资源环境科技发展态势分析平台

El Nino-Southern Oscillation (ENSO) has significant impact on global climate and relevance for seasonal forecasts. Recently, a simple modeling framework was developed that captures the ENSO diversity, where state-dependent stochastic wind bursts and nonlinear advection of sea surface temperature are coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. In this article, the coupled model is compared with observations using reanalysis data over the last 34 yr, where the observed non-Gaussian statistics and the overall mechanisms of ENSO are both captured by the model. Then the formation mechanisms of both the central Pacific (CP) and the traditional El Nino in the model are systematically studied. First, ocean Rossby waves induced by easterly trade wind anomalies facilitate the heat content buildup. Then the reflected ocean Kelvin waves and the nonlinear advection lead to positive SST anomalies in the CP region and create a CP El Nino. Second, two formation mechanisms are revealed for the traditional El Nino, including the super (extreme) El Nino. The first mechanism indicates a preferred wind structure with easterly wind bursts (EWBs) leading westerly wind bursts (WWBs), where the EWBs build up heat content and then the WWBs trigger the El Nino. The second mechanism links the two types of El Nino, where a CP El Nino favors a heat content buildup and the advent of a traditional El Nino. This article also highlights the mechanisms of La Nina formation and El Nino termination.