# Equivalent potential temperature

From AMS Glossary

## equivalent potential temperature

(

*Also called*wet-equivalent potential temperature.) A thermodynamic quantity, with its natural logarithm proportional to the entropy of moist air, that is conserved in a reversible moist adiabatic process.It is given most accurately as where θ

_{e}is the equivalent potential temperature,*c*_{pd}is the heat capacity at constant pressure of dry air,*r*_{t}is the total water mixing ratio,*c*is the heat capacity of liquid water,*T*is the temperature,*R*_{d}is the gas constant for dry air,*p*_{d}is the partial pressure of dry air,*p*_{0}is a reference pressure (usually 100 kPa),*L*_{v}is the latent heat of vaporization,*r*_{v}is the vapor mixing ratio,*R*_{v}is the gas constant for water vapor, and Η is the relative humidity. Neglect of the quantity*r*_{t}*c*, where it appears, yields a simpler expression with good accuracy.Paluch, I. 1979. J. Atmos. Sci.. 36. 2467–2478.

Emanuel, K. A. 1994. Atmospheric Convection. Oxford University Press, . 580 pp.