共查询到19条相似文献，搜索用时 93 毫秒
1.
南海北部沿岸冬季水位亚潮波动特征研究 总被引：1，自引：0，他引：1
用时间序列分析方法研究了南海北部水位亚潮波动的基本特征。结果表明南海北部冬季水位亚潮波动能量以福建南部沿岸最强,广东沿岸仅为台湾海峡南部的一半左右,但二者具有相似的谱特征。各站的功率谱峰均出现在3.2,6.4,3.6和2.3d频带。其中3.2和6.4d波动能量最强。此外,在珠江口附近还有10.7d的较弱谱峰。与东海沿岸冬季情况类似,南海北部沿岸水位波动有很高的空间相关性,说明冬季我国东南沿海的亚潮波动受某一共同机制的控制。分析还表明水位波动一致地从东北向西南传播,但在不同岸段传播特征有相当差异。 相似文献
2.
珠江磨刀门河口亚潮频率水位的控制论研究 总被引：3，自引：0，他引：3
本文应用现代控制论研究河口非潮汐海平面变化及其与影响要素的关系。两年连续的水位及水文气象要素资料表明,在0.01—0.50cpd的频带上水位有相当高能的波动,这些波动的能量主要直接或间接来自风应力、河流径流以及河口外的海平面波动。本文应用1982年时间序列辨识了五个二阶的MISO CAR模型,系统输出是河口亚潮频率海平面;系统输入是河流人注流量、风应力和气压。模型检验后对1983年亚潮频率海平面进行一步和多步后报,符合良好。系统仿真定量地估计了各控制因素对水位的相对重要性。频域和时域分析都表明河口水位系统具有振荡特性。 相似文献
3.
《热带海洋学报》2017,(3)
文章为大亚湾潮汐动力学系列研究论文的第二部分,主要关注大亚湾双峰水位现象和涨潮流速双峰现象的产生机制。基于前人研究成果和数学解析方法,得出在大亚湾海域水位的双峰现象主要是由以M_2为代表的半日分潮与四分之一日分潮(如M_4分潮)和六分之一日分潮(如M-_6分潮)共同作用造成的。并对产生双峰水位和涨潮流速双峰的条件进行了数学解析,利用数值模拟结果发现,M_2/M_4分潮组合在大亚湾并不能产生双峰水位现象,而M_2/M_6分潮组合只能在大亚湾东北的范和港产生双峰水位现象。相对而言,M_2、M_4和M_6 3个分潮叠加的组合在双峰水位的产生范围和双峰间落差上都要大于上述2个分潮的组合。在大亚湾湾内区域,涨潮流速双峰可以由M_2/M_4分潮组合,M_2/M_6分潮组合和M_2/M_4/M_6分潮组合产生,M_2/M_4/M_6分潮产生的涨潮流速双峰强度要比另外两组分潮组合大。 相似文献
4.
台湾海峡冬季亚潮频水位波动的初步研究 总被引：4，自引：0，他引：4
冬季台湾海峡两岸水位存在较强亚潮频波动,西岸尤为显著.波动能量在32、10.7、4.6、3.6和2.9天频带出现谱峰.分析表明除主要由风场波动造成的埃克曼增减水(32、3.6天波动)外,海峡风场的波动还激发了周期为4.6和2.9天的陆架波,16天波动也具有陆架波的物理性质,但源于东海,非海峡风场所致. 相似文献
5.
《热带海洋学报》2017,(3)
文章作为大亚湾潮汐动力学系列研究的第一部分,展现了大亚湾水动力的最新观测结果,并借助于不规则三角网格海洋模式建立了高时空分辨率的三维潮汐潮流数值模型,重现大亚湾潮位和潮流变化状况。结合实测资料与模拟结果,得到了较以往更为精细的大亚湾潮波系统特征。浅水分潮,尤其是六分之一日分潮在大亚湾内快速增长,成为大亚湾潮波系统的显著特征。在大亚湾范和港M_6分潮振幅达到与M_4、S_2分潮相同的量级。大亚湾外开阔海域的潮流以旋转流为主,但进入湾内后潮流椭圆迅速扁平化,往复流占据主导。在湾内主要潮流通道内,M_6潮流椭圆主轴流速超过了M_4和K_1分潮。潮能通量分析揭示了大亚湾内高频分潮的强耗散,M_6分潮的能量耗散率和半日周期内耗散的总能量均超过了M_4、M_2和K_1分潮。观测到的欧拉余流表现出其湾内不一致的大小潮变化以及湾外所受沿岸流的影响。模拟出的欧拉余流则揭示了大亚湾内的余流多涡旋结构和水体弱交换能力。 相似文献
6.
