Hi Tom,
Thanks for your suggestions :-).
This is not really my field, but I have worked a bit with isotopes and fluxes, so wanted to comment on your second question.
>From a CF point of view, I think it would be a mistake for one type of variable (sinking_flux) to have different physical units and definitions (mass/m2/sec vs ratio) . I am not aware of any such case that has been approved.
On a separate point, as a modeler I have always preferred to treat the fluxes and reservoirs separately for each isotope, and then calculate any needed ratios. I am not really sure, in general, what it means to talk about a flux of a ratio, without also providing the mass fluxes and the sizes of the reservoirs. That said, ratios do have uses, so for the ratios I would suggest something like
composition_ratio_of_silicon_30_to_silicon _28_in_sinking_flux.
(note that I just typed this without carefully harmonizing with other std_names in order to move the discussion forward, so I reserve the right to criticize myself if people pick up on this ;-).
As a more minor point, I would prefer sinking_mass_flux over sinking_flux_mass, just for consistency with all the other mole_flux and mass_flux existing std_names.
My 2 cents :-),
Philip
-----------------------------------------------------------------------
Dr Philip Cameron-Smith, pjc at llnl.gov, Lawrence Livermore National Lab.
-----------------------------------------------------------------------
> -----Original Message-----
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of
> Thomas Trull
> Sent: Thursday, October 10, 2013 2:28 AM
> To: <mlankhorst at ucsd.edu>
> Cc: cf-metadata at cgd.ucar.edu; OceanSITES Data Management Team
> Subject: Re: [CF-metadata] standard names for sediment trap data
>
> Hi Matthias,
> I like your proposed canonical units and terms. The names are also systematic
> and clear. I do not see the need to include the word total when an elemental
> flux is not split into molecular or other components. Items that I think might
> need further consideration:
> 1. In the list of XXX items, would it be clearer to specify silicon rather than silica
> for all terms related to silica (since the molecular composition of lithogenic,
> biogenic silica forms are often unknown)? Or do we have to write XXX as
> '_biogenic_silica_as_silicon'
> 2. Is it worth settling on a standard approach to isotopic (and other)
> compositions ? For example, 13C-POC. Units of flux rather than composition
> would be somewhat unusual for isotopes, making variables starting with
> 'sinking_mass_flux' somewhat odd. That is unfortunate, since indicating sinking
> flux as the overall sample type seems to be the top category worth retaining.
> One way around this would be a slight reordering to two groups of variables,
> e.g.:
> sinking_flux_mass_lithogenic_silicon
> sinking_flux_composition_lithogenic_silicon_isotopic_ratio_30_28
>
> Or is that clumsy?
>
> Of course we could force all compositional information (isotopes, diatom
> species relative abundances, etc. )into mass flux units, with satisfyingly simple
> units, but then they all have to be reconverted into units people want to use.
> This would mean carrying absolute isotopic abundance for standards within the
> files for completeness.
>
> As usual there are many ways to skin a cat, but none are easy when the cat sees
> you coming!
>
> Best wishes,
> Tom
>
>
> On 10/10/2013, at 10:16, "Matthias Lankhorst" <mlankhorst at ucsd.edu> wrote:
>
> Dear CF community,
>
> in the OceanSITES project, we would like to publish data from sediment traps in
> files, using the CF conventions. Sediment traps are devices moored underwater
> in the ocean, which collect sinking particles (detritus) in a funnel and into sample
> bottles for later analyses. Analyses can be done for a variety of substances. It
> looks like we need a few more standard names for these, and possibly a
> discussion whether some of them should be expressed as mass fluxes or as
> substance amount (mole) fluxes.
>
> I noticed that CF already has these standard names, all as mole fluxes with
> canonical units of mol m-2 s-1:
>
> sinking_mole_flux_of_aragonite_expressed_as_carbon_in_sea_water
> sinking_mole_flux_of_calcite_expressed_as_carbon_in_sea_water
> sinking_mole_flux_of_particulate_iron_in_sea_water
> sinking_mole_flux_of_particulate_organic_matter_expressed_as_carbon_in_se
> a_water
> sinking_mole_flux_of_particulate_organic_nitrogen_in_sea_water
> sinking_mole_flux_of_particulate_organic_phosphorus_in_sea_water
> sinking_mole_flux_of_particulate_silicon_in_sea_water
>
> Here is the list of quantities that we need to address in OceanSITES. My initial
> proposal is to introduce them all as mass fluxes with canonical units of kg m-2 s-
> 1. If we should rather go with mole fluxes like the ones above, please chime in.
>
> Total/organic mass:
> Propose new standard names:
> sinking_mass_flux_of_particulate_matter_in_sea_water
> sinking_mass_flux_of_particulate_organic_matter_in_sea_water
> (I suppose these are understood as dry mass, i.e. weighed after water has
> evaporated.)
>
> Particulate organic, inorganic, total carbon:
> Propose new standard names:
> sinking_mass_flux_of_particulate_organic_carbon_in_sea_water
> sinking_mass_flux_of_particulate_inorganic_carbon_in_sea_water
> sinking_mass_flux_of_particulate_carbon_in_sea_water
> (or should we include "total" somewhere in the latter?)
>
> Particulate organic, inorganic, total nitrogen:
> Propose new standard names:
> sinking_mass_flux_of_particulate_organic_nitrogen_in_sea_water
> sinking_mass_flux_of_particulate_inorganic_nitrogen_in_sea_water
> sinking_mass_flux_of_particulate_nitrogen_in_sea_water
> (or should we include "total" somewhere in the latter?)
>
> Other particulate substances from a list:
> Propose new standard names for each of the following, to be constructed as:
> sinking_mass_flux_of_particulate_XXX_in_sea_water,
> where XXX is:
> - aluminum
> - iron
> - phosphorous
> - silica
> - biogenic_silica
> - lithogenic_silica
> - calcium
> - titanium
> - manganese
> - barium
> - magnesium
>
> Your expert comments are highly appreciated!
>
> Respectfully, Matthias
>
>
> --
> _______________________________________
>
> Dr. Matthias Lankhorst
> Scripps Institution of Oceanography
> 9500 Gilman Drive, Mail Code 0230
> La Jolla, CA 92093-0230
> USA
>
> Phone: +1 858 822 5013
> Fax: +1 858 534 9820
> E-Mail: mlankhorst at ucsd.edu
> http://www-pord.ucsd.edu/~mlankhorst/
>
>
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Received on Thu Oct 10 2013 - 14:41:49 BST
