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Version 4.9.1 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:

Version 4.9.1 contains an important bugfix for vertical interpolation, and two small new features for ncclimo and ncpdq. It also fixes some autoconf-build issues that affected some users with Intel compilers, and those attempting parallel builds of NCO.

New Features

1. ncremap changes the default regridder algorithm from ESMF "bilinear" to NCO "nco_con", a first-order conservative algorithm (similar to ESMF "conserve") that requires no external dependencies. Because the default algorithm comes with NCO, users without access to ESMF and/or TempestRemap can perform a full regridding workflow. Of course many/most users will still wish to employ ESMF or TR, and their algorithms are easily accessed:

   ncremap -a nco -s grd_src.nc -d grd_dst.nc -m map.nc   # New default
   ncremap -a bilin -s grd_src.nc -d grd_dst.nc -m map.nc # Old default
   ncremap -a fv2fv -s grd_src.nc -d grd_dst.nc -m map.nc # Tempest

   http://nco.sf.net/nco.html#alg_typ
   http://nco.sf.net/nco.html#ncremap
2. ncclimo can now output spatial-average timeseries. The new --glb_avg (or --global_average) option causes ncclimo to perform a spatial mean over the timeseries constructed from the input data. The main limitation is that it only works for timeseries whose horizontal spatial dimension is "ncol" and whose area weight is named "area", as in CAM SE/EAM. Let us know if this function would be useful to you for other models and we can easily add options to make these hardwired values specifiable from the command-line.

   ls *mdl*.nc | ncclimo --glb_avg -s 1979 -e 1981 --drc_out=drc_out

   http://nco.sf.net/nco.html#ncclimo
   http://nco.sf.net/nco.html#glb_avg
3. ncpdq has a new map, flt_dbl, to convert single-precision to double-precision floating point variables. The resulting variables are not packed. All single-precision variables, including coordinates, are promoted. Some software requires geospatial data in double precision, and this feature simplifies the dataset conversion.

   ncpdq -M flt_dbl in.nc out.nc
   ncpdq -M sgl_dbl in.nc out.nc

   http://nco.sf.net/nco.html#flt_dbl
   http://nco.sf.net/nco.html#ncpdq

Additional details are available in the ChangeLog.