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, [email protected] 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: [email protected] STFC Rutherford Appleton Laboratory
R25, 2.22 Harwell Campus, Didcot, OX11 0QX, U.K.
-----Original Message----- From: CF-metadata
[mailto:[email protected]] On Behalf Of Jonathan
Gregory Sent: 25 February 2016 10:13 To: [email protected]
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 _______________________________________________
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--
-----------------------------------
Dr.-Ing. Andreas Groh
Institut für Planetare Geodäsie
Geodätische Erdsystemforschung
Technische Universität Dresden
D-01062 Dresden, Germany
phone : +49-351-463.33416
fax : +49-351-463.37063
email : [email protected]
web : tu-dresden.de/geo/ipg/gef
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