Analysis of snowpack accumulation and the melting process of wet snow using a heat balance approach that emphasizes the role of underground heat flux

Abstract

Summary Snowpack accumulation and melting, including the role of the heat flux underground, were investigated by employing the bulk transfer method and setting roughness lengths of Z O = Z T = 0.005 m and Z T = 0.007 m. Heat balance data were recorded for a period of 4 years, from the fall of 2009 to the spring of 2013, at a forest experiment station in the Hokuriku region, which lies along the Japan Sea. The findings of the research are as follows: (1) The observed temporal changes in the snowpack depth were well reproduced by our model using observed and estimated densities. (2) The importance and roles of the heat balance components were clarified. The total heat input during the 4 years was 252.2 MJ/m 2 on average; 41.4% was provided by net radiation ( R n ), 37.8% by sensible heat flux ( H ), and 13.2% by underground heat flux ( G ). The total output was 120.7 MJ/m 2 , of which 56.2% was accounted for by R n and 31.1% by latent heat flux ( lE ). (3) Of the total heat input, 45.2% was released as freezing energy from the surface side and 2.6% was released from the bottom. (4) In the very cold season (December–February), the total input energy was 115.8 MJ/m 2 on average; 75.0% was supplied by the surface and the remaining 25.0% from underground. In an anomalous year, 40.8% of the energy was supplied from underground.