A parcel theory approach to β-plane inertial stability

The problem of the orbit of a parcel from its initial location at which there might be a momentum anomaly is here considered for a β-plane. The solutions represent a generalisation of the recent work of Wan and Yang (1990, Adv. Atmos. Sci., 7:409–422). A physical interpretation of the orbits, in which they are related to flow stability, is given for both extratropics and tropics. The possible effect of dissipation on these results is also discussed.