Thanks you, Alison, Roy, Elodie and all -
Nan
On 6/22/16 9:32 AM, alison.pamm...@stfc.ac.uk wrote:
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
<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 19^th July.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email:
alison.pamm...@stfc.ac.uk <mailto:j.a.pamm...@rl.ac.uk>
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Campus, Didcot, OX11 0QX, U.K.
\
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* Nan Galbraith (508) 289-2444 *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 *
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