Document Type

Thesis

Degree

Master of Science (MS)

Department

Geosciences

First Advisor's Name

Hugh E. Willoughby

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Ping Zhu

Third Advisor's Name

Haiyan Jiang

Keywords

Vortex Rossby Waves, Vorticity, Wave Energy, Critical Radius, Cut-off Frequency, Tropical Cyclone, Streamfunction, Barotropic Non-divergent, Wavenumber 2 Forcing

Date of Defense

2-21-2012

Abstract

Wavelike spiral asymmetries are an intriguing aspect of Tropical Cyclone dynamics. Previous work hypothesized that some of them are Vortex Rossby Waves propagating on the radial gradient of mean–flow relative vorticity. In the Intermittently Forced Vortex Rossby Wave theory, intermittent convection near the eyewall wind maximum excites them so that they propagate wave energy outward and converge angular momentum inward. The waves’ energy is absorbed as the perturbation vorticity becomes filamented near the outer critical radii where their Doppler–shifted frequencies and radial group velocities approaches zero. This process may initiate outer wind maxima by weakening the mean–flow just inward from the critical radius. The waves are confined to a relatively narrow annular waveguide because of their slow tangential phase velocity and the narrow interval between the Rossby wave cut–off frequency, where the radial wavenumber is locally zero, and the zero frequency, where it is locally infinite.

Identifier

FI12041105

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