THE STUDY OF THE YELLOW SEA WARM CURRENT AND ITS SEASONAL VARIABILITY

The Yellow Sea Warm Current (YSWC) penetrates northward along the Yellow Sea Trough, and brings warm and saline water towards the Bohai Sea. The YSWC becomes much less intrusive in summer and is limited mostly in the southern trough, contrasting with a deep winter penetration well into the trough. The seasonal variability of the YSWC has prompted a debate regarding which controls the YSWC and its seasonal variability. In this article, the annual mean and seasonal variability of the YSWC was examined by using a 3-D ocean model together with several experiments. The results show that in the annual mean the YSWC is a compensating current firstly for the southward Korea Coastal Current (KCC), which is mainly caused by the Kuroshio Current (KC). The local wind-stress forcing plays an important but secondary role. However, the local monsoonal forcing plays a prominent role in modulating the seasonal variability. A deep northwestward intrusion of the YSWC in winter, for instance, is mainly due to a robustly developed China Coastal Current (CCC) which draws water along the Yellow Sea trough to feed a southward flow all the way from the Bohai Sea to the Taiwan Strait.     

THE RELATIONSHIP BETWEEN THE TAIWAN WARM CURRENT AND TSUSHIMA WARM CURRENT

The Taiwan Warm Current (TWC) and the Tsushima Warm Current (TSWC) flow northward over the shelf in the East China Sea (ECS), which some previous studies regard as a Taiwan-Tsushima Warm Current (TTWC) System. But the roles of the TWC and TSWC in the formation of the TTWC system have not been clarified. This article will show that the TSWC is more important in the TTWC system. Using a three-dimensional baroclinic model, we conducted several numerical experiments to reveal the dynamic relationship between the TWC and TSWC. The results show that the TWC has little effect on the TSWC, while the TSWC has a significant effect on the TWC. A source-sink driven mechanism along isobaths may be used to explain this phenomenon. The perennial northward flow through the Tsushima Strait pumps the response over the northern shelf in the ECS that gives rise to the TWC. Although the TSWC is located at the "downstream" region, it could induce about 0.5 Sv to TWC in annual mean values.     

SIMULATION OF GENERAL CIRCULATION IN THE EAST CHINA SEA AND THE YELLOW SEA

Based on a three-dimensional primitive equation dynamic numerical mod-el,the general circulation in the East China Sea and the Yellow Sea is studied with a O.25°×0.25°horizontal grid and a realistic bottom topography.As the first step,we con-sider the tidel current and Kuroshio(Japan current).The main results are:1)the modeltidal harmonic constants agree surprisingly well with the observations at the 81 coastlinestations in this area.The average amplitude difference is 1.7cm and the average phase dif-ference is 5.2°for the diurnal component,and those for the semi-diurnal tide 4.1 cm and3.7 °2)the path of the Kuroshio agrees with long—term observations; 3)after enteringthe studied area, a branch of the Kuroshio enters the East China Sea.This pattern agreeswith the nation-wide comprehensive ocean investigations; 4)a branch of the Kuroshiogoes northward and forms the Tsushima warm current,and the origin of Tsushima warmcurrent is multi-source.In the Tsushima Strait,the warm current goes into the Sea o     

NUMERICAL STUDY ON THE THREE-DIMENSIONAL CHARACTERISTICS OF THE TIDAL CURRENT AROUND HARBOR ENTRANCE

A three-dimensional (3-D) numerical model is established to investigate the tidal current motion characteristics around the harbor entrance. Computational approaches consist of the finite difference method, time-splitting technique, C-grid, and a high-order turbulence closure model. The Ocean General Circulation Model (OGCM) inundation scheme is incorporated in the model. An engineering application, Lianyungang Harbor, China, is used as a real-life case. The model is validated by showing that the simulated results agree well with the field data. In the approach channel, the tidal current shows a deflection effect especially in the bottom layer. As for Lianyungang Harbor, a jet flow forms at the tip of the northern breakwater, which drives a circulation flow at the inner side of the harbor entrance. In the vertical, the flow is significantly stratified at the entrance section within the channel, where the flow direction varies between layers and the speed distribution is quite uniform. These 3-D features become less evident to the offshore. Additionally, the sensitivity analysis shows that the flow deflection is related to the channel depth. Simulation results also imply that the siltation rate at the entrance section of the approach channel tends to be more uniform by the 3-D flow motion feature, and could be more significant with the increase of the channel depth.     

