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| Titel |
Long-term dust climatology in the western United States reconstructed from routine aerosol ground monitoring |
| VerfasserIn |
D. Q. Tong, M. Dan, T. Wang, P. Lee |
| 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 ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-14), S.5189-5205 |
| Datensatznummer |
250011235
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| Publikation (Nr.) |
 copernicus.org/acp-12-5189-2012.pdf |
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| Zusammenfassung |
| This study introduces an observation-based dust identification approach and
applies it to reconstruct long-term dust climatology in the western United
States. Long-term dust climatology is important for quantifying the effects
of atmospheric aerosols on regional and global climate. Although many routine aerosol monitoring networks exist, it is often difficult to obtain
dust records from these networks, because these monitors are either deployed
far away from dust active regions (most likely collocated with dense
population) or contaminated by anthropogenic sources and other natural
sources, such as wildfires and vegetation detritus. Here we propose an
approach to identify local dust events relying solely on aerosol mass and
composition from general-purpose aerosol measurements. Through analyzing the
chemical and physical characteristics of aerosol observations during
satellite-detected dust episodes, we select five indicators to be used to
identify local dust records: (1) high PM10 concentrations; (2) low
PM2.5/PM10 ratio; (3) higher concentrations and percentage of
crustal elements; (4) lower percentage of anthropogenic pollutants; and (5)
low enrichment factors of anthropogenic elements. After establishing these
identification criteria, we conduct hierarchical cluster analysis for all
validated aerosol measurement data over 68 IMPROVE sites in the western
United States. A total of 182 local dust events were identified over 30 of
the 68 locations from 2000 to 2007. These locations are either close to the
four US Deserts, namely the Great Basin Desert, the Mojave Desert, the
Sonoran Desert, and the Chihuahuan Desert, or in the high wind power region
(Colorado). During the eight-year study period, the total number of dust
events displays an interesting four-year activity cycle (one in 2000–2003
and the other in 2004–2007). The years of 2003, 2002 and 2007 are the three
most active dust periods, with 46, 31 and 24 recorded dust events,
respectively, while the years of 2000, 2004 and 2005 are the calmest
periods, all with single digit dust records. Among these deserts, the
Chihuahuan Desert (59 cases) and the Sonoran Desert (62 cases) are by far
the most active source regions. In general, the Chihuahuan Desert dominates
dust activities in the first half of the eight-year period while the Sonoran
Desert in the second half. The monthly frequency of dust events shows a peak
from March to July and a second peak in autumn from September to November.
The large quantity of dust events occurring in summertime also suggests the
prevailing impact of windblown dust across the year. This seasonal variation
is consistent with previous model simulations over the United States. |
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