ECMWF has in the past produced three major reanalyses: FGGE, ERA-15 and ERA-40. Now progress is being made in producing 'ERA-Interim'. ERA-Interim has progressed beyond the end of ERA-40. After completion of the first four years it was decided to revise the configuration of the system and to rerun the initial segment. Other shorter reruns for later periods have been completed as needed for technical reasons. ERA-Interim reanalysis is expected to catch up with operations in late 2008. The reanalysis will then be continued in near-real time with the same system in order to support climate monitoring. This experiment contains surface-data with a forecast-step of 12 hours and a time-step of 12 hours. The grid is unreduced. The data sets contain monthly mean values.
ECMWF quality information (status 2018-06-13; source: https://confluence.ecmwf.int/display/CKB/ERA-Interim+known+issues : ERA-Interim known issues: 1. Surface photosynthetically active radiation (surface PAR) values are too low 2. Convective Available Potential Energy (CAPE) values are erroneously zero 3. ERA-Interim issues with cloud cover 4. Sea Surface Temperature has values over land in ERA-Interim and other ERA products 5. Anomalies at certain dates and locations 6. Over oceans geopotential (and potentially derived fields too) shows a 'spectral ripples' pattern. 7. It is not possible to obtain full (archived) resolution ERA-Interim data from the point and click web interface. Instead you get: a. For spectral data, when grid=128 is selected, automatic truncation to T213 occurs. b. The option "Grid default (as archived)" gives a 0.75x0.75 lat/long grid for both spectral and grid point data, again with automatic truncation to T213 for spectral fields. c. The Gaussian grids all appear to be full grids, not reduced, with no means of requesting the latter. d. There is no T255 option 8. Sunshine duration is defined in a non-standard manner which leads to underestimation of this quantity.
European Centre for Medium-Range Weather Forecasts
Dr. Martina Stockhause
Max-Planck-Institut fuer Meteorologie
Is described by
 DOIDee, D. P.; Uppala, S. M.; Simmons, A. J.; Berrisford, P.; Poli, P.; Kobayashi, S.; Andrae, U.; Balmaseda, M. A.; Balsamo, G.; Bauer, P.; Bechtold, P.; Beljaars, A. C. M.; van de Berg, L.; Bidlot, J.; Bormann, N.; Delsol, C.; Dragani, R.; Fuentes, M.; Geer, A. J.; Haimberger, L.; Healy, S. B.; Hersbach, H.; Hólm, E. V.; Isaksen, L.; Kållberg, P.; Köhler, M.; Matricardi, M.; McNally, A. P.; Monge-Sanz, B. M.; Morcrette, J.-J.; Park, B.-K.; Peubey, C.; de Rosnay, P.; Tavolato, C.; Thépaut, J.-N.; Vitart, F. (2011). The ERA-Interim reanalysis: configuration and performance of the data assimilation system. doi:10.1002/qj.828