Possible Heavy Turbulent Exchange between the Extratropical Tropospheric Air and the Polar Stratospheric Air

Abstract

In 1941 the present author pointed out that there exists a criterion for the development of heavy (horizontal) turbulence in zonal motion which deviates widely from the well known criterion of dynamic stability. If the anticyclonic wind shear is greater than the critical anticyclonic shear given by the condition of zero absolute vorticity, the zonal motion is dynamically unstable; and if the wind shear is greater than a proper critical cyclonic shear, heavy dynamic turbulence results. The wind shear reaches this critical cyclonic value in a narrow zone just north of the latitude of the jet stream. Then, there must be a zone of heavy turbulent exchange of air masses between the extratropical tropospheric air and the stratospheric air through the slit between the extratropical and polar tropopauses.