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Add some marine variables #131

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f7fd6ba
Add some marine variables
svahl991 Dec 31, 2025
2cfaeb5
Update md file
svahl991 Dec 31, 2025
7c9475d
Differentiate between practical and absolute salinity
svahl991 Jan 2, 2026
36f43b1
update md file with script
svahl991 Jan 2, 2026
bd83e9b
Conform to CF naming
svahl991 Jan 2, 2026
c5f139e
Update md file with script
svahl991 Jan 2, 2026
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12 changes: 12 additions & 0 deletions Metadata-standard-names.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
* [coordinates](#coordinates)
* [state_variables](#state_variables)
* [land_surface](#land_surface)
* [marine](#marine)
* [diagnostics](#diagnostics)
* [atmospheric_composition](#atmospheric_composition)
* [atmospheric_composition: GOCART aerosols](#atmospheric_composition-gocart-aerosols)
Expand Down Expand Up @@ -544,6 +545,17 @@ Note that appending '_on_previous_timestep' to standard_names in this section yi
* `real`: units = m3 m-3
* `volume_fraction_of_liquid_water_in_soil_at_wilting_point`: volume fraction of water in liquid phase in soil at wilting point
* `real`: units = m3 m-3
## marine
* `potential_temperature_of_sea_water`: sea water potential temperature
* `real`: units = K
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@Dooruk Dooruk Jan 5, 2026

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I will comment here that while K is used in some products, degC is more common. MOM6 (model SOCA interfaces) outputs model fields in degC. Looking at a few common products I see they differ though, like so:

OISST, SODA, ORAS5 uses degC
EN4, OSTIA (GHRSST) uses K

I guess we can't make up our mind.

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@twsearle twsearle Jan 6, 2026 •
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just a note here that GHRSST includes a lot of members from all over the world https://www.ghrsst.org/about-ghrsst/ not just OSTIA (Australian Bureau Of Meterology, NOAA, Canadian Meterological and Oceanographic Society, among many others from elsewhere in Europe etc). See here for a list:
https://www.ghrsst.org/ghrsst-data-services/for-sst-data-producers/ghrsst-catalogue/#/search?from=1&to=30

The GHRSST conventions follow the CF conventions as far as possible with a little extra metadata. Documented in GDS2.1 (page 83, convention is Kelvin for SST variable there).

* `sea_water_depth`: The depth below the surface of the sea
* `real`: units = m
* `sea_water_salinity`: The practical salinity of sea water
* `real`: units = PSU
* `sea_water_absolute_salinity`: The absolute salinity of sea water
* `real`: units = g kg-1
* `sea_water_temperature`: The temperature of sea water
* `real`: units = K
## diagnostics
* `total_precipitation_rate_at_surface`: Total precipitation rate at surface
* `real`: units = m s-1
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22 changes: 22 additions & 0 deletions standard_names.xml
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Expand Up @@ -1000,6 +1000,28 @@
<type units="m3 m-3">real</type>
</standard_name>
</section>
<section name="marine">
<standard_name name="potential_temperature_of_sea_water"
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@guillaumevernieres guillaumevernieres Jan 5, 2026

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sea_water_potential_temperature to stay consistent with the salinity naming convention that you define below.

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@svahl991 svahl991 Jan 5, 2026

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sea_water_potential_temperature to stay consistent with the salinity naming convention that you define below.

I've commented above on why I have this naming inconsistency.

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@guillaumevernieres guillaumevernieres Jan 5, 2026

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@svahl991 Oops, sorry, I missed your comment. Should we follow the same convention for salinity then?

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@svahl991 svahl991 Jan 5, 2026

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Should we follow the same convention for salinity then?

Do you mean salinity_of_sea_water instead of sea_water_salinity? I thought about that, but decided it was silly since I don't think you would measure salinity of air. There's a whole list of rules about how to construct ESM names, and the first rule is to use CF names if a good one exists that doesn't cause naming inconsistencies. I feel the CF names for salinity are OK, and right now we're just deciding how many of the CF salinity names to add to ESM, and what units they should have.

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@guillaumevernieres guillaumevernieres Jan 5, 2026 •
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FYI @svahl991 : the CF name for sea water potential temperature is sea_water_potential_temperature ... Most of the naming convention in soca attemps to follow CF.

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@svahl991 svahl991 Jan 5, 2026

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ESM naming has diverged from CF naming in some aspects. I notice that CF has air_potential_temperature and ESM has potential_temperature_of_air. Whatever the reasoning was for that divergence, I suspect it would apply to sea water as well. I know this causes inconvenience for models using CF naming. I don't know what the reasoning was for this divergence, but I know a lot of discussion went into it.

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@twsearle twsearle Jan 6, 2026

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just to say, met office marine models have already been using the sea_water_potential_temperature CF names for multiple years. I think we notified that we wanted these in these standards a few years ago? CF standard names would be preferred if you want to share with other modelling centers? @svahl991 has a spreadsheet with the names we discussed on it somewhere I think.

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@guillaumevernieres guillaumevernieres Jan 7, 2026

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just to say, met office marine models have already been using the sea_water_potential_temperature CF names for multiple years. I think we notified that we wanted these in these standards a few years ago? CF standard names would be preferred if you want to share with other modelling centers? @svahl991 has a spreadsheet with the names we discussed on it somewhere I think.

