Paul,
regarding the unit of an implemented quantity, in the SIA library
we have added unit tags to any of them, such as sea_density_si
where "_si" indicates that the value is given in SI basic units,
kg/m3 in this case. If non-basic SI units or non-SI units are
used, this is explicitly indicated in the tag, such as
absolute_salinity_gkg if the unit associated with salinity is g/kg.
Such tags permit some flexibility in the units to be used and help
to avoid confusion. absolute_salinity_si would then mean kg/kg.
Regarding PSS-78, I think "_psu" may be best understood by any user.
I know that even "mpsu" (milli-psu) is used by some authors, so
practical_salinity alone may not be enough to avoid ambiguity.
Rainer
> Thanks for all your work getting this fairly scattered discussion into a
> submittable shape Alison!
>
> I've supplemented your comments with some additional descriptive text
> below. I have additionally added a "References:" attribute for each of
> these proposed variables if applicable, I am not sure whether the format
> of the current standard_names table can deal with this suggestion?
>
> The new proposed name sea_water_cox_salinity has also been added (this is
> a new one).
>
> I am also wondering if while we're trying to tidy up this all, if we
> propose the "units": "PSS-78", "ppt" and "psu" to become part of an update
> to the udunits codebase? I am not sure how we would go about this
> however.. It seems arbitrary that we continue to use the canonical units
> of 1e-3 for salinity, as you note we currently scale this. A nice thing
> with TEOS-10 is that we get back units, so g kg-1 rather than the ratio of
> the past, however I would note that regardless of the notation it's still
> 1e-3.. I apologise below my units are a little all over the place..
>
> I have also rearranged the name of "specific_enthalpy" to
> sea_water_specific.. I think it is better to maintain the convention of
> sea_water_X, as this then lists together when viewing the entire table
> alphabetically..
>
> As noted below I believe that 5 of the 8 proposed new names would benefit
> from a change_over_time_in_X name too, and the notation you have proposed
> with the ..."change_over_time_in_X" means change in a quantity X... Seems
> reasonable to me.
>
> I have appended my suggested edits below.. If anyone notes any issues
> below, please fix and resubmit this..
>
> Cheers,
>
> P
>
> ***
> Add PSS-78, ppt & psu to udunits ? provide request info to Unidata?
>
> sea_water_salinity
> Definition: The standard name sea_water_salinity is the salt content of
> sea water normally on the Practical Salinity Scale of 1978 (PSS-78), and
> is usually based on the electrical conductivity of sea water in
> observations since the 1960s. There are standard names for the more
> precisely defined salinity quantities sea_water_knudsen_salinity
> (1901-1966), sea_water_cox_salinity (1967-1977),
> sea_water_practical_salinity (1978-present day),
> sea_water_absolute_salinity and sea_water_preformed_salinity. The more
> precise standard names should be used where appropriate for both modelled
> and observed salinities. In particular, the use of sea_water_salinity to
> describe salinity observations made from 1978 onwards is now deprecated in
> favour of the term sea_water_practical_salinity which is the salinity
> quantity stored by national data centres for post-1978 observations. The
> only exception to this is where the observed salinities are definitely
> known not to be recorded on the Practical Salinity Scale.
> Canonical units: 1e-3; practical salinity units, which is dimensionless.
> The use of parts per thousand (ppt) was expressed for
> sea_water_knudsen_salinity and sea_water_cox_salinity.
>
> 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 sea water (as well as temperature and pressure). This name should be
> used to describe salinity observations made from 1978 onwards; practical
> salinity is the salinity quantity stored by national data centres for
> post-1978 observations. The only exception to this is where the observed
> salinities are definitely known not to be recorded on the Practical
> Salinity Scale. More recently remote salinity measurements from satellites
> (SMOS/AQUARIUS) also provide surface estimates of salinity presented in
> S_P, however these are not obtained from conductivity measurements. In
> these cases information about calibration and validation techniques to
> convert remotely sensed salinity to S_P should be documented ? within the
> variable "comment" attribute. There are also standard names for the
> precisely defined salinity quantities sea_water_absolute_salinity and
> sea_water_preformed_salinity. Salinity quantities that do not match any of
> the precise definitions should be given the more general standard name of
> sea_water_salinity.
> Canonical units: Officially S_P is unitless, so that, while convenient,
> and while it is common practice, it is not officially sanctioned to say
> S_P = 35 psu. Often authors use PSS-78, as in S_P = 35 PSS-78. If salinity
> was measured using remote satellite techniques, then it is recommended
> that additional metadata (calibration/validation information) be described
> in the variable comment attribute.
> Reference: www.teos-10.org
>
> sea_water_cox_salinity
> Definition: Cox Salinity, S_C, is defined unitless as a fraction per mil
> (0/00). S_C was the standard salinity measure until S_P (Practical
> Salinity) was established with PSS-78 (1978). Chlorinity Cl is calculated
> from the conductivity of a seawater sample, and since the work of the
> Joint Panel for Oceanographic Tables (1966) is converted into Cox Salinity
> using S_C = 1.80655 Cl. This type of salinity was called simply ?salinity?
