Simulation of the extreme waves generated by typhoon Bolaven (1215) in the East China Sea and Yellow Sea

Record-breaking high waves occurred during the passage of the typhoon Bolaven (1215) (TYB) in the East China Sea (ECS) and Yellow Sea (YS) although its intensity did not reach the level of a super typhoon. Winds and directional wave measurements were made using a range of in-situ instruments mounted on an ocean tower and buoys. In order to understand how such high waves with long duration occurred, analyses have been made through measurement and numerical simulations. TYB winds were generated using the TC96 typhoon wind model with the best track data calibrated with the measurements. And then the wind fields were blended with the reanalyzed synoptic-scale wind fields for a wave model. Wave fields were simulated using WAM4.5 with adjustment of C_d for gust of winds and bottom friction for the study area. Thus the accuracy of simulations is considerably enhanced, and the computed results are also in better agreement with measured data than before. It is found that the extremely high waves evolved as a result of the superposition of distant large swells and high wind seas generated by strong winds from the front/right quadrant of the typhoon track. As the typhoon moved at a speed a little slower than the dominant wave group velocity in a consistent direction for two days, the wave growth was significantly enhanced by strong wind input in an extended fetch and non-linear interaction.     

台风“灿鸿”影响下海浪的数值模拟研究

台风是影响中国黄东海的强天气现象,其引起的强风、巨浪和台风增水严重威胁着沿海地区人民的生命与财产安全。本文以海浪模式SWAN(Simulating Waves Nearshore)与区域海洋模式ROMS(Regional Ocean Modeling System)为基础,构建了中国黄东海海域在201509号台风"灿鸿"影响下的海浪-海洋耦合模式。通过浮标与Jason-2高度计有效波高数据验证了模式结果的准确性。进行了敏感性实验分析,对比耦合(ROMS+SWAN)与非耦合(SWAN)下以及使用不同地形数据(ETOPO1、ETOPO2、GEBCO)、不同物理参数化方案(风能输入、白冠耗散、底摩擦耗散)下的模拟结果差异。结果发现在射阳与前三岛浮标处,使用GEBCO地形数据(15弧秒间隔)下的模拟效果更好且稳定。在空间分布上,台风中心附近的浪流相互作用显著,在其前进方向右侧表现为耦合的有效波高值低于非耦合有效波高值,差值最高可达1米。选择不同风输入与耗散项方案时的模拟差异主要发生在最大波高处,选择不同的风能输入与白冠耗散项方案带来的差异接近0.4米,而底摩擦项方案选择不同带来的差异接近1米。...     

黄海海浪季节变化的数值模拟研究

利用第三代海浪数值模式SWAN,研究了黄海海浪有效波高的季节变化特征及相关的物理过程。结果表明,在黄海的大部分区域,混合浪有效波高的最大值出现在冬季,而最小值则基本出现在夏季。北黄海北部和山东半岛南岸的近海海域呈现稍微不同的季节变化,有效波高的最大值出现在春季。全年4个季节中混合浪有效波高的空间分布基本一致:均在济州岛西南最大,沿黄海中部区域向北和由中部区域向近岸区域逐渐减小。黄海海浪为风浪占主,涌浪有效波高远小于风浪有效波高。在黄海的大部分区域,白冠耗散和四波非线性相互作用对黄海海浪的季节变化均至关重要;对于外海区域,四波非线性相互作用更为重要,而对于近海区域,白冠耗散则影响更大。本研究旨在研究黄海海浪的季节变化特征及其物理过程,为进一步探讨该海域海浪在其他时间尺度上的变异特征和动力学过程提供研究基础。     

两类典型台风路径影响下的黄、渤海海浪场特征研究

台风引起的海浪灾害对我国黄、渤海沿岸影响巨大,严重威胁相关区域人民群众生命财产安全.本文主要利用ERA5(the fifth generation European Center for Medium-Range Weather forecasts atmospheric reanalysis of the globa...     

Nonlinear saturation-based whitecapping dissipation in SWAN for deep and shallow water

This study investigates the effectiveness of a revised whitecapping source term in the spectral wind wave model SWAN (Simulating WAves Nearshore) that is local in frequency space, nonlinear with respect to the variance density and weakly dependent on the wave age. It is investigated whether this alternative whitecapping expression is able to correct the tendency towards underprediction of period measures that has been identified in the default SWAN model. This whitecapping expression is combined with an alternative wind input source term that is more accurate for young waves than the default expression. The shallow water source terms of bottom friction, depth-induced breaking and triad interaction are left unaltered. It is demonstrated that this alternative source term combination yields improved agreement with fetch- and depth-limited growth curves. Moreover, it is shown, by means of a field case over a shelf sea, that the investigated model corrects the erroneous overprediction of wind-sea energy displayed by the default model under combined swell-sea conditions. For a selection of field cases recorded at two shallow lakes, the investigated model generally improves the agreement with observed spectra and integral parameters. The improvement is most notable in the prediction of period measures.     

