共查询到20条相似文献，搜索用时 31 毫秒
1.
Yukio Masumoto 《Journal of Oceanography》2004,60(2):313-320
The generation of small meanders of the Kuroshio south of Kyushu has been investigated using a high-resolution ocean general
circulation model of the North Pacific Ocean. The small cyclonic meander develops in the region east of the Tokara Strait
with a period of about one month, then propagates downstream along the Kuroshio path to the longitude of the Kii Peninsula,
which is similar to the so-called trigger meanders for the formation of the large-meander of the Kuroshio south of Japan.
It turns out that the generation of the small meander is a local phenomenon, strongly associated with anticyclonic eddies
that propagate northeastward along the Kuroshio path in the East China Sea. The vorticity balance indicates that the accumulation
of positive vorticity during the developing phase of the small meander occurs mainly from the balance between the stretching
and the advection terms.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Various kinds of datasets, such as satellite-derived sea surface temperature (SST), sea surface height, surface velocity produced
by combining surface drifter and satellite altimeter data, and hydrographic data, led to the discovery of an anticyclonic
eddy with lower SST than those of surrounding waters in the Kuroshio recirculation region south of Shikoku, as if the eddy
were cyclonic. This anticyclonic eddy was formed east of Kyushu in late August to early September 1999 from the merger of
two anticyclonic eddies which had migrated in the recirculation region to the sea south of Japan from the east. After the
merger, the anticyclonic eddy strengthened abruptly and began to exhibit the low SST. In October, this eddy coalesced with
the Kuroshio and moved swiftly eastward, accompanied by an amplitude growth of the Kuroshio meander. In mid November, off
the Kii Peninsula, the eddy detached from the meandering Kuroshio. It then moved southwestward and again slowly propagated
westward along the 30°N line. During this period, at least from late October 1999 to January 2000, SSTs over the anticyclonic
eddy were found to be continuously lower than those of surrounding waters. This case tells us that we have to pay careful
attention to the interpretation of mesoscale SST distributions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Trajectories of mesoscale eddies in the Kuroshio recirculation region were investigated by using sea surface height (SSH)
anomaly observed by the TOPEX/POSEIDON and ERS altimeters. Cyclonic and anticyclonic eddies have been traced on maps of the
filtered SSH anomaly fields composed from the altimeter observations every ten days. Both the cyclonic and anticyclonic eddies
propagate westward in the Kuroshio recirculation region from a region south of the Kuroshio Extension. The propagation speed
of these eddies has been estimated as about 7 cm s−1, which is much faster than the phase speed theoretically estimated for the baroclinic first-mode Rossby wave in the study
area. It was also found that in the Izu-Ogasawara Ridge region, most of eddies pass through the gap between the Hachijojima
Island and Ogasawara (Bonin) Islands, and some of the eddies decay around the Izu-Ogasawara Ridge. It seems that the trajectory
of the eddies is crucially affected by the bottom topography. In the region south of Shikoku and east of Kyushu, some of the
eddies coalesce with the Kuroshio. It is also suggested that this coalescence may trigger the path variation of the Kuroshio
in the sea south of Japan.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
综述东海和琉球群岛以东海域若干气旋型和反气旋型涡旋的研究.对东海陆架、200m以浅海域,主要讨论了东海西南部反气旋涡、济州岛西南气旋式涡和长江口东北气旋式冷涡.东海两侧和陆坡附近出现了各种不同尺度的涡旋,其动力原因之一是与东海黑潮弯曲现象有很大关系,其次也与地形、琉球群岛存在等有关.东海黑潮有两种类型弯曲:黑潮锋弯曲和黑潮路径弯曲.黑潮第一种弯曲出现了锋面涡旋,评述了锋面涡旋的存在时间尺度与空间尺度和结构等;也指出了黑潮第二种弯曲,即路径弯曲时在其两侧出现了中尺度气旋式和反气旋涡,讨论了它们的变化的特性.特别讨论了冲绳北段黑潮弯曲路径和中尺度涡的相互作用,着重指出,当气旋式涡在冲绳海槽北段成长,并充分地发展,其周期约在1~3个月时,它的空间尺度成长到约为200km(此尺度相当于冲绳海槽的纬向尺度)时,黑潮路径从北段转移到南段.也分析了东海黑潮流量和其附近中尺度涡的相互作用.最后指出在琉球群岛以东、以南海域,经常出现各种不同的中尺度反气旋式和气旋式涡,讨论了它们在时间与空间尺度上变化的特征. 相似文献
5.
