LONG-TERM VARIATIONS OF STRATOSPHERIC CIRCULATIONS - A COMPARISON OF MEAN FIELDS IN THE 1980S WITH CIRA-1986 MODELS

On the basis of a careful comparison of routine satellite observations in the 1980s with the CIRA-1986 models as being representative of obs ervations in the 1970s, long-term variations of stratospheric circulat ions are investigated. In most parts of the stratosphere, cooling occu rs, independent of the month, while warming occurs in some places. In particular, warming in winter is conspicuous over the south polar regi on of the middle stratosphere. The non-uniform changes of temperature fields bring about changes of temperature gradients and zonal mean zon al winds: the westerly polar night jet becomes strong in the winter he misphere while the easterly jet becomes weak in the summer hemisphere. In the southern hemisphere winter, wave activities become weak, corre sponding to the strengthening of the polar night jet.