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Abstract

The potential temperature is a widely used quan-
tity in atmospheric science since it is conserved for dry air’s
adiabatic changes of state. Its definition involves the specific
heat capacity of dry air, which is traditionally assumed as
constant. However, the literature provides different values of
this allegedly constant parameter, which are reviewed and
discussed in this study. Furthermore, we derive the poten-
tial temperature for a temperature-dependent parameterisa-
tion of the specific heat capacity of dry air, thus providing
a new reference potential temperature with a more rigorous
basis. This new reference shows different values and vertical
gradients, in particular in the stratosphere and above, com-
pared to the potential temperature that assumes constant heat
capacity. The application of the new reference potential tem-
perature is discussed for computations of the Brunt–Väisälä
frequency, Ertel’s potential vorticity, diabatic heating rates,
and for the vertical sorting of observational data.