Further Studies of Dynamics for El Nino-Southern Oscillation (ENSO) Diversity and Complexity

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The El Niño-Southern Oscillation (ENSO) phenomenon exhibits complex behaviors with two main groups of patterns known as the Central Pacific and Eastern Pacific El Niño events that evolve very differently in time. Such spatio-temporal complexity (STC) of ENSO has great implications on various aspects on the global climate. To date, the fundamental dynamics and essential multiscale interactions resulting in this ENSO complexity remains unclear. This proposal aims to advance current understanding of the fundamental dynamics associated with ENSO STC. The results from this work can lead to an improved prediction skills and increased confidence in climate change projections of ENSO and its global impacts. The work will train a graduate student and a young research scientist.The proposed study will conduct a systematic investigation of ENSO STC by developing and applying new theoretical approaches and using a set of models (of differing complexity) together with existing observations and climate model outputs. The investigator will assess how linear and nonlinear sensitivity of the leading coupled ENSO mode gives rise to a unique regime of ENSO STC, how ENSO interacts with the annual cycle, transient tropical phenomena (e.g., the Madden-Julian Oscillation), and other tropical modes of variability, and how ENSO STC responds to various climate mean state biases and scenarios of climate changes. In addition to training the next generation of scientists, this work can lead to (i) new ENSO conceptual models extending the simple canonical ENSO recharge oscillator paradigm to better capture the essential mechanism of ENSO complexity, (ii) better understandings of key physical and dynamical processes for ENSO complexity, and (iii) new insights into causes of deficiency in climate model simulation of ENSO complexity and potentials for improving ENSO’s forecasting skill and assessed changes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.