add a variable for Florida Strait transports, volume and heat (sftrans, sfhtrans)

[jmecki]

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Please note that it is fine to group together a number of proposals in a single GitHub issue (i.e. it is not necessary to open a separate issue for each vocabulary term). Change proposals should include the following information as applicable.

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[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[jmecki]

Sorry forgot to add CMIP7 to the title

[sol1105]

@jmecki In the following my attempt to assist in this proposal. I would suggest the following standard_names for the CMIP7 variables you proposed:

Volume Transport Through Florida Strait

standard_name: ocean_volume_transport_across_line (existing standard name)
canonical units: [m3 s-1]
description: 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.

This is an already existing standard_name and you could add the actual description of the line (in this case the Florida Strait) as a variable comment or - as it was done in CMIP6 - as entry along an additional region character dimension of the data array - that means that the final dataset would have the following dimensions: time region, with region meaning: oline/region (character, opening, passage, strait, channel, etc.).

For example, for CMIP6 we submitted the variable mfo (sea water transport across line) for the following regions (i.e. entries of the character dimension): barents_opening,bering_strait,canadian_archipelago,denmark_strait,drake_passage,english_channel,pacific_equatorial_undercurrent,faroe_scotland_channel,florida_bahamas_strait,fram_strait,iceland_faroe_channel,indonesian_throughflow,mozambique_channel,taiwan_luzon_straits,windward_passage

Heat Transport Through Florida Strait

standard_name: ocean_heat_transport_across_line
canonical units: [W]
description: Ocean heat transport" means total heat transport by the ocean by all processes. 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.

This would be a new standard_name. I constructed it by using bits from the following existing standard_names: northward_atmosphere_heat_transport, ocean_heat_x_transport, ocean_volume_transport_across_line

[jmecki]

Thank you that sounds good. Would it be possible to also include a freshwater or salt transport variable?

i.e. ocean_salt_transport_across_line or ocean_freshwater_transport_across_line

[sol1105]

@jmecki you would need to propose these variables for the CMIP7 data request, as you did with the previous ones (https://wcrp-cmip.org/cmip7/cmip7-data-request/public-consultation/). When proposing the new variables you would be referencing this issue thread as the CF standard name proposal. The standard_names you suggested look fine to me. A full description could look like this:

Ocean Salt Transport Across Line

standard_name: ocean_salt_transport_across_line
canonical units: [kg s-1]
description: "Ocean salt transport" refers to the mass of salt being transported by the ocean by all processes. 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.

Related standard_names: northward_ocean_salt_transport, ocean_salt_x_transport, ocean_volume_transport_across_line

Ocean Freshwater Transport Across Line

standard_name: ocean_freshwater_transport_across_line
canonical units: [kg s-1]
description: Ocean transport means transport by all processes, both sea water and sea ice. 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.

Related standard_names: northward_ocean_freshwater_transport, ocean_volume_transport_across_line

I think it would be good, if you updated your initial post in this issue thread with the four descriptions we came up with, since so far the post only shows a template.

[taylor13]

I would have been happier if the existing names for salt transport had somewhere included the word "mass", since several different quantities associated with a substance can be transported by it (mass, energy, momentum, volume, moles, ...). With river fluxes, we were clear with names like water_volume_transport_in_river_channel and carbon_mass_transport_in_river_channel, and I hope if it is requested, we would define water_mass_transport_in_river_channel, rather than water_transport_in_river_channel. I think this would avoid misinterpretation.

All this is to suggest replacing in #218 (comment) ocean_salt_transport_across_line with ocean_salt_mass_transport_across_line.

[As a footnote regarding the CMIP7 data request, it is good practice (and reduces the size of the data request) if we avoid defining variables that can be obtained through simple subtraction (or any other simple operation) from existing variables. Given that to excellent approximation the total mass transport is just the some of the freshwater transport and the ocean salt mass transport, request only 2 of these 3 variables.]

[github-actions]

This issue has had no activity in the last 30 days. Accordingly:

• If you proposed this issue or have contributed to the
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• If there has been little or no discussion, please comment
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• If the proposal seems to have come to a consensus, please
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Standard name moderators are also reminded to review @feggleton @japamment @efisher008

[efisher008]

Dear Jenny @jmecki,

Was there an outcome from this proposal in the CMIP7 data request? If you could provide an update on the status of the names suggested in this issue, that would be very appreciated.

Best regards,
Ellie

[github-actions]

This issue has had no activity in the last 30 days. Accordingly:

• If you proposed this issue or have contributed to the
  discussion, please reply to any outstanding concerns.
• If there has been little or no discussion, please comment
  on this issue, to assist with reaching a decision.
• If the proposal seems to have come to a consensus, please
  wait for the moderators to take the next steps towards
  acceptance.

