The following tools are very useful for working with NARCCAP data.

ncdump

Outputs contents of a netCDF file as ascii. From Unidata, part of the NetCDF libraries. http://www.unidata.ucar.edu/software/netcdf/index.html

Useful options:
ncdump -h -- prints headers
ncdump -v variable -- prints a variable
ncdump -f n1,n2 -- specify precision of output
ncdump -l length -- specify line length of output

Example output: pr-ncdump.csv -- produced using ncdump -p 5,5 -l 2000 pr_WRFP_2001010103_clim.nc

NCO

NCO is a package of command-line utilities for manipulating netCDF files. Each NCO command does one very specific kind of manipulation, but you can combine them to powerful effect.

There are a number of options common to most or all NCO commands. These include -v for specifying the variable and -d for choosing a dimensional slice. Some NCO commands make use of a "record" dimension. This needs to be the first dimension and is unlimited in extent. In NARCCAP data, this is always the time dimension.

• ncap and ncap2: netCDF Arithmetic Processors (examples) -- algebraic manipulation of data
• ncatted: netCDF Attribute Editor (examples) -- modify metadata
• ncbo: netCDF Binary Operator (includes ncadd, ncsubtract, ncmultiply, ncdivide) -- (examples) -- math involving two files
• ncea: netCDF Ensemble Averager (examples) -- average across multiple input files
• ncecat: netCDF Ensemble Concatenator (examples) -- combine files into a single record
• ncflint: netCDF File Interpolator (examples) -- combine inputs via weighted interpolation
• ncks: netCDF Kitchen Sink (examples) -- copies data to ascii or output file
• ncpdq: netCDF Permute Dimensions Quickly, Pack Data Quietly (examples) -- rearrange dimensions or pack data
• ncra: netCDF Record Averager (examples) -- average across time (record dimension)
• ncrcat: netCDF Record Concatenator (examples) -- combine sequential files
• ncrename: netCDF Renamer (examples) -- rename dimensions, variables, or attributes
• ncwa: netCDF Weighted Averager (examples) -- weighted average over one file

Example

seasonal-average -- Shellscript using NCO commands to generate seasonal climatology

NCL

NCL is an interpreted programming language for scientific analysis and visualization. It is designed with NetCDF in mind and allows easy and transparent access to NetCDF data files. It has a large and powerful plotting library oriented toward geophysical data.

NCL's syntax is FORTRAN-like. It supports the idea of coordinate variables and attributes associated with variables. Most parameters are passed to functions via "resource" attributes.

Examples

2d-time-plot.ncl Plot a timeslice from a file. Used in NARCCAP QC process. Example results.

Extensive reference and support materials are available on the NCL website: http://www.ncl.ucar.edu/

• http://www.ncl.ucar.edu/Applications/lcnative.shtml -- Plotting Examples
• http://www.ncl.ucar.edu/Applications/list_dataP.shtml -- Data Processing Examples
• http://www.ncl.ucar.edu/Training -- Materials from NCL training courses
• http://www.ncl.ucar.edu/Document/Language -- Language syntax reference
• http://www.ncl.ucar.edu/Document/Functions -- Documentation for NCL functions
• http://www.ncl.ucar.edu/Document/Graphics/Resources -- Documentation for NCL resources (options and parameters for graphics functions)

Other Tools

There are a number of other tools for working with netCDF data.