A comprehensive eigen-mode analysis of an intermediate coupled model linearized with respect to arrays of basic states is performed to study the regimes of leading ocean-atmosphere coupled modes of relevance to the El Niño Southern Oscillation phenomenon. Different kinds of leading modes are found to coexist and to become unstable under wide ranges of basic states and parameter conditions. In particular, two main kinds of modes have periods around 4 years and 2 years. They are thus referred as to quasi-quadrennial (QQ), quasi-biennial (QB) modes, respectively. The positive coupled feedback destabilizes and quantizes the near-continuous spectrum for the low-frequency modes of the upper ocean dynamics giving rise to these leading modes with distinct periodicities. The QQ mode can be understood to a large extent by the mechanisms elucidated in the simple conceptual recharge oscillator which relays on slow oceanic dynamic adjustment of equatorial heat content, whereas anomalous advection of sea surface temperature by equatorial zonal current anomalies plays an important role in the QB mode. One of the findings of this study is that the QQ and QB mode may coalesce under realistic conditions through a codimension-2 degeneracy in the parameter space. The coexistence or multiplicity of ENSO-related coupled modes under present climate conditions may provide a plausible explanation for the observed dominating QQ and QB variability of rich ENSO behaviors. / A Dissertation Submitted to the Geophysical Fluid Dynamics Institute in Partial
Fulfillment of the Requirements for the Degree of Doctor of Philosophy. / Summer Semester, 2006. / April 17, 2006. / Advective Feedback, Thermocline Feedback, Heat Budget Analysis, Stability Analysis, Unstable Coupled Modes, Coexistence / Includes bibliographical references. / Fei-Fei Jin, Professor Directing Dissertation; Guosheng Liu, Outside Committee Member; Xiaolei Zou, Committee Member; Ming Cai, Committee Member; Allan Clarke, Committee Member; James J. O'Brien, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_175766 |
| Contributors | Bejarano-Avendano, Luis Fernando (authoraut), Jin, Fei-Fei (professor directing dissertation), Liu, Guosheng (outside committee member), Zou, Xiaolei (committee member), Cai, Ming (committee member), Clarke, Allan (committee member), O'Brien, James J. (committee member), Program in Geophysical Fluid Dynamics (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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