4D-Var symposium on 26 January 2018

Diagram illustrating the principle of 4D-Var

Twenty years ago ECMWF added an extra dimension – time – to the assimilation of observational data into weather models. This pioneering ‘4D-Var’ technique has led to substantial improvements in the Centre’s forecasts.

Developing a 4D variational data assimilation system was one of ECMWF’s biggest-ever projects. It culminated in the operational implementation of 4D-Var on 25 November 1997, less than two years after the introduction of 3D-Var.

4D-Var symposium live stream

A symposium to mark the 20th anniversary will be held at ECMWF on 26 January.

The event will be live-streamed from 09:00 to 13:00 GMT.

More details are available on the 4D-Var symposium web page.

What is 4D-Var?

ECMWF Director-General Florence Rabier, ECMWF scientists Massimo Bonavita and Tony McNally, and Professor Olivier Talagrand explain how 4D-Var works and why it is so important for numerical weather prediction.

You can find out more about the development of this sophisticated data assimilation method at ECMWF in the following news items:

20 years of 4D-Var: better forecasts through a better use of observations

Progress with running IFS 4D-Var under OOPS