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

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Results from this renewal project will improve the ability of climate models in predictions of El Nino-Southern Oscillation (ENSO), its impacts and in projections of future changes in ENSO activity. It is anticipated that the theoretical and methodological techniques that are developed by the Principal Investigator (PI) through this effort will have broad applicability in the climate science community. Dissemination of the scientific results will occur through publications, presentations at conferences and professional meetings, channels of the University of Hawaii, and outreach to the local and broader communities. A graduate student and two early-career scientists will be trained through this project.El Nino/La Nina events that occur every few years are characterized by massive warming/cooling over the eastern tropical Pacific Ocean together with weakening/strengthening of trade winds. This strong inter-annual fluctuation of the global climate system is referred to as the ENSO phenomenon. It accompanies by systematic changes in atmospheric and oceanic circulations, affecting global weather and climate systems, marine and terrestrial ecosystems, and fisheries, and thereby having a great impact on economics of well-being and people's life. The ENSO phenomenon exhibits rich diversity in its strength, duration and patterns of warming/cooling and in its global impacts. Fundamental issues concerning ENSO remain to be better addressed. For example, whether there exist roughly two groups of ENSO typical patterns, namely the so-called Central Pacific and Eastern Pacific El Nino is an active research topic in the scientific community. Furthermore, how influences of ENSO in the tropic Pacific are spread into the highly complex global climate system and ecosystem, remains a question to be better understood. The PI will conduct systematic theoretical, diagnostic, and numerical modeling investigations to achieve the following three objectives: (1) further advancing linear and nonlinear theories for the origins of the ENSO pattern diversity; (2) better understanding of the mechanisms causing ENSO complex temporal evolution and their impacts (3) further investigating the sensitivity of ENSO patterns and temporal characteristics to biases and future changes in tropical climate mean state and in parameters of key physical processes of the climate models. New theoretical approaches will be developed and a model hierarchy ranging from simple to fully coupled Global Climate Models will be adopted to address the outstanding questions and to achieve the three objectives.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.