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Dear Christiane

I am going on holiday tomorrow, back 24th. Here are some brief answers.

>> IN_AIR >> The mole_fraction and mass_fractions for the chemical gases in air are >> related to humid air. I have only defined _in_air, which from my >> understanding would mean 'in air what ever it contains, i.e. humid air' >> But it is this clear enough or do we need to have in_dry_air and >> in_humid_air?

I think in_air is fine. My understanding is the same as yours.

>> EMISSIONS >> I have defined surface_ and atmosphere_ emissions, e.g. >> surface_emission_mole_flux_of_ozone mole/m2/s >> atmosphere_emission_mole_flux_of_ozone mole/m3/s >> Is it allowed to have a flux per m3?

Interesting! It's not really a flux, is it - not a flow through an area, which is what flux means to me. I think we may need to consider using a different word. What word is usually used in atmos chem for this?

>> CMOR >> You mentioned this software for the creation of CF conform netCDF files. >> However, I cannot download it from the PCMDI site, and Karl Taylor does >> not answer his emails. Can you help us?

Try Bob Drach drach@llnl.gov or Dean Williams (also at PCMDI).

>> CF-COMPLIANCE CHECKER >> After discussion with HTAP people, Martin Schultz in particular, I feel >> that it would be nice, if the compliance checker could be more >> informative. It would be helpful to obtain more information on why >> compliance is not reached. Is this possible?

It depends on software engineering effort. Of course, I agree with you. Do you have any effort available from your project? I would hope that either Kyle or Alison might be able to work on this at some point, but at present both of them are still learning about CF, so I don't foresee any immediate help.

>> In addition, the web site http://titania.badc.rl.ac.uk/cgi-bin/cf-checker.pl >> does not respond today, could you please have a look?

Ask Bryan Lawrence, Ag Stephens or Alison Pamment. b.n.lawrence@rl.ac.uk A.Stephens@rl.ac.uk j.a.pamment@rl.ac.uk

>> CF HOME PAGE AND DOCUMENTATION >> It would be good to have a very simple and short summary of what the >> main objectives of CF and what CF-compliance means. The documents >> provided on line are not that easy to understand, and there are many of >> them, I found 6 relevant links, see >> http://wiki.esipfed.org/index.php/Air_Quality/Chemistry_Naming_Resources >> Would it be possible to have one simple and short version for CF-beginners?

Again, this would depend on someone else being spun-up enough to write it. Do you think you or anyone else might produce a draft? http://www.cgd.ucar.edu/cms/eaton/cf-metadata/clivar_article.pdf (on the CF home page) is supposed to be something anyone could understand, and it states the objectives of CF near the start. Is this doc too complicated?

>> I have still some questions, for example in section 4 of the >> http://www.cgd.ucar.edu/cms/eaton/cf-metadata/CF-current.html document, >> no standard_names are given, instead long_names are used. Do I >> misunderstand something?

No. Some of the examples were written before standard names were defined. Standard names are optional, though.

>> NOy all_nitrogen_oxides >> I have defined it as >> standard_name: "atmosphere_mole_fraction_of_all_nitrogen_oxides" >> explanation: " volume mixing ratio of all simulated nitrogen oxides NOy, >> i.e., sum of moles_fractions of all simulated oxidized nitrogen species, >> out of NO, NO2, HNO3, NO3aerosol, N2O5, NO3(radical), HNO4, PAN, other >> organic nitrates (N2O5 is only counted once!)" >> unit: "1=mole/mole" >> Another difficulty arises from N2O5, that contains to N atmos. Frank >> wrote 2*N2O5 in his definition, but if we count in mole or kg - not >> kgN!, this is not correct. Therefore, I have added (N2O5 is only counted >> once!) Is this ok?

I don't think you have to list them all explicitly, do you? Different people might have different lists of things in NOy. Can you state generally that it is expressed in moles of N, to get round the multiple counting?

>> But a quantity with a unit of kg m-2 day-1 is a flux rather than a >> rate which would have kg/day? See also

"Rate" is not a precisely defined term, I would say. It has the idea of s-1 but doesn't imply what other dimensions. I suppose a surface emission in kg m-2 s-1 might be called either a rate or a flux. Which is more usual in atmos chem?

>> surface_dry_deposition_due_to_turbulence_mole_monthly_flux_of_sulfur_dioxide

No, I don't think we should put a time unit in the standard name. If you are dealing with real calendar months, I think you'll have to use an amount (no s-1). The time bounds will show the months to which it applies. Is this a bad solution for you?

>> And do we finally need an extra variable for the grid-box area? is nco >> able to understand the CF information on the grid, including the >> vertical axis? If not, we definitely need extra variables, or a very >> fast extension of nco....

I don't expect that nco will recognise the cell_measures, if you mean use it to do global sums etc. However your own analysis software could use this, couldn't it. If you think nco should be extended, please write to them to ask for it. They are aware of CF.

I am sorry I don't have solution for all these. I agree with you that extensions and tools are needed. That is why over the last year we have been trying get people in post to work on CF, but more effort would still be valuable.

Best wishes

Jonathan