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1.
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
2.
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
3.
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
4.
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
5.
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
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.
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
8.
Three Kuroshio small meanders off the southeast coast of Kyushu that occurred during 1994 to 1995 were investigated by using
satellite-derived sea surface temperature (SST) and sea surface height (SSH) maps, World Ocean Circulation Experiment (WOCE)
Hydrographic Program (WHP) repeat section and Japan Meteorological Agency (JMA) hydrographic observations. Based on the satellite
data, we observed that the three small meanders are formed by different processes: the triggering and growth of these meanders
are caused by a cyclonic eddy propagating from the Kuroshio recirculation region or Kuroshio front meanders traveling from
the East China Sea. Investigation of the two small meanders in 1994 and 1995 spring that are captured by the WHP observation
showed quite consistent hydrographic features. On the nearshore side of the meandering Kuroshio, a countercurrent appears,
associated with vertically uniform upward lifts of the isopycnals from sea surface to bottom at the boundary between the countercurrent
and the Kuroshio. In the countercurrent region, the waters in the density ranges of the North Pacific subtropical mode water
(NPSTMW) and the North Pacific Intermediate Water (NPIW) are more saline and less saline than typical waters that the Kuroshio
carries in a non-small meander state, respectively. There are indications that high-salinity NPSTMW and low-salinity NPIW
distributed off the Kuroshio was supplied to the countercurrent region. In the meandering Kuroshio flow, while there is no
notable change in properties around the NPSTMW density range, salinity of the NPIW is significantly higher than that carried
by the Kuroshio in a non-small meander state, but not higher than that in the Kuroshio at the Tokara Strait, which suggests
that saline NPIW from the Tokara Strait, less mixed with low-salinity NPIW off the Kuroshio, may be carried by the meandering
Kuroshio.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
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
10.
Historical GEK data provided by JODC is analyzed to investigate the characteristic variation in velocity of the Kuroshio, with special reference to the formation of small meanders south of Kyûshû. It is found that, during or prior to the period of small meander formation, there is a tendency for an abrupt increase in the current velocity west of Yaku-Shima (Yaku-Island), representing an increase in the main current intensity upstream. Also, there are apparent time lags in the variation in current velocity along the path of the Kuroshio between the upstream and the downstream regions of the small meander area. Namely, it is apparent that the increase in Kuroshio velocity in the Satsunan Strait procedes that offshore of Shikoku during the period of the small meander formation, by the order of one month. These results indicate that a nonlinear effect due to the increase in current velocity is a possible cause of the generation of small meanders. 相似文献
11.
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
12.
The processes underlying the development of the Kuroshio large meanders that occurred in 1986 and 1989 are investigated using
a satellite SST data set and hydrographic data. In both processes visible on the satellite SST images, a round-shaped, lower
SST region with a diameter of about 200 km is found to the east of the Kuroshio small “trigger” meander (Solomon, 1978) until
the region became extinguished near theEnshu Nada. The lower SST region can be interpreted as an anti cyclonic eddy, mainly because of the existence of a warm water mass in
the subsurface layer of this region. The warm water mass is characterized by a constant temperature of 18–19°C, the maximum
thickness of which is about 400 m. The satellite images show that the eddy is closely related to the Kuroshio path transforming
into a shape like the letter “S”. This means that the eddy plays an important role in the development of the Kuroshio large
meander since this, too, tends to follow an “S”-shaped path. Added to this, the subsurface layer structure of the eddy is
similar to that of the warm water mass offShikoku. This similarity, together with the eddy behavior visible on the satellite SST images, implies that the examined eddy corresponds
to the warm water mass offShikoku. In other words, the warm water mass offShikoku can be advected near to theEnshu Nada when the Kuroshio large meander occurs. 相似文献
13.
Sea level changes south of Japan associated with the non-large-meander path of the Kuroshio 总被引：1，自引：0，他引：1
Masaki Kawabe 《Journal of Oceanography》1989,45(3):181-189
Sea levels south of Japan from 1964 to 1975 are examined in terms of the nearshore and offshore non-large-meander (NLM) paths of the Kuroshio and the transitions between them.The sea-level anomalies from the annual variations on the south coast of Japan are much larger during the transition from the nearshore to offshore NLM paths than during the reverse transition by 9 cm on average. This characteristic can be seen only in the coastal region of the Kuroshio-flowing area, so that the sea-level difference of Naze minus Nishinoomote (indicator of Kuroshio velocity) during the offshore to nearshore transition is larger by 15 cm than during the reverse transition.The transition from the offshore to nearshore NLM paths occurs when the velocity of the Kuroshio is large or increasing, while the nearshore to offshore transition occurs when it is small or decreasing. The former transition occurs whenever the velocity increases greatly, whereas the latter one does not always occur even though the velocity decreases.The sea-level difference between Kushimoto and Uragami is highly coherent with the alternate appearance of the nearshore and offshore NLM paths. Offshore NLM paths longer than 2.5 months appear during large falls of the sea-level difference of Kushimoto minus Uragami, while large rises of the sea-level difference correspond to long-lasting nearshore NLM paths. The mean sea-level difference during the nearshore NLM path is larger by 4 cm than that during the offshore NLM path. 相似文献
14.
