Dear Martin Thanks for the examples. Actually all the other cases seem fine to me, but they help to clarify why
gross_primary_productivity_of_biomass_expressed_as_13C seems odd to me. Every organic aerosol particle, and every molecule of a VOC, calcite and carbon dioxide, contains carbon; every molecule of NOx and every zooplankton (I assume) contains nitrogen. However, not every molecule of biomass contains 13C, or even less 14C. But I appreciate that the ratios of constituent to total are variable in the other cases as well, although never zero, so perhaps this isn't so different. I guess it makes sense, although it surprised me! Best wishes Jonathan ----- Forwarded message from Martin Juckes - UKRI STFC <[email protected]> ----- > Date: Wed, 25 Apr 2018 08:59:39 +0000 > From: Martin Juckes - UKRI STFC <[email protected]> > To: Jonathan Gregory <[email protected]>, "[email protected]" > <[email protected]> > Subject: Re: [CF-metadata] PMIP (including 1 or more that originated in > C4MIP) Standard Names: Carbon and Nitrogen terms > > Hello Jonathan, > > > It is definitely the mass of 13C atoms that we want, not the 13C plus oxygen > atoms that it was attached to prior to becoming part of the biomass. > > > Some examples of the broader use of "A_expressed_as_B" (in which the amount > of A cannot generally be inferred from A): > > mass_fraction_of_particulate_organic_matter_dry_aerosol_particles_expressed_as_carbon_in_air > > mole_concentration_of_mesozooplankton_expressed_as_nitrogen_in_sea_water > > atmosphere_moles_of_anthropogenic_nmvoc_expressed_as_carbon > > mole_fraction_of_nox_expressed_as_nitrogen_in_air > > > For comparison (where A is a molecule or ion, and B an atomic component): > > sinking_mole_flux_of_calcite_expressed_as_carbon_in_sea_water > > surface_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon > > > There are 270 standard names using "expressed_as", and those using it in the > narrow sense are, I think, a small fraction. There are a large number like > the nox/nitrogen example in which A refers to a collection of related > molecules, and many more in which A is biological organism or organic process. > > > regards, > > Martin > > > > ________________________________ > From: CF-metadata <[email protected]> on behalf of Jonathan > Gregory <[email protected]> > Sent: 24 April 2018 17:16 > To: [email protected] > Subject: [CF-metadata] PMIP (including 1 or more that originated in C4MIP) > Standard Names: Carbon and Nitrogen terms > > Dear Martin > > Tricky! I'm not sure that is better. Yes, I think you've correctly described > why I'm uncomfortable. Could you give other examples of this expanded use of > expressed_as, for comparison? > > What do we actually want to mean with these new GPP names? Is it just the mass > of 13C atoms in the GPP? Or is it the mass of all C atoms in molecules which > contain (at least) one 13C atom? It seems not so clear to me in "biomass" as > in CO2, where there is only one C atom. > > Best wishes > > Jonathan > > ----- Forwarded message from Martin Juckes - UKRI STFC > <[email protected]> ----- > > > Date: Tue, 24 Apr 2018 15:21:22 +0000 > > From: Martin Juckes - UKRI STFC <[email protected]> > > To: Jonathan Gregory <[email protected]> > > CC: "[email protected]" <[email protected]> > > Subject: Re: [CF-metadata] PMIP (including 1 or more that originated in > > C4MIP) Standard Names: Carbon and Nitrogen terms > > > > > > Hello Jonathan, > > > > > > I think the usage of "expressed_as" has crept into new areas, while > > remaining consistent with the definition as given in the standard names. > > The current help text says "It means that the quantity indicated by the > > standard name is calculated solely with respect to the B contained in A, > > neglecting all other chemical constituents of A", what you are implying is > > a more restrictive interpretation with some understanding that > > "A_expressed_as_B" is an alternative representation of A (as > > surface_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon