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Version 4.5.5 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:

What's new?
NCO fully supports CDF5-format datasets, ncremap continues to accrue useful features, and some corner case bugs were fixed.

New Features

1. NCO supports the CDF5 file type first introduced by pnetCDF and now supported in Unidata netCDF as of version 4.4.0. CDF5 uses 64-bit offsets for a large address space (like the netCDF 64BIT type) AND arrays may have more than 2³² elements. Use '-5' , '--5' , '--fl_fmt=[cdf5|64bit_data|pnetcdf]' .
   
   Conversion to and between all netCDF filetypes is supported:

   ncks -5 in_3.nc out_5.nc
   ncks -5 in_7.nc out_5.nc
   ncks -7 in_5.nc out_7.nc

   http://nco.sf.net/nco.html#cdf5
2. ncremap: -P option triggers filetype-specific workflow procedures (such as automatic permutation). Currently filetype-specific handling is defined for AIRS, HIRDLS, MLS, and MPAS files:

   ncremap -P airs   -i airs.nc -m map.nc -o out.nc
   ncremap -P hirdls -i airs.nc -m map.nc -o out.nc
   ncremap -P mls    -i airs.nc -m map.nc -o out.nc
   ncremap -P mpas   -i mpas.nc -m map.nc -o out.nc

   One aspect of this handling is to rearrange dimension ordering from the way NASA/MPAS distributes generates these datasets so that horizontal spatial dimensions (lat, lon) come last. This is friendlier for regridding applications.
3. ncremap: -m map_fl supplies names to generated mapfiles and ncremap annotates map-files it creates with full history. This helps retain provenance in generated mapfiles. And ncremap has a friendlier mode, "map-only" mode, to generate mapfiles for later use. To use this mode, call ncremap without any input files to remap.

   ncremap will then generate the mapfile then exit.
   ncremap -i in.nc -d dst.nc -m map.nc -o out.nc # Named mapfile
   ncremap -s grd_in.nc -g grd_out.nc -m map.nc # Map-only mode

   http://nco.sf.net/nco.html#ncremap
4. ncremap -j job_nbr option for MPI parallelism
   http://nco.sf.net/nco.html#ncremap
5. ncra/nces/ncwa: New operation tabs()=total_absolute_value . The the -y tabs option is like -y ttl except the sum is over absolute values. tabs() , mibs() , mebs() , and mabs() are analogous to ttl() , min() , mean() , and max().

   nces -y tabs in.nc in.nc out.nc
   ncra -y tabs in.nc in.nc out.nc
   ncwa -y tabs in.nc out.nc

   http://nco.sf.net/nco.html#op_typ
6. Improve support for Cygwin builds

Additional details are available in the ChangeLog.