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Kawamura, Hideyuki; Hirose, Naoki*; Nakayama, Tomoharu*; Ito, Toshimichi
JAEA-Data/Code 2021-004, 34 Pages, 2021/05
JAEA-Data-Code-2021-004.pdf:3.72MB
The Japan Atomic Energy Agency measured the ocean current across the Tsugaru Strait using an Acoustic Doppler Current Profiler attached on a ferryboat from October 1999 to January 2008. The characteristics of the ocean current in the Tsugaru Strait must be understood for predicting oceanic dispersion of radioactive materials released from nuclear facilities around the strait. Furthermore, it is critical to elucidate the mechanism of the Tsugaru Warm Current from an oceanography viewpoint. The dataset obtained in this investigation consists of daily ocean current data files that record the components of the current speed in the east-west and north-south directions from the surface layer to the bottom layer. The dataset stores 2,211 daily ocean current data files, despite some data periods missing from October 1999 to January 2008. In this study, information on the dataset is described for users to analyze the dataset properly for their purposes. Section 1 provides the background and purpose of the ocean current measurement, Section 2 explains the methodology of measurement using an Acoustic Doppler Current Profiler, and Section 3 explains the record format of the daily ocean current data files and data acquisition rate and presents analysis results. Finally, Section 4 concludes this study.
Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Miyazawa, Yasumasa*; Usui, Norihisa*
Journal of Environmental Radioactivity, 180, p.36 - 58, 2017/12
Times Cited Count：11 Percentile：35.55(Environmental Sciences)This study simulates the oceanic dispersion of Fukushima-derived Cs-137 by an oceanic dispersion model and multiple oceanic general circulation models. The models relatively well reproduced the observed Cs-137 concentrations in the coastal, offshore, and open oceans. Multiple simulations in the coastal, offshore, and open oceans consistently suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Quantification of the Cs-137 amounts suggested that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layers in the North Pacific.
Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; In, Teiji*; Ishikawa, Yoichi*; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*
Reports of Research Institute for Applied Mechanics, Kyushu University, (143), p.111 - 117, 2012/09
Because of the Fukushima Dai-ichi Nuclear Power Plant disaster, some radionuclides were released into the ocean from the Fukushima Dai-ichi Nuclear Power Plant. In response to this situation, numerical experiments were carried out at Japan Atomic Energy Agency using an oceanic dispersion model and an ocean general circulation model to estimate an effect of the radionuclides on marine environment. It was suggested that the radionuclides deposited from the atmosphere mainly in the middle of March after the disaster spread over a comparatively wide area of the Pacific Ocean east of Japan. On the other hand the radionuclides directly released into the ocean from the Fukushima Dai-ichi Nuclear Power Plant were carried along the coast and then spread along the Kuroshio extension.
I and 
Cs discharged into the ocean because of the Fukushima Daiichi Nuclear Power Plant disasterKawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; In, Teiji*; Ishikawa, Yoichi*; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*
Journal of Nuclear Science and Technology, 48(11), p.1349 - 1356, 2011/11
Times Cited Count：180 Percentile：99.79(Nuclear Science & Technology)Numerical experiments were carried out to predict the spreading of I and Cs released into the ocean due to the Fukushima Daiichi Nuclear Power Plant incident. Results in the numerical experiments were in good agreement with the concentrations of I and Cs in the monitoring data. It was suggested that the high I concentration detected in the young lancefish caught off Kitaibaraki city was due to the deposition from the atmosphere. The numerical experiments suggest that the deposition of radionuclides released into the atmosphere in the middle March largely effected the concentrations of radionuclides east of Japan in the Pacific Ocean.
