Atmospheric Aerosol Deposition on Snow Surfaces and Its Effect on Albedo

This paper investigated how atmospheric aerosol deposition into snowpack affects snow albedo reduction using radiation budget observation, atmospheric aerosol monitoring, and snow pit work during the winter of 2003/2004 in Sapporo, Japan. The mass concentration of snow impurities was less than 10 parts per million by weight (ppmw) in the core accumulation season and exceeded 100 ppmw in the melting season due to a heavy dust event on March 11 to 12, 2004. The relationship between the visible albedo and snow impurities suggested the considerable effect of snow impurities in reducing the visible albedo even during the accumulation season in Sapporo. After the dust event, high impurity concentrations of approximately 600 ppmw in the top snow layer were maintained, but the visible albedo still decreased because the increasing snow grain size continued to reduce the visible albedo. The size distribution of snow impurities measured from a snow sample with a Coulter counter during the dust event was compared with the size distributions of snow impurities calculated as wet and dry depositions from a laser optical particle counter for atmospheric aerosols. The result confirmed that the contribution from wet depositions was important except for giant particles with a radius larger than 2.5 mu m.