Hi Jonathan,
I have snipped out the detailed text of your background explanation purely for
readability, below.
Jonathan Gregory wrote:
> Dear All
[... snip...]
> Summary of proposals:
>
> (1) Retain the default "point" interpretation and clarify what it means.
>
> (2) Make cell_methods mandatory if standard_name is supplied.
I'm probably confused. If not then I am concerned with this proposal. Listening
to the general community chatter there's no doubt that plenty of groups have
picked up the "standard_name" attribute and are thrilled to have found it. They
are now creating files which have "standard_name" attributes. In most cases they
lack cell_methods attributes. They believe that they are creating CF 1.0
compliant files. Does your proposal "(2)" imply that valid CF 1.0 files which
use "standard_name" will become invalid CF 2.0 files? If so isn't this a serious
backwards compatibility concern?
Cell methods are described in Appendix E of CF 1.0. Adding complex and subtle
appendices to a standard in order to meet the needs of highly specialized users is
acceptable with the implicit assumption that the material is in appendices because
it is optional. Making an appendix mandatory should require a relatively serious
rethinking of the substance.
> (3) Clarify that unqualified gridbox area-mean implies the entire gridbox.
>
> (4) Introduce "over TYPE" qualifiers for spatial and temporal cell_methods.
>
> (5) Introduce "area:" entries for spatial cell_methods.
Before we introduce further complexity to the sub-grid cell_methods machinery
(which is not one of the more "transparent" aspects of CF already), has there been
a serious exploration of alternatives? The standard name semantics seem to reach
tentacles out into several places. A value of "Variance" in the cell method
changes the underlying dimensions of the standard_name for example. (A little
startling!) Standard name modifiers are appended after blanks and imply radical
changes of semantics. Some standard_names embed the semantics in ever-longer
names -- as in
tendency_of_air_temperature_due_to_diabatic_processes
tendency_of_air_temperature_due_to_dry_convection
tendency_of_air_temperature_due_to_large_scale_precipitation
tendency_of_air_temperature_due_to_longwave_heating
tendency_of_air_temperature_due_to_longwave_heating_assuming_clear_sky
...
I'm tempted to think that a thoughtful discussion on how to systematize these
modifiers is in order. But I confess that months go by without my listening
closely to the CF discussions, so I feel like an outsider making these comments.
My apologies if I have stepped on any toes.
- steve
> Cheers
>
> Jonathan
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--
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Steve Hankin, NOAA/PMEL -- Steven.C.Hankin at noaa.gov
7600 Sand Point Way NE, Seattle, WA 98115-6349
ph. (206) 526-6080, FAX (206) 526-6744
Received on Mon Feb 07 2005 - 19:23:03 GMT
