Baroclinic instability: Energy transfer and the role of potential vorticity conservation

In this note some aspects of the dynamics involved in the process of baroclinic instability are discussed using simple physical arguments. In particular, the connection between the requirement for unstable perturbations to release potential energy from the mean state and the conservation of potential vorticity is examined. It is shown how the conservation of potential vorticity results in perturbation phase propagation relative to the mean flow, which is a necessity for potential energy to be released from the mean state. Eady's (1949) problem is discussed as an illustrative example.