Hygroscopic growth and cloud activation of pollen: a laboratory and modelling study

This study investigates the hygroscopic growth of pollen. An electrodynamic balance was used to measure the water uptake on pollen and an environmental scanning electron microscope was used to visualize the response of the pollen to subsaturated humidities. Pollen was found to be moderately hygroscopic and its surface wettable at high humidities. The hygroscopicity data were parameterized using ?-Kohler theory and used in a rising parcel cloud model to investigate the effect of pollen on sulfate activation. Our data suggest that extreme pollen concentrations (>1000 m-3) may interfere with the activation of the background sulphate aerosol mode in pristine environments. Copyright (c) 2012 Royal Meteorological Society