基于 T/P 资料分析南海海面风、浪场特征及其关系

本文以T/P卫星高度计提供的海面风、浪资料为基础,利用自然正交函数对南海海面风、浪场进行展开,然后找出统计上显著的几个典型场,探讨南海海风、浪场的时空分布特征及其关系。分析结果显示,南海海面风、浪场的第一、第二模态具有很好的相似性,第三模态却表现出明显不同的特征,这一结果可以很好地反映南海海面风、浪场间的关系,从而为海浪场的经验预报和分析提供参考。     

南海海啸反问题预报模式

通过COMCOT海啸模型计算南海马尼拉海沟潜在震源区单元板块单位滑动产生的海啸波在区域内传播过程,将计算结果组成相应南海海啸波数据库.采用浮标监测数据与数据库结合通过最小二乘法构建南海海啸预报模式.以假想马尼拉海沟发生8.3级地震海啸为案例,应用预报模式对华南地区进行海啸预测,采用30 min和60 min监测数据分别反演计算,在三个近岸验证点的波高和正问题结果比较误差分别在25％和17％之内,到达时间及相位基本一致,预报的计算时间在2 min以内.     

Effects of high-order nonlinearity and rotation on the fission of internal solitary waves in the South China Sea

A variable coefficient, rotation-modified extended Kortweg-deVries (vReKdV) model is applied to the study of the South China Sea (SCS), with focus on the effects of the high-order (cubic) nonlinearity and the rotation on the disintegration process of large-amplitude (170 m) Internal Solitary Waves (ISWs) and the semi-diurnal internal tide propagating from the deep basin station to the slope and shelf regions in a continuously stratified system. The numerical solutions show that the high-order nonlinearity significantly affects the wave profile by increasing the wave amplitude and the phase speed in the simulated area. It is shown that the initial KdV-type ISW will decay faster when the rotation dispersion is considered, however the wave profile does not change significantly and the rotation effect is not important. The simulations of the semi-diurnal internal tide indicate that the phase of the wave profile is shifted earlier when the rotation effect is included. A solitary wave packet emerges on the shelf, and the wave speed is also greater when considering the rotation dispersion. In addition, the effects of the background currents are discussed further in this paper. It is found that the background currents generally change the magnitude and occasionally change the sign of the nonlinear coefficients in the northern SCS.     

Numerical simulation of sea surface directional wave spectra under typhoon wind forcing

Numercial simulation of sea surface directional wave spectra under typhoon wind forcing in the South China Sea （SCS） was carreid out using the WAVEWATCH-Ⅲ wave model. The simulation was run for 210 h until the Typhoon Damrey （2005） approached Vietnam. The simulated data were compared with buoy observations, which were obtained in the northwest sea area of Hainan Island. The results show that the significant wave height, wave direction, wave length and frequency spetra agree well with buoy observations. The spatial characteristics of the signifciant wave height, mean wave period, mean wave length, wave age and directional spectra depend on the relative position from the typhoon center. Also, the misalignment between local wind and wave directions were investigated.     

南海潮波三维同化数值模拟

采用POM模式,考虑引潮力的作用,优化开边界并把TOPEX/POSEIDON高度计资料同化到模式中去,数值模拟了南海的M2、S2、K1、O1主要分潮的潮汐和潮流,结果较好地体现了南海的潮波特征。通过比较63个验潮站的计算值和模拟值,所得结果的振幅平均误差分别为5.5cm、2.1cm、3.3cm、5.5cm,迟角平均误差分别为8.7°、13.5°、5.6°、7.9°。计算与实测符合良好。     

Numerical simulation of the internal wave propagation in continuously densitystratified ocean

