Type of Document	Dissertation
Author	Bejarano-Avendano, Luis Fernando
Author's Email Address	luisfba@met.fsu.edu
URN	etd-04292006-123413
Title	Coexistence of Leading Equatorial Coupled Modes for ENSO
Degree	Doctor of Philosophy
Department	Geophysical Fluid Dynamics Institute
Advisory Committee	Advisor Name Title Fei-Fei Jin Committee Chair Allan Clarke Committee Member Guosheng Liu Committee Member James J. O'Brien Committee Member Ming Cai Committee Member Xiaolei Zou Committee Member
Keywords	Advective Feedback Thermocline Feedback Heat Budget Analysis Stability Analysis Unstable Coupled Modes Coexistence
Date of Defense	2006-04-17
Availability	unrestricted
Abstract ABSTRACT 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 Niņo 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.
Files	Filename       Size       Approximate Download Time (Hours:Minutes:Seconds)     28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access    Bejarano-Avendano, LDissertation.pdf 15.63 Mb 01:12:21 00:37:12 00:32:33 00:16:16 00:01:23