Understanding snowmelt characteristics in forest areas is essential for the effective use of water resources because forests cover most of the mountainous areas in Japan. However, most previous studies investigating the snowmelt characteristics in open and forest areas have been conducted in March or later in the spring. In Japan, few studies have analyzed the energy balance of the snowmelt over an entire winter season, including the severe winter months. We selected Ishikawa Prefecture as the study area to clarify the characteristics of the energy balance for snowmelt in open and forest areas over the entire period of snow cover. The reduction of shortwave radiation by the forest was small during the severe winter months between December and February. The amount of longwave radiation was greater by approximately 25−85 MJ m -2 day -1 in the forest, which is significantly higher than that observed in the open area. We found that there are cases in which the energy available for snowmelt in the forest is larger than that in the open area, and that forests had no effect in terms of slowing the snowmelt during the severe winter months.

No abstract

Understanding the relation between forests and snow, including determinants of differences in the snow disappearance date between open and forested areas, is fundamentally important for assessing the ability of forests to store snow and to delay snowmelt. For this study, using a meta-analysis, we analyzed factors that determine the difference in snow disappearance date (ΔSDD) between open and forested areas, where positive (negative) values indicate whether the snow cover in the forest (open) remains longer. Results indicate that ΔSDD was mostly distributed in the period from 0 to +10 days, with a mean of +6 days. Negative correlation was found between ΔSDD and mean winter temperature. Relation between ΔSDD and mean winter temperature on a global scale was compared to that of Japan, where results showed that ΔSDD can be either positive or negative. Compared to the same temperature zone on a global scale, the snow storage functions of forest areas are demonstrated well in Japan, but these might decline in the future. In addition to ΔSDD, using the ratio of the snow water equivalent in the forest to that in the open (coefficient a) is important. The ratio of the average snowmelt rate in the forest to that in the open (coefficient b), is also important when comparing the snow storage functions of forests.