共查询到20条相似文献，搜索用时 449 毫秒
1.
We performed investigations of synoptic variability of bottom and surface currents, the flow rate of the Mzymta River, and the wind speed measured with high resolution (10 min periodicity) in the coastal zone of the city of Sochi in May 2009, 2010, 2011, and 2012. Based on the measurements, a Fourier spectral analysis and harmonic analysis were carried out for both low-frequency and high-frequency components of the variability of the current velocities and wind speed. The analysis revealed a similarity of the structures of the main oscillation periods for the currents in the low-frequency spectrum and significant fluctuation periods for the currents in the high-frequency range. In addition, we studied the internal waves generated by the river plume. 相似文献
2.
S. G. Boguslavsky L. A. Koveshnikov S. T. Kaminsky A. A. Markov 《Physical Oceanography》1992,3(5):357-365
Principal regularities of the coastal velocity field formation have been revealed on the basis of processing and analysis of multi-annual measurements of currents at a bold coast. The influence produced by the coastline, the wind force and its spatial-temporal variability, pycnocline, and the general circulation pattern on this field is estimated. The seiche and inertial currents in this region are characterized. Patterns of the transversal upwelling-downwelling circulations are developed for winter and summer.Translated by Mikhail M. Trufanov. 相似文献
3.
The Southern Ocean plays an important role in the global overturning circulation as a significant proportion of deep water is converted into intermediate and deeper water masses in this region. Recently, a secular trend has been reported in wind stress around the Southern Ocean and it is thought theoretically that the strength of the ACC is closely related to wind stress, so one consequence should be a corresponding increase in ACC transport and hence changes in the rate of the global overturning. There are no long-term data sets of ACC transport and so we must examine other data that may also respond to changing wind stress. Here we calculate surface currents in Drake Passage every seven days over 11.25 years from 1992 to 2004. We combine surface velocity anomalies calculated from satellite altimeter sea surface heights with measured surface currents. Since 1992, the UK has regularly occupied WOCE hydrographic section SR1b across the ACC in Drake Passage. From seven hydrographic sections surface currents are estimated by referencing relative geostrophic velocities from CTD sections with current measurements made by shipboard and lowered acoustic Doppler current profilers. Combining the seven estimates of surface currents with the altimeter data reduces bias in the estimates of average currents over time through Drake Passage and we show that surface current anomalies estimated by satellite and in situ observations are in good agreement. The strongest surface currents are found in the Subantarctic and Polar Fronts with average speeds of 50 cm/s and 35 cm/s, respectively and are inversely correlated, so that maximum westward flow in one corresponds to minimum westward flow in the other. The average cross-sectional weighted surface velocity from 1992 to 2004 is 16.7 ± 0.2 cm/s. A spectral analysis of the average surface current has only weakly increasing energy at higher frequencies and there is no dominant mode of variability. The standard deviation of the seven day currents is 0.68 cm/s and a running 12 month average has only a slightly smaller standard deviation of 0.52 ± 0.16 cm/s. The southern annular mode (SAM) measures the circumpolar average of wind stress and like the surface currents its spectrum has slightly increased energy at frequencies greater than 1 cpy. A cospectral analysis of these, averaging cospectra of five slightly overlapping 36 month segments improve statistical reliability, suggests that there is coherence between them at 1 cpy with the currents leading changes in the Southern annular mode. We conclude that the SAM and average Drake Passage surface currents are weakly correlated with no dominant co-varying modes, and hence predicting Southern Ocean transport variability from the SAM is not likely to give significant results and that secular trends in surface currents are likely to be masked by weekly and interannual variability. 相似文献
4.
We generalize the problem of evaluation of currents caused by the action of breeze winds to the three-dimensional case. In
the “solid-lid” approximation, the problem is reduced to the numerical solution of a two-dimensional equation for the integral
current function (with complex-valued coefficients) with subsequent evaluation of the components of current velocity according
to analytic formulas. The breeze is specified as acting in a narrow coastal strip in the form of a zonal wind. The three-dimensional
structure and the variations of currents near the west boundary of the Kerch Strait as functions of time are studied in detail. 相似文献
5.
V. B. Titov 《Physical Oceanography》1993,4(1):63-69
Average and extreme values of the current velocity, seawater temperature, and their standard deviations are considered on the basis of measurements carried out at three moorings deployed in the Florida Strait. The contributions of the low-frequency (synoptic) and mesoscale variations of currents and the seawater temperature to their temporal variability are estimated. The kinetic energy values of the averaged current and the synoptic and mesoscale variations are given. Their contributions to the general (total) kinetic energy of currents are determined. It is shown that the pulsations of the north-east trade wind can be one of the reasons for the synoptic variations in the field of currents and seawater temperature.Translated by Mikhail M. Trufanov. 相似文献
6.
