An observation-based approach to identify local natural dust events from routine aerosol ground monitoring
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Title:
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An observation-based approach to identify local natural dust events from routine aerosol ground monitoring |
Author:
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Tong, D. Q.; Dan, M.; Wang, T. and Lee, P.
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Abstract:
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Dust is a major component of atmospheric aerosols in many parts of the world. Although there exist many routine aerosol monitoring networks, 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 a new 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 pe-
riod, 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 Chihuahua Desert (59 cases) and the Sonoran
Desert (62 cases) are by far the most active source regions. In general, the Chihuahua
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. |
URI:
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http://10.0.0.98/xmlui/handle/1/1362
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Date:
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2012 |
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