A numerical model is proposed to simulate the internal wave propagation in a continuously density-stratified ocean, and in the model, the momentum equations are derived from the Euler equations on the basis of the Boussinesq approximation. The governing equations, including the continuity equation and the momentum equations, are discretized with the finite volume method. The advection terms are treated with the total variation diminishing （TVD） scheme, and the SIMPLE algorithm is employed to solve the discretized governing equations. After the modeling test, the suitable TVD scheme is selected. The SIMPLE algorithm is modified to simplify the calculation process, and it is easily made to adapt to the TVD scheme. The Sommerfeld＇s radiation condition combined with a sponge layer is adopted at the outflow boundary. In the water flume with a constant water depth, the numerical results are compared to the analytical solutions with a good agreement. The numerical simulations are carried out for a wave flume with a submerged dike, and the model results are analyzed in detail. The results show that the present numerical model can effectively simulate the propagation of the internal wave.     

Discussion on the extended form of internal solitary wave models between two typical stratification systems

The two-layer fluid system and the continuous density system are based on two typical simplified stratification conditions to support the propagation of the internal solitary waves(ISWs).The aim of this study is to establish several extension methods of the classical ISW models across the stratification systems in an attempt to find a simple ISW structure that can propagate more stably,and to determine whether the stable ISW structure in the two typical stratification systems can be expressed in terms of a consistent nonlinear model.For the constructed ISW structures,the propagation stability has been investigated by taking the Euler equations as the evolution equations.The results show that the ISW structure constructed from the Miyata-Choi-Camassa(MCC)model undergoes two stages of instability and the re-stable ISW has a larger available potential energy and a smaller kinetic energy than the initialized condition.This illustrates the limitation of the weakly dispersive assumption in the MCC model.In contrast,the ISW structure constructed from the Dubreil-Jacotin-Long(DJL)model for the two-layer fluid system is generally stable,due to the fact that the Boussinesq approximation introduced in the derivation of the DJL model will be automatically satisfied in this system.The initial condition interpolated from the DJL model with a thin pycnocline thickness can be regarded as an appropriate ISW structure for the two-layer system and is even more stable than that initialized by the MCC model.In addition,the effect of the Boussinesq approximation is also included in the discussion.The approximation can be considered equivalent to a weakly dispersive assumption and should not be ignored for the ISW problem in the continuous density system.     

波浪传播数值模型波向角计算

波浪传播变形数值模型的抛物型近似在近海工程大范围水域的波浪推算中应用十分广泛,本文就抛物型缓坡方程（PMSE）数值计算中波浪方向的计算作了分析。首先从椭圆型缓坡方程（MSE）推导了波向角的计算方法;然后介绍大范围水域波浪折射绕射传播变形缓坡方程的抛物型近似法以及波向角的计算;最后,利用抛物型缓坡方程和椭圆型缓坡方程法分别对Berkhoff实验室地形条件下波浪场进行计算,比较两种方法计算得到的波向线图。比较结果显示抛物型缓坡方程法计算波向角结果与椭圆型缓坡方程法计算结果是一致的,抛物型近似法计算波向角是可行的。     

Process control of the sand wave migration in Beibu Gulf of the South China Sea

Based on the environment characteristics of the Beibu Gulf of South China Sea, a quasi-three-dimensional physical model is built.By coupling the bottom boundary layer with the two-dimensional tidal current field near the seabed surface, the quasi-three-dimensional hydrodynamic numerical simulation is carried out.The sand wave migration process is dealt with by coupling the hydrodynamic model with the sediment transport model.The computational results are shown to be in good agreement with the observed data,...     

Responses of thermal structure and vertical dynamic structure of South China Sea to Typhoon Chanchu

The response of the South China Sea (SCS) to Typhoon Chanchu (2006) was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the velocity forcing was introduced in the eastern boundary and the computational schemes of heat fluxes at the surface were introduced. Comparison with the observation data shows that the simulated results are reliable. In the response process of the SCS to Typhoon Chanchu, the influence of the heat fluxes on thermal structure of the SCS was regionally different. Strong wind forcing would lead to upwelling phenomenon in the lateral boundary of deep water basin. Furthermore, the Ekman pumping theory was used to discuss subsurface upwelling and downwelling phenomenon in typhoon forced stage.