This commit changes the horizontal interpolation from a four-point

bilinear interpolation to a sixteen point overlapping parabolic
interpolation for both initialization of the state variables from
an existing analysis (e.g. GFS, ERA5, etc; case 7 for init_atmosphere)
and for interpolating lateral boundary values for the regional MPAS-A
configuration (case 9 for init_atmosphere).

Author: skamaroc

src/core_init_atmosphere/mpas_init_atm_cases.F

@@ -3469,7 +3469,8 @@ subroutine init_atm_case_gfs(block, mesh, nCells, nEdges, nVertLevels, fg, state
 
       do while (istatus == 0)
 
-         interp_list(1) = FOUR_POINT
+         ! interp_list(1) = FOUR_POINT
+         interp_list(1) = SIXTEEN_POINT
          interp_list(2) = SEARCH
          interp_list(3) = 0
 
@@ -5261,7 +5262,8 @@ subroutine init_atm_case_lbc(timestamp, block, mesh, nCells, nEdges, nVertLevels
 
       do while (istatus == 0)
 
-         interp_list(1) = FOUR_POINT
+         ! interp_list(1) = FOUR_POINT
+         interp_list(1) = SIXTEEN_POINT
          interp_list(2) = SEARCH
          interp_list(3) = 0