Thanks Jonathon,
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).
As for the "to", yes the same ambiguity exists for waves as for winds. However, it would be good to avoid multiple names where possible. So, at this point I would only suggest "_mean_square_slope_to_direction" as we are trying to specify a positive axis against which to have our "_along/_across" parameters referenced against, and that should be the pre-dominant direction of wave travel I think. What we really want to avoid in the long run is a whole load of "_along_to, _along_from" names, so perhaps two catchall names:
sea_surface_wave_mean_square_slope_along_direction_axis
sea_surface_wave_mean_square_slope_across_direction_axis
would suffice. These can then be linked to the prescribed direction as appropriate in the variable metadata? I've added the term _axis here to make the name more readable (to me!) but possibly not needed (direction_line seemed a bit weird)?
Cheers
Andy
PS. Being Cornish, we hate directional ambiguity - so a local with always use "where 'ee goin' to" when asking where someone is going; the reply is "up Plymouth" or "down St Just" depending on direction of travel :-)
-----Original Message-----
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> On Behalf Of Jonathan Gregory
Sent: 27 September 2018 13:18
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] standard names for sea surface roughness variables
Dear Andy
> In this case "dominant" (which infers a method of calculation) is not the same as "primary" (which is used in the existing wave standard names to denote ranking of swell components). However, I agree we could omit the "dominant" to bring this more in line with other wave directions, and provide metadata to determine the method of calculation elsewhere - that would enable a more flexible approach....
Good. I agree. In that case, do you still need a new standard name for the direction of the slope? Maybe you could use the existing
sea_surface_wave_to_direction
for this purpose?
> sea_surface_wave_mean_square_slope_parallel_to_direction
> sea_surface_wave_mean_square_slope_normal_to_direction
I agree that the "to" here could be misunderstood. That's not your fault, of course, but due to our peculiar use of "to" as a sort of adjective!
> I guess an alternative would be to use _along/_across instead of _parallel_to/_normal_to?
There are some existing names containing across_line, where "across" means "normal to", so it would be consistent to use that word. There aren't any existing names containing normal, perpendicular, along or parallel. I suggest
> sea_surface_wave_mean_square_slope_along_wave_to_direction
> sea_surface_wave_mean_square_slope_across_wave_to_direction
which might alleviate the ambiguity, perhaps? Or maybe we don't need to include the "to" in any case for waves. Does the same ambiguity exist, when talking about waves, as we have with winds being eastward or easterly etc.?
Best wishes
Jonathan
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Received on Fri Sep 28 2018 - 02:34:21 BST
