CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE)

CAPE provides a measure of the total increase in kinetic energy (per unit mass) that an updraft could realize through positive buoyant acceleration. In addition to the conversion of potential energy associated with interchanging less dense air below with more dense air, a positive buoyancy is caused by a warming of the updraft parcel of air owing to the latent heat released when water changes phase (condenses) from a vapor to a liquid, thus making the parcel warmer than the environment. Since the buoyant acceleration acting on the parcel is not constant with height, a line integral must be used to compute the work. CAPE is proportional to a maximum theoretical updraft velocity at the level near cloud top where the cloud is in equilibrium (zero buoyancy) with the environment.