On one model of the upper boundary layer of the ocean

A steady model of the ocean's upper boundary layer is considered. It uses the dependence on the velocity gradient, suggested in ref. 1, which is analogous to formulae of the Prandtl type for the coefficient of turbulence. The analytical solution of the problem is provided. A numerical estimate of the model's parameters points to satisfactory concordance with the field data for various characteristics.Translated by Mikhail M. Trufanov.     

The determination and prediction of longitudinal dispersion coefficients in a narrow,shallow estuary

Measurements of velocity and salinity for parts of a flood and an ebb tide in the Conwy estuary have been used to evaluate the time-dependent longitudinal dispersion coefficients due to vertical and transverse oscillatory shear effects. The values have been compared with semi-analytical predictive formulae. Simple empirical expressions are suggested for relating the dispersion coefficients to hydraulic parameters for the conditions observed.     

An empirical formula for friction coefficient of a perforated wall with vertical slits

The friction coefficient in the permeability parameter of a perforated wall has been estimated on the basis of a best fit between measured and predicted values of such hydrodynamic coefficients as reflection and transmission coefficients. In the present study, an empirical formula for the friction coefficient is proposed in terms of known variables, i.e., the porosity and thickness of the perforated wall and the water depth. This enables direct estimation of the friction coefficient without invoking a best fit procedure. To obtain the empirical formula, hydraulic experiments are carried out, the results of which are used along with other researchers' results. The proposed formula is used to predict the reflection and transmission coefficients of various types of structures including a perforated wall. The concurrence between the experimental data and calculated results is good, verifying the appropriateness of the proposed formula. It is also shown that the proposed formula can be used for irregular waves as well.     

Model of the Tropical Atlantic incorporating the upper mixed layer

We present a multilayer ocean model incorporating a non-local integral model of the upper mixed layer (UML). In the framework of a three-layer Tropical Atlantic model, we study the model's response to various closure hypotheses for heat fluxes at the UML lower boundary.Translated by V. Puchkin.     

2008年夏季南海北部海区生物光学特性的垂向变化特征

Vertical variability in the bio-optical properties of seawater in the northern South China Sea(NSCS) including inherent optical properties(IOPs) and chlorophyll a concentration(Chl) were studied on the basis of in situ data collected in summer 2008 using an absorption/attenuation spectrophotometer. An empirical model was developed to estimate Chl profiles based on the absorption line height at long wavelengths, with a relative root mean square error of 37.03%. Bio-optical properties exhibited large horizontal and vertical spatial variability. As influenced by coastal upwelling and the Zhujiang River(Pearl River) discharge, both IOPs and Chl exhibited high values in the surface waters of the inner shelf, which tended to decrease with distance offshore. Subsurface maximum layers of IOPs and Chl were observed in the middle and outer shelf regions, along with significantly higher values of attenuation coefficients beneath this layer that rapidly increased towards the bottom. In the open ocean, both IOPs and Chl exhibited consistent variability, with the subsurface maximum layer typically located at34–84 m. Phytoplankton were found to be one of the major components in determining the vertical variability of bio-optical properties, with their vertical dynamics influenced by both physical forcing and light attenuation effects. The depth of the subsurface maximum layer was found to be closely related to the fluctuation of the oceanic thermocline and the depth of the euphotic zone, which also affected the total integrated biomass of the upper ocean. Typically high values of attenuation coefficients observed in the bottom waters of the continental shelf reflected the transport of particulate matter over the bottom boundary layer. Our results reveal large spatial differences in bio-optical profiles in response to complex marine ecodynamics in the NSCS. From the perspective of marine research, high-resolution optical measurements are clearly advantageous over conventional bottle sampling.     

Effectiveness of data assimilation using probabilistic techniques in a model for synoptic velocity field evolution

The results of numerical experiments involving data assimilation by linear and non-linear models for synoptic ocean dynamics are presented. This paper considers the model's response to data assimilation at diverse values of the relative error in the determination of the initial fields and space-time discreteness of data assimilation. The data obtained using the optimal filtering are compared with those provided by the optimal interpolation (OI). A qualitative difference in the response of the linear and non-linear models to data assimilation is noted. The limiting values of the time-space discreteness of observations assimilation are determined, which allow correct application of OI.Translated by Vladimir A. Puchkin.     

