THE DYNAMICS OF THE ARCTIC POLAR VORTEX DURING THE EASOE CAMPAIGN

A blocking ridge over the Atlantic and N.W.Europe was the most persist ent feature of the upper troposphere during the winter of 1991/1992. W ith brief intermissions, blocking lasted for almost three months. It p roduced large anomalies in the mean ozone fields for December 1991 and for January 1992; record low amounts of total ozone were reported ove r Europe. The influence of this blocking system on the structure of th e polar vortex is discussed. In the lower stratosphere there was a per sistent collocation of the core of the jet stream with temperatures lo w enough to promote heterogeneous processes, subjecting a large amount of air to chemical processing. However the minor warmings of mid-Janu ary and February make it difficult to identify chemical ozone loss aga inst the background of the large anomalies present in 1991/92.