| Project/Area Number |
14340141
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
AWAJI Toshiyuki Kyoto University, Dept.of Geophysics, Professor, 大学院・理学研究科, 教授 (40159512)
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| Co-Investigator(Kenkyū-buntansha) |
KONDA Masanori Kyoto University, Dept.of Geophysics, Assistant Professor, 大学院・理学研究科, 助手 (10273434)
ISHIKAWA Yoichi Kyoto University, Dept.of Geophysics, Assistant Professor, 大学院・理学研究科, 助手 (70335298)
FUKAZAWA Masao JAMSTEC, IORGC, Program Director, 地球環境観測研究センター, プログラムディレクター (10143546)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥14,500,000 (Direct Cost: ¥14,500,000)
Fiscal Year 2004: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2003: ¥4,500,000 (Direct Cost: ¥4,500,000)
Fiscal Year 2002: ¥5,900,000 (Direct Cost: ¥5,900,000)
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| Keywords | 4-dimensional variational ocean data assimilation / Heat and water mass transports / State estimation / Variability and predictability / 海洋データ同化 / 4次元熱配分 / 予測 |
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| Research Abstract |
The main objective of our research is to construct an innovative 4-dimensional variational(4D-VAR) data assimilation system capable of providing high-quality comprehensive datasets. Synthesis of observational data and state-of-the-art general circulation models by the variational approach has the ability to produce a dynamically self-consistent space-time dataset. Such datasets are urgently required for more accurate prediction and for better estimation of the dynamical state of the Pacific Ocean associated with global warming.
In order to achieve our goal, we have successfully constructed a 4D-VAR data assimilation system on a parallel computer machine, and have applied it to a long-term reanalysis experiment during the period after the late 1980's. This experiment assimilated all the observational data available into an ocean general circulation model. The obtained reanalysis dataset shows good consistency with previous knowledge of important climate events. For example, the evolution
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of Nino3 SST is well reproduced (its error value reduces to about 1/2 of that from the earlier simulations), which supports the notion that our dataset accurately represents the climate variability in this region. Further, our reanalysis dataset exhibits realistic subsurface water mass distribution and enables us to clarify the water mass formation and movement processes. An application of a sensitivity experiment to the dichothermal and mesothermal water pathways that characterize the northwest North Pacific circulation is performed in which we investigate the sensitivity to an artificial cost given in the subarctic Pacific region. The distribution of adjoint variables shows good consistency with previous studies of the subtropical Kuroshio Extension region and western subarctic region. Similarly, intermediate waters can be traced back to their source regions. Using our reanalysis data set, we estimated meridional heat and water mass transports associated with the overturn in the Pacific Ocean. A close look at the meridional distributions reveal that the annual mean and the seasonal change are by and large consistent with previous knowledge. These results confirm that our 4D-VAR data assimilation system is a powerful tool for the understanding and prediction of the dynamical state of the Pacific Ocean. Less
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