Talk:CF Standard Names - OLD Submitted Atmospheric Chemistry and Aerosol Terms

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Submission of HTAP names, CT, 18.8.2008

Dear all,

I would like to propose you new_standard names for aerosols and chemical variables. These names will be used in the model intercomparisons in the framework of the Task Force on Hemispheric Transport of Air Pollution (http://www.htap.org/, http://aqm.jrc.it/HTAP/) and the European Integrated Project GEMS (http://www.ecmwf.int/research/EU_projects/GEMS/).

The proposed names have been extensively discussed by a 'virtual workgroup' activity through a wiki page http://wiki.esipfed.org/index.php/Air_Quality/Chemistry_Naming_Conventions with the aid of some CF experts to whom we are very grateful for their support.

Many other people who contributed to discussion: Olivier Boucher, Frank Dentener, Rudy Husar, Jonathan Gregory, KyleHalliday, BryanLawrence, Vincent-Henri Peuch, Sebastian Rast, Martin Schultz, Michael Schulz, Ranjeet Sokhi, David Stevenson, Karl Taylor, Christiane Textor, Peter van Velthoven.

Please find attached a file with the proposed standard names. More information on how these names are constructed can be found at http://wiki.esipfed.org/index.php/CF_Standard_Names_-_Future_Atmospheric_Chemistry_and_Aerosol_Terms

I am looking forward to your comments.

Best regards, Christiane Textor

(on vacation until September 11)

Comment from Roy Lowry, 11.9.2006

Hello Christine,

My main comment is that your work is a first step taking CF into a new area. I therefore feel definitions are especially important. Whilst there are some really good definitions in your list (e.g. NOy) there are other areas where more information would be extermely helpful The ones that hit me straight away are mercury_0, mercury_2, 'surface_emission_mass_flux', the aerosol terms (does this include solid particulates or just liquid phase?), 'pm10' and 'pm2p5', but there may be others.

A little more work on this area would I think greatly enhance a good piece of work.

Cheers, Roy

Reply from CT, 11.9.2006

Hello Roy,

Thank you very much for your comment! It is the only one I got so far during the three weeks since submission. As you say a little more work is needed and I would appreciate some more input (as my colleagues and I did already quite a bit of work). I would very much appreciate more comments on the proposed aerosol and chemistry names, especially as they will be used in their current form within the HTAP model intercomparison that is starting these days.

Concerning you comments:

What is wrong with surface_emission_flux?

The state of aerosols (liquid or dry) is dependent on their composition and the ambient humidity. The proposed aerosol terms state clearly if they relate to dry aerosol, or to which humidity they refer (e.g. mass_fraction_of_pm10_aerosol_at_50_percent_relative_humidity_in_air mass_fraction_ of_dust_dry_aerosol_in_air)

Do you have any suggestions for the mercury variables?

Best regards, Christiane

Comment from Roy Lowry, 12.9.2006

Hello Christiane,

I think you misunderstand. I don't necessarily have a problem with the names per se. I just do not understand what some of them represent. I am a geochemist turned oceanographic data manager, not an atmospheric chemist and hence depend on the definitions, not the terms, to understand what is being proposed as I don't speak the domain jargon. For example, with the mercury, what is the difference between '2' and '0' - oxidation state, form of chemical complexing, something else?

I had noticed the lack of reaction on the list to your proposal. It may be that the CF list isn't reaching any domain experts beyond the group who have already been involved in the discussions. For example, does anyone know if the UK groups like UMIST and UEA watch the list?

Cheers, Roy.

Comment from Jonathan Gregory, 21.9.2006

Dear Christiane et al.

Regarding Roy's comment, it would be fair to say that these names do already result from consultation among some experts on atmos chemistry within your group, wouldn't it? I think what is mostly needed here is comments on how chemical names of this kind fit with CF standard names in general. Roy's comment shows that they may need to be more self-explanatory. It is generally the case that we have to make standard names more explicit than domain experts would expect, so that people from other disciplines can understand them easily. That kind of issue has occurred before, with meteorologists assuming that oceanographers will understand them and vice-versa, etc.

