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1.
横向流 (垂直于海湾主轴方向的流动) 对横向动量以及物质分布具有重要影响。已往研究表明,潮汐应变对横向流的垂向空间结构具有重要的调控作用。但这种认识仅局限于强层化海区,弱层化条件下潮汐应变对于横向流空间结构的影响仍未可知。为此,本文以象山港为例,基于实测数据阐释了弱层化条件下潮汐应变对横向流及其余环流垂向空间结构的调控作用。结果显示,象山港内湾横向流的垂向空间结构随大小潮呈现出明显的变化规律。大潮时,潮汐应变现象明显,涨潮时较强的垂向混合使得横向流在高潮阶段呈现出一层结构;落潮时垂向混合较弱,横向流在低潮时呈现两层结构。小潮时,潮汐应变受到抑制,垂向混合在涨落潮时均较弱,因此横向流在高低潮阶段均呈现出两层结构。经过潮时均进一步得到的横向余环流呈现出上层向南、下层向北的两层结构。由于潮汐应变的大小潮变化,横向余环流的反转深度反转点自大潮到小潮呈现出上升的趋势。  相似文献   

2.
ＭｏｄｅｌｌｉｎｇｏｆｔｈｅｂａｒｏｔｒｏｐｉｃｐｒｏｃｅｓｓｅｓｉｎｔｈｅＢｏｈａｉＳｅａ￥ＨｕａｎｇＤａｊｉ；ＣｈｅｎＺｏｎｇｙｏｎｇａｎｄＳｕＪｉｌａｎ（ＳｅｃｏｎｄＩｎｇｔｉｔｕｔｅｏｆＯｃｅａｎｏｇｒａｐｈｙ，ＳｔａｔｅＯｃｅａｎｉｃＡｄｍ...  相似文献   

3.
On the basis of the results derived by theoretical analysis [1] and laboratory physical modelling [2] of the circulation seawater and stratification, induced by buoyancy fluxes, the suggestion has been made that, possibly, the Black Sea currents system is three-layered. It has been supposed that an anticyclonic current flows in the basin. To verify this deduction, the data from MHI's archived dataset have been treated, and results from twoad hoc expeditions are submitted here. Analysis of the vertical structure of currents, based on thein situ velocity measurements, using various means and calculations of the geostrophic circulation, has confirmed that a flow with the theoretically predicted parameters may exist in the Black Sea. Translated by Vladimir A. Puchkin.  相似文献   

4.
Time-dependent wind drift currents in a basin with finite depth have been solved analytically in order to understand their fundamental behavior in coastal waters. The drift currents due to the land/sea breeze, as a typical example of time-dependent winds, have been examined with attention to the manner of their oscillation in their vertical profiles. The theoretical analysis indicates that the drift current due to the land/sea breeze might be amplified effectively around the southern part of Japan, where the oscillating period of the wind is near to the inertial period. The analysis of the physical process of the drift current reveals the following two important aspects: the Ekman boundary layer in a rotating frame is physically consistent with the Stokes boundary layer due to oscillating currents in an inertial frame, and so the inertial motion due to the wind is dispersed to the deeper level by the vertical viscosity in a rotating frame. The harmonic analysis was performed for the residual data after removal of the four main tidal constituents, M2, S2, K1 and O1, from the raw data observed in Suonada sound, the Seto Inland Sea. The feature of the analytically solved drift currents corresponded well to the observed picture. The vertical viscosity in this field has been estimated at 10−3 m2/s by adjusting the harmonically analytical result of the observed data to the vertical profile of the analytically solved drift current.  相似文献   

