The spectrometer for ice nuclei (SPIN): An instrument for continuous measurements of ice nuclei

Ice in clouds has major impacts on precipitation formation and cloud characteristics including cloud dynamics and radiation. Primary nucleation of ice crystals at temperatures warmer than about −38 C occurs through heterogeneous nucleation by aerosol particles via several possible mechanisms. Droplet Measurement Technologies is producing a commercial ice nuclei (IN) counter sensitive to deposition and immersion/condensation freezing that features a parallel plate diffusion chamber. A high efficiency refrigeration system allows control of the cold wall to temperatures as low as approximately −70 C and the warm wall to temperatures as low as approximately −40 C, allowing measurements of IN activity over a wide range of atmospherically-relevant temperatures and water/ice saturations. Newly formed ice crystals are detected using an optical particle counter that features detection of polarized scattered light to identify ice crystals and distinguish them from liquid droplets. An actively controlled evaporation...