Séminaire
One of the major issues concerning the study of a dynamical system is the response to perturbations. In climate dynamics, for example, it is of major interest to understand how a given variable, e.g., the temperature, is sensitive to alterations of some other component of the system, e.g., the greenhouse gas concentration.
We review the connection between equilibrium and non-equilibrium properties, also known as Fluctuation-Relaxation Relation, and its main aspects in chaotic and turbulent systems. We consider, in particular,the effects of the fast variables on the slow variables in a multiscale system, as far as the sensitivity properties are concerned.
Two examples about (widely speaking) climate modelling are discussed: the Lorenz-96 model and the double-potential well model. Both of them, despite their apparent simplicity, hide the same kind of interesting features of much more complex systems.
Riwal Plougonven
Laboratoire de Météorologie Dynamique
Ecole Normale Supérieure
24 rue Lhomond
75231 Paris Cedex 05, France
tel. (+33) 1 44 32 27 31