Release of ice-nucleating particles from leaves during rainfall.

Plant surfaces are a major source of particles able to initiate ice formation in clouds little below 0 °C. Rainfall promotes the release of such ice-nucleating particles (INPs) from vegetation. However, the pattern of their release throughout rain events remains unexplored. Here, we investigate at a high temporal resolution INP dynamics in rain impacting and running off single leaflets of Juglans regia during two rain events and relate the results to total INP inventories on the leaflets. Throughout both events, leaf runoff was distinctly enriched in INPs as compared with rainwater. A large fraction of INPs washed off during rainfall was released already at the beginning of the events. Except for the highest temperature interval, less than 40% of detachable INPs from leaf surfaces had been removed after the rain events. We hypothesise that surfactant excretion of INP-producing bacteria shapes the observed pattern of release.