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| Titel |
Estimated impact of black carbon deposition during pre-monsoon season from Nepal Climate Observatory – Pyramid data and snow albedo changes over Himalayan glaciers |
| VerfasserIn |
T. J. Yasunari, P. Bonasoni, P. Laj, K. Fujita, E. Vuillermoz, A. Marinoni, P. Cristofanelli, R. Duchi, G. Tartari, K.-M. Lau |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 14 ; Nr. 10, no. 14 (2010-07-19), S.6603-6615 |
| Datensatznummer |
250008640
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| Publikation (Nr.) |
 copernicus.org/acp-10-6603-2010.pdf |
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| Zusammenfassung |
| The possible minimal range of reduction in snow surface albedo due to dry
deposition of black carbon (BC) in the pre-monsoon period (March–May) was
estimated as a lower bound together with the estimation of its accuracy,
based on atmospheric observations at the Nepal Climate Observatory – Pyramid
(NCO-P) sited at 5079 m a.s.l. in the Himalayan region. A total BC
deposition rate was estimated as 2.89 μg m−2 day−1 providing
a total deposition of 266 μg m−2 for March–May at the site, based
on a calculation with a minimal deposition velocity of 1.0×10−4 m s−1
with atmospheric data of equivalent BC concentration. Main BC
size at NCO-P site was determined as 103.1–669.8 nm by correlation analyses
between equivalent BC concentration and particulate size distributions in
the atmosphere. The BC deposition from the size distribution data was also
estimated. It was found that 8.7% of the estimated dry deposition
corresponds to the estimated BC deposition from equivalent BC concentration
data. If all the BC is deposited uniformly on the top 2-cm pure snow, the
corresponding BC concentration is 26.0–68.2 μg kg−1, assuming
snow density variations of 195–512 kg m−3 of Yala Glacier close to
NCO-P site. Such a concentration of BC in snow could result in 2.0–5.2%
albedo reductions. By assuming these albedo reductions continue throughout
the year, and then applying simple numerical experiments with a glacier mass
balance model, we estimated reductions would lead to runoff increases of
70–204 mm of water. This runoff is the equivalent of 11.6–33.9% of the
annual discharge of a typical Tibetan glacier. Our estimates of BC
concentration in snow surface for pre-monsoon season is comparable to those
at similar altitudes in the Himalayan region, where glaciers and perpetual
snow regions begin, in the vicinity of NCO-P. Our estimates from only BC are
likely to represent a lower bound for snow albedo reductions, because we
used a fixed slower deposition velocity. In addition, we excluded the
effects of atmospheric wind and turbulence, snow aging, dust deposition, and
snow albedo feedbacks. This preliminary study represents the first
investigation of BC deposition and related albedo on snow, using atmospheric
aerosol data observed at the southern slope in the Himalayas. |
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