20.6 TO-DO List (How to set up open boundaries)

This list is only a sketch of what is necessary to use the open boundary options in MOM 2. The interference with new options (e.g. new diffusion schemes) must be tested carefully. It must be kept in mind that the geographical position of the open boundaries and the prescribed data can substantially affect the solution.

1.

Choose regions of open boundaries carefully at locations where the barotropic velocity is mostly perpendicular to the boundary.

2.

Open the grid one cell further for open boundaries, so the open boundary conditions reside at the second row (column) in the domain. The first row(column) is only a virtual dummy point. Topography is set automatically by subroutine topog.F similar to the open boundary row(column). If the researcher does not want the drastic choice of setting the next three rows(columns) identically, the corresponding lines in topog.F must be commented out and it is up to the researcher to insure that the bottom topography is not sloping upward within the next two rows away from the boundary.

3.

Choose a restoring time scale (USER INPUT in obc.F) and create tracer values at the open boundaries either from Levitus or FERRET written data.

4.

Choose $\psi$ values at the open boundaries in obcpsi.F or read FERRET written data to create $\psi$ values.

5.

If $\psi$ values at the open boundaries indicate a net transport through the domain, land masses have to be set to a non-zero value. This has to be done at the end of the subroutine adobcpsi.F. In the following example (Fig. 20.2) open western and eastern boundaries are chosen, transporting $130 \, Sv$ through the domain. $psiwall\_west$ and $psiwall\_east$ rise from zero at the northern end to $130 \; Sv$ at the southern end, whereby the shapes of the curves can be different. To guide the current through the domain all southern land masses must set to $130 \; Sv$.

do jrow=1,jpsimax+1
  do i=1,imt
    if (map(i,jrow) .ne. 0) then
      psi(i,jrow,1) = 130.e12
      psi(i,jrow,2) = 130.e12
    endif
  enddo
enddo