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Ito, Toshimichi; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Onishi, Mitsuyo*; Isoda, Yutaka*
no journal, ,
During Nov. 1999-Dec. 2007, JAEA carried out an observation of the Tsugaru Strait Throghflow using a ship-board Acoustic Doppler Current Profiler with voluntary cooperation by Higashi-Nihon Ferry Co. Ltd.,. From the analysis of volume transports estimated at 20 current monitoring points, it is elucidated in the period between Apr. 2002 and Mar. 2004 that; (1) most of the transport occurred in the part of the opening mouth of the strait, (2) in the area south of the main stream, west of Shimokita Peninsular, a topographically generated returning flow system was established by the wake of Shimokita Peninsular and a part of its volume transport was expected to join together with the transport of main stream, and (3) the minimum appeared in spring while the maximum was in fall showing significant amplitude of variation with 20-30 days period. The volume transport in this period varied in the range 0.5-1.8 Sv (1 Sv = 1
10
m
s
) and the mean transport was estimated to 1.2 
0.2 Sv, slightly smaller than previously reported value.
Kawamura, Hideyuki; Ito, Toshimichi; Kobayashi, Takuya; Otosaka, Shigeyoshi; Hirose, Naoki*
no journal, ,
Observation had been carried out to clarify distribution of anthropogenic radionuclides in the Japan Sea in the period between 1997 and 2002 by Japan Atomic Energy Agency. This study aims at reproducing the distribution of anthropogenic radionuclides with a numerical model and clarifying their movement in the Japan Sea. Deposition densities by global fallout are applied as boundary conditions for strontium 90 and cesium 137 at the sea surface. Numerical results show that concentration of strontium 90 and cesium 137 is compared with the observed one in the surface layer and the intermediate layer, although the concentration below 1000 m depth is quite low. More numerical experiments will be performed modifying parameters and boundary conditions of the numerical model in the future.
Takayama, Katsumi*; Hirose, Naoki*; Kawamura, Hideyuki; Shimizu, Daisuke*; Watanabe, Tatsuro*
no journal, ,
An ocean general circulation model in the Japan Sea has been being developed to reproduce and forecast movement of pollutants at JAEA. It was demonstrated that an assimilation of sea level variation at tide stations along the Japanese coast is effective to reproduce oceanic condition in the nearshore region. In this study, an effect of assimilation of satellite altimeter data, CTD data and tide data is quantitatively surveyed. As a result, it was demonstrated that this assimilation scheme improves the oceanic condition.