Hello again,
The CO2 example was a bit contrived, so let's concentrate on nitrogen. Let's say we have a flux of 1 mole/m2/s of NO2 plus 1 mole/m2/s of N2O and 1 mole/m2/s of NO. This gives a total flux for the three oxides of nitrogen of 3 moles/m2/s, but a flux of 4 moles/m2/s of nitrogen_oxides_as_nitrogen as each mole of N2O contains two moles of nitrogen. The same sort of thing happens with mass fluxes - to convert a mass_flux_of_NO2 to a mass_flux_of_NO2_as_nitrogen you multiply by a factor of (14/(14+16+16)) taking 14 and 16 as the atomic weights of nitrogen and oxygen.
Converting all forms of C to CO2 is maybe not useful, but determination of elemental fluxes without distortions due to stoichiometry is, which is why people express in terms of nitrogen.
Does the phrase 'expressed_as' do a better job?
Cheers, Roy.
>>> Jonathan Gregory <j.m.gregory at reading.ac.uk> 10/09/06 8:49 AM >>>
Dear Roy
> We need to be very careful about changing meaning here. To me, 'mass_flux_of_nitrogen_as_all_nitrogen_oxides' implies that nitrogen in other forms such as ammonia/ammonium has been included in the flux. However, 'mass_flux_of_all_nitrogen_oxides_as_nitrogen' is the flux of oxidised nitrogen species stoichmetrically recalculated as nitrogen.
>
> Using this construct we need to have the actual 'thing' followed by the 'thing' it is expressed as. 'carbon_as_carbon_dioxide' and 'carbon_dioxide_as_carbon' are two completely different things.
I think your understanding of X_as_Y is the same as Christiane's and opposite
to what I assumed it to mean. That is, I thought mass_flux_of_carbon_as_carbon_
dioxide would mean the mass flux of the carbon contained in the CO2, but that
is what you understand by mass_flux_of_carbon_dioxide_as_carbon. Is that right?
You are suggesting there is another interpretation too, but I have not grasped
what it means. What do you mean by mass_flux_of_carbon_as_carbon_dioxide?
Perhaps it is a flux of C in all species, turned into CO2 mass equivalent?
Is that a generally useful concept?
Since this is not intuitively clear to non-experts (if I am representative) it
suggests we need more explicit language such as expressed_as instead of as,
for instance. Perhaps you, or others familiar with this terminology, have
suggestions?
Cheers
Jonathan
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Received on Mon Oct 09 2006 - 06:22:23 BST
