Potential temperature

The potential temperature of a parcel of fluid at pressure ${\displaystyle P}$ is the temperature that the parcel would attain if adiabatically brought to a standard reference pressure ${\displaystyle P_{0}}$, usually 1,000 hPa (1,000 mb). The potential temperature is denoted ${\displaystyle \theta }$ and, for a gas well-approximated as ideal, is given by

${\displaystyle \theta =T\left({\frac {P_{0}}{P}}\right)^{R/c_{p}},}$

where ${\displaystyle T}$ is the current absolute temperature (in K) of the parcel, ${\displaystyle R}$ is the gas constant of air, and ${\displaystyle c_{p}}$ is the specific heat capacity at a constant pressure. ${\displaystyle R/c_{p}=0.286}$ for air (meteorology). The reference point for potential temperature in the ocean is usually at the ocean's surface which has a water pressure of 0 dbar.^[1] The potential temperature in the ocean doesn't account for the varying heat capacities of seawater, therefore it is not a conservative measure of heat content.^[1] Graphical representation of potential temperature will always be less than the actual temperature line in a temperature vs depth graph.^[1]