Same Equations, different applications: The Recharge Oscillator View of ENSO and Episodic Convection

The El Niño??"Southern Oscillation (ENSO) is a major source of interannual climate variability, shaping rainfall, drought, and weather extremes. Yet even state-of-the-art climate models show substantial biases in reproducing ENSO amplitude, spectral behavior, and the frequency of extreme events. Pinpointing which processes are misrepresented is difficult in comprehensive models because strong coupling between the ocean and atmosphere obscures causality.

In this talk, we introduce the Recharge Oscillator (RO) framework??"a reduced-order model that represents ENSO with two coupled equations for two state variables (Jin 1997). We show that the RO reproduces key ENSO features while linking physical processes to a small set of interpretable parameters. Its low dimensionality enables large ensembles to quantify ENSO internal variability and highlight pitfalls in inferring greenhouse-warming trends from limited records.

Finally, we extend the RO-style framework beyond ENSO to describe oscillatory convection regimes. Prior work (e.g., Seeley & Wordsworth 2021) suggests warming may shift rainfall from quasi-steady precipitation to episodic deluges. We show how an RO-type mechanism reproduces this transition through changes in a single parameter, providing a compact physical interpretation of episodic rainfall. Overall, this two-equation framework offers a powerful tool to understanding diverse modes of climate variability.

Speaker: Sooman Han, Yale University

Room 350/372