共查询到20条相似文献，搜索用时 31 毫秒
1.
On the parameterization of drag coefficient over sea surface 总被引：1，自引：0，他引：1
Six parameterization schemes of roughness or drag coefficient are evaluated on the basis of the data from six experiments. They present great consistency with measurement when friction velocity u*<0.5 m/s (approximately corresponding to 10 m wind speed U10 <12 m/s) and large deviation from measurement when u*≥0.5 m/s (approximately U10≥12 m/s). In order to improve the deviation, a new parameterization of drag coefficient is derived on the basis of the similarity theory, Charnock relationship and Toba 3/2 power law. Wave steepness and wind-sea Reynolds number are considered in the new parameterization. Then it is tested on the basis of the measurements and shows significant improvement when u*≥0.5 m/s. Its standard errors are much smaller than the ones of the other six parameterizations. However, the new parameterization still needs more tests especially for high winds. 相似文献
2.
Surface waves are the roughness element of the ocean surface. The parameterization of the drag coefficient of the ocean surface is simplified by referencing to wind speed at an elevation proportional to the characteristic wavelength. The dynamic roughness is analytically related to the drag coefficient. Under the assumption of fetch limited wave growth condition, various empirical functions of the dynamic roughness can be converted to equivalent expressions for comparison. For datasets covering a wide range of the dimensionless frequency (inverse wave age), it is important to account for the variable rate of wave development at different wave ages. As a result, the dependence of the Charnock parameter on wave age is nonmonotonic. Finally, the analysis presented here suggests that the significant wave steepness is a sensitive property of the ocean surface and a single variable normalization of the dynamic roughness using a wavelength or wave height parameter actually produces more robust functions than bi-variable normalizations using wave height and wave slope. 相似文献
3.
On the basis of data on the statistical characteristics of individual waves in laboratory wind waves reported in part I of this series, a self-consistent similarity regime is found to exist among properties of the individual waves, such as the nondimensional frequency, the wave number, the phase speed, and the steepness. Also, it is shown that forms of past empirical formulas for the development of the peak wave can be derived starting from the 3/2-power law, as an extension of the persent laboratory experimental data. In the derivation, only values of the coefficient of the 3/2-power law, and the fraction of momentum transferred from the wind retained by the wind waves, remain on an empirical basis. 相似文献
4.
利用新近提出的海面风应力系数线性参数化理论,定性地分析了已有风应力和风浪的观测数据。分析发现这些观测数据表明在小波陡的情形下海面风应力系数随风速的变化较大波陡的情形更加迅速。结果定性地倾向于支持Toba等的结果,即成熟的风浪较年轻的风浪更加粗糙。 相似文献
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6.
两参量的海面阻力系数模式的探讨 总被引：4，自引：0，他引：4
从风浪的能量平衡方程出发，引进若干风要素与波要素以及波要素之间的定性关系，经演算可导出海面阻力系数（Ｃｐ）或是风速（Ｕ）和波龄（β）或是Ｕ和波高（Ｈ）的函数，然后沿用最小二乘法，终将得出４组１２个回归方程。当β（或β）或Ｈ为某一给定值，惟有Ｕ为唯一参量时，所提各式均可简化为非线性方程：ＣＤ＝ａ＋ｂ，Ｕ＋ｃ．Ｕ＾２；式中ａ，ｂ和ｃ为三个经验系数，就所检验的例子而言，本文的结果与实际的符合前人的为好。 相似文献
7.
由量纲分析导出海面粗糙度与波龄及海面涌浪的状况有关,并对与波龄和波陡有关的两种海面粗糙度模型方案进行了敏感性测试,得出利用波龄模型方案计算粗糙度的误差比利用波陡模型方案小。基于国际上6个不同水深、风区和海况条件的海气交换试验资料,将其分为两组,一组是纯风海或以风海为主海况条件,另一组是以涌浪为主海况条件,测试波龄、波陡模型海面粗糙度方案在不同试验条件下的适用性。结果得出:在各种海况条件下,波龄模型粗糙度方案比波陡模型具有更好的普适性。在纯风海或以风海为主海况条件下,PS07,DGHQ03方案计算的粗糙度长度与实测资料计算结果最接近,GW06方案次之,O02方案计算结果明显偏高;涌浪为主海况条件下两种模型方案计算的粗糙度长度均偏低,O02方案计算的粗糙度长度误差相对较小,TY01方案误差最大。 相似文献
8.
