CDS Service disruption ENDED on 11 November 2022


UPDATE on 14 Nov 2022

We are delighted to inform our users that the DHS Move completed on 11 November 2022.

This means that access to all CDS data served from MARS tapes is fully restored.

UPDATE on 03 Nov 2022

The DHS-Move is expected to complete in the week commencing 7 Nov 2022. 

While CDS data served from MARS tapes is gradually coming back online, users should not be attempting to retrieve such data until a further announcement is made, as results may be inconsistent.

The Support team can only provide limited support until access to the archive is fully restored.

As of 23 March, the Climate Data Store (CDS) and Atmosphere Data Store (ADS) are the first two user facing services operationally supported from our new Data Centre in Bologna. Following that successful migration, we would like to update you on the next steps in the transition to the Bologna Data Centre.

Following successful tests earlier this year (dry-runs of 5 April 2022, 26-28 April 2022 and 28 June-5 July), the ECMWF Data Handling System (DHS) Move, causing 28 days of reduced MARS (Meteorological Archival and Retrieval System) and ECFS (ECMWF's File Storage system (ECFS) service) service, is due to start on 8th September 2022

This degradation of the service may impact some of our Climate Data Store (CDS) data users. This is because some of the data made available from the CDS are served from tapes in the ECMWF MARS system.

CDS data users should expect that the following CDS datasets served from MARS tapes will not be accessible during the DHS move. Users may still submit CDS data requests which will remain in the queue until data access is resumed.

Click here to see the list of affected CDS datasets (i.e. served from MARS)

The information above is based on current expectations. For more details and to get notified about further updates and changes, please “Watch”  our dedicated confluence space. We recommend our users to "Watch" this page announcement also.

Thank you for your patience during this significant migration to our new data centre which will enable exciting scientific developments and an overall better service to all ECMWF users.

ECMWF Support

During the data migration, I want to use the reanalysis-era5-complete dataset to drive the flexpart model, which is urgent for me, is there a transitional data download solution? Thanks for any help!!! 

Me too! DO you solved?

We're in the same boat. I have contacted the ECMWF support and they told me the ERA5 'complete' dataset is indeed unavailable for a number of weeks. Though, other CDS ERA5 datasets - e.g.!/dataset/reanalysis-era5-single-levels?tab=form - will be available.


FYI, as well as the CDS ERA5 datasets, the most recent 3 months of ERA5-complete should still be available via the CDS API ; see

How to download ERA5

section 4 ("Option B")

Hope that helps,


is ERA5 for FLEXPART is open to all countries now ?  it is only for EU Member States before.


since yesterday, I'm getting errors requesting most recent ERA5 data with no reason given. Is this related to the service disruption?

Internal error whilst executing user request


Hello,Has the imigration project success? 

Users who are highly-depended on ERA5 model level data are in very urgent.

Please let us known when the availibilty is ok.



Dear ECMWF Support,

The promised timeframe of 5-6 weeks from 8 September has already elapsed but I am still failing to download the data this morning as I keep getting the AccessError -2. Given the urgent data needs that many of us are facing, I was wondering if you could provide us an update?

Many thanks,


As indicated in our announcement above, please refer to the ECMWF dedicated confluence space about the DHS move and when MARS data will be made accessible again. Thank you.

ECMWF Support

Thanks Anabelle !