共查询到20条相似文献，搜索用时 580 毫秒
1.
为了解各向异性随机粗糙海面的微波双站散射机制及其特性，本文利用解析近似的积分方程模型以及一种改进的半经验海浪谱模型实现了对各向异性随机粗糙海面的全极化微波散射仿真模拟，并与卫星观测数据、经验的地球物理模式函数及已有的解析近似散射模型仿真结果进行了对比，验证了仿真结果的可行性和准确性。利用该模型分析了入射波频率、入射角、极化方式、海面风速及风向等参数对各向异性海面双站散射的影响。模拟结果表明，在不同的入射角、散射角及方位角等观测几何条件下，海面不同波段的双站散射表现出不同的空间散射特性，且对风速、风向等海面动力学参数表现出不同的敏感性，以L波段为例，海面向后半球双站散射在各个极化方式下都对风速较为敏感，而在同极化方式下，其对风向的响应在中低风速和高风速条件下相反，整体而言，低风速下海面双站散射对风向更为敏感。这表明对于海面动力参数的反演，双站散射可以提供比传统单站雷达后向散射更丰富的物理信息。本文探讨了各向异性海面微波双站散射特性，为基于主动式及分布式微波传感器的海洋动力参数遥感反演提供了理论分析基础。 相似文献
2.
3.
4.
以墨西哥湾同步高度计、浮标资料为例,研究了海浪成长状态对高度计风速反演的影响。同步的高度计风速和浮标风速比较显示,在墨西哥湾地区,海浪成长状态对高度计风速反演有较大影响。在考虑海浪成长状态影响的条件下,利用谱模型反演高度计风速,取得了较好的效果。与目前TOPEX/Poseidon高度计风速反演业务化算法相比,在海浪未充分成长条件下,考虑海浪成长状态影响后,根据谱模型反演获得的风速与浮标风速之间的均方根误差减小了30%,平均误差减小了83%。在利用谱模型算法反演高度计风速时,谱模型中的波龄因子(表示海浪成长状态)可以根据高度计测得的有效波高和风速获得,因此该方法具有广泛的适用性。 相似文献
5.
6.
GPS浮标数据反演海浪谱的理论仿真与试验验证 总被引：1，自引：1，他引：0
GPS浮标作为一种新型的海洋测量设备,近年来在海面高度现场测量和星载高度计定标方面取得了重要应用。通过仿真试验对反演海浪谱的方法和流程进行研究,旨在探索从GPS浮标测量的海面高度序列中提取海浪谱的方法。首先,使用Longuest模型生成了海浪波面位移时间序列,并通过Pierson-Moscowitz风浪谱对波面位移的统计特性进行约束,其随机性由相位引入。结合典型潮汐和GPS浮标仪器噪声的仿真时间序列,合成了仿真时间长度1h的1Hz(每秒1次)随机海面高度序列。然后,利用自相关函数法,进行高通滤波和数据压缩,得到了仿真的海浪谱。该仿真结果和理论海浪谱非常接近,可满足海浪谱反演的需求。最后,通过山东石岛外海的GPS浮标现场试验,验证了本文提出的反演方法的适用性。本文的研究解决了GPS浮标反演海浪谱的关键问题,丰富了海浪谱反演的手段,拓展了GPS浮标的应用领域,有望为未来我国的星载波谱仪定标服务。 相似文献
7.
8.
9.
10.
表面更新理论给出气体交换速率k与海面附近的海水湍动能耗散率呈1/4次方关系,而波浪能量耗散率Dt与湍动能耗散率密切相关。本文利用两种海浪谱耗散模型——Hasselmann模型和Phillips模型,结合深水浮标海浪频谱的观测数据计算了波浪能量耗散率。以前人给出的k与海面上10m高度处的风速U10关系式的平均值为标准,采用最小二乘的方法得到了k与Dt的经验关系。在此基础上,进一步利用SWAN和WAVEWATCHIII海浪数值模式计算了理想深水情况下的波浪能量耗散率,探讨了由海浪模式计算的波浪能量耗散率与气体交换速率之间的关系。结果表明,与SWAN模式相比,WAVEWATCHIII海浪数值模式结果与实际观测更为接近。 相似文献
11.
