波向对变风向的响应

由能量平衡方程导出匀质波场局地风生浪平均波向对变风向的响应。结果表明,响应的时间尺度不但取决于波能的成长速率,还取决于方向分布函数和风向与平均波向之夹角。按文圣常提出的在局地风作用下的标准风浪成长曲线,对其响应时间尺度的定量估计结果表明,本文提出的无因次响应时间尺度与无因次能量和无固次峰频率的关系,与现已提出的模式比较与实测更符合。     

波场非匀质性对波向对变风向响应的影响

本文基于波能平衡方程，通过考虑波的传播项，即，研究波场非匀质性对波向对变风向的响应的影响。导出的结果表明，响应的时间尺度可由３部分表示：１．匀质情形响应的贡献；２．波能分布非匀质性的影响；３．平均波向分布非匀质性的影响。在理论上，它暗示波场的非匀质性在波向响应中起着实质性的作用；在实际情况下，对匀质和平稳风场，波场的非匀质性总是使响应时间尺度减少这一事实进行了讨论。     

基于第三代浅水波浪模型的海区泥沙骤淤数值预报及工程应用

在简要介绍现有近岸波浪数值模型的基础上,对应用了最新波浪研究成果、适用于海岸、湖泊和河口地区的第三代浅水波浪数值预报模型的研究和应用进行了详细论述。通过该模型数值计算得到黄程山局部区域不同风向的有效波高分布,将模型与海区泥沙骤淤机理相结合,进而得到整个区域平均含沙量的分布,并数值预报近岸区域骤淤量随时间的变化,研究成果可为海区大风浪情况下骤淤预报提供理论指导,本文最后讨论了泥沙骤淤计算模型未来发展的趋势。     

Local balance in the air-sea boundary processes

In the course of the new treatment of the growth process of wind waves presented in part I of the present series of the articles, there was a point where the wave energy and wave momentum were not related correctly. This point has been revised with critical argument, and at the same time, the form of the ratior, between the wind stress that directly enter the wind waves and the total wind stress, has been derived analytically. The growth equation, under the condition that the wind stress is constant, is still the same with that derived in part I, with the exception that the ratior is given analytically.A comparison between the ratior obtained analytically and that estimated empirically in part I, raises a problem to be studied about the wave current of the actual wind waves.     

Local balance in the air-sea boundary processes

A new growth equation for wind waves of simple spectrum is presented upon three basic concepts. The period and the wave height of significant waves in dimensionless forms, which are considered to correspond to the peak frequency and the energy level, respectively, are used as representative quantities of wind waves. One of the three basic concepts is the concept of local balance, and the other two concern the acquisition of wave energy and the dissipation of wave energy, respectively. It is shown from some actual data that the equation, together with two universal constants concerning the acquisition and the dissipation of wave energy (B=6.2×10^?2 andK=2.16×10^?5, respectively), is applied universally to wide ranges of wind waves from those in a wind-wave tunnel to fully developed sea in the open ocean. “The three-second power law for wind waves of simple spectrum”, and a few relations as the lemmas, are derived, such that the mean surface transport due to the orbital motion of wind waves is always proportional to the friction velocity in wind, and that the steepness is inversely proportional to the root of the wave age. It is also derived that the portion of wind stress which directly enters the wind waves decreases exponentially with increasing wave age and is 7.5 % of the total wind stress for very young waves. Also, equations are presented as to the increase of momentum of drift current, and as to the supply of turbulent energy by wind waves into the upper ocean.     

