Available energy and the maintenance of a moist circulation

Moist available energy is defined as the amount by which the potential plus internal (including latent) energy of a given atmospheric mass field exceeds that of a hypothetical reference field, which can be constructed from the given field by rearranging the atmospheric mass, under reversible dry-adiabatic and moist-adiabatic processes, to minimize the potential plus internal energy. Dry available energy is equal to the amount of moist available energy which would be present in a dry atmosphere having the same temperature field as the given moist atmosphere, and is identical with available potential energy.

Graphical procedures are presented for determining the moist and dry reference fields, and evaluating the available energies. In general the moist available energy exceeds the dry available energy.

Both heating and cooling can produce and can also destroy moist and dry available energy. Evaporation can produce moist available energy, while precipitation can destroy it. Preliminary computations based upon averages indicate that the total production of moist available energy by evaporation-precipitation is at least as great as the production by heating-cooling, and possibly much greater.