基于数值模拟的三维随机海面,从时间域和空间域两个角度对海浪的外观特征和内部结构间的关系进行了研究,得出了一些在工程应用上有参考价值的结果.文章认为,将波面看作是若干随机正弦波叠加的海浪结构模型,用于描述平稳、均匀和窄谱的海况时,其频谱分析结果与外观统计结果基本上是一致的;但是,当海面处于谱宽度较大的风浪或混合浪状态时,一些频谱分析结果必须经过修正才能应用.同一海况下,海面波动的时间过程和沿主波向的空间分布是明显不同的.当海面有突发性大浪时,外频谱能够很好地反映不平稳海况,而频谱则把这种不平稳性平滑了.文章着重讨论了波长和波陡的计算、频谱和外频谱的差异. 相似文献
12.
An approach to the retrieval of sea wave spatial spectra based on satellite optical imagery in linear and nonlinear approximations is described. Physical mechanisms of the formation of disturbed sea surface brightness fields recorded by remote sensing equipment are analyzed. Wave spectra retrieval methods using brightness field formation models that consider linear and nonlinear dependencies on sea surface slopes are suggested. A method for the construction of operators that retrieve the spatial spectra of surface wave slopes and elevations from aerospace imagery and take into account nonlinear modulations of disturbed sea surface brightness fields is developed. This method is based on the numerical simulation of sea surface images and the construction of a retrieving operator with respect to a set of parameters determined by aerospace imaging conditions. Examples of the use of the developed methods are given. 相似文献
13.
波浪在斜坡地形上破碎,破波后稳定波高多采用物理模型试验方法进行研究,利用近岸波浪传播变形的抛物型缓坡方程和波能流平衡方程,导出了适用于斜坡上波浪破碎的数值模拟方法。首先根据波能流平衡方程和缓坡方程基本型式分析波浪在破波带内的波能变化和衰减率,推导了波浪传播模型中波能衰减因子和破波能量流衰减因子之间的关系;其次,利用陡坡地形上的高阶抛物型缓坡方程建立了波浪传播和波浪破碎数学模型;最后,根据物理模型试验实测数据对数值模拟的效果进行验证。数值计算与试验资料比较表明,该模型可以较好地模拟斜坡地形的波浪传播波高变化。 相似文献
14.
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. 相似文献
15.
Andrs E. Tejada-Mart&#x; nez Chester E. Grosch Ann E. Gargett Jeff A. Polton Jerome A. Smith J.A. MacKinnon 《Ocean Modelling》2009,30(2-3):115-142
A three-dimensional numerical model for large-eddy simulation (LES) of oceanic turbulent processes is described. The numerical formulation comprises a spectral discretization in the horizontal directions and a high-order compact finite-difference discretization in the vertical direction. Time-stepping is accomplished via a second-order accurate fractional-step scheme. LES subgrid-scale (SGS) closure is given by a traditional Smagorinsky eddy-viscosity parametrization for which the model coefficient is derived following similarity theory in the near-surface region. Alternatively, LES closure is given by the dynamic Smagorinsky parametrization for which the model coefficient is computed dynamically as a function of the flow. Validation studies are presented demonstrating the temporal and spatial accuracy of the formulation for laminar flows with analytical solutions. Further validation studies are described involving direct numerical simulation (DNS) and LES of turbulent channel flow and LES of decaying isotropic turbulence. Sample flow problems include surface Ekman layers and wind-driven shallow water flows both with and without Langmuir circulation (LC), generated by wave effects parameterized via the well-known Craik–Leibovich (C–L) vortex force. In the case of the surface Ekman layers, the inner layer (where viscous effects are important) is not resolved and instead is parameterized with the Smagorinsky models previously described. The validity of the dynamic Smagorinsky model (DSM) for parameterizing the surface inner layer is assessed and a modification to the surface stress boundary condition based on log-layer behavior is introduced improving the performance of the DSM. Furthermore, in Ekman layers with wave effects, the implicit LES grid filter leads to LC subgrid-scales requiring ad hoc modeling via an explicit spatial filtering of the C–L force in place of a suitable SGS parameterization. 相似文献
16.
