The stratospheric polar vortex and sub-vortex: fluid dynamics and midlatitude ozone loss

This chapter assesses fluid-dynamical thinking about flow through the vortex. Any large export of vortex air in the lower stratosphere can be assumed to take place mainly along the isentropic surfaces of the strong stable stratification. An important corollary is that the sub-vortex could act as a dehydration and chlorine-activation site through which large masses of air could be efficiently transported, to and from middle latitudes at any time during winter. The predictions of radiative studies receive independent support from direct, balloon-borne observations of descent of nitrous oxide isopleths within the Arctic polar vortex. The relatively slight diversion of the rising branch of the stratospheric circulation toward the summer hemisphere shows just how weakly the stratospheric circulation pattern is influenced by solar heating, and how strongly by the gyroscopic pumping effects associated with the Earth’s rapid rotation.