[CF-metadata] new TEOS-10 standard names

From: Trevor.Mcdougall at csiro.au <Trevor.Mcdougall>
Date: Wed, 27 Jul 2011 06:27:32 +1000

A couple of quick comments following on from Jonathan's post.

(1) I know of at least 6 pre-TEOS-10 expressions for density used in models, with authors like
         Fofonoff & Millard,
         Cox,
         Wright,
         Jackett & McDougall,
         McDougall et al.
         Jackett et al.
and they are all written in terms of Practical Salinity. I know of none used in ocean models
that use any other type of salinity (until TEOS-10 has come along). So we can safely say that
ocean and climate models have had their sea water equations of state written in terms of Practical Salinity.

(2) The fact that a model variable drifts should not be a reason to use a different name for that variable. For example, we do not change the name "potential temperature" to something else just because model temperatures are not perfect and they drift.

    Trevor


-----Original Message-----
From: Jonathan Gregory [mailto:j.m.gregory at reading.ac.uk]
Sent: Wednesday, 27 July 2011 1:45 AM
To: McDougall, Trevor (CMAR, Hobart)
Cc: ngalbraith at whoi.edu; CF-metadata at cgd.ucar.edu; Durack, Paul (CMAR, Hobart); Barker, Paul (CMAR, Hobart); rainer.feistel at io-warnemuende.de; rich at eos.ubc.ca; bak at noc.soton.ac.uk; Stephen.Griffies at noaa.gov
Subject: Re: [CF-metadata] new TEOS-10 standard names

Dear all

I understand the need to be clear, with new standard names, which observational
quantity is being collected in future. I do not agree, however, that we should
make the plain "salinity" name an alias for something more precise. This is
partly because that might change the meaning of existing data, possibly
incorrectly as Trevor points out. Partly it is also because I think it is
quite possible that models, perhaps idealised, may be used in which it would
not be meaningful to be more precise than just "salinity".

Trevor argues that existing ocean models use practical salinity because (a)
they are initialised with observations of that and (b) they assume so in their
equation of state. I don't think (a) is necessarily so. In some cases, they
might not be initialised with observations, for instance in idealised
investigations of spin-up. Even when initialised from obs,
they will almost certainly drift to a less realistic state. I don't know enough
about it to be sure about (b). Unless we could be certain this is always the
case, I think plain "salinity" should be retained for possible use in models.
However, we could certainly recommend that models should use one of the new
more precise terms if definitely appropriate. This recommendation could be
included in the standard_name definition of plain "salinity".

I understand the existing standard name sea_water_temperature to mean in-situ
temperature, as it does for air temperature. This could be stated in the
definition.

The purpose of standard names themselves is not to prescribe or recommend what
quantities people should store in netCDF files. It is to allow them to describe
with sufficient precision the quantities they have chosen to store, in order
to make it possible to decide which quantities from different datasets should
be regarded as comparable.

Standard names are all in lower case, regardless of what case is used in
ordinary writing. This is for simplicity in matching strings. Case-sensitive
matching would inevitably trip people up and cause a nuisance when they got
it wrong.

Best wishes

Jonathan
Received on Tue Jul 26 2011 - 14:27:32 BST