  The total amount of solar irradiance falling on the earth's surface is an
important area of study amongst the photo-voltaic (PV) engineers and remote
sensing analysts. The received solar irradiance impacts the total amount of
generated solar energy. However, this generation is often hindered by the high
degree of solar irradiance variability. In this paper, we study the main
factors behind such variability with the assistance of Global Positioning
System (GPS) and ground-based, high-resolution sky cameras. This analysis will
also be helpful for understanding cloud phenomenon and other events in the
earth's atmosphere.
