Software upgrade for data extraction of a geographical area from selected CAMS global datasets

Announcements CAMS - Announcements
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On 25th of February 2026, as part of regular operational software upgrades, the software handling area extraction for regular lat-lon gridded datasets will be updated to a new version to correct a behaviour that caused an interpolation of the data during the area extraction.

What is the reason for this change?

Until now, area extraction has triggered an interpolation onto a new grid whose south west corner is that given in the supplied area. This interpolation has been identified as undesirable behaviour. In order to preserve the original values it has been decided the software should instead only crop the existing data, returning just those grid points that lie inside the area without modification.

What will be the effect on the data?

Requests that specify a geographical area may now return data on a slightly different grid which will be displaced from the original grid by up to one grid length, and the number of grid points returned may also differ.

Please refer to our Knowledge Base article on Software upgrade for regular lat-lon gridded data extraction of a geographical area, which graphically explains the change in behaviour and also provides a workflow to help users identify whether or not this change is affecting their requests.

Which datasets are affected?

The change described above will apply exclusively to data requested for a specific area, and only in cases where the latitude and longitude of the user-provided bounding box do not exist in the original global dataset before area extraction, regardless of how the data was downloaded (i.e. either using the web interface or the API service), and for the following CAMS datasets ONLY:

What should users do if they have downloaded sub-area data (as described above) from the listed datasets?

If your requests are affected by this software upgrade, then the recommendation is to download a new test data sample (from date of implementation on 25 February 2026) and compare it with the data previously downloaded. This will allow you to decide on whether or not any modifications are needed to your workflows following the software upgrade.
Users of the CAMS global atmospheric composition forecasts and global greenhouse gas forecasts may be given access to test data (via API only) ahead of implementation on 25 February 2026 by raising a ticket enquiry (ECMWF login required) through the ECMWF Support Portal to request access.

For any enquiries on this topic, please contact us (ECMWF login required).

ECMWF Support
on behalf of the Data Stores Service