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Version 4.7.9 of the netCDF Operators (NCO) has been released. NCO is an Open Source package that consists of a dozen standalone, command-line programs that take netCDF files as input, then operate (e.g., derive new data, average, print, hyperslab, manipulate metadata) and output the results to screen or files in text, binary, or netCDF formats.

The NCO project is coordinated by Professor Charlie Zender of the Department of Earth System Science, University of California, Irvine. More information about the project, along with binary and source downloads, are available on the SourceForge project page .

From the release message:

Producing data for submission to CMIP6 has led to many improvemnts to the two workflow tools ncclimo and ncremap. Dozens of changes have made both tools more robust, clearer, and better documented. Notable changes include include improved sub-gridscale remapping, adding depth coordinates, CDL updates for hidden attributes, and support for GCC9 and OpenMP 5.0.0.

New Features

1. ncremap now names the SGS map as per the -m map_fl option. Previously there was no way to name SGS maps for archival. This capability eases the generation of SGS maps for CMIP6, since models (like ELM, CTSM) with time-invariant land units can regrid all variables with the same SGS map.
   http://nco.sf.net/nco.html#sgs
2. ncremap and ncclimo support MPAS files with a 'depth' dimension, and also adding a depth coordinate to raw MPAS output files. Both add 'depth' to MPAS files with the new option --dpt_fl:

   ncremap -P mpas --dpt_fl=refBottomDepth_60lyr.nc ...
   ncremap -m mpaso --dpt_fl=refBottomDepth_60lyr.nc ...

   To work, the Python code add_depth.py must be on the $PATH, and dpt_fl must contain the MPAS-Ocean field refBottomDepth. Thanks to Xylar Asay-Davis of LANL for creating a robust add_depth.py.
   http://nco.sf.net/nco.html#dpt
   http://nco.sf.net/nco.html#dpt_fl
3. The regridder utilizes the lat_dmn_nm and lon_dmn_nm options, when specified, to name the dimensions for regridded logically rectangular files. Previously these options were only used to specify horizontal dimension names in input file. Consistent with this, lat_nm_out and lon_nm_out now specify only the horizontal variable names, not the dimension names as before. The indepdendent configurability of dimension and variable names allows ncremap to regrid files with map projections as expected by Panoply and other software. Thanks to Xylar Asay-Davis of LANL for suggesting this feature.

   ncremap --rgr_opt='--rgr lat_dmn_nm=x#lon_dmn_nm=y'

   We realize this API is ugly and will create more aesthetic options like ncremap --lat_dmn=x --lon_dmn=y if enough users lovingly petition our representatives now standing-by at call centers.
   http://nco.sf.net/nco.html#rgr_opt
4. ncclimo writes more explicit information about parallelism, including job_nbr, var_nbr, and nd_nbr. This will help users tune throughput for large climatology and splitting jobs.
   http://nco.sf.net/nco.html#ncclimo
5. The splitter in ncclimo now outputs progress more clearly, and shows the elapsed time to split each timeseries.
   http://nco.sf.net/nco.html#split
6. ncra/ncrcat now perform time-rebasing in rec_apn mode using calendar units from the destination not the source file. This makes more sense when you think about it. Thanks to Ian McHugh of Monash University for prompting this.
   http://nco.sf.net/nco.html#rbs
7. NCO now writes more intelligible error messages with HINTS for likely causes of and responses to NC_EHDFERR and NC_EBADCHUNK errors.
   http://nco.sf.net/nco.html#hdf
   http://nco.sf.net/nco.html#cnk
8. ncks emulates ncdump more closely and prints hidden attribute _NoFill (not _NOFILL) values as "true" or "false" not 1 or 0.

   ncks --hidden -m in.nc

   http://nco.sf.net/nco.html#cdl
9. ncks prints CDL for hidden _Filters attribute, if any, with all filter values.

   ncks --hidden -m in.nc

   http://nco.sf.net/nco.html#cdl
10. ncks prints hidden _Endianness attribute for floating point types not just multi-byte integers as before.

    ncks --hidden -m in.nc

    http://nco.sf.net/nco.html#cdl

Additional details are available in the ChangeLog.