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Onishi, Mitsuyo*; Ito, Toshimichi
Rikatan (Rika No Tanken), 3(6), p.26 - 27, 2009/06
This document is written for primary and secondary school student to explain the measurement of ocean flow using acoustic signal. In this document, principle and ferry mounted method of Acoustic Doppler Current Profiler (ADCP) measurement are introduced, and a part of results obtained through the measurement in the Tsugaru Strait is shown. Additionally, the importance of the measurement in the study of the Japan Sea is mentioned shortly. The measurement was carried out under the cooperative research between JAEA and Japan Marine Science Foundation getting a voluntary help from Higashi-Nihon Ferry Co. Ltd..
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
m
s
), 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
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.
Ito, Toshimichi; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Isoda, Yutaka*; Onishi, Mitsuyo*
no journal, ,
no abstracts in English
Ito, Toshimichi; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Onishi, Mitsuyo*; Isoda, Yutaka*
no journal, ,
The volume transport through the Tsugaru Strait, which was estimated from ADCP observation data, in the period between Apr. 2000 and Jun. 2002 was examined. Through the analysis, following features were elucidated: (1) The range of volume transport with mean value, (2) The prevailing periods in the variation, (3) the correlation with the sea level differences (along and across direction of the Strait) and its seasonal dependency, and (4) relationships with the Tsushima Warm Current.
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.
Ito, Toshimichi; Kawamura, Hideyuki; Onishi, Mitsuyo*; Isoda, Yutaka*; Nakayama, Tomoharu*; Shima, Shigeki*
no journal, ,
The results of JAEA's observation and study on the throughflow in the Tsugaru Strait is reviewed for the period of Apr. 2000 - Jun. 2002. In this period, the volume transport varied in the range of 0.6-2.5 Sv (10ms) with mean value of 1.30.3 Sv. The transport showed the maximum around autumn. Additionally, the variability with period of 20-30 days was observed. The variation was closely connected with that of sea-level difference arround the strait and correlation between the both more significant in wintertime implying the effect of baroclinic velocities became small. The transport is also connected with that in the Tsushima Strait with delay of 4 months in maximum. The transport in Tsugaru Strait corresponded 40-50% of that in the Tsushima Strait. It is required to elucidate the effect of wind and/or stratification on the transport and to study the variation with 20-30 days period.
Ito, Toshimichi; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Onishi, Mitsuyo*; Isoda, Yutaka*
no journal, ,
We had measured the 3-D velocity distribution of throughflow in the Tsugaru Strait during Nov. 1999 and Dec. 2007. In this observation, an ADCP (RDI, 150 kHz) had been mounted on the bottom of voluntary ferry (VIRGO, Higashi-nihon Ferry co. ltd.,) regularly operated in the strait. Main results of the observation for the period of Apr. 2002-Mar. 2004 are as follows; (1) velocity distribution was elucidated, (2) volume transport of the throughflow ranged 0.77-1.80 Sv (1Sv=110 ms) and its mean was 1.30 Sv with standard deviation 0.24 Sv, (3) the volume transport showed relatively weak seasonal variation and relatively strong periodicity with period of 20-30 days, (4) the variation was controlled by sea level difference around the strait, and (5) mean volume transport for in this period, in which missing data were filled using sea level difference data around the strait, was estimated to be 1.340.24 Sv.
Ito, Toshimichi; Kawamura, Hideyuki; Onishi, Mitsuyo*; Isoda, Yutaka*; Nakayama, Tomoharu*; Shima, Shigeki*
no journal, ,
no abstracts in English
Ito, Toshimichi; Kawamura, Hideyuki; Onishi, Mitsuyo*; Isoda, Yutaka*; Nakayama, Tomoharu*; Shima, Shigeki*
no journal, ,
no abstracts in English
