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NetCDF Usage

Unidata's netCDF continues to be one of the most commonly used data interfaces in the geosciences. For example, searching for "netCDF" on Google yields 134,000 matches. With support for remote access to subsets and aggregations of netCDF data in MATLAB, IDL, GrADS-DODS Servers, other OPeNDAP servers, through Unidata's Integrated Data Viewer, in VisAD, and in many other applications, its use is expected to continue to grow. A recent book, Parallel I/O for High Performance Computing by John May, features several sections on the netCDF data model and libraries in a chapter on Scientific Data Libraries. The netCDF software distribution is the most popular Unidata software download.

Recent additions to the UPC web page Software for Manipulating or Displaying NetCDF Data include:

• ncBrowse, a graphical netCDF file browser developed at NOAA PMEL
• new netCDF interfaces for the Ruby language and for the Ada-95 language
• a new Java application, Panoply, for plotting global latitude-longitude gridded data
• two new tools ncregrid and ncdx for regridding geoscience data
• a package for reading netCDF data into the R environment for statistical computing and graphics

In addition, other recent netCDF developments include:

• NetCDF 3.5.1-beta10 with fixes for new platforms, better C++ standard conformance, Fortran90 interface fixes, Mac OS X port, ...
• a new web document "Writing NetCDF Files: Best Practices"
• NetCDF Markup Language (NcML), a new XML representation for netCDF data
• the NetCDF Java Library (version 2) which includes an interface to OPeNDAP datasets, NcML to allow the definition of virtual netCDF datasets, and direct HTTP access to netCDF files on remote web servers.

NetCDF Support

NetCDF support questions require about 450 email responses per year:

NetCDF Development Plans

With only 0.25 FTE assigned to netCDF support and development over the last two years, the pace of development at the UPC has slowed to glacial. Recognized limitations in the netCDF format and libraries include:

• 32-bit file offsets in the format that limit general netCDF files to 2 Gbytes (workarounds in some cases permit larger files that follow specific file structures);
• lack of parallel I/O support, that makes netCDF I/O a bottleneck in simulation models;
• lack of support for packed data types that make GRIB a better choice for some gridded data that must be highly compressed.

A recent proposal to a NASA NRA proposes development plans for netCDF enhancements based on a merger with the HDF5 format.

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