Abstract
A strong, persistent and significant oscillation of about 24-day periodicity is observed in hemispheric-scale energy parameters during the winter season. The characteristics of this cycle are defined using 9.5 years of daily NMC gridded height and temperature fields. Analysis of northward eddy heat flux strongly suggests that baroclinic processes are involved in this oscillation. The vacillation acts primarily on the planetary-wave scale and some of its synoptic characteristics are investigated. A decomposition of eddy available potential energy by zone wavenumber shows that the vacillation tends to favor different wavenumbers in different years. The concept of a vacillation in orientation of trough and ridge line tilt is not substantiated.
