Some Sensitivity Experiments with an African Wave Model

Abstract

The response of a linearized numerical model of African waves to changes in the specification of the zonally-averaged flow is investigated. The growth rate and wavelength of the most unstable mode are found to depend on both the magnitude of the maximum shear and the relative magnitudes of horizontal and vertical shears. Attention is paid particularly to the mechanisms by which the wave energy grows. For jets similar to the observed African jet, the wave becomes more unstable as baroclinic processes are suppressed. Suppression of barotropic processes stabilizes the wave. These results help to clarify discrepancies in previous model results, and to explain some regional differences in the observed waves.