共查询到20条相似文献，搜索用时 15 毫秒
1.
利用普林斯顿海洋环流模式(POM)，通过一系列的理想试验，探讨了夏季长江冲淡水的扩展机制。结果表明：(1)倾斜底形是夏季长江冲淡水向东北偏转的一个必要条件；夏季冲淡水向东北偏转是南风、斜压效应和底形的共同作用的结果，其中风应力和底形的相互作用占主导地位；单纯的底形东倾不能使冲淡水向北偏转。平底时，南风和淡水浮力强迫都不能使冲淡水向北偏转。(2)无风时，人海淡水可以在河口附近强迫出一个反气旋涡旋和贴岸南下的狭窄的沿岸流，反气旋涡旋与淡水浮力强迫(斜压效应)有关，南下沿岸流则与质量输入有关；平底时，反气旋涡旋位于河口正东，倾斜底形时，反气旋涡旋向北拉伸，冲淡水的一部分沿岸向北扩展；人海淡水在河口附近强迫出一个闭合的垂直环流圈：上层为离岸流，淡水向外海扩展，约在离岸30—45km处有下降流；低层有高盐水沿海底流向河口，约在离河口。lOkm处与向海的径流相遇，引起上升流。 相似文献
2.
Kiyoshi Tanaka Yutaka Michida Teruhisa Komatsu Kenji Ishigami 《Journal of Oceanography》2009,65(2):165-177
We have investigated the spreading of river water in Suruga Bay by performing numerical experiments and conducting field surveys
with drifting buoys. There are clear seasonal variations in the large river discharges into the bay: increased discharge in
the rainy summer season and decreased discharge in the dry winter season. The numerical model reproduces the main feature
that has been observed in the actual sea: the river water extends gradually from the northwestern to the southeastern regions
in the bay, especially in summer. The river water spreading is greatly influenced by the bottom topography of the bay: the
Fuji River water spreads over a deep continental slope as a surface-advected plume and extends well offshore, since a large
bulge (anticyclonic eddy at the river mouth) extends well offshore and effectively transports the river water offshore. On
the other hand, the Oi River water tends to flow parallel to isobaths (along a coastline) on a shallow continental shelf as
a bottomadvected plume. Moreover, the influences of seasonal variations in the stratification and a bay-scale, wind-driven
circulation are also investigated. Trajectories of the drifting buoys, which were released around the Fuji River mouth, certainly
suggest that the bulge exists there. 相似文献
3.
建立了一个描述中尺度涡的新的非线性方程,然后利用变分原理研究了孤立涡旋的Liapunov稳定性,指出反气旋和气旋涡都是稳定的。数值计算结果发现在β效应的作用下这些涡旋都向西移动而不存在向南的移动,然而在反气旋涡的上游存在一个孤立地形(例如海山)的话,孤立地形会使反气旋涡向南移动,而且移动的轨迹取决于孤立地形的位置。当两个反气旋涡同时存在并发生相互作用时,上游孤立地形使这两个反气旋涡产生弱合并并出现弱分离。而且孤立地形的位置对这两个涡的移动和旋转有重要影响。 相似文献
4.
The seasonal variation of water circulation in the Seto Inland Sea is investigated using a high resolution, three-dimensional
numerical ocean model. The model results are assessed by comparison with long-term mean surface current and hydrographic data.
The simulated model results are consistent with observations, showing a distinct summer and winter circulation patterns. In
summer the sea water is highly stratified in basin regions, while it is well mixed near the straits due to strong tidal mixing
there. During this period, a cold dome is formed in several basins, setting up stable cyclonic eddies. The cyclonic circulation
associated with the cold dome develops from May and disappears in autumn when the surface cooling starts. The experiment without
freshwater input shows that a basin-scale estuarine circulation coexists with cyclonic eddy in summer. The former becomes
dominant in autumn circulation after the cold dome disappears. In winter the water is vertically well mixed, and the winter
winds play a significant role in the circulation. The northwesterly winds induce upwind (downwind) currents over the deep
(shallow) water, forming a “double-gyre pattern” in the Suo-Nada, two cyclonic eddies in Hiuchi-Nada, and anticyclonic circulation
in Harima-Nada in vertically averaged current fields. 相似文献
5.
