A major contribution to proposed coordinate conventions

Russ Rew (russ@unidata.ucar.edu)
Fri, 13 Jun 1997 08:59:31 -0600


Independently of our recent discussion of netCDF coordinate conventions
and the merits of "multidimensional coordinate variables" vs. "referential
attributes", Jonathan Gregory, Bob Drach and Simon Tett have just
published a draft of "Proposed netCDF conventions for climate data",
available for review at


or in PostScript form from 


This document extends the COARDS conventions, and in particular provides
a good specification for the meaning and use of multidimensional
coordinate variables.

I've created a link to the document from the netCDF Conventions page at


The authors have asked for feedback:

    Our principal interest in proposing this convention is to facilitate
    the exchange of data among climate centres. NetCDF offers an
    appropriate format for this purpose, and these conventions aim to
    standardise the representation of metadata sufficiently that data
    from different sources can be easily compared. We recognise that
    there are limits to what a standard can practically cover; we
    restrict ourselves to issues which we believe to be of common and
    frequent concern in the design of climate metadata. Our convention
    is mostly compatible with the existing COARDS convention, but we
    have extended the scope and detail.

    We are aware that some climate centres are already using netCDF as
    their archive format. We would be very interested to have comments
    from them, for instance on how our suggestions differ from what they
    do, and on what lessons they have learned from experience. We would
    welcome feedback from anyone on these conventions, such as on what
    has been omitted, what could be improved, and how we should carry
    this proposal forward. The exercise will only be useful if it has
    the support of a number of climate centres, of course. One
    application which will adopt this standard is the LATS software
    distributed by the Program for Climate Model Diagnosis and
    Intercomparison (PCMDI), sponsor of AMIP II. LATS will have an
    option to generate netCDF files which conform to this standard.

    Our second interest in developing this standard is its relation to a
    logical model of the data and metadata. Describing how the data
    should be stored in netCDF inevitably involves considering how it is
    organised logically. We hope to be make a proposal for a
    language-independent data model, which could be implemented in
    various programming languages as a method of handling data either in
    memory or in files. If this were done, it would offer a way of
    making analysis programs more easily portable.

    Please send any comments you may have on the proposed standard or
    any of the above to any of us. Feel free to circulate it further if
    you know others who would be interested. Thank you.

    Jonathan Gregory   jmgregory@meto.gov.uk
    Bob Drach          drach@llnl.gov
    Simon Tett         sfbtett@meto.gov.uk



Russ Rew                                         UCAR Unidata Program
russ@unidata.ucar.edu                     http://www.unidata.ucar.edu