Abstract
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.
Highlights
As one of the most striking interannual climate variations in the world, El Niño-Southern Oscillation (ENSO) manifests as a basin scale air-sea interaction phenomenon characterized by sea surface temperature (SST) anomalies in the equatorial central to eastern Pacific (EP)
The three-region multiscale stochastic model In this work, a deterministic three-region conceptual model with the zonal advective feedback[34] is adopted as a starting model. It is a general extension of the classical recharge oscillator model[3] and depict the air-sea interactions over the entire western, central Pacific (CP) and EP
A simple stochastic process describing the tropical atmospheric intraseasonal wind disturbances of the westerly wind bursts (WWBs), the easterly wind bursts (EWBs) and the MJO, which involves a multiplicative noise that describes the modulation of the wind bursts by the interannual SST, is incorporated into the starting model
Summary
As one of the most striking interannual climate variations in the world, El Niño-Southern Oscillation (ENSO) manifests as a basin scale air-sea interaction phenomenon characterized by sea surface temperature (SST) anomalies in the equatorial central to eastern Pacific (EP). Evolving in the equatorial Pacific region, ENSO can affect climate, ecosystems, and economies around the world through atmospheric pathways[1,2]. Based on the features during their mature phase, they were named as the EP and the central Pacific (CP) types when the largest SST anomaly is located near the coast of the South America and the dateline region, respectively[9,10]. The shift of the main heating location has significant impacts on the air-sea coupling processes in the tropical Pacific, which is the way ENSO affecting the global climate, and brings serious challenges to ENSO predictions[11,12]. Since the concept of CP El Niño emerged, understanding the differences in the patterns, strengths, evolution processes, physical mechanisms, and global influences between the two types of ENSO has attracted great attention
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