The stochastic parametrization module aims to explicitly simulate uncertainties in the model. More particularly, Brankart  has shown that, because of the nonlinearity of the seawater equation of state, unresolved scales represent a major source of uncertainties in the computation of the large scale horizontal density gradient (from T/S large scale fields), and that the impact of these uncertainties can be simulated by random processes representing unresolved T/S fluctuations.
The stochastic formulation of the equation of state can be written as:
Gurvan Madec and the NEMO Team
NEMO European Consortium2017-02-17