磨刀门口夏冬季沿岸流特征及成因分析 总被引：1，自引：0，他引：1
根据2011—2012年磨刀门口的夏、冬季大、中、小潮定点观测资料,对欧拉余流、斯托克斯余流以及拉格朗日余流进行分析。结果表明:（1）外海测点的欧拉余流和拉格朗日余流,冬季在各潮型下均为一致的西南沿岸方向,夏季除东、西汊道点在强径流下表现为顺汊道指向外海方向,其余外海各点仍以西南沿岸方向为主;（2）斯托克斯余流远小于欧拉余流,夏季明显大于冬季,方向基本与欧拉余流相反;（3）冬季磨刀门口海域具有稳定西南向沿岸流特征,南海东北季风的驱动作用是其形成的主要原因;夏季磨刀门口各潮型下沿岸流特征各异,其影响的主要因素为径流和风,同时地形的影响不可忽略,特别是拦门沙形成的汊道分流作用,对强径流作用下水沙输移影响十分显著。 相似文献
7.
河口区斜压梯度对余水位的累积影响及其机制探讨 总被引：1，自引：1，他引：0
余水位（即潮平均水位）是河口区径潮相互作用的典型结果,研究其形成演变机制对探讨河口区的水资源高效开发利用具有重要科学意义。本文基于不同径潮边界条件下的三维斜压水动力数值模拟及切比雪夫机制分解,初步探讨了概化地形条件下斜压梯度对余水位沿程变化的影响。数值模拟结果表明:河口区余水位的沿程变化明显受径流量、潮波振幅、辐聚地形及斜压梯度等因素的共同影响,斜压梯度对余水位的影响是一种累积效应且影响区域集中在回水区,同时其影响强度具有明显的大小潮变化、洪枯季变化。利用数值模型提供的水位及流速场信息,通过切比雪夫分解非线性摩擦项分离出控制余水位变化的3个主要因素,即径流、潮流和径潮相互作用因子,并与斜压梯度产生的余水位进行对比分析,结果表明:回水区域余水位主要以径潮相互作用因子为主导;斜压梯度对余水位影响主要体现在小潮期间,有可能成为影响余水位变化的主控因子。 相似文献
8.
根据珠江河口磨刀门水道的三灶站、大横琴站、灯笼山站、竹银站2010年全年的逐时潮位资料,利用小波分析方法研究磨刀门河口区亚潮变化的周期特征。采用小波相干方法,分析亚潮与气压、风速、流量之间的相关关系。研究结果表明:(1)磨刀门河口亚潮主要存在5~6 d、14 d、21 d周期性波动。(2)亚潮5~6 d的周期波动的能量来源于气象要素及入海径流;亚潮14 d左右的周期波动的能量来源于天文大小潮、气象要素及入海径流的叠加效应;磨刀门水道下游站点亚潮21 d的周期性波动受到气象要素及入海径流的联合作用,而上游站点亚潮21 d的周期性波动主要受到入海径流因素的影响。(3)在不同季节,亚潮对气象要素的响应情况会产生不同影响。 相似文献
9.
10.
利用实测资料分析重构了大亚湾和大鹏湾潮汐水位“双峰”现象,确定了浅水分潮的异常增长是潮位“双峰”现象的主要成因,其中四分之一日分潮和六分之一日分潮起着至关重要的作用。通过SCHISM模型构建大亚湾和大鹏湾附近海域高分辨率水动力模型,模拟结果表明近岸海域,在大亚湾以东,潮汐类型为不规则全日潮,以西为不规则半日潮,在两个海湾内均为不规则半日潮;研究海域的潮流均表现为不规则半日潮流。四分之一日分潮和六分之一日分潮在大亚湾和大鹏湾的不同变形过程是造成两个相邻海湾水文差异的直接原因。通过构建不同底摩擦强度、消除水底地形以及改变海湾水深的数值实验研究表明,分潮传播方向与水深变浅方向是否一致,是导致两个海湾潮波浅水变形不同的根本原因。 相似文献
11.
