Ice nucleus counter for laboratory and field measurements

Description

Ice clouds regulate a significant portion of precipitation formation and have major influence on cloud characteristics such as cloud dynamics and radiation. Modeling has been difficult with regard to these items, as the ice-nucleating properties of aerosols are complex to measure. Droplet Measurement Technologies is producing a commercial ice nucleus counter based on the parallel plate chamber design, coupled with a high-efficiency refrigeration system and a single-particle detector that uses depolarization of the scattered light to identify liquid or ice particles. The system is completely automated and designed for continuous, unattended operation. The refrigeration system can cool the cold wall to -70°C, and the warm wall can be cooled to -40°C. A new variable-speed DC-powered compressor is used, which provides rapid cooling and a high degree of temperature control. An optical particle counter has been designed specifically for the ice nucleus counter. The unit is designed to handle the entire flow from the IN chamber with a high degree of resolution for the particle size. Light is collected in side scatter, as the primary sizing detector. Backscattered light is passed through a polarizing prism, separating the scattered light into the S and P polarizations. The electronics provide for binning of the data as well as particle-by-particle recording of the signal intensity. Particle sizing is from 0.4 to 10 microns.