5.
我国南方强潮海岸红树植物对潮流的调制作用   总被引：2，自引：0，他引：2  
至今,关于红树植物对潮流的调制作用的研究非常有限,尤其是红树植物对垂向流速剖面的影响还不清楚。本研究利用自主研发的自动升降架于大潮期间对浙江南部乐清湾西门岛秋茄种植区的红树林滩进行垂向多点观测。结果表明,在所研究的红树林内,整个垂向剖面的流速普遍较低。树干和冠层引起的拖曳力在垂向上的增加,使得红树林内垂向流速剖面呈现"流速随距底高度增大而减小"的规律。此外,湍流能量密度在垂向上也呈现出与红树植物垂向结构相对应的变化。与光滩（半对数）和盐沼（近"J"形）内流速的垂向结构相比,红树植物以一种不同的方式对垂向流速剖面产生重要影响。  相似文献   

6.
Using thein situ currents measurements conducted during Cruise 41 of the R/VAkademik Vernadsky, we have considered the structure of the Guiana Current in winter over the shelf, continental slope and in the deep-water part of the ocean, adjoining the Brazilian coast. Regular variations of the current velocity with depth have been identified, and the current velocity's stability and variability determined. The paper examines how the barocline component of the hydrostatic pressure horizontal drop influences the current velocity's vertical profile. An attempt has been made to evaluate the current's transport. Translated by Vladimir A. Puchkin.  相似文献   

7.
The paper discusses a method for the statistical evaluation of the vertical current velocity componentV z(z) using data provided by profilers. The calculation of theV z(z) profiles involves the determination of the root-mean-square deviation of the error of determination of the vetical current velocity component at each level and the RMS deviation of the sample statistical variability of this quantity's estimates. ProfilesV z(z) have been computed for the north-western Black Sea using three surveys, with the involvement of an OLT profiler. The computations have shownV z(z) to have a two-layer structure, with zero being crossed in the main pycnocline. Such structure of the current velocity vertical component is consistent with the hydrodynamic model of the field of currents induced by buoyancy fluxes through the lateral boundaries of the basin. The availability of the zero values of the vertical current velocity in the pycnocline yields a tool for gaining insight into the mechanism controlling the emergence of the oxic/anoxic interface and areas with sharp vertical gradients of chemical and hydro-optical characteristics. Translated by Vladimir A. Puchkin.  相似文献   

8.
We analyze geostrophic currents with nonmonotonic vertical profiles, of velocity and present the distributions of the density of water and hydrostatic pressure corresponding to possible types of the vertical kinematic structure. To prove the existence of the indicated complex layered structures, we use, the data of instrumentalin situ measurements of currents in the Black Sea and in the west part of the Tropical Atlantic. Translated by Peter V. Malyshev and Dmitry V. Malyshev  相似文献   

9.
Quantifying the characteristics of the turbidity currents that are responsible for the erosion, lateral migration and filling of submarine channels maybe useful for predicting the distribution of lithofacies in channel fill and levee reservoirs. This paper uses data from a well-studied submarine channel in Amazon Fan in an attempt to reconstruct the velocity, thickness, concentration, duration, recurrence rates and vertical structure of turbidity currents in this long sinuous channel. Estimates of flow conditions are derived from the morphology of the channels and the characteristics of the deposits within them. In particular, the availability of information on the sediment distribution with respect to the channel topography at the time of deposition allows for insights into the vertical structure of the flow, a key property that has been so far poorly understood. Integration of flow constraints from well and seismic data or from detailed analysis of outcrop with numerical flow models is a critical step toward a complete understanding of the flow and associated deposits. Turbidity currents in sinuous submarine channels, exemplified by Amazon Channel, are found to last for tens of hours and occur on a regular, quasi-annual basis. Model results suggest that these flows had, on average, velocities ranging from 2 to 4 m/s in the canyon/upper fan which decreased to 0.5–1 m/s in the lower fan, travelling in excess of 800 km. The model turbidity currents were subcritical over most of the channel length, indicating a low degree of water entrainment and low rate of deceleration down the channel. The formation of such long, sinuous channels is intrinsically associated with frequent, long-duration, subcritical turbidity currents carrying a silt-dominated sediment load.  相似文献   

