New Snow Density Across An Elevational Gradient in the Park Range of Northwestern Colorado

A study was conducted to examine the spatial variability of new snow density across an elevational gradient on the windward side of a mountain. It was hypothesized that the density of new snowfall would decrease with an increase in elevation. Furthermore, it was hypothesized that select meteorological parameters could be utilized to explain variability and to create a predictive model of new snow density. A field campaign was conducted at the Storm Peak Laboratory in February, 2005 on Mt. Werner in northwestern Colorado. Snow sampling and in-situ meteorological measurements were conducted along an elevational gradient at five sites ranging in elevation from 2200 m to 3244 m above MSL. Snow was intermittently sampled during snow events from snow boards. New snow density was calculated from measurements of snow water equivalent and new snow depth. Meteorological measurements of air temperature, relative humidity, wind speed, and direction were continuously logged at five minute intervals throughout the month. In addition, supplemental observations of snow crystal habit, size, and degree of riming were noted at each sampling visitation.

The results indicated mean new snow density did not decrease with an increase in elevation. Observed mean new snow densities ranged from 83 kg m^-3 to 101 kg m^-3 with the lowest mean densities found at 2200 m and 2771 m. Individual densities measurements ranged from 26 kg m^-3 to 188 kg m^-3. Considerable site specific intra-storm variability in density was observed. The results of correlation analysis indicated a direct relationship between new snow density and several explanatory meteorological variables, such as, approximated 700 millibar air temperature (0.74), lifted condensation level air temperature (0.59), wind speed (0.55), and surface air temperature (0.55). Wind and degree of riming were concluded as being associated with higher densities values. Linear regression analysis utilizing the best single predictor variable (~700 millibar level air temperature) resulted in an R² = 0.54.