Dear Jonathon, Before I put in a version for all the components, does the form of the below look OK?
sea_surface_wave_directional_spread units: degree Directional spread represents the (one-sided) directional width 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. Many thanks Andy -----Original Message----- From: CF-metadata [mailto:[email protected]] On Behalf Of Jonathan Gregory Sent: 03 May 2018 17:33 To: [email protected] Subject: Re: [CF-metadata] proposed additional names for sea_surface_wave parameters Dear Andy Yes, I agree, that is a sufficiently different quantity that it can't clearly be seen as a statistic describable by cell_methods and so needs its own name. Maybe you could add something more to the definition. Best wishes and thanks Jonathan ----- Forwarded message from "Saulter, Andrew" <[email protected]> ----- > Date: Thu, 3 May 2018 10:34:03 +0000 > From: "Saulter, Andrew" <[email protected]> > To: "[email protected]" <[email protected]> > Subject: Re: [CF-metadata] proposed additional names for sea_surface_wave > parameters > > Thanks Jonathon, > > Re the directional_spread parameters in section 4, the "one-sided directional > width" as its described in Holthuijsen's book (Waves in Oceanic and Coastal > Waters) is perhaps more precisely defined by Tucker and Pitt (Waves in Ocean > Engineering) as "half the beam-width as usually described: that is, it is > from the beam axis to the root mean square width". > > So in principle there is a statistical relationship between this value and a > mean_wave_direction that is also computed from moments of the directional > wave spectrum. However, there is a lot of detail here; first Tucker and Pitt > note that this is an approximation. Rather more detail is given by Kuik et > al. (1988, > https://doi.org/10.1175/1520-0485(1988)018%3C1020:AMFTRA%3E2.0.CO;2 ) who > explain potential differences in calculation of directional characteristics > using linear or circular moments - the latter being necessary for wave > measurements, where spreading is then estimated based on the Fourier > components of the directional wave spectrum rather than a direct calculation > of directional spectrum statistics. > > So the parameter feels a bit more complex and nuanced than a cell_methods > application to wave_direction would allow. I think giving it its own name is > more appropriate in this case? > > Cheers > Andy > > > -----Original Message----- > From: CF-metadata [mailto:[email protected]] On Behalf > Of Jonathan Gregory > Sent: 02 May 2018 13:32 > To: [email protected] > Subject: [CF-metadata] proposed additional names for sea_surface_wave > parameters > > Dear Andy > > Your new proposals of sections 1-3 following existing patterns, as you say, > and look fine to me. > > For those of section 4, can you say precisely what "one-sided directional > width" means? The way you describe it, I wonder whether it could be described > as a processed version of the wave_direction theta. For example, if it was > the standard deviation of theta, cell_methods could describe it. > > Best wishes > > Jonathan > > ----- Forwarded message from "Saulter, Andrew" > <[email protected]> ----- > > > Date: Wed, 2 May 2018 07:28:05 +0000 > > From: "Saulter, Andrew" <[email protected]> > > To: "[email protected]" <[email protected]> > > Subject: Re: [CF-metadata] proposed additional names for sea_surface_wave > > parameters > > > > Adding a minor amendment to the units for the > > 'wave_energy_at_variance_spectral_density_maximum' parameters. These should > > be 'm2 s' rather than 'm2s' in order to be parsed by UDUNITS. > > > > Andy > > > > From: CF-metadata [mailto:[email protected]] On > > Behalf Of Saulter, Andrew > > Sent: 01 May 2018 09:27 > > To: [email protected] > > Subject: [CF-metadata] proposed additional names for > > sea_surface_wave parameters > > > > Hi all, > > > > Please find proposals for some additional sea_surface_wave parameters, > > which will be provided as part of Met Office operational forecast products > > in the near future. Hopefully nothing too contentious as mostly an > > extension of some existing CF names. > > > > > > 1. Addition of 'tertiary_swell' names for existing wave parameters > > defined under 'wind_wave', 'primary_swell' and 'secondary_swell' > > categories. So would add: > > > > sea_surface_tertiary_swell_wave_from_direction > > units: degree > > The quantity with standard name > > sea_surface_tertiary_swell_wave_from_direction is the direction from which > > the third most energetic swell waves are coming. Swell waves are waves on > > the ocean surface and are the low frequency portion of a bimodal wave > > frequency spectrum. The tertiary swell wave is the third most energetic > > swell wave. 