wave Spectra of the Black Sea.

L.J. Lopatoukhin, A.V. Boukhanovsky, V.A. Rozhkov and B.V. Divinsky 97

10. Sensitivity of a Wave Model to the Wind Input in the Catalan Coast.

Sonia Ponce de León A. and Agustín Sánchez-Arcilla 112

11. A Comparative Study of the WAM and a Second Generation Wave Model in the Mediterranean Sea.

Valdir Innocentini, Ernesto S. Caetano Neto and Luigi Cavaleri 123

12. Hindcast and Calibration of the Wave Conditions in the Black Sea.

Luigi Cavaleri, Luciana Bertotti, Jean Bidlot, Mauro Sclavo, Gunnar Mørk, Steve Barstow, Gerassimos Athanassoulis, and Christos Stefanakos 139

13. Hindcast Data Role on Offshore Development West Black Sea.

Emilio N. Corona, Vincent J. Cardone, Ronald C. Stamey, and Tulga Ulaş 153

14. Sea Surface Wind and Wave Forecasting System for the Eastern Mediterranean.

I. Gertman, S. Kariel, L. Raskin and D.S. Rosen 171

15. Sea-21 Forecasting Operability of Marine Installations.

Michael Stiassnie and Michael Glozman 181

16. Method for Calculation of Extreme Metocean Events.

V.A. Rozhkov, A.V. Boukhanovsky and L.J. Lopatoukhin 189

17. Persistence Wave Statistics For Black And Baltic Seas.

A.V. Boukhanovsky, I.V. Lavrenov, L.J. Lopatoukhin, V.A. Rozhkov, B.V. Divinsky, R.D. Kos'yan, Erdal Özhan and Saleh Abdalla 199

18. Assessment of Long-Term Directional Wave Conditions Based on Nearshore Wind – Wave Correlations.

Jan-Ole Witte, Peter Fröhle, Thomas Fittschen and Sören Kohlhase 211

19. Statistical Assessment of Sea State within Extreme Events.

Peter Fröhle and Sören Kohlhase 221

20. Wave Climate Evaluation for Sedimentological Studies.

Alexander Perlin and Eliezer Kit 237

21. Eurowaves: The Easy Approach to the Evaluation of the Local Wave Climatology.

Luigi Cavaleri, Gerassimos A. Athanassoulis and Steve Barstow 251

22. A Wave Climate Data Base for the Black Sea and the Turkish Coast.

David Hurdle, Saleh Abdalla and Erdal Özhan 263

23. .Adriatic High Sea State Characteristics

Marko Prsic, Ante Smircic and Nenad Leder 277

24. On Wave Nonlinearity Parameters.

Samir Abohadima and Masahiko Isobe 295

25. An Accurate Numerical Method for Water Wave Propagation.

P. Avilez-Valente and F.J. Seabra-Santos 311

26. Numerical Simulation Of Long Waves Propagation.

Abdelaziz A. Rabie 327

27. Sensitivity Analysis on the Transfer of Wave Conditions to a Coastal Location.

Mauro Sclavo and Luigi Cavaleri 341

28. Sea Breeze Generated Waves and Coastal Morphology.

Henk Jan Verhagen and Boyan Savov 349

29. Wave-Current Interaction.Fundamental Problems and Applications in Coastal Engineering.

Izmail Kantardgi 361

30. One-Dimensional Model for Wave Dynamics and Long-Shore Sediment Transport across the Surf Zone over Real Bathymetric Profiles.

Marco Venturi and Floriano Gianfelici 377

31. Statistical Approach to Wind Data and Its Effects on the Currents of Yzmir Bay.

Erdem Sayyn and Esin Üçüncüo?lu

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Erdal Özhan and Saleh Abdalla

Middle East Technical University, 06531, Turkey. Tel. +90-312-210 5437 Fax. +90-312-210 1412 E-mail: erdal-ozhan@metu.edu.tr, abdalla@metu.edu.tr

NATO TU-WAVES Project is a major that aims to find out the wave climate affecting the whole Black Sea as well as the Turkish coasts on other seas. The project started at the beginning of 1994 within the framework of the NATO SfS programme-Phase III. The main objectives of this project are to obtain detailed knowledge on and to establish a reliable data bank of wind waves affecting the whole Black Sea and the other Turkish coasts, to implement a third generation wave model for the seas surrounding Turkey, and to construct a wind and wave atlas for the Black Sea and the other Turkish coasts. This atlas, which is expected to be ready soon, will provide accurate and reliable information on wind and sea state parameters needed for most coastal and marine activities. In addition to METU-KLARE, the lead organization, three Turkish organizations and eight other institutes from four Black Sea riparian countries (Bulgaria, Romania, Russia, and Ukraine) are collaborating within the framework of the NATO TU-WAVES Project.

