Talk:CF Standard Names - Discussed Atmospheric Chemistry and Aerosol Terms
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Vincent-Henri PEUCH - replies by Christiane Textor (CT) and Jonathan Gregory (JG)
- 2) there is always the problem that "NOy" has no fully agreed definition in the literature... It is perhaps unwise to use it in the name? Could we use "total_nitrogen_oxides" instead?
- (JG))I think it's a good idea to avoid the word "total" if we can, as it is not always obvious what aspect is being totalled! total_nitrogen_oxides is probably clear enough, but maybe all_nitrogen_oxides might be better?
- (CT) But what does 'all' include? anyway, I changed it.
- We have also to chose :
- - if only the species with the name listed go in the sum
- - or if it is up to the modeller to select all nitrogen oxides in his/her chemical scheme.
- (CT) would go for the second option. Included in the comment/explanation.
- The explanation is "includes all nitrogen oxides included in the model, to be specified in by the modeller in the long_name attribute if possible ???" I doubt however, that this is CF conform, as long_names are not part of CF...
- 3) the description of the "troposphere_content*" variables is not enough detailed because it is indeed verticaly integrated, but up to the tropopause only. We can specify in the explanation "up to the tropopause level", but we probably also have to specify the tropopause definition to be used (2PVU,380K ?) as the value is quite sensitive to the specific criterion used (for species with strong vertical gradients at the tropopause like ozone). A drawback of specifying is that any other type of hypotheses (other "tropopause" definition : 150 ppb of ozone, 100 hPa,...) or other ways of computation (specific tracer in the model) would then no longer fit with the name. I don't know the solution...
- (CT)Very good point! I explain my ideas below. The 150ppb O3 isosurface is a good measure for atmospheric chemsitry problems and has been used in ACCENT/PHOTOCOMP. Changed to up_to_chemical_tropopause_content as in e.g. "up_to_chemical_tropopause_content_of_ozone_in_air". See also below.
- 5) the variable "mole_fraction_of_ozone_from_stratosphere_in troposphere" is a modeler's concept, with no chance of being measured. The way it is implemented in a model has an impact on the actual values, due to non linearities etc... I would not be in favor of including it as a standard variable. What do you think?
- (CT) I ask this question to the GEMS-GRG and HTAP communities
- (JG) Remark by Vincent-Henri Peuch: "The variable mole_fraction_of_ozone_from_stratosphere_in troposphere is a modeler's concept." Yes, that is true, but if modellers want to store this quantity, and compare it among models, then it should be given a standard name. There are many quantities like this, which aren't really observable. To begin with CF was designed for models, rather than the real world!
- (CT) At the GEMS GRG meeting in Toulouse we agreed on including this variable in the diagnostics. mole_fraction_of_ozone_from_stratosphere_in troposphere includes the question of what would be the tropopause, which is discussed below.
Christiane Textor: Tropopause definition comments by Jonathan Gregory (JG)
- Several tropopause definitions exist:
- - chemical tropopause (150 ppb O3 isosurface)
- - lapse rate tropopause (the lowest level at which the lapse rate decreases to 2 °C/km or less,
- provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2 °C/km. WMO definition of Tropopause)
- - potential vorticity (PVU2 (at the 2 PVU surface) or PVU1.5 (at the 1.5 PVU surface))
- - potential temperature surface
- For chemical purposes it seems appropriate to define up_to_chemical_tropopause with the explanation from the surface up to chemical tropopause (150 ppb O3 isosurface).
- (JG) You have a number of names of the form up_to_chemical_tropopause_content_of_X_in_air. This order is rather unnatural, I'd say. Also in_air probably isn't right, as here you mean a large-scale quantity. I know that we discussed whether "atmosphere" goes at the start or the end, and I remarked it usually was at the start, but a complete phrase is more awkward at the start. Would you consider X_content_of_chemical_troposphere or X_content_of_atmosphere_below_chemical_tropopause?
- (CT) I have put in_air because satellites only see the fraction in the gas phase, so atmosphere is not correct. below_chemical_tropopause sounds good. This would lead to X_mole_content_below_chemical_tropopause_in_air or X_mole_content_in_air_below_chemical_tropopause. What do you think?
- (JG) If you need to distinguish different definitions of the tropopause, this could be done by defining different standard names. This issue is rather like the definition of the ocean mixed layer, for which we have several standard names:
- If there are particular numbers which are needed for the definition (like your 150 ppb O3) they could be specified as standard name parameters (but we still haven't agreed the mechanism for this!).
- (CT) This would then give X_mole_content_in_air_below_tropopause_defined_by_150ppv_O3_iso_surface.
Jonathan Gregory - replies by Christiane Textor (CT)
- I would suggest that due_to_turbulence comes after of_X, because there could be a quantity dry_deposition_flux_of_X, of which dry_deposition_flux_of_X_due_to_turbulence is a part.
- (CT) It is :dry_deposition_mole_flux_of_X=dry_deposition_mole_flux_of_X_due_to_turbulence+dry_deposition_mole_flux_of_X_due_to_sedimentation, so I would rather like to leave the due_to_turbulence and due_to_sedimentation close to deposition, so I would like to change it to dry_deposition_mole_flux_of_X=dry_deposition_due_to_turbulence_mole_flux_of_X+dry_deposition_due_to_sedimentation_mole_flux_of_X, ok?
- grid_box_area. Do you have a data variable containing area? If the only purpose of this is to provide weights, you can use cell_measures to supply the area variable (CF 7.2). However if you do have them as data variables, I agree you need a standard name. I'd suggest surface_area. I think this is really the quantity, isn't it. It is analogous to sea_ice_area (m2), for example. These are extensive quantities in space; they implicitly depend on the size of the grid box.
- (CT) I reread the CF documentation yesterday and realized the possibility of using the cell methods for the grid information, sorry for that. We do not need an additional standard_name.