Density of Freshly Fallen Snow in the Central Rocky Mountains

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New snow density distributions are presented for six measurement sites in the mountains of Colorado and Wyoming. Densities were computed from daily measurements of new snow depth and water equivalent from snow board cores. All data were measured once daily in wind-protected forest sites. Observed densities of freshly fallen snow ranged from 10 to 257 kg m−3. Average densities at each site based on four year's of daily observations ranged from 72 to 103 kgm−3. Seventy-two percent of all daily densities fell between 50 and 100 kg m−3. Approximately 5% of all daily snows had densities below 40 kg m−3. The highest frequency of low densities occurred at Steamboat Springs and Dry Lake. The relationship between air temperature and new snow density exhibited a decline of density with temperature with a correlation coefficient of 0.52. No obvious reversal toward higher densities occurred at cold temperatures, as some previous studies have reported. No clear relationship was found between snow density and the depth of new snowfalls. Correlations of daily densities between measurement sites decreased rapidly with increasing distance between sites. New snow densities are strongly influenced by orography, which contributes to density differences over short distances.

*USDA Forest Service (retired), Rocky Mountain Research Station, Fort Collins, Colorado.

+Colorado Climate Center, Atmospheric Science Department, Colorado State University, Fort Collins, Colorado.

Corresponding author address: Nolan J. Doesken, Atmospheric Science Department, Colorado State University, Fort Collins, CO 80523-1371. E-mail: nolan@ccc.atmos.colostate.edu

New snow density distributions are presented for six measurement sites in the mountains of Colorado and Wyoming. Densities were computed from daily measurements of new snow depth and water equivalent from snow board cores. All data were measured once daily in wind-protected forest sites. Observed densities of freshly fallen snow ranged from 10 to 257 kg m−3. Average densities at each site based on four year's of daily observations ranged from 72 to 103 kgm−3. Seventy-two percent of all daily densities fell between 50 and 100 kg m−3. Approximately 5% of all daily snows had densities below 40 kg m−3. The highest frequency of low densities occurred at Steamboat Springs and Dry Lake. The relationship between air temperature and new snow density exhibited a decline of density with temperature with a correlation coefficient of 0.52. No obvious reversal toward higher densities occurred at cold temperatures, as some previous studies have reported. No clear relationship was found between snow density and the depth of new snowfalls. Correlations of daily densities between measurement sites decreased rapidly with increasing distance between sites. New snow densities are strongly influenced by orography, which contributes to density differences over short distances.

*USDA Forest Service (retired), Rocky Mountain Research Station, Fort Collins, Colorado.

+Colorado Climate Center, Atmospheric Science Department, Colorado State University, Fort Collins, Colorado.

Corresponding author address: Nolan J. Doesken, Atmospheric Science Department, Colorado State University, Fort Collins, CO 80523-1371. E-mail: nolan@ccc.atmos.colostate.edu
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