Q. J. R. Meteorol. Soc., 115, 1301-1323

On the Zonal-Scale Selection and Vertical Structure of Equatorial Intraseasonal Waves

Bin WANG and Jiukang CHEN
Department of Meteorology, University of Hawaii at Manoa, Honolulu, Hawaii

(Received 29 June 1988, revised 1 February 1989)


Observed tropical intraseasonal oscillations exhibit a preferential zonal scale of wavenumber one or two and a baroclinic structure with largest flow field amplitude in the upper troposphere. Unstable interaction of boundary layer friction-induced moisture convergence with condensational heating could cause the scale selection and result in the asymmetric baroclinic structure by means of coupling of vertical normal modes. A vertically continuous linear model describing two-dimensional equatorial motion demonstrates this feedback mechanism and permits detailed study of vertical structure of unstable moist Kelvin waves.

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