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1.
《中国海洋大学学报(英文版)》2019,(6)
An improved method for computing the three-dimensional(3 D) first-order Lagrangian residual velocity(uL) is estab-lished. The method computes tidal body force using the harmonic constants of the zeroth-order tidal current. Compared with using the tidal-averaging method to compute the tidal body force, the proposed method filters out the clutter other than the single-frequency tidal input from the open boundary and obtains uL that is more consistent with the analytic solution. Based on the new method, uL is calculated for a wide bay with a longitudinal topography. The strength and pattern of uL are mostly determined by the parts of the tidal body force related to the vertical mixing of the Stokes' drift and the Coriolis effect, with a minor contribution from the advection effect. The geometrical shape of the bay can influence uL through the topographic gradient. The magnitude of uL increases with the increases in tidal energy input and vertical eddy viscosity and decreases in terms of the bottom friction coefficient. 相似文献
2.
There are two different modeling approaches which have been proposed and utilized to derive residual currents: the first approach
is equivalent to deducing residual currents from current-meter records using filtering techniques or time averages of time-series
records to remove tidal variations; in the second approach, filters or time averages over several tidal cycles are applied
to the hydrodynamic equations to generate the governing equations for residual circulation. Based on the latter, both the
baroclinic dynamic models of residual circulation are proposed, of which one is a two-dimensional transport model and the
other is a three-dimensional model with variable eddy viscosity. The two-dimensional transport model is a direct generalization
from the barotropic model of residual circulation presented by Nihoul and Randy (1975) and Heaps (1978) to the baroclinic
model. In the three-dimensional model with variable eddy viscosity, using a Sturm-Liouville system adopted in the reference
[5], the nondimensional problem for residual circulation reduces to the nondimensional problem of the elevation and the expression
of residual currents.
It should be pointed out that both the baroclinic models developed in the present paper are confined to describe the Eulerian
residual circulation only. 相似文献
3.
《山地科学学报》2021,(8)
The quadratic rheology model considers the yield stress, viscous stress, turbulent stress and disperse stress, so it is used in this study to derive the velocity profile of debris flows. The quadratic model with the parabolic eddy viscosity was numerically solved, and an analytical solution was derived for the quadratic model with a constant eddy viscosity. These two solutions were compared with the Arai-Takahashi model that excluded the viscous stress and the yield stress. The three models were tested by using 17 experiment cases of debris flows over rigid beds. The results prove that the quadratic model with parabolic and constant eddy viscosities is applicable to muddy and granular flows, whereas the Arai-Takahashi model tends to overestimate the flow velocity near the water surface if a plug-like layer exists. In addition, the von Karman constant and the zero-velocity elevation in the three models are related to sediment concentration. The von Karman constant decreases first and then increases as the sediment concentration increases. The zero-velocity elevation is below the bed surface, likely due to the invalidity of the non-slip boundary condition for the debris flows over fixed beds. 相似文献
4.
WANG Liang SHENG Jinyu 《中国海洋大学学报(英文版)》2005,4(4):349-356
An advanced ocean observatory has been established in Lunenburg Bay of Nova Scotia, Canada as part of an interdisciplinary research project of marine environmental prediction. The development of a high-resolution coastal circulation model is one of important components of the observatory. The model horizontal resolution is 60m and the vertical resolution is about 1 m. The coastal circulation model is used to simulate the semi-diurnal tidal circulation and associated nonlinear dynamics with the M2 forcing specified at the model open boundaries. The model is also used to simulate the storm-induced circulation in the bay during Hurricane Juan in September 2003, with the model forcing to be the combination of tides and remotely generated waves specified at the model open boundaries and wind stress applied at the sea surface. The model results demonstrate strong interactions between the local wind stress, tidal forcing, and remotely generated waves during this period. Comparison of model results with the surface elevation and current observations demonstrates that the coastal circulation model has reasonable skills in simulating the tidal and storm-induced circulation in the bay. 相似文献
5.
