Doctor of Philosophy (PhD)
Earth Systems Science
First Advisor's Name
Hugh E. Willoughby
First Advisor's Committee Title
Second Advisor's Name
Second Advisor's Committee Title
Third Advisor's Name
Third Advisor's Committee Title
Fourth Advisor's Name
Fourth Advisor's Committee Title
Fifth Advisor's Name
Fifth Advisor's Committee Title
tropical cyclone, vortex Rossby wave, waveguide, critical radius, turning point, Doppler-shifted frequency, cutoff frequency, vorticity, trailing spirals, trochoidal motion
Date of Defense
Vortex Rossby waves (VRWs) have been shown to influence tropical cyclone (TC) structure and intensity change. However, the role of VRWs in TC motion and analyses of the inner waveguide within which the waves propagate have received limited attention. Therefore this dissertation primarily focuses on modeling wavenumber-1 VRWs in a barotropic, nondivergent context to investigate TC-like vortex motion, acquire deeper understanding of propagation within the widest possible inner waveguide, and compare with higher-wavenumber studies.
A mass source-sink pair rotating with a specified frequency is imposed in a mean vortex’s eyewall to excite VRWs. Forced waves manifest as vorticity filaments that accumulate at an outer critical radius to produce a ring of trailing spirals that resemble observed TC rainbands. Within the inner waveguide, inward-propagating waves are Doppler-shifted to the cutoff frequency, reflect from a turning point, propagate outward, and are ultimately absorbed at a critical radius. The specified frequency dictates how far VRWs can propagate. Meanwhile, the vortex center exhibits trochoidal motion, resembling observed TC eye wobbles. Orbital speed and track depend upon the specified frequency. Lastly, VRWs produce angular momentum and energy fluxes. The former accelerates the mean flow at the radius of maximum wind.
Model sensitivity studies are also undertaken to gain additional insight into VRW dynamics. The first set of experiments adjusts relevant forcing parameters and performs beta-plane simulations to determine the vortex response. The second set adjusts vortex parameters to demonstrate that TC intensity can also influence VRW propagation. Additionally, modeling TC-like vortices calls into question the consistency of mean-flow vorticity monopoles on a closed, spherical manifold, and is addressed using the Circulation Theorem. Vortices with differently shaped wind profiles are also considered to examine effects on waveguide geometry.
Lastly, the VRW paradigm offers insight into analogous, synoptic-scale Rossby Waves in a horizontally sheared flow. Rossby waves propagate within a meridional waveguide confined between a cutoff and zero frequency. A forcing imposed near the middle of a large meridional domain, produces an eastward-propagating wavetrain of comma-cloud-shaped gyres that resemble observed frontal cyclones, whose trailing spirals correspond to the “weathermaker” cold fronts that affect the Southern US.
Gonzalez, Israel, "Wavenumber-1 Vortex Rossby Wave Propagation in the Inner Waveguide of a Modeled, Barotropic Nondivergent Tropical Cyclone" (2019). FIU Electronic Theses and Dissertations. 4275.
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