> 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 understand your comment. Are you pointing out that ppm is not the same as ppmv, even though they are usually so close that most people ignore the difference? > That is, we remove the recommendation to use 1e-6 for ppm. Hi @JonathanGregory . I certainly prefer using ppm than 1e-6 because it helps distinguish from other dimensionless units, such as kg/kg (a common source of mistakes). However, what should a user do for a concentration that is smaller than udunits allows? There is also the downside that programs reading the data need to be told to recognize ppm/ppb/etc and multiply by 1e-6/1e-9/etc, rather than simply multiplying by the units. Personally, I would sacrifice this convenience for avoiding confusion between molar concentrations and mass concentrations. -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/cf-convention/cf-conventions/issues/260#issuecomment-617998170 This list forwards relevant notifications from Github. It is distinct from [email protected], although if you do nothing, a subscription to the UCAR list will result in a subscription to this list. To unsubscribe from this list only, send a message to [email protected].
