Surface roughness change associated with fresh snow metamorphosis

Snow surface roughness is an important in understanding surface-atmosphere interactions, and is used in bulk transfer modeling of sublimation. At the plot scale and finer, it is hypothesized that the surface roughness of a snowpack varies rapidly after a fresh snowfall as the snowpack metamorphoses. This change is driven by wind and radiation loading. Four laboratory experiments were performed to estimate mass loss to sublimation under controled conditions. Surface and near surface meteorological variables were measured and used to estimate sublimation from bulk transfer modeling. Comparison of the measured and modeled sublimation indicates that there is a rapid decrease in the roughness of the snow surface as the crystals at and near the surface undergo destructive metamorphosis. Daily measurements of meteorology and sublimation by Williams (1959) were used with an estimate of time since the last snowfall events and indicated the opposite of the laboratory experiments; for modeled sublimation estimates to equal sublimation measurements, the snow surface roughness must be less for fresh snow than for aged snow. Other datasets [e.g., Sverdrup, 1936] are examined to illustrate the systematic change in snowpack surface roughness. Sverdrup, H.U., The eddy conductivity of the air over a smooth snow field, Geofysiske Publikasjoner, 11(7), 69pp, 1936. Williams, G.P., Evaporation from snow covers in Eastern Ontario, National Research Council of Canada, Division of Building Research, Research Paper No. 73, 1959.