Abstract: We examine the dynamics of low-frequency variability in a simple global model with zonally homogeneous boundary conditions. Low-frequency structure comprises trains of nearly equivalent barotropic Rossby waves with weak ...

Abstract: The invertibility of potential vorticity is used to investigate how flows in the middle atmosphere are determined. The distribution of potential vorticity associated with an observed flow is computed. The inversion problem, ...

Abstract: A wave-1 minor warming is simulated in a mechanistic, global, primitive equation model. The modification of the zonal flow by the rearrangement of potential vorticity on a middle stratospheric isentrope is compared in a ...

Abstract: Mechanisms of low-frequency variability are examined in an extended run of a two-level nonlinear global model with a single isolated mountain. The presence of the mountain modifies the low-frequency behavior, compared with ...

Abstract: No abstract available.

Abstract: A mechanistic approach is used to determine the nature and frequency dependence of transient eddy feedbacks on zonally symmetric low-frequency variability. The zonal momentum of a simple though fully nonlinear atmospheric ...

Abstract: Reasoning in terms of potential vorticity provides physical explanations for the dissipative destabilization of external Rossby waves and for the acceleration of the zonal mean jet during baroclinic life cycles. Both ...

Abstract: The dynamics of variability in the zonal index are studied using a simple circulation model. Results from simulations with differing drag suggest that variability in the zonal index involves a positive feedback from transient ...

Abstract: A baroclinic mechanism for the positive eddy feedback on the zonal index is proposed. The author considers the quasigeostrophic response of the zonally averaged flow to forcing by baroclinic eddies. The transient response ...

Abstract: In this paper an atmospheric jet is considered self-maintaining if the overall effect of baroclinic eddies is to preserve or enhance its westerly shear with height. Observations suggest that the wintertime jets in Earth?s ...