10.
To examine the surface circulation and vertical structure of currents in the region of the Keum River (KR) plume, we analyzed the subinertial surface currents obtained by high frequency radar and the vertical profiles of currents measured at a station (M1) located 10 km distance from the estuary mouth for one month in late spring 2008. Monthly-mean surface circulation is composed of the westward flow from the estuary mouth and the northward flow in the offshore. These surface mean currents are a gradient (geostrophic) current around the monthly-mean plume bulge. Dominant variabilities of the surface currents, winds, and KR-outflow are decomposed by the Empirical Orthogonal Functions (EOF). The first current EOF mode, explaining 39% of total variation, is primarily related to the first wind EOF mode varying along the coast and the second current mode, explaining 33% of total variation, is mainly related to the first KR-outflow EOF mode varying along the mean KR-outflow direction. Meanwhile, vertical profile of the monthly-mean current at M1 shows a two-layer structure of the current flowing offshore (onshore) in the upper (lower) layer because the water column is divided by a pycnocline at 7-9 m depths below the plume water. This two layer structure is a background persisting current structure, at least in spring, maintained by the geostrophic balance induced by the sea level slope and density gradient along the line normal to the westward mean surface current direction due to monthly-mean plume bulge off the KR estuary. EOF analysis of vertical current profiles reveals that the first mode, explaining 43% of total variation, represents the two-layer structure of the current variability. The upper-layer current varies along a line normal to the mainland coastline and the low-layer one varies approximately along a line parallel to the coastline, with direction difference of about 115° between the upper-and low-layer. From the correlation analysis it is found that 60% of the first mode variation is influenced by the first mode of KR-outflow and 36% by the first mode of wind. Any forcing modes of KR-outflow and wind influencing the other current vertical modes could not be found in the present study.  相似文献   

11.
南海环流的三维数值模拟   总被引：1，自引：0，他引：1  
本文采用Backhaus的三维海流模式,运用半隐式及C-网格方法求解基本方程,对南海各季的平均海流流场进行了数值模拟。将模拟结果与已有的研究结果进行比较,其主要流系基本上是相符的,夏季表层基本上为一反气旋型环流;冬季则转变成气旋型;在冬季,从50m层起开始显露出“南海暖流”的存在。这些表明南海海流的某些主要特征基本上已经被此模型成功地再现出来,同时此模型又给出了垂直方向各层的海流情况,在目前尚缺乏深层实测海流资料的情况下,上述深层海流的模拟结果有一定参考意义。  相似文献   

12.
潮流垂直结构的基本特征——理论和观测的比较   总被引：7，自引：0，他引：7  
关于潮流垂直结构的研究历来为海洋学家们所重视。这不仅因为它是海洋潮汐动力学的基本课题之一,而且对于其它海洋动力过程,如海洋湍流、物质扩散特别是沉积物的运动都有密切的关系。同时从事于军事、航运和海洋工程等工作的人员对此也十分关心。 对于潮流垂直结构的研究除了直接的现场观测外,理论研究大致可分两个方面。一个方面研究的侧重点是为了了解其基本特征,从定性方面来解释海洋中实际观测到的潮流垂直变化,指出哪些变化是具有普通意义的,这些变化主要与哪些因素有关,并且预测在观测中未曾注意到的而  相似文献   

13.
We describe the methodology and software developed for the numerical analysis of the characteristics of the horizontal and vertical structure of geostrophic currents. We present the results of computation of these characteristics according to the data of the summer survey of the Black Sea carried out as a part of the ComSBlack-92 program. The distinctive features of the space structure of geostrophic currents discovered as a result and the established parameters of their variability may supplement the existing data on the current field in the Black Sea.  相似文献   

14.
在我校与美国俄勒岗大学等单位联合黄河口调查期间,作者用简易方法对该区潮流铅直分布进行了专门观测。将获得的资料与一种浅海理论公式计算值进行了比较。首次计算了该区粗糙度参量Z_0值的分布。提出了最大潮流速铅直分布与相对粗糙度参量的关系。  相似文献   

