Wavenumber-1 Vortex Rossby Wave Propagation in the Inner Waveguide of a Modeled, Barotropic Nondivergent Tropical Cyclone

Authors

Israel GonzalezFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Earth Systems Science

First Advisor's Name

Hugh E. Willoughby

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Robert Burgman

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Sundararaman Gopalakrishnan

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Seyedmasoud Sadjadi

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Ping Zhu

Fifth Advisor's Committee Title

Committee member

Keywords

tropical cyclone, vortex Rossby wave, waveguide, critical radius, turning point, Doppler-shifted frequency, cutoff frequency, vorticity, trailing spirals, trochoidal motion

Date of Defense

5-20-2019

Abstract

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.

Identifier

FIDC007709

Recommended Citation

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.
https://digitalcommons.fiu.edu/etd/4275