Marine Hydrophysical Institute, National Academy of Sciences of the Ukraine, Sevastopol, 335000, Kapitanskaya St., 2, Crimea, Ukraine.

E-mail: efimov@alpha.mhi.iuf.net

During last decades the north-western part of the Black Sea was a place of many wind-wave studies carried out, in particular, by Marine Hydrophysical Institute. A research platform in Katzively in the Crimean coastal region and a gas-oil platform placed in the north-western part of the Black Sea in Karkinitskaya bay on distance 40-60 km offshore were used for these studies. Experiments conducted on the two platforms during past decade had main purpose to study the dependence of integral wave parameters from fetch and age of waves in the condition of well controlled weather situation as well as to study of features of frequency-wave number spectra. On Katziveli platform the experiments were directed also on studying physics of wave disturbances in the boundary layers of the atmosphere and ocean.

In framework of NATO TU-WAVES Project the continuous measurements of wind-wave parameters on the Katzively and Karkinitskaya platforms were carried out using specially manufactured instruments. They included the measurements of velocity and direction of wind, variance and peak frequency of wave spectra averaged over 10 min, as well as a continuous record of surface wave elevation. Also other meteorological parameters were measured. The data of last years wind-wave measurements were transmitted to METU and were also used for study of wave characteristics, wave physics, and numerical wind-wave modeling etc.

Now, the transmission of measured hydrometeorological and wave parameters via satellite ARGOS system is in an operation. It gives a possibility to obtain wind-wave and other meteorological parameters such as atmosphere pressure, humidity, air and sea temperatures for operational purposes, and to repair any damages of instruments in short time.

Chia Chuen Kao ^(1), Laurence Z. Chuang⁽²⁾, Yen-pin Lin⁽²⁾ and Beng-chun Lee ⁽³⁾

An operational data buoy system including: buoy hull, mooring, measurement instruments, data acquisition and control, data processing and analysis, communication, power, and auxiliary sub-systems has been successfully designed, integrated and deployed for marine meteorology observations in Taiwan since 1992. A series of test were executed to check the stability and to calibrate the accuracy. Data collected from and processed at the offshore buoy are transmitted to the shoreside operation system in nearly real time via radio telemetry. The data quality control procedure will then be triggered in the Coastal Ocean Monitoring Center after receiving data from local stations. Following final data processes and data checks, information are loaded into database system and automatically distributed to the Marine Meteorology Center, Central Weather Bureau (CWB) for operational forecast.

Pierre Queffeulou

 Abstract

Measurements of sea surface wind speed and significant wave height are performed from satellite borne altimeters. These two parameters are estimated from the analysis of the waveform of the altimeter backscattered power, using methods that were established and validated for open ocean sea state and wind conditions. It has been shown that in fetch limited conditions, the altimeter wind speed was not correctly estimated. In such conditions the altimeter backscatter coefficient depends not only on wind speed but also on a parameter linked to the wave age or to the fetch. Preliminary results are presented, using TOPEX and ERS-2 altimeter measurements in conjunction with meteorological model data and sea surface measurements acquired during the FETCH campaign. The FETCH experiment was conducted in the western Mediterranean Sea (Gulf of Lion) in March-April 1998, and was devoted to surface flux measurements and remote sensing of wind and waves in high wind and short fetch conditions.

M.V. Shokurov and V.V. Efimov

Abstract

Because of absence of the complete theory for the dependence of integral wind wave parameters on fetch for fetch-limited conditions, experimental measurements are still important to test wind wave models. The north-western region of the Black Sea is fairly proper place to fulfill such measurements. Wind wave measurements were conducted on a gas-oil platform on water depth 30m more than 50km from the shore in 1995-1998. To study the fetch dependencies, the records during stable off-shore wind conditions were selected. Special selection of records was conducted to isolate influence of swell on results. Two main integral wave parameters, dimensionless variance and spectrum peak frequency, were studied in dependence on dimensionless fetch. Conditional power dependencies take place. The results were compared with the known results of previous experiments. Scattering of points on the plots is explained mainly by uncontrollable stratification of atmospheric boundary layer and by possible nonhomogeneity of wind along fetch from the shore to the measurement point. In general, 3-year duration of field measurements gave high statistical significance of dependencies under study.

