Potential temperature
The potential temperature of a parcel of fluid at pressure P {\displaystyle P} is the temperature that the parcel would attain if adiabatically brought to a standard reference pressure P 0 {\displaystyle P_{0}} , usually 1,000 hPa (1,000 mb). The potential temperature is denoted θ {\displaystyle \theta } and, for a gas well-approximated as ideal, is given by θ = T ( P 0 P ) R / c p , {\displaystyle \theta =T\left({\frac {P_{0}}{P}}\right)^{R/c_{p}},} where T {\displaystyle T} is the current absolute temperature (in K) of the parcel, R {\displaystyle R} is the specific gas constant of air, and c p {\displaystyle c_{p}} is the specific heat capacity at a constant pressure.