Snow Cover Dynamics and Ecology: an Analysis of Modis Time Series in the Italian Alps

Snow cover is a critical factor among environmental variables in mountainous ecosystems. It influences several processes such as water supply, avalanche triggering, species lifecycles, soil properties, etc. Currently, the timing and duration of a snow cover is hardly predictable due to climatic variability and rough topography, therefore its trend reconstruction in time is a valuable dataset that can be exploited in multiple ways, particularly to improve the comprehension of several environmental phenomena, and to help forecasting future tendencies. In order to reconstruct the past snow cover dynamics a geomatic approach was applied in a mountainous area, the Verbania Province (North-Western Italy; 46°29’N; 7°52’E–45°46’N;8°44’E). MODIS satellite time series (2001-2010) of the study area were processed through an automated procedure, in Visual Basic and R. Each scene was reclassified in “Snow - No Snow - No Data” values, according to pixel values, and grouped in yearly summarizing tables. These preliminary results allowed to process yearly snow cover duration maps of the entire area. These outputs were then validated by means of additional independent snow depth data measured by snow sensors, installed on automated nivo-meteorological stations. Moreover, snow cover duration was related to morphological parameters, by employing a Digital Terrain Model, thus computing snow cover indexes allowing the evaluation of snow cover distribution in the last decade and highlighting different patterns in the investigated years and their influence on site environmental dynamics.