[CF-metadata] Standard names for wave model data.

From: Jonathan Gregory <j.m.gregory>
Date: Sat, 3 Jun 2006 14:11:29 +0100

Dear John

> Thanks for the comments. I agree that just 'wave' is ambiguous. I like
> 'ocean_surface_wave' instead.
I think I should have suggested sea rather than ocean, to be more general and
consistent with other names, such as sea_surface_height. Would that be OK?

Maybe we should change the existing wind_wave and swell_wave to
sea_surface_wind|swell_wave to be clearer about them.

> > standard_name = "wave_spectrum_direction" ;
> > standard_name = "direction_of_wave_velocity" ;
> The reason for 2 directions was that one represents a coordinate
> variable, and the other represents the principal wave direction (the one
> associated with the peak in the energy spectrum). However, I think we
> can use the 'cell_methods' here with 'wave_energy: maximum'.
OK. So you're proposing just direction_of_[sea_surface_]wave_velocity now.

> >The units of m2 are not units of energy. Perhaps it's the square of
> >the wave amplitude, or the RMS amplitude?
> True. It is really a 'variance density spectrum' but wave modellers seem
> to refer to this as an 'energy density spectrum'. A factor of (rho * g)
> relates the two, so I have removed 'energy' from the name. Now I suggest
> ocean_surface_wave_spectrum_density, units m^2 s-1 rad-1
Why not put in "variance" explicitly, as I see you suggest later? This might be
useful because it's always possible that one day someone might want a name for
the energy spectrum (in energy units) or some other spectrum. I think
wave_variance would be a reasonable name for the quantity in m2.

I'm puzzled why this one is rad-1. In your original proposal it was the extra
"directional" which made in rad-1, and I understood that. Should it be

sea_surface_wave_variance_spectrum_density in m2 s-1
sea_surface_wave_directional_variance_spectrum_density in m2 s-1 rad-1

One further minor point - would spectral be equally acceptable? If so it might
be preferable because it's the word used for radiation. But if spectrum is
always the term used, then it's better for this application.

> The 'zero up-crossing' period is a standard means of measuring wave
> period. It is defined using the time the surface height passes upward
> over the mean level. Other definitions of wave periods include peak and
> mean. Peak could be defined using cell_methods ('wave_energy : maximum')
and mean could also be defined with a cell_methods, which would make it
precise since you have then to specify what is the independent variable
over which the mean is calculated.
>
> ocean_surface_wave_zero_upcrossing_period, units s
> ocean_surface_wave_frequency, units s-1 (Hz)
> ocean_surface_wave_from_direction, units degrees
> ocean_surface_wave_to_direction, units degrees
> (Convention is for direction toward which energy travels for wave
> spectra with frequency & direction, but the direction from which waves
> are coming [like wind] in other contexts.)
OK.

> ocean_surface_wave_significant_height, units m
The standard name table already has significant_height_of_wind_and_swell_waves,
and corresponding terms for wind and swell separately. If no-one objects, we
could make the existing name an alias for your new name, and swap round the
others to make them sea_surface_wind|swell_wave_significant_height.

> wind_wave_zero_upcrossing_period, units s
> swell_wave_zero_upcrossing_period, units s
OK. Perhaps with sea_surface_ prefixed, as suggested above.

Best wishes

Jonathan
Received on Sat Jun 03 2006 - 07:11:29 BST