Thank you, Roy, for heading up this effort.
I still have a problem with including the word mean in the standard
name for sea_surface_wave_period, and would like to suggest that
we add another standard name without that word. If this is model
data, or a high frequency record, it may not in fact be a mean. If
we need 2 terms for surface wave periods in order to make all the
wave standard names consistent, so be it.
Also, I think the word 'significant' is a modifier of the word wave,
and therefore sea_surface_wave_significant_period could be
sea_surface_significant_wave_period. The definition uses the phrase
'significant wave period', not wave significant period, as well.
I'm sorry I didn't work harder to resolve these issues in the off-list
discussion, it's been a busy time here.
Cheers - Nan
Quoting "Lowry, Roy K." <rkl at bodc.ac.uk>:
> Hello Jonathan,
>
> Whilst the cell-method approach might look feasible for the wave
> period sub-proposal taken in isolation (remember I have split the
> original proposal into three parts: wave heights, wave periods and
> wave directions), it doesn't work well for the wave heights and for
> other more complex wave statistics that could be encountered in the
> future. Remember also the precedent of the existing wave Standard
> Names that incude 'mean'.
>
> Having one 'rule' for all wave Standard Names seems a much more
> manageable approach than having some wave statistics with 'mean' and
> 'maximum' in the Standard Name, whilst using the cell method
> approach for others.
>
> Cheers, Roy.
>
> -----Original Message-----
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On
> Behalf Of Jonathan Gregory
> Sent: 25 May 2016 15:34
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] Wave periods sub-proposal
>
> 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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> ----- End forwarded message -----
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Received on Tue May 31 2016 - 05:59:50 BST