Sorry for my slow response. I have a few comments.

On names of species:

• The construction X_as_Y seems fine to me, to indicate that you mean X when it

comes as a constituent of Y. But it some cases I wonder if it is really necessary. What is meant by ammonium_as_ammonium?

• You have organic_carbon_as_particulate_organic_carbon_dry_aerosol and

organic_carbon_as_particulate_organic_carbon_dry_aerosol. In these cases, could you not omit the first "organic"? - since carbon is carbon, and whether it is organic depends on what it is a constituent of.

• How can you have a wet deposition flux of a dry aerosol? What does "dry

aerosol" mean, I wonder.

• Like Roy, I don't know what mercury_0 and mercury_2 mean.

• I don't understand aerosol_water_ambient_aerosol.

• I can understand non_methane_volatile_organic_compounds but I don't know what

they are. Are they a well-known group so that this is obvious to an expert? Later they appear as NMVOC. I think we should have one or the other, and putting it in full seems more consistent with your other names.

• CO should appear as carbon_monoxide.

Use of dimensions:

• Some of the names have numerical values in them. This is not in keeping with

usual practice in standard names. For instance, we do not have standard names for surface air temperature at 1.5 m or 2 m height. Instead, we use coordinates for independent variables. In names like these:

mole_fraction_of_CO_with_lifetime_of_25_days_in_air

pm10_aerosol_ambient_optical_depth_at_550_nm

mass_fraction_of_pm10_aerosol_at_50_percent_relative_humidity_in_air

I think the lifetime, particle radius, wavelength and relative humidity should be coordinates (probably scalar coordinate variables), rather than being in the standard name. This requires standard names to be defined for the independent variables you need.

• In a similar way, you have phrases from_North_America, from_South_Asia and so

on. I know this is similar to the construction from_stratosphere which we discussed in your guidelines, but I don't think we ought to include geo- graphical areas in standard names. We have already defined a standard_name of region for use as a geographical "coordinate". Your use is not quite the same because you want to identify where something comes from, rather than its present location, so perhaps we should introduce a new name of source_region for instance, with the same possible values as region; these come from a list which can be extended as required.

Other points:

• grid_cell_area and _height. These are metrics for the grid, rather than

quantities which need standard names. Grid cell area should be specified by a cell_measures variable of area (CF 7.2). Grid cell height can be deduced as the difference between the lower and upper boundary in the vertical coordinate. If it has to be stored separately we could add a cell_measures for it.

• atmosphere_mass_content_of_air. I think we agreed this would be named in the

more obvious way atmosphere_mass_per_unit_area, since it seems strange to give something a "content" name for its entire content!

• "of" is missing in surface_emission_mass_flux_ammonia.

Best wishes

Jonathan

Response from CT 26.9.2006

Dear Jonathan, Roy, and others,

I agree that it is important not to use the jargon of in a specific field of research in the standard names. Comments from people from other domains are 'needed' now, because the standard names I proposed are indeed the results of extensive discussion within the atmospheric chemistry/aerosol community, see also the wiki page http://wiki.esipfed.org/index.php/Air_Quality/Chemistry_Naming_Conventions

But how to distinguish jargon from real definitions? E.g., in our community the definition of an aerosol is very clear, but maybe there is no official definition. Where can I find such official definitions?

I have updated the list of names according to this email, see attachment and http://wiki.esipfed.org/index.php/CF_Standard_Names_-_Proposed_names_for_TF_HTAP

Here my reponses to Roy's comments:

>mercury_0, mercury_2:

I agree, but I am not expert here myself. I have contacted a colleague.

>surface_emission_mass_flux

what is wrong with this?
it means the mass flux of emissions at the surface... ?

There is a clear definition of what aerosol is:
A gaseous suspension of fine solid or liquid particles.
So it can be both, dependent on the environmental conditions.

