1997 Vol. 16, No. 3

Display Method:
An ADI technique for solving three-dimensional coastal circulation
Yang Lianwu, José Ozer
1997, (3): 281-302.
A three-dimensional hydrodynamic model has been presented in this study. The model is a three-dimensional coastal water model, in corporating a turbulence closure model to provide a realistic parameterization of the vertical mixing processes. The governing equations with boundary conditions are solved by an alternating direction implicit (ADf) finite difference technique with a total variation diminishing (TVD) scheme for solving advective equations.
The model has been performed in the Belgian coastal wne (BCZ) which has very complex topography and strong current. The wmparisons between observed and computed results have been made. The results show that the main features in the BCZ can be well reproduces.
Numerical simulation for dynamical processes of sea ice
Wu Huiding, Bai Shan, Zhang Zhanhai, Li Guoqing
1997, (3): 303-325.
Sea ice dynamics plays a pivotal role in describing sea-air interaction in polar regions. This paper discusses the behavior of ice dynamics and shows a momentum balance describing ice drift, the creation of leads and the building of ice ridge, and the nature of sea ice rheology relating the ice stress to the ice deformation and strength. A numerical is presented for the simulation of sea ice dynamical processes. The ice dynamical processes describe ice drift and deformation based on the principles of the conservation of mass and momentum, and contribute to determining the variation of ice thickness and open water or lead area in the ice-covered sea. In the the ice thickness distribution is described with three idealized levels:open water, level ice and rubble. The deformation funcdons are induced into the prognostic equations of the three variables and a parameterization method is employed to simulate the ice ridge and leads. For modelling the ice interaction, the sea ice is considered to be a nonlinear viscous compressible material obeying the viscous-plastic constitutive law. The numerical scheme for the model is outlined and discussed in the paper.The air and water stresses are obtained by using the conventional quadratic law from data or forecasting results of winds and currents. This model is applied to simulate ice drift for the Bohai Sea, the Bothnia Gulf of the Baltic Sea end the Labrador Sea, respectively. The model results show that ice drift in the Bohai Sea has a strong periodical change caused by tides. The creation of leads and ridges in the Bohai Sea are simulated and a sensitivity study of the ice rheology parameters is conducted. The ice model is linked to an atmospheric model with a boundary layer model for numerical sea ice prediction and the results for the Bohai Sea are presented in the paper.
Entropy of sea wave height field and its annual variation in Northwest Pacific Ocean
Sun Fu, Guo Peifang
1997, (3): 327-337.
A kind of entropy is defined by the statistical distribution of observed wave heights of a sea surface during a specified period and calculated from the wave height data of Northwest Pacific Ocean (NWPO) given by GEOSAT altimeter. The results obtained show that there is an annual variation of the entropy with the peak of its value in winter and the trough in summer. In consideration of the fact that the roughness and the wind stress of sea surface are connetted with wave heights, it is expected that the present results might have some potential applications in the research on large scale atmosphere and ocean dynamics.
Measurements of dissolved organic carbon (DOC) in sea water by high temperature combustion method
Guo Laodong, Peter H. Santschi
1997, (3): 339-353.
Dissolved organic carbon (DOC) is the largest organic carbon reservoir in sea water and plays an imporrant role in the marine carbon cycle and other biogeochemical processes in the ocean. Accurate and precise determinalion of the bOC concentration in sea water is thus a prerequisite for any interpretation of DOC biogeochemistry. A key factor in analytical quality control is an accurate determination of the blank. The assessment and distinction of DOC blanks are essential for the precise measurements of oceanic DOC. The total DOC blank includes instrument and water blanks in the high temperature catalytic oxidation (HTCO) method. DOC can be measured accurately using the HTCO method only when the instrument blank is correctly distinguished from the total DOC blank and corrected in the sample measurements. Low DOC blanks can be achieved by extensive conditioning of new catalysts and the whole instrument system, whereas instrument blanks can be quantified by subtracting the water blank from the total DOC blank. We have been able to produce low carbon nanopure water[ ≤ 2μmol/dm3(C)] and have a low instrumental blank[< 5-6 μmol/dm3(C)] when using the HTCO method. Results of concentrations and distributions of DOC in the Gulf of Mexico and the North Atlantic are oceanographically consistent. Results from DOC measurements on samples from the international DOC methods comparison program further confirmed our low values of both nenopure water and the instrument blank.
Two-dimensional numerical simulation of vertical distributions of dissolved oxygen in Huanghai Sea
Liu Kexiu, Zhao Baoren
1997, (3): 355-367.
