Hayashi, Y., and S. Miyahara, 1987: A three-dimensional linear response model of the tropical intraseasonal oscillation. Journal of the Meteorological Society of Japan, 65(6), 843-852.

Abstract: The propagation and structure of the tropical intraseasonal oscillation are studied by the use of a three-dimensional linear response model and compared with those obtained from the FGGE data.

It is assumed that the imposed thermal forcing oscillates with a 40 day period and propogates eastward. Although the amplitude of the forcing is assumed to be large over a certain longitude band and small elsewhere, the responding zonal wind oscillation has significant components that propagate eastward around the earth as observed. This oscillation is also associated with an observed longitudinal node in the region of the maximum forcing. When the imposed forcing is strictly confined over some longitudes, the zonal wind oscillation propagates eastward and westward away from the forced region as in the case of a two-dimensional mode. The eastward moving wavenumber 1 component is associated with the observed wave pattern of the combined Kelvin-Rossby mode in the upper troposphere, while it is dominated by that of the Rossby mode in the lower troposphere. This component also takes the observed structure of the Walker cell modified by a frictional meridional convergence in the boundary layer. The dominance of the Rossby mode in the lower troposphere is due to the effect of surface friction.