•In the Mid-latitudes,
the primary energy source for synoptic-scale disturbances is the zonal available potential energy
associated with the latitudinal
temperature gradient; and latent heat release and radiative heating are usually secondary contributors.
•In the tropics,
however, the storage of available potential energy is small due to the very small temperature gradients in the
tropical atmosphere. Latent heat
release appears to be the primary energy source.
•The dynamics of
tropical circulations is very complicate, and there is no simple theoretical framework, analogous to
quasi-geostrophic theory for
the mid-latitude dynamics, that can be used to provide an overall understanding of large-scale tropical motions.