`air_pressure_at_sea_level` or `air_pressure_at_mean_sea_level` or both?

[ss421]

As part of a recent code sprint, we adopted the CCPP name air_pressure_at_sea_level. This replaced the variable name surface_pressure_at_mean_sea_level. It was pointed out after the sprint that the new name omits mean and others have questioned why mean was removed. Based on post sprint discussion we have had in the UKMO, we feel the omission of mean is potentially ambiguous.

In further discussion with others in JEDI, it was also pointed out that according to the CF convention, _sea_level is short for _mean_sea_level, so they're the same and that _sea_surface is the instantaneous sea surface. Its not clear to me why CF have two names for the same thing other than one had been established and changing it was difficult (if someone knows the actual reason then please let me know).

While digging into the CCPP I see that this variable was added in 2021 via: #10 so it is an established CCPP name. The suffex at_sea_level is a defined: https://github.com/ESCOMP/CCPPStandardNames/blob/583a37926449110445411b8efb4496b7e1497b93/StandardNamesRules.rst?plain=1#L173 although it does appear that it is only used by air_pressure.

Looking at the CCPP PR where this variable was added, there does not appear to be any discussion about the use of mean as we have highlighted here.

What do others think about this?

Tagging individuals involved in the original PR for further details and feedback: @cacraigucar @nusbaume @gold2718 @peverwhee

and those involved in the code sprint for referabce: @svahl991 @mikecooke77 @fmahebert @ncrossette @rtodling @sking112 @danholdaway @travissluka @BenjaminTJohnson @stemiglio

Thanks, Steve

[dudhia]

At mean sea level usually refers to pressures corrected to mean sea level which may be greater than the surface pressure over land. So it would be shorthand for corrected to mean sea level that involves an extrapolation from the surface using local temperatures. The intent is to remove elevation signals from the pressure.

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On Tue, Nov 5, 2024 at 6:07 AM Steven Sandbach ***@***.***> wrote: As part of a recent code sprint, we adopted the CCPP name air_pressure_at_sea_level. This replaced the variable name surface_pressure_at_mean_sea_level. It was pointed out after the sprint that the new name omits mean and others have questioned why mean was removed. Based on post sprint discussion we have had in the UKMO, we feel the omission of mean is potentially ambiguous. In further discussion with others in JEDI, it was also pointed out that according to the CF convention, _sea_level is short for _mean_sea_level, so they're the same and that _sea_surface is the instantaneous sea surface. Its not clear to me why CF have two names for the same thing other than one had been established and changing it was difficult (if someone knows the actual reason then please let me know). While digging into the CCPP I see that this variable was added in 2021 via: #10 <#10> so it is an established CCPP name. The suffex at_sea_level is a defined: https://github.com/ESCOMP/CCPPStandardNames/blob/583a37926449110445411b8efb4496b7e1497b93/StandardNamesRules.rst?plain=1#L173 although it does appear that it is only used by air_pressure. Looking at the CCPP PR where this variable was added, there does not appear to be any discussion about the use of mean as we have highlighted here. What do others think about this? Tagging individuals involved in the original PR for further details and feedback: @cacraigucar <https://github.com/cacraigucar> @nusbaume <https://github.com/nusbaume> @gold2718 <https://github.com/gold2718> @peverwhee <https://github.com/peverwhee> and those involved in the code sprint for referabce: @svahl991 <https://github.com/svahl991> @mikecooke77 <https://github.com/mikecooke77> @fmahebert <https://github.com/fmahebert> @ncrossette <https://github.com/ncrossette> @rtodling <https://github.com/rtodling> @sking112 <https://github.com/sking112> @danholdaway <https://github.com/danholdaway> @travissluka <https://github.com/travissluka> @BenjaminTJohnson <https://github.com/BenjaminTJohnson> @ytremolet <https://github.com/ytremolet> Thanks, Steve — Reply to this email directly, view it on GitHub <#82>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIZ77BGCFBCTQM5UWKWMZLZ7C7KLAVCNFSM6AAAAABRGQJZRSVHI2DSMVQWIX3LMV43ASLTON2WKOZSGYZTKNBRGIYTEOI> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[nusbaume]

In general I support the more verbose names for quantities, so in this case it would be _mean_sea_level, but at the same time I do think it is generally understood that _sea_level implies the mean sea level, as I am actually not sure how one would determine "sea level" on land without using the mean value.

In other words I think either option works for us here at NCAR-CGD.

Alternatively, we could also just specify in the rules that sea_level means the average value, and then just leave the actual standard names as-is, at least until we find a use case where that no longer works?

[dudhia]

It should also be understood that mean sea level is specifically a global altitude reference.

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On Tue, Nov 5, 2024 at 4:08 PM Jesse Nusbaumer ***@***.***> wrote: In general I support the more verbose names for quantities, so in this case it would be _mean_sea_level, but at the same time I do think it is generally understood that _sea_level implies the mean sea level, as I am actually not sure how one would determine "sea level" on land without using the mean value. In other words I think either option works for us here at NCAR-CGD. Alternatively, we could also just specify in the rules that sea_level means the average value, and then just leave the actual standard names as-is, at least until we find a use case where that no longer works? — Reply to this email directly, view it on GitHub <#82 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIZ77EPJKLUNRKAPVGX7KDZ7FFXNAVCNFSM6AAAAABRGQJZRSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDINJYGM3TQMJZGA> . You are receiving this because you commented.Message ID: ***@***.***>

[ss421]

Thank-you for the replies. We agree that being explicit about this is preferable and it seems fairly non-controversial and likely low impact. I'd be happy to progress that but its not urgent.

What do people think we should do?

[climbfuji]

I don't have a strong opinion, but in order to move this forward, shall we go with _mean_sea_level?

[dustinswales]

I concur with _mean_sea_level, just to avoid any ambiguity.

[dudhia]

I agree.

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On Wed, Dec 11, 2024 at 8:07 AM Dustin Swales ***@***.***> wrote: I concur with _mean_sea_level, just to avoid any ambiguity. — Reply to this email directly, view it on GitHub <#82 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIZ77BHBWCSDTISREUAHWD2FBIMTAVCNFSM6AAAAABRGQJZRSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMZWGI3DANZTGE> . You are receiving this because you commented.Message ID: ***@***.***>

[nusbaume]

I also agree!