Matching between interactive and prescribed SST

[rfarneti]

When the dynamic ocean domain is smaller than the atmospheric domain, there could be regions of the coupled grid which are ocean/sea but are not part of the oceanic grid. In this case the atmosphere reads the SST from an input file. If the prescribed SST is in contact with grid points from the oceanic grid, sharp gradients could be generated as the atmospheric domain merges both SST fields which are not consistent.
A smoothing algorithm along the boundary of the ocean model that reduces SST differences gradually to prevent sharp gradients should be implemented. This should be done at the level of the driver/coupler in order to be generic and support both MITgcm and ROMS.