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1.
渤海及黄海北部的风海流数值计算及余流计算 总被引：1，自引：1，他引：1
依据黄渤海实测风的资料对渤海及北黄海进行了月平均风海流数值计算。计算表明 ,1月份在西北风的作用下 ,在渤海出现 1个逆时针旋转的环流 ,在辽东湾北部及黄海北部出现 1个顺时针旋转的环流 ,渤海海峡的海流北进南出。 7月份在南风和东南风的作用下 ,风海流的变化形式与 1月份大致相反 ,海峡处呈南进北出的形式。对渤海中部某点 1年的潮流资料通过低通滤波的方法计算逐时的余流值 ,得到该点 1年内表层最大的实测余流为 31.9cm/ s,全年 90 %多的时间内表层余流小于 10 cm/ s。对辽东湾北部某点和渤海湾西南部某点数月潮流资料也进行了低通滤波 ,并将得到的逐时余流与同步风作了比较。依据该 2点风和余流的关系以及黄海北部 6个点风和余流的关系验证了风海流数值计算的结果 ,表明在这些点上实测与计算结果拟合良好 相似文献
2.
The Gulf of Finland is a 400-km long and 48–135-km wide tributary estuary of the Baltic Sea featuring the longitudinal two-layer estuarine flow modified by transverse circulation. Longitudinal volume transport in the deep layer is investigated by decomposing it into an averaged, slowly changing estuarine component (due to large-scale density gradients, river discharge and mean wind stress) and wind-driven fluctuating component. The derived expression relates the total deep-layer transport to the projection of wind stress fluctuation to a site-specific direction. The relationship is tested and calibrated by the results from numerical experiments carried out with the three-dimensional baroclinic circulation model. For the entrance to the Gulf of Finland, winds from northeast support standard estuarine circulation and winds from southwest work against the density-driven and riverine flow. The deep estuarine transport may be reversed if the southwesterly wind component exceeds the mean value by 4–5.5 m s−1. According to the data from hydrographic observations in the western Gulf of Finland, an event of advective halocline disappearance was documented in August 1998. Comparison of the deep-water transport estimates calculated from the wind data in 1998 with the observed salinity variations showed that the events of rapid decay of estuarine stratification were coherent with the estimated reversals of deep-layer volume transport, i.e. events of salt wedge export from the gulf. 相似文献
3.
ＭｏｄｅｌｌｉｎｇｏｆｔｈｅｂａｒｏｔｒｏｐｉｃｐｒｏｃｅｓｓｅｓｉｎｔｈｅＢｏｈａｉＳｅａ￥ＨｕａｎｇＤａｊｉ；ＣｈｅｎＺｏｎｇｙｏｎｇａｎｄＳｕＪｉｌａｎ（ＳｅｃｏｎｄＩｎｇｔｉｔｕｔｅｏｆＯｃｅａｎｏｇｒａｐｈｙ，ＳｔａｔｅＯｃｅａｎｉｃＡｄｍ... 相似文献
4.
基于非结构有限体积法海洋模型FVCOM(Finite-Volume Community Ocean Model), 建立了马六甲海峡及其毗邻海域高分辨率水动力数值模型, 研究了风和潮流作用下的余环流结构以及水体输运特征。结果表明, 马六甲海峡航道中央潮流运动以往复流为主, 边缘存在旋转流; 主要研究区域内落潮流速略大于涨潮流速, 东南窄道处流速最大; 因峡道束窄变浅, 在涨落潮过程中潮流发生汇聚与分离; 主要研究区域东南段存在3个显著的潮致余环流; 东北季风驱动时模型响应为海峡海流整体向西北方向流动, 西南季风时反之; 季风期间潮致表层余环流结构被破坏, 但底层余流仍存在水平环流结构, 且随着风速增加, 底层余环流的数目、大小、形状、位置均会产生变化; 季风过渡期余环流结构也会发生部分改变, 尤其是小潮期间风场影响效果显著。 相似文献
5.
