ERA-Interim production stopped on 31st August 2019
For ERA-Interim (1st January 1979 to 31st August 2019) access through the ECMWF Web API stopped on 01 June 2023
Its successor ERA5 is available from the Climate Data Store (CDS) (What are the changes from ERA-Interim to ERA5?) and users are strongly advised to migrate to ERA5 (How to download ERA5).
For those users who still need access to ERA-Interim after 01 June 2023 (subject to further notice), they can do so via the Climate Data Store (CDS) API.
At ECMWF, the variables TCWV (Total Column Water Vapour) and VIWV (Vertical Integral of Water Vapour) are essentially the same, but are produced by different software.
TCWV is generally produced by the ECMWF NWP forecast system (using the IFS) and is available in the analyses and forecasts.
VIWV is produced by the ERA post processing budget software and, for ERA-Interim, is only available in the analyses.
More information is available in the ERA-Interim archive document:
http://www.ecmwf.int/en/elibrary/8174-era-interim-archive-version-20
The units of both TCWV and VIWV are kgm-2.
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). 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.
