A High-Resolution Record of Ice Nuclei Concentrations Between −20 to −30 °C for Fall and Winter at Storm Peak Laboratory with the autonomous Continuous Flow Diffusion Chamber Ice Activation Spectrometer

Abstract. Ice nucleating particles (INPs) influence the timing and amount of precipitation in mixed-phase clouds by acting as seeds for supercooled liquid droplets to form ice upon. High-resolution, long-term measurements of ice nucleating particles (INPs) have been impeded by complex instrumentation that requires a trained on-site technician to operate or analyze offline. We have significantly updated the well-characterized continuous flow diffusion chamber (CFDC) instrument to run autonomously with minimal in-person handling and easy remote access. This new CFDC, the CFDC-Ice Activation Spectrometer (CFDC-IAS) was deployed for four months (October 2020–January 2021) at the mountain-top Storm Peak Laboratory site in Colorado and provided 5-minute resolution measurements daily at target temperatures of -20, -25, and -30 °C. Concentrations of INPs across all temperatures had a median value of 6 per standard liter (sL^-1), and a mean of 10 sL^-1 with a range of ~0–470 sL^-1. The CFDC-IAS was served once a week by a technician who changed out diffusion dryer desiccant and replaced the nitrogen tank as needed, and otherwise was operated remotely for desired changes in the sampling routine.