Calculated Effects of Haze Droplets on Visibility in Natural and Treated Warm Fogs

This paper presents recent measurements, obtained with the use of electro-optical particle counters, of the sizes and concentrations of droplets in warm fogs. These measurements show that high concentrations of haze droplets coexist in the fog with fog droplets of the usual size range. The measurements are used to calculate the visibility within the fog. It is clear from the calculations that the haze droplets contribute significantly to the degradation of visibility in certain of the fogs. Calculations are then performed that show the effects of hygroscopic seeding on the visibility within the fog. The results indicate that the presence of the haze droplets impairs the clearing of the fog. Any system for clearing fogs must include a means of removing, or at least reducing the haze droplets.