Snow cover extent and duration in MODIS time series: A comparison with in-situ measurements (Provincia Verbano Cusio Ossola, NW Italy)

An automated approach is presented, with the purpose of computing snow cover duration from satellite imagery and to, validate them with in-situ measured data. In the present study the employed MODIS dataset has a spatial domain covering the entire study area, while its temporal domain covers the last ten years, i.e. 2000 – 2010. Snow depth records from sensors integrated in automated nivo-meteorological stations were used to provide field measurements for comparison with the MODIS data. The meteorological network records snow and climate variables such as snow depth, air temperature, wind speed, and soil temperature. Snow depth is measured from above with an ultrasonic snow depth sensor (mounted on a mast 6 m above ground). The two independent automated procedures to derive snow patterns and particularly to define the end of snowmelt have shown a fairly good agreement. Moreover, the study has shown that a strong influence on the relationship between MODIS and snow-sensor derived snow melts may be due to the elevation, with higher sites showing longer lasting snowpacks under the snow sensor than over the 500 m-side grid.