Dear Elodie,
Following my comments on Hs, here are some comments on the rest of your
proposals for additional wave height Standard Names. Most of the comments
follow the same theme of placing statistic derivation methods out of the
Standard Name. My proposed changes will affect your definitions, but let's
discuss names first to keep things manageable.
sea_surface_wave_zero_upcrossing_average_height_of_highest_tenth
Use sea_surface_wave_average_height_of_highest_tenth as the Standard Name with
the derivation method in the long name. If zero-upcrossing analysis is based on
the method specified by Tucker and Draper then include ‘Tucker-Draper’ in the
label.
sea_surface_wave_zero_upcrossing_average_height
Suggest sea_surface_wave_average_height This raises the question of whether
‘average’ should be handled by a cell method? However, there is a precedent for
the inclusion of statistics in the name already established for waves e.g.
sea_surface_wave_zero_upcrossing_average_height.
sea_surface_wave_maximum_height
OK
sea_surface_wave_zero_upcrossing_maximum_height
Use sea_surface_wave_maximum_height and Long Name for the derivation method.
sea_surface_wave_crest_through_maximum_height
Should ‘through’ be ‘trough’? Also, I’m not clear on exactly what this is. Is
it the distance from the deepest trough to the highest crest in the analysis
(i.e. the sum of sea_surface_wave_deepest_trough and
sea_surface_wave_height_of_the_highest_crest) or the greatest crest to
following trough distance in the analysis. Could you clarify then I’ll suggest
a change to the name?
sea_surface_wave_deepest_through
Assume you mean sea_surface_wave_deepest_trough, in which case OK.
sea_surface_wave_height_of_the_highest_crest
OK
sea_surface_primary_swell_wave_significant_height
‘Spectral’ removed from your suggestion with derivation moved to
Long Name.
sea_surface_secondary_swell_wave_significant_height
‘Spectral’ removed from your suggestion with derivation moved to
Long Name.
Your other height proposal (sea_surface_wind_wave_spectral_significant_height)
is covered by the pre-existing Standard Name
sea_surface_wind_wave_significant_height.
Cheers, Roy.
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________________________________
From: CF-metadata <[email protected]> on behalf of Elodie
Fernandez <[email protected]>
Sent: 28 April 2016 16:18
To: [email protected]
Cc: [email protected]
Subject: [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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