Luncheon Seminar #193: The 21st-Century El Niño: Its Changing Properties, Dynamics, and Impacts

Abstract

The El Niño is one of the most powerful climate variation phenomena and has profound impacts throughout the Asian-Pacific region. Extensive research since the 1970s has produced theoretical frameworks capable of explaining the observed properties and impacts of El Niño as well as predictive models. However, the properties and impacts of the El Niño events observed so far in the 21^st century have been noticeably different from those observed in the 20^th century. These discrepancies have motivated the research community to revise conventional views of the El Niño.

The changes include shifting the El Niño location from the tropical eastern Pacific to the tropical central Pacific and the El Niño evolution from a single-year pattern to a multi-year pattern. Associated with these changes, the El Niño’s impacts on broad areas of the Asian-Pacific region have become different from those documented during the 20^th century. There is substantial evidence that the underlying dynamics of the 21^st-century El Niño are also different from those in the 20^th century, making its behavior more difficult to predict. While the 20^th-century El Niño dynamics resides mostly within the tropical Pacific, the 21^st-century El Niño dynamics invokes more of the subtropical Pacific forcing and inter-basin interactions.

In the talk, I will discuss the views that I have developed during the past decade to explain the changing properties, dynamics, and impacts of the 21^st-century El Niño and how they differ from those of the traditional El Niño. Possible reasons for the recent change in the El Niño will also be discussed.