[CF-metadata] additional standard name for ISMIP6

alison.pamment at stfc.ac.uk alison.pamment at stfc.ac.uk
Thu Feb 9 07:12:56 MST 2017

Dear Jonathan,

Thank you for looking at the ISMIP6 names again. I'm responding here to two of your comments.

I wrote:
> 18. grounded_ice_sheet_area (m2)
> Okay, so the quantity you need is the actual area of the grounded ice sheet.
> Unfortunately, we can't just call it 'area' because the definition of the existing
> names refers to the area within a grid cell. I think we would have to call it an
> integral. You say that it is summed over the entire grid, so is this a truly global
> quantity? If so, we could perhaps call it
> global_integral_of_grounded_ice_sheet_area by analogy with the existing
> global_average_sea_level names. If you want to be able to calculate the
> quantity for individual ice sheets then we'd have to call it something like
> integral_of_grounded_ice_sheet_wrt_xy, where xy essentially means the
> horizontal coordinates. You could then supply bounds on the coordinate
> variables to show the geographical extent of the area integral. What do you
> think?

Jonathan replied:
> Are you sure we can't call it area? It seems to me it's fine to call it that
> if the coordinates indicate it refers to the whole world (regarded as one
> grid cell) or to some large region (containing an entire ice sheet).

I certainly agree that it seems more natural to call it grounded_ice_sheet_area. The definitions of the four existing "X_area" names say '"X_area" means the horizontal area occupied by X within the grid cell'. When I made my previous comments I was thinking about summing areas across multiple grid cells each of which contains a part of the ice sheet, but actually if the 'grid cell' in this case covers the entire area of the ice then it's not a problem. Perhaps the definition should be modified to emphasize that a bit more. Maybe something like:
' "X_area" means the horizontal area occupied by X within the grid cell. The extent of an individual grid cell is defined by the horizontal coordinates and any associated coordinate bounds or by a string valued auxiliary coordinate variable with a standard name of "region".' Does that sound OK?

> > 21. floating_ice_sheet_area_fraction (1)
> > ' "X_area_fraction" means the fraction of horizontal area occupied by X. A
> "floating ice sheet", sometimes called an "ice shelf", indicates where the ice
> sheet is flowing over sea water.'
> Shouldn't that be floating_ice_shelf_area_fraction?

You're right, it should be floating_ice_shelf_area_fraction to be consistent with the new area type of floating_ice_shelf that we have just introduced for ISMIP6. I think the terminology changed part way through the conversation and I neglected to update the standard name. I will create an alias (floating_ice_sheet_area_fraction -> floating_ice_shelf_area_fraction) and modify the definition accordingly. This will be included in the next update of standard names, planned for 21st February.

Best wishes,

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.

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