Olivier Talagrand

The 2014 Lewis Fry Richardson Medal is awarded to Olivier Talagrand for the development of data assimilation techniques, in particular the theoretical formulation of the adjoint method, and the implementation of these techniques in various applications in meteorology, climate and operational weather forecasts.

Olivier Talagrand has profoundly influenced the field of data assimilation for predicting the dynamical behaviour of planetary fluid flows. He developed both a conceptual basis and practical methods for using, testing and assessing ensemble methods for weather forecasts. Talagrand’s approach efficiently takes into account the strongly nonlinear character of the dynamical equations for weather prediction while also minimising the cost function that characterises the difference between predictions and observations.

Talagrand’s adjoint method of data assimilation, which in atmospheric science is called 4-dimensional variational approach, has changed the way that atmospheric and oceanic modellers estimate the current and future states of the atmosphere and ocean. This method has been implemented in various applications, including the model that the European Centre for Medium-Range Weather Forecasts currently uses for weather forecasting. Talagrand has also pioneered the application of general circulation models to atmospheres on other planets. This has provided an important test of a general circulation model for a different parameter range.

Talagrand’s contributions to the nonlinear aspects of data assimilation, observation sensitivity, and predictability form an essential part of present day nonlinear model analysis. He is well known for his openness to new ideas, including those that offer alternatives to the adjoint method. Talagrand’s view is that traditional ideas are there to be challenged.

The concepts from control and optimisation theory used by Talagrand serve as the basis of modern numerical weather prediction, a field founded by Lewis Fry Richardson. Thus it is wholly fitting that Talagrand be awarded the 2014 Lewis Fry Richardson Medal.