The oceans offer climate scientists something that they always wished for: the ability to predict climate variations months, years, and even decades ahead of time. While the atmosphere is known to have a relatively short memory of several days to weeks, the oceans are believed to be capable of remembering what has happened in the atmosphere weeks, years, decades, and even centuries in the past. Fluctuations in the atmosphere leave footprints in the oceans through the exchanges of heat, momentum, and fresh water at the ocean surface. Over time these footprints expand to influence depths well below the surface and these footprints can emerge out of the ocean at later times to affect the atmosphere and lead to climate variations. If we understand the dynamical keys to how the atmosphere and oceans interact and where the ocean memory resides, we will be able to make successful long-term climate predictions.

Professor Jin-Yi Yu’s research group focuses on understanding and predicting climate variations on interannual to decadal time scales resulting from atmosphere-ocean interactions in the tropical Pacific and Indian Oceans, where two important climate phenomena reside: El Niño and the Asian-Australian monsoons. Together these two phenomena have the ability to substantially impact large portions of the population in Asia, Australia and North and South America.  They use statistical analysis methods and numerical models of the climate system running on supercomputers to understand how the oceans control the intensity and frequency of occurrence of El Niño and abnormal monsoon activity. Their goal is to develop dynamical and statistical methods to predict these two influential climate phenomena seasons to decades ahead of the time.

Professor Yu’s recent efforts have concentrated on the changing behavior of El Niño, which has occurred more frequently since the beginning of the twenty-first century and whose central location has moved from the eastern Pacific to the central Pacific. He terms this new type of El Niño the Central-Pacific El Niño to differentiate it from the traditional type of Eastern-Pacific El Niño. He believes this new type of El Niño has an underlying dynamic that is distinct from the traditional El Niño and that it affects global climate in new ways. By analyzing climate data and by conducting climate model experiments on supercomputers, Professor Yu’s research group is working to isolate the dynamical keys to explain and to predict this emerging change in the behavior of El Niño, which may be a consequence of global warming.  A more complete understanding of these dynamical keys will lead to increases in the accuracy of predictions of El Niño behavior and its impacts.

Research Update

Based on the latest citation statistics, a paper published by Professor Jin-Yi Yu of ESS and his former PhD student Dr. Hsun-Ying Kao is the most cited paper published on Journal of Climate in 2009. The paper, entitled "Contrasting Eastern-Pacific and Central-Pacific Types of ENSO", Journal of Climate, 22, 615-632", reported the discovery of two distinct types of El Nino-Southern Oscillation (ENSO) phenomenon in the tropical Pacific and has attracted a lot of attention in the climate research community. A series of follow-up papers have been published by Professor Yu's group to further the understandings of the underlying dynamics and global impacts of these two types of ENSO. More information of these exciting research works can be found at http://www.ess.uci.edu/~yu/ .