The paper "The ERA-40 re-analysis", published in 2005, has been identified by Thomson Reuters Scientific's /Essential Science Indicators/ as one of the most highly cited papers in the field of Geosciences, and has been designated as a "Current Classic" for February.
See Thomson Reuters Scientific's /Essential Science Indicators/
Several scientists from ECMWF were among the authors. See also interview with Sakari Uppala, one of the authors.