The development and application of a Freezing Ice Nucleation Detector Array （FINDA） instrument on immersion mode measurement

To quantify the ice nucleating particle (INP) concentrations in precipitation (rain, snow, hail, et al.) and the atmosphere, a new offline Freezing Ice Nucleation Detector Array (FINDA) instrument is developed to detect the immersion mode INPs. The temperature sensor is modified and calibrated. The horizontal temperature bias of cold stage is measured with an infrared camera and calibrated. A software is developed to automatically control the frozen experiment and data analysis. FINDA is validated by performing an ultra-pure water experiment and measuring INPs in snow water and air. The result shows that uncertainty of temperature changes linearly with decreasing temperature and the bias is within ±0.75℃ at −25℃. The starting frozen temperature is −21.27±1.45℃, and the medium frozen temperature is 25.65±0.64℃. The INPs in snow water measured by FINDA compare well with measurements by other instruments with an offset less than 2℃. The result of INPs concentration in the air measured by FINDA is slightly higher than that by Continuous-Flow Diffusion Chamber, and compares well with other studies. With FINDA, the INPs concentration between 0 and −25℃ at 0.25℃ interval is measured effectively. The INPs induced by ultra-pure water and the experiment itself have little impact on the result. The application of FINDA will not only help to further understand the role of INPs in mixed-phase clouds, but also improve the datum and theory support for the development of local weather forecast and cloud models as well as the cloud and precipitation theory.