The observations assimilated in ERA-Interim are described in Section 4: "Observations" of an article on the ERA-Interim reanalysis in the Quarterly Journal of the Royal Meteorological Society.
The overwhelming majority of data originate from satellites.
- For upper-air temperatures, wind and specific humidity, observations from satellites, radiosondes, pilot balloons, aircraft, and wind profilers were assimilated.
- For surface pressure, 2m temperature, and 2m relative humidity, observations from ships, drifting buoys, and land stations were assimilated.
- For near-surface (10 m) winds, only observations over sea were assimilated, coming from scatterometers, ships and buoys.
ERA-Interim assimilates only data that is supplied through the WMO GTS, and there only data that
- is supplied in in near-real-time
- meets certain quality criteria and file format standards
Regarding data from field campaigns, in case campaign data was supplied to the GTS in near-real-time, and meets the relevant data format standards, the data was assimilated. We have no records of individual campaign's names or acronyms though.
ERA-Interim production to stop on 31st August 2019
As ERA5 is now available (What are the changes from ERA-Interim to ERA5?), we are preparing to stop the production of ERA-Interim on 31st August 2019. This means that the complete span of ERA-Interim data will be from 1st January 1979 to 31st August 2019.
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 2019.
For the time being and until further notice, ERA-Interim shall continue to be accessible through the ECMWF Web API. ERA5 is available from the Climate Data Store (CDS).