Comment 2 for bug 1099943

With debugging the problem fails in serial too with an assertion failure.

Think I've found the issue. In combine_r_meshes (Combine_meshes.F90) there's an if clause for when sigma_layers are used:
        if (sigma_layers) then
          ! If we have sigma layers we will first use one chain to chain to create a dummy
          ! 'mesh' that has the correct topological properties. We will later over write the
          ! vector field with the correct one. We always have chain '1', so we'll use that now.
          call append_to_structures_radial(column, r_meshes(1), out_mesh, last_seen)
        else
          call append_to_structures_radial(column, r_meshes(column), out_mesh, last_seen)
        end if

As far as I can tell this "chaining" is completely incorrect on the sphere, though removing the clause might not result in true sigma layers. Anyone confirm this or have an opinion?