I support the original request. CF should accept well known units such as ppm
and ppmv without error, warning, or prejudice. These only improve the
information content, not detract. Such units are more meaningful to humans
than current recommendations like "1" and "1e-6".
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You are
The last point, raised by Ryan @dopplershift, is of course a reasonable
question and has been raised before. If others agree with my answer, we should
put it in the FAQ.
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I agree with what has been said by @martinjuckes, @cameronsmith1 and
@roy-lowry. I don't think dimensionless units should be used to distinguish
between dimensionless quantities, since that's the purpose of standard names,
but Roy's preference for explicitly describing the dimensionless ratios
I have always had a problem with the ambiguity of units like ppm. An oxygen
measurement in the atmosphere in ppm could have two different values, one in
mass/mass and the other in volume/volume. Consequently, the use of ppmv by
some but my preference has always been to be semantically explicit
Hi @martinjuckes . I think you are correct, and I agree with you.
Fortunately, if people don't follow what you say the consequence will probably
be negligible.
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Hi @cameronsmith1 : I'm asking whether we accept them as defined in `udunits2`.
In `udunits2`, `ppm` and `ppmv` are exactly equivalent and interchangeable. My
opinion is closer to yours: these two units are similar, but not equivalent.
Hence, it might be worth excluding `ppmv` and other
> Does this mean that we accept both `ppm` and `ppmv` (parts per million by
> volume), which are equivalent in `udunits2` (i.e. they conform and `1 ppm = 1
> ppmv`)? I ask because this appears to stretch the concept of physical
> equivalence of units.
Hi @martinjuckes . I am not sure I
thanks to @mathiasbockwoldt for pointing this out and to @JonathanGregory for
proposed wording, which I support.
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I think the proposed change sounds good, and I support it.
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https://github.com/cf-convention/cf-conventions/issues/260#issuecomment-617927988
This list forwards relevant
Dear @mathiasbockwoldt
Thanks for raising this. I am glad to learn that udunits has been updated!
Since CF1.8 gives https://www.unidata.ucar.edu/software/udunits/ as its
reference for udunits, which means udunits 2 in effect, I agree that the text
should be changed. We need to agree a
# Title
udunits supports ppm, but documentation states it does not
# Moderator
None at the moment
# Requirement Summary
The documentation states that udunits does not support dimensionless ratios
like parts-per-million. But udunits does support such units.
# Technical Proposal Summary
Change
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