Calibration and verification of a spectral wind–wave model for Lake Okeechobee

A spectral wind wave model SWAN (Simulation WAves Nearshore) that represents the generation, propagation and dissipation of waves was applied to Lake Okeechobee. This model includes the effects of refraction, shoaling, and blocking in wave propagation. It accounts for wave dissipation by whitecapping, bottom friction, and depth-induced wave breaking. The wave–wave interaction effect also is included in this model. Measurements of wind and wave heights were made at different stations and different time periods in Lake Okeechobee. Significant wave height values were computed from the recorded data. The correlation between wind stress and significant wave height also was analyzed. A 6-day simulation using 1989 data was conducted for model calibration. Another 6-day simulation using 1996 data was conducted for model verification. The simulated significant wave heights were found to agree reasonably well with measured significant wave heights for calibration and verification periods. Agreement between observed and simulated values was based on graphical comparisons, mean, absolute and root mean square errors, and correlation coefficient. Comparisons showed that the model reproduced both general observed trends and short term fluctuations.     

A Model for Nonlinear Irregular Waves in Coastal Area

Based on the refraction-diffraction theory of irregular waves in the waters of slowly-varying cur-rents and depths,and the generation dissipation theory of wind wave,a model for nonlinear irregular wavesin coastal area is developed.In light of the specific conditions of coastal wave character and engineering ap-plication,a practical mathematical model for the nonlinear irregular waves is presented.with directional spec-trum in coastal area.Coast effect,refraction,whitecapping.bottom friction.current,wind and nonlinearaction are considered in this model.The numerical methods and schemes for wave refraction ray,energy con-servation of propagation,energy balance of the generation and dissipation of wind waves have been studied.Finally,the model is used for the directional wave spectrum computation in the Daya Bay.Compared withthe measured data with 956 wave bouys in the Daya Bay,the model results are in good agreement with themeasured results.     

Simulation of Typhoon-Driven Waves in the Yangtze Estuary with Multiple-Nested Wave Models

Typhoon-generated waves are simulated with two numerical wave models, the SWAN model for the coastal and Yangtze Estuary domain, nested within the WAVEWATCHIII （WW3） for the basin-scale East China Sea domain. Typhoon No. 8114 is chosen because it was very strong, and generated high waves in the Estuary. WW3 was implemented for the East China Sea coarse-resolution computational domain, to simulate the waves over a large spatial scale and provide boundary conditions for SWAN model simulations, implemented on a fine-resolution nested domain for the Yangtze Estuary area. The Takahashi wind model is applied to the simulation of the East China Sea scale （3-hourly） and Yangtze Estuary scale （1-hourly） winds. Simulations of significant wave heights in the East China Sea show that the highest waves are on the right side of the storm track, and maxima tend to occur at the eastern deep-water open boundary of the Yangtze Estuary. In the Yangtze Estuary, incoming swell is dominant over locally generated waves before the typhoon approaches the Estuary. As the typhoon approaches the Estuary, wind waves and swell coexist, and the wave direction is mainly influenced by the swell direction and the complex topography.     

Comparison Study on Wind Input and Whitecapping Dissipation Expressions in Numerical Simulation of Typhoon Generated Waves

In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN （Simulating WAves Nearshore） model. The three experiments adopt the Komen, Janssens, and Westhuysen expressions for wind input and whitecapping dissipation, respectively. Besides the above-mentioned source tems, other parameterization schemes in these experiments are the same. It shows that the experiment with the Westhuysen expression result in the least simulation errors while that with the Janssens expression has the most. The results from the experiments with Komen and Westhuysen expressions show that the differenees in significant wave height （SWH） have a good correlation with the differences in dissipation energy caused by whiteeapping. This indicates that the whitecapping dissipation source term plays an important role in the resultant differences of the simulated SWH between the two experiments.     

