Atmospheric drydeposition at the surface depends on certain surface 
properties including soil and land use properties.  In most cases, 
these calculations can be handled in the land model and passed to 
the atmosphere through the coupler.  This method is the default 
namelist setting drydep_method='xactive_lnd'. 

However with modal areosols, this method is not adequate, and we 
must recalculate these fields in the atmosphere (see subroutine 
interp_map in mo_drydep.F90).  

For unstructured grids, it was determined to create this offline 
interpolation tool rather than generalize the subroutine interp_map.  


1. Locate or create scrip mapping files for the 1x1 degree input grids
   and the desired model output grid.

2. Generate mapping weights from 1x1 grid to target grid. This can be done using 
   ESMF with the following command (assuming an ESMF build is in your PATH):
   
   ESMF_RegridWeightGen --source <path to 1x1 scrip file> \
                     --destination <path to target scrip file> \
                     --weight <name of output mapping file> \
                     --method conserve

3. Edit nml_atmsrf and put the name of this file made in Step 2 in the srf2atmFmapname 
   field with full paths.  Edit other fields as appropriate.

4. Load the compiler and netcdf library in your environment and update Makefile accordingly.

5. Compile using "make" command and run mkatmsrffile executable.
