Stricter selection limits on ERA5-Land were unfortunately necessary as the large requests were causing backlogs in the Climate Data Store (CDS) queueing system. Since imposing the limits a much higher level of service across the system was achieved, a 20-50% increase in quantity of data delivered per day.
It became obvious quite quickly that this limit impacted our users more than anticipated and so the Climate Data Store (CDS) team looked into ways of improving the situation while preserving compute resources on the CDS.
We are pleased to let you know that the limit has been reviewed and increased from 1,000 to 12,000 fields which means that you may now download up to 12 variables per month at once. Using an API script, users may loop through months and years. There are API examples for doing this in the CDS Documentation at: https://confluence.ecmwf.int/display/CKB/Climate+Data+Store+%28CDS%29+documentation#ClimateDataStore(CDS)documentation-CDSAPIandCDSToolboxexamples
While many users may prefer to download the data in NetCDF format, we strongly recommend that data is downloaded in its native format (GRIB) to avoid disappointment (the GRIB to NetCDF conversion is likely to fail on larger requests unfortunately). Keep in mind that with downloading data on a month by month basis in GRIB format, you may then concatenate say 12 monthly GRIB files to make one yearly GRIB file (see our Knowledge Base article on (How to merge multiple GRIB or NetCDF files).
Regards,
ECMWF Support