What is "potential temperature"

n. The temperature a parcel of air would have if brought adiabatically to a standard reference pressure

The potential temperature of a parcel of fluid at pressure P is the temperature that the parcel would acquire if adiabatically brought to a standard reference pressure P, usually 1000 millibars. The potential temperature is denoted θ and, for air, is often given by

$\theta = T \left(\frac{P_0}{P}\right)^{R/c_p},$

where T is the current absolute temperature (in K) of the parcel, R is the gas constant of air, and c is the specific heat capacity at a constant pressure. R/c = 0.286 for air (meteorology).