Hi Alison, Looks good to me.
Cheers, Roy. I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. ________________________________ From: CF-metadata <cf-metadata-boun...@cgd.ucar.edu> on behalf of Alison Pamment - UKRI STFC <alison.pamm...@stfc.ac.uk> Sent: 21 February 2019 12:52 To: cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] New standard name for 14CO2 Dear Roy, On reflection, I think you're right that it is better not to put the reference standard into the definition. One could argue that, even if everyone is currently using the same reference material, it is still an experimental detail and therefore doesn't belong in either the standard name or its definition. Using a different reference would change the value of (14C/12C)standard) in the first formula, but not the formula itself, so the standard name would apply to all Delta14C measurements. As you say, experimental details should be specified using long_name and/or comment attributes. That would be consistent with our usual approach to standard names while providing a means of recording the precise details of how the data values were calculated. Here's the revised version (including the addition of our standard sentence about 14C that was accidentally omitted last time): enrichment_of_14C_in_air_expressed_as_uppercase_delta_14C (Canonical unit: 1e-3) 'Isotopic enrichment of 14C, often called d14C or delta14C (lower case delta), is used to calculate the fossil fuel contribution to atmospheric carbon dioxide using isotopic ratios of carbon. It is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a reference standard. It is computed using the formula (((14C/12C)sample / (14C/12C)standard) - 1) * 1000. The quantity called D14C, or Delta14C (upper case delta) is d14C corrected for isotopic fractionation using the 13C/12C ratio as follows: D14C = d14C - 2(dC13 + 25)(1+d14C/1000). If the sample is enriched in 14C relative to the standard, then the data value is positive. Reference: Stuiver, M. and H.A. Polach, 1977, Discussion reporting of 14C data, Radiocarbon, Volume 19, No. 3, 355-363, doi: 10.1017/S0033822200003672. The reference standard used in the calculation of delta14C should be specified by attaching a long_name attribute to the data variable. "C" means the element carbon and "14C" is the radioactive isotope "carbon-14", having six protons and eight neutrons and used in radiocarbon dating.' Best wishes, Alison ----------------------------------------------------------------------------------------------------------- Alison Pamment Tel: +44 1235 778065 NCAS/Centre for Environmental Data Analysis Email: alison.pamm...@stfc.ac.uk STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Oxford, Didcot, OX11 0QX, U.K. From: Lowry, Roy K. <r...@bodc.ac.uk> Sent: 20 February 2019 19:30 To: Pamment, Alison (STFC,RAL,RALSP) <alison.pamm...@stfc.ac.uk>; cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] New standard name for 14CO2 Dear Alison, I would suggest that if the reference standard isn't included in the Standard Name then I wouldn't put it into the definition. I don't like the idea of having narrower semantics in the definition compared to the name. How about putting a recommendation that the standard be specified in the long name into the definition? Cheers, Roy. I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. ________________________________________ From: CF-metadata <mailto:cf-metadata-boun...@cgd.ucar.edu> on behalf of Alison Pamment - UKRI STFC <mailto:alison.pamm...@stfc.ac.uk> Sent: 20 February 2019 16:40 To: mailto:cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] New standard name for 14CO2 Dear Katherine, Roy, Jonathan, Daniel, Thank you all for the very clear and interesting discussion - I have learned a lot from reading all your comments and the various references. It seems that we are inching towards agreement on: enrichment_of_14C_in_air_expressed_as_uppercase_delta_14C (Canonical unit: 1e-3). Certainly it is shorter and more readable if we don't include the reference standard in the name itself. I suggest that we include it in the definition for completeness, but leave it out of the name. In future, if someone were to propose a similar quantity based on a different standard we could add more detail into the names and turn the original one into an alias. However, the references I have looked at seem to