A numerical study of tidal asymmetry: preferable asymmetry of nonlinear mechanisms in Xiangshan Bay,East China Sea 总被引：1，自引：0，他引：1
In-situ measurements in Xiangshan Bay, the East China Sea, show that the duration of the rising tide is shorter than that of the falling tide around the bay mouth, while it becomes much longer in the inner bay. A finite volume coastal ocean model (FVCOM) with an unstructured mesh was applied to simulate the asymmetric tidal field of Xiangshan Bay. The model reproduced the observed tidal elevations and currents successfully. Several numerical experiments were conducted to clarify the roles of primary mechanisms underlying the asymmetric tidal field. According to the model results, the time-varying channel depth and nonlinear advection prefer shorter duration of the rising tide in Xiangshan Bay, while the time-varying bay width favors longer duration of the rising tide. The overtides generated by these two opposite types of nonlinear mechanisms are out of phase, resulting in smaller M4 amplitude than the sumfold of each individual contribution. Although the bottom friction as a nonlinear mechanism contributes little to the generation of overtide M4, it is regarded as a mechanism that could cause a shorter duration of the rising tide, for it can slow down the M2 phase speed much more than it slows down the M4 phase speed. The time-varying depth, nonlinear advection and bottom friction are dominating factors around the bay mouth, while the time-varying width dominates in the inner bay, causing the tidal elevation asymmetry to be inverted along the bay. 相似文献
6.
Feng Shizuo 《中国海洋湖沼学报》1984,2(2):177-187
Considerable scientific and practical interest exists in ascertaining the dynamic processes in shallow seas. This is especially
true for China having a vast area of shallow seas. To simulate the observed data and study the dynamical mechanism of waves
and currents in shallow seas a numerical model is developed in this paper. In view of the notable nonlinearity of shallow
sea waves and currents, and in order to solve the current distribution in the vertical direction, and to examine the effect
of variable eddy viscosity, the model proposed is a three-dimensional nonlinear one with variable eddy viscosity. The eddy
viscosity can be considered as a physically acceptable arbitrary function of depth, which is realized in terms of a Sturm-Liouville
System. The currents are expressed by using the eigenfunctions satisfying the Sturm-Liouville System just mentioned. A boundary-value
problem (or an initio-boundary-value problem) of free surface elevation is derived. And then, the application of the proposed
shallow sea model to nonlinear tides, ultra-shallow water storm surges and steady circulation is given, respectively. Finally,
a generalized linear law between the bottom friction and the transport is derived.
This paper was presented at the Joint Oceanographic Assembly (J.O.A.) held at Halifax, Canada, August 2–13, 1982, and included
in “Poster Abstract” Vol. I. 相似文献
7.
ＩＮＴＲＯＤＵＣＴＩＯＮＪｉａｏｚｈｏｕＢａｙｉｓａｓｈａｌｌｏｗｓｅｍｉ ｃｌｏｓｅｄｂａｙｗｉｔｈｔｏｔａｌａｒｅａｏｆａｂｏｕｔ 40 0ｋｍ2 ａｎｄａｖｅｒａｇｅｗａｔｅｒｄｅｐｔｈｏｆ7ｍ .Ｔｈｅｍａｘｉｍｕｍｗａｔｅｒｄｅｐｔｈｉｓｏｖｅｒ 5 0ｍａｔｔｈｅｃｅｎｔｅｒｏｆｔｈｅｓｔｒａｉｔｃｏｎｎｅｃｔｉｎｇｔｏｔｈｅＹｅｌｌｏｗＳｅａ.Ｔｈｉｓｓｔｒａｉｔｃｅｎｔｅｒｗａｔｅｒｉｓｃａｌｌｅｄｂａｙｍｏｕｔｈｗａｔｅｒ,ｔｈｅｗａｔｅｒｉｎｔｈｅｎｏｒｔｈｅｒｎｐａｒｔｏｆｔｈｅｓｔｒａｉ… 相似文献
8.
