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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-471
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 Jun 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Snow-darkening versus direct radiative effects of mineral dust aerosol on the Indian summer monsoon: role of the Tibetan Plateau
Zhengguo Shi1,2,3, Xiaoning Xie1, Xinzhou Li1,2, Liu Yang1, Xiaoxun Xie1, Jing Lei1, Yingying Sha1, and Xiaodong Liu1,2 1State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
2CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China
3Open Studio for Oceanic-Continental Climate and Environment Changes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
Abstract. Mineral dust aerosol exerts complicated effects on the climate system and two of which are through their direct radiative forcing and snow-darkening forcing. Especially, the snow-darkening effect of dust on climate have been scarcely explored till now. When depositing in snow, dust can reduce the albedo of snow by darkening it and increase the snow melt. In this study, the snow-darkening effect of dust, as well as the direct radiative effect, on the Indian summer monsoon are evaluated by atmospheric general circulation model experiments, with a special focus on the role of Tibetan Plateau. The results show that, the snow-darkening and direct radiative forcing of dust have both significant impacts on the onset of Indian monsoon but they are distinctly opposite. The snow-darkening effect weakens the Indian monsoon precipitation during May and June while the direct radiative forcing intensifies it. The surface temperature over western Tibetan Plateau and Central Asia becomes warmer due to the dust-induced decrease in snow cover, which leads to a local low-level cyclonic anomaly as well as an anticyclonic anomaly over Indian subcontinent and Arabian Sea. This circulation pattern allows air current penetrating into Indian subcontinent more from Central Asia but less from Indian Ocean. In contrast, the direct radiative forcing of dust cools Tibetan Plateau and adjacent areas but warms Arabian Peninsular, which intensifies the moisture convergence and upward motion over Indian monsoon region. The upper tropospheric atmospheric circulation over Asia is also sensitive to both effects. Our results highlight a potential role of snow-albedo feedback in the effects of dust, which significantly amplifies the response of temperature over Tibetan Plateau. Thus, links between the climatic impact of dust, Tibetan Plateau thermal condition and surface snow cover are of importance and require to be clarified accurately.
Citation: Shi, Z., Xie, X., Li, X., Yang, L., Xie, X., Lei, J., Sha, Y., and Liu, X.: Snow-darkening versus direct radiative effects of mineral dust aerosol on the Indian summer monsoon: role of the Tibetan Plateau, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-471, in review, 2018.
Zhengguo Shi et al.
Zhengguo Shi et al.
Zhengguo Shi et al.

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Short summary
Asian dust is one of important components in modern and past climate change via its climatic effects including snow darkening and direct radiative ones. In this study, we employed model experiments to evaluate these effects on Indian monsoon and found that the monsoon onset responds significantly to both. Snow darkening effect weakens the monsoon but direct radiative effect intensifies it. A strong feedback of snow-albedo over Tibetan Plateau is also simulated.
Asian dust is one of important components in modern and past climate change via its climatic...
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