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
>_______________________________________________
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>CF-metadata at cgd.ucar.edu
>http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Received on Mon Nov 28 2011 - 16:03:20 GMT