15.
The vertical structure of the M2 tidal current in the Yellow Sea is analyzed from data acquired using an acoustic Doppler current profiler. The observed vertical profiles of the M2 tidal current are decomposed into two rotating components of counter-clockwise and clockwise, and restructured using a simple one-point model with a constant vertical eddy viscosity. The analyzed results show that the internal fictional effect dominates the vertical structure of the tidal current in the bottom boundary layer. In the Yellow Sea, the effect of the bottom friction reduces the current speed by about 20–40% and induces the bottom phase advance by about 15–50 minutes. In the shallower coastal regions, the effects of bottom topography are more prominent on the vertical structure of tidal currents. The vertical profile of the tidal current in summer, when the water column is strongly stratified, is disturbed near the pycnocline layer. The stratification significantly influences the vertical shear and distinct seasonal variation of the tidal current.  相似文献   

16.
This paper has two purposes. The first is to study the circulation and salinity in Hooghly Estuary, along the east coast of India and the second is to compare the performance of two turbulence closure schemes by modelling it. A breadth averaged numerical model using a sigma co-ordinate system in the vertical is briefly described. Vertical diffusion of momentum and salt are parameterized by a simple first-order turbulent closure or by a one equation model for turbulent kinetic energy (TKE) which uses a specified mixing length. The results are compared with the available neap and spring tide observations along the estuary for both low and high discharge periods.The computed elevations and currents are in reasonable agreement with the observations showing no major differences in vertical current profiles by both the turbulent schemes. However, there is a slight under-prediction of bottom currents. The salinity profiles predicted by TKE model show better matching with observations. Statistical tests are also conducted to study the comparative performance of the turbulent closure schemes. The maintenance of two layer structure in residual currents and salt variability are also studied by using the model.  相似文献   

17.
The 28.6 d time series of ADCP currents at 27 depth levels, (11,15,…,115m) which are obtained from a mooring station at the northern South China Sea continental slope, have been decomposed into barotropic and baroclinic components. The emphasis in this paper is on the analysis of the time series of baroclinic currents by means of several methods,such as the tidal harmonic analysis, the power spectra and the kinetic energy estimation.The major results are as follows: (1) In respect of the baroclinic currents, the values of several parameters first decrease and then increase with depth. These parameters include the temporal mean value of the cross-shelf component, the standard deviations, the amplitudes of K1 constituents, the mean eddy kinetic energy, as well as the significant peaks of the power spectra of the cross-shelf components. (2) The diurnal period of the baroclinic currents is dominant. The diumal tidal current rotates clockwise and the major axis of current ellipse is located along the directions of NW-SE. The vertical distribution of the phases of the diurnal constituent varies with the different water layers. Around the 67m depth level, the phase changes very much.At those layers far away from the 67m depth level, the vertical distribution of the phase is relatively stable, but with opposite phases in the upper and lower water layers. For the upper layers between the surface and 67m,the phases are around 300°; for the lower layers between 67m and 115m, the phases are around 120° .(3) The mean eddy kinetic energy of the baroclinic current is quite large, accounting for 41% of the mean kinetic energy of the measured currents. The cross-shelf component is larger than the along-shelf one. The two baroclinic current components correspond to the major and minor axes of the current ellipse of the diurnal constituent respectively. (4) The power spectra of the baroclinic currents show a singnificant period of about 24h, with 23.6h at both 19m and 99m and 24.4h at 55m. The vertical distributions of the significant spectra-peak values of the power spectra of both the crossshelf and along-shelf components of both the baroclinic currents are different. The former increases with depth, then decreases and finally increases again while the latter decreases with depth.  相似文献   