J.D. Wang 《Estuarine, Coastal and Shelf Science》1998,46(6):901-915
Recent observations using moored current meters, shipboard ADCP transects, salinity mapping and drifters have been used to study the residual circulation including wind drift in western Florida Bay.Rapid, nearly synoptic surveys of salinity over a large area was an effective tracer-mapping technique, when salinity gradients were sufficiently strong, and provided qualitative information on Lagrangian water motion for the entire study area. The salinity maps indicated a general south-eastward advection, which was only subordinate to tidal mixing in a narrow zone adjacent to the Florida Keys.Drifter data collected simultaneously, allowed quantitative estimates to be added to the transport pattern suggested by salinity maps. The selectively deployed drifters yielded estimates of total drift velocities. In addition, moored current meters and shipboard current profiling were used to determine the distribution of flow across the mouth of the bay facing the Gulf of Mexico and the transport through Long Key Channel, a major connection between the bay and the Atlantic Ocean.Analysis showed that from 64 to over 92% of the drifter trajectory variances could be explained by the combination of a local wind drift, expressed in terms of a wind drift factor multiplied by the surface shear velocity, and an ambient current. For a 1 m high drifter deployed at the surface of the water column, the wind drift factor was found to be approximately 0·125m, making the drift speed roughly equal to 0·45% of wind speed. The mean drifter speeds were linearly proportional to mean transport estimates derived from the current meter observations in Long Key Channel, enhancing confidence in both data sets.The total south-eastward directed residual current varied between 100 and 5000 m day−1and was weaker in summer than in winter, when southward winds associated with periodic passage of cold fronts boost the residual flow. The estimated contribution from local wind drift varied between 500 m day−1in summer to 1000 m day−1in winter. The remaining contribution to the observed Lagrangian residual circulation in western Florida Bay is caused by other forcing, including tidal rectification, remote wind forcing and large-scale current systems (the Gulf Stream and Florida Current systems). 相似文献
6.
Low-frequency current and temperature variability on the southeast US continental shelf during summer conditions of weak wind forcing and vertical stratification was found to be similar in many aspects to previous findings for winter, when stronger wind forcing and vertical homogeneity prevails. Subtidal variability in the outer shelf is dominated by the weekly occurrence of Gulf Stream frontal eddies and meanders. These baroclinic events strongly affect the balance of momentum in the outer shelf, but not at mid-shelf. A negative alongshore sea level slope of order −10−7 is required to balance mean along-shelf momentum at the shelf edge, similar to oceanic estimates, and can contribute to the observed northward mean flow over the shelf.Low-frequency flow at mid-shelf and coastal sea level fluctuations appear to occur as a forced wave response to local alongshore wind stress events that are coherent over the shelf domain. Momentum balances indicate a trapped wave response similar to the arrested topographic wave found in the mid-Atlantic Bight (CSANADY, 1978). Density driven currents from river discharge do not appear to be significant at mid-shelf. Cold, subsurface intrusions of deeper, nutrient rich Gulf Stream waters can occasionally penetrate to mid- and inner-shelf regions north of Cape Canaveral, causing strong phytoplankton and zooplankton responses. These events were observed following the simultaneous occurrence of upwellings from northward winds and Gulf Stream frontal eddies at the shelf break during periods when the Stream was in an onshore position. Subsurface Gulf Stream intrusions to mid-shelf occur only during the summer, when the shelf is vertically stratified and cross-shelf density gradients do not present a barrier as in winter. 相似文献
7.
