The slab mixed-layer ocean model assumes a fixed mixed-layer depth (default value is 50 meters). The SST is determined by the energy balance between radiative flux at surface, latent and sensible heat fluxes and Q-flux, which crudely simulates the ocean transport. Q-flux is typically taken from a control QTCM1 run when SST is specified as observations or climatology. Or estimates of observed net flux may be used. In either case, the implied ocean heat transport is calculated by the balance between net surface fluxes and rate of change of SST. It can be annually averaged or monthly averaged. The air-sea coupling interval is 1 day, i.e., SST is updated every 24 hours. To activate the mixed-layer ocean model, use the pre-processor macro ``MXL_OCEAN''.
A variant of mixed-layer ocean model is to combine it with prescribed observed SST in specific regions, defined by SST mask file. This option is implemented by defining the preprocessor macro ``BLEND_SST''. When the SST mask value is 1, the read-in observed SST is used. When the SST mask is 0, SST computed from the mixed-layer ocean is used.