The Role of Vortex Structure in Tropical Cyclone Motion.
Abstract
The role of vortex structure in tropical cyclone motion is studied using a moving-grid, nondivergent barotropic model on a beta plane in a no flow environment. Initial condition sensitivity tests reveal that the northwestward beta drift of the vortex is controlled by the symmetric circulation in the r = 300 - 800 km critical annulus. Enhanced cyclonic or anticyclonic flow in this critical annulus leads to long-term cyclonic or anticyclonic turning motions. The dynamics of the motion process is examined in terms of the symmetric and asymmetric circulations. When the vortex is moving in a quasi-steady manner, the asymmetric flow appears as a pair of large-scale, counter-rotating gyres. A second much smaller pair is found near the center. The interaction between these two sets of gyres and the symmetric flow governs the motion process as revealed by a streamfunction tendency analysis and dynamical sensitivity tests in which the model equation is modified during the integration. Beta drift can be described as a balancing process between linear Rossby dispersion which generates the asymmetric gyres and nonlinear advection that moves the vortex to limit gyre development. Vortex structure is the key to this balance as it determines both the linear generation of the asymmetric forcing and the nonlinear interaction between the symmetric and asymmetric circulations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1987
- Accession Number
- ADA190961
Entities
People
- Michael Fiorino
Organizations
- Naval Postgraduate School