[CF-metadata] aerosol and chemistry names - continuation

From: Jonathan Gregory <j.m.gregory>
Date: Sat, 6 Jan 2007 17:32:46 +0000

Dear Christiane

> The issue of X_expressed_as_Y seams to be settled: X=Y is the standard,
> and the extension _expressed_as_Y it is only added if X\=Y.
> The name particulate_organic matter seams to be accepted as well.
Yes. Thank you for carrying this debate through to a happy conclusion.

> If there are no further objections, I would like to move the following
> quantities from the proposed to the almost-accepted table:
>
> surface_dry_deposition_mass_flux_of_X
> surface_wet_deposition_mass_flux_of_X
> mass_fraction_of_X_dry_aerosol_in_air
> mole_fraction_of_dimethyl_sulfide_in_air
> chemical_gross_production_rate_of_mole_concentration_of_X
> chemical_gross_destruction_rate_of_mole_concentration_of_X
They all look fine to me.

> atmosphere_emission means a source within the atmosphere, e.g. from the
> surface or from an air plane.
Ah, OK. Why is the surface included? You have separate surface fluxes.

> atmosphere_production means production within the atmosphere, this
> includes direct sources and chemical production from precursors.
So production = emission (from sources) + chemical net production
It seems to me potentially confusing to have production in these two different
senses on the left and right of the equation. What about saying "addition" on
the left e.g. NOx is added to the atmosphere by emission from aircraft and by
chemical production. The opposite of "addition" might be "removal", which
comes about by deposition and chemical destruction. Do we also need to
distinguish gross and net addition?

> re-emission refers to the source of a pollutant that is not directly
> emitted by human activities, but re-emitted after previously being
> deposited and accumulated in soils or water.
I see. Is reemission included in emission? This might be a source of confusion.

> These names were understood in our community (for the HTAP experiments),
> are they not clear enough?
Definitions help, of course, thanks. However it might be that wrong guesses
by the ignorant could be reduced.

> water_in_ambient_aerosol_optical_depth follows this systematic, it is
> the optical depth due to the water contained in aerosol.
Sorry to revisit this. That is what I understood it to mean, but I didn't
believe it! I think that this long phrase is quite difficult to parse, and
it would be easier to understand
optical_depth_due_to_water_in_ambient_aerosol
Perhaps, as with named surfaces, it might be acceptable (if not too
complicated) to say X_optical_depth if X is one word (since that is convenient
and what people usually say e.g. for cloud and aerosol), and
optical_depth_due_to_X if X is several words (to make it easier to understand).

But the existing standard_name is
atmosphere_optical_thickness_due_to_aerosol
- not depth. Optical depth and thickness are both in the American Met Soc
glossary, for instance. Optical depth means the optical thickness above some
specified altitude (the idea of depth being that one is looking from above),
and optical thickness is along any path. I suppose that by saying "atmosphere"
we are defining the path to be the whole atmosphere, so they are synonymous.
A more general quantity, such as the existing standard name
optical_thickness_of_atmosphere_layer_due_to_aerosol
should be thickness, not depth. Hence I still have a preference for thickness.

Best wishes

Jonathan
Received on Sat Jan 06 2007 - 10:32:46 GMT