1989 Fiscal Year Final Research Report Summary
Internal Gravity Waves as the Background Disturbance in the Earth's Atmosphere
| Project/Area Number |
63460047
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
FUKAO Shoichiro Kyoto Univ./RASC,Professor, 超高層電波研究センター, 教授 (30026249)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Toru Kyoto Univ./Dept.Eng.,Lecturer, 工学部・電気工学第二教室, 講師 (60162450)
YAMAMOTO Mamoru Kyoto Univ./RASC,Instructor, 超高層電波研究センター, 助手 (20210560)
YAMANAKA Manabu Kyoto Univ./RASC,Lecturer, 超高層電波研究センター, 講師 (30183982)
TSUDA Toshitaka Kyoto Univ./RASC,Assoc.Prof., 超高層電波研究センター, 助教授 (30115886)
KATO Susumu Kyoto Univ./RASC,Professor, 超高層電波研究センター, 教授 (10025827)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Middle atmosphere / Internal gravity waves / MST radar observations / Wave-mean flow interaction / Spectral analysis / Momentum flux / Radiosonde observations / Vertical stratification |
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| Research Abstract |
Continuous observations on the middle-atmosphere dynamics by the MU radar of Kyoto University since the MAP (Middle Atmosphere Program; 1982-85) period lead to a hypothesis that the earth's atmosphere is fulfilled by the internal gravity waves re-distributing momentum. This study is to verify this hypothesis quantitatively.
In the first fiscal year (1988), we carried out (1) vertical-wavenumber and frequency spectral analyses of the middle-atmospheric wind disturbances based on the MU radar observations; (2) confirmation of the saturation and breaking of the internal gravity waves by the MU radar observations; and (3) observations and analyses of temperature fluctuations by radiosondes. These studies have provided us some clear evidences of gravity-wave saturation and breaking such as an amplitude modification and a selective transmission. In the final fiscal year (1989), we made (4) climatological analyses of vertical-wavenumber spectrum, momentum flux, vertical group velocity and turbulence intensity; and (5) a preliminary modeling of activities of internal gravity wave and breaking turbulence.
Now we can conclude that
(i) the internal gravity waves near Japan have vertical wavelengths shorter/longer than the deilsity scale height in the stratosphere/mesosphere;
(ii) they seem most active in winter/summer in the stratosphere/mesosphere;
(iii) the global distribution of the internal gravity waves has a striking vertical dependence and weak meridional and time dependences; and
(iv) the generation of those waves cannot be explained by a unique source such as surface orography and tropospheric cyclones.
Much more observations are necessary in particular for thermospheric and equatorial regions in order to extend the results of this study.
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