Evaporative available potential energy

From Glossary of Meteorology

evaporative available potential energy

(Abbreviated EAPE.) Analogous to convective available potential energy, except that it is related to the negative buoyancy associated with evaporative cooling of liquid water within a sinking cloudy air parcel.

On a thermodynamic diagram, if a line is drawn corresponding to a sinking cloudy air parcel (follow a moist adiabat downward while the parcel is cloudy, and then after all liquid water has evaporated, continue below cloud base by following a dry adiabat), the EAPE is the area between this air-parcel line and a line corresponding to the environmental sounding. The resulting EAPE can be related to the kinetic energy associated with a negatively buoyant, sinking air parcel, and is useful for determining attributes of downdrafts and downbursts from thunderstorms.