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1.
本文采用Regional Ocean Modeling System（ROMS）来研究西南黄海夏季环流,模拟的结果与浮标和锚定观测符合的很好。表层的海流流向东北,离岸一侧的流速大于近岸的流速,表层以下为约沿着25米等深线的气旋式流动。我们通过一系列过程导向实验研究海表风应力和底层温度锋面对环流的影响,结果表明,东南风驱动了表层东北向流动,底层温度锋面驱动了表层以下气旋式流动。底层温度锋面形成于近岸垂向混合充分水体和离岸层化水体之间。 相似文献
2.
1IntroductionAlotofworkonthestudyofthecircula-tionintheHuanghai(Yellow)Sea(HS)andEastChinaSea(ECS)hasbeenmadeandreviewedbyscientists,suchasSu(1998),Suetal.(1994),Guan(1985),YuanandSu(1983,2000),Yuanetal.(1997,1988,1994,2001),Tangetal.(2000)andsoon.Inthispapertheseworks willnotbereviewedagainduetolimitationofpages.Thejointinvestigationontheair-seainteractionprocessofcycloneoutbreakoverthesouthernHuanghaiSeaandEastChinaSeawascarriedoutinthecooperativestudybytheChinese(in-clusiveofTaiwa… 相似文献
3.
Conditions for the formation of large meander (LM) of the Kuroshio are inferred from observational data, mainly obtained in the 1990s. Propagation of the small meander of the Kuroshio from south of Kyushu to Cape Shiono-misaki is a prerequisite for LM formation, and three more conditions must be satisfied. (1) The cold eddy carried by small meander interacts with the cold eddy in Enshu-nada east of the cape. During and just after the propagation of small meander, (2) the Kuroshio axis in the Tokara Strait maintains the northern position and small curvature, and (3) current velocity of the Kuroshio is not quite small. If the first condition is not satisfied, the Kuroshio path changes little. If the first condition is satisfied, but the second or third one is not, the Kuroshio transforms to the offshore non-large-meander path, not the LM path. All three conditions must be satisfied to form the large meander. For continuance of the large meander, the Kuroshio must maintain the small curvature of current axis in the Tokara Strait and a medium or large range of velocity and transport. These conditions for formation and continuance may be necessary for the large meander to occur. Moreover, effects of bottom topography on position and structure of the Kuroshio are described. Due to topography, the Kuroshio changes horizontal curvature and vertical inclination of current axis in the Tokara Strait, and is confined into either of two passages over the Izu Ridge at mid-depth. The former contributes to the second condition for the LM formation. 相似文献
4.
2012年南海西北陆架冬季水文特征的观测分析 总被引：1，自引：0，他引：1
本文基于2012年12月南海西北部陆架海区的温盐和流速实测资料,分析了粤西和琼东陆架海区冬季三维温、盐结构和流场特征,给出沿陆架和跨陆架方向的水体和热盐通量。结果表明：（1）在50m以浅,粤西和琼东海区温度均由近岸向外海递增,深层则相反;冬季近岸海区混合层较深,外海密度跃层位于60—120m深度且层结较强,浮力频率大于10–2/s;（2）海流大致沿等深线向西南流动,30m以深流速大小在0.03—0.40m/s之间,且随着深度增加而略有减小;琼东海区100m等深线附近在60m以浅水层观测到水体辐聚并有明显温度锋面存在;（3）沿陆架方向的水体和热盐输送均大于跨陆架方向,其中粤西单位面积沿/跨陆架水体通量平均值为0.13×10–6/0.03×10–6Sv/m2,低于琼东海区的0.91×10–6/0.56×10–6Sv/m2。 相似文献
5.
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
6.
Interannual variability in the Mindanao Eddy and its impact on thermohaline structure pattern 总被引：2，自引：0，他引：2
The major feature,interannual variability and variation cause of the Mindanao Eddy and its impact on the thermohaline structure are analyzed based on the Argo profiling float data,the history observed data and the SODA data.The analysis results show that the Mindanao Eddy is a permanent cyclonic meso-scale eddy and spreads vertically from about 500 m depth upward do about 50 m depth.In addition to its strong seasonal variability,the Mindanao Eddy displays a remarkable interannual variability associated with ENSO.It strengthens and expands eastward during El Nin o while it weakens and retreats westward during La Nin a.The interannual variability in the Mindanao Eddy may be caused by the North Equatorial Counter Current,the North Equatorial Current,the Mindanao Current and the Indonesian Through Flow.The eddy variability can have a great influence on the thermohaline structure pattern in the local upper ocean.When the eddy is strong,the cold and low salinity water inside the eddy moves violently upward from deep layer,the thermocline depth greatly shoals,and the subsurface high salinity water largely decreases,with the upper mixed layer becoming thinner,and vice versa. 相似文献
7.
