Soot on Snow experiment : bidirectional reflectance factor measurements of contaminated snow

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http://hdl.handle.net/10138/166248

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Peltoniemi , J I , Gritsevich , M , Hakala , T , Dagsson-Waldhauserova , P , Arnalds , O , Anttila , K , Hannula , H -R , Kivekas , N , Lihavainen , H , Meinander , O , Svensson , J , Virkkula , A & de Leeuw , G 2015 , ' Soot on Snow experiment : bidirectional reflectance factor measurements of contaminated snow ' , Cryosphere , vol. 9 , no. 6 , pp. 2323-2337 . https://doi.org/10.5194/tc-9-2323-2015

Title: Soot on Snow experiment : bidirectional reflectance factor measurements of contaminated snow
Author: Peltoniemi, J. I.; Gritsevich, M.; Hakala, T.; Dagsson-Waldhauserova, P.; Arnalds, O.; Anttila, K.; Hannula, H. -R.; Kivekas, N.; Lihavainen, H.; Meinander, O.; Svensson, J.; Virkkula, A.; de Leeuw, G.
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2015
Language: eng
Number of pages: 15
Belongs to series: Cryosphere
ISSN: 1994-0416
URI: http://hdl.handle.net/10138/166248
Abstract: In order to quantify the effects of absorbing contaminants on snow, a series of spectral reflectance measurements were conducted. Chimney soot, volcanic sand, and glaciogenic silt were deposited on a natural snow surface in a controlled way as a part of the Soot on Snow (SoS) campaign. The bidirectional reflectance factors of these soiled surfaces and untouched snow were measured using the Finnish Geodetic Institute's Field Goniospectropolariradiometer, FIGIFIGO. A remarkable feature is the fact that the absorbing contaminants on snow enhanced the metamorphism of snow under strong sunlight in our experiments. Immediately after deposition, the contaminated snow surface appeared darker than the natural snow in all viewing directions, but the absorbing particles sank deep into the snow in minutes. The nadir measurement remained the darkest, but at larger zenith angles, the surface of the contaminated snow changed back to almost as white as clean snow. Thus, for a ground observer the darkening caused by impurities can be completely invisible, overestimating the albedo, but a nadir-observing satellite sees the darkest points, underestimating the albedo. Through a reciprocity argument, we predict that at noon, the albedo perturbation should be lower than in the morning or after-noon. When sunlight stimulates sinking more than melting, the albedo should be higher in the afternoon than in the morning, and vice versa when melting dominates. However, differences in the hydrophobic properties, porosity, clumping, or size of the impurities may cause different results than observed in these measurements.
Subject: LIGHT-ABSORBING IMPURITIES
BLACK-CARBON
SPECTRAL ALBEDO
DIRTY SNOW
MODEL
MELT
SURFACE
1171 Geosciences
114 Physical sciences
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