三维斜压陆架海模式的应用: 南海上混合层的季节变化

从一个三维斜压陆架海模式的数值模拟结果来揭示南海上混合层的季节变化规律,结果表明:(1)在南海北部上混合层的厚度(即混合层的下界深度)具有明显的季节性变化,与在南海南部上混合层的变化明显不同,前者的混合强度的变化幅度远比后者的要大得多.(2)在中南半岛中部东岸外海的西边界区域内,由于经常受冷涡控制,下层冷水涌升,上层水体层化显着,使得该海区垂直混合减弱.(3)在一些气旋(反气旋)涡的边缘,混合层厚度等值线分布密集,且水平梯度较大.(4)南海上混合层的厚度分布特征与上层环流的分布格局之间存在着较好的地转调整关系.     

Estimating the extent of the spraying zone on a sea-going ship

The maximum extent of ship spraying for a medium-sized fishing trawler (MFV) of Soviet type has been considered. A simple geometrical model for generating the spray due to ship-wave collisions has been applied to determine the maximum height of the spray source above the ship deck. The maximum height of the spray source has been assumed to depend on the ship speed relative to the moving waves and an empirical constant specific to a given type of ship. A unique field data set (Kuzniecov et al., 1971) of the height of the upper limit of ice accretion on the foremast of an MFV has been used to determine the value of the empirical constant for this vessel. For documented air-sea and ship motion parameters, the trajectories of droplets hitting the upper parts of the accretion on the foremast have been calculated using the equation of droplet motion for each reported icing event.The heights of the spray source computed by the trajectory method for each case of icing were compared with the heights of the spray source determined by a correlation involving the ship speed relative to the waves and the vertical extent of spray. The best fit was obtained for an empirical constant value of 0.535.The model performance was tested using an independent data set (Sharapov, 1971) on the spraying zone of an MFV. The tests showed that this model predicts the extent of the spraying zone over the ship with satisfactory accuracy and suggest that it should be incorporated into an integrated ship icing model.Finally, the model was run for several ship speeds, headings and wind speeds to examine the effect of these parameters on the maximum height of the spray hitting the ship's foremast. It was found that this height increases with wind speed and ship speed and is maximum for ship headings of 120–130°.     

静力触探技术在东海陆架工程勘察中的应用研究

通过对东海大陆架海底浅表层土样的静力触探参数进行统计分析,得到该区域细砂、粘土、淤泥质土和淤泥的静力触探统计值,建立了研究海区基于静力触探参数的土类判别图,可用于快速判定土的类别.根据静力触探参数,并应用经验公式估算了海底粘性土的抗剪强度和灵敏度,对估算公式经验系数选择进行了深入研究,提出在研究海区应用经验公式进行粘性...     

A model for predicting SST in limited region-Ⅰ. The dynamical equations

Starting from physical oceanology characteristics of the China seas and for the short-term operational prediction of SST in the region,a two-dimensional (vertically integrated) primitive equation model,physically reasonable and operationally feasible,on the upper mixed layer is constructed and given here,which consists of three parts,the nondivergent residual current (the monthly mean field of the Kuroshio and its branches) equations,the dynamic forecasting equations,and the equation of model''s physics consisting of surface heat flux,coolings of the upper mixed layer due to the Ekman pumping and the entrainment by gale.This model may be used primarily to forecast the sea surface temperature,and to give estimations of the mean wind-driven current and the sea level,for a period of 3-5 d.In part 1 of this series,the physical conditions for establishing model equations are discussed first,that is,1.the existence of the upper well mixed layer in the region; 2.the distinguishability of currents 3.the splitting of thermodynamical equation.The equations of nondivergent residual current,and the dynamic forecasting equations with initial values and boundary conditions are also discussed.     

