On the Maintenance of the Polar Front jet Stream

Abstract

A calculation of the mean transverse circulation about the polar front jet stream is performed by using a diagnostic balance, ?-equation method. The results show a thermally-direct mean transverse circulation about the jet stream system for this case study. An examination of the kinetic energy balance of this jet stream reveals that the direct transverse circulation is probably strong enough to maintain the jet against frictional dissipation but not enough to provide large lateral export of energy. However, significant amounts of energy are transferred upward across the tropopause. Further considerations are employed to argue that the mean transverse circulation obtained here is compatible with the observed distributions of temperature and potential vorticity about the jet core.