Dear Jonathan,
The two pH variants I knew of before I prodded John for information were NBS, which is based on hydrogen ion concentration per unit volume (moles/litre), and free scale based on hydrogen ion concentration per unit mass (moles/kg). Both of these are what I would consider to be 'pure' pH based solely on the abundance of hydrogen ions. So, what to call them? Could we go with:
pH_per_unit_mass_in_sea_water for free scale
pH_per_unit_volume_in_sea_water for NBS
This follows the precedent set by Standard Names such as 'moles_of_silicate_per_unit_mass_in_sea_water'
As for the other two variants I agree with Jonanthan that they need to have more explicit naming, maybe along the lines of:
mole_concentration_of_H_and_HSO4_per_unit_mass_in_sea_water_expressed_as_pH
mole_concentration_of_H_and_HSO4_and_HF_per_unit_mass in_sea_water_expressed_as_pH
These are more 'Standard Essays' than 'Standard Names' but they tell somebody with my level of chemistry instantly what's going on whereas 'pH_seawater_scale' would have me searching out references.
Another question I would ask now that I've been educated by John's input is whether for the purposes of CF we need all four or could we just have the first two?
Cheers, Roy.
-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Jonathan Gregory
Sent: 28 April 2009 08:32
To: cf-metadata at cgd.ucar.edu; Lowry, Roy K
Subject: [CF-metadata] new standard name request for pH
Dear John
There is a large backlog of standard name proposals at present, which Alison
is working through.
>From an inexpert point of view, I believed that pH always measured hydrogen ion
concentration, what you call "free scale". It's interesting to learn that it's
more complicated than that. Nonetheless, it might be useful to have a
standard name of sea_water_pH, for cases where users do not wish to be precise,
for instance for model data that does not represent the complex chemistry of
sea water, so that these distinctions cannot be drawn.
For the more specific applications, I would propose that we introduce names
as they are required, as usual. You require "total scale" at present.
I have a difficulty with "free scale", "total scale" and "seawater scale", that
these terms, while no doubt well-known to experts, do not convey information
to non-experts about what the distinction is. I would suggest that it would be
more helpful to have names that indicate that the pH measures H+ only, H+ and
HSO4-, or H+ HSO4- and HF, respectively, as your definitions indicate.
Best wishes
Jonathan
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Received on Tue Apr 28 2009 - 02:29:19 BST