Determining the age of water and long-term transport timescale of the Chesapeake Bay 总被引：5，自引：0，他引：5
The concept of age of water (AW) is applied to the Chesapeake Bay to investigate the long-term transport properties for dissolved substances. A real-time calibrated hydrodynamic Chesapeake Bay model in 3 Dimensions (CH3D), employing a boundary-fitted curvilinear grid, is used for the study. The long-term transport properties, represented by AW, are investigated under the conditions of low river inflow of 1995 and high river inflow of 1996, as well as for constant mean inflows. The influences of freshwater, density-induced circulation, and wind-induced transport on age distribution have been investigated. Model results show that river inflows, wind stress, and density-induced circulation play important roles in controlling the long-term transport in the Bay. The model results shows that it requires 120–300 days for a marked change in the characteristics of the pollutant source discharged into the Bay from the Susquehanna River to affect significantly the conditions near the mouth under different hydrodynamic conditions. An increase of river discharge results in increases of downstream residual current and gravitational circulation, and thus reduces AW. The density-induced circulation contributes to the transport substantially. The dissolved substances discharged into the Bay are transported out of the Bay more rapidly when the estuary becomes more stratified. Southeasterly and southwesterly winds have strong impacts on the transport compared to the northeasterly and northwesterly winds. The former increases lateral and vertical mixing significantly. Consequently, the gravitational circulation is reduced and the transport time is increased by 50%. The model results provide useful information for understanding the long-term transport processes in the Bay. 相似文献
8.
L. J. Paul 《新西兰海洋与淡水研究杂志》2013,47(3):535-558
The changing pattern of water temperature in the Hauraki Gulf at approximately two‐monthly intervals during one and one‐half seasonal cycles in 1965–66 was determined from sea surface temperatures and bathythermograph profiles. Surface and bottom temperatures ranged from 22.0°c and 20.5°c respectively in March to 12.5°c and 13.0°c in July‐September. Seasonal temperature ranges and short‐term variations were greatest in the shallow south‐west Gulf. In winter the Gulf water was coolest close to shore. It was typically isothermal in depth but a temperature inversion of approximately l°c frequently formed, probably because of the combination of strong winds and an increased outflow of cool, low salinity water from harbours and bays. A similar inversion in Colville Channel may have been caused by more complex tidal and/or ocean current conditions. In spring and summer the Gulf became thermally stratified, with warmest temperatures in the shallow areas. Thermoclines were generally irregular in position and size, and probably represented solar heating and minor current boundaries rather than a distinct separation of major water masses. In late summer and autumn bottom temperatures increased and almost equalled the maximum surface temperature. During autumn surface water temperatures close to land decreased rapidly to return the Gulf to its winter isothermal condition. Local factors (wind, rainfall, tides, depth of water, and proximity to land) probably influence sea temperatures in the Gulf. Seawards of a line from Cape Rodney to Cape Colville oceanic conditions prevail; water temperatures are more constant and increase to seaward in both winter and summer. Oceanic and Gulf waters meet and mix in the Rodney‐Colville area, and Gulf water is transported east through Colville Channel. The extent of oceanic water penetration into the Gulf at depth is unknown. 相似文献
9.
10.
Residual (i.e. non-tidal) components of flow in the Dover Straits are determined from measurements recorded by the OSCR H.F. Radar system. The data are divided into 10 monthly sets, obtained from 5 months of dual radar deployments on the English side of the Straits and a corresponding 5 months from the French side. For each of these sets the tidal component was removed by subtracting constituents derived from separate (monthly) harmonic analyses.In each deployment, surface currents were measured at 700 locations at 20-min intervals, providing spatial resolution on a grid as fine as 660 m. This fine spatial resolution reveals distinct patterns of monthly-mean residual circulations never previously recognized. In particular, a residual gyre is shown to be a dominating feature along the French side, with currents exceeding 20 cm s-1 and a diameter of 20 km. The previous obscurity of this feature may be attributable to the large (> 1·5 m s-1) and strongly spatially variable tidal currents. In these conditions, tidal advection will rapidly smear any surface signature obtained from satellite observations. Likewise, fine resolution (grid spacings of an order of 1 km) is required to reproduce these gyre dynamics in numerical models.The time-varying residual currents were correlated with wind recordings. Significant correlations were obtained for an 'open-sea' response (as represented by Ekman theory), with the wind-driven surface current veering at angles of up to 45° to the right of the wind direction. This 'open-sea' response is modified close to the coast where the generation of surface gradients force the currents to align with the topography.Larger-scale residual motions were identified from modal analyses. The primary modes, on both sides, involved large-scale flows through the Straits partially correlated with local winds. However for winds aligned approximately north-south, the components of these flows on the English and French sides are in opposition. These modes also revealed large oscillatory motions with periods of between 20 and 40 h.Estimates of net residual flows through the Straits from the radar measurements confirm earlier calculations of the range of variability in this parameter. However the increasing complexity of the flow patterns revealed in this study emphasizes the difficulty in quantifying the long-term net flow. 相似文献
11.
