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A page describing what we want in regridders for ACME is at: Regridding - v0.3 AMIP runs. Based on analysis described on Validation and Benchmarking of Regridders, NCO and UV-CDAT regridders both satisfy these requirements and are suitable for use. The purpose of this page is to describe how to use these regridders. Regridding occurs in 2 3 steps: first, files containing the grid for the original and target grids are acquired. Second, these grids are used to create a mapping file is obtained which contains the matrix which, when multiplied by an array of input data for some variable, yields the regridded array for that variable. Instructions for obtaining this mapping file are given in the "Getting Mapping Files" section below. Basically, these files are probably already created for you and you can just download them. The second step is passing the input file and the mapping file to the regridder code, which then does the matrix multiply for each variable and returns a file containing the requested variables on the output grid.

Getting Mapping Files:

See Regridding – obtaining mapping files

Third, the "acme regridders" create output on the target grid by combining native-grid data and mapping files. These steps are explained in more detail below.

Getting GRID FILES in SCRIP format (as long as mapping files for your input and target grids exist, you can ignore this section)

Mapping files for the resolutions ACME runs and for the target resolutions we think are appropriate are available at: https://acme-svn2.ornl.gov/acme-repo/acme/mapping/grids/ If you need a login for the ACME inputdata repo, check these instructions: ACME Input Data Repository. Here are the grids we currently support:

  1. ne30np4_091226_pentagons.nc  (1 degree CAM-SE grid)

  2. ne120np4_pentagons_100310.nc  (1/4 degree CAM-SE grid)

  3. 129x256_SCRIP.nc*    Similar to T85, but equally spaced (1.4 degrees) points in both latitude/longitude, including points at both poles.  
  4. 256x512_SCRIP.nc*    Equi-angle lat/lon grid (.70 degrees)
  5. 801x1600_SCRIP.nc*   Equi-angle lat/lon grid (0.225 degrees)

NOTE: Grid files indicated by "*" contain flaws and will be replaced ~20150901. For more information on the new grids and mapfiles, visit Why and how to migrate to updated grids and mapfiles and/or contact Charlie Zender.

Getting MAPPING FILES:  

Mapping files for the above grids are available from the ACME inputdata server https://acme-svn2.ornl.gov/acme-repo/acme/mapping/maps/ Again, If you need a login for the ACME inputdata repo, check these instructions: ACME Input Data Repository. In this repo, you will currently find 4 options:

  1. map_ne30np4_fv129x256_aave.150418.nc*         area averaged (ESMF algorithm) for downscaling 
  2. map_ne30np4_fv257x512_bilin.150418.nc*         bilinear to a finer grid, to preserve all scales
  3. map_ne120np4_fv257x512_aave.150418.nc*           area averaged (ESMF algorithm) for downscaling 
  4. map_ne120np4_fv801x1600_bilin.150418.nc*            bilinear to a finer grid, to preserve all scales

If you need to make your own mapping file, see Regridding – obtaining mapping files

NOTE: map-files ending in "*" contain flaws and will be replaced ~20150901. For more information on the new grids and mapfiles, visit Why and how to migrate to updated grids and mapfiles and/or contact Charlie Zender.

Regridding using UV-CDAT:

see: ACME regridder instructions

Regridding using NCO:

see http://nco.sourceforge.net/nco.html#regrid

Regridding using NCL:

NCL is much slower than either of the above regridders and its metadata is worse, so we don't recommend its use. However, we did create a confluence page documenting how to use it so I'm including it here for posterity: /wiki/spaces/WORKFLOW/pages/16253082... But in general, don't use this code!