Regional behavior of minimum temperatures in Switzerland for the period 1979-1993

A series of anomalously cold and warm winters which occurred in Switzerland during the 15-year period from 1979 to 1993 has been analyzed in detail in terms of temperature minima. The warm winters between 1988-1992 were particularly marked in the Alps, where lack of snow had severe consequences for the tourist-based economies of mountain communities. The investigations presented here focus primarily on minimum temperature records for up to 88 climatological observing sites distributed over Switzerland. Analyses of the departures of temperature minima from the 15-year means in warm and cold winters has shown that there is a very significant altitudinal dependency of the anomalies except at low elevations which are subject to fog or stratus conditions; the stratus tends to decouple the underlying stations from processes occurring at higher altitudes. It is also shown that there is a switch in the gradient of the temperature anomaly with height from cold to warm winters. For warm winters, the higher the elevation, the stronger the positive anomaly; the reverse is true for cold winters. The statistics for the 88 observational stations provide a measure of the damping of the climate signal as an inverse function of height. The altitudinal dependency of temperature departures from the mean are the most important feature, followed by latitudinal effects (north and south of the Alps); continentality is not seen to be a major factor in determining the geographical distribution of temperature anomalies at this scale. The present investigation also emphasizes the fact that high elevation records can more readily identify significant interannual climatic fluctuations than at lower-elevation sites. This is also likely to be the case for longer-term climate change, where possible greenhouse-gas warming would presumably be detected with more clarity at higher elevations. This type of study can help orientate future high-resolution climate model studies of climate change and in particular the assessment of model capability in reproducing a range of possible temperature anomalies and their altitudinal dependency.