Netcdf is a data format commonly used in climatology and GIS applications. Although designed as a direct-access storage so data-retrieval is efficient, the nature of the data stored in netcdf files is such that these files can be very large.

Ncextract is a program that extracts data from netcdf files in the form of arbitrary shapes and time-trajectories (hyperslabs). This subset of data is usually what the user is interested in (weather balloons, airplanes, satellites). The trajectory data can be stored in files for repeated extraction from different data sets, as well as the output data. The program also allows for conversion functions between the indexes of the stored data and output format.

The included extraction module is for WRF output, but it can be customized to work with other types of input files.

Disclaimer:
This program was written using the Portland Group Fortran 90 compiler, pgf90, on an Intel PC running Linux, for my own work. I am making it publicly available for people who might want to do similar extractions. In September 2006, I cleaned up and tried to optimise the original code. There might be bugs because of that, so use it at your own risk, as well as portability issues. To contact me, email sigma@gps.caltech.edu.

Ncextract 2.0 source in a tarball
Documentation in nice html format

Other links:
The Unidata Netcdf site
The NCO suite useful set of netcdf application functions

Some Tentatively Useful Fortran Functions in a library

Under construction...