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Version 4.5.2 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 NCO release improves regridding features, ncra weighting, and ncatted flexibility, and contains a raft of minor fixes and tunings. Also, in case you need updated NCO versions at US computing centers, know that we now maintain up-to-date NCO in ~zender/[bin,lib] at ANL/ALCF (cooley), NCAR/NWSC (yellowstone), LBNL/NERSC (edison), and ORNL/OLCF (rhea).

New Features

1. All operators can now add user-specified global attributes to output files using the --glb switch. The switch takes mandatory arguments --glb att_nm=att_val where att_nm is the desired name of the global attriute to add, and att_val is its value. Currently only text attributes are supported (recorded as type NC_CHAR, and regular expressions are not allowed (unlike ncatted ). Multiple invocations simplify the annotation of output file at creation (or modification) time, and incur no performance penalty. Should users emit a loud hue and cry, we will consider ading the the functionality of ncatted to the front-end of all operators, i.e., accepting valid arguments to modify attributes of any type and to apply regular expressions.
   

   ncra --glb machine=${HOSTNAME} --glb created_by=${USER} in*.nc out.nc
   

   http://nco.sf.net/nco.html#glb
2. Grid generation: ncks generates SCRIP-format gridfiles for select grid types, in cluding uniform/equi-angular, cap/FV, and Gaussian. Options pertinent to the grid geometry and metadata are passed to NCO via key-value pairs prefixed by " --rgr ". Pass at least six key-value pair arguments to create a fully explicitly specified, well-annotated grid. The six arguments, and their corresponding keys in parentheses, are: grid title ( grd_ttl ), filename to write the grid to ( grid ), number of latitudes ( lat_nbr ), number of longitudes ( lon_nbr ), latitude grid type ( lat_typ ), and longitude grid type ( lon_typ ). Four other arguments (the NSEW bounding box) are necessary to construct regular regional (non-global) grids.
   

   ncks -grid=FV129x256.nc \
   --rgr lat_nbr=129 --rgr lon_nbr=256 --rgr lat_typ=cap
   --rgr lon_typ=grn_ctr ~zender/nco/data/in.nc ~/foo.nc
   ncks -grid=T42.nc \
   --rgr lat_nbr=64 --rgr lon_nbr=128 --rgr lat_typ=gss
   --rgr lon_typ=grn_ctr ~zender/nco/data/in.nc ~/foo.nc
   

   http://nco.sf.net/nco.html#grid
3. Regrid regional datasets with ESMF, SCRIP, and TempestRemap mapfiles. Please give it a try and send us feedback!
   

   # Regrid global file to regional domain
   ncks --map map_conusx4v1_to_fv0.1x0.1_US_bilin.nc in.nc out.nc
   

   http://nco.sf.net/nco.html#regrid
4. Multi-file operators support a new extension to the -n option that understands calendar month counting. It is now possibly to automatically generate series of filenames whose right-most two digits increment from a specified minimum (e.g., 03) by a specified amount (e.g., 1) until a specified maximum (e.g., 05) is reached and then the leftmost digits (i.e., the year) increments by one, and the whole process is reapeated until the total specified number of filenames is generated.
   

   ncrcat -n 3,6,1,12,1,yyyymm 198512.nc 198512_198602.nc
   

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

Additional details are available in the ChangeLog.