El Niño-Southern Oscillation (ENSO) exhibits diverse characteristics in spatial pattern, peak intensity, and temporal evolution. Here we develop a three-region multiscale stochastic model to show that the observed ENSO complexity can be explained by combining intraseasonal, interannual, and decadal processes. The model starts with a deterministic three-region system for the interannual variabilities. Then two stochastic processes of the intraseasonal and decadal variation are incorporated. The model can reproduce not only the general properties of the observed ENSO events, but also the complexity in patterns (e.g., Central Pacific vs. Eastern Pacific events), intensity (e.g., 10–20 year reoccurrence of extreme El Niños), and temporal evolution (e.g., more multi-year La Niñas than multi-year El Niños). While conventional conceptual models were typically used to understand the dynamics behind the common properties of ENSO, this model offers a powerful tool to understand and predict ENSO complexity that challenges our understanding of the twenty-first century ENSO.

厄尔尼诺-南方涛动（ENSO）在空间格局、峰值强度和时间演变方面表现出不同的特征。在这里，我们开发了一个三区域多尺度随机模型，以表明观察到的 ENSO 复杂性可以通过结合季节内、年际和年代际过程来解释。该模型从年际变化的确定性三区域系统开始。然后将季节内和年代际变化的两个随机过程结合起来。该模型不仅可以重现观测到的 ENSO 事件的一般特性，还可以重现模式的复杂性（例如，中太平洋与东太平洋事件）、强度（例如，极端厄尔尼诺现象的 10-20 年再次发生）和时间演变（例如，多年拉尼娜现象多于多年厄尔尼诺现象）。