EVALUATION OF POTENTIAL-VORTICITY CHANGES NEAR THE TROPOPAUSE AND THE RELATED VERTITCAL MOTIONS, VERTICAL ADVECTION OF VORTPCITY, AND TRANSFER OF RADIOACTIVE DEBRIS FROM STRATOSPHERE TO TROPOSPHERE
Individual potential-vorticity change, vertical motion, vertical advection of vorticity and flow from stratosphere to troposphere are evaluated at different levels and for different times in an extratropical disturbance. Vertical motions are obtained from trajectories on three isentropic surfaces for two different times. The isentropes pass through or near a front in the upper troposphere, the lower stratosphere, and the high troposphere on the cold side of the front. Vertical motion is also evaluated at 500 mb from an adiabatic method designed to give instantaneous values to the extent that the system moves without change of shape. Negative extremes of 8 to 10 cm sec−1 occur in the upper-air front, with positive extremes of the same magnitude a short distance to the northeast, coinciding with the eastern exit of the frontal zone. From theory, it is shown that potential vorticity is not conserved if there is either a gradient of diabatic heating or a component of curl, normal to the isentropic su... Abstract Individual potential-vorticity change, vertical motion, vertical advection of vorticity and flow from stratosphere to troposphere are evaluated at different levels and for different times in an extratropical disturbance. Vertical motions are obtained from trajectories on three isentropic surfaces for two different times. The isentropes pass through or near a front in the upper troposphere, the lower stratosphere, and the high troposphere on the cold side of the front. Vertical motion is also evaluated at 500 mb from an adiabatic method designed to give instantaneous values to the extent that the system moves without change of shape. Negative extremes of 8 to 10 cm sec−1 occur in the upper-air front, with positive extremes of the same magnitude a short distance to the northeast, coinciding with the eastern exit of the frontal zone. From theory, it is shown that potential vorticity is not conserved if there is either a gradient of diabatic heating or a component of curl, normal to the isentropic su...