Brisk, persistent easterly trade wind influences define Holocene patterns of carbonate sedimentation across the Caicos Platform (southeastern Bahamas). Resultant predictive sedimentary facies models based on trade wind influences are more widely applicable to the exploration for subsurface carbonate plays than are existing models based on the northern Bahamas facies patterns, which are characterized by gentle trade winds and strong platform-margin-related oceanic processes (swells and tidal currents). The Caicos Platform relationships may be more applicable because many ancient shallow carbonate depositional environments were within the trade wind belts and commonly within broad intracratonic seas that were little influenced by oceanic processes.The grainstone-dominated Caicos Platform exhibits reservoir potential over much of its surface, in contrast to northern Bahamian platforms, where oceanic tidal currents or swells and gentle easterly trade winds confine higher energy environments with reservoir potential to platform margins. Strong easterly trade winds across Caicos Platform promote widespread Holocene platform-interior oolitic, skeletal and grapestone grainstone bodies on this platform. Orientations of ooid sand bodies vary depending on preexisting topography, water depth and bottom energy. Shallow subtidal ooid sand shoals orient parallel to these winds. Ooid sands developed along older shorelines orient parallel to the shorelines but prograde perpendicular into these winds. Deeper platform-interior oolitic sands exist as widespread, sheet-like deposits. These trade winds allow reefs and ooids to coexist in many settings, permit isolated linear reefs to flourish on certain leeward platform margins, and promote effective off-bank transport of carbonate sands that create onlapping grainstone wedges. These relationships are very applicable to the rock record.Strong trade wind influences, such as seen on Caicos Platform, better explain the occurrence of Cretaceous reef and/or oolitic grainstone reservoirs developed well in from platform margins (Fairway Field in East Texas; Black Lake Field in Louisiana) than do existing northern Bahamian models. Depositional models based on conditions in the northern Bahamian models would predict low-energy facies in these platform-interior settings. A trade-wind-driven depositional model, characterized by strong persistent easterlies, also better explains the origin of the onlapping wedge of skeletal grainstones at Poza Rica oilfield in Mexico.The Caicos Platform easterly trade-wind-driven depositional model should generally apply to any ancient shallow carbonate environment that developed 5–22° north or south of the paleoequator, whether or not a platform margin was near by. Future carbonate exploration or exploitation should always factor in not only geological age, but also physiographic, latitudinal and climatic setting at a global and local scale. 相似文献
12.
Hydrodynamic model application to Buzzards Bay is performed using a three-dimensional Boundary-fitted Hydrodynamic model in this study. The model is forced with observed tidal harmonic constants along the open boundaries and winds on the surface. The main focus of the present study is to model the detailed wind and tide-induced circulation in Buzzards Bay. The observed surface elevations and currents given in [Butman, B., Signell, R., Shoukimas, P., Beardsley, R.C., 1988. Current Observations in Buzzards Bay, 1982–1986. Open File Report 88-5. United States Geological Survey] and the tide and current harmonics given in [Signell, R.P., 1987. Tide- and Wind-forced Currents in Buzzards Bay, Massachusetts. Technical Report WH-87-15. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts] are used to validate the model predictions. The calibrated model is then used to study the relative contributions of tidal and wind forcing on the instantaneous and residual circulation in Buzzards Bay. The amplitudes and phases of the principal tidal constituents at 10 tidal stations in Buzzards Bay obtained from a harmonic analysis of a 60-day simulation compare well with the observed data. The predicted amplitude and phase of the M2 tidal constituent of surface elevations at these stations are, respectively, within 4 cm and 5° of the observed data. The errors in the model-predicted M2 harmonic principal current speeds are less than 6 cm/s, and the principal current directions and phases are within 14° of the observations. The observed surface elevations and currents given in [Butman, B., Signell, R., Shoukimas, P., Beardsley, R.C., 1988. Current Observations in Buzzards