[CF-metadata] new chemical species

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 1 Aug 2007 14:23:10 +0100

Dear Philip

> 1) One of the current problems with chemistry output is that there is
> currently NO agreed upon list of species names: many species have various
> common names, and those names are often abbreviated in codes, which can
> lead to confusion and incompatible files (eg ACET could refer to acetone
> or acetaldehyde)
>
> It would be really good if an agreed upon list of names could be agreed
> upon bf CF.

I think that we are doing this, in effect, in CF, because we would always use
the same name for a given species in the standard name table. Of course we have
to be careful to choose the species names in a reasonable way. Christiane has
thought about this e.g. when a common name can be used instead of a IUPAC name.
We would not decide in advance a complete set of species names, however; as
usual, we add them as the need arises. Use of codes and abbreviations would not
be consistent with the self-describing intentions of CF, so I don't think we
ought to do that.

> 2) The internal structure containing chemicals in models does NOT have to
> be the same as that used in the NetCDF output, and my preference is to
> have them be different.
...
> If the
> netCDF structure just uses a dimension for species, it is a pain to create
> new input files: I often find myself needing to add or remove species, or
> scale some of the species. For analysis, I also usually find myself
> wanting to extract a long time history of just one or two species (out of
> a hundred), which is also a real nuisance with a single array for all
> species, and the process is prone to error.
> nuisance that if a single specie is extracted, the degenerate dimension
> needs to be handled.
>
> Lastly, it is usually sufficient to output a small subset of species
> (saving a lot of file-space), in which case the output array will not
> match the internal array anyway.
...
> I have used codes that handled this situation both ways. Personally, I
> prefer to have each specie separate in the netCDF: the ease and accuracy
> of post-processing easily outweighs the disadvantages.

Those are interesting points. There is no reason why CF should not support
both approaches. At the moment we are following your preferred approach, which
means giving standard names with the species names in them. That means the
standard name table is larger, but I don't think it matters.

Cheers

Jonathan
Received on Wed Aug 01 2007 - 07:23:10 BST