Catherine Nicolis

The 2011 Lewis Fry Richardson Medal is awarded to Catherine Nicolis for her highly original contributions to the understanding of the behaviour of stochastic and deterministic non-linear systems and the application of these ideas in meteorology and climate dynamics.

Catherine Nicolis has been a leader in non-linear geosciences over a career spanning several decades. She has made key contributions to both the deterministic and the stochastic aspects of non-linear phenomena and processes. To do so, she introduced key concepts and methods from other areas of the physical and life sciences into the geosciences and applied them in original and creative ways. In the stochastic area, Katy has discovered what is now called stochastic resonance. Her approach, via the Fokker-Planck equation governing a non-linear, periodically and stochastically perturbed process, is distinct from and provides complementary insights to that of the Italian group’s. An important contribution on the deterministic side was to seize upon the “kinetic logic” of R. Thomas in genetics in order to describe oscillatory phenomena in palaeoclimates. Her approach led to the development of Boolean delay equations by M. Ghil and associates. The latter in turn discovered the presence of chaotic behaviour in this Boolean setting, a presence not allowed by the Thomas formulation but recently confirmed by the experimental results. More recently, Katy has made important contributions to the theory of recurrent and extreme events in deterministic systems. As was the case in the past, some of these are joint with her husband Grégoire and, lately, with their son Stamatis C. Nicolis. These are clearly fruitful collaborations that add to, rather than subtract from her highly original and meritorious contributions. Aside from many other seminal papers, Katy also played an important organizational role in the Nonlinear Geosciences community. She was one of the first chairs of EGSs Nonlinear Processes (NP) section and the key organizer of a remarkably interdisciplinary, week-long meeting in Crete, in the summer of 1985. The resulting proceedings, “Irreversible Phenomena and Dynamical Systems Analysis in the Geosciences,” edited by C. Nicolis and G. Nicolis (D. Reidel, 1987), are a unique compendium of key contributions to the NP saga.