> from 1967 to 1978 and had the ?units? of 0/00, or ?parts per thousand? or
> ppt. Practical Salinity replaced Cox Salinity in 1978.
> Canonical units: (0/00) or ?parts per thousand?.
> Reference: Cox et al., 1967 doi: 10.1016/0011-7471(67)90006-X
>
> sea_water_knudsen_salinity
> Definition: Knudsen Salinity, S_K, is defined unitless as a fraction per
> mil (0/00) and was calculated from the titration of inorganic salts from a
> sample of sea water after a commission to study the problem of determining
> salinity and density was initiated by the International Council for the
> Exploration of the Sea (ICES) in 1899. S_K was the standard salinity
> measure until S_C (Cox Salinity) was established in 1967. Chlorinity Cl is
> calculated by titration from a sample of seawater, and since the work of
> Knudsen (1901) is converted into Knudsen Salinity using S_K = 0.030 +
> 1.805 Cl. This type of salinity was called simply ?salinity? from 1901 to
> 1966 and had the ?units? of 0/00, or ?parts per thousand? or ppt. From
> 1950 onwards electrical conductivity was used to estimate the Knudsen
> Salinity rather than chemical titration, which was the standard before
> this time. Cox Salinity replaced Knudsen Salinity in 1967.
> Canonical units: (0/00) or ?parts per thousand?.
> Reference: Knudsen, 1901; Thomas et al., 1934 doi: 10.1093/icesjms/9.1.28;
> Lyman, 1969 doi: 10.4319/lo.1969.14.6.0928; Wooster et al., 1969 doi:
> 10.4319/lo.1969.14.3.0437; Lewis, 1980 doi: 10.1109/JOE.1980.1145448;
> Millero et al., 2008 doi: 10.1016/j.dsr.2007.10.001;
>
> sea_water_reference_salinity
> Definition: If a seawater sample has the Reference Composition (dissolved
> solutes, additional to Cl), then its Reference Salinity is the best
> available estimate of its Absolute Salinity. For general purposes,
> Reference Salinity is (35.16504 g kg-1)/35 times Practical Salinity.
> Canonical units: g kg-1
> Reference: www.teos-10.org; Millero et al., 2008 doi:
> 10.1016/j.dsr.2007.10.001
>
> sea_water_absolute_salinity
> Definition: Absolute salinity, S_A, is defined as a term in the
> Thermodynamic Equation of Seawater 2010 (TEOS-10) which was adopted in
> 2010 by the Intergovernmental Oceanographic Commission (IOC). It is the
> mass fraction of dissolved material in sea water and TEOS-10 prescribes
> units of g kg-1. Absolute Salinity incorporates the spatial variations in
> the composition of seawater. This type of absolute salinity is also called
> "Density Salinity". 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
> Reference Composition. In practice, Absolute Salinity is often calculated
> from Practical Salinity using a pre-defined value for the Absolute
> Salinity Anomaly, which is provided in the form of a global climatology.
> It is recommended that the version of (TEOS-10) software and the
> associated Absolute Salinity Anomaly climatology be specified within
> metadata ? within the variable "comment" attribute. Standard names exist
> for the related quantity, S_*, Preformed Salinity. Salinity observations
> made using measurements of the conductivity of sea water after 1978 should
> be given the standard name of sea_water_practical_salinity.
> Canonical units: g kg-1
> Reference: www.teos-10.org; Millero et al., 2008 doi:
> 10.1016/j.dsr.2007.10.001
>
> sea_water_preformed_salinity
> Definition: Preformed Salinity, S*, is defined as a term in the
> Thermodynamic Equation of Seawater 2010 (TEOS-10) which was adopted in
> 2010 by the Intergovernmental Oceanographic Commission (IOC). Preformed
> Salinity is a salinity variable that is designed to be as conservative as
> possible, by removing the estimated biogeochemical influences on the sea
> water composition. Preformed Salinity is Absolute Salinity, S_A (which has
> the standard name sea_water_absolute_salinity), minus all contributions to
> sea water composition from biogeochemical processes. Preformed Salinity
> incorporates the spatial variations in the composition of sea water
> because of its relationship to Absolute Salinity. It is a mass fraction of
> dissolved material in sea water and TEOS-10 prescribes units of g kg-1.
> Salinity observations made using measurements of the conductivity of sea
> water after 1978 should be given the standard name of
> sea_water_practical_salinity.
> Canonical units: g kg-1
> Reference: www.teos-10.org; Pawlowicz et al., 2011 doi:
> 10.5194/os-7-363-2011; Wright et al., 2011 doi: 10.5194/os-7-1-2011
>
> sea_water_conservative_temperature
> Definition: Conservative Temperature is defined as a term in the
> Thermodynamic Equation of Seawater 2010 (TEOS-10) which was adopted in
> 2010 by the Intergovernmental Oceanographic Commission (IOC). Conservative
> Temperature is specific potential enthalpy (which has the standard name
> specific_potential_enthalpy_of_sea_water) divided by a fixed value of the
> specific heat capacity of sea water, namely cp_0 = 3991.86795711963 J kg-1
> K-1. Conservative Temperature is a more accurate measure of the "heat
> content" of sea water, by a factor of one hundred, than is potential
> temperature. Because of this, it can be regarded as being proportional to
> the heat content of sea water per unit mass. Enthalpy can be written
> either as (1) CpT, where Cp is heat capacity at constant pressure, T is
> absolute temperature, or (2) U+pV, where U is internal energy, p is
> pressure and V is volume.
