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." <r...@bodc.ac.uk> ----- > Date: Wed, 25 May 2016 10:09:21 +0000 > From: "Lowry, Roy K." <r...@bodc.ac.uk> > To: "cf-metadata@cgd.ucar.edu" <cf-metadata@cgd.ucar.edu> > CC: "m...@puertos.es" <m...@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 > enquir...@bodc.ac.uk<mailto:enquir...@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. > ________________________________ > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
