FREQUENCY CHANGES OF WEATHER TYPES IN THE ALPINE REGION SINCE 1945

The annual occurrence of different weather types of Schuepp's synoptic classification in the Alpine region has significantly changed since t he beginning of its recording in 1945. The annual frequency (number of days per year) has shifted towards more convective and less advective weather types. Since 1945 the number of long-lasting convective episo des rose and the number of long-lasting advective episodes lessened. M ost of these changes took place in winter. The annual frequencies of w eather types and the annual mean of certain local meteorological param eters are significantly correlated. On the large scale there is a stro ng interdependence between the high pressure weather type and the Nort h Atlantic Oscillation (NAO) index which is based on the sea-level pre ssure difference between Portugal and Iceland.