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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 7 | Copyright
Atmos. Chem. Phys., 18, 4981-5000, 2018
https://doi.org/10.5194/acp-18-4981-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Apr 2018

Research article | 12 Apr 2018

Concentrations and source regions of light-absorbing particles in snow/ice in northern Pakistan and their impact on snow albedo

Chaman Gul1,2,3, Siva Praveen Puppala2, Shichang Kang1,3,4, Bhupesh Adhikary2, Yulan Zhang1, Shaukat Ali5, Yang Li3, and Xiaofei Li1 Chaman Gul et al.
  • 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
  • 3University of Chinese Academy of Sciences, Beijing, China
  • 4CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China
  • 5Global Change Impact Studies Centre (GCISC), Ministry of Climate Change, Islamabad, Pakistan

Abstract. Black carbon (BC), water-insoluble organic carbon (OC), and mineral dust are important particles 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±1560ngg−1 in summer samples, 2883±3439ngg−1 in autumn samples, and 992±883ngg−1 in winter samples. The average water-insoluble OC concentration overall was 1839±1108ngg−1 in summer samples, 1423±208ngg−1 in autumn samples, and 1342±672ngg−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 the 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 are 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 daytime using the Snow, Ice, and Aerosol Radiation (SNICAR) model. The daily mean albedo was reduced by 0.07–12.0%. The calculated radiative forcing ranged from 0.16 to 43.45Wm−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 modeling. 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.

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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 concentrations of black carbon, organic carbon, and dust were reported. Snow albedo and radiative forcing were estimated for the snow samples. Possible source regions 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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