Ice nucleating particles in a boreal environment

Research profile seminar

Ice nucleation is an important pathway for cloud formation and initiation of precipitation in the atmosphere, thus affecting the Earth¿s hydrological cycle, energy and radiative balance.

Ice nucleation is an important pathway for cloud formation and initiation of precipitation in the atmosphere, thus affecting the Earth¿s hydrological cycle, energy and radiative balance. An intensive measurement campaign took place at the SMEAR II station in the winter/spring 2018 in an attempt to measure the concentration and characteristics of ambient ice nucleating particles (INPs). Portable Ice Nucleation Chamber (PINC) was deployed to characterise the ice nucleation IN behaviour of ambient aerosol particles in condensation freezing mode at a temperature of -31°C and RHw of 105%. Measured INP concentrations in the boreal environment were relatively high, with values as high as 400 L-1. However, no correlations of the entire INP time series with any of the examined external variables (weather, aerosol particle concentrations at different sizes, black carbon, chemical groups) were found. The absence of any correlation highlights the rarity of ambient INPs. Correlations improve when IN behaviour under particular weather conditions is examined. The analysis demonstrates that different particles act as INPs at different times, and a high resolution of INP measurements is key.