The process of upwelling/sinking and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. Further,precipitation and monsoonal floods, apart from the marine meteorological parameters, are expected to influence the sea level fluctuations along the coast. This study comprises determining the sea level from the various parameters together with the pure wind stress forcing, which is compared with the observed cycle. However, it is found that there is considerable difference between the computations and observations. This suggests that the sea level is dependent not just on the local forcing alone, but also on the induced background circulation as well. For example, the sea level changes along the east coast of India, particularly the northern region, are more sensitive to freshwater discharge from various rivers joining the Bay of Bengal. This is due to more frequently occurring pre- and postmonsoon cyclonic storms and the associated surges in the Bay of Bengal as compared to the Arabian Sea. Hence the salinity effects are particularly important in the coastal waters off the east coast of India during monsoon months (June-September). For the west coast of India, however, it is expected that the large-scale coastal circulation may play a role in determining sea level changes in addition to other forcings. The salinity effects are negligible along the west coast in the absence of any major river systems that join the Arabian Sea. The local advection currents caused by the offshore directed freshwater discharge from various estuaries joining the coastal bay also seemed to influence the sea level. In order to elucidate the essential dynamics involved and to study the effect of the remote forcing, a three-dimensional baroclinic, nonlinear numerical model is used with appropriate open boundary conditions. The local effect of the current has been incorporated in the west coast model by means of opening a channel at Cochin through which the rainwater is carried away to the model ocean. The low saline plume, cascading from north along the east cost of India, has been incorporated in the east coast model through a proper forcing applied at the northern boundary of the model. With the inclusion of these remote forcings in the models, the disagreement between the simulations and the observations is minimized. 相似文献
12.
The process of upwelling/sinking and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. Further,precipitation and monsoonal floods, apart from the marine meteorological parameters, are expected to influence the sea level fluctuations along the coast. This study comprises determining the sea level from the various parameters together with the pure wind stress forcing, which is compared with the observed cycle. However, it is found that there is considerable difference between the computations and observations. This suggests that the sea level is dependent not just on the local forcing alone, but also on the induced background circulation as well. For example, the sea level changes along the east coast of India, particularly the northern region, are more sensitive to freshwater discharge from various rivers joining the Bay of Bengal. This is due to more frequently occurring pre- and postmonsoon cyclonic storms and the associated surges in the Bay of Bengal as compared to the Arabian Sea. Hence the salinity effects are particularly important in the coastal waters off the east coast of India during monsoon months (June-September). For the west coast of India, however, it is expected that the large-scale coastal circulation may play a role in determining sea level changes in addition to other forcings. The salinity effects are negligible along the west coast in the absence of any major river systems that join the Arabian Sea. The local advection currents caused by the offshore directed freshwater discharge from various estuaries joining the coastal bay also seemed to influence the sea level. In order to elucidate the essential dynamics involved and to study the effect of the remote forcing, a three-dimensional baroclinic, nonlinear numerical model is used with appropriate open boundary conditions. The local effect of the current has been incorporated in the west coast model by means of opening a channel at Cochin through which the rainwater is carried away to the model ocean. The low saline plume, cascading from north along the east cost of India, has been incorporated in the east coast model through a proper forcing applied at the northern boundary of the model. With the inclusion of these remote forcings in the models, the disagreement between the simulations and the observations is minimized. 相似文献
13.
14.
