1990 Fiscal Year Final Research Report Summary
Variations of Subtropical Mode Water and its Role in the Climatic Change
| Project/Area Number |
63460042
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
気象・海洋・陸水学
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| Research Institution | Tohoku University |
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Principal Investigator |
HANAWA Kimiko Dept. Geophys., Fac. Sci., Tohoku University Associate Professor, 理学部, 助教授 (40142921)
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| Co-Investigator(Kenkyū-buntansha) |
TOBA Yoshiaki Dept. Geophys., Fac. Sci., Tohoku University Professor, 理学部, 教授 (50025277)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Kurosio / Kuroshio meander / Subtropical Mode Water / XBT / XBT monitoring / Mixed layer / Kurosio recirculation system / NOAA satellite |
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| Research Abstract |
Works made in this research can be summarized as the following three items.
1. Analysis for the accumulated historical data
The hydrographic data compiled by the Japan Oceanograhic Data Center, The Ohshima Branch of the Tokyo Cosmopolitan Fisheries Laboratory and the Ogasawara Fisheries Center have been analyzed from the various viewpoints. As a result, it was found that the Subtropical Mode Water (STMW) is formed in the Kuroshio Extension area due to te active mixing process for the severe wintertime cooling, and as seasons go, STMW moves following the Kuroshio recirculation system. This recirculation system changes its structure depending on the meander or none-mender of the Kuroshio.
2. XBT monitoring of the Kuroshio system and observation of STMW by the research vessels
The XBT monitoring for the Kurosio system by using a ferry, Ogasawara-Maru, which shuttles between Tokyo and the Ogasawara Islands has been made since 1988. In addition, observations of the distribution of STMW and the mixed layer have been made every year by using the research vessels. observation facts strongly support the features described in the item (1). Especially, the data of XBT monitoring clearly show the westward movement of STMW over the Izu Ridge.
3. Reexamination of depth error in XBT data
The free-fall velocity of the XBT T-7 probe has been re-examined by using the accumulated CTD-XBT data sets. As s results, it was found that the free-fall velocity provided by the XBT manufacturer is different from the actual velocity. This result agrees with the results previously made by the authors.
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