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Journal Articles

Identification of coral spawn source areas around Sekisei Lagoon for recovery and poleward habitat migration by using a particle-tracking model

Takeda, Naoya*; Kashima, Motohiko*; Odani, Sachika*; Uchiyama, Yusuke*; Kamidaira, Yuki; Mitarai, Satoshi*

Scientific Reports (Internet), 11(1), p.6963_1 - 6963_10, 2021/03

 Times Cited Count:6 Percentile:65.91(Multidisciplinary Sciences)

A massive coral bleaching event occurred in 2016 in the interior of Japan's largest coral lagoon, the Sekisei Lagoon, located in the Kuroshio upstream region in southwestern Japan. Recovery of the coral lagoon will require the influx of coral spawn and larvae; therefore, it is important to identify and conserve source sites. A surface particle tracking simulation of coral spawn and larvae was used to identify source areas in the exterior Sekisei Lagoon for restoration of the interior lagoon. The northern coastal zone of Iriomote Island, including Hatoma Island, was identified as a major source area. Hatoma Island was also identified as a key source for the Kuroshio downstream region, making it one of the most important source areas in the Nansei Archipelago.

Journal Articles

Influences of the Kuroshio on interisland remote connectivity of corals across the Nansei Archipelago in the East China Sea

Uchiyama, Yusuke*; Odani, Sachika*; Kashima, Motohiko*; Kamidaira, Yuki; Mitarai, Satoshi*

Journal of Geophysical Research; Oceans (Internet), 123(12), p.9245 - 9265, 2018/12

 Times Cited Count:14 Percentile:63.68(Oceanography)

no abstracts in English

Journal Articles

Influence of the Kuroshio on dispersal of coral spawn and larvae around Ryukyu Islands

Odani, Sachika*; Uchiyama, Yusuke*; Kashima, Motohiko*; Kamidaira, Yuki; Mitarai, Satoshi*

Doboku Gakkai Rombunshu, B2 (Kaigan Kogaku) (Internet), 73(2), p.I_1315 - I_1320, 2017/10

no abstracts in English

Journal Articles

Eddy-induced transport of the Kuroshio warm water around the Ryukyu Islands in the East China Sea

Kamidaira, Yuki; Uchiyama, Yusuke*; Mitarai, Satoshi*

Continental Shelf Research, 143, p.206 - 218, 2017/07

 Times Cited Count:31 Percentile:86.42(Oceanography)

In this study, an oceanic downscaling model in a double-nested configuration was used to investigate the role played by the Kuroshio warm current in preserving and maintaining biological diversity in the coral coasts around the Ryukyu Islands (Japan). A comparison of the modeled data demonstrated that the innermost submesoscale eddy-resolving model successfully reproduced the synoptic and mesoscale oceanic structures even without data assimilation. The Kuroshio flows on the shelf break of the East China Sea approximately 150-200 km from the islands; therefore, eddy-induced transient processes are essential to the lateral transport of material within the strip between the Kuroshio and the islands. The model indicated an evident predominance of submesoscale anticyclonic eddies over cyclonic eddies near the surface of this strip. An energy conversion analysis relevant to the eddy-generation mechanisms revealed that a combination of both the shear instability due to the Kuroshio and the topography and baroclinic instability around the Kuroshio front jointly provoke these near-surface anticyclonic eddies, as well as the subsurface cyclonic eddies that are shed around the shelf break. Both surface and subsurface eddies fit within the submesoscale, and they are energized more as the grid resolution of the model is increased. An eddy heat flux (EHF) analysis was performed with decomposition into the divergent (dEHF) and rotational (rEHF) components. The rEHF vectors appeared along the temperature variance contours by following the Kuroshio, whereas the dEHF properly measured the transverse transport normal to the Kuroshio's path. The diagnostic EHF analysis demonstrated that an asymmetric dEHF occurs within the surface mixed layer, which promotes eastward transport toward the islands. Conversely, below the mixed layer, a negative dEHF tongue is formed that promotes the subsurface westward warm water transport.

Journal Articles

Impact of mesoscale recirculation of the Kuroshio on asymmetric oceanic structure around Okinawa Island

Uchiyama, Yusuke*; Odani, Sachika*; Yamanishi, Takafumi*; Kamidaira, Yuki; Mitarai, Satoshi*

Doboku Gakkai Rombunshu, B2 (Kaigan Kogaku) (Internet), 72(2), p.I_481 - I_486, 2016/11

no abstracts in English

Journal Articles

An Eddy heat flux analysis on enhancement of submesoscale mixing around the Ryukyu Islands

Kamidaira, Yuki; Uchiyama, Yusuke*; Mitarai, Satoshi*; Nakada, Shohei*

Doboku Gakkai Rombunshu, B2 (Kaigan Kogaku) (Internet), 71(2), p.I_1219 - I_1224, 2015/11

BB2015-0179.pdf:4.2MB

no abstracts in English

Journal Articles

Eddy current-adjusted plasma shape reconstruction by Cauchy condition surface method on QUEST

Nakamura, Kazuo*; Jiang, Y.*; Liu, X.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Hasegawa, Makoto*; Tokunaga, Kazutoshi*; Zushi, Hideki*; et al.

