Comparison of surface energy balance of seasonal snow cover for three sites in Japanese alpine region

Process of snow ablation is one of the indicator of global climate change. Particularly, seasonal snowcover in temperate region are significantly sensitive to the ambient climate and meteorological condition, and affect the local climate. Therefore, it is vital to investigate how the seasonal snowcover forms and melts in temperate region in order to validate the effect of global climate change.

Surface energy balance (SEB) is an important information to discuss a snow ablation process. SEB is sensitive to regional atmospheric conditions. This presentation offers the result of SEB analysis in the central Japanese alpine region, Kamikochi (1490 m a.s.l.), Norikura highland (1590 m a.s.l.) and Nishi-Hodaka (2355 m a.s.l.) to reveal the characteristic of SEB of seasonal snowcover and snowmelt processes in Japanese sub-alpine region.

Three automatic weather stations, operated by Shinshu University, were located each area in snow covered period of 2016/17 (Hydrological year). SEB analysis was conducted using surface energy balance method, and an analysis of turbulent heat flux was done using the bulk aerodynamic method. SEB analysis were conducted only snow covered period from October, 2016 to June, 2017.

The major energy source was net shortwave radiation, and negative energy fluxes were net longwave radiation and latent heat flux in every site. Those characteristics were often reported in continental regions and such as an alpine region, because the atmospheric condition in those regions are often cold and dry so that incoming turbulent enegy flux were restrained. Japanese climate has been generally regarded as a maritime climate, but in the central Japanese alpine region, it showed SEB properties similar to a continental climate.

This seems to be attributed to synoptic-scale process offering snowfall in Japan. Air mass aquiring large amount of moisuture from the Japan Sea is advected to Japan, however, due to high precipitation and elevation gradient, relatively drier air mass is probably advected in the central Japanese alpine region than Japan Sea coast area. Thus, the properties of SEB balance revealed in this study are suggested to be formed by a snowfall mechanism of synoptic air mass advection process and topographic factors.