Potentialtemperatur

Potentialtemperatur, also known as Potentielle Temperatur, is a thermodynamic quantity used in atmospheric physics and oceanography to describe the temperature a parcel would have if it were moved adiabatically to a standard reference pressure p0 (commonly 1000 hPa). For dry air, it is defined by the relation θ = T (p0/p)^(R/cp), where T is the absolute temperature in kelvin, p is the parcel’s current pressure, R is the specific gas constant for dry air, and cp is the specific heat at constant pressure. Since the process is adiabatic, no heat is exchanged with the surroundings, and θ remains constant for a dry parcel undergoing vertical motion with no mixing or phase changes. This constancy makes potential temperature a useful passive tracer and a convenient vertical coordinate in atmospheric analyses such as radiosonde soundings and weather models.

In moist air, condensation and latent heat release mean that θ is not strictly conserved. Meteorologists therefore use related quantities such as the equivalent potential temperature (θe) or moist potential temperature to account for moisture effects and buoyancy, enabling assessments of stability and convection.

In oceanography, a closely related concept is used for seawater: potential temperature is the temperature a parcel would have if moved adiabatically to a reference pressure, aiding the comparison of water masses and the analysis of stratification. Across both air and water, potential temperature provides a practical, largely conservative description of thermal structure under adiabatic processes.