Dear Sophie,
Thanks for your additional proposals and updates to the ones originally made in
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2015/058516.html. The current status of all your standard name proposals can be viewed in the CEDA vocabulary editor here:
http://cfeditor.ceda.ac.uk/proposals/1?status=active&namefilter=&proposerfilter=&descfilter=&unitfilter=&yearfilter=&commentfilter=ISMIP6&filter+and+display=Filter.
Proposals for new area types don?t appear in the editor but I have taken note of the three names you are suggesting. They can be discussed on the mailing list in the same way as the standard names and I will update both tables once the new terms are agreed.
Please see below for my detailed comments on each of your proposals.
1. snow_land_ice_interface_temperature (K)
'Surface Temperature that is used to force ice sheet models. It is the temperature at the base of the snowpack models, and does not vary with seasons. Report surface temperature of ice sheet where snow thickness is zero.'
I think the name itself is clear and that not mentioning firn (unless strictly necessary) makes the name easier to understand for non-experts as well as experts. Units of K are fine.
The definition should contain a sentence explaining "land_ice" as with existing names. I'm not sure that the bit about reporting zero for areas without snow really belongs in the CF definition - I think it is really a CMIP6 requirement. Other users of the name might prefer to report a missing data value, for example, so we should be careful not to be too prescriptive in the definition. I'd prefer to refer to a "upper boundary" rather than a "surface" temperature in the definition so as to be clear we are not talking about the interface at the bottom of the atmosphere. (I assume this is an upper boundary i.e. the top of the ice sheet?) With these changes, I suggest the following wording for the definition:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The quantity with standard name snow_land_ice_interface_temperature is the upper boundary temperature that is used to force ice sheet models. It is the temperature at the base of the snowpack models, and does not vary with seasons.'
Is that OK?
2. land_ice_basal_temperature (K)
' Basal temperature that is used to force the ice sheet models. Report temperature AT interface. Beneath ice shelves it is the temperature AT ice ocean interface. Beneath grounded ice, it is the temperature AT ice bedrock interface.'
The name and units both look fine.
Again we need to make the wording of the definition consistent with other names where applicable. I suggest:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The quantity with standard name land_ice_basal_temperature is the lower boundary temperature that is used to force ice sheet models. Beneath ice shelves it is the temperature at the ice-ocean interface. Beneath grounded ice, it is the temperature at the ice-bedrock interface. In all instances the temperature is that of the interface itself and not that of the medium above or below the interface.'
OK?
3. land_ice_surface_melt_flux (kg m-2 s-1)
' Loss of ice mass resulting from surface melting. Computed as the total surface melt water on the land ice portion of the grid cell divided by land ice area in the grid cell.'
The name and units are both fine.
Again, the wording of the definition needs to be made consistent with other names. Defining this as a 'surface' name means that only melting at the atmosphere-ice interface is included (I assume this is the intention). So as not to make the definition too prescriptive I have added the advisory sentence about using cell_methods to give additional information about the portion of the grid cell over which the quantity is calculated. I have also added a cross-reference to the existing name surface_snow_and_ice_melt_flux. Hence, I suggest:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. The surface called "surface" means the lower boundary of the atmosphere. The land_ice_surface_melt_flux is the loss of ice mass resulting from surface melting. For an area-average, the cell_methods attribute should be used to specify whether the average is over the area of the whole grid cell or the area of land ice only. There is also a standard name for the quantity surface_snow_and_ice_melt_flux.'
We should also add a cross-reference to this new name in the definition of surface_snow_and_ice_melt_flux.
OK?
4. land_ice_basal_specific_mass_balance_flux (kg m-2 s-1)
'Specific mass balance means the net rate at which ice is added per unit area at the land ice base. Computed as the total basal mass balance on the land ice portion of the grid cell divided by land ice area in the grid cell. A negative value means loss of ice.'
The proposed name is consistent with the existing name land_ice_surface_specific_mass_balance_flux (which is why I suggested it in the first place!) and the units are fine. Looking again at the existing name and its definition, I am starting to wonder whether we really need the word "flux" at all (perhaps Jonathan Gregory can comment on this). It seems to me that "specific mass balance" is defined as net addition of ice per unit area and that having "flux" in the name is simply repeating the fact that it is per unit area and therefore superfluous. Perhaps the names should really be land_ice_surface_specific_mass_balance and land_ice_basal_specific_mass_balance. I'd welcome other people's thoughts on this.