indicate that the same international standard has been in use since the 1950s, so it isn't something that changes on a regular basis. Based on Roy's suggested definition, other comments in the discussion, and text used in the definitions of existing standard names, we would have something like the following: 'Isotopic enrichment of 14C, often called d14C or delta14C (lower case delta), is used to calculate the fossil fuel contribution to atmospheric carbon dioxide using isotopic ratios of carbon. It is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a reference standard, in this case the radiocarbon absolute reference standard, Oxalic Acid I. It is computed using the formula (((14C/12C)sample / (14C/12C)standard) - 1) * 1000. The quantity called D14C, or Delta14C (upper case delta) is d14C corrected for isotopic fractionation using the 13C/12C ratio as follows: D14C = d14C - 2(dC13 + 25)(1+d14C/1000). If the sample is enriched in 14C relative to the standard, then the data value is positive. Reference: Stuiver, M. and H.A. Polach, 1977, Discussion reporting of 14C data, Radiocarbon, Volume 19, No. 3, 355-363, doi: 10.1017/S0033822200003672.' Does that sound okay? Best wishes, Alison ----------------------------------------------------------------------------------------------------------- Alison Pamment Tel: +44 1235 778065 NCAS/Centre for Environmental Data Analysis Email: mailto:alison.pamm...@stfc.ac.uk STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Oxford, Didcot, OX11 0QX, U.K. Hi Jonathan and Roy, I do not feel there is need to mention the reference material. Oxalic Acid has been agreed upon as the primary reference material and any other reference materials are all traceable to the primary standards for radiocarbon analysis. Thanks, Katherine On 16/02/2019, 16:04, "CF-metadata on behalf of Jonathan Gregory" <mailto:cf-metadata-boun...@cgd.ucar.edu on behalf of j.m.greg...@reading.ac.uk> wrote: Dear Roy I went for "big" because it's shorter and a bit more amusing. If we have "uppercase" it would also be OK - no need for _ in the middle of it, I think. Yes, it would be good to hear an authoritative view on whether there is more than one standard in use. Best wishes Jonathan ----- Forwarded message from "Lowry, Roy K." <mailto:r...@bodc.ac.uk> ----- > Date: Fri, 15 Feb 2019 15:24:06 +0000 > From: "Lowry, Roy K." <mailto:r...@bodc.ac.uk> > To: Jonathan Gregory <mailto:j.m.greg...@reading.ac.uk>, "mailto:cf-metadata@cgd.ucar.edu"; > <mailto:cf-metadata@cgd.ucar.edu> > Subject: Re: [CF-metadata] New standard name for 14CO2 > > Dear Jonathan, > > I am almost happy with 'big_delta14C', but would prefer 'upper_case_delta14C'. > > I still feel that unless explicitly told otherwise by a domain expert the reference standard needs to be there. As I mentioned in a previous posting there have been multiple 14C standards used over the past 40 years, although I cannot say for certain whether more than one is in current use. > > Cheers, Roy. > > > I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. > > ________________________________ > From: CF-metadata <mailto:cf-metadata-boun...@cgd.ucar.edu> on behalf of Jonathan Gregory <mailto:j.m.greg...@reading.ac.uk> > Sent: 15 February 2019 15:00 > To: mailto:cf-metadata@cgd.ucar.edu > Subject: Re: [CF-metadata] New standard name for 14CO2 > > Dear all > > Thank you for the clarifications. Actually I still do not understand what the > normalisation does, but evidently it's a well-defined procedure. > > I'm in favour of precision, of course, when there is a danger of ambiguity. > Roy proposes > > enrichment_with_respect_to_radiocarbon_absolute_reference_standard_of_14C_in_carbon_dioxide_in_air_expressed_as_D14C > > I would like to ask if we could make it > > enrichment_of_14C_in_carbon_dioxide_in_air_expressed_as_big_delta14C > > That is: (a) Do we have to mention the reference standard? Katherine does not > specify this. Is there more than one standard in use? If so, we do need to > include it, I agree. (b) It seems clearer to me to spell out delta than to > put just D. (c) I appreciate that the small-delta version is obsolete but we > can't rule out it being needed sometime (or perhaps a similar distinction is > in actual use with other isotopes?), and I think it would be unreliable to > distinguish two standard names just because one had a small d where the other > had a big D. If we ever need the small-delta version we can put small_delta. > > Best wishes > > Jonathan > > ----- Forwarded message from "Robert M. Key" <mailto:k...