Aerosol Optical Thickness (AOT) is a measure of solar spectral extinction. Long term AOT data analysis gives a picture of air quality for that location. This type of analysis is useful in the study of impact of urbanization on local climate. Aerosols are one of the most important but poorly understood factors that influence global climate change (IPCC, 2001). This calls for a need to regularly monitor the global aerosol distributions and study how they are changing over time.