| Project/Area Number |
63540308
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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 | OCEAN RESEARCH INSTITUTE, UNIV. OF TOKYO |
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Principal Investigator |
YOSHIZAKI Masanori Ocean Research Institute, Univ of Tokyo Research Associate, 海洋研究所, 助手 (60101101)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1989: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1988: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | OROGRAPHIC PRECIPITATION / NUMERICAL MODEL OF CUMULUS CONVECTION / 積雲対流モデル / 数値モデル / 雲物理過程 / 積雲と地形の相互作用 |
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| Research Abstract |
The convective clouds are sometimes enhanced around the mountains by orographic lifting and bring heavy rainfall in some regions, leading to flash flood. In order to study orographic-convective precipitation, the numerical model was made first and applied to the case observed at Okinawa Island. And sensitivity of the orographic convective system to the mountain heights and environmental fields was also examined.
Our work is summarized as follows: (1) The basic concepts such as governing equations written with terrain-following coordinates and physical processes concerning to orographic precipitation were reviewed. The review was published in Japanese, whose title is "A Guide of Convection Model to Simulate Orographic Precipitation". (2) The two-dimensional compressible model of Yoshizaki and Ogura (1988) was reconstructed following (1), and extended to include the subgrid-scale eddy viscosity as a prognostic variable in the model. The new model can stretch grid sizes in both directions.
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(3) This model was applied to the case study of the precipitation system observed at Okinawa Island in the Balu season by Akaeda et al.(1990). The simulated convective system has stationary and propagating stages, and the multicellular structure in the latter stage. Such features agree qualitatively with the observations. (4) Sensitivity of the orographic convective system to the mountain heights and environmental fields was examined. In the case of no mountain, the convective system propagates freely, while it is trapped over the mountain in the case of high mountains. In the cases of moderate mountains, the first rainfall appears in the leeside of the mountain and two stages are seen; stationary and propagating stages. At the stationary stage the cold pool develops under the precipitating region and is blocked by the mountain. The transition occurs when the cold pool overwhelms it and the convective system moves rapidly. (5) At the present, we are extending this model to be 3-dimensional and to include the ice phase in the cloud physics parameterization. Less
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