Analytically Derived Wind Wave Growth Relations 总被引：3，自引：1，他引：3
By the use of the 3/2 power law presented by Toba combined with the significant wave energy balance equation for wind wave, wind wave growth at a limited fetch is analytically investigated. The new wind wave growth relations (WWGRs) are analytically derived with shehering coefficient and wind drag coefficient as parameters. The geometrical average of observational values of shehering coefficient and the arithmetic average of observational values of wind drag coefficient are applied to detennine the new WWGRs. Comparisons with existing empirical WWGRs are made. 相似文献
9.
SWAN模型中不同风拖曳力系数对风浪模拟的影响 总被引：1，自引：1，他引：0
本文以荷兰哈灵水道海域为实验区域,通过敏感性实验,研究了在14 m/s、31.5 m/s和50 m/s（分别代表一般大风、强热带风暴和强台风的极端条件）定常风速下SWAN模型中不同风拖曳力系数对风浪模拟的影响程度。结果表明,对于近岸浅水区域（水深小于20 m）,风拖曳力系数计算方案的选择对有效波高影响较小,而且当风速增加到一定程度后,波浪破碎成为影响波高值的主要因素;对于深水区域（水深大于30 m）,一般大风条件下风拖曳力系数计算方案的选择对有效波高影响仍然较小,随着风速的继续增大,风拖曳力系数计算方案的选择对有效波高的影响逐渐显著。对于平均周期,风拖曳力系数计算方案的选择和风速的改变对其影响均较小,而由水深变浅导致的波浪破碎对其影响较为显著。根据敏感性实验结果,本文对SWAN模型中风拖曳力系数计算方案的选择做出如下建议:计算近岸浅水区域风浪场或深水区域一般大风条件风浪场时,其风拖曳力系数可以直接采用模型默认选项;而对于深水区域更大风速条件,可首先采用模型默认选项试算,然后结合当地海域实测波浪资料进行修正。 相似文献
10.
Modeling of the eddy viscosity by breaking waves 总被引：1，自引：1，他引：0
Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing,heat and gases exchange across air-sea interface.The energy loss from wave breaking and the bubble plume penetration depth are estimated.As a consequence,the vertical distribution of the turbulent kinetic energy(TKE),the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided.It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface.High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than υwl(=κuwz),the value predicted for the wall layer scaling close to the surface,where uw is the friction velocity in water,κ with 0.4 is the von Kármán constant,and z is the water depth,and the strength of the eddy viscosity depends both on wind speed and sea state,and decays rapidly through the depth.This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer,well above the classical values expected from the similarity theory.Deeper down,however,the effects of wave breaking on the vertical mixing become less important. 相似文献
11.
Variations are found in the shape and the steepness of wind-generated surface gravity waves between very young waves, such
as seen in a laboratory tank, and larger waves of various wave ages encountered at sea as the result of wind stress over larger
fetches. These differences in the characteristic shape of wind waves are presented as a function of the wave age. The wave
steepness is also expressed as a function of wave age, the measurement of which is consistent with the 3/2-power law connecting
wave height and characteristic period, normalized by the air friction velocity. 相似文献
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海草所形成的植物消波体系能有效防止岸线的侵蚀。利用Sánchez-González等的实验数据分析了波浪非线性对海草消波特性的影响。研究结果表明,相对水深和波陡对海草床的波能衰减系数影响依赖于海草淹没度。相对波高一定时,拖曳力系数随相对水深的增大而增大。对给定的相对水深,拖曳力系数随波陡的增大而减小。波浪非线性对于规则波和非规则波海草消波特性的影响并不一致。用无量纲参数（邱卡数、雷诺数、厄塞尔数）表达拖曳力系数的效果取决于拖曳力系数与无量纲参数的关系中是否充分考虑波浪非线性对拖曳力系数的影响。 相似文献
14.
Paul A. Hwang 《Journal of Oceanography》2004,60(5):835-841
Surface waves are the roughness element of the ocean surface, the air-sea interaction processes are influenced by the wave
conditions. The dynamic influence of surface waves decays exponentially with distance from the air-water interface. The relevant
length scale characterizing the decay rate is the wavelength. The parameterization of drag coefficient and surface roughness
can be significantly improved by using wavelength as the reference length scale of atmospheric measurements. The wavelength
scaling of drag coefficient and dynamic roughness also receives support from theoretical studies of wind and wave coupling. 相似文献
15.