A hydro-dynamic model is established on basis of MIKE21 FM to simulate the hydro-dynamic characteristics of Xinghua Bay and investigate the influence of reclamation project on the tidal elevation and tidal currents. Tidal elevation data was obtained at the six tide gauge stations around the Xinghua Bay, and another six current stations were established to observe the tidal current velocity and direction. Validation shows that the model-simulated tidal elevation and tidal currents agree well with observations made at different stations. Predictions are made according to the reclamation project proposed in the regional marine planning of Hanjiang Industrial Park around the port in Putian City. The variations of hydro-dynamic factors, such as tide, current velocity and direction and tidal influx are obtained, and the adverse effect of reclamation on marine environment is discussed. It is shown that the tidal level inside the Xinghua Bay during high tide decreases after the reclamation project is completed. The tidal currents during flooding tide generally decrease in the southeast of the reclamation region, with the maximum decreasing amplitude reaching 0.44 m s-1. On the other hand, the tidal currents during flooding tide increase around the southeast and southwest corners of the reclamation region. The tidal currents during ebb tide increase around the southeast and southwest corners of the reclamation region, with the maximum increasing amplitude attaining 0.18 m s-1. The results in this paper can give some guidance for the marine environment management and the effective utilization of land in Putian. 相似文献
9.
A Lagrangian tracer model is set up for Hangzhou Bay based on Coupled Hydrodynamical Ecological model for Regional Shelf Sea
(COHERENS). The study area is divided into eight subdomains to identify the dominant physical processes, and the studied periods
are March (the dry season) and July (the wet season). The model performance has been first verified by sea-surface elevation
and tidal current observations at several stations. Eight tracer experiments are designed and Lagrangian particle tracking
is simulated to examine the impact of physical processes (tide, wind and river runoff) on the transport of passive tracer
released within the surface layer. Numerical simulations and analysis indicate that: (1) wind does not change the tracer distribution
after 30 days except for those released from the south area of the bay during the wet season; (2) the tide and the Qiantang
River runoff are important for particle transport in the head area of the bay; (3) the Changjiang River runoff affects the
tracer transport at the mouth of the bay, and its impact is smaller in the dry season than in the wet season.
Supported by the Natural Science Foundation of China (No.40576080); National High Technology Research and Development Program
of China (863 Program, No. 2007AA12Z182) 相似文献
10.
11.
Nonlinear numerical models of continuously stratified seas are developed for vertical sections to study the mechanism of coastal
upwelling and coastal jets in two kinds of seas: the so-called finite or closed sea bounded by two vertical coastal coasts,
without elevation of sea surface, but with a flat bottom; and the semi-infinite sea bounded by only one vertical coast, with
both an elevation of sea surface and a flat or inclined bottom. Constant wind stress in the first case, and constant wind
stress or negative wind stress curl in the second case, are abruptly imposed. The key procedure for the mathematical analysis
is to calculate the horizontal pressure gradient first by a special treatment. In the first case, the variation of horizontal
components of velocity is changed with time to show three successive time intervals. The results show that the width of baroclinic
jets depends upon (σS)1/2, and that distribution of isopycnic lines delineates the warm and cold regions. The relative importance of each term in the
equilibrium among forces is thus determined. Distribution of stream function in vertical section reveals the upper and bottom
Ekman layers. Two coastal jets are found with different alongshore velocities. The distribution of density anomalies displays
the horizontal diffusion adjustment. An unstable case appears at different surface boundary conditions. In the second case,
the vertical velocity will be stronger in the sea with less stratification, with an inclined bottom, and with a negative wind
stress curl. The horizonatal offshore velocity increases in strength in a sea with inclined bottom and with negative wind
stress curl. The vertical circulation pattern reveals the upwelling only. The distribution of density shows the isopycnic
lines lifted upward near the shores. Obviously, the range of elevation of sea surface near the shore is larger than that far
offshore. The jet width is less than the Rossby radius of deformation. A stronger jet will occur in more shallow water with
negative wind stress curl. The coastal jet does not develop when the coefficient of horizontal turbulence increases to a certain
limiting value. 相似文献
12.
《中国海洋湖沼学报》2021,(4)
Impact factors on the salinity budget,especially the eddy salt fluxes and smaller-scale diffusive salt fluxes for the upper 50 m of the Bay of Bengal(BoB) in 2014 are investigated using a box model based on the Regional Ocean Modeling System(ROMS) daily outputs.The model results reproduce that the precipitation and river runoffs are the dominant factors modulating the sharp salinity decrease during the summer monsoon season.The analysis shows that the salinity increase after the summer monsoon is mostly due to the meridional advective and diffusive salt fluxes.The vertical advective salt flux,which is sensitive to the different signals of the wind stress curl,plays an important role in balancing the salinity change induced by the meridional advective salt flux during both the summer and winter monsoon seasons.Distinctive spatial mesosc ale structures are presented in the eddy salt flux throughout the year,and their contributions are sizeable(over 30% in the meridional direction and about 10%-30% in the vertical direction).The meridional eddy salt flux is larger in the monsoon seasons than that in the inter-monsoon seasons,and in a positive pattern near the western boundary during the winter monsoon and autumn inter-monsoon.The vertical eddy salt flux makes an important contribution to the salinity budget,especially along the coastal area and around the Andaman and Nicobar Islands.The vertical eddy salt flux becomes large when a tropical cyclone passes the area. 相似文献
13.
