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The light scattering of atmospheric aerosols are important in
radiative forcing in global warming. Among factors affecting
aerosol light-scattering coefficient (ssp), aerosol size
distribution has been known to be a major one. Although ssp is
an integrating effect from all sizes of aerosols, a revelation
of significant sizes in determining ssp is crucial in
evaluating the control measures for atmospheric visibility. In
the present study, a system consists of a scanning mobility
particle sizer (SMPS, TSI Model 3934) and an integrating
nephelometer (TSI Model 3563) was set up to assess shape
effects on ssp size distribution and measure ssp size
distribution. For the same mobility diameter, ssp is shown
increased with an increasing ratio of long-to-short axis among
sphere, short prism, and long prism. Meanwhile, aerosol back-
scattering coefficient is decreased for an increasing ratio of
long-to-short axis. The ssp size distribution was measured
both at the campus of National Central University (NCU, in a
suburban area) and at Sun-chun air quality monitoring station
(on a traffic laden road). The results at NCU site showed a
uni-modal ssp size distribution with a peak diameter at 0.5mm
and the ssp in the range of 0.06~0.14Km-1. In contrast, Sun-
chun site showed a bi-modal ssp size distribution with peak
diameters at 0.45mm and 0.65 mm, individually, and the ssp in
the range of 0.08~0.36Km-1. In the present study, a
theoretical ssp size distribution is calculated from Mie theory
and the measured aerosol size distribution. For a comparison,
the ratio of the sum from theoretical ssp size distribution to
that from measured ssp size is 89% and 82% at NCU site and
Sun-chun site, individually. Meanwhile, the ratio of
theoretical ssp to the sum from theoretical ssp size
distribution is 80% and 81% at NCU site and Sun-Chun site
,individually.
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