+1 to @twsearle 's post above, keeping the CF name would be preferential.

description="sea water potential temperature">
<type units="K">real</type>
</standard_name>
<standard_name name="sea_water_depth"
description="The depth below the surface of the sea">
<type units="m">real</type>
</standard_name>
<standard_name name="sea_water_salinity"
description="The practical salinity of sea water">
<type units="PSU">real</type>
</standard_name>
<standard_name name="sea_water_absolute_salinity"
description="The absolute salinity of sea water">
<type units="g kg-1">real</type>
</standard_name>
Comment on lines +1012 to +1019
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@svahl991 svahl991 Jan 2, 2026

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I took a look at the CF conventions, and added their names for these two quantities. It looks to me like CF uses ppt, not PSU for the units of sea_water_salinity. But I stuck with PSU here since that is what @Dooruk and @travissluka recommended.

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@svahl991 svahl991 Jan 2, 2026

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OK, I looked again, closer, and CF naming has three names:

  • sea_water_salinity with units of 1e-3 (which I think means the same as ppt?)
  • sea_water_practical_salinity with units of 1 (which Travis says is the same as PSU)
  • sea_water_absolute_salinity with units of g kg-1

Do we want to duplicate all three names in ESM? I need scientific guidance here.

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@lren20 lren20 Jan 5, 2026

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@Dooruk referred me to this issue.
Here are my suggestions and perspective on this issue:

sea_water_salinity with units of 1e-3 (which I believe is equivalent to ppt): I don’t think it is necessary to keep this variable, as it reflects an older and less precise definition of salinity.

sea_water_practical_salinity with units of 1 (which Travis noted is equivalent to PSU): This variable should be retained, as it is consistent with in-situ observations and is useful for validation and diagnostic analyses.

sea_water_absolute_salinity with units of g kg⁻¹: This represents the most recent and precise definition of salinity and is therefore also worth keeping.

If only one salinity variable were to be retained, I would lean toward sea_water_absolute_salinity, assuming it comes directly from the model output.

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@svahl991 svahl991 Jan 5, 2026

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Thanks, @lren20 , for your insights. That's very helpful. Since these variables are all new to this ESM naming standard, we are free to do what makes sense and is clear for the modern community. We can look to CF naming for insight, but don't need to be constrained by it. Given what you've said, I propose we add two salinity names to ESM Naming in this PR:

  1. Either sea_water_salinity or sea_water_practical_salinity, with units of PSU either way. Going with sea_water_salinity probably means fewer changes in legacy code, but we would be changing the units for this name from the CF convention, so we're possibly introducing some confusion there. Conversely, using sea_water_practical_salinity for the ESM name conforms to the CF standard and is completely unambiguous, but probably requires more changes to legacy code, since then sea_water_salinity will not be an ESM name.
  2. Also add the name sea_water_absolute_salinity with units of g kg-1, since this is the most recent and precise salinity definition.

Regarding the two options described in 1) above, currently this PR contains sea_water_salinity with units of PSU. I'm now leaning toward changing this name to sea_water_practical_salinity. Then the ESM names would be consistent with CF, but would be missing the older, somewhat ambiguous term sea_water_salinity.

I will make that change later today unless I hear objections.

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@Dooruk Dooruk Jan 5, 2026 •
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  1. I would rather stick with sea_water_practical_salinity but that would require SOCA changes and potential downstream impacts for EMC and GMAO.
  2. Sounds good

i will ask @sinakhani and @guillaumevernieres input here (please see temperature unit comment above as well).

@ss421 I see this turned out to be a can of worms, we could also discuss it during the Thursday JCSDA meeting?

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@svahl991 svahl991 Jan 5, 2026

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I would rather stick with sea_water_practical_salinity but that would require SOCA changes and potential downstream impacts for EMC and GMAO.

To be clear, it is only in JEDI generic code (such as VADER, SABER, and UFO) where we make a strong attempt to conform to using ESM names for the model variables. This is because it is most important in generic code to be clear and unambiguous about what the variables represent (and what units they have) since the code can be used by multiple models and organizations. So if, say, we choose to use the ESM name sea_water_practical_salinity in the VADER code, that doesn't mean all of SOCA needs to change all its code to using that name. It just means SOCA will need to do a variable name change when it passes the variable into VADER. This sort of thing is done in multiple model interfaces to JEDI.

We also need to make sure we know which salinity units are appropriate for the new VADER code that inspired this PR (referenced in the PR description), so that we are sure to have an appropriate name for use there. (i.e., if the code formulas in VADER are expecting salinity to be in ppt, then we better have a name with those units.)

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@Dooruk Dooruk Jan 5, 2026

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Ok thanks, that separation makes more sense now.

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@sinakhani sinakhani Jan 5, 2026

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I think [ppt] is identical to [g/kg] based on their definitions. If I am also not wrong, 1 PSU should approximately equal to 1 ppt in oceanography (PSU is more recent definition for salinity but ppt is an older one). I expect all these three variables to be very close -- are they very different in your data outputs?

For temperature, I think it is a choice to use degC or K since they only differ by a constant 273.15. As long as the dataset gives a unit for temperature, either choice is fine in my view.

<standard_name name="sea_water_temperature"
description="The temperature of sea water">
<type units="K">real</type>
</standard_name>
</section>
<section name="diagnostics">
<standard_name name="total_precipitation_rate_at_surface">
<type units="m s-1">real</type>
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