Fog‐droplet sampling using a modified impactor technique

Possible errors in sampling fog droplets with the cascade impactor are discussed and data are presented which were obtained from 25 fogs by the use of a specially modified impactor in a small portable wind-tunnel. A very wide range of drop diameter ( 100 μ) was found, with great numbers of very small drops and great variability in size-distribution. Agreement between the visual range as calculated from the drop measurements and the actual visual range was usually closer than a factor of two, though in some cases there was no such agreement.