| Policy |
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Explanations |
| 1. Field Short Name |
- Define a set of common definitions used by all COSMO members.
- The master tables are managed by DWD (grib2/localConcepts/edzw).
- MeteoSwiss provides a script to synchronize fieldextra dictionaries and
localConcepts definition files (in both directions).
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COSMO software uses alphanumeric names (short names) to refer to specific
fields, e.g. U, P, T, HSURF, etc.
- These short names are supported by grib_api as a local concept. Definition files
have to be provided in grib2/localConcepts/<center>, where
<center> is the short cut for the originating center
(e.g. edzw or 78 for DWD).
- Fieldextra uses a self-defined dictionary (as external ASCII file).
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| 2. Center specific Table Values |
- Define a set of common values used by all COSMO members, avoid as much as
possible local values not part of this set.
- The master tables are managed by DWD (grib2/tables/local/edzw/<version>)
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The GRIB 2 standard reserves in all tables a range of values for local use
(e.g. bytes 192-254 for one byte values). Such center specific table values are
supported by grib_api and by fieldextra:
- In grib_api by the use of local tables, provided in:
grib2/tables/local/<center>/<version>, where <version>
is the version of the local table.
- In fieldextra by hardcoded internal tables (in order to be independent
from input and output format, fieldextra translates all meta-information in some
internal codes).
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| 3. Model Name |
- The name of each model in operation in the COSMO centers is uniquely
defined by the n-tuple (center, subcenter, product category,
generating process identifier)
- The associated information is always coded in each GRIB record
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No provision exists in the GRIB 2 standard to code the model name.
Support for model name:
- In grib_api no support for a model name is available (at the moment).
- In fieldextra model names are hardcoded by internal tables.
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| 4. COSMO Standard Keys and Local Use Section |
- COSMO standard keys are:
- 'localNumberOfExperiment' (unsigned integer coded on 2 bytes)
- COSMO standard keys are coded in the local use section.
- A default local use section, with localSectionNumber = 250, and
containing all COSMO standard keys, is defined for each center.
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Besides the model name considered in Sect. 3, there is a need to define
additional meta-information shared in the COSMO consortium, but not part
of the GRIB 2 standard. The local use section is the mechanism provided
by the GRIB 2 standard to code such additional meta information.
Support for local use section:
- In GRIB API: each local use section is defined by the file
grib2/local.<center>.<localSection>.def, where <center> is the
originating center identifier (e.g. 78 for DWD) and <localSection> is
the local use identifier.
- In fieldextra: hardcoded internal tables
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| 5. GRIB API Definition Files |
- A COSMO set of definition files is maintained, which is compatible
with all COSMO software
- Local modifications to the official ECMWF definition files should be
put in the local part of the GRIB API definitions (e.g. localConcepts,
tables/local), with the following exceptions:
- Bug fixes (should be communicated to ECMWF)
- Typing errors and units corrections (should be communicated to ECMWF)
- New features not yet in the official definitions, but planned
for the next GRIB API release
- Modifications which are absolutely needed (e.g. new alias):
document and clearly mark these modifications in the definition files,
try to convince ECMWF to put these in the next release
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The GRIB API definition files are used by multiple COSMO software (e.g.
INT2LM, COSMO, fieldextra). A unified set of definition files should be
provided to facilitate their maintenance. Furthermore, local
modifications to these files should be organized in such a way that the
definition files can be easily upgraded when a new release of the GRIB
API is provided by ECMWF.
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| 6. Information Flow |
- The COSMO TAG is responsible to coordinate the use of GRIB 2 within the consortium
- It is informed about any planned modification of GRIB 2 coding at DWD
(e.g. new short name, new local value), and has the opportunity to
give a recommendation to the DWD
- It is informed about any local requirement by a COSMO member,
and will propose a solution
- The cosmo-tag mailing list is used for communication
- The following information is maintained on the COSMO web
- COSMO model names and associated n-tuples
- COSMO standard keys and their definitions
- Local table values common to all COSMO members
(or the full GRIB 2 tables, with the COSMO local values inserted as in
http://www.nco.ncep.noaa.gov/pmb/docs/grib2)
- Master table for COSMO short names
- For each center:
- list and content of each local sections
- definition of additional short names not integrated in common COSMO table
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It is important to avoid incompatible developments coming from different places.
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