[CF-metadata] Wave periods sub-proposal
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--- > All wave periods have Canonical Units of seconds. > > > Existing Standard Name Changes > > 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. > > 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. This proposed alias looks fine and, as with the existing wave height names, I think it is a sensible approach to use the long name to indicate the precise method by which the data values were obtained. The proposed definition seems general enough to cover all eventualities. In the last sentence "average period" should say "mean period" (consistent with the wave height names). This alias is accepted for inclusion in the standard name table. > 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. As with proposal 1, in the penultimate sentence of the definition "average period" should be replaced by "mean period" (consistent with the wave height names). Otherwise this looks fine. This alias is accepted for inclusion in the standard name table. > 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. As with proposal 1, in the penultimate sentence of the definition "average period" should be replaced by "mean period" (consistent with the wave height names). Otherwise this looks fine. This alias is accepted for inclusion in the standard name table. --- > 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. Units of s is fine and the proposed name is consistent with the existing name sea_surface_wave_significant_height. For consistency with the accepted aliases and existing wave height names "average period" in the definition should be replaced by "mean period". Taking account of Nan's suggestion to change the order of the sentences in the definition we would then have: 'Significant wave period is a statistic computed from wave measurements and corresponds to the mean wave period of the highest one third of the waves. 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.' With these cosmetic changes this new name is accepted for publication in the standard name table. > 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. Units of s is fine. The proposed name and definition are consistent with the existing name sea_surface_wave_mean_height_of_highest_tenth. Again, replacing "average period" with "mean period" and changing the order of sentences in the definition we would have: 'Wave mean period is the mean period measured over the observation duration. Mean period of the highest tenth is the mean period of the highest one-tenth of the waves during the observation duration. 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.' With these cosmetic changes this new name is accepted for publication in the standard name table. > 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. Units of s is fine. The proposal is consistent with existing wave maximum height/depth names. Changing the order of the sentences in the definition as suggested by Nan we would have: 'The maximum wave period is the longest wave period measured during the observation 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.' With this cosmetic change this new name is accepted for publication in the standard name table. > 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. Units of s is fine. The name itself looks fine. Changing the order of the sentences in the definition as suggested by Nan we would have: '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. 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.' With this cosmetic change this new name is accepted for publication in the standard name table. > 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. Units of s is fine. The proposed name is consistent with the syntax of existing names and proposed wave direction names. Changing the order of the sentences in the definition as suggested by Nan, replacing "average period" with "mean period", and making the wording consistent with the proposed name sea_surface_primary_swell_wave_from_direction, the definition can be written as follows: 'The quantity with standard name sea_surface_primary_swell_wave_mean_period is the mean period of the most energetic swell waves. Swell waves are waves on the ocean surface and are in the low frequency portion of a bimodal wave frequency spectrum. The primary swell wave is the most energetic swell 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 mean period is the average period measured over the observation duration. OK? > 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. Units of s is fine. The proposed name is consistent with the syntax of existing names and proposed wave direction names. Changing the order of the sentences in the definition as suggested by Nan, replacing "average period" with "mean period", and making the wording consistent with the proposed name sea_surface_secondary_swell_wave_from_direction, the definition can be written as follows: 'The quantity with standard name sea_surface_secondary_swell_wave_mean_period is the mean period of the second most energetic swell waves. Swell waves are waves on the ocean surface and are in the low frequency portion of a bimodal wave frequency spectrum. The secondary swell wave is the second most energetic wave in the low frequency portion of a bimodal wave frequency spectrum. 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.' OK? --- Best wishes, Alison ------ Alison Pamment Tel: +44 1235 778065 Centre for Environmental Data Analysis Email: alison.pamment at stfc.ac.uk STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Campus, Didcot, OX11 0QX, U.K. ________________________________ This message (and any attachments) is for the recipient only. 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