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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-667
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
28 Aug 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Concentrations and source regions of light absorbing impurities in snow/ice in northern Pakistan and their impact on snow albedo
Chaman Gul1,2,5, Siva Praveen Puppala2, Shichang Kang1,3,5, Bhupesh Adhikary2, Yulan Zhang1, Shaukat Ali4, Yang Li3, and Xiaofei Li1 1State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 73000, China
2International Centre for Integrated Mountain Development (ICIMOD), G.P.O. Box 3226, Kathmandu, Nepal
3CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China
4Global Change Impact Studies Centre (GCISC), Ministry of Climate Change, Islamabad, Pakistan
5University of Chinese Academy of Sciences, Beijing, China
Abstract. Black carbon (BC), water-insoluble organic carbon (OC), and mineral dust are important particulate impurities in snow and ice, which significantly reduce albedo and accelerate melting. Surface snow and ice samples were collected from the Karakoram–Himalayan region of northern Pakistan during 2015 and 2016 in summer (six glaciers), autumn (two glaciers), and winter (six mountain valleys). The average BC concentration overall was 2130 ± 1560 ngg−1 in summer samples, 2883 ± 3439 ngg−1 in autumn samples, and 992 ± 883 ngg−1 in winter samples. The average water insoluble OC concentration overall was 1839 ± 1108 ngg−1 in summer samples, 1423 ± 208 ngg−1 in autumn samples, and 1342 ± 672 ngg−1 in winter samples. The overall concentration of BC, OC, and dust in aged snow samples collected during the summer campaign was higher than the concentration in ice samples. The values are relatively high compared to reports by others for the Himalayas and Tibetan Plateau. This is probably the result of taking more representative samples at lower elevation where deposition is higher and the effects of ageing and enrichment more marked. A reduction in snow albedo of 0.1–8.3 % for fresh snow and 0.9–32.5 % for aged snow was calculated for selected solar zenith angles during day time using the Snow, Ice, and Aerosol Radiation (SNICAR) model. Daily mean albedo was reduced by 0.07–12.0 %. The calculated radiative forcing ranged from 0.16 to 43.45 Wm−2 depending on snow type, solar zenith angle, and location. The potential source regions of the deposited pollutants were identified using spatial variance in wind vector maps, emission inventories coupled with backward air trajectories, and simple region tagged chemical transport modelling. Central, South, and West Asia were the major sources of pollutants during the sampling months, with only a small contribution from East Asia. Analysis based on the Weather Research and Forecasting (WRF-STEM) chemical transport model identified a significant contribution (more than 70 %) from South Asia at selected sites. Research into the presence and effect of pollutants in the glaciated areas of Pakistan is economically significant because the surface water resources in the country mainly depend on the rivers (the Indus and its tributaries) that flow from this glaciated area.

Citation: Gul, C., Puppala, S. P., Kang, S., Adhikary, B., Zhang, Y., Ali, S., Li, Y., and Li, X.: Concentrations and source regions of light absorbing impurities in snow/ice in northern Pakistan and their impact on snow albedo, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-667, in review, 2017.
Chaman Gul et al.
Chaman Gul et al.

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Short summary
Snow and ice samples were collected from six glaciers and multiple mountain valleys from northern Pakistan. Samples were analyzed for black carbon and water insoluble organic carbon. Relatively high concentration of black carbon, organic carbon and dust were reported. Snow albedo and radiative forcing were estimated for the snow samples. Possible source region of pollutants were identified through various techniques.
Snow and ice samples were collected from six glaciers and multiple mountain valleys from...
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