Abstract
An objective break criterion is utilized to investigate the manner in which the slowly varying component of the atmosphere ( 10-90 day frequency band) actually varies. It is found that a great deal of the behavior appears to be made up of relatively infrequent large amplitude transitions between quasi-persistent states. The most frequent time interval over which these transition events occur is between five and six days. The rapid speed of these events strongly suggests that some type of baroclinic instability mechanism is involved in the transition process.
