[CF-metadata] Is "psu" a valid cf unit?

V Balaji - NOAA Affiliate v.balaji at noaa.gov
Tue Jul 18 07:59:53 MDT 2017


Oh sorry, Roy. I assumed one was without -35 and /1000

On Tue, Jul 18, 2017 at 7:06 PM, Lowry, Roy K. <rkl at bodc.ac.uk> wrote:

> Dear Balaji,
>
>
> I think there are some crossed wires here. The dimensionless Practical
> Salinity and a Practical Salinity in PSU are exact numeric equivalents. The
> only difference is the name that's given to the unit of measure - that's
> why to make this crystal clear CF includes the scaling factor of 10^-3. So
> I don't think that this can affect storage precision.
>
>
> 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:* V. Balaji - NOAA Affiliate <v.balaji at noaa.gov>
> *Sent:* 18 July 2017 14:12
> *To:* Lowry, Roy K.
> *Cc:* martin.juckes at stfc.ac.uk; cf-metadata at cgd.ucar.edu;
> d.c.hassell at reading.ac.uk; r.s.hatcher at reading.ac.uk
> *Subject:* Re: [CF-metadata] Is "psu" a valid cf unit?
>
> The ocean modeling community is adamant that they will continue to use
> PSUs for salinity: it's this unit, rather than its SI or dimensionless
> equivalent, that gives the maximum digits of precision in a floating-point
> representation of salinity.
>
> It's a valid concern, and CF should perhaps reconsider, with a new
> discussion giving weight to the views of modelers as well as physical
> oceanographers.
>
> Thanks,
>
> Lowry, Roy K. writes:
>
> > Hello Martin,
> >
> >
> > This topic has been debated at length in CF. To cut a long story short,
> the term 'Practical Salinity Unit' was coined when the 1978 Practical
> Salinity scale was devised. However, the term fell out of favour with the
> physical oceanographic community whose current recommended practice is that
> Practical Salinity - a ratio - should be a dimensionless number.  CF
> followed this recommendation and so PSU is not a part of CF.
> >
> >
> > Have a dig around in the mailing list archive if you want to find out
> more.
> >
> >
> > 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
> martin.juckes at stfc.ac.uk <martin.juckes at stfc.ac.uk>
> > Sent: 18 July 2017 13:43
> > To: cf-metadata at cgd.ucar.edu; d.c.hassell at reading.ac.uk;
> r.s.hatcher at reading.ac.uk
> > Subject: [CF-metadata] Is "psu" a valid cf unit?
> >
> > Hello David, all,
> >
> > Is "psu" a valus CF unit? It is not in Udunits, but it is added in
> cf-python as a unit alias and also appears to be accpeted by the
> cf-checker. I can't see any mention of it in the CF Convention document:
> the latter only lists level, layer, and sigma_level permitted departures
> from Udunits,
> >
> > regards,
> > Martin
> >
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> --
> V. Balaji                               Office:  +1-609-452-6516
> <(609)%20452-6516>
> Head, Modeling Systems Group, GFDL      Mobile:  +1-917-273-9824
> <(917)%20273-9824>
> Princeton University                    Email: v.balaji at noaa.gov
> https://www.gfdl.noaa.gov/v-balaji-homepage
> v-balaji-homepage – Geophysical Fluid Dynamics Laboratory
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> www.gfdl.noaa.gov
> Bio Dr. V. Balaji is affiliated with Princeton University's Cooperative
> Institute on Climate Sciences. He has headed the Modeling Systems Group at
> NOAA's Geophysical ...
>
>
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>



-- 

V. Balaji                               Office:  +1-609-452-6516
Head, Modeling Systems Group, GFDL      Mobile:  +1-917-273-9824
Princeton University                    Email: v.balaji at noaa.gov
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