NetCDF¶

NetCDF (Network Common Data Form) is a set of software libraries and machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data. This includes the NetCDF library as well as the NetCDF Operators (NCO), Climate Data Operators (CDO), NCCMP, and NCVIEW packages.

Using NetCDF at NERSC¶

NetCDF libraries on the Cori and Perlmutter are provided by HPE, for each of the PrgEnvs. To check the available Cray installations and versions use the following command:

module avail cray-netcdf    (# on Cori)
module spider cray-netcdf   (# on Perlmutter)

No compile or link options are required as long as you use the Cray compiler wrappers ftn, cc, and CC. Below is an example:

module load cray-netcdf
ftn my_netcdf_code.f90
cc  my_netcdf_code.c
CC  my_netcdf_code.cpp

Known issues on Cori¶

• The Cray HDF5 and NetCDF libraries may break with errors mentioning problems with file locking. See the known issues section of the HDF5 docs page.

Other NetCDF tools at NERSC¶

NERSC provides several tools which can be useful for analyzing and manipulating NetCDF data.

NetCDF Operators (NCO)¶

The NetCDF Operators (NCO) are a suite of file operators that facilitate manipulation and analysis of self-describing data stored in the NetCDF or HDF4/5 formats.

To access NCO on Cori, load the nco module file.

NCO on Perlmutter is installed within the E4S software package. Below are the steps to access NCO on Perlmutter:

module load e4s
spack env active -V gcc
spack load nco
module load cudatoolkit/11.5

There are many NetCDF Operator tools, including:

• ncap2: netCDF Arithmetic Processor
• ncatted: netCDF ATTribute EDitor
• ncbo: netCDF Binary Operator (addition, multiplication...)
• ncclimo: netCDF CLIMatOlogy Generator
• nces: netCDF Ensemble Statistics
• ncecat: netCDF Ensemble conCATenator
• ncflint: netCDF FiLe INTerpolator
• ncks: netCDF Kitchen Sink
• ncpdq: netCDF Permute Dimensions Quickly, Pack Data Quietly
• ncra: netCDF Record Averager
• ncrcat: netCDF Record conCATenator
• ncremap: netCDF REMAPer
• ncrename: netCDF RENAMEer
• ncwa: netCDF Weighted Averager

Find usage information via <nco_tool_name> --help.

NCCMP¶

The NCCMP tool compares two NetCDF files bitwise or with a user-defined tolerance (absolute or relative percentage). To use NCCMP, just load the nccmp module file with the module load nccmp command. This command will automatically load the NetCDF module file.

To access NCO on Cori, load the nccmp module file.

NCCMP on Perlmutter is installed within the E4S software package. Below are the steps to access NCCMP on Perlmutter:

module load e4s
spack env active -V gcc
spack load nccmp

NCCMP usage:

nccmp [OPTION...] file1 [file2]

Find more information via nccmp --help.

CDO¶

Climate Data Operators (CDO) is a large set of tools for working on climate data. NetCDF 3/4, GRIB (including SZIP compression), EXTRA, SERVICE, and IEG are supported as I/O-formats. CDO can also be used to analyse any kind of gridded data not related to climate science. CDO has very small memory requirements and can process files larger than physical memory.

To access NCO on Cori, load the cdo module file.

CDO on Perlmutter is installed within the E4S software package. Below are the steps to access CDO on Perlmutter:

module load e4s
spack env active -V gcc
spack load cdo

CDO usage:

cdo  [Options]  Operator1  [-Operator2  [-OperatorN]]

Find more information via cdo --help.

NCView¶

NCView is a visual browser for NetCDF format files. To use NCView, first set up the necessary X11 environment (NERSC strongly recommends using NoMachine). Or use ssh -Y cori.nersc.gov or ssh -Y perlmutter-p1.nersc.gov to connect to NERSC.

To access NCView on Cori, load the ncview module file.

NCView on Perlmutter is installed within the E4S software package. Below are the steps to access NCView on Perlmutter:

module load e4s
spack env active -V gcc
spack load ncview

NCView usage:

ncview [options] datafiles

Find more information via ncview --help.

NetCDF4-python¶

netCDF4-python is an object-oriented python interface to the NetCDF library. It is available via the python module.