Request too large, item limit for ERA5-Land data

Hi, 

I recently tried to download data from single levels ERA5-Land and the limit is actually 1000 items. I am quite sure that it was 100 000, is it normal ?

Thanks,

Colin Chanteloube

Please refer to the announcement of 19th December 2023: https://confluence.ecmwf.int/x/04NcEg which says:

"Please be aware that there is a new selection limit in place that allows to download no more than a month at the time in a single request (more specifically, no more than a 1000 items at a time)."

Thank you for the precision !

Kind regards,

Colin

Does anyone know why they have suddenly imposed this ridiculously low limit? It makes no sense, it effectively shuts down any serious access to data. ERA5 doesn't have this limit, so why have they imposed this on ERA5-Land now? I have put in an info request, but I suspect they won't explain much...

Any insights welcome!

Andreas

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