NetCDF Status

Ed Hartnett, Russ Rew
September 21, 2007

This report updates the last status report of Unidata's netCDF development efforts since the User Committee meeting in May 2007.

NetCDF and Unidata

Work in maintaining, supporting, and developing the netCDF data model and software is associated with Endeavor 6: Improved scientific data access infrastructure from the Unidata 2008 proposal. NetCDF has become a key infrastructure element for data providers and users of climate, atmosphere, and ocean data.

Recent netCDF development aims at generalizing the netCDF data model, improving interoperability with other representations for scientific data, making the netCDF interface more suitable for use on high-end parallel platforms with high-resolution models, and providing netCDF software on a wide range of platforms.

Cyberinfrastructure Proposal Funded

In August, NSF announced award and funding to and Unidata of a proposal for Software Development for Cyberinfrastructure (SDCI). The work seeks to improve OPeNDAP and netCDF Integration by

OPeNDAP and Unidata will each be recruiting and hiring development assistance to collaborate with this work.

A Software Development Student Assistant III position has been opened, and is currently being advertised on the UCAR web site. Please plass this on to any interested graduate or undergraduate who is a good programmer.

NetCDF-4/HDF5 Development

NetCDF-4, the next major upgrade to netCDF, uses the HDF5 format to read and write data files through the netCDF API. This allows the introduction of many new features, including compression, parallel I/O, groups, user-defined data types, and more. NetCDF-4.0 depends on HDF5 version 1.8.0, which is currently in beta release.

The netCDF-4.0-beta1 release has been available since April, 2007. A netCDF-4 snapshot is maintained for users who need a more recent development version. Recent development work has refined group and type interfaces and continued implementation of ncdump as the first generic application for netCDF-4 data.

Several important bugs have been fixed in both netCDF-4.0 and HDF5-1.8.0 as a result of netCDF beta testing, including the functioning of fill values for strings and user-defined types, and the correct ordering of variable attributes.

The NetCDF C Interface Guide for version-4.0-beta1, which now documents all new interfaces for user-defined types and groups, was completed in September.

libcf - The CF Conventions Library

The NetCDF CF Library supports the creation of scientific data files conforming to the Climate and Forecast (CF) conventions, using the netCDF API. It assists users in correctly writing and interpreting data conforming to CF conventions.

Ed Hartnett presented a talk on the libcf library at the Sixth GO-ESSP (Global Organization for Earth System Science Portal) workshop in June. Workshop attendees expressed interest and enthusiasm for the continued development of libcf and agreed on the desirability of supporting a new CF proposal (Gridspec) within libcf.

Russ Rew presented a talk on the development of CF conventions and use of the netCDF-4 classic data model to participants in the GO-ESSP Workshop.

Seminars and Training Workshops

In June John Caron and Russ Rew presented a webcast seminar on "Writing NetCDF Files: Best Practices". The seminar was well attended and had about 20 remote participants.

In July, Ed Hartnett and Russ Rew presented the "NetCDF for Developers and Data Providers" training workshop to 38 registered participants. The workshop also included short talks by two invited speakers on parallel netCDF and HDF5.

Other NetCDF Developments

During the summer, a new C++ API prototype was developed by returning SOARS protegé Shanna Forbes. In addition to taking advantage of C++ features standardized since the current C++ API was developed, it also supports new netCDF-4 features. The new C++ API is intended for the netCDF 4.1 release. Some further development, and much more testing and documentation, remains to be accomplished before it is released.

New logos for netCDF, netCDF-4, and LibCF appeared on the web site in May. (Special thanks to Jen Oxelson).

A new mailing list, netcdf-porting, has been started to help users port netCDF to new platforms.

The netCDF/LibCF testing system was refactored; this achieved better performance, more command line options, the consolidation of 9 shell scripts into 3 scripts.

Strategic Planning Notes

For planning purposes, a 5 year vision document of netCDF development plans has been developed. It can be found here.

During the next five years, Unidata should

by Russ Rew