Kobayashi, Takuya; In, Teiji*; Ishikawa, Yoichi*; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*; Togawa, Orihiko
Progress in Nuclear Science and Technology (Internet), 2, p.682 - 687, 2011/10
When the reprocessing plant is in routine operation, radionuclides are released to the coastal ocean as scheduled. Released radionuclides migrate in the ocean by physical, chemical and biological processes. Thus, for environmental safety, it is important to understand the migration behavior due to routine releases of radionuclides to the coastal ocean from the reprocessing plant. A numerical simulation model system that consists of an ocean general circulation model and a particle random-walk model to describe the radionuclide migration behavior in Rokkasho coastal region has been developed. The particle random-walk model, SEA-GEARN, calculates the radionuclides migration in the ocean. The system has been applied to simulate the nowcast of Rokkasho coastal region in 2007 and hypothetical radionuclide release has been carried out.
Kobayashi, Takuya; Togawa, Orihiko; Ito, Toshimichi; Otosaka, Shigeyoshi; Kawamura, Hideyuki; Hayashi, Keisuke*; Shima, Shigeki*; Nakayama, Tomoharu*; In, Teiji*
JAEA-Research 2009-040, 63 Pages, 2009/12
JAEA-Research-2009-040.pdf:12.19MB
A spent nuclear fuel reprocessing plant has the possibility of routine releases of liquid radioactive wastes from a discharge pipe to the off Shimokita region during its operations. Thus, for environmental safety, it is important to assess the migration processes of released radionuclides from the plant. Therefore, an ocean circulation prediction code and an oceanic radionuclides migration prediction code, which were developed by Japan Atomic Energy Agency, has been improved to describe the migration behavior of radionuclides in the off Shimokita region. Parameters on characteristics and dynamics of particulate materials in seawater have also been obtained in the study area for the adjustment and verification of the oceanic radionuclides migration prediction code. This report summarizes the primary results of the study which was carried out at the off Shimokita region from FY2003 to 2008.
Kobayashi, Takuya; In, Teiji*; Ishikawa, Yoichi*; Matsuura, Yasutaka*; Shima, Shigeki*; Nakayama, Tomoharu*; Awaji, Toshiyuki*; Kawamura, Hideyuki; Togawa, Orihiko
Nihon Genshiryoku Gakkai Wabun Rombunshi, 7(2), p.112 - 126, 2008/06
The radionuclides migration forecasting system in the off Shimokita region has been developed to predict the routine and accidental releases of liquid radioactive wastes during the operations of a spent nuclear fuel reprocessing plant in Aomori prefecture, Japan. The results obtained from the case studies are as follows; (1) The ocean general circulation model by using the techniques of data assimilation and nesting reproduced well the flow pattern of a coastal area. (2) The estimated internal dose due to ingestion of marine products from hypothetical release of 
H was 0.45 
Sv/y. (3) The results of hypothetical release of Cs showed that about four percent of the whole deposited on the seabed after a 60-day calculation. The concentration of Cs of hypothetical release from the off Shimokita region is the same or less than that of global fallout measured at the same area.
Ito, Toshimichi; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Onishi, Mitsuyo*; Isoda, Yutaka*
Proceedings of International Workshop on Monitoring and Forecasting of the Rapid Change in Ocean-Atmosphere Environment in the East Asia, p.13 - 14, 2007/11
The volume transport of the Tsugaru Warm Current (TgWC) from April 2000 to June 2002, which was estimated based on the ferry-borne ADCP observation was examined in this study. The estimated transport varied from about 0.6 Sv to 2.5 Sv (=10
ms
), and the mean value was estimated to be about 1.3 Sv with 
0.3 Sv showing the similar level as that in the preliminary result. The temporal variation with a period of about 20-30 days seemed to be remarkable in the anterior half of this observation period rather than seasonal variation. By contrast, the seasonal variation was dominant in the posterior half in which the minimum and maximum values appear in the spring and autumn, respectively. The temporal change of the transport showed good correlation with the sea level differences around the strait as expected. In addition, the present result suggests that the change of local wind around the strait also lead in part of the change of the transport.