Kuo-Chuin Wong Brian Dzwonkowski William J. Ullman 《Estuarine, Coastal and Shelf Science》2009,84(4):440-446
The instantaneous sea level determined at two sites in the Murderkill Estuary, a tributary of Delaware Bay, results from the superposition of temporal variability operating over different time and spatial scales. Over the relatively short tidal time scales, the semidiurnal tides that represent the dominant tidal constituents in lower Delaware Bay show a modest increase in tidal amplitudes from the bay mouth (Lewes, Delaware), up to Bowers Beach (the mouth of the Murderkill Estuary). However, as the tides propagate into the Murderkill Estuary, the semidiurnal constituents undergo heavy attenuation, resulting in a 48% reduction in tidal amplitude from Bowers to Frederica (approximately the extent of saline intrusion). The diurnal tide, on the other hand, experiences only a 25% reduction in amplitude. The limited tidal asymmetry that is observed may be a result of interaction between flows in the tidal channel and the adjacent salt marsh. At longer time scales, the subtidal sea level experiences no attenuation. The Murderkill Estuary thus behaves like a low pass filter to preferentially damp out high frequency sea level forcing from lower Delaware Bay. The subtidal volume flux in the Murderkill is highly coherent with the time rate of change of sea level, indicating that the Murderkill basically co-oscillates with Delaware Bay in a standing wave fashion over the subtidal time scale. This remote coupling controls more than 90% of the variance in subtidal sea level in the estuary. The surface slopes in the lower bay and the Murderkill Estuary are closely correlated with winds along the orientation of the two waterways, consistent with the effect of local wind on subtidal sea level. 相似文献
15.
Air-Sea Interaction, Coastal Circulation and Primary Production in the Eastern Arabian Sea: A Review
Air-sea interaction, coastal circulation and primary production exhibit an annual cycle in the eastern Arabian Sea (AS). During
June to September, strong southwesterly winds (4∼9 m s−1) promote sea surface cooling through surface heat loss and vertical mixing in the central AS and force the West India Coastal
Current equatorward. Positive wind stress curl induced by the Findlater jet facilitates Ekman pumping in the northern AS,
and equatorward-directed alongshore wind stress induces upwelling which lowers sea surface temperature by about 2.5°C (compared
to the offshore value) along the southwestern shelf of India and enhances phytoplankton concentration by more than 70% as
compared to that in the central AS. During winter monsoon, from November to March, dry and weak northeasterly winds (2–6 m
s−1) from the Indo-China continent enhance convective cooling of the upper ocean and deepen the mixed layer by more than 80 m,
thereby increasing the vertical flux of nutrients in the photic layer which promotes wintertime phytoplankton blooms in the
northern AS. The primary production rate integrated for photic layer and surface chlorophyll-a estimated from the Coastal
Zone Color Scanner, both averaged for the entire western India shelf, increases from winter to summer monsoon from 24 to 70
g C m−2month and from 9 to 24 mg m−2, respectively. Remotely-forced coastal Kelvin waves from the Bay of Bengal propagate into the coastal AS, which modulate
circulation pattern along the western India shelf; these Kelvin waves in turn radiate Rossby waves which reverse the circulation
in the Lakshadweep Sea semiannually. This review leads us to the conclusion that seasonal monsoon forcing and remotely forced
waves modulate the circulation and primary production in the eastern AS.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
《African Journal of Marine Science》2013,35(4):525-536
As the Agulhas Current flows along the south-east coast of South Africa, a number of processes operate that bring cold, deep water up onto the narrow shelf. As a consequence, upwelling along the coastline is enhanced farther southward and downstream. This situation is investigated off Algoa Bay and along the south-east coast to Port Alfred, where measurements demonstrate that marked temperature variability occurs at the coastline, particularly in summer when temperature structures are more intense and easterly-component winds more common. There is no indication that upwelling is more prevalent at Port Alfred; increasing variability farther south is evident at Woody Cape/Cape Padrone, where the coastline veers westwards, forming the eastern boundary of Algoa Bay. Here it is found that, after a wind change to north-easterly, cold water is upwelled along the shoreline between 19 hours and 2.5 days later. Such upwelling progresses north-eastwards with the movement of the wind and weather systems, although colder water also moves south-westwards into Algoa Bay. Winds, currents, sea level and sea temperatures are highly correlated, with fluctuations in sea level measuring >50 cm being associated with coastal trapped waves (CTWs). Such barotropic wind-driven CTWs are frequently active during upwelling, although it is unclear whether there is any interaction between the two phenomena. 相似文献
17.
