ERA-Interim production stopped on 31st August 2019
For the time being and until further notice, ERA-Interim (1st January 1979 to 31st August 2019) shall continue to be accessible through the ECMWF Web API. Keeping in mind that ERA-Interim is published with an offset of about three months from the dataset's reference date, ERA-Interim August 2019 data will be made available towards the end of October 2019.
ERA5 is now 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 migrate from ECMWF Web API to CDS API).
TCWV (Total Column Water Vapour) and VIWV (Vertical Integral of Water Vapour) are essentially the same, but produced by different software.
TCWV is produced by the IFS (ECMWF forecast system) 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
Both TCWV and VIWV are in kg m^-2.
