Hi Nan,
When I saw what we had for waves in CF I just wanted to do something!
The request for 'sea_surface_wave_period' in addition initially worried me a little. However, I notice that we already have sea_surface_wind_wave_period and sea_surface_swell_wave_period and are proposing to add mean periods to them, so what you are proposing is internally consistent. I guess the definition would be:
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.
I'd overlooked upgrading the definitions for sea_surface_wind_wave_period and sea_surface_swell_wave_period. These should be:
sea_surface_swell_wave_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. Swell waves are the low frequency portion of a bimodal wave frequency distribution.
sea_surface_wind_wave_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. Wind waves are the high frequency portion of a bimodal wave frequency distribution.
I don't think sea_surface_wave_significant_period should change. I understand 'significant_period' to mean 'mean period of the highest one third' so leaving asis is syntactically equivalent to sea_surface_wave_mean_period_of_highest_tenth. This is clarified in the definition, where 'Significant wave period' is explicitly defined.
Cheers, Roy.
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. Please also use this e-mail if your requirement is urgent.
________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Nan Galbraith <ngalbraith at whoi.edu>
Sent: 31 May 2016 12:59
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Wave periods sub-proposal
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.
>>
>>
>> ________________________________
>> This message (and any attachments) is for the recipient only. NERC
>> is subject to the Freedom of Information Act 2000 and the contents
>> of this email and any reply you make may be disclosed by NERC
>> unless it is exempt from release under the Act. Any material
>> supplied to NERC may be stored in an electronic records management
>> system.
>> ________________________________
>
>
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>
> ----- End forwarded message -----
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