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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-799
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Impacts of absorbing aerosol deposition on snowpack and hydrologic cycle in the Rocky Mountain region based on variable-resolution CESM (VR-CESM) simulations
Chenglai Wu1,2, Xiaohong Liu1, Zhaohui Lin2,3, Stefan R. Rahimi-Esfarjani1, and Zheng Lu1 1Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming, USA
2International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
3University of Chinese Academy of Sciences, Beijing, China
Abstract. Deposition of light-absorbing aerosols (LAAs) such as black carbon (BC) and dust onto snow cover has been suggested to reduce the snow albedo, and modulate the snowpack and consequent hydrologic cycle. In this study we use the variable-resolution Community Earth System Model (VR-CESM) with a regionally refined high-resolution (0.125º) grid to quantify the impacts of LAAs in snow in the Rocky Mountain region during the period of 1981–2005. We first evaluate the model simulation of LAA concentrations both near the surface and in snow, and then investigate the snowpack and runoff changes induced by LAAs in snow. The model simulates similar magnitudes of near-surface atmospheric dust concentrations as observations. Although the model underestimates near-surface atmospheric BC concentrations, the simulated BC-in-snow concentrations are overall comparable to observations. Regional mean surface radiative effect (SRE) due to LAAs in snow reaches up to 0.6–1.7 W m−2 in spring, and dust contributes to about 21–43 % of total SRE. Due to positive snow-albedo feedbacks induced by the LAAs' SRE, snow water equivalent reduces by 2–50 mm and snow cover fraction by 5–20 % in the two regions around the mountains (Eastern Snake River Plain and Southwestern Wyoming), corresponding to an increase of surface air temperature by 0.9–1.1 °C. During the snow melting period, LAAs accelerate the hydrologic cycle with monthly runoff increases of 0.15–1.00 mm day−1 in April–May and reductions of 0.04–0.18 mm day−1 in June–July in the mountainous regions. Of all the mountainous regions, Southern Rockies experience the largest reduction of total runoff by 15 % during the later stage of snow melt (i.e., June and July). Our results highlight the potentially important role of LAA interactions with snowpack and subsequent impacts on the hydrologic cycles across the Rocky Mountains.

Citation: Wu, C., Liu, X., Lin, Z., Rahimi-Esfarjani, S. R., and Lu, Z.: Impacts of absorbing aerosol deposition on snowpack and hydrologic cycle in the Rocky Mountain region based on variable-resolution CESM (VR-CESM) simulations, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-799, in review, 2017.
Chenglai Wu et al.
Chenglai Wu et al.
Chenglai Wu et al.

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Short summary
This study utilizes the newly-developed variable-resolution Community Earth System Model (VR-CESM) with a refined high resolution (0.125º) to quantify the impacts of absorbing aerosol (BC and dust) deposition on snowpack and hydrologic cycles in the Rocky Mountains. BC and dust in snow significantly reduce the snowpack around the mountains. BC and dust in snow also accelerate the hydrologic cycles in the mountainous regions with runoff increased in spring but reduced in summer.
This study utilizes the newly-developed variable-resolution Community Earth System Model...
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