Preprints
https://doi.org/10.5194/tc-2020-238
https://doi.org/10.5194/tc-2020-238

  02 Sep 2020

02 Sep 2020

Review status: this preprint is currently under review for the journal TC.

Enhancement of snow albedo reduction and radiative forcing due to coated black carbon in snow

Wei Pu1, Tenglong Shi1, Jiecan Cui1, Yang Chen1, Yue Zhou1, and Xin Wang1,2 Wei Pu et al.
  • 1Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
  • 2Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China

Abstract. When black carbon (BC) is internally mixed with other atmospheric particles, BC light absorption is effectively enhanced. This study is the first to explicitly resolve the optical properties of coated BC in snow, based on core/shell Mie theory and a snow, ice, and aerosol radiative model (SNICAR). Our results indicate that a "BC coating effect" enhances the reduction of snow albedo by a factor of 1.1–1.8 for a non-absorbing shell and 1.1–1.3 for an absorbing shell, depending on BC concentration, snow grain radius, and core/shell ratio. We develop parameterizations of the BC coating effect for application to climate models, which provides a convenient way to accurately estimate the climate impact of BC in snow. Finally, based on a comprehensive set of in situ measurements across the Northern Hemisphere, we find that the contribution of the BC coating effect to snow light absorption has exceeded that of dust over northern China. Notably, the high enhancements of snow albedo reductions by BC coating effect were found in the Arctic and Tibetan Plateau, suggesting a greater contribution of BC to the retreat of Arctic sea ice and Tibetan glaciers.

Wei Pu et al.

 
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Wei Pu et al.

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Short summary
We have explicitly resolved optical properties of coated BC in snow for explaining complex enhancement of snow albedo reduction due to coating effect in real environments. The parameterizations are developed for climate models to improve the understanding of BC in snow on global climate. We demonstrated that the contribution of BC coating effect to snow light absorption has exceeded dust over North China and will significantly contribute to the retreat of Arctic sea ice and Tibetan glacier.