8.
J. G. Bruce 《Geo-Marine Letters》1995,15(3-4):185-194
A considerable amount of the Amazon River water that is discharged into the equatorial Atlantic is then advected northward along the shelf by the strong North Brazil Current (NBC). Being relatively fresh, this water remains in the near-surface layer and can serve as an excellent tracer for the complex and variable flow of the offshore mesoscale eddies. Both surface salinity observations and CZCS (Coastal Zone Color Scanner) imagery can be mapped to estimate the circulation patterns of the eddies. Presented here are two sets of XBT (expendable bathythermograph) sections that give the thermal structure of eddies off the Demerara Rise (6–9°N). They were occupied nearly contemporaneously with CZCS imagery obtained during October 1980 and November 1981. Several studies have shown from ship drift data, from CZCS observations, and from Geosat altimetry that, particularly during late summer and fall, the NBC is found to retroflect offshore to the east, supplying the North Equatorial Counter Current (NECC) and is associated with eddies along the coast. Good agreement is shown between the CZCS and a NAVOCEANO AXBT (airborne bathythermograph) survey during this period as well as observations of surface phytoplankton and geopotential anomaly from an earlier 1964 survey. Estimates of volume transport within the eddy structure indicate that at times the offshore retroflection during spring as well as autumn can amount to 10 × 106 m3 s–1. The pronounced eddy variability off South America is shown by comparing a number of past hydrographic surveys. These suggest that considerable spatial variability can occur as can seasonal changes in volume transport of the NBC and the associated eddy circulation. 相似文献
9.
In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer (BBL). Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath (under the lowest tidal level), a tripod system was installed with AWAC (Acoustic Wave And Current), ADCP (Acoustic Doppler Current Profilers), OBS-3A (Optical Backscatter Point Sensor), ADV (Acoustic Doppler Velocimeters), etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt: 1) The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m3 and the average value being 0.03 kg/m3; 2) The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension. 相似文献
10.
Masahiro Endoh 《Journal of Oceanography》1973,29(4):140-147
Investigated is a possibility of two-dimensional model in the study of the dynamics of the western boundary current by a numerical experiment. Emphasis is laid on the effect of bottom barrier corresponding to the Izu Ridge.The western boundary current in the model is formed by source and sink of the water prescribed at an artificial eastern wall (600 km offshore). The bottom topographyconsists of a continental slope parallel to the straight western coast, and a ridge protruding from the western coast to 500 km offshore (1,500 m deep and 400 km wide). The grid size of 12 km× 25 km (offshore and longshore directions, respectively) resolves both the western boundary current and the bottom topography.The assumption of homogeneity of the water density makes the western boundary current detour along the isobath of the ridge.A steady state solution is obtained under the assumptions that the horizontal velocity does not change direction vertically (equivalent barotropic), and that the geostrophic relationship holds at the bottom. Homogeneity of the water density is not assumed. The solution shows that most of the volume transport of the western boundary current cross the ridge and the current has cyclonic vorticity near the summit of the ridge. It seems to suggest that the investigation by three-dimensional models is neccesary in order to study the complete dynamics of the western boundary current crossing the ridge. 相似文献
11.
E. M. Lemeshko A. N. Morozov S. V. Stanichnyi L. D. Mee G. I. Shapiro 《Physical Oceanography》2008,18(6):319-331
The profiles of absolute current velocity obtained by using a lowered acoustic doppler current profiler (LADCP) are presented. In the course of the BSERP-3 expedition, the measurements were carried out in the regions of the Rim Current, anticyclonic eddy, and northwest shelf.
In the core of the Rim Current, a unidirectional motion of waters is traced in layers below the main pycnocline down to depths
greater than 500 m. Its characteristic velocity can be as high as 0.08 m/sec. It is shown that the direct action of the eddy
is detected in the shelf region at distances larger than 20 km from the outer edge of the shelf in the zone bounded by an
isobath of 100 m. The formation of multilayer vertical structures in the field of current velocities is revealed in the region
of interaction of the anticyclonic eddy with irregularities of the bottom on the side of the shelf. A two-layer structure
of currents with specific features in the layer of formed seasonal pycnocline is observed in the region of the shelf down
to an isobath of 100 m. The profiles of the moduli of vertical shears of currents averaged over the casts ensemble are presented
for the abyssal and shelf parts of the sea. It is shown that the shears induced by the geostrophic currents and wave processes
in the region of the main pycnocline are comparable. Below the pycnocline, the shears are mainly determined by the wave processes.
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 25–37, November–December, 2008. 相似文献
12.
