Mobile Ice Nucleus Counter

Ice crystals can form spontaneously from the freezing of water droplets at temperatures colder than -38C - homogeneous nucleation - or from multiple processes termed heterogeneous nucleation that occur on refractory/insoluble substances at warmer temperatures. Heterogeneous nucleation occurs at temperatures warmer than the homogeneous threshold and includes the direct deposition of water vapor on the surfaces of aerosols (deposition nucleation), freezing of deliquesced aerosols (immersion nucleation) and freezing of water droplets that come in contact with an aerosol particle (contact nucleation). As a whole, the particles which induce freezing are known as ice nuclei (IN). Each of these nucleation processes can occur over a range of temperatures and relative humidities and depend on the chemical composition as well as the morphology of the particle. This complexity in processes leading to ice formation presents perhaps the greatest challenge to the atmospheric science community today. Commercial Applications and Other Benefits: In this proposal, the work will focus on the adaptation and development of the parallel plate IN counter into a commercial instrument. The first phase of this work will involve improvements in the refrigeration system and the adaptation of an optical particle spectrometer with depolarization to separately determine water and ice particles.