ABSTRACT Aerosols are microscopic liquid or solid particles which enter the atmosphere through natural and man-made processes. Atmospheric aerosols influence the Earth’s weather and climatic system in many ways, both directly and indirectly, although the magnitude of this influence remains uncertain even today (IPCC, 2007). Interactions between aerosols and clouds have become the subject of scientific research because of the importance of clouds in controlling climate. In this thesis, we have examined the temporal variations (time series analysis) in aerosol particles over Ethiopia and the impact of these variations on various optical properties of clouds using Moderate Resolution Imaging Spectroradiometer (MODIS) data from January 2003 to December 2018. The maximum aerosol optical depth (AOD) was found at summer period with minimum values in winter. During summer air temperature is high leads to hold abundant atmospheric water vapor facilitated the hygroscopic growth of aerosols. We then analyzed the relationships between AOD and other cloud parameters, namely water vapour (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP) to provide a better understanding of aerosol–cloud interaction. The correlation between AOD and cloud fraction (CF), water vapor (WV) was positive for Ethiopian continent, while negative correlation with cloud top temperature (CTT) and cloud top pressure (CTP). Key words: MODIS, AOD, CF, CTP, CTT, WV and Ethiopia