CONSIDERATIONS ON SNOW AND TEMPERATURES TIME SERIES IN WESTERN ITALIAN ALPS

In the frame of MEDARE (MEditerranean DAta Rescue) and STRADA (Strategies of Adaptation to climate change) projects, Western Italian Alps precipitation and snow depth time series recorded in stations located between 960 and 2316 m a.s.l. have been analysed in order to investigate variability and trends over the 1925- 2010 period. The results outline a significant decrease of snow depth over seasonal time scale in the period 1951- 2010. The snow depth decrease ranges from -0.19 cm/y up to -1.40 cm/y and the contribution to this negative trend comes mainly from spring months. The climatic conditions that caused this considerable snow depth reduction have been examined. Below 1000 m a.s.l. the snow depth decrease is due to a significant decrease in snow precipitation, as a consequence of significant increase of maximum and minimum temperatures. At higher elevation the negative trend is more marked for the combination of a stronger increase in minimum temperatures and stronger decrease in the number of days with Tmax<0 with respect to low elevation sites.