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1.
日本南部黑潮存在多种路径模态:近岸非大弯曲路径、离岸非大弯曲路径和大弯曲路径。黑潮延伸体的路径存在两种典型模态:收缩态和伸展态。从地理位置看, 日本南部黑潮和黑潮延伸体是相邻的, 但它们的路径状态是否存在关联一直存在争议。本文基于卫星观测的海表高度资料和长期的海洋高分辨率再分析资料, 对日本南部黑潮和黑潮延伸体路径状态之间的关联性进行定量分析, 结果表明:日本南部黑潮和黑潮延伸体的路径状态存在一定的关联。当日本南部黑潮处于近岸非大弯曲和大弯曲路径时, 黑潮延伸体主要处于伸展态; 当日本南部黑潮处于离岸非大弯曲时, 黑潮延伸体处于伸展态和收缩态的比例相当。进一步分析表明, 黑潮流轴处于伊豆海脊的位置部分决定了上述关系, 可能存在其他因素调制了两者的关联性。 相似文献
2.
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
3.
The influences of mesoscale eddies on variations of the Kuroshio path south of Japan have been investigated using time series
of the Kuroshio axis location and altimeter-derived sea surface height maps for a period of seven years from 1993 to 1999,
when the Kuroshio followed its non-large meander path. It was found that both the cyclonic and anticyclonic eddies may interact
with the Kuroshio and trigger short-term meanders of the Kuroshio path, although not all eddies that approached or collided
with the Kuroshio formed meanders. An anticyclonic eddy that revolves clockwise in a region south of Shikoku and Cape Shionomisaki
with a period of about 5–6 months was found to propagate westward along about 30°N and collide with the Kuroshio in the east
of Kyushu or south of Shikoku. This collision sometimes triggers meanders which propagate over the whole region south of Japan.
The eddy was advected downstream, generating a meander on the downstream side to the east of Cape Shionomisaki. After the
eddy passed Cape Shionomisaki, it detached from the Kuroshio and started to move westward again. Sometimes the eddy merges
with other anticyclonic eddies traveling from the east. Coalescence of cyclonic eddies, which are also generated in the Kuroshio
Extension region and propagate westward in the Kuroshio recirculation region south of Japan, into the Kuroshio in the east
of Kyushu, also triggers meanders which mainly propagate only in a region west of Cape Shionomisaki.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
基于1.5层浅水方程模式,利用条件非线性最优参数扰动(CNOP-P)方法,研究模式参数的不确定性对黑潮大弯曲路径预报的影响。研究表明,单个模式参数误差如侧向摩擦系数误差、界面摩擦系数误差以及在不同季节具有不同约束的风应力大小误差,对黑潮大弯曲路径预报的影响较小,并且对背景流场的选取具有一定的敏感性;所有模式参数误差同时存在时对黑潮大弯曲路径预报具有一定的影响,并且预报结果在9个月左右不能被接受。因此,要提高黑潮大弯曲路径的预报技巧,模式中的参数需要给出更好的估计。 相似文献
5.
过去的研究认为,黑潮延伸体的年代际振荡受来自其下游的太平洋年代际振荡（PDO）相关联的信号主导,但最近的观测表明这种调控机制在2017年9月之后不再成立。与此同时,黑潮延伸体的上游即日本南部黑潮正在发生一次大弯曲事件。利用26年（1993–2018年）的卫星高度计提供的海表高度距平数据和自组织映射（SOM）方法,本文研究了日本南部黑潮与黑潮延伸体的时空模态及其因果关系。结果表明,SOM能有效地提取两个海区的典型空间模态,且它们的演变轨迹表明当日本南部黑潮处于大弯曲（离岸型非大弯曲）路径时,黑潮延伸体趋于稳定（不稳定）态。基于SOM识别得到的海表面高度距平（SLA）特征区及特征时间模态,我们进一步利用一种最近发展的定量因果分析方法研究了两个流系之间的因果关系。研究发现,当黑潮大弯曲发生时,日本南部黑潮和黑潮延伸体之间存在双向因果,但因果关键区不同。前者对后者的影响集中在纪伊半岛东南侧及黑潮延伸体“两脊一槽”区域,而后者对前者的影响则集中在黑潮延伸体“两脊一槽”区域及黑潮再循环流区域。这说明黑潮大弯曲的发展对黑潮延伸体的稳定性有重要作用,同时黑潮延伸体通过调制南部再循环流影响日本南部黑潮的路径。不同的是,当离岸型非大弯曲路径发生时,只有从日本南部黑潮向黑潮延伸体的单向因果关系,且因果性主要集中在伊豆海脊及再循环流区域。这与该时期海表高度负异常沿日本南岸不断向位于下游的黑潮延伸体再循环流的传播有关,它使得黑潮延伸体变得不稳定。 相似文献
6.
