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1.
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
2.
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
3.
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
4.
5.
Variability of Kuroshio velocity assessed from the sea-level difference between Naze and Nishinoomote 总被引：1，自引：0，他引：1
Masaki Kawabe 《Journal of Oceanography》1988,44(6):293-304
Variations of current velocity of the Kuroshio are examined using the 1965–1983 sea-level difference between Naze and Nishinoomote, located on the offshore and onshore sides of the Kuroshio in the Tokara Strait south of Kyûshû.Interannual variations of Kuroshio velocity are large, especially at periods longer than five years and around 2.1 years. They are almost determined by those of sea level on the offshore side of the Kuroshio. They are highly coherent with the offshore sea level at periods longer than 1.7 years, and incoherent with the onshore sea level at periods longer than 2.8 years.The mean seasonal variation averaged for 19 years is at its maximum in July and at its minimum in the second half of October, with a sharp decrease in August and September. However, such a variation does not repeat every year. Amplitude, dominant period and phase are greatly different by year, and they can be roughly divided into four groups: small-amplitude group, semiannual-period group, and two annual-period groups with different phases. The only feature found in almost all years is a weak velocity from September to December.The amplitude of seasonal variation tends to be large in the formation years of the large meander (LM) of the Kuroshio and small during the LM period. It is also large in the years preceding El Niño, and diminishes remarkably in El Niño years.Kuroshio velocity in the Tokara Strait is incoherent with position of the Kuroshio axis over the Izu Ridge, but highly coherent with 70-day variations of coastal sea levels which are dominant during the LM period. 相似文献
6.
Masaki Kawabe 《Journal of Oceanography》1980,36(4):227-235
The sea level difference between Naze and Nishinoomote and sea level anomalies (the residuals after removal of seasonal variations) around the Nansei Islands were examined in relation to the large meander in the Kuroshio south of central Japan. They are indices of surface velocity and geostrophic transport of the Kuroshio in the Tokara Strait and in the East China Sea, respectively. All of them were large during the meandering period, and each of them reached a maximum before or after the generation of the large meander in 1975. Thus the surface velocity and the geostrophic transport of the Kuroshio in the Tokara Strait and the East China Sea were large during the meandering period. The sea level difference between Naze and Nishinoomote (or Makurazaki) shows that the surface velocity and geostrophic transport in the Tokara Strait were significantly larger during the extinction stage in 1963 and during the generation stage in 1975 and were correlated with the position of the Kuroshio east of Kyûshû in 1974 and 1975 before the generation of the large meander.The surface velocity of the Kuroshio southeast of Yakushima (E-line) based on dynamic calculation referred to 1,000 db was weak during the meandering period, and was out of phase with the variation of surface velocity in the Tokara Strait monitored by tide gauge data. The analysis of GEK and hydrographic data shows that southwestward flow existed below 600 m in the slope region on the E-line and weakened during the meandering period. Thus, the out-of-phase variation in surface velocity mentioned above seems to be partly explained by the variation in velocity on the reference level at the E-line. 相似文献
7.
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
8.
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
9.
Index and Composites of the Kuroshio Meander South of Japan 总被引：1，自引：0，他引：1
Nikolai Maximenko 《Journal of Oceanography》2002,58(5):639-649
Using the merged NOAA National Oceanographic Data Center (NODC)/Japan Oceanographic Data Center (JODC)/Marine Information
Research Center (MIRC) historical hydrographic dataset, a new Kuroshio large meander (LM) index is introduced. This index
helps to distinguish between the LM events and other types of Kuroshio Current (KC) variability south of Japan. Observations,
re-systematized according to the index, provide composite patterns of typical formation and decay of the LM. The patterns
reveal a remarkable similarity between individual LMs and support the deterministic rather than the stochastic model of LM
evolution on a time-scale of one year. A “trigger” meander (TM) occurs on composite maps six months prior to the LM formation
as a 1° latitude southward shift of the KC axis south of Kyushu. When propagating eastward along the coast of Japan, TM gradually
increases in area. In principal the emergence of LM takes only one month. East of TM and LM a remarkable onshore shift of
the KC is noticed, supplying the coastal region with warm water. Other warm anomalies are found on the warm side of KC next
to the propagating TM and in the larger warm eddy area southeast of Kyushu. Different LMs survive for different times and
decay in some months after KC “jumps” across the Izu Ridge. Changes of water properties on isopycnals in the interior of LM
can be roughly described by two-layer kinematics with an interface at σθ = 27 which suggests a strong inflow of deep Kuroshio waters into the LM core during the formation of the latter.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
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
11.
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
12.
