Slantwise convective available potential energy
From AMS Glossary
slantwise convective available potential energy
(Abbreviated SCAPE.) The total amount of potential energy available for conversion into kinetic energy in the slantwise-upward displacement of a particular sample of air in an atmosphere that is unstable to slantwise convection.
It is given by
where Rd is the gas constant for dry air; Tρ is the density temperature of the sample in question, lifted to a pressure p by a reversible adiabatic process; Tρe is the density temperature of the environment through which the sample is lifted, PNB is the pressure at which the lifted sample has the same density temperature as its environment; and
denotes that the sample should be lifted slantwise along a surface of constant absolute momentum, or, in circularly symmetric flows such as tropical cyclones, constant angular momentum.