CDS download for ERA5 sdor,cvh,cvl,fsor sometimes fails

(trac ticket #333 created by terhardt)

I ran into the issue, that flex_extract downloads for ERA5 would sometimes fail for the sdor, cvh, cvl and fsor files with a data availability error.

After reaching out to the ECMWF support I was told that the retrieval with either the codes or short names can lead to unpredictable results and that the retrieval with the long parameter names as per the tables on the ERA 5 documentation (​https://confluence.ecmwf.int/display/CKB/ERA5%3A+data+documentation) was the only supported way.

For now I have just disable the conversion to codes for this retrieval and it seems to be okay, at least for the data that I am still missing.

I have attached a simple script that illustrates the problem outside of flex_extract