Kiriaki Haralambidou Georgios SylaiosVassilios A. Tsihrintzis 《Estuarine, Coastal and Shelf Science》2010
The dynamics of a seasonally formed salt-wedge propagating along the micro-tidal channel of Strymon River estuary, Northern Greece, and its consequences on river water quality, are thoroughly studied through intensive sampling campaigns. The wedge is developed at the downstream river part, under the summer limited freshwater discharge conditions (Q < 30 m3/s). The geometric features of the wedge (length and thickness) appeared directly related to Strymon River discharge. A maximum intrusion length of 4.7 km along Strymon River estuary was observed under minimum river discharge of almost 6 m3/s. Relations produced from in situ data illustrate that limited river flow expands the wedge horizontally, reducing its vertical dimension, while higher flows lead to increased wedge thickness. Estuarine flushing time ranges between 0.2 and 1.5 days, exponentially dependent on Strymon River discharge. Wedge velocities depicted tidal asymmetry between tidal phases, with consistent inward motion, even under the ebb tidal stage. Strong vertical stratification prevails throughout the tidal cycle, proving the limited vertical mixing between the two layers, although higher interfacial stresses are produced in ebb. Bottom topography plays an interesting role in wedge propagation, as the presence of an underwater sill either prevents saline intrusion during flood or isolates the front of the wedge from its core at the ebb. Ecological consequences of salt-wedge propagation in Strymon River estuary are the frequent evidence of bottom hypoxic conditions and the increased TSS levels, leading to the occurrence of a turbidity maximum at the tip of the salt-wedge. Higher BOD and ammonium levels were mostly observed at the river end, associated to point and non-point pollution sources. Nitrates and silicates were found associated with freshwater fluxes, while ammonia levels were related to saline intrusions. The reduced phosphorus freshwater fluxes, resulting from phosphorus uptake at the upstream reservoir (Kerkini Lake) and the increased bottom turbidity induced by the salt-wedge seem responsible for the limited chlorophyll-a levels along Strymon River estuary. 相似文献
6.
LIAO Guanghong YANG Chenghao XU Xiaohu SHI Xingang YUAN Yaochu HUANG Weigen 《海洋学报(英文版)》2012,31(5):26-40
The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary wave propagation. An ocean eddy is produced by a quasi-geostrophic model in f-plane, and the one-dimensional nonlinear variable-coefficient extended Korteweg-de Vries (eKdV) equation is used to simulate an internal solitary wave passing through the mesoscale eddy field. The results suggest that the mode structures of the linear internal wave are modified due to the presence of the mesoscale eddy field. A cyclonic eddy and an anticyclonic eddy have different influences on the background environment of the internal solitary wave propagation. The existence of a mesoscale eddy field has almost no prominent impact on the propagation of a smallamplitude internal solitary wave only based on the first mode vertical structure, but the mesoscale eddy background field exerts a considerable influence on the solitary wave propagation if considering high-mode vertical structures. Furthermore, whether an internal solitary wave first passes through anticyclonic eddy or cyclonic eddy, the deformation of wave profiles is different. Many observations of solitary internal waves in the real oceans suggest the formation of the waves. Apart from topography effect, it is shown that the mesoscale eddy background field is also a considerable factor which influences the internal solitary wave propagation and deformation. 相似文献
7.
