Hi there folks..
I'm just revisiting this now as I am hoping to generate some CF-1.x compliant netcdf files and was intending to use the standard names: "sea_water_practical_salinity" and "change_over_time_in_sea_water_practical_salinity".. As we have discussed sea_water_salinity is not specific enough..
Was there some conclusion drawn about these proposed standard_names? Just for clarity the proposed names were (from a much earlier email):
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Sent: Thursday, 7 July 2011 11:45 AM
To: CF-metadata at cgd.ucar.edu
Cc: McDougall, Trevor (CMAR, Hobart)
Subject: [ExternalEmail] Re: [CF-metadata] new TEOS-10 standard names
Fair point Nan..
We should then do this..
Convert the current "sea_water_salinity" (to be discontinued in its use) to be an alias of the new standard name "sea_water_practical_salinity".
An updated definition for "sea_water_absolute_salinity" following your suggestion is included below, plus a new definition for "sea_water_practical_salinity".
I would recommend each of the new standard names also has an additional copy created, with the prefix "change_over_time_in_*"
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sea_water_conservative_temperature
Definition: Conservative Temperature is potential enthalpy divided by a fixed value of the specific heat of seawater, namely cp_0 = 3991.86795711963 J kg-1 K-1. Conservative temperature is designed to be as close as possible to potential temperature, but is two orders of magnitude more conservative in the ocean. Because of this, Conservative Temperature can be regarded as being proportional to the heat content of seawater per unit mass.
Canonical units: K
Reference: www.teos-10.org
sea_water_absolute_salinity
Definition: Absolute Salinity, S_A, is the mass fraction of dissolved material in seawater. In fact TEOS-10 estimates Absolute Salinity as the salinity variable that, when used with the TEOS-10 expression for density, yields the correct density of a seawater sample even when the sample is not of Standard Composition. In practice Absolute Salinity is often calculated from Practical Salinity and a value of Absolute Salinity Anomaly which is found using computer software via a global look-up table.
Canonical units: g kg-1
Reference: www.teos-10.org
sea_water_practical_salinity
Definition: Practical Salinity, S_P, is defined on the Practical Salinity Scale of 1978 (PSS-78) and is calculated from the electrical conductivity of seawater (as well as temperature and pressure).
Canonical units: 1e-3, parts per thousand. Officially S_P is unitless, but often authors use psu, as in S_P = 35 psu.
Reference: www.teos-10.org
sea_water_preformed_salinity
Definition: Preformed Salinity is a salinity variable that is designed to be as conservative as possible, by removing the estimated biogeochemical influences on the seawater composition from other forms of salinity.
Canonical units: g kg-1
Reference: www.teos-10.org
sea_water_potential_enthalpy
Definition: Potential enthalpy is the enthalpy of a seawater parcel after an adiabatic and isohaline change in pressure from its in situ pressure to the sea pressure p = 0 dbar.
Canonical units: J kg-1
Reference: www.teos-10.org
***
So for clarity, the new proposed names are:
sea_water_conservative_temperature
sea_water_absolute_salinity
sea_water_practical_salinity
sea_water_preformed_salinity
sea_water_potential_enthalpy
change_over_time_in_sea_water_conservative_temperature
change_over_time_in_sea_water_absolute_salinity
change_over_time_in_sea_water_practical_salinity
change_over_time_in_sea_water_preformed_salinity
change_over_time_in_sea_water_potential_enthalpy
***
Cheers,
P
________________________________________
From: cf-metadata-bounces at cgd.ucar.edu [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Paul.Durack at csiro.au [Paul.Durack at csiro.au]
Sent: Wednesday, 27 July 2011 9:33 PM
To: McDougall, Trevor (CMAR, Hobart); j.m.gregory at reading.ac.uk
Cc: CF-metadata at cgd.ucar.edu; rich at eos.ubc.ca; bak at noc.soton.ac.uk; Barker, Paul (CMAR, Hobart); rainer.feistel at io-warnemuende.de; Stephen.Griffies at noaa.gov
Subject: [ExternalEmail] Re: [CF-metadata] new TEOS-10 standard names
To follow on from Trevor's comments, most CMIP3-grade ocean models were initialised, at least in their pre-coupled ocean state from a variant of the World Ocean Atlas (WOA). Listed on the CMIP3 Climate Model Documentation, References, and Links webpages (
http://www-pcmdi.llnl.gov/ipcc/model_documentation/ipcc_model_documentation.php) these suggest that initialisation fields were sourced mostly from:
LEV82: Levitus (1982);
LEV94: Levitus et al., (1994), Levitus and Boyer (1994);
LEV98: Conkright et al.,(1999);
LEV: unspecified Levitus database
Just selecting one model from the ~24 or so which comprise the CMIP3 suite, CNRM-CM3, under section 5 - Simulation Details indicates:
Picntrl/Run_1:
This preindustrial control simulation was initialized from a coupled simulation of a previous version of CNRM coupled model initialized an ocean at rest with temperature and salinity profiles specified from Levitus (1982) climatology, integrated for 30 years with a relaxation of surface temperature to the monthly mean Reynolds climatology for 1950.
Subsequent runs are often then initialised from a previously completed spinup..
So I think it is fair to say that most model fields are then a modelled version of practical salinity..
Cheers,
P
________________________________________
From: McDougall, Trevor (CMAR, Hobart)
Sent: Wednesday, 27 July 2011 6:27 AM
To: Jonathan Gregory
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
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
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Received on Mon Oct 03 2011 - 13:01:01 BST
