[CF-metadata] standard names for column amounts (atmospheric chemistry)

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 21 Dec 2012 13:30:03 +0000

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" <m.schultz at fz-juelich.de> -----

> From: "Schultz, Martin" <m.schultz at fz-juelich.de>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> 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:cf-metadata-bounces at cgd.ucar.edu] On Behalf
> > Of Andreas Hilboll
> > Sent: Wednesday, December 19, 2012 2:53 AM
> > To: cf-metadata at cgd.ucar.edu
> > 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.
Received on Fri Dec 21 2012 - 06:30:03 GMT