The Study of Aerosol Microphysical and Optical Parameters, Total Columnar Ozone and Water Vapor Content Derived from Sunphotometer
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Date
2009-07
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Addis Ababa University
Abstract
The spectral aerosol optical depth measurements are estimated over Addis Ababa
(09.033N , 38.7E) at 2445m a.m.s.l. from the measurements of direct solar irradiance
at different wavelengthes in the range between 305.3-1020nm using a hand held
5-channel Microtops II sunphotometer (Solar light co. USA) for the first time. Results
show wavelength dependence of aerosol optical depth (AOD) which gradually
decreases with increasing wavelength, having mean value of 0.209 (±0.0625) at 1020
nm optical channel. The °Angstrom exponent and turbidity were found to be
inversely related with a good anticorrelation (R = −0.807) and the °Angstrom exponent
was observed to be small in the range from (0.204) to (0.993) with a mean
value of (0.627) indicates the presence of coarse mode particles over the site. Temporal
variation of both AOD and retrieved columnar size distribution (ASD) show
minimum value during the noon time. Large value with large variability in AOD
and ASD are observed in April, 2009 as compered to March and May, 2009. This is
attributed to the long range transported aerosols from different source. A good positive
correlation between aerosol optical depth (AOD) and precipitable water content
(PWC) were observed during the measurements of March and may which attributed
to the presence of hygroscopic aerosols over the site. The day-to-day variations in
total columnar ozone (TCO) were found to be in fair agreement (10−14%) deviation
from TOMS satellite data for all the experimental days, having mean observed value
of 294.45 (±6.61) DU over the station.
Keywords: Aerosols; Aerosol optical depth; Aerosol size distribution; °Angstrm parameters;
total columnar ozone; and precipitable water content
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The Study of Aerosol Microphysical