The Thermal Structure of Tropical Easterly Waves

Abstract

A procedure is introduced to derive a general balance condition for synoptic-scale disturbances in the tropics. The condition describes a balance between the mean pressure and momentum fields, and the pressure forcing by cumulus clouds. A simple and explicit diagnostic relationship between the mean pressure and momentum fields is obtained when this balance condition is applied to slowly evolving tropical easterly waves. This relationship suggests that the thermal structure of tropical easterly waves reflects not so much the distribution of latent heat release by cumulus clouds, but the thermal structure required to maintain the dynamic structure of the waves. The temperature field of tropical easterly waves calculated from this diagnostic relationship, using the dynamic field of the composite easterly wave presented by Thompson et al., shows reasonably good agreement with observations.