Wednesday, December 7, 2016

Melting snow faster

There may be snow in cold months. The Japanese use biochar on the snow to melt it. The biochar makes the snow darker and it can therefore absorb solar energy and melt days sooner than without the biochar. This could help animals trapped in the snow. One could also use ordinary dark earth dust to decrease albedo and get snow to melt earlier. Snow reflects sunlight during the day and keeps cool during the day in this manner. Snow has a high emissivity (a measure of its closeness to a blackbody in thermal properties) and gets very cold at night (releases its heat to surroundings and space).
By my calculations, roughly 1/3 of the energy emitted on a clear night by snow can radiate out to space through the 8 to 14 micron "atmospheric window" (the fraction of the total energy radiated by the snow that has wavelength of between 8 and 14 microns is about 1/3 - I used Planck's law and integrated). If one plowed the snow the albedo would decrease (more solar energy would be absorbed).

Even by making furrows in the snow one decreases the albedo of the snow (increases absorptivity for solar energy). This is because sunlight entering into a furrow can get reflected back and forth and eventually be absorbed by the sides. This is well known in agriculture where plowing decreases albedo.,%20Helsinki/presentations/COST_2016_Manninen.pdf
says, " Surface roughness reduces the albedo of the surface due to
multiple reflection and in some cases by trapping the incoming
radiation completely. "

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