Dear Jean-Yves, Didier,
please could you take a look at the following question about the CMIP6 variable "sw2h" which has title "Isotopic Ratio of Deuterium in Sea Water" and description "Ratio of abundance of hydrogen-2 (2H) atoms to hydrogen-1 (1H) atoms in sea water", and proposed standard name: "isotope_ratio_of_2H_to_1H_in_sea_water_excluding_solutes_and_solids".
As it stands, the working definition implies that this should be: ( [DH0] + 2[D2O] )/ [H2O] ), where "[]" indicates the abundance of the molecule and "D" is deuterium. I.e. the ratio of the number density of deuterium atoms contained in water molecules to the number density of hydrogen atoms in water molecules. Is this the quantity which is needed for you analysis?
regards,
Martin
________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk>
Sent: 05 July 2018 10:39
To: Pamment, Alison (STFC,RAL,RALSP); CF-metadata (cf-metadata at cgd.ucar.edu); Didier M. Roche; Jean-Yves Peterschmitt
Subject: Re: [CF-metadata] CMIP6: just one name remaining!
Dear Didier, Jean-Yves,
we need to clear up one remaining ambiguity in the definition of the variable sw2H, which is related to deuterium in sea water.
In the table that Jean-Yves posted on github (
https://github.com/cmip6dr/CMIP6_DataRequest_VariableDefinitions/issues/316) it is described with a long name "1H2HO in sea water" and description "Ratio of 2H in sea water".
Is the quantity you want the ratio of 1H.2H.O the number of molecules to the total 1H2.O molecules?
For the sw18O and sw17O variables we used standard names which refer to the ration of 18O atoms to 16O atoms (e.g. isotope_ratio_of_18O_to_16O_in_sea_water_excluding_solutes_and_solids -- the last part is needed because "sea_water" in standard names is interpreted as including not only the H2O but also the solutes and suspended solids that go with it). That approach won't work here if we are dealing with only the deuterium in water molecules which contain a single deuterium atom.
The term "isotope" is usually, as far as I can tell, interpreted as referring to atoms, but can be used to refer to molecules. I suggest we mention the fact that we are referring to a ratio of molecular isotopes in the standard name (if my interpretation above is correct). We have some agreed terms such as precipitation_flux_containing_single_2H (for pr2H) which are related to 1H.2H.O molecules. We decided not to try to use a name for the molecule, as different people have different names for these isotopes, and instead we have tried to spell out the detail in the standard name.
Following that approach here, we might use:
water_molecule_isotope_ratio_of_single_2H_to_double_1H_in_sea_water_excluding_solutes_and_solids
Does that make sense? I'm I correct in thinking that you want the ration of 2H.1H.O to 1H2.O for this variable?
regards,
Martin
________________________________
From: Pamment, Alison (STFC,RAL,RALSP)
Sent: 04 July 2018 16:19
To: CF-metadata (cf-metadata at cgd.ucar.edu); Juckes, Martin (STFC,RAL,RALSP)
Subject: CMIP6: just one name remaining!
Dear Martin,
After all the progress in recent weeks we have now reached the position where there is just one CMIP6 name remaining to be agreed.
It is the PMIP name:
isotope_ratio_of_2H_to_1H_in_sea_water_excluding_solutes_and_solids (1)
?The phrase "ratio_of_X_to_Y" means X/Y. The phrase "isotope_ratio" is used in the construction isotope_ratio_of_A_to_B where A and B are both named isotopes. It means the ratio of the number of atoms of A to the number of atoms of B present within a medium. "H" means the element "hydrogen" and "2H" is the stable isotope "hydrogen-2", usually called "deuterium". "1H" is the stable isotope "hydrogen-1". The phrase "in_sea_water_excluding_solutes_and_solids" means that the standard name refers to the composition of the sea water medium itself and does not include material that may be dissolved or suspended in the medium.?
The question that we need to resolve is whether '2H' includes water composed of both HDO and D2O. The name as it stands could be understood to mean the ratio of all 2H to 1H in sea water, regardless of whether the 2H occurs in heavy or semiheavy water, but this may not be the intention.
To publish the last few CMIP names I am planning a ?mini update? to the standard name table next week. It would be great if we could sort out this remaining one in time to include it!
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
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Received on Wed Oct 16 2019 - 10:07:36 BST
