The Effect of Atmospheric Stability on the Surface-Layer Characteristics in a Low-Wind Area of Tropical West Africa     

O.O. Jegede  T.A. Fasheun  Z.D. Adeyefa  A.A. Balogun 《Boundary-Layer Meteorology》1997,85(2):309-323

This study details the observed effects ofatmospheric stability on characteristics of thesurface layer in a low wind speed (U = 1.5 m s-1)regime of tropical West Africa. Theaerodynamic roughness length, z0, anddisplacement height, d, obtained from profilewind-speed data at our bush land site (height 2 m)have values of 0.24 ± 0.10 m and 1.54 ± 0.04 mrespectively. In the unstable range (-2.5 < Ri < -0.1; Riis gradient Richardson number), thestandard deviation in wind speed fluctuations, u, increased from 0.57 ± 0.19 m s-1 toa maximum of 0.7 ± 0.2 m s-1 in near-neutralconditions, and in the stable range, the parameterdecreased rapidly to 0.41 ± 0.15 m s-1 at Ri 0.2.In the same stability range, the horizontal winddispersion, , decreased withincreasing stability from 19 ± 8 deg. to 13 ± 5 deg.The surface-layer integral quantity, u/u*, when plottedas a function of stability, is in agreement with theempirical results. The ratio ofsensible heat flux (estimated) to the net radiationranged between 0.1 and 0.2 at nighttime,increasing to about 0.5 during the daytime, and showeda strong dependency on season.  相似文献   

箱模式的一种应用     

徐静琦 《中国海洋大学学报(自然科学版)》1996,(1)

用简化的箱模式进行区域环境气体污染物日均浓度的模拟计算。实例计算表明，用区域内占优势烟源的有效高度作为箱体高度是合理的。  相似文献   

Numerical Modeling of Wave-Enhanced Turbulence in the Oceanic Upper Layer     

Le Ngoc Ly  Roland W. Garwood 《Journal of Oceanography》2000,56(4):473-483

A coupled model of air-wave-sea interaction is modified based on a new roughness formulation and the latest data. The model parameters for aerodynamic roughness from below (ARB) and wave-dependent roughness from above (ARA, z _0a ) are assumed equal. The combined roughness is assumed to be a function of friction velocity, gravity, air and seawater densities, and wave age (c _w ). The model is used in a study of wave-enhanced turbulence under breaking waves to predict turbulent dissipation (), ARA, and drag coefficient (C _d ). Both waves and shear production are considered as sources of ocean turbulent energy. The atmospheric part of the model is used only to specify a correct condition at the interface. Numerical experiments are performed to study the -distribution, z _0a and C _d , and to compare with data. The major achievement is model verification using all available data. The first full application of this model is in conjunction with an ocean circulation model in a coupled circulation-wave system. Simulations show that the -distribution is strongly dependent on local wind-forced wave heights. For each wind and wave state there is a particular wave-dependent depth that is verified by data. The comparison shows that the model predicted agrees well with the observed of the z ^–4 law distribution of Gargett (1989). Simulations also show that waves have an important role in causing to differ from the classical wall-layer theory and z _0a , with a value of 0.30 for the empirical constant a _a . The model-predicted , z _0a , C _d and C _gd agree well with data.  相似文献   

Analysis of Wave Height in Front of a Wave Absorbing Structure with Rubble Foundation   总被引：1，自引：0，他引：1  

Li Rongqing Xie Shileng Engineer  The First Design Institute of Navigation Engineering  The Ministry of Communications  Tianjin Professor  Senior Engineer  Deputy Chief Engineer  The First Design Institute of Navigation Engineering  The Ministry of Communications  Tianjin 《中国海洋工程》1992,(3)

Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the structure are analysed using an approximative calculation method, and the dissipating effect of the structure is verified. On the basis of the results of regular waves, the relative wave heights of irregular waves in front of the wave absorbing structure as well as in the chamber have also been analysed.  相似文献   

The effects of sediment characteristics and wave height on shape-parameter for representing equilibrium beach profiles     

U. Türker  M.S. Kabdal&#x; 《Ocean Engineering》2006,33(2):281-291

The shape parameter helps determining the shape of equilibrium beach profile in terms of offshore distance and water depth. The shape parameter therefore, should represent the effect of all the environmental factors involved in beach profile formation, such as wave climate and sediment properties. However, all the previous studies carried out to define shape parameter only consider the effects of sediment characteristics in their definitions. The aim of this study is to add the effect of wave climate also in the definition of shape parameter. This is achieved by integrating wave energy dissipation rate per unit volume at the surf zone. The result yields equilibrium wave energy dissipation rate that leads to theoretical definition of equilibrium beach profiles involving the effects of both the grain size and the wave climate parameters. It is found that the sediment grain size and the incoming wave height affect the value of shape parameter; whereas, the effects of wave period can be neglected. By means of energy equation, it is also possible to observe in macro scale the strength of wave energy on beach profile for different grain sizes. The findings also bring about the possibility of defining shape parameter such that any two arbitrary beach profiles owning the same sediment grain sizes can have the opportunity to have different beach profile formations. Finally, by adding the effect of wave height in the definition of shape parameter the graphical representation of the parameter, previously given by Moore (1982) is improved herein.  相似文献   

