Updated Extrapolation Method to ESMF regridding

[arango]

The ESMF library version 8.0.0 includes new extrapolation methods for unmapped points in the destination field. The routine ESMF_FieldRegridStore includes several new arguments to specify the extrapolation method and associated parameters. The unmapped points can be extrapolated using the nearest source to destination (ESMF_EXTRAPMETHOD_NEAREST_STOD), nearest inverse distance average (ESMF_EXTRAPMETHOD_NEAREST_IDAVG), or creep fill methods (ESMF_EXTRAPMETHOD_NEAREST_CREEP).

• The coupling metadata input file coupling_esmf.dat was modified to include the new extrapolation methods for an exchanged field:

  !       Cinfo(11)     Field regridding method from source to destination:
  !                       'bilinear'      => bilinear interpolation         
  !                       'patch'         => high-order patch recovery          
  !                       'conservative1' => first-order conservative
  !                       'conservative2' => second-order conservative
  !                       'nearest'       => nearest neighbor interpolation
  !       Cinfo(12)     Field extrapolation method for unmapped points:
  !                       'none'          => no extrapolation
  !                       'nearest'       => nearest source to destination
  !                       'idavg'         => nearest inverse distance average
  !                       'creep'         => creep fill at specified level
  !                       '2steps'        => Turuncoglu's 2 steps extrapolation
  ...
  
  'SST'
    'sea_surface_temperature'                        ! standard name
    'sea surface temperature'
    't(:,:,N,itemp)', 'ROMS'                         ! source variable, ROMS
    'C'                                              ! source units
    'Center'                                         ! source grid-cell
    'tsea', 'COAMPS'                                 ! destination variable, COAMPS
    'K'                                              ! destination units
    'Center'                                         ! destination grid-cell
    'SST'                                            ! DATA Model file variable
    'bilinear'                                       ! regridding method
    'nearest'                                        ! unmapped extrapolation method
    .TRUE.                                           ! connected to coupler
    273.15d0                                         ! importing add offset
    1.0d0                                            ! importing scale
  

• Standard input script file coupling_esmf.in now includes a new parameter for the creep fill extrapolation:

  ! Internal ESMF parameters (see below for information).
  
     extrapNumLevels =  4     ! number of levels for creep fill extrapolation
  

  which specifies the number of levels for the creep fill extrapolation of unmapped destination points during regridding. After regular regridding, the creep fill method of unmapped points repeatedly moves data from mapped locations to the neighboring unmapped locations by the specified extrapNumLevels amount. For each creeped point, the extrapolation value is the average of the immediate neighbors from regridding. See ESMF Reference Manual (version 8.0 or higher) for ESMF_EXTRAPMETHOD_CREEP flag to ESMF_FieldRegridStore.

• Added the generic metadata file for COAMPS (coupling_esmf_coamps.dat) and WRF (coupling_esmf_wrf.dat) that can be used to couple to ROMS and DATA components.