Change in Fresh Snow Density in Tianshan Mountains, China

The density of fresh snow from February 21st to March 5th 2009 was observed using snow analyzer (Snow Fork) at Tianshan Research Station for Snow-cover and Avalanche of Chinese Academy of Sciences (TRS). Results show that fresh snow density increases from 5 h to 291 h with a coefficient of determination equal to 94% dramatically, representing an average rate of increase of 4.0×10-4 gcm-3/h. Analysis shows that fresh snow density is negatively correlated with compaction rate (R2 = -0.96). Inversely, fresh snow viscosity is positively correlated with density (R2 = 0.90). In relation to meteorological factors, increasing ground temperature (taken at 40 cm beneath the ground surface) is the major driving factor of snow density. Temperature increase in fresh snow layer and decrease in depth hoar layer have the most prominent impact on the snow density increase in the afternoon. Principal component analysis shows that the determinant factors of fresh-snow density change can be grouped into three as follows: a) dynamic factor contributes about 69.71% of density change during 5-106 h of snowfall; b) exogenous energy factor contributes about 20.91% of snow density change at the 130th h; and c) endogenous energy factor contributes about 9.38% of snow density change at the 130th and 195th h of snowfall.