Variables for ocean surface waves

[andrelanfer]

As discussed within the Sea-Ice and Ocean Task Team I would like to propose some new standard names, divided in 3 groups: total wave, swell wave and sea wave

Total Wave Name: swh Title: Total Significant Wave Height CF Standard Name: ocean_surface_significant_wave_height Units: m Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model , wave Height

Name: mpw Title: Total Waves Mean Period CF Standard Name: ocean_surface_wave_mean_period Units: s Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, mean period

Name: wpp Title: Total Waves peak period CF Standard Name: ocean_surface_wave_peak_period Units: s Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, spectral peak period

Name: wdir Title: Total Waves Direction CF Standard Name: ocean_surface_wave_direction Units: degrees Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, mean wave direction

Swell Wave

Name: swellswh Title: Swell Significant Wave Height CF Standard Name: ocean_surface_significant_wave_height_swell Units: m Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model , swell wave height

Name: swellmpw Title: Swell Waves Mean Period CF Standard Name: ocean_surface_wave_mean_period_swell Units: s Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, swell mean period

Name: swellwpp Title: swell waves peak period CF Standard Name: ocean_surface_wave_peak_period_swell Units: s Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, swell spectral peak period

Name: swellwdir Title: swell waves direction CF Standard Name: ocean_surface_wave_direction_swell Units: degrees Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, swell mean wave direction

Sea Wave

Name: seaswh Title: Sea Significant Wave Height CF Standard Name: ocean_surface_significant_wave_height_sea Units: m Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model , sea wave height

Name: sealmpw Title: Sea waves mean period CF Standard Name: ocean_surface_wave_mean_period_sea Units: s Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, sea mean period

Name: seawpp Title: sea waves peak period CF Standard Name: ocean_surface_wave_peak_period_sea Units: s Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, sea spectral peak period

Name: seawdir Title: sea waves direction CF Standard Name: ocean_surface_wave_direction Units: degrees Description: Wind driven surface gravity waves at the ocean surface, generated by the wave model, sea mean wave direction

Thank's for considering this proposal Proposer's name: André Lanfer Date: 16 September 2024

[github-actions[bot]]

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.

[JonathanGregory]

Dear @andrelanfer

Thanks for your proposals. I suspect that many or all of the quantities you wish to name can already be found in the standard name table, but they start with sea_surface, not ocean e.g. the first one is sea_surface_wave_significant_height. Please could you check?

Best wishes

Jonathan

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

[efisher008]

Dear @andrelanfer,

Thank you for your proposal. The following names are already in the standard names table that I could find approximating your proposed terms:

• Your name: ocean_surface_significant_wave_height Table name: sea_surface_wave_significant_height Units: m

• Your name: ocean_surface_wave_mean_period Table name: sea_surface_wave_mean_period Units: s

• Your name: ocean_surface_wave_direction Table name: sea_surface_wave_from_direction Units: degrees

• Your name: ocean_surface_significant_wave_height_swell Table name: sea_surface_swell_wave_significant_height Units: m

• Your name: ocean_surface_wave_mean_period_swell Table name: sea_surface_swell_wave_mean_period Units: s

• Your name: ocean_surface_wave_direction_swell Table name: sea_surface_swell_wave_from_direction Units: degrees

I could not find any existing names relating to sea_surface and peak_period.

I also wanted to ask the difference between ocean_surface_significant_wave_height and ocean_surface_significant_wave_height_sea. Is the only distinction that ocean_surface_significant_wave_height_sea is specified in a "sea" area type? What is the reasoning for these being separate terms (and indeed the other names which only differ by adding the suffix _sea, e.g. ocean_surface_wave_peak_period_sea vs. ocean_surface_wave_peak_period)?

I also believe that your last name, seawdir, is meant to have the _sea suffix to distinguish it from the wdir term proposed above i.e. ocean_surface_wave_direction.

Thank you and kind regards, Ellie Fisher

[ChrisBarker-NOAA]

I also wanted to ask the difference between ocean_surface_significant_wave_height and ocean_surface_significant_wave_height_sea.

In the wave world, we often make the distinction between "seas": the locally generated, shorter period waves, and "swell": the long period waves, usually generated far away. In many cases, there is a clear distinction between these in the wave spectrum.

I think that's what these mean:

ocean_surface_significant_wave_height: the significant wave height calculated from the entire spectrum.

ocean_surface_significant_wave_height_sea: the significant wave height calculated from just the "seas", i.e. the short period waves, portion of the spectrum.