A two-dimensional model is established to study the temporal evolution of the maximum of vertical distribution of dissolved oxygen in the Huanghai Sea. Three major processes which regulate the variations of dissolved oxygen, i. e.,vertical mixing, biological activity of marine organisms and gas exchange at the air-sea interface, are discussed. It is shown that the major mechanisms of forming and retaining the maximum of dissolved oxygen are the weakened vertical mixing near the bottom of the thermocline, the gas exchange at the air-sea interface and the consumption of oxygen due to the oxidation of organic matter under euphotic layer and at the bottom during the warming periods. Since the thermocline lies in the euphotic zone in the Huanghei Sea area, the biological production contributes to the maximum but does not determine the maximums formation or retention. Most of the biological production in the upper mixing layer get into the air by the gas exchange in the air-sea interface. The transfer velocity of gas exchange can affect the concentration of dissolved oxygen in the upper mixing layer, but has very little influence on the maximum.
A model of profile evolution on wave-dominated mud coast
Zhang Yong, Yu Zhiying, Jin Liu
1997, (3): 369-385.
This paper developed a theory model to simulate the evolution of nearshore profile on wave-dominated mud coast of the abandoned Huanghe Delta, which has been undergoing erosion since the shift of the Huanghe River in 1855. The model is established according to the computation of wave-induced shear stresses on mud profile, and the calculation of mud erosion rate. The sea level fluctuation caused by tide is introduced into the model. A new idea of the effective scouring waves, derived from local wave climate, is proposed in this paper to numerically incorporate the influences of the geological processes occurring during coast erosion. The eroded nearshore profiles exhibit monotonous concave upward. The maximum curvature of profile lies below the mean low tidal level. As the erosion continues,the maximum curvature moves down and shoreward. The position of the maximum curvature of nearshore mud profile can be used as a measure to estimate the evolution states of the mud coast on the abandoned Huanghe Delta. In Lianyungang, the mud profile approaches a steady state when the maximum curvature reaches down to the water depth of about 6 m below the mean sea level.
The application of the fractal geometry in the study of sea-floor volcano
Tao Chunhui, Jin Xianglong, Lu Wenzheng, Hua Zugen
1997, (3): 387-394.
A fractal dimension measurement was made to the contours of the sea floor volcano of the South China Sea in this paper. It was found that the contours of the volcano end there are have stable fractal dimensions in its vicinity. The topography of the volcano end its vicinity can be divided into three parts by using fractal dimension:the mouth of the volcano, the steep waist part of the volcano end the plane sea floor near the volcano. Their fractal dimensions are about 1.12 which are lower than those of the lend. This points out that the basalt volcano has scale inflexibility even it is not very old, and it will have a fractal dimension with little difference after received some marine deposit.
Arietellus unisetosus-a new species of calanoid copepod from the tropical waters of the central Pacific Ocean
Lian Guangshan, Qian Honglin
1997, (3): 395-401.
A new species, Arietellus unisetosus n. sp, (Copepods, Calanoida, Arietellidae, Arietellus) sampled from the tropical waters of the central Pacific Ocean is described. It is easily distinguished from the other known congeneric species by the following some characters (female):the caudal rami asymmetrical, the outer margin of left ramus swollen, knob-like; leg 5:both knob-like endopods each with a long apical seta; both lobate exopods without any terminal spine, etc.
Application of one-line model to the prediction of shoreline change
Qin Chongren, He Jiangcheng
1997, (3): 403-417.
This paper applies the one-line (shoreline) model to a typical sandy shoreline of a harbour city in the northen part of China and the numerical model is used to simulate shoreline change.
The paper consists of two parts, the first describes the principles of the shoreline model, and the proper choice of the model's parameters. As an important part, a breaking wave model, in which the combined deformation of wave refraction, diffraction and shoaling is considered, is established. A pragmatic method is used to compute the breaking wave height and angle. The second presents the results of numerical simulation of shoreline change at site. First, a calibration and a verification are carried out by the use of known wave data, topographic data and the corresponding shoreline data. Then the shoreline position at the site after five years from 1992 is forecast, and several engineering plans are proposed to protect the beach, their protecting effect is studied by the use of one-line model. The results of numerical simulation agree with the shoreline change situation observed fairly well.
A preliminary study on stocks of round scad Decapterus maruadsi from Minnan-Taiwan Bank Fishing Ground
Yang Shengyun, Qiu Shuyuan
1997, (3): 419-428.