THE EFFECTS OF MONSOONS AND CONNECTIVITY OF SOUTH CHINA SEA ON THE SEASONAL VARIATIONS OF WATER EXCHANGE IN THE LUZON STRAIT

Seasonal variations of water exchange in the Luzon Strait are studied numerically using the improved Princeton Ocean Model (POM) with a consideration of the effects of connectivity of South China Sea (SCS) and monsoons. The numerical simulations are carried out with the strategy of variable grids, coarse grids for the Pacific basin and fine grids for the SCS. It is shown that the Mindoro Strait plays an important role in adjusting the water balance between the Pacific and the SCS. The SCS monsoon in summer seasons hinders the entrance of the Pacific water into the SCS through the Luzon Strait while the SCS monsoon in winter seasons promotes the entrance of Pacific water into the SCS through the Luzon Strait. However, the SCS monsoon does not affect the annual mean Luzon Strait transport, as is mainly determined by the Pacific basin wind.     

NUMERICAL SIMULATION OF THE TIDAL MOTION AND SUSPEND EDSEDIMENT TRANSPORT IN THE RADIAL SANDBANK AREA OF THE SOUTHERN YELLOW SEA

A coupled 2-D numerical model for hydrodynamic-sediment transport was established and applied to simulate the tides, tidal currents and sediment movement in the submarine Radial Sandbank area of the southern Yellow Sea.With a high-resolution topography dataset used in the model,the simulation reproduced a fine-structured current field and erosion-siltation distribution. The modeled results show that,in the area of Radial Sandbanks, reversing tidal current and seabed erosion occurs within troughs while tidal current with more rotary feature and deposition occurs above sandbanks,which indicates the tidal-induced formation of the Radial Sandbanks. During a tidal period, associating with the variation of current speed, erosion alternates with siltation. The seabed deformation depends on the relative strength of erosion and siltation in a tidal period.     

NUMERICAL MODELLING OF THE QUASI-GLOBAL OCEAN CIRCULATION BASED ON POM

A free surface quasi-global ocean circulation model, Princeton Ocean Model (POM), was adopted to simulate the climatological circulation. The horizontal resolution of the model was 1/2~X 1/2~ with 16 vertical sigma layers. The initial temperature and salinity fields of the model were interpolated from the Levitus data, and the COADS(Comprehensive Ocean-Atmosphere Data Set ) monthly mean SST and wind fields were used as the surface forcing. The integral time length is 6a. The main general circulation components such as the equatorial current, the equatorial undercurrent, the south and north equatorial currents, the Antarctic Circumpolar Current (ACC), the Kuroshio and the Gulf Stream were well reconstructed. The volume transports of PN section and ACC agree well with the estimations on field survey. Up to now there is no global or quasi-global circulation model results using POM in literature. Our results demonstrate that POM has sound ability to simulate the coastal circulation as well as the general ocean circulation. And this result can provide open boundary conditions for fine resolution regional ocean circulation models.     

