Preprints
https://doi.org/10.5194/acp-2020-985
https://doi.org/10.5194/acp-2020-985

  29 Oct 2020

29 Oct 2020

Review status: a revised version of this preprint is currently under review for the journal ACP.

Enhanced light absorption and reduced snow albedo due to internally mixed mineral dust in grains of snow

Tenglong Shi1, Jiecan Cui1, Yang Chen1, Yue Zhou1, Wei Pu1, Quanliang Chen2, Xuelei Zhang3, and Xin Wang1,4 Tenglong Shi et al.
  • 1Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
  • 2College of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China
  • 3Key laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
  • 4Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China

Abstract. Mineral dust is a major light-absorbing aerosol, which can significantly reduce snow albedo and accelerate snow/glacier melting via wet and dry deposition on snow. In this study, three scenarios of internal mixing of dust in ice grains were analyzed theoretically by combining asymptotic radiative transfer theory and (core/shell) Mie theory to evaluate the effects on absorption coefficient and snow albedo. In general, snow albedo was substantially reduced at wavelengths of < 1.0 μm by internal dust–snow mixing, with stronger reductions at higher dust concentrations and larger snow grain sizes. Moreover, calculations showed that a non-uniform distribution of dust in snow grains can lead to significant differences in the values of the absorption coefficient and snowpack albedo at visible wavelengths relative to a uniform dust distribution in snow grains. Finally, using comprehensive in situ measurements across the Northern Hemisphere, we found that broadband snow albedo was further reduced by 5.2 % and 9.1 % due to the effects of internal dust–snow mixing on the Tibetan Plateau and North American mountains. This was higher than the reduction in snow albedo caused by black carbon in snow over most North American and Arctic regions. Our results suggest that significant dust–snow internal mixing is important for the melting and retreat of Tibetan glaciers and North American mountain snowpack.

Tenglong Shi et al.

 
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Tenglong Shi et al.

Tenglong Shi et al.

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Short summary
We assess the effect of dust external/internal mixing with snow grains on the absorption coefficient and albedo of snowpack. The results suggest that dust-snow internal mixing strongly enhances snow absorption coefficient and albedo reduction relative external mixing. Meanwhile, the possible non-uniform distribution of dust in snow grains may lead to significantly different values of absorption coefficient and albedo of snowpack in the visible spectral range.
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