Simulations of monthly variation in snowfall over complicated mountainous areas around Japan's Northern Alps

We investigated the seasonal variation of snow cover at different altitudes using station data, satellite data, and a high-resolution numerical model around the Japan's Northern Alps during three winters (2011/12, 2012/13, and 2013/14). The satellite data showed that the snow cover fraction was largest in 2012/13 before late December, which indicates that much of snowfall occurs at higher elevations in the early winter. In midwinter, the snow cover fraction was over 90% in 2011/12, while it was approximately 70% and 60% in 2012/13 and 2013/14, respectively. The station data also showed the greatest snow depth at lower elevations in 2011/12 among the three winters. The numerical model well simulates the year-to-year and monthly variations of the snow cover fraction, although the threshold of snow depth are larger than that of the satellite data. The numerical simulations indicate that the total amount of snowfall is controlled by spring snowfall as much as by winter snowfall at higher elevations. The year-toyear variations of spring snowfall are relatively larger than those of winter snowfall, resulting in different year-to-year variations of snow cover at lower and higher elevations.