DYNAMICS OF THE KUROSHIO INTRUSION INTO THE SOUTHEAST CHINA ADJACENT WATERS-A NUMERICAL STUDY

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｗｅｓｔｗａｒｄｉｎｔｒｕｓｉｏｎｏｆｔｈｅＫｕｒｏｓｈｉｏｏｃｃｕｒｓｉｎｔｈｅＬｕｚｏｎＳｔｒａｉｔａｎｄｏｆｆＴａｉｗａｎｎｏｒｔｈｅａｓｔｃｏａｓｔ.Ｔｈｅｂｅｈａｖｉｏｒｓａｎｄｓｔｒｕｃｔｕｒｅｓｏｆｔｈｅｉｎｔｒｕｄｉｎｇｆｌｏｗｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｂｙｍａｎｙｏｃｅａｎｏｇｒａｐｈｅｒｓ ,ｙｅｔｎｏｔｆｕｌｌｙｋｎｏｗｎ .Ｔｈｅｄｙｎａｍｉｃａｓｐｅｃｔｓｏｆｔｈｅｉｎｔｒｕｓｉｏｎｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｂｙｆｅｗｉｎｖｅｓｔ…     

THE INTRUSION AND INFLUENCES OF INTRASEASONAL LONG ROSSBY WAVES IN THE EAST CHINA SEA

The analysis of sea level data from tide stations and ocean general circulation model (OGCM) shows that the intraseasonal long Rossby wave results in the intraseasonal variations of Kuroshio axis and transport in the upper reaches of the Kuroshio in the East China Sea (ECS). Due to the transport modulation induced by Ryukyu Islands, the intraseasonal variation is very weak in the lower reaches of the Kuroshio in the ECS. A two-layer model reveals the relation among Kuroshio frontal unstable wave with topography,transport and the axis position of the Kuroshio, from which we can infer that the intrusion of intraseasonal long Rosshy wave may stimulate the Kuroshio frontal unstable wave in the upper reaches of the Kuroshio in the ECS. The altimeter data also shows that the sea level anomaly resulting from intraseasonal long Rossby wave could pass the channel between Taiwan and Ryukyu Islands and propagate northeastward in accord with the Kuroshio frontal unstable wave. However, the sea level anomalies passingIslands are relative weak and Kuroshio variation.through the gaps of Ryukyu have negligible effects on the Kuroshio variation.     

CYCLONIC RECIRCULATION ON THE LEFT SIDE OF THE KUROSHIO IN THE EAST CHINA SEA

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＫｕｒｏｓｈｉｏｅｎｔｅｒｓｔｈｅＥａｓｔＣｈｉｎａＳｅａ (ＥＣＳ)ｅａｓｔｏｆＴａｉｗａｎａｎｄｆｌｏｗｓａｌｏｎｇｔｈｅｓｈｅｌｆｅｄｇｅｉｎｔｈｅＯｋｉ ｎａｗａＴｒｏｕｇｈｕｎｔｉｌａｒｏｕｎｄ 2 9°30′Ｎ ,ｗｈｅｒｅｉｔｓｅｐａ ｒａｔｅｓｆｒｏｍｔｈｅｓｈｅｌｆａｎｄｒｅｅｎｔｅｒｓｔｈｅＰａｃｉｆｉｃＯｃｅａｎｔｈｒｏｕｇｈｔｈｅＴｏｋａｒａｓｔｒａｉｔ.Ｉｔａｆｆｅｃｔｓｄｉｒｅｃｔｌｙｔｈｅｏｕｔｅｒｓｈｅｌｆｃｉｒｃｕｌａｔｉｏｎａｎｄｔｈｅｒｍｈａ…     

NUMERICAL SIMULATION AND EXPERIMENTAL STUDY OF THE FLOW FIELD AROUND A CIRCULAR CYLINDRICAL ARTIFICIAL ISLAND UNDER THE ACTION OF WAVES AND VISCOUS CURRENT

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＡＮＤＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＯＦＴＨＥＦＬＯＷＦＩＥＬＤＡＲＯＵＮＤＡＣＩＲＣＵＬＡＲＣＹＬＩＮＤＲＩＣＡＬＡＲＴＩＦＩＣＩＡＬＩＳＬＡＮＤＵＮＤＥＲＴＨＥＡＣＴＩＯＮＯＦＷＡＶＥＳＡＮＤＶＩＳＣＯＵ...     