@princeton.edu> ----- > > > Date: Wed, 13 Feb 2019 14:31:58 +0000 > > From: "Robert M. Key" <mailto:k...@princeton.edu> > > To: Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk> > > CC: "Lowry, Roy K." <mailto:r...@bodc.ac.uk>, Jonathan Gregory > > <mailto:j.m.greg...@reading.ac.uk>, "mailto:cf-metadata@cgd.ucar.edu"; > > <mailto:cf-metadata@cgd.ucar.edu> > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > What Katherine listed is correct. I’m not going to try to use D/delta here because it so often changes from one computer to the next. > > > > Ever since Minze Stuiver’s paper came out, almost all ocean radiocarbon measurements have been reported as D14C (o/oo). Oceanic 13C measurements on the other hand are reported in the standard d13C ( eq. 2 in Katherine’s note with 13 instead of 14). In a few publications you do see D14C converted to atoms/KG, but that is only for inventories and similar because you can’t integrate permil units. > > > > Air measurements are, I think, not so consistent, but generally reported in the same way. > > Minze Stuiver was a tree ring specialist, so I assume those data are also D14C (rather than d14C) > > > > In seawater the measurements are routinely made on dissolved inorganic carbon. These data are listed as the seawater D14C value without mention of inorganic component. This is equivalent to what Katherine listed in her first line. > > > > AMS techniques allow 14C measurements on the oceanic dissolved organic carbon (Ellen Druffel and a few others). These data are routinely listed as DO14C where here the D indicates dissolved rather than the previously used Delta (that is, Delta 14C on Dissolved Organic Carbon). > > > > bob > > > > On Feb 13, 2019, at 5:30 AM, Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk> wrote: > > > > The measurements I would like to report are <image001.png>. Here is the complete definition of how we have calculated <image002.png>. > > > > The isotopic composition can be expressed in delta values, in units of per mil (‰). The small delta (δ) is the isotopic ratio R (heavy C / light C) of a sample relative to the isotope ratio of a standard substance (Equation 2, Stuiver & Polach (1977)). > > <image003.png> (2) > > Here, 14C sample is the 14C content of sample, C sample is the carbon content of sample, 14C std is the 14C content of standard and C standard is the carbon content of standard. δ14C is used to calculate Δ14C. > > 14C can also be expressed as capital delta Δ14C (Equation 3, (Stuiver and Polach, 1977)). The Δ14C is normalized to a δ13C value of -25 ‰, this is done to account for fractionation. Fractionation effects discriminate against 14C twice as much as for 13C (Stuiver and Polach, 1977). Normalising 14C measurements to a common δ13C should, therefore, remove reservoir specific differences caused by fractionation, > > <image004.png> (3) > > where δ14C is 14C signature [‰] and δ13C is 13C signature [‰]. > > <image005.png> (4) > > <image006.png> (5) > > Here, 13CO2 i is the abundance 13CO2 from sector i [mol mol-1]<image007.png> 13CO2 i is 13CO2 signature sector i [‰], CO2 i = abundance CO2from sector i [mol mol-1], 13R ref is the ratio of reference standard [(mol mol-1)/ (mol mol-1)] and CO2 is the total abundance CO2 enhancement [mol mol-1] from Equation 1. > > <image008.png> (6) > > <image009.png> (7) > > Where, 14CO2 i is the abundance 14CO2 from sector i [mol mol-1]<image010.png> 14CO2 i is the 14CO2 signature sector i [‰], 12CO2 i is the abundance CO2 from sector i [mol mol-1], 14R ref is the ratio of reference standard [(mol mol-1)/ (mol mol-1)], 12CO2 is the total abundance CO2 enhancement [mol mol-1] from Equation 1 and<image011.png> 13CO2 is the 13CO2 signature [‰] from Equation 5. > > > > > > From: "Lowry, Roy K." <mailto:r...@bodc.ac.uk> > > Date: Wednesday, 13 February 2019 at 10:06 > > To: Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk>, Jonathan Gregory <mailto:j.m.greg...@reading.ac.uk>, "mailto:cf-metadata@cgd.ucar.edu"; <mailto:cf-metadata@cgd.ucar.edu> > > Cc: Bob Key <mailto:k...