East-west oriented jets are observed in the high latitudes of the troposphere, the oceans and other planetary atmospheres. Explanations of "eddy-forced" zonal jets usually require some external influence, such as geometrical boundaries or localized forcing, to account for their spatial persistence. Preliminary calculations indicate that, when motions are quasi-geostrophic, energy arising from the instability of an imposed, spatially uniform, north-south temperature gradient can be organized into jets of a persistence not directly linked to feature of the forcing. The scale of the jet is self-determined, so that once a region is sufficiently wide to support one jet, further widening of the region increases the number of jets. The goal of this research project is to examine the source of this persistence and its scale using (relatively) simple two- layer models embodying various numbers of wave-wave interactions. Special attention will be paid to how maintenance and persistence are affected during the transition from a regime that supports a single jet to one supporting two. The influence of linear wave dynamics in determining the scale of the jets will be examined using different indices of wave activity. An examination of the transition regime may also indicate which low frequency processes play a prominent role in the Northern Hemisphere where a second jet does not emerge.
