| Project/Area Number |
17K14389
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Fukui Prefectural University (2020-2021)
The University of Tokyo (2017-2019) |
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Principal Investigator |
Tanaka Yuki 福井県立大学, 海洋生物資源学部, 准教授 (80632380)
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| Project Period (FY) |
2017-04-01 – 2022-03-31
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| Project Status |
Completed (Fiscal Year 2021)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2018: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2017: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Keywords | 赤道太平洋 / 熱帯不安定波 / ロスビー波 / 内部波 / 鉛直乱流混合 / 線形安定性解析 / 数値シミュレーション / 海底地形 / 捕捉波 / 渦解像海洋大循環モデル / 渦位勾配 / 順圧不安定 / 1.5層浅水モデル / 順圧／傾圧不安定 / 固有モード / パラメタリゼーション |
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| Outline of Final Research Achievements |
In the equatorial Pacific Ocean, there exists a prominent disturbance propagating westward at a speed of ~0.5 m/s with a wavelength of ~1000 km, called tropical instability waves. It is pointed out that a front of tropical instability waves radiates internal waves downward to the ocean interior, which induce turbulent mixing in the thermocline and control the heat transport from the surface to the deep layers, thereby affecting the sea surface temperature and air-sea interaction in the equatorial Pacific Ocean. In this study, the generation mechanism of tropical instability waves in the equatorial Pacific Ocean is clarified in terms of the coupling of two Rossby waves that are trapped in a local potential vorticity gradient in a narrow latitudinal band just north of the equator and are propagating in the opposite directions with each other. Furthermore, the radiation mechanism of internal waves from tropical instability waves is examined in detail.
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| Academic Significance and Societal Importance of the Research Achievements |
赤道太平洋の熱帯不安定波は、鉛直乱流混合や熱輸送を通じて熱帯域の海面水温分布に大きな影響を与える重要な現象である。本研究では、熱帯不安定波の発生メカニズムを明らかにしただけでなく、赤道のすぐ北に存在する局所的な負の渦位勾配の強度が熱帯不安定波の活動度を表す良い指標になっていることを指摘した。この渦位勾配は低解像度の海洋大循環モデルでも比較的容易に再現可能であることから、今後、熱帯不安定波に伴う熱輸送や乱流混合強度のパラメータ化を進めていく上で非常に有効であると考えられる。
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