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| NCO (NetCDF Operators) | |
|---|---|
| Name | NCO (NetCDF Operators) |
| Author | Martin J. Verity |
| Developer | University of Colorado Boulder team |
| Released | 1995 |
| Operating system | Linux, macOS, Windows |
| Genre | Scientific software, data processing |
| License | GNU General Public License |
NCO (NetCDF Operators) is a suite of command-line programs for manipulation and analysis of array-oriented scientific data stored in the Network Common Data Form family of formats. It is widely used in the climate science and oceanography communities for tasks such as subsetting, averaging, concatenation, and metadata manipulation across large collections of satellite and model outputs. Developers integrate NCO into workflows alongside tools like GrADS, Panoply, CDO, and Python libraries such as xarray and netCDF4-python.
NCO provides modular utilities to perform file-level and variable-level operations on NetCDF files created by software from institutions like NOAA, NASA, ECMWF, and NCAR. The suite emphasizes non-interactive, reproducible processing suitable for automated pipelines used by projects including IPCC assessments, CMIP experiments, and observational datasets from missions like MODIS and Aqua. NCO operates on data produced by models run at centers such as GFDL, Hadley Centre, and MPI-M.
NCO originated in the mid-1990s, developed by researchers affiliated with University of Colorado Boulder and collaborators at nation-state laboratories including NOAA and NCAR. Its evolution paralleled growth in community standards like CF (Climate and Forecast) metadata convention and the expansion of gridded datasets from projects such as CMIP3, CMIP5, and CMIP6. Over successive releases maintainers added support for newer netCDF-4 features, integration with HDF5, and portability across platforms used by organizations such as ESRL and JPL.
NCO implements operations common to studies undertaken at IPCC, WMO, and research groups within Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory. Capabilities include variable arithmetic used in analyses by NOAA-GFDL and NCAR CESM users, statistical reductions used in NASA GISS studies, dimension transposition relevant to ECMWF post-processing, and global/ regional subsetting utilized in Copernicus services. Metadata management aligns with CF Convention and complements tools from IOOS and THREDDS.
The suite comprises individual executables patterned after Unix utilities common at institutions like Los Alamos National Laboratory and Lawrence Berkeley National Laboratory. Commands such as ncks, ncrcat, ncap2, and ncwa are invoked in batch scripts executed on clusters managed by schedulers like SLURM and PBS. Flag syntax and piping conventions follow practices used in GNU toolchains and integrate with shells popular at MIT and Caltech research groups. Users often combine NCO commands with bash scripts and wrappers in languages developed at Bell Labs and AT&T.
NCO supports netCDF-3, netCDF-4, and hybrid files leveraging HDF5 containers, enabling interoperability with datasets distributed by NOAA ESRL, ESA, and USGS. This compatibility ensures NCO works with output from modeling centers such as EC-Earth, UK Met Office, and CNRM-CERFACS, and with observational archives maintained by NSIDC, EUMETSAT, and GHRSST. NCO also respects metadata conventions endorsed by CF Convention and used by repositories like PANGAEA.
For high-throughput environments at facilities like NERSC, XSEDE, and Argonne National Laboratory, NCO operations are optimized for single-node efficiency and can be combined with parallel I/O strategies developed for MPI-based workflows. While core NCO binaries are not intrinsically MPI-parallel, they are commonly executed in parallel across files using orchestration frameworks from Slurm Workload Manager and parallelization tools used at Oak Ridge National Laboratory. Performance tuning often involves filesystem choices promoted by centers such as National Energy Research Scientific Computing Center.
Common use cases include variable extraction for CMIP6 diagnostics, time averaging for PODAAC data, regridding preparation for Model Intercomparison Projects, and creation of analysis-ready datasets for Reanalysis products like ERA5 and MERRA-2. Researchers at institutions like NOAA and NCAR use NCO in conjunction with visualization tools such as Matplotlib, NCL, and Ferret. Example workflows often appear in documentation produced by ESGF nodes and tutorials from UCAR and University of Washington.
NCO is distributed under the GNU General Public License and maintained by contributors from academic and government institutions including University of Colorado Boulder, NOAA, and NCAR. Development discussions occur on mailing lists and issue trackers used by projects like Unidata and are cited in community workshops run by AGU and AMS. Users contribute patches and documentation via repositories and collaborate through training events at centers such as NERSC and ESGF nodes.
Category:Scientific software Category:Earth sciences software