Two very high-frequency radars (VHFRs), operating in the southern Channel Isles region (English Channel) in February–March 2003, provided a continuous 27-day long dataset of surface currents at 2 km resolution over an area extending approximately 20 km offshore. The tidal range in the region of study is one of the highest in the world and the coastal circulation is completely dominated by tides. The radar data resolve two modes which account for 97% of the variability of the surface current velocities, with the major contribution of the first mode. This mode accounts for oscillating tidal currents whereas the second mode represents motions emerging from the interaction of tidal currents with capes and islands (eddy in the vicinity of the Point of Grouin and jet south of Chausey). A fortnightly modulation of the modal amplitudes causes the exceptional (more than 600%) variability of currents which is well captured by the VHFR observations. The radar data revealed that tidal circulation in the region is flood-dominated with a strong asymmetry of current velocity curve. Wind events and fortnightly variability affect the course of tidal cycle by modifying the magnitude and duration of ebb and flood. In addition to expected features of coastal circulation (tidally dominated flow, eddies) and high wind-current coupling, the residual currents revealed a strong cross-shore structure in the mean and a significant variability which has the same order of magnitude. 相似文献
13.
The circulation in the southern Huanghai Sea and northern East China Sea in June 1999 总被引：1，自引：0，他引：1
Yaochu Yuan Yonggang Liu Mingyu Zhou Arata Kaneko Zhou Yuan Noriaki Gohda 《海洋学报(英文版)》2003,22(3):321-332
On the basis of hydrographic data and current measurement (the mooring system, vessel-mounted ADCP and toward ADCP) data obtained in June 1999, the circulations in the southern Huang-hai Sea (HS) and northern East China Sea (ECS) are computed by using the modified inverse method. The Kuroshio flows northeastward through eastern part of the investigated region and has the main core at Section PN, a northward flow at the easternmost part of Section PN, a weaker anti-cyclonic eddy between these two northward flows, and a weak cyclonic eddy at the western part of Section PN. The above current structure is one type of the current structures at Section PN in ECS. The net northward volume transport (VT) of the Kuroshio and the offshore branch of Taiwan Warm Current (TWCOB) through Section PN is about 26.2×106m3/s in June 1999. The VT of the inshore branch of Taiwan Warm Current (TWCIB) through the investigated region is about 0.4×106m3/s. The Taiwan Warm Current (TWC) has much effect on the currents over the 相似文献
14.
《African Journal of Marine Science》2013,35(3):343-350
This paper describes the westward movement of a cyclonic eddy across the Mozambique Channel and the subsequent south-westward propagation of the eddy along the east coast of South Africa and its interaction with the shelf. A hydrographic survey on 13 September 2006 off Nine-mile Reef (NMR), Sodwana Bay, showed a well-developed Agulhas Current along the continental shelf inshore of a cyclonic eddy flanked by two anti-cyclonic eddies, further offshore. A satellite-tracked drifter and complementary altimetry data confirmed the dimensions of the eddy and tracked its movement towards the coast. Shelf-edge upwelling was measured at NMR by an underwater temperature recorder (UTR) when the cyclonic eddy first came into contact with the shelf and again when the cyclonic eddy interacted with the leading edge of the anti-cyclonic eddy moving onto the shelf. Further shelf–eddy interactions off Aliwal Shoal, south of Durban, and consequent upwelling were similarly caused by the same cyclonic eddy as it progressed south-westward along the east coast. Analysis of UTR data between 2004 and 2006 indicated that between two and five cyclonic eddies impact the shelf off NMR per year. 相似文献
15.
1995与1996年夏季琉球群岛两侧海流 总被引：7，自引：3，他引：4
基于1995,1996年夏季日本调查船的观测资料,采用P矢量方法对琉球群岛两侧的海流进行了计算.结果表明:黑潮为琉球群岛以西海域的一支东北向强流,1996年夏季的流速比1995年夏季的强,在深层出现南向逆流.黑潮东、西两侧分别存在一个反气旋式暖涡和一个弱的气旋式冷涡.1995年夏季,琉球群岛以东,从表层至以下层都存在一支沿岸北上的海流,即琉球海流.该海流来自黑潮分支,为本海区的一个主要物理特征.琉球海流以下出现弱的南向流.冲绳岛以东海域,在25°～25°30'N,128°30'～129°10'E附近从表层至700m水深存在一个中尺度的反气旋式暖涡.在温、盐水平分布图上,对应的出现一个较高温、低密水块.1996年夏季,冲绳岛西南海域存在一个中尺度的反气旋式暖涡和一个气旋式冷涡,形成一个偶极子,中间为较强的南向流,该现象为本海区的一个重要物理特征,属首次报道.冲绳岛以东表层主要被南向流控制,琉球海流不明显.200m以深在近岸出现北向流,这表明琉球海流的核心位于次表层.琉球海流的下面出现南向流.计算海区东北部从表层到700m水深出现一个中尺度的反气旋式暖涡,与1995年夏季时比较,其位置向北移动.此外在1996年夏季从近表层到深层,垂直方向和水平方向上的等温线、等盐线波动很大,例如在C断面上冷、暖涡相间出现,且暖 相似文献
16.
