[CF-metadata] SIMIP: 5 standard names and one area type for CMIP6

From: Dirk Notz <dirk.notz>
Date: Tue, 19 Jun 2018 21:54:21 +0200

Dear Alison,

thanks for your thoughtful summary. I agree with all your comments,
except for the following:

> ' "Sea_ice" means all ice floating on the sea with the exception of floating ice shelves, which are regarded as land ice in models.' Is this an accurate description? As you will see, I have already added this definition to names that I have accepted. However, I can adjust the definitions before publishing the names if we need to make any changes to the suggested text.

Sea ice does neither include icebergs nor snow drifting in the water,
for example. Maybe this definition works better:
"Sea ice means all ice floating in the sea which has formed from
freezing sea water"

> 1.14 Proposed as tendency_of_surface_snow_amount_due_to_drifting [kg m-2 s-1]
> the rate of change of snow mass through wind drift of snow divided by
> grid-cell area
>
> The name and units look fine. I have added a definition as follows:
> tendency_of_surface_snow_amount_due_to_drifting (kg m-2 s-1)

Martin's suggestion tendency_of_surface_snow_amount_due_to_drifting_into_sea
captures indeed better what this variable is meant to imply.

> 1.19 salt_flux_into_sea_water_from_sea_ice [kg m-2 s-1]
> Total flux of salt from water into sea ice divided by grid-cell area;
> salt flux is upward (negative) during ice growth when salt is embedded
> into the ice and downward (positive) during melt when salt from sea ice
> is again released to the ocean
>
> Does this one represent salt fluxes at the sea ice base and due to lateral growth and melting?

Yes, it does.

> 28. sea_ice_mass_transport_across_line [kg s-1]
> "net (sum of transport in all directions) sea ice mass transport through
> given passages, positive into the Arctic Ocean
>
> For this quantity it was agreed to use the existing name sea_ice_transport_across_line. However, in the same way that we normally qualify the term 'flux' in standard names, e.g. mass_flux, heat_flux, longwave_flux, etc., I think it would be preferable to describe the existing transport names as mass_transport when that is what is intended. We already have volume_transport and heat_transport names and 8 existing ocean mass_transport names. Thus I suggest creating the alias sea_ice_transport_across_line -> sea_ice_mass_transport_across_line.

I am happy with this suggestion.
I don't have a strong opinion on the inclusion of
"*water_mass_transport*" as an alias for "water_transport".

>
> 29. sea_ice_area_transport_across_line [kg s-1]
> "net (sum of transport in all directions) sea ice area transport through
> given passages, positive into the Arctic Ocean
>
> This is a new quantity to standard names and this particular proposal did not receive any comments during the original discussion. I think it would be okay to introduce area_transport for a quantity such as sea_ice, but the units should then surely be m2 s-1. Then we would have:
> sea_ice_area_transport_across_line (m2 s-1)
> 'Transport "across_line" means that which crosses a particular line on the Earth's surface; formally this means the integral along the line of the normal component of the transport. "Sea_ice" means all ice floating on the sea with the exception of floating ice shelves, which are regarded as land ice in models.'
>
> Okay?

Yes, it should be m2 s-1. Thanks for catching this!

>> (1) siflfwdrain Freshwater flux from sea-ice surface [kg m-2 s-1]
>>
>> I think this variable was added later than the others. We already have, in the CF editor: water_flux_into_sea_water_from_sea_ice
>>
>> The variable name refers to the process of drainage, so I suggest we use the standard name construction referring to a specific process:
>> water_flux_into_sea_water_from_sea_ice_due_to_surface_drainage
>>
>
> The water_flux_into_sea_water_from_sea_ice name you refer to in the editor was Dirk's proposal 1.20, for which it was eventually agreed the existing name water_flux_into_sea_water_due_to_sea_ice_thermodynamics should be used. Using a similar due_to_process pattern would be appropriate for the proposed quantity and I wonder whether it would be useful to be even more explicit about the source of the water being drained. I suggest something like
> water_flux_into_sea_water_due_to_drainage_from_melt_ponds (kg m-2 s-1)
> '"Water flux into sea water" means the freshwater entering the sea water as a result of precipitation, evaporation, river inflow, sea ice effects and water flux correction (if applied). 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. Melt ponds occur on top of the existing sea ice.'
>
> We already use the term "melt pond" in area types, I think we could also use it in standard names. What do you think?

The term melt pond is too restrictive. Most models will simply transfer
any meltwater from snow melt directly into the ocean, without any
intermediate ponding in melt ponds. Hence, I prefer
"_due_to_surface_drainage" as it captures all freshwater flux and not
only the one from melt ponds implied by "_drainage_from_melt_ponds".

I'll get back to you regarding
>> (3a) sishevel Maximum shear strain rate of sea-ice velocity field (s-1)
>> (3b) sistremax Maximum shear stress in sea ice (N m-1)
>> (3c) sistresave Average normal stress in sea ice (N m-1)
after consultation with more knowledgeable people :-)

Thanks again.

 Dirk
Received on Tue Jun 19 2018 - 13:54:21 BST