@princeton.edu> > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > Hello again, > > > > Bob Key contacted me off-list to point out that d14C and D14C are different, but didn't tell me how. Reading around (http://www.c14dating.com/agecalc.html) I find that D14C is d14c with the 13C correction applied using the equation D14C=d14C - 2(dC13 + 25)(1 + d14C/1000) per mille where d14C is what I'd described in the draft definition. Bob also made it clear that the carbon dating community regard d14C and D14C as significantly different measurements, with d14C consigned to history. > > > > So, Katherine's measurements are D14C. I just need to be sure that the fractionation correction she has applied is as given above - Katherine? > > > > Following Bob's intervention I feel the Standard Name and definition should be for D14C, not d14C such as: > > > > enrichment_with_respect_to_radiocarbon_absolute_reference_standard_of_ 14C_in_carbon_dioxide_in_air_expressed_as_D14C > > > > Isotopic enrichment of 14C (d14C or delta14C), is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a standard, in this case the radiocarbon absolute reference standard. It is computed using the formula (((14C/12C) sample / (14C/12C) standard) - 1) * 1000. D14C or Delta14C is d14C corrected for isotopic fractionation using the 13C/12C ratio. D14C = d14C - 2(dC13 + 25)(1 + d14C/1000). If the sample is enriched in 14C then the value is positive. > > > > I know Jonathan won't be comfortable with this, but carbon chemistry is a discipline where precise measurement semantics is very important. > > > > Cheers, Roy. > > Radiocarbon Date calculation - c14dating.com > > Figure 1: Decay curve for C14 showing the activity at one half-life (t/2). The terms "%Modern", or "pmC" and D14C are shown related in this diagram along with the Radiocarbon age in years BP (Before 1950 AD). > > www.c14dating.com<http://www.c14dating.com> > > > > > > > > I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. > > > > From: Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk> > > Sent: 13 February 2019 08:35 > > To: Lowry, Roy K.; Jonathan Gregory; mailto:cf-metadata@cgd.ucar.edu > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > Hi Roy, Jonathan, > > > > The normalisation mathematically corrects for the effects of isotopic fractionation, such that the processes which naturally fractionate during exchange have no impact on atmospheric Delta14C and thus, only disequilibrium terms need to be considered. For example, photosynthetic uptake of CO2. > > > > Thanks, > > > > Katherine > > > > > > On 12/02/2019, 10:58, "CF-metadata on behalf of Lowry, Roy K." <mailto:cf-metadata-boun...@cgd.ucar.edu on behalf of r...@bodc.ac.uk> wrote: > > > > Dear Jonathan, > > > > Whilst I initially favoured relegating the standard to the long name, after a bit of thought and reading around I changed my mind. Whilst multiple standards may not be in use today, a number have been favoured at different times over the past 50 years. See for example > > > > https://www.researchgate.net/publication/222399840_Future_needs_and_requirements_for_AMS_14C_standards_and_reference_materials > > > > Consequently, I feel inclusion of the name of the standard in the Standard name is prudent. > > > > I think I understand what the 13C normalisation is about, but I'll leave it to Katherine to explain in case I haven't got it exactly right. > > > > Cheers, Roy. > > > > -----Original Message----- > > From: CF-metadata <mailto:cf-metadata-boun...@cgd.ucar.edu> On Behalf Of Jonathan Gregory > > Sent: 12 February 2019 10:13 > > To: mailto:cf-metadata@cgd.ucar.edu > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > Dear Katherine and Roy > > > > Thanks for the information. I think enrichment is fine. Unlike Roy, I would favour not mentioning the standard (and likewise I would not mention pee dee belemnite in d13O) unless there is more than one standard routinely in use, so that we need to distinguish. Are there any others in this case? > > > > I am curious to know what this means: > > > The sample ratio is normalised to – 25 per mil delta13C (to correct for isotopic fractionation). > > (although I understand Roy's remark that it doesn't affect the definition). > > > > Best wishes > > > > Jonathan > > > > > > ----- Forwarded message from "Lowry, Roy K." <mailto:r...@bodc.ac.uk> ----- > > > > > Date: Mon, 11 Feb 2019 16:05:13 +0000 > > > From: "Lowry, Roy K." <mailto:r...@bodc.ac.uk> > > > To: Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk>, Alison Pamment - > > > UKRI STFC <mailto:alison.pamm...