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Abstract
The scattering and/or absorption of atmospheric aerosols to
solar radiation play an important role in direct
radiative forcing of climate. Atmospheric aerosols were
collected at Tainan for nearly two month in the springtime of
1997. An aerosol spectrometer (PMS model PCASP-
X) was used to measure aerosol size distribution,
and an integrating nephelometer (TSI model 3563) was set up to
acquire aerosol light-scattering coefficient
(ssp). Moreover, two collocated MOUDI (Micro-orifice
Uniform Deposit Impactor) samplers were installed at the site to
collect sub-micron aerosols for chemical analysis.
The daily averages of ssps from green-wavelength measured at
Tainan were in the range of 0.06 to 0.48 Km-1.
The results are consistent with those measured at other
urban areas in the world. Meanwhile, the ssp is found in this
work to have a close relation with meteorological
factors. A rapid increase of ssp is shown when relative
humidity reaches 75~80% and above. This environmental humidity
is consistent with the deliquescent point of
hygroscopic aerosols. Another finding displays wind speed
exhibits an inverse relationship with ssp. The pollution event
analysis shows that source emissions or dense fog has a
great effect on short term ssp, sub-micron particles are
found to be influenced most among all sizes.
For springtime aerosols collected at Tainan, the resolved major
chemical species including sulfates, nitrates,
elemental carbon, and organic carbon. As a correlation
matrix analysis shows, the ssp is related to sub-micron aerosol
mass, nitrates, sulfates, ammonium ions, and aerosol water
contents. Both the linear regression model and
simplified theoretical model for estimating ssp are very
consistent with the measured ssp. The results imply
that either aerosol physical property (theoretical model) or
chemical property (regression model) for estimating ssp is
applicable.
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