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![Diagram illustrating the principle of 4D-Var Diagram illustrating the principle of 4D-Var](/sites/default/files/4D-Var-754px_13.jpg)
Developing a 4D variational data assimilation system was one of ECMWF’s biggest-ever projects. A symposium to mark the 20th anniversary of the operational implementation of 4D-Var took place at the Centre on 26 January.
The speakers' presentations and recordings of the talks are available on the 4D-Var symposium web page.