'pm10' and 'pm2p5'
These are common in aerosol research and legislation:
PM stands for particulate matter suspended in air.
PM followed by a number refers to all particles with a certain maximum size (aerodynamic diameter). All smaller particles are included.
PM0.1 is particulate matter with an aerodynamic diameter of up to 0.1 µm, referred to as the ultrafine particle fraction.
PM2.5 is particulate matter with an aerodynamic diameter of up to 2.5 µm, referred to as the fine particle fraction (which per definition includes the ultrafine particles).
PM10 is particulate matter with an aerodynamic diameter of up to 10 µm, i.e. the fine and coarse particle fractions combined.

Please find detailed reponses to Jonathan's comments below:
> > * The construction X_as_Y seems fine to me, to indicate that you mean X when it
> comes as a constituent of Y. But it some cases I wonder if it is really
> necessary. What is meant by ammonium_as_ammonium?

In our community, the mass of molecules like NH4 (or SO4) are sometimes given as N (or S). To avoid this ambiguity, I have added ammonium_as_ammonium or sulfate_as_sulfate.

> > * You have organic_carbon_as_particulate_organic_carbon_dry_aerosol and
> organic_carbon_as_particulate_organic_carbon_dry_aerosol. In these cases, could
> you not omit the first "organic"? - since carbon is carbon, and whether it is
> organic depends on what it is a constituent of.

In the aerosol community, organic_carbon describes a wild mixture of unknows organic carbon emissions from plants and industry. It is (as above for NH4 and SO4) sometimes given as mass of carbon and sometimes as mass of particulate carbon with a vague conversion factor of about 1.3 to 1.4.

But it should be changed to particulate_organic_carbon_as_particulate_organic_carbon_dry_aerosol

> > * How can you have a wet deposition flux of a dry aerosol? What does "dry
> aerosol" mean, I wonder.

Aerosol takes up ambient water depending the relative humidity and its composition, this is known hygroscopic growth. Dry_aerosol means aerosol without water.

Wet deposition flux means the aerosol mass transported downwards within precipitation, i.e. scavenging by rain/snow/graupel etc. Therefore, it is consistent to have wet deposition of dry aerosol, althought it sound strange, I agree.

>
> * Like Roy, I don't know what mercury_0 and mercury_2 mean.
>

I will check this.

> * I don't understand aerosol_water_ambient_aerosol.

Aerosol takes up ambient water depending the relative humidity and its composition, this is know hygroscopic growth. Dry_aerosol means aerosol without water.... and aerosol_water is the water contained in aerosol. The suffix _ambient_aerosol is added to be consistent with the suffix _dry_aerosol elsewhere.

>
> * I can understand non_methane_volatile_organic_compounds but I don't know what
> they are. Are they a well-known group so that this is obvious to an expert?
> Later they appear as NMVOC. I think we should have one or the other, and
> putting it in full seems more consistent with your other names.

I put non_methane_volatile_organic_compounds everywhere. non_methane_volatile_organic_compounds is a widely used term to describe a wild mixture of compounds, the composition of which is not entirely known (similar to particulate_organic_carbon for the aerosols), this is why they are summarized in this expression. However, it is known what they are NOT, i.e. methane. I think it is important to include it as standard name.

> * CO should appear as carbon_monoxide.

d'accord!

> Use of dimensions:
>
> * Some of the names have numerical values in them. This is not in keeping with
> usual practice in standard names. For instance, we do not have standard names
> for surface air temperature at 1.5 m or 2 m height. Instead, we use coordinates
> for independent variables. In names like these:
> mole_fraction_of_CO_with_lifetime_of_25_days_in_air
> pm10_aerosol_ambient_optical_depth_at_550_nm
> mass_fraction_of_pm10_aerosol_at_50_percent_relative_humidity_in_air
> I think the lifetime, particle radius, wavelength and relative humidity should
> be coordinates (probably scalar coordinate variables), rather than being in the
> standard name. This requires standard names to be defined for the independent
> variables you need.

Let me explain:

> mole_fraction_of_CO_with_lifetime_of_25_days_in_air

is an artificial tracer for a specific sensitivity study, so maybe it needs a coordinate variable, similar to those emitted in specific regions

> pm10_aerosol_ambient_optical_depth_at_550_nm

550 nm is one of the few wavelenghts for which the optical depth is measured. The use a coordinate variable is feasable.