Wind- and wave-field measurements using marine X-band radar-image sequences

This paper describes two algorithms for the retrieval of high-resolution wind and wave fields from radar-image sequences acquired by a marine X-band radar. The wind-field retrieval algorithm consists of two parts. In the first part, wind directions are extracted from wind-induced streaks, which are approximately in line with the mean surface wind direction. The methodology is based on the retrieval of local gradients from the mean radar backscatter image and assumes the surface wind direction to be oriented normal to the local gradient. In the second part, wind speeds are derived from the mean radar cross section. Therefore, the dependence of the radar backscatter on the wind vector and imaging geometry has to be determined. Such a relationship is developed by using neural networks (NNs). For the verification of the algorithm, wind directions and speeds from nearly 3300 radar-image sequences are compared to in situ data from a colocated wind sensor. The wave retrieval algorithm is based on a methodology that, for the first time, enables the inversion of marine radar-image sequences to an elevation-map time series of the ocean surface without prior calibration of the acquisition system, and therefore, independent of external sensors. The retrieved ocean-surface elevation maps are validated by comparison of the resulting radar-derived significant wave heights, with the significant wave heights acquired from three colocated in situ sensors. It is shown that the accuracy of the radar-retrieved significant wave height is consistent with the accuracy of the in situ sensors.     

A probabilistic description of the wind over Liverpool Bay with application to oil spill simulations

Surface winds from the UK Meteorological Office mesoscale (12 km grid) atmospheric model have been used to define the wind at a location in Liverpool Bay during 1997–2001. Winds from the SW (centred on 240°) with a speed of about 10 m/s (20 knots) were the most frequent, although weaker winds from the SE were also common. The wind spectra were red in character and showed no evidence for a peak at the synoptic (2–5 day) time scale; however, a zero-up-crossing analysis suggested a dominant periodicity at 3.1 days, and at this time scale the winds were spatially coherent over a distance of 300 km. A wind direction transition matrix was derived to quantify the probability with which the wind changed between two specified directions. This information was then used with an estimate of the mean duration of a wind event to compute a stochastic wind time series that contained a similar energy level, periodicity, and direction variability to the archived wind data. The archived and stochastic winds were then used in 1000 oil spill contingency simulations during which estimates of the mean and minimum times taken for oil to reach the coastline, and the percentage of the oil impacting selected sites were computed. The stochastic winds provided more realistic results, when compared against those derived using the wind archive, than those obtained using a wind rose representation of the winds. The derivation and use of a stochastic wind time series has application to a range of modelling studies.     

关于风浪预报公式和风区宽度的注记

从定常波的风浪波高随风距成长的预报公式出发 ,在一定条件下 ,导出各波向上风浪波高分量与该波向上的风距之间的关系 ,以便在不规则风区上推算风浪波高和平均波向 ;同时 ,对风区宽度作了定量化的分析。     

缓变风场驱动下正压环流中的多涡结构

利用正压涡度方程，研究了缓变风场驱动下水平尺度1000km平底方形海盆中海洋环流的响应。结果表明，缓变风场驱动下海洋环流的响应是多涡型的，线性情形下多涡结构表现为共振受迫Rossby波；非线性情形下受迫Rossby波被扭曲，多涡结构是由受迫Rossby波和次海盆尺度的惯性再循环共同构成。无论是稳定风场还是缓变风场，非线性作用越强，环流越趋于不稳定；非线性作用强且水平耗散作用弱时，非线性不稳定过程可能完全掩盖了变化的风旋度向海盆涡度输人的影响，此时风的变化对环流型式不再重要。     

A model for wave growth in fetch-limited conditions

In this paper, it is held that the universal relationships of wave growth in fetch-limited conditions , i. e.,(f|~) p=A(x|~)-Band (m|~)0= C(x|~) Dshould satisfy the Toba 3/2 power law and the wave energy balance equation. In the ideal generation situation, theoretically it can be derived that the ideal fetch-limited wave growth relationship should have D=3B and D B =1, (i.e., B = 0.25, D = 0.75 ) and A3C=2. 1×l(T4C~(1/2)_d , where Cd is the drag coefficient. The 3/2 power law, the wave energy balance equation and the decrease of wave steepness with increasing fetch have became three requirements which should be satisfied by fetch-limited wave growth algorithms. A semi-empirical and semi-theoretical model for fetch-limited wave growth is presented. In the application to the slanting wind situation an un(?)ersal relationship of dimensionless wave energy vs dimensionless peak frequency is presented and the comparisons show that the model is in good agreement with observations.     