《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(2):245-266
During the autumn–winter of 1996–1997, drifting buoy trajectories and infrared satellite images provided new information on the characteristics of several mesoscale phenomena generated by the Algerian Current (AC) in the western Mediterranean Sea. A mesoscale event, as defined by previous studies, consists of a meander of the current associated with a surface anticyclonic eddy inside its crest, a transitory surface cyclonic eddy (Ec) upstream from the crest, and a deep anticyclonic eddy just below the meander. Most events propagate eastward along the coast at a few km per day until they are forced, mainly by the topography at the entrance to the channel of Sardinia, to detach from the coast and propagate seaward. They thus become open-sea anticyclonic eddies and generally complete an anticlockwise circuit in the Algerian basin. Surface buoys were launched upstream from an event and across it near 1°E. They made it possible to characterise the anticyclonic and cyclonic surface eddy features, and for the first time clearly showed the meander, which is in general not well depicted with images. It has thus been definitely demonstrated that most of the AC (speeds of several tens of cm/s) crosses the relatively slowly propagating events. As usual, the event we sampled reached a mature stage characterised by a vanishing of the Ec, and increased up to ∼100 km. Its arrest and decrease before it reached the channel of Sardinia, which is not so usual, was contemporaneous to the reappearance of the Ec and could be related to the growing of another coastal eddy upstream. At the entrance to the channel of Sardinia (near 7–8°E), the trajectories and images also documented another event which was larger (up to ∼120 km) and in the phase of detachment. Since the buoys drifted alternately to the west and to the east between this event and the coast, it is clear that an event can detach only temporarily and allow part of the AC to flow eastward directly. As indicated by infrared images, the definitive detachment occurred after all the buoys escaped from the event. The whole in situ and satellite data set is fully consistent with all the previous observations of the AC mesoscale variability, and quantitatively supports the proposed hypotheses for the event structure. It is consistent with laboratory experiments and some results of numerical models of coastal instability processes. 相似文献
8.
The development and evolution of the persistent counterclockwise circulation in Suo-Nada have been studied in detail using
a three-dimensional numerical model. The realistic circulation has been reproduced from the monthly climatological fields
of salinity, temperature along the open boundary, wind, heat flux and buoyancy input from twenty-two major rivers surrounding
the basin. The seasonal variation of fresh-water discharge from the rivers proved to be the most important forcing mechanism
driving the circulation. The expansion and contraction of coastal low salinity water well corresponded with the development
of counterclockwise circulation from spring to summer and dissipation from autumn to winter. The circulation was found to
be vertically homogenous and quasi-barotropic. However, confined along the coastal zone is an estuarine flow (i.e., oppositely
directed currents in the upper and lower layers) whose horizontal dimension conforms to the period of maximum buoyancy flux
from the rivers. This indicates that the flow pattern in Suo-Nada can be separated into two distinct regions where the relative
dominance of estuarine circulation plays a significant role. Furthermore, the monthly water exchange capacity for autonomous
purification of the basin has been evaluated from the average residence time of conservative material based on the calculated
current field. It is demonstrated that the kinetic energy of the basin is directly responsible in promoting water exchange
in Suo-Nada.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
This paper describes the water circulation in the Kuril Basin and its role in the formation and seasonal variation in intensity
of the large anticyclonic eddies which occur in the basin. Oceanographic data for the period June 1977 through June 1979 suggest
that these eddies develop in summer and decay in winter. In summer, the eddy development is associated with a deepening of
the isopycnals caused by the surface flow of the Soya Warm Current over the basin, and the deep advection of cold, less saline,
oxygen-rich water from Terpenia Bay and the eastern continental shelf of Sakhalin Island. In winter, the eddy decay is caused
by surface cooling and convective mixing downward of the warm, saline surface water, which causes the isopycnals to rise and
leads to an attenuation of the eddies. This combination of the summer influx of water into the region, and the fall and winter
cooling of the eddies leads to the annual variation in eddy intensity. 相似文献
10.