Comparison Study on Wind Input and Whitecapping Dissipation Expressions in Numerical Simulation of Typhoon-Generated Waves

In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN (Simulating WAves Nearshore) model.The three experiments adopt the Komen, Janssens, and Westhuysen expressions for wind input and whitecappingdissipation, respectively. Besides the above-mentioned source terms, other parameterization schemes in these experiments are the same. It shows that the experiment with the Westhuysen expression result in the least simulationerrors while that with the Janssens expression has the most. The results from the experiments with Komen and Westhuysen expressions show that the differences in significant wave height (SWH) have good correlation with thedifferences in dissipation energy caused by whitecapping. This indicates that the whitecapping dissipation sourceterm plays an important role in the resultant differences of the simulated SWH between the two experiments.     

Numerical investigation of ocean waves generated by three typhoons in offshore China

The influences of the three types of reanalysis wind fields on the simulation of three typhoon waves occurred in2015 in offshore China were numerically investigated. The typhoon wave model was based on the simulating waves nearshore model(SWAN), in which the wind fields for driving waves were derived from the European Centre for Medium-Range Weather Forecasts(ECMWF) Re-Analysis-Interim(ERA-interim), the National Centers for Environmental Prediction climate forecast system version 2(CFSv2) and cr...     

Improvement and application of a saturation based wave dissipation function in SWAN model

Wave dissipation characteristics in SWAN (Simulating Waves Nearshore) model are investigated through numerical experiments. It is found that neither the fully developed integral parameters of wind waves (significant wave height and peak frequency) nor the high frequency spectral tail can be well reproduced by the default wave dissipation source terms. A new spectral dissipation source term is proposed, which comprises saturation based dissipation above two times of peak frequency and improved whitecapping dissipation at lower frequency spectrum. The reciprocal wave age (u /c p ) is involved into the whitecapping model to adjust dissipation rate at different wind speed. The Phillips higher frequency saturation parameter in the saturation-based dissipation is no longer taken as a constant, but varies with wave age. Numerical validations demonstrate that both the wind wave generation process and higher frequency spectrum of wind waves can be well simulated by the new wave dissipation term.     

近岸区不规则波成长模型的研究 Ⅰ.模型的建立

以不规则波在缓变地形和缓变流场水域的折射-绕射理论以及风浪的成长、衰减理论为基础,得到近岸区不规则波成长模型。结合近岸波浪特性和海洋工程应用的实际情况,建立综合考虑海岸、折射、白浪、底摩擦、流、风和非线性作用诸因素的近岸不规则波数值计算模型。该模型具有二维波谱特性及实用性。文章力图使模式更合理地反映近岸波浪的传播、成长和衰减规律,而整个计算工作量则较小,可在微型电子计算机上得以实现。     

非结构网格模型在闽东沿海台风浪模拟中的应用

基于加密的非结构三角网格,以Holland模型风场叠加美国国家环境预报中心（NCEP）海面风场构造的合成风场驱动第三代浅水波浪数值模型（SWAN）对2017年影响闽东海域的“纳沙”和“泰利”台风过程进行数值模拟,并运用浮标站的实测数据对模拟结果进行验证.结果表明,模型计算的风速、有效波高与实测值符合较好,合成风场能较好地模拟台风期间的风速变化过程,SWAN模式能够合理地再现闽东沿海台风浪的时空分布特征.由模拟结果可见：台风“纳沙”中心越过台湾岛进入台湾海峡北部海面,受海峡地形的约束,其波浪场呈NE—SW向椭圆状分布,北部海域的浪高大于南部,闽东沿海遍布大范围的巨浪到狂浪;超强台风“泰利”未登陆闽东,当其台风中心与大陆的距离最近时,海面波浪场分布与台风风场结构一致,台风中心附近海域为14 m以上的怒涛区,巨浪遍布于闽东沿海.研究结果可为闽东沿海台风浪灾害预警和应急管理提供技术支撑和参考依据.     

非对称风场对台风浪模拟效果的比较研究

分析四象限非对称风场模型与叠加风场模型的优缺点,将模型结果与实测风速进行对比验证;利用上述两种风场模型分别驱动第三代海浪模式SWAN,对发生在南海海域的三场台风浪进行了数值模拟计算。结果显示:四象限非对称模型关于风速的计算值与实测值吻合度更高,尤其是当台风中心距离测站较近时;四象限非对称模型驱动SWAN模拟的台风浪精度优于叠加风场模型,适用于南海台风浪的数值模拟。     

强台风“珍珠”引起的近岸波浪场数值分析

台风浪的研究对于船舶航行、避风以及港口、海洋和近岸建筑物的安全有着重要的现实意义.本文基于考虑波浪折射、底部损耗及波浪破碎等的波谱模型,在充分考虑风能量输入、白帽耗散、水深诱导以及波-波间的非线性相互作用等物理过程,对袭击广东省和福建省沿海的0601号强台风“珍珠”引起的台风浪过程进行了数值模拟计算,计算结果与云澳海洋...     

