Dear Roy
Thanks for these updated proposals. With the rephrasing, it now seems to me
there is a less strong argument for including "mean" and "maximum" in the
standard names. Why not have sea_surface_wave_period and use cell_methods with
time-bounds to describe the period of observation over which the mean etc.
is calculated?
Best wishes
Jonathan
----- Forwarded message from "Lowry, Roy K." <rkl at bodc.ac.uk> -----
> Date: Wed, 25 May 2016 10:09:21 +0000
> From: "Lowry, Roy K." <rkl at bodc.ac.uk>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> CC: "mar at puertos.es" <mar at puertos.es>
> Subject: [CF-metadata] Wave periods sub-proposal
>
> Dear All,
>
> What follows is a modification of part of the proposal initially submitted by Elodie Fernandez following off-list work between Elodie, Marta, Chris Barker, Nan Galbraith and myself. It includes a change (deprecation plus creation of an alias) to three existing Standard Names, plus the creation of six new wave period Standard Names. Every effort has been made to maintain compatibility between this and the separate wave height sub-proposal submitted a couple of weeks ago.
>
> Each proposed Standard Name is followed by its definition. All wave periods have Canonical Units of seconds.
>
> Cheers, Roy.
>
> PS I have formatted this message in Rich Text to make it easier to follow. It is also attached as a Word Document for those who prefer.
>
>
> Wave Period Proposal
>
> Existing Standard Name Changes
> 1) sea_surface_wave_zero_upcrossing_period
> A period is an interval of time, or the time-period of an oscillation. The zero upcrossing period is defined as the time interval between consecutive occasions on which the surface height passes upward above the mean level.
>
> Replace this by:
> sea_surface_wave_mean_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave mean period is the average period measured over the observation duration.
>
> 2) sea_surface_wind_wave_zero_upcrossing_period
> A period is an interval of time, or the time-period of an oscillation. The zero upcrossing period is defined as the time interval between consecutive occasions on which the surface height passes upward above the mean level. Wind waves are waves on the ocean surface. Wind is defined as a two-dimensional (horizontal) air velocity vector, with no vertical component. (Vertical motion in the atmosphere has the standard name upward_air_velocity.)
>
> Replace this by:
> sea_surface_wind_wave_mean_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave mean period is the average period measured over the observation duration. Wind waves are the high frequency portion of a bimodal wave frequency distribution.
>
> 3) sea_surface_swell_wave_zero_upcrossing_period
> A period is an interval of time, or the time-period of an oscillation. The zero upcrossing period is defined as the time interval between consecutive occasions on which the surface height passes upward above the mean level. Swell waves are waves on the ocean surface.
>
> Replace this by:
> sea_surface_swell_wave_mean_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave mean period is the average period measured over the observation duration. Swell waves are the low frequency portion of a bimodal wave frequency distribution.
>
> Justification for change:
>
> The classical Tucker-Draper analysis specifies multiple wave period statistics such as zero-upcrossing period (Tz) and crest period (Tc) and the protocols used could cause these to differ. However, wave theory states that period of a waveform should be uniform for all reference points on the waveform and so the possibility of variation should be considered an artefact and the geophysical variable should simply be wave period. The long name can be used if required to specify the waveform reference and measurement protocol used, as proposed for wave height Standard Names.
>
> Additional Standard Names for Copernicus Proposal
> 1) sea_surface_wave_significant_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Significant wave period is a statistic computed from wave measurements and corresponds to the average wave period of the highest one third of the waves.
> 2) sea_surface_wave_mean_period_of_highest_tenth
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave mean period is the average period measured over the observation duration. Mean period of the highest tenth is the average period of the highest one-tenth of the waves during the observation duration.
> 3) sea_surface_wave_maximum_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. The maximum period is the longest wave period measured during the observation period.
> 4) sea_surface_wave_period_of_highest_wave
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave period of the highest wave is the period determined from wave crests corresponding to the greatest vertical distance above mean level during the observation period.
> 5) sea_surface_primary_swell_wave_mean_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave mean period is the average period measured over the observation duration. The primary swell wave is the most energetic wave in the low frequency portion of a bimodal wave frequency distribution.
> 6) sea_surface_secondary_swell_wave_mean_period
> A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level. Wave mean period is the average period measured over the observation duration. The secondary swell wave is the second most energetic wave in the low frequency portion of a bimodal wave frequency distribution.
>
>
> Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquiries at bodc.ac.uk<mailto:enquiries at bodc.ac.uk>. Please also use this e-mail if your requirement is urgent.
>
>
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