Geography Reference
In-Depth Information
CHAPTER 11
Tropical Dynamics
Throughout the previous chapters of this topic, we have emphasized circulation
systems of the extratropical regions (i.e., the regions poleward of about 30
◦
lati-
tude). This emphasis should not be regarded as an indication of a lack of interesting
motion systems in the tropics, but is a result, rather, of the relative complexity of
the dynamics of tropical circulations. There is no simple theoretical framework,
analogous to quasi-geostrophic theory, that can be used to provide an overall under-
standing of large-scale tropical motions.
Outside the tropics, the primary energy source for synoptic-scale disturbances
is the zonal available potential energy associated with the latitudinal temperature
gradient. Observations indicate that latent heat release and radiative heating are
usually secondary contributors to the energetics of extratropical synoptic-scale
systems. 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, at least for those distur-
bances that originate within the equatorial zone. Most latent heat release in the
tropics occurs in association with convective cloud systems, although much of
the actual precipitation falls from mesoscale regions of stratiform clouds within
such systems; the cloud systems are themselves generally embedded in large-scale
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