Seasonal trends and temperature dependence of the snowfall/precipitation-day ratio in Switzerland

This paper analyzes the proportion of snowfall days relative to precipitation days, in order to assess the impact of changing temperatures on snowfall, while minimizing the impact of variations in precipitation frequency and intensity. We analyzed the ratio of snowfall days to precipitation days for up to 100 years at 76 meteorological stations, spanning elevations from 200 to 2700 m asl in Switzerland. Our results show clear decreasing trends in snowfall days relative to precipitation days. These decreases are connected to increasing temperatures. The decrease in snowfall days was stronger at lower elevations, i.e., at locations with temperatures closer to the melting point. We observed a baseline seasonal temperature threshold of -2.7 degrees C +/- 0.8 degrees C in winter and -3.8 degrees C +/- 0.6 degrees C in spring, above which the decrease in snowfall days grew rapidly. From these observations, we developed an empirical model that can be used to evaluate the impact of future temperature increases on snowfall, independent of changes in the frequency and intensity of precipitation events. Citation: Serquet, G., C. Marty, J.-P. Dulex, and M. Rebetez ( 2011), Seasonal trends and temperature dependence of the snowfall/precipitation-day ratio in Switzerland, Geophys. Res. Lett., 38, L07703, doi:10.1029/2011GL046976.