Many thanks Alison, I'm perfectly happy with your suggested change of 'average' to 'mean' in the proposed height Standard Names.
Cheers, Roy. From: CF-metadata [mailto:[email protected]] On Behalf Of [email protected] Sent: 22 June 2016 14:32 To: [email protected] Subject: Re: [CF-metadata] Waves Dear Roy, Elodie, Nan, Jonathan, Chris, et al, Many thanks to Elodie for her original wave name proposals, to Roy for doing so much work on designing a systematic approach to CF wave names and to all those who have worked to improve these proposals on and off the list. My apologies for taking a while to respond to this discussion. I think it is useful to continue Roy’s approach of breaking the original set of proposals into three groups, so here I will address just the height names. I will address the other sets of proposals separately. I note the discussion around the use of mean, maximum and minimum in the standard name, rather than our more usual approach of placing such information in the cell_methods attribute. We do already have eleven existing names that refer to “wave_mean_period”. I looked back at the original discussion of these names in 2006 in which it was agreed to use “mean” in the name because wave quantities can be calculated in many and diverse ways from the power spectrum and it is not useful to come up with separate cell_methods for them all. I think Roy made a similar point earlier on in this discussion. In fact, I don’t think that putting the quantities in cell_methods would greatly reduce the number of new names required in this instance. Also, I’m strongly in favour of Roy’s approach of adopting as far as possible a consistent convention for all wave standard names so I support the use of mean, maximum and minimum in these proposals for consistency with the existing names. I note the general point made by Nan about the ordering of sentences in the definitions of new wave names (http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2016/058843.html). I’m broadly supportive of adopting this approach as we go along (so this doesn’t mean we need to review all existing wave name definitions during the current discussion). I think the definitions of the wave height proposals are in any case consistent with Nan’s approach. For the two mean_height names, I suggest a minor change in which we replace the word “average” in the definitions with the word “mean” for clarity and consistency with the names themselves, otherwise they look fine. These two names would therefore be as follows: sea_surface_wave_mean_height (m) ‘Wave height is defined as the vertical distance from a wave trough to the following wave crest. The mean wave height is the mean trough to crest distance measured during the observation period.’ sea_surface_wave_mean_height_of_highest_tenth (m) ‘Wave height is defined as the vertical distance from a wave trough to the following wave crest. The height of the highest tenth is defined as the mean of the highest ten per cent of trough to crest distances measured during the observation period.’ If Roy and Elodie are happy with this small change, then these names can be accepted for publication. The remaining height names look fine and are accepted for publication in the standard name table: sea_surface_wave_significant_height (m) (Modification to definition of existing name) ‘Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.’ sea_surface_wind_wave_significant_height (m) (Modification to definition of existing name) ‘Wind waves are waves on the ocean surface and are the high frequency portion of a bimodal wave frequency spectrum. Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.’ sea_surface_swell_wave_significant_height (m) (Modification to definition of existing name) ‘Swell waves are waves on the ocean surface and are the low frequency portion of a bimodal wave frequency spectrum. Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.’ sea_surface_primary_swell_wave_significant_height (m) ‘Swell waves are waves on the ocean surface and are the low frequency portion of a bimodal wave frequency spectrum. The primary swell wave is the most energetic swell wave. Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.’ sea_surface_secondary_swell_wave_significant_height (m) ‘Swell waves are waves on the ocean surface and are 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. Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.’ sea_surface_wave_maximum_height (m) ‘Wave height is defined as the vertical distance from a wave trough to the following wave crest. The maximum wave height is the greatest trough to crest distance measured during the observation period.’ sea_surface_wave_maximum_crest_height (m) ‘The crest is the highest point of a wave. Crest height is the vertical distance between the crest and the calm sea surface. Maximum crest height is the maximum value measured during the observation period.’ sea_surface_wave_maximum_trough_depth (m) ‘The trough is the lowest point of a wave. Trough depth is the vertical distance between the trough and the calm sea surface. Maximum trough depth is the maximum value measured during the observation period.’ The current status of these names can also be viewed in the CEDA vocabulary editor: http://cfeditor.ceda.ac.uk/proposals/1?status=active&namefilter=height+trough&proposerfilter=Roy+Elodie&descfilter=&unitfilter=&yearfilter=&commentfilter=&filter+and+display=Filter. The next update of the standard name table will take place on 19th July. Best wishes, Alison ------ Alison Pamment Tel: +44 1235 778065 Centre for Environmental Data Analysis Email: [email protected]<mailto:[email protected]> STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Campus, Didcot, OX11 0QX, U.K. From: CF-metadata [mailto:[email protected]] On Behalf Of Chris Barker Sent: 13 May 2016 17:13 To: Nan Galbraith Cc: [email protected]<mailto:[email protected]> Subject: Re: [CF-metadata] Waves On Wed, May 11, 2016 at 9:18 AM, Nan Galbraith <[email protected]<mailto:[email protected]>> wrote: Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest. works for me. Thanks, -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception [email protected]<mailto:[email protected]> ________________________________ 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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