積雪の粘性圧縮理論による降雪深の推定 Estimation of depth of new snowfall based on the viscous compression theory of snow cover
This paper describes a method to estimate depth of new snowfall automatically from measurements of hourly total snow depth and precipitation, based on viscous compression theory. Depth of new snow deposited for a time interval is given by adding settlement depth of old snow to the change of total snow depth during the interval, because snow cover is continuously settling due to its own weight.Then, assuming that a relation between compressive viscosity η and dry density ρ<SUB>dry</SUB> of snow is expressed by η=C(ρ<SUB>dry</SUB>)<SUP>a</SUP> with constants of C and a, an equation computing time variation of thickness of a snow layer from data of precipitation was derived theoretically. Using the equation, the settlement depth was computed and the depth of daily new snowfall was estimated. The results using C=0.392 Pa·s (kg·m<SUP>-3</SUP>)<SUP>-a</SUP> and a=3.6, which are nearly equal to the values obtained for dry snow, were found to be in a good agreement with data of daily new snow depth measured in Tohkamachi during three winters from 1992-1993. The average and maximum errors were 1.71cm and about±5cm, respectively.
雪氷 60(1), 13-23, 1998-01-15
The Japanese Society of Snow and Ice