An Examination of Tropical Cyclone Dynamics Utilizing the 3-Way Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) Model

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Title: An Examination of Tropical Cyclone Dynamics Utilizing the 3-Way Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) Model
Author: Zambon, Joseph Brendan
Advisors: Dr. Ruoying He, Committee Chair
Dr. John Warner, Committee Member
Dr. Gary Lackmann, Committee Member
Abstract: Tropical Cyclones are fundamentally connected to the environment in which they exist. Currently most numerical models do not represent the interactions between the atmosphere, ocean, and wave environments. These environments are drastically modified by the existence of the tropical cyclone and therefore drastically modify the tropical cyclone as a continuous feedback mechanism. As a result, improvement of solutions provided by the individual numerical models representing the atmosphere, ocean, and waves is sought through coupling these models together. In the first chapter, the dynamic feedback mechanisms are explored in depth through literature review of previous studies into the reaction of the ocean to tropical cyclones. Several analytical and numerical studies are researched in order to provide sufficient background into the problem, provide motivation into developing a coupled numerical model, and provide a base from which hypotheses for experimentation may be drawn. In the second chapter, experiments will be based off of an atmospheric model tied to a simple 1-dimensional ocean model. Three different experiments are carried out, with the sea surface condition as the only variable between them. By including this simple configuration allowing ocean feedback, hypotheses regarding track, intensity, and sea surface temperature changes will tested. In the third chapter, the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) model is introduced. An idealized tropical cyclone is placed into the model domain and the COAWST model is tested. Three experiments of increasing complexity are used in testing the coupling scheme and examining the dynamical differences in the modeled solution. The idealized tropical cyclone is used to test several hypotheses based on modeled track, intensity, size, sea surface temperature change, and significant wave height. The COAWST model performs as expected and the initial proof of concept is successful. In the fourth chapter, the COAWST model is tested with a realistic case, a hindcast simulation of Hurricane Ivan. The model is initialized within a spatial and temporal domain that was found to provide the best solution for a Hurricane Ivan hindcast using only the atmospheric model. Five experiments are carried out, with increasing complexity in resolving the ocean condition. Hypotheses for the realistic case are tested based on modeled track, intensity, size, sea surface temperature change, heat exchange, and significant wave height. The COAWST model demonstrates reasonable skill in the Hurricane Ivan hindcast, although additional improvement in the initial condition is desired. The final chapter serves to review the discussions of the previous chapters and seeks to provide a platform for future research. The utility of coupled numerical modeling is reiterated and the success of the study highlighted. Likewise, significant improvement of the initial condition in the realistic hindcast will be sought in future research. In addition, several questions remain in improving and examining the coupled numerical solution of a tropical cyclone.
Date: 2009-12-01
Degree: MS
Discipline: Marine, Earth and Atmospheric Sciences
URI: http://www.lib.ncsu.edu/resolver/1840.16/475


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