Ice-nucleating Macromolecules from Alpine Forests as Possible Contributors to Cloud Glaciation Processes

Ice nucleation in the atmosphere leads to the formation of mixed-phase as well as cirrus clouds in the upper troposphere. Cloud glaciation can either occur homogeneously at temperatures below -38°C or heterogeneously in the presence of ice-nucleating particles (INPs) at temperatures higher than -38°C. Depending on the aggregate state of a cloud, it’s life time and radiative properties vary and thus affect regional and global climate. The influence of biogenic INPs on atmospheric processes as well as the transport of these particles from the land surface to the atmosphere remains elusive. Several plants from boreal and alpine forests are known to contain ice-nucleating macromolecules (INMs) to survive in extreme conditions. However, less is known about chemical characteristics and actual emission rates of such INMs.

We present here our investigation of surface extracts from different tree tissues (Betula pendula and Pinus sylvestris). We were able to extract INMs from nearly all samples. Furthermore, we analyzed the ability of these INMs to be released during rain fall events in-situ. To investigate possible transport mechanisms of INMs from the canopy of studied tree species to the atmosphere we sampled aerosols with two small scale drones, carrying our self-build sampling systems called DAPSI (Drone-based Aerosol Particles Sampling Impinger/Impactor). Results indicate that birches and pines outline an important source of airborne biogenic INPs.