Topography-induced locking of drifting Rossby–Haurwitz waves

Abstract

Atmospheric blockings are persistent large-scale climate patterns that lock in a geographic position for days and even weeks. In principle, blockings might involve a large number of waves interacting non-linearly, and a conclusive description for their onset and duration is still elusive. In this paper, we introduce a simplified account for this phenomenon by means of a single-triad of Rossby–Haurwitz waves perturbed by one topographic mode. It is shown that the dynamical features of persistent flow patterns have zero measure in the phase space for an unperturbed triad, but such a measure becomes finite for the perturbed dynamics. By this account, we suggest that static inhomogeneities in the two-dimensional atmospheric layer are required for locking the flow patterns to the planetary rotation.