potentialtemperaturen

Potential temperature is a concept used in atmospheric science and oceanography to describe the temperature a parcel of fluid would have if it were moved adiabatically to a reference pressure. This means that any changes in temperature due to compression or expansion as the parcel moves vertically are accounted for, but changes due to heat exchange with the surroundings are ignored. The reference pressure is typically chosen to be at the surface of the Earth, often 1000 hectopascals.

The primary utility of potential temperature lies in its conservation during adiabatic processes. Unlike actual temperature, which changes with pressure, potential temperature remains constant for a parcel of air or water as it ascends or descends through the atmosphere or ocean, provided no heat is added or removed. This makes it a valuable tool for tracking air masses and water masses, as well as for understanding atmospheric stability and ocean circulation.

For dry air, potential temperature (θ) can be calculated using the formula θ = T(P₀/P)^(R/cp), where T is the actual temperature, P is the actual pressure, P₀ is the reference pressure, R is the specific gas constant for dry air, and cp is the specific heat capacity of dry air at constant pressure. For moist air, the calculation becomes more complex due to the presence of water vapor, and moist potential temperature or equivalent potential temperature are often used instead. In oceanography, a similar concept is used, but it typically refers to a reference pressure at the surface and accounts for the density of seawater.