A POSSIBLE INFLUENCE OF RECENT POLAR STRATOSPHERIC COOLINGS ON THE TROPOSPHERE IN THE NORTHERN-HEMISPHERE WINTER

A possible influence of the recent cooling trends in the polar stratosphere on the tropospheric circulation in the Northern Hemisphere winter is studied over the period from 1979 to 1992. Changes in circulation associated with cooling trends in the stratosphere are compared with those triggered by heating due to volcanic aerosols in the stratosphere, which are considered as a prototype of the atmospheric responses to an external forcing. In both cases, strengthening of the stratospheric polar night jets are observed in early winter and perturbations in zonal-mean zonal winds propagate down into the troposphere by forming dipole type anomalies which are associated with changes in planetary waves.