Light-absorption of dust and elemental carbon in snow in the Indian Himalayas and the Finnish Arctic
Light-absorbing impurities (LAIs) deposited in snow have the potential to substantially affect the snow radiation budget, with subsequent implications for snow melt. To more accurately quantify the snow albedo, the contribution from different LAIs needs to be assessed. Here we estimate the main...
| Main Authors: | , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-03-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/11/1403/2018/amt-11-1403-2018.pdf |
| Summary: | Light-absorbing impurities (LAIs) deposited in snow have the
potential to substantially affect the snow radiation budget, with subsequent
implications for snow melt. To more accurately quantify the snow albedo, the
contribution from different LAIs needs to be assessed. Here we estimate the
main LAI components, elemental carbon (EC) (as a proxy for black carbon) and
mineral dust in snow from the Indian Himalayas and paired the results with snow
samples from Arctic Finland. The impurities are collected onto quartz filters
and are analyzed thermal–optically for EC, as well as with an additional
optical measurement to estimate the light-absorption of dust separately on
the filters. Laboratory tests were conducted using substrates containing soot
and mineral particles, especially prepared to test the experimental setup.
Analyzed ambient snow samples show EC concentrations that are in the same
range as presented by previous research, for each respective region. In terms
of the mass absorption cross section (MAC) our ambient EC surprisingly had
about half of the MAC value compared to our laboratory standard EC (chimney
soot), suggesting a less light absorptive EC in the snow, which has
consequences for the snow albedo reduction caused by EC. In the Himalayan
samples, larger contributions by dust (in the range of 50 % or greater for
the light absorption caused by the LAI) highlighted the importance of dust
acting as a light absorber in the snow. Moreover, EC concentrations in the
Indian samples, acquired from a 120 cm deep snow pit (possibly covering the
last five years of snow fall), suggest an increase in both EC and dust
deposition. This work emphasizes the complexity in determining the snow
albedo, showing that LAI concentrations alone might not be sufficient, but
additional transient effects on the light-absorbing properties of the EC need
to be considered and studied in the snow. Equally as imperative is the
confirmation of
the spatial and temporal representativeness of these data by comparing data
from several and deeper pits explored at the same time. |
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| ISSN: | 1867-1381 1867-8548 |