2022 Fiscal Year Final Research Report
Elucidation and formulation of swell impacts on growth of wind waves and generation of surface turbulence in real oceans
| Project/Area Number |
20H01969
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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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| Review Section |
Basic Section 17020:Atmospheric and hydrospheric sciences-related
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Komatsu Kosei 東京大学, 大学院新領域創成科学研究科, 准教授 (30371834)
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| Co-Investigator(Kenkyū-buntansha) |
田中 潔 東京大学, 大気海洋研究所, 准教授 (20345060)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | うねり / 風波 / 海洋表層乱流 / 実海域 |
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| Outline of Final Research Achievements |
Surface waves, ocean near-surface turbulences and ocean wind turbulences were observed simultaneously using a high-frequency ADCP and a triaxial ultrasonic anemometers in Otsuchi Bay, Iwate Prefecture, Japan, to elucidate the actual effects of the presence of swells on the development of wind waves and the generation of near-surface turbulences. Waves in Otsuchi Bay are characterized by predominant swells propagating from the offshore region. The swell effects were analyzed separately for winds blowing in the same direction as the swell (forward wind) and for winds blowing in the opposite direction (head wind). The presence of swell was found to suppress the development rate of wind waves by up to 50% during forward winds, while enhancing it by up to 20% during head winds, and to suppress the energy generation rate of near-surface turbulences by up to 30% during forward winds, while enhancing it by up to 20% during head winds.
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| Free Research Field |
海洋物理学
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| Academic Significance and Societal Importance of the Research Achievements |
波浪は、その場に吹く風によって発達過程にある「風波」と遠方から伝播して来て減衰過程にある「うねり」に区別され、現実の波浪は両者が混在した状態にある。しかし、うねりと風波の相互作用は不明な点が多く、一因として実海域での研究が不足していることが挙げられる。本研究では、規則的なうねりが外洋域から伝播して来る特徴を有する岩手県大槌湾を「天然の造波機付き風洞水槽」に見立てて、湾内の波浪、海上風乱流、海洋表層乱流の同時連続観測を実施し、うねりの存在が、風波の発達率と海洋表層乱流の生成率を変化させることを定量的に明らかにした。この成果は、現業の波浪予測の精度向上や巨大波の発生機構の理解に大きく寄与する。
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