The water is assumed to be stagnant below the wind-driven circulation. The thickness of the mixed layer can be constant or latitude-dependent. The PR model becomes identical with the LPS model if the mixed layer thickness in the PR model is set to zero. The parameters of the LPS model are the eastern boundary condition, the wind field, the subduction latitudes of layers 2 and 3 and the densities of the 4 layers. The PR model parameters are mainly the same as the parameters of the LPS model.
Additional parameters are the mixed layer thickness and the density distribution in the mixed layer.
The densities of layers 1 and 2 depend on the mixed layer density at the subduction latitudes of layers 2 and 3, respectively. The densities of layer 3 and layer 4 have to be prescribed. The original models were adapted to the conditions on the southern hemisphere. Some limitations of the LPS model were relaxed. The introduction of a realistic coastline apparently leads to improved transport estimates.