19.1.1.2 Interpolations to atmos grid

Each surface boundary condition is interpolated one at a time using essentially the following steps:

• For limited ocean domains, prescribe SST in $sbcatm_{i^\prime,j^\prime}$ outside the mom domain as described above. When ocean and atmosphere domains match, this is not necessary.

• Extrapolate into land areas on the mom grid. This is done by solving $\nabla^2(\SSTij)=0$ over land cells using ocean as boundary conditions^19.16. The idea is to get reasonable in land adjacent to coastlines but not necessarily to produce accurate in the middle of continents. Where land and ocean areas on the ocean and atmosphere grids are mismatched, this extrapolation will ameliorate the sensing of erroneous by the atmosphere. Such situations are common when coupling spectral atmospheres to MOM which has an Arakawa B-grid.

• Interpolate to . The ocean resolution is typically higher than that of the atmosphere because the Rossby radius is larger in the atmosphere. To prevent aliasing, the interpolation is an area average of for those cells which fall within each A $_{i^\prime,j^\prime}$ grid cell^19.17. The interpolation is carried out using subroutine ftc^19.18 which can easily be replaced by subroutine ctf^19.19 (or something else) if ocean resolution is less than atmosphere resolution.

• Set cyclic conditions on and convert to units expected by the atmosphere.

• Compute global mean of

The structure of gasbc is arranged such that components can be removed or replaced with more appropriate ones if desired.

Caveat

In the process of constructing no attempt has been made at removing small scale spatial features from the grid which could potentially be a source of noise for the atmosphere model.