利用三维斜压流体动力学模型 ,通过对东海沿岸海区冬、夏季的斜压环流及其温盐结构的数值研究 ,揭示研究海区垂直环流及其温盐结构的动力过程及其成因。垂直环流的模拟结果表明 :冬季 ,沿岸海区的垂直环流以逆时针流动 ,近表层为向岸流 ,沿岸为下降流 ,近表层以下为离岸流 ,其在外海有明显的上升趋势 ,沿岸下降流自表层至底层逐渐由强变弱 ;夏季 ,沿岸海区的垂直环流以顺时针流动 ,近表层以下为向岸流 ,沿岸为上升流 ,近表层为离岸流 ,其在外海有明显的下降趋势 ,沿岸上升流自底层至表层逐渐由弱变强。就整个沿岸海区而论 ,冬季沿岸下降流和夏季沿岸上升流的强度都随着岸界地形坡度、风速及风向与岸线偏角的变化而变化。沿岸下降流形成的主要原因是由于冬季东北风与岸界地形的耦合效应及海区温盐分布不均匀所致 ,而沿岸上升流形成的主要原因则是由于夏季西南风与岸界地形的耦合效应及海区温盐分布不均匀所致。 相似文献
7.
Data on the Tsushima Current and its neighboring coastal current are analyzed to examine short-term variability of the currents and storm events due to typhoons. A three current-meter array was deployed in a strong current region of the east Tsushima channel during summer in 1983 and 1984, and other two current-meter arrays in the eastern coastal area of the channel (the Sea of Genkai) in the summer and autumn in 1983. The observations of coastal current show that the kinetic energy of the subtidal current component was larger in summer than in autumn by a factor of about 2. A comparison of the wind stresses and the estimated values of mixed layer depth in the summer and autumn season suggest that this seasonal change is closely associated with that of the mixed layer depth rather than with that of the wind stress. The Tsushima Current was greatly influenced by two storm events: its speed increased by a factor of 2 in one event and decreased to nearly zero in the other. Such a large variation of mean current during the storm was observed only for the Tsushima Current and not for the coastal current, suggesting that the Tsushima Current may temporarily change its regular course as a result of a storm. 相似文献
8.
Using a combination of Quick Scatterometer (QuikSCAT), Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E),
and Lagrangian drifter measurements, we demonstrate that wind data alone are not sufficient to derive ocean surface stress
(momentum flux) over mid-latitude ocean fronts, specifically the Kuroshio Extension. There was no continuous and large-scale
stress measurement over ocean until the launch of the scatterometers. Stress had been derived from winds through a drag coefficient,
and our concept of stress distribution may be largely influenced by our knowledge of wind distribution. QuikSCAT reveals that
the variability of stress could be very different from wind. The spatial coherence between the magnitude of stress and sea
surface temperature (SST), between the divergence of surface stress and the downwind SST gradient, and between the vorticity
of stress and crosswind SST gradient, are the inherent characteristics of stress (turbulence production by buoyancy) that
would exist even under a uniform wind field. The coherence between stress vorticity and SST gradient is masked by the rotation
of ocean currents over the Kuroshio meanders. Surface stress rotates in the opposite direction to surface currents because
stress is the vector difference between wind and current. The results are in agreement with a previous study of the Agulhas
Extension and confirm the unique stress measuring capability of the scatterometer. 相似文献
9.
根据浙江中部近海2018年4月—2018年10月的近岸锚系流速观测数据和同步的风速风向数据,结合锚系点周边水域全潮大、中、小潮水文观测资料,进而分析了该海域水流的变化特征。锚系点余流主要沿着与等深线平行的方向(东北-西南向),余流散点图的主轴方向为25.5°(东北偏北向),沿着主轴方向的余流与垂直于主轴方向的余流标准差分别为0.12m/s和0.02m/s。余流北分量和风速北分量具有良好的相关性,两者月平均时间序列的相关系数达到了0.96,逐时整点时间序列的相关系数为0.69。锚系点余流具有13.37 d和28.49 d的周期性变化特征,该周期与大、小潮的更替周期非常接近。小潮期间,潮流的强度相对较弱,余流对风的响应较为显著,余流和风的相关性较好,两者相关系数为0.72;而在大潮期间,潮差较大且潮流流速较强,余流和风的相关性相对较差,两者相关系数为0.30。本研究,得到了锚系点及其周边水域的流速分布特征,初步获悉天文潮和风场等的非线性作用对研究区域潮流和余流的影响,可以为浙江中部沿岸海洋开发和环境保护提供动力学方面的依据。 相似文献
10.
