mom_eos_Jackett06 module reference¶

Detailed Description¶

Jackett et al. 2006 (Hycom-25-term) equation of state¶

Jackett et al. (2006) provide an approximation for the in situ density as a function of potential temperature, salinity, and pressure. This 25 term equation of state is frequently used in Hycom for a potential density, at which point it only has 17 terms and so is commonly called the “17-term equation of state” there. Here the full expressions for the in situ densities are used.

The functional form of this equation of state includes terms proportional to salinity to the 3/2 power. This introduces a singularity in the second derivative of density with salinity at a salinity of 0, but this has been addressed here by setting a floor of 1e-8 PSU on the salinity that is used in the denominator of these second derivative expressions. This value was chosen to imply a contribution that is smaller than numerical roundoff in the expression for density, which is the field for which the Jackett et al. equation of state was originally derived.

References¶

Jackett, D., T. McDougall, R. Feistel, D. Wright and S. Griffies (2006), Algorithms for density, potential temperature, conservative temperature, and the freezing temperature of seawater, JAOT doi.org/10.1175/JTECH1946.1