The ``cooking'' stage

The following transformations are available in the ``cooking'' part of OASIS3, controlled by cookart.f.

• CONSERV:

  CONSERV (routine oasis3/src/conserv.f) ensures a global modification of the coupling field. This `cooking'' stage operation should not be mixed with SCRIPR/CONSERV conservative remapping (see section 6.4).

  This analysis requires one input line with one argument:

  # CONSERV operation
       $CMETH
  

  where $CMETH is the method required:
  • with $CMETH = GLOBAL, the field is integrated on both source and target grids, without considering values of masked points, and the residual (target - source) is uniformly distributed on the target grid; this option ensures global conservation of the field

  • with $CMETH = GLBPOS, the same operation is performed except that the residual is distributed proportionally to the value of the original field; this option ensures the global conservation of the field and does not change the sign of the field

  • with $CMETH = BASBAL, the operation is analogous to GLOBAL except that the non masked surface of the source and the target grids are taken into account in the calculation of the residual; this option does not ensure global conservation of the field but ensures that the energy received is proportional to the non masked surface of the target grid

  • with $CMETH = BASPOS, the non masked surface of the source and the target grids are taken into account and the residual is distributed proportionally to the value of the original field; therefore, this option does not ensure global conservation of the field but ensures that the energy received is proportional to the non masked surface of the target grid and it does not change the sign of the field.

  Note that for this operation to be correct, overlapping grid cells on the source grid or on the target grid must be masked.

• SUBGRID:

  SUBGRID can be used to interpolate a field from a coarse grid to a finer target grid (the target grid must be finer over the whole domain). Two types of subgrid interpolation can be performed, depending on the type of the field.

  For solar type of flux field ($SUBTYPE = SOLAR), the operation performed is:
  

  $$\Phi_{i} = \frac{1-\alpha_i}{1-\alpha} F$$
  
  
  where $\Phi_{i}$ ($F$) is the flux on the fine (coarse) grid, $\alpha_i$ ($\alpha$) an auxiliary field on the fine (coarse) grid (e.g. the albedo). The whole operation is interpolated from the coarse grid with a grid-mapping type of interpolation; the dataset of weights and addresses has to be given by the user.

  For non-solar type of field ($SUBTYPE = NONSOLAR), a first-order Taylor expansion of the field on the fine grid relatively to a state variable is performed (for instance, an expansion of the total heat flux relatively to the SST):
  

  $$\Phi_{i} = F + \frac{\partial F}{\partial T} ( T_i - T )$$
  
  
  where $\Phi_{i}$ ($F$) is the heat flux on the fine (coarse) grid, $T_i$ ($T$) an auxiliary field on the fine (coarse) grid (e.g. the SST) and $\frac{\partial F}{\partial T}$ the derivative of the flux versus the auxiliary field on the coarse grid. This operation is interpolated from the coarse grid with a grid-mapping type of interpolation; the dataset of weights and addresses has to be given by the user.

  This analysis requires one input line with 7 or 8 arguments depending on the type of subgrid interpolation.

  1. If the the SUBGRID operation is performed on a solar flux, the 7-argument input line is:

     # SUBGRID operation with $SUBTYPE=SOLAR 
       $CFILE  $NUMLU  $NID  $NV  $SUBTYPE  $CCOARSE $CFINE
     

     where $CFILE and $NUMLU are the subgrid-mapping file name and associated logical unit (see section 7.5 for the structure of this file); $NID the identificator for this subgrid-mapping dataset within the file build by OASIS based on all the different SUBGRID analyses in the present coupling; $NV is the maximum number of target grid points use in the subgrid-mapping; $SUBTYPE = SOLAR is the type of subgrid interpolation; $CCOARSE is the auxiliary field name on the coarse grid (corresponding to $\alpha$) and $CFINE is the auxiliary field name on fine grid (corresponding to $\alpha_i$). These two fields needs to be exchanged between their original model and OASIS3 main process, at least as AUXILARY fields. This analysis is performed from the coarse grid with a grid-mapping type of interpolation based on the $CFILE file.

  2. If the the SUBGRID operation is performed on a nonsolar flux, the 8-argument input line is:

     # SUBGRID operation with $SUBTYPE=NONSOLAR
       $CFILE $NUMLU $NID $NV $SUBTYPE $CCOARSE $CFINE $CDQDT
     

     where $CFILE, $NUMLU, $NID, $NV are as for a solar subgrid interpolation; $SUBTYPE = NONSOLAR; $CCOARSE is the auxiliary field name on the coarse grid (corresponding to $T$) and $CFINE is the auxiliary field name on fine grid (corresponding to $T_i$); the additional argument $CDQDT is the coupling ratio on the coarse grid (corresponding to $\frac{\partial F}{\partial T}$) These three fields need to be exchanged between their original model and OASIS3 main process as AUXILARY fields. This operation is performed from the coarse grid with a grid-mapping type of interpolation based on the $CFILE file.

  
  
  
  

• BLASNEW:

  BLASNEW (routine oasis3/src/blasnew.f) performs a linear combination of the current coupling field with any other fields after the interpolation. These can be other coupling fields or constant fields.

  This analysis requires the same input line as BLASOLD.

• MASKP:

  A new analysis MASKP can be used to mask the fields after interpolation. MASKP has the same generic input line as MASK.