Abstract:
Aerosols are minute liquid or solid particles suspended in the atmosphere. Aerosol optical Depth (AOD) and Angstrom Exponent (AE) are significant parameters to study the concentration and size or type of aerosol over an area, respectively. These parameters vary in space and time. Few studies were reported in Ethiopia using ground based instruments, such as sun photometer but are unable to provide complete spatial coverage in Ethiopia. In this thesis, daily and seasonal variations of AOD and AE over Ethiopia are investigated using Moderate resolution imaging spectroradiometer (MODIS) satellite data from January, 2013 to December, 2015. In addition, to study the spatiotemporal pattern of aerosols, the spatial and temporal variability of AOD and AE around three areas (Debretabour, Gojjam and Addis Ababa) over Ethiopian highlands are presented. Those regions are representative of non-industrial, agricultural and industrial areas, respectively. In addition comparisons between continental aerosols of Debretabour, Addis Ababa and Gojjam with Marine aerosols of Djibouti are also discussed. Descriptive statistics like average, standard deviation and coefficient of variation (CV) were used and processed in MATLAB software to understand the spatiotemporal variability of aerosol concentration and type or size. The results show that average monthly variation of AE indicates, urban pollution and biomass aerosols are dominate over Addis Ababa and Gojjam respectively and both dust and biomass aerosols are present over Debretabour, while Djibouti is dominated by sea spray aerosols. The percentage of coefficient of variations (CVs) of AOD are 94.21%, 77.7%, 67.69%, and 57.16% for Debretabour, Gojjam, Addis Ababa and Djibouti, respectively. The aerosols in Debretabour are highly variable compared to the other three stations. An assessment of seasonal variability of AOD for non-industrial, continental, marine and agricultural area revealed maximum AOD values during the kiremt (summer) and minimum during bega (winter) over all areas except Addis Ababa region.