A survey of fog and related optical propagation characteristics

Abstract

A thorough literature survey of drop size distributions, liquid water contents, and vertical thicknesses of fogs throughout the world is discussed and summarized in tables. The information on drop size distributions is then used to obtain estimates of extinction of different wavelengths of electromagnetic energy. The relative attenuations of visible wavelengths and wavelengths near 10 µm depend crucially upon the shape of drop size distributions. Attenuation of wavelengths near 1 mm by fog drops is always less than attenuation by the much shorter wavelengths. However, attenuation by water vapor is significant near 1 mm even in window regions between strong absorption lines. Sample computations on German data compare total attenuation in German fogs in different seasons.