NetCDF

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Network Common Data Form
File extension : .nc, .cdf
MIME type : application / netcdf application / x-netcdf
Magic number : CDF \ x01

( ASCII-C notation )

Developed by: UCAR
Container for: scientific data
Extended by: CDF



Network Common Data Format (netCDF) is a file format for the exchange of scientific data. It is a binary file format that is machine-independent because the byte order is specified in the header . NetCDF is an open standard ; the project is supervised by the University Corporation for Atmospheric Research (UCAR).

NetCDF is based on NASA's similar sounding Common Data Format (CDF) , but has evolved from it and is no longer compatible. The current version is netCDF 4 (netCDF4). Version 4 is based on Hierarchical Data Format Version 5 (HDF5) and thus includes HDF5 features such as deflate (compression). Version 3 was still independent of the Hierarchical Data Format. The netCDF4 library allows you to continue to work with files in the classic netCDF (netCDF version 3).

NetCDF is mainly used in earth system modeling (e.g. in numerical weather forecast or climatology ) and can be used in geographic information systems.

Format description

The file format is self-describing - there is a header in which not only metadata (in the form of ordered pairs of keys and attributes ) but also the structure of the data area is described. The data itself is stored as (one- or multi-dimensional) arrays , which enables quick access.

The programming interface (API, for English. Application programming interface ) version 3 differs markedly from the API version 2, but which is completely contained for backward compatibility. The current version 4 of the netCDF API uses the HDF5 format as a basis , but the API is also backwards compatible with the old data formats. This enables new functions for netCDF programs when using the new format, for example larger files and an unlimited number of data dimensions. Thus, the performance of the HDF5 format is to be combined with the simple use of the netCDF API.

software

The UCAR has a program library that offers read and write access to netCDF files. This library is written in C , but there are interfaces to C ++ , Fortran , R , Perl , Python , Ruby , Matlab , IDL and Octave . UCAR also has an implementation in Java .

The following programs for working with netCDF files are available:

  • only visualization:
    • NcBrowse: A netCDF file viewer with support for graphics, animations and 3D visualization. It runs on Linux , macOS and Microsoft Windows .
    • NcView: A simple netCDF file viewer; offers animations, changing the color palette, viewing different dimensions of the data sets, etc. It runs on Linux and macOS .
    • Panoply: netCDF file viewer written in Java, developed by the Goddard Institute for Space Studies with a focus on the representation of geospatial data and support for map projections. It runs on Linux , macOS and Microsoft Windows .
  • processing only:
    • Climate Data Operators (cdo): A command line program with diverse operators for processing data in netCDF and GRIB format.
    • NetCDF Operators (NCO): A collection of programs for analyzing and processing netCDF files.
  • Script languages for processing and visualization:
    • Ferret Data Visualization and Analysis: Visualization program for oceanographers and meteorologists , with a Mathematica- like interactive interface and options for any shaped sections.
    • NCAR Command Language (NCL): A language for the scientific processing and visualization of data in the formats netCDF, HDF , GRIB , shape and ASCII .
  • Python modules:
    • netcdf4-python: official Python interface to the netCDF-C library from Unidata
    • PyNIO: Python module for access to different file formats such as netCDF, HDF and GRIB
    • xarray: Python module based on NumPy and pandas

Parallel netCDF

For use on parallel computers was parallel netCDF from Argonne National Laboratory and Northwestern University developed. This is based on MPI-I / O, the I / O extension from MPI .

Web links

Individual evidence

  1. ↑ Example netCDF files. unidata, accessed April 9, 2020 .
  2. ↑ What are netCDF data? esri, accessed April 9, 2020 .
  3. ↑ Global radiation (services of the DWD). DWD, accessed on April 9, 2020 .
  4. ↑ Unidata NetCDF at GitHub. Unidata, accessed April 9, 2020 .
  5. ↑ netCDF-4 C ++ library at GitHub. Unidata, accessed April 9, 2020 .
  6. ↑ Unidata NetCDF Fortran Library at GitHub. Unidata, accessed April 9, 2020 .
  7. ↑ ncdf4: Interface to Unidata netCDF (Version 4 or Earlier) Format Data Files. David Pierce, accessed April 9, 2020 .
  8. ↑ RNetCDF: Interface to 'NetCDF' Datasets. Milton Woods and Pavel Michna, accessed April 9, 2020 .
  9. ↑ netCDF4 Python module at GitHub. Unidata, accessed April 9, 2020 .
  10. ↑ netCDF-java. unidata, accessed April 9, 2020 .