Hi,
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
http://www-pcmdi.llnl.gov/drach/netCDF.html
or in PostScript form from
http://www-pcmdi.llnl.gov/drach/netCDF.ps.Z
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
http://www.unidata.ucar.edu/packages/netcdf/conventions.html
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@xxxxxxxxxxx
Bob Drach drach@xxxxxxxx
Simon Tett sfbtett@xxxxxxxxxxx
--Russ
_____________________________________________________________________
Russ Rew UCAR Unidata Program
russ@xxxxxxxxxxxxxxxx http://www.unidata.ucar.edu