Ito, Toshimichi; Kawamura, Hideyuki; Onishi, Mitsuyo*; Isoda, Yutaka*; Nakayama, Tomoharu*; Shima, Shigeki*
Proceedings of 14th PAMS/JECSS Workshop, p.222 - 223, 2007/05
no abstracts in English
In, Teiji*; Nakayama, Tomoharu*; Matsuura, Yasutaka*; Shima, Shigeki*; Ishikawa, Yoichi*; Awaji, Toshiyuki*; Kobayashi, Takuya; Kawamura, Hideyuki; Togawa, Orihiko; Toyoda, Takahiro*
Proceedings of International Symposium on Environmental Modeling and Radioecology, p.58 - 64, 2007/03
The northwestern part of the Pacific Ocean off the Shimokita Peninsula assumes a complex water mass structure. It is necessary to accurately reproduce the striking circulation patterns and the complicated water mass structures in this area with an ocean general circulation model. We have planned to make use of a one-way nesting method. To initialize the forecast system, we use a 4-dimensional variational method of data assimilation. The assimilated data consist of hydrographic observations collected through the Global Temperature-Salinity Profile Program, sea surface temperature and sea surface height data observed by satellites. A forecast experiment on the basis of oceanographic observations made in 2003 illustrates the good performance of our system. We shall focus, in particular, on the shift from the coastal mode to the gyre mode and vice versa.
In, Teiji*; Shima, Shigeki*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Togawa, Orihiko; Kobayashi, Takuya; Kawamura, Hideyuki
Gekkan Kaiyo, 37(9), p.674 - 680, 2005/09
no abstracts in English
Kuroda, Hiroshi*; Isoda, Yutaka*; Onishi, Mitsuyo*; Iwahashi, Masayuki*; Sato, Chizuru*; Nakayama, Tomoharu*; Ito, Toshimichi; Iseda, Kenichi*; Nishizawa, Keisuke*; Shima, Shigeki*; et al.
Umi No Kenkyu, 13(6), p.553 - 564, 2004/11
no abstracts in English
Onishi, Mitsuyo*; Isoda, Yutaka*; Kuroda, Hiroshi*; Iwahashi, Masayuki*; Sato, Chizuru*; Nakayama, Tomoharu*; Ito, Toshimichi; Iseda, Kenichi*; Nishizawa, Keisuke*; Shima, Shigeki*; et al.
Hokkaido Daigaku Suisan Kagaku Kenkyu Iho, 55(2), p.105 - 119, 2004/10
Transport variations and characteristics of tidal currents in the Tsugaru Strait (TS) are investigated using the ship-mounted ADCP data obtained during October 29, 1999 - March 31, 2000. The Tsugaru Strait connects the North Pacific Ocean (NPO) and Japan/East Sea (JES), and is a main output for Tsushima Warm Current (TWC) in the JES. The strong northeastwards mean current was found in the center of the strait, and counter flows exist near the Hokkaido and Honshu coasts. The estimated mean net eastward transport is 1.8 Sv (1Sv=10ms). In the TS, the transports of K1 and M2 across the strait are 0.72 Sv and 0.52 Sv, respectively. From the phase analysis, it is understood the K1 is progressive wave-like while the M2 is standing wave-like. We also find a significant barotropic fortnightly oscillation. The Mf tide is more energetic along the JES coast with the amplitude of 1-3cm, while the Mf tide amplitudes in the NPO are less than 1 cm. It is inferred that observed fortnightly oscillation may be generated by the difference of Mf tide amplitude between both sides of the TS.
Ito, Toshimichi; Togawa, Orihiko; Onishi, Mitsuyo*; Isoda, Yutaka*; Nakayama, Tomoharu*; Shima, Shigeki*; Kuroda, Hiroshi*; Iwahashi, Masayuki*; Sato, Chizuru*
Geophysical Research Letters, 30(13), p.11_1 - 11_4, 2003/10
The variation of velocity and volume transport of the Tsugaru Warm Current (TWC) is investigated based on the data of continuous and cross-sectional current monitoring in the Tsugaru Strait. During November 1999 - March 2000, the structure of the velocity transection across the strait was almost stable in which the TWC occupied the central part of the strait, while the returning flows existed in the northern and southern part of the strait, and these indicate a totally declining trend. The volume transport of the TWC varies from 2.1 to 1.1 Sv, with the mean value of 1.5 Sv, following the variation of the TWC. The temporal variation of the volume transport shows a linear correlation with that of the sea level difference between the Japan Sea and the Pacific Ocean. The contribution of the sea level difference to the volume transport is estimated to be roughly 70 %.