For the definition I suggest the following (the bit in square brackets would only be needed if we keep "flux" in the name):
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. Specific mass balance means the net rate at which ice is added per unit area at the land ice base. A negative value means loss of ice. [In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.] For an area-average, the cell_methods attribute should be used to specify whether the average is over the area of the whole grid cell or the area of land ice only.'
5. land_ice_specific_mass_flux_due_to_calving (kg m-2 s-1)
'Loss of ice mass resulting from iceberg calving. Computed as the rate of mass loss by the ice shelf (in kg s-1) divided by the horizontal area of the ice sheet (m2) in the grid box.'
I think calling this one a mass flux does make sense because it is a loss from the ice shelf and so there is a real flux from the shelf to floating icebergs. This is not a net quantity so it is a mass flux rather than a mass balance. However, I'm now thinking that we don't really need "specific" in this name because it's essentially just repeating the "per unit area" so perhaps this name should simply be land_ice_mass_flux_due_to_calving. Again I'd welcome comments on this point.
For the definition I suggest the following (the bit in square brackets would only be needed if we keep "specific" in the name):
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. "[Specific] mass flux due to calving" means the loss of land ice mass per unit area resulting from iceberg calving. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. 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. For an area-average, the cell_methods attribute should be used to specify whether the average is over the area of the whole grid cell or the area of land ice only.'
6. land_ice_specific_mass_flux_due_to_calving_and_ice_front_melting (kg m-2 s-1)
' Total mass balance at the ice front (or vertical margin). It includes both iceberg calving and melt on vertical ice front.'
As per my comments on proposal 5, I think perhaps we don't need "specific", so the name would then be land_ice_mass_flux_due_to_calving_and_ice_front_melting. The units are fine.
I am assuming the sign convention here is the same as in proposal 5, i.e. that a positive flux means an ice loss, and I suggest the following definition:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. "[Specific] mass flux due to calving and ice front melting" means the loss of land ice mass resulting from iceberg calving and melting on the vertical ice front. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. 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. For an area-average, the cell_methods attribute should be used to specify whether the average is over the area of the whole grid cell or the area of land ice only.'
7. water_flux_into_sea_water_from_land_ice (kg m-2 s-1)
' Computed as the water flux into the ocean due to land ice (runoff water from surface and base of land ice or melt from base of ice shelf or vertical ice front) into the ocean divided by the area ocean portion of the grid cell.'
The name and units are fine.
Fleshing out the definition for consistency with existing names I suggest:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The water flux into sea water from land ice is the freshwater entering as a result of runoff from the surface and base of the ice and melting from the ice shelf base and vertical ice front. For an area-average, the cell_methods attribute should be used to specify whether the average is over the area of the whole grid cell or the area of the ocean portion only.'
OK?
8. land_ice_surface_x_velocity (m s-1)
'u-velocity at land ice surface.'
The name and units look OK to me.
I notice that your name refers to 'x' component of velocity while your definition refers to 'u' component. In CF you could have either land_ice_x_velocity or land_ice_eastward_velocity as a standard name. Using 'x' means your data can be on any horizontal grid (as long as it is properly described in your file) whereas 'eastward' (which is what I would understand by u-velocity) may be a better choice if your data are on a lat-lon grid and your x coordinate really does mean degrees east. Which of these best fits your quantity?
The details of the definition depend on your choice of 'x' or 'eastward' . For 'x' it would be as follows:
'A velocity is a vector quantity. "x" indicates a vector component along the grid x-axis, positive with increasing x. "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The surface called "surface" means the lower boundary of the atmosphere.'
For 'eastward' it would be as follows:
' A velocity is a vector quantity. "Eastward" indicates a vector component which is positive when directed eastward (negative westward). "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The surface called "surface" means the lower boundary of the atmosphere.'
9. land_ice_surface_y_velocity (m s-1)
' v-velocity at land ice surface.'
The name and units are fine.
As per my comments on proposal 8, you have a choice between 'y' component or 'northward' component of velocity, depending on your horizontal grid. Which one best fits your data?
Again the definition depends on your choice of 'y' or 'northward'. For 'y' it would be:
' A velocity is a vector quantity. "y" indicates a vector component along the grid y-axis, positive with increasing y. "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The surface called "surface" means the lower boundary of the atmosphere.'
For 'northward' it would be:
' A velocity is a vector quantity. "Northward" indicates a vector component which is positive when directed northward (negative southward). ). "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. The surface called "surface" means the lower boundary of the atmosphere.'
