Dear Herman,
The current situation is that there are wave Standard Names in CF with definitions that are incorrect rather than just 'not very good', such as 'Height is the vertical distance above the surface. Swell waves are waves on the ocean surface.' is the current definition for significant_height_of_swell_waves. There are currently three proposals (wave heights, wave periods and wave directions) working their way through the Standard Name update process to replace the worst of these with improved (but less than perfect) definitions as well as adding new Standard Names.
Once this is complete my plan is to prepare a new document by exporting all wave Standard Names and their definitions from the master system. I will then offer this off-list to volunteers to see what we can do to further improve the definitions. Once review and update is completed, the new definitions will be submitted to the CF list as a separate proposal.
I chose to do things this way because collating information across a live system, three 'in progress' updates and e-mail comments using a variety of clients on an open list became - for me at least - an impossible challenge. A significant beneficial side effect of doing things this way is that we end up with consistency across all wave CF Standard Name definitions.
I trust I can take this e-mail as an offer to contribute to the above-mentioned review once we've got the three sets of wave Standard Name updates loaded into the master system. I will be in touch later in the year.
Cheers, Roy.
From: Peters, Herman (CIV) [mailto:herman.peters at rws.nl]
Sent: 13 July 2016 12:54
To: 'cf-metadata-bounces at cgd.ucar.edu'
Cc: 'cf-metadata at cgd.ucar.edu'; 'mar at puertos.es'; Lowry, Roy K.; Chris Barker; Elodie Fernandez; 'Jonathan Gregory'; 'Steve Emmerson'; Hebden, Mark; Haaring, Pieter (CIV); Jeurissen, Petra (CIV)
Subject: FW: [CF-metadata] Waves
Dear sir/madam,
I recently had a swift look at your document, in which the spectral and time domain wave parameters are defined and described. I must admit that I was a bit worried, because the quality of these definitions was in my opinion not very good.
However, the last version I saw, dates back to the beginning of May. So it is quite possible that the document has significantly been improved in the meantime.
Would you, therefore, be so kind as to send me the latest version at your disposal?
If possible and if still relevant, I might then give my comments.
Best regards,
Herman.
Ir. Herman C. Peters
Measurements advisor
Rijkswaterstaat
Centrale Informatie Voorziening (CIV)
Directie IGA
Afdeling Vaste Meetnetten
P. O Box 5023
2600 GA Delft
The Netherlands
GSM: 06-27038240
E-mail: herman.peters at rws.nl<mailto:herman.peters at rws.nl>
[cid:image001.jpg at 01D1DD09.7D43BB10]
Van: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] Namens Elodie Fernandez
Verzonden: donderdag 28 april 2016 17:19
Aan: cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>
CC: mar at puertos.es<mailto:mar at puertos.es>
Onderwerp: [CF-metadata] Waves
Hi all,
So here are our proposals for wave variables that will be available through the European Copernicus Marine service. It's split in two "categories": names for the whole spectrum and names for the partitions. I added in copy for this topic Marta de Alfonso Alonso-Munoyerro who is an expert in waves from Puertos del Estado.
-------------------------------------
Whole partition
-------------------------------------
1. Height
Significant height can be measured using different methods, so we think that the already existing definition should be more precise and that new names should be added.
1.a "sea_surface_significant_height" (modification of definition)
unit m
Height is the vertical distance above the surface. Significant wave height can be estimated by zero upcrossing analysis and by spectral analysis. The generic significant wave height is used when the estimator is unknown.
1.b "sea_surface_wave_spectral_significant_height"
unit m
Height is the vertical distance above the surface. It can be defined from spectral analysis. The wave directional spectrum can be written as a five dimensional function S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. S has the standard name sea_surface_wave_directional_variance_spectral_density. S can be integrated over direction to give S1= integral(S dtheta) and this quantity has the standard name sea_surface_wave_variance_spectral_density. Frequency moments, M(n) of S1 can then be calculated as follows: M(n) = integral(S1 f^n df), where f^n is f to the power of n. Spectral significant wave height is defined as 4* sqrt (M(0)) = 4 * sqrt ( integral(S1 df) )
1.c "sea_surface_wave_zero_upcrossing_significant_height"
unit m
Height is the vertical distance above the surface. The significant wave height is defined from zero upcrossing analysis as the average height of the highest one third waves.
1.d. "sea_surface_wave_zero_upcrossing_average_height_of_highest_tenth"
unit m
Height is the vertical distance above the surface. The average height of highest tenth waves is defined from zero upcrossing analysis as the average height of the highest one tenth waves.
1.e "sea_surface_wave_zero_upcrossing_average_height"
unit m
Height is the vertical distance above the surface. The average height is defined from zero upcrossing analysis as the average of wave heights.
