Dear Andreas and Martin I agree with Martin that if layers can be defined numerically these numerical limits should not appear in the standard_name. The usual way to do it would be with a coordinate variable (either with a dimension of size 1, or a scalar coordinate variable) whose bounds specify the limits concerned e.g. a variable of air_pressure with bounds of 500 and 750 hPa.
This will not work straightforwardly when one of the bounds is numerically defined and the other is a named surface such as the tropopause. That hasn't come up before. Still, I think we should find a solution which avoids having a number in the standard_name. Best wishes Jonathan ----- Forwarded message from "Schultz, Martin" <[email protected]> ----- > From: "Schultz, Martin" <[email protected]> > To: "[email protected]" <[email protected]> > Date: Fri, 21 Dec 2012 07:55:00 +0000 > Subject: Re: [CF-metadata] standard names for column amounts (atmospheric > chemistry) > > Hi Andreas, > > > -----Original Message----- > > From: CF-metadata [mailto:[email protected]] On Behalf > > Of Andreas Hilboll > > Sent: Wednesday, December 19, 2012 2:53 AM > > To: [email protected] > > Subject: Re: [CF-metadata] standard names for column amounts > > (atmospheric > > chemistry) > > > > in addition to what Philip said, let me try to guide you a little more > specifically concerning some of your questions. Don't feel frightened about > the discussions that are going to come up. Eventually, there will be an > agreement, and in the end it's usually a wise decision if you look at it from > a little distance later. The following comments may help you to identify the > potential areas for discussion - the better your proposal will address these > points "in the spirit" of existing CF names, the easier it will be to get the > proposal accepted smoothly. > > > * The canonical way to specify tropospheric NO2 columns in > > molecules cm^-2 would be to use the standard name > > "mole_content_of_nitrogen_dioxide_in_troposphere_layer", or rather > > "troposphere_mole_content_of_nitrogen_dioxide", > > together with a units attribute of "molecules cm^-2"? > > I agree with Philip here, that "troposphere_mole_content..." seems the more > natural choice. Obviously, this can easily be extended to > "stratosphere_mole_content..." if you provide a clear definition of what > "stratosphere" means (in fact I just saw that "troposphere" is also not > defined very well, it only says "in this layer of the atmosphere"!). We > should probably change this definition to something more specific, such as > "the layer of the atmosphere between the earth surface and the tropopause. > Generally, the tropopause will be defined via the reversal of the temperature > gradient with altitude as specified by WMO. Other definitions of tropopause > are possible, and if one of these is used, it should be explained in a > comment attribute." -- In analogy, the "stratosphere" should be defined as > the layer between the tropopause and the stratopause. > > > > > > * What can I do for > > "atmosphere_mole_content_of_nitrogen_dioxide_between_surface_and_XhPa > > ", > > where X is 500? > > Here, my suggestion would be to go for the general term "atmosphere_layer" > and request either a generic comment attribute or a more specific attribute > (something like "layer_extent" ?) where the exact specification of "between > ... and ..." should be provided. I don't believe that it would be possible to > agree on a small confined set of numbers, and since a standard_name is static > and cannot contain variable elements, one would have to define thouands of > standard names in order to be able to distinguish any layer between X and Y. > > > > > * What about > > "atmosphere_mole_content_of_nitrogen_dioxide_between_XhPa_and_tropopa > > use", > > where X is 500? > > Here again, we should try to find a general solution with an additional > attribute. In fact this discussion could/should be broader than for > atmospheric composition only, because similar problems might be present for > soil variables (soil layer between X and Y), and in the ocean as well. In > fact you can look into the definition of "frozen_water_content_of_soil_layer" > as an example. This is formulated rather vaguely, I think. So, perhaps this > could be a starting point for a more general discussion on how to uniformly > express "layers" in the CF model. _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