On the wave damping due to a permeable seabed

Laboratory experiments were performed to study the wave damping induced by a porous bed. During the propagation of waves over a porous medium the wave characteristics change: a significant wave height attenuation of about 20–30% is observed and, in almost all cases, an increase in wavelength. The wave decay is found to depend on the wave characteristics like the wave height, the wavelength and the wave shape. We have also studied the influence of the geometric properties of the porous bed (i.e. thickness and length) on the wave dissipation. It is found that the attenuation of the wave height increases with the permeable bed thickness and that there is a maximum wave dissipation for a length of the porous seabed equal to 2.0–2.5 times the wavelength. A comparison is also made of our findings with available literature results. A parametric study of the wave damping has been performed by varying the values of the resistance coefficients derived by both literature and experiments. Literature analytical models have been applied by using the resistance coefficients that better describe our flow conditions. All models in use underpredict the observed wave attenuation for any sensible values of the resistance coefficients.     

Aerodynamic loads on a typical tension leg platform

The wind load effects on tension leg platforms have been recognized to be a significant environmental loading. An accurate assessment of the aerodynamic loads is, therefore, a prerequisite for the design of an economic and a reliable structure. The design codes and specifications recommend the use of a projected area approach that is thought to be conservative. The code recommendations fail to quantify aerodynamically induced forces in directions different to the mean wind flow. The interference and shielding effects suggested in some specifications provide only a simplistic view. Physical modeling as reported in this paper, therefore, continues to serve as the most accurate and practical means of predicting aerodynamic loads.The mean aerodynamic force and moment coefficients of a typical tension leg platform for various approach wind directions were measured on a scale model exposed to simulated flow conditions in a boundary layer wind tunnel. Major components on the upper deck of the model were designed for easy removal so that measurements could be obtained for different platform configurations. A parametric study was conducted to determine shielding and interference effects, i.e. the manner in which aerodynamic coefficients are influenced by the location and orientation of the ancillary structures on the platform, e.g. living quarters, flare boom, derricks, etc. The present paper addresses the wind tunnel modeling procedures and automated data acquisition and reduction methods. The aerodynamic force and moment coefficients with respect to the body and flow axes were reduced from the experimental measurements for azimuth angles of 0 to 360 degrees at 15-degree intervals. A total of eight configurations were monitored ranging from a platform configuration that included all the ancillary structures to the case where every deck component was removed. The aerodynamic coefficients obtained from the classification society recommended procedures provided conservative estimates in comparison with the measured values for all configurations. The results also illustrate that the interference effects among various ancillary structures on the platform are significant.     

中国近海异常海温数值预报模式研究Ⅰ.模式的建立

本文从近海异常海温的定义和形成机制出发,在原有的海表温度数值预报模式的基础上,考虑了上层海洋对强天气强迫的动力响应和浅海效应,前者包括卷入和卷出、冷水抽吸和暖水辐聚,后者包括潮混合和浅海对短波吸收之影响,从而建立了一个以混合层的温、流、深度为变量的中国近海异常海温数值预报模式.     

Estimates of the characteristics of the horizontal turbulent exchange in the northwestern part of the Pacific Ocean

Estimates of the characteristics of the horizontal turbulent exchange (coefficients of horizontal exchange, scales of deviations of the velocity of geostrophic currents from the background flows, and horizontal scales of perturbations) in the upper ocean layer were obtained on the basis of the data of expeditions held in 1978 and 1980 in the northwestern part of the Pacific Ocean. It is shown that the characteristics of the horizontal turbulent exchange strongly depend on the structure of the background flows, and one of the causes of their variability is related to tropical cyclones. A tendency to a decrease (to different degrees) of the turbulent coefficients in the wake of a tropical cyclone is noted.     