Variability of the Kuroshio in the East China Sea in 1993 and 1994 总被引：11，自引：1，他引：10
INTRODUCTIONTherearemanyworksabouttheKuroshioVTintheEastChinaSeaanditsseasonalvariabil*ThisprojectwassupportedbytheNationalNaturalScienceFoundationofChinaundercontractNo.49776287.1.SecondinstituteofOceanography,StateOceanicAdministration,Hangzhou310012,Chinaity(Guan,1988;Nishizawaetal.,1982;SunandKaneko,1993;Yuanetal.,1990,1993,1994,1995).Thecomputationmethodusedtobethedynamicmethod(Guan,1988;Nishizawaetal.,1982;SunandKaneko,1993),butrecentlytheinverseandthemodifiedinversemetho… 相似文献
13.
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
14.
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
15.
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16.
The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands 总被引：3，自引：0，他引：3
In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i 相似文献
17.
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
18.
Variations of water and flow in Sagami Bay in relation to the Kuroshio path variations are examined by using 100m-depth temperature and salinity data from 25 stations as well as sea level data from five stations (Minami-Izu, ItÔ, Ôshima, Aburatsubo, Mera). In regard to temperature, anomalies from the mean seasonal variations are used. Results show that water properties are clearly different between the three typical paths of the Kuroshio. The difference is more remarkable in temperature than in salinity; temperature is higher during the typical large-eander (LM) path, and lower during the offshore non-large-meander (NLM) path, compared with the nearshore NLM path. Temperature anomaly and salinity distributions, as well as the Ôshima minus Minami-Izu and Ôshima minus Mera sea-level differences strongly suggest that the flows during the typical LM path are distributed as hitherto described in past studies, that is, water in the mouth region of the bay flows clockwise around Ôshima from the west channel to the east channel, and a counterclockwise eddy exists in the interior. On the other hand, flows during the nearshore and offshore NLM paths seem to be quite different from those during the typical LM path; velocities are very weak, and the directions of circulation is frequently reversed. This tendency also can be seen during parts of LM period in which the Kuroshio takes a non-typical LM path.Water properties in Sagami Bay are most characteristic during transitions between nearshore and offshore NLM paths. During transitions from nearshore to offshore NLM paths, temperatures are extremely high as a whole in the bay, while during reverse transitions, both temperatures and salinities are very low in the entire region. 相似文献
19.
Distribution of the sea surface temperature (SST) across the Kuroshio has been measured in the Tokara Strait by the Kagoshima Prefectural Experimental Fishery Station, using a thermometer installed on boardEmerald-Amami, a ferry that operates regularly between Kagoshima and Naha. The data from 1 October 1978 to 30 September 1981 were analyzed in this paper.A sharp temperature front is usually formed at the northern edge of the current zone of the Kuroshio, and its position is very variable and moves north and south between Satamisaki and Nakanoshima. The northward migration of the front can easily be traced, but the southward migration is obscure in many cases. Some of the southward migrations seem to be understood as arising from the alternate appearance of two different fronts, namely a weakening of the northern front and a strengthening of the southern front, which are associated with the double structure of the Kuroshio front. The temperature contrast across the Kuroshio front is very weak in August through October, and the phase of its seasonal variation lags a few months behind that of temperature itself. Transitions between the states with and without temperature contrast occur suddenly, though the transition times differ year by year. Periodical fluctuations with a period of several tens of days are often observed in the migration region of the Kuroshio front. The fluctuations sometimes look very periodical within limited time periods, but the fluctuations are very changeable in nature from year to year.The results show that continuous observation of the SST distribution across the Tokara Strait yields a good tool for monitoring fluctuations of the Kuroshio path and the occurrence of the Ohsumi Branch Current, at least in the season when a large horizontal temperature contrast exists. 相似文献
20.
Elizabeth M. Douglass Steven R. Jayne Frank O. Bryan Synte Peacock Mathew Maltrud 《Journal of Oceanography》2012,68(5):625-639
A high-resolution ocean model forced with an annually repeating atmosphere is used to examine variability of the Kuroshio, the western boundary current in the North Pacific Ocean. A large meander (LM) in the path of the Kuroshio south of Japan develops and disappears in a highly bimodal fashion on decadal timescales. The modeled meander is comparable in timing and spatial extent to an observed feature in the region. Various characteristics of the LM are examined, including relative vorticity, transport, and velocity shear. The many similarities between the model and observations indicate that the meander results from intrinsic oceanic variability, which is represented in this climatologically forced model. Each LM is preceded by a smaller “trigger” meander that originates at the south end of Kyushu, moves up the coast, and develops into the LM. However, there are also many meanders very similar in character to the trigger meander that do not develop into LMs. Formation of an LM only occurs when a deep anticyclone associated with the trigger meander forms near Koshu Seamount. Furthermore, the major axis of that deep anticyclone must be oriented away from the coast, rather than alongshore. In the specific case of interaction of a trigger meander with a deep anticyclone with major axis oriented away from the coastline, LM formation occurs. 相似文献