The Study of Aerosol Microphysical and Optical Parameters, Total Columnar Ozone and Water Vapor Content Derived from Sunphotometer

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Addis Ababa University


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



The Study of Aerosol Microphysical