Short-term wave statistics by the measurements of the buoy near the Russian coast of the Black Sea

A. Boukhanovsky⁽¹⁾, B. Divinsky⁽²⁾, R. Kos'yan⁽²⁾, L. Lopatoukhin⁽¹⁾, S. Abdalla ⁽³⁾ E. Özhan ⁽³⁾

Abstract

Within the framework of the NATO TU-WAVES Project a wave buoy was operating in the Black Sea near the coast of Russia (offshore Gelendzhik), and Turkey (offshore Synop and Hopa). Measured wave heights and periods allowed to make comprehensive investigation of short-term statistics. Namely:

• one-dimensional (marginal) wave height and period distributions;
• one-dimensional (conditional) distributions of wave heights with the prescribed periods and wave periods with the prescribed wave heights;
• two-dimensional wave heights and periods distributions;
• extreme wave heights distributions;
• moments and quantiles of the distributions.

The comparision of probability distributions for Black Sea with the results, known from publications is made. Rayleigh distribution for the wave heights is confirmed. The Weibull distribution with the shape parameter of periods in mean is equal to 3.0 (In contrast with the value 4.0 still used by some scientists). The conditional distributions are the Weibull one with the shape parameters, depending on condition and varying from 2.0 till 7.0. The regressions and skedastic ratios of two-dimensional distributions are nonlinear and in a good agreement with the relations, obtained previously by Russian investigators and published in the Handbook of Russian Register of Shipping. During almost 5 years of buoys operating a set of storm situations were measured. The distribution of extreme wave heights is investigated and some results will be presented in the paper.

Wind Wave in the Coastal Zone as a Nonlinear Probability Process

Zhivelina Cherneva

A nonlinear second order interactions and their influence on the statistical properties of wind wave in the coastal zone are investigated. Cumulantum and momentum descriptions of the process of surface displacement are made too. A frequency-directional bispectrum of wind wave for a basin with constant depth is obtained. Theoretical results are compared with experimental data. The conclusion made is that two kinds of interactions of second order are important: a) interactions of two waves with frequencies equal to the peak frequency of the first order spectra and b) interactions in which one wave has peak frequency and other has frequency greater than the peak one.

Some New Result of Non-Linear Energy Transfer in the Wind Wave Spectrum

In the article non-linear interaction in wind waves spectrum is studied by methods of numerical integration of the highest accuracy. The value of non-linear energy transfer is non zero in wide frequency - angular range. The influence of the frequency - angular spectrum distribution on non-linear energy transfer is investigated in this work. The calculation results show the presence of non-linear energy transfer to spectral components, which propagation is opposite to wind direction. The theoretical study explains the experimental measurement data of frequency-angular spectrum of wind waves, in which there are spectral components directed against a wind.

The definition of sustainable climatic wave states (natural clusters) is introduced and justified. Within the ranges of a state the functionally similar spectral densities are hold. The sustainable climatic wave states in the Black sea are identified by mean of the regular buoy wave measurements near Gelendzhik. These measurements were a part of the NATO TU-WAVE project. More than 6000 frequency spectra are calculated, this enables to estimate climatic wave spectra for every sustainable state.

To assess the sensitivity of the WAM model cycle 4.0, to different wind inputs data, the model was applied to Western Mediterranean Sea area (-6° W, 20° E, 34° N, 45° N). The emphasis was on the Catalan coastal region, where significant wave height and peak period maps are analysed for a selected meteorological situation. The simulation period is 15 days from 20.10.97 to 4.11.97, corresponding with one typical Llevant event (winds blowing from NE). The hindcasted wave parameters are verified against wave buoy data (placed at 50 m of depth) near Delta del Ebro. The wave buoy reported a maximum of 4.7 m significant wave height, while the simulated value is around 2.8 m. The mean error over all the simulated interval is 40 cm, whereas the RMS of Hs (time series) differences is 60cm.

The WAM and a second generation (SG) wave models are used to hindcast the surface state of Mediterranean Sea with the wind fields provided by the ECMWF initialised analysis during December 1992. The wave hindcasts were evaluated against time series of measured significant wave height, period, and direction obtained at eight buoys moored near shorelines of Mediterranean Sea. The wave height time series for a deep ocean point are quite similar in both models simulations during the wave growth stage. The SG model tends to delay the beginning of the decay stage and simulates wave peaks slightly greater. Conclusions regarding the performance of both models in shallow water and coastal zones cannot be simply stated. Appropriate spatial and temporal resolutions, and a wind analysis approach, incorporating non-conventional wind data with the global centres gridded analysis, have to be considered.

A seven year hindcast of wave conditions in the Black Sea has been performed using ECMWF surface wind fields and the WAM wave model. The results have been validated and calibrated using Topex satellite altimeter data. General statistics have been evaluated for the whole basin. The results provide a perfect input to evaluate the wave conditions at any nearshore location, using the Eurowaves methodology, which is described in a parallel paper at this conference.

