sfwf_formulation options:

'restoring':

a simple restoring of the top layer salinity in the model to a data value, dS/dt = (S_data - S_model) / τ, where τ is a time scale. S_data represents a space- and possibly time-dependent array of values of sea-surface salinity (SSS) and is the only necessary forcing field. If this option is chosen, then a value for the space- and time-independent restoring time-scale variable sfwf_restore_tau (in days) also needs to be specified.

'bulk-NCEP':

calculate fluxes based on atmospheric state variables similar to coupled mode (and using bulk flux formulations extracted from the NCAR flux coupler). Necessary forcing fields consist of (in order) SSS and precipitation.If this option is chosen, it is necessary to also choose 'bulk-NCEP' for shf_formulation since the evaporation rate (part of the sfwf_formulation) must be proportional to the latent heat flux (part of the shf_formulation).