[JonathanGregory]

I guess the distinction that @ChrisBarker-NOAA mentions is the one between "wind waves" and "swell waves". We already have distinct standard names for these, as well as combined ones e.g.

sea_surface_wave_significant_height
sea_surface_swell_wave_significant_height
sea_surface_wind_wave_significant_height

[ChrisBarker-NOAA]

yes, that's right :-) -- at least from my perspective, the OP might have a different definition of "seas" -- but looking now, I think my interpretation is correct -- "seas" == "wind waves"

[efisher008]

Dear @ChrisBarker-NOAA, @JonathanGregory,

If I interpreted your replies correctly, it would be appropriate to change your "sea wave" names (which use the suffix _sea refer to locally generated, shorter period waves) to instead include wind_wave? In doing so, they become these:

• ocean_surface_significant_wave_height_sea -> ocean_surface_significant_wind_wave_height

• ocean_surface_wave_mean_period_sea -> ocean_surface_wind_wave_mean_period - we have the existing standard name sea_surface_wind_wave_mean_period - is this suitable?

• ocean_surface_wave_peak_period_sea -> ocean_surface_wind_wave_peak_period

• ocean_surface_wind_wave_direction - there is the existing name sea_surface_wind_wave_directional_spread, but I'm not convinced this is describing the same quantity (the spread is "the directional width of the wind wave component of a sea").

The description of windwave in the CF phrase list is as follows: "Wind waves are waves on the ocean surface and are the high frequency portion of a bimodal wave frequency spectrum."_

Best wishes, Ellie

[ChrisBarker-NOAA]

That (sea => wind_wave) looks good to me - -but we should get the OP's confirmation.

As for: ocean_surface_wind_wave_direction there is the existing name sea_surface_wind_wave_directional_spread

that is not the same -- again, we need to ask the OP -- but I think this is the existing:

sea_surface_wind_wave_from_direction

unless someone wants the "to" rather than "from" version.

[JonathanGregory]

I agree with Chris. All the existing wave names have sea_surface, not ocean_surface. There are about 90 of them! Among them are

sea_surface_wind_wave_significant_height
sea_surface_wind_wave_from_direction
sea_surface_wind_wave_to_direction
sea_surface_wind_wave_mean_period
sea_surface_wind_wave_period

so I think we may already have what is needed.

[JonathanGregory]

Sorry - spoke too soon. We don't have a "peak" period. I wonder what this means. If it's the period corresponding to the peak in the spectrum, then maybe sea_surface_wind_wave_period_at_variance_spectral_density_maximum is appropriate.

[efisher008]

Hi @andrelanfer @ChrisBarker-NOAA,

Do you have an opinion on the new name structure suggested by @JonathanGregory for names including peak_period? If I understood right (please correct me if not, Jonathan!), this period_at_variance_spectral_density_maximum phrase can be used in the following 3 proposed names like so:

• ocean_surface_wave_peak_period -> sea_surface_wave_period_at_variance_spectral_density_maximum

• ocean_surface_wave_peak_period_swell -> sea_surface_swell_wave_period_at_variance_spectral_density_maximum

• ocean_surface_wave_peak_period_sea -> sea_surface_wind_wave_period_at_variance_spectral_density_maximum

@andrelanfer, it would also be great to know if you are satisfied with using the existing names found for these 6 proposed names in place of adding new names...

As well as using these existing names for the (other) 3 proposed _sea names (history here, here and here):

• ocean_surface_significant_wave_height_sea -> ocean_surface_significant_wind_wave_height -> sea_surface_wind_wave_significant_height

• ocean_surface_wave_mean_period_sea -> ocean_surface_wind_wave_mean_period -> sea_surface_wind_wave_mean_period

• ocean_surface_wind_wave_direction -> ocean_surface_wind_wave_direction -> sea_surface_wind_wave_from_direction

If I am not mistaken, this covers all 12 names in the original proposal: with 6 new names, and 6 existing names which can be used in place of the rest. I would be happy to hear any thoughts or issues with this interpretation!

Best, Ellie

[ChrisBarker-NOAA]

I'd really like to hear from the OP on this one -- and I've been out of the "wave biz" for a while, but:

from: https://www.ndbc.noaa.gov/faq/wavecalc.shtml

Dominant or peak wave period, DPD, is the period corresponding to the frequency band with the maximum value of spectral density in the nondirectional wave spectrum.

(lots) More detail in this doc: https://www.ndbc.noaa.gov/wavemeas.pdf

I think "spectral density" is energy spectral density -- but the difference from "variance_spectral_density" is the essentially the units -- so the peaks should be in the same place, so good there.

so:

ocean_surface_wave_peak_period -> sea_surface_wave_period_at_variance_spectral_density_maximum

ocean_surface_wave_peak_period_swell -> sea_surface_swell_wave_period_at_variance_spectral_density_maximum

ocean_surface_wave_peak_period_sea -> sea_surface_wind_wave_period_at_variance_spectral_density_maximum

My only question here is having a peak of swell and peak of sea, rather than an overall peak. NDBC, at least, does appear to report these, and I'm not that sure how clearly defined the difference is between swell and sea. But that distinction is made elsewhere, so probably OK here too.

If someone want to dig into the vocabulary, this might be helpful:

https://www.researchgate.net/publication/242337289_Semantics_of_Spectral_Density_for_Ocean_Waves

I have not read it myself :-)