Effects of wave breaking on wave statistics for deep-water random wave train     

Nobuhito Mori   《Ocean Engineering》2003,30(2):658-220

The experimental studies of the breaking effects on wave statistics for deep-water random waves are presented. It is especially focused on the behavior of kurtosis of surface elevations due to wave breaking. Wave breaking suppresses the maximum limit of kurtosis of the surface elevation, although skewness depends on characteristic wave steepness. The mean instantaneous wave steepness of breaking waves defined using the zero-down-crossing method was much lower than expected from the Stokes waves.  相似文献   

JASON-1与TOPEX/POSEIDON卫星高度计数据在中国海和西北太平洋的一致性分析及印证   总被引：1，自引：0，他引：1  

于振涛  陈锐 《中国海洋大学学报(自然科学版)》2006,36(Z1):189-196

利用JASON-1和TOPEX/POSEIDON卫星高度计在相互校正阶段的观测资料,对两者在中国海和西北太平洋测得的海面风速、有效波高、后向散射截面、海平面高度等参数进行一致性分析;利用j,v模型及主要分潮的调和常数,对中国陆架浅海的JASON-1海平面高度数据进行浅海潮汐修正,使用验潮站月平均水位资料对修正结果加以印证。结果显示,2颗高度计观测的海洋环境参数具有强相关性,JASON-1具备了完成延续TOPEX/POSEIDON数据集这一使命的条件。但是,2套系统对于同一海洋环境参数的观测还是存在不能忽略的差异,对这种差异进行了分析,并给出了修正模型。所使用的浅海潮汐修正方法有效地抑制了中国陆架浅海潮波对海平面高度反演的影响,所使用浅海水域的5个验潮站月平均水位资料与JASON-1高度计经过浅海潮汐修正后的海平面高度的相关系数为0.738,标准偏差为0.096m。通过进一步融合JASON-1和TOPEX/POSEIDON在并行飞行期间的海平面高度数据并与验潮站资料比较显示,两者的相关系数提高到0.83,标准偏差为0.067m。  相似文献   

微尺度滑动平均方法计算海浪谱奇阶矩的公式   总被引：2，自引：0，他引：2  

郑桂珍  徐德伦 《海洋学报》2001,23(2):18-24

Glazman提出了一种计算海浪谱高阶谱矩的微尺度平均方法,但是,他利用随机过程理论导出的计算偶阶矩的公式和参照偶阶矩结论定义的奇阶矩计算公式之间存在着内在的不一致性.本文在Glazman工作的基础上根据随机过程理论推导了“微尺度平均方法”计算奇阶谱矩的公式,纠正了他的错误.上述结论随即应用于讨论破碎对波面水质点水平速度分布的影响.通过破碎的加速度判据考虑了破碎对速度分布的限制,给出了未破碎波面上水质点水平速度的的统计分布的初步结果.该分布取决于谱宽度参数及白浪覆盖率的大小,当白浪覆盖率较大时明显偏离正态分布.  相似文献   

Vibrating-Rocking Motion of Caisson Breakwater Under Breaking Wave Impact   总被引：2，自引：0，他引：2  

WANG Yuanzhan 《中国海洋工程》2001,(2):205-216

The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding and vibrating-rocking motions. The models of vibrating motion and vibrating-sliding motion have been proposed in an early paper. In this paper, a model of vibrating-rocking motion of caisson breakwaters under breaking wave impact is presented, which can be used to simulate the histories of vibrating-rocking motion of caisson breakwaters. The effect of rocking motion on the displacement, rotation, sliding force and overturning moment of breakwaters is investigated. In case the overturning moment exceeds the stability moment of a caisson, the caisson may only rock. The caisson overturns only in case the rocking angle exceeds the critical angle. It is shown that the sliding force and overturning moment of breakwaters can be reduced effectively due to the rocking motion. It is proposed that some rocking motion should be allowed in breakwater design.  相似文献   

利用波能平衡方程研究波浪折射——绕射的数学模型及数值模拟   总被引：2，自引：1，他引：2  

徐世凯  王红川  洪广文 《海洋工程》1996,(4)

波能平衡方程是研究风浪要素及波能传播问题的很有效的方法，计算较为简单，在海洋学及海岸动力学中得到广泛的应用。本文采用考虑波能侧向传递机制和耗损制约的波能平衡方程组作为研究波浪折射——绕射变形的控制方程。对数学模型用差分法进行了数值模拟，并用两个例题进行了验证  相似文献