Snowfall amounts are measured both by depth and by snow water equivalent depth or SWE, which is the depth of the snow if it were melted. Typical snowfall rates are 1 cm h-1 of depth or 0.8 mm h-1 of SWE. The most intense storms occur when a persistent flow of very cold air traveling across open water warms rapidly, picks up moisture, and creates a steep lapse rate. Cumulonimbus clouds form in the unstable air and deposit heavy snowfall on the lee side of the body of water. These storms can be further intensified by orographic uplift.
The density of newly fallen snow varies between about 20 and 300 kg m-3, but is typically 60-120 kg m-3 for dry snow falling in low to moderate winds. Higher densities occur for warm, wet snow, sleet, and wind-packed snow. In general, smaller crystals with simpler shapes pack the most efficiently and lead to snow layers with higher density. In the case of mixed rain and snow precipitation, the new-snow density can exceed 300 kg m-3. Because snow falling in strong winds is typically fragmented and small-grained, density generally increases by about 20 kg m-3 for each m s-1 of wind speed (Jordan et al., 1999a). Large, dendritic snow crystals falling under calm, cold conditions produce the lightest snow covers.
Blowing and drifting snow and the topography of the underlying ground can lead to considerable spatial variability in snow depth. Pressure-induced variations in wind speed lead to scouring of snow on the upwind side and deposition on the lee side of hills or other convex barriers. Snowfall interception by tree canopies reduces snow accumulation on forest floors. As much as 60% of winter snowfall, for instance, may be intercepted by boreal forests (Pomeroy and Schmidt, 1993; Hedstrom and Pomeroy, 1998). Canopy snow coverage is subsequently lost through evaporation/sublimation, melting, or unloading, which forms cone-shaped accumulation rings around the peripheries of coniferous trees (Sturm, 1992; Hardy et al., 1997).
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.