日本南部黑潮路径变异对北太平洋地区的气候和环境具有显著的影响,对黑潮路径变异的研究具有重要的意义。本文利用POM(Princeton Ocean Model)数值模式模拟了日本南部黑潮的路径变异情况,分析了黑潮大弯曲路径形成的可能机制。研究结果表明,当黑潮处于非大弯曲路径时,相对位势涡度的平均值呈现递减趋势,说明日本南部低位势涡度水在不断积累,这样会使得四国再循环流的强度增强,迫使黑潮保持平直路径,同时,近岸黑潮垂直流速剪切增大,斜压不稳定性的作用也逐渐增大;当黑潮从非大弯曲路径向大弯曲路径过渡时,再循环流强度的减弱会导致黑潮的流速剪切减小。根据海表高度异常场以及海洋上层流场信息发现,近岸黑潮附近的气旋涡会随着再循环流区域反气旋涡的东侧向南运动,最终导致黑潮大弯曲的发生。分析涡流的能量,结果显示,黑潮大弯曲路径的形成与斜压不稳定性密切相关。 相似文献
6.
Masaki Kawabe 《Journal of Oceanography》1980,36(2):97-104
Sea level variations from 1974 through 1976 at 9 stations on the south coast of Japan (from west to east, Aburatsu, Tosa-shimizu, Muroto-misaki, Kushimoto, Uragami, Owase, Toba, Maisaka and Omaezaki) were analysed in relation to the large meander in the Kuroshio. From May to July in 1975, a small maximum in sea level variation was observed at every station west of Cape Shionomisaki from Aburatsu to Kushimoto. It propagated eastward along with the eastward propagation of a small meander in the Kuroshio until it reached Kushimoto, when the sea levels at Uragami and Owase started to rise sharply. This remarkable rise appeared at all stations in August when a large meander in the Kuroshio was established. The mean sea level at the stations east of Cape Shionomisaki from Uragami to Omaezaki rose by about 10 cm. The difference in sea level variations between the regions east and west of Cape Shionomisaki, which had been present before the rise, disappeared. A similar characteristic of sea level variation was also found in the generation stage of the large meander in 1959. The sea level variations along the south coast of Japan indicate that, prior to the generation of the large meander, the small meander in the Kuroshio was generated southeast of Kyushu and propagated eastward and that, just when this meander reached off Cape Shionomisaki, a large scale oceanic event covering over the whole region of the south coast of Japan occurred. This large scale event seems to be one of the necessary conditions for the generation of the large meander in the Kuroshio off Enshû-nada. 相似文献
7.
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
8.
基于正压出入流模式, 利用条件非线性最优扰动(CNOP)方法研究初始异常的位置与模态对日本南部黑潮路径变异的影响。以模式模拟出的黑潮平直路径的平衡态作为参考态, 计算CNOP, 考察该扰动随时间的发展, 并与随机扰动的发展进行对比。结果表明, CNOP 能够导致黑潮弯曲路径发生, 随机扰动则不能。因此, CNOP 可以作为导致日本南部黑潮路径发生弯曲的一种最优前期征兆。通过分析CNOP 和随机扰动的发展过程, 可以得出: (1) CNOP 使黑潮发展成弯曲路径的过程是一个气旋涡向下游传播并增长的过程。(2) 气旋涡的向东传播都是非线性项的作用, 也就是涡度平流造成的。(3) CNOP和随机扰动发展过程中所产生的气旋涡均会传播到下游区域, 但是CNOP 产生的气旋涡能够增强, 最终导致弯曲路径发生, 而随机扰动产生的气旋涡则会减弱, 并不能导致弯曲路径发生。分析发现, 在CNOP 实验中, 非线性作用使气旋涡增大; 但在随机扰动实验中, 非线性作用使气旋涡减弱, 所以非线性作用对日本南部黑潮路径发生弯曲有重要影响。(4) 底摩擦效应对日本南部黑潮路径变异影响较小。本文揭示的黑潮路径发生弯曲的最优前期征兆及其非线性发展机制, 对提高黑潮路径变异的预报技巧具有重要意义。 相似文献
9.
