[CF-metadata] Seeking new CF standard names (9) for sea surface wave parameters

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 11 Oct 2010 19:09:34 +0100

Dear Andrew et al.

This is to summarise briefly the discussion we have had in emails not on
the list. You proposed the following standard_names:

sea_surface_wave_mean_wave_height
sea_surface_wave_root_mean_square_wave_height
sea_surface_wave_mean_wave_height_of_highest_one_tenth
sea_surface_wave_maximum_wave_height
sea_surface_wave_root_mean_square_amplitude

sea_surface_wave_zeroth_spectral_moment

sea_surface_wave_mean_crest_period
sea_surface_wave_significant_wave_period
sea_surface_wave_period_at_second_peak_of_the_spectrum

where the heights are in m, the moment is in m2 and the periods are in s.

I agree with the proposals for new wave periods. I note that we have another
such existing name viz sea_surface_wave_zero_upcrossing_period.

You note that sea_surface_wave_significant_height is an existing standard_name
and your proposals have this style. Roy explained that these measures of wave
height are evaluated from very high-frequency sampling. I think they can be
described with cell_methods of the time axis. The advantages of using
cell_methods are that (a) it is consistent with CF treatment of other
quantities (b) it clarifies which dimension "mean" etc applies to - time in
this case, not space (c) it reduces the number of standard names required.

I therefore propose we introduce a standard_name of sea_surface_wave_height,
and new cell_methods of root_mean_square and mean_of_upper_decile (highest one
tenth); we already have cell_methods of mean and maximum, of course. I have
not understood quite what root_mean_square_amplitude means, and how it relates
to the wave height distribution sampled at high frequency. I note that the
significant wave height could be described by a cell_method of
mean_of_upper_tercile, but I would not propose that because it's a widely
used term and we have a standard_name for the corresponding period.

You commented that this means splitting up the information which describes a
quantity into two attributes. That's quite true, but it's exactly what we have
done in other such cases. The aim of the proposed common_concepts convention,
on which the discussion has not been concluded, is to provide an additional
attribute to "label" such groups of metadata. But for your own use, or for a
particular project, you could of course define your own additional convention,
which standardises the long_name, for example, to serve this purpose.

Regarding the moment, I wonder whether this is related to the moments
referred to by the existing standard_names sea_surface_wave_mean_period_from_
variance_spectral_density_first|second_frequency_moment.

Best wishes

Jonathan
Received on Mon Oct 11 2010 - 12:09:34 BST