The moist static energy is a thermodynamic variable that describes the state of an air parcel, and is similar to the equivalent potential temperature.
[2] The moist static energy, S, can be described mathematically as: where Cp is the specific heat at constant pressure, T is the absolute air temperature, g is the gravitational constant, z is the geopotential height above sea level, Lv is the latent heat of vaporization, and q is water vapor specific humidity.
[3][4] Note that many texts use mixing ratio r in place of specific humidity q because these values tend to be close (within a few percent) under normal atmospheric conditions, but this is an approximation and not strictly correct.
Through the study of moist static energy profiles, Herbert Riehl and Joanne Malkus determined in 1958 that hot towers, small cores of convection approximately 5 kilometres (3.1 mi) wide that extend from the planetary boundary layer to the tropopause, were the primary mechanism that transported energy out of the tropics to the middle latitudes.
As with the tropics as a whole, the budget of moist static energy in the MJO is dominated by advection, but also is influenced by the wind-driven component of the surface latent heat flux.