ACME model output (on unstructured grids) and observational data (on a variety of grids) are often remapped in a post-processing step to structured lat/lon analysis grids for use and visualization by analysis tools. There are numerous small problems with these analysis grids employed for remapping by ACME (and CESM) prior to 20150901. These flaws or limitations propagate into the weights and/or grids output by the weight-generation utility. Flawed weights produce undesirable outcomes (loss of precision, gaps) when converting from source to destination grids. All tested regridders correctly apply the weights they are supplied, and migrating to improved grids (and to mapfiles generated from those grids, e.g., by ESMF_RegridWeightGen or TempestRemap) can automatically improve both the numerical accuracy and the data and metadata completeness and consistency of the files produced by the regridding procedure. None of the problems described below affect the accuracy of the model results on the native grid. The affected grids include many CAM-FV (plain and staggered) and Gaussian grids known to be used for ACME analysis, mapfiles produced from those grids, and all mapfiles employing bilinear interpolation. The new grids improve the accuracy of diagnostics and the aesthetics of plots produced from regridded files.
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| Old (flawed) Gridfile | New (corrected) | CAM-FV Grid Generation: |
|---|---|---|
| 129x256_SCRIP.20150901.nc | ncremap -G ttl='CAM-FV scalar grid 129x256'#latlon=129,256#lat_typ=cap#lon_typ=grn_ctr -g ${DATA}/grids/${DATA}/grids/ 129x256_SCRIP.20150901.nc | |
| 257x512_SCRIP.130510.nc | 257x512_SCRIP.20150901.nc | ncremap -G ttl='CAM-FV scalar grid 257x512'#latlon=257,512#lat_typ=cap#lon_typ=grn_ctr -g ${DATA}/grids/${DATA}/grids/ 257x512_SCRIP.20150901.nc |
ncremap -G ttl='CAM-FV scalar grid 801x1600'#latlon=801,1600#lat_typ=cap#lon_typ=grn_ctr -g ${DATA}/grids/${DATA}/grids/ 801x1600_SCRIP.20150901.nc |
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| Old (flawed) Gridfile | New (corrected) | Gaussian Grid Generation: |
|---|---|---|
| T42_001005.nc | t42_SCRIPscrip.2015090120181001.nc | ncremap -G ttl='T42 Gaussian grid. Updated with exactly symmetric latitude interfaces.'#latlon=64,128#lat_typ=gss#lon_typ=grn_ctr -g ${DATA}/grids/g t42_scrip.20181001.nc |
| T62_040121.nc | t62_SCRIPscrip.2015090120181001.nc | ncremap -G ttl='T62 Gaussian grid. Updated with exactly symmetric latitude interfaces.'#latlon=94,192#lat_typ=gss#lon_typ=grn_ctr -g ${DATA}/grids/ t62_scrip.20181001.nc |
| T85_011127.nc | ncremap -G ttl='T85 Gaussian grid.Updated with exactly symmetric latitude interfaces.'#latlon=128,256#lat_typ=gss#lon_typ=grn_ctr -g ${DATA}/grids/g t85_scrip.20181001.nc |
Note that ACME gridfiles and mapfiles are date-stamped. The new grid and mapfiles were produced on or after 20150724. Cubed-sphere gridfiles produced before 20150724 are still considered good. Many other atmosphere gridfiles produced before 20150724 contain the flaws mentioned above. Gridfile flaws propagate to mapfiles so in most cases mapfiles must be updated too
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