Adiabatic Lapse Rate

The adiabatic lapse rate is the rate at which a fluid parcel changes temperature as it rises or sinks with no heat exchange with its surroundings, set entirely by the pressure work of expansion or compression. In the atmosphere the dry adiabatic rate is about 9.8 K per km; the saturated rate falls to roughly 4 to 7 K per km once latent heat is released. The ocean has an analogous adiabatic temperature gradient, near 0.1 to 0.2 K per km in the deep sea, which is why oceanographers convert in-situ temperature to potential temperature to remove this pressure effect before comparing water masses.