10. land_ice_surface_upward_velocity (m s-1)
The name and units are fine.
For the definition I suggest:
'A velocity is a vector quantity. "Upward" indicates a vector component which is positive when directed upward (negative downward).'
OK?
11. land_ice_basal_upward_velocity (m s-1)
' Upward velocity at land ice surface.'
The name and units are fine.
For the definition I suggest:
'A velocity is a vector quantity. "Upward" indicates a vector component which is positive when directed upward (negative downward).'
OK?
12. magnitude_of_shear_stress_at_land_ice_base (Pa)
' The magnitude of the shear stress at land ice base'
13. magnitude_of_normal_stress_at_land_ice_base (Pa)
' The magnitude of the normal stress at land ice base'
14. magnitude_of_longitudinal_stress_at_land_ice_base (Pa)
' The magnitude of the longitudinal stress at land ice base'
The syntax of these three names is consistent with existing sea ice names. We have one existing "magnitude of stress" name, magnitude_of_surface_downward_stress, which represents the magnitude of the x/y or eastward/northward surface stress components and specifies "downward", i.e. positive when momentum is transferred from upper to lower medium. Should your quantities be regarded as "downward" (momentum passing from the ice to the underlying surface) or "upward"? Units of Pa are fine.
The definitions will of course depend on the sign conventions of the stresses:
' "magnitude_of_X" means magnitude of a vector X. ["Downward" indicates a vector component which is positive when directed downward (negative upward).] OR [" Upward" indicates a vector component which is positive when directed upward (negative downward).]'
Please can you also provide some brief descriptions of ice shear stress, normal stress and longitudinal stress that I can add into the definitions?
15. upward_geothermal_heat_flux_at_ground_level (W m-2)
'The geothermal heat flux beneath land ice is the geothermal heat flux at the ice-bedrock interface, where ground level means under the ice, in regions covered by land ice.'
We have an existing name similar to this proposal, upward_geothermal_heat_flux_at_sea_floor (W m-2), with which your name is consistent. We also have existing names upward_heat_flux_at_ground_level_in_snow and upward_heat_flux_at_ground_level_in_soil. I think it is OK to include 'geothermal' in your name as we do have a precedent for that. Assuming that your quantity is the heat entering the ice sheet model at its lower boundary, would it be better to call it 'upward_geothermal_heat_flux_at_ground_level_in_land_ice'? From your definition, I assume this quantity does not include any upward heat flux from the ocean into an ice shelf, so we should of course make that clear in the CF definition.
16. land_ice_mass (kg)
'The mass of land ice (glaciers, ice caps, ice sheet and ice shelves), computed as the ice volume times density.'
The name and units are fine.
We have two existing names, sea_ice_mass (currently undefined) and sea_water_mass defined as ' The quantity with standard name "sea_water_mass" is the total mass of liquid seawater in the global oceans, including enclosed seas.' Is your quantity globally integrated like the sea_water name or does it refer to the mass in an individual grid cell? We need to be clear in the definition. I think the method of calculation doesn't belong in the standard name definition (you could add it elsewhere, e.g., the comment attribute, for CMIP6 data).
17. land_ice_mass_not_displacing_sea_water (kg)
'The mass of land ice that does not displace sea water if removed, computed as the ice volume times density. It excludes ice shelves, and components of the grounded ice sheet that would not displace sea level (for example, in regions where the ice rests on a bedrock that sits below sea level).'
The name and units are fine.
As per my comments on proposal 16, is this a globally integrated or local quantity? Again, I don't think the method of calculation belongs in the standard name definition but it could be reported elsewhere in the metadata.
18. grounded_ice_sheet_area (m2)
' Total area of the grounded ice sheet, where grounded indicates that the ice rests on bedrock, and therefore excludes ice shelves.'
Units of m2 are fine. This name brings to mind a recent discussion we had about two existing names, sea_ice_area and sea_ice_extent and I think there are two possible approaches for your name.
The first approach would be to use the name as proposed, in which case it would need to be defined similarly to other X_area names:
' "X_area" means the horizontal area occupied by X within the grid cell. "Grounded ice sheet" means glaciers, ice-caps and ice-sheets resting on bedrock. It does not include ice shelves.'
Taking this route means that the name itself does not represent a total. You would instead need to include a cell_methods of "area: sum" and coordinate variables with bounds to delineate the area over which the land ice total area was calculated.
