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 Thu Apr 28 2016 - 09:18:52 BST