Fusion Engineering and Design, 86(6-8), p.1080 - 1084, 2011/10

 Times Cited Count:4 Percentile:32.68(Nuclear Science & Technology)

Journal Articles

Magnetic sensor dependence of CCS method to reproduce ST plasma shape

Wang, F.*; Nakamura, Kazuo*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Sato, Konosuke*; Zushi, Hideki*; Hanada, Kazuaki*; Sakamoto, Mizuki*; et al.

Kyushu Daigaku Oyo Rikigaku Kenkyujo RIAM Foramu 2006 Koen Yoshi, p.138 - 141, 2006/06

no abstracts in English

Journal Articles

Development of completely Solenoidless tokamak operation in JT-60U

Ushigome, Masahiro*; Ide, Shunsuke; Ito, Satoshi*; Jotaki, Eriko*; Mitarai, Osamu*; Shiraiwa, Shunichi*; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; Fujita, Takaaki; et al.

Nuclear Fusion, 46(2), p.207 - 213, 2006/02

 Times Cited Count:11 Percentile:37.02(Physics, Fluids & Plasmas)

This papaer studies on tokamak plasma start-up completely without central solenoid (CS). On the JT-60 tokamak it is demonstrated that a completely CS-less Ip start-up to 100 kA was achieved even without any null-point by Electron cyclotron range of frequencies (ECRF) and outer PF coil current swing only. Necessary conditions (the EC power, the toroidal field etc.) were clarified. Moreover, it was succeded to maintain Ip = 260kA for 1 sec without CS by NB only. In addition Ip ramp-up by EC and NB only (without LHCD) from 215 to 310kA was achieved. In a high confinement reversed shear discharge, a result suggesting bootstrap over drive was obtained.

Journal Articles

Formation of advanced tokamak plasmas without the use of an ohmic-heating solenoid

Shiraiwa, Shunichi*; Ide, Shunsuke; Ito, Satoshi*; Mitarai, Osamu*; Naito, Osamu; Ozeki, Takahisa; Sakamoto, Yoshiteru; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; et al.

Physical Review Letters, 92(3), p.035001_1 - 035001_4, 2004/01

 Times Cited Count:46 Percentile:82.99(Physics, Multidisciplinary)

no abstracts in English

Oral presentation

SVD in plasma shape reconstruction by CCS method

Nakamura, Kazuo*; Matsufuji, Shinji*; Tomoda, Seiji*; Wang, F.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Sato, Konosuke*; Zushi, Hideki*; et al.

no journal, , 

no abstracts in English

Oral presentation

SVD in plasma shape reconstruction by CCS method

Nakamura, Kazuo*; Matsufuji, Shinji*; Tomoda, Seiji*; Wang, F.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Sato, Konosuke*; Zushi, Hideki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Feature of SVD in plasma shape reconstruction by CCS method

Nakamura, Kazuo*; Matsufuji, Shinji*; Tomoda, Seiji*; Wang, F.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Sato, Konosuke*; Zushi, Hideki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Eddy current effect on plasma shape reconstruction based on CCS method in QUEST

Nakamura, Kazuo*; Yi, J.*; Liu, X.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Hasegawa, Makoto*; Tokunaga, Kazutoshi*; Zushi, Hideki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Real time reconstruction of spherical tokamak plasma shape by CCS method with eddy current in QUEST

Yi, J.*; Nakamura, Kazuo*; Liu, X.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Hasegawa, Makoto*; Tokunaga, Kazutoshi*; Zushi, Hideki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Impact of the Kuroshio on dispersal of coral spawn and larvae around Ryukyu Islands in the East China Sea

Odani, Sachika*; Uchiyama, Yusuke*; Kashima, Motohiko*; Kamidaira, Yuki; Mitarai, Satoshi*

no journal, , 

We conduct a double nested high-resolution synoptic ocean modeling using ROMS with grid spacing down to 1 km coupled with an offline Lagrangian particle tracking model. The modeled dispersal of coral spawn and larvae released from about 20 major islands and lagoons are examined to quantify connectivity using Lagrangian probability density functions (PDFs) of the Lagrangian particles among Ryukyu Islands. We introduce 145 patches with a diameter of 1km around Sekisei Lagoon between Yaeyama and Ishigaki Islands close to Taiwan to compare with an in-situ surface drifter measurement. Lagragian particles are released from the patches in spring for 2012-2015 and are tracked for the advection time of 3 weeks suitable to representing active spawning and lifespan of coral spawn and larvae. The PDF analyses suggest that the particles mostly remain near the released areas, while about 10% of the particles are entrained by the Kuroshio to travel long distance, leading to inter-island connectivity. Some of these particles are further transported northeastward, and then partially trapped by the Kuroshio Counter Current formed between the Kuroshio and Main Island to approach Okinawa Main Island. We reveal that eastward current in the south the lagoon occurred shortly after the releases suppresses the entrainment and the resultant long-distance transport.

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