The second approach would be to have a name of grounded_ice_sheet_extent. You would need to supply coordinate variables with bounds to indicate the region of the earth over which the ice extent was calculated. By analogy with the sea_ice_extent name, this quantity would be regarded as a total area (so you wouldn't need the cell_methods), but it's important to note that it would be the total area of the grid cells containing land ice, rather than that of the land ice itself. Following the sea_ice_extent definition, the definition of your quantity would then be something like the following (you may or may not need the wording about thresholds, depending on how you identify your grid cells):
' The term grounded_ice_sheet_extent means the total area of all grid cells in which the grounded ice sheet area fraction equals or exceeds a threshold, often chosen to be 15 per cent. The threshold must be specified by supplying a coordinate variable or scalar coordinate variable with the standard name of grounded_ice_sheet_area_fraction. The horizontal domain over which the grounded ice sheet extent is calculated is described by the associated coordinate variables and coordinate bounds or by a coordinate variable or scalar coordinate variable with the standard name of "region" supplied according to section 6.1.1 of the CF conventions. "Grounded ice sheet" means glaciers, ice-caps and ice-sheets resting on bedrock. It does not include ice shelves.'
Either approach would be OK with me, so the choice of which name to use really depends on the details of how you calculate the area.
19. floating_ice_shelf_area (m2)
'Total area of the floating ice shelves, which is the land ice component that flows over sea water.'
Units of m2 are fine. As with proposal 18, this name could be the one proposed, or floating_ice_shelf_extent, with the appropriate definitions and accompanying coordinates and cell_methods attributes as appropriate. Again the best choice depends on the details of how the area is calculated.
20. grounded_ice_sheet_area_fraction (1)
'Fraction of grid cell covered by grounded ice sheet, where grounded indicates that the quantity correspond to the ice sheet that flows over bedrock.'
I note here also your proposal A3 to add a new entry of grounded_ice_sheet to the area_type table.
'Grounded ice sheet indicates where the ice sheet rest over bedrock and is thus grounded.'
These standard name and area type proposals are consistent and both look good. Certainly I agree that you need the new area type for use with cell_methods when describing many of your output variables.
Your area type proposal A1 for a new entry of ice_sheet, defined as 'Ice sheet indicates where ice sheets are present. It includes both grounded ice sheet resting over bedrock and ice shelves flowing over the ocean, but excludes ice-caps and glaciers (in contrast to land_ice, which includes all components)' also looks good to me and I agree that we should add it.
The definition of the ice_sheet (A1) area type excludes ice-caps and glaciers. But are they included in grounded_ice_sheet (A3)? I tend to think that they must be, because that would be consistent with the definition of your grounded_ice_sheet_area standard name. We need to ensure that the standard name and area type definitions are all consistent (and clear).
Regarding the proposed standard name, you note in your original proposal that either we can introduce the new name or you could use the existing name area_fraction with an area_type coordinate variable (which would then have a string value of "grounded_ice_sheet". Either approach is equally valid CF. We will in any case add the area_type. I don't have a strong view either way about whether to add the new standard name, so I'm happy to go with the majority view on this one.
21. floating_ice_sheet_area_fraction (1)
'Fraction of grid cell covered by ice sheet flowing over seawater (also called ice shelf).'
I note here also your proposal A2 to add a new entry of floating_ice_shelf to the area_type table.
'Floating ice shelf indicates where ice shelf are present. Ice shelf are the component of ice sheets that flows over the ocean.' I agree that this new area_type is needed and should be added to the table.
As with proposal 20, I don't have a strong opinion about whether we should also add the new standard name or just use area_type and area_fraction. Again I'm happy to go with the majority view.
22. land_ice_runoff_flux (kg m-2 s-1)
'Runoff flux over land ice is the difference between any available liquid water in the snowpack less any refreezing. Computed as the sum of rainfall and melt of snow less any refreezing or water retained in the snowpack'
The name and units both look fine.
To make the definition consistent with existing runoff names I suggest:
'Runoff is the liquid water which drains from land. If not specified, "runoff" refers to the sum of surface runoff and subsurface drainage. Runoff flux over land ice is the difference between any available liquid water in the snowpack due to rainfall and melting minus any refreezing and liquid water retained in the snowpack. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.'
OK?
23. magnitude_of_land_ice_basal_drag (Pa)
'The magnitude of basal drag at land ice base.'
