Kd. Perry et al., LONG-RANGE TRANSPORT OF NORTH-AFRICAN DUST TO THE EASTERN UNITED-STATES, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 102(D10), 1997, pp. 11225-11238
The long-range transport of North African dust to the Middle East, Eur
ope, South America, and the Caribbean has been well documented during
the past 25 years. With the advent of routine collection and analysis
of fine aerosoIs at national parks, monuments, and wilderness areas in
the continental United States, these North African dust incursions ca
n now be tracked, characterized, and quantified across much of the eas
tern half of the United States. Identification of the North African so
urce of these dust episodes is confirmed by mass distribution measurem
ents, a characteristic Al/Ca ratio, isentropic backward air mass traje
ctories, and sequential plots of the spatial distribution of the dust
plumes. North African dust incursions into the continental United Stat
es persist for similar to 10 days and occurred, an average, 3 times pe
r year from 1992 to 1995. Fine soil mass usually exceeds 10 mu g m(-3)
during these dust episodes and dominates local fine soil dust by an o
rder of magnitude or more, even in the so-called ''dust bowl'' states
of the central United States. Size-resolved measurements of elemental
composition taken during July 1995 indicate that the mass mean diamete
r of the transported North African dust is < 1 mu m. The high mass sca
ttering efficiency and abundant particle surface area associated with
these submicron soil aerosols could have important consequences for bo
th the radiative balance of the region and the chemistry of the local
aerosols during summer when the long-range transport of North African
dust to the United States is most common.