Long-term monthly sea level and sea surface temperature (SST) anomalies from central California show that during winter months, positive anomalies are associated with El Niño events and the negative ones with La Niña events. There is no significant impact on monthly mean anomalies associated with Pacific decadal oscillations, although there is a tendency for more extreme events and greater variance during positive decadal oscillations. The very strong 1997–1998 El Niño was analyzed with respect to the long-term historic record to assess the forcing mechanisms for sea level and SST. Beginning in the spring of 1997, we observed several long-period (>30 days) fluctuations in daily sea level with amplitudes of over 10 cm at San Francisco, California. Fluctuations of poleward long-period alongshore wind stress anomalies (AWSA) are coherent with the sea level anomalies. However, the wind stress cannot entirely account for the observed sea level signals. The sea level fluctuations are also correlated with sea level fluctuations observed further south at Los Angeles and Tumaco, Columbia, which showed a poleward phase propagation of the sea level signal. We suggest that the sea level fluctuations were, to a greater degree, forced by the passage of remotely generated and coastally trapped waves that were generated along the equator and propagated to the north along the west coast of North America. However, both local and remote AWSA can significantly modulate the sea level signals. The arrival of coastally trapped waves began in the spring of 1997, which is earlier than previous strong El Niño events such as the 1982–1983 event. 相似文献
18.
Yan Zhang Lili Zeng Qiang Wang Bingxu Geng Changjian Liu Rui Shi Na Liu Weiping Wang Dongxiao Wang 《海洋学报(英文版)》2021,40(7):88-99
The seasonal structure and dynamic mechanism of oceanic surface thermal fronts(STFs) along the western Guangdong coast over the northern South China Sea shelf were analyzed using in situ observational data, remote sensing data, and numerical simulations. Both in situ and satellite observations show that the coastal thermal front exhibits substantial seasonal variability, being strongest in winter when it has the greatest extent and strongest sea surface temperature gradient. The winter coastal thermal front begins to appear in November and disappears after the following April. Although runoff water is more plentiful in summer, the front is weak in the western part of Guangdong. The frontal intensity has a significant positive correlation with the coastal wind speed,while the change of temperature gradient after September lags somewhat relative to the alongshore wind. The numerical simulation results accurately reflect the seasonal variation and annual cycle characteristics of the frontal structure in the simulated area. Based on vertical cross-section data, the different frontal lifecycles of the two sides of the Zhujiang(Pearl) River Estuary are analyzed. 相似文献
19.
Characteristics of coastal trapped waves along the southern and eastern coasts of Australia 总被引：1，自引：0，他引：1
The spatial structures and propagation characteristics of coastal trapped waves (CTWs) along the southern and eastern coasts
of Australia are investigated using observed daily mean sea level data and results from a high-resolution ocean general circulation
model (OGCM), and by conducting sensitivity studies with idealized numerical models. The results obtained from the sea level
observations show that shortterm variations, with a typical period of 1 to 2 weeks, dominate the sea level variability in
the southern half of Australia. The signal propagates anticlockwise around Australia with a propagation speed of 4.5 m/s or
faster in the western and southern coasts and 2.1 to 3.6 m/s in the eastern coast. Strong seasonality of the wave activity,
with large amplitude during austral winter, is also observed. It turns out that the waves are mainly generated by synoptic
weather disturbances in the southwestern and southeastern regions. The numerical experiment with idealized wind forcing and
realistic topography confirms that the propagating signals have characteristics of the CTW both in the southern and eastern
coasts. Sensitivity experiments demonstrate that the difference in the phase speed between the coasts and reduction of the
amplitude of the waves in the eastern coast are attributed to the different shape of the continental shelf in each region.
The structures and the propagation characteristics of the CTWs around Australia are well reproduced in OFES (OGCM for the
Earth Simulator) with dominant contribution from the first mode, although meso-scale eddies may modify the structure of the
CTWs in the eastern coast. It is also found that generation or reinforcement of the waves by the wind forcing in the southern
part of the eastern coast is necessary to obtain realistically large amplitude of the CTWs in the eastern coast. 相似文献