> mass_fraction_of_pm10_aerosol_at_50_percent_relative_humidity_in_air

The use a coordinate variable for the rel. hum is feasable, but to be consistent, the use of _dry_aerosol should than be substituted by also using this coordinated variable with rel.hum.=0. But what if rel.hum=ambient humidity, i.e. not a numerical value? Is it possible to have both _dry and _ambient and for all other cases a coordinate variable?

>
> * In a similar way, you have phrases from_North_America, from_South_Asia and so
> on. I know this is similar to the construction from_stratosphere which we
> discussed in your guidelines, but I don't think we ought to include geo-
> graphical areas in standard names. We have already defined a standard_name of
> region for use as a geographical "coordinate". Your use is not quite the same
> because you want to identify where something comes from, rather than its
> present location, so perhaps we should introduce a new name of source_region
> for instance, with the same possible values as region; these come from a list
> which can be extended as required.

The this is in principal a good idea. The source_regions have specific spatial extensions, which might be different for different experiments.

variables:
float VMR_CO(time,lat,lon,lbl);

VMR_CO:unit="1";

VMR_CO:coordinates="source_region";

VMR_CO:standard_name="mole_fraction_of_CO_in_air";

double time(time) ;

time:long_name = "time" ;

time:units = "days since 1990-1-1 0:0:0" ;

float lat(lat) ;

lat:long_name = "latitude" ;

lat:units = "degrees_north" ;

float lon(lon) ;

lon:standard_name = "longitude" ;

lon:long_name = "longitude" ;

lon:units = "degrees_east"

char region_name(lbl,strlen) ;

region_name:standard_name="source_region"

region_name:bounds = "region_bnds" ;

float region_bnds(lbl,latmin,latmax,lonmin,lonmax) ;

or

float region_bnds(lbl,regbnds) ; with regbnds=4

or something like that?? (I do not understand, why 'region' has the dimension 'strlen' in your examples, it seems redundant to me, or is it necessary for netcdf?

However, in the context of HTAP it would be better to specify a coordinate variable for mole_fraction_of_CO_in_air indicating the different experiments with CO tagged per source region, but also including the artificial mole_fraction_of_CO_with_lifetime_of_25_days_in_air

Is this possible?

> > Other points:
>
> * grid_cell_area and _height. These are metrics for the grid, rather than
> quantities which need standard names. Grid cell area should be specified by a
> cell_measures variable of area (CF 7.2). Grid cell height can be deduced as the
> difference between the lower and upper boundary in the vertical coordinate. If
> it has to be stored separately we could add a cell_measures for it.
>

Yes, I know that the cell_measures exist, but it is convenient to have the grid information stored in variables. It would be nice if these names could be added.

> * atmosphere_mass_content_of_air. I think we agreed this would be named in the
> more obvious way atmosphere_mass_per_unit_area, since it seems strange to
> give something a "content" name for its entire content!
it should then be atmosphere_mass_of_air_per_unit_area to exclude preciptation etc. or other particles (or planes?)

> > * "of" is missing in surface_emission_mass_flux_ammonia.

d'accord

"expressed_as_such"

Dear Christiane and others,

I am confused by the expression "expressed_as_such". I have not been part of the discussions that have created the current version of the standard names, so I expect there is a good reason for using this term, but I don't know it and the meaning is not intuitively clear to me.

For example: surface_dry_deposition_mass_flux_of_divalent_mercury_expressed_as_such

Does this mean that the corresponding variable gives the mass of the divalent mercury compound that is dry deposited? Rather than the mass of mercury within the deposited mercury compound?

Some names are still confusing (e.g. the dry_aerosol entries): surface_dry_deposition_mass_flux_of_mercury_expressed_as_such_dry_aerosol

If I am interpreting the term "expressed_as" correctly, maybe this should be: surface_dry_deposition_mass_flux_of_mercury_dry_aerosol_expressed_as_mercury

-Chris