Fog and cloud droplet size spectra measured with a low-cost optical particle counter

This study explores the possibilities of using a Climet CI-8060 optical particle counter as a fog and cloud droplet counter in ambient conditions. Intercomparisons with an AERAS cascade impactor (modified for fog measurements) show that the performance of the instrument is excellent and yields accurate droplet size distributions in the range of 0.54 to 25 μm in one-minute time resolution. The CI-8060 was applied successfully in a field experiment investigating in-cloud scavenging of air pollutants. It is shown that the cloud droplet size distribution is a key parameter for the depletion of pollution by wet deposition. Being aware of the fact that commercial instruments built particularly for the purpose of cloud droplet sizing exist, the CI-8060 has some advantages: it is inexpensive, and it is rugged and easy to use in the field.