The issue described here has been fixed. It is kept here for information only.

What's wrong?

In November 2018,  an error was reported affecting the following data in the climate data store (CDS):

CDS Dataset

ERA5 hourly data on pressure levels from 1979 to present

Parameters affectedU-component of wind, V-component of wind
LevelAll pressure levels
Time periods affected

01 Jan. 2000 - 31 Dec. 2008

01 Jun. 2018 - present

This problem was caused by the computation of U/V from Vorticity (Vo) and Divergence (D) already interpolated on a regular grid in CDS. U/V should have been computed from Vo and D in spherical harmonics representation (the native model representation) and then interpolated to a regular grid before saving to the Climate Data Store.

What can I do if I downloaded the wrong data?

Because this error has not yet been fixed, this means that any data corresponding to the description above is totally wrong, and will continue to be wrong until a fix is in place. You should not use this data and wait until the problem is fixed.

This issue was fixed in January 2019.

When will the issue be fixed?

It is estimated the problem will be fixed in January 2019. Exact details of when the problem is fixed will be provided on this page.

This document has been produced in the context of the Copernicus Climate Change Service (C3S).

The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.

The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.