Standard name : Area fraction of ridged sea ice

[abiardeau]

Hello,

I am Aurore BIARDEAU from Mercator Ocean international. Date 23/06/2022

We didn't find any variable in CF Conventions for the area fraction of ridged sea ice.

Here are our proposals :

area_fraction_of_ridged_sea_ice or sea_ice_area_fraction_due_to_ridging

With the following description : "Area fraction" is the fraction of a grid cell's horizontal area that has some characteristic of interest. It is evaluated as the area of interest divided by the grid cell area. Sea ice area fraction is area of the sea surface occupied by sea ice. It is also called "sea ice concentration". "Sea ice" means all ice floating in the sea which has formed from freezing sea water, rather than by other processes such as calving of land ice to form icebergs. The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. Sea ice "ridging" occurs in rough sea conditions. The motion of the sea surface can cause areas of sea ice to deform and fold resulting in ridged upper and lower surfaces. The ridges can be as much as twenty metres thick if thick ice is deformed.

Unit : no unit (fraction)

Thanks Aurore BIARDEAU

[abiardeau]

Dear all,

Does anyone have an idea about the variable name that we could use for the area fraction of ridged sea ice ?

Thanks a lot for your help,

Aurore

[taylor13]

Many different area_fraction(s) were requested for the CMIP6 archive (fraction of area covered by "vegetation", "trees", "shrubs", etc.) Rather than request new standard names for each of these, they all were identified as "area_fraction" and assigned different variable names (vegFrac, treeFrac, shrubFrac, etc.). Each of these variables was provided with a scalar dimension that had the standard name area_type and was assigned an appropriate value (vegetation, trees, shrubs, etc.) taken from the CF table of area_types.

One of the CMIP6 variables is just the one you have an interest in: the area fraction of sea_ice_ridges. Note that sea_ice_ridges is already in the CF table of area types. So you could store this variable in a variable named, say, "sirdgconc" (which is what the CMIP6 name was), and assign dimensions: sirdgconc(lon, lat, time, areatype) where areatype="sea_ice_ridges" and this coordinate (areatype) has the standard name "area_type".

[taylor13]

I would note that we haven't been wholly consistent in practice. There are specific standard names used in CMIP6 for different area fractions. Among them are: land_area_fraction, sea_area_fraction, sea_ice_area_fraction, land_ice_area_fraction, surface_snow_area_fraction, floating_ice_shelf_area_fraction, and grounded_ice_sheet_area_fraction. I think the major ones (land, sea, sea_ice, and land_ice) have been around for a long time. I'm not sure why others have been added rather than relying on the method described above. Can anyone suggest a rule for this?

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[JonathanGregory]

Dear Karl @taylor13

I would suggest that the future policy should be to define no more X_area_fraction standard names, unless any use-cases come forward which can't satisfactorily be dealt with using area_fraction given a (possibly new) area_type instead.

Also if someone has time to do it we should (a) check that all the X_area_fraction standard names have corresponding area types, with consistent definitions, (b) insert a comment in the descriptions of all those standard names to say that using area_fraction with area_type is equivalent in meaning, and more flexible.

Best wishes

Jonathan

[feggleton]

Hi all, looks like we've concluded that we will not be adding a new standard name here. I will keep this open to go through the existing names and come up with a plan.

[efisher008]

Hi @feggleton,

Regarding your comment last year about keeping this issue open to review existing _area_fraction standard names, has there been progress on this topic? Does this issue still need to be open, or can it now be concluded? I notice there are other currently open issues re. area_fraction names, e.g. #45, #24, #25, which might have interlinking discussions. This might suggest there is still work to be done on this?

Thanks and best wishes, Ellie

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