Bay, 1982–1986. Open File Report 88-5. United States Geological Survey] are used to validate the model-predicted low-frequency surface elevations and currents. The model predictions in low-frequency surface elevations at Woods Hole closely follow the trends seen in the observations with a correlation coefficient of 0.735, but fail to capture some of the peak surges seen in the observations. The model-predicted low-frequency currents in the east–west direction at stations in Buzzards Bay compare well with the observations with the correlation coefficient exceeding 0.811 and the model capturing the trends seen in the observations, for the most part. However, the model-predicted north–south velocities does not compare well with the observations. The model-predictions agree with the observations that the tidal currents in Vineyard Sound lagged the currents in Buzzards Bay by more than 3 h. The interaction of wind stress with large bathymetric gradients was shown to cause many vortices in Buzzards Bay, as seen from the model predictions. Model simulations show that the winds play a more dominant role than the tides in the generation of the barotropic residual currents in Buzzards Bay, while the model-predicted tide-induced residual current was seen to be small. 相似文献
13.
Shallow water depth retrieval from space-borne SAR imagery 总被引：1，自引：1，他引：0
Kaiguo Fan Weigen Huang Hui Lin Jiayi Pan Bin Fu Yanzhen Gu 《Journal of Oceanography》2011,67(4):405-413
Based on shallow water bathymetry synthetic aperture radar (SAR) imaging mechanism and the microwave scattering imaging model
for oceanic surface features, we developed a new method for shallow water depth retrieval from space-borne SAR images. The
first guess of surface currents and winds are estimated from the normalized radar crossing section (NRCS) profile of shallow
water bathymetry SAR imagery, according to the linear theory and geophysical model function. The NRCS profile is then simulated
by the microwave scattering imaging model. Both the surface currents and winds are adjusted by using the dichotomy method
step by step to make the M4S-simulated NRCS profiles approach those observed by SAR. Then, the surface currents and the wind
speeds are retrieved when a best fit between simulated signals and the SAR image appears. Finally, water depths are derived
using the Navier–Stokes equation and finite difference method with the best estimated currents and the surface winds. The
method is tested on two SAR images of the Taiwan Shoal. Results show that the simulated shallow water NRCS profile is in good
agreement with those measured by SAR with the correlation coefficient as high as 85%. In addition, when water depths retrieved
from the SAR image are compared with in situ measurements, both the root mean square and relative error are less than 3.0 m
and 6.5%, respectively, indicating that SAR images are useful for shallow water depth retrieval and suggesting that the proposed
method in this paper is convergent and applicable. 相似文献
14.
15.
Seasonal and spatial distributions of phytoplankton biomass associated with monsoon and oceanic environments in the South China Sea 总被引：5，自引：3，他引：2
Seasonal variations of phytoplankton/chlorophyll-a （Chl-a） distribution, sea surface wind, sea height anomaly, sea surface temperature and other oceanic environments for long periods are analyzed in the South China Sea （SCS）, especially in the two typical regions off the east coast of Vietnam and off the northwest coast of Luzon, using remote sensing data and other oceanographic data. The results show that seasonal and spatial distributions of phytoplankton biomass in the SCS are primarily influenced by the monsoon winds and oceanic environments. Off the east coast of Vietnam, Chl-a concentration is a peak in August, a jet shape extending into the interior SCS, which is associated with strong southwesterly monsoon winds, the coastal upwetling induced by offshore Ekman transport and the strong offshore current in the western SCS. In December, high Chl-a concentration appears in the upwelling region off the northwest coast of Luzon and spreads southwestward. Strong mixing by the strong northeasterly monsoon winds, the cyclonic circulation, southwestward coastal currents and river discharge have impacts on distribution of phytoplankton, so that the high phytoplankton biomass extends from the coastal areas over the northern SCS to the entire SCS in winter. These research activities could be important for revealing spatial and temporal patterns of phytoplankton and their interactions with physical environments in the SCS. 相似文献
16.