would be, > > for most climate modellers, a simple multiple of > > surface_downward_mass_flux_of_carbon_dioxide [if the latter existed in the > > standard name table]). There are a number of terms in the standard name > > table for which this additional implication does not hold. > > > > > > Looking at the existing names I noticed there construction "content_of", > > which cannot be used directly here, but might be helpful, as in > > "vegetation_mass_content_of_13C". For the gpp terms we can't use "content", > > but could perhaps replace it with "flux": > > gross_primary_productivity_of_biomass_mass_flux_of_13C. > > > > > > This would require, I think, a change of the existing term > > gross_primary_productivity_of_biomass_expressed_as_carbon to > > gross_primary_productivity_of_biomass_mass_flux_of_carbon > > > > > > Would that be an improvement? > > > > > > regards, > > > > Martin > > > > ________________________________ > > From: Jonathan Gregory <[email protected]> > > Sent: 24 April 2018 15:28 > > To: Juckes, Martin (STFC,RAL,RALSP) > > Cc: [email protected] > > Subject: Re: [CF-metadata] PMIP (including 1 or more that originated in > > C4MIP) Standard Names: Carbon and Nitrogen terms > > > > Dear Martin > > > > Yes, I see what you mean, but nonetheless it seems odd to me. Is it normal > > to express GPP as mass of 13C? For example, this would be like expressing > > anthropogenic CO2 emissions as 13C. If 13C is about 1% of all the C in > > fossil > > fuels (I don't know what % it is - this is just an example), that means we'd > > say fossil fuel emissions containing 9 Gt of C per year could be "expressed > > as" > > 90 MtC of 13C per year. It seems more natural to me to say that 90 Mt per > > year > > of 13C are contained in the emissions of CO2. > > > > What you propose is consistent and logical, and I haven't managed to work > > out > > why it sounds strange. > > > > Best wishes > > > > Jonathan > > > > On Tue, Apr 24, 2018 at 01:47:29PM +0000, Martin Juckes - UKRI STFC wrote: > > > Date: Tue, 24 Apr 2018 13:47:29 +0000 > > > From: Martin Juckes - UKRI STFC <[email protected]> > > > To: Jonathan Gregory <[email protected]>, > > > "[email protected]" <[email protected]> > > > Subject: Re: [CF-metadata] PMIP (including 1 or more that originated in > > > C4MIP) Standard Names: Carbon and Nitrogen terms > > > > > > Dear Jonathan, > > > > > > > > > It is a logical extension, I believe, in the existing usage in terms such > > > as "gross_primary_productivity_of_biomass_expressed_as_carbon", for which > > > the help text states: "The phrase "expressed_as" is used in the > > > construction A_expressed_as_B, where B is a chemical constituent of A. It > > > means that the quantity indicated by the standard name is calculated > > > solely with respect to the B contained in A, neglecting all other > > > chemical constituents of A", i.e. the new terms are meant to refer to the > > > mass of 13C/14C which is contained in the biomass. > > > > > > regards, > > > Martin > > > > > > ________________________________ > > > From: CF-metadata <[email protected]> on behalf of > > > Jonathan Gregory <[email protected]> > > > Sent: 24 April 2018 13:35 > > > To: [email protected] > > > Subject: [CF-metadata] PMIP (including 1 or more that originated in > > > C4MIP) Standard Names: Carbon and Nitrogen terms > > > > > > Dear Martin > > > > > > Thanks for the new proposals. > > > > > > > gross_primary_productivity_of_biomass_expressed_as_13C > > > > gross_primary_productivity_of_biomass_expressed_as_14C > > > > > > These don't seem quite right to me. They imply you can express the > > > *entire* GPP > > > as kg of 13C or 14C. Does it means the mass of 13C or 14C in the GPP? > > > > > > Best wishes > > > > > > Jonathan > > > _______________________________________________ > > > CF-metadata mailing list > > > [email protected] > > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > ----- End forwarded message ----- > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
