In order to gain a greater understanding of the physical processes acting in the lower stratosphere during a
major breakdown of the polar night vortex, a computation of the direction and magnitude of the mean meridional
circulation is performed by employing a heat budget method. This computation reveals that the mean cell operates
to produce rising motion over the polar regions before, during, and after the breakdown period. The calculations
show that horizontal eddy heat flux provides the predominant mechanism for the large temperature increases observed
over the polar cap during the time of the vortex breakdown. As a supplement to thea bove computation, mean vertical
velocities were determined with respect to a curvilinear coordinate system oriented along a line of maximum circulation
intensity at 50 mb. The result showed that the mean cell operates in the direct sense prior to the major breakdown
when measured relative to this curvilinear system.
This research was sponsored by the U.S. Atomic Energy Commission under Contract Numbers AT(ll-1)-1340 and AT(49-7)-3206.