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Version 4.5.1 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:

This release improves regridding features, ncra weighting, and ncatted flexibility, and contains a raft of minor fixes and tunings. Notably, most implementation-specific dimension/variable names involved in regridding can be specified at the command line, and the regridder understands mapfiles generated by TempestRemap. ncra can now weight records by a 1-D record variable in the file. And ncatted supports regular expressions in both the variable name AND the attribute name (simultaneously, too).

New Features

1. Regrid global datasets with TempestRemap mapfiles (in addition to ESMF and SCRIP, which were already supported). Tempest mapfiles use slightly different conventions than the other two, and this release accounts for those differences. This capability makes NCO's regridder a drop-in replacement for the Tempest program ApplyOfflineMap with global (source and destination) maps. The two produce the same results, modulo metadata. Please give it a try and send us feedback!
   

   # Regrid entire file, same output format as input:
   ncks --map=map.nc in.nc out.nc
   # Deflated netCDF4 output, threading, selected variables:
   ncks -4 -L 1 -t 8 -v FS.?,T --map=map.nc in.nc out.nc
   

   http://nco.sf.net/nco.html#regrid
2. ncatted now supports regular expressions in both the variable name AND the attribute name (simultaneously, too). Previously, ncatted accepted regular expressions only in the variable name. The new functionality simplifies sculpting metadata topiary from files with baroque metadata annotations, since whole groups of attributes may now be added/modified/deleted with a single command. For example, delete all attributes whose names end in "_iso19115" from all variables whose names contain "H2O".
   

   ncatted -a '.?_iso19115$','^H2O*',d,, in.nc
   

   http://nco.sf.net/nco.html#ncatted
3. Add mibs/mabs/mebs methods and operators to ncap2 . These are the absolute-value analogues of min/max/mean , so that, e.g., mibs() returns the minimum absolute-value of the operand.
   

   tpt_max=temperature.max();
   tpt_max=max(temperature);
   tpt_mabs=temperature.mabs();
   tpt_mabs=mabs(temperature);
   

   http://nco.sf.net/nco.html#mibs
   http://nco.sf.net/nco.html#ppc
   http://nco.sf.net/nco.html#ncap2
4. Prevent operators from repeating existing cell_methods attribute. Previously NCO would append new operations, e.g., "time: mean" to the existing cell_methods attribute, if any. Now it first checks to see whether that method has been applied and, if so, declines to write a duplicate operation.
   http://nco.sf.net/nco.html#cll_mth

Additional details are available in the ChangeLog.