The ocean drift current consists of a (local) pure drift current generated by the interaction of wind and waves at the sea surface, to which the surface geostrophic current is added vectorially. We present (a) a similarity solution for the wave boundary layer (which has been validated through the prediction of the 10-m drag law), from which the component of pure drift current along the direction of the wind (and hence the speed factor) can be evaluated from the 10-m wind speed and the peak wave period, and (b) a similarity solution for the Ekman layers of the two fluids, which shows that under steady-state neutral conditions the pure drift current lies along the direction of the geostrophic wind, and has a magnitude 0.034 that of the geostrophic wind speed. The co-existence of these two similarity solutions indicates that the frictional properties of the coupled air-sea system are easily evaluated functions of the 10-m wind speed and the peak wave period, and also leads to a simple expression for the angle of deflection of the pure drift current to the 10 m wind. The analysis provides a dynamical model for global ocean drift on monthly and annual time scales for which the steady-state neutral model is a good approximation. In particular, the theoretical results appear to be able to successfully predict the mean surface drift measured by HF Radar, which at present is the best technique for studying the near surface velocity profile. 相似文献
16.
In this paper experimental wind wave data are analyzed. It is found that differences in spectral width will give rise to differences in wave height distribution. The effect of spectral width on the distribution is mainly in the high wave range. The effect of wave steepness is in low, medium and high wave ranges. In the high wave range the effect of spectral width is comparable to that of wave steepness. Differences in spectral width in the observations may give rise to discrepancies in the result when wave steepness is the only parameter in the distribution. 相似文献
17.
Li Luping 《海洋学报(英文版)》1997,16(1):45-56
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. 相似文献
18.
海气动量通量研究综述 总被引：1，自引：0，他引：1
海气界面动量通量也称为风应力,是海流和表面海浪的主要驱动力,是海洋从大气获得动量的重要途径。因此,合理可靠的海洋表面风应力的参数化对于海洋、大气和波浪以及气候模式的准确预报都具有非常重要的科学意义和实用价值。对风应力拖曳系数的参数化是风应力参数化的主要内容。近来的观测发现,风应力拖曳系数随着风速的增加出现了先增后减的趋势,同时还与海面的波浪状态以及海流有关。基于观测或理论分析,目前已经得到了一系列的风应力拖曳系数计算方法或公式,有的考虑了海浪的作用,有的没有,但这些方案大都是适合中低风速,在高风速下的适用性还有待检验。本文回顾了目前在海气动量通量观测和参数化方面的研究进展,并建议应增加高风速下风速、海流以及海浪等的同步观测,以进一步完善风应力参数化方案。 相似文献
19.
基于多致灾因子相似的热带气旋检索方法研究:以风暴潮-海浪灾害预评估为例 总被引：2，自引：1，他引：1
热带气旋引起的风暴潮-海浪灾害成灾频率高、致灾强度大,对我国沿海地区造成的人员和经济损失惨重。预评估阶段需要在灾前对研究区可能造成的损失等进行快速的综合判定。从历史热带气旋中检索出与目标热带气旋位置及各种致灾因子强度相似的热带气旋是快速、准确地预评估风暴潮-海浪灾害的重要方法。面向风暴潮-海浪灾害预评估,提出了一种基于多致灾因子的相似热带气旋检索方法。用于相似检索的致灾因子数据包括:从中国气象局西北太平洋热带气旋最佳路径数据集中提取并经处理得到的1949~2013年影响湛江市的112场热带气旋的路径中心点位置、中心气压、最大风速、最大风速半径及移动速度数据,112场热带气旋的模拟风场、风暴潮及海浪数据。首先,利用相似离度方法对热带气旋进行路径相似性检索;其次,利用最优相似系数方法计算中心气压、最大风速半径、最大风速、移动速度、风场、风暴潮及海浪强度指标的相似系数进行一次检索;然后,根据风场、风暴潮及海浪模拟数据的获取情况,分别基于路径-强度及风场-风暴潮-海浪综合相似性指标进行二次检索;最终给出历史热带气旋的综合相似排序。以2013年尤特热带气旋为例,利用上述方法检索了与其最为相似的5场历史热带气旋。该方法综合考虑了热带气旋路径及多种致灾因子的相似,兼顾了检索的速度及质量,是进行快速、准确的风暴潮-海浪灾害预评估的重要基础。 相似文献
20.
A new empirical formula for the aerodynamic roughness of water surface waves has been derived from laboratory experimental results using dimensional analysis. The formula has different forms according to wind speed: at moderate wind speeds the formula is a function of the friction velocity of wind, the surface tension, the water density, the kinematic viscosity of water and the acceleration of gravity; at strong winds the formula is expressed by the Charnock relation. The aerodynamic roughness does not depend on such wave state parameters as the spectral peak frequency or the steepness of waves, unlike almost all parameterizations that have been proposed to date. The drag coefficient at moderate winds depends on the surface tension of water and the water temperature through the temperature dependence of the kinematic viscosity of water. 相似文献