Dear Andy
Thanks for your persistence and patience! Yes, I think are looking sensible
now, as you say.
> [Thinking even more long term, upwave/downwave slopes could be assigned different values based on wave asymmetry, but lets not go there yet...]
... but it is sufficient reason for future-proofing I think.
I'm happy with all these except that I would suggest putting the component
immediately before "slope", which is what it most closely applies to i.e.
> sea_surface_wave_mean_square_x_slope
> sea_surface_wave_mean_square_y_slope
> sea_surface_mean_square_upwave_slope
> sea_surface_mean_square_crosswave_slope
This would be consistent with existing stdnames e.g.
downward_x_stress_at_sea_ice_base
land_ice_x_velocity
Best wishes
Jonathan
----- Forwarded message from "Saulter, Andrew" <andrew.saulter at metoffice.gov.uk> -----
> Date: Fri, 5 Oct 2018 10:40:56 +0000
> From: "Saulter, Andrew" <andrew.saulter at metoffice.gov.uk>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> Subject: Re: [CF-metadata] standard names for sea surface roughness variables
>
> Dear Jonathon,
>
> Thanks a lot, that is really helpful. Whilst I appreciate your point about whether or not '_upwave/_downwave' are necessary if MSS is unsigned, I think it wold still be useful to have this since the _mean_square_slope_*_direction may well get compared with _wave_*_direction and/or _wind_*_direction. Since and these latter follow a convention it is useful/necessary not to have any ambiguity in how these are referenced. [Thinking even more long term, upwave/downwave slopes could be assigned different values based on wave asymmetry, but lets not go there yet...]
>
> So, I think we have enough now to summarise the proposed new names and see how we are doing...
>
> Agreed so far (I think) from earlier mails:
>
> charnock_coefficient_for_surface_roughness_length_for_momentum_in_air
> Units: 1
> Coefficient value, based on the Charnock (1955) empirical expression for deriving surface_roughness_length_for_momentum_in_air over the ocean. The surface called "surface" means the lower boundary of the atmosphere.
>
> sea_surface_wave_mean_square_slope
> Units: 1
> Wave slope describes an aspect of sea surface wave geometry related to sea surface roughness. Mean square slope describes a derivation over multiple waves within a sea-state, for example calculated from moments of the wave directional spectrum.
>
> sea_surface_wave_x_mean_square_slope
> Units: 1
> Wave slope describes an aspect of sea surface wave geometry related to sea surface roughness. Mean square slope describes a derivation over multiple waves within a sea-state, for example calculated from moments of the wave directional spectrum. "x" indicates that slope values are derived from vector components along the grid x-axis.
>
> sea_surface_wave_y_mean_square_slope
> Units: 1
> Wave slope describes an aspect of sea surface wave geometry related to sea surface roughness. Mean square slope describes a derivation over multiple waves within a sea-state, for example calculated from moments of the wave directional spectrum. "y" indicates that slope values are derived from vector components along the grid y-axis.
>
> Testing the new 'upwave' names:
>
> sea_surface_upwave_mean_square_slope_direction
> Units: degree
> Wave slope describes an aspect of sea surface wave geometry related to sea surface roughness. Mean square slope describes a derivation over multiple waves within a sea-state, for example calculated from moments of the wave directional spectrum. " direction" is used to assign a directional axis along which wave energy is travelling, with "upwave" used to indicate that this is equivalent to a "from_direction".
>
> sea_surface_upwave_mean_square_slope
> Units: 1
> Wave slope describes an aspect of sea surface wave geometry related to sea surface roughness. Mean square slope describes a derivation over multiple waves within a sea-state, for example calculated from moments of the wave directional spectrum. "upwave" indicates that slope values are derived from vector components along (parallel to) the axis from which waves are travelling.
>
> sea_surface_crosswave_mean_square_slope
> Units: 1
> Wave slope describes an aspect of sea surface wave geometry related to sea surface roughness. Mean square slope describes a derivation over multiple waves within a sea-state, for example calculated from moments of the wave directional spectrum. "crosswave" indicates that slope values are derived from vector components across (normal to) the axis from which waves are travelling.
>
> Hope these are beginning to sound sensible :-)
>
> Cheers
> Andy
>
>
> -----Original Message-----
> From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> On Behalf Of Jonathan Gregory
> Sent: 01 October 2018 18:29
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] standard names for sea surface roughness variables
>
> Dear Andy
>
> Thanks. I think your suggestion of "upwind" is certainly clearer than "from"
> (and "downwind" would be much better than "to"). Your middle options would be fine.
