On Monday 04 August 2003 18:51, Jonathan Gregory wrote:
> Dear John
>
> > in_situ_density_of_seawater kg/m^3
> > potential_density_of_seawater kg/m^3
> > downwelling_photosynthetically_active_radiation microE/m^2/s
>
> For the first two, we already have sea_water_density
> and sea_water_potential_density. I will clarify the help to indicate that
> plain density means in-situ.
Yes it is, my apologies, I'll look more carefully next time.
>
> Yes, the 1000 can't be subtracted off without comment.
>
> > I assume that the first sentence means that "kg/m^3 _at_ -1000" is
> > definitely not allowed?
>
> That's right. However, I think the add_offset attribute could be used. What
> do you think - would that be appropriate? If not, we can instead define
> standard names for the "sigma" quantities (i.e. -1000).
I guess it would depend upon what the interpretation of the unpacked data
coupled with the units would be. If the packed data was in the 1024-1028
range, then having an add_offset of -1000 would make the unpacked data
technically not agree with the units? Maybe this would just be a good place
for the "comment" attribute?
>
> What is the unit microE? If this is an energy unit, then the quantity is
> a radiative flux, so we should call it
> downwelling_photosynthetically_active_radiative_flux W/m2
> like the other ones. Would that be OK? Also, should it be
> surface_downwelling_...? - or is a quantity with a vertical coordinate, in
> which case we should append _in_sea_water, by analogy with
> e.g. downward_heat_flux_in_air.
Again, I should have researched it a bit more carefully, and not just run it
thru udunits to see if it was accepted or not. "E" is short for einsteins,
which I guess is an old unit of measurement. And "einsteins" isn't even
accepted by udunits (it interpreted "E" as 1e+18 instead!!!) The correct
unit would be "moles", making the full unit specification as
"micromoles/m^2/s.
As for the 2nd part, good question, it would appear to be both in our case, as
we measure this both at the surface and at various depths in the water
column.
--
John Evans
johnevans at acm.org
Received on Mon Aug 04 2003 - 14:30:20 BST
