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| Titel |
A climatology of dust emission events from northern Africa using long-term surface observations |
| VerfasserIn |
S. M. Cowie, P. Knippertz, J. H. Marsham |
| 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 ; 14, no. 16 ; Nr. 14, no. 16 (2014-08-25), S.8579-8597 |
| Datensatznummer |
250118972
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| Publikation (Nr.) |
 copernicus.org/acp-14-8579-2014.pdf |
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| Zusammenfassung |
Long-term (1984–2012) surface observations from 70 stations in the Sahara
and Sahel are used to explore the diurnal, seasonal and geographical
variations in dust emission events and thresholds. The frequency of dust
emission (FDE) is calculated using the present weather codes of SYNOP
reports. Thresholds are estimated as the wind speed for which there is
a 50% probability of dust emission and are then used to calculate strong
wind frequency (SWF) and dust uplift potential (DUP), where the latter is an
estimate of the dust-generating power of winds. Stations are grouped into six
coherent geographical areas for more in-depth analysis.
FDE is highest at stations in Sudan and overall peaks in spring north of
23° N. South of this, where stations are directly influenced by the
summer monsoon, the annual cycle in FDE is more variable. Thresholds are
highest in northern Algeria, lowest in the latitude band 16–21° N
and have greatest seasonal variations in the Sahel. Spatial variability in
thresholds partly explain spatial variability in frequency of dust emission
events on an annual basis. However, seasonal variations in thresholds for the
six grouped areas are not the main control on seasonal variations in FDE.
This is demonstrated by highly correlated seasonal cycles of FDE and SWF
which are not significantly changed by using a fixed, or seasonally varying,
threshold. The likely meteorological mechanisms generating these patterns
such as low-level jets and haboobs are discussed. |
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