V. I. Kuzin G. A. Platov E. N. Golubeva 《Izvestiya Atmospheric and Oceanic Physics》2010,46(6):770-783
A numerical simulation with a coupled sea-ice model of the Arctic and North Atlantic oceans is used to study the influence
that the interannual variations in the Siberian river discharge have on the distribution and propagation of freshwater in
this region. In numerical experiments we compared simulations with the use of observational data on the discharge of the most
significant Siberian rivers (Ob, Yenisei, and Lena) against the results of climatic seasonally average variations of their
discharges. This comparison showed that the interannual variations may have significant consequences despite their smallness
when compared with oceanic-scale water transport. These consequences include (1) the intensification of either cyclonic or
anticyclonic components of motion of the subsurface Arctic Ocean waters and, as a result, the redistribution of freshwater
fluxes from Arctic regions between the Fram Strait and the straits of the Canadian Archipelago. A change in the store of fresh
Arctic Ocean waters due to interannual variations in the Ob, Yenisei, and Lena discharges is approximately ±400 km3, whereas the volume of water redirected in this regard, which forms a link between some straits, reaches 15 thousand km3. On the other hand, (2) insignificant changes in the propagation direction of freshwaters are multiply enhanced in the process
of their motion in the North Atlantic as part of the subpolar gyre because of their smaller or larger involvement in the processes
of vertical mixing. As a result of this, anomalies of freshwater develop considerably far from the river mouths, like in the
region of the Azores islands, and are 5–6 times larger than the maximum values of the accumulated variability volumes of the
river discharge. 相似文献
11.
通过对海洋中长生命反气旋涡在Ｇａｕｓｓ型孤立地形上演变的研究,发现地形对长生命反气旋涡的发展和传播有相当重要的影响。在无地形作用的情况下,仅有反气旋涡能够存在于向西的均匀基流中,这个涡是长生命的,并且在西移过程中有明显的向西倾斜。然而当其上游存在一个孤立地形时,可以发现这个涡有一个向东的倾斜,它的强度将增强且向西的移速会增加,其规迹象陀螺的运动。另一方面,当两个强度相同的反气旋涡同时存在时,这两个 相似文献
12.
A 3D,time-dependent,baroclinic,hydrodynamic and salinity model was implemented and applied to the Oujiang River estuarine system in the East China Sea.The model was driven by the forcing of tidal elevations along the open boundaries and freshwater inflows from the Oujiang River.The bottom friction coefficient and vertical eddy viscosity were adjusted to complete model calibration and verification in simulations.It is demonstrated that the model is capable of reproducing observed temporal variability in the water surface elevation and longitudinal velocity,presenting skill coefficient higher than 0.82.This model was then used to investigate the influence of freshwater discharge on residual current and salinity intrusion under different freshwater inflow conditions in the Oujiang River estuary.The model results reveal that the river channel presents a two-layer structure with flood currents near the bottom and ebb currents at the top layer in the region of seawater influenced on north shore under high river flow condition.The river discharge is a major factor affecting the salinity stratification in the estuarine system.The water exchange is mainly driven by the tidal forcing at the estuary mouth,except under high river flow conditions when the freshwater extends its influence from the river’s head to its mouth. 相似文献
13.