2015年12月在辽东湾中部西岸浅水海域进行了8个站、连续半个月的坐底ADCP海流剖面观测,通过对分层潮流和余流分析,得到该海域的海流特征如下:1)实测海流以潮流特征占主导,潮流特征为规则半日潮流,优势分潮为M2;M2椭圆长轴大小为25~50 cm/s、方向多为NE-SW向,具有显著的往复流特征。2)观测期间的平均余流为1~10 cm/s,方向多为SW向,平均余流在水平和垂向上的空间差异明显,日均余流波动剧烈;表层余流方向与局地风向具有很好的同步一致性,且距岸较近站位的表层余流受风影响更大;中、底层余流与风的相关性较差。本文得到的余流方向不支持冬季辽东湾北部的边界顺时针环流的存在。 相似文献
17.
INTROOCCrIOWWiththeimplementationoftimeseriesobservationsspanningseveralsynopticweathersystempassages,theimPOrtanceoftheattnosphericallyforcedpartofestuarinecirculationbecameclearinthe1970s.WeisbetgandSturges(1976)examinedthewindeffectindrivingthenetcirculationintheWestPassageoftheNarragansettBay.Usingvelocitymeasurementsofapproximatelyonemonthduration,theyconcludedthatthelocalwindscoulddominatethegravitationalconvectionindeterminingthenetestuarinecirculationprofileofapartiallymixedestu… 相似文献
18.
INTRODUCTIONWindsWithhorizontalshearareliabletoinduceoceanicupwelling.Forexample,theresPOnseoftheoceantotheatmOSphericjetasshowninFig.Ihascausedacurlthatinducesupwellinginoneregion,downwellinginanother.IftheoceanisinfinitelydeepandhasconstantBrunt--V... 相似文献
19.
David Prandle 《Progress in Oceanography》1991,27(3-4)
Since 1984 the OSCR HF Radar system has been used in over 50 deployments to measure near-shore surface currents for both scientific and engineering applications. The enhanced scope, resolution and accuracy of these measurements have yielded new insights into the tidal, wind and density driven dynamics of the near-shore zone.Tidal current ellipses obtained from these radar measurements have been shown to be in good aggrement with values calculated by numerical models both for the predominant constituents and also for higher harmonics. Coherent patterns of wind-forced currents ahve been determined with strong evidence of a “slab-like” surface response. In one deployment, with offshore winds blowing over relatively deep water, this “slab” rotated clockwise at near-inertial frequency. Strong (up to 20cm s−1), persistent surface residual currents are commonly observed, these are almost certainly generated by (small) horizontal density gradients. These observed surface residuals provide ideal data for rigorous testing of 3-D numerical models.With a threatened rise in sea level, HF Radar is well-suited for observing the expected changes in the dynamics of near-shore regions. Continuing development of these radar systems offers exciting prospects of remote sensing of both surface waves and currents. Future applications may extend beyond the near-shore region to measurements along the shelf-edge, in oceanic gyres and for “beach-processes”. 相似文献
20.
Simultaneous wind, wave, and current data during 21 storms spanning four winters at Tromsøflaket (230 m depth) were analysed to determine joint probabilities of occurrence. Waves were measured with a Waverider Buoy, winds with a recording anemometer onboard a vessel and currents at up to five depths with Aandera RCM-4 current meters. Measured currents were filtered to separate tidal currents from residual currents. In most of the statistical analyses, the actual current profiles were replaced with a simplified “equivalent” profile (constant above 50 m depth) whose magnitude was chosen to give the same drag load on a single pile as the actual profile when both profiles were combined with wave orbital velocities. The data suggest that the equivalent current is weakly correlated with the wave height. Within the range of the data analysed, an in-line equivalent residual current of 30 cm sec−1 is adequate for design drag force calculations.The data presented here are used to illustrate a procedure for data analysis and are not suitable for use as design criteria. 相似文献