>
> > Parallel component:
> > sea_surface_wave_mean_square_slope_along_upwave_direction
> > Normal component:
> > sea_surface_wave_mean_square_slope_across_upwave_direction
>
> and your first options would be OK too, except I wonder if they'd be better as
>
> > Parallel component: sea_surface_mean_square_upwave_slope
> > Normal component: sea_surface_mean_square_crosswave_slope
>
> since it's the slope which is along or across the direction, and I made crosswave into one word like upwave, upward, eastward, etc. I think I'd prefer these shorter ones myself.
>
> But I still have a question about whether upwave and downwave need to be distinguished anyway for a mean square slope. Isn't avg((dh/dx)^2) the same regardless of the sign convention of x, if x is the wave direction? If it's not, don't you have to say whether cross-wave is leftward or rightward, correspondingly?
>
> Best wishes
>
> Jonathan
>
>
> ----- Forwarded message from "Saulter, Andrew" <andrew.saulter at metoffice.gov.uk> -----
>
> > Date: Mon, 1 Oct 2018 09:30:03 +0000
> > From: "Saulter, Andrew" <andrew.saulter at metoffice.gov.uk>
> > To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> > Subject: Re: [CF-metadata] standard names for sea surface roughness
> > variables
> >
> > Good morning Jonathon,
> >
> > Was nice to have a weekend's reflection on this, not least because I also got a bit more feedback from some of my other waves colleagues (thanks Fabrice).
> >
> > A quick fundamental, the reason we need to have some form of 'along' and 'across' follows the same argument as the 'spread' conversation. Basically, wave energy in a given sea-state is not uni-directional, so we have a dominant/mean direction that gets calculated, but there will be a component of wave energy (with associated height, period, slope characteristics etc.) that runs normal to this.
> >
> > In terms of what the "direction" really is, the suggestion I've been given is "upwave", i.e. a wave equivalent of "upwind" and, therefore, same as "wave_from_direction" (correcting my initial suggestion of "to" in the previous post).
> >
> > This gives us a few choices for names I think?
> >
> > Least verbose:
> > Direction: sea_surface_upwave_mean_square_slope_direction /
> > sea_surface_wave_mean_square_slope_from_direction*
> > Parallel component: sea_surface_upwave_mean_square_slope
> > Normal component: sea_surface_cross_wave_mean_square_slope
> >
> > More verbose (but perhaps more clear?):
> > Direction: sea_surface_upwave_mean_square_slope_direction /
> > sea_surface_wave_mean_square_slope_from_direction*
> > Parallel component:
> > sea_surface_wave_mean_square_slope_along_upwave_direction
> > Normal component:
> > sea_surface_wave_mean_square_slope_across_upwave_direction
> >
> > More consistent with existing names (but possibly least clear?):
> > Direction: sea_surface_wave_mean_square_slope_from_direction
> > Parallel component:
> > sea_surface_wave_mean_square_slope_along_from_direction
> > Normal component:
> > sea_surface_wave_mean_square_slope_across_from_direction
> >
> > * if we use _from_direction in conjunction with _upwave, then we need to add some text to link the two terms in the standard name definition.
> >
> > Any of these make sense?
> > Cheers
> > Andy
> >
> > PS. Devon is geographically 'up' from Cornwall - but definitely 'down' in terms of the quality of pasties, clotted cream and beer....
> >
> >
> >
> > -----Original Message-----
> > From: Jonathan Gregory <j.m.gregory at reading.ac.uk>
> > Sent: 28 September 2018 13:46
> > To: Saulter, Andrew <andrew.saulter at metoffice.gov.uk>
> > Cc: cf-metadata at cgd.ucar.edu
> > Subject: Re: [CF-metadata] standard names for sea surface roughness
> > variables
> >
> > Dear Andy
> >
> > > Re the direction of the _mean_square_slope, the parameter and calculation method from the wave spectrum is sufficiently different from that for _wave_[to/from]_direction that it should stand alone. There has already been a precedent set for this with waves, where different forms of parameter calculation from the spectrum are given their own names because there is not only a calculation difference but a different physical interpretation of each parameter (e.g. the various type of wave period).
> >
> > OK, fair enough. So you need sea_surface_wave_mean_square_slope_to_direction.
> >
> > I'm still stuck with what this "direction" really is. Can we insert anything else for ? in
> > sea_surface_wave_mean_square_slope_along_?_direction
> > sea_surface_wave_mean_square_slope_across_?_direction
> > Apparently you want to quantify the mean square slope along and across the direction of the mean square slope. Is that right? I'm not sure what it means.
> > Without the "mean square", I'd think that the slope normal to the direction of the slope must be zero, but it must be more subtle than that in this case!
> >
> > Is there really an ambiguity of to/from with a mean square slope? It seems to me that it must be the same (unsigned) number regardless of whether you go backwards or forwards on a particular direction.
> >
> > Is Devon up or down from Cornwall?
> >
> > Best wishes
> >
> > Jonathan
> >
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
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Received on Fri Oct 05 2018 - 07:25:03 BST