@stfc.ac.uk>, "mailto:cf-metadata@cgd.ucar.edu"; > > > <mailto:cf-metadata@cgd.ucar.edu> > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > Thanks Katherine, > > > > > > That looks a complete set of information to me. I think we're all happy using 'enrichment'. Next issue to resolve is whether two items of information - the standard used and the delta13C normalisation - are built into the Standard Name or consigned to the Long Name. I would argue that the normalisation is an experimental detail and policy has been not to include these in Standard Names. However, to me the standard used is a fundamental attribute of what has been measured so I would go for its inclusion giving us: > > > > > > > > > enrichment_with_respect_to_radiocarbon_absolute_reference_standard_of_ > > > 14C_in_carbon_dioxide_in_air > > > > > > Her'e a straw man for a definition > > > > > > Isotopic enrichment of 14C, sometimes called Delta14C or delta14C, is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a standard, in this case the radiocarbon absolute reference standard. It is computed using the formula (((14C/12C) sample / (14C/12C) standard) - 1) * 1000. If the sample is enriched in 14C then the value is positive. > > > > > > Cheers, Roy. > > > > > > > > > > > > I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. > > > > > > ________________________________ > > > From: Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk> > > > Sent: 11 February 2019 14:33 > > > To: Alison Pamment - UKRI STFC; Lowry, Roy K.; > > > mailto:cf-metadata@cgd.ucar.edu > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > > > > Hi All, > > > > > > > > > > > > Thank you, Roy, Jonathon and Alison, for your feedback on this new standard name. > > > > > > > > > > > > Some more information on how the measurements are made and calculated. > > > > > > > > > > > > Measurements are made using Accelerator Mass Spectrometry. > > > > > > Roy is correct Delta14C is calculated similar to delta13C. > > > > > > Delta14C = (((14C/12C) sample / (14C/12C) standard) - 1) * 1000 per mil in accordance to Stuiver and Polach (1977). > > > > > > The standard this is calculated in relation to is the radiocarbon absolute reference standard, Oxalic Acid I. The sample ratio is normalised to – 25 per mil delta13C (to correct for isotopic fractionation). > > > > > > > > > > > > Either of the names Roy suggests > > > (enrichment_of_14C_in_carbon_dioxide_in_air or > > > delta14C_in_carbon_dioxide_in_air > > > > > > ) could work. > > > > > > > > > > > > Thanks, > > > > > > > > > > > > Katherine > > > > > > > > > > > > From: CF-metadata <mailto:cf-metadata-boun...@cgd.ucar.edu> on behalf of > > > Alison Pamment - UKRI STFC <mailto:alison.pamm...@stfc.ac.uk> > > > Date: Monday, 11 February 2019 at 12:59 > > > To: "mailto:r...@bodc.ac.uk"; <mailto:r...@bodc.ac.uk>, "mailto:cf-metadata@cgd.ucar.edu"; > > > <mailto:cf-metadata@cgd.ucar.edu> > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > > > > > > > Hi Roy, > > > > > > > > > > > > Okay, thank you for spotting that! > > > > > > > > > > > > Best wishes, > > > > > > Alison > > > > > > > > > > > > ------ > > > > > > Alison Pamment Tel: +44 1235 778065 > > > > > > NCAS/Centre for Environmental Data Archival Email: mailto:alison.pamm...@stfc.ac.uk > > > > > > STFC Rutherford Appleton Laboratory > > > > > > R25, 2.22 > > > > > > Harwell Oxford, Didcot, OX11 0QX, U.K. > > > > > > > > > > > > From: Lowry, Roy K. <mailto:r...@bodc.ac.uk> > > > Sent: 11 February 2019 12:55 > > > To: Pamment, Alison (STFC,RAL,RALSP) <mailto:alison.pamm...@stfc.ac.uk>; > > > mailto:cf-metadata@cgd.ucar.edu > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > > > > > > > Hi Alison, > > > > > > > > > > > > One slight misunderstanding. 'per mil' means parts per thousand not parts per million so the units should be written as '1e-3' rather than '1e-6'. > > > > > > > > > > > > Cheers, Roy. > > > > > > > > > > > > I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. > > > > > > > > > > > > ________________________________ > > > > > > From: CF-metadata > > > <mailto:cf-metadata-boun...@cgd.ucar.edu<mailto:cf-metadata-boun...@cgd.ucar. > > > edu>> on behalf of Alison Pamment - UKRI STFC > > > <mailto:alison.pamm...@stfc.ac.uk<mailto:alison.pamm...