Equivalent potential temperature

Summary

The equivalent potential temperature of moist air is a potential temperature that counts the latent heat of its water vapour. It is the potential temperature the air would have after all its vapour has condensed and the released heat has warmed the air. Unlike the potential temperature, it stays nearly constant when a rising parcel becomes saturated and forms cloud. It is used to follow moist air masses and to judge the stability of the atmosphere to moist convection.