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| Titel |
Development of a global model of mineral dust aerosol microphysics |
| VerfasserIn |
Y. H. Lee, K. Chen, P. J. Adams |
| 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 ; 9, no. 7 ; Nr. 9, no. 7 (2009-04-03), S.2441-2458 |
| Datensatznummer |
250007161
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| Publikation (Nr.) |
 copernicus.org/acp-9-2441-2009.pdf |
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| Zusammenfassung |
| A mineral dust module is developed and implemented into the global aerosol
microphysics model, GISS-TOMAS. The model is evaluated against long-term
measurements of dust surface mass concentrations and deposition fluxes.
Predicted mass concentrations and deposition fluxes are in error on average
by a factor of 3 and 5, respectively. The comparison shows that the model
performs better near the dust source regions but underestimates surface
concentrations and deposition fluxes in more remote regions. Including only
sites with measured dust concentrations of at least 0.5 μg m−3,
the model prediction agrees with observations to within a factor of 2. It
was hypothesized that the lifetime of dust, 2.6 days in our base case, is
too short and causes the underestimation in remote areas. However, a
sensitivity simulation with smaller dust particles and increased lifetime,
3.7 days, does not significantly improve the comparison. These results
suggest that the underestimation of mineral dust in remote areas may result
from local factors/sources not well described by the global dust source
function used here or the GCM meteorology. The effect of dust aerosols on
CCN(0.2%) concentrations is negligible in most regions of the globe;
however, CCN(0.2%) concentrations change decrease by 10–20% in dusty
regions the impact of dust on CCN(0.2%) concentrations in dusty regions
is very sensitive to the assumed size distribution of emissions. If
emissions are predominantly in the coarse mode, CCN(0.2%) decreases in
dusty regions up to 10–20% because dust competes for condensable
H2SO4, reducing the condensational growth of ultrafine mode
particles to CCN sizes. With significant fine mode emissions, however,
CCN(0.2%) doubles in Saharan source regions because the direct emission
of dust particles outweighs any microphysical feedbacks. The impact of dust
on CCN concentrations active at various water supersaturations is also
investigated. Below 0.1%, CCN concentrations increase significantly in
dusty regions due to the presence of coarse dust particles. Above 0.2%,
CCN concentrations show a similar behavior as CCN(0.2%). |
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