@stfc.ac.uk>> > > > Sent: 11 February 2019 12:49 > > > To: mailto:cf-metadata@cgd.ucar.edu<mailto:cf-metadata@cgd.ucar.edu> > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > > > > > > > Dear Katherine, All, > > > > > > Katherine and I had briefly discussed this name before it was proposed to the mailing list - the suggestion of using mole_fraction was originally mine. Evidently I had misunderstood the quantity in question, and it's clear from the discussion so far that it wouldn't be appropriate to use mole_fraction in this case. Thank you to Roy and Jonathan for clarifying this (and my apologies to Katherine for misleading advice - I've not come across this quantity before). > > > > > > It does seem that we will need to introduce some new terminology into standard names. Of Roy's two suggestions I prefer enrichment_of_14C_in_carbon_dioxide_in_air. From Roy's explanation, it looks like the quantity is in effect a ratio of ratios. While I appreciate that this may be referred to as a 'delta' in the chemistry community, 'delta' is often used as a mathematical symbol for calculating a difference or change, so I feel that it's best avoided in the standard name. > > > > > > Regarding the units of 'per mil', the canonical unit in the standard name table would be written as '1e-6'. > > > > > > Whichever terminology we choose, certainly we do need a clear definition - in particular if the quantity is being calculated with reference to a particular standard we should include that in the information. Katherine, please could you give us some more details about exactly how this quantity is being measured/calculated in your data? > > > > > > Best wishes, > > > Alison > > > > > > ------ > > > Alison Pamment Tel: +44 1235 778065 > > > NCAS/Centre for Environmental Data Archival Email: mailto:alison.pamm...@stfc.ac.uk<mailto:alison.pamm...@stfc.ac.uk> > > > STFC Rutherford Appleton Laboratory > > > R25, 2.22 > > > Harwell Oxford, Didcot, OX11 0QX, U.K. > > > > > > > > > -----Original Message----- > > > From: CF-metadata > > > <mailto:cf-metadata-boun...@cgd.ucar.edu<mailto:cf-metadata-boun...@cgd.ucar. > > > edu>> On Behalf Of Jonathan Gregory > > > Sent: 11 February 2019 04:57 > > > To: mailto:cf-metadata@cgd.ucar.edu<mailto:cf-metadata@cgd.ucar.edu> > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > Dear all > > > > > > I agree with Roy that delta-14C is not a mole fraction, but a way of expressing the deviation of an isotopic ratio in a sample from a standard isotopic ratio. > > > The definition Roy gives for delta-13C is shown in several websites. I think we need the precise definition of the quantity being proposed, because there appear to be variou quantities with big and small delta and D, and maybe they are all different, and would need distinct standard names. I think Roy is right that we have not given standard names to such quantities before. > > > > > > Best wishes > > > > > > Jonathan > > > > > > ----- Forwarded message from "Lowry, Roy K." > > > <mailto:r...@bodc.ac.uk<mailto:r...@bodc.ac.uk>> ----- > > > > > > > Date: Fri, 8 Feb 2019 12:55:31 +0000 > > > > From: "Lowry, Roy K." <mailto:r...@bodc.ac.uk<mailto:r...@bodc.ac.uk>> > > > > To: Katherine Pugsley <mailto:katherine.pugs...@bristol.ac.uk<mailto:katherine.pugs...@bristol.ac.uk>>, > > > > "mailto:cf-metadata@cgd.ucar.edu<mailto:cf-metadata@cgd.ucar.edu>" > > > > <mailto:cf-metadata@cgd.ucar.edu<mailto:cf-metadata@cgd.ucar.edu>> > > > > Subject: Re: [CF-metadata] New standard name for 14CO2 > > > > > > > > I think that delta-14CO2 is not the same thing as the mole fraction. Rather, it is an expression of isotopic enrichment/depletion with respect to a standard. Whilst I have no experience of atmospheric 14C, I have come across delta notation a lot with other isotopes in geology and oceanography such as 13C and 18O. There, delta is an expression of the ratio of the target isotope to another isotope in the sample relative to some standard - ((sample 13C/12C ratio / standard 13C/12C ratio) - 1) * 1000 to give a result scaled to per mil. I presume that delta-14C is no different. > > > > > > > > I am unaware (i.e. I couldn't find) a precedent for delta values in CF Standard Names. The issue of describing these things has been addressed at length in the BODC parameter descriptions with almost 400 measurement descriptions. A typical example is: > > > > > > > > Enrichment with respect to Vienna