Standard name moderators are also reminded to review @feggleton @japamment @efisher008

[japamment]

Dear Jenny and Martin, @jmecki @sol1105

Thank you for proposing these ocean transport names and thank you @taylor13 for commenting. Apologies for the delay in looking in detail at these proposals.

Martin has pointed out that we already have an existing name ocean_volume_transport_across_line which can be used for the first CMIP7 variable, so that one is fine.

However, I have a general question which occurred to me when reading through all our existing ocean transport names as well as the ones proposed in this issue. The great majority of the existing names have a clear sign convention associated with them, for example, northward_ocean_heat_transport or ocean_heat_x_transport, where northward is defined as ' "Northward" indicates a vector component which is positive when directed northward (negative southward)' and x is defined as ' "x" indicates a vector component along the grid x-axis, positive with increasing x.' This prompts me to ask how is sign handled in quantities for transport across a line, especially as a line could potentially be at any orientation on the earth's surface? I think we should if possible add a sign convention to all the transport_across_line names, both existing and proposed, and provide some additional text in the descriptions.

Regarding the individual propoals in this issue, I have the following comments:
(1) ocean_heat_transport_across_line
Units: W
Description: "Ocean heat transport" means total heat transport by the ocean by all processes. 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.

For the existing standard name northward_ocean_heat_transport, we use the following description:
'Ocean transport means transport by all processes, both sea water and sea ice'.

Would you be happy to use this existing wording which could apply to a line anywhere on the earth's surface? (I appreciate that sea ice is unlikely to be present in the Florida Strait!). In looking at this name, I've realised that many existing ocean heat transport names are in fact missing this part of the description, so if we can agree the wording I will apply it to all the existing names as well as the one proposed here.

The question about sign convention is relevant to this proposal, so we may need to add more text in the description.

(2) ocean_salt_transport_across_line
Units: kg s-1
Description: "Ocean salt transport" refers to the mass of salt being transported by the ocean by all processes. 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.

I agree with the suggestion from @taylor13 to change this one to ocean_salt_mass_transport_across_line for clarity and consistency with ocean heat transport names and river mass transport names. I agree also that this should apply to existing names, hence we would need to create the following seven aliases:
northward_ocean_salt_transport -> northward_ocean_salt_mass_transport
northward_ocean_salt_transport_due_to_diffusion -> northward_ocean_salt_mass_transport_due_to_diffusion
northward_ocean_salt_transport_due_to_gyre -> northward_ocean_salt_mass_transport_due_to_gyre
northward_ocean_salt_transport_due_to_overturning -> northward_ocean_salt_transport_due_to_overturning
northward_ocean_salt_transport_due_to_parameterized_eddy_advection -> northward_ocean_salt_mass_transport_due_to_parameterized_eddy_advection
ocean_salt_x_transport -> ocean_salt_mass_x_transport
ocean_salt_y_transport -> ocean_salt_mass_y_transport

The question about sign convention is relevant to this proposal, so we may need to add more text in the description.

(3)ocean_freshwater_transport_across_line
Units: kg s-1
Description: Ocean transport means transport by all processes, both sea water and sea ice. 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.

For consistency with Karl's comments regarding mass transport for salt, I suggest that we also clarify in this name that we are talking about mass of freshwater, so it would become ocean_freshwater_mass_transport_across_line.

As with proposals (1) and (2), the question about sign convention is relevant, so we may need to add more text in the description.

[JonathanGregory]

Dear Alison @japamment , Jenny @jmecki, Karl @taylor13 et al.

That's a good question about the sign convention of across_line transports. It's interesting that it wasn't noticed before! For CMIP6, Griffies et al. 2016 list the set of "lines" in Appendix J, Tables J1 and J2. Their names are in the CF region list e.g. florida_bahamas_strait, bering_strait. In general, a transport "across line" would be perpendicular to that line, but all the CMIP6 lines are north-south or east-west. Griffies et al. say

For many ocean model grids, the requested transports can be diagnosed by aligning the section along a model grid axis. In this case, it is straightforward to assign a positive sign to transports going in a pseudo-north or pseudo-east direction, and negative signs for the opposite direction. We use the term pseudo here as it refers to an orientation according to the model grid lines, which in general may not agree with geographical longitude and latitude lines. The sign convention chosen for the recorded transport should be indicated in the metadata information for the transport field.

They don't say what to do if neither model grid direction is close to the direction of the line. They would expect the modeller to choose something oceanographically appropriate.

I suggest that it might be better to use names for the currents, instead of the regions. Then we could indicate their sign conventions as part of these names. In fact a couple of them are already names of currents e.g. pacific_equatorial_undercurrent, which could be changed to eastward_pacific_equatorial_undercurrent. We could keep the current names in the regions table, if we generalised its name from "region names" e.g. to "geographical names".

I notice that the sign is not stated also for the river transports. I assume these are implicitly downstream, but should we include that word?

Best wishes

Jonathan