FPJ Nehama 《African Journal of Marine Science》2015,37(4):593-604
A model for the Zambezi River plume, the largest on the Indian Ocean coast of Africa, is presented and the results of experiments with different discharges and wind forcings are analysed. Although the river plays an important role in the southern African economy through power generation on large dams, artisanal fisheries, and frequent flooding events that impact greatly on local populations, the plume has not been well studied. Observations during the period 2004–2007, when the winds were mainly easterly or south-easterly, indicated that the plume waters can extend both downstream (equatorwards) and upstream (polewards) of the Zambezi Delta with a recirculating bulge near the river mouth. The model is constructed using the Regional Ocean Modeling System (ROMS), with a 40-km long, 3-km wide river discharging into a rectangular coastal ocean with a linearly sloping bottom. When the model is forced only by a constant river discharge of 1 000?m3 s?1 (typical of observed discharge amounts in summer), the Kelvin and Froude numbers for the resulting plume imply a ‘large-scale’ buoyant discharge with a coastal current that is close to being in geostrophic balance with the across-shore pressure gradient and a recirculating ageostrophic bulge near the mouth. The distributions of the bulge and plume waters are found to be relatively insensitive to the discharge amount. Under constant wind forcing, the plume distribution changes dramatically. Northerly and easterly winds produce the largest changes with the latter able to deflect the plume up to 180° due to Ekman drift. When sea breeze-like winds are imposed, accumulation of water in the bulge occurs with substantial spreading upstream. Stronger sea breezes lead to less downstream spreading of the plume than gentle winds. When the winds are mainly across-shore, Ekman drift dominates, but the dynamics become almost geostrophic when the winds are roughly aligned to the coast. These experiments suggest that the Zambezi River plume is sensitive to the winds on diurnal to synoptic time-scales. 相似文献
14.
青岛-石岛近海反气旋中尺度涡旋存在证据及数值模拟 总被引：3，自引：1，他引：2
系统整理的历史实测海流和温盐资料显示出青岛-石岛近海水域全年都存在着中尺度反气旋式涡旋运动.利用二维数值模式,首次模拟出该涡旋的存在,并对这一涡旋的形成机制进行了探讨,数值模拟结果和实测吻合良好.数值计算表明:在冬季盛行风的作用下,山东半岛南岸出现减水,迫使北上的黄海暖流中的一部分向西北方向延伸,在到达山东半岛近海后向右转向,形成东北向沿岸流,这样,与绕过山东半岛大约沿40～50m等深线南下的黄海沿岸流作用,在青岛-石岛近海形成一个中尺度反气旋涡旋.夏季由于偏南风的作用,致使山东半岛南部近海浅水区域海水都向东北方向流动,与沿黄海冷水团锋面南下的黄海沿岸流相作用,由于流速切变也形成了上述涡旋. 相似文献
15.
The continental slope in the northern South China Sea(SCS) is rich in mesoscale eddies which play an important role in transport and retention of nutrients and biota. In this study, we investigate the statistical properties of eddy distributions and propagation in a period of 24 years between 1993 and 2016 by using the altimeter data. A total of 147 eddies are found in the continental slope region(CSR), including 70 cyclonic eddies(CEs) and 77 anticyclonic eddies(ACEs). For those eddies that appear in the CSR, the surrounding areas of Dongsha Islands(DS) and southwest of Taiwan(SWT) are considered as the primary sources, where eddies generated contribute more than 60% of the total. According to the spatial distribution of eddy relative vorticity, eddies are weakening as propagating westward. Although both CEs and ACEs roughly propagate along the slope isobaths, there are discrepancies between CEs and ACEs. The ACEs move slightly faster in the zonal direction, while the CEs tend to cross the isobaths with large bottom depth change. The ACEs generally move further into the basin areas after leaving the CSR while CEs remain around the CSR. The eddy propagation on the continental slope is likely to be associated with mean flow at a certain degree because the eddy trajectories have notable seasonal signals that are consistent with the seasonal cycle of geostrophic current. The results indicate that the eddy translation speed is statistically consistent with geostrophic velocity in both magnitude and direction. 相似文献
16.
