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
>
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----- End forwarded message -----
Received on Mon Oct 01 2018 - 11:29:21 BST
