Over the years, ECMWF has built one of the largest archive of numerical weather prediction models outputs. The archive holds today more than 7 billions meteorological fields from ECMWF operational forecasts, various scientific projects, research experiments and two reanalyses, one of which (ERA-40) covers a period of 45 years, starting late 1957.

In the last couple of years, ECMWF has developed two online services to provide access to these data:

- A public data server, from which researchers can download a large selection of the Centre's 45-year reanalysis at a 2.5 degree resolution.

- An online ordering system that allows users outside ECMWF Member States to order any of the archived data. This system is based on the 'shopping cart' metaphor and provides the user with a comprehensive catalogue of the archive, including various search mechanisms, and documents changes and defects in the archive. Order processing is fully automated from data retrieval to media writting.