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. > > > > sea_surface_tertiary_swell_wave_mean_period > > units: s > > The quantity with standard name sea_surface_tertiary_swell_wave_mean_period > > is the mean period of the third most energetic swell waves. Swell waves are > > waves on the ocean surface and are the low frequency portion of a bimodal > > wave frequency spectrum. The tertiary swell wave is the third 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 mean period measured over the observation > > duration. > > > > sea_surface_tertiary_swell_wave_significant_height > > Swell waves are waves on the ocean surface and are the low frequency > > portion of a bimodal wave frequency spectrum. The tertiary swell wave is > > the third 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. > > > > > > > > 2. Addition of peak wave period parameter to 'wind_wave', > > 'primary_swell', 'secondary_swell' and 'tertiary_swell' categories. This > > follows the existing standard for > > 'sea_surface_wave_period_at_variance_spectral_density_maximum' and adds: > > > > sea_surface_wind_wave_period_at_variance_spectral_density_maximum > > units: s > > The quantity with standard name > > sea_surface_wind_wave_period_at_variance_spectral_density_maximum is the > > period of the most energetic waves within the wind wave component of a sea. > > Wind waves are waves on the ocean surface and are the high frequency > > portion of a bimodal wave frequency spectrum. A period is an interval of > > time, or the time-period of an oscillation. The phrase > > "wave_period_at_variance_spectral_density_maximum", sometimes called peak > > wave period, describes the period of the most energetic waves within a > > given sub-domain of the wave spectrum. > > > > sea_surface_primary_swell_wave_period_at_variance_spectral_density_m > > ax > > imum > > units: s > > The quantity with standard name > > sea_surface_primary_swell_wave_period_at_variance_spectral_density_maximum > > is the period of the most energetic waves within the primary swell wave > > component of a sea. 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 wave component 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. The phrase > > "wave_period_at_variance_spectral_density_maximum", sometimes called peak > > wave period, describes the period of the most energetic waves within a > > given sub-domain of the wave spectrum. > > > > sea_surface_secondary_swell_wave_period_at_variance_spectral_density > > _m > > aximum > > units: s > > The quantity with standard name > > sea_surface_secondary_swell_wave_period_at_variance_spectral_density_maximum > > is the period of the most energetic waves within the secondary swell wave > > component of a sea. 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 most energetic wave component 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. The phrase > > "wave_period_at_variance_spectral_density_maximum", sometimes called peak > > wave period, describes the period of the most energetic waves within a > > given sub-domain of the wave spectrum. > > > > sea_surface_tertiary_swell_wave_period_at_variance_spectral_density_ > > ma > > ximum > > units: s > > The quantity with standard name > > sea_surface_tertiary_swell_wave_period_at_variance_spectral_density_maximum > > is the period of the most energetic waves within the tertiary swell wave > > component of a sea. Swell waves are waves on the ocean surface and are the > > low frequency portion of a bimodal wave frequency spectrum. The tertiary > > swell wave is the third most energetic wave component 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. The phrase > > "wave_period_at_variance_spectral_density_maximum", sometimes called peak > > wave period, describes the period of the most energetic waves within a > > given sub-domain of the wave spectrum. > > > > > > > > 3. Addition of energy_at_variance_spectral_density_maximum parameter > > to existing 'wind_wave', 'primary_swell', 'secondary_swell' and > > 'tertiary_swell' categories. This follows the existing standard for > > 'sea_surface_wave_energy_at_variance_spectral_density_maximum' and adds: > > > > sea_surface_wind_wave_energy_at_variance_spectral_density_maximum > > units: m2s > > The quantity with standard name > > sea_surface_wind_wave_energy_at_variance_spectral_density_maximum is the > > energy of the most energetic waves within the wind wave component of a sea. > > Wind waves are waves on the ocean surface and are the high frequency > > portion of a bimodal wave frequency spectrum. The phrase > > "wave_energy_at_variance_spectral_density_maximum", sometimes called peak > > wave energy, describes the maximum value of the > > wave_variance_spectral_density within a given sub-domain of the wave > > spectrum. > > > > sea_surface_primary_swell_wave_energy_at_variance_spectral_density_m > > ax > > imum > > units: m2s > > The quantity with standard name > > sea_surface_primary_swell_wave_energy_at_variance_spectral_density_maximum > > is the energy of the most energetic waves within the primary swell wave > > component of a sea. 