#156: Extension to external_variables Syntax for Masks and Area Fractions
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Reporter: martin.juckes | Owner: cf-conventions@…
Type: enhancement | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Resolution: | Keywords:
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Description changed by martin.juckes:
Old description:
> Ticket #145, now accepted, proposes a new attribute,
> `external_variables`, to indicate when a variable referred to in the
> `cell_measures` attributes is in another file. This ticket relates to
> masks and area fractions used in the `cell_methods` attribute which may
> be associated with another variable. For instance, if we have
> `cell_methods = area: mean where sea_ice` and, in another file, a
> variable `siconc` which contains the sea ice area fraction. At present,
> there is no way within the convention to indicate, in the file containing
> the `cell_methods` statement, that the variable `siconc` is supplied
> separately.
>
> The proposal is to allow the `external_variables` attribute to include
> terms of the form `sea_ice:siconc` to indicate that an `area_type` has an
> associated variable in an external file.
New description:
Ticket #145, now accepted, proposes a new attribute, `external_variables`,
to indicate when a variable referred to in the `cell_measures` attributes
is in another file. This ticket relates to masks and area fractions used
in the `cell_methods` attribute which may be associated with another
variable. For instance, if we have `cell_methods = area: mean where
sea_ice` and, in another file, a variable `siconc` which contains the sea
ice area fraction. At present, there is no way within the convention to
indicate, in the file containing the `cell_methods` statement, that the
variable `siconc` is supplied separately. In earlier CMIP archives it was
reasonably easy to determine when a mask or area fraction was available
for a particular cell methods operation. For CMIP6 this is not so easy, as
there are a substantial number of area fraction arrays covereing different
aspects of the cryosphere and land surface.
The proposal is to allow the `external_variables` attribute to include
terms of the form `sea_ice:siconc` to indicate that an `area_type` has an
associated variable in an external file.
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Ticket URL: <http://cf-trac.llnl.gov/trac/ticket/156#comment:1>
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