Sky Distribution

Introduction

When observed from the ground, the distribution of light over the skydome is rarely uniform. Solar radiation from the Sun travelling through the Earth’s atmosphere can be absorbed, reflected and scattered in all directions by gas and dust particles as well as clouds of moisture vapour. Cloudiness and turbidity are also highly dynamic and, when driven by winds in the upper atmosphere, can change the characteristics of the entire sky within minutes. Figure 1 shows some examples of different types of real sky conditions commonly experienced - in this case overcast, partly cloudy and clear skies.