Observation of the surface mixed layer and its modeling
| Project/Area Number |
10640421
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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 |
YAMAZAKI Hidekatsu Tokyo University of Fisheries, Department of Ocean Sciences, Associate Professor, 水産学部, 助教授 (80260537)
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| Co-Investigator(Kenkyū-buntansha) |
NAGASHIMA Hideki Tokyo University of Fisheries, Department of Ocean Sciences, Professor, 水産学部, 教授 (10087570)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2000: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1998: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | turbulence / mixing / mixed layer / closure model / Kelvin-Helmholtz instability |
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| Research Abstract |
We have developed a new microstructure instrument to observe both physical and biological parameters simultaneously. The instrument is equipped with standard turbulence sensors and temperature gradient, as well as bio-optical sensors for measuring in situ chlorophyll and turbidity variations. Simultaneous measurements with this profiler and an acoustic Doppler velocimeter were carried our in a flow tank, and data from both instrument agreed well. Turbulence spectra computed from both instruments agreed with the Kolmogorov inertia subrange hypothesis over more than 1.5 decades in wavenumber space. Data from field tests conducted with the profiler showed that turbulence spectra measure in situ agreed with the empirical Nasmyth spectrum when corrections were made for the shear probe's spatial averaging. Dissipation rates as low as 5x10^<-10> W kg^<-1> were resolved.
A new high-resolution bio-optical sensor is developed and calibrated. The probe enables us to perform high-resolution measure
… More
ments of in-situ chlorophyll and turbidity. The sensitivity and the spatial resolution of the probe are tested in several laboratory experiments. Analysis of the test data shows that this probe is capable of resolving spatial distributions of chlorophyll as small as 0.02 m. Analysis of the spectral characteristics of chlorophyll and turbidity signals recorded in field tests corroborate the laboratory results.
From a previously conducted field experimental data we identified a Kelvin-Helmholtz billow from vertical turbulence velocity and instantaneous heat flux signals obtained from airfoil shear probes and thermistors mounted on a research submarine. The vertical turbulence velocity indicates that the horizontal scale of the billow was about 3.5 m. The spectral slope of the vertical turbulence velocity component is close to -2, revealing the flow is two-dimensional. We show a remarkable agreement between the length scales of the observed billow and those computed from direct numerical simulations based on similar conditions.
In order to combine the new field measurements with numerical models, we are developing a random walk simulation model for phytoplankton production making use of 2.5 level Mello-Yamada closure model. We have compared this new approach with a simple Ekman layer model. We report a rapid deeping revealed in Mello-Yamada model makes a significant difference in the random walk trajectories, however, the total productions at the end of the simulation show similar results. Less
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Report
(4 results)
Research Products
(3 results)