Kunio Kutsuwada 《Journal of Oceanography》1988,44(2):68-80
Relationships of the sea level differences between Naze and Nishinoomote and between Kushimoto and Uragami with wind stress over the North Pacific are examined for interannual variability. These sea level differences are considered to be indications of Kuroshio transport in Tokara Strait and Kuroshio path south of Enshu-nada, respectively. In the sea level difference between Kushimoto and Uragami, dominant variations are found to have periods of about seven years and 3–4 years. The variation of about 7-year period, which corresponds to that in the Kuroshio path between the large meander and non-large meander, is coherent with the variation of the wind stress curl in a region about 2,400 km east of the Kii Peninsula, where negative stress curl weakens about two years before the sea level difference drops (i.e. the large meander path in the Kuroshio generates). The variation of the 3–4 year period is coherent with that of the wind stress in a large area covering the eastern equatorial Pacific, which suggests that it links with global-scale atmospheric variations. Interannual variation in sea level difference between Naze and Nishinoomote is not coherent with that between Kushimoto and Uragami, which suggests that it is not related to the variation of the Kuroshio path south of Enshu-nada, but is coherent with that of the zonally-integrated Sverdrup transport in the latitudinal zone along 30°N. It is suggested that the interannual variation of the Kuroshio transport in Tokara Strait can be explained by the barotropic response to the wind stress. 相似文献
7.
Nagano Akira Yamashita Yusuke Hasegawa Takuya Ariyoshi Keisuke Matsumoto Hiroyuki Shinohara Masanao 《Marine Geophysical Researches》2019,40(4):525-539
Since September 2017, the Kuroshio has taken a large-meander (LM) path in the region south of Japan. We examined characteristics of the 2017–present LM path in comparison with previous LM paths, using tide gauge, altimetric sea surface height, and bottom pressure data. The 2017–present LM path was formed from a path passing through a channel south of Hachijo-jima Island, while a typical LM path originated from a path through a channel north of Miyake-jima Island. The meander trough of this atypical path was found to be shifted far to the east and to vary on a timescale of months. These characteristics are different from those of a typical LM path but they are similar to those of the 1981–1984 LM path. Therefore, we identified two types of LM path; a stable and unstable LM paths. The 2017–present unstable type large meander has a zonal scale greater than that of the 2004–2005 stable type large meander and protrudes from the eastern boundary of the Shikoku Basin, i.e., Izu-Ogasawara Ridge. No significant bottom pressure depression was observed, associated with the formation of the 2017–present LM path, indicating that baroclinic instability was not important in the formation of this LM path. Due to no significant bottom steering, even during the 2017–present LM period, a mesoscale current path disturbance occurred southeast of Kyushu, propagated eastward, and amplified the offshore displacement of the Kuroshio.
相似文献8.
