Hi Mark
Sorry, silence doesn't mean consent.
I think it is exactly the place of standard names to be completely proscriptive about what terms mean.
The you say x, I say x, and we both mean different things, is what we need to avoid, and in particular we must not change definitions of existing quantitities.
Admittedly, your change wouldn't strictly change anything retrospectively, since it's an inclusive change, but it's probably a dangerous thing to do. (My sense of deja vu tells me we've been here before, and I may even have been on the other side of the argument :-).
If you are importing something where x is used as the coordinate, and it is longitude, then why not put that in other metadata? The point of the CF standard is that it just that ....
Bryan
>
> There have not been any responses to this post in the last 10 days.
>
> I know that this is a dangerous philosophy, but can I suggest that, in this case, silence equals consent?
>
> If it is, I would like to see these amendments in the standard_name publications as soon as possible. Would this cause concern?
>
> many thanks
> mark
>
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu on behalf of Hedley, Mark
> Sent: Thu 05/04/2012 17:35
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] identification of vector components
>
>
> There is a statement in the definition of many standard names which are used for vector component definitions, e.g.:
>
> x_wind
> alias: grid_eastward_wind
> "x" indicates a vector component along the grid x-axis, when this is not true longitude, positive with increasing x. Wind is defined as a two-dimensional (horizontal) air velocity vector, with no vertical component. (Vertical motion in the atmosphere has the standard name upward_air_velocity.)
>
> I think that the statement 'when this is not true longitude' is problematic, particularly for software converting from other formats, where x indicates the grid i direction, independent of rotation or projection. I do not think it is the place for standard_name to limit the use of the term 'x' to cases where the horizontal coordinate reference system is not 'true latitude longitude'
>
> I propose that these terms be removed from all standard names which have 'x' or 'y' as a modifier.
>
> This would enable all x-ward and y-ward definitions to be used, independent of the grid_mapping, as standard names.
>
> eastward and northward remain useful modifiers as many models may choose to output eastward vector components where east is not the x direction for the model grid.
>
> The work on vector containers in:
> https://cf-pcmdi.llnl.gov/trac/ticket/79
> has indicated a good way forward for identifying vector components, and identifying that vectors are with respect to a grid_mapping. I think this proposed change would interface nicely to the proposal in ticket 79
>
> How would this proposal be viewed by the community?
>
> mark
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--
Bryan Lawrence
University of Reading: Professor of Weather and Climate Computing.
National Centre for Atmospheric Science: Director of Models and Data.
STFC: Director of the Centre for Environmental Data Archival.
Ph: +44 118 3786507 or 1235 445012; Web:home.badc.rl.ac.uk/lawrence
Received on Wed Apr 18 2012 - 04:34:24 BST