太湖大浦口湖区湖流特征分析 总被引：1，自引：0，他引：1
湖流是造成湖泊污染扩散,泥沙起动与输移等过程的主要动力学因素。构成湖水运动的物理机制很杂。风将其部分能量传给湖水,湖水在湖盆形态因素制约下,在吸收风能的同时,产生摩擦流。在派生力场,水位压力梯度场的作用下,形成风波流及补偿流。另外,由于湖水定振振荡而引起的波流也是重要形式。湖泊中以密度流和吞吐流形式存在的流场一般较弱。本文所分析的湖流,实为各种形式湖流的合成流。 相似文献
11.
近海海流受多种动力过程及岸线岛屿的作用呈现空间和时间尺度上的复杂变化,而地波雷达由于其探测面积广、时间分辨率高的特点成为研究这些变化的有效手段。本文利用舟山海域多年高频地波雷达资料,通过潮流调和分析、低通滤波和相关性分析对该海域海流潮周期、极端事件、季节、年际尺度的动力过程进行了解译。研究表明,舟山海域属于正规半日潮,潮流运动形式以顺时针旋转流为主,流速大小在空间上为东北方向较大,往西南方向逐渐减小,并在近岸处得到增强。余流的年际变化并不显著,但存在着明显的季节变化,例如冬季为南向流,流速减小,空间分布上近岸较外海大,而夏季与之反向,为北向流,流速较大,空间分布较为均匀。进一步分析了风与余流之间的相关性,在大风期间,风与余流的速度相关系数在0.48～0.90之间,方向相关系数在0.55～0.68之间。极端事件发生时,速度、方向的相关系数分别高达0.92与0.91。总体而言,通过分析高频地波雷达数据能够较好地反映舟山海域海流的时空特征,为海洋灾害监测和污染物、藻华的输运研究提供依据。 相似文献
12.
A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 ×10 -3 cm s -1 is predicted in July in the southern region off the coast. 相似文献
13.
A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 2 10 -3 cm s -1 is predicted in July in the southern region off the coast. 相似文献
14.
B.T. Kuebel Cervantes J.S. Allen 《Deep Sea Research Part II: Topical Studies in Oceanography》2006,53(25-26):2956
The three-dimensional circulation on the continental shelf off northern California in the wind events and shelf transport (WEST) experiment region during summer 2001 is studied using the primitive equation regional ocean modeling system (ROMS). The simulations are performed with realistic topography and initial stratification in a limited-area domain with a high-resolution grid. Forcing consists of measured wind-stress and heat flux values obtained from a WEST surface buoy. The general response shows a southward coastal upwelling jet of up to and a weakening or reversal of currents inshore of the jet when upwelling winds relax. Model results are compared to WEST moored velocity and temperature measurements at five locations, to CODAR surface current observations between Pt. Reyes and Bodega Bay, and to hydrographic measurements along shipboard survey lines. The model performs reasonably well, with the highest depth-averaged velocity correlation (0.81) at the inshore mooring (40 m water depth) and lowest correlation (0.68) at the mid-depth mooring (90 m depth). The model shows generally stronger velocities than those observed, especially at the inshore moorings, and a lack in complete reversal of southward velocities observed when upwelling winds relax. The comparison of surface velocities with CODAR measurements shows good agreement of the mean and the dominant mode of variability. The hydrography compares closely at the southern and northern edges of the survey region (correlation coefficients between 0.90 and 0.97), with weaker correlations at the three interior survey lines (correlation coefficients between 0.44 and 0.76). Mean model fields over the summer upwelling period show slight coastal jet separation off Pt. Arena and significant separation off Pt. Reyes. The cape regions also experience relatively strong bottom velocities and nonlinearity in the surface flow. Across-shelf velocity sections examined along the shelf reveal a double jet structure that appears just north of Bodega Bay and shows the offshore jet strengthening to the south. We examine the dynamics during an upwelling and subsequent relaxation event in May 2001 in which the WEST measurements show evidence of a strong flow response. The alongshelf variability in the upwelling and relaxation response introduced by Pt. Reyes is evident. Analysis of term balances from the depth-averaged momentum equations helps to clarify the event dynamics in different regions over the shelf. A clear pattern in the nonlinear advection term is due to the spatial acceleration of the southward jet around the capes of Pt. Arena and Pt. Reyes during upwelling. Results from a three-dimensional Lagrangian analysis of water parcel displacement show significant southward displacement in the coastal jet region, including a strong signal from the double jet. Alongshelf variability in parcel displacements and upwelling source waters due to the presence of Pt. Arena and Pt. Reyes is also apparent from the Lagrangian fields. A cyclonic eddy-like recirculation feature offshore of Pt. Arena prior to the upwelling event causes large patches of onshore-displaced parcels. Additionally, across-shelf variability in the response of water parcels along the D line includes decreased vertical displacement and increased alongshelf displacement in the offshore direction. 相似文献
15.
