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
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
Received: 22 Sep 2020 – Accepted for review: 27 Oct 2020 – Discussion started: 29 Oct 2020
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.
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.
We assess the effect of dust external/internal mixing with snow grains on the absorption...