| Project/Area Number |
04640420
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
気象・海洋・陸水学
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| Research Institution | Kyushu University |
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Principal Investigator |
IMAWAKI Shiro Kyushu University, Research Institute for Applied Mechanics, Professor, 応用力学研究所, 教授 (40025474)
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| Co-Investigator(Kenkyū-buntansha) |
ALEXANDER Ostrovskii Kyushu University, Research Institute for Applied Mechanics, Associate Professor, 応用力学研究所, 助教授 (70243962)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1993: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1992: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | satellite altimeter / optimal interpolation / satellite observation / sea surface dynamic topography / Pacific ocean / sea level fluctuation / アルティメーター(海面高度計) |
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| Research Abstract |
Satellite altimeters can directly measure the dynamical property of sea surface height, and therefore are epoch-making for physical oceanography. In the present study, recent altimeter data are analyzed to investigate features of sea surface fluctuations for a wide wave-length range from the basin scale to the meso-scale. Followings are the results ;
(1) On the basis of Geosat altimeter data from the first two years (1986-88) of the Exact Repeat Mission, temporal fluctuation of the sea surface dynamic topography (SSDT) is detected ; here the SSDT is the departure of the actual sea surface from the geoid and whose gradient gives the geostrophic velocity at the sea surface. There are found clear westward phase propagations in the fluctuation field of the SSDT in the western half of the North Pacific. Their Phase speeds are close to the theorretical value for the long baroclinic Rossby wave, but there are some discrepancies between them which cannnot be explained by the latest theory.
(2) O
… More
n the basis of the same data, it is shown that the Kuroshio Extension region is filled with clear cyclonic and anti-cyclonic disturbances propagating westward. Those disturbances are confirmed to have baroclinic feature, using satellite sea surface temperature data. It is also shown that the intensity of the Kuroshio Countercurrent located south of the Kuroshio Extension fluctuates correlatively with the Kuroshio Extension, and therefore the seasonal cycle of the Kuroshio Extension seems to represent fluctuations of a local sub-gyre (with horizontal scales of 1,000-2,000 km), instead of the whole subtropical gyre of the North Pacific.
(3) On the basis of TOPEX/Poseidon altimeter data from the first one year (1992-93) of the mission, fluctuations of the Kuroshio axis south of Japan are analyzed. Approximated absolute SSDT is derived from combination of the altimeter data and the climatological mean SSDT.Geostrophic velocities at the sea surface are estimated from its horizontal gradient. The results are compared with fluctuations of location of the Kuroshio axis derived from in situ surface velocity data. The comparison shows that the distribution of the approximated geostrophic velocity can describe the fluctuation of the Kuroshio axis reliably. Less
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