Zhao Shiqing 《中国海洋湖沼学报》1986,4(2):171-182
A generalized finite difference scheme is presented for the solution of two-dimensioned tidal current equations (averaged
over the depth of water). This method has been used to simulate the tidal currents in the Changjiang River estuary, with computed
results being in good agreement with the field observations. The two-dimensional domain consists of triangular elements with
acute angles. First- and second-order partial derivatives are defined at nodal points. In addition, the basic tidal current
equations contain an extra term to account for horizontal eddy viscosity. The method has the great advantage of allowing a
wide flexibility in configuration simulation, thereby exhibiting the capability to arbitrarily subdivide the region of interest
as well as to provide a more accurate boundary shape, and what is more, it offers savings in computing costs.
This paper was published in Chinese in the Ocean. et Limn. Sinica.16(1):18–27, 1985 相似文献
14.
????GRACE?????????????????P3M6?????????????350 km?????????????????????????2004?????????Mw9.3????????????????????????????????????????????????仯??4.6 μGal??????????????仯?????-8.3 μGal???y????????λ????????????????????????????н????????????7 a????????????仯????5.6 μGal?????????仯???|?????????????????仯???0.6 μGal????????仯????11%????????????????????????????????????????????????????????????????????????Ч??????????Σ???????????????仯|???????????????????????????????????????????????????????????μ??????仯????С?? 相似文献
15.
Resonance due to critical slope makes the internal wave generation more effectively than that due to supercritical or subcritical slopes(Zhang et al., 2008). Submarine ridges make a greater contribution to ocean mixing than continental margins in global oceans(Müller, 1977; Bell, 1975; Baines, 1982; Morozov, 1995). In this paper, internal wave generation driven by tidal flow over critical topography is examined in laboratory using Particle Image Velocimetry(PIV) and synthetic schlieren methods in synchrony. Non-tidal baroclinic velocities and vertical isopycnal displacements are observed in three representative regions, i.e., critical, outward-propagating, and reflection regions. Temporal and spatial distributions of internal wave rays are analyzed using the time variations of baroclinic velocities and vertical isopycnal displacement, and the results are consistent with those by the linear internal wave theory. Besides, the width of wave beam changes with the outward propagation of internal waves. Finally, through monitoring the uniformly-spaced 14 vertical profiles in the x-z plane, the internal wave fields of density and velocity fields are constructed. Thus, available potential energy, kinetic energy and energy fluxes are determined quantitatively. The distributions of baroclinic energy and energy fluxes are confined along the internal wave rays. The total depth averaged energy and energy flux of vertical profiles away from a ridge are both larger than those near the ridge. 相似文献
16.
从大地测量学的角度论述了垂线偏差概念从传统到现代的发展和演变,比较全面地探讨了现代垂线偏差的含义和测定方法。通过对垂线偏差量级和误差大小的具体分析,得出结论一般长周期的、幅度较小的非潮汐变化要小于潮汐变化,但短周期的、幅度较大的非潮汐变化则可能与潮汐变化相当,个别地区甚至还会超过潮汐变化,这种情况完全可以用重复重力测量的方法检测到,这也说明重复测量的方法是可行的。 相似文献
17.
