Dear Markus
Thanks for your comments.
> 1)
> "surface_particle_number_concentration_at_stp_in_aerosol (and other similar names). Could this be said more clearly as surface_number_concentration_of_aerosol_in_air_at_stp?
> That would be consistent with existing names e.g.
> number_concentration_of_coarse_mode_ambient_aerosol_in_air"
>
> The standard names I proposed use the term "aerosol" according to its proper textbook definition, i.e. meaning the system of particles and carrier gas. Your wording implies that "aerosol" consists of particles only, which is a common, but colloquial jargon use of the term. I respect the use of "aerosol" in standard names so far, so I worded the proposed names to be backward compatible.
I agree with you about the textbook definition but it appears that existing
CF names are not consistent. We have some names with a construction
number_concentration_of_X_aerosol_in_air
and some with
atmosphere_number_content_of_aerosol_particles
The difference between concentration and content is that the first is 3D and
the second a vertical integral, so that's not a problem. We could change the
first construction in existing names e.g.
number_concentration_of_ambient_aerosol_in_air to
number_concentration_of_X_aerosol_particles_in_air
i.e. insert "particles". Would that be correct? I suppose that in_air is
needed because aerosol is not necessarily in air (although the word looks
like it should be). It could be any gas. Then for consistency, could you use
number_concentration_of_aerosol_particles_at_stp_in_air
in your new names?
> 2)
> You draw attention to the inclusion of "surface" in the above, but I'm not clear why it's there. Is the measurement actually exactly at the ground? If not, surface should be omitted, and the height indicated by a numerical coordinate, or some other phrase e.g. in_atmosphere_boundary_layer (that one already appears in the stdname table).
>
> The term "surface" is used according to the description given in the "Guidelines for Construction of CF Standard Names" at
> http://cf-pcmdi.llnl.gov/documents/cf-standard-names/guidelines
4-5 m above the ground is not really the surface. The constructions
surface_ and _at_surface mean the same thing; they're chosen according to
which seems to be easier to read in the context concerned. So I'd prefer
> 2) Include in the definition the requirement that the sampling height needs to be included as numerical coordinate.
That's what we do with screen-height temperature, for example. Although it
is often called "surface air temperature", its standard name is air_temperature
and it has a height coordinate (e.g. 1.5 m or 2.0 m).
> 3)
> Clouds do not usually occur at the surface, so "surface" is surprising for CCN.
>
> Not really. The number of cloud condensation nuclei active at a given water vapour supersaturation is independent of the actual existence of a cloud. The instrument measuring this property exposes the aerosol particles to a generated, defined supersaturation, i.e. generates its own "cloud" inside the instrument.
OK, I see.
> 4)
> electrical_mobility_particle_diameter. I think the "electrical" here refers to the means of measurement. Usually the CF standard name describes the geophysical quantity itself. Would it be OK to say aerosol_particle_diameter?
>
> The electrical mobility particle diameter is one of many aerosol particle diameters, as opposed to for example the aerodynamic particle diameter (how a particle follows a streamline) or the optical particle diameter (how the particle scatters light). By only saying "aerosol particle diameter", the property is somewhat ill-defined since most aerosol particles aren't spherical. The proposed name avoids this ambiguity.
OK. So it's really part of the definition of a geophysical quantity, not a
method of measurement.
> 5)
> sizing_relative_humidity. Could "sizing" be omitted? The definition of your standard names can specify what the role of the RH is.
>
> This standard name would be used together with reporting particle size resolved CCN concentrations, i.e. CCN concentrations as function of both, supersaturation and dry particle size. In this context, we need to distinguish between the RH for which the CCN concentration is measured (a few 10ths above 100%), and the RH at which the particle size is selected (usually below or just above 40%). I couldn't find any other way of distinguishing this easily except defining a separate standard name.
I see the need for two distinct standard names. However I wonder if
sizing_relative_humidity could be made more self-explanatory somehow, and
also whether for the other RH you also need a new and more explicit
standard name, in order to make the distinction clearer?
Best wishes
Jonathan
Received on Thu Oct 17 2013 - 03:04:39 BST
