Dear Jonathan,
I seem to remember the 'what is spread' discussion coming up last time we encountered wave directional spread Standard Names. The Standard Name sea_surface_wave_directional_spread has the definition:
Directional spread is the (one-sided) directional width within a given sub-domain of the wave directional spectrum, S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. For a given mean wave (beam) direction the quantity approximates half the root mean square width about the beam axis, as derived either directly from circular moments or via the Fourier components of the wave directional spectrum.
This seems to have been omitted from Rob's definition, which should I think read:
The quantity with the Standard Name sea_surface_wave_directional_spread_at_variance_spectral_density_maximum is the directional spread of the most energetic waves. Directional spread is the (one-sided) directional width within a given sub-domain of the wave directional spectrum, S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. For a given mean wave (beam) direction the quantity approximates half the root mean square width about the beam axis, as derived either directly from circular moments or via the Fourier components of the wave directional spectrum.
Cheers, Roy.
I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address.
________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jonathan Gregory <j.m.gregory at reading.ac.uk>
Sent: 28 September 2018 13:26
To: Rob Thomas
Cc: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Spectral wave direction spread parameter
Dear Rob
>From the responses it's clear we need a name for this. I'm a bit nervous about
"spread", which sounds vague to me. Can you clarify it?
Best wishes and thanks
Jonathan
On Fri, Sep 28, 2018 at 07:47:51AM +0000, Rob Thomas wrote:
> Date: Fri, 28 Sep 2018 07:47:51 +0000
> From: Rob Thomas <Rob.Thomas at Marine.ie>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> Subject: [CF-metadata] Spectral wave direction spread parameter
>
> Hi,
>
>
>
> Please can I propose/request a new standard name for the list:
> "sea_surface_wave_directional_spread_at_variance_spectral_density_maximum"
>
>
>
> The rationale for this request is that in assessing our mappings of spectral wave parameters to the CF standard names we have mapped "Peak Direction" (described as "Dirp Direction for waves at peak of wave energy spectrum from which the waves are coming") to "sea_surface_wave_from_direction_at_variance_spectral_density_maximum" with definition:
>
>
> The quantity with standard name sea_surface_wave_from_direction_at_variance_spectral_density_maximum is the direction from which the most energetic waves are coming. The spectral peak is the most energetic wave in the total wave spectrum. The phrase "from_direction" is used in the construction X_from_direction and indicates the direction from which the velocity vector of X is coming. The direction is a bearing in the usual geographical sense, measured positive clockwise from due north. The wave directional spectrum can be written as a five dimensional function S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. S has the standard name sea_surface_wave_directional_variance_spectral_density. S can be integrated over direction to give S1= integral(S dtheta) and this quantity has the standard name sea_surface_wave_variance_spectral_density.
>
>
>
> It does not appear there is an appropriate partner term for Peak Spread (described as "Dsprp Directional spread of waves at peak of wave energy spectrum") because the options currently available do not appear to tie in to the peak wave energy spectrum/spectral peak information.
>
>
>
> Kind regards,
>
> Rob
>
>
>
> Dr. Rob Thomas
>
> Senior Data Analyst - European Data Management Projects Team Leader
>
>
>
> Marine Institute, Rinville, Oranmore, County Galway, H91 R673, Ireland
>
> Tel: (+)353 (0)91 387 409
>
> Mob: (+)353 (0)87 952 3467
>
> Email: rob.thomas at marine.ie<mailto:rob.thomas at marine.ie>
>
> ORCID: 0000-0001-6068-4924
>
> Web: http://data.marine.ie/
data.marine.ie - Marine Environment<
http://data.marine.ie/>
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