Detecting fluctuations of the Kuroshio axis south of Japan using TOPEX/POSEIDON altimeter data

Imawaki, Shiro; Gotoh, Mikio; Yoritaka, Hiroyuki; Yoshioka, Noriya; Misumi, Atsunobu

doi:10.1007/bf02236533

Cited by 6 publications

(5 citation statements)

References 37 publications

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“…Especially, the case of 16 April 1993 corresponds to the lack of TOPEX observations in the repeat cycle 20 because of operation of the POSEIDON altimeter. Imawaki et al (1995) reported that locations of the Kuroshio axis observed by the TOPEX altimeter along each ground track in each cycle agreed with hydrographic observations. Locations of the Kuroshio axis detected by the TOPEX altimeter along each track and by the TOLEXADCP are plotted in Fig.…”

Section: Resultssupporting

confidence: 59%

“…Th• p•siti•n •f the Kur•sl•• axis is one of the most robust signals detectable from the satellite altimetry, has been pointed by previous studies (e.g., Tai, 1990;Qiu et al, 1991;Qiu, 1992;Imawaki et al, 1995).…”

mentioning

confidence: 95%

“…In the Kuroshio region south of Japan, Imawaki et al (1995) constructed sea surface topography profiles, by composing the climatological mean surface dynamic height with fluctuations derived by the TOPEX altimeter, and qualitatively compared the detected locations of the Kuroshio axis with hydrographic observations.…”

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confidence: 99%

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Comparison of surface current variations observed by TOPEX altimeter with TOLEX-ADCP data

Ebuchi

Hanawa

1995

J Oceanogr

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Variations of surface current velocity derived by the TOPEX altimeter are compared with data from Tokyo-Ogasawara Line Experiment (TOLEX)-Acoustic Doppler Current Profiler (ADCP) monitoring for a period from October 1992 to July 1993. Since the locations of ADCP ship track and TOPEX altimeter ground tracks do not coincide with each other, and the temporal and spatial sampling are also different between the ADCP and altimeter observations, re-sampling, interpolation and smoothing in time and space are needed to the ADCP and altimeter data. First, the interpolated TOPEX sea surface height is compared with sea level data at Chichijima in the Ogasawara Islands. It is found that aliasing caused by the tidal correction error for M2 constituent in the TOPEX data is significant. Therefore, comparison of the TOPEX data with the TOLEX-ADCP data is decided to be made by using cross-track velocity components of the surface current, which are considered to be relatively less affected by the errors in the tidal correction. The cross-track velocity variations derived from the TOPEX sea surface heights agree well with those of the ADCP observations. The altimeterderived velocity deviations associated with transition of the Kuroshio paths coincide with the ADCP data. It is quantitatively confirmed that the TOPEX altimeter is reliable to observe the synoptic variations of surface currents including fluctuations of the Kuroshio axis.

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Section: Resultssupporting

confidence: 59%

mentioning

confidence: 95%

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Comparison of surface current variations observed by TOPEX altimeter with TOLEX-ADCP data

Ebuchi

Hanawa

1995

J Oceanogr

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“…After the launch of the ocean topography experiment (TOPEX)/Poseidon in 1992, altimeter-derived sea surface height (SSH) became widely available and enabled us to capture oceanic variations, including the variations of the Kuroshio path. Imawaki et al (1996) successfully detected the fluctuations of the Kuroshio axis south of Japan using the TOPEX/Poseidon altimeter data. Ebuchi and Hanawa (2001) investigated the trajectory of the mesoscale eddies in the Kuroshio recirculation region and pointed out that the interaction between the mesoscale eddy and the Kuroshio east of the Kyushu may trigger meanders.…”

Section: Introductionmentioning

confidence: 95%

Short-range prediction experiments of the Kuroshio path variabilities south of Japan

Usui¹,

Tsujino²,

Fujii³

et al. 2006

Ocean Dynamics

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Assimilation and prediction experiments of the Kuroshio path variability south of Japan were conducted to investigate the predictability of the Kuroshio path. The assimilation and prediction system is composed of an eddyresolving model and a three-dimensional variational analysis scheme with vertical coupled temperature-salinity empirical orthogonal function modes. The sea surface height (SSH) variability and the variations of the Kuroshio path of the assimilation fields are in good agreement with those observed. The results of the assimilation are then used as the initial conditions for 138 cases of 90-day prediction experiments conducted from 1993 to 2004. The predictive limit of our system is assessed by the SSH anomaly in the assimilation field and is found to be around 40-60 days, which is much longer than that of the persistence. The prediction results show good performance in the transition stage from a straight to a meandering path. For example, a large meandering event that occurred in August 2004 is successfully predicted in a 2-month forecast. Two types of failure cases are investigated. One is a case where the eastward propagation speed of the meander is faster than a real state. The dynamical response of the model to the assimilation revealed that an initial shock, caused by the dynamically unbalanced initial condition, induces the fast eastward propagation of the meander. The other case exhibits an unrealistic meander. In this case, a cold anomaly at an intermediate layer in the initial condition grows rapidly and results in the unrealistic meander. This implies that the Kuroshio path south of Japan has a chaotic nature. These facts revealed by the failure cases give us some insight for improving the predictive skill of the Kuroshio path variability.

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“…They combine the temporal fluctuation of sea surface dynamic topography (SSDT) with the climatological mean SSDT to obtain a composite SSDT. Imawaki et al [3] studied the fluctuations of the Kuroshio axis south of Japan using TOPEX/Poseidon altimeter data.…”

Section: Introductionmentioning

confidence: 99%

The relationship between time series sea surface slope and El Nino event from satellite altimetry: a potential indicator

Chen²,

Guan³

et al.

IGARSS 2001. Scanning the Present and Resolving the Future. Proceedings. IEEE 2001 International Geoscience and Remote Sensing

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China suffered a serious flooding in the summer of 1998, which is regarded as initiated by the 1997/1998 El Niño. From previous investigators we know that the sea water transportation across Takara Strait is closely related with the occurrence of El Niño event. As the geostrophic current Kuroshio flows almost perpendicularly across the Takara Strait, the net volume transportation at this site may be well described by the sea surface slope. In the present study, decadal monthly averaged sea surface slope across Takara Strait are derived and presented combining the ERS-1,2/ALT measurements of 35-day repeat and the TOPEX/Posidon data of 10 day repeat. It is found that an abnormally high peak takes place in the October of 1996, i.e., one year prior to the 1997/1998 El Niño. To further test the feasibility of the method, the time series sea surface slope across PN section were also examined through which the Kuroshio in the East China Sea goes perpendicularly as well. It is revealed that an abnormally low peak appears exactly in the October of 1996. This is just the opposite to what happens in Takara Strait during the same period. However, the geostrophic transport at PN section is out-of-phase with that at Takara Strait on the basis of field investigations, which shows the two results are virtually in support of each other. Our preliminary results demonstrate the sea surface slope at Takara Strait may be regarded as an index for the upcoming El Niño event. Relevant dynamic mechanisms are discussed.I.

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Detecting fluctuations of the Kuroshio axis south of Japan using TOPEX/POSEIDON altimeter data

Cited by 6 publications

References 37 publications

Comparison of surface current variations observed by TOPEX altimeter with TOLEX-ADCP data

Comparison of surface current variations observed by TOPEX altimeter with TOLEX-ADCP data

Short-range prediction experiments of the Kuroshio path variabilities south of Japan

The relationship between time series sea surface slope and El Nino event from satellite altimetry: a potential indicator

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