| Project/Area Number |
17340137
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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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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Hokkaido University |
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Principal Investigator |
TANIMOTO Youichi Hokkaido University, Faculty of Environmental Earth Science, Associate Professor (00291568)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Hisashi University of Tokyo, Department of Earth and Planetary Science, Associate Professor (10251406)
KOBASHI Fumiaki Tokyo University of Marine Science and Technol.ogy, Faculty of Marine Technol.ogy, Associate Professor (80377077)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥16,180,000 (Direct Cost: ¥15,400,000、Indirect Cost: ¥780,000)
Fiscal Year 2007: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2006: ¥5,700,000 (Direct Cost: ¥5,700,000)
Fiscal Year 2005: ¥7,100,000 (Direct Cost: ¥7,100,000)
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| Keywords | Kuroshio Extension / Ocean-atmosphere interaction / Atmospheric boundary layer / Cloud regime / GPS radio sonde sounding / Baiu / 海上気象観測 / 黒潮続流域 |
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| Research Abstract |
Over the western North Pacific east of the Japan, sea surface temperature (SST) shows a steep front across the Kuroshio Extension (KE). The SST gradient near the KE is 5℃/200 km through seasons, therefore changes in SST are very large in that region. In the present study, we conducted global positioning system (GPS) radio sonde atmospheric soundings across the front in July 2005 (January 2006) as a research cruise of research vessel (R/V) Roger Revelle, Scripps Institute of Oceanography (R/V Hakuho-maru, Ocean Research Institute, University of Tokyo).
In early summer, whilst the lower atmosphere overlying the KE region exhibits synoptic disturbances, SST front is nearly the same for several weeks during the cruise due the large inertia of the ocean. Analyses of the atmospheric soundings and ceilometer measurement show that the vertical structure of atmospheric boundary layer is modified across the front. In case of warm/moist (cold/dry) air mass overlying the KE region, a cloud regime shift from cumulus to low-level stratus, occasionally to fog (from stratus with solid cloud deck to broken stratus scattering with lower cloud base) is observed across warm-to-cold SST.
In deep winter, the near surface is always unstable because of warm ocean and cool/dry atmosphere. Hence, the main inversion is formed at the top of well-mixed layer. Temporal variation of the mixed layer top (MLT), which is mostly corresponding to the observed cloud base, is well correlated with surface heat flux. The lag correlation becomes the maximum when the flux leads by 5-12 hours the MLT. After a passage of synoptic storm, the surface heat flux occasionally exceeded 800W m^<-2> and thereby the stratus and stratocumulus were formed at the MLT.
These observational findings indicate that the marine atmospheric boundary layer is modified by the spatial changes in SST along the KE front even though the overlying atmosphere displays its synoptic distrubances.
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