Pee Dee Belemnite (VPDB) of > > > > carbon-13 in carbonate in the sediment > > > > > > > > This particular example includes information on the specific standard used. Many do not because the information is often unavailable for older data. > > > > > > > > A straw man alternative to Kate's proposal could be > > > > > > > > enrichment_of_14C_in_carbon_dioxide_in_air > > > > > > > > If information on the standard is available then that could be added as an 'enrichment_with_respect_to_whatever' clause or the information could be confined to the long name. The better solution depends upon the use case (e.g. does it require inclusion of data where standard is unknown). > > > > > > > > Another approach could be to adopt community vocabulary such as: > > > > > > > > delta14C_in_carbon_dioxide_in_air > > > > > > > > Others may have alternative suggestions. > > > > > > > > I went for 'enrichment of x' in the BODC dictionary because it provides a better fit to a normalised semantic model for mapping purposes. One only has to include one 'enrichment' rather than a long list of 'deltas' in the semantic element. > > > > > > > > Cheers, Roy. > > > > > > > > > > > > I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address. > > > > > > > > ________________________________ > > > > From: CF-metadata > > > > <mailto:cf-metadata-boun...@cgd.ucar.edu<mailto:cf-metadata-boun...@cgd.uca > > > > r.edu>> on behalf of Katherine Pugsley > > > > <mailto:katherine.pugs...@bristol.ac.uk<mailto:katherine.pugs...@bristol.ac > > > > .uk>> > > > > Sent: 08 February 2019 10:46 > > > > To: mailto:cf-metadata@cgd.ucar.edu<mailto:cf-metadata@cgd.ucar.edu> > > > > Subject: [CF-metadata] New standard name for 14CO2 > > > > > > > > > > > > Dear All, > > > > > > > > I'd like to request an addition to the standard name list for atmospheric 14CO2 measurements. Here are the details of the proposed standard name. > > > > > > > > Proposal for a new standard variable name > > > > > > > > Name: mole_fraction_of_14C_dioxide_in_air > > > > > > > > Canonical Units: 1 > > > > > > > > Description: Atmospheric 14CO2 measurements are reported in Δ14C notation with units of per mil, the deviation from the absolute radiocarbon reference standard. Δ14C is used to calculate fossil fuel CO2 content. The long name will contain information that the variable is Δ14C. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Katherine > > > > > > > > > > > > > > > > > > > > This email and any attachments are intended solely for the use of the named recipients. If you are not the intended recipient you must not use, disclose, copy or distribute this email or any of its attachments and should notify the sender immediately and delete this email from your system. > > > > UK Research and Innovation has taken every reasonable precaution to minimise risk of this email or any attachments containing viruses or malware but the recipient should carry out its own virus and malware checks before opening the attachments. UK Research and Innovation does not accept any liability for any losses or damages which the recipient may sustain due to presence of any viruses. > > > > Opinions, conclusions or other information in this message and attachments that are not related directly to UK Research and Innovation business are solely those of the author and do not represent the views of UK Research and Innovation. > > > > > > > > > > > _______________________________________________ > > > > CF-metadata mailing list > > > > mailto:CF-metadata@cgd.ucar.edu<mailto:CF-metadata@cgd.ucar.edu> > > > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > > > > > > > ----- End forwarded message ----- > > > _______________________________________________ > > > CF-metadata mailing list > > > mailto:CF-metadata@cgd.ucar.edu<mailto:CF-metadata@cgd.ucar.edu> > > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > _______________________________________________ > > > CF-metadata mailing list > > > mailto:CF-metadata@cgd.ucar.edu<mailto:CF-metadata@cgd.ucar.edu> > > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > > > > > > > This email and any attachments are intended solely for the use of the named recipients. If you are not the intended recipient you must not use, disclose, copy or distribute this email or any of its attachments and should notify the sender immediately and delete this email from