I assume this quantity is essentially a deceleration of the land ice flow towards the sea? Is it perhaps the sum of the stress terms in proposals 12 - 14? Please can you provide a bit more detail about what is causing the drag?
24. tendency_of_land_ice_mass_due_to_surface_mass_balance (kg s-1)
'The total surface mass balance flux over land ice is a spatial integration of the surface mass balance flux.'
The name and units look sensible to me. You would need to use coordinate variables with bounds to describe the area over which the mass integration is calculated. We have the existing name land_ice_surface_specific_mass_balance_flux and clearly this new quantity is the spatial integration of that one. Now I'm wondering what is really meant here by 'surface' - does it mean the lower boundary of the atmosphere or the upper boundary of the ice (which may have snow lying on it)? I'm guessing the latter, so we may need to use something like 'ice_surface' in both the new and existing names to distinguish from our usual use of 'surface'.
I suggest the following wording for the definition:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. Mass balance means the net rate at which ice is accumulated. A negative value means loss of ice. "tendency_of_X" means derivative of X with respect to time. 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. The tendency in ice mass due to the [ice] surface mass balance is the spatial integral of the quantity with standard name land_ice_surface_specific_mass_balance_flux. The horizontal domain over which the quantity is calculated is described by the associated coordinate variables and coordinate bounds or by a coordinate variable or scalar coordinate variable with the standard name of "region" supplied according to section 6.1.1 of the CF conventions.'
We would also need some words about 'surface' or 'ice_surface' as appropriate. (The wording should also be updated if we decide to drop 'flux' from the mass balance name as discussed in proposal 4).
25. tendency_of_land_ice_mass_due_to_basal_mass_balance (kg s-1)
'The total basal mass balance flux over land ice is a spatial integration of the basal mass balance flux'.
The name and units look fine.
I suggest the following definition:
' "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves. Mass balance means the net rate at which ice is accumulated. A negative value means loss of ice. "tendency_of_X" means derivative of X with respect to time. The tendency of land ice mass is the spatially integrated mass balance. 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. The tendency in ice mass due to the basal mass balance is the spatial integral of the quantity with standard name land_ice_basal_specific_mass_balance_flux. The horizontal domain over which the quantity is calculated is described by the associated coordinate variables and coordinate bounds or by a coordinate variable or scalar coordinate variable with the standard name of "region" supplied according to section 6.1.1 of the CF conventions.'
(The wording should also be updated if we decide to drop 'flux' from the mass balance name as discussed in proposal 4).
26. tendency_of_land_ice_mass_due_to_calving (kg s-1)
'The total calving flux over land ice is a spatial integration of the calving flux.'
The name and units look fine.
I suggest the following definition:
' "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. 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. The tendency in ice mass due to calving is the spatial integral of the quantity named land_ice_specific_mass_flux_due_to_calving. The horizontal domain over which the quantity is calculated is described by the associated coordinate variables and coordinate bounds or by a coordinate variable or scalar coordinate variable with the standard name of "region" supplied according to section 6.1.1 of the CF conventions.'
(The wording should also be updated if we decide to drop 'specific' from the calving name as discussed in proposals 5 and 6).
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That concludes my comments on all the current ISMIP6 proposals. I appreciate that there is a lot to digest here so please don't feel you need to respond to all my comments in one go (unless you want to!) I'm happy to continue discussing the names in smaller batches if that is helpful and I think some of them can probably be agreed and accepted for publication fairly easily while others may need a bit more work.
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.
From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Nowicki, Sophie (GSFC-6150)
Sent: 03 October 2016 21:20
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] additional standard name for ISMIP6
Dear CF community,
On behalf of ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6), I wanted to add a few names to our initial request (29th October 2015, see below), and ask if 3 names in our initial request could be slightly modified.
I look forward to any comments that you may have,
Kind regards and many thanks,
Sophie on behalf of ISMIP6
Note, in all cases where land_ice is used, we follow the CF definition of?"Land ice" meaning glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves (the later is part of the ice sheet that flows over the ocean).
When ISMIP6 talks about ice sheet models, it generally includes both ice-sheets resting on bedrock and ice shelves, although some models may not include ice shelves. This is the reason that sometime "grounded" is used: to emphasis that when a model includes both ice sheet and ice shelf, we only want the grounded ice sheet part.
