Abstract: In this paper, by the method of power-spectra analysis, the collapse processes of the mid-winter polar vortex in the Northern Hemisphexe are investigated. It is shown that they are the consequence of interactions between atmosphere circuladons of higher and middle latitudes. The northward development of long-wave ridges of middle latitudes favors the collapsing and southward transport of positive angular momentum from higher latitudes favors the setting-up of the polar high.