Formation and Optical Properties of a Warm Cloud in a Slow–Expansion Cloud Chamber

Abstract

The formation of a warm cloud was studied in a 1.1 m?3, isothermal, slow?expansion cloud chamber. The evolution of the precloud haze droplet population into the incloud haze and cloud droplet populations was measured in unprecedented detail. The chamber environment was found to closely reproduce cloud formation in an adiabatically expanding parcel. Further, the microphysical characteristics of the cloud resembled those of a marine stratocumulus cloud. A procedure for estimating subsaturated and supersaturated relative humidity values was developed and shown to reproduce modeled values. Unique measurements of cloud droplets evaporating into haze droplets were obtained. The visual range within the chamber was calculated to he 4 m, a value sufficiently low to conduct electromagnetic energy propagation experiments.