Dear Andreas,
Thank you for the explanation. I agree that for your data it would not be straightforward to provide the time bounds of any ice mass change.
So that leaves us with:
change_in_land_ice_amount (canonical units: kg m-2)
' "Amount" means mass per unit area. Zero change in land ice amount is an arbitrary level. "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves.'
This name is accepted and will be added to the standard name table.
As regards the definition of land ice, I think it was probably proposed alongside some of the existing standard names that use it. I am not an expert on ice, but certainly I don't think we should alter the definition unless it is factually incorrect because it could affect the interpretation of data that have already been written with the existing names. If it were an issue for your data we could make it clear that ice shelves are not included by using a standard name like change_in_land_ice_amount_excluding_ice_shelves. Would that be better? Both names can be added to the standard name table if they are needed.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Campus, Didcot, OX11 0QX, U.K.
> -----Original Message-----
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf
> Of Andreas Groh
> Sent: 03 March 2016 08:53
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] ice mass change standard name
>
> Dear Alison and Jonathan
>
> Thanks for considering my previous post as a proposal. Unfortunately I
> missed to post an official proposal.
>
> I am fine with your proposed definition. I would not call it
> change_over_time_in_land_ice_amount, since the dataset usually provides
> a time series of mass changes wrt an arbitrary zero level, instead of a
> single value for the mass change over a certain period. Of course, the
> mass change at every step of the time series can be interpreted as the
> mass change over the period defined by the difference between the actual
> time and the time at which the mass change is zero by definition. But
> this period is not directly accessible and needs to be derived from the
> time dimension (with additional information on the time of zero mass
> change). Hence, I would stick to the name change_in_land_ice_amount
> without referring to the time. This is comparable to the definition of
> global_average_sea_level_change.
>
> Another point to be discussed is the definition of "land ice", which
> says that it also include ice-shelves. Usually, if the change in land
> ice is investigated one aims on that portion of ice contributing to a
> change in global sea level. This is not the case for the already
> floating ice-shelves. I am not aware of any investigation focussing on
> the mass of ice-shelves, while their thickness and velocity is subject
> to many studies. However, the same definition of "land ice" seems do be
> used for all standard names. This makes perfect sense and using a
> deviating definition here would be confusing. Moreover, it should not be
> a problem for the proposed standard name, since the spatial domain of
> the dataset indicates whether ice-shelves are included or not.
>
> To sum up, I think that your proposed definition describes the dataset
> appropriately:
>
> change_in_land_ice_amount (canonical units: kg m-2) ' "Amount" means
> mass per unit area. Zero change in land ice amount is an arbitrary
> level. "Land ice" means glaciers, ice-caps and ice-sheets resting on
> bedrock and also includes ice-shelves.'
>
> Best regards,
>
> Andreas
>
>
> On 02.03.2016 18:39, alison.pamment at stfc.ac.uk wrote:
> > Dear Jonathan and Andreas,
> >
> > I will regard this name as having been proposed! So I think at the
> > moment we have:
> >
> > change_in_land_ice_amount (canonical units: kg m-2) ' "Amount" means
> > mass per unit area. Zero change in land ice amount is an arbitrary
> > level. "Land ice" means glaciers, ice-caps and ice-sheets resting on
> > bedrock and also includes ice-shelves.'
> >
> > I note that many of our existing "change" names actually say
> > "change_over_time_in_X" defined as ' "change_over_time_in_X" means
> > change in a quantity X over a time-interval, which should be defined
> > by the bounds of the time coordinate.' I wonder if that would be
> > appropriate for your variable?
> >
> > Best wishes, Alison
> >
> > ------ Alison Pamment
> > Tel: +44 1235 778065 Centre for Environmental Data Analysis
> > Email: alison.pamment at stfc.ac.uk STFC Rutherford Appleton Laboratory
> > R25, 2.22 Harwell Campus, Didcot, OX11 0QX, U.K.
> >
> >
> >
> >> -----Original Message----- From: CF-metadata
> >> [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Jonathan
> >> Gregory Sent: 25 February 2016 10:13 To: cf-metadata at cgd.ucar.edu
> >> Subject: Re: [CF-metadata] ice mass change standard name
> >>
> >> Dear Andreas
> >>
> >>> I think a variable of the form change_in_land_ice_amount [kg
> >>> m-2] would be appropriate, since my dataset describes the amount
> >>> of land ice with reference to an arbitrary level. The description
> >>> of the standard name global_average_sea_level_change includes the
> >>> sentence: "Zero sea level change is an arbitrary level.". An
> >>> equivalent phrase ("Zero change in land ice amount is an
> >>> arbitrary level.") added to the description of a potential
> >>> standard name change_in_land_ice_amount would unambiguously
> >>> describe the dataset I am working on.
> >>
> >> That makes sense to me.
> >>
> >>> How could such a new standard name be defined and added to the
> >> conventions?
> >>
> >> If you propose the new standard name, its canonical unit, and the
> >> definition to this list, anyone else might comment; once there is
> >> agreement, or if there is no disagreement expressed, Alison will
> >> schedule the new name to be added to the table.
> >>
> >> Best wishes
> >>
> >> Jonathan _______________________________________________
> >> CF-metadata mailing list CF-metadata at cgd.ucar.edu
> >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> > _______________________________________________ CF-metadata mailing
> > list CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >
>
> --
> -----------------------------------
> Dr.-Ing. Andreas Groh
> Institut f?r Planetare Geod?sie
> Geod?tische Erdsystemforschung
> Technische Universit?t Dresden
> D-01062 Dresden, Germany
> phone : +49-351-463.33416
> fax : +49-351-463.37063
> email : andreas.groh at tu-dresden.de
> web : tu-dresden.de/geo/ipg/gef
> -----------------------------------
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Received on Thu Mar 03 2016 - 10:17:10 GMT
