ABSTRACT
The earth’s atmosphere can be looked upon as a heat engine in which part of the radiant energy received from the sun is converted into the mechanical energy of the winds. The details of the energy conversion in this heat engine have been among the main problems of general circulation studies. The consensus of the various observational and theoretical studies and numerical simulations about the middle latitude zonal westerlies is that large-scale eddies grow by conversion from zonal available potential energy and transport zonal momentum towards the zonal maximum wind and thus maintain the westerly jet. In the vertical, the force of gravity very nearly balances the vertical pressure gradient force and the work of expansion by the small residual non-hydrostatic force produces vertical kinetic energy. The source for both horizontal and vertical kinetic energy is the internal energy. The source for eddy available potential energy is the zonal available potential energy.
