Dear Jonathan,
Although long-winded your suggestion of:
concentration_of_colored_dissolved_organic_matter_in_sea_water_expressed_as_equivalent_mass_fraction_of_quinine_sulfate_dihydrate
has the great advantage of preventing any confusion between this measurement and a true CDOM concentration determined by some other method. Having mass_fraction in there is particularly valuable as when we encountered this measurement the stock solutions used to calibrate the sensors had the QSD concentrations expressed in nM rather than ppb.
I also agree dimensionless is the best choice for the Canonical Unit.
Cheers, Roy.
Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquiries at bodc.ac.uk. Please also use this e-mail if your requirement is urgent.
________________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jonathan Gregory <j.m.gregory at reading.ac.uk>
Sent: 24 March 2016 19:47
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] request for new CF standard_name: CDOM
Dear John
Thanks for the proposal. It would be good to add some more context, in the
style of other CF standard_names. I would suggest
concentration_of_colored_dissolved_organic_matter_in_sea_water
if that makes sense to you. Even so, "concentration" is rather vague - we
usually make it clear whether it's mole concentration or mass concentration,
for instance. To be really explicit (and long) we could say
concentration_of_colored_dissolved_organic_matter_in_sea_water_expressed_as_equivalent_mass_fraction_of_quinine_sulfate_dihydrate
if I understand your description correctly. Is that correct?
Since qsde is not a udunit, I think the canonical unit for this quantity
should be 1 i.e. it is dimensionless, and the definition can make clear
what the unit means. In practice you could give 1e-9 as the unit, which is
equivalent to 1 i.e. both are dimensionless.
Best wishes
Jonathan
----- Forwarded message from John Maurer <jmaurer at hawaii.edu> -----
> Date: Wed, 23 Mar 2016 09:12:28 -1000
> From: John Maurer <jmaurer at hawaii.edu>
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] request for new CF standard_name: CDOM
>
> Hi all,
> This is a request to have a new standard_name added to the CF table for the
> following parameter:
>
> standard_name: colored_dissolved_organic_matter
> alias: chromophoric_dissolved_organic_matter
> alias: cdom
> units: QSDE
>
> CDOM plays an important role in the carbon cycling and biogeochemistry of
> coastal waters. It occurs naturally in aquatic environments primarily as a
> result of tannins released from decaying plant and animal matter, which can
> enter coastal areas in river run-off containing organic materials leached
> from soils. When present in high concentrations, it imparts a brown or
> yellowish color to water. Its presence can negatively impact fish
> populations by reducing dissolved oxygen concentrations to harmful levels
> and by releasing nutrients and metals that contaminate the water. Increased
> understanding of the role of CDOM will further our ability to manage and
> protect coastal ecosystems.
>
> More about the units (QSDE):
>
> Sensors are commonly calibrated against a 100 parts per billion (ppb)
> quinine sulfate dihydrate solution, a fluorescent reference standard
> commonly used with CDOM sensors. CDOM sensors therefore report in "QSDE"
> (quinine sulfate dihydrate equivalents). It is important to note, however,
> that CDOM concentrations in QSDE are not necessarily equivalent to the *in
> situ* CDOM concentrations in ppb.
>
> Thanks,
> John Maurer
> Pacific Islands Ocean Observing System (PacIOOS)
> University of Hawaii at Manoa
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> CF-metadata at cgd.ucar.edu
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----- End forwarded message -----
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Received on Fri Mar 25 2016 - 03:05:08 GMT
