Insights from a Year-long Study on Ice-Nucleating Particles in Helsinki

This study explores the seasonal dynamics of ice-nucleating particles (INPs) in Helsinki over a year. Using an automatic sampler, we collected atmospheric particle samples daily onto filters, which were subsequently analyzed offline through drop freezing experiments in our laboratory. The year-long measurements are used to study the temporal variations and seasonal patterns of INP concentrations in Helsinki. Measurements of different meteorological variables are also considered for the study. Additionally, we present case studies with higher temporal resolution. The offline laboratory analysis of the collected filters enables the characterization of INP concentrations in an urban environment with changing aerosols sources in different seasons. The presented results contribute to the understanding of the variation of INPs in an environment where anthropogenic activity is a main contributor to the present aerosol load.