Dear Dirk and Martin,
Thank you both for looking through all the SIMIP proposals again.
Thank you, Dirk, for providing a better definition of sea ice. I've taken your sentence and added a little more, in the hope of making the intention as clear as possible: ' "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.' Is that okay?
1.14 Martin suggested, and we are now agreed, that this one should be:
tendency_of_surface_snow_amount_due_to_drifting_into_sea (kg m-2)
' The phrase "tendency_of_X" means derivative of X with respect to time. "Amount" means mass per unit area. The phrase "surface_snow" means snow lying on the surface. 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 quantity with standard name tendency_of_surface_snow_amount_due_to_drifting is the rate of change of snow amount caused by wind drift of snow into the sea. The snow is assumed to melt as soon as it enters the sea.'
I have amended the definition slightly, based on Martin's explanation.
Martin wrote:
> Mass fluxes and transports.
> I note that there are also 15 terms referring to "water_flux" and one using "liquid_water_mass_flux". We also 12 "precipitation_flux" terms
> which are mass fluxes (and no precipitation_mass_flux terms). I would hold off on this change for now, and try to look at the issue in more detail.
> It is a good idea to rationalise the usage here, but I'd hesitate to make so many changes without more time for consideration.
Okay, that's a fair point. I won't create the suggested aliases for now and that will give time to discuss the issue in a separate thread. For proposal 28 (which uses the existing name sea_ice_transport_across_line) I will also not make the alias for the time being, so the name will stay as it is.
>
> 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?
Dirk wrote:
> Yes, it should be m2 s-1. Thanks for catching this!
Okay, thank you. This name is now accepted for publication in the standard name table and will be added in the July 2nd update.
I think this concludes the discussion of Dirk's original proposals.
>> (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".
Okay, thank you. In that case, let's go with Martin's original proposal:
water_flux_into_sea_water_from_sea_ice_due_to_surface_drainage (kg m-2 s-1)
'The water flux into the ocean is 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. "Surface drainage" refers to all water melting at the sea ice surface and subsequently running into the sea.'
Is this okay?
This name is still under discussion.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
-----Original Message-----
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> On Behalf Of Dirk Notz
Sent: 19 June 2018 20:54
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] SIMIP: 5 standard names and one area type for CMIP6
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
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Received on Thu Jun 21 2018 - 00:43:32 BST