Path Transition of the Kuroshio Due to Mesoscale Eddies: A Two-Layer, Wind-Driven Experiment 总被引：1，自引：0，他引：1
We have executed numerical experiments using a two-layer, wind-driven ocean model with simplified coastal geometry and bottom
topography to investigate the possibility of the Kuroshio path transition due to mesoscale eddies. A straight path easily
changes into a meandering path due to the eddy action. For this transition, an anticyclonic eddy is preferable to a cyclonic
one when imposed in the beginning region of the Kuroshio (east of Taiwan). When imposed southeast of Kyushu, on the other
hand, a cyclonic eddy is more effective than an anticyclonic one. The reverse transition, from a meandering to a straight
path, did not occur at all in this experiment.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Numerical study on the interactions between a mesoscale eddy and a western boundary current 总被引：4，自引：3，他引：1
A reduced-gravity primitive equation eddy resolving model has been used to study the decay of a mesoscale eddy as it migrates
toward a western boundary current (WBC) region. The model results indicated that the gradient of the relative vorticity to
the east of the WBC is an important factor in the interaction between an eddy and a WBC. A circular eddy is deformed into
an elliptical form during the eddy–WBC interaction with the major axis of a cyclonic/anticyclonic eddy aligning in the NW/NNE
direction, respectively. Because of the difference in the major axes orientations for the cyclonic and anticyclonic eddies,
the kinetic energy transfer between a WBC and a particular eddy has very different behavior. A cyclonic eddy loses its energy
to the mean field, whereas an anticyclonic eddy can obtain energy from the mean flow during the WBC–eddy interaction. An anticyclonic
eddy, however, still decayed from losing its water and friction dissipation during the interaction period. 相似文献
18.
黑潮在冬季常以流套的方式入侵南海,并多伴随着反气旋涡的脱落,脱落的反气旋涡将黑潮高温、高盐水带入南海,影响南海东北部水文要素和声速场的空间分布,目前尚未有对黑潮流套脱落反气旋涡声学效应的研究。利用2009～2020年卫星高度计数据和再分析数据,在南海东北部选取了6个冬季黑潮流套脱落反气旋涡,研究了其水文和声场结构,并应用Bellhop高斯射线模型仿真给出了其对声传播的影响。结果表明:(1)6个黑潮脱落反气旋涡平均半径为110～135km,垂向深度可达1 000～1 200 m,最大旋转速度为0.4～0.6 m/s。反气旋涡中心暖水下沉,温度异常均为正异常,暖核位置位于100～250 m处,最大正异常达到2.5°C。中心盐度异常呈现负-正-负的三核结构。反气旋涡在100～900 m深度声速为正异常,最大正异常超过8 m/s,出现在400 m左右。(2)声波从涡外穿过涡旋和从涡内向外传播,当地形不会影响声线的反转时,会聚区的位置发生后移,后移的距离在5～10 km;当地形阻碍声线的反转时,声线与地形接触的位置不同,会聚区可能出现前移或后移,后移最大为29km,前移最大可达23km。(3)当... 相似文献
19.
20.
Anh Duc Nguyen Hubert H.G. Savenije Duc Nghia Pham Duc Thang Tang 《Estuarine, Coastal and Shelf Science》2008
The fresh water discharge is an important parameter for modelling salt intrusion in an estuary. In alluvial converging estuaries during periods of low flow, when salinity is highest, the river discharge is generally small compared to the tidal flow. This makes the determination of the fresh water discharge a challenging task. Even if discharge observations are available during a full tidal cycle, the fresh water discharge is seldom much larger than the measurement error in the tidal discharge. Observations further upstream, outside the tidal region, do not always reflect the actual flow in the saline area due to withdrawals or additional drainage. Discharge computation is even more difficult in a complex system such as the Mekong Delta, which is a multi-channel estuary consisting of many branches, over which the freshwater discharge distribution cannot be measured directly. This paper presents a new approach to determine the freshwater discharge distribution over the branches of the Mekong Delta by means of an analytical salt intrusion model, based on measurements made during the dry season of 2005 and 2006. It appears that the analytical model agrees well with observations and with a hydraulic model. This paper demonstrates that with relatively simple and appropriate salinity measurements and making use of the analytical salt intrusion model, it is possible to obtain an accurate discharge distribution over the branches of a complex estuary system. This makes the analytical model a powerful tool to analyze the water resources in tidal regions. 相似文献