Suddenly ECMWF files have a GRIB2 message with shortName=unknown

[anphi]

There was a reported problem that since the 25th of November 2020 the GRIB2 surface field message snow depth has a shortName=unknown instead of sd.

[anphi]

Why do we have this problem?
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In October, there was an announcement of a change in default modules on ECMWF servers on Wednesday 25 November 2020 10:00 - 10:30 UTC.
​https://confluence.ecmwf.int/pages/viewrecentblogposts.action?key=UDOC

They changed the default version of eccodes from 2.17. to 2.19.1. Since version 2.19.0 there is
a change in the encoding of the snow depth parameter 141 in GRIB2 format:

​https://confluence.ecmwf.int/display/ECC/ecCodes+version+2.19.0+released

This causes all older versions of eccodes to misinterpret the GRIB2 message of snow depth if the conversion of GRIB1 to GRIB2 was done with eccodes version >= 2.19.0.

The new GRIB2 snow depth message has parameter ID 254 while the old one has 11.

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Possible solutions
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1. Fix the eccodes version on ECMWF servers to the old one: 2.17. In case you use flex_extract > version 6, you need to fix exact module version of eccodes in the templates for submitting installation or run scripts. Names of these files depend on the version. In flex_extract v7.1.2. they are found in the Templates directory and are called installscript.template and jobscript.template

2. Select FORMAT = GRIB1 in flex_extract retrievals to have surface fields in GRIB1. The problem would no longer occure.

3. Since this problem is a pure problem of a "wrong" or changed entry in the definition tables of GRIB1 and GRIB2, there is always the option (on local servers) that one has to explicitly set the GRIB parameter number for snow depth to 11 again. This is of course very annoying. But then eccodes would recognize the message as snow depth again. This would be a one-line command but has to be applied on all files.

4. Update the eccodes version on local servers to version 2.19.0 or higher which will have the correct definition table.