Diffuse Sky Radiation - Under An Overcast Sky

Under An Overcast Sky

There is essentially no direct sunlight under an overcast sky, so all light is then diffuse sky radiation. The flux of light is not very wavelength dependent because the cloud droplets are larger than the light's wavelength and scatter all colors approximately equally. The light passes through the translucent clouds in a manner similar to frosted glass. The intensity ranges (roughly) from 1⁄₆ of direct sunlight for relatively thin clouds down to 1⁄₁₀₀₀ of direct sunlight under the extreme of thickest storm clouds.