基于SWAN模型的南中国海“莫拉菲”台风浪研究

我国的水运工程建设频繁受到台风浪的侵袭。为了对台风浪的防灾减灾提供有益帮助,本文基于第三代海浪模式SWAN建立了南中国海台风浪数值模型,并以“0906”号台风“莫拉菲”为例对模拟结果进行了分析。结果表明,台风风场与波浪场相似,即大小均由中心向外围递减,方向均为逆时针旋转;台风风场呈圆对称分布,而波浪场由于受到海底地形与岸线影响,呈现椭圆对称分布。有效波高等值线亦从中心向外围递减,且形状受地形与岸线影响较大。对台风浪组成机制的探讨结果显示风浪和涌浪均可组成台风浪,且海底地形与岸线(例如岛屿效应)亦对台风浪特性有所影响。     

南海北部海底沙波迁移规律及其在台风作用下的响应研究

本文在南海北部海底沙波已有研究的基础上,总结分析了研究区表层沉积物以及沙波的形态、分布、迁移特征;使用区域海洋模式（ROMS）模型模拟了研究区2010-2011年的底部流场数据;利用Rubin公式模拟计算了海底沙波的迁移规律,并与搜集所得资料进行对比分析;结合台风资料及底流数据,分析了台风对海底沙波运移的影响。研究结果显示:海底沙波运移方向的计算结果与搜集所得资料比较吻合,均为向东向南方向;不同站点的迁移距离在0~21.8 m之间,且为往复累积的结果。这表明:Rubin公式在ROMS模型模拟所得底流资料的支撑下,可以再现海底沙波的迁移过程。模拟计算的研究区内两个站位在"凡亚比"台风影响期间的迁移距离分别为2.0 m、2.9 m,分别占其年运移量的9.17%和26.36%,说明台风过境能对海底沙波的迁移产生重大的影响。     

复杂地形下海浪数值模式的特征线计算格式

LAGFD-WAM海浪数值模式是一种第三代海浪数值模式，通过求解波数谱平衡方程，并考虑风输入、波浪破碎耗散、底摩擦耗散、波波非线性相互作用和波流相互作用等源函数，模拟波数空间下的海浪方向谱，并依此获得海浪的波高、周期和平均波向。该模式的一个显著特点是采用特征线嵌入格式求解海浪的传播。在进行浅水区域的海浪模拟时，特征线嵌入格式的数值计算方案是否合理对海浪数值模拟结果产生直接的影响。为此LAGFD-WAM海浪数值模式提出了一种新的特征线混合数值计算格式，并应用于浅水海浪数值模拟。结果表明，采用该计算方法，能够使数值模拟结果与实测结果很好符合。     

Wave model predictions in the Black Sea: Sensitivity to wind fields

This paper evaluates the impact of using different wind field products on the performance of the third generation wave model SWAN in the Black Sea and its capability for predicting both normal and extreme wave conditions during 1996. Wind data were obtained from NCEP CFSR, NASA MERRA, JRA-25, ECMWF Operational, ECMWF ERA40, and ECMWF ERA-Interim. Wave data were obtained in 1996 at three locations in the Black Sea within the NATO TU-WAVES project. The quality of wind fields was assessed by comparing them with satellite data. These wind data were used as forcing fields for the generation of wind waves. Time series of predicted significant wave height (H_mo), mean wave period (T_m02), and mean wave direction (DIR) were compared with observations at three offshore buoys in the Black Sea and its performance was quantified in terms of statistical parameters. In addition, wave model performance in terms of significant wave height was also assessed by comparing them against satellite data.The main scope of this work is the impact of the different available wind field products on the wave hindcast performance. In addition, the sensitivity of wave model forecasts due to variations in spatial and temporal resolutions of the wind field products was investigated. Finally, the impact of using various wind field products on predicting extreme wave events was analyzed by focussing on storm peaks and on an individual storm event in October 1996. The numerical results revealed that the CFSR winds are more suitable in comparison with the others for modelling both normal and extreme events in the Black Sea. The results also show that wave model output is critically sensitive to the choice of the wind field product, such that the quality of the wind fields is reflected in the quality of the wave predictions. A finer wind spatial resolution leads to an improvement of the wave model predictions, while a finer temporal resolution in the wind fields generally does not significantly improve agreement between observed and simulated wave data.