TOPEX/POSEIDON altimeter data from October 1992 to June 2002 are used to calculate the global barotropic M2 tidal currents using long-term tidal harmonic analysis. The tides calculated agree well with ADCP data obtained from the South China Sea (SCS). The maximum tide velocities along the semi-major axis and semi-minor axis can be computed from the tidal ellipse. The global distribution of M2 internal tide vertical energy flux from the sea bottom is calculated based on a linear internal wave generation model. The global vertical energy flux of M2 internal tide is 0.96 TW, with 0.36 TW in the Pacific, 0.31 TW in the Atlantic and 0.29 TW in the Indian Ocean, obtained in this study. The total horizontal energy flux of M2 internal tide radiating into the open ocean from the lateral boundaries is 0.13 TW, with 0.06 TW in the Pacific, 0.04TW in the Atlantic, and 0.03 TW in the Indian Ocean. The result shows that the principal lunar semi-diurnal tide M2 provides enough energy to maintain the large-scale thermohaline circulation of the ocean. 相似文献
18.
基于GRACE重力卫星数据,采用P3M6去相关滤波技术、350 km半径的高斯平滑技术与差分方法,提取2004年苏门答腊Mw9.3地震的同震和震后重力场时空演化过程。该地震断层下盘同震重力变化达到4.6 μGal,上盘同震重力变化最大值为-8.3 μGal,该结果与球体位错理论计算结果在量级和分布形态上具有较好的一致性。震后7 a断层下盘重力变化累计达到5.6 μGal,超过同震变化信号|而断层上盘震后重力变化只有0.6 μGal,仅为同震变化信号的11%。该现象表明,断层下盘所在海洋地层的粘滞性较低,地层相对柔软,其地层在震后由于较大的粘滞性松弛效应而持续变形,并伴随较大的重力变化|而断层上盘所在的地层接近陆地地壳特性,地层相对脆硬,震后受地层的粘滞性响应而导致的重力变化相对较小。 相似文献
19.
潮滩是陆地与海洋之间重要的生态过渡地带,具有复杂的生态过程和重要的服务功能。受陆海交互作用及人类活动的影响,潮滩处于高度动态变化过程中,而传统测绘技术受到潮滩可达性影响无法快速获取潮滩地形信息。为解决潮滩高程数据获取困难的问题,本文提出一种基于潮汐动态淹没过程和时序遥感影像的潮滩地形信息提取算法,利用K-means++聚类方法实现水域提取,并通过时序淹没特征计算潮滩淹没频率提取潮滩范围信息,最终综合区域潮汐特征反演潮滩地形。研究以崇明东滩为例,利用2016—2020年所有可用Sentinel-2和Landsat-8时序遥感影像,实现潮滩范围提取与高程反演,并通过实测高程数据进行精度验证。研究结果表明,潮滩范围提取总体精度为97.73%,F1_score为0.98;高程反演平均绝对误差为0.15 m,潮滩高程的反演精度与可用影像的数量呈正相关。研究利用该算法进一步反演长江口地区主要潮滩地形特征,结果表明区域内潮滩面积为346.93 km2,高程范围为1.00~3.84 m,且与现有潮滩范围数据集相比,本研究提取的长江口潮滩范围更为完整。该算法为潮滩地形的快速反演提供了可能,对潮滩资源动态监测和管理具有重要意义。 相似文献
20.
Xiamen Bay in South China has experienced extensive coastal exploitation since the 1950s,resulting in some severe environmental problems.Local authorities now have completed or are implementing many environmental restoration projects.Evaluating the cumulative impact of exploitation and restoration activities on the environment is a complicated multi-disciplinary problem.However,hydrodynamic changes in the bay caused by such coastal projects can be characterized directly and definitively through numerical modeling.This paper assesses the cumulative effect of coastal projects on the hydrodynamic setting using a high-resolution numerical modeling method that makes use of tidal current speeds and the tidal prism as two hydrodynamic indices.Changes in tidal velocity and the characteristics of the tidal prism show that hydrodynamic conditions have declined from 1938 to 2007 in the full-tide area.The tidal current speed and tidal prism have decreased by 40% in the western part of the bay and 20% in the eastern part of the bay.Because of the linear relationship between tidal prism and area,the degraded hydrodynamic conditions are anticipated to be restored to 1972 levels following the completion of current and proposed restoration projects,i.e.33% and 15% decrease in the hydrodynamic conditions of 1938 for the western and eastern parts of the bay,respectively.The results indicate that hydrodynamic conditions can be restored to some extent with the implementation of a sustainable coastal development plan,although a full reversal of conditions is not possible.To fully assess the environmental changes in a region,more indices,e.g.,water quality and ecosystem parameters,should be considered in future evaluations. 相似文献