D. V. Ivonin V. A. Telegin P. V. Chernyshov S. A. Myslenkov S. B. Kuklev 《Oceanology》2016,56(4):591-600
We present the results of development and testing of a coastal X-band radar system for monitoring wind waves and currents at the Black Sea (near Gelendzhik) created on the basis of nautical radars. Radar measurements of wave heights were validated by data from a wave buoy and a moored acoustic Doppler current profiler (ADCP). The conditions for successful radar measurements of waves in the coastal environment have been determined. It was shown that a radar with an aperture 1° could successfully measure wave heights at a distance of 1.2 km from the radar, when waves arrive at an angle of ±31° to the main sensing direction. In this case, for wave height measurements, the correlation coefficient between the radar and independent data is 0.82 and the standard deviation is 0.26 m. 相似文献
16.
A Wind stress–Current Coupled System (WCCS) consisting of the HYbrid Coordinate Ocean Model (HYCOM) and an improved wind stress algorithm based on Donelan et al. [Donelan, W.M., Drennan, Katsaros, K.B., 1997. The air–sea momentum flux in mixed wind sea and swell conditions. J. Phys. Oceanogr. 27, 2087–2099] is developed by using the Earth System Modeling Framework (ESMF). The WCCS is applied to the global ocean to study the interactions between the wind stress and the ocean surface currents. In this study, the ocean surface current velocity is taken into consideration in the wind stress calculation and air–sea heat flux calculation. The wind stress that contains the effect of ocean surface current velocity will be used to force the HYCOM. The results indicate that the ocean surface velocity exerts an important influence on the wind stress, which, in turn, significantly affects the global ocean surface currents, air–sea heat fluxes, and the thickness of ocean surface boundary layer. Comparison with the TOGA TAO buoy data, the sea surface temperature from the wind–current coupled simulation showed noticeable improvement over the stand-alone HYCOM simulation. 相似文献
17.
基于天津港主航道连续观测点31 d的实测海流资料,利用调和分析对主航道潮流和余流特征进行研究,同时结合同步风速资料研究风对表层余流的影响。结果表明:(1)航道附近属于弱流海区,表层平均流速为31.4 cm/s,流速总体上由表至底逐渐减小,流速方向大致集中在NW—SE向。(2)观测海域潮流以正规半日往复潮占主导,优势分潮为M2,浅水分潮较为显著,涨潮流流速大于落潮流流速。(3)观测期间表层平均余流流速为2.8~13.8 cm/s,随着深度增加余流流速逐渐减小,方向大多为NW向。该站表层余流受风的影响显著,东南风将使余流方向偏向西北。 相似文献
18.
基于合成孔径雷达的长江口海表流场反演 总被引：1，自引：0，他引：1
Range Doppler velocities derived from the Envisat advanced synthetic aperture radar（ASAR） wide swath images are analyzed and assessed against the numerically simulated surface current fields derived from the finite volume coastal ocean model（FVCOM） for the Changjiang Estuary. Comparisons with the FVCOM simulations show that the European Space Agency（ESA） Envisat ASAR based Doppler shift anomaly retrievals have the capability to capture quantitative information of the surface currents in the Changjiang Estuary. The uncertainty analysis of the ASAR range Doppler velocity estimates are discussed with regard to the azimuthal and range bias corrections, radar incidence angles, inaccuracy in the wind field corrections and the presence of rain cells.The corrected range Doppler velocities for the Changjiang Estuary area are highly valuable as they exhibit quantitative expressions related to the multiscale upper layer dynamics and surface current variability around the East China Sea, including the Changjiang Estuary. 相似文献
19.
20.
Field measurements during the Bay of Bengal Monsoon Experiment (BOBMEX-99), data from a deep sea moored buoy, and satellite altimeter were used to describe variability in the hydrographic and meso-scale features in the Bay of Bengal (BoB) during the summer monsoon of 1999. The thermohaline fields showed two regions of upsloping of isopleths centered at 82°E and 84.75°E, ～110 km and 450 km away from the coast, respectively, followed by downsloping. The upsloping/downsloping of isopleths and the alternating currents was part of cyclonic and anti-cyclonic circulation patterns in the western BoB. In this region, both wind and current were important in the dynamics of coastal upwelling. The observations showed a relationship between the propagating waves and eddy on variability of thermohaline fields. On an annual cycle, four Kelvin waves were observed in the BoB, but only the downwelling Kelvin wave formed during October entered the Arabian Sea. During the monsoon season, four eddies were formed in the western BoB, of which the anticyclonic eddy centered at 15°N, 84°E and the cyclonic eddy centered at 17.5°N, 84.5°E were prominent. The baroclinic instability caused by the opposing currents along the east coast and the wind stress curl favored the formation of eddies. Okhubo-Weiss and Isern-Fontanet parameter confirmed the presence of eddies in the BoB. 相似文献