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Version 4.9.3 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:

Version 4.9.3 contains many regridding fixes and features: This version updates adds robustness to the NCO weight-generator for PG2 grids, updates default options for TempestRemap, implements a high frequency mode for the splitter, and fixes some issues with ncremap, ncclimo, and ncrcat and works-around a backwards incompatibility with the latest netCDF library, 4.7.4.

New Features

1. ncatted prints additional diagnostics when referenced attributes are not found.
   http://nco.sf.net/nco.html#ncatted
2. ncclimo adds a new clm_md='hf' type for splitting high-frequency (hgh_frq) datasets. Currently these datasets must be daily means.
   http://nco.sf.net/nco.html#ncclimo
3. ncremap now automatically parallelizes the loading of data into KD-trees during regridding when OpenMP is available. This significantly improves weight-generation throughput.
   http://nco.sf.net/nco.html#ncremap
4. The ncks --frac_b_nrm and --area_wgt options both now automatically imply --chk_map.
   http://nco.sf.net/nco.html#chk_map
5. Options for TempestRemap have been updated to current guidance: No TR algorithms invoke the TR --volumetric option anymore. Many TR algorithms now add the TR --correct_areas option.
   http://nco.sf.net/nco.html#tempest
6. ncremap's grid intersection algorithms are improved. In particular, "physics grids" (aka PG2 grids) intersections are now more robust for all resolutions in both directions up to ne1024.
   http://nco.sf.net/nco.html#ncremap
7. ncks accepts a new option --cell_area_quad which implements the TempestRemap quadrature algorithm instead of the NCO piecewise constant algorithm to compute cell areas. The TR algorithm often produces slight improved map statistics, though sometimes produces worse statistics. We are working to understand this better before deciding whether to adopt it as the default area algorithm.
   http://nco.sf.net/nco.html#ncks
8. ncks includes a workaround to the backwards incompatible changes to nc_inq_var_filter() inadvertently introduced in netCDF 4.7.4. Without this workaround, NCO may quit when printing files that store results compressed with non-DEFLATE filters.
   http://nco.sf.net/nco.html#ncks
9. ncap2 eliminated an old and little-used custom correlation procedure that worked for data with missing values yet that ran afoul of the NCO's new BSD license.
   http://nco.sf.net/nco.html#ncap2
10. The Users Guide now fully documents the ncremap and ncks options chk_map, job_nbr, par_typ, SGS, and unq_sfx.
11. Add --frac_b_nrm option to ncks map-checker.
    http://nco.sf.net/nco.html#chk_map

Additional details are available in the ChangeLog.