Development of Instrumentation for Characterization of Ice and Water Clouds

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New instruments will be designed and constructed to measure the liquid water and the ice content of atmospheric clouds together with the shape and density of ice particles. The instruments will be deployed in the field both at the earth's surface and in aircraft to characterize clouds from the standpoints of aircraft icing, radiative transfer, and precipitation and thunderstorm processes. Emphasis is on the characterization of mixed-phase clouds, in which ice crystals and liquid drops coexist. The cloud probe collects either ice and water or ice alone, depending on the configuration of the collector. The precipitation probe collects particles at the stagnation point of a forward-facing sapphire window and records their images on a video camera. Both instruments work on the principle of particle collection on a surface maintained at constant temperature. The power required to hold the temperature steady is proportional to the latent heat of vaporization of the collected material, and hence the particle mass per unit volume of air. These instruments will be applied to investigations of chemical, radiative, and electrical processes in the little-studied mixed-phase regions of clouds.