1996 Fiscal Year Final Research Report Summary
The Role of Double Diffusive Convection in the Mixing process of the Ocean
| Project/Area Number |
07640569
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | TOKYO UNIVERSITY OF FISHERIES |
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Principal Investigator |
YOSHIDA Jiro Tokyo University of Fisheries, Department of Ocean Sciences, Associate Professor, 水産学部, 助教授 (30174931)
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| Co-Investigator(Kenkyū-buntansha) |
SENJYU Tomoharu National Fisheries University, Department of Fisheries, Assistant Professor, 漁業学科, 助手
NAGASHIMA Hideki Tokyo University of Fisheries, Department of Ocean Sciences, Associate Professor, 水産学部, 助教授 (10087570)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Ovashio Front / Temperature inversion / Double diffusive convection / Double diffusive intrusion / Vertical and horizontal diffusivities / Salt finger / Three dimensional numerical modeling |
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| Research Abstract |
1.Detailed CTD and XBT data at the Oyashio Frontal region were analyzed.
(1) Temperature inversion layrs were frequently observed, but are compensated by the corresponding salinity distribution, and resulting density distributions were statically stable.
(2) Temperature inversion layrs had 50-80m scales in the vertical, and about 7km in the horizontal. They were kept observed for several tens of hours. From the analysis of continuous CTD observation, these inversion layrs are inferred to be caused by the intrusion of water masses having different temperature-salinity properties driven by the double diffusive convection. This is the first evidence of double diffusive diffusively driven intrusions in the Oyashio frontal regions.
(3) The behavior of double intrusion was analyzed more from the observations and laboratory experiment. It is found that there were substantial differences in the behavior of intrusions (advancing velocity, thickness) whether they advance as a single layr or multiple layrs. Observed intrusion was estimated as a single layr from the experimentally determined parameters. Advancing velocity was estimated from the stratification and the thickness of intrusion, and is used for estimating vertical and horizontal effective diffusivities, and are 10^<-4>m^21s、10m^21s, respectively.
2.Three dimensional numerical experiment on the salt finger convection was done.
(1) Salt finger convection having irregular configuration was successfully reproduced.
(2) The width of salt finger agress well with the linear stability theory and laboratory experiments.
(3) Vertical transport of heat and salt in density terms are slightly lower than those from laboratory experiment.
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