your system. > > > UK Research and Innovation has taken every reasonable precaution to minimise risk of this email or any attachments containing viruses or malware but the recipient should carry out its own virus and malware checks before opening the attachments. UK Research and Innovation does not accept any liability for any losses or damages which the recipient may sustain due to presence of any viruses. > > > Opinions, conclusions or other information in this message and attachments that are not related directly to UK Research and Innovation business are solely those of the author and do not represent the views of UK Research and Innovation. > > > > > > > > > This email and any attachments are intended solely for the use of the named recipients. If you are not the intended recipient you must not use, disclose, copy or distribute this email or any of its attachments and should notify the sender immediately and delete this email from your system. > > > UK Research and Innovation has taken every reasonable precaution to minimise risk of this email or any attachments containing viruses or malware but the recipient should carry out its own virus and malware checks before opening the attachments. UK Research and Innovation does not accept any liability for any losses or damages which the recipient may sustain due to presence of any viruses. > > > Opinions, conclusions or other information in this message and attachments that are not related directly to UK Research and Innovation business are solely those of the author and do not represent the views of UK Research and Innovation. > > > > > > > > _______________________________________________ > > > CF-metadata mailing list > > > mailto:CF-metadata@cgd.ucar.edu > > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > > > > ----- End forwarded message ----- > > _______________________________________________ > > CF-metadata mailing list > > mailto:CF-metadata@cgd.ucar.edu > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > > > > This email and any attachments are intended solely for the use of the named recipients. If you are not the intended recipient you must not use, disclose, copy or distribute this email or any of its attachments and should notify the sender immediately and delete this email from your system. > > UK Research and Innovation has taken every reasonable precaution to minimise risk of this email or any attachments containing viruses or malware but the recipient should carry out its own virus and malware checks before opening the attachments. UK Research and Innovation does not accept any liability for any losses or damages which the recipient may sustain due to presence of any viruses. > > Opinions, conclusions or other information in this message and attachments that are not related directly to UK Research and Innovation business are solely those of the author and do not represent the views of UK Research and Innovation. > > > > _______________________________________________ > > CF-metadata mailing list > > mailto:CF-metadata@cgd.ucar.edu > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > > > > > > > > This email and any attachments are intended solely for the use of the named recipients. If you are not the intended recipient you must not use, disclose, copy or distribute this email or any of its attachments and should notify the sender immediately and delete this email from your system. > > UK Research and Innovation has taken every reasonable precaution to minimise risk of this email or any attachments containing viruses or malware but the recipient should carry out its own virus and malware checks before opening the attachments. UK Research and Innovation does not accept any liability for any losses or damages which the recipient may sustain due to presence of any viruses. > > Opinions, conclusions or other information in this message and attachments that are not related directly to UK Research and Innovation business are solely those of the author and do not represent the views of UK Research and Innovation. > > > > ----- End forwarded message ----- > _______________________________________________ > CF-metadata mailing list > mailto:CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > This email and any attachments are intended solely for the use of the named recipients. 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