EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-1873 An improved Freezing Ice Nucleation Detection Analyzer (FINDA) for droplet immersion freezing measurement Wang Kaiqi 1 2 3 Bi Kai 1 11 Chen Shuling 2 3 4 Hartmann Markus https://orcid.org/0000-0001-9700-1701 5 Wu Zhijun 6 Gao Jiyu 7 Xu Xiaoyu 2 3 4 Cheng Yuhan https://orcid.org/0009-0004-3566-6563 2 3 4 Huang Mengyu https://orcid.org/0000-0001-5121-5499 1 11 Chen Yunbo 1 Xue Huiwen 6 Wang Bingbing 7 Hu Yaqiong 8 Zhang Xiongying 9 Ma Xincheng 1 Li Ruijie 1 Tian Ping https://orcid.org/0000-0002-8795-5605 1 Möhler Ottmar https://orcid.org/0000-0002-7551-9814 8 Wex Heike https://orcid.org/0000-0003-2129-9323 5 Startmann Frank https://orcid.org/0000-0003-1977-1158 5 Chen Jie https://orcid.org/0000-0001-5353-1110 10 Gong Xianda https://orcid.org/0000-0001-7274-0639 2 3 Beijing Weather Modification Center, Beijing Meteorological Service, Beijing, China Research Center for Industries of the Future, Westlake University, Hangzhou, 310030, China Key Laboratory of Coastal Environment and Resources of Zhejiang Province, School of Engineering, Westlake University, Hangzhou, 310030, China College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China Leibniz Institute for Tropospheric Research, Leipzig, 04318, Germany State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China College of Ocean and Earth Sciences, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361102, China Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany School of Earth Sciences, Yunnan University, Kunming, 650504, China Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, 8092, Switzerland Field Experiment Base of Cloud and Precipitation Research in North China, China Meteorological Administration, Beijing, 101200, China 19 05 2025 2025 1 29 Copyright: © 2025 Kaiqi Wang et al. 2025 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1873/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1873/egusphere-2025-1873.pdf

Heterogeneous ice nucleation initiated by atmospheric ice-nucleating particles (INPs) is a key microphysical process for cloud formation. Detecting the ice nucleation ability (INA) and concentration of INPs is essential for improving global climate models. Droplet freezing techniques (DFTs) are among the widely used tools for measuring the immersion freezing of INPs, which is a predominant ice nucleation process in mixed-phase clouds. To enhance the efficiency and accuracy of DFTs, we developed a Freezing Ice Nucleation Detection Analyzer at Westlake University (FINDA-WLU) with an improved hardware setup, user-friendly software, precise droplet freezing detection, and rigorous temperature calibrations. The temperature uncertainty of FINDA-WLU is about ±0.60 °C, considering both vertical heat transfer efficiency and horizontal temperature heterogeneity. The system is tested with Milli-Q ultrapure water and reference materials like Arizona Test Dust and Snomax®, and the results are consistent with previous studies. We also use the FINDA-WLU to measure INPs in precipitation samples collected in China. Overall, FINDA-WLU proved to be a reliable and precise method for measuring INA and INP concentrations.

 National Natural Science Foundation of China 42275087 42105091 41930968 42375069 Westlake University 103110746022301 210000006022303