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 wave component in the low frequency > > portion of a bimodal wave frequency spectrum. The phrase > > "wave_energy_at_variance_spectral_density_maximum", sometimes called peak > > wave energy, describes the maximum value of the > > wave_variance_spectral_density within a given sub-domain of the wave > > spectrum. > > > > sea_surface_secondary_swell_wave_energy_at_variance_spectral_density > > _m > > aximum > > units: m2s > > The quantity with standard name > > sea_surface_primary_swell_wave_energy_at_variance_spectral_density_maximum > > is the energy of the most energetic waves within the secondary swell wave > > component of a sea. 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 component in the low frequency > > portion of a bimodal wave frequency spectrum. The phrase > > "wave_energy_at_variance_spectral_density_maximum", sometimes called peak > > wave energy, describes the maximum value of the > > wave_variance_spectral_density within a given sub-domain of the wave > > spectrum. > > > > sea_surface_tertiary_swell_wave_energy_at_variance_spectral_density_ > > ma > > ximum > > units: m2s > > The quantity with standard name > > sea_surface_tertiary_swell_wave_energy_at_variance_spectral_density_maximum > > is the energy of the most energetic waves within the tertiary swell wave > > component of a sea. Swell waves are waves on the ocean surface and are the > > low frequency portion of a bimodal wave frequency spectrum. The tertiary > > swell wave is the third most energetic wave component in the low frequency > > portion of a bimodal wave frequency spectrum. The phrase > > "wave_energy_at_variance_spectral_density_maximum", sometimes called peak > > wave energy, describes the maximum value of the > > wave_variance_spectral_density within a given sub-domain of the wave > > spectrum. > > > > > > > > 4. And finally... Addition of 'directional_spreading' parameter to > > 'sea_surface_wave', 'wind_wave', 'primary_swell', 'secondary_swell' and > > 'tertiary_swell' categories. Giving the additional parameters: > > > > sea_surface_wave_directional_spread > > units: degree > > Directional spread is the (one-sided) directional width 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. > > > > sea_surface_wind_wave_directional_spread > > units: degree > > The quantity with standard name sea_surface_wind_wave_directional_spread is > > the directional width of the wind wave component of a sea. Wind waves are > > waves on the ocean surface and are the high frequency portion of a bimodal > > wave frequency spectrum. The phrase "wave_directional_spread" describes 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 . > > > > sea_surface_primary_swell_wave_directional_spread > > units: degree > > The quantity with standard name > > sea_surface_primary_swell_wave_directional_spread is the directional width > > of the primary swell wave component of a sea. 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 wave component in > > the low frequency portion of a bimodal wave frequency spectrum. The phrase > > "wave_directional_spread" describes 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 . > > > > sea_surface_secondary_swell_wave_directional_spread > > units: degree > > The quantity with standard name > > sea_surface_secondary_swell_wave_directional_spread is the directional > > width of the secondary swell wave component of a sea. 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 component in the low frequency portion of a bimodal wave frequency > > spectrum. The phrase "wave_directional_spread" describes 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 . > > > > sea_surface_tertiary_swell_wave_directional_spread > > units: degree > > The quantity with standard name > > sea_surface_secondary_swell_wave_directional_spread is the directional > > width of the tertiary swell wave component of a sea. Swell waves are waves > > on the ocean surface and are the low frequency portion of a bimodal wave > > frequency spectrum. The tertiary swell wave is the third most energetic > > wave component in the low frequency portion of a bimodal wave frequency > > spectrum. The phrase "wave_directional_spread" describes 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 . > > > > > > Phew! > > Many thanks > > Andy > > > > Andy Saulter > > Surge, Waves and Metocean Projects Manager Met Office FitzRoy Road > > Exeter Devon EX1 3PB > > Tel: +44 (0)1392 884703 Fax: +44 (0)1392 885681 > > [email protected]<mailto:[email protected]. > > uk > > > http://www.metoffice.gov.uk > > > > > _______________________________________________ > > CF-metadata mailing list > > [email protected] > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > ----- End forwarded message ----- > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
