Monday 14 Jan 2019: Resonance and universality in dynamical systems - a discussion
Dr. John Bruun - University of Exeter
Harrison 170 14:30-16:30
Many earth systems exhibit noisy, turbulent and random looking features. Where the systems signal-to-noise ratio is low this can make it hard to distinguish its defining physical properties. Resonances can be viewed as a repeating response eigenmodes and in certain configurations these have universal features, such as for the period-doubling map (quasi-periodic, periodic and/or intermittent properties) established for turbulence by Feigenbaum. These features can help us identify the type of dynamic system, even for low signal-to-noise settings. Resonance features can be assessed using time-regular sampled data (from theory, simulation and/or observation) and I’ll give a background to these signal-analysis inference methods. Any system’s transport properties are effectively due to the balance of forcing, wave propagation, interface coupling and boundary conditions. Climatic forcing can alter the chaotic properties and resonance response by pushing the system through a tipping point – which is of contemporary concern. In this talk I’ll discuss some generic concepts of universality developed in condensed matter physics and related recent theoretical and observational analysis results that focuses on resonance modes of the El Nino Southern Oscillation (ENSO). This includes current ideas on the wave-dispersion and resonance structure of ENSO and universality in the context of the tropical wave guide, the ocean gyres and the whole Pacific basin.