Dynamic Structure of the Kuroshio South of Kyushu in Relation to the Kuroshio Path Variations 总被引：1，自引：1，他引：1
The variation of velocity and potential vorticity (PV) of the Kuroshio at the PN line in the East China Sea and the TK line
across the Tokara Strait were examined in relation to the path variations of the Kuroshio in the southern region of Japan,
using quarterly data from a conductivity-temperature-depth profiler and a shipboard acoustic Doppler current profiler during
1987–97. At the PN line the Kuroshio has a single stable current core located over the continental slope and a significant
maximum of PV located just onshore of the current axis in the middle part of the main pycnocline. On the other hand, the Kuroshio
at the TK line has double current cores over the two gaps in the Tokara Strait; the northern core has a much larger velocity
than the southern core on average during periods of the large meander of the Kuroshio, while the difference in strength between
the double cores is small during the non-large-meander (NLM) period. At the TK line, PV in the middle pycnocline is variable;
it is small and nearly uniform throughout the section for 40% of the total observations, while it has a significant maximum
near the northern core for 30% and two maxima corresponding to the double current cores for 23%. The small, nearly uniform
PV occurs predominantly during the NLM period, and is closely related to the generation of the small meander of the Kuroshio
southeast of Kyushu.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
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
16.
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
17.
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
18.
Empirical orthogonal function(EOF) analysis was applied to a 50-year long time series of monthly mean positions of the Kuroshio path south of Japan from a regional reanalysis. Three leading EOF modes characterize the contributions from three typical paths of the Kuroshio meander: the typical large meander path, the offshore nonlarge meander path, and the nearshore non-large meander path, respectively. Accordingly, the spatial variation characteristics of oceanic anomaly fields can be depicted by... 相似文献
19.
The influence of the Kuroshio flow on the horizontal distribution of North Pacific Intermediate Water (NPIW) in the Shikoku
Basin is examined based upon observational data collected by the training vessel “Seisui-maru” of Mie University together
with oceanographic data compiled by the Japan Oceanographic Data Center (JODC). Although it has been stated that the NPIW
with salinity less than 34.2 psu had been confined to the south of the Kuroshio main axis along the PT (KJ) Line on the eastern
side of the Izu Ridge, a similar tendency can be detected on the western side of the Izu Ridge. Namely, the NPIW on the southern
side of the Kuroshio main axis in the Shihoku Basin does not indicate a tendency to go northward across the Kuroshio main
axis without an increase in salinity of more than 34.2 psu. However, the JODC data show that less saline water (<34.2 psu)
was present on the northern side of the Kuroshio main axis south of the Kii Peninsula in May 1992. Satellite observed sea
surface temperature (SST) data suggested that the Kuroshio approaches the Kii Peninsula after forming a small meander off
Kyushu and some intrusions of the NPIW into the northern coastal side of the Kuroshio main axis occurred in this period. It
is concluded that intrusion of the NPIW with salinity less than 34.2 psu to the northern coastal side through the Kuroshio
main axis occurred during the decay period of the small meander path in May 1992. Based on these observational results, the
source of the salinity minimum water on the northern coastal side of the Kuroshio main axis is discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Harold Solomon 《Journal of Oceanography》1978,34(3):81-84
Current path records of the Kuroshio off southern Japan have been examined for the period 1960–1977. Together with previously published results (S.Yoshida, 1961;Shoji, 1972) this evidence indicates that all major changes in the path of the Kuroshio off Cape Shiono were preceded by the formation of a small trigger meander off Kyushu and its downstream propagation to Cape Shiono. The periods of occurrence of these trigger meanders, most of which decay without propagating downstream, are documented. Small meanders off Kyushu occur throughout the year, but all of those which triggered changes off Cape Shiono were initially generated in the period January–April.Contribution No. 4 of the Pacific International Research Association. 相似文献