  The exergy of the dry atmosphere can be considered as another aspect of the
meteorological theories of available energies. The local and global properties
of the dry available enthalpy function, also called flow exergy, were
investigated in a previous paper (Marquet, Q. J. R. Meteorol. Soc., Vol 117,
p.449-475, 1991). The concept of exergy is well defined in thermodynamics, and
several generalizations to chemically reacting systems have already been made.
Similarly, the concept of moist available enthalpy is presented in this paper
in order to generalize the dry available enthalpy to the case of a moist
atmosphere. It is a local exergy-like function which possesses a simple
analytical expression where only two unknown constants are to be determined, a
reference temperature and a reference pressure. The moist available enthalpy,
$a_m$, is defined in terms of a moist potential change in total entropy. The
local function $a_m$ can be separated into temperature, pressure and latent
components. The latent component is a new component that is not present in the
dry case. The moist terms have been estimated using a representative cumulus
vertical profile. It appears that the modifications brought by the moist
formulation are important in comparison with the dry case. Other local and
global properties are also investigated and comparisons are made with some
other available energy functions used in thermodynamics and meteorology.