1.f "sea_surface_wave_maximum_height"
unit m
Height is the vertical distance above the surface. Estimated maximum wave height is not measured but estimated from others parameters like significant wave height.
1.h "sea_surface_wave_zero_upcrossing_maximum_height"
unit m
Height is the vertical distance above the surface. Maximum zero crossing wave height is the measured maximum height of the waves separated by zero upcrossing analysis.
1.i "sea_surface_wave_crest_through_maximum_height"
unit m
Height is the vertical distance above the surface. Maximum crest trough wave height is the measured maximum height of the waves separated by crests method.
1.j "sea_surface_wave_deepest_through"
unit m
Trough is the vertical distance below 0 to the minimum in a wave. Depth of the deepest trough is the maximum value of wave troughs.
1.k "sea_surface_wave_height_of_the_highest_crest"
unit m
Crest is the vertical distance above 0 to the maximum in a wave. Height of the highest crest is the maximum value of wave crests.
2. Energy
2.a "sea_wave_spectrum_peak_energy"
unit mms (meter*meter*second)
The wave directional spectrum can be written as a five dimensional function S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. S has the standard name sea_surface_wave_directional_variance_spectral_density. S can be integrated over direction to give S1= integral(S dtheta) and this quantity has the standard name sea_surface_wave_variance_spectral_density. Wave spectrum peak energy is the maximum value of the variance spectral density (max(S1)).
3. Period
3.a "sea_surface_wave_mean_period"
unit s
A period is an interval of time, or the time-period of an oscillation. Mean or averaged wave period is the average value of the wave periods and can be estimated by zero upcrossing analysis and by spectral analysis. The generic average wave period is used when the estimator is unknown.
3.b "sea_surface_wave_zero_upcrossing_significant_wave_period"
unit s
A period is an interval of time, or the time-period of an oscillation. The significant wave period is defined from zero upcrossing analysis as the average period of the highest one third waves.
3.c "sea_surface_wave_zero_upcrossing_average_one_tenth_wave_period"
unit s
A period is an interval of time, or the time-period of an oscillation. The average period highest one tenth waves is defined from zero upcrossing analysis as the average period of the highest one tenth waves.
3.d "sea_surface_wave_maximum_period"
unit s
A period is an interval of time, or the time-period of an oscillation. The maximum wave period is defined from zero upcrossing analysis as the maximum period of the waves.
3.e "sea_surface_wave_period_of_highest_wave"
unit s
A period is an interval of time, or the time-period of an oscillation. The period of the highest wave is defined from zero upcrossing analysis as the period of the highest wave.
4. Direction
4.a "sea_surface_wave_from_mean_direction"
unit degree
from_direction is used in the construction X_from_direction and indicates the direction from which the velocity vector of X is coming. The mean wave direction is the average direction from which waves are coming.
4.b "sea_surface_wave_from_direction_at_spectral_peak"
unit degree
from_direction" is used in the construction X_from_direction and indicates the direction from which the velocity vector of X is coming. The spectral peak is the most energetic wave in the total wave spectrum. The wave direction at spectral peak is the direction from which waves are coming at the spectral peak.
5. Steepness
5.a "sea_surface_wave_maximum_steepness"
unit dimensionless
The wave steepness is defined as the ratio of the wave height divided by the wavelength. The maximum wave steepness is the maximum value.
-------------------------------------
Partitions
-------------------------------------
We also wish to add names for the three "main" variables defining waves for three partitions: the wind wave, the primary swell wave and the secondary swell wave. These three variables are
- the spectral significant height (1.b of our proposal sea_surface_wave_spectral_significant_height)
- the direction (4.b of our proposal sea_surface_wave_from_direction_at_spectral_peak)
- the period (already existing name sea_surface_wave_mean_period_from_variance_spectral_density_first_frequency_moment)
So we propose for all three to replace in the name "sea_surface_wave" with "sea_surface_wind_wave", "sea_surface_primary_swell_wave" and "sea_surface_secondary_swell_wave". And we believe the definitions should be the definitions already existing or proposed on this email, with the addition at the end of the definition of the partition itself: "The directional wave spectrum can be separated into several partitions: wind wave contribution (WW), primary swell (SW1) contribution (the most energetic swell) and secondary swell contribution (SW2).", with a bit more detail for the wind wave: "Wind waves are waves on the ocean surface generated by the local wind."
For example:
sea_surface_secondary_swell_wave_from_direction
unit degree
The directional wave spectrum can be separated into several partitions: wind wave contribution (WW), primary swell (SW1) contribution (the most energetic swell) and secondary swell contribution (SW2). The mean wave direction is the average direction from which waves are coming for the secondary swell wave partition.
Regards,
Elodie Fernandez
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Received on Wed Jul 13 2016 - 06:45:11 BST
