50 years of Alpine Weather Statistics (AWS)

Abstract

Since 1945 a total of 34 daily parameters called the Alpine Weather Statistics (AWS) has been available for the central European Alps. The parameters are defined by the Swiss Meteorological Institute based as much as possible on objective criteria. The long-term mean temperature time series of Alpine weather stations, all clearly located higher than 2000 m above msl, shows that within the available 50 year parameter time series of the AWS, the years between 1945 and 1994 cover the warmest period of the 159 years long temperature curve in the Alps. Even though the definition of the single parameters was carried out very carefully, inhomogeneities due to changes in personnel and instrumentation could not be avoided (inter alia the determination of the geostrophic surface wind direction turned out to be quite difficult). The seasonal sequence of the 500-1000 hPa thickness for the 13 year period between 1982 and 1994 shows a clear trend towards higher values in the central summer and winter months and lower values during some shorter periods in the transition months of spring and autumn. The 50 year time series of the Schüepp weather situation system with 40 weather patterns is particularly valuable with regard to climate change studies. In its seasonal course it shows the strong continental influence on climate expressed with high frequencies of convective weather situations in summer, and of northerlies to northeasterlies with cold air advection in winter. The interannual variability is characterised by the well-known trend towards a more zonal circulation pattern (positive mode of the North Atlantic Oscillation) after about 1975.

Keywords

• daily parameters
• european alps
• schüepp weather situation system
• alpenraum
• alpenwetterstatistik (aws)