单突堤后的波浪绕射

波浪绕射现象是确定港域掩护状况的主要因素,在设计港口防波堤工程时必须予以考虑,以便根据港口使用要求,选择最佳的外堤布置方案,确保船舶作业安全并节省工程投资。防波堤工程可有各种不同布局,其中最常见的一种为单突堤。其它如岛堤、双突堤,从计算堤内水域波况的观点着眼,在一定条件下其性质亦属于单突堤一类。因此,研究单突堤后的波浪绕射规律具有较普遍的实际意义。     

Applying POT methods to the Revised Joint Probability Method for determining extreme sea levels

Newly exposed concepts of POT declustering (Bernardara et al., 2014) within the GPD-Poisson model are applied to the joint probability of tide and surge for determining extreme sea levels, as a variation of the Revised Joint Probability Method (RJPM, Tawn and Vassie, 1989). A mixture model is proposed for the meteorological residual (surge) component with a non-parametric (empirical) density for the bulk values and parametric models for both the lower and upper tails. In particular, a distinction is made between values observed at regular time steps, called sequential values, and the clusters of extreme values, or events, on which the statistical extrapolations are performed. The sea level distribution is obtained by convolution of the tide and surge density functions. Confidence intervals are also proposed. This model is applied to the case study of Brest, France using both hourly and high water values. Two methods for handling tide–surge interaction are presented and discussed and a comparison with a direct approach is made.     

南中国海神狐海域天然气水合物上覆地层不排水抗剪强度预测

浅层沉积物不排水抗剪强度（Su）是深水作业的关键参数之一。为了获取南海神狐海域首次海域天然气水合物试采区W18-19框体的基本工程地质特征,试采工程准备阶段开展了原位孔压静力触探测试（CPTU）及大量的室内实验。本文将主要基于CPTU计算不排水抗剪强度的基本模型,采用微型十字板、电动十字板、袖珍贯入仪及不固结不排水三轴实验,确定该区域不排水抗剪强度的基本模式,并提出适用于南海神狐钙质黏土层的不排水抗剪强度纵向分布规律计算模型,对该区域水合物上覆层的不排水抗剪强度进行预测。 结果表明,基于总锥端阻力、有效锥端阻力、超孔隙压力的模型系数分为13.8、4.2、14.4。综合考虑地层压实效应和含气情况,本文提出的分段函数预测模型与室内结果的一致性较好,可用于工程设计阶段进行工区不排水抗剪强度纵向分布规律的预测。另外,基于有效锥端阻力的不排水抗剪强度经验模型适应于浅层极软-较硬压实的钙质粘土层,基于超孔隙压力的不排水抗剪强度模型适用于较硬-坚硬的不含气层,而基于总锥端阻力的不排水抗剪强度计算模型则适用于坚硬含气的钙质黏土层。本文提出的分段函数模型有效的提高了经验模型在南海神狐水合物赋存区的适用性,计算结果可为工程安全评价提供支撑。     

Assessment of the effectiveness of POLYMODE data assimilation by a numerical barotropic model for synoptic motions

This paper considers the results of numerical experiments involving POLYMODE data assimilation by a barotropic model for synoptic ocean dynamics. The model's response the data assimilation for various space-time discretenesses of assimilation is studied. Results derived from the application of optimal interpolation algorithms and modified optimal filtration algorithms are compared. Qualitative similarity to the calculations carried out through the simulation modelling technique is noted. Optimal assimilation algorithms are determined, depending on the space-time discreteness used. An optimal sampling discreteness for the POLYMODE conditions is suggested.Translated by Vladimir A. Puchkin.     

A method for the statistical prediction of hydrological and chemical fields,exemplified by computation of the oxygen content in the Sea of Azov surface layer

To predict the concentration of oxygen in the Sea of Azov, the paper relies on the decomposition of this parameter by a system of empirical orthogonal functions and on the prediction of decomposition coefficients via a grouped consideration of arguments. This method is applied to construct an optimal model for predicting the spatial distribution of oxygen in various seasons of the year, using a data on the mean seasonal dissolved oxygen concentration compiled at 32 reference stations occupied from 1958 to 1988. The experimentally derived numerical data indicate that the method can be effectively used to make short-term predictions. Translated by Vladimir A. Puchkin.