Applications of sediment sudden deposition model based on the third-generation numerical model for shallow water wave

The existing numerical models for nearshore waves are briefly introduced, and the third-generation numerical model for shallow water wave, which makes use of the most advanced productions of wave research and has been adapted well to be used in the environment of seacoast, lake and estuary area, is particularly discussed. The applied model realizes the significant wave height distribution at different wind directions. To integrate the model into the coastal area sediment, sudden deposition mechanism, the distribution of average silt content and the change of sediment sudden deposition thickness over time in the nearshore area are simulated. The academic productions can give some theoretical guidance to the applications of sediment sudden deposition mechanism for stormy waves in the coastal area. And the advancing directions of sediment sudden deposition model are prospected.     

海浪方向谱阵列资料实例分析

根据傅氏级数展开法和贝叶斯方法,对现场获得的阵列资料进行了方向谱实例分析。结果表明,实测风浪方向谱能量的相对分布与相应的波场类型密切相关。涌浪和由稳定风场引起的风浪方向谱各组成波能量相对于方向呈单峰对称分布。大风引起的风浪方向谱能量的相对分布,虽也近似为单峰,但对称性差。不同波场类型的风浪方向谱各组成波的谱密度极值方向不同,表明不同频率的组成波有不同的主方向。     

EFFECTS OF WIND ON THE WAVE ADVANCING TOWARDS SHORE

The effects of wind on wave propagation in shallow water are approached in this paper. The equations for calculating wave elements in shallow water are derived by the law of wave refraction and the equation of wave energy flux. The numerical results calculated by the electronic computer show that under the influence of wind, the wave elements, wave direction angle and the conditions of wave breaker change greatly. Consequently, the effects of wind on the water wave propagating in shallow water need to be considered in practice.     

Nearshore directional wave measurements by surface-following buoy and acoustic Doppler current profiler

Directional energy spectra of nearshore surface waves were measured for a 3-year period (2004–2007) at a site with mean depth 14 m and mean tidal range 2.1 m. Triaxys surface-following wave buoys reported hourly directional wave energy spectra and wave parameters near the offshore end of the Savannah River Entrance Channel, Georgia, USA. An acoustic Doppler current profiler (ADCP) was located beside the wave buoy for 3 months. Directional and non-directional surface wave energy spectra and the corresponding bulk wave parameters (height, period, and direction) are compared for the two systems. Most parameters derived from the spectra agree closely; the most significant differences were found at the upper and lower frequency measurement limits, where signal-to-noise ratios were lower. The wave buoy consistently reports a small amount of energy below 0.05 Hz that does not appear in the ADCP-derived spectra and does not appear to be related to the mooring system. This leads to larger mean and peak periods reported by the buoy. All directional spectra were computed using the Maximum Entropy Method for both instruments, but the buoy, with spectra derived from six independent time series, provides lower directional resolving power than the ADCP, which utilizes twelve time series. Both systems gave similar results defining mean and peak wave directions, with the primary difference being that the ADCP indicates energy to be more tightly concentrated around the peak direction.     

An evaluation of model estimates of ocean wave directions

The potential accuracy of local models is investigated to determine the mean direction of waves from the time history of locally observed significant wave height (or peak frequency) and locally observed wind. This is done by comparing results of such models with observations at a location in the southern North Sea for a period of six weeks. The model results are also compared with results of two synoptic models which require large scale wind information to estimate the local mean wave direction.For significant wave heights larger than 1.5 m the rms-error of the estimated mean wave direction was about 30° for the best performing local model and about 15° for the best performing synoptic model.     

波向对变风向响应理论模式的检验

基于文圣常等提出的风浪成长标准曲线和普遍采用的无因次方法,将理论导出的波向对变风向响应模式表达成在资料处理中常采用的无因次形式,分别用Holthuijsen等的观测结果和Gao等用WAM模式数值计算的结果进行检验和比较.结果表明,所提出的理论结果较其他计算结果更与实测值相吻合.     

