available potential energy
From Glossary of Meteorology
That portion of the total potential energy that may be converted to kinetic energy in an adiabatically enclosed system.
If the atmosphere were horizontally stratified, none of its potential energy would be so convertible. Thus, the available potential energy for the atmosphere in a given state is the difference between the value of the total potential energy in the given state and the value it would have after an adiabatic redistribution of mass had produced a horizontal stratification.
Lorenz, E. 1955. Available potential energy and the maintenance of the general circulation. Tellus. 7. 157– 167.
Gill, A. E. 1982. Atmosphere–Ocean Dynamics. Academic Press, . 219–225.
Holton, J. R. 1992. An Introduction to Dynamic Meteorology. 3d edition, Academic Press, . 243–246.