为了探究东海黑潮周边涡旋分布、形成机理及运动规律,基于法国国家空间研究中心(CNES)卫星海洋学存档数据中心(AVISO)的中尺度涡旋数据集展开了研究。首先,统计了近27年东海黑潮周边的涡旋分布,发现在黑潮弯曲海域产生了650个涡旋,在黑潮中段海域产生了271个涡旋,其中直径100~150 km之间的涡旋数量最多,涡旋振幅主要集中在2~6 cm。其次,分析了东海黑潮的运动路径和涡运动过程,结果表明,黑潮气旋式弯曲海域内侧易产生气旋涡,且移动路径较长,如台湾东北海域黑潮流轴气旋式弯曲处产生的涡旋,其平均位移达到了87.6 km;当反气旋式弯曲海域内侧产生反气旋涡时,涡旋往往做徘徊运动。黑潮中段海域的涡旋呈现出气旋涡在黑潮主轴西侧、反气旋涡在黑潮主轴东侧的极性对称分布特征,两类涡都沿黑潮主轴向东北方向移动。最后,结合再分析的流场、海面高度数据,讨论了涡旋运动规律和生成机制。黑潮弯曲处涡旋的生成与黑潮流体边界层分离有关,奄美大岛南部到冲绳岛西侧的黑潮逆流对黑潮中段海域涡的极性对称分布起到了关键作用,涡旋在运动过程中通常经历生长、成熟和衰变三个阶段。 相似文献
10.
采用1977年1月至2006年12月高分辨率全球大洋环流模型OFES输出结果对琉球群岛附近海域的中尺度涡进行了研究分析。结果表明:(1)尺度较大的涡旋的分布密集区主要有台湾以东海域、琉球海沟上层海域和四国以南海域。(2)琉球海流流经海域的反气旋涡旋占优势,有利于琉球海流的发展。(3)琉球海流受中尺度涡的影响十分显著,纬度越低,其受中尺度涡的影响越明显,而黑潮相对比较稳定,受中尺度涡的影响并不显著。(4)四国以南海域暖涡从黑潮脱落之后向西南移动,该涡旋的移动对琉球海流和黑潮产生特别显著的影响。文章的最后还讨论了中尺度涡与黑潮弯曲以及琉球海流可能存在的联系。 相似文献
11.
The occurrence of the small meander of the Kuroshio, generated south of Kyushu and propagating eastward, was examined using
sea level data collected during 1961–1995 along the south coast of Japan. Intra-annual variation of the sea level was expanded
by the frequency domain empirical orthogonal function (FDEOF) modes, and it was found that the second and third modes are
useful for monitoring the generation and propagation of the small meander. The third FDEOF for periods of 10–100 days has
a phase reversal between Hosojima and Tosa-shimizu with significant amplitude west of Kushimoto, and the amplitude of its
time coefficient is large during the non-large-meander (NLM) period and has a significant peak when the small meander exists
southeast of Kyushu. The second FDEOF for periods of 20–80 days has a phase reversal between Kushimoto and Uragami, and the
amplitude of its time coefficient is large when the small meander propagates to the south of Shikoku. The third FDEOF mode
allowed us to conclude that the small meander occurred 42 times from July 1961 to May 1995, most of them (38) occurring during
the NLM periods. The second FDEOF mode permits the conclusion that half of the 38 small meanders reached south of Shikoku.
Of these, five small meanders influenced transitions of the Kuroshio path from the nearshore NLM path; one caused the offshore
NLM path and four brought about the large meander. About one-tenth of the total number of small meanders are related to the
formation of the large meander. 相似文献
12.
The coastal sea level propagating westward along the south coast of Japan and the impact of the disturbance on the generation
of the Kuroshio small meander have been examined. The propagation occurs in sea level variations for periods shorter than
10 days and is remarkable for periods of 4–6 days. Characteristics of the 4–6 day component have been studied using the extended
empirical orthogonal function (EEOF). The first and second modes of EEOF are almost in-phase throughout the south coast of
Japan. The higher four modes of EEOF are significantly excited when the Kuroshio takes the non-large-meander path, and propagate
westward with phase speeds of 2.8 m s−1 (third and fourth modes) and 1.6 m s−1 (fifth and sixth modes) in the Kuroshio region west of Mera in the Boso Peninsula. The analysis shows that more than 70%
of the small meanders generate in two months after a significant propagating disturbance reaches south of Kyushu when the
velocity of the Kuroshio is high. This effect of coastal disturbance is examined by numerical experiments with a 2.5-layer
model in which coastal disturbance is excited by vertical displacement of the upper interface. The result is that offshore
displacement of the Kuroshio occurs southeast of Kyushu only in the case of significant upward displacement of the interface
under the influence of a high Kuroshio velocity. The significant coastal disturbance, which is associated with upward displacement
of the density interface, and a high Kuroshio velocity can therefore be important factors in generating small meanders. 相似文献
13.
