Hi all -
I'm finally catching up with this discussion, after being at sea for the
past
month. I have to agree with Seth McGinnis; I vote no.
We're happy with the CF terms and their definitions. The last sentence
in the
definition of surface_downwelling_shortwave_flux_in_air (and probably
some of
the other flux terms) states:
In accordance with common usage in geophysical disciplines, "flux"
implies per
unit area, called "flux density" in physics.
This seems perfectly clear. If flux_density is technically more correct,
so be it; the
canonical units and the definitions clarify the meaning. We could make
*lots* of standard
names longer and more technically complete; in reading through the
threads on this
request, I just haven't seen a clear explanation of why the existing
flux terms now
need to change.
Cheers - Nan
On 5/19/15 6:25 PM, Seth McGinnis wrote:
I vote no.
As mentioned, using "flux" to refer to what is technically "flux
density" is commonplace and normal in many geoscience fields, and it's
clear by the lack of questions about it that this does not cause
problems for users.
Deprecating names and replacing them with an alias creates the
opportunity for confusion, and given the number and popularity of the
names that would be affected, I think this change would create a great
deal of confusion. A reasonable alternative solution
("integrated_flux") has been suggested for handling "proper" fluxes, and
as Karl says, we'd likely want to use that even if we did make the
change to avoid confusion with the old names.
So it seems to me that there's no real benefit to changing flux to
flux_density, and the potential for a very large downside.
Cheers,
--Seth McGinnis
On 5/19/15 3:23 PM, Jonathan Gregory wrote:
Dear all
Like Karl, I thought that many people would have opinions, but so far there
are none. Please express your views! Shall we rename flux quantities in units
of something per m2 to flux_density in all existing standard names? Here are
the kinds of flux [density] we name:
carbon energy evaporation graupel heat longwave mass melt mole momentum
photon precipitation radiative rainfall refreezing runoff salt shortwave
snowfall sublimation throughfall transpiration water_vapor water
With regard to your point, Karl, I think we would not use plain "flux" in the
area-integral sense. We would avoid using it altogether. We already have ways
of working round it e.g. northward heat transport in W and there is no need
to change those names.
Best wishes and thanks
Jonathan
----- Forwarded message from Karl Taylor <[email protected]
Date: Thu, 14 May 2015 10:47:55 -0700
From: Karl Taylor <[email protected]>
To: [email protected]
Subject: Re: [CF-metadata] flux
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0)
Gecko/20100101 Thunderbird/31.6.0
Dear Jonathan,
My oh my, this is bound to generate lots of opinions. I do recall
the original discussion conclusion that although "flux density" was
the proper name, we'd be lax in this case and go with common usage,
"flux". An argument against the common usage is that if we want to
define the flux density integrated over some surface, then we
couldn't call it "flux", which is what it is. Perhaps to
distinguish this from "flux" (W m-2), we would call this
"integrated_flux" (W). Do we have examples of having to do this
kind of thing in the current standard names?
Even if we rename "flux" "flux density", we probably wouldn't want
to refer to the integrated flux as simply "flux" because so many
fields have already been written named "flux" when "flux density"
was meant.
It's not going to be easy.
Karl
On 5/14/15 9:37 AM, Jonathan Gregory wrote:
Dear all
In connection with the radiative flux from the sun, the question has come up
of whether we should use the phrase flux_density for a flux per unit area in
all the standard names which currently have the word "flux". This would be
correct in physical terminology, but years ago we chose to use "flux" because
it's the normal terminology in many geosciences. There are more than 200
standard names of "flux" - radiative fluxes, mass fluxes and mole fluxes. In
some of them I don't think "flux density" is ever used e.g. I have never
heard of an "ocean flux density adjustment", and Google finds one hit for
"snowfall flux density". However we could rename them all and establish aliases
to the present names, if that would be an advantage for users of standard
names. Should this be done?
Cheers
Jonathan
--
*******************************************************
* Nan Galbraith Information Systems Specialist *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 (508) 289-2444 *
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