Data and code from: Propagation of the Madden–Julian oscillation as a deterministic chaotic phenomenon

The Madden–Julian oscillation (MJO), a gigantic weather system marked by
eastward travel of cumulus cloud clusters over the Indo-Pacific, often
causes severe weather and climate events worldwide. Despite its frequent
realization, the physics and predictability characteristics of MJO
propagation are not well understood. We here reveal the chaoticity of MJO
propagation, using 4,000-member ensemble global cloud-system-resolving
simulations of two MJOs. Against previous linearized thinking, multiple
regimes supporting MJO propagation emerge under a single atmosphere-ocean
background, depending critically on the equatorial asymmetry of
climatological sea surface temperature. Selection of the bifurcated
regimes results from the stochastic modulation of moisture transport via
westward-propagating equatorial waves, fostered or inhibited by
tropical-extratropical interplay. Tracking the nonlinear processes we
found gives metrics for predicting the timing of MJO propagation.