18.
Recent observations over the Sigsbee Escarpment in the Gulf of Mexico have revealed extremely energetic deep currents (near 1 m s−1), which are trapped along the escarpment. Both scientific interest and engineering needs demand dynamical understanding of these extreme events, and can benefit from a numerical model designed to complement observational and theoretical investigations in this region of complicated topography. The primary objective of this study is to develop a modeling methodology capable of simulating these physical processes and apply the model to the Sigsbee Escarpment region. The very steep slope of the Sigsbee Escarpment (0.05–0.1) limits the application of ocean models with traditional terrain-following (sigma) vertical coordinates, which may represent the very complicated topography in the region adequately, can result in large truncation errors during calculation of the horizontal pressure gradient. A new vertical coordinate system, termed a vanishing quasi-sigma coordinate, is implemented in the Navy Coastal Ocean Model for application to the Sigsbee Escarpment region. Vertical coordinate surfaces for this grid have noticeably gentler slopes than a traditional sigma grid, while still following the terrain near the ocean bottom. The new vertical grid is tested with a suite of numerical experiments and compared to a classical sigma-layer model. The numerical error is substantially reduced in the model with the new vertical grid. A one-year, realistic, numerical simulation is performed to simulate strong, deep currents over the Escarpment using a very-high-resolution nested modeling approach. The model results are analyzed to demonstrate that the deep-ocean currents in the simulation replicate the prominent dynamical features of the observed intense currents in the region.  相似文献   

19.
内潮对吕宋海峡地转流动力计算的影响   总被引：1，自引：0，他引：1  
利用2008年8~9月份吕宋海峡121°E断面上19.5°N~21°N之间4个连续站的CTD资料,讨论了内潮引起的温、盐剖面扰动对地转流诊断计算的影响,指出:在吕宋海峡,内潮引起的温、盐剖面扰动对地转流诊断计算的干扰不可忽略。因此,地转流诊断计算必须剔除温、盐剖面中的"内潮噪声"。另外,本文根据4个连续站时间平均后的温、盐剖面,通过动力计算法得到了吕宋海峡121°E断面上的地转流场,得出结论如下:吕宋海峡地转流速度较大部分多位于350 m以浅,流速最大值出现在表层;黑潮入侵南海主要发生于19.8°N~21°N的上层;在19.5°N~21°N之间,50~1 700 m深度范围内,海水体积通量呈现"上进下出"的垂向结构,350 m以浅为入流,流量约为2.6 Sv(1 Sv=1×106m3.s-1),350 m以深为出流,流量约为3.1 Sv。同期观测所得121°E断面上的盐度分布验证了本文所得地转流场的合理性。  相似文献   

20.
南海北部陆架陆坡区海流观测研究   总被引：3，自引：0，他引：3  
针对2006-2009年期间,南海北部陆架陆坡区3个站ADCP海流连续观测资料,采用功率谱分析、潮流调和分析方法,重点分析了陆架陆坡区100 m,200 m和1 200 m水深海域海流的垂向结构,探讨了环流的季节变化和空间分布特征,特别讨论了南海暖流和北陆坡流的时空变化特征。结果表明,陆架陆坡区潮流类型属于不规则日潮,深水站点中层表现为正规全日潮类型,垂向为"三层结构",甚至更加复杂。O1,K1,M2,S2等分潮总体上为顺时针旋转,在深水站点,基本表现为西北－东南走向的往复流形态。从能量角度看,表层和底层海流中,潮流所占份额较大,分别占30%~40%和40%~50%,中层较小,约为20%。对东沙群岛西南陆架陆坡区环流,观测计算结果证实了西向强流的存在,且垂向结构具有显著的季节变化,在200 m水深处没有明显的南海暖流,只是10~30 m以上层次存在逆风海流。海南岛以东海域连续15个月表层环流的结果表明,冬季明显受到南海暖流的影响,存在东北向的逆风海流,夏秋季的环流表现为西南向,流速较强,夏季也存在逆风情况,造成上述情形的原因可能是该地南海暖流的流轴具有季节性变化——冬季偏南,夏季偏北。  相似文献   

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