The sea level difference between Kushimoto and Uragami, located to the west and east of the southern tip of the Kii Peninsula, is relatively large in periods of non-large meander path (nLMP) of the Kuroshio south of Japan in comparison with periods of large meander path (LMP). Based on this clear relationship, the sea level difference between Kushimoto and Uragami has been used as an index showing the periods of nLMP and those of LMP of the Kuroshio south of Japan. It has been pointed out that warm and saline Kuroshio water, separated from the main path of the Kuroshio, has a tendency to approach the western area off Kii Peninsula to off Muroto Peninsula in periods of nLMP, while it approaches the eastern area off Kii Peninsula to Omae-zaki in periods of LMP. On the basis of this observational evidences, the dynamic background underlaying the well-known relationship between the Kuroshio path and the sea level difference between Kushimoto and Uragami is examined in the present study, using the temperature and salinity data observed by Wakayama Prefectural Fisheries Experimental Station and Fisheries Research Institute of Mie. It is shown that deviations in vertically integrated specific volume off Kushimoto and Uragami almost equal deviations in observed sea level at Kushimoto and Uragami, respectively. It is also shown that the difference in vertically integrated specific volume between off Kushimoto and off Uragami almost equals the difference in observed sea level between Kushimoto and Uragami. As for the Kuroshio water, the high-temperature contribution is predominant for its specific volume rather than that of high salinity, which yields thermal expansion in comparison with coastal water. Because the difference in vertically integrated specific volume between off Kushimoto and off Uragami almost equals the difference in observed sea level between Kushimoto and Uragami, it is concluded that the relationship between the Kuroshio path and sea level difference between Kushimoto and Uragami is caused by the different approaching of the warm Kuroshio water between in nLMP periods and in LMP periods. 相似文献
9.
INTRODUCTIONBeing a current of high temperature and high salinity, the Kuroshio carries a large amount ofheat from low latitude tropical ocean to high latitude ocean, and plays an imPOrtant role in theheat balance in East Asia. The variability of the Kurosl,io can affect the climate of East Asia, aswell as the ocean environment and the fishery resources. A lot of studies showed that the variabilitiies of the Kuroshio were related to the global changes especially to the onset of ENSO.… 相似文献
10.
Numerical Study of the Generation and Propagation of Trigger Meanders of the Kuroshio South of Japan
We examine the processes underlying the generation and propagation of the small meander of the Kuroshio south of Japan which occurs prior to the transition from the non-large meander path to the large meander path. The study proceeds numerically by using a two-layer, flat-bottom, quasi-geostrophic inflow-outflow model which takes account of the coastal geometries of Kyushu, Nansei Islands, part of the East China Sea, and the Izu Ridge. The model successfully reproduces the observed generation and propagation features of what is called "trigger meander" until it passes by Cape Shiono-misaki; presumably because of the absence of the bottom topography, the applicability of the present numerical model becomes questionable after the trigger meander passes by Cape Shiono-misaki. The generation of the trigger meander off the south-eastern coast of Kyushu is shown to be associated with the increase in the supply of cyclonic vorticity by the enhanced current velocity in the upper layer along the southern coast of Kyushu where the no-slip boundary condition is employed. Thereafter, the trigger meander propagates eastward while inducing an anticyclone-cyclone-cyclone pair in the lower layer. The lower-layer cyclone induced in this way, in particular, plays a crucial role in intensifying the trigger meander trough via cross-stream advection in the upper layer; the intensified trigger meander trough then further amplifies the lower-layer cyclone. This joint evolution of the upper-layer meander trough and the lower-layer cyclone indicates that baroclinic instability is the dominant mechanism underlying the rapid amplification of the eastward propagating trigger meander. 相似文献
11.
Masaki Kawabe 《Journal of Oceanography》1986,42(4):319-332
I summarize the variations of the path of the Kuroshio and of the Tsushima Current mainly based on the results of my studies. The Tsushima Current forms three branches just after it enters the Japan Sea through the Tsushima Strait. The first and third branch currents flow along the Japanese and Korean coasts, respectively, and the second branch current flows from the western channel of the Tsushima Strait to the west of the Oki Islands only in summer from June to August. Properties of the topographic waves which are thought to work on the formation of the second branch are described mainly in terms of the dispersion relations. The Kuroshio has three typical paths,i.e., the nearshore and offshore non-large-meander paths and the typical large-meander path. The Kuroshio alternately takes the nearshore and offshore paths in the non-large-meander period, occasionally changes from the nearshore nonlarge-meander path to the large-meander path and, after having taken the large-meander path for several years, changes to the offshore non-large-meander path. Sea levels south of Japan are clearly different between the non-large-meander and large-meander periods, while they are not different between the periods of the nearshore and offshore non-large-meander paths. But, sea level and water properties in the coastal region show remarkable features during short periods of transitions between the typical non-large-meander paths. Future problems and subjects of studies on these currents are indicated. Especially, importance of velocity monitoring of the Kuroshio is emphasized, and a design of the observation across the Tokara Strait is proposed. 相似文献
12.
