Dear Alison,
Thanks for adding the new standard name.
I think it is not necessary to explicitly exclude the ice shelves here.
In principle the mass of ice shelves can change, so there might by a
need for this standard name with respect to the ice shelves. For my data
set I would just add a comment to the meta data clarifying that the data
solely refer to the grounded part of land ice.
On this occasion, one could think about adding a second variable
referring to the time derivative of the change_in_land_ice_amount.
For example, in this way the pattern of the linear trend of the
change_in_land_ice_amount could be described. I propose the following:
tendency_of_change_in_land_ice_amount (canonical units: kg m-2 s-1) '
"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. "tendency_of_X" means
derivative of X with respect to time. '
Best regards,
Andreas
On 03.03.2016 18:17, alison.pamment at stfc.ac.uk wrote:
> 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
>> -----------------------------------
>> _______________________________________________ CF-metadata mailing
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> _______________________________________________ CF-metadata mailing
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--
-----------------------------------
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
-----------------------------------
Received on Fri Mar 04 2016 - 01:07:33 GMT
