The influence of mean field variations on the realization of planetary normal modes is investigated by examining the mode response and structure in the presence of simple background nonuniformities. Gradients in the mean wind and temperature fields have the collective effect of depressing, shifting and broadening the characteristic response. While nonuniformities in both the wind and temperature fields contribute to the reduction in resonant response, spectral shifting and broadening are induced principally by variations in the mean wind field. The eigenperiods, for the most part, are influenced by the mean winds in the lowest three scale heights. The characteristic structure is modified through a change in evanescence according to the local index of refraction. In regions of reduced refractive index, for example, strong westerlies relative to the wave or a poleward temperature gradient, the mode's vertical growth rate is retarded. Conversely, in regions of increased refractive index, for example... Abstract The influence of mean field variations on the realization of planetary normal modes is investigated by examining the mode response and structure in the presence of simple background nonuniformities. Gradients in the mean wind and temperature fields have the collective effect of depressing, shifting and broadening the characteristic response. While nonuniformities in both the wind and temperature fields contribute to the reduction in resonant response, spectral shifting and broadening are induced principally by variations in the mean wind field. The eigenperiods, for the most part, are influenced by the mean winds in the lowest three scale heights. The characteristic structure is modified through a change in evanescence according to the local index of refraction. In regions of reduced refractive index, for example, strong westerlies relative to the wave or a poleward temperature gradient, the mode's vertical growth rate is retarded. Conversely, in regions of increased refractive index, for example...