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
13.
Relationship between the path of the Kuroshio in the south of Japan and the path of the Kuroshio Extension in the east 总被引：2，自引：0，他引：2
A relationship between paths of the Kuroshio and Kuroshio Extension (KE) is investigated, using the satellite-derived altimetry
dataset of 1993–2008. When the Kuroshio takes the nearshore nonlarge meander path or typical large meander path and resultantly
goes through the deeper channel (about 2500 m) of the Izu-Ogasawara Ridge, the KE path adopts a relatively stable state with
the two quasi-stationary meanders. On the other hand, when the Kuroshio takes the offshore nonlarge meander path and then
passes over the shallower part of the Ridge (about 1000 m), the KE path tends to be convoluted, i.e., an unstable state. 相似文献
14.
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
15.
Masaki Kawabe 《Journal of Oceanography》1987,43(2):111-123
Spectral properties of sea levels at Naze, Nishinoomote, Kushimoto, Uragami, Miyake-jima and HachijÔ-jima are examined for the non-large-meander (February 1964 – May 1975) and large-meander (October 1975 – December 1979) periods, and the periodicity of variation of the Kuroshio path is clarified.The large meander of the Kuroshio occurs with a primary period of about 20 years and secondary period of 7 to 8. 5 years. During the non-large-meander period, the Kuroshio alternately takes the nearshore and offshore non-large-meander paths with a primary period of 1. 6–1. 8 years. This variation is moreover composed of 110-day, around 195-day and annual periods. The 110-day variation of the Kuroshio path appears to have influence on the coastal sea levels between the Kii Peninsula and the Izu Ridge;i. e., the coastal sea levels rise and fall with one-month time lag after the Kuroshio has begun to approach and leave the Japanese coast. During the large-meander period, the 70 and 110-day variations are remarkable in sea levels south of Japan except Miyake-jima and HachijÔ-jima. The 70-day variation is highly coherent throughout the south coast of Japan; the coherent area of the 110-day variation seems to be smaller.The sea-level variations at Naze and Nishinoomote are not significantly coherent for any of the periods except for annual and semiannual cycles during both the non-large-meander and large-meander periods. That is, the sea-level variations are incoherent between the onshore and offshore sides of the Kuroshio, except for seasonal variation. 相似文献
16.
Yoichi Ishikawa Toshiyuki Awaji Nobumasa Komori Takahiro Toyoda 《Journal of Oceanography》2004,60(2):293-301
A sensitivity experiment has been performed by assimilating altimetric data into a 1.5-layer primitive equation model as a
first attempt to examine the impact of initialization on forecasts of the Kuroshio path variability south of Japan. By exploiting
the advantage of an adjoint model, our approach clearly shows that a small meander off Shikoku Island has a large impact on
the prediction of meander growth in the Kuroshio region. Further, the strengthening of the Kuroshio current and its recirculation
clearly becomes an important factor in the development of the meander. These results demonstrate the effectiveness of our
assimilation approach in identifying efficient initialization schemes on numerical forecasting of the Kuroshio south of Japan
and should help in the construction of an effective observing system for improving the forecasting.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
A method of quantifying the penetration of the Kuroshio into the Luzon Strait is improved with simulated salinity. The new method is applied in an area bounded by 0.6 correlation coefficient contour to the point of 20 N, 118 E which is determined by EOF analysis. The results suggest that the method is suitable for indicating Kuroshio’s intrusion into the South China Sea quantitatively. As an indicator, the Kuroshio penetrating the Luzon index (KLI) reveals obvious annual cycle and weak bimodality. For annual periods, indexes on the surface and subsurface which point the same events have totally opposite signs due to the winter burst of surface westward current. On long-term period, the surface and subsurface indexes have consistent signs. A subsurface index on 150 m avoiding high frequency signals from the surface can be used for indicating long-term Kuroshio intrusion variation. An anti-phase pattern in wavelet coherence map between KLI and Japan large meander index shows that the Luzon Strait is a "smoother" reducing the variability of the Kuroshio transport changes on long-term periods. 相似文献
18.
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
19.
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
20.
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