The Zonal Wavelength of the Quasi-Stationary Rossby Waves Trapped in the Westerly Jet

Terao Toru

doi:10.2151/jmsj1965.77.3_687

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Other Title

偏西風帯にトラップされる準定常ロスビー波の東西波長について
The Zonal Wavelength of the Quasi-Stationary Rassby Waves Trapped in the Westerly Jet
Zonal Wavelength of the Quasi-Stationary Rassby Waves Trapped in the Westerly Jet

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Properties of the quasi-stationary Rossby waves along the westerly jets are investigated with the space-time spectral analysis of 200hPa meridional wind velocity for four regions in the Northern Hemisphere summer using ECMWF data for 1980 to 1993. The observed zonal wavenumber of eastward (westward) propagating disturbances increases (decreases) as the frequency increases. The eastward propagating disturbances are stronger than the westward propagating ones. The quasi-stationary Rossby waves are seen not only in 10- to 30-day time scales but also in 30- to 90-day time scales.<br>These observed zonal wavenumber-frequency relationships are reproduced by a β-channel model with step-like basic states. Calculated zonal wavenumber of eastward (westward) propagating solution of this model increases (decreases) as the frequency increases. The eastward propagating solutions are more strongly trapped in the westerly jet than the westward propagating ones. For these four waveguides mentioned, the results of the spectral analysis agree with the properties of the solutions deduced from the β-channel model with basic states derived from the climatological basic flow near these waveguides.

Journal

Journal of the Meteorological Society of Japan. Ser. II

Journal of the Meteorological Society of Japan. Ser. II 77 (3), 687-699, 1999

Meteorological Society of Japan

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