NEW STANDARD NAMES
Proposed standard name:?land_ice_runoff_flux
Units:?kg m-2 s-1
Long name:?Land ice runoff flux
Definition: Runoff flux over land ice is the difference between any available liquid water in the snowpack less any refreezing. Computed as the sum of rainfall and melt of snow less any refreezing or water retained in the snowpack
Proposed standard name:?magnitude_of_land_ice_basal_drag
Units: Pa
Long name:?Magnitude of land ice basal drag
Definition:?The magnitude of basal drag?at land ice base
Proposed standard name: tendency_of_land_ice_mass_due_to_surface_mass_balance
Units: kg s-1
Long name: Total surface mass balance flux
Definition: The total surface mass balance flux over land ice is a spatial integration of the surface mass balance flux
Proposed standard name: tendency_of_land_ice_mass_due_to_basal_mass_balance
Units: kg s-1
Long name: Total basal mass balance flux
Definition: The total basal mass balance flux over land ice is a spatial integration of the basal mass balance flux
Proposed standard name tendency_of_land_ice_mass_due_to_calving
Units: kg s-1
Long name: Total calving flux
Definition: The total calving flux over land ice is a spatial integration of the calving flux
Martin Juckes also suggested that ISMIP6 request for three new Area Types need to be added to the ?Area Type Table?. (
http://cfconventions.org/Data/area-type-table/4/build/area-type-table.html?). These are needed when a variable such as ?land_ice_basal_temperature? is a result of two different models (depending whether the land ice rests on the bedrock, or floats over the ocean). The ISMIP6 data request for the CMIP6 effort would then ask for 2 variables, using the same standard name but different cell methods and long names.
For example: with standard name: ?land_ice_basal_temperature?
On the side where land ice rest on bedrock:
short name: litempotl
standard name: land_ice_basal_temperature
long name: Basal temperature of grounded land ice
cell_methods:are: mean where grounded_ice_sheet
While on the side where land ice floats on sea water:
short name: litempoto
standard name: land_ice_basal_temperature
long name: Basal temperature of floating ice shelf
cell_methods:are: mean where floating_ice_shelf
A1) Proposed standard term to be added to the CF Area Type Table:?ice_sheet
Definition:?ice sheet indicates where ice sheet are present. It includes both grounded ice sheet resting over bedrock and ice shelves flowing over the ocean, but excludes ice-caps and glaciers (in contrast to land_ice, which includes all components).
A2) Proposed standard term to be added to the CF Area Type Table:?floating_ice_shelf
Definition:?floating ice shelf indicates where ice shelf are present. Ice shelf are the component of ice sheets that flows over the ocean.?
A3) Proposed standard term to be added to the CF Area Type Table:?grounded_ice_sheet
Definition:?grounded ice sheet indicates where the ice sheet rest over bedrock and is thus grounded.
MODIFICATION FROM 29th October 2015 email. Note that the names that?were?submitted have not yet been approved, hence why we suggest the modifications based on feedback that we have?received from our community:
Proposed standard name:?snow_land_ice_interface_temperature
Units: K
Long name:?Temperature at the interface between land ice and snow?
Definition:?Surface Temperature that is used to force ice sheet models. It is the temperature at the base of the snowpack models, and does not vary with seasons. Report surface temperature of ice sheet where snow ?thickness is zero
WAS INITIALLY PROPOSED AS: temperature_at_ground_level_in_snow_or_firn
MOTIVATION FOR ?CHANGE: ?initial name ?led to confusions (in particular the use of firn).
Proposed standard name:?grounded_ice_sheet_area
Units: m2
Long name: Area covered by grounded ice sheet
Definition:?Total area of the grounded ice sheet, where grounded indicates that the ice rests on bedrock, and therefore excludes ice shelves.
WAS INITIALLY PROPOSED AS:?grounded_land_ice_area
MOTIVATION FOR CHANGE: more consistent with another proposed standard name (grounded_ice_sheet_area_fraction, entry 20 in email of 29th October 2016)?
Proposed standard name:?floating_ice_shelf_area_fraction
Units: 1
Long name: Floating?Ice Shelf Area Fraction
Definition:?Fraction of grid cell covered by ice sheet flowing over seawater (also called ice shelf).
WAS INITIALLY PROPOSED AS:?floating_ice_sheet_area_fraction, (see entry 21)
MOTIVATION FOR CHANGE: the modification would allow for more symmetry with proposed name floating_ice_shelf_area (entry 19)?
Received on Thu Oct 06 2016 - 08:36:44 BST
