An Eady model, modified by two Ekman layers of different strengths, is used to study analytically and numerically the behavior of strongly nonlinear, baroclinic waves. By means of a truncated spectral expansion, the model is reduced to a nonlinear autonomous system of equations which describes the dynamics of a single zonal wave number disturbance with its lowest two y-modes, and of the mean flow correction with its lowest four y-modes. Each y-mode consists of a baroclinic and a barotropic pattern. / Travelling steady waves, amplitude vacillation and structural vacillation are found in the model. / The transition from symmetric flow to steady wave flow is due to baroclinic instability of the symmetric flow with respect to a sin(pi)y-perturbation. Steady waves are stable when the flow is energetically balanced between baroclinicity and the Ekman dissipation through nonlinearity. / The transition from travelling, steady waves to amplitude vacillation is due to the baroclinic instability of the travelling, steady, sin(pi)y-wavy flow with respect to a sin(pi)y-perturbation. A typical amplitude vacillation is the vacillation of wave potential energy with time, via interference of nonlinear barotropic and baroclinic patterns of the lowest y-mode of the wave. / The transition from amplitude vacillation to structural vacillation is due to both the baroclinic instability of the vacillating, sin(pi)y-wavy flow with respect to a sin2(pi)y-perturbation and the nonlinear mode-mode interaction. This transition occurs gradually in a parameter region. A typical structural vacillation is the vacillation of the redistribution of wave kinetic energy in the meridional direction with time, via interference of the lowest two nonlinear y-modes of the wave. / Most vacillations in the atmosphere may be viewed as a mixed vacillation in the transition region from amplitude vacillation to structural vacillation. The possible applications of the mechanisms of amplitude vacillation and structural vacillation to the atmospheric vacillation are discussed. / The Ekman dissipation seems to play two roles: large amounts of dissipation are stabilizing, and small amounts of dissipation are destabilizing. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0200. / Thesis (Ph.D.)--The Florida State University, 1984.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75504 |
| Contributors | HENGYI, WENG., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 168 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
Page generated in 0.002 seconds