Mesoscale Eddies Observed by TOLEX-ADCP and TOPEX/POSEIDON Altimeter in the Kuroshio Recirculation Region South of Japan 总被引：1，自引：0，他引：1
Mesoscale eddies in the Kuroshio recirculation region south of Japan have been investigated by using surface current data measured by an Acoustic Doppler Current Profiler (ADCP) installed on a regular ferry shuttling between Tokyo and Chichijima, Bonin Islands, and sea surface height anomaly derived from the TOPEX/POSEIDON altimeter. Many cyclonic and anticyclonic eddies were observed in the region. Spatial and temporal scales of the eddies were determined by lag-correlation analyses in space and time. The eddies are circular in shape with a diameter of 500 km and a temporal scale of 80 days. Typical maximum surface velocity and sea surface height anomaly associated with the eddies are 15–20 cm s–1 and 15 cm, respectively. The frequency of occurrence, temporal and spatial scales, and intensity are all nearly the same for the cyclonic and anticyclonic eddies, which are considered to be successive wave-like disturbances rather than solitary eddies. Phase speed of westward propagation of the eddies is estimated as 6.8 cm s–1, which is faster than a theoretical estimate based on the baroclinic first-mode Rossby wave with or without a mean current. The spatial distribution of sea surface height variations suggests that these eddies may be generated in the Kuroshio Extension region and propagate westward in the Kuroshio recirculation region, though further studies are needed to clarify the generation processes. 相似文献
14.
Motivated by an analysis of a satellite sea surface temperature image suggesting that a train of extra-tropical cyclones induces amplification of the Kuroshio meander, a regional Kuroshio/Oyashio general circulation model was used to investigate the impact of high-frequency wind on the Kuroshio path variations. Near Japan, the standard deviation of the wind stress curl can be 10 times larger than the monthly mean, so the synoptic variations of the wind stress curl cannot be neglected. With the bimodal Kuroshio case realized in the model, sensitivity tests were conducted using monthly and daily mean QuikSCAT-derived wind stress forcings. The comparison showed that the high-frequency local wind perturbed the Shikoku recirculation gyre (SRG) and caused a transition of the path from straight to meander. The strong anticyclonic eddy within the SRG triggered the meander in the latter case. The high-frequency wind perturbed the motion of the eddy that would have otherwise detached from the Kuroshio, migrated south and terminated the meandering state. The result reinforces the suggestion from previous studies that the anticyclonic eddy within the SRG plays an active role in controlling the Kuroshio path variations. 相似文献
15.
Taiwan Current (Kuroshio) and Impinging Eddies 总被引：16，自引：1，他引：15
Considerable westward or nothwestward propagating eddies were found east of Taiwan that cross-explains the anomalies in the repeated hydrography, trajectory of drifting buoys and altimetric analyses. The sea level differences (SLD) across the Taiwan Current (Kuroshio) in the East Taiwan Channel (ETC) are utilized in order to examine the possible implication of eddies in the Taiwan Current transport. It is concluded that Taiwan is impinged by both cyclonic and anticyclonic mesoscale eddies at an interval of about 100 days. An approaching anticyclonic eddy will result in a higher SLD across the ETC and a larger mass transport of Taiwan Current, and, vice versa, a reduction of both SLD and the mass transport in the ETC as a cyclonic eddy arrives. The SLD-inferred northward transport in the ETC is highly coherent at the 100-day band with westward propagating eddies that originated in the interior ocean. The generation mechanism of these eddies are, however, still unclear. Leakage of the Kuroshio water to the east of the Ryukyu Islands is suggested due to the presence of cyclonic eddies. This 100-day rate of eddy-impingement invalidates any observation of 4 months or less, whether with direct or indirect measurements, because any conclusions depend on the presence or absence of eddies. To minimize the contamination from eddies, either long-term observations or eddy-removal procedures are required. 相似文献
16.
Kaoru Ichikawa 《Journal of Oceanography》2001,57(1):55-68
Temporal variations of the Kuroshio volume transport in the Tokara Strait and at the ASUKA line are decomposed by phase-propagating Complex EOF modes of high-resolution sea surface dynamic topography (SSDT) field during the first tandem period of TOPEX/POSEIDON and ERS-1 (from October 1992 to December 1993). Both variations are dominated by a mode with nearly semi-annual cycle, which indicates a series of interactions between the Kuroshio and meso-scale eddies. Namely, northern part of a westward-propagating meso-scale eddy at 23°N is captured into the southern side of the Kuroshio at the south of Okinawa, then it moves downstream along the Kuroshio path passing the Tokara Strait, and reaches to the ASUKA line where it merges with another eddy propagating from the east at 30°N. The variation at the ASUKA line is, however, less dominated by this mode; instead, it includes the SSDT variations in the south of Shikoku and the east of Kyushu which would be directly affected by eddies from the east without passing the Tokara Strait. On the other hand, the same analysis for movements of the Kuroshio axis in the Strait indicates that they are governed by short-term variations locally confined to the Kuroshio in the East China Sea without being induced by meso-scale eddies. This results, however, seem to depend strongly on a time scale of interest. It is suggested that the long-term movements of the Kuroshio axis in the Strait would demonstrate coincidence with SSDT variation in the south of Japan. 相似文献
17.