TYPHOON PROCESS AND ITS IMPACT ON THE SURFACE CIRCULATION IN THE NORTHERN SOUTH CHINA SEA

A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An air-sea model system (MM5 and Princeton Ocean Model(POM))was built to simulate meteorological dynamics and ocean circulation in the South China Sea(SCS).In the POM the output of MM5 was used as the input data.With an increased number of vertical levels,a high-resolution planetary boundary layer scheme and updated landuse/vegetation data,the accuracy of computing wind,temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations.The simulated trajectory and wind speed of Utor are close to the observed results.The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta(PRD)area.At different meteorological stations in Hong Kong,the wind,temperature and sea surface pressure are well simulated.The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor,and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track.The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C.     

A NUMERICAL STUDY FOR MICROWAVE BACKSCATTERING CROSS-SECTION OF SEA SURFACE

Based on Tian et al. ＇s theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relationships between the calculated backscattering cross section and the environmental parameters, such as wind speeds, azimuthal angles and incidence angles, were studied. Compared with the traditional two-scale scattering model, the results are much more coincident with the observations under the condition of moderate incidence angles, which is very useful to make up for the two-scale model. To make the new calculation model to be used conveniently in the practice, its simplified form was proposed.     

NUMERICAL STUDY ON THE PURIFICATION PERFORMANCE OF RIVERBANK

During the rain time, the runoff infiltrates into the riverbank through the collecting gutter and slope surface. The city runoff is generally polluted by organic, oil, heavy metal particulates, etc. The pollutants moving with the water through the riverbank experience advection, dispersion, diffusion, adsorption, biochemical reaction and plant uptaking processes. In this article, a mathematical model was developed to simulate the performance of pollutant removal of the riverbank. The model took those main mechanisms into account. The modified Richards equation was used in simulating flow field. The mass balance law was employed in deriving the equation for pollutant transport, where the diffusion and dispersion were described with the Fick-type law, the adsorption was macroscopically expressed as form isotherm, and the bio-chemical degradation process was assumed to follow the Monod kinetics. The NH3-N and TP were considered in the present model. The mathematical model was descritized with a finite element numerical model, which was applied to two types of model riverbanks. In the model test, the hydraulic loading was assumed to have the intermittent pattern simulating the storm runoff of certain return period, and the values of the rainfall runoff and concentrations of the NH3-N and TP were taken from the model test. The computed overall removal rates for the NH3-N and TP in 6 cases are in the range of 88%-98%, 87%-97%, respectively. The differences between the computed and tested overall removal rates for the NH3-N and TP are less than 5%. The time-varying oscillation pattern of the concentrations of the NH3-N and TP were rationally simulated, which shows that the model presented in this article can be used to assess the purification performance of the riverbank constructed with sand or soil.     

A NUMERICAL STUDY ON MECHANISM OF S-STARTS OF NORTHERN PIKE （ESOX LUCIUS）

Northern pike is regarded as a specialist in swimming acceleration. The force production mechanism of northern pike,Esox lucius,during its predation S-starts was numerically studied in this article. The problem was reasonably simplified to a loose-coupling problem of fish swimming dynamics and hydrodynamics just in the swimming direction. The approach involved the simulation of the flow by solving the two-dimensional unsteady incompressible Navier-Stokes equations and decribing the fish motion dynamics based on Newton’s Second Law. Visualizations of flow fields and vortex structures were performed. The results show that the large acceleration is obtained mainly in the first undulatory cycle in which the amplitude increases. In the second cycle,a couple of vortices are generated and induce a jet. In the third cycle,the jet is strengthened by the mergence of the vortices in the same direction. Through discussing the effects of various controllable factors on the swimming performance,it is found that the actual locomotion mode of the northern pike in nature is just the best choice.     

