1998 Fiscal Year Final Research Report Summary
Numerical Simulation of Blocking and Abnormal Weater in General Circulation
| Project/Area Number |
09640518
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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 | University of Tsukuba |
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Principal Investigator |
TANAKA Hiroshi L. Inst.Geosci, University of Tsukuba Asst.Professor, 地球科学系, 講師 (70236628)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Blocking / Abnormal Weather / Barotropic model / Energetics / Baroclinic Instability / Synoptic Waves / General Circulation / Rossby Wave Breaking |
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| Research Abstract |
Abnormal weather in the atmosphere is closely related to tlie occurrence of block-ing high. Understanding of blocking is thus important for the study of extended-range forecasting. In this study, a series of numerical simulations of blocking is conducted using a simple barotropic model which implements a wavemaker as a parametarization of baroclinic instability. It is shown that the model successfuly simulates the life-cycle of blocking.
In the model atmosphere, the synoptic disturbances are amplified exponentially by the wavemaker. The exponential growth soon saturates with nonlinear scattering of energy from synoptic to planetary waves associated with a Rossby wave breaking. The analysis of potential vorteity (PV) indisates that the onset of blocking in brought by the Rossby wave breaking. The overturning of high and low PVs tends to oeeur at the topographic stationary ridge.
Once a block is formed by the Rossby wave breaking. subsequent. Ross by waves are blocked by it and undergo meridional stretch. The stretched wave then breaks down. depositing fresh low PV at the north and high PV at the south of the blocking system to maintain the block. The result is consistent with the so-called eddy straining mechanism. It is suggested from the result that the expouential growth of synoptic disturbances is esscetial both for the onset and the maintenance of blocking.
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