The theoretical foundation of a wave–ice interaction model is reported in Part 1 of this study. The model incorporates attenuation of ocean surface waves by sea ice floes and the concomitant breaking of the floes by waves that determines the structure of the marginal ice zone (MIZ). A numerical implementation of the method is presented here. Convergence of the numerical method is demonstrated, as temporal and spatial grids are refined. A semi-analytical method, which does not require time-stepping, is also developed to validate the numerical results, when dispersion is neglected. The wave energy lost during ice breakage is parameterized, as part of the numerical method. Sensitivity studies are conducted in relation to the energy loss and also dispersive effects, the choice of the attenuation model, the properties of the wave field, and sea ice properties such as concentration, thickness and breaking strain. Example simulations intended to represent conditions in the Fram Strait in 2007, which exploit reanalyzed wave and ice model data, are shown to conclude the results section. These are compared to estimates of MIZ widths based on a concentration criteria, and obtained from remotely-sensed passive microwave images. 相似文献
17.
In this paper further mathematical analysis on "correlation transfer technique" by Polge el al. is carried out, the tenable conditions and the extent of suitability for the said method are proved as well. In consideration of the influence of skewness of the sea surface elevation on spectral shape, a "quasi-correlation transfer techique" is developed by the modification of the simulated target spectrum. Meanwhile, the numerical simulation of the non-Gaussian process of wind waves is carried out in view of the two conditions of the surface elevation probability distribution and the spectrum. By using its simulated results, the influence of skewness of the sea surface elevation on two parameters in the distribution of wave heights (which had been fitted by using the Weibull distribution) is analysed. The "quasi- correlation tranfer technique" is verified and compared with the selection wave data observed in the Jiaozhou Bay in the period of 1980 to 1981. Results make clear (hat, as far as the statistical d 相似文献
18.
The paper studies the parametric stochastic roll motion in the random waves. The differential equation of the ship parametric roll under random wave is established with considering the nonlinear damping and ship speed. Random sea surface is treated as a narrow-band stochastic process, and the stochastic parametric excitation is studied based on the effective wave theory. The nonlinear restored arm function obtained from the numerical simulation is expressed as the approximate analytic function. By using the stochastic averaging method, the differential equation of motion is transformed into Ito's stochastic differential equation. The steady-state probability density function of roll motion is obtained, and the results are validated with the numerical simulation and model test. 相似文献
19.
In conventional marine seismic exploration data processing, the sea surface is usually treated as a horizontal free boundary. However, the sea surface is affected by wind and waves and there often exists dynamic small-range fluctuations. These dynamic fluctuations will change the energy propagation path and affect the final imaging results. In theoretical research, different sea surface conditions need to be described, so it is necessary to study the modeling method of dynamic undulating sea surface. Starting from the commonly used sea surface mathematical simulation methods, this paper mainly studies the realization process of simple harmonic wave and Gerstner wave sea surface simulation methods based on ocean wave spectrum, and compares their advantages and disadvantages. Aiming at the shortcomings of the simple harmonic method and Gerstner method in calculational speed and sea surface simulation effect, a method based on wave equation and using dynamic boundary conditions for sea surface simulation is proposed. The calculational speed of this method is much faster than the commonly used simple harmonic method and Gerstner wave method. In addition, this paper also compares the new method with the more commonly used higher-order spectral methods to show the characteristics of the improved wave equation method. 相似文献
20.
An efficient focusing model for generation of freak waves 总被引：1，自引：1，他引：0
Based on the Longuet-Higgins wave model theory, the previews studies have shown that freak waves can be generated in finite space and time successfully. However, as to generating high nonlinear freak waves, the simulation results will be unrealistic. Therefore, a modified phase modulation method for simulating high nonlinear freak waves was developed. The surface elevations of some wave components at certain time and place are positive by modulating the corresponding random initial phases, then the total surface elevation at the focused point is enhanced and furthermore a freak wave event is generated. The new method can not only make the freak wave occur at certain time and place, but also make the simulated wave surface time series satisfy statistical properties of the realistic sea state and keep identical with the target wave spectrum. This numerical approach is of good precision and high efficiency by the comparisons of the simulated freak waves and the recorded freak waves. 相似文献