Potential temperature (θ) removes the altitude effect on temperature: by "bringing" the parcel to 1,000 hPa (adiabatic compression), all parcels are compared on equal footing. If θ is constant with height, the atmosphere is neutral; if it increases, it is stable.
Use in meteorology
It is fundamental in soundings and numerical models for identifying air masses: polar air has low θ (~270–280 K), tropical air high θ (~310–330 K). Equivalent potential temperature (θe) adds the effect of latent humidity and is the ideal parameter for tracking moist air masses and identifying convective instability.