A Note Concerning the Effect of Gravitational Stability upon the CISK Model of Tropical Disturbances

Abstract

In a model for unstable tropical cyclones, Charney and Eliassen have examined a type of convective instability which depends critically upon the equivalent static stability and a characteristic scale of the disturbance. However, the converging mass of moist air rising out of the boundary layer must first overcome the gravitational field imposed by the stratification of the environment before latent heating at greater heights will energize the circulation. When this effect is introduced into the model, the growth rate is sharply reduced, and may even be zero when ??/?p = constant ? 0. This sensitivity to low-level stratification suggests that the seasonal and geographical variations in the sea surface temperature and trade wind inversion in the tropical zone may exert an important controlling influence on the growth of incipient tropical disturbances.