Ground based measurements of immersion-freezing in the eastern Mediterranean

Abstract

Abstract. Ice Nuclei were measured in immersion-freezing mode on the Tel Aviv University campus using the FRIDGE-TAU chamber. The sampling was done under different meteorological conditions and air pollution levels and then analyzed in the laboratory using a drop freezing method. The droplets froze from −12 °C down to −29 °C, the average temperature at which 50% of the drops froze occurred at −21 °C. Immersion-Freezing Nuclei (FN) concentrations between 0.32 L−1 to 211 L−1 were found with a~concentration of 1 L−1 observed at −15.5 °C. The measurements were divided into dusty and clean conditions based on their back trajectory maps and aerosol mass concentrations (PM10). Droplets from the dusty days froze at warmer temperatures than from clean days. The Dusty days had higher FN concentrations and active fraction (AF) values than clean days.