[CF-metadata] Sea water pH values: at standard or in-situ conditions?

John Dunne - NOAA Federal john.dunne at noaa.gov
Thu Jun 8 11:58:18 MDT 2017


Hi Matthias,

I'm going to have to go with in-situ, unless someone can correct me
otherwise.  I'm 86.33% confident, however.  I have been looking at Jim
Orr's documentation (
http://www.geosci-model-dev-discuss.net/gmd-2016-155/gmd-2016-155.pdf), and
it cites:

Dickson, A. G., Sabine, C. L., and Christian, J. R.: Guide to best
practices for ocean CO2 measurements, , PICES Special Publication 3, 191
pp., http://aquaticcommons.org/1443/, 2007.
which gives the calculations for pH on the total scale in SOP6a and SOP6b
as a function of insitu T as a variable.  Also, I would argue from an
environmental science perspective that we *should* be posting the insitu
variable.

Hope that helps! John





On Thu, Jun 8, 2017 at 5:56 AM, Matthias Tuma <mtuma at wmo.int> wrote:

> Hello all,
>
> we had a question come up for the "sea_water_ph_reported_on_total_scale"
> standard name: it appears that for some communities, in particular on the
> measurement side, pH would regularly be reported only after first having
> converted to its equivalent at standard conditions (25C, 0dbar). In other
> communities, pH would most regularly be reported at in-situ conditions
> (temperature and pressure at actual measurement spot).
>
> While we assume that the CF conventions would implicitly assume values to
> be reported at in-situ conditions (i.e., the latter variant), my two
> questions are:
> 1) whether someone can confirm this, to be 100% certain?, and
> 2) whether adding a few according clarifying words to the description
> would be seen as useful?
>
> Thanks and best,
> Matthias
>
> --
> Matthias Tuma
> WCRP Junior Professional Officer
> c/o WMO
> 7bis, avenue de la Paix
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> Email: mtuma at wmo.int
> http://www.wcrp-climate.org
>
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