Peter Hamilton 《Progress in Oceanography》1987,19(3-4)
The structure of the current and temperature fields along 30°N over the mid-shelf and western Blake Plateau in the South Atlantic Bight has been investigated by combining two moored instrument experiments in the summer of 1981. The shelf moorings were part of the second Georgia Bight Experiment (GABEX-II) and the Gulf Stream mooring data on the Blake Plateau have been described by LEE and WADDELL (1983). Empirical Orthogonal Functions (EOF) in the frequency domain are used to extract shelf and Gulf Stream coherent current and temperature fluctuations in the two- to 14-day period band. Three modes are found, of which the first two are interpreted as Gulf Stream meander and frontal eddy circulations. The difference between them is chiefly in the shelf motions; the first mode is primarily restricted to the shelf edge, whereas the second mode penetrates to the 40m isobath. The third mode dominates at mid-shelf and is the only mode that shows strong coherence with the windstress and local sea-level fluctuations. The relationship of the modes to the occurrence of mid- and inner-shelf cold sub-surface intrusions, generated by shelf-edge Gulf Stream frontal eddies, is examined. All three modes are found to play a role in the initiation, growth and decay of these structures. 相似文献
17.
In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension. 相似文献
18.
Tatsuro Watanabe Daisuke Simizu Kou Nishiuchi Toru Hasegawa Osamu Katoh 《Journal of Oceanography》2009,65(6):791-801
We examined the surface current structure in the Tsushima Warm Current (TWC) region of the Japan Sea based on a dataset from
satellite-tracked surface drifters, including our new deployments during 2004–2008. The gridded mean current velocity and
mean kinetic energy (KE) fields calculated from all available drifter data revealed the structure and seasonality of the three
branches of the TWC. By comparing the eddy kinetic energy (EKE) field to the KE field, we found four regions where the ratio
of EKE to KE was high. In particular, this ratio became extremely high east of the Oki Islands located between the first branch
of the TWC (FBTWC) and the second branch of the TWC (SBTWC). Our analysis suggests that the generation of alternate warm and
cold eddies east of the Oki Island induced this high ratio. The occurrence of a warm or cold eddy was related to the route—either
nearshore or offshore—of the SBTWC. When the offshore route of the SBTWC became dominant, a warm eddy was frequently generated
east of the Oki Islands. In contrast, when the nearshore route of the SBTWC became dominant, a cold eddy was more likely to
be generated. 相似文献
19.
基于水下滑翔机在2019年8至10月观测到的温盐资料,本研究分析了西北太平洋混合层总体的变化情况,并探讨了混合层异常变化的原因。结果表明,混合层温度总体上呈现随季节转换逐渐降低的趋势,混合层深度总体上呈现随季节转换逐渐增大的趋势。进一步的相关性分析得出,该海域混合层温度、混合层深度的变化特征主要是由外部大气强迫场(海面风场和净热通量)所决定的。水下滑翔机还观测到了混合层温度异常降低、混合层深度异常变浅的现象。通过计算混合层热收支发现,垂向夹卷作用是海洋混合层内温度降低和混合层深度变浅的主要原因。通过进一步计算研究海域冷涡的上升速度与海水垂向夹卷速度的变化情况,并结合卫星遥感资料,得出海洋的中尺度涡旋活动主导了混合层异常现象的发生。 相似文献
20.
ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｙｅａｒｓ’ｓｔｕｄｙｈａｓｐｒｉｍａｒｉｌｙｓｈｏｗｎｔｈａｔｔｈｅＳＣＳｈａｓａｎｉｍｐｏｒｔａｎｔｉｎｆｌｕｅｎｃｅｏｎｔｈｅｍｏｎｓｏｏｎｃｕｒｒｅｎｔｓａｎｄｏｎｔｈｅｆｌｏｏｄａｃｔｉｖｉｔｉｅｓｏｃｃｕｒｒｅｄｉｎｔｈｅｒｅｇｉｏｎｏｆＣｈｉｎａ (Ｓｕｎｅｔａｌ .,1 999,Ｄｉｎｇｅｔａｌ.,1 999) .ＴｈｅｍｏｎｓｏｏｎｏｎｓｅｔｉｎｅｖｉｔａｂｌｙｃａｕｓｅｓｔｈｅａｄｊｕｓｔｍｅｎｔｏｆｔｈｅＳＣＳｃｉｒｃｕｌａ ｔｉｏｎ ,ａｎｄｉｎｔｕｒｎ ,ｔｈ… 相似文献