Yoshihiko Sekine 《Journal of Oceanography》1989,45(3):190-203
The topographic effect of a meridional marine ridge on the spin-down of a cyclonic eddy is discussed by use of a two layer model. It is shown that cyclonic eddies on the eastern side of a marine ridge decay in a shorter time in comparison with those on the western side. The fast decay on the eastern side is mainly due to the planetary effect, which carries the eddy westward to a shallower region on the ridge, where remarkable frictional spin-down is carried out. Conversely, westward shift of the similar cyclonic eddy yields a weak bottom effect in the western side. It is inferred that the resulting remarkable spin-down on the eastern side of a marine ridge is one of the causes of the observed fast decay of the cyclonic cold water mass accompanied by the large meander of the Kuroshio on the eastern side of the Izu Ridge south of Japan. 相似文献
18.
Variations of the Kuroshio Axis South of Kyushu in Relation to the Large Meander of the Kuroshio 总被引：1，自引：0，他引：1
The characteristics of the Kuroshio axis south of Kyushu, which meanders almost sinusoidally, are clarified in relation to
the large meander of the Kuroshio by analyzing water temperature data during 1961–95 and sea level during 1984–95. The shape
of the Kuroshio axis south of Kyushu is classified into three categories of small, medium, and large amplitude of meander.
The small amplitude category occupies more than a half of the large-meander (LM) period, while the medium amplitude category
takes up more than a half of the non-large-meander (NLM) period. Therefore, the amplitude and, in turn, the curvature of the
Kuroshio axis is smaller on average during the LM period than the NLM period. The mean Kuroshio axis during the LM period
is located farther north at every longitude south of Kyushu than during the NLM period, with a slight difference west of the
Tokara Islands and a large difference to the east. A northward shift of the Kuroshio axis in particular east of the Tokara
Islands induces small amplitude and curvature of the meandering shape during the LM period. During the NLM period, the meandering
shape and position south of Kyushu change little with Kuroshio volume transport. In the LM formation stage, the variation
of the Kuroshio axis is small west of the Tokara Islands but large to the east due to a small meander of the Kuroshio. In
the LM decay stage, the Kuroshio meanders greatly south of Kyushu and is located stably near the coast southeast of Kyushu.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Primary Study of the Mechanism of Eddy Shedding from the Kuroshio Bend in Luzon Strait 总被引：10，自引：0，他引：10
The mechanism of the anticyclonic eddy's shedding from the Kuroshio bend in Luzon Strait has been studied using a nonlinear
2 1/2 layer model, in a domain including the North Pacific and South China Sea. The model is forced by steady zonal wind in
the North Pacific. Energy analysis is adopted to detect the mechanism of the eddy shedding. Twelve experiments with unique
changes of wind forcing speed (to obtain different Kuroshio transports at Luzon Strait) were performed to examine the relationship
between the Kuroshio transport (KT) and the eddy shedding events. In the reference experiment with KT of 22.7 Sv (forced with
zonal wind idealized from the annual mean wind stress from the COADS data set), the interval of eddy shedding is 70 days and
the shed eddy centers at (20°N, 117.5°E). When the Kuroshio bend extends westward, the southern cyclonic perturbation grows
so rapidly as to form a cyclonic eddy (18.5°N, 120.5°E) because of the frontal instability in the south of the Kuroshio bend.
In the evolution of the cyclonic eddy, it cleaves the Kuroshio bend and triggers the separation of the anticyclonic eddy.
In statistical terms, anticyclonic eddy shedding occurs only when KT fluctuates within a moderate range, between 21 Sv and
28 Sv. When the KT is larger than 28 Sv, a stronger frontal instability south of the Kuroshio bend tends to generate a cyclonic
eddy of size similar to the width of the Luzon Strait. The bigger cyclonic eddy prevents the Kuroshio bend from extending
into the SCS and does not lead to eddy shedding. On the other hand, when the KT decreases to less than 21 Sv, the frontal
instability south of the Kuroshio bend is so weak that the size of corresponding cyclonic eddy is smaller than half the width
of the Luzon Strait. The cyclonic eddy, lacking power, fails to cleave the Kuroshio bend and cause separation of an anticyclonic
eddy; as a result, no eddy shedding occurred then, either. 相似文献
20.
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