Dear Martin
Ah, I see. Sorry, I hadn't grasped that point. I certainly don't want to try
to persuade LS3MIP to provide something to suit CF. CF should try to describe
what people want to use.
I think your suggestion below is a good one. We could use the standard_name of
depth with a coordinate variable soil_temperature=0 degC and a cell_methods
specification "where unfrozen_ground", for example. We already use "ground"
in the phrase at_ground_level in several standard names; it means the top of
the soil or rock surface, underneath the snow and ice, if any. "ground" is in
some other names too, and the bare_ground area_type. "unfrozen" is in the
guidelines and in one extant name.
Best wishes
Jonathan
----- Forwarded message from Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk> -----
> Date: Fri, 18 May 2018 08:29:34 +0000
> From: Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>,
> "j.m.gregory at reading.ac.uk" <j.m.gregory at reading.ac.uk>
> Subject: Re: [CF-metadata] Standard names for LS3MIP: 8 temporal changes + 1
> feature depth
>
> Dear Jonathan,
>
>
> I agree that the 0C isotherm does not exist everywhere, but it is still a different variable to the one requested. You could try to persuade LS3MIP to use the variable you are describing, but I'm not yet convinced that we can't provide a means of describing the variable they want.
>
>
> You are defining a variable X representing an isotherm which may lie below frozen soil or below thawed soil. They want a variable Y which only represents the isotherm below thawed soil. Y is a masked version of X -- but to describe that masking in CF we would need a new area type to indicate areas for which the surface soil temperature is above zero.
>
>
> regards,
>
> Martin
>
>
> ________________________________
> From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jonathan Gregory <jonathan.gregory at ncas.ac.uk>
> Sent: 18 May 2018 08:47
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] Standard names for LS3MIP: 8 temporal changes + 1 feature depth
>
> Dear Martin
>
> I agree that the quantity doesn't exist everywhere, but that's the same if you
> give it a name of its own rather than the more general name of depth. I suggest
> that specifying the coordinate as soil_temperature specifically implies that
> it must be non-existent where 0degC is above ground or there is no ground. The
> value to be given in that case needs a convention, though not necessarily as
> part of the standard name definition; it could be a CMIP6 convention. It's like
> the non-existent thickness of sea ice in ice-free sea or land areas.
>
> Best wishes
>
> Jonathan
>
> ----- Forwarded message from Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk> -----
>
> > Date: Thu, 17 May 2018 17:26:58 +0000
> > From: Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk>
> > To: Jonathan Gregory <j.m.gregory at reading.ac.uk>, "cf-metadata at cgd.ucar.edu"
> > <cf-metadata at cgd.ucar.edu>
> > Subject: Re: [CF-metadata] Standard names for LS3MIP: 8 temporal changes + 1
> > feature depth
> >
> > Dear Jonathan,
> >
> >
> > Yes, it should be 0C, not 0K.
> >
> >
> > I don't think the approach you suggest will work because what we need is the depth of the first 0C isotherm assuming surface temperature above 0C. We don't want the depth of the 0C isotherm in regions where the surface temperature is < 0C. I can't see any way to include these conditions in existing CF attributes, can you?
> >
> >
> > regards,
> >
> > Martin
> >
> >
> >
> > ________________________________
> > From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jonathan Gregory <j.m.gregory at reading.ac.uk>
> > Sent: 17 May 2018 17:30
> > To: cf-metadata at cgd.ucar.edu
> > Subject: [CF-metadata] Standard names for LS3MIP: 8 temporal changes + 1 feature depth
> >
> > Dear Martin
> >
> > All the change_over_time ones look fine to me, thanks.
> >
> > > 2.1 dmlt Depth to soil thaw [m] (CliC)
> > > Depth from surface to the zero degree isotherm. Above this isotherm T > 0o, and below this line T < 0o.
> > >
> > > When the surface temperature is above 0K and there is frozen soil at some point beneath the surface, thawed_soil_depth is the distance from the surface to the first 0K isotherm. When there is no thawed soil layer, the parameter should be reported as missing.
> > >
> > > + Proposed: thawed_soil_depth
> >
> > Could we use the standard_name of depth for this, with a coordinate
> > variable of soil_temperature=0degC?
> > (I think 0degC is intended above, not absolute zero)
> >
> > Best wishes
> >
> > Jonathan
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
> ----- End forwarded message -----
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Received on Fri May 18 2018 - 06:48:41 BST
