1999 Fiscal Year Final Research Report Summary
New synoptic meteorology : dynamics on baroclinic wares, medium-scale waves, and gravity wares
| Project/Area Number |
08404026
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | KYOTO UNIVERSITY |
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Principal Investigator |
HIROTA Isamu Kyoto Univ., Dept. of Geophysics, Professor, 大学院・理学研究科, 教授 (70025485)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Kaoru National Institute of Polar Research, Arctic Environment Research Center, Associate Professor, 助教授 (90251496)
YODEN Shigeo Kyoto Univ., Dept. of Geophysics, Associate Professor, 大学院・理学研究科, 助教授 (30167027)
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| Project Period (FY) |
1996 – 1999
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| Keywords | infer annual variations / dynamical coupling / gravity waves / medium-scale waves / baroclinic waves / planetary waves / high-resolution climate model / wave-mean flow interaction |
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| Research Abstract |
1. Data analyses of large-scale phenomena : Interannual variations of the tropospheric and stratospheric circulations in both hemispheres were studied with a 40-year long global reanalysis data. Dynamical effects of atmospheric waves on the maintenance and variation of the mean zonal-flow were investigated. By a statistical analysis some new findings and questions were obtained on the dynamical coupling between the troposphere and stratosphere, and the coupling between the equatorial region and mid-latitudes.
2. Data analyses of small and medium-scale phenomena : Using various data from the MU radar, radiosondes, forecast models, and global analysis by ECMWF, stratospheric gravity waves and tropopausal medium-scale waves were examined. Through a special observation by the MU radar over three weeks, the existence of a monochromatic inertial gravity waves was discovered in a weak wind layer in the stratosphere. Climatology of medium-scale waves was established and mechanisms to maintain t
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he wave amplitudes were elucidated.
3. Numerical experiments of large-scale phenomena : Two-dimensional and three-dimensional global atmospheric models were developed to investigate the low-frequency variations of atmospheric circulation through nonlinear interactions between planetary-scale flow and synoptic disturbances. The dynamical processes were divided into three idealized situations and the mechanisms of low-frequency variations in each system were clarified : interactions between (1) topographically-forced waves and the mean zonal-flow; (2) baroclinic disturbances and the mean zonal-flow; (3) baroclinic disturbances, forced planetary waves and the mean zonal-flow.
4. Theory and numerical experiments of small and medium-scale phenomena : Based on the quasi-geostrophic framework, theoretical consideration on the existence of the medium-scale waves was made. The medium-scale waves can be interpreted as a neutral mode trapped into large positive maximum of potential vorticity around the midlatitude tropopause. Moreover, simulation of realistic gravity waves by a high-resolution climate model was succeeded. A global view of the generation, propagation and action of gravity waves was obtained. Less
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