The density is assumed to be a function of salinity and temperature. If you select barotropic mode, both temperature and salinity (TS) will be constant and the density will not be updated during the simulation. When the density is considered to be a function of temperature and/or salinity (baroclinic mode), the transport equation for the temperature and/or salinity must be solved. The solution of these equations is automatically invoked and the density is updated from the TS fields.
The specification of the setup for the solution of additional transport equations is described in the TEMPERATURE/SALINITY MODULE.
The density is calculated using UNESCO's standard equation of state for sea water. These relations are applicable for temperatures ranging from –2.1 ºC to 40.0 ºC and salinities in the range from 0 to 45 PSU (Practical Salinity Unit).
The reference temperature and salinity can be used to improve the accuracy of the density calculation, as these are subtracted from the TS fields before the density calculation. If density is a function of temperature alone, the density is calculated using the actual temperature and the reference salinity, and vice versa for salinity.
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