A hindcast study is carried out to support Türkiye Petrolleri A.O's (TPAO) and ARCO Turkey Inc. (ARCO)'s joint exploration effort in the western region of the Black Sea. This area of more than 30,000 sq. km, is unexplored with few wells drilled in shallow waters. This study presents new descriptions of the normal and extreme wind and wave climate of the Turkish sector of the Black Sea. These descriptions are developed to provide more accurate data than provided by analysis of observations from operational weather stations situated on land, and/or summarization of the small available historical data base of ships weather observations. Our approach is to adapt well proven hindcast models at high resolution to the Black Sea, and to make a continuous wind and wave hindcast covering a 10-year period. The required statistical descriptions of the environment in the study area are derived directly from the hindcast time histories. The design data generated in this study are being used for such activities as: (1) drilling rig selection for exploratory activities; (2) technical analysis of the selected drilling unit including motion and downtime analysis; (3) feasibility studies and preliminary design associated with possible future production developments.

A 48-hours wind and wave forecasting system for the Eastern Mediterranean has been working in operational mode since fall 1997. The core of the system is the WAM numerical wave model Cycle 4 with a coarse space grid resolution of 1/2 degree and fine space grid resolution of 1/6 degree. For input wind field estimation, sea-surface atmospheric pressure fields (SSP) are used. These are calculated using a regional atmospheric model MM4, run by the Israel Military Meteorological Center (IMMC) every 12 hours providing 48 hours forecast. The SSP forecast has a time step of 1 hour and covers the Mediterranean region with a spatial resolution of 80 km. A sea surface wind (SSW 10 m) computation is performed according to equations of geostrophic wind and empirical relationships between SSW 10 m and the geostrophic wind. Results of the wind and wave hindcast provided by the above mentioned system for March 1998 are contrasted against ground true data gathered at the Hadera GLOSS station number 80, 2 km off the coast of Israel .

Forecasting operability conditions of marine installations requires sophisticated software packages, based on up-to-date knowledge of nonlinear water-wave theories. Sea-21 is CAMERI's most recent answer to this engineering challenge. The present note contains simplified explanations of the most relevant physical processes that affect the quality of loading/unloading conditions of ships in harbors. Simple calculations provide approximate results, which indicate the importance of appropriate handling of near-resonant conditions.

The statistical approaches to calculate T years metocean events is presented. The advantages and shortcomings of other methods of extreme wave height calculations are briefly described. A method, based on the joint probabilities of wave heights in number of storms in a year during several years is elaborated. Multivariable long-term quantile function of wave heights is proposed and estimated. Extreme wave heights in Black, Baltic and Barents Seas are calculated.

Synoptic variability of sea waves on the long-term time series of wave height in Black and Baltic seas is investigated. The probability characteristics of general variability parameters, e.g. wave height in a storms and calms, storm and calm duration, are obtained. The approximation of joint distributions of storm and calm duration and wave heights both in storms and calm are proposed. The probabilistic impulse modulated model is developed for simulation of synoptic and annual variability of wave height in Black and Barents seas.

For engineering purposes wave information are needed over long periods to assess the wave climate in the respective research area. According to restricted time for planning processes measured data are usually available for comparatively short periods only. These durations are often too short for the design and construction of coastal structures.

Since the measurement of wave data is expensive and time-consuming, it is necessary to develop approaches to extend time series of wave parameters from measured wave data. This can be done on the basis of wind data, which are usually available for comparatively long periods.

The wind – wave correlation for time series provides the opportunity to calculate time series of wave parameters based on the time series of wind data. The wind – wave correlation for frequency distributions is used to estimate the influences of the influencing parameters on the long-term mean wave conditions e.g. water level and wind conditions (speed and direction).

The two approaches for wind – wave correlations are developed within two research projects at the Institute of Hydraulic and Coastal Engineering of the University of Rostock. The paper presents the methods and some results from the project areas

Statistical Assessment of Sea State within Extreme Events

For the design of coastal structures and the assessment of the interactions of coastal structures with adjacent coastal areas, it is necessary to know the wave climate, i.e. the temporal and local variability of wave conditions. Besides other influences the influence of changing water levels must be included in the analysis of the wave data. Some aspects of the statistical evaluation of wave data are outlined by the example of wave data measured off the Island of Sylt. Since extreme wave conditions - especially during storm surge conditions - are of particular interest for structural design, special attention is paid on the assessment of long-term wave data with respect to probabilities of extreme wave heights and the duration of extreme wave conditions.

A Wave Climate Data Base for the Black Sea and the Turkish Coast