上海沿岸海域灾害性大风特征研究与预报检验

选取2011-2017年上海沿岸海域5个浮标站点的风场和海浪数据,分析了大风过程的时间和空间特征;对海浪成长过程进行风向分类,运用滑动相关分析统计了8个风向的海浪滞后时间;计算了大风起风时间的预报提前和滞后量,进行了风速风向的误差和准确率检验。结果表明:越往东部海域,大风时数越多,长江口区东部风速较大;大风极值主要出现在8月份台风过程,出现时段都为傍晚到半夜,大浪极值浪向以东北到东南向为主;秋冬季大风时数多,5-6月大风时数最少;大风风向以西北到东北风为主;海浪成长过程风向分布是东南-西北走向,海浪对风的响应滞后时间平均为3~4 h;大风起风时间预报较实况略有滞后,风速预报的准确率总体在70%以上,预报值较实况值偏小,口外浮标偏小最为明显,偏强率都为0;风向预报准确率低,误差大。     

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 global climate)风场研究了两类不同移动路径下的台风(1909号台风“利奇马”和1109号台风“梅花”)在黄、渤海区域的海浪场的时空分布特征及风-浪成长关系。结果表明:两个台风引起的海浪的有效波高空间分布明显不同,波高的分布和风速对应,而海浪周期与风速、波高的分布无明显相关性,波向较风向偏于台风移动方向且两者偏差较大;两个台风进入黄海之前就形成一个从黄海向渤海的“涌浪舌”。海浪成分方面,台风“利奇马”引起的沿海区大浪主要是风浪,而台风“梅花”移动路径的右侧以风浪为主,左侧则主要是涌浪;通过建立无因次波高与无因次周期的幂律关系、以及有效波高关于风速的二次多项式变化关系,研究了风-浪成长特性,结果发现,台风浪的成长特性与台风过程关系不明显,但与所处水域的水深和海底地形地貌有关,表现为两个台风在黄海区域的台风浪成长较渤海区域更为充分。     

Wave Energy Estimation by Using A Statistical Analysis and Wave Buoy Data near the Southern Caspian Sea

Statistical analysis was done on simultaneous wave and wind using data recorded by discus-shape wave buoy. The area is located in the southern Caspian Sea near the Anzali Port. Recorded wave data were obtained through directional spectrum wave analysis. Recorded wind direction and wind speed were obtained through the related time series as well. For 12-month measurements(May 25 2007-2008), statistical calculations were done to specify the value of nonlinear auto-correlation of wave and wind using the probability distribution function of wave characteristics and statistical analysis in various time periods. The paper also presents and analyzes the amount of wave energy for the area mentioned on the basis of available database. Analyses showed a suitable comparison between the amounts of wave energy in different seasons. As a result, the best period for the largest amount of wave energy was known. Results showed that in the research period, the mean wave and wind auto correlation were about three hours. Among the probability distribution functions, i.e Weibull, Normal, Lognormal and Rayleigh, "Weibull" had the best consistency with experimental distribution function shown in different diagrams for each season. Results also showed that the mean wave energy in the research period was about 49.88 k W/m and the maximum density of wave energy was found in February and March, 2010.     

Examination of wind-wave interaction source term in WAVEWATCH III with tropical cyclone wind forcing

Results of drag coefficient(CD) from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave interaction source term in WAVEWATCH Ⅲ has been modified to examine its behavior with tropical cyclone wind forcing. Using high resolution wind input,numerical experiments under idealized wind field and tropical cyclone Bonnie(1998) were designed to evaluate performance of the modified models. Both experiments indicate that the modified models with reduced CD significantly decrease wind energy input into the wave model and then simulate lower significant wave height(SWH) than the original model. However,the effects on spatial distribution of SWH,mean wavelength,mean wave direction,and directional wave spectra are insignificant. Due to the reduced wind energy input,the idealized experiment shows that the modified models simulate lower SWH than the original model in all four quadrants. The decrease in the front quadrants is significantly larger than that in the rear quadrants;it is larger under higher winds than lower winds. The realistic experiment on tropical cyclone Bonnie shows that the modified model with the various downward trends of CD in high winds creates a simulation that agrees best with scanning radar altimeter observations.