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| Titel |
Modelling the surface deposition of meteoric smoke particles |
| VerfasserIn |
James S. A. Brooke, Wuhu Feng, Graham W. Mann, Sandip S. Dhomse, Charles G. Bardeen, John M. C. Plane |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132556
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| Publikation (Nr.) |
 EGU/EGU2016-13073.pdf |
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| Zusammenfassung |
| The flux of meteoric smoke particles (MSPs) in Greenland and Antarctica has been measured
using Ir and Pt observations in ice cores, by Gabrielli et al. [1,2]. They obtained MSP
deposition fluxes of 1.5 ± 0.45 × 10−4 g m−2 yr−1 (209 ± 63 t d−1) in Greenland and
3.9 ± 1.4 × 10−5 g m−2 yr−1 (55 ± 19 t d−1) in Antarctica, where the values in parentheses
are total atmospheric inputs, assuming a uniform global deposition rate. These
results show reasonable agreement with those of Lanci et al. [3], who used ice core
magnetisation measurements, resulting in MSP fluxes of 1.7 ± 0.23 × 10−4 g m−2 yr−1
(236 ± 50 t d−1) (Greenland) and 2.0 ± 0.52 × 10−5 g m−2 yr−1 (29 ± 5.0 t d−1)
(Antarctica).
Atmospheric modelling studies have been performed to assess the transport and
deposition of MSPs, using WACCM (Whole Atmosphere Community Climate Model), and
the CARMA (Community Aerosol and Radiation Model) aerosol microphysics package. An
MSP input function totalling 44 t d−1 was added between about 80 and 105 km. Several
model runs have been performed in which the aerosol scavenging by precipitation was varied.
Wet deposition is expected (and calculated here) to be the main deposition process; however,
rain and snow aerosol scavenging coefficients have uncertainties spanning up to two
and three orders of magnitude, respectively [4]. The model experiments that we
have carried out include simple adjustments of the scavenging coefficients, full
inclusion of a parametrisation reported by Wang et al. [4], and a scheme based on
aerosol removal where relative humidity > 100 %. The MSP fluxes obtained vary
between 1.4 × 10−5 and 2.6 × 10−5 g m−2 yr−1 for Greenland, and 5.1 × 10−6
and 1.7 × 10−5 g m−2 yr−1 for Antarctica. These values are about an order of
magnitude lower than the Greenland observations, but show reasonable agreement for
Antarctica.
The UM (Unified Model), UKCA (United Kingdom Chemistry and Aerosols Model), and
GLOMAP (GLObal Model of Aerosol Processes) have also been used. The maximum height
of this model is 85 km, and so MSP concentrations have been taken from WACCM and
imposed above about 65 km. The important MSP-sulphate interaction has only very recently
been implemented in GLOMAP. GLOMAP contains a modal treatment of aerosol
microphysics, in contrast to the full sectional description in CARMA. The predicted
evolution of the MSP size distribution and deposition fluxes from both models will be
compared.
[1] P. Gabrielli et al., Nature 432, 1011 (2004)
[2] P. Gabrielli et al., Earth Planet. Sci. Lett. 250, 459 (2006)
[3] L. Lanci et al., Quaternary Sci. Rev. 33, 20 (2012)
[4] X. Wang et al., Geosci. Model Dev. 7, 799 (2014) |
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