Three Ways of Thinking About ENSO

Abstract:
El Niño-Southern Oscillation (ENSO), the phenomenon that gives rise to El Niño and La Niña events, has long been a subject of study by applied mathematicians. This phenomenon is a quasi-periodic oscillation between El Niño (warm) and La Niña (cool) events which occur every 2-7 years via air-sea coupled processes in the ocean and atmosphere of the equatorial Pacific. These events, by perturbing patterns of atmospheric circulation, produce changes to local weather on every continent, making this a phenomenon with global consequences.
The physical processes that give rise to ENSO have characteristics of chaotic systems, while also displaying a range of spatial and temporal patterns. In this talk, I will discuss three very different mathematical framings of the tropical Pacific system: first, as a dynamical system with regime-like behaviours; second, as a discrete system with three different states; and third, using Bayesian quantile regression to characterize spatial changes to the system over time. Each of these lenses has resulted in new insights into how to predict ENSO and understand how it is changing over time.
Dr Nandini Ramesh:
Dr Nandini Ramesh is a Senior Research Scientist in Natural Hazards and Climate Risk at Data61, CSIRO. She received her PhD in Ocean and Climate Physics from Columbia University as a NASA Earth and Space Science Fellow. She then worked as a Postdoctoral Scholar at the University of California, Berkeley, following which she was a Research Fellow and Chief Investigator at the ARC Centre for Data Analytics for Resources and the Environment at the University of Sydney.
Her research focuses on the physics of tropical climate on seasonal to decadal timescales, with a particular interest in the impacts of large-scale phenomena such as El Niño and La Niña events and monsoons on rainfall. She uses a range of techniques spanning dynamical systems theory, machine learning, computational fluid dynamical modelling and geospatial data analysis to answer questions about fundamental physical processes and the predictability of these phenomena.