| Project/Area Number |
14540411
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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 | Meteorological Research Institute, Japan Meteorological Agency (JMA) |
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Principal Investigator |
FUJIBE Fumiaki Meteorological Research Institute, Japan Meteorological Agency (JMA), Forecast Research Department, Senior Researcher, 予報研究部, 主任研究官 (60343886)
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| Co-Investigator(Kenkyū-buntansha) |
SHOJI Yoshinori Meteorological Research Institute, Japan Meteorological Agency (JMA), Forecast Research Department, Senior Researcher, 予報研究部・主任研究官 (70354446)
SEKO Hiromu Meteorological Research Institute, Japan Meteorological Agency (JMA), Forecast Research Department, Senior Researcher, 予報研究部・主任研究官 (60354445)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2002: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | heavy rainfall / precipitation system / mesoscale precipitation system / Tokyo metropolitan area / Kanto district |
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| Research Abstract |
The spatial patterns of summer afternoon rainfall in Kanto Plain were statistically analyzed in search of the relationship between rainfall distribution and surface wind fields. We find that the rainfall in the central area of Tokyo is typically preceded by the convergence of winds in the vicinity of Tokyo : ones are easterlies from the eastern coast and others southerlies from the southern coast of Kanto Plain.
Long-term changes in the hour occurrence frequency of precipitation in 24 hours were analyzed using data for 42 years in Japan. The result shows a relative increasing trend of nighttime precipitation frequency in comparison to the daytime frequency.
We analyzed a case of heavy rainfall in Tokyo (21July 1999) using Doppler radar data paying attention to the development of wind fields in the life cycle of the storm. We find that low-level convergence of humid air plays an important role to the generation of the storm, and the cold outflow from pre-existing rainfall area contributed to the intensification of the storm. We also carried out three-dimensional numerical experiments to simulate the precipitation system which caused the heavy rainfall. We find that assimilation of Doppler radar data is effective in simulating the precipitation system in Tokyo.
We also executed some case studies on the behavior of moisture fields accompanying heavy rainfall systems in Kanto Plain using integrated water vapor between receiver and satellite along each GPS ray-path (Slant Water Vapor : SWV). Three components, that is, vertical component (Precipitable Water Vapor : PWV), first order gradient, and higher-order inhomogeneity, were retrieved from SWV We find that generation of heavy rainfall systems is preceded by increase in PWV and increase of inhomogeneity component of SWY as well as increase of the ratio of PWV to surface mixing ratio. These results indicate that the use of the dense network GPS is very effective for nowcasting local severe rain.
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