Page Comparison

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1. fluxes:  
   1. if source grid resolution uniformly  >> target grid resolution:  TR aave 
   2. otherwise:    FV2+CAAS 
2. state and vector maps:  
   1. ocn→atm: The state map's non-zero pattern must be a superset of the ocn→atm flux map.  
      1. ocn resolution uniformly >> atm resolution:  TR aave 
      2. otherwise:   FV2+CAAS    or intbilin
      3. avoid bilin due to ocean/land mask consistency issues
   2. lnd↔atm and atm→ocn
      1. if source grid resolution uniformly >> target grid resolution (fine-to-coarse):  TR  aave or intbilin
      2. if source grid resolution uniformly << target grid resolution (coarse-to-fine):  TR bilin or intbilin  (bilin slightly faster)
      3. otherwise:   TR intbilin or FV2+CAAS  (intbilin faster)
      4. For lnd→atm: avoid bilin due to ocean/land mask consistency issues (i.e. 
   3. riv → ocn
      1. continue to use custom maps generated by E3SM/cime/tools/mapping/gen_mapping_files/runoff_to_ocn

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There is a python package that can perform a more detailed analysis of mapping files used within a configured E3SM case:  (see  Map file analysis).   It will create a PDF document with a page for each mapping file which:

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can compute the following additional checks:  

• Row sums:  For atmosphere target grids, separates row sums into those over atm cells that are 100% land or ocean (all row sums should be 1), and partial land/ocean cells (row sums should range from 0 to 1) 
• Column sums: For atm2ocn grids: separate column sums into those over atm cells that are 100% ocean ( should be 1 for conservative maps) and partial ocean cells (row sums should range from 0 to 1 for conservative maps)
• For atmosphere target grids, check if the map is consistent with the atmosphere land fraction mask defined by the flux map (i.e. the map must produce land or ocean data for atm cells that have land or ocean fractions>0)  
• Measure mapping error using a standard test function, plotting the results and computing L2 and max errors.  These For atmosphere target grids, separates errors into those over atm cells that are 100% land or ocean, and partial land/ocean cells (which can have much larger errors).     These errors can be compared to know working configurations to determine if they are sufficiently small. 

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