This page is devoted to instruction in ncremap. It describes steps necessary to create grids, and to regrid datasets between different grids with ncremap. Some of the simpler regridding options supported by ncclimo are also described at Generate, Regrid, and Split Climatologies (climo files) with ncclimo. This page describes those features in more detail, and other, more boutique features often useful for custom regridding solutions.
The Zen of Regridding
Most modern climate/weather-related research requires a regridding step in its workflow. The plethora of geometric and spectral grids on which model and observational data are stored ensures that regridding is usually necessary to scientific insight, especially the focused and variable resolution studies that E3SM models conduct. Why does such a common procedure seem so complex? Because a mind-boggling number of options are required to support advanced regridding features that many users never need. To defer that complexity, this HOWTO begins with solutions to the prototypical regridding problem, without mentioning any other options. It demonstrates how to solve that problem simply, including the minimal software installation required. Once the basic regridding vocabulary has been introduced, we solve the prototype problem when one or more inputs are "missing", or need to be created. The HOWTO ends with descriptions of different regridding modes and workflows that use features customized to particular models, observational datasets, and formats. The overall organization, including TBD sections (suggest others, or vote for prioritizing, below), is:
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At a minimum, install a recent version NCO on your executable $PATH with the corresponding library on your $LD_LIBRARY_PATH. NCO installation instructions are are here (fxm: link). We highly . Unless you have reason to do otherwise, we recommend installing NCO through the conda Conda package. That will automatically install another important piece of the regridding toolchainThe Conda NCO package automagically installs two other important regridding tools, the ESMF_RegridWeightGen (aka ERWG) executable and the TempestRemap (aka TR) executables. Execute 'ncremap --config' to verify you have a working installation:
zender@aerosol:~$
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ncremap
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--configncremap,
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the
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NCO
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regridder
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and
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map-
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and
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grid-generator,
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version
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4.7.6-alpha03...[Legal
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Stuff]...Config:
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ncremap script located in directory /Users/zender/binConfig:
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NCO
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binaries
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located in
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directory
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/Users/zender/bin
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, linked to netCDF library version 4.7.3Config:
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No
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hardcoded
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machine-dependent path/module
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overrides. (If desired, turn-on NCO hardcoded paths at supported national labs with "export NCO_PATH_OVERRIDE=Yes").Config: External (non-NCO) program availability:Config: ESMF weight-generation command ESMF_RegridWeightGen version 7.1.0r found as /opt/local/bin/ESMF_RegridWeightGenConfig:
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MOAB-Tempest weight-generation command mbtempest not foundConfig: MPAS depth coordinate addition command add_depth.py found as /Users/zender/bin/add_depth.pyConfig: TempestRemap weight-generation
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command
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GenerateOfflineMap
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found
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as
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/usr/local/bin/GenerateOfflineMap
Only NCO is required for basic ncremap operationmany ncremap operations including conservative weight-generation. To create new mapfile you will want ERWG. TempestRemap a new map-file with weights generated by ERWG or TR you will need those packages (both of which come with the NCO Conda package). MOAB-Tempest (MBTR) is not yet available in a pre-packaged format and must currently be built from scratch . It (MBTR is expected to come as a Conda package sometime in 2020). MBTR is only required for power-users. Make sure ncremap reports a sufficiently working status as above before proceeding further.
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