Dear Alison In existing names we generally use "atmosphere" to indicate a property of the atmosphere as a whole (or a large portion of it) and "in_air" to indicate a local property within the atmosphere. We don't use both phrases at once. These quantities can be regarded as means of local properties, I think, so just in_air would be sufficient. If no vertical coordinate is specified, it should apply to the entire atmosphere, but to make that clear a cell_method could be added to record that it's a vertical mean.
Best wishes Jonathan ----- Forwarded message from [email protected] ----- > Date: Tue, 19 Jan 2016 16:39:38 +0000 > From: [email protected] > To: [email protected] > CC: [email protected], [email protected], > [email protected], > [email protected] > Subject: [CF-metadata] New standard names for ESA GHG CCI quantities > > Dear All, > > I have been asked to re-propose two standard names that were originally > proposed by Maximilian Reuter in 2014 but which did not receive any comments > at the time: > http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057373.html. > > I have rephrased the original proposal to make the names more CF like and > have added some standard definition text, so the names are now proposed as > follows: > atmosphere_mole_fraction_of_methane_in_dry_air (canonical units: 1) > 'Mole fraction is used in the construction "mole_fraction_of_X_in_Y", where X > is a material constituent of Y. A chemical species denoted by X may be > described by a single term such as "nitrogen" or a phrase such as > "nox_expressed_as_nitrogen". The "atmosphere mole fraction" of a quantity > refers to the column average from the surface to the top of the atmosphere. > Methane is a member of the group of hydrocarbons known as alkanes. There are > standard names for the alkane group as well as for some of the individual > species. The chemical formula for methane is CH4.' > > atmosphere_mole_fraction_of_carbon_dioxide_in_dry_air (canonical units: 1) > 'Mole fraction is used in the construction "mole_fraction_of_X_in_Y", where X > is a material constituent of Y. A chemical species denoted by X may be > described by a single term such as "nitrogen" or a phrase such as > "nox_expressed_as_nitrogen". The "atmosphere mole fraction" of a quantity > refers to the column average from the surface to the top of the atmosphere. > The chemical formula for carbon dioxide is CO2.' > > These names reflect the original proposal, and generally follow the syntax > of existing names such as mole_fraction_of_carbon_dioxide_in_air. I have > prepended these names with the word "atmosphere" as a way of indicating a > column amount, similar to existing atmosphere_mass_content names. > > We don't currently have any "dry_air" names in CF. When this topic last came > up on the mailing list (as far back as 2008 under the thread entitled "mixing > ratio") it was concluded that the current "in_air" names don't tie the > definition down to either dry or ambient air. The reason for this > (deliberate) vagueness is that numerically the quantities in dry or moist air > are not very different except in the case of water vapour itself where we > define humidity_mixing_ratio to mean " ratio of the mass of water vapor to > the mass of dry air". The gist of the 2008 conversation was that if we ever > needed to be very precise about making the distinction between ambient air > and dry air then we would be able to introduce appropriate names at a later > stage, but there wasn't a pressing need at the time. An offline conversation > I had more recently with Jonathan Gregory and Martin Schultz went along > similar lines, basically saying that we wouldn't change any existing names > where the deliberate impre ci > sion isn't important, but reiterating that we could introduce new names if > there are cases where it does matter, specifying dry or ambient. > > Please could Maximilan, Veronica or another member of the CCI team answer the > question about whether there is a real need to specify "dry_air" in the case > of these names, or can we get away with being a bit more vague? If vagueness > is OK, then the names would simplify to > atmosphere_mole_fraction_of_methane_in_dry_air and > atmosphere_mole_fraction_of_carbon_dioxide. Also, do others agree with my > using "atmosphere" here to indicate the column average? All comments are > welcome. > > Best wishes, > Alison > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