NUMERICAL SIMULATION OF A MATHEMATICAL MODEL FOR WAVE PROPAGATION ON NON-UNIFORM CURRENT AND DEPTH

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｒｋｈｏｆｆ( 1 972 )ｄｅｒｉｖｅｄｔｈｅｗｅｌｌ ｋｎｏｗｎｃｏｍ ｂｉｎｅｄｒｅｆｒａｃｔｉｏｎ ｄｉｆｆｒａｃｔｉｏｎｅｑｕａｔｉｏｎｗｈｉｃｈｗａｓａｌｓｏｎａｍｅｄａｓｍｉｌｄ ｓｌｏｐｅｅｑｕａｔｉｏｎ .Ｔｈｅｅｑｕａｔｉｏｎｏｖｅｒ ｃｏｍｅｓｔｈｅｓｈｏｒｔｃｏｍｉｎｇｓｏｆｏｎｌｙｄｉｓｃｕｓｓｉｎｇｒｅｆｒａｃｔｉｏｎｐｈｅｎｏｍｅｎｏｎｆｏｒｔｈｅｒｅｆｒａｃｔｉｏｎｍｏｄｅｌａｎｄｏｎｌｙｓｔｕｄｙ ｉｎｇｄｉｆｆｒａｃｔｉｏｎｐｒｏｂｌｅｍｆｏ…     

INTERANNUAL VARIABILITY OF KUROSHIO CURRENT AND ITS EFFECT ON THE NEARSHORE BRANCH IN JAPAN/EAST SEA

Based on the Hybrid Coordinate Ocean Model (HYCOM), this article presents simulations of the three-dimensional dynamic and thermal structure of the North Pacific Ocean (NPO) in the time domain from January 1991 to December 2000. The baroclinic current field and its interannual variability in Northwest Pacific Ocean (NWPO), especially, the Kuroshio Current (KC) and the Japan/East Sea (JES) are analyzed and discussed. The results show that the HYCOM covers a complete dynamic and thermo process with adequate representations of the eddy fields and variability in main spatial and temporal scales. The model is used to simulate the strong interanual variability of the KC, which may affect the strength of the eastern bifurcation of the Tsushima Warm Current (TSWC), named the Nearshore Branch (NB) in the JES. When the KC is strong and its axis is close to the Japan Island, the TSWC and its bifurcations in the JES would intensify accordingly. Our results confirm once again the hypothesis of Yang et al. that the KC determines the annual mean NB in the JES via the “island integral constraint”. This article further extends this hypothesis to study the KC role in the NB on a time dependent scale.     

NUMERICAL STUDY ON EFFECT OF WAVING BED ON THE SURFACE WAVE

1. INTROUCTION There have been lot of researches on the effect of the bottom on the surface wave, in which, most of them involved the fixed bottom with concave, convex, or periodical shapes [1-3]. It seems that very few ones on waving bed are available up…     

A STUDY ON NUMERICAL METHOD OF NAVIER-STOKES EQUATION AND NON-LINEAR EVOLUTION OF THE COHERENT STRUCTURES IN A LAMINAR BOUNDARY LAYER

1. INTRODUCTION A high accuracy compact finite difference scheme has been extensively applied to direct simulation of turbulence coherent structure’s complicated and remote physical phenomena [1-5]. The Fourier spectralexpansion was previously commonly …     

SEASONAL REVERSE OF SEA SURFACE SLOPE IN THE NORTHERN YELLOW SEA AND ITS DYNAMIC RELATION WITH MONSOON EFFECTS

Based on the monthly average sea level data from the tide gauge measurement (1999-2001), the seasonal variability of the sea level in the Northern and Middle Yellow Sea is studied to reveal that the sea surface height at all the tide gauges becomes higher in summer than that in winter. In addition, the sea surface height of the Northern Yellow Sea is higher than the one of the Middle Yellow Sea with a slope downward from the north to the south in summer, while it is lower with a reversed slope in winter. The seasonal reverse of the sea surface slope can be attributed to the monsoon effects i.e. the annual reverse of the monsoon direction and the annual variation of the monsoon rainfall. A set of equations are established in light of the dynamic principles to expound how the monsoon forcing and the sea surface slope generate a summer outflow and a winter inflow in the Yellow Sea.