The Generation of Equatorial Transient Planetary Waves: Control Experiments with a GFDL General Circulation Model

Abstract

In order to study the generation of transient planetary waves in the tropics, the effects of topography, midlatitude disturbances and condensational heat are eliminated one by one from a GFDL general circulation model during the period June and July. The time development and three-dimensional propagation of waves are examined by a space-time spectral analysis using the maximum entropy method. It is found that the characteristic scale and period of Kelvin and mixed Rossby-gravity waves do not depend on land-sea contrast or the zonal variation of sea surface temperature. Even if midlatitude disturbances are eliminated, both these waves appear in the stratosphere due to the effect of latent heat release in the troposphere. In contrast to Kelvin waves, however, mixed Rossby-gravity waves can be significantly intensified by westward moving midiatitude disturbances which are found to propagate intermittently toward the equator.