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In this study, a modified multi-dimensional ensemble empirical mode decomposition (MEEMD) is devised and employed to understand the temporal-spatial evolution of the sea surface temperature anomalies (SSTAs) of interannual timescales. We take the advantage of empirical orthogonal function (EOF) in lossy compression of temporal-spatially coherent data and decompose the data in the transformed EOF space using ensemble empirical mode decomposition (EEMD) to accelerate the computation of MEEMD. It is demonstrated that the modified MEEMD can eliminate temporally and spatially incoherent noise and recover accurately the temporal-spatial structures of SSTAs on interannual or longer time scales. The modified MEEMD is then applied to characterize the evolution of the observed El Niño-Southern Oscillation (ENSO) phenomenon for the period from 1880 to 2009. To identify the ENSO events through that period, an alternative and more consistent Niño 3.4 index is defined. 31 ENSO warm events are identified with this alternative index and the evolution of each event is examined. It is found that isolated SSTAs off Baja California can propagate southwestward to the equatorial region near dateline in about one year and then propagates eastward with amplification and a faster speed to shape up an El Niño event. In this sense, SSTAs off Baja California are instrumental to ENSO development, especially in triggering the so called central Pacific (CP) ENSO or ENSO Modoki after 1980.
A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science.
Includes bibliographical references.
Zhaohua Wu, Professor Directing Thesis; Guosheng Liu, Committee Member; Philip Sura, Committee Member.
Florida State University
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