> Canonical units: K (or usually, degrees Celsius)
> Reference: www.teos-10.org; McDougall, 2003 doi:
> 10.1175/1520-0485(2003)033<0945:PEACOV>2.0.CO;2
>
> sea_water_specific_potential_enthalpy
> Definition: The potential enthalpy of a sea water parcel is the enthalpy
> after an adiabatic and isohaline change in pressure from its in situ
> pressure to the sea water pressure p = 0 dbar. "specific" means per unit
> mass. Enthalpy can be written either as (1) CpT, where Cp is heat capacity
> at constant pressure, T is absolute temperature, or (2) U+pV, where U is
> internal energy, p is pressure and V is volume.
> Canonical units: J kg-1
> Reference: www.teos-10.org; McDougall, 2003 doi:
> 10.1175/1520-0485(2003)033<0945:PEACOV>2.0.CO;2
>
>
> change_over_time_in_X: append text "change_over_time_in_X" means change in
> a quantity X over a time-interval, which should be defined by the bounds
> of the time coordinate.
> Canonical units: unit of X + s-1
>
>
> So for clarity, the new proposed names are:
> sea_water_practical_salinity
> sea_water_cox_salinity
> sea_water_knudsen_salinity
> sea_water_reference_salinity
> sea_water_absolute_salinity
> sea_water_preformed_salinity
> sea_water_conservative_temperature
> sea_water_potential_enthalpy
> change_over_time_in_sea_water_practical_salinity
> change_over_time_in_sea_water_absolute_salinity
> change_over_time_in_sea_water_preformed_salinity
> change_over_time_in_sea_water_conservative_temperature
> change_over_time_in_sea_water_potential_enthalpy
> ***
>
>
>
>
>
> -----Original Message-----
> From: "Paul.Durack at csiro.au" <Paul.Durack at csiro.au>
> Date: Mon, 28 Nov 2011 09:12:14 -0800
> To: "Durack, Paul J." <durack1 at llnl.gov>
> Subject: Re: [CF-metadata] new TEOS-10 standard names
>
>>
>>________________________________________
>>From: cf-metadata-bounces at cgd.ucar.edu [cf-metadata-bounces at cgd.ucar.edu]
>>On Behalf Of Jonathan Gregory [j.m.gregory at reading.ac.uk]
>>Sent: Tuesday, 29 November 2011 1:05 AM
>>To: cf-metadata at cgd.ucar.edu
>>Subject: Re: [CF-metadata] new TEOS-10 standard names
>>
>>Dear Alison
>>
>>This is great. Thanks for going through it so thoroughly.
>>
>>> (b) sea_water_temperature
>>> There is agreement to retain the standard name sea_water_temperature as
>>>this is useful particularly for observations. It currently has no
>>>explanatory text. In response to the discussion I propose to add the
>>>following sentence: 'Sea temperature is the in situ (bulk) temperature
>>>of the sea water, not the surface or skin temperature.'
>>
>>It is important for models too; although the prognostic is often
>> potential
>>temperature, in-situ temperature is considered sometimes. Since this is a
>>very general term, maybe we can leave it vague (and thus sidestep the
>> need
>>to define surfaces). It is the in-situ temperature of sea water. SST is a
>>species of sea_water_temperature. It is analogous to air_temperature.
>>
>>> (d) Do we need to modify the explanations of all the existing salinity
>>>quantities?
>>> As I mentioned, there are twelve salinity names already in the standard
>>>name table.
>>
>>I think these terms can remain vague too. In their vagueness, they are
>>parallel to sea_water_salinity, which we are retaining, though
>>deprecating for
>>future obs quantities, and models where applicable. If salinity is
>>generic,
>>these generic quantities can also be used for specific purposes. When it
>>becomes necessary to be specific about *which* salinity is meant by e.g.
>> product_of_northward_sea_water_velocity_and_salinity
>>then a new specific standard name can be defined. We could modify the
>>definitions to say that they can be used with any definition of salinity
>>(but specific ones could be proposed if required to make distinctions).
>>
>>> (b) sea_water_knudsen_salinity
>>
>>Yes, I believe this should be in units of 1e-3.
>>
>>> (c) sea_water_reference_salinity
>>> There has been a suggestion that this quantity should also be
>>>introduced as a standard name. No comments have so far been received on
>>>this proposal.
>>
>>Please could you remind us of the context?
>>
>>Best wishes
>>
>>Jonathan
>>_______________________________________________
>>CF-metadata mailing list
>>CF-metadata at cgd.ucar.edu
>>http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
Received on Mon Nov 28 2011 - 23:34:51 GMT