Kuroda, Hiroshi*; Isoda, Yutaka*; Onishi, Mitsuyo*; Iwahashi, Masayuki*; Sato, Chizuru*; Nakayama, Tomoharu*; Ito, Toshimichi; Iseda, Kenichi*; Nishizawa, Keisuke*; Shima, Shigeki*; et al.
Umi No Kenkyu, 12(2), p.195 - 214, 2003/03
Variabilities of the periodical current fluctuations on the shelf in Hidaka Bay were examined with use of ferry-mounted ADCP data obtained during 2000-2001. As the result of analysis, (1) three periodical variations around 10-, 25- and 60-day period are found, (2) the horizontal phase lag of these variations is little along the ship track, and the vertical phase lag is little at 10- and 25-day variations while several-day at 60-day variation, and (3) the 10-day variation shows coherent cross-correlation between current and wind.
Matsuura, Yasutaka*; Nakayama, Tomoharu*; In, Teiji*; Gasa, Shinichi*; Shima, Shigeki*; Kobayashi, Takuya; Togawa, Orihiko; Ishikawa, Yoichi*; Awaji, Toshiyuki*
no journal, ,
no abstracts in English
Ishikawa, Yoichi*; Awaji, Toshiyuki*; In, Teiji*; Nakayama, Tomoharu*; Matsuura, Yasutaka*; Shima, Shigeki*; Toyoda, Takahiro*; Kobayashi, Takuya; Togawa, Orihiko; Kawamura, Hideyuki
no journal, ,
no abstracts in English
In, Teiji*; Nakayama, Tomoharu*; Matsuura, Yasutaka*; Shima, Shigeki*; Ishikawa, Yoichi*; Awaji, Toshiyuki*; Kobayashi, Takuya; Kawamura, Hideyuki; Togawa, Orihiko; Toyoda, Takahiro*
no journal, ,
no abstracts in English
In, Teiji*; Nakayama, Tomoharu*; Matsuura, Yasutaka*; Shima, Shigeki*; Ishikawa, Yoichi*; Awaji, Toshiyuki*; Kobayashi, Takuya; Kawamura, Hideyuki; Togawa, Orihiko; Toyoda, Takahiro*
no journal, ,
The Shimokita Peninsula (hereafter SP)is located at the northeast tip of Honshu (the main island of Japan) and borders on the northwestern part of the North Pacific Ocean (hereafter NWNP) in the east and the Tsugaru Strait (hereafter TS) in the north. It is known that the NWNP off the SP assumes a complex water mass structure. Seawater of Japan Sea origin, called the Tsugaru Warm Water (TWW) component, takes on a characteristic seasonal variation. Conlon (1982) pointed out that during winter and spring, the TWW in the NWNP propagates southward along the coast of the peninsula (the coastal mode), and swirls off the peninsula from summer to autumn (the gyre mode). It is necessary to accurately reproduce the striking circulation patterns and the complicated water mass structures in this area with an ocean general circulation model (OGCM). We need to use a fine-scale grid, probably such as 1-2 km in size to reproduce the water mass structure around the TS and the off the SP in detail. To initialize the forecast system, we use a 4-dimensional variational method of data assimilation. A forecast experiment on the basis of oceanographic observations made in 2003 (a hindcast experiment) illustrates the good performance of our system. We shall focus, in particular, on the shift from the coastal mode to the gyre